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Background: Soil microbial community composition with stand development may be changed due to the variations in canopy structure, understory vegetation, root traits, edaphic conditions, and litter inputs. However, it is still uncertain to what extent these biotic and abiotic factors shape the soil microbial community composition in Chinese fir (Cunninghamia lanceolata) plantations, which are widely planted in southern China. Methods: Amplicon sequencing was used to analyze the diversity and composition of soil bacterial and fungal communities at two soil depths across four developmental stages of Chinese fir plantations. Results: Both the bacterial and fungal communities were significantly different between stand age groups. As stand aged, oligotrophic bacteria decreased in abundance while copiotrophic bacteria increased. Meanwhile, fungal functional groups connected to plants decreased in abundance while that of saprotrophic fungi significantly increased. The variance in bacterial community was mainly attributed to soil variables regarding carbon and nutrient availability, whereas the greatest fraction of fungal community dissimilarity was determined by plant-specific factors such as aboveground stand structure and tree root traits. The chemical composition of litter had a major effect on the soil fungal community, whereas the litter traits had no effect on the bacterial community. Conclusions: The potential drivers of soil fungi and bacteria differ in Chinese fir plantations. By accounting for the impacts of various environmental components, it is possible to anticipate the response of soil bacterial and fungal assemblages to forest management regime implemented in Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Background: The prevalence of understory removal and anthropogenic nitrogen (N) deposition has significantly altered the ecological processes of forest ecosystems at both regional and global scales. However, it remains a pressing challenge to understand how N deposition and understory removal affect leaf nutrient dynamics, nutrient resorption, litter decomposition, and their linkages for better managing forest ecosystems under nutrient imbalances induced by N enrichment. To address this research gap, a field manipulation experiment was carried out in a subtropical Cunninghamia lanceolata plantation with four treatments including: control (CK), canopy N addition (CN), understory removal (UR), and canopy N addition plus understory removal (CN × UR). Green and senesced leaf N and phosphorus (P) concentrations, N and P resorption efficiencies, litter decomposition, and their correlations were measured. Results: The results revealed that the average N concentrations of green early and late leaves in UR were increased by 6.61 and 18.89% compared to CK. UR had the highest whereas CN had the lowest P concentrations in green leaves across the two sampling seasons. Following this, UR, leaf type, season, and their interactions significantly affected leaf N, P, and N:P (P < 0.05). The highest leaf N resorption (32.68%) and P resorption efficiencies (63.96%) were recorded in UR. Litter decomposition was significantly retarded in UR (P < 0.01) relative to CN. The regression analysis demonstrated that leaf nutrient status was significantly interconnected with leaf nutrient resorption efficiencies. In addition, leaf nutrient dynamics were strongly correlated with litter nutrients, indicating that both were coupled. Conclusion: These findings can deepen our knowledge of biogeochemical cycling and reveal contrasting nutrient-acquisition strategies on N and P limitation in response to UR and CN. Considering the P limitation, it is important to note that P was resorbed more efficiently, illustrating a remarkable nutrient preservation approach for nutrient-limitations. Resorption may be a crucial mechanism for keeping nutrients in these forests, so better understory management practices are required to prevent reliance on external nutrient pools. Overall, this study sheds meaningful insights into the ability of forest adaptation in response to global climatic change. [ABSTRACT FROM AUTHOR]

Little is known about below-ground competition in mixed-species plantations under increasing nitrogen (N) deposition. This study aims to determine the effects of N addition on root competition in coniferous and broad-leaved species mixed plantations. A pot experiment was conducted using the coniferous species Cunninghamia lanceolata and the broad-leaved species Phoebe chekiangensis planted in mixed plantations with different competition intensities under N addition (0 or 45 kg N ha-1 yr-1). Biomass allocation, root morphology, root growth level, and competitive ability were determined after five months of treatment. Our findings indicated that root interactions in mixed plantations did not influence biomass allocation in either C. lanceolata or P. chekiangensis but promoted growth in C. lanceolata when no N was added. However, N addition decreased biomass accumulation in both species in the mixed plantation and had a negative effect on the root growth of C. lanceolata due to intensified competition. Addition of N increased the relative importance of root predatory competition in P. chekiangensis, and increased the allelopathic competitive advantage in C. lanceolata. This suggests that N addition causes a shift in the root competitive strategy from tolerance to competition. Overall, these findings highlight the significant impact that the addition of N can have on plant interactions in mixed plantations. Our results provide implications for the mechanisms of root competition in response to increasing atmospheric N deposition in mixed plantations. [ABSTRACT FROM AUTHOR]

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Chinese fir (Cunninghamia lanceolata) is a major timber species in China, and obtaining and monitoring the parameters of Chinese fir plantations is of great practical significance. With the help of the K-means algorithm and UAV-LiDAR data, the efficiency of forestry surveys can be greatly improved. Considering that the traditional K-means algorithm is susceptible to the influence of initial cluster centers and outliers during the process of individual tree segmentation, it may result in incorrect segmentation. Therefore, this study proposes an improved K-means algorithm that uses the methods of local maxima and height weighting to optimize and improve the algorithm. The research results are as follows: (1) Compared to the traditional K-means algorithm, the producer accuracy and user accuracy of this research algorithm have imsproved by 10.72% and 11.46%, respectively, with significant differences (p < 0.05). (2) The research algorithm proposed in this study can adapt to Chinese fir plantations of different age groups, with average producer accuracy and user accuracy reaching 78.48% and 83.72%, respectively. In summary, this algorithm can be effectively applied to the forest parameter estimation of Chinese fir plantations and is of great significance for sustainable forest management. [ABSTRACT FROM AUTHOR]

Cunninghamia lanceolata is an important species in plantations and is widely planted in sub-tropical regions of China because of its fast-growing and productive characteristics. However, the monoculture planting is carried out in the pursuit of economic value. This planting mode has led to problems such as the exhaustion of soil fertility, decrease in vegetation diversity, and decrease in woodland productivity. In order to restore soil fertility and increase timber production, the introduction of broad-leaved tree species to plantations is an effective transformation model. Understanding how forest age changes and stand structure differences drive the composition and diversity of soil microbial communities is helpful in understanding the trend of soil–microbial changes in plantations and evaluating the effects of the introduction of broad-leaved tree species in soil–plant–microbial ecosystems in plantations. Therefore, the purpose of our study is to investigate the effects of forest age and pure forest conversion on C. lanceolata–P. bournei-mixed forest soil microbial community structure and diversity by detecting soil nutrients, enzyme activities, and soil microbial 16S and ITS rRNA gene sequencing. According to the findings, the diversity and abundance of bacterial communities in C. lanceolata plantations of different ages increased first and then decreased with the increase in forest age, and the max value was in the near-mature forest stage. The fungal abundance decreased gradually with stand age, with the lowest fungal diversity at the near-mature stand stage. During the whole growth process, the bacterial community was more limited by soil pH, nitrogen, and phosphorus. After introducing P. bournei into a Chinese fir plantation, the abundance and diversity of the bacterial community did not improve, and the abundance of the fungal community did not increase. However, soil nutrients, pH, and fungal community diversity were significantly improved. The results of these studies indicate that the introduction of broad-leaved tree species not only increased soil nutrient content, but also had a significant effect on the increase in the diversity of soil fungal communities, making the microbial communities of mixed forests more diverse. [ABSTRACT FROM AUTHOR]

Background: Microbial residues are significant contributors to stable soil organic carbon (SOC). Soil aggregates effectively protect microbial residues against decomposition; thus, microbial residue accumulation and distribution among soil aggregates determine long-term SOC stability. However, how tree species influence accumulation and distribution of soil microbial residues remains largely unknown, hindering the chances to develop policies for SOC management. Here, we investigated microbial residue accumulation and distribution in soil aggregates under four subtropical tree species (Cunninghamia lanceolata, Pinus massoniana, Michelia macclurei, and Schima superba) after 29 years of afforestation. Results: Accumulation of microbial residues in the 0–10 cm soil layer was 13.8–26.7% higher under S. superba than that under the other tree species. A structural equation model revealed that tree species affected the accumulation of microbial residues directly by altering fungal biomass. Additionally, tree species significantly affected microbial residue distribution and contribution to SOC in the top 20 cm soil. In particular, microbial residue distribution was 17.2–33.4% lower in large macro-aggregates (LMA) but 60.1–140.7% higher in micro-aggregates (MA) under S. superba than that under the other species in the 0–10 cm soil layer, and 14.3–19.0% lower in LMA but 43–52.1% higher in MA under S. superba than that under C. lanceolata and M. macclurei in the 10–20 cm soil layer. Moreover, the contribution of microbial residues to SOC was 44.4–47.5% higher under S. superba than under the other tree species. These findings suggest a higher stability of microbial residues under S. superba than that under the other studied tree species. Conclusions: Our results demonstrate that tree species influence long-term microbial persistence in forest soils by affecting accumulation and stabilization of microbial residues. [ABSTRACT FROM AUTHOR]

Aims: Conversion from pure plantations to mixed plantations can significantly increase forest productivity and provide better ecosystem services, yet there is still a lack effective of assessment methods to determine how this conversion affects belowground biodiversity and ecological functions. Methods: We conducted an in-situ experiment to investigate the impacts of forest conversion (Cunninghamia lanceolata pure plantations vs. C. lanceolata-Betula luminifera mixed plantations) on soil multifunctionality, bacterial composition, network patterns and assembly mechanisms in southern subtropical China. Results: The results showed that compared with monoculture plantations, most soil physicochemical properties and enzyme activities were higher in mixed plantations. The mixed plantations increased bacterial α-diversity, and community structure differed between the two forest types. Network analysis showed that the network structure of the mixed plantation was more complex and stable, and contained more keystone taxa. Furthermore, stochastic processes primarily governed the assembly of bacterial communities. Forest conversion increased habitat niche breadth and the importance of stochastic processes. Based on PICRUSt2, the mixed plantations significantly increased soil multifunctionality and bacterial functions (e.g., carbohydrate metabolism and energy metabolism). Moreover, variations in the bacterial community and functionality were highly correlated with soil pH and nutrients. Conclusions: Our study showed that the conversion of monoculture plantations into mixed plantations enhances soil fertility and has more positive benefits. The changes in soil bacterial composition and function were mainly mediated by soil pH and nutrient increases caused by forest conversion, which contributes to assessing the eco-environmental effects of mixed planting in reforestation. [ABSTRACT FROM AUTHOR]

Forty-year-old Chinese fir (Cunninghamia lanceolata) plantations from 16 different provenances in China were selected as the study object to identify the differences in the phenotypes of the anatomical traits of their fine roots, and the characteristics of the responses of the functional traits of fine roots to different geographical environments were analyzed. The fine root diameter (FRD), stele diameter (SD), cortical thickness (CT), ratio of stele to root diameter (SDR), and ratio of cortex to cross-section (CCS) of the fine roots were measured. The differences in the anatomical traits of the fine roots of Chinese fir were compared at the distribution area level, and the correlation between these anatomical traits and environmental factors were examined. The findings revealed significant differences in the anatomical traits of the fine roots among the different provenances (P＜0.05). The FRD and SD of the fine roots of Chinese fir in different locations were ranked in the following descending order: northern belt＞east of middle belt＞center of middle belt＞west of middle belt＞southern belt. The FRD and SD of the fine roots of the trees in Shanghang (Fujian) and Xinyang (Henan) were larger than those in the other provenances, whereas those of the fine roots of the trees in Shangrao (Jiangxi) were the smallest. The CT of the fine roots of Chinese fir in the different areas decreased in the following order: northern belt＞west of middle belt＞east of middle belt＞center of middle belt＞southern belt. The CT of the fine roots of trees in Xinyang (Henan) was thinner than that in other provenances, whereas the fine roots of the trees in Shangrao (Jiangxi) and Luotian (Hubei) showed thicker cortical tissue. The results of redundancy analysis showed that the CT and CCS of the fine roots positively correlated with the soil phosphorus content and significantly negatively correlated with the soil nitrogen content (P＜0.05). The SDR of the fine roots showed a significant positive correlation with latitude (P＜0.05) and a significant negative correlation with soil phosphorus content (P＜0.05). The response characteristics of the anatomical traits of the fine roots of Chinese fir in different habitat conditions differed, indicating that the fine roots of Chinese fir produce variations in functional traits and implement various ecological strategies to adapt to the environmental conditions in different provenances. [ABSTRACT FROM AUTHOR]

Successive planting is the main pattern for cultivating Chinese fir (Cunninghamia. lanceolata (Lamb.) Hook.). However, the influence of this management has not been totally investigated, especially with respect to the changes in the soil microbial community and the relationship to soil properties. This study investigated the physical and chemical properties of the soil, its enzyme activities, and its microbial diversity in three adjoining plantations managed with different successive planting models (long-term continuous growth without harvest, M1; single harvest cutting followed by the construction of a pure plantation, M2; and double harvest cutting followed by the construction of a mixed plantation, M3) to evaluate the impact of these forest management practices. In most soil layers, M1 was observed to have significantly higher content of Na and Al ions, as well as more polyphenol oxidase (PPO) activity, and M2 had a significantly higher field moisture capacity (FMC) and content of Mg ions, while M3 had significantly higher urease (URE) activity. Changes in the totals of N (TN) and C (TC), alongside the availability of P (AP), C/P, N/P, URE, sucrose (SUC), and PPO values, correlated significantly with bacterial diversity, whereas the dynamics of total K (TK), Na, C/P, N/P, and PPO levels were significantly related to fungal diversity. Among the models, soil bacterial genera, including Burkholderia–Caballeronia–Paraburkholderia, Acidothermus, and Paenibacillus, were mostly affected by TN, TC, AP, organic matter (OM), C/N, C/P, N/P, SUC, and the performance of URE. The distribution of fungal genera in different models showed significant differences. Talaromyces, Trichoderma, and Aspergillus were relatively abundant in M1, while Umbelopsis and Saitozyma exhibited more adaptation in M3. These results illustrated better soil properties and higher abundance of microbial diversity in M1 and M3, and furthermore, demonstrated the strategic benefit of both prolonging the rotation period and of creating mixed artificial plantations to maintain diversity. This study improves the understanding of the impact of a successive planting strategy in C. lanceolata plantation sustainability. [ABSTRACT FROM AUTHOR]

The species of Calonectria include many notorious plant pathogens and are widely distributed around the world. Leaf blight caused by Calonectria species is considered one of the most prominent diseases in Eucalyptus plantations in China. Some Calonectria species isolated from soils in Eucalyptus plantations are highly pathogenic to inoculated Eucalyptus genotypes. In southern China, the plantation trees Cunninghamia lanceolata, Eucalyptus spp., and Pinus massoniana are always adjacently planted, especially in FuJian, GuangDong, GuangXi, and YunNan Provinces. The aim of this study was to understand the diversity and distribution of Calonectria in soils from plantations of different tree species in different geographic regions. Soil samples were collected from 12 sampling sites in Eucalyptus urophylla × E. grandis, P. massoniana, and C. lanceolata plantations in FuJian, GuangDong, GuangXi, and YunNan Provinces. Approximately 250 soil samples were collected from each sampling site, and a total of 2991 soil samples were obtained. A total of 1270 Calonectria isolates were obtained from 1270 soil samples. The 1270 isolates were identified based on DNA sequence comparisons of the partial gene regions of act, cmdA, his3, rpb2, tef1, and tub2. These isolates were identified as 11 Calonectria species: Calonectria aconidialis (69.50%), C. kyotensis (13.10%), C. hongkongensis (10.80%), C. ilicicola (2.50%), C. asiatica (2.36%), C. curvispora (0.31%), C. chinensis (0.24%), C. pacifica (0.24%), C. yunnanensis (0.16%), and C. canadiana (0.08%) in the C. kyotensis species complex and C. eucalypti (0.71%) in the C. colhounii species complex. The three dominant species, C. aconidialis, C. kyotensis, and C. hongkongensis, were widely distributed. The richness of Calonectria (percentage of soil samples that yielded Calonectria) in soils in the eastern regions (relatively humid regions) was higher than that in the western regions. The Calonectria richness of E. urophylla × E. grandis, P. massoniana, and C. lanceolata plantations decreased gradually. For each of the three dominant species, its richness in the eastern regions was generally higher than that in the western regions; the species richness was highest in E. urophylla × E. grandis plantations for C. aconidialis, while for each of C. kyotensis and C. hongkongensis, its species richness was highest in P. massoniana plantations. The genetic variation in C. aconidialis, C. kyotensis, and C. hongkongensis was more greatly affected by geographic region than by plantation tree species. This study expanded our understanding of the richness, species diversity, and distribution characteristics of Calonectria in soils from the plantations of different tree species in different geographic regions in southern China. Results in this study enhanced our understanding of the influencing characteristics of geographic region and tree species on the species and genetic diversity of soilborne fungi. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata) is a kind of evergreen coniferous tree species, the expansion of its pure forest area and multiple generations of continuous planting has led to a decline of stand quality and woodland fertility. To further investigate the relationship between leaf, litter, and soil stoichiometry, microbial community status, and microbial resource limitation of Chinese fir after continuous planting. We studied the C, N, and P stoichiometries of leaf, litter, and soil from successive rotations of Chinese fir plantations. In addition to this, soil microbial biomass C, N, and P, extracellular enzymes, as well as the soil microbial community composition, were determined. The continuous planting of Chinese fir significantly increased the leaf N and P contents and decreased the C content of litter, and the soil C:N and C:P ratios, thus leading to a soil stoichiometric imbalance. The continuous planting of Chinese fir plantations significantly increased the soil microbial biomass. Compared with the first-generation plantations, the N and P contents of the second- and third-generation plantations increased by 37.11%, 21.83% and 46.28%, 73.38%, respectively, thus alleviating the restriction of microbial N and P. Under continuous planting, the extracellular enzyme activities of N (NAG + LAP) and P (AP) were significantly decreased, and those of the second- and third-generation plantations were significantly decreased by 7.05%, 9.43% and 11.79%, 48.94%, respectively, compared with those of the first-generation plantations, resulting in an increase of 7.85 and 3.19% in carbon-use efficiency. The fungi:bacteria (F:B) ratio of the soil microbial community was elevated in successive plantations. The least squares pathway model (PLS-PM) indicated that the stoichiometric ratio of ecological enzymes had an indirect negative effect on CUE, and was the strongest predictor. This study showed that the successive plantation of Chinese fir resulted in a leaf, litter, and soil stoichiometric imbalance, further affecting community composition and resource limitation of soil microorganisms. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi can establish mutual association with most land plants, and impact a series of important ecological processes, including plant productivity, ecological succession and soil carbon (C) accumulation. Understanding the AM fungal diversity and community assembly, and their associated soil C sequestration, could be a crucial interest for the forest ecologist. In this study, the AM fungal abundances and community structure as well as glomalin-related soil protein (GRSP) concentrations were investigated in typical development stages (young, middle and mature) of Cunninghamia lanceolate plantations, which are widely distributed species in subtropical regions. The mycorrhizal colonization, spore density, AM fungal biomass and diversity were higher in mature than younger stands. The development of C. lanceolata also increased soil GRSP concentrations, and enhanced their C contribution to soil organic C. Soil difficulty extractable (DE) GRSP demonstrated a greater C contribution to soil organic C relative to easily extractable (EE) GRSP. Linkage analyses found that AM fungal biomass demonstrated a positive correlation with GRSP concentrations, and soil organic C positively related to DE-GRSP and total (T) GRSP. Soil AM fungal community structure differed dramatically across all studied C. lanceolata plantations with a decrease in Gigasporaceae and increase in Acaulosporaceae. Soil AM fungal community assembly was more phylogenetic clustering than expected by chance and primarily shaped by deterministic processes, with a non-shift during the development of C. lanceolata. Collectively, C. lanceolata development shaped the AM fungal communities and enhanced their biomass and GRSP contents, which might, in turn, partially contribute to soil C accumulation. [ABSTRACT FROM AUTHOR]

Purpose: There is a large area of coniferous plantations, such as Cunninghamia lanceolata and Pinus massoniana, in subtropics. Recent evidence has demonstrated that environmental factors and tree species mixtures have significant influences on soil organic carbon (SOC) storage in plantations. However, the diverse functional groups of SOC reveal different chemical stability. Therefore, the functional groups of SOC in subtropical plantations need to research. Methods: The SOC functional groups analyzed by 13C nuclear magnetic resonance, and their distribution were compared among subtropical plantations from northern, middle, and southern latitudes, and between monospecific and conifer-broadleaf mixed plantations. Results: Compared to that of the northern and middle latitude subtropical plantations, the evenness of the four SOC functional groups was higher in the southern latitude subtropical plantations. The temperature and soil bacterial α-diversity were positively correlated, and the soil fungal α-diversity was negatively correlated with the evenness of the SOC functional groups. The proportion of the recalcitrant SOC functional group (alkyl C) was higher in the conifer-broadleaf mixed plantations than in the coniferous plantations, particularly in C. lanceolata plantations. The climatic factors, soil pH and soil microbial α-diversity, rather than the functional groups of leaf litter and fine root C, led to the differences in the SOC functional groups between the monospecific and mixed plantations. Conclusion: Our findings highlight that there is a minor risk of C decomposition in the southern subtropical plantations, and converting coniferous plantations to mixed plantations, which could improve the chemical stability of SOC in subtropical regions. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata) is the main plantation species in the subtropical region of China. However, the shift in ecosystem multifunctionality with stand development remains largely unexplored for these plantations. This study used a chronosequence to investigate the variations of ecosystem multifunctionality by employing individual functions and identified its driving factors in Chinese fir plantations. The findings provide strong evidence that the individual functions of carbon stocks, water regulation and wood production increased with stand ages, but the tradeoff of individual functions did not significantly increase ecosystem multifunctionality. Soil microbial parameters (the abundances of bacteria, fungi and actinomycete), soil properties (soil moisture, total carbon and total nitrogen), and plant parameters (the shrub layer cover and total understory cover) exhibited positive correlations with ecosystem multifunctionality. The structural equation model revealed that plants, soil properties and microbes pathways explained 83% of the total variance in ecosystem multifunctionality. Results showed that plants, soil microbes and properties directly and significantly affected ecosystem multifunctionality with path coefficients of 0.404, 0.487 and 0.334, respectively. Soil microbes were identified as the top direct predictor for ecosystem multifunctionality, while plant and soil properties had strong direct and positive effects on ecosystem multifunctionality. These results verified that soil microbes, plants and soil properties directly and positively regulated ecosystem multifunctionality. Our findings demonstrate that ecosystem multifunctionality should be considered as a comprehensive ecological indicator for ecosystem services and functions, and sustainable plantation management. This study highlights the importance of conserving soil microbes for maintaining multifunctionality in Chinese fir plantations. [ABSTRACT FROM AUTHOR]

Background: Continuous nitrogen (N) deposition interferes with soil N cycling in forests, which highly impacts soil nitrous oxide (N2O) emissions and accelerates global warming. Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the most widely planted species in southern China, and is usually located in areas with high N deposition rates. However, the impact of N deposition on soil N2O emissions in subtropical Chinese fir plantations and the potential risk of increasing N input remain elusive. Methods: Here, we conducted an in situ study in a subtropical Chinese fir plantation at Fengyang Mountain Nature Reserve, China, from 2019 to 2020 with four N addition rates: control (CK: ambient N deposition), low-N (LN: 50 kg N ha−1 yr−1), medium-N (MN: 100 kg N ha−1 yr−1), and high-N (HN: 200 kg N ha−1 yr−1). Results: We found that soil N2O emission rates increased with N addition rates by 71%, 176%, and 241% under LN, MN, and HN treatment compared to CK, respectively, and reached a significant level only under HN. Soil moisture was significantly reduced together with increased leaf N concentrations under N addition. Meanwhile, the microbial biomass in the middle of the growing season was significantly lower than at the end of the growing season. These results may suggest that N deposition stimulated plants to take up more N and water, which intensified plant-microbe competition and therefore alleviated further increases in N2O emissions under N deposition, especially under low N inputs. N deposition enhanced the abundance of ammonia oxidizing archaea and bacteria and the accumulation of NO3−-N in the soil but did not affect the abundance of nitrate-reducing bacteria (nirS and nirK). The results likely support that nitrification processes act as the major source of enhanced N2O emissions under N fertilization. Conclusions: Our study advances our understanding of the impacts of N deposition on the soil N2O emissions in the Chinese fir plantations and highlights that plant N acquisition needs to be incorporated as an important explanatory variable when predicting N2O fluxes under global increases in N deposition. [ABSTRACT FROM AUTHOR]

Plantation cultivation plays an important role in improving terrestrial ecosystem functions and services. Understanding the water-use patterns of major afforestation species is vital for formulating ecological restoration strategies and predicting the response of plantation to climate change. However, the impacts and drivers of forest types on water-use patterns of key tree species are poorly understood. Here, the combined methods of dual stable isotope of δD and δ18O and Bayesian mixed framework (MixSIAR) were employed to investigate the water-use patterns of Cunninghamia lanceolata (Chinese fir) in a monoculture, mixed forest with Cinnamomum camphora, and mixed forest with Alnus cremastogyne under different rainfall events in subtropical China. Furthermore, the relative contribution of different soil and plant factors to the water-use patterns of Chinese fir was quantified using a random forest model. Our results showed that Chinese fir in the mixed forests (with C. camphora or with A. cremastogyne) utilized less water from shallow soil compared to that in a monoculture but significantly improved the proportion of water absorbed from deep soil with the increase of 55.57%-64.90% and 68.99%-108.83% following moderate and heavy rainfall events, respectively. The most important factors contributing to the differences in water-use patterns of Chinese fir among monoculture and mixed forests were tree attributes (i.e., leaf biomass, eco-physiological regulation, and fine root biomass). These findings reveal that Chinese fir in mixed forests could optimize water-use patterns by adjusting plant properties for interspecific niche complementarity, improving the utilization of deep soil water. Overall, this study suggests that mixed-species plantations could improve water-use efficiency and reduce the sensitivity of tree species to precipitation change, indicating they are better able to cope with expected climate variability. [ABSTRACT FROM AUTHOR]

Trees can resorb nutrients to preserve and reuse them before leaves fall, which could efficiently adapt to environmental changes. However, the nutrient requirements of trees in different months with seasonal climate changes are often neglected. In this study, we selected plantations of an evergreen broadleaf tree (Castanopsis carlesii (Hemsl.) Hayata) and a coniferous tree (Cunninghamia lanceolate (Lamb.) Hook.) in the subtropics. The monthly dynamics of leaf nitrogen (N) and phosphorus (P) resorption efficiencies and C:N:P stoichiometric ratios were checked along a growing season from April to October 2021. Trees in both plantations exhibited efficient N and P resorption but with significant monthly variations. The N and P resorption efficiencies in the Cunninghamia lanceolata plantation ranged from 34.26% to 56.28% and 41.01% to 54.85%, respectively, and were highest in September. In contrast, N and P resorption efficiencies in the Castanopsis carlesii plantation ranged from 11.25% to 34.23% and 49.22% to 58.72%, respectively, and were highest in July. Compared with the Cunninghamia lanceolata, the C:N of the Castanopsis carlesii plantation was significantly lower, while its C:P was significantly higher in May and September. The Castanopsis carlesii plantation was strongly limited by P (the N:P ratios in mature leaves were higher than 20), whereas the Cunninghamia lanceolata plantation might be limited by both N and P (the N:P ratios in mature leaves were between 10 and 20). In addition, the statistical analyses revealed that temperature and precipitation were significantly associated with N and P resorption efficiencies, but the relationships were controlled by forest types. These findings highlight that efficient resorption of N and P may be beneficial in regulating nutrient limitation and balance in subtropical forest ecosystems. These results contribute to the understanding of N and P utilization strategies of trees and provide a theoretical basis for vegetation management in the subtropics. [ABSTRACT FROM AUTHOR]

Evaluation of the impacts of environmental factors and microbial communities on soil organic phosphorus (Po) availability is needed to clarify P cycling and regulate plantations productivity. However, the effects on Po accumulation and transformation of converting pure Chinese fir plantation to multi-layered mixed plantation and their regulatory mechanisms remain unclear. The aim of this study was to examine the impacts of the transformation of pure stand of Chinese fir (Cunninghamia lanceolata ; PP) to mixed plantation with multiple tree species (C. lanceolata, Castanopsis hystrix , and Michelia hedyosperma ; MP) on Po accumulation and transformation within topsoil (0–10 cm) aggregates in subtropical China. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), ammonium nitrogen (NH 4 +-N), and available phosphorus (AP), as well as the carbon‑nitrogen ratio of soil (C/N soil) and carbon‑phosphorus ratio of soil (C/P soil) were significantly higher (P < 0.05) of all aggregates in MP than those in PP. The quantities of soil microbial biomass C, N, P (MBC, MBN, and MBP) in all different aggregates were significantly greater (P < 0.05) in MP than in PP. The phospholipid fatty acid contents related to bacteria, fungi, arbuscular mycorrhizal fungi (AMF), and actinomycetes were significantly greater in all aggregate classes (P < 0.05) in MP relative to PP. The activities of all tested C, N, and P hydrolytic enzymes, as well as labile organic P, moderately labile organic P, moderately resistant organic P, and highly resistant organic P contents, were significantly higher of most aggregate size classes in MP. Finally, redundancy analysis (RDA) suggested that Po fractions were primarily affected by the NH 4 +-N, litterfall biomass (LF), carbon‑nitrogen ratio of litter (C/N litter), SOC and fine root biomass (FR). Our findings suggest that converting pure Chinese fir plantations into multi-layered mixed plantations may represent an effective management strategy for promoting organic P accumulation and transformation by regulating soil and microbial properties in degraded soils of Chinese fir plantations. [Display omitted] • Multi-layered mixed silviculture increased soil Po accumulation and availability. • Po fractions accumulation was jointly driven by plant, soil, and microbial traits. • Multi-layered mixed silviculture may be an effective management to promote P cycling. [ABSTRACT FROM AUTHOR]

Carbon sequestration in forest soil is critical for reducing atmospheric greenhouse gas concentrations and slowing down global warming. However, little is known about the difference in soil organic carbon (SOC) among different stand ages and the relative importance of biotic and abiotic variations such as soil microbial community and soil physicochemical properties in the regulation of SOC in forests. In the present study, we measured the SOC of the topsoil (0-10 cm) in Chinese subtropical Cunninghamia lanceolata plantations of three different stand ages (young plantation of 6 years, middle-aged plantation of 12 years, and mature plantation of 25 years). We further measured microbial community composition by phospholipid fatty acid (PLFA) analysis and soil organic carbon physical fractions by wet sieving and density floating as well as other physicochemical properties. The effects of the main impact factors on SOC were investigated. The results showed that: the middle-aged plantation had significantly higher SOC (10.63 g kg-1) than the young plantation (5.33 g kg-1), and that of the mature plantation (7.83 g kg-1) was in between. Besides, the soil total PLFAs and all the functional groups (i.e., bacteria, fungi, actinomycetes, Gram-positive bacteria, and Gram-negative bacteria) of PLFAs were significantly higher in the middle-aged plantation than in the young plantation and the mature plantation. Soil physicochemical properties, including physical fractions, differed among plantations of the three stand ages. Notably, the proportion of organic carbon protected within microaggregates was significantly higher in the middle-aged plantation (40.4%) than those in the young plantation (29.2%) and the mature plantation (27.8%), indicating that the middle-aged Cunninghamia lanceolata plantation had stronger soil organic carbon stability. Both soil microbial community and physicochemical properties exerted dominant effects on SOC and jointly explained 82.7% of the variance of SOC among different stand ages. Among them, total and all the functional groups of PLFAs, nitrate nitrogen, total nitrogen, and organic carbon protected within microaggregates had a significant positive correlation with SOC. These results highlight the important role of soil biotic and abiotic factors in shaping the contents of SOCin forests of different stand ages. This study provides a theoretical basis for forestry management and forest carbon cycling models. [ABSTRACT FROM AUTHOR]

The site quality evaluation of plantations has consistently been the focus in matching tree species with sites. This paper studied the site quality of Chinese fir (Cunninghamia lanceolata) plantations in Lin'an District, Zhejiang Province, China. The site quality model was constructed using the algebraic difference approach (ADA) to classify the site quality grades. The rough set algorithm was used to screen out the key site factors affecting the site rank of Chinese fir plantations. Site quality classification models based on random forest were established, and the importance of key site factors was evaluated. The results are as follows. The random forest model based on the rough set algorithm had small scale and low complexity, and the training and testing accuracies of the model were 92.47% and 78.46%, respectively, which were better than the model without attribute reduction. The most important factors affecting Chinese fir growth in the study area were the slope aspect, slope grade, and canopy closure. The least important factors were the humus layer thickness, soil layer thickness, naturalness, and stand origin. The attribute reduction method proposed in this study overcame the subjectivity of traditional site factor selection, and the site quality classification model constructed improved the model accuracy and reduced the complexity of the algorithm. The methods used in this study can be extended to other tree species to provide a basis for matching tree species with sites and to improve the level of forest management in the future. [ABSTRACT FROM AUTHOR]

Most forest research focuses either on the silvicultural aspects of forest management or the economic optimisation of an objective function to answer a specific policy question. This paper investigated optimum rotation ages for harvest, under both economic and biological theories, to discover the conditions that maximise both profit and sustainability. Both the optimum biological rotation for maximising sustainable yields (MSY), and economic rotation based on the Faustmann model were calculated through observation data from Chinese fir (Cunninghamia lanceolata) plantations in Fenyi, Jiangxi Province, China. It was found that the economic rotations of Chinese fir were longer than the biological rotations by almost 2 years when the discount rate equaled 0.05. If the discount rate increased as high as the inverse of the biological rotation time plus the incremental growth rate of the stumpage price, the rotations under both Faustmann and MSY rules coincided. Under these conditions, the ratio of regeneration costs to the value of timber in a stand should be low to keep forest management profitable. These findings are of practical importance for forest managers in relation to forest investment, planting decisions and harvesting for bussiness. [ABSTRACT FROM AUTHOR]

Soil microbial residues contribute to the majority of stable soil organic carbon (SOC) pools, and their distribution among aggregate fractions determines long-term soil carbon (C) stability and, consequently, soil productivity. However, how microbial residue accumulation and distribution respond to stand age remains unexplored. To fill this knowledge gap, we investigated microbial residues in bulk soil and soil aggregate fractions under a chronosequence of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook) plantations with stands aged 3, 17, 27, and 36 years. The results showed that microbial residues in topsoil did not change across the different stand ages, but the residues in the subsoil increased from 3 to 17 years of age and then remained constant. Moreover, microbial residue distribution in microaggregates decreased with stand age, and the residue distribution in small macroaggregates was lower at age 17 years than at other stand ages. The effect of stand age on microbial residue distribution was due to the fact of their effect on aggregate distribution but not microbial residue concentrations in aggregate fractions. Collectively, our results indicate that microbial residue stability decreased with stand age, which has significant implications for the management of SOC in subtropical plantations. [ABSTRACT FROM AUTHOR]

Aims: Our aim was to investigate how N addition affects arbuscular mycorrhizal fungal (AMF) growth in Chinese fir plantations. Methods: A Chinese fir plantation was treated with four different N addition treatments for one and half years starting in April 2019. AMF colonization, hyphal length density, community composition, and soil properties were under measurement. Results: N addition caused inapparent effects on AMF colonization, hyphal length density, and functional guilds (rhizophilic, edaphophilic, and ancestral). The predominant AMF species in the soil was Septoglomus viscosum. N addition altered AMF community and some rare species (e.g., Entrophospora infrequens) disappeared with N addition. Conclusion: AMF community structure was more sensitive to short-time N deposition than the symbiotic relationship between AMF and host plants. [ABSTRACT FROM AUTHOR]

Forests are among the most important N pools of all terrestrial ecosystems. Elevated atmospheric N deposition in recent decades has led to increased interest in the influences of N application on forest N cycles. However, accurate assessments of N storage in forest ecosystems remain elusive. We used a 14-year experiment of a Chinese fir [ Cunninghamia lanceolata (Lamb.) Hook] plantation to explore how long-term N fertilization affected N storage and recovery rates. Our study plots were located in a field that had been continuously fertilized over 14 years (2004–2017) with urea at rates of 0 (N0, control), 60 (N60, low-N), 120 (N120, medium-N), and 240 (N240, high-N) kg N hm−2a−1. Data were collected that included N content and biomass in the understory, litter, and various plant organs (i.e., leaves, branches, stems, roots, and bark), as well as soil N content and density at different depths. Results showed that the total ecosystem N storage in the N-fertilized plots was 1.1–1.4 times higher than that in the control plots. About 12.36% of the total ecosystem N was stored in vegetation (plant organs, litter, and understory) and 87.64% was stored in soil (0–60 cm). Plant organs, litter, and soil had higher N storage than the understory layer. Significantly higher plant N uptake was found in the medium-N (1.2 times) and high-N (1.4 times) treatments relative to the control. The N recovery rate of the understory layer in the N-fertilized treatments was negative and less than that in the control. Application of long-term N fertilizer to this stand led to a low N recovery rate (average 11.39%) and high loss of N (average 91.86%), which indicate low N use efficiency in the Chinese fir plantation ecosystem. Our findings further clarify the distribution of N in an important terrestrial ecosystem and improve our understanding of regional N cycles. [ABSTRACT FROM AUTHOR]

Increased nitrogen (N) inputs in subtropical forest ecosystems were widely reported. Extra N additions were reported to cause nutrient imbalance and phosphorus (P) limitation in many tropical and subtropical forests, and further result in changes in soil nitrous oxide (N2O) and methane (CH4) fluxes. Here, we conducted experiments with N (high N addition: 15 g N/m2, HN), P (low: 5 g P/m2, LP; high: 15 g P/m2, HP) and their interactive (HNLP and HNHP) treatments to investigate how N and P additions affected CH4 and N2O exchanges in an N-rich Chinese fir plantation (Cunninghamia lanceolata), and further explored the underlying mechanisms through the structural equation model (SEM) analysis. The results indicated that N addition alone (HN) significantly (p < 0.05) increased the soil N2O emissions by 30.15% and 80.47% over annual and 4-month periods, mainly owing to the elevated NH4+-N content. P addition alone (LP and HP) did not significantly affect the soil N2O emissions as compared with the control. The SEM analysis indicated that increased N2O emissions under N addition were primarily explained by the increase in available N and contributed more to the stimulated NH4+-N contents. N and P interactive additions slightly (not significant) stimulated the N2O emissions as compared with that under the N addition alone treatment. High-dose P addition significantly increased the soil CH4 uptake by 15.80% and 16.23% under the HP and HNHP treatments, respectively, while N addition alone and low P addition (LP and HNLP) did not significantly affect CH4 uptake as compared with the control. The increased water-soluble organic carbon and microbial biomass carbon explained the increased CH4 uptake under high P addition. The fertilization effects on N2O emissions and CH4 uptake mainly occurred in the first 4 months and diminished after that. Our results suggested that the direction, magnitude and timing of the N and P addition effects on N2O emissions and CH4 uptake would depend on the soil nutrient status and plant–microbial competition for N and P in subtropical forests. [ABSTRACT FROM AUTHOR]

Ecological stoichiometry is increasingly acknowledged as one of the main control factors for microbial activity and diversity. Soil carbon/nitrogen (C/N) and carbon/phosphorus (C/P) ratios are usually much higher than microbial nutrient requirements and vary with planting density and stand age in forestlands. However, how microorganisms cope with such stoichiometric imbalances and how they regulate nutrient cycling remain unclear. Here, 5- and 35-year-old experimental Cunninghamia lanceolata [Lamb.] Hook plantations with five planting densities (1,667, 3,333, 5,000, 6,667, and 10,000 stems ha−1) were used to explore the underlying mechanism of the response of microorganisms to stoichiometric imbalances. We found that (i) enzyme activity and microbial biomass and diversity increased with planting density at age 5 but decreased at age 35; (ii) soil microorganisms were P-limited at age 5, but gradually shifted from P- to N-limitation during the development of plantations from 5 to 35 years; and (iii) significantly negative relationships between microbial biomass stoichiometry and enzymatic stoichiometry were observed. The adaptive pathways of soil microorganisms to cope with stoichiometric imbalances include (i) adjusting the stoichiometry of microorganisms and enzymes; (ii) changing the relative abundance of the dominant microbial phyla; and (iii) increasing the ratio of fungal to bacterial diversity. These results highlight how to use the ecological stoichiometry method to identify soil microbial nutrient limitations with planting density during the development of plantations. By underlining the important role of stoichiometry on microbial growth and activity, these findings furthermore emphasize the dependency of organic matter transformation and nutrient cycling on the microbial community. [ABSTRACT FROM AUTHOR]

Purpose: Glomalin-related soil protein (GRSP) is an essential component of soil organic C for maintaining soil quality and structure and plays a critical role in soil carbon (C) sequestration. However, how GRSP changes under nitrogen (N) deposition remains poorly understood. Materials and methods: We assessed total GRSP (T-GRSP) and easily extractable GRSP (EE-GRSP) under a control (no N input), low N addition (LN, 40 kg N ha−1 year−1), and high N addition (HN, 80 kg N ha−1 year−1) treatments in 2015 and 2016 in a Chinese fir (Cunninghamia lanceolata) plantation in the subtropical China. We also analyzed soil properties contents and explored the stoichiometric ratios of soil organic C (SOC), total N (TN), and total phosphorus (TP) with GRSPs. Results: Compared to the control, both T-GRSP and EE-GRSP were significantly reduced under the HN treatment, but had no significant difference under the LN treatment. The ratio of T-GRSP and EE-GRSP was reduced by the N addition. Soil organic C (SOC) and dissolved organic C (DOC) were significantly affected by N addition treatments. The ratios of GRSP-C to SOC and of EEGRSP-C to SOC ranged from 6.29 to 16.07% and 1.34 to 3.52%, respectively. T-GRSP and EE-GRSP were positively correlated with SOC/TN ratio, but negatively correlated with soil TN/TP and SOC/TP ratios. Conclusion: Our results indicated that the GRSP reductions under N deposition in soil are mediated by soil C, N, and P stoichiometry, and particularly, the reduction of EE-GRSP by DOC. This study improved our mechanistic understanding of dynamics of GRSPs under increasing N enrichment in subtropical plantation ecosystems. [ABSTRACT FROM AUTHOR]

To evaluate the influence of different plantations on the stability of soil aggregates, we selected 5 typical plantations in south subtropical region: Pinus massoniana (PM), Cunninghamia lanceolata (CL), Eucalyptus urophylla×E. grandis (EU), Mytilaria laosensis (ML) and Castanopsis hystrix (CM). Soil aggregate stability was determined by the Le Bissonnais method and included three disruptive treatments. FW caused the greatest damage to the soil aggregate structure, after which the soil aggregates were mainly 0.2–0.5 mm in size. The MWD and GMD values of the three treatments were basically the same, i.e., WS > SW > FW, and gradually decreased with increasing soil depth. Compared to the plantations, the natural forest had higher MWD and GMD but lower RSI and RMI. Among the 5 plantation types, the SOM of the EU was lowest in five soil layers. SOM, Fe and Al had significantly positive correlations with MWD but negative correlations with Mn (p < 0.05), which indicated that SOM, Fe and Al were involved in the formation of macroaggregates and increased the stability of soil aggregates. Reasonable forest management measures will contribute to the formation of soil aggregates and the improvement of soil quality. [ABSTRACT FROM AUTHOR]

Cunninghamia lanceolata var. Luotian (herein, Luotian), a natural variety of Cunninghamia lanceolata (Chinese fir, herein Lanceolata), shows great potential for agricultural protection short-period and highdensity plantations because of its narrow, pointed, tower-shaped crowns, thin braches and older drooping branches that die naturally at 6-7 years old. The physiological mechanisms of the pendulousness and the natural death of the branches are still unclear. To investigate these mechanisms, phytohormone levels and nutritional ingredients of different positions of branches in Luotian and Lanceolata were determined. Phytohormone analyses showed that IAA and ZR played critical functions on the branch initial growth, and that GA3 was related to bending of branches. Meanwhile, ABA may enhance abscission of the branches in Luotian. Nutritional ingredient analyses showed that the accumulation of nutritional ingredients in Luotian and Lanceolata were consistent with the morphology of their branches. An integrated analysis implied that phytohormones had a strong influence on pendulous characteristics by interacting with other factors. This study helps to elucidate the mechanism governing the pendulous trait and provides theoretical basis and technical support for its cultivation, introduction, plantation management and genetic improvement. [ABSTRACT FROM AUTHOR]

Thinning is a widely used practice in forest management, but the acclimation mechanisms of fine roots to forest thinning are still unclear. We examined the variations in fine root traits of different branching orders and functional groups along a thinning intensity gradient in a 26-year-old Chinese fir (Cunninghamia lanceolata) plantation. With increasing thinning intensity, the root C concentration (RCC), root N concentration (RNC), specific root area (SRA), and specific root length (SRL) of the absorptive roots (the first two orders) significantly decreased, while root abundance (root biomass and root length density) and root tissue density (RTD) significantly increased. Fifty-four percent of the variation in the absorptive root traits could be explained by the soil N concentration and the biomass and diversity of the understorey vegetation. Conversely, transport root (third- and higher-order) traits did not vary significantly among different thinning intensities. The covariation of absorptive root traits across thinning intensities regarding two dimensions was as follows: the first dimension (46% of the total variation) represented changes in root abundance and chemical traits (related to RCC, RNC), belonging to an extensive foraging strategy; the second dimension (41% of the total variation) represented variations in root morphological traits (related to RTD, SRL and SRA), which is an intensive foraging strategy (i.e., root economic spectrum). These results suggested that the absorptive roots of Chinese fir adopt two-dimensional strategies to acclimate to the altered surroundings after thinning. [ABSTRACT FROM AUTHOR]

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Subtropical plantations have been undergoing understory removal and increased plant litter inputs due to global change and anthropogenic activities. However, how understory removal and increased litter inputs affect litter decomposition is still unclear in these plantations. Using a field manipulation experiment, we assessed the effects of understory removal and litter addition on decomposition rates of leaf litter, twig litter, and mixed leaf and twig litter over 16 months of incubation in a subtropical Chinese fir (Cunninghamia lanceolata) plantation in southern China. We also examined the changes in soil chemical properties and fungal and bacterial phospholipid fatty acids (PLFAs) after understory removal and litter addition. Litter decomposition rates were inhibited by understory removal due to the decreased fungal PLFAs and the associated declines in the ratio of fungal to bacterial biomass. Litter addition also retarded litter decomposition rates, despite the increases in soil NH4+‐N concentration and fungal PLFAs. However, both litter decomposition rates and soil microbial PLFAs remained unchanged in the presence of both understory removal and litter addition. In all treatments, mixed leaf and twig litter produced additive effects on litter decomposition rates. These results suggest that understory removal and litter addition interact to affect litter decomposition dynamics and highlight that litter mixture decomposition rates could be easily predicted from component litter in subtropical Chinese fir plantations of southern China. [ABSTRACT FROM AUTHOR]

The Eucalyptus spp. is fast-growing and is usually harvested at a young age, which enables efficient and sufficient timber supply. However, its negative impact on soil fertility incurs wide debates. Therefore it is necessary to study on the growing traits of eucalytpus to provide scientific guidance on its plantation management and associated policy-making. In this study, we collected the sample plot data from 9 National Forest Inventories (NFIs) during 1973–2018, China Forest-Land Database Map in 2003 and 2016, as well as climate and elevation data and analyzed how the spatial distribution of eucalyptus plantations in China changes with time. We quantitatively characterized and evaluated the productivity, carbon accumulation capacity, and abandonment rate of eucalyptus plantations. Statistical models on how eucalyptus productivity and abandonment rate change with time are established to evaluate the soil fertility and feasibility for growing eucalyptus plantations and predict the temporal productivity variation. The results show that regions with annual mean temperature of 19–21 °C, annual precipitation of 1400–1600 mm, and elevation of 0–300 m above sea level is most suitable for the growth of eucalyptus. The annual mean productivity of eucalyptus plantations ranges from 4.14–8.57 m3 hm−2 a−1. Higher productivity (9.32–10.88 m3 hm−2 a−1) could be reached in newly cultivated lands. Based on data from the 9th inventory (2014–2018), the mean carbon fixation of eucalyptus is 5.29 t hm−2 a−1, which is 2.95 and 2.18 times greater than Pinus massoniana Lamb. and Cunninghamia lanceolata Lamb. Its plantations area accounts for 6.85% of total plantations in China, but it contributes to more than 17.96% of total annual cut from plantations. In Guangdong and Guangxi provinces, areas of eucalyptus plantations are 30.32% and 34.91% of the total plantation area in each province respectively, but eucalyptus plantations contribute to 66.29% and 49.97% of harvested timber stock volume Eucalyptus pla consumes soil fertility significantly. The cumulative abandonment rate (based on area) is about 25%, 50%, and 75% after 5, 10, and 20 years of growing eucalyptus, respectively. The soil fertility decreases significantly after 50 years of growing eucalyptus continuously. In such case, it is difficult to restore the soil fertility. It is suggested that with improved management measures such as proper crop rotation rotating crops properly, it is possible for the abandoned plantations to be reused for growing eucalyptus. Currently the rates of replanting eucalyptus are still below 20% and 30% after 20 and 50 years of without growing eucalyptus, respectively. Although the proportion of eucalyptus area replanted to its abandoned area is now less than 20% in 20 years and less than 30% in 50 years, there is potential to keep increasing the replanting rate. We argue that developing eucalyptus plantations could contribute to global timber supply, help to protect natural forests, increase global carbon storage and fixation, and help to slow down global warming. In conclusion, we should not stop growing eucalyptus despite its high consumption of soil fertility. [ABSTRACT FROM AUTHOR]

Aims: The litter decomposition rate is strongly related to litter chemical quality, which is altered by increased nitrogen (N) and phosphorus (P) availability induced by global changes and human activity in plantation forest ecosystems. However, the effects of litter cell wall carbohydrate composition on litter decomposability after long-term N and P additions remain unclear. Methods: A field nutrient manipulation experiment was conducted in a subtropical Cunninghamia lanceolata plantation. Leaf litter and green leaves were collected and divided into 1- and 2-year-old tissues after N and P additions for 5 years. Litter organic carbon (OC), N and P concentrations and their stoichiometries, and cell wall carbohydrate fractions were determined. The leaf litter decomposability was determined by 150 days of decomposition in the laboratory. Results: Nitrogen addition decreased leaf litter C/N, whereas P addition decreased C/N and C/P. P addition decreased cell wall pectin, hemicellulose, total extractable carbohydrate (TEC) concentrations and their percentage relative to OC. Litter OC, N and P and their stoichiometries were unaffected by litter age, whereas TEC and TEC/OC increased with increasing litter age. Leaf litter decomposition rate increased by 7.3% with P addition, decreased by 16.8% with increasing litter age, and was unaffected by N addition given the negative correlation between TEC/OC and litter decomposition rate. Conclusions: Cell wall carbohydrates constitute an effective indicator of litter quality to predict litter decomposability. Phosphorus but not N addition increases litter decomposability through alterations in carbohydrate composition. Tissue age should be considered when investigating N and P additions effects on litter decomposition in forest ecosystems. [ABSTRACT FROM AUTHOR]

Aims: The introduction of broadleaf species into Cunninghamia lanceolata monoculture plantations could be a sustainable silvicultural practice for restoring soil fertility. We hypothesize that the addition of Phoebe bournei tree species will change soil physicochemical factors and microbial composition. Methods: Soil physicochemical factors were determined. Bacterial composition and N-cycling functional genes were investigated by Illumina MiSeq sequencing and qPCR, respectively, and by using a co-occurrence network to explore the connections between the relative abundance of bacteria and soil physicochemical parameters. Results: The introduction of P. bournei into C. lanceolata plantations increased available nutrients in the soil, decreased toxicity (Al3+ level), and slightly increased the soil bacterial diversity. The relative abundance of the total Acidobacteria community, as well as the most abundant subgroups (1, 2, and 3), were significantly higher in the monospecific stands. Different Acidobacteria subgroups behaved differently, i.e., Gp2 correlated negatively with soil nutrients and positively with the Al3+ level, while Gp17 showed the opposite behavior. Quantification of seven nitrogen cycling genes revealed that the nifH, nrfA, and nosZ abundances were higher in the mixed stands, while the nirK abundance was higher in the monospecific plantations. Co-occurrence network analyses showed a strong correlation between soil properties and the bacterial community. Conclusion: P. bournei introduction into C. lanceolata plantations improved soil nutrients and affected the soil bacterial community. The higher nitrogen nifH and nrfA abundance in the mixed stands indicated a higher nitrogen fixation and dissimilatory nitrate reduction potential. Acidobacterial subgroups showed the opposite behavior to P. bournei introduction and could be used as indicators of soil nutrient changes. [ABSTRACT FROM AUTHOR]

Large-scale planting of Chinese fir (Cunninghamia lanceolata) can bring considerable economic benefits but also seriously alters soil properties, disrupting soil microbial survival patterns and giving rise to distinct microbial communities. Nitrous oxide (N 2 O) reduction is the sole recognized biological sink for N 2 O, thereby playing a critical role in forest nitrogen cycling. However, the distribution of N 2 O reducers in Chinese fir plantation soils and the underlying factors at a regional scale remain unclear. Here, we assessed the abundance, diversity, and community structure of nosZ I-type N 2 O reducers in soil samples collected from nine state-owned forest farms in Fujian Province, China. The abundance of nosZ I-type reducers exhibited significant variation across sites, with altitude exerting the greatest influence, positively influencing their abundance. Soil organic carbon (SOC) and dissolved organic carbon (DOC) were the strongest predictors of alpha-diversity. Interestingly, SOC and DOC exhibited a negative association with nosZ I-type reducer alpha-diversity. Additionally, DOC played a significant role in influencing community structure. All nosZ I sequences were associated with Alphaprotebacteria and Betaproteobacteria, with Alphaproteobacteria dominating nosZ I-type reducer communities in all soils, accounting for over 90 % of the total sequences. Moreover, the modified stochasticity ratio values exceeded 0.5 at all sampling sites except for one, characterized by the lowest pH and relatively lower nutrient content, indicating the predominance of stochastic processes in community assembly. Taken together, our results provide novel evidence that the augmentation of organic carbon content could potentially reduce diversity and alter the structure of nosZ I-type reducer communities, with potential implications for N 2 O emissions in Chinese fir plantations. • Soil N 2 O reduction rates were positively associated with nosZ I gene abundance. • SOC and DOC were negatively associated with nosZ I-type reducer alpha-diversity. • DOC was a critical factor influencing nosZ I-type reducer community structure. • Alphaproteobacteria accounting for >90 % of nosZ I-type reducer sequences. • Stochastic processes dominated the community assembly of nosZ I-type reducer. [ABSTRACT FROM AUTHOR]

Analyzing the incidence of stand mortality, constructing a predictive mortality model, and identifying the factors influencing mortality can provide an evidence-based framework for managing forest growth and productivity. This study investigated the mortality of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations in Jiangxi Province, a subtropical region of China, utilizing national forest inventory data from 2006 to 2016. A total of 18 potential factors were identified across three categories: stand, site, and climate variables. Four statistical models were evaluated, including the zero-inflated Poisson model, zero-inflated negative binomial model, hurdle Poisson model, and hurdle negative binomial model, with incorporation for random effects at the plot-level to determine the most effective mortality model. The results showed that incorporating random effects at the plot-level significantly improved the fit and predictive capabilities, with the zero-inflated negative binomial model, which accounts for random effects in canopy cover, performing best. Mortality increased with higher canopy cover, stand basal area, elevation, and mean warmest month temperature, but decreased with greater humus thickness. It is advisable to maintain litter within the plantations to increase humus thickness. Moreover, implementing strategic thinning is vital for reducing inter-tree competitive pressures, managing microclimate conditions to promote temperature reduction and humidity enhancement during hot seasons and temperature elevation and humidity increase during cold seasons. These management approaches are projected to decrease mortality. • The stand mortality counts showed a zero-inflated state during 2006–2016. • Variability of stand mortality is explained by competition, humus, and temperature. • Thinning can effectively reduce the stand mortality counts. [ABSTRACT FROM AUTHOR]

Mixed-stand plantations are not always as beneficial for timber production and carbon sequestration as monoculture plantations. Systematic analyses of mixed-stand forests as potential ideal plantations must consider the physiological-ecological performance of these plantations. This study aimed to determine whether mixed moso bamboo (Phyllostachys pubescens (Pradelle) Mazel ex J. Houz.) and Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) stands exhibited better physiological-ecological performance than monoculture plantations of these species. We analyzed leaf photosynthesis, chlorophyll fluorescence, antioxidant enzyme activities, chlorophyll content and leaf chemistry in a moso bamboo stand, a Chinese fir stand and a mixed stand with both species. The results showed that both species in the mixed stand exhibited significantly higher leaf net photosynthesis rate (Amax), instantaneous carboxylation efficiency (CUE), chlorophyll content, maximum quantum yield of photosynthesis (Fv/Fm), photochemical quenching coefficient (qP), PSII quantum yield [Y(II)], leaf nitrogen content, and antioxidant enzyme activities than those in the monoculture plantations. However, the non-photochemical quenching (NPQ) in Chinese fir and 2-year-old moso bamboo was significantly lower in the mixed stand than in the monocultures. In addition, the water use efficiency (WUE) of Chinese fir was significantly higher in the mixed stand. The results suggest that the increase in leaf net photosynthetic capacity and the improved growth in the mixed stand could be attributed primarily to the (i) more competitive strategies for soil water use, (ii) stronger antioxidant systems, and (iii) higher leaf total nitrogen and chlorophyll contents in the plants. These findings suggest that mixed growth has beneficial effects on the leaf photosynthesis capacity and physiological resistance of moso bamboo and Chinese fir. [ABSTRACT FROM AUTHOR]

Anatomical characteristics of the plantation tree, Cunninghamia lanceolata were studied. Clonal variability and intra-tree variation, as well as its possibilities of application to the wood industry were analyzed for four clones. Tracheid length from the first to 17th annual ring within clones increased rapidly at first, and then plateaued. The maximum value appeared at the 14th annual ring of clone IV (3795 µm), and the minimum value appeared at the 1st annual ring of clone I (849 µm). Tracheid width and tracheid double wall thickness increased first and then tended to be flat or slightly decreased; tracheid length to width ratio showed an overall increasing trend; the variation of tracheid double wall thickness was not significant. Between clones, the variation coefficient of tracheid width, double wall thickness, and wall to cavity ratio were large. The tissue proportion within clones from large to small was the following: tracheid proportion > wood ray proportion > parenchyma proportion, and there was no significant difference between clones. The basic density within clones showed a gradual increase but a certain fluctuation; the difference between clones was not significant. The maximum crystallinity appeared in clone II (sapwood 55.1%, heartwood 51.2%), and the difference between clones was not significant. [ABSTRACT FROM AUTHOR]

The regular planting and periodic harvesting of a single tree species are features of plantations, which are associated with a reduction of biodiversity. Such plantations are strongly encouraged to be converted into mixed forests. However, the spatial structure dynamics of plantations during the conversion process are poorly understood. In subtropical regions, thinned forest of Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) and mixed forest of Chinese fir and Michelia macclurei Dandy are considered two ideal modes of plantation management. In this study, we analyzed the spatial structure dynamics of two forest stands and their six main tree populations over a rotation of 27 years, using spatial point analyses. We found that Chinese fir and M. macclurei had a regular distribution pattern (scale, r = 0-1 m) in the early stages of planting (1993), and Chinese fir maintained this pattern after experiencing self-thinning and selective cutting. In addition, non-planted tree species (i.e., natural regeneration of late-seral species, NRLSS) displayed significantly intraspecific clumping, which resulted in the distribution patterns of the forest stands changing from regular to aggregated (r = 0-5.5, 1-20 m), and the species distribution of mixed forest changed from random to clumped (r = 0-20 m). Moreover, during the management period (1993-2018), individuals were significantly differentiated in terms of size, and some small trees in the thinned forest were aggregated together. For the NRLSS, the diameter at breast height was randomly distributed (r = 0-20 m). Furthermore, Chinese fir and M. macclurei were separated at r = 0-1 m in the planting stage, but any pair of the six main populations in the thinned forest and mixed forest were randomly correlated over a rotation. Finally, the nearest neighbor distance of the stands became shorter after conversion, while the values for Chinese fir increased. After 25 years, the mixed plantation and the thinned plantation had a complex spatial structure. They develop towards natural forests and could be used as a template for future plantation management. [ABSTRACT FROM AUTHOR]

Although stand age affects biomass partitioning and allometric equations, the size of these effects and whether it is worth incorporating stand age into allometric equations, requires further attention. We sampled a total of 90 trees for 10 Chinese fir (Cunninghamia lanceolata) plantations at seven stand age classes to obtain the data of tree component biomass using destructive harvesting. A multilevel modeling approach was applied to examine how stand age effects differ among tree components and predictor variables (diameter at breast height, DBH and tree height, H). Age class-specific allometric equations and the best fitting generalized equation that included stand age as a complementary variable were developed for each tree component. Large differences in both the intercept and slope for different stand age classes indicated that stand age affected allometric models. Branch and leaves were more sensitive to the environment and were the tree components most affected by stand age. Age class-specific allometric equations fitted well (R2 > 0.65, p < 0.001) using DBH and the combined form DBH2H as predictor variables. Including stand age as a complementary variable improved the fit of generalized allometric equations. Stem, aboveground and total tree biomass predicted by the multilevel model and generalized equation were comparable to the observed data. However, the multilevel model and generalized equations had a relatively low predictive capacity for branch, leaf and root biomass. These results could improve our capacity to evaluate carbon sequestration and other ecosystem functions in plantations. [ABSTRACT FROM AUTHOR]

The sustainability of coniferous monoculture plantations is facing challenges with respect to yields, ecology, and biodiversity. Conversion of monocultural coniferous plantations into mixed stands using thinning or direct mixed planting is widely considered to be a key strategy for overcoming these challenges and transforming the characteristics of plantations on a regional scale. Substantial amounts of deadwood may be produced in mixed forests (MFs); this material is important for evaluating and modifying forest management methods, understanding the dynamics of forest stands, and achieving biodiversity conservation. We assessed the quantitative characters and diameter distributions of deadwood in mixed and thinned Chinese fir [ Cunninghamia lanceolata (Lamb.) Hook.] forests over one rotation. We used the g (r) function and spatial parameters to analyze the spatial structure of deadwood, and used logistic regression and Hegyi's competition index (HCI) to explore competition and mortality. Our results indicate that: (1) Chinese fir dominated in all groups of deadwood (snags, broken wood, and fallen wood), and the abundance, volume, and mortality rates of deadwood were much lower in the thinning forest compared to the MF. (2) Later coming populations (LCPs) comprised the majority of the small diameter classes in the thinning forest, but only accounted for a small proportion of the MF. (3) Broken wood in the thinning forest was randomly distributed, while the other types of deadwood were clustered at most spatial scales. In contrast, the spatial patterns in the MF were random at most spatial scales. (4) Total deadwood in both stands was in a status of intermediate and was randomly surrounded by its four nearest neighbors. All types of deadwood were highly mixed in the thinning forest and moderately mixed in the MF. Our case study suggests that thinning and mixing result in different stand development processes and thus influence the type, amount, and structure of deadwood. Thinning significantly reduces competition, which is the main driver of tree mortality. Converting pure Chinese fir plantations into mixed stands by thinning should be taken in future. Understanding tree mortality after conversion is essential to select appropriate silvicultural treatments and achieve ultimately sustainable forest management. [ABSTRACT FROM AUTHOR]

Plantations are playing an increasingly important role in providing forest products and improving the ecological environment, but they also face many challenges, such as low biodiversity, severe pest and disease problems, reduced productivity, and diminished soil fertility. Reasonable management strategies are vital for their sustainability. In this study, we took a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation as an example to demonstrate the effects of thinning and mixing on the species diversity and structural diversity of plantations at the stand level over a rotation period (1993–2018). An intermediate thinning (26% of plant abundance) was conducted in a Chinese fir pure plantation in mid-age (2008), and a mixed forest stand of Chinese fir and Michelia macclurei Dandy was established directly. Thinning and mixing greatly increased the species diversity at the stand level, enhanced the mixture, transformed the pattern from regular to random distribution, and made the size differentiation of trees random. Thinning and mixing also greatly improved the mixture and dominance of Chinese fir. M. macclurei had an obvious advantage in tree size and maintained a high mixture proportion. Moreover, the diameter classes of the stands were bimodal. Chinese fir and M. macclurei showed a unimodal distribution of diameter, but other later-coming species with a larger number of individuals displayed a typical reverse J-shaped distribution. Our results suggest that both thinning and mixed planting may promote species diversity and structure over a long timescale, but thinning achieves these characteristics earlier because thinning directly manipulates structure in a way that accelerates stand development. [ABSTRACT FROM AUTHOR]

Litter decomposition, an important component of nutrient cycling, is often one of the limiting factors for the development of monoculture tree plantations for restoration, and how to improve the litter decomposition rate remains as a major challenge. To help resolve this issue, we developed a mixed-litter transplantation approach to improve the litter decomposition and nutrient cycling in Schima superba, Cunninghamia lanceolata, Eucalyptus urophylla, and Acacia mangium monoculture plantations in China. The monospecific leaf litters of the four species were collected and their possible two-, three- and four-species combinations were transplanted between plantations. We examined the influences of home/away field, litter species richness, and litter composition on litter decomposition during 24 months treatment. A significant effect of litter composition on litter decomposition (Duration × Composition effect) was detected in E. urophylla plantation. The influence of litter richness on litter decomposition was significant in A. mangium plantation (Duration × Richness effect). The litter of C. lanceolata and A. mangium had a distinct home-field advantage, while the litter of S. superba had a distinct away-field advantage in decomposition. We observed a positive relationship between richness and litter decomposition in C. lanceolate plantation. The effect of Duration × Species Interaction on litter decomposition, was significant in E. urophylla plantation, indicating a non-additive effect. Litter decomposition in E. urophylla plantation could be explained by idiosyncratic model, and the rivet model may be appropriate to illustrate the litter decomposition in A. mangium plantation. Finally, since the litter decomposition in degraded A. mangium plantations had a distinct home-field advantage and was significantly affected by litter richness, transplanting mixed litters of neighboring plantations may be beneficial to improve its litter decomposition rate. Transplanting of S. superba litters due to the distinct home-field advantage to neighboring plantations such as E. urophylla plantation whose litter decomposition is significantly affected by litter composition, may be an effective management method for improving litters decomposition. [ABSTRACT FROM AUTHOR]

The nutrient limitation hypothesis has often been used to explain the late stage decline in productivity of tree plantations. However, few studies have considered the role of fine roots (≤ 2 mm) may play in the process, and even fewer have considered the impact of understory vegetation. Here we assessed how fine root morphological traits, such as specific root length (SRL) and root tissue density (RTD), as well as fine root biomass (FRB) and root length density (RLD), varied in Chinese fir (Cunninghamia lanceolata) and associated understory plants with stand development. Results showed that, for Chinese fir fine roots, the SRL significantly decreased, while the RTD significantly increased, with stand development. There was no significant increase in the relative belowground biomass allocation (indicated by the ratio of total FRB or total RLD to stand basal area) of Chinese fir. This may reflect decreased nutrient foraging by Chinese fir fine roots during the later stage of stand development. Interestingly, understory vegetation had both significantly higher SRL and lower RTD than Chinese fir in every plantation. The weighted mean depth of FRB or RLD of understory vegetation was significantly lower than that of Chinese fir. In the later stage of stand development, understory vegetation tended to dominate the total RLD of the stand in the topsoil, reflecting intense belowground competition of understory plants on Chinese fir. Our study emphasizes that, besides the declined nutrient foraging ability of Chinese fir itself, the intense nutrient competition from understory vegetation could exacerbate nutrient limitation of Chinese fir, which may be an overlooked factor contributing to the decline in plantation productivity during the later stage of stand development. • SRL of Chinese fir decreased whereas RTD increased with stand age. • Understory vegetation had higher SRL and lower RTD than Chinese fir. • Understory fine roots dominated the topsoil in later stage of stand development. • Niche segregation of fine roots occurred between Chinese fir and understory. [ABSTRACT FROM AUTHOR]

Chinese fir [ Cunninghamia lanceolata (Lamb.) Hook.] is a critical timber tree species for its fast growth and high yield in southern China and is widely planted in subtropical regions of the country. However, the management of Chinese fir in the form of a monoculture plantation is not conducive to the maintenance of soil fertility and improvements in forest productivity. The establishment of mixed conifer–broad–leaved forests through near-natural transformation is developing into a promising method of forest cultivation for replacing large pure coniferous plantations. Bacteria and fungi are an important part of the soil microbiota and are involved in the soil nutrient cycle. Therefore, this study investigated the response of soil bacterial and fungal communities to the introduction of broad–leaved trees in three types of Chinese fir plantations [ Cunninghamia lanceolata monoculture plantation (CMP), C. lanceolata–Castanopsis hystrix Hook. f. & Thomson ex A. DC.–Michelia hedyosperma Law. mixed plantation (CCM), and C. lanceolata–Castanopsis fissa (Champ. ex Benth.) Rehder & E.H.Wilson–Erythrophleum fordii Oliv. mixed plantation (CCE)] located in Guangxi Province, China. And the effect of soil layers (0–20, 20–40, and 40–60 cm soil depths) on the soil microbial communities was further analyzed. The results suggested that tree species mixing significantly affected bacterial and fungal communities, but soil depth only significantly affected bacterial communities (P < 0.01). The relative abundance of Basidiomycetes in CCE (53.91–78.76 %) was significantly higher than that in pure forest (P < 0.05). Bacteria exhibited more complex and multilinked networks in the mixed stands, particularly for the CCE plantation. Mixed planting patterns significantly enhanced bacterial nitrogen fixation and the presence of symbiotic fungi. Redundancy analysis (RDA) and correlation analyses indicated that the microbial community structure was strongly affected by soil environmental factors, with bacteria affected mainly by available phosphorous (AP) and fungi affected mainly by soil enzyme activity and total potassium (TK). In summary, the introduction of broad–leaved species (especially C. fissa and E. fordii) had a significant impact on the soil microbial community, increasing the relative abundance of bacterial nitrogen fixation and symbiotic fungi and generating a complex microbial network. We suggest that changes in AP, TK, and fungal communities should be considered in the near-natural transformation of Chinese fir or soil fertility maintenance and sustainable management to maintain soil fertility. [Display omitted] • Tree species mixing significantly affected soil microbial communities. • Mixture improved the bacterial nitrogen fixation, symbiotic fungi, and networks complex. • Bacteria had a stronger spatial dependence than fungi. • AP, enzyme activities, and TK were key variables influencing the soil microbial communities. [ABSTRACT FROM AUTHOR]

Successive rotation and monoculture, as common silvicultural practices, are extensively applied worldwide, particularly in subtropical Chinese fir (Cunninghamia lanceolata) plantations in southern China. Although regeneration failure and productivity decline are frequently observed in continuous monoculture plantations, the potential mechanisms are still unclear. In this study, high-throughput sequencing was used to compare the diversity and composition of bacterial and fungal communities among different generations of Chinese fir plantation (first rotation, FRP; second rotation, SRP; third rotation, TRP) and natural forest (NF) in December and June. Our results showed significant declines in richness and diversity of bacterial and fungal communities in TRP compared with FRP and SRP, but no significant difference between FRP and SRP. The fungal phyla with high relative abundance were Basidiomycota (12.9–76.9%) and Ascomycota (14.3–52.8%), while the bacterial phyla with high relative abundance were Acidobacteria (39.1–57.7%) and Proteobacteria (21.2–39.5%) in all treatments at both sampling months. On average, the relative abundance of Basidiomycota in TRP increased by 53.4%, while that of Ascomycota decreased by 37.1% compared with FRP and SRP. Moreover, soil NH4+–N, pH, and DOC appear to be the key factors in shaping the fungal communities, while soil NH4+–N, DOCN, and AP primarily drive the changes in bacterial communities. Collectively, our findings highlighted the alteration of soil bacterial and fungal communities induced by changes in soil nutrient environment in different generations of continuously cultivated Chinese fir plantation. [ABSTRACT FROM AUTHOR]

Background. High-density conditions are global issues that threaten the sustainable management of plantations throughout the world. Monocultures and untimely management practices have identically resulted in the simplex of community structures, decreases in biodiversity, and long-term productivity losses in plantations China. The most popular measure which is commonly used to address these issues is thinning, which potentially results in increases in the development of understory plants in plantations. However, there is limited information currently available regarding the community composition of understory vegetation and the associated environmental factors, which has limited the sustainable management of China's fir plantation ecosystems. Method. In the present study, a thinning experiment was implemented which included a control check (CK: no thinning), as well as low intensity thinning (LIT: 20%), moderate intensity thinning (MIT: 33%), and high intensity thinning (HIT: 50%) in Chinese fir plantations located in the Southeastern China. During the investigation process, the understory vegetation examined three years after thinning measures were completed, in order to analyze the impacts of different thinning intensities on the growth and community composition of the understory plants. At the same time, the associated environmental factors in the fir plantations were also investigated. Results. The species richness, total coverage, and biomass of the understory vegetation were observed to be apparently increased with increasing thinning intensity. In addition, it was found that the thinning measures had prominently influenced the soil nutrients. The community compositions of the understory vegetation were significantly different among the four thinning intensity levels, especially between the CK and the HIT. Furthermore, the development of the understory vegetation was found to be significantly correlated with the soil nutrient contents, and the community compositions of the understory vegetation were prominently driven by the tree densities, slope positions, and soil nutrient contents. [ABSTRACT FROM AUTHOR]