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In order to study the effects of wildfires on soil carbon dioxide (CO2) emissions and microbial communities in planted forests, Pinus massoniana Lamb. and Cunninghamia lanceolata (Lamb.) Hook. forests were selected as the research subjects. Through a culture test with 60 days of indoor constant temperature, the soil physical and chemical properties, organic carbon mineralization, organic carbon components, enzyme activity, and microbial community structure changes of the two plantations after fire were analyzed. The results showed that wildfires significantly reduced soil CO2 emissions from the Pinus massoniana forests and Cunninghamia lanceolata forests by 270.67 mg·kg−1 and 470.40 mg·kg−1, respectively, with Cunninghamia lanceolata forests exhibiting the greatest reduction in soil CO2 emissions compared to unburned soils. Bioinformatics analysis revealed that the abundance of soil Proteobacteria in the Pinus massoniana and Cunninghamia lanceolata forests decreased by 6.00% and 4.55%, respectively, after wildfires. Additionally, redundancy analysis indicated a significant positive correlation between Proteobacteria and soil CO2 emissions, suggesting that the decrease in Proteobacteria may inhibit soil CO2 emissions. The Cunninghamia lanceolata forests exhibited a significant increase in soil available nutrients and inhibition of enzyme activities after the wildfire. Additionally, soil CO2 emissions decreased more, indicating a stronger adaptive capacity to environmental changes following the wildfire. In summary, wildfire in the Cunninghamia lanceolata forests led to the most pronounced reduction in soil CO2 emissions, thereby mitigating soil carbon emissions in the region. [ABSTRACT FROM AUTHOR]

Recent studies on the intra-annual dynamics of trees were mainly focused on mature trees in natural forests; however, less is known about how topography (e.g., slope's position and aspect) shape the intra-annual xylem formation dynamics of young trees in plantation forests. We monitored intra-annual xylem formation dynamics of 6-year-old Chinese fir (Cunninghamia lanceolata (Lamb.)) trees across two different aspects (northeast and southwest) and three different positions (upper, middle, and lower) of the slope in a planted forest in subtropical China. We found that the intra-annual xylem formation of trees on the northeast slope aspect (176.98 ± 34.52 cells) was significantly higher than that on the southwest slope aspect (140.19 ± 36.07 cells) due to the higher growth rate (0.67 ± 0.11 cells/day vs. 0.53 ± 0.10 cells/day). In the middle slope position, xylem formation (187.89 ± 19.81 cells) was also significantly higher than that of the upper (147.35 ± 29.08 cells) and lower slope positions (140.51 ± 48.36 cells), resulting from higher growth rate rather than longer growing season length. Our study demonstrated that intra-annual xylem formation dynamics of Chinese fir were altered by different topographic features and therefore encourage the implementation of management strategies that consider different slope aspects and positions to maximize forest productivity. [ABSTRACT FROM AUTHOR]

[Objectives] This study was conducted to provide good basic research data for Cunninghamia lanceolata plantations in southern Anhui, so a to improve local ecological, economic and social benefits. [Methods] A22-year-old near-mature C. lanceolata plantation in Lingnan Forest Farm, Xiuning County, Huangshan City, Anhui Province was investigated and analyzed by sample plot survey. [Results] The average DBH value of the C. lanceolata plantation at the lower slope was the largest, 24.7% and 19.2% higher than those at the upper and middle slopes, respectively. The average single plant wood volume at the lower slope was 47.6% and 49.1% higher than those in the upper and middle slopes, respectively. However, the average tree heights at various slope positions showed little difference. Meanwhile, all the indexes showed the phenomenon of semi-shady slope > sunny slope > shady slope under different slope directions. Among them, the effect of slope position on DBH was extremely significant, but the effect of slope direction on DBH was not significant, and slope position, slope direction and the interaction of slope direction and slope position had no significant effects on the tree height of the C. lanceolata plantation. In addition, slope direction and slope position had extremely significant effects on single plant wood volume. From the overall growth situation of the C. lanceolata plantation in Lingnan Forest Farm, the slope position factor had greater effects on various indexes of forest growth than the slope direction factor, mainly manifested in that the lower slope was better than the middle slope, and the middle slope position was better than the upper slope, while although slope direction had some effect on the growth of the C. lanceolata plantation, the influence degree was not a significant as that of slope position. [Conclusions] This study provides some reference for the adjustment and optimization, development and renew of C. lanceolata plantation structure in the later period in this area, a well as some data support for other theoretical research on economic forests. [ABSTRACT FROM AUTHOR]

【Objective】The study was conducted to investigate the spatial distribution and content differences of asymbiotic nitrogen fixation (ANF) in different ecosystem components of Cunninghamia lanceolata, Eucalyptus, Pinus massoniana plantation forests in different growing seasons.【Method】By using ordinary kriging interpolation, analysis of variance and correlation analysis, we conducted a characterisation study of spatial variability and content differences in ANF of Cunninghamia lanceolata, Eucalyptus, Pinus massoniana plantation forests in Guangxi Gaofeng Forestry by determining the amount of ANF in soil, litter and canopy leaves in the growing season and non-growing season.【Result】In both growing and non-growing seasons, the trends of ANF in each component of plantation forests were different and significant, with strong spatial correlation and heterogeneity. In the growing season, the distribution of soil ANF was low in the northeast and high in the southwest, while the distributions of litter and canopy leaves were high in the northeast and low in the southwest; in the nongrowing season, the spatial distributions of soil and canopy leaves were generally similar to those in the growing season, and that of the litter showed the opposite result. Soil ANF was the highest in plantation forests, at 1.2834 and 0.5668 kg/hm²·y, and the lowest was in canopy leaves, at 0.0009 and 0.0028 kg/hm² ·y. ANF in soil differed significantly from that in litter and canopy leaves. In the growing season, the amount of soil ANF was significantly negatively correlated with litter, and the correlation between the other components was not significant; in the non-growing season, the amount of ANF between the components did not have a significant correlation. 【Conclusion】The spatial differentiation of ANF in various components of Cunninghamia lanceolata, Eucalyptus, Pinus massoniana plantation forests in different seasons was significant and strong, and ANF mainly existed in the soil fraction. Therefore, the application of a certain amount of nitrogen fertilizer to the soil during the planting of Cunninghamia lanceolata, Eucalyptus and Pinus massoniana can promote the growth of plantation forests. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata [Lamb.] Hook.) is a widely planted species of plantation forest in China, and heat treatment can improve its dimensional stability defects and improve its performance. The wood samples were heat-treated at various temperatures (160, 180, 200, and 220 °C) for 2 h. To clarify the effect of heat treatment on wood hygroscopicity, the equilibrium moisture content (EMC) was measured, the moisture adsorption and desorption rates were determined, the hygroscopic hysteresis was examined, and the Guggenheim, Anderson, and de Boer (GAB) model was fitted to the experimental data. The moisture absorption isotherms of all samples belonged to the Type II adsorption isotherm, but the shape of the desorption isotherm was more linear for heat-treated wood samples, especially when the heat treatment temperature was higher. According to the results analyzed with ANOVA, there were significant differences in equilibrium moisture content between the control samples and the heat-treated samples under the conditions of 30%, 60%, and 95% relative humidity (RH, p < 0.05), and the results of multiple comparisons were similar. The decrease in hygroscopicity was more pronounced in wood treated at higher temperatures. The EMC of the 160–220 °C heat-treated samples of the control samples was 14.00%, 22.37%, 28.95%, and 39.63% lower than that of the control sample at 95% RH. Under low RH conditions (30%), water is taken up mainly via monolayer sorption, and multilayer sorption gradually predominates over monolayer sorption with the increase in RH. The dynamic vapor sorption (DVS) analysis indicated that the heat-treated wood revealed an increase in isotherm hysteresis, which was due to the change in cell wall chemical components and microstructure caused by heat treatment. In addition, the effective specific surface area of wood samples decreased significantly after heat treatment, and the change trend was similar to that of equilibrium moisture content. [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]

The EFSA Panel on Plant Health performed a pest categorisation of Lepidosaphes pineti Borchsenius the pine oyster scale, Lepidosaphes pini (Maskell) the Oriental pine scale and Lepidosaphes piniphila Borchsenius (Hemiptera: Diaspididae) for the EU, following a commodity risk assessment of dwarfed Pinus parviflora grafted onto P. thunbergii from China in which the three Lepidosaphes species were identified as pests of possible concern to the EU. All three species are native to Asia. L. pineti is only known from China; L. piniphila occurs in China, Japan and Malaysia; and L. pini is present in China, Japan, South Korea, Taiwan, and has been introduced to the USA. All three species feed primarily on Pinus spp., including several important forestry and ornamental trees, and L. pineti and L. pini have adapted to feed on North American species of pine. L. pineti also feeds on Torreya grandis; L. pini on Abies sp., Cunninghamia lanceolata, Cycas spp., Podocarpus spp., Taxus sp. and Torreya sp.; and L. piniphila on Podocarpus spp. and T. grandis. All developmental stages occur on the foliage. Host plants for planting and cut branches with foliage could provide pathways into the EU. However, prohibitions on the import of Pinus close the main pathway. Certain dwarfed Pinus spp. from Japan are provided with a derogation for entry into the EU. The main hosts (Pinus spp.) occur throughout the EU in climate zones that match those where the three Lepidosaphes species occur in Asia. If any of the three Lepidosaphes species were to enter the EU, conditions in most of the EU are conducive to establishment. Following establishment, impacts on pines by L. pineti and L. pini would be expected. There are no published reports of L. piniphila causing damage to pine. L. pineti and L. pini satisfy the criteria that are within the remit of EFSA to assess for them to be regarded as potential Union quarantine pests. L. piniphila does not satisfy the criteria, as there is no evidence that it is harmful; however, there is a key uncertainty regarding whether it is synonymous with a closely related species, L. pitysophila, which is recorded as a pest of pine in China. [ABSTRACT FROM AUTHOR]

In terrestrial ecosystems, leaf litter is the main source of nutrients returning to the soil. Understanding how litter decomposition responds to stand age is critical for improving predictions of the effects of forest age structure on nutrient availability and cycling in ecosystems. However, the changes in this critical process with stand age remain poorly understood due to the complexity and diversity of litter decomposition patterns and drivers among different stand ages. In this study, we examined the effects of stand age on litter decomposition with two well-replicated age sequences of naturally occurring secondary forests and Chinese fir (Cunninghamia lanceolata) plantations in southern China. Our results showed that the litter decomposition rates in the secondary forests were significantly higher than those in the Chinese fir plantations of the same age, except for 40-year-old forests. The litter decomposition rate of the Chinese fir initially increased and then decreased with stand age, while that of secondary forests gradually decreased. The results of a structural equation model indicated that stand age, litter quality and microbial community were the primary factors driving nutrient litter loss. Overall, these findings are helpful for understanding the effects of stand age on the litter decomposition process and nutrient cycling in plantation and secondary forest ecosystems. [ABSTRACT FROM AUTHOR]

Background: Plants can directly affect litter decomposition by producing litter materials of different qualities. However, whether living plants have indirect effects on litter decomposition by affecting changes in forest microenvironments is presently unclear in plantation forests. Methods: We addressed this issue by studying the decomposition of the leaf litter and fine roots of Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.], a timber species widely planted in China, in 113 non-neighboring quadrats of varying basal area of the dominant plant species (i.e., Chinese fir) and distinct basal areas and species richness of regenerated woody plants (i.e., species other than Chinese fir) in a subtropical Chinese fir forest. Results: Our results showed that fine roots decomposed significantly more rapidly than leaf litter possibly because fine roots were easier access to mineralized nutrients and microbes compared with leaf litter. Further analyses showed that leaf litter and fine root decomposition rates were significantly controlled by the plant community attributes. The decomposition of both leaf litter and fine roots was mainly controlled by woody species regenerated during stand development rather than by Chinese fir. Specifically, leaf litter and fine root decomposition rates decreased with increasing basal area of regenerated woody plants, possibly due to nutrient competition and/or reduced photodegradation. Conclusions: This study provides empirical evidence that woody species regenerated during stand development play a certain role in determining litter decomposition rates through plant-soil interactions in Chinese fir plantations. Regenerated woody plants should be considered in future studies on soil carbon and nutrient cycling in plantation forest. [ABSTRACT FROM AUTHOR]

To meet the growing demand for wood and pulp products, Eucalyptus plantations have expanded rapidly during the past two decades, becoming an integral part of the southern China landscape. Leaf blight caused by various Calonectria spp., is a serious threat to these plantations. In order to explore the diversity and distribution of Calonectria spp. in Fujian Province soils, samples were collected in Eucalyptus plantations and adjacent plantings of Cunninghamia lanceolata, Phyllostachys heterocycle and Pinus massoniana as well as in natural forests. Three hundred and fifty-three Calonectria isolates were recovered from soil samples and they were identified based on a comparison of multilocus DNA sequence data for the act (actin), cmdA (calmodulin), his3 (histone H3), rpb2 (the second largest subunit of RNA polymerase), tef1 (translation elongation factor 1-alpha) and tub2 (β-tubulin) gene regions, as well as morphological characteristics. Six known taxa including Calonectria aconidialis, Ca. hongkongensis, Ca. ilicicola, Ca. kyotensis, Ca. pacifica, Ca. pseudoreteaudii and one novel species described here as Ca. minensis sp. nov. were identified. Of these, Ca. aconidialis and Ca. kyotensis were the most prevalent species, and found in eight and seven sites, and four and five forest types, respectively. Calonectria spp. were most abundant in soils from Eucalyptus stands, followed by P. heterocycle and natural forests. Relatively few species were found in the soils associated with Cunninghamia lanceolata and Pinus massoniana. The abundance of known Calonectria spp. suggests that these fungi have been relatively well sampled in Fujian. The results are also consistent with the fact that most Calonectria diseases are found on Angiosperm as opposed to Gymnosperm plants. [ABSTRACT FROM AUTHOR]

To study the effect of target tree management on the spatial structure of Cunninghamia lanceolata plantation, three types of forest of different age (8, 12, and 21 years) were allocated to three standard plots. Target tree, disturbance tree, and general tree were determined by selecting the spatial structural parameters such as uniform angle index, size ratio, openness, competition index, and DBH to construct a comprehensive evaluation index model. The change in the spatial structure parameters were computed and analyzed after simulated cutting of disturbance tree. The results showed that the spatial structural unit comprised one central tree and five to six neighbor trees. The competition pressure of 8,year,old and 12,year,old trees was high? and the number of disturbance trees was approximately 30% of the total. The trees of three forest ages were randomly distributed? with evident differentiation, limited growth space, and great pressure. After simulated cutting of disturbance tree? the size ratio of target trees at each age decreased and exhibited a dominant state. The spatial distribution pattern of the 8-year-old and 12-year-old trees was optimized? whereas that of 21-year-old tree was inconspicuous, the openness increased, growth space was basically sufficient, and the competition index decreased, indicating that the pressure of target tree decreased significantly. [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]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Tree-crown and height are primary tree measurements in forest inventory. Convolutional neural networks (CNNs) are a class of neural networks, which can be used in forest inventory; however, no prior studies have developed a CNN model to detect tree crown and height simultaneously. This study is the first-of-its-kind that explored training a mask region-based convolutional neural network (Mask R-CNN) for automatically and concurrently detecting discontinuous tree crown and height of Chinese fir (Cunninghamia lanceolata (Lamb) Hook) in a plantation. A DJI Phantom4-Multispectral Unmanned Aerial Vehicle (UAV) was used to obtain high-resolution images of the study site, Shunchang County, China. Tree crown and height of Chinese fir was manually delineated and derived from this UAV imagery. A portion of the ground-truthed tree height values were used as a test set, and the remaining measurements were used as the model training data. Six different band combinations and derivations of the UAV imagery were used to detect tree crown and height, respectively (Multi band-DSM, RGB-DSM, NDVI-DSM, Multi band-CHM, RGB-CHM, and NDVI-CHM combination). The Mask R-CNN model with the NDVI-CHM combination achieved superior performance. The accuracy of Chinese fir's individual tree-crown detection was considerable (F1 score = 84.68%), the Intersection over Union (IoU) of tree crown delineation was 91.27%, and tree height estimates were highly correlated with the height from UAV imagery (R2 = 0.97, RMSE = 0.11 m, rRMSE = 4.35%) and field measurement (R2 = 0.87, RMSE = 0.24 m, rRMSE = 9.67%). Results demonstrate that the input image with an CHM achieves higher accuracy of tree crown delineation and tree height assessment compared to an image with a DSM. The accuracy and efficiency of Mask R-CNN has a great potential to assist the application of remote sensing in forests. [ABSTRACT FROM AUTHOR]

Aims: Aboveground litter inputs have been modified by global changes in plantation forests, where understory management is also prevalent, which may alter soil fertility and stand productivity. This study aimed to quantify the specific roles of litter and understory in affecting soil carbon (C) and nitrogen (N) dynamics. Methods: A field experiment was established with four treatments, namely, litter addition (LA), understory removal (UR), litter addition and understory removal (LA + UR), and a control, in a subtropical Cunninghamia lanceolata plantation. Topsoil δ13C, organic C concentration, storage and decomposition, mineral N, N mineralization, and C and N hydrolase activities were analyzed. Results: Litter addition significantly increased soil organic C, macro-particulate organic C (macro-POC) and mineral N at a 0–5 cm depth, but decreased δ13Cmacro-POC at 0–5 cm and 5–10 cm depths. Understory removal significantly increased soil NH4+-N, the rates of nitrification and net N mineralization as well as the soil organic C respiration rate at the two depths, while it decreased the C storage in bulk soil, especially in mineral protected pools. The activities of β-glucosidase and β-N-acetylglucosaminidase increased with litter addition and understory removal, respectively. Conclusions: Litter addition tends to improve soil C quantity and quality due to fresh organic C inputs, while understory removal helps increase the N supply via the acceleration of N mineralization and the absence of understory plant uptake. [ABSTRACT FROM AUTHOR]

Tree performance in mixed-species forest plantations is ultimately the net result of positive and negative interactions among species. Despite increasing knowledge of interspecific interactions, relatively little is known about the chemical mechanisms mediating such interactions. We constructed mixed planting systems with two species including Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) and broadleaf species Cinnamomum camphora L. Presl, Elaeocarpus decipiens Hemsl, Liquidambar formosana Hance, or Michelia macclurei Dandy. Based on a series of manipulative experiments, we investigated the performance of Chinese fir and analyzed root placement patterns and the composition of main soil microbial groups. The broadleaf trees influenced the growth of Chinese fir roots more than the growth of shoots. Furthermore, C. camphora roots released allelochemicals into the soil environment, resulting in growth inhibition of Chinese fir and changes in main soil microbial groups. However, when grown with E. decipiens and M. macclurei, the growth of Chinese fir was consistently promoted. It responded by enhancing its root growth and altering root behavior, resulting in a shift from growth inhibition to chemical facilitation. These positive inter-specific interactions also stimulated changes in the composition of soil microbes. Complementary experiments indicated that non-toxic signaling molecules in the root exudates of E. decipiens and M. macclurei may be responsible for mediating positive root-root interactions and regulating the composition of main soil microbial groups. Thus, our study demonstrated that broadleaf species chemically mediate the growth of Chinese fir through root exudates. Such a novel mechanism offers many implications and applications for reforestation programs undertaken to rehabilitate forest plantations that suffer from declining productivity related to densely planted monocultures. [ABSTRACT FROM AUTHOR]

Background and aims: Anthropogenic activities have increased nitrogen (N) and phosphorus (P) inputs to terrestrial ecosystems, which may significantly alter P cycle through accumulation and resorption. Methods: We measured the concentrations of four different P fractions (inorganic, nucleic, sugar, and residual P) in both live leaves and senescent leaves in N and P additions in an evergreen plantation forest of subtropical China. Results: Adding moderate N plus P increased total, inorganic, and sugar P concentrations, which sustained the leaf N/P balance and alleviated P limitation in Chinese fir (Cunninghamia lanceolata) plantation. Nitrogen and P (total, nucleic, and residue P) resorption proficiencies did but P (each of various fractions) resorption efficiency did not respond to nutrient addition. The concentrations and resorption efficiencies of most P fractions were lower in the old than young leaves, but their resorption proficiencies except for sugar P weren't different. Conclusions: Internal P cycles of Chinese fir could be strongly altered through increasing accumulation of inorganic P and sugar P factions in respond to soil P enrichment when combined with suitable N addition. The easily degradable P (inorganic and sugar P) were preferentially resorbed regardless of nutrient addition. Leaf age was a key-factor influencing the resorption extent of P fractions in Chinese fir. [ABSTRACT FROM AUTHOR]

Copyright of Forest Research is the property of Forest Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Rainfall partitioning was compared for a natural forest and a plantation forest. • The plantation had a greater understory but smaller overstory interception loss. • The total interception loss and surface runoff converged between the two forests. • Understory interception is an important component in rainfall partitioning. Litter and vegetation under forest canopy (i.e., understory vegetation) are known to reduce soil erosion and contribute substantially to evapotranspiration. However, previous studies rarely examined understory water interception. We conducted a comprehensive study of rainfall partitioning using a water balance equation that included both overstory and understory components in a Chinese fir (Cunninghamia lanceolata) plantation and a nearby naturally regenerated Castanopsis (C. carlesii) forest of similar age in southeastern China. Understory interception was measured by submerging understory components (vegetation and litter) in water for 24 h, which gave an estimate of the amount of water retained (i.e., water holding capacity). The total interception loss of rainfall events (>9.8 mm) that generated surface runoff converged between the two forests, a result of a smaller overstory interception loss (20%) coupled with a greater understory interception loss (14%) in the Chinese fir plantation relative to the Castanopsis forest (overstory 25% and understory 11%). The convergence of the total interception contributed to the convergence of the surface runoff, 1% of the rainfall in both forests. Furthermore, the throughfall partition (78%) was greater whereas the stemflow partition (2%) was smaller in the Chinese fir plantation relative to the Castanopsis forest (throufhfall 70% and stemflow 5%). These patterns in rainfall partitioning could be explained by the greater development of the understory vegetation (hence greater understory interception loss) in the Chinese fir plantation, lower canopy leaf area index (hence smaller overstory interception loss and greater throughfall), and rougher barks (hence smaller stemflow) of Chinese fir trees compared to that of Castanopsis trees. Our study illustrated that a comprehensive evaluation of interception loss must take into account understory components. [ABSTRACT FROM AUTHOR]

Aims: This study aimed to determine the influence of tree species on soil microbial community structure. Methods: We conducted a litter and root manipulation and a short-term nitrogen (N) addition experiment in 19-year-old broadleaf Mytilaria laosensis (Hamamelidaceae) and coniferous Chinese fir ( Cunninghamia lanceolata) plantations in subtropical China. Phospholipid fatty acid (PLFA) analysis was used to examine treatment effects on soil microbial community structure. Redundancy analysis (RDA) was performed to determine the relationships between individual PLFAs and soil properties (soil pH, carbon (C) and N concentration and C:N ratio). Results: Soil C:N ratio was significantly greater in M. laosensis (17.9) than in C. lanceolata (16.2). Soil C:N ratio was the key factor affecting the soil microbial community regardless of tree species and the litter, root and N treatments at our study site. The fungal biomarkers, 18:1ω9 and 18:2ω6,9 were significantly and positively related to soil C:N ratio and the abundance of bacterial lipid biomarkers was negatively related to soil C:N ratio. N addition for 8 months did not change the biomass and structure of the microbial community in M. laosensis and C. lanceolata soils. Soil nutrient availability before N addition was an important factor in determining the effect of N fertilization on soil microbial biomass and activity. PLFA analysis showed that root exclusion significantly decreased the abundance of the fungal biomarkers and increased the abundance of the Gram-positive bacteria. Rootless plots had a relatively lower Gram-positive to Gram-negative bacteria ratio and a higher fungi to bacteria ratio compared to the plots with roots under both M. laosensis and C. lanceolata. The response of arbuscular mycorrhizal fungi (16:1ω5) to root exclusion was species-specific. Conclusions: These observations suggest that soil C:N ratio was an important factor in influencing soil microbial community structure. Further studies are required to confirm the long-term effect of tree species on soil microbial community structure. [ABSTRACT FROM AUTHOR]

Understanding the distribution and productivity of Chinese fir (Cunninghamia lanceolata) under climate change is critical given the ecological and economic importance of the species. Recently, process-based growth models have grown in their popularity given their simplicity and data availability, and they are increasingly being used to map the distribution and productivity of tree species. In this paper, we study the extent of variation of the current range shift and the productivity of the species under a changing climate. We used the Physiological Principles in Predicting Growth (3-PG) model, which calculates the extent to which climatic variables affect photosynthesis and growth of a species. These variables were then used in a decision-tree model to develop rules to provide a basis for predicting the distribution of the species under current climatic conditions. Once the distribution model was developed the productivity of the species was then assessed. Using climate projections we then simulated the growth and distribution into the future. Results indicate a northward shift from the current range. The growth model also indicates minor increases in productivity in some of the existing distribution areas, principally in central China with limited productivity predicted in newly emerged stands. We conclude that this dual modeling approach has potential to quantify impacts of climate change on selected species and examining differences in climate projections on range and productivity estimation. [ABSTRACT FROM AUTHOR]

Background and aims: Across the world, about 264 million ha forest plantations are monospecific. This practice has been found to cause site productivity and soil fertility decline in the regions where forests have been harvested several times. To mitigate these problems, mixed-species plantations, especially with broadleaved and coniferous species, are preferred. Understanding the effects of introducing broadleaved tree in monospecific coniferous plantation on ecosystem carbon (C) storage and soil organic C (SOC) stability is critical to improve our understanding of forest C sequestration and C cycle. Methods: Plots were established in subtropical plantations with a randomized block design to examine the influence of introducing Michelia macclurei trees into pure Cunninghamia lanceolata plantation on biomass C storage, SOC storage of total, labile, and recalcitrant fractions (0-40 cm depth), and SOC stability. Results: Introducing M. macclurei trees increased biomass C by 17.9 % and 14.2 % compared with monospecific C. lanceolata and M. macclurei plantations, respectively. Storage of different SOC fractions was not significantly different between monospecific C. lanceolata and mixed plantations. SOC stability in bulk soils was not affected, although it differed in 10-20 cm and 20-40 cm soil depth among three plantations. Conclusions: Mixed species plantations can increase C sequestration, and in the subtropical forest ecosystem examined this was mainly attributed to an increase in biomass C. [ABSTRACT FROM AUTHOR]

Abstract: Chinese fir [(Cunninghamia lanceolata (Lamb.) Hook (Taxodiaceae)] plantations are helping to meet China''s increasing demands for timber, while, at the same time, sequestering carbon (C) above and belowground. The latter function is important as a means of slowing the rate that CO2 is increasing in the atmosphere. Available data are limited, however, and even if extensive, would necessitate consideration of future changes in climatic conditions and management practices. To evaluate the contribution of Chinese fir plantations under a range of changing conditions a dynamic model is required. In this paper, we report successful outcome in parameterizing a process-based model (3-PG) and validating its predictions with recent and long-term field measurements acquired from different ages of Chinese fir plantations at the Huitong National Forest Ecosystem Research Station. Once parameterized, the model performed well when simulating leaf area index (LAI), net primary productivity (NPP), biomass of stems (W S), foliage (W F) and roots (W R), litterfall, and shifts in allocation over a period of time. Although the model does not specifically include heterotrophic respiration, we made some attempts to estimate changes in root C storage and decomposition rates in the litterfall pool as well as in the total soil respiration. Total C stored in biomass increased rapidly, peaking at age 21 years in unthinned stands. The predicted averaged above and belowground NNP (13.81tha−1 a−1) of the Chinese fir plantations between the modeling period (from 4 to 21-year-old) is much higher than that of Chinese forests (4.8–6.22tha−1 a−1), indicating that Chinese fir is a suitable tree species to grow for timber while processing the potential to act as a C sequestration sink. Taking into account that maximum LAI occurs at the age of 15 years, intermediate thinning and nutrient supplements should, according to model predictions, further increase growth and C storage in Chinese fir stands. Predicted future increases (approximately 0–2°C) in temperature due to global warming may increase plantation growth and reduce the time required to complete a rotation, but further increases (approximately 2–6°C) may reduce the growth rate and prolong the rotational age. [Copyright &y& Elsevier]

The conversion of forests could change soil characteristics and, in turn, impact the microbial community. However, the long-term effect of forest transformation on bacterial and archaeal composition and diversity, especially on nitrogen functional communities, is poorly understood. This study aimed to explore the response of soil bacterial and archaeal communities, as well as nitrogen functional groups, to the conversion from natural broadleaved forests to Chinese fir (Cunninghamia lanceolate (Lamb.) Hook.) plantations in subtropical China by 16S rRNA amplicon sequencing. Except for soil bulk density (BD) and ammonium nitrogen (NH4+–N) content, other soil properties all decreased with the conversion from natural forests to plantations. Alpha diversity of bacteria and archaea declined with the transformation from natural forests to plantations. The composition of bacteria and archaea was significantly different between natural forests and plantations, which could be mainly attributed to the change in the content of soil organic carbon (SOC), total nitrogen (TN), nitrate nitrogen (NO3−–N), and available phosphorus (AP). The conversion of natural forests to plantations decreased the gene copies of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and nifH (nitrogen fixation function) but increased denitrification gene copies (i.e., nirS, nirK, and nosZ). In summary, our study emphasizes the long-term negative effect of the conversion from natural broadleaved forests into Chinese fir plantations on the diversity and richness of soil microbial communities, thereby deeply impacting the cycling of soil nitrogen. [ABSTRACT FROM AUTHOR]

• We assessed litterfall in a natural forest and two plantations over 10 years. • Total litterfall was 21–25% lower in the plantations than in the natural forest. • N input from litterfall in plantations was 38–48% of that in the natural forest. • Litter decay rates in the plantations were only half that of C. carlesii litter. • Litter N and P release were lower in the plantations than in the C. carlesii litter. The rapid conversion of natural broadleaved forests to plantations (mainly Cunninghamia lanceolata and Pinus massoniana) in subtropical China has resulted in a substantial decline in soil fertility, but the biogeochemical mechanism behind this decline remains not fully understood. Litterfall is an important source of nutrients that are returned to soils through litter deposition and decomposition. We assessed various types of litterfall (leaves, twigs, flowers, fruits and unidentified litter) monthly and their carbon (C), nitrogen (N), phosphorus (P) and potassium (K) inputs to soils in a natural broadleaved forest (Castanopsis carlesii) and in P. massoniana and C. lanceolata plantations over 10 years. The total litterfall was 21–25% lower in plantations than in the C. carlesii forest, resulting in much lower C (−17% and −14%), N (−62% and −52%), P (−24% and −32%) and K (−53% and −40%) inputs from litterfall in the P. massoniana and C. lanceolata plantations. Leaves accounted for 72–76% of the total litterfall, so we compiled available data on the nutrient release from the three foliar litters during the 1st year of decomposition throughout subtropical China. The decomposition rates of P. massoniana and C. lanceolata needle litter were only half that of C. carlesii leaf litter, and the lower initial quality of P. massoniana and C. lanceolata needle litter relative to C. carlesii leaf litter resulted in significantly lower amounts of N (−95% and −76%) and P (−48% and −25%) being released. These results suggest that low nutrient (N, P and K) inputs due to low litter production and slow nutrient release due to slow litter decomposition are two important biogeochemical reasons for the decline in soil fertility in plantations in subtropical China. [ABSTRACT FROM AUTHOR]

With the continuous increase in plantation areas, the reduction of natural forest areas, and the unreasonable management of plantations by human beings, the service function of forest ecosystems has gradually reduced. Therefore, close-to-natural forestry has become important for the sustainable development of modern forestry. However, the differences in soil properties, enzyme activities, microbial diversities, and undergrowth vegetation species diversities have not been systematically explained for Chinese fir (Cunninghamia lanceolata). How do these indicators interact? The purpose of this paper was to study the difference in soil properties and biodiversity in different aged Chinese fir plantations and close-to-natural forests to explore their interactions and to provide direction for close-to-nature management. The results showed that the above indicators were significantly different in different aged Chinese fir plantations, soil pH, organic matter, total nitrogen, total phosphorus, total potassium, alkali-hydrolyzed nitrogen, available phosphorus concentrations, and urease activities in close-to-natural forests were significantly higher than plantations. It is worth mentioning that the richness of undergrowth vegetation species diversity (especially shrubs) and soil microbial diversities (especially fungi) in the close-to-natural forests were obviously higher than those in plantations. The correlation analysis results showed that the diversity of shrub species with respect to soil properties presented a higher correlation than herb species, the diversity of fungi with respect to soil properties presented a higher correlation than that observed for bacteria, and the diversity of fungi were significantly correlated with the diversity of undergrowth vegetation species diversities, but the correlation between bacteria and undergrowth vegetation species diversities was not significant. Our results suggest that the above factors are fundamental factors for the transformation of Chinese fir plantations to close-to-natural forests. To realize close-to-natural forestry, we must change the tree structure, combine the difference of those factors in different aged plantations, restore undergrowth vegetation species diversity, and thus improve microbial diversity and increase decomposition, transformation, and improvement of soil properties. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species on rhizosphere soil and coniferous tree P dynamics is unclear. In our study, eight plots of a single species of a Chinese fir plantation (pure plantation, PP) and eight mixed plantations (mixed plantation, MP) with broadleaved tree species (Michelia macclurei Dandy in Hunan Province or Schima superba Gardn. et Champ. in Fujian Province) were selected in subtropical China. Six P fractions in the rhizosphere and bulk soils were analyzed by a modified Hedley P fractionation method. Phosphorus fractions and nitrogen (N) concentrations in different root orders, different age fresh needles and twigs, and needle and twig litter of Chinese fir were measured. Our results showed that available P, slowly released P, occluded P, and the total extractable P in rhizosphere soil were significantly higher in MP than PP (p < 0.05). In contrast, P and N concentrations in the transportive roots and two-year old needles were generally higher in PP than MP. Meanwhile, the slowly released P, occluded P, total extractable P, and residual P in rhizosphere soil were negatively correlated with P concentrations in young (absorptive and transportive roots, one- and two-year old needles) but not old tissues (storative roots, three-year old needles and litters). In conclusion, mixture may increase soil P availability through the rhizosphere effect, but can decrease P and N concentration of Chinese fir tissues by competition between Chinese fir and broadleaved species. Clearly, the mixture effect may differ in soil and plant nutrients, and this issue needs be taken into consideration when converting a pure conifer plantation into a mixed-species forest. [ABSTRACT FROM AUTHOR]

Key message: Carbon (C) concentrations inCunninghamia lanceolata(Lamb.) Hook plantations differed significantly among tissue types and were greater for aboveground than belowground tissues. Plantation C stock increased with a developmental stage from young to mature to overmature, but at all stages, the majority occurred as soil organic carbon (SOC) and was more influenced by belowground fine roots than by aboveground litterfall. Context: Failing to account for tissue-specific variation in the C concentration can result in inaccurate forest C stock estimates. Aims: We aimed to quantify the relative magnitudes of C stock for Chinese fir plantations at different developmental stages. Specifically, we focused on assessing tissue-specific C concentrations and C dynamics return of above- and belowground litterfall. Methods: Carbon traits (C concentration, C flux, C stock, and distribution at tree and ecosystem scales) were quantified in a chronosequence of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) monoculture plantation stands at young (10), mature (22), and overmature (34 years old) developmental stages. Results: Carbon concentrations differed significantly among tissue types, with mean values of 48.5 ± 0.1% and 42.5 ± 0.2% for above- and belowground biomass, respectively. The aboveground tissue C concentration, tree- and plantation-scale C stock, and SOC stock depended on developmental stage. Carbon return in litterfall, tree C stock, and SOC increased from the young to the overmature stage. SOC stock accounted for the majority of plantation C stock at all developmental stages (78.3, 59.6, and 55.7% in the young, mature, and overmature stages, respectively) and was more highly influenced by belowground fine roots than aboveground litterfall. Carbon stocks in Chinese fir plantations were 86, 129, and 153 t ha−2 at the young, mature, and overmature stages. Conclusion: Prolonging Chinese fir rotation increases C sequestration potential and should be the focus of forest management strategies. The tissue-specific C concentrations provide detailed information for more accurate biomass C stock estimates for Chinese fir plantations and other subtropical coniferous forests. They indicate that current guidelines result in an overestimation of belowground biomass C stocks. Using the standard 0.47 biomass to C conversion factor, the belowground C stock would have been overestimated by 7.6–13.0% for the Chinese fir developmental stages investigated, while tree C stock would be underestimated by 0.08–3.24%. Therefore, developing species- and tissue-specific conversion factors are required for supporting C plantation and forest C accounting strategies. [ABSTRACT FROM AUTHOR]

Obtaining accurate measurements of tree height and diameter at breast height (DBH) in forests to evaluate the growth rate of cultivars is still a significant challenge, even when using light detection and ranging (LiDAR) and three-dimensional (3-D) modeling. As an alternative, we provide a novel high-throughput strategy for predicting the biomass of forests in the field by vegetation indices. This study proposes an integrated pipeline methodology to measure the biomass of different tree cultivars in plantation forests with high crown density, which combines unmanned aerial vehicles (UAVs), hyperspectral image sensors, and data processing algorithms using machine learning. Using a planation of Cunninghamia lanceolate, which is commonly known as Chinese fir, in Fujian, China, images were collected while using a hyperspectral camera. Vegetation indices and modeling were processed in Python using decision trees, random forests, support vector machine, and eXtreme Gradient Boosting (XGBoost) third-party libraries. The tree height and DBH of 2880 samples were manually measured and clustered into three groups—"Fast", "median", and "normal" growth groups—and 19 vegetation indices from 12,000 pixels were abstracted as the input of features for the modeling. After modeling and cross-validation, the classifier that was generated by random forests had the best prediction accuracy when compared to other algorithms (75%). This framework can be applied to other tree species to make management and business decisions. [ABSTRACT FROM AUTHOR]

The amount to be invested and the timing of clearcutting are central concerns in timber production. To assess the impact of the initial planting density on optimal economic rotation, we explicitly included the distribution of stand diameter classes and price differences representing the quality of stumpage in a model of forest land expected value (LEV). We selected five initial planting densities of 35-year old China fir (Cunninghamia lanceolata (Lamb.) Hook) plantations to fit the distribution of diameter classes along with stand age using a three-parameter Weibull theoretical growth model and then the Faustmann formula was used to calculate LEVs under different conditions. We found that the difference in the values of the growth rate of the stand volume and the discount rate affected the direction of the impact of initial planting density on the optimal economic rotation. If the value of the growth rate of the stand volume exceeded that of the discount rate, then the initial planting density had a negative impact on optimal economic rotation and vice versa. In addition, the quality effect, which means the shift in diameter class to a higher value attributed to the initial planting density, determined the extent of the impact of the initial planting density on the optimal economic rotation. The proportion of large-sized timber increased at a faster pace in accordance with the age of the stand in stands where the planting density was low compared with the proportion of such timber in stands with a higher initial planting density. The corresponding net stumpage price difference resulted in significant differences in LEVs. We concluded that a low-density stand of China fir was a preferred planting option for obtaining the highest LEV. [ABSTRACT FROM AUTHOR]