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Phosphate-solubilizing bacteria (PSB) offer an eco-friendly approach to boost plant growth in soils low or deficient in phosphorus (P). In this study, we isolated 97 PSB strains from the soil around moso bamboo roots in Jiangxi Province, China. The RW37 strain was identified as Enterobacter soli through its physical characteristics and genetic sequencing. Our experiments revealed that RW37 could dissolve phosphate at levels exceeding 400 mg L−1 across a wide range of environmental conditions, including temperature (25–35 °C), pH levels (3.5–7.2), salinities (0–2.0%), and volumes of medium (1/5–3/5 of flask volume), showcasing its adaptability. Furthermore, RW37 showed remarkable phosphate-solubilizing abilities at various pH levels using different phosphate sources, with the highest capacity observed in a medium containing CaHPO4. This study also found a negative correlation between P-solubilizing capacity and fermentation broth pH, indicating that RW37 likely secretes organic acids to dissolve phosphate sources. Pot experiments demonstrated that applying RW37 significantly improved the plant height, biomass, root growth, and P uptake of moso bamboo seedlings in red soil. Our results highlight the potential of RW37 as an eco-friendly biofertilizer for subtropical bamboo forests. [ABSTRACT FROM AUTHOR]

Thinning and understory clearance are among the two most popular forest management practices carried out to improve stand productivity in subtropical plantations. Unfortunately, studies have not fully explored the single and combination effect of thinning and understory clearance on soil microbial properties. By conducting a field manipulation experiment in a subtropical moso bamboo (Phyllostachys edulis) plantation in Southern China, we assessed the effects of thinning, understory clearance, and their combination on soil microbial phospholipid fatty acids (PLFAs) three years after treatments were first applied. We also examined the changes in soil properties after thinning and/or understory clearance. Thinning decreased soil fungal and bacterial PLFAs, and consequently soil total microbial PLFAs due to the increased soil NH4+-N, and NO3−N concentrations. Understory clearance decreased soil pH and soil water content resulting in increased soil fungal PLFAs and the ratio of soil fungal to bacterial (F:B). In addition, thinning and understory clearance caused apparent interactive effects on soil total microbial PLFAs and bacterial PLFAs, and the negative influence of thinning on soil total microbial and bacterial PLFAs were partly compensated by understory clearance. These results suggest the contrasting and interactive effect of thinning and understory clearance should be considered to assess the changes of soil microbial community and ecological processes in subtropical moso bamboo (Phyllostachys edulis) plantations in southern China. [ABSTRACT FROM AUTHOR]

Bark is an essential component of tree branches, yet its role in controlling branch-leached dissolved organic matter (DOM) characteristics remains unknown in forests. Here, we collected branches (about 1.5 cm in diameter) of two evergreen coniferous trees, two deciduous broadleaf trees, and three evergreen broadleaf trees from a subtropical forest in southern China, and subsequently used a bark removal experiment to determine the effects of bark on branch-derived DOM quantity and bioavailability. Regardless of tree type, the presence of bark reduced tree branch-leached dissolved organic carbon (DOC), dissolved total nitrogen (DTN), and dissolved total phosphorus (DTP) productions. Moreover, DOC, DTN, and DTP productions leached from the branches containing bark were always much lower than the expected values summed from barks and the branches without bark. The presence of bark increased DOM aromaticity in the broadleaf tree branch leachates but reduced DOM aromaticity in the coniferous tree branch leachates. During 42 days of incubation, the presence of bark decreased broadleaf tree branch-leached DOM bioavailability and the relative increments of aromaticity, whereas the opposite trends were observed for the coniferous tree branch-leached DOM. Tree branch-derived DOM bioavailability correlated negatively with SUVA254 values, but exhibited no relationship with either DOC:DTN ratio or DOC:DTP ratio. These observations highlight that tree bark can prevent DOM leaching from branches and regulate branch-leached DOM bioavailability via its effect on DOM aromaticity in subtropical forests. [ABSTRACT FROM AUTHOR]

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]

Root nutrients are required for the growth and development of roots and shoots, which are closely related to soil quality and fruit productivity. In this study, trees of contrasting stand ages, including young, middle-aged, and old trees, were selected in field sites with common management practices in the navel orange (Citrus sinensis) orchards of Southern China. The fine root N decreased with soil depth and the fine root P was higher of old trees (1.82 g kg-1) than young (1.57 g.kg-1) and middle-aged trees (1.37 g. kg-1). Soil organic C, total N, and P generally increased with plant age in the rhizosphere and bulk soils, while reverse trend was found for sucrase and urease activities. Interestingly, acid phosphatase activity was much higher at a lower depth (202 and 82 g.kg-1 OC d-1 for rhizosphere and bulk soils, respectively) than at an upper depth (46 and 43 g.kg-1 OC d-1 for rhizosphere and bulk soils, respectively). In conclusion, root and soil nutrients generally increased with plant growth. Fine root N decreased while fine root P remained unchanged with soil depth due to the content and rhizosphere effect of index at different soil layers related to N and P, respectively. [ABSTRACT FROM AUTHOR]

In south China, eucalyptus plantations typically consist of a single-species overstory (a eucalyptus monoculture) and a dense understory of a dominant fern species. In the current study, we assessed the effects of four treatments [control (CK), understory removal (UR), tree removal (TR), and all-plant removal (PR)] on the abundances of soil nematode genera, which can provide insight into the ecological functions of understory plants and trees. Soil nematodes were sampled six times (once before and five times after treatments were implemented) at 0–5 and 5–10 cm soil depths. The temporal dynamics of nematode genera were analyzed by the principle response curves (PRC) method. At 0–5 cm depth, the abundances of most nematode genera rapidly increased shortly after vegetation removal but then gradually decreased; the effects of UR were stronger than the effects of TR. The results might be explained by the pulsed input of plant debris to soil and its subsequent depletion. At 5–10 cm depth, the nematode communities were relatively unaffected by vegetation removal within the first 162 days, but the abundances of most genera sharply decreased on day 258 and then sharply increased on day 379 (the last sampling time). The results indicated that most nematode genera, even r -selected genera, were sensitive to vegetation removal in the upper soil layer and that understory vegetation can greatly affect soil nematode communities and presumably soil food webs. The nematode genera Prismatolaimus and Diphtherophora may be good indicators of the effects of vegetation removal. The results increase our understanding of the relationships between soil nematode genera and forest plant communities and of how soil biota is affected by forest management practices. [ABSTRACT FROM AUTHOR]

Despite the importance of understory vegetation for ecosystem processes and functions, its contribution to the dynamics of phosphorus (P) fractions in decomposing litter has rarely been studied in subtropical plantations. Herein, by conducting an understory removal (UR) experiment in a moso bamboo (Phyllostachys edulis) plantation of South China, we assessed the effect of understory species on leaf litter mass loss and P fractions (inorganic P, sugar P, nucleic P, and residual P) of moso bamboo over a 12‐month incubation period. We also examined the effect of UR on soil physicochemical properties, as well as fungal and bacterial phospholipid fatty acids (PLFAs). Our results showed that UR reduced litter decomposition rate (6.0–12.4%), but exhibited no effect on total P remaining in decomposing litter. Furthermore, UR produced variable effects on the amounts of P fractions in decomposing litter. Despite no changes were observed in the amount of inorganic and sugar P fractions, UR accelerated nucleic P release (3.0–6.6%), and residual P immobilization (9.2–27.9%) in decomposing litter. Moreover, UR increased fungal PLFAs (8.0–44.9%) but decreased bacterial PLFAs (18.7–36.8%) in the soil, leading to an increase in fungal to bacterial PLFAs ratio (34.5–80.9%). The correlation analysis showed that accelerated litter nucleic P release after UR was mainly attributed to the increases in soil fungal PLFAs, while decelerated litter residual P release was mainly resulted from the increased soil fungal PLFAs and decreased soil bacterial PLFAs. These results indicate that understory vegetation can mediate the dynamics of litter P fractions via its effect on soil microbial composition in subtropical plantations and suggest that understory vegetation is crucial to maintain soil P availability in moso bamboo plantations. [ABSTRACT FROM AUTHOR]

Transforming plantation monocultures into sustainable, mixed-species forests that contain native species is an important goal in South China. The establishment of native species in Eucalyptus plantations is generally considered difficult, however, because of the potential allelopathic effects of Eucalyptus . In this study, a field trial with completely randomized block was conducted to determine the degree to which Eucalyptus litter and Eucalyptus roots limit the establishment of native trees in Eucalyptus plantations. Growth of seedlings of four native tree species ( Schima superba , Michelia macclurei , Cinnamomum burmannii , Cinnamomum camphora ) that were tested was inhibited by Eucalyptus roots. Seedling emergence was less sensitive than subsequent seedling growth to inhibition by Eucalyptus roots. In contrast, litter enhanced the emergence and growth of seedlings of most of the tested species ( Castanopsis chinensis , Elaeocarpus sylvestris , S. superba , Liquidambar formosana , C. burmannii , and C. camphora ), suggesting that retaining litter on the forest floor may promote the establishment and growth of native tree species in Eucalyptus plantations. We propose the following strategies for establishing native tree species in Eucalyptus plantations: (1) direct sowing of the native tree species C. chinensis , Castanea henryi , Erythrophleum fordii , and C. camphora ; (2) transplanting of E. sylvestris , S. superba , and Tsoongiodendron odorum , which had low germination rates but high seedling establishment rates; and (3) the exclusion of Eucalyptus roots via inter-row trenching to enhance the establishment of S. superba , L. formosana , C. burmannii , and C. camphora . [ABSTRACT FROM AUTHOR]

The application of quantifying phylogenetic information into measures of forest β-diversity is increasing for investigating the underlying drivers of community assembly along environmental gradients. In terms of assessing evolutionary inferences of community processes, a variety of plant DNA barcodes has been widely used in phylogenetic diversity measurements. However, relatively few studies have evaluated the effectiveness of DNA barcodes with using nuclear region in estimating phylogenetic β-diversity, particularly for communities in tropical or subtropical forests. In this study, we employed DNA barcodes combing with the nuclear region to construct the community phylogeny and examined the patterns of phylogenetic β-diversity of three mid-subtropical evergreen broad-leaved forests (EBLFs) in South China. Three phylogenetic construction methods were performed, including a Phylomatic-generated tree and two ML trees based on the combination of rbcL + matK + ITS with or without a constrained tree. Our results showed that the DNA barcodes including nuclear ITS constructed a highly resolved phylogenetic tree, but the application of a constrained tree had little influence on estimation of phylogenetic diversity metrics (mean pairwise distances and mean nearest taxon distances) based on branch lengths. Using both metrics and their standardized effect size metrics, we found that the patterns of phylogenetic β-diversity in mid-subtropical forests were non-random. There was a slight decline of phylogenetic β-diversity with increasing latitudes, but no trend was found along the altitude gradient. According to the analysis of variation partition, both environmental filtering and dispersion limitation could explain the variation of phylogenetic dissimilarity between communities in mid-subtropical EBLFs of China. Our results highlight the importance of neutrality and the niche conservatism in structuring the patterns of species diversity in subtropical woody communities. [ABSTRACT FROM AUTHOR]