Explore the vast range of titles available.

In mountain ecosystems, the native altitude acclimation and transplantation altitude response strategies of plant seedlings may provide theoretical guidance and strong evidence for addressing the continuous reduction of species' suitable habitats caused by global changes. However, our understanding of the adaptation to native altitude, altitude gradient responses, and underlying mechanisms of native mountain tree species in North China is still unclear. We designed a field experiment in mountainous areas where seedlings from different provenance altitudes (low altitude: 1600 m; high altitude: 2400 m) were transplanted to four typical altitudes. By measuring 18 functional trait indicators related to physiology, leaf characteristics, and nutrients, we attempted to reveal the adaptation of Picea asperata to native altitude and the differential responses and mechanisms to altitude changes. The results showed that: (1) Native altitude regulated the seedling's photosynthetic strategy (Pn), water strategy (WUE, gsw), morphological strategy (SLA), and nutrient storage (N), but did not affect leaf structure (AvgPA, AvgSL, AvgSW) or carbon storage; (2) Seedlings adapted to altitude changes by altering nutrient storage (NSC, Sugar, Protein) and leaf morphology (AvgPA, AvgSL, AvgSW, SLA); (3) Low-altitude seedlings of Picea asperata exhibited environmental dynamic plasticity and achieved coordinated growth of physiological functions, leaf morphology, and carbon storage at 1900 m (the optimal altitude); (4) High-altitude seedlings showed advantages in their native environment, but their adaptability decreased with decreasing transplantation altitude, reflecting the adaptation to native environment conditions; (5) Random forest model and PLS-PM confirmed that low-altitude seedlings tended to adjust leaf morphology to regulate leaf nutrients and photosynthetic physiological functions, while high-altitude seedlings regulated physiological functions by adjusting leaf nutrient changes. Seedlings from different provenance altitudes had differential adaptation pathways and regulatory strategies in response to altitude changes.

Autotrophic carbon-fixing microbes can assimilate atmospheric carbon dioxide into biomass via the Calvin–Benson–Bassham (CBB) cycle (their primary carbon fixation pathway), thereby reinforcing soil carbon sequestration in the plantation ecosystem; however, the succession of RubisCO-harboring microbial communities across stand ages remains poorly understood. Here, we investigated the community succession of microbes carrying the gene encoding RubisCO, a key enzyme in the CBB cycle, across a stand-age chronosequence in a Picea asperata plantation ecosystem. Our results revealed a progressive decrease in microbial α-diversity and a significant restructuring of community composition with increasing stand age, characterized by an enrichment of Proteobacteria and a concomitant depletion of Actinobacteria. While the Shannon–Wiener index was most strongly correlated with soil total nitrogen content, redundancy analysis identified soil pH as the predominant environmental driver of community turnover, a relationship that was found to be threshold-dependent, with substantial community shifts occurring in response to pH variations of 0.5 to 1.0 units. These findings suggest that sustaining the diversity of RubisCO-harboring microbes in older stands—a process potentially enhanced by soil nitrogen management—provides a viable strategy for augmenting the carbon sequestration capacity of managed forests through targeted microbiome regulation.

The interactive effects of environmental heterogeneity caused by forest gaps and ectomycorrhizae on fungal community characteristics remain insufficiently explored. To address this knowledge gap, we established a three-year field manipulation experiment in a Picea asperata (Picea asperata Mast.) plantation located in the subalpine region of western Sichuan, China. Growth bags with three mesh sizes—1000 μm (allowing ectomycorrhizae and hyphae), 48 μm (excluding ectomycorrhizae), and 1 μm (excluding both)—were placed across forest gaps (closed canopy, gap edge, and gap center) to investigate how gap disturbances influence soil fungal communities via changes in ectomycorrhizal and hyphal turnover alongside soil physicochemical properties. Soil fungal α-diversity was significantly lower under closed-canopy conditions than at forest gap centers and remained unaffected by ectomycorrhizal and hyphal treatments. Particularly, species diversity increased by 9%, and phylogenetic diversity increased by 10% in forest gap centers compared to the closed canopy. In contrast, soil fungal β-diversity responded to both ectomycorrhizal/hyphal treatments (R2 = 0.061; p = 0.001) and forest gap positions (R2 = 0.033; p = 0.003). Pairwise comparative analyses revealed significant distinctions between treatments, concurrently excluding ectomycorrhizal and hyphal treatments versus other experimental treatments, as well as between closed-canopy conditions and forest gap centers. The fungal community was dominated by four major phyla: Ascomycota (25.6%–71.0%), Basidiomycota (17.7%–43.7%), Mortierellomycota (1.4%–24.5%), and Rozellomycota (0.4%–2.9%), the relative abundances of which were unaffected by either ectomycorrhizal/hyphal treatments or forest gap positions. The biomass of ectomycorrhizal and saprotrophic fungi showed no significant response to ectomycorrhizal/hyphal treatments. Notably, the exclusion of ectomycorrhizae and hyphae enhanced the significant correlations between fungal community characteristics and soil physicochemical properties. Hierarchical partitioning analysis revealed that the soil water content (SWC) and dissolved organic carbon content were the key determinants of soil fungal community characteristics beneath closed-canopy conditions. In contrast, at forest gap edges and centers, the fungal communities were predominantly shaped by the SWC and dissolved carbon and nitrogen contents. This study highlights the impacts of forest gap disturbances and ectomycorrhizal treatments on soil fungal communities, offering valuable insights for the sustainable management and biodiversity conservation of subalpine forest ecosystems.

Understanding the variations in soil and plants with stand aging is important for improving management measures to promote the sustainable development of plantations. However, few studies have been conducted on the dynamics of stoichiometric traits and carbon (C), nitrogen (N), and phosphorus (P) pools across Picea asperata Mast plantations of different ages in subalpine regions. In the present study, we examined the stoichiometric traits and C, N, and P stocks in different components of three different aged (22-, 32-, and 42-year-old) P. asperata plantations by plot-level inventories. We hypothesized that the stoichiometric traits in mineral soil could shape the corresponding stoichiometric traits in soil microbes, tree roots and foliage, and the C, N, and P stocks of the total P. asperata plantation ecosystem would increase with increasing stand age. Our results show that the N:P ratio in mineral soil was significantly correlated with that in tree foliage and herbs. Additionally, the C:N ratio and C:P ratio in mineral soil only correlated with the corresponding stoichiometric traits in soil microbes and forest floor, respectively. Both the fractions of microbial biomass C in soil organic C and microbial biomass N in soil total N decreased with increasing stand age. The C, N, and P stocks of the total ecosystem did not continuously increase across stand development. In particular, the P stock of the total ecosystem exhibited a trend of increasing first and then decreasing. The aboveground tree biomass C accounted for more than 55% of the total ecosystem C stock regardless of stand age. In contrast, mineral soil and forest floor were the major contributors to the total ecosystem N and P stocks in all stands. This study suggested that all three different stands were N limited, and the stoichiometric homeostasis in the roots of P. asperata was more stable than that in the foliage. In addition, the soil microbial community assembly may change with increasing stand age for P. asperata plantations in the subalpine region.

Significant CO2 fluxes from snow-covered soils occur in cold biomes. However, little is known about winter soil respiration on the eastern Tibetan Plateau of China. We therefore measured winter soil CO2 fluxes and estimated annual soil respiration in two contrasting coniferous forest ecosystems （a Picea asperata plantation and a natural forest）. Mean winter soil CO2 effluxes were 1.08 μmol m-2 s-1 in the plantation and 1.16 μmol m-2 s-1 in the natural forest. These values are higher than most reported winter soil CO2 efflux values for temperate or boreal forest ecosystems. Winter soil respiration rates were similar for our two forest ecosystems but mean soil CO2 efflux over the growing sea- son was higher in the natural forest than in the plantation. The estimated winter and annual soil effluxes for the natural forest were 176.3 and 1070.3 g m-2, respectively, based on the relationship between soil respiration and soil temperature, which were 17.2 and 9.7 % greater than their counterparts in the plantation. The contributions of winter soil respiration toannual soil efflux were 15.4 % tor the plantation and 16.5R for the natural forest and were statistically similar. Our results indicate that winter soil CO2 efflux from frozen soils in the alpine coniferous forest ecosystems of the eastern Tibetan Plateau was considerable and was an important component of annual soil respiration. Moreover, reforesta- tion （natural coniferous forests were deforested and refor- ested with P. asperata plantation） may reduce soil respiration by reducing soil carbon substrate availability and input.

Increasing warming and drought intensity and frequency have led to profound impacts on forest ecosystems around the world. However, few studies have assessed the impacts of climate change on the alpine forests of different tree species at the regional scale on the eastern Tibetan Plateau (TP). We established 40 standard tree ring width chronologies based on 2137 cores from 1161 trees for five conifer species on the Gannan Plateau, located in eastern TP. Climate data from CRU grids are employed to study the relationships between radial growth and climate factors at each site during a common period of 1961–2019. A mixed-effects model is used to disentangle the relative contributions of elevation and species on the relationships between tree radial growth and climatic variables. The results highlight that tree growth responses to climate varied between species, which mainly results from species distribution being determined by elevation. Specifically, tree growth at higher elevations is mainly constrained by low temperature in the growing season, while drought is the controlling factor limiting tree growth at lower elevations. Moreover, elevation plays a more important role in determining the tree growth response to climate than species. The radial growth of Picea purpurea and Abies fargesii at higher elevations might benefit from future warming due to a positive correlation with temperature in the growing season, which might promote an upward shift in species distribution. While increasing warming and drought intensity may restrict tree growth of Picea asperata, Picea wilsonii, and Pinus tabulaeformis or even cause tree mortality at lower elevations, this may lead to future species composition changes and distribution range constriction.

Soil microbial biomass and composition are affected by resource supply and water availability. However, the response of soil microbial communities to nitrogen fertilization under different water availability conditions is unclear. Therefore, this study conducted a 6-year pot experiment comprising five watering regimes (40%, 50%, 60%, 80%, and 100% of field capacity (FC)) and three nitrogen fertilization levels (NH 4 NO 3 solution; 0 [N0], 20 [N1], and 40 [N2] g N m −2  year −1 ) to investigate soil microbial biomass, composition, and properties. The results indicated that soil microbial biomass and composition were more strongly affected by nitrogen fertilization compared with water regime. Nitrogen fertilization increased soil microbial biomass and altered soil microbial community composition, especially under low soil water availability. Soil microbial biomass was positively linearly associated with soil water regimes under N0, whereas it responded polynomially to soil water regimes under N1 and N2. The maximal soil microbial biomass was observed at FC80 for N1 and FC60 for N2. Furthermore, the biomass of soil microbial groups with high nitrogen and carbon acquisition ability as well as the enzyme activities of carbon and nitrogen cycling (β-1,4-glucosidase and β-1,4-N-acetyl-glucosaminidase, respectively) were stimulated by nitrogen fertilization. Soil microbial biomass was affected directly by nitrogen fertilization and indirectly by nitrogen and water regimes, via altering soil pH, dissolved inorganic nitrogen (NH 4 + -N and NO 3 − -N) concentration, and soil organic carbon concentration. This study provides new insights into the effect of interaction between soil nitrogen and water availabilities on soil microbial biomass, composition, and its underlying mechanism. Graphical abstract

Soil labile organic carbon (LOC) responds rapidly to environmental changes and plays an important role in carbon cycle. In this study, the seasonal fluctuations in LOC, the activities of carbon-cycle related enzymes, and the bacterial and fungal communities were analyzed for soils collected from two forests, namely Betula albosinensis (Ba) and Picea asperata Mast . (Pa), in the Qinling Mountains of China. Results revealed that the seasonal average contents of microbial biomass carbon (MBC), easily oxidized organic carbon (EOC), and dissolved organic carbon (DOC) of Pa forest soil were 13.5%, 30.0% and 15.7% less than those in Ba soil. The seasonal average enzyme activities of β-1,4-glucosidase (βG), and β-1,4-xylosidase (βX) of Ba forest soils were 30.0% and 32.3% higher than those of Pa soil while the enzyme activity of cellobiohydrolase (CBH) was 19.7% lower. Furthermore, the relative abundance of Acidobacteria was significantly higher in summer than in winter, whereas the relative abundance of Bacteroidetes was higher in winter. Regarding the fungal communities, the relative abundance of Basidiomycota was lowest in winter, whereas Ascomycota predominated in the same season. In addition, the soil LOC was significantly positively correlated with the CBH, βG and βX activities. Changes in LOC were significantly correlated with Acidobacteria , Bacteroidetes and Basidiomycota . We conclude that the seasonal fluctuations in forest soil LOC fractions relied on carbon cycle-associated enzymatic activities and microorganisms, which in turn were affected by climatic conditions.

Pine wilt disease was first discovered in Dongtang town, Liaoning Province, China, in 2017. However, no record of Monochamus alteratus existed in Fengcheng, where M. saltuarius is an indigenous insect, and no experimental evidence has thus far indicated that M. saltuarius can transport the Bursaphelenchus xylophilus in China. In this study, we investigated whether M. saltuarius is a vector of B. xylophilus in China. On the sixth day after eclosion, beetles began to transmit nematodes into the twigs. The transmission period of nematodes is known to be able to last for 48 days after beetle emergence. In laboratory experiments, M. saltuarius fed and transmitted B. xylophilus not only on pines but also on other non-Pinus conifers. The non-Pinus conifers preferred by M. saltuarius for feeding are Picea pungens, Picea asperata, and Abies fabri. The experimental results show that M. saltuarius functions as a vector of B. xylophilus in northeast China.

PurposeSoil nematodes are among the most important fauna in soils and participate actively in soil ecological processes. However, whether and how soil nematodes are involved in the effects of tree species type on soil fertility remain unclear, especially during subalpine forest secondary succession.MethodsA monoculture pot experiment of two broadleaf (Betula platyphylla and Betula albosinensis) and two coniferous (Picea asperata and Abies faxoniana) trees, using sterilized soils inoculated with unsterilized soils beneath dominant plants from different successional stages, was conducted in a greenhouse. After a period of plant growth, soil nematode communities and soil fertility in each pot were investigated.ResultsSignificant differences were noted in nematode community composition under the broadleaf and coniferous trees. Coniferous trees accumulated more abundant microbivores and omnivore-predators than broadleaf trees. Moreover, the contrasting effects of tree species type on soil nematode communities were associated with successional stages, with the greatest differences noted in the early successional stages. In addition, soil nematodes might play a significant mediating role in the effects of broadleaf and coniferous trees on soil fertility. However, the indirect regulatory effects induced by soil nematodes weakened with the successional stages.ConclusionOverall, our study suggested that tree species type might affect soil fertility by regulating soil nematode communities across successional stages. Compared with broadleaf trees, more abundant microbivores under coniferous trees might contribute to the improvement of soil nitrogen mineralization but not to the increase in soil carbon storage, which might be limited by new carbon input into soils.