Search Results (57)

Ecological restoration has increasingly been employed to reverse land degradation and increase carbon (C) sink, especially in ecologically fragile karst areas. Microbial necromass carbon (MNC) constitutes a critical pool within soil organic carbon (SOC), contributing substantially to long-term C sequestration through mineral stabilization. However, its distribution patterns across soil profiles and grassland restoration stages in karst areas remain unclear. To address this knowledge gap, the contents of bacterial necromass C (BNC), fungal necromass C (FNC), and their contributions to SOC were estimated based on glucosamine and muramic acid contents across the soil profile (0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm) for four subalpine restoration stages (grazing enclosure for 5, 11, 17, and 25 years) in the karst region. Our findings demonstrated that both soil depth and grassland restoration stages effectively influenced the BNC and FNC contents. On average, the soil BNC, FNC, and total MNC at the depth of 80–100 cm reduced by 70.50%, 59.70%, and 62.18% compared with in topsoil (0–20 cm), respectively. However, the FNC/BNC ratio gradually increased with the increase in soil depth, which was 43.15% higher at 80–100 cm soil depth than in topsoil, suggesting that the accumulation efficiency of FNC was higher compared to BNC in the deep soil. The BNC, FNC, and MNC were positively correlated with the grassland restoration stage, while FNC/BNC ratio had a negative relationship with the restoration stage (R² = 0.45, p < 0.001). FNC contributed significantly more to SOC (28.6–36.4%) compared to BNC (7.7–9.9%) at all soil depths, indicating that soil fungal necromass has an essential effect on SOC sequestration. The results of the random forest model and distance-based redundancy analysis identified that pH, soil water content, and dissolved organic carbon were the three most essential predictors for the contribution of MNC to SOC. Our study highlights the importance of microbial necromass to SOC accumulation, providing significant scientific implications for the C pool management during the restoration of degraded grasslands in karst regions. Full article

Treelines are advancing upward on mountain slopes due to climate warming and reduced grazing intensity. However, the effects of initial vegetation changes on soil C, N, and P retention, microbial biomass, and catabolic diversity in the subalpine meadows during the early stages of treeline shifts remain poorly understood. This research aimed to better understand the direction and drivers of microbial processes related to C, N, and P cycles in the soil of subalpine natural and grazed meadows, with treatments involving meadow grasses alone (GR, control) and as a mixture with forest litter, specifically birch leaves (BLs), in a one-year microcosm experiment. The addition of BLs with GR resulted in a 12–67% decrease in the retention of C, N, and P in soil microbial biomass, but an 8–9% increase in catabolic diversity compared to the control. The most pronounced effect was observed in the N content of the soil microbial biomass (MBN) for both land uses. The increased proportion of recalcitrant plant residue fractions (acid-insoluble and non-polar extractables) contributed to the decrease in soil MBN content. This shift also reduced the microbial metabolic response to carbohydrates in total substrate-induced respiration, leading to a more balanced and catabolically diverse microbial community. These results improve our understanding of the early response of C, N, and P cycling in mountain soils to treeline shifts mediated by climate warming. Full article

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. Full article

Studying the altitudinal variation and driving factors of soil acid phosphomonoesterase (ACP) activity in subalpine regions is crucial for understanding nutrient cycling processes within mountainous ecosystems. This study focused on fir (Abies fabri (Mast.) Craib) forests located at three altitudes (2781 m, 3044 m, and 3210 m) on the eastern slope of Mt. Gongga in southwest China. We measured soil ACP activity alongside soil climate, nutrients, and microorganisms at various depths and elevations to investigate how these factors influence ACP activity. The results indicated that in the organic matter horizons (Oe and Oa horizons), ACP activity gradually decreased with elevation. However, the surface mineral horizon (A horizon) did not show a decline in ACP activity with increasing elevation, which could be attributed to significantly lower ACP activity recorded at the 2781 m sample site compared to the 3044 m site. Variance partitioning analysis revealed that among soil climate, nutrients, and microorganisms, soil nutrients had the most substantial impact on ACP activity across all horizons, with a particularly high contribution of 89.4% observed in the A horizon. Random forest model analysis further demonstrated that soil total carbon (TC) played a crucial role in determining ACP activity in the Oe and Oa horizons, with importance values of 8.5% and 7.3%, respectively. Additionally, soil total nitrogen (TN) was identified as the primary factor influencing ACP activity in the A horizon, with an importance value of 12.6%. Furthermore, soil ACP activity was positively regulated by the soil TC:TP and TN:TP ratios, indicating a stoichiometric control of ACP activity in the Abies fabri (Mast.) Craib forests on Mt. Gongga. Full article

Subalpine forests provide crucial ecosystem services and are increasingly threatened by human alterations like bare-cut slopes from highway construction. External soil spray seeding (ESSS) is often employed to restore these slopes, but the cement it introduces can negatively affect soil fungi, which are vital for the ecological sustainability of restored slopes. Despite previous extensive discussions about ESSS-restored slopes, fungal dynamics and their underlying ecological mechanisms during ESSS-based restorations still remain elusive. Here, we conducted a 196-day simulation experiment using natural soils from a subalpine forest ecosystem. By using nuclear ribosomal internal transcribed spacer (ITS) sequencing, we revealed soil fungal dynamics and their ecological mechanisms during simulated ESSS-based restorations. Results showed a decline in fungal α-diversity and significant shifts in community structures from the initial day to day 46, followed by relative stabilities. These dynamics were mainly characterized by ectomycorrhizal, plant pathogenic, and saprotrophic fungi, with ectomycorrhizal fungi being depleted, while saprotrophic and pathogenic fungi showed enrichment over time. Shifts in nitrate nitrogen (${\mathrm{NO}}_3^{-}$−N) content primarily regulated these dynamics via mediating homogeneous selections. High ${\mathrm{NO}}_3^{-}$−N levels at later stages (days 46 to 196, especially day 46) might exclude those poorly adapted fungal species, resulting in great diversity loss and community shifts. Despite reduced homogeneous selections and ${\mathrm{NO}}_3^{-}$−N levels after day 46, fungal communities did not show a recovery but continued to undergo changes compared to their initial states, suggesting the less resilient of fungi during ESSS-based restorations. This study highlights the need to manage soil ${\mathrm{NO}}_3^{-}$−N levels for fungal communities during ESSS-based restorations. It provides novel insights for maintaining the ecological sustainability of ESSS-restored slopes and seeking new restoration strategies for cut slopes caused by infrastructure in subalpine forests. Full article

To explore the role of leaching in mountainous nutrient cycling, we investigated the altitudinal distribution of soil carbon (C), nitrogen (N), and phosphorus (P) in the subalpine coniferous forest ranging from 2628 to 3044 m on the eastern slope of Mt. Gongga. The results revealed that concentrations of C and N, as well as the atomic ratios of C:N and N:P, showed no significant difference among the sampling sites (p > 0.05) in O horizons. The concentrations of P in O horizons increased gradually with altitude. In contrast, notable variations in C, N, and P concentrations and stoichiometry were observed in the mineral horizons. Lower concentrations of C, N, and P were found in A horizons, while higher contents were present in B and C horizons compared to previous studies. Additionally, results of the random forest model indicated that C and N concentrations in the O, B, and C horizons, as well as P concentration in the B horizons, were primarily influenced by Fe_ox concentrations. This suggested that these nutrients leached from O horizons and accumulated in B and C horizons alongside Fe_ox. Except for C:N ratios in the O horizon, the C:N, C:P, and N:P ratios in the O, B, and C horizons were mainly affected by concentrations of Fe_ox or Al_ox. These results underscored the substantial impact of leaching processes on the spatial distribution of soil C, N, and P, ultimately leading to changes in the gradient distribution of soil C:N:P stoichiometry. Specifically, the C:N ratio in the mineral horizons at the 2781 m site was significantly higher compared to other sites (p < 0.05), indicating a greater movement of C relative to N. The C:P and N:P ratios in the B horizon at the 2781 m site were notably higher than at other sampling sites (p < 0.05). Conversely, the N:P ratio in the A horizon at the 2781 m site was relatively low. Furthermore, concentrations of C and N in the B horizon at the 2781 m site were significantly higher than in other sampling points, while P concentrations were notably lower (p < 0.05). This suggested a more pronounced downward leaching of C and N compared to P at the 2781 site, indicating stronger leaching effects. Overall, this study emphasizes the significant influence of leaching processes on the spatial distributions of soil C, N, and P in subalpine coniferous forests in Southwest China. Full article

Fire in the Northern Alps is comparatively rare. Yet, previous human-ignited fire events in subalpine forests up to the treeline have triggered severe fire damage to vegetation and soil. Here, we investigate post-fire vegetation dynamics in the Northern Limestone Alps about 80 years after disturbance. We observed higher species richness in burned compared to unburned vegetation and clearly distinct floristic communities emerging after fire-driven forest removal, with several alpine specialist species uniquely found in the burned subalpine sites. The functional composition of vegetation was also distinct, with higher relative forb cover in burned plots. This difference was likely driven by disturbance-related environmental changes, such as increased light availability, offering safe sites for subalpine and alpine species. Due to a general lack of tree encroachment, we consider this a case of arrested succession after fire. We conclude that the recovery of fire-affected subalpine forests is modulated by complex interactions of climatic and biotic filters producing extreme site conditions, controlling the recolonization of the disturbed areas by forest species while providing safe sites for the establishment of a rich subalpine and alpine low-statured flora. The coupling of disturbance and abiotic filters makes high-elevation treeline ecotones very vulnerable to climate change. Full article

The main objective of this study is to investigate the supply of ecosystem services (ESs) within peri-urban watersheds (PUWs) across Greece, utilizing earth observation (EO) data and empirical models. To achieve these goals, several open-access geospatial datasets were utilized and processed within a GIS environment. Specifically, the supply of soil conservation and water retention services was assessed at the watershed scale. The results indicates that the supply soil conservation service withing the examined PUWs range from 44.41 t ha⁻¹ y⁻¹ to 441.33 t ha⁻¹ y⁻¹ with an average value of 161.99 t ha⁻¹ y⁻¹. Water retention services vary from 35.09 to 154.63 mm within the PUWs, with an average of 91.45 mm. Additionally, the variation in ES values across distinct altitudinal zones and ecosystem types provides useful insights for implementing protection and management measures. It is evident from the analysis that the soil conservation service gradually increases with elevation, with alpine and subalpine areas exhibiting the highest values. Moreover, mountainous and semi-mountainous regions demonstrate higher values compared to the estimated average soil conservation services of the entire study area. Furthermore, the provision of water retention services varies across different altitudinal zones. Specifically, the mountainous and semi-mountainous areas exhibit the highest values, followed by the subalpine and hilly regions, while lower values are observed in the lowland and alpine regions. The analysis also reveals distinct patterns in ecosystem services across various ecosystem types within the PUWs. Woodland and forest, along with heathland and shrubs, demonstrate higher values in terms of both soil conservation and water retention services. Our findings contribute to understanding the dynamics of ESs in PUWs, highlighting their significance for sustainable land management, and informing policy decisions aimed at preserving ecosystem health and resilience. Full article

Many plant species are well-adapted to historical fire regimes. An increase in the severity, frequency, and extent of wildfires could compromise the regenerative capacity of species, resulting in permanent shifts in plant diversity. We surveyed extant vegetation and soil seed banks across two forest types with contrasting historical fire regimes—Shrubby Dry Forest (fire return interval: 10–20 years) and Sub-Alpine Woodland (50–100 years). Over the past 20 years, both forests have been subject to repeated, high-severity wildfires at intervals significantly shorter than their historical return intervals. We examined the soil seed bank response to fire-cued germination, and whether the plant diversity in soil seed banks and extant vegetation demonstrated similar responses to short-interval, high-severity wildfires. The soil seed bank demonstrated a positive response to heat in combination with smoke, and for the Sub-Alpine Woodland, this was limited to sites more frequently burnt by fire. With an increase in fire frequency, there was a decline in species richness and Shannon’s Diversity and a shift in species composition in both extant vegetation and the soil seed bank. The fire frequency effects on the relative richness of trait associations were restricted to the Shrubby Dry Forest, and included an increase in short-lived obligate seeders, wind-dispersed species, and ant-dispersed shrubs in burnt relative to long unburnt sites in both extant vegetation and the soil seed bank. Graminoids were the most abundant component of the soil seed banks of Sub-Alpine Woodlands, and this increased with more frequent fire, with a similar trend (p = 0.06) in extant vegetation. Clear shifts in plant diversity in both soil seed banks and extant vegetation in forest types with contrasting historical fire regimes suggest that emerging fire regimes are pushing ecosystems beyond their historical range of variability, including potentially more flammable states and a decline in the buffering capacity of soil seed banks. Full article

Abundant and rare bacteria exhibit unequal responses to environmental changes and disturbances, potentially resulting in differential contributions to the altitudinal characteristics of total community in natural and disturbed soils. Although the altitude patterns of soil bacteria have been widely studied, it remains unclear whether these patterns are consistent among bacteria with varying predominance levels, and which subpopulation contributes more to maintaining these patterns in natural and disturbed subalpine forest soils. In this study, we collected 18 natural subalpine forest soil samples and 18 disturbed ones from three altitudes (2900 m a.s.l., 3102 m a.s.l., and 3194 m a.s.l.) along the Wenma highway in Miyaluo, Lixian, Sichuan, Southwest China. By partitioning total bacterial communities based on species predominance, we found that bacteria with higher predominance levels tended to exhibit altitude patterns (α-diversity, community structure, and functional redundancy) similar to those of total bacteria in both natural and disturbed subalpine forest soils, although they only occupied a small portion of the community. Abundant bacteria might play critical roles in maintaining the regional ecological characteristics of total community across the altitude gradient, while the rare and hyper-rare ones might contribute more to local diversity and functional redundancy. In natural soils, the altitude patterns of α-diversity inferred from total, abundant, and rare bacteria were mainly shaped by ${\mathrm{NO}}_3^{-}$-N, while soil conductivity mainly drove the altitude patterns of α-diversity inferred from hyper-rare bacteria. Additionally, the community structures of total, abundant, rare, and hyper-rare bacteria were mainly shaped by ${\mathrm{NO}}_3^{-}$-N, while the altitude patterns of functional redundancy inferred from total, abundant, and rare bacteria were mainly shaped by soil conductivity in natural soils. In disturbed subalpine forest soils, the influences of ${\mathrm{NO}}_3^{-}$-N for the altitude patterns of α-diversity and community structure, and those of soil conductivity for functional redundancy, were relatively weak in total, abundant, rare, and hyper-rare bacteria. This study examined the roles of bacteria with varying predominance levels in maintaining the altitude pattern of bacteria in both natural and disturbed subalpine forest soils, providing novel insights for devising strategies to conserve biodiversity and ecologically restore disturbed soils in subalpine ecosystems. Full article

At the southeastern periphery of the Tibetan Plateau, the subalpine ecosystem hosts grasses as some of the most substantial species. However, the community and function of arbuscular mycorrhizal fungi (AMF) around the rhizospheres of grasses in the subalpine zone are still poorly understood. In the present study, 28 soils and 11 species of dominant grasses collected from four microhabitats (shrubland, grassland, woodland, and forest) in the subalpine zone of northwestern Yunnan, China, were used to investigate the AMF community by Illumina MiSeq high-throughput sequencing technology as well as nutrient contents. Among the four microhabitats, the maximum soil nutrient levels around the rhizospheres of grasses were observed in woodland. The nitrogen, phosphorus, and potassium concentrations in Dactylis glomerata shoots were significantly higher than those in the other 10 grass species. The AMF diversity of grassland in summer was substantially greater than that of the other three microhabitats (p < 0.05). Discrepancies were observed within a given plant species across microhabitats; for example, in summer, the nitrogen concentration in the shoot of Iris tectorum in woodland was significantly higher than that in both forest and shrubland (p < 0.05). A total of eight genera were detected in the AMF communities, which were dominated by Glomus, with a relative abundance of 45.4%–94.4% in summer and 60.5%–84.3% in winter. Moreover, the abundance of Glomus was significantly positively correlated with the content of alkali-hydrolyzable nitrogen in soil and nitrogen in grasses according to the Mantel test. As a critical nutrient element in soil, nitrogen is beneficial for plant growth. Thus, these results provide a better understanding of the resilience of soil AMF community and the ecological adaptability of grasses in the subalpine ecosystems of northwestern Yunnan. Full article

Soil fungi often operate through diverse functional guilds, and play critical roles in driving soil nutrient cycling, organic matter decomposition and the health of above-ground vegetation. However, fungal functional guilds at the early-stage restoration of disrupted subalpine forest soils remain elusive. In the present study, we collected 36 soil samples along an altitudinal gradient (2900 m a.s.l., 3102 m a.s.l., and 3194 m a.s.l.) from cut slopes (CS) (from Wenma highway) and natural soils (NS) at the Miyaluo of Lixian County, Southwest China. By applying nuclear ribosomal internal transcribed spacer (ITS) sequencing, this study revealed the ecological characteristics of fungal functional guild in the early-stage restoration of cut slope soils. The results showed that the predicted prevalence of ectomycorrhizal fungi decreased, while plant pathogens and arbuscular mycorrhizal fungi increased in CS. In the high-altitude regions (3102 m a.s.l. and 3194 m a.s.l.), the differences in communities between natural and cut slope soils were more pronounced for total soil fungi, soil saprotroph, litter saprotroph, arbuscular mycorrhizal fungi and ectomycorrhizal fungi, in contrast to the low altitude communities (2900 m a.s.l.). An opposite pattern was evident for plant pathogens. Variations in the differences of both soil properties (mainly soil pH) and community assembling processes (e.g., heterogeneous selection, dispersal limitation and drift) between natural and cut slope soils across the altitudinal gradient likely shaped the shifting patterns of community difference. This study provides valuable insights for devising restoration approaches for cut slopes in subalpine forest ecosystems, emphasizing the importance of taking soil fungal functional guilds into account in evaluating the restoration of cut slopes, and underscoring the necessity for increased attention to the restoration of soil fungi in cut slopes at the high-altitude ecosystems. Full article

Background: Investigations that are focused on arbuscular mycorrhizal fungus (AMF) biodiversity is still limited. The analysis of the AMF taxa in the North Caucasus, a temperate biodiversity hotspot, used to be limited to the genus level. This study aimed to define the AMF biodiversity at the species level in the North Caucasus biotopes. Methods: The molecular genetic identification of fungi was carried out with ITS1 and ITS2 regions as barcodes via sequencing using Illumina MiSeq, the analysis of phylogenetic trees for individual genera, and searches for operational taxonomic units (OTUs) with identification at the species level. Sequences from MaarjAM and NCBI GenBank were used as references. Results: We analyzed >10 million reads in soil samples for three biotopes to estimate fungal biodiversity. Briefly, 50 AMF species belonging to 20 genera were registered. The total number of the AM fungus OTUs for the “Subalpine Meadow” biotope was 171/131, that for “Forest” was 117/60, and that for “River Valley” was 296/221 based on ITS1/ITS2 data. The total number of the AM fungus species (except for virtual taxa) for the “Subalpine Meadow” biotope was 24/19, that for “Forest” was 22/13, and that for “River Valley” was 28/24 based on ITS1/ITS2 data. Greater AMF diversity, as well as number of OTUs and species, in comparison with that of forest biotopes, characterized valley biotopes (disturbed ecosystems; grasslands). The correlation coefficient between “Percentage of annual plants” and “Glomeromycota total reads” r = 0.76 and 0.81 for ITS1 and ITS2, respectively, and the correlation coefficient between “Percentage of annual plants” and “OTUs number (for total species)” was r = 0.67 and 0.77 for ITS1 and ITS2, respectively. Conclusion: High AMF biodiversity for the river valley can be associated with a higher percentage of annual plants in these biotopes and the active development of restorative successional processes. Full article

Aboveground biomass (AGB) is the most dynamic carbon pool in forest ecosystems and is sensitive to biotic and abiotic factors. Previous studies on AGB have mostly focused on tropical and temperate forests, while studies on AGB and its determinants in subalpine coniferous forests are lacking and the mechanisms are not yet clear. Here, we systematically investigated all woody plants in 630 subplots (20 m × 20 m) in the Wanglang Plot (25.2 ha) to explore the spatial distribution of AGB and the effects of topography, soil, and stand structure on AGB. The results showed that AGB varied remarkably among different subplots with an average of 184.42 Mg/ha. AGB increased significantly with aspect, soil organic matter, maximum DBH, and important value of spruce–fir, while it decreased significantly with slope, total phosphorus, and stem density. Stand structure exerted greater influences than topography and soil factors, and especially maximum DBH determines the variation of AGB. Our results are of great significance to accurately estimate and predict the productivity of this forest type, and can provide insights into the diversity maintenance of subalpine coniferous forests as well as the conservation and management of forest ecosystems. Full article

Humus forms and organic matter decomposition are influenced by climate, plants and soil decomposers. Yet, whether different humus forms could be experimentally linked to litter decomposition has still to be fully assessed. To assess the link between humus systems and organic matter decomposition, we worked in two regions of the Swiss Alps (Valais and Ticino) along elevational gradients by following a north/south exposure design. We quantified humus forms macrorests proportion types by the Ponge small-volume method and measured the decomposition of green tea and rooibos tea within the Parasystems and Terrosystems. We found that Parasystems and Terrosystems differed in tea decomposition rates, with a slower decomposition in Parasystems than in Terrosystems. We also observed that elevation, and hence, vegetation type (i.e., forest in the subalpine versus grassland in the alpine), drove humus form distribution, with Parasystems found in the alpine and subalpine in Ticino, while in Valais Parasystems were only found in the alpine and Terrosystems in the subalpine levels. Further analyses are however needed to identify other variables that best correlate with variation in decomposition processes within humus systems, such as soil decomposer community composition. Full article