Search Results (437)

Nitrogen (N)-fixing plants are commonly employed in the restoration of degraded terrestrial ecosystems due to their ability to increase soil N capital and boost ecosystem productivity. Given the close coupling between N and phosphorus (P) in soil, the effects of N-fixing plants on soil P fractions and availability in karst forests remain largely unexplored. Herein, we compared soil P pools, fractions, and availability in the rhizosphere and non-rhizosphere soils of N-fixing and non-N-fixing plants, and explored associated drivers, such as soil, microbial, and plant properties, in a subtropical karst forest. The results showed that the N-fixing plants increased total P, inorganic P, and available P in both the rhizosphere and non-rhizosphere soils. The nitrogen-fixing plants increased soil labile P (LP) and non-labile P (NLP), but decreased moderately labile P (MLP), particularly in the rhizosphere soils, due to transformations among different soil P fractions. Soil P fractions were primarily influenced by soil inorganic P, root and leaf N, and microbial biomass N in the N-fixing plant treatment, whereas soil inorganic P, dissolved organic carbon (DOC), and dissolved organic N (DON) were the key factors in the non-N-fixing plant treatment. Consequently, soil properties, microbial attributes, plant nutrients, and soil P fractions collectively exerted both direct and indirect effects to increase soil P availability in the N-fixing plant treatment. In contrast, soil P fractions directly and soil properties indirectly influenced soil P availability in the non-N-fixing plant treatment. Our results revealed the unique role of N-fixing plants in driving soil P availability in subtropical karst forests. These findings are essential for developing effective strategies for P nutrient management and guiding the selection of appropriate plant species for vegetation restoration in karst regions. Full article

This study analyzed the changes in landscape patterns and the ecological health status of karst plateau wetlands, providing valuable insights into their conservation. Using land cover data from 1996 to 2021, DEM, and Landsat series satellite imagery, this study employed landscape ecology methods and the pressure–state–response (PSR) model framework. A regional landscape grid was constructed, and 13 indicators were selected to establish an ecological health evaluation system for karst plateau wetlands. This allowed us to explore the spatiotemporal change characteristics of the landscape pattern and the ecological health of karst plateau wetlands. The results showed that over a 25-year period, farmland, grassland, and construction land areas have increased, whereas forested land areas have decreased. Water bodies remained relatively stable but showed a trend of transitioning into grassland. Unused land showed no significant change. Landscape analysis indicated that grasslands experience the highest rate of fragmentation, complex shapes, and greater heterogeneity, whereas water bodies have the lowest fragmentation, more regular shapes, and lower heterogeneity. Other landscape types exhibited moderate characteristics. Overall, the landscape of the study area exhibited high fragmentation, specific patch aggregation, moderate patch density, and low diversity. A comprehensive ecological health evaluation revealed that the wetland health value remained at an “unhealthy” level from 1996 to 2021. Although there was a brief improvement in 2010, effective long-term recovery was not achieved. Spatially, the proportion of “diseased” areas peaked in 2006, and most grid zones remained in an “unhealthy” state over the years, with none reaching the “healthy” standard. These findings highlight the severe challenges faced by the wetland ecosystem. Full article

The main dominant tree species of karst forest at the microtopography and the microhabitat scale were taken as the research object in this study, and the stoichiometric characteristics of different components and their influencing factors were analyzed in order to reveal the survival strategy of karst forest plants in harsh habitats and their mechanism of adaptation to complex terrain. The results showed that the nutrient distribution among different components of the plant was closely related to its organizational structure and functional attributes. The microtopography had a significant effect on plant nutrient accumulation. However, the effect of the microhabitat on plant stoichiometric characteristics was relatively small. Different ecological factors had various regulatory effects on the stoichiometric characteristics of plant components, among which the specific leaf area (SLA) was the most critical biological factor affecting the stoichiometric characteristics of new leaves. Leaf dry matter content (LDMC) had the greatest effect on mature leaves, litter, and branches, and the trunks were mainly affected by plant species. There are synergistic tradeoffs between different plant components, and the interaction between each element mainly shows antagonistic and synergistic effects. Plants adapt to the changes in the karst microtopography and microhabitat by adjusting resource allocation and structural and functional traits. In the upslope, shady slope, and semi-shady slope regions and slopes above 25°, the plants adopted a conservative strategy. In depressions, on sunny slopes, and on flat land, as well as on slopes below 25°, the resource acquisition strategy was adopted. This is the result of the interaction of biological and abiotic factors, which reflects the resource acquisition and nutrient allocation strategies of plants in different habitats, and it is also an mechanism of adaptation to a complex and changeable environment. Full article

Human-induced environmental changes threaten the functional stability of natural forest ecosystems. Understanding the dominant factors influencing both functional space and stability in extremely heterogeneous environments is crucial for elucidating the stability of heterogeneous forest ecosystems. Here, 30 forest dynamic plots were established along the successional pathway in Maolan National Nature Reserve in Southwest China. By measuring 15,725 stems across 286 distinct species’ six key plant functional traits, we constructed the key plant functional traits for functional space and quantified functional redundancy (FR) and functional vulnerability (FV) to represent functional stability, and we further utilized the line model and multiple linear regression model to explore the key biotic/abiotic indicators influencing functional stability along the successional pathway of degraded karst forests. Additionally, as the successional pathway unfolded, the contribution of the six plant traits to the overall functional space increased, from 59.85% to 66.64%. These traits included specific leaf area (SLA), leaf dry matter content (LDMC), leaf thickness (LT) and leaf nitrogen content (LNC), which played a crucial role in driving functional space. With the increasing species richness (FR), functional entities (p < 0.001) and FR (p < 0.001) increased, while FV (p < 0.01) decreased. The results also demonstrated a higher FR in degraded karst forests (FR > 2). However, over 51% of FEs consisted of a single species, with the majority of species clustered into a few functional entities (FEs), indicating an elevated level of FV in karst forests. Soil nutrient availability significantly influences the ecosystem’s functional stability, explaining 87% of FR variability and 100% of FV variability. Finally, the rich SR of karst forests could provide sufficient insurance effects; soil pH and available potassium (AK) enhance resilience, and exchangeable calcium (Eca), total phosphorus (TP) and total potassium (TK) indicate the resistance of functional stability in degraded karst forests. This study highlights the complex mechanisms of functional stability in extreme habitat conditions, thereby deepening our understanding of ecosystem function maintenance. Full article

Coarse woody debris (CWD) is an essential component in forest ecosystems, playing a significant role in enhancing biodiversity, soil formation, and nutrient cycling through decomposition processes. CWD also contributes to greenhouse gas fluxes, particularly through CO₂ emissions. This study investigated the physical and chemical properties of CWD and the CO₂ effluxes from CWD of different decay classes. For this study, a range of CWD—from recently dead to highly decomposed wood—of native tree species such as silver birch (Betula pendula Roth), black alder (Alnus glutinosa (L.) Gaertn.), and Norway spruce (Picea abies (L.) H. Karst.) in hemiboreal forests were investigated. The findings showed that CWD properties significantly differed among tree species and CWD decay classes. Significant variations in wood density and total nitrogen (N) were observed in the early stages of CWD decay, with the highest values found for the deciduous tree species. The concentration of organic carbon (C) increased throughout the decomposition. The lowest CO₂ efflux from CWD was found for spruce CWD from all decay classes and it was the highest for black alder and silver birch, especially for the 3rd and 4th decay classes. CO₂ efflux was mainly influenced by the degree of decomposition, which was represented by the CWD decay class, followed by wood density and C content. Full article

Soil enzyme activities serve as the key indicators of microbial nutrient limitations. Vegetation types after farmland is returned modify both the biological and abiotic properties of the soil, thereby impacting the soil nutrient cycle and the stability of forest ecosystems. However, soil enzyme activities and microbial nutrient limitations in degraded karst forests under different vegetation types after farmland return remain unclear. Therefore, this study investigated the soil physicochemical properties, enzyme activities, and microbial resource limitations in different vegetation types (grasslands (G), transitional grass–shrub (SG), shrubland (S), and secondary forest (F)) after returning farmland on dip and anti-dip slopes in a karst trough valley. The relationships among the factors influencing soil enzyme activities were analyzed to identify the drivers of microbial nutrient limitation. The results revealed that soil enzyme activities and physicochemical properties were significantly greater on anti-dip slopes than on dip slopes. Total nitrogen (27.4%) and bulk density (24.4%) influenced mainly soil enzyme activity and its stoichiometric ratio, whereas carbon and phosphorus limitations impacted soil microorganisms on the dip slopes of the F and G vegetation types. The soil physicochemical properties and enzyme characteristics accounted for 85.5% and 75.6%, respectively, of the observed influence. Notably, the total phosphorus content (36.8%) on the anti-dip erosion slope was significantly greater than that on the other slopes. These factors, especially bedrock strata dip and vegetation type, significantly affect soil enzyme activity. This study confirms that vegetation type enhances soil enzyme activities on anti-dip erosion slopes, providing a scientific basis for karst ecosystem restoration. Full article

Global warming has exacerbated the impact of regional drought on vegetation ecosystems, especially in typical karst areas with fragile ecosystems that are more severely affected by drought. However, the response mechanisms of vegetation ecosystems in karst areas to drought stress are still uncertain. With drought stress in the summer of 2022, we examined the spatiotemporal patterns of drought in a World Heritage karst site, Guilin, China, and revealed the exacerbated drought impacts on vegetation ecosystems in karst areas with various vegetation indices. Firstly, we analyzed the spatiotemporal characteristics of drought from 2000 to 2022, utilizing the temperature vegetation dryness index (TVDI), highlighting the intra-annual variability of drought in 2022. Additionally, we compared the responses of different vegetation types to drought stress in karst and non-karst areas and explored the exacerbated impacts of drought stress on vegetation ecosystems within the same year with three vegetation indices, namely, the Normalized Difference Vegetation Index (NDVI), Leaf Area index (LAI), and Gross Primary Production (GPP) in karst areas. The results showed that drought started in July and persisted from August to November at moderate to severe levels (with severe drought in September), eventually easing in December. Karst areas exhibited severe drought (TVDI = 0.76), which more significantly impacted regional vegetation ecosystems than those in non-karst areas. Different vegetation types also experienced greater drought stress in karst areas compared to non-karst areas. The vegetation indices increased at the early- to mid-stages of drought (July to September) compared to those in the baseline year (2020–2021), mainly due to the increase in non-karst areas. However, vegetation indices decreased at the late drought stage (October to November), primarily due to the decrease in karst areas, indicating that the karst topography exacerbated the impact of drought on regional vegetation ecosystems. Since LAI and GPP exhibited similar changing patterns to TVDI, with GPP showing particularly strong alignment, they can be used to reveal the response mechanisms of ecosystems to drought stress in karst areas. We emphasize the importance of monitoring the responses of vegetation ecosystems to climate-induced droughts stress and enhancing their resilience to future climatic challenges, particularly in karst areas. Full article

The ecosystems and human social systems in karst areas are undergoing rapid development. In this context, effectively identifying changes in the various functions of karst areas is crucial for formulating accurate sustainable development policies. However, few studies have discussed the ecological, production, and social functions of karst areas within an integrated framework. Therefore, this paper utilizes comprehensive evaluation methods, standard deviation classification, and coordination models to analyze the spatiotemporal changes in these functions of karst areas from 2000 to 2020. The results indicate that over the 20-year period, the ecological function, production function, and social function in karst areas have shown an annual growth trend with noticeable spatiotemporal differentiation. The dominant functions of the area have undergone significant changes, with the ecological function being dominant in 2000, the production function becoming dominant in 2010, and the social function taking the lead in 2020. Over the past 20 years, the lagged development type has remained the predominant combined function type. The coordination levels among the three functions have significantly improved, with the coordination between the ecological function and the production function transitioning from non-coordination to coordination in 2010. Furthermore, the coordination between the ecological function and the social function, and between the production function and the social function, achieved coordination status in 2020. This study enhances the understanding of the multifunctional evolution in karst areas and provides theoretical and practical guidance for ecological restoration, industrial development, and social reconstruction in karst areas. Full article

Soil organic carbon (SOC), a critical component of the global carbon cycle, represents the largest terrestrial carbon reservoir, and is thus a major component of influencing climate regulation and ecosystem health. Grasslands store substantial carbon in their soils, but this carbon reservoir is easily degraded by both grazing and mowing, particularly in vulnerable karst landscapes. This study investigates the potential of biochar, a carbon-rich soil amendment, as a management tool to maintain SOC or mitigate the degradation of SOC during mowing in karst grasslands in Southern China, using both red acidic and calcareous soils as experimental variables. T SOC fractions, soil enzyme activities, and soil pH were measured to determine the effect of mowing and biochar application on carbon stability and microbial activity. Consistent with expectations, mowing increases belowground biomass and promotes carbon loss through increased microbial activity, particularly in calcareous soils where mowing also decreases soil pH, increasing acidity and reducing the stability of Ca–carbon complexes. Biochar, however, counteracted these effects, increasing both particulate organic carbon (POC) and mineral-associated organic carbon (MAOC), especially in red soils where the addition of biochar greatly increased soil pH (from 5.4 to 6.33) (an effect not observed in the already-alkaline karst soils). Enzyme activities related to carbon degradation, such as β-D-Glucosidase and peroxidase, increased in biochar-amended soils (β-D-Glucosidase increased from 12.77 to 24.53 nmol/g/h and peroxidase increased from 1.1 to 2.36 mg/g/2h), each of which contribute to the degradation of carbon containing organic matter so that it may be ultimately stored in more recalcitrant forms. Mowing led to reduced polyphenol oxidase activity, but the presence of biochar mitigated these losses, protecting SOC pools (increased from 0.03 to 0.79 mg/g/2h). This study highlights biochar as an effective tool for enhancing SOC stability in karst grasslands, particularly in acidic soils, and suggests that integrating biochar into mowing regimes may optimize carbon sequestration while reducing fire risk. These findings offer valuable theoretical guidance for developing sustainable land management in sensitive ecosystems. Full article

The land use in agricultural areas contributes to economic growth while concurrently accompanied by a series of environmental pollution issues. Xingguo County, Ganzhou City, Jiangxi Province, is a typical agricultural area with selenium-rich soil, and the rice and navel oranges grown there have high nutritional value. This study analyzed the distribution of heavy metals in the soil of this area through the kriging interpolation method, evaluated the risks of heavy metals in the soil using different pollution index methods, and quantitatively analyzed their sources using principal component analysis (PCA) and positive matrix factorization (PMF), with the aim of protecting the ecological resources of this area and providing theoretical references for avoiding heavy metal pollution of crops in the soil. The research results indicate the following: (1) Based on the background values of Ganzhou, Jiangxi Province, all heavy metals have caused pollution to the soil except for As and Hg, among which Cd poses the highest potential ecological risk in the study area. According to the values of the Environmental Quality Standards for Soil (EQSS), the concentrations of heavy metals have not exceeded the standards and have relatively low potential ecological risks. (2) In terms of health risks, all soil heavy metals basically do not bring non-carcinogenic risks but acceptable carcinogenic risks to adults and children, except for Cd. The carcinogenic and non-carcinogenic risks of soil heavy metals for children are higher than those for adults, and the main exposure route is ingestion. Among different land use types, the carcinogenic and non-carcinogenic risks of soil heavy metals in orchards are the highest. (3) Combining the kriging interpolation method and the PCA and PMF models, it can be determined that there are two main sources of heavy metals in the study area: one is natural and the other is anthropogenic. Among the anthropogenic sources, agricultural sources contribute the most to soil heavy metal pollution. Through these research results, it can be found that soil heavy metal detection should be conducted in agricultural land, and risk-based management measures should be implemented. Full article

Changes in species’ habitats provide important insights into the effects of climate change. Woonyoungia septentrionalis, a critically endangered species endemic to karst ecosystems, has a highly restricted distribution and is a key biological resource. Despite its ecological importance, the factors influencing its habitat suitability and distribution remain poorly understood. This study employed ecological niche modeling to predict the potential distribution of Woonyoungia septentrionalis across China and analyzed shifts in centroid location to explore migration pathways under current and future climate scenarios. The model exhibited high predictive accuracy (AUC = 0.988), indicating its robustness in assessing habitat suitability. Under current climatic conditions, Woonyoungia septentrionalis is predominantly found in the Guizhou–Guangxi border region, southeastern Yunnan, eastern Sichuan, southeastern Tibet, and parts of Chongqing, Hunan, and Hubei. Among these, the Guizhou-Guangxi border represents the primary suitable habitat. Temperature factors, particularly bio6 (minimum temperature of the coldest month) and bio7 (annual temperature range), were the most significant determinants of habitat suitability, contributing 43.29% and 12.65%, respectively. Soil cation exchange capacity (CEC) accounted for 15.82%, while precipitation had a relatively minor impact. Under future climate scenarios, suitable habitats for Woonyoungia septentrionalis are projected to shrink and shift toward higher altitudes and latitudes, increasing the risk of extinction due to the “mountain trap” effect, where migration is constrained by limited habitat at higher elevations. Stable habitats, particularly in Libo (Guizhou) and Huanjiang (Guangxi), are identified as critical refugia. We recommend prioritizing shrinking and stable habitats in Guizhou, Guangxi, and Yunnan for in situ conservation. Ex situ conservation efforts should focus on areas identified based on key environmental factors and predicted migration pathways to ensure the species’ long-term survival. This study provides both theoretical and practical guidance for the conservation of this species and its vulnerable habitat. Full article

The scarcity of landslide samples poses a critical challenge, impeding the broad application of machine learning techniques in landslide susceptibility assessment (LSA). To address this issue, this study introduces a novel approach leveraging a deep convolutional generative adversarial network (DCGAN) for data augmentation aimed at enhancing the efficacy of various machine learning methods in LSA, including support vector machines (SVMs), convolutional neural networks (CNNs), and residual neural networks (ResNets). Experimental results present substantial enhancements across all three models, with accuracy improved by 2.18%, 2.57%, and 5.28%, respectively. In-depth validation based on large landslide image data demonstrates the superiority of the DCGAN-ResNet, achieving a remarkable landslide prediction accuracy of 91.31%. Consequently, the generation of supplementary samples via the DCGAN is an effective strategy for enhancing the performance of machine learning models in LSA, underscoring the promise of this methodology in advancing early landslide warning systems in western Sichuan. Full article

The diversity of arbuscular mycorrhizal fungi (AMF) is a crucial indicator for determining the productivity of forest ecosystems and for assessing degraded areas. At present, the effect of tree age and vegetation restoration strategies on AMF diversity in karstic rocky desertification areas remains unclear. This study investigated AMF diversity and abundance in soils planted with Delavaya toxocarpa Franch. for 18, 11, and 4 years in a karstic desertification area of southwestern China. Additionally, it explored AMF community composition in soils of an 18-year-old D. toxocarpa plantation, a secondary forest naturally restored since 2005, and an abandoned land with no human intervention. High-throughput sequencing revealed that the mean Chao1 and richness indices of AMF increased with tree age, as indicated by the highest AMF α-diversity in 18-year-old plantations. The various vegetation restoration strategies resulted in significant differences in AMF abundance and evenness indices. Although no significant differences (p = 0.33) were found between the different restoration strategies, the AMF α-diversity index showed a decreasing trend from plantation forest to secondary forest and then to abandoned land. Overall, soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) significantly influence AMF diversity. Additionally, soil TN, AP, hydrolysable nitrogen (HN), and urease activity (URE) shape AMF community composition. These properties varied with tree age and vegetation restoration strategies. Our findings point to good recovery results of artificial afforestation in karstic rocky desertification areas. The process accelerates vegetation restoration and enhances the mutually beneficial relationship between vegetation and AMF compared with natural restoration. However, the tree age selected in this study only represents the forest stands before mature forests, and the microbial diversity and structure in karst rocky desertification soils after mature and over-mature forest stands remain to be studied. Full article

Accurate analysis of soil organic carbon (SOC) under different land uses in ecologically fragile arid zones is essential for effective regulatory measures and improvement of ecological quality. This study selected the ecologically fragile Tarim River source area as an example, aiming to quantitatively assess the SOC content, storage, carbon sequestration potential, and stratification ratio (SR) of different ecological land use types. Soil depths from 0–50 cm were determined and analyzed using the K₂Cr₂O₇-H₂SO₄ oxidation method, the equivalent soil mass method and mathematical statistics. Forest, shrubland, and grassland ecological land types were included. The results show the following: (1) Both SOC content and storage showed a decrease with increasing soil depth. The total SOC content and storage sequence from high to low were natural forest, grassland, and shrubland. (2) There are variations in the SOC sequestration potential among the different ecological land types and shrubland (40.64 Mg C ha⁻¹) > grassland (37.69 Mg C ha⁻¹). (3) The SRs of the SOC in the forest were significantly greater than those in the shrubland and grassland. The different ecological land types had significant impacts on SR2, SR3, and SR4. SR2 could serve as a reliable index for assessing the impact of management practices on soil quality. The study area has a high potential for soil carbon sequestration in the future under these ecological conservation and management measures. Full article

Phyllostachys praecox is a valuable tree species in karst ecosystems, but improper mulching practices can worsen soil degradation. Understanding soil nutrient limitations is crucial for successful restoration and sustainable development. However, it remains unclear whether and how mulching management of Phyllostachys praecox affects soil enzyme stoichiometry and nutrient limitation in karst areas. Here, we conducted a field experiment in Chongqing karst bamboo forest ecosystems with four mulching treatments: 1-year (T1), 2-years (T2), 1-year and recovery and 1-year (T3), and no mulching (CK). We investigated the activities of the C-acquiring enzyme β-1,4-glucosidase (BG), N-acquiring enzymes L-leucine aminopeptidase (LAP) and β-1,4-N-acetylglucosaminidase (BNA), as well as P-acquiring enzyme phosphatase activity (AP), to assess the limitations of C, N or P and identify the main factors influencing soil microbial nutrient limitation. Compared with the CK treatment, both the T2 and T3 management treatments significantly increased the SOC, TN, MBC, and MBN. Furthermore, the soil enzyme stoichiometric ratio in the karst bamboo forests deviated from the global ecosystem ratio of 1:1:1. T1 > T3 > CK > T2 presented higher values of C/(C + N) and C/(C + P), with T1 having values that were 1.10 and 1.12 greater than those of T2, respectively. Additionally, there was a significant negative correlation between microbial C and N limitations and total nutrients, but a positive correlation with microbial biomass ratios. In conclusion, changes in mulching management of Phyllostachys praecox affect soil enzyme stoichiometry activities and their ratios by influencing total nutrients and microbial biomass ratios. This study suggests an alternate year cover pattern (mulching in one year and resting in the next) as a scientific management approach for bamboo forests, contributing to a better understanding of nutrient limitation mechanisms in karst bamboo forest ecosystems. Full article