Karst Region Of China Research Articles

Morphology and multigene phylogeny reveal four new Xylaria (Xylariales, Xylariaceae) species from karst region in China.

This study presents the identification of four novel Xylaria species, discovered in the karst region of China. The discovery was facilitated by a rigorous analysis that encompassed both morpho-anatomical features and multi-locus phylogenetics utilizing sequences from the ITS, rpb2, and TUB2 loci. The newly identified species are designated as Xylariajichuanii sp. nov., X.nanningensis sp. nov., X.orientalis sp. nov., and X.taiyangheensis sp. nov. The distinction of these species from their known counterparts was verified through comparison of morphological features and phylogenetic analysis. The study further provides detailed morphological descriptions, illustrative representations, and a phylogenetic tree, all of which contribute to the taxonomic positioning of these novel species.

Spatiotemporal evolution of ecosystem health and its driving factors in the southwestern karst regions of China

As one of the most typical karst landscapes globally, the karst regions in southwestern China are characterized by prominent rocky desertification and fragile ecological conditions. Consequently, exploring the spatiotemporal evolution and driving influences on ecosystem health (EH) in this region is of great significance for the improvement of ecosystems and green development. This study focuses on assessing EH in these regions from 2000 to 2020 using the “vitality-organization-recovery-service” (VORS) framework. Spatiotemporal changes in EH are analyzed through hotspot analysis, and the functional relationship between driving factors and EH is quantified using XGBoost and SHAP models. Key findings include: (1) Over the past two decades, the proportion of cities experiencing enhanced EH has generally improved in 73% of cities compared to 27% experiencing deterioration. (2) Spatial analysis reveals EH clustering in three regions. One cold spot cluster in the central north and two hot spot clusters in the southwest and southeast. (3) Urbanization level exhibits an inverse logarithmic relationship with EH. Precipitation affects EH in a cubic polynomial pattern—initial decrease, subsequent increase, and final decrease. Temperature impacts EH through a quartic polynomial function with fluctuating increases and decreases. PM2.5 shows a monotonically decreasing relationship with EH, while the normalized difference vegetation index demonstrates a monotonically increasing association. This research contributes to understanding EH dynamics in southwestern China’s karst landscapes, crucial for advancing ecosystem management and sustainable development efforts.

Determination of contamination, source, and risk of potentially toxic metals in fine road dust in a karst region of Southwest China.

Understanding the pollution situation of potentially toxic metals (PTMs) in fine road dust (FRD) in emerging industrialized cities and identifying priority control factors is crucial for urban environmental management, resident health protection, and pollution control. This study conducted a comprehensive investigation on PTMs pollution in FRD in Zunyi, a representative emerging industrialized city in the karst region of southwestern China. The average contents of Ni, Cr, Mn, Cu, Zn, Ba, Pb, V, and Co in the FRD were 43.2, 127.0, 1232.1, 134.4, 506.6, 597.8, 76.1, 86.8, and 16.2mgkg-1, respectively, which were obviously higher than the corresponding background levels of the local soil except for V and Co. The comprehensive pollution level of the determined PTMs in the FRD was very high, primarily caused by Zn and Cu. The sources of PTMs in Zunyi FRD were traffic, industrial, construction, and natural sources, accounting for 38.0, 23.7, 21.9, and 16.4% of the total PTMs content, respectively. The PTMs in Zunyi FRD exhibited a low to moderate overall ecological risk level, mainly contributed by Cu and traffic source. The cancer risks of PTMs in Zunyi FRD were high for all populations. The non-carcinogenic risk of PTMs in Zunyi FRD was acceptable for adults, but cannot be ignored for children. According to the source-specific probabilistic health risk estimation results, the priority control source is industrial source and the priority control PTM is Cr. Local governments need to give more attention to the carcinogenic risks and health hazards posed by PTMs in the FRD.

Functional Traits Affect the Contribution of Individual Species to Beta Diversity in the Tropical Karst Seasonal Rainforest of South China

In a community, due to the different characteristics of each species, their contributions to community beta diversity may vary. Quantifying the contribution of each species to overall beta diversity (SCBD) is essential for explaining the patterns of beta diversity. However, there is currently limited research linking SCBD with species functional traits, and how species functional traits influence SCBD remains unclear. This study is based on tree census data, species functional traits, and environmental variables from a 15 ha permanent monitoring plot in a tropical karst rainforest in south China. By calculating species-specific SCBD based on abundance and presence–absence data, as well as functional distinctiveness and species ecological niche characteristics (niche position and niche width), we applied structural equation modeling (SEM) to analyze how functional traits, distinctiveness, and niche characteristics jointly influence SCBD. The results revealed that SCBD based on abundance is positively correlated with occupancy and abundance, whereas SCBD based on presence–absence data exhibits a hump-shaped relationship with occupancy and abundance. Species ecological niche characteristics directly influence SCBD, with species occupying central ecological niches having a negative effect on SCBD and niche width having a positive effect. Functional traits and functional distinctiveness indirectly impact SCBD through their influence on species ecological niche characteristics. SEM models based on the presence–absence data provide higher explanatory power. In summary, in the seasonal rainforest communities of northern tropical karst regions in China, the combined effects of species’ functional traits, functional distinctiveness, and ecological niche characteristics determine SCBD. This not only contributes to a deeper understanding of how species traits influence β-diversity, making SCBD a more applicable tool for biodiversity conservation, but also allows for the development of more effective biodiversity protection strategies by elucidating the link between SCBD and ecosystem multifunctionality.

Genome-wide identification of Rosa roxburghii CML family genes identifies an RrCML13-RrGGP2 interaction involved in calcium-mediated regulation of ascorbate biosynthesis

Calmodulin-like proteins (CMLs) are an essential family of calcium sensors involved in multiple Ca2+-mediated cellular processes in plants. Rosa roxburghii Tratt, known for the abundance of L-ascorbic acid (AsA) in its fruits, is widely distributed in calcium-rich soil of the karst region in southwestern China. The aim of this study was to identify key CMLs that respond to exogenous Ca2+ levels and regulate AsA biosynthesis in R. roxburghii. A genome-wide scan revealed the presence of 41 RrCML genes with 1–4 EF-hand motif (s) unevenly distributed across the 7 chromosomes of R. roxburghii. qRT-PCR analysis revealed that RrCML13, RrCML10, and RrCML36 responded significantly to exogenous Ca2+ treatment, and RrCML13 was positively correlated with GDP-L-galactose phosphorylase encoding gene (RrGGP2) expression and AsA content in the developing fruit. Overexpression of RrCML13 in fruits and roots significantly promoted the transcription of RrGGP2 and the accumulation of AsA, while virus-induced silencing of RrCML13 reduced the transcription of RrGGP2 and the content of AsA. Furthermore, Moreover, the yeast two-hybrid and bimolecular fluorescence complementation (BiFC) analysis confirmed the interaction between RrCML13 and RrGGP2 proteins, indicating that RrCML13 plays a regulatory role in calcium-mediated AsA biosynthesis. This study enhances our understanding of R. roxburghii CMLs and sheds light on the calcium-mediated regulation of AsA biosynthesis.

Improving grassland ecosystem services for human wellbeing in the karst desertification control area: Anthropogenic factors become more important

Elucidating the spatial and temporal patterns of grassland ecosystem service value (ESV) changes under different karst geomorphic types (KGTs) is crucial for promoting regional sustainable development and enhancing human well-being. Karst ecosystems are characterized by high spatial heterogeneity. However, analyses of the drivers of spatial and temporal changes in ESV in karst grasslands at multiple scales are lacking. In this study, the South China Karst (SCK) region was selected as the focus area, the gross ecosystem product (GEP) accounting method was used to quantify the grassland ESV from 2000 to 2020, and the GeoDetector model was used to elucidate the spatial and temporal evolution of the GEP, the drivers, and their interactions in different KGTs. The results indicate the following: (1) Over the past 20 years, the grassland GEP of SCK has increased from ¥ 14,844.24 × 108 in 2000 to ¥ 17,174.90 × 108 in 2020. Among the various KGTs, the karst gorge exhibited the fastest GEP increase (24.93 %) and karst hilly depressions the slowest (6.22 %). (2) The karst grassland GEP showed a strong positive spatial correlation with significant clustering characteristics (p < 0.05). (3) There are significant differences in the factors influencing the GEP of grasslands with different KGT values, and although they are generally influenced by factors such as NPP, precipitation, and population density, anthropogenic factors are becoming increasingly important. In addition, the multifactor interaction explained GEP better than the single factor. Based on our findings, we propose targeted grassland ESV restoration approaches and management recommendations for various KGTs dominated by distinct factors. Our results provide a scientific basis for decision-making regarding karst ecosystem service enhancement and value realization.

Effects of vegetation restoration on the temporal variability of soil moisture in the humid karst region of southwest China

Study regiona typical humid karst region of southwestern China. Study focusTemporally stable soil moisture variability (SMV) helps clarify stress on vegetation growth. In the humid karst region of southwest China, large-scale vegetation restoration has affected the soil moisture. However, most studies here have focused on changes in the soil moisture content, and changes in the SMV have not been considered. New hydrological insights for the regionIn this study, changes to the SMV after vegetation restoration were analyzed using two indicators: the soil moisture coefficient of variation(SMCV) and soil moisture memory(SMM). The results showed that the SMCV decreased by an average of 22.3 % and the SMM increased by an average of 17.2 % in the Karst region of southwest China. the SMV had significantly decreased after vegetation restoration, and the overall decrease was larger on 15-day, monthly, and yearly scales and smaller on the weekly scale.When the effects of different vegetation types were considered, SMV greatly decreased in forestland and grassland on the 15-day and monthly scales, in shrubland on the annual scale, and in sparse woodland on the 15-day, monthly, and annual scales. Four geomorphic regions in particular showed large reductions in the SMV: the karst basin, peak cluster depression, peak forest plain, and non-karst region. In addition, changes in SMV after vegetation restoration have a significant positive influence on geochemical and climatic factors and a non-significant negative influence on geological structure factors. Among them, the significant influence factors of CaO content and MgO content are greater than SiO2 content by 0.71 and 0.63. precipitation and temperature are greater than vapor pressure difference by 0.51 and 0.4. Overall, vegetation restoration was found to make the SMV in the humid karst region more stable.

Overestimating the involvement of nitric acid derived from nitrification in carbonate dissolution under a calcareous soil system

This study aimed to quantify the effect of base cation exchange (BCE) in the buffering of nitric acid produced by soil nitrification and evaluate the impact of this process on karst carbon sinks. We collected limestone soils from subtropical karst regions in southern China and established five pot simulation experiments with different fertiliser gradients. The results follow: (1) Soil calcium carbonate (CaCO3) and alkaline cations decreased gradually with increasing nitrogen application. Furthermore, the concentrations of soil leachate nitrate (NO3–N), calcium (Ca), and magnesium (Mg) gradually increased and varied within the ranges of 0.15–15.33, 28.10–85.76, and 6.53–34.35 mg L−1, respectively. (2) Soil buffering against nitrification-generated acid could be accomplished fully in the top 10 cm of the soil. At a fertiliser application rate of 100 kg N ha−1a−1, nitrification acid production was fully buffered by BCE, and soil CaCO3 was dissolved entirely by soil CO2. When the fertiliser application rate increased from 250 to 700 kg N ha−1a−1, BCE buffered approximately 55% of the H+. Soil carbonate buffering was approximately 45%. (3) Losses of Ca and Mg from the soil were induced by three processes: carbonic acid dissolving soil CaCO3, BCE and nitric acid dissolving soil CaCO3. Previous studies have ignored the contribution of BCE to groundwater Ca and Mg, leading to an overestimation of approximately 55% in the previously calculated proportion of nitric acid involved in the dissolution of carbonates.

Multi-elements linear discriminant analysis of herbaceous and woody plants in southwest china karst region using orthogonal partial least squares model

Multi-elements linear discriminant analysis of herbaceous and woody plants in southwest china karst region using orthogonal partial least squares model

Quantifying the water use efficiency of karst ecosystems and response to environmental factors

Study regionThe study area is located in Guizhou province, the centre of the karst region in southwest China. Study focusAs a typical karst region, Guizhou has long faced challenges with water scarcity. Quantifying water use efficiency (WUE) is crucial for the efficient use of water resources and sustainable management. This study examined the spatio-temporal evolution patterns and its driving factors on WUE in Guizhou using Theil-Sen's slope, partial correlation methods, and the geographic detector model. New hydrological insights for the region(1) The multi-annual mean WUE of non-karst region (NKR, 2.75 gC kg−1 H2O yr−1) is higher than that of karst region (KR, 2.10 gC kg−1 H2O yr−1) during 2001–2020. (2) The rate of increase of WUE was three times higher in KR than in NKR. (3) Precipitation and temperature were identified as the key factors influencing WUE. Interactions between each environmental factors were observed to have both bi-variate and non-linear enhancement effects. Notably, in the NKR, soil moisture, vegetation type and leaf area index were the dominant factors influencing WUE, with interactions between environmental factors had both enhanced and weakened effect on WUE. (4) The synergistic effects of these interactions exceeded the individual or cumulative effects of the two environmental factors. These findings contribute to our understanding of the environmental factors driving changes in WUE in the KR.

Comprehensive assessment of rocky desertification treatment in Southwest China karst

AbstractRocky desertification is a prominent ecological issue in Southwest China's karst region, ranking among the nation's three primary ecological challenges alongside soil erosion and desertification. The government initiated the Rocky Desertification Treatment Program in 2008, lacking a comprehensive evaluation of its benefits. This study evaluates the program's impact on ecosystem services over the last two decades using remote sensing, ecosystem models, and field data. The results indicated a continuous net decrease of rocky desertification, 48% in the eight southwestern provinces from 2005 to 2021. The average annual growth rate of vegetation cover reached 2.54% in key counties for rocky desertification control, significantly higher than that of all the 451 rocky desertification counties from 2016 to 2020. Additionally, ecosystem productivity increased by 35.8% in rocky desertification counties from 2000 to 2020, which is 1.34 times greater than that observed in non‐rocky desertification counties. It was found that the ecosystem service promotion after the net reduction of rocky desertification area in 2010–2020 is more significant, especially the carbon sequestration in 2010–2020 of key counties for rocky desertification control is 2.7 times than that in 2000–2010. It indicates that the rocky desertification treatment enters the stage of ecosystem service promotion on the basis of achieving rapid “greening,” leading to significant improvements in ecosystem structures and services in the karst region of Southwest China. To mitigate the risk of rocky desertification, tailored measures must be implemented considering local climate, lithology, landform types, and human–land relations for effective treatment zoning and classification.

Vegetation cover change and its response to human activities in the southwestern karst region of China

Vegetation to some extent can reflect the overall state of the ecological environment, and increasing vegetation cover can improve the quality of the ecological environment. The southwest karst region of China is a typical ecologically fragile area and an important ecological barrier. Against the backdrop of intensified human activities, the vegetation dynamics in the karst region have attracted widespread attention. Analyzing vegetation cover changes and their responses to human activities is important for regional ecological development. This study is based on SPOT-VGT NDVI data from 1998 to 2020 and employs trend analysis, “baseline” determination, multiple regression, residual analysis, and principal component analysis to investigate the characteristics of vegetation cover changes in the southwest karst region of China. Additionally, it quantifies the specific impacts of various human activities on these changes. The research findings indicate that (1) over the past 23 years, the interannual variability and seasonal differences in the NDVI of the southwest karst region have been significant, exhibiting an overall increasing trend. Spatially, the vegetation in this region demonstrates a decreasing trend from south to north and southwest to northeast. (2) Over time, the areas where vegetation has improved gradually expand, and the effectiveness of vegetation restoration increases with time. (3) Overall, human activities influence vegetation growth in the southwest karst landscape region of China. (4) The socioeconomic factors affecting vegetation cover changes in the southwest karst region of China primarily include economic development level, population and labor migration, urbanization development, and vegetation construction. These results provide a scientific basis for formulating reasonable ecological environment protection strategies by humans.

Assessing rainfall erosivity changes over China through a Bayesian averaged ensemble of high-resolution climate models

Spatiotemporal variation in rainfall erosivity resulting from changes in rainfall characteristics due to climate change has implications for soil erosion in developing countries. To promote soil and water conservation planning, it is essential to understand past and future changes in rainfall erosivity and their implications on a national scale. In this study, we present an approach that uses a Bayesian model averaging (BMA) method to merge multiple regional climate models (RCMs), thereby improving the reliability of climate-induced rainfall erosivity projections. Our multi-climate model and multi-emission scenario approach utilize five RCMs and two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenarios for the baseline period (1986–2005) and future periods (2071–2090) to characterize the spatiotemporal projection of rainfall erosivity and assess variations in China. Our results indicate that the two models outperform other models in reproducing the spatial distribution and annual cycle of rainfall erosivity in China. Moreover, we found an increasing trend in the annual rainfall erosivity from the baseline climate up to the RCMs for all models, with an average change in erosivity of approximately 10.9% and 14.6% under RCP4.5 and RCP8.5, respectively. Our BMA results showed an increase in the absolute value of rainfall erosivity by 463.3 and 677.0 MJ·mm·hm−2·h−1, respectively, in the South China red soil region and the Southwest China karst region under the RCP8.5 scenario. This increase indicates that climate warming will significantly enhance the potential erosion capacity of rainfall in these regions. Additionally, our study revealed that the Southwest China karst region and the Northwest China Loess Plateau region are more sensitive to radiation forcing. To mitigate the risk of soil erosion caused by climate change, it is necessary to consider changes in rainfall erosivity, local soil conditions, vegetation coverage, and other factors in different regions and take appropriate soil and water conservation measures.

Regionally differential water pricing strategy: An example from Karst region of China

Abstract The study objective is to analyze the water expenditure of 4315 rural households in the Karst region of China. The empirical results have been analyzed by using the extended linear expenditure system model. The study has been based on water expenditure, which provides a feasible differential water pricing strategy in the karst region of China. The result shows that (1) the coefficient for water expenditure has been examined as low. The coefficient of water expenditure in the Karst region ranges from 0.534 to 1.025%, the average value is 0.723%, and the modified coefficient ranges from 0.814 to 1.508%, with an average value of 1.070%. (2) The marginal consumption propensity of rural residents in the Karst region is 0.2%, and the marginal consumption propensity in each province ranges from 0.1 to 1%. (3) The per capita basic water demand has 3 m3. In this scenario, the study recommended that basic water prices range from CNY 2.091 to CNY 3.468 per cubic meter. If the water consumption exceeds basic demand (3 m3 per month), then the bearing water price shall not be lower than CNY 2.091 to CNY 3.468 per cubic meter and not higher than CNY 7.122 per cubic meter.

Terrestrial algae: pioneer organisms of carbonate rock solutional weathering in South China karst.

The formation of soil in karst ecosystem has always been a scientific problem of great concern to human beings. Algae can grow on the exposed and non-nutrition carbonate surface, inducing and accelerating weathering of rock substrates, thus promoting soil formation. Yet the actual contribution of algae to solutional weathering intensity remains unclear. In this study, we performed weathering simulation experiment on two algae species (Klebsormidium dissectum (F.Gay) H.Ettl & G.Gärtner and Chlorella vulgaris Beijerinck), which were screened from carbonated rock surfaces from a typical karst region in South China. The results showed: (1) both algae have solutional weathering effect on carbonate rock, (2) there is no difference of solutional intensity observed, yet the solutional modes are different, suggesting different ecological adaptative strategies, (3) algae on carbonate rocks have higher carbonic anhydrase activity (CAA) and secrete more extracellular polysaccharide (EPS), accelerating rock weathering. (4) The absolute dissolution amount of carbonate rock with algae participation is 3 times of that of without algae. These results indicate the significant impact of terrestrial algae on carbonate rock solutional weathering and provides quantitative evidence that terrestrial algae are pioneer species. It also contributes to our further understanding of soil formation in karst ecosystems in South China.

Laboratory and field characterization of preferential flow under consideration of geometric fracture features in a karst region in southwest China

As a result of the widespread distribution of soil fractures in karst regions, preferential flow is a well-known occurrence there, and understanding how it moves is crucial for the cognition of the local hydrological process. This study used indoor column experiments in conjunction with dye tracing to simulate the widely dispersed soil fractures in the karst region, and analysed the movement of preferential flow under various fractures. On the basis of indoor test results, field experiments were designed to measure the real-time infiltration process of the preferential flow under two typical forests. Results revealed that preferential flow only occurred when the fracture was connected to the soil surface. The connectivity of fractures and their angle affected the movement of preferential flow, as well as the magnitude of wetting adjacent to the preferential flow paths. The magnitude of flow imbibition into the matrix system is ranked as follows: soil with fractures connected to the surface > soil with fractures not connected to the surface > homogeneous soil without fracture. In addition, the wetting area in the soil was larger when two adjacent fractures were inwardly inclined than when two fractures were vertical or outwardly inclined, but the degree of preferential flow development was relatively lower. The cumulative infiltration volume and steady infiltration rate of the preferential flow under the mixed forest were higher than those of the matrix flow, whereas the opposite was true for the Pinus massoniana pure forest. The cumulative infiltration volume and steady infiltration rate of both matrix flow and the preferential flow under the mixed forest were greater than those of the P. massoniana pure forest. The response of soil fracture characteristics on the preferential flow could not be ignored, and it can provide directions for the hydrological processes in the karst region.

Research and prospects on ecosystem services and trade-offs/synergies relationships in the karst regions of southwestern China

Research and prospects on ecosystem services and trade-offs/synergies relationships in the karst regions of southwestern China

Identification of the Pollution Mechanisms and Remediation Strategies for Abandoned Wells in the Karst Areas of Northern China

Abandoned well pollution is a critical component of global environmental issues and a historical legacy issue of national development. Despite this, the specific mechanisms by which abandoned wells pollute groundwater remain unclear, particularly in the karst regions of Northern China, where no scientifically effective remediation methods exist. To address this gap, this study focuses on Yangquan City in Shanxi Province and employs field investigations, the analytic hierarchy process, high-definition deep-well logging technology, and qualitative analysis to assess the pollution risk of all abandoned wells in the study area, identifying those with high pollution risk. Through the analysis of extensive image and video data for these high-risk wells, we propose a conceptual model of cross-strata channels in abandoned wells and elucidate the mechanisms by which they pollute groundwater. The results show that, from a single-well perspective, the pollution mechanism is cross-strata pollution. From a regional perspective, the pollution mechanisms are hydraulic connectivity and solute migration and transformation. Based on these findings, we present a scientifically effective remediation strategy tailored to the typical characteristics of abandoned wells in the study area, offering a viable solution to the abandoned well pollution problem in Yangquan City. This research not only augments the theoretical framework in the domain of groundwater pollution but also advances sustainable groundwater security and management strategies. Moreover, the study furnishes theoretical foundations and pragmatic solutions for the remediation of abandoned wells in Yangquan City, which are crucial for the sustainability of the groundwater ecosystem.

Assessing and decoupling ecosystem services evolution in karst areas: A multi-model approach to support land management decision-making

Incorporating Ecosystem Service Value (ESV) into land use planning provides a fresh perspective for informed land management decisions. ESV, influenced by socio-economic and natural factors, has complex driving mechanisms, particularly in China's southwestern karst regions. Studying mediating variables helps elucidate these mechanisms. Further research into ecosystem services interactions and effective land use policies in karst areas is needed. This study evaluates the ESV of Guizhou Province, located in southern China's karst region, using the benefit transfer approach. Combining the Guizhou Provincial Land Use Planning Outline (2006–2020) with the multi-objective programming (MOP) model optimized by genetic algorithm and the patch-generating land use simulation (PLUS) model, four future development scenarios were designed. The response of ESV to land use and land cover (LULC) changes at the county scale under four different development scenarios from 2000 to 2020 and in the future was analyzed. A partial least squares structural equation model (PLS-SEM) was used to decouple the driving mechanism affecting ESV. The results show that over the past two decades, with the implementation of various ecological restoration projects, the total ESV has increased. The ESV for natural development scenarios, ecological conservation scenarios, economic development scenarios, and sustainable development scenarios are CNY 238.278 billion, CNY 400.514 billion, CNY 283.201 billion, and CNY 323.615 billion, respectively. The direct impacts of karst surface characteristic factors (KSCF), meteorological factors (MF), socio-economic factors (SEF) and transportation location factors (TLF) on ESV are positive (0.098), negative (−0.098), positive (0.336), and positive (0.109) respectively. The total effect of KSCF on ESV through influencing socio-economic factors and LULC is (−0.738), with SEF playing a complete mediating role. MF indirectly affect ESV by influencing LULC, with LULC playing a complete mediating role in this process. The PLS-SEM model shows that under the dominant position of LULC, the interaction between natural environmental factors and socio-economic factors on ESV is very complex. This study offers valuable insights that can guide managers in this region, as well as in other karst regions globally, in the development of sustainable land use policies.

Phytohormone Response of Drought-Acclimated Illicium difengpi (Schisandraceae).

Illicium difengpi (Schisandraceae), which is an endemic, medicinal, and endangered species found in small and isolated populations that inhabit karst mountain areas, has evolved strategies to adapt to arid environments and is thus an excellent material for exploring the mechanisms of tolerance to severe drought. In experiment I, I. difengpi plants were subjected to three soil watering treatments (CK, well-watered treatment at 50% of the dry soil weight for 18 days; DS, drought stress treatment at 10% of the dry soil weight for 18 days; DS-R, drought-rehydration treatment at 10% of the dry soil weight for 15 days followed by rewatering to 50% of the dry soil weight for another 3 days). The effects of the drought and rehydration treatments on leaf succulence, phytohormones, and phytohormonal signal transduction in I. difengpi plants were investigated. In experiment II, exogenous abscisic acid (ABA, 60 mg L-1) and zeatin riboside (ZR, 60 mg L-1) were sprayed onto DS-treated plants to verify the roles of exogenous phytohormones in alleviating drought injury. Leaf succulence showed marked changes in response to the DS and DS-R treatments. The relative concentrations of ABA, methyl jasmonate (MeJA), salicylic acid glucoside (SAG), and cis-zeatin riboside (cZR) were highly correlated with relative leaf succulence. The leaf succulence of drought-treated I. difengpi plants recovered to that observed with the CK treatment after exogenous application of ABA or ZR. Differentially expressed genes involved in biosynthesis and signal transduction of phytohormones (ABA and JA) in response to drought stress were identified by transcriptomic profiling. The current study suggested that the phytohormones ABA, JA, and ZR may play important roles in the response to severe drought and provides a preliminary understanding of the physiological mechanisms involved in phytohormonal regulation in I. difengpi, an endemic, medicinal, and highly drought-tolerant plant found in extremely small populations in the karst region of South China.