The antimicrobial spectrum of the extracts from different parts of Loropetalum chinense was determined to lay a foundation for their protection, comprehensive development and utilization. The results showed that the ethyl acetate extracts (EtOAc) from the branches and leaves of L. chinense had significant inhibitory effects on 9 plant pathogenic fungi and 9 animal pathogenic bacteria, except that the inhibition rate against Pestalotiopsis theae and Alternaria citri were respectively 25.58% and 48.30% at 5 g/L of the EtOAc extract of branches, the inhibition rate against the other seven plant pathogenic fungi exceeds 50%, with an EC₅₀ value of 0.297 8-3.768 8 g/L. Among them, the extract of branches had much higher virulence against Alternaria oleracea, Colletotrichum capsici, and Cochliobolus miyabeanus, respectively with EC₅₀ values of 0.756 4, 0.297 8,and 1.361 2 g/L, less than 2 g/L, and especially had higher virulence against Colletotrichum capsici, with an EC₅₀ value less than 0.5 g/L. The EtOAc extract of leaves had an inhibition rate of over 50% against the other 8 tested pathogens except for the Pestalotiopsis theae at 26.77%. The EC₅₀ values of 8 tested pathogens range from 1.036 0 to 3.807 6 g/L. Similarly, the EtOAc extract of leaves also had high toxicity against C. miyabeanus, A. oleracea, and C. capsici, respectively with EC₅₀ values of 1.812 6, 1.376 7, and 1.036 0 g/L, less than 2 g/L. The EtOAc extracts of the branches and leaves had significant inhibitory effects on 9 animal pathogenic bacteria with MICs of 0.156 25-2.500 00 g/L and 0.156 25-1.250 00 g/L, respectively. There was relatively higher inhibitory activity of the branches extract against 5 animal pathogens, including Bacillus anthraci, Staphyloccocus aureus, Bacillus subtilis, Bacillus cereus, and Micrococcus luteus, with MIC values less than 1 g/L. For the leaves extract, except for the MIC of 1.25 g/L for Escherichia coli, the MIC was less than 1 g/L for the other 8 tested animal pathogenic bacteria. In addition, its inhibitory activity of leaves extract against five pathogenic bacteria, i.e., Bacillus cereus, Micrococcus luteus, Bacterium paratyphosum B, Micrococcus lysodeikticus, and Bacillus megaterium, was higher than that of branches extract. The research results indicated that L. chinense has broad-spectrum antimicrobial activity, and laid a foundation for its application in agricultural and medical antimicrobial activities.

The glomalin-related soil protein (GRSP)is a crucial constituent of soil organic matter, contributing to the enhancement of soil aggregate water stability and the promotion of soil carbon storage. This study focused on investigating the variations in GRSP content and its influencing factors during karst vegetation restoration in northern Guangxi. Rhizosphere soil, non-rhizosphere soil, and farmland (control) soil from three different stages of vegetation restoration (shrub stage, transition stage with irrigation, and forest stage) were selected as research subjects. The analysis included total glomalin-related soil protein (T-GRSP), as well as easily extractable glomalin-related soil protein (EE-GRSP), along with an examination of key environmental factors affecting changes in GRSP content. The findings revealed significantly higher T-GRSP and EE-GRSP contents in rhizosphere soils at each vegetation restoration stage compared with those in farmland (P<0.05). Additionally, the T-GRSP content was highest during the forest stage. The ratios of T-GRSP/SOC ranged from 4.45% to 18.05%, while the ratios of EE-GRSP/SOC ranged from 0.23% to 1.35%. Furthermore, these ratios were significantly higher in farmland than at each vegetation restoration stage (P<0.001). Notably, T-GRSP content was significantly higher in rhizosphere soils than non-rhizosphere soils during both transition and forest stages (P<0.05). Soil organic carbon and nitrate nitrogen content emerged as key factors driving positive changes in T-GRSP content; meanwhile, the contents of total nitrogen, organic carbon, and microbial nitrogen were identified as key influencers for positive changes observed in EE-GRSP. In conclusion, karst vegetation restoration in northern Guangxi effectively promotes GRSP accumulation and subsequently enhances SOC accumulation and stability.

To promote and assess the feasibility of artificial cultivation of endangered medicinal plant Cinnamomum migao H. W. Li, this study filtered and evaluated the potential growth-promoting abilities of 109 fungi isolated from the rhizosphere of C. migao. The fungi were filter for their abilities to solubilize phosphate, release potassium, produce indole-3-acetic acid (IAA), and produce siderophores. Plate culture method was employed to evaluate the fungal strains’ abilities in phosphate solubilization, potassium release, IAA production, and siderophore production. The fungal strains that simultaneously exhibited all four growth-promoting activities were subjected to pairwise confrontation and evaluated for antagonistic effects and enzymatic activity. The results showed that 44 fungi strains exhibited abilities in phosphate solubilization, potassium release, IAA production, and siderophore production. N. polythalama, T. cucumeris, B. cucumeris, S. boydii, and G. butleri possessed all growth-promoting abilities. In the pairwise confrontation experiments, only the confrontation between B. cibotii LD19 and S. boydii XL1 did not have obvious antagonistic zones or pigment zones, with improved enzymatic activity during their confrontation. There was no significant antagonistic effect between B. cibotii LD19 and S. boydii XL1, and they demonstrated good growth-promoting abilities, making them an ideal combination for a growth-promoting strain formula.

The antifungal activities of different solvent extracts from fermentation products of 5 endophytic fungi isolated from Paederia scandens (Lour.) Merr. were determined by a mycelium growth rate method. The optimal active strain and its extraction layers were screened out, and the virulence was further determined. Based on the bioactivity-guiding, the active compound was separated by silica gel column chromatography, and the structure of the compounds was identified by nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GC-MS). The antifungal effect of active compound was also evaluated. The results showed that the ethyl acetate extraction layer of strain PsJ3 had the best antifungal activity against the 7 tested plant pathogenic fungi, with the effective medium concentration (EC₅₀) ranging from 0.086 9 to 1.104 3 g/L. Among them, there was the most significantantifungal effect on C. paradoxa with the EC₅₀ value at 0.086 9 g/L, Followed by Alternaria oleracea and Pestalotiopsis theae with the EC₅₀ values at 0.208 2 and 0.239 7 g/L. It had the lowest antifugal effect on Phytophthora parasitica var with the EC₅₀ value at 1.104 3 g/L. The active compound fusaric acid was obtained from the ethyl acetate layer of the strain PsJ3. It showed significant antifungal activity against all the above seven plant pathogenic fungi, with EC₅₀ values ranging from 0.018 0 to 0.390 5 g/L. Similarly, it had the best antifungal effect against C. paradoxa, with EC₅₀ value of 0.0180 g/L, followed by A. oleracea and P. theae with the EC₅₀ values of 0.030 3 and 0.038 2 g/L. The Antifungal effect on P. parasitica var was the worst, with the EC₅₀ value at 0.390 5 g/L. The results showed that the endophytic fungus of Paederia scandens (Lour.) Merr. contained a broad spectrum antifungal activity of secondary metabolites against plant pathogenic fungi, and provided a reference for the application of endophytic fungi associated with Paederia scandens (Lour.) Merr. in agricultural antifungal activity.

In this paper, the citrus canker pathogen, was isolated and identified, and the inhibitory activity of endophytic fungi associated with Stephania dielsiana Y. C. Wu against the pathogen was studied, which will lay a foundation for the development of microbial control agents for citrus canker disease. The pathogenic strain KY(F) was isolated from the infected Orah citrus leaves with canker disease using tissue isolation and streak plate methods. The bacterial colonies on NA medium were yellow, round, viscous, full edge, glossy, and slightly raised on the surface. After staining and morphological observation, it was found that it is a gram-negative bacterium with polar single flagella and a capsule. The PCR results showed that strain KY(F) could amplify a target band of expected size (413 bp), with a unique conserved protein gene similar to that of citrus canker pathogen. According to the Koch’s rule, the pathogen was inoculated to healthy detached leaves of Orah citrus, and typical symptoms of citrus canker disease was formed. The results indicated that strain KY(F) was a citrus canker pathogen. The inhibitory activity of ethyl acetate extracts from 18 endophytic fungi isolated from S. dielsiana against this pathogen was determined using the toxin plate method. When the test concentration was 5 g/L, all 18 extracts could completely inhibit strain KY(F), with a MIC value ranging from 0.312 5 g/L to 5 g/L. The extracts of six endophytic fungi (Stdif6, leaf-7, leaf -9, J-10, J-29, and Y-10) showed the highest inhibitory activity against strain KY(F), with MICs ranging from 0.312 5 g/L to 0.625 g/L, all less than 1 g/L. Next were extracts of 5 endophytic fungi (J-8, J-21, J-36, Y-64, and YB-5), with MICs all at 1.25 g/L, all less than 2 g/L. Extracts of Stdif9 and Y-66 also had high inhibitory activity against citrus canker pathogenic strain KY(F), with MICs both at 2.5 g/L. The inhibitory activity of the five extracts, leaf-11, Y-51, Y-59, YB-25, and YB-26, against strain KY(F) is lower than that of other extracts, with MICs all at 5 g/L. The research results laid a foundation for the application of secondary metabolites of endophytic fungi associated with S. dielsiana in the prevention and control of citrus canker disease.

In this study, the effect of selenium on the uptake and transport of cadmium in rice were evaluated by exogenous application of selenium (selenium-soaked seeds, foliar selenium spraying and selenium-soaked seeds combined with foliar selenium spraying treatments) using rice (T-Young 109 and Shenliangyou 5814) as experimental subjects. The results showed that selenium-soaked seeds combined with foliar spraying of selenium treatment had the best effect on reducing cadmium content in rice plants, and the selenium-soaked seeds combined with foliar spraying of selenium treatment significantly reduced cadmium content in roots, stems, leaves and spikes of T-Young 109 rice at the spike stage and milky ripening stage (P<0.05), which were reduced by 26.64%, 25.81%, 6.25%, and 20.00%, respectively, and 22.05%, 17.23%, 27.42% and 18.95% respectively, when compared with the control group. Selenium-impregnated seeds combined with foliar spraying of selenium treatment significantly reduced cadmium content in roots, stems, leaves and spikes of Shenliangyou 5814 rice by 9.30%, 29.41%, 35.39% and 19.83%, respectively, as compared with the control, and selenium-impregnated seeds combined with foliar spraying of selenium both significantly reduced the cadmium enrichment coefficients of the roots, stems, leaves and spikes of the two types of rice (P<0.05). Exogenous selenium application could reduce the cadmium content of rice grains and increase the weight of rice spikes, among which the selenium-soaked seeds combined with foliar spraying of selenium had the best effect. Under the same selenium fertiliser treatment, the effect of reducing the cadmium content in brown rice and increasing the yield of kernel weight of T-Young 109 rice was better than that of Shenliangyou 5814 rice.

In order to investigate the effect of sodium selenite on the growth and physiological characteristics of quinoa under saline and alkaline stress, and to clarify its optimal spraying concentration under saline and alkaline stress, Long quinoa No. 4 was selected as the experimental material, and a one-factor completely randomized design was adopted using the method of pot planting test, with different concentrations of sodium selenite as the variables, five Na₂SeO₃ concentration gradients, and control group (without salt stress) were set up to study the effects of foliar spraying with different concentrations of sodium selenite on plant height, stem thickness of quinoa under different saline stresses, fresh weight, antioxidant enzyme activities, osmoregulatory substances and root vigor of quinoa under different saline and alkaline stresses. The results of the study showed that compared with control group, saline stress caused some degree of damage to quinoa’s morphological constructs, physiological characteristics, and even affected the growth and development of quinoa. Through foliar spraying of sodium selenite, the degree of damage to quinoa by saline stress was slowed down, plant height, stem thickness and fresh weight of quinoa were significantly increased, antioxidant enzyme activities and osmoregulatory substances of quinoa were improved, damage to quinoa membrane cells by saline stress was slowed down, root vigor of quinoa was improved, absorption of soil nutrients and water by quinoa under saline stress was promoted, and ultimately quinoa’s resistance of quinoa to salinity stress was improved. The results of the integrated affiliation function values indicated that the concentration of sodium selenite at 15 mg/kg was the most favorable to alleviate the salinity stress of quinoa. In conclusion, foliar spraying of sodium selenite had a significant effect on the growth and physiological characteristics of quinoa under saline and alkaline stress, and the best effect was achieved at a concentration of 15 mg/kg.

In recent years, microplastics (MPs) and cadmium (Cd) have attracted significant attention due to their combined toxic effects on aquatic organisms. Rice flower carp (Cyprinus carpio var. Quanzhounensis) is a characteristic local species in Quanzhou County, Guangxi, China. The effects of combined exposure to MPs and Cd on C. carpio remain unclear. The present study was performed to determine the individual (0.25, 0.5, 1.0, and 2.0 mg/L Cd or 0.25, 0.5, 1.0, and 2.0 mg/L MPs) and combined effects of MPs and Cd on the oxygen consumption rate (η_OC), ammonia excretion rate (η_AE), and O/N ratio (η_O/N) of C. carpio var. Quanzhounensis. The results showed that, under single Cd stress, the η_OC initially increased and then decreased with increasing Cd concentration, while η_AE increased, and the η_O/N continuously decreased with increasing Cd concentration. More importantly, the η_O/N was dropped below 7 when the Cd concentration exceeded 1.0 mg/L. Under single MPs stress, the η_OC and η_O/N showed a decreasing trend, which leveled off when the MPs concentration exceeded 0.5 mg/L; Similarly, the η_O/N was also dropped below 7 when the MPs concentration exceeded 1.0 mg/L; In addition, η_AE initially increased and then also exhibited a leveling-off trend when the MPs concentration exceeded 0.5 mg/L. Interestingly, compared with the single exposure groups, the change patterns of oxygen consumption rate, ammonia excretion rate and η_O/N in the co-exposure groups were similar, but with a significantly greater magnitude, indicating a synergistic effect of MPs and Cd on the standard metabolism of C. carpio. Two-way ANOVA showed that the interaction between Cd and MPs significantly affected η_OC, η_AE, and η_O/N (P>0.05). Moreover, binary logistic regression analysis revealed that Cd had a greater impact on C. carpio than that of MPs. Taken together, both single and combined MPs and Cd affect the standard metabolism of C. carpio; Synergistic toxic effects of MPs and Cd were observed in this study, and the toxicity of Cd was stronger than that of MPs on C. carpio; With increasing exposure concentration, the η_O/N less than 7, indicating that C. carpio may rely exclusively on proteins as an energy source, leading to diminished protein synthesis, which in turn hampers the increase in body weight and harmful to the health of C. carpio.

This study explores the anti-aging effects of osmanthus essential oil on human neuroblastoma SH-SY5Y cells and an acute aging mouse model. In vitro experiments, the anti-aging effects of osmanthus essential oil was assessed by measuring its impact on the expression of aging markers and the levels of reactive oxygen species (ROS) in SH-SY5Y cells. The results indicate that osmanthus essential oil at concentrations of 2-100 μg/mL is non-toxic to SH-SY5Y cells and significantly reduces H₂O₂-induced ROS levels and improved aging cell characteristics, including reducing the expression of senescence-associated secretory phenotype (SASP) genes and aging-related genes (P16, P53, and P21), and decreasing SA-β-gal production. The vivo experiments showed that different doses of osmanthus essential oil (0.012 5, 0.025, and 0.05 μL/g) significantly increased antioxidant enzyme (SOD, CAT) activities in the serum of acutely aged mice, while reducing MDA and ROS levels. Combining the results in vitro and vivo experiments, osmanthus essential oil significantly delays the aging process in cellular and animal models through its potent antioxidant effects, providing strong scientific evidence for its application in anti-aging treatments.

Citrus peel and pomace are by-products of citrus juice processing industry and are known for their abundance of high-quality dietary fiber. However, the traditional method of preparing citrus fiber involves the use of chemicals, which not only contributes to environmental pollution but also results in resource wastage. In light of the principle of comprehensive utilization, this study seeks to develop a physical processing technique for citrus fiber concentrate. The physicochemical, functional, and structural characteristics of citrus peel and pomace powders following modification through ultra-high pressure, superfine grinding, and soaking-autoclaving treatments are investigated, respectively. Compared with ultra-high pressured and superfine ground citrus peel and pomace powders, soaking-autoclaved counterparts exhibit superior physicochemical and functional properties, albeit slightly darker color that might impose limitation on their utilizations in light-colored food products. These findings offer new perspectives on how to prepare high-value citrus fiber concentrateas functional food ingredients.

The soluble dietary fiber (SDF) in navel orange peel was extracted by ultrasonic wave combined with cellulase-assisted extraction method. The extraction process of SDF was optimized by single factor test and response surface methodology and its in vitro prebiotic activity was evaluated, so as to provide technical reference for developing high quality navel orange peel SDF. The results showed that the optimal conditions to extract orange peel SDF of ultrasonic wave combined with cellulase-assisted extraction method were as follows: liquid-solid ratio 16 mL/g, ultrasonic power 45 W/L, ultrasonic time 40 min and enzyme addition 10.0 μL/g. Under these conditions,the extraction yield of SDF was 11.88%. In vitro fermentation experiments showed that the SDF from modified navel orange peel by ultrasonic wave combined with cellulose treatment exhibited excellent probiotic activity. Therefore, ultrasonic wave combined with cellulase hydrolysis can be considered as an excellent method to modify dietary fiber of navel orange peel, which can provide reference for its application in functional foods.

Tea (Camellia sinensis), is extremely sensitive to climate change, so the impact of climate change on the distribution of tea in Yunnan Province is evaluated to formulate a development plan for tea-growing areas and protect biodiversity. Based on 100 tea distribution points (50 presence distribution points and 50 pseudo-absence distribution points, respectively) and 14 environmental variables, the suitable habitat areas of tea in Yunnan Province under different scenarios (SSP1-2.6, SSP3-7.0 and SSP5-8.5) at present and in future 2041-2060 and 2081-2100 were simulated and predicted based on RF model and ArcGIS spatial analysis technology. The results showed that: 1) The accuracy of the RF model is 0.92, which was a very good level. Factors such as annual average rainfall, slope, rainfall in the driest season, average rainfall in the coldest season, annual temperature fluctuation range, slope aspect, curvature and other factors had significant effects on the distribution of tea. 2) At present, the most suitable and suitable areas for tea trees gradually decrease from south to north, showing a C-shaped distribution, with 8.10×10⁴ km² being highly suitable, accounting for approximately 21.07% of Yunnan Province, and approximately 9.18×10⁴ km² being suitable, accounting for approximately 23.88% of Yunnan Province. 3) With future climate change, the suitable areas of tea plants will expand andmove northward, showing a W-shaped distribution change; the suitable areas of tea plante in Baoshan, Lincang, northern Pu’er, Honghe, and other areas will considerably expand. In the future, the newly-developed area of suitable areas of tea will encroach on the forest area, which may lead to the conflict between the reclamation of new tea plantations and the conservation of forest area and biodiversity.

Under the context of the development of high-tech industries, Guilin City, as a China’s innovation demonstration zones for the 2030 agenda for sustainable development with the theme of sustainable utilization of landscape resources, faced with a contradictory issue at present, which is how to promote the integration of landscape, environment and industry. This study taked Qixing District in Guilin City as an example, and used ArcGIS and Fragstats 4.2 software to analyze the landscape connectivity and stability of urban green spaces in Qixing District from multi-scale perspective of “area-street-site”. The findings indicated that the scenic areas constituted 67% of the total area, while residential and construction zones made up 33%, exhibiting an east-west distribution. Qixing District had good diversity as an important patch of human settlements, ecology, production and recreation, and the landscape connectivity was basically good with 0.554 9, but there was still a phenomenon of fragmentation. The results can provide reference for the subsequent development of landscape resource protection and production and life construction in Qixing District, and promote the harmonious coexistence of human-land relationship.

Assessing the spatiotemporal evolution of the ecosystem service values (ESV) in typical tourist cities plays a crucial role in formulating policies for urban conservation and environmental management. However, there is still a dearth of research on the spatiotemporal changes and spatial transfer networks of ESV in Guilin, Guangxi. With the six urban districts of Guilin, Guangxi Zhuang Autonomous Region, as the study area, this research employs equivalent factor correction and grid analysis methods to analyze the spatiotemporal changes in ESV based on land-use data spanning from 2000 to 2020. Leveraging the ecological service value equivalent factor table for Guilin, the breakpoint model and field strength model for ecological value transfer are applied to quantify the ESV transfer within the six districts, and visualize the spatial transfer network. The results indicated: (1) From 2000 to 2020, the total ESV in the six districts of Guilin showed a downward trend, decreasing from 2,866,942,700 yuan to 2,836,185,100 yuan. During the study period, each individual ESV component in these districts decreased over time, with the regulating services experiencing the most significant change. This suggested that urban expansion and land-use changes accompanying tourism development have had adverse impacts on ESV. (2) Among ecosystem service functions, climate regulation and hydrological regulation account for the largest proportions. The ranking of secondary ESV was: climate regulation > hydrological regulation > soil conservation > nutrient cycling maintenance > gas regulation > biodiversity > environmental purification > aesthetic landscape > food production > raw material production > water supply. The significant contribution of climate regulation is attributed to the vast forest area in Guilin, which played a pivotal role in regulating the climate. Climate and hydrological regulation were indispensible components of ecosystem services, essential for maintaining climatic stability, ensuring water supply, and mitigating natural disasters. (3) At a 1 km × 1 km grid scale, there were notable differences in the spatial distribution of ESV in Guilin. From 2000 to 2020, the area of high-ESV regions decreased over time, while the low-ESV regions were primarily concentrated in the northern part of Xiangshan District, the western part of Xiufeng District, the eastern part of Qixing District, and the southwest of Diecai District. Meanwhile, the area of regions with relatively high ESV increased over time, with Linggui District experiencing the most significant increase. This may be linked to urban development and construction, especially the "county-to-district" administrative reformation in Linggui. (4) The outward transfer of ESV among districts within the study area was ranked from largest to smallest as: Linggui District > Yanshan District > Diecai District > Xiufeng District > Xiangshan District > Qixing District. Hydrological regulation represented the service function with the highest transfer volume, accounting for 18.78% of the total ESV transfer in the study area. Regions with higher ESV tended to transfer more ESV externally. This study explores the status of ESV in the six urban districts of Guilin, Guangxi over a 20-year period and reveals the spatial transfer relationships among districts. It provides valuable insights into the spatiotemporal evolution of ESV in these districts, serving as a reference for future urban ecological protection, regional environmental management, and sustainable resource development.

The study of soil microbial biomass carbon and nitrogen is of great significance for the study of the forest soil nutrient status and carbon and nitrogen cycle, in order to find out the distribution characteristics and seasonal and soil layer change rules of forest soil microbial biomass carbon and nitrogen under different stand structure in degraded red soil region. The contents of soil microbial biomass carbon and nitrogen were taken as the measurement indexes,the soil of the Pinus massoniana pure plantation and Schima superb pure plantation planted in 1991 were taken as the control, and the effects of the P. massoniana replanted with broad-leaved treest of S. superb on soil microbial biomass carbon and nitrogen contents in different soil layers and their seasonal laws were analyzed. The results showed as follows: (1) Soil MBC content of S. superb plantation and the mixed plantation of P. massoniana and S. superb plantation was significantly higher than that of P. massoniana plantation (P<0.05), the content of soil MBC was significantly increased after the P. massoniana forest was thinned and replanted with broad-leaved trees of S. superb(P<0.05) and the soil MBC of all plantations decreased with the depth of soil layer. Seasons had a significant effect on soil MBC (P<0.05), and the soil MBC content of the three plantations was almost the highest in spring and the lowest in winter; (2) Soil MBN content of S. superb plantation and the mixed plantation of P. massoniana and S. superb plantation was significantly higher than that of P. massoniana plantation (P<0.05), the content of soil MBN was significantly increased after the P. massoniana forest was thinned and replanted with broad-leaved trees of S. superb (P<0.05). and the soil MBN of all plantations decreased with the depth of soil layer. Seasons had a significant effect on soil MBN, and the soil MBN content of the three plantations was almost the highest in spring and the lowest in summer (P<0.05); (3)There was significant positive correlation between soil MBC and soil MBN (P<0.01), the soil MBN was significantly positively correlated with litter N (P<0.05), and negatively correlated with litter C and litter C/N (P<0.01). The results showed that the content of soil MBC and MBN was significantly increased after the P. Massoniana plantation was thinned and replanted with broad-leaved trees of S. superb (P<0.05), which was more conducive to the improvement of soil fertility.

Soil microorganisms and enzyme activities play a crucial role in the quality of the soil environment and the sustainable use of soil nutrients. In order to further reveal the mechanisms of soil microbial biomass, soil enzyme activity, and their vector characteristics in response to litter addition and removal during the natural succession stage of the Loropetalum chinense community in karst areas, this study used a spatial instead of temporal research method to select the understory soil of different stages of natural succession of the L. chinense community as the research subjects. Litter addition and removal experiments were conducted in the early stage (shrub stage), middle stage (arbor stage), and late stage (aged forest stage) of natural succession of the L. chinense community. The effects of apophyte addition and removal on soil microbiomass carbon, nitrogen and phosphorus, soil accessible carbon, nitrogen and phosphorus enzyme activities and their stoichiometric ratios and vectorial characteristics in fringe flower communities were analyzed, and the correlation with soil physico-chemical properties was also analyzed to explore the main driving factors affecting changes in soil enzyme activities and their stoichiometric ratios and vectorial characteristics. The results showed that: the MBC content and QMB value in the late successional stage of fringe flower community were significantly higher than those in the pre-successional and mid-successional stages; the MBN and MBP contents in the pre-successional stage were significantly lower than those in the mid-successional and post-successional stages; apomictic and root removal significantly reduced the soil water content in the pre-successional stage of the fringe flower community as well as the organic carbon and total nitrogen contents in the three successional stages when compared with the control; the root and contents of the root removal treatment were lower than those of the napier removal; and the doubled napier addition significantly increased the SOC, TN, microbial biomass carbon, microbial biomass nitrogen, and microbial biomass phosphorus contents of the three successional stages; NL, NR, NI, and DL treatments significantly reduced the NAG activity in the late stage of succession and the AP activity in the early stage of succession; NI treatment significantly increased the AP activity in the middle stage of succession, while NR treatment significantly increased the AP activity in the later stage of succession; The average value of soil extracellular enzyme C/N was 0.32, the average value of C/P was 1.21, and the average value of N/P was 4.47. The vector angle of soil extracellular enzymes in the karst fringe flower community was lower than 45° under all treatment conditions, indicating that N was the main limiting factor affecting soil nutrients in this community. The redundancy analysis showed that the main factors affecting the activity of soil enzyme β-1,4-glucosidase were SOC, TN, pH and QMB; the main factors affecting the activity of soil enzyme NAG were the microbial quotient, SOC and TN; and the main factors affecting the activity of soil enzyme AP were soil MBP, MBN and TP. This study showed that the natural succession stage of fringe flower community and apomictic treatment had certain influence on soil microbial amount, enzyme activity and soil nutrient limitation in karst area.

Soil continuous cropping obstacle in Siraitia grosvenorii (Luo Han Guo) farmland can be effectively alleviated, meanwhile, soil fertility also can be improved by interplanting with potatoes and application with organic matter. In this study, the effects of rice straw and its biochar on soil enzyme activity and bacterial diversity in Siraitia grosvenorii farmland were analyzed. Firstly, five treatments, ie., Siraitia grosvenorii only, Siraitia grosvenorii interplanting with potato, Siraitia grosvenorii interplanting with potato+rice straw, Siraitia grosvenorii interplanting with potato+rice straw biochar, and Siraitia grosvenorii interplanting with potato+rice straw and biochar were set up. And the effects of different treatments on soil enzyme activities and bacterial diversity are analyzed. The results showed that the activities of soil urease, sucrase, and catalase activities all could be improved by interplanting with potatoes in Siraitia grosvenorii farmland. However, in comparsion with Siraitia grosvenorii monoculture, soil phosphatase activity only was decreased with 0.75 mg·g^-1·d^-1. Meanwhile, the diversity and richness indexes, such as Chao1, ACE and Shannon were all increased by intercropping with potatoes 624.56, 643.5, and 0.47, respectively, but at the phylum level, the relative abundance of Proteobacteria and Actinobacteria all decreased in Siraitia grosvenorii interplanting with potato treatment. Under the intercropping mode, rice straw and its biochar returning to field increased the activities of soil urease, phosphatase, and sucrase, while decreased the activities of soil catalase by 30.89% to 69.29%. Furthermore, the bacterial diversity and richness, such as the index of Chao1, ACE, and Shannon were all improved by Siraitia grosvenorii interplanting with potato+rice straw, Siraitia grosvenorii interplanting with potato+rice straw biochar, and Siraitia grosvenorii interplanting with potato+rice straw and biochar treatment with 309.23, 465.20, and 0.46, respectively. Meanwhile, in comparison with the monoculture, the relative abundances of Proteobacteria in other four treatment were all increased. In conclusion, compared with monoculture, interplanting potato promoted the conversion of soil carbon components by increasing the activities of soil urease, sucrase, and catalase; under the interplanting mode, the urease, phosphatase, and sucrase activities of soil were increased by the mixed application of rice straw and its biochar, which helped to improve soil fertility and promote soil health.

Surface temperature (LST) is an important factor affecting the energy exchange and water cycle between land and atmosphere, and plays a key role in monitoring drought, freezing damage, forest fire prevention and other disasters. Based on the LST data from 2000 to 2020, the spatial distribution characteristics and variation trend of annual, seasonal, monthly and diurnal LST in central Yunnan were analyzed by means of GIS spatial analysis, multi-ring buffer zone and geographic detector, and the key influencing factors of annual LST were discussed in combination with multi-source remote sensing data. The results show that: 1) The spatial distribution of annual average LST, annual average daytime and annual average night LST was lower in northeastern Yunnan and higher in southwestern Yunnan, all showed a warming trend, and the annual average night LST changes at the highest rate (0.043 4 ℃·a^-1); The seasonal variation rates of annual LST were summer >autumn >spring >winter; The average annual LST showed a strong symmetry pattern with June as the midpoint, with the lowest value in December and the highest value in june. 2) Air temperature, DEM, DSR, DNMI and NDVI were the main influencing factors of LST, and the explanatory power of air temperature and DEM was extremely enhanced when they interacted with other influencing factors. With every 100 m of elevation increased in central Yunnan, the annual average, annual average daytime and annual average night LST decreased by 0.48, 0.46 and 0.49 ℃, respectively. The average annual LST of different underlying surfaces was construction land > cultivated land > grassland > woodland > water. The intensity of urban heat island effect in the selected ring area was Mengzi City > Chuxiong City > Hongta District > Qilin District, while Wuhua District belongs to the urban cold island effect. The spatial pattern analysis of land surface temperature in central Yunnan can provide some theoretical support for the planning of regional agriculture and fire protection undertakings.

Rainfall is the main cause of geological disasters, and frequent rainfall in Yunnan Province leads to frequent geological disasters, posing a serious threat to the safety of people’s lives and property. Geological disaster meteorological risk forecasting is an effective means of disaster prevention and reduction. This study takes the high mountain canyon area of Nujiang Prefecture as an example, constructs information thresholds based on information value models, optimizes samples based on information thresholds, evaluates the susceptibility of comprehensive geological disasters in Nujiang Prefecture using machine learning models, calculates the effective rainfall coefficient of Nujiang Prefecture to establish a meteorological risk forecasting model, and verifies the accuracy of the model using historical disaster points. The results showed that the AUC values of landslide and debris flow disaster evaluation models optimized by information threshold samples were 0.97 and 0.99, respectively, with prediction accuracies of 0.93 and 0.98. The comprehensive geological disaster risk in Nujiang Prefecture was extremely high, and high-risk areas were mainly distributed along rivers and roads in the canyon. The meteorological risk warning model had a forecast hit rate of 90.91%, a missed report rate of 0, and a false alarm rate of 22.22%. The area of high-risk areas at the end of rainfall was 472.24 km². Optimizing samples with information thresholds has greatly improved the predictive and generalization capabilities of machine learning models, and the meteorological forecast model with a decay coefficient of 0.5 has improved the accuracy of geological disaster meteorological risk forecasting. The overall research results can provide substantial support for disaster prevention and reduction work in Nujiang Prefecture and similar areas.

Water ecological protection and sustainable utilization of water resources are key factors for the current sustainable development of the economy and society. Therefore, it is necessary to take timely measures for water ecological restoration to ensure the sustainable utilization of water resources and the stability of water ecosystems. This study takes Cijiang River as the research subjects, and establishes a comprehensive river and lake health status assessment system including hydrology, water quality, morphology, biology, social services, and river management, based on the correlation between the environment and indicators of Cijiang River. A comprehensive health assessment of Cijiang River is conducted. The results showed that the health score of Cijiang was 77.218 points, and the health status of Cijiang was rated as “healthy”. The main indicators with lower scores were the degree of water quality, ecological buffer zone index, and phytoplankton diversity index. This indicated that the main diseases of Cijiang were manifested in narrow buffer zones, low vegetation coverage, low water quality grades which can’t meet the requirements of functional zones, and fluctuating water quality indicators. It is recommended to regularly evaluate the health status of water resources, strengthen water resource management, improve water quality, aquatic biological environment, and aquatic ecological carrying capacity, increase vegetation coverage in buffer zones, and hope to provide reference for other river water ecological health assessments and sustainable development of water resources in the future.

Yulin’s GDP is at the forefront of the whole region, but its per capita water resources are at the bottom. Due to regional water shortage and unreasonable water resources development and utilization, some urban areas have the problems of water cut off or restricted water supply during peak periods, which has made Yulin’s sustainable economic and social development face severe challenges. In order to make scientific and rational use of water resources in Yulin City, based on the extension matter element evaluation model, 18 evaluation indexes were selected by the principal component analysis method, and the comprehensive weights of subjective and objective weights were calculated by the game theory to evaluate the water resources carrying capacity of Yulin City from 2010 to 2020. The results showed that the water resources carrying capacity of Yulin City fluctuated and increased from 2010 to 2020, but the change range was small; The carrying capacity of water resources was weak in 2011, and medium in other years. In 2010, 2014 and 2018, there was a trend of transformation from V₃ (medium load) to V₄(Relatively weak load). The main influencing factors of water resources carrying capacity in Yulin City were the utilization rate of water resources development, ecological water use rate, water consumption per ten thousand yuan GDP and population density. At the same time, considering the actual situation that the precipitation in Yulin was relatively rich but the spatial and temporal distribution is uneven, it is suggested that improvement of the water resources allocation capacity of Yulin should be considered as the key content of work, and the strictest water resources management system should be implemented to comprehensively improve Yulin’s water resources carrying capacity, and achieve sustainable social and economic development.