We investigated the spatiotemporal pattern of an endangered Hainania trichosperma population in a 15 hm2 permanent plot in the karst seasonal rainforest of southwestern Guangxi. Using spatial point pattern analysis and zero-inflated models, we analyzed population size and spatial distribution of H. trichosperma in 2011, 2016, and 2021, aiming to elucidate its spatiotemporal patterns and key habitat characteristics. We found a decline in population size (from 1978 to 1142 individuals), with the diameter-class structure shifting from an "inverted-J" to a "bell-shaped" distribution over the past decade. Spatially, the population showed distinct topographic differentiation, primarily aggregating on the midslopes with a southwestern aspect. In all the three years, individuals of different developmental stages aggregated at the 0-50 m scale, but randomly or uniformly distributed at larger spatial scales. The intensity of aggregation at the 0-50 m scale increased significantly over the study period, mainly due to the shifts in the spatial pattern of saplings. The species distribution range was significantly influenced by slope aspect, soil water content, and soil potassium concentration. While the abundance was primarily associated with altitude, soil bulk density, soil phosphorus and total potassium. Habitat preferences differed markedly between developmental stages. Adult trees favored upperslope positions with higher soil water content, phosphorus but lower potassium, whereas saplings preferred midslope habitats rich in phosphorus, low in calcium, and with lower soil pH. Taken together, H. trichosperma population, despite being in a protected area, displayed a declining trajectory. Therefore, conservation efforts should prioritize the protection of unstable small diameter individuals and consider stage-specific habitat preferences in future population reinforcement or restoration programs to mitigate further decline.

The karst peak-cluster depression landscape is characterized by pronounced topographic and edaphic heterogeneity, resulting in a high degree of spatial variability in resource availability. Such a complex environmental mosaic influences plant functional traits and their adaptive strategies. However, the patterns of trait variation and their underlying environmental drivers in karst peak-cluster depressions remain poorly understood. In this study, we investigated a 15-ha forest dynamics plot in the Nonggang Nature Reserve, Guangxi. We used linear mixed models to partition variance, principal component analysis to examine trait covariation, and redundancy analysis combined with hierarchical partitioning to evaluate the effects of topographic and edaphic factors on leaf functional traits at the community, species and intraspecific levels. The results showed that trait variation was mainly driven by interspecific differences, with part of the variation attributable to evolutionary history. Morphological traits and physiological traits exhibited relatively higher intraspecific and interspecific variation, respectively. The trait covariation patterns revealed that several leaf chemical traits exhibited atypical modes of coordinated variation. The explanatory power of topographic and edaphic factors for trait variation differed among ecological levels, being highest at the species level, followed by the community and intraspecific levels. Among these, the soil carbon-to-nitrogen ratio and slope were identified as the main drivers of species-level variation. Overall, our findings reveal functional shifts in plant ecological strategies in complex karst landscapes and emphasize the differential influence of topographic-soil factors across hierarchical levels, providing empirical evidence for understanding plant adaptive mechanisms along multidimensional environmental gradients.

Litter decomposition is a key process in nutrient cycling, shaped by both environmental factors and litter quality. However, in complex karst ecosystems, where shallow soils, high rock exposure, and fragmented terrain create strong abiotic and biotic heterogeneity, the dominant drivers of decomposition remain unclear. To explore these effects, we conducted two litter decomposition experiments, using litter deposited in situ and through reciprocal litter transplants, in the seasonal rainforests of karst (KF) and non-karst (NKF) regions. Although we observed no differences in litter mass loss rates or evidence of a home-field advantage (i.e., faster decomposition of litter in its native environment due to local adaptation of decomposer communities) between KF and NKF, the primary drivers of litter decomposition appeared to differ between the two areas. Notably, the litter nitrogen-tophosphorus ratio (N:P) was the most significant factor influencing litter decomposition in both KF and NKF. In KF, structural equation modelling showed that topographical factors were significantly correlated with leaf quality and soil elemental nutrient content, which in turn indirectly influenced litter decomposition. In NKF, tree diversity, soil elemental content, and other abiotic factors had quantitively similar effects on decomposition, with no single factor standing out as particularly dominant. Overall, our results suggest that nutrient acquisition strategies, particularly N:P and phosphorus acquisition, play a key role in shaping litter decomposition pathways. Additionally, in karst forests, topography significantly influences other factors, further affecting decomposition processes. These findings provide a basis for improving forest management approaches, optimizing nutrient cycling, and guiding species selection for afforestation and restoration in karst ecosystems.

东京桐（Deutzianthus tonkinensis）是国家二级重点保护野生植物，以其为建群种的群落是北热带喀斯特季节性雨林主要珍稀植被类型之一，蕴含丰富的生物多样性和特有种类，具有重要的生态价值和经济价值。然而，其群落物种多样性的动态特征及驱动机制目前仍不清楚。为探明东京桐群落时序动态及其驱动因素，该文基于广西弄岗1个1 hm 2 东京桐群落长期固定监测样地3次周期性的复查数据，分析其群落物种多样性在2012—2022年间的时序动态变化，探讨地形因子对群落物种多样性动态的影响。结果表明：（1）优势种重要值保持稳定，胸高断面积增加，物种多度下降。（2）共有18个稀有种与偶见种退出群落；物种丰富度减少了14%,Shannon-Wiener指数显著下降（P<0.05）。（3）对β多样性具有显著贡献的样方数减少了2%,80%的样方时间β多样性指数下降，样地的物种减少明显超过了物种增加。（4）海拔对样地内物种减少具有显著影响（P<0.05）。综上表明，虽然东京桐群落结构在10年间总体保持稳定，但α多样性与β多样性均变化明显，稀有种与偶见种丧失驱动了多样性变化，地形因子中的海拔对物种多样性的变化具有显著影响。该研究结果对深入认识喀斯特季节性雨林生物多样性动态及其驱动机制具有重要意义。

Radial growth, a key indicator of forest carbon sequestration, exhibits strong seasonal dynamics. However, tropical karst forests remain poorly understood, largely due to their complex topography, shallow soils, and high diversity. This study investigated seasonal radial growth patterns in a northern tropical karst seasonal rainforest in southern China by monitoring 348 trees (30 species) over five years. We analyzed correlations between annual and seasonal growth, compared wet- and dry-season growth, and examined interspecific differences. Environmental drivers (climate, topography, soil, and community factors) were assessed through multivariate analyses and mixed-effects modeling. We found that annual growth significantly correlated with both wet- and dry-season growth (p < 0.001), with wet-season growth significantly higher (p < 0.001). However, some trees exhibited enhanced dry-season growth, exceeding 36 % across all habitats and 47 % in depressions, highlighting dual-season importance and high carbon sink potential. Despite high species richness, few significant interspecific differences emerged within seasons. This suggests that carbon sequestration relative variation can be reliably assessed with minimal species sampling, providing a critical insight for managing species-rich forests. Climate variables (temperature, precipitation) were key predictors across seasons, with lagged effects from prior conditions. Notably, community factors (gap area, vertical structure diversity) dominated in the dry season, surpassing climatic influences and buffering environmental fluctuations. These findings highlight the importance of integrating seasonal dynamics, climatic legacies, and community processes into forest management. Such integration can improve carbon sequestration assessments in tropical karst regions under environmental change.

Stand spatial structure and sapling diversity are essential for maintaining ecosystem stability. However, the dynamic characteristics of stand spatial structure, its driving factors, and its influence on sapling diversity remain unclear. This study was conducted in a 15-ha forest dynamics plot located in the seasonal rainforest of the northern tropical karst region. We analyzed stand dynamics by characterizing multivariate distributions of stand spatial structure within random structural units, together with stand growth, mortality, and recruitment processes. To evaluate spatial autocorrelation and its drivers, we constructed spatial lag models and spatial error models. Generalized additive models were further applied to assess the effects of topography on stand spatial structure, as well as the influence of stand spatial structure on sapling diversity. The overall stand exhibited a uniform angle index of 0.5, a mingling index of 0.75, and a dominance index of 0.49, indicating random species distribution with moderate to high mingling. Null, univariate, bivariate, and trivariate distributions of stand spatial structure exhibited no significant change over the past decade. At the individual-tree level, however, survival, mortality, and recruitment processes induced notable shifts in spatial structure, which were more pronounced than the overall stand-level dynamics. Topography strongly influenced spatial structural metrics: elevation explained 31.35% and 64.99% of the variance in mingling and dominance, respectively, making it the most important factor for these indices, while slope accounted for 22.53% of the variance in the uniform angle index, serving as its primary driver. Among structural attributes, mingling had overwhelming explanatory power for sapling diversity, accounting for 99.68% of the variance in the Shannon–Wiener index, 99.70% in the Simpson index, 54.88% in Pielou’s evenness index, and 99.69% in Margalef’s diversity index, identifying it as the dominant factor regulating sapling diversity. These findings demonstrate that considering the dynamic changes of stand spatial structure at the individual-tree level, together with its effects on sapling diversity, is essential for understanding the structural and functional properties of tropical karst forests.

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.

Lianas are a crucial component of karst seasonal rainforests, yet research on them has predominantly focused on non-karst regions. Consequently, their abundance and species richness remain relatively understudied within karst ecosystems. We aimed to document the abundance and species richness of lianas and investigate their relationships with abiotic and biotic factors, based on data from a fully mapped 15 ha plot in a karst seasonal rainforest of Nonggang (SW China). Structural equation models (SEMs) were employed to estimate the path coefficients and variation of dependent variables, enabling a comprehensive analysis of the factors affecting the abundance and species richness of liana. Within the 15 ha plot, a total of 23,819 lianas were identified, encompassing 113 species from 34 families. These lianas constituted 24.16% of the total woody plant density and 33.44% of the species present, but only 4.32% of the total woody plant basal area. Lianas are primarily influenced by abiotic factors, especially elevation and phosphorus (P), with less impact from biotic factors. Our findings reveal that lianas, despite constituting a relatively small percentage of the total woody plant basal area, significantly contribute to the density and diversity of the forest. Notably, abiotic factors such as elevation and phosphorus availability predominantly shape the distribution and richness of lianas, highlighting the importance of these environmental variables. The findings offer valuable insights for future liana studies and the preservation of karst forests’ biodiversity.

Forest biomass accumulation is fundamental to ecosystem stability, material cycling, and energy flow, and pit lays a crucial role in the carbon cycle. Understanding the factors influencing aboveground biomass (AGB) is essential for exploring ecosystem functioning mechanisms, restoring degraded forests, and estimating carbon balance in forest communities. Tropical karst seasonal rainforests are species-rich and heterogeneous, yet the impact mechanisms of biotic and abiotic factors on AGB remain incompletely understood. Based on the survey data of a 15 ha monitoring plot in a karst seasonal rainforest in Southern China, this study explores the distribution characteristics of AGB and its intrinsic correlation with different influencing factors. The results show that the average AGB of the plot is 125.7 Mg/ha, with notable variations among habitats, peaking in hillside habitats. Trees with medium and large diameters at breast height (DBH ≥ 10 cm) account for 83.94% of the aboveground biomass (AGB) and are its primary contributors; dominant tree species exhibit higher AGB values. Both biotic and abiotic elements substantially influence AGB, with biotic factors exhibiting the largest influence. Among abiotic factors, topographic factors have a strong direct or indirect influence on AGB, while soil physicochemical properties have the smallest indirect impact. This research provides a comprehensive understanding of AGB distribution and its influencing factors in tropical karst forests (KFs), contributing to the management of carbon sinks in these ecosystems.

Spatial patterns can reveal many ecological processes in forest communities; thus, understanding the spatial patterns of trees and their interactions is key to exploring forest dynamics. However, few studies have explored the spatial patterns and interactions between adults and recruits over longer time spans in tropical karst forests. A forest dynamics census was conducted (2011–2021) in a 15-ha karst seasonal rainforest plot at the Nonggang National Nature Reserve, in Guangxi, China. The tree community structure, which included a total of 20 tree species (≥ 50 individuals) at various states of recruitment, survival, and mortality, were selected and investigated via detailed analyses. First, univariate pair correlation functions and bivariate mark correlation functions were utilized to analyze the spatial patterns of dead recruits, surviving recruits, and adults. Aggregation was the dominant intraspecific distribution pattern in the plot that decreased at larger scales, which indicated that dispersal was limited. The segregation of bivariate patterns in most species suggested that there was scramble competition between the surviving and dead recruits, which translated to their not clustering around adults. Second, it was revealed through testing that density dependence was not prevalent. However, negative density dependence was more common in species that exhibited density dependence, as various species respond differently to changes in population density. Third, most recruits had a low probability of survival, which for several dominant species was influenced by neighborhood effects. This study did not support the Janzen-Connell hypothesis, as the survival probability of most recruits was not enhanced with the distance from adults. This meant that the effects of distance from adults on the growth of recruits in Nonggang forests were negligible. These results suggested that dispersal limitations and habitat heterogeneity played more significant roles in the regulation of tree spatial patterns and seedling growth (or mortality) in tropical karst seasonal rain forests. This work will contribute to the restoration and conservation of fragile forest communities in Karst regions, while providing a theoretical basis for biodiversity research, forest management planning, and ecosystem services.

Effects of different nitrogen fertilizer application rates on fruit quality of pitaya under the condition of calcareous soil in karst area were discussed in order to investigate the effects of nitrogen fertilizer application level on fruit quality of pitaya under calcareous soil condition in karst area.The'Taiwan Dahong'pitaya were used as the experiment material.Based on 0.216 kg of phosphorus(P)and 0.324 kg of potassium(K),four nitrogen(N)application levels(CK,T1,T2,T3)were setted.Twenty-one fruit quality indexes were determined,and the quality differences of pitaya with different N application levels(CK,T1,T2,T3)were compared.At the same time,eleven appearance quality indexes were comprehensively analyzed by principal component analysis.The results were as follows:(1)Compared with the control,N application could increase the contents of soluble sugar and soluble solids of fruit,reduce the contents of protein and dietary fiber,and the high nitrogen treatment(T3)was significantly different from other treatments.With the increase of N application,the contents of titratable acid and vitamin C of fruit increased firstly and then decreased,while the solid-acid ratio decreased firstly and then increased.T3 significantly increased the fruit vertical and horizontal diameters,fruit shape index and single fruit weight.(2)Compared with the control,N application treatment reduced the N content of pitaya fruit and increased the P content,and the N and P contents of each treatment were significantly different.The K content of fruit increased with the increase of N application.N application increased fruit boron(B)content and decreased fruit cuprum(Cu)content.The contents of manganese(Mn),ferrum(Fe),calcium(Ca)and magnesium(Mg)in different treatments were ranked as T3＞T1＞CK＞T2.The content of zinc(Zn)decreased firstly and then increased with the increase of N application.(3)The principal component comprehensive evaluation score of the high N treatment was the highest,indicating that when selecting brown calcareous soil in Guilin karst area to grow pitaya,supplemented by a certain amount of P and K fertilizers,high N treatment was more conducive to improving the quality of pitaya.Therefore,in actual production,it is necessary to make appropriate adjustments according to the soil fertility status of the plantation.

Parashorea chinensis is a symbolic tree species in tropical seasonal rain forests in China. Its primeval habitat forest communities show clear adaptations to a tropical seasonal environment, and have the greatest diversity of tree species and the highest proportion of tropical flora, in China. Recently, a P. chinensis with a height of 72.4 m was discovered in the primeval forest of tropical karst peak cluster depression in Nonggang, Guangxi. This tree broke the record for the tallest tree in China's karst areas. Here we examine the properties of the forests that can support such remarkable trees, in order to update our understanding of the vegetation characteristics of tropical karst forests. We draw on four primeval forest community survey plots of P. chinensis in Nonggang, in order to summarize the characteristics of layer structure, species composition, plant areal types, leaf features, ecological habits, and dominant genera of these forest communities. The characteristics of the region around the tall tree were compared with those of other communities of P. chinensis in China. The results were as follows: (1) Giant trees exceeding 50 m in height are scattered across the canopy of the tallest tree's community. The continuous arbor and shrub layer can be divided into four layers, approximately 36.9 m, 25.6 m, 9.5 m, and 2.7 m high. There are 64 tree species, 24 shrub species, 31 vine species, 26 grass species, and 8 epiphyte species within the 2400 square meter plots. (2) The arbor layer is dominated by tropical flora plants such as P. chinensis and Dracontomelon duperreanum, karst endemic plants such as Excentrodendron tonkinense and Cephalomappa sinensis, and deciduous trees such as Garuga forrestii and Allospondias lakonensis. (3) Species of tropical flora account for 93.7% of the trees in the arbor layer, with species from tropical Asia (Indo-Malay) accounting for 65.6%. Mega-phanerophytes account for 15.6%; evergreen plants account for 85.9%; compound leaf plants account for 39.1%; leathery leaf plants account for 60.9%; and typical karst plants account for 28.1%. (4) The greatest similarity to the dominant tree forest is shown by Napo County in Guangxi. Maguan and Mengla Counties in Yunnan, Bama, Tianyang, and Dahua Counties in Guangxi are progressively less similar. These relationships indicate that the influence of tropical climate on community forest structure is greater than that of their geology. In summary, the primeval forest communities of P. chinensis in Nonggang thrive in the closed habitat environment of the tropical karst peaks cluster depressions, benefiting from the relatively humid and warm local climate. Characterized by the presence of iconic tropical giant trees such as P. chinensis and Dracontomelon duperreanum, these forests exhibit the intricate forest layers of a tropical seasonal rain forest. Due to the combined influence of the tropical northern margin's geographical location and karst landform, these communities' forest canopies contain a certain proportion of deciduous tree species, with relatively low proportions of mega-phanerophytes and epiphytic plants. The communities are rich in drought-resistant plants with features such as leathery leaves, microphyll leaves, compound leaves, and typical karst plants.

In order to study the adaptive strategies of dominant tree species in a karst seasonal rain forest to heterogeneous habitat conditions, seven dominant tree species in a virgin forest in Nonggang, China, were taken as the research objects. The leaf micromorphological physiological characteristics of adult individuals of each tree species and the photosynthetic indexes of leaves in the growing season of these trees were measured, and the response of leaf structure and function of tree species to heterogeneous habitat in karst peak-cluster mountain was discussed. The results were as follows: (1) Along the karst habitat gradient from valley to hilltop, nine leaf micromorphological indexes, such as leaf compactness, palisade tissue thickness, cuticle thickness, and epicuticle thickness, showed a significant upward trend, while leaf looseness showed a significant downward trend. (2) Along the karst habitat gradient from valley to hilltop, the light compensation points, dark respiration rate, and maximum transpiration rates of these leaves all showed a significant upward trend. However, the maximum water use efficiency, the maximum intercellular CO2 concentration, and the apparent quantum efficiency showed a significant downward trend. (3) Leaf compactness was positively correlated with photosynthetic and transpiration ability indexes. Leaf looseness was negatively correlated with these two types of indexes. In conclusion, there is a trade-off relationship between photosynthetic efficiency and drought tolerance in leaf functional traits of dominant tree species in the karst seasonal rain forest. Trees distributed in the valley have obvious adaptive characteristics to weak light. Trees distributed on the slope show extensive habitat adaptability. Due to the limitation of strong light, high temperature and exposed rock, the trees distributed on the hilltop show strong drought adaptability and conservative ecological adaptive strategies.

Aims:Saplings are an important component of maintaining the species diversity of forest ecosystems.Their diversity is related to forest community structure and growth dynamics.Therefore,it is very important to study the spatial distribution pattern and potential mechanism of sapling regeneration for forest community dynamics.To strengthen the understanding of the dynamic changes of the northern tropical karst seasonal rainforest,we will study the spatial distribution pattern and mechanism of sapling regeneration in 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang,southwestern Guangxi. Methods:Based on the survey data from 2011 to 2016,the individual number,spatial pattern characteristics,and influencing factors of new saplings(DBH ≥ 1 cm)in five years were analyzed by spatial point pattern and redundancy analysis. Results:A total of 101 species of new saplings were observed,accounting for 45.3％of the surveyed species in 2011,and the sapling density was 196.5 ind./ha.The newly increased saplings showed aggregated distribution at 0-7 m and 10-16 m scale,and random distribution above 16 m scale.Altitude is the main factor affecting the regeneration of saplings,followed by topographic wetness.Biological factors had a weak impact on sapling regeneration.The number of saplings was negatively correlated with increasing altitude,and positively correlated with topographic wetness.Moderate positive correlation between adult tree individuals and young tree regeneration was observed. Conclusion:In this karst seasonal rainforest,sapling regeneration and spatial distribution pattern are synergistically affected by various influencing factors,which may be related to limited seed dispersal and habitat heterogeneity.

Excentrodendron tonkinense is a constructive species of karst seasonal rainforest and a karst obligate plant, which is also one of the national secondary key protected wild plant and an IUCN endangered plant, with high ecological economic value. In order to explore how the potential suitable areas of E. tonkinense change in the context of global change and its key driving factors, we used the maximum-entropy (MaxEnt) model to analyze the potential geographical distribution changes in China under future climate scenarios (SSP1-2.6 and SSP5-8.5), and tested the influence of the karst geological background distribution on predicting the suitable areas of karst obligate plants. The results were as follows: (1) In the case of adding karst geological background data, the average AUC value of the prediction model for the suitable area was 0.997, which had a good prediction effect. And the model prediction results were strictly limited to the karst region, consistent with the characteristics of karst obligate plant E. tonkinense. (2) According to the fitting results of the model, the karst geological background, the precipitation of the warmest quarter (800-950 mm), and the minimum temperature of the coldest month (7-11℃) were the key factors limiting the distribution of E. tonkinense. (3) With the increase of temperature in the future, the potential suitable areas for E. tonkinense would continue to expand in higher latitude karst areas; large areas of stable habitats existed in parts of southwestern Guangxi and southeastern Yunnan. In conclusion, the karst geological distribution is essential as predicting the potential geographic distribution of karst obligate plants such as E. tonkinense; if the temperature continues to rise in the future, its potential suitable areas will expand to high latitudes, and the degree of endangerment may be affected by climate, which means that it is not obvious under the influence of climate change; parts of Southwest Guangxi and Southeast Yunnan are suitable areas for the conservation and utilization of E. tonkinense under the climate change scenarios in the future. The results provide some scientific reference for the introduction, cultivation, sustainable management, protection and utilization of E. tonkinense.

Aims:Mineral elements are important determinants of soil nutrients and are related to forest community composition and nutrient cycling.There is high terrain heterogeneity in karst seasonal rainforest local scale,but there is still lack of research on how terrain and other abiotic and biotic factors affect the spatial distribution of soil mineral elements in karst area. Methods:In this study,we set up 100 litter fall traps along the elevation gradient in the 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang,southwestern Guangxi,and conducted soil sampling at the litter fall trap sites.We tested soil samples for the content of mineral elements such as K,Ca,Mg.We performed quantitative analysis of the association between ecological factors and soil K,Ca,Mg in karst seasonal rainforests based on methods such as spatial regression models and variation partitioning. Results:Soil K,Ca and Mg in the study area were all spatially autocorrelated,with Ca significantly positively correlated with elevation and convexity(P＜0.05),mainly clustered in the hilltop;K significantly positively correlated with topographic wetness index,mainly clustered in low-lying land;Mg showed clustering characteristics in the hillside.Variation partitioning shows that ecological factors drove the spatial distribution of soil K,Ca and Mg more than spatial structure.Elevation was the highest predictor variable among the individual ecological factors,and abiotic factors were higher than biotic factors in general,and species richness was the highest among biotic factors,while the aggregation of Mg elements was accompanied by a higher level of species richness. Conclusion:In this study,the soil K,Ca and Mg in the 15 ha northern tropical karst seasonal rainforest dynamics plot in Nonggang have spatial autocorrelation,and the spatial distribution of the three soil elements was significantly different.In the karst seasonal rainforest in southwestern Guangxi,ecological factors such as altitude have a strong driving effect on the spatial distribution of soil K,Ca and Mg.However,in terms of the accuracy of the analysis results,adding more ecological factors and expanding soil sampling points may further enhance the interpretation of ecological factors and spatial variables on the spatial distribution of soil elements.

Rural agricultural activity generates cropland, secondary vegetation and straggling primary forest and can modify the soil seed bank (SSB), potentially impacting the restoration of preferred species. The interaction between vegetation and seed banks during the recovery process is dependent on management practices and recovery pathways. This study was carried out in Guilin of southwest China to assess the variation in plant diversity and species composition of both aboveground and soil seed banks across three typical vegetation types with different human interventions: orchard, bamboo shrub and primary forest. The results show that there were significant differences in the species composition and diversity of aboveground vegetation and SSB, as well as in soil properties among three typical vegetation types. The primary forest had the highest aboveground species diversity, while the orchard had the highest species diversity and seed density of SSB. In addition, principal component analysis (PCA) and canonical correspondence analyses (CCAs) showed that the species composition and plant life forms of the three typical vegetation types were significantly influenced by soil properties. Based on these findings, the characteristics of aboveground vegetation and the soil seed bank and their correlations with soil properties are expected to drastically change with human intervention. These results imply that unsustainable land use has greatly impacted soil properties, and consequently, the aboveground vegetation and SSB. Nevertheless, vegetation will recover quickly after farming is abandoned. The successful restoration of fragmented ecosystems requires the addition of seeds and seedlings of target species, especially perennial woody plants from the relevant natural ecosystems, to accelerate succession from bamboo shrub to forest.

以广西弄岗北热带喀斯特季节性雨林15 hm2森林动态监测样地为对象,结合2011年和2016年两次调查数据,分析5年间样地树木死亡个体的数量、径级结构和空间格局特征等.结果显示:2011年至2016年,样地有86.5％的树种出现了个体死亡的现象,死亡个体占个体总数的14.4％;死亡个体的聚集程度随空间尺度的增大而逐渐减弱;小径级个体死亡与周边邻体和环境的关联性较大;竞争是影响弄岗北热带喀斯特季节性云林树木死亡的主要因素.综合来看,北热带喀斯特季节性雨林内树木死亡并非是一个完全随机的过程,而是树木本身特征和生物与非生物环境共同作用的结果.

森林凋落物是森林生态系统极其重要的组成部分,了解凋落物分解过程有助于理解森林生态系统的物质循环和养分平衡的机理.本研究以桂西南喀斯特季节性雨林凋落叶为研究对象,将2018年全年收集的凋落叶混合均匀后采用分解袋法进行原位分解实验,探讨桂西南喀斯特季节性雨林凋落物的分解特征.结果发现:凋落叶在分解过程中整体失重模式呈现先快后慢的变化趋势,且不同生境类型下凋落叶失重率为:洼地>坡地>峰顶;分解过程中C含量呈波动状态,但总体表现为下降趋势,而N含量呈无规则波动;失重率与海拔呈显著负相关,并在分解初期和中后期与坡度呈显著负相关,C含量变化同海拔呈显著正相关,而与其他环境因子的相关性则随分解时间的变化而变化.桂西南喀斯特季节性雨林凋落叶分解速率低于亚热带常绿落叶阔叶混交林,但与同类型的喀斯特森林退化区相当;喀斯特季节性雨林不同生境类型代表的微环境因子对凋落叶的分解具有重要影响,其中海拔引起的温度和湿度的差异是影响喀斯特季节性雨林凋落叶分解速率和C、N含量变化的主要因素.

不同的品种抗性不同,为进一步探究不同火龙果品种之间的抗性差异,为后续火龙果抗性育种提供参考,该研究利用Illumina HiSeq 2000测序平台对'普通白肉'(BR)和'厄瓜多尔黄龙'(EY)两个品种进行转录组测序分析,并参考GO Ontology、KEGG等公共数据库对差异表达基因进行功能分类与富集分析.结果表明:(1)BR与EY共有14248个差异基因,其中5446个基因上调,8802个基因下调.(2)相关GO功能分析表明这些差异基因主要参与酶催化活性、细胞组分、代谢过程等,其中参与氧化还原酶活性的349个差异基因在BR中表达量上调.(3)KEGG通路分析显示,大部分差异基因富集在新陈代谢和生物合成等,其中参与角质、木栓质和蜡质生物合成的差异基因有12个,如CYP86和CER1等.参与氧化还原酶活性的差异基因在BR中较EY表达量上调,且显著富集,表明BR与EY在生长发育和细胞代谢过程差异显著.参与角质、木栓质和蜡质生物合成的差异基因在BR中表达量上调,此类基因在BR中具有较高的表达量且显著富集,表明BR可能具有较强的抗旱和抗病能力.