The northern sand prevention belt is a key area for combating sandification and desertification in China. This region is characterized by arid conditions, water scarcity, barren soil, severe desertification, and salinization, with prominent conflicts between open-pit mining and ecological conservation. Taking the large-scale open-pit mining areas in Inner Mongolia, which have the largest area and production capacity in the northern sand prevention belt, as the research object, this study adhered to the systematic engineering concept of addressing both symptoms and root causes. Following the research framework of "damage-reduction mining → three-dimensional water conservation → soil construction and activation → systematic restoration → integrated supervision" this study adopted a whole-chain integrated technical route of ''theoretical research → technology development → equipment development → integrated demonstration → promotion and application''. Key scientific issues in large-scale open-pit mining areas of the northern sand prevention belt were analyzed, including ecological degradation mechanism, damage-reduction mining mechanism, and ecological self-maintenance mechanism. A technical system was developed and established for ecological damage reduction, protection, and restoration in these mining areas. The research results will contribute to achieving damage-reduction mining, scientific restoration, precise management and control, and self-maintenance of ecosystems in large-scale open-pit mining areas, as well as constructing ecological protection-oriented coal bases and an important ecological security barrier in northern China.

Karst regions are among the area most severely affected by rocky desertification and are recognized as some of the world’s most ecologically fragile landscapes. Graben basins represent a distinctive geomorphic unit in the karst region of Southwest China, where large-scale afforestation faces a fundamental conflict between plant water demand and limited soil-water availability. However, the seasonal dynamics of transpiration and water uptake patterns of plantation species in these drought-prone landscapes remain poorly quantified. In this study, we investigated two representative plantation species, Eucalyptus globulus and Pinus massoniana, in a karst graben basin of Southwest China. By integrating sap flow monitoring with stable isotope analysis, we quantified seasonal variations in plant water sources and transpiration. The results revealed pronounced seasonal and species-level differences in water use between the two plantations. During the dry season, E. globulus primarily obtained water from the 20–100 cm soil layer, which accounted for 68.2% of its total water uptake, indicating a relatively flexible water use strategy. In contrast, P. massoniana mainly relied on the 0–60 cm soil layers, which contributed 70.4% of its water uptake, suggesting a more conservative strategy. During the rainy season, with increased precipitation input, both plantations preferentially used shallow soil water from the 0–20 cm layer. Transpiration was most active during the rainy season. Monthly mean transpiration of E. globulus was 2.1 and 1.5 times that of P. massoniana in the dry and rainy seasons, respectively. Overall, during the observation period, both plantation types adjusted their water uptake depth and transpiration processes in response to seasonal changes in water availability. These findings provide evidence for understanding soil-plant water relations in plantation ecosystems of karst graben basins and offer practical insights for site-specific species selection and plantation water management. Nevertheless, the long-term ecological and hydrological effects of these plantations require further evaluation through multi-year monitoring.

Uncovering the intricate relationships within the realm of ecosystem services (ESs) across various spatial and temporal dimensions, as well as their nonlinear relationships with natural–social factors, is a fundamental condition for regional ecosystem management. This study focuses on Honghe Prefecture, Yunnan Province, and it quantifies the supply of ESs at the grid and township scales, clarifies the interrelationships among ESs and influencing elements, and proposes cross-scale regional ecological management strategies. The findings indicate the following: (1) ESs exhibited spatial variability. In the last 20 years, the supply capacity of food production (FP) increased by about 46%, while other ESs showed a downward trend. (2) Synergistic effects among ESs primarily occurred between WY, habitat quality (HQ), carbon sequestration (CS), and soil conservation (SC), while trade-off effects mainly took place between FP and other ESs. (3) Significant and dramatic changes in the ecosystem service bundles were observed in the southern mountainous areas. At the grid scale, the overall area of the integrated ecological bundle declined by approximately 88%. However, the proportion of the HQ-CS key synergy bundle increased from 15.68% to 40.60%. Similar spatial patterns and trends were also observed at the township scale. (4) There was a notable reduction in the comprehensive supply of the ecosystem service index (ESI) in the southwest, in which human activities and climate drought factors played a major negative driving role, and some driving factors had threshold effects with the ESI. Existing research often ignores the nonlinear relationship between complex spatiotemporal dynamics and ecosystem services. Thus, this study constructed a comprehensive cognitive framework for regional ES status from the perspective of “supply–interaction–driving–threshold” for ESs, providing a more comprehensive understanding of regional ES management.

[目的]河北省围场满族蒙古族自治县(简称围场县)的小滦河流域位于中国北方典型的农牧交错带,土地沙化问题严重.探究小滦河流域土地沙化变化过程,了解土地利用变化和海拔对土地沙化的影响,为流域土地沙化的防治和山水林田湖草沙综合治理提供理论依据.[方法]基于谷歌地球引擎(Google Earth Engine)和ArcGIS平台分析 2000、2010、2020年Landsat系列遥感数据,通过构造归一化植被指数(NDVI)和地表反照率(Albedo)特征空间,建立荒漠化差值指数(DDI)模型,对沙化土地进行程度划分,分析区域土地沙化的时空变化特征.[结果]20 a间小滦河流域土地沙化总体呈好转趋势,极重度、重度沙化土地面积分别减少近 80%和 56%,流域以轻度沙化、非沙化土地为主,约占流域面积的 65%.沙化土地改善速率在后期有所降低,集中分布在塞罕坝林场及小滦河下游.流域沙化景观趋向于集中,景观破碎化程度持续降低.林地、草地的沙化状况改善作用明显,土地沙化程度随海拔升高呈降低趋势.[结论]2000年来小滦河流域土地沙化状况整体有所好转,而御道口镇及牧场等区域存在土地沙化恶化趋势.今后需加强对流域沙化的改善措施,开展精准治沙,进而实现小滦河流域的可持续发展.

[目的]探究南水北调中线工程水源区内岩溶地貌背景下,不同植被恢复模式土壤养分与化学计量特征,评价南方岩溶连片分布区北缘林地生境土壤养分供给状况,以期为南水北调中线工程水源涵养区林分经营管理、退化生态系统恢复重建和石漠化治理提供理论依据.[方法]以河南淅川县岩溶区栓皮栎天然次生林、侧柏人工林和杉木人工林下土壤为研究对象,通过室内实验对土壤有机碳(SOC)、全氮(TN)、全磷(TP)、全钾(TK)、碱解氮(AN)、速效磷(AP)和速效钾(AK)含量进行测定,并计算土壤各元素的化学计量比,分析不同恢复模式林地生境土壤养分变异状况.[结果]岩溶区不同植被恢复模式下土壤SOC、TN、TP含量分别为10.23～28.99、0.89～2.42、0.43～0.77 g/kg;土壤碳氮质量比(C:N)、碳磷质量比(C:P)、氮磷质量比(N:P)均值分别为10.41～11.89、13.69～80.00、0.18～6.61.土壤养分含量与化学计量比受植被类型与土层深度的影响,表现为表层土壤(0～10 cm)高于下层土壤(>10～20 cm、>20～30 cm).除TP含量外,两种植被恢复模式土壤养分含量表现为天然次生林高于人工林.相关分析表明,不同植被恢复模式下土壤SOC、TN、TP含量间存在显著相关关系,说明三者空间分布有较一致的变化规律.[结论]在南水北调水源区,自然恢复的栓皮栎次生林是较为理想的植被恢复模式,而3种林分在生长过程中均受到氮或磷元素的限制.在日后的林分经营管理中,针对天然林可适度施用磷肥补给,对人工林添加氮肥,并通过抚育间伐等措施,提高植被对养分的吸收效率,从而促进植被土壤间的协调发展.

The formation and continued maintenance of beta diversity are essential factors contributing to the effective conservation of plant community biodiversity and sustainable development of ecosystem functions. While it is widely acknowledged that two different patterns, including turnover and nestedness, strongly influence plant community beta diversity, their relative importance in the unique dry and hot valleys of Southwest China is yet to be fully understood. For this study, we established a 100 km belt transect in the Nujiang dry and hot valley of Southwest China and conducted community investigations. The calculations of species and phylogenetic beta diversity composition patterns allowed us to explore the relative importance of environmental and dispersal limitations in terms of their contributions to beta diversity. The findings indicated that in the Nujiang dry and hot valley of Northwest Yunnan, species and phylogenetic beta diversity in the plant communities were mainly composed of the turnover component. The values of phylogenetic beta diversity and its turnover components were lower than those of species beta diversity. Both environmental and dispersal limitations played a role in partitioning beta diversity in the region, with environmental limitations being more dominant than dispersal limitations. The analysis of specific environmental factors revealed that climate factors, such as mean annual precipitation and Hargreaves reference evaporation, and soil factors, such as pH, were the primary drivers of species and phylogenetic beta diversity in the region. In addition, we observed that various limiting environmental factors related to the growth and development of different life forms existed within the dry and hot valley communities. The study highlighted the potential benefits of establishing conservation reserves featuring multiple dominant shrub species in the Nujiang dry and hot valley of Southwest China for the protection of the vegetation. The findings demonstrated that environmental factors, particularly hydrothermal conditions, played a significant role in constraining the maintenance of beta diversity in plant communities in the dry and hot valley region at a regional scale, given the geological history and environmental changes that have occurred over time.

环境变迁下生物多样性格局形成及维持机制研究是生物多样性研究的核心科学问题之一.滇西北和滇东南两地曾在地质历史上具有相似森林植被,随着板块运移,两地出现明显环境区化,植被类型亦产生巨大变化,仅在两地干热河谷生长着相似外貌和类型的植物群落,而其物种组成和生物多样性格局有何异同尚不清晰.该研究分别在怒江和元江干热河谷设置100 km样带,每间隔4 km布设样地,对其植被进行群落学调查.通过计算两地不同生活型植物重要值、Alpha及Beta多样性指标,拟阐明起源相近、外貌相似的两地植被在环境变迁后群落物种组成及生物多样性的变化规律.结果表明:①滇西北干热河谷共调查到维管植物125种(51科104属),滇东南干热河谷共调查到114种维管植物(44科102属).滇西北乔木和灌木物种丰富度均略高于滇东南,草本反之.滇西北乔木多度极显著高于滇东南(P<0.01),灌木多度未出现显著性差异,草本多度滇东南显著高于滇西北(P<0.05).②从科水平分析,滇西北和滇东南乔木和草本优势科组成种类相似,但灌木优势科组成种类差异性较大.从种水平分析发现,两地乔木优势种种类差异较大,而灌木和草本组成相似.③滇西北植物群落Shannon-Wiener指数、Simpson指数均略低于滇东南,但无显著性差异,而Pielou指数显著低于滇东南(P<0.05).滇西北干热河谷植物群落中优势种单一,物种分布具有聚集性;滇东南植物群落物种分布较均匀,物种多样性丰富.④两地植物群落之间相异性系数较高,处于极不相似水平,群落间生境差异性较大,不同生活型植物Beta多样性差异极显著(P<0.001),其中以灌木物种组成的相异性最大.研究显示,起源相近、外貌相似的滇西北与滇东南干热河谷的植物群落物种组成存在明显差异,Alpha多样性差异不明显,Beta多样性存在显著性差异,环境变迁后区域环境差异改变了植物群落结构.

The distribution of karst landscapes over the Earth's surface, to a large extent, follows the distribution of carbonate (limestone and dolomite) and gypsum rocks and together these make up about 12% of the Earth's land area, and the largest karst region in to world is in Southwestern China. Characterized by a unique set of landforms, these geographical areas also differ from other geomorphic regions by the presence of cave systems in the subsurface. Unfortunately, due to human disturbances, such as deforestation, agricultural expansion, livestock overgrazing and fire, these regions have been affected by varying degrees of degradation, which could also be worsened if water and soil erosion phenomena typical of these areas are considered. Therefore, there is a need to implement measures and strategies to protect these karst areas and develop plans to restore vegetation in this region. To support local and national authorities to achieve this goal, this study aims to characterize nutrient deficiencies in degraded areas and estimate what could be the thresholds required to facilitate the restoration of vegetation in karst areas in southwest China. The results obtained confirm that the total element concentrations for Soil Organic Carbon (SOC), N, K, Ca, P, S and Mg were relatively high in the study karst area in southwest China. However, the total amounts of soil nutrients stored were very low due to the limited amount of soil identified as a consequence of previous deforestation processes undertaken within this study area and this aspect needs to be taken into consideration if aiming at a positive success of future restoration processes.

[目的]通过研究南水北调源头渠首岩溶区不同林分生长及其影响的主导因子,为科学指导岩溶区植被恢复、林地管理与林分改造提供依据.[方法]以南水北调水源地中线渠首所在地淅川县岩溶区为研究对象,基于结构方程模型构建乔木层生物量与基岩裸露度、土壤厚度、树种多样性以及林分密度的模型,进行关系耦合.[结果]基岩裸露度与林分密度为正相关关系(P<0.01),与树种多样性为极显著正相关关系(P<0.01),与建群种生物量为极显著负相关关系(P<0.01).基岩裸露度对林分密度的直接影响系数为0.198,对树种多样性的直接影响系数为0.519,对建群种生物量的总影响系数、直接影响系数及间接影响系数分别为?0.659、?0.722和0.063,对林分生物量的间接影响系数为?0.604.土壤厚度与建群种生物量呈显著正相关关系(P<0.05),与树种多样性、林分密度与建群种生物量为正相关关系.土壤厚度对建群种生物量的直接影响系数为0.258,对林分总生物量的间接影响系数为0.262;树种多样性对建群种的直接影响系数为0.084,对林分总生物量的总影响系数、直接影响系数及间接影响系数分别为0.211、0.126和0.085;林分密度对建群种的直接影响系数为0.096,对林分总生物量的间接影响系数为0.098.建群种生物量与林分总生物量为显著正相关关系(P<0.01),建群种生物量对林分总生物量的总影响系数为1.014.[结论]基岩裸露度、土壤厚度、树种多样性及林分密度与建群种生物量、林分总生物量之间存在着复杂的关系,在岩溶区降低基岩裸露度、增加土壤厚度(即提升立地条件)能够改善林分结构增加建群种和全林分的生物量.生物量与立地条件、树种多样性和林分密度呈正相关,提升立地条件、抚育改变林分结构能够促进个体生长,增加生物量的积累,改善岩溶区的生态环境.

[目的]研究南水北调中线渠首岩溶区不同恢复年限天然次生林群落物种组成、生物多样性与结构特征,了解岩溶区植被现状,为区域植被保护与修复、生物多样性保护和石漠化综合治理与评估提供科学依据.[方法]采用"空间代替时间"的研究方法,以河南省淅川县岩溶区6种林龄(20、28、35、40、53、70 a)天然次生林为研究对象,按照森林群落调查方法调查乔木层、灌木层及草本层,计算群落物种重要值、多样性指数、群落结构和群落相似系数.[结果]在18个固定样地10800 m2区域内,共调查到维管束植物63种,隶属40科58属;随着恢复年限增加,物种丰富度不断增加,增加的物种多为单科单属单种.各个层物种多样性指数随着恢复年限增加表现出不同的特点,但总体表现为缓慢上升;乔木层Shannon多样性指数、Simpson多样性指数及Pielou均匀度指数均以P5样地(恢复时间53 a)最大,P1样地(恢复时间20 a)最小;灌木层和草本层的Shannon多样性指数、Simpson多样性指数缓慢上升.Jaccard相似性系数结果表明:不同恢复年限的样地间为极不相似水平,物种组成差异性较高;除密度外,群落平均高度、盖度、胸径等结构在恢复20和70 a以上存在显著差异(P<0.05),其余恢复年限样地之间差异不显著.[结论]相对于西南岩溶区,南水北调中线渠首岩溶区物种丰富度较低,群落均以栓皮栎Quercus variflora为建群种,单科单属单种居多,群落间差异性较大,岩溶区植被恢复后期植被生长缓慢,树高和胸径主要集中在Ⅱ和Ⅲ级.

研究自然植被恢复过程中的物种组成、群落结构及生物多样性的变化,能够为人工促进植被恢复的树种选择与群落结构的优化配置提供重要依据.本研究以空间代替时间对喀斯特断陷盆地典型区云南省建水县不同天然植被(草丛、灌丛、乔木林)进行群落学调查,对不同恢复阶段的植物群落按乔木、灌木、草本进行分层,分析各恢复阶段植物群落的物种组成、水平和垂直结构、生物多样性.结果 表明:在总面积为3200 m2的12个样地中,共记录43科72属94种维管束植物,优势种以壳斗科(Fagaceae)、鼠李科(Rhamnaceae)、紫金牛科(Myrsinaceae)、蔷薇科(Rosaceae)、木犀科(Oleaceae)等科的植物为主;在草丛→灌丛→乔木林的恢复过程中,群落物种组成中的科数、属数、种数逐渐增加,低矮和小径级植物个体数所占比例逐渐减少,但整体仍以低矮的小径级植物为主.草本植物的丰富度和Shannon指数在植被恢复的初期即草丛阶段最大,而均匀度指数则以灌丛阶段最大;木本植物的丰富度和Shannon指数随着植被的恢复逐渐增大,但均匀度指数随着植被的恢复逐渐下降;随着植被的恢复,草本层和乔木层的生态优势度逐渐增大,灌木层的生态优势度逐渐减小;草本植物由早期一年或多年生的喜阳、耐旱、耐贫瘠的草本向抗逆性强的多年生草本过渡,并逐渐向中性和阴性转变,其中刺芒野古草(Arundinella setosa)能够很好地适应该地区的环境;薄叶鼠李(Rhamnus leptophylla)、铁仔(Myrsine africana)、假虎刺(Carissa spinarum)、小石积(Osteomeles anthyllidifolia)等阳性树种为该地区植被恢复的先锋种,其早期的出现为其他植物的恢复创造条件,后期又逐渐被喜阴的植物替代,在植被恢复初期可利用这些物种;在植被恢复后期,壳斗科的铁橡栎(Quercus cocciferoides)成为建群种,可在灌丛阶段植被恢复时利用该物种,也可以选择使用该物种植树造林;在整个植被恢复过程中,优势度从以矮小植物为主朝着高大植物发展、优势种寿命越来越长的趋势十分明显.

The effective restoration of degraded areas, resulting in the sequestration of significant amounts of soil organic carbon (SOC) and labile soil organic carbon fractions (LOCF), is essential for mitigating global climatic changes. It is therefore important to improve our understanding of the responses and magnitudes of SOC and LOCF during restoration processes in degraded land like karst ecosystems. In this study, we selected four different restoration strategies: (1) not subjected to any management practices, mainly bare land (BL); (2) Pinus yunnanensis plantation (PY), native and characterized by slow growth and high drought resistance; (3) Eucalyptus maideni plantation (EM), non-native and characterized by rapid growth and high adaptability; (4) natural regeneration of secondary forest (SF). The SOC concentrations, SOC stocks, sensitive indicators of LOCF (microbial biomass C (MBC), permanganate oxidizable C (KMnO4-C), dissolved organic C (DOC), water soluble organic C (WSOC)), non-labile C (NLC), and the carbon pool management index (CPMI) were investigated. The different reforestation strategies had significant effects (p < 0.05) on SOC stocks; compared with BL, the SOC stocks of SF, EM, and PY increased by 57.7, 38.0, and 26.9%, respectively. Both the LOCF and the NLC stocks were significantly increased by the different restoration strategies relative to the BL, while natural vegetation restoration was more beneficial for C sequestration than afforestation. Compared with BL, in SF, EM, and PY, the CPMI increased by 70.1, 35.8, and 32.6%, respectively. These findings suggest that although afforestation can significantly increase C sequestration, natural regeneration may be a more effective approach in terms of SOC sequestration. Soil C accumulation would be limited by nitrogen and phosphorus during the vegetation restoration in the karst areas. In degraded karst ecosystems, the CPMI could be used as a representative index in evaluating the impacts of vegetation restoration on SOC concentration and soil quality.

在丹江口库区喀斯特地区,研究分析自然降雨条件下5种不同植被覆盖类型（疏林地（C1）、乔木林地（C2）、坡耕地（C3）、荒草地（C4）、灌草地（C5））坡面侵蚀泥沙的氮、磷、钾养分流失及泥沙粒径分布特征,探讨泥沙养分流失与粒径分布的关系。结果表明:（1）侵蚀泥沙以粉粒（2～50μm）、砂粒（50～2 000μm）为主,0～20μm颗粒含量随降雨强度的增加而减少。0～2μm颗粒富集度集中在3.08～6.62,2～20μm颗粒富集度集中在2.48～3.58,20～2 000μm颗粒富集度集中在1左右。C4的0～2μm颗粒含量及其富集度明显高于其他植被覆盖类型。（2）速效钾的流失量远高于速效氮、磷流失量。氮素富集度集中在1左右,TP富集度集中在1.41～1.96,AP富集度集中在5.00～8.77,AK富集度集中在1.79～3.05,泥沙对磷、钾养分有明显富集作用,而对氮素富集作用很小。不同植被覆盖类型中,C4的TP、AK含量显著高于C1、C2、C3、C5（P＜0.05）,C4有增加TP、AK养分含量的作用,且C2、C4的氮、磷富集度相对较大。C3的养分流失总量最大,C1、C2、C4、C5有明显减小养分流失的作用,其中C2控制养分流失的效果最明显。（3）侵蚀泥沙的TN、TP、AP、AK含量与0～2,2～20,20～50μm含量呈正相关关系,且与0～2μm的相关性显著（P＜0.05）,侵蚀泥沙的养分含量会随着0～50μm颗粒含量的增加而增多。

Afforestation is a widely accepted measure to control soil erosion around the world. A large area of forest has been built to prevent slope soil erosion in the red soil region of southern China since the 1980s. The vegetation coverage has significantly increased; however, there is still moderate or severe soil erosion under the forest. In order to improve the situation, it is necessary to study the effects of canopy on soil erosion under the forest. Standard runoff plots were established on two typical sites, which represented pure Pinus massoniana Lamb. forest and bare land, respectively. Precipitation redistribution and throughfall indices including raindrop size, raindrop velocity, and the kinetic energy (KE) of raindrops were quantified. The results showed that 29.3% of the precipitation was directly prevented from reaching the forest land surface. The canopy interception effect was better under low rainfall intensity than high rainfall intensity. Compared with open rainfall, throughfall raindrops were 16.3% fewer in number, larger in size, and the range of throughfall drop size distribution (DSD) was enlarged. The volume ratio of large drops was larger with higher rainfall intensity. When the rainfall intensity was less than 14 mm h−1, throughfall kinetic energy (TKE) was higher than open rainfall kinetic energy (OKE) owing to the higher volume ratio of large raindrops. When the rainfall intensity was more than 14 mm h−1, TKE was smaller owing to the large raindrops failing to reach their final velocities: their mean velocity was 80% of their final velocity. The sediment yield was the largest under high rainfall intensity and the effect of sediment reduction was the largest under moderate rainfall intensity. Therefore, the largest KE did not lead to the maximum sediment yield; canopy interception was also an important factor affecting sediment yield.

[Objective]Natural restoration and artificial reconstruction of vegetation are the mainmeasures to accelerate the restoration of karst ecosystems and improve soil quality. Studying the soil organic carbon fraction and enzyme activities under different restoration patterns in karst area can reveal the effect of different restoration methods on soil quality, and aims to provide scientific basis for the screening of ecological restoration patterns and evaluation of restoration effects in karst areas. [Method]Based on the naturally restored secondary forest and artificially restored Pinus yunnanensis needle forest and Eucalyptus robusta broadleaved forest in Jianshui County, Yunnan Province of southwestern China, the soil organic carbon fraction, carbon pool management indexes and enzyme activity distribution characteristics and their correlations in different soil layers were analyzed. [Result]The soil organic carbon (SOC) content was 9. 076-56. 855 g/kg, the dissolved organic carbon (DOC) content was822. 311-1 175. 778 mg/kg, the microbial biomass carbon (MBC) content was 332. 933-2 035. 244 mg/kg, and the easy oxidation organic carbon (EOC) content was 2. 381-6. 094 g/kg. Under the same vegetation restoration mode, except for the content of EOC under the Pinus yunnanensis forest, the content of each organic carbon component decreased with the increase of soil depth, and the local soil depth fluctuated. The content of EOC in the subsurface (10-20 cm) soil of Pinus yunnanensis was significantly higher than that in the surface layer (0-10 cm) and deep layer (20-30 cm) . The impacts of different vegetation restoration methods on DOC, EOC and SOC contents were roughly as follows: natural secondary forest＞ Eucalyptus robusta forest＞ Pinus yunnanensis forest, and the MBC content of Pinus yunnanensis forest was always significantly higher than that in the Eucalyptus robusta forest. The organic carbon components and SOC showed very significantly (P ＜ 0. 01) or significantly (P ＜ 0. 05) positive correlations; the ability of different vegetation restoration methods to improve the soil carbon pool management indexes was: secondary forest＞ eucalypt forest＞ Pinus yunnanensis forest. SOC had very significant and significant correlations with CPI and CPMI, and EOC also had very significant (P ＜0. 01) or significant (P ＜ 0. 05) correlations with CPAI, CPI, and CPMI. Each vegetation restoration method increased soil SOC, EOC, etc., thereby increasing the soil carbon pool management indexes. As a whole, the soil enzyme activities decreased with the deepening of the soil layer, and there was fluctuation in the local range. Soil enzyme activities varied differently under different vegetation restoration methods. The activities of catalase and amylase were shown as secondary forest＞ Pinus yunnanensis forest＞ Eucalyptus robusta forest. The SOC, MBC, DOC, and EOC contents were positively correlated with the four soil enzyme activities under various vegetation restoration patterns, and most of them were significant or very significant. [Conclusion]The three vegetation restorations improved soil organic carbon fraction, carbon pool management indexes and soil enzyme activities to varying degrees.Among them, secondary forests have the highest ability to improve the overall soil quality. Eucalyptus robusta forests have a significant increase in the content of total organic carbon and active carbon components, while the Pinus yunnanensis forest has a significantly greater ability to increase the activities of catalase and amylase. Therefore, it is necessary to speed up the transformation of land management methods in suitable forest lands in karst areas and give priority to natural restoration, and pay attention to the utilization and optimization management of broadleaved trees when selecting artificial afforestation.

The importance of assembly processes in shaping biological communities is poorly understood, especially for microbes. Here, we report on the forces that structure soil bacterial communities along a 2000 m elevational gradient. We characterized the relative importance of habitat filtering and competition on phylogenetic structure and turnover in bacterial communities. Bacterial communities exhibited a phylogenetically clustered pattern and were more clustered with increasing elevation. Biotic factors (i.e., relative abundance of dominant bacterial lineages) appeared to be most important to the degree of clustering, evidencing the role of the competitive ability of entire clades in shaping the communities. Phylogenetic turnover showed the greatest correlation to elevation. After controlling the elevation, biotic factors showed greater correlation to phylogenetic turnover than all the habitat variables (i.e., climate, soil and vegetation). Structural equation modelling also identified that elevation and soil organic matter exerted indirect effects on phylogenetic diversity and turnover by determining the dominance of microbial competitors. Our results suggest that competition among bacterial taxa induced by soil carbon contributes to the phylogenetic pattern across elevational gradient in the Tibetan Plateau. This highlights the importance of considering not only abiotic filtering but also biotic interactions in soil bacterial communities across stressful elevational gradients.

Natural regeneration and reforestation have been widely adopted to improve the degraded soil and promote ecological services in the karst regions of southwestern China. A better understanding the effects of different vegetation types on soil quality and the nutrient limiting factors is very important for each approach. In this study, a secondary forest (SF) and two plantations, Eucalyptus maideni F. V. Muell. (EM, exotic, deciduous broad-leaved) and Pinus yunnanensis Franch. (PY, native, conifer species), were selected in the karst graben basins of southwest China to explore the soil quality using Total Data Set (TDS) and Minimum Data Set (MDS) methods. The results indicated most soil parameters showed significant differences between the different recovery approaches. The TDS method is more precise than the MDS method, but the MDS method can also adequately represent the TDS method for the evaluation of soil quality with different vegetation restoration schemes. In the MDS method, soil organic carbon, available potassium, ammonium nitrogen, acid phosphatase, microbial metabolic quotient, and the Pielou index of the soil microbes were found to be the most important indicators for assessing soil quality. The pure plantation of PY had a negative effect on the soil quality, causing soil nutrient deficiency, compared to the SF and EM plantation, indicating that natural regeneration may be a more effective approach to the amelioration of soil quality in the karst areas. These findings provide an empirical and theoretical basis for the protection, restoration, and management of forest in the degraded karst areas.

The structure and dynamics of microbial communities may be influenced by environmental selection, spatial processes and competition. However, the relative strengths of these processes need to be further elucidated. Here, with a large scale sampling along an elevational gradient of 2000 m in the Qinghai-Tibetan Plateau, we examined the interplay among the three processes, as well as their relative importance to the biogeography of bacterial communities. Variation partitioning showed that environmental selection, competition and spatial variables jointly explained 37% of the total variation among the bacterial communities. The non-spatially structured environmental variables explained more variation than spatial distance or competition. Two environmental factors, elevation and soil pH, were shown to be the main cues determining soil bacterial communities. Environmental variables and spatial distance also exerted indirect effects on community variation via competition. The main conclusion of this study is consistent with the idea that "the environment selects". Competition and spatial processes were less important in shaping bacterial communities of Qinghai-Tibetan Plateau.

Objective]Approximately 22. 5% of the total distance of the Qinghai-Tibet railway has been affected by sand damage,a major threat to the safe operation of the railway. In this study,we calculated the volume of sand deposition under each sand control measure through field investigation, and analyzed the influence of their spatial distribution on sand blocking capability,aiming to provide a scientific basis for deploying effective sand barriers to reduce the impact of sand damage to the railway and to guarantee the safety of railway operation.[Method]In this study,We focused on Nanshankou section of the Qinghai-Tibet railway,which was partially deployed with sand control measures. Four sand control measures and a control with no measures were established to compare their effectiveness. Area Ⅰ with&nbsp;no sand control measures was used as control,area Ⅱ was deployed with PE ( polyethylene ) checkerboard barriers ( PCBs); area Ⅲ with sand fences ( SFs ) and PCBs; area Ⅳ with SFs; and area Ⅴ with sand blocking PE nets ( SBPNs) and SFs. By measuring cross-section elements and depth of the sand deposition,the volume of sand deposition in different areas were calculated,respectively. The effectiveness of the sand control measures were evaluated using annual deposited-sand volume per unit width in different areas with different models of sand control measures as the main indicator,and the influence of their spatial distribution on sand blocking capability were analyzed. [Result]1 ) Our investigation showed that no sand accumulation on the railway track and no evidently visible abrasion of the rail in the area I,indicating that the degree of sand damage in Nanshankou section was mild and no need to have sand barriers. Inappropriate sand barriers may lead to extra sand accumulation and causing damage to the railway embankment. 2 ) Annual deposited-sand volume per unit width in the area Ⅲ was 1. 125 m3·m -1 ,the highest among the 4 areas,indicating minimum average annual sand flux at Nanshankou area was 1. 125 m3·m -1. 3) Annual deposited-sand volume per unit width in the area Ⅳ was 0. 978 m3·m -1 ,accounting for approximately 87% of those in the area Ⅲ,indicating that SFs was an effective single sand control measure;4 ) Annual deposited-sand volume per unit width in the area Ⅴ was 0 . 782 m3·m -1 ,accounting for 70% of those in the area Ⅲ,indicating SBPNs did not enhance the amount of sand deposition, even weaken the effects of sand blocking of SFs,the main reason was that they were settled too close to each other and to the railway. 5) Considering the sand blocking effects and economic costs,our investigation showed that the optimum width of the PCBs in Nanshankou section was 13 m; and single measure of SFs could play an important role in the sand control of Nanshankou railway section,which cost less. [Conclusion]The sand barriers in Nanshankou area: the large width of the PCBs resulted in a waste of material and the optimum width of the PCBs was 13 m;SBPNs did not enhance the amount of sand deposition,even weaken the effects of sand blocking of SFs,because they were settled too close to each other and to the railway; SFs was an effective single sand control measure in the study areas. Moreover,our investigation showed that the degree of sand damage of Nanshankou section was mild and no sand barrier was needed. If necessary,single measure of SFs can be used for sand control for Nanshankou section with a low cost. The result can provide a basis for scientific arrangement of mechanical sand barriers in mild sand damage railway sections.

In order to evaluate the impacts of hydropower development on the ecological environment, the impacts of the cascade development of hydropower projects in the main stream of the Tongtian River on the terrestrial ecological environment were analyzed and evaluated using the “3S” technology combined with the methods of landscape ecology and the ecological security index, as well as data from digital images and field surveys. The results show that, subsequent to cascade hydropower development, the water area increased by 300. 72 km2 , the grassland area decreased by 296. 80 km2 , and there was no significant change in the main vegetation types and land use patterns. Grassland was the dominant landscape type in the basin, followed by bare land and woodland. Landscape fragmentation decreased after hydropower development, while landscape dominance and diversity increased, which was conducive to the stability of regional ecosystem. Cascade hydropower development did not significantly affect the productivity of vegetation in the basin and the richness of species on both sides of the river. The productivity of vegetation decreased by 1. 83×105 t/a, and the productivity after the development only accounted for 0. 78% of that before the development. The ecological security index of the overall basin was 0. 819 after the development, 0. 001 higher than that before it, indicating a high ecological security index. In summary, since there were no major changes in landscape patterns or in ecosystem features and functions, cascade hydropower development does not pose a threat to the ecological environment and safety in the Tongtian River Basin.