青藏高原植物群落类型和土壤类型复杂多样，生态环境脆弱，群落结构和植物功能性状的变化深刻影响着生态系统功能，因此，系统了解青藏高原的植物群落结构和植物功能性状特征及其对土壤质量的响应，是实施合理的生态保护措施、保障青藏高原地区生态系统稳定的基础。本文通过青藏高原野外调查的122个样方，比较青藏高原不同植被型群落结构特征和植物功能性状的差异，分析植物群落结构、个体和群落水平植物功能性状对土壤质量的响应特征，探究环境-植物功能性状-群落结构的作用模式。主要结果如下： 1. 基于双向指示种分析法(TWINSPAN)，本研究调查的122个样方可分为6个植被型，12个群系。6个植被型分别为高寒草甸、高寒草原、温性草原、荒漠草原、盐生草甸和荒漠。其中高寒草甸包括高山嵩草(Kobresia pygmaea)草甸、退化高寒草甸和高山嵩草+垫状点地梅(Androsace tapete)/蚤缀属(Arenaria sp.)草甸，高寒草原包括紫花针茅(Stipa purpurea)草原和异针茅(Stipa aliena)草原，温性草原为芨芨草(Achnatherum splendens)+冰草(Agropyron cristatum)草原，荒漠草原为沙生针茅(Stipa caucasica subsp. glareosa)草原，盐生草甸包括赖草(Leymus secalinus)草甸和芦苇(Phragmites australis)盐生草甸，荒漠包括多枝柽柳(Tamarix ramosissima)灌丛、蒿叶猪毛菜(Salsola abrotanoides)+红砂(Reaumuria songarica)+合头草(Sympegma regelii)荒漠和梭梭(Haloxylon ammodendron)荒漠。高寒草甸、高寒草原和温性草原的物种多样性高于荒漠草原、盐生草甸和荒漠，均匀度在各植被型间的差异相对较小。个体水平平均叶片碳含量为418.12±52.85 mg/g，叶片氮含量为23.03±7.28 mg/g，叶片磷含量为1.12±0.41 mg/g，叶片碳氮比为20.28±9.02，叶片氮磷比为21.97±7.21，叶片干物质含量为270.58±94.74 mg/g，叶片厚度为0.17±0.08 mm，植株高度为24.25±35.31 cm。个体和群落水平的植物功能性状均表现出形态性状变异较大而化学计量性状变异小的特征。 2. 青藏高原土壤质量最小数据集包括土壤容重、砾石含量、砂粒含量、土壤无机碳和土壤总氮5个土壤指标。土壤质量综合指数平均为0.593，并呈现出高寒草甸>温性草原>盐生草甸＞荒漠＞荒漠草原＞高寒草原的特点。群落盖度、Shannon-Wiener指数、Simpson指数和物种丰富度均随土壤质量综合指数的增大而增加，当土壤总氮、土壤总有机碳和土壤黏粒含量增加时，群落盖度、Shannon-Wiener指数、Simpson指数和物种丰富度显著增加。相反，当土壤无机碳和土壤pH值增加时，群落盖度和物种多样性降低。土壤指标对个体水平植株高度和叶片厚度的解释率分别为42%和16%，对群落水平植株高度和叶片厚度的解释率分别为62%和59%，表明群落水平的植物功能性状能更好的响应土壤指标。当土壤紧实度、水分和养分都下降，而土壤碱性增强时，植物叶片的碳、氮以及磷含量呈增加趋势，而养分利用效率下降，形态特征表现为叶片厚度和植株高度增加。 3. 青藏高原植物群落结构和植物功能性状均受到气候、土壤和地理位置的影响。环境因素对植物群落结构变化的解释要优于群落水平的化学计量性状，群落加权平均性状中，环境因子只对群落叶片干物质含量、叶片厚度和植株高度的解释度较高，解释率分别为55%、77%和85%，说明群落结构和物种多样性对环境的变化更敏感，而植物功能性状中形态性状更容易受到环境因子的影响。群落加权平均叶片氮含量、叶片磷含量、叶片碳氮比和叶片厚度能够被土壤解释的部分均超过50%，表明这些性状受到土壤因素的影响较大。在青藏高原，环境直接影响群落加权平均性状、群落结构和物种多样性，并通过影响群落加权平均性状和群落结构间接影响物种多样性。随着水分和养分的增加，群落加权平均叶片氮含量和叶片干物质含量表现出明显的下降，群落高度减小，而盖度增加，物种多样性增加。在青藏高原高寒环境胁迫下，土壤养分和降水量成为影响植物功能性状、群落结构和物种多样性的关键环境因子。

Plant community and soil types on the Qinghai-Tibet Plateau are complex and diverse, and the ecological environment is fragile. Changes in community structure and plant functional traits profoundly affect ecosystem functions. Therefore, a systematic understanding of plant community structure, plant functional traits, and their responses to soil quality is the basis for implementing reasonable ecological protection measures and ensuring the stability of the Qinghai-Tibet Plateau ecosystem. In this article, through a field survey of 122 samples of the Qinghai-Tibet plateau, we compared the community structure and plant functional traits of different vegetation formations, analyzed the response characteristics of plant community structure, individual and community level plant functional traits to soil quality, and explored the interaction mechanism between environment - plant functional traits - community structure. The main results are as follows:

1. Based on two-way indicator species analysis, 122 samples could be divided into 6 vegetation formations and 12 alliances. The six vegetation formations are alpine meadow, alpine steppe, temperate steppe, desert steppe, halophytic meadow, and desert. Alpine meadow includes  Comm. Kobresia pygmaea, Degraded alpine meadow, and Comm. Kobresia pygmaea+Androsace tapete+Arenaria sp.; alpine steppe includes Comm. Stipa purpurea and Comm. Stipa aliena; temperate steppe includes Comm. Achnatherum splendens+Agropyron cristatum; desert steppe includes Comm. Stipa caucasica subsp. glareosa; halophytic meadow includes Comm. Leymus secalinus and Comm. Phragmites australis; desert includes Comm. Tamarix ramosissima, Comm. Salsola abrotanoides+Reaumuria songarica+Sympegma regelii and Comm. Haloxylon ammodendron.The species diversity of alpine meadow, alpine steppe, and temperate steppe was higher than that of the desert steppe, halophytic meadow and desert, and evenness among vegetation formations was not much different. The variation of morphological traits was larger than that of stoichiometric traits at individual and community levels.

2. The minimum data set of soil quality in the Qinghai-Tibet Plateau includes five soil indexes: soil bulk density, rock fragments content, sand content, soil inorganic carbon, and soil total nitrogen. The average soil quality index of the Qinghai-Tibet Plateau was 0.593, the soil quality index showed alpine meadow > temperate steppe > halophytic meadow > desert > desert steppe > alpine steppe. Community coverage, Shannon-Wiener index, Simpson index, and species richness increased with the increase of soil quality index. When soil total nitrogen, soil total organic carbon and soil clay content increased, community coverage, Shannon-Wiener index, Simpson index and species richness increased significantly. On the contrary, when soil inorganic carbon and soil pH value increased, community coverage and species diversity decreased. The explaining rates of plant height and leaf thickness at individual level were 42% and 16%, respectively, and the explaining rates of plant height and leaf thickness at community level were 62% and 59%, respectively, suggesting that plant functional traits at community level could better respond to soil indexes. When soil compactness, water and nutrients all decreased, while soil alkalinity increased, the leaf carbon, nitrogen and phosphorus contents increased, while the nutrient utilization efficiency decreased, and leaf thickness and plant height increased.

3. The community structure and plant functional traits on the Qinghai-Tibet Plateau are affected by climate, soil and geographical location. Explanation of environmental factors on community structure is superior to the plant stoichiometric traits. Only leaf dry matter content, leaf thickness and plant height at community level could be better explained by environmental factors, explain rates were 55%, 77% and 85%. These results indicated that community structure, species diversity and morphological traits were more susceptible to environmental factors. More than 50% of leaf nitrogen content, leaf phosphorus content, leaf carbon/nitrogen ratio and leaf thickness at community level could be explained by soil, indicating that these traits were greatly affected by soil factors. On the Qinghai-Tibet Plateau, the environment directly affects community weighted mean traits, community structure, and species diversity, and indirectly affects species diversity through community weighted mean traits and community structure. With the increase of water and nutrients, CWM-LNC and CWM-LDMC decreased significantly, and the community height decreased, while the community coverage increased, and the species diversity increased. Soil nutrients and precipitation were the key environmental factors affecting plant functional traits, community structure and species diversity under high altitude and low-temperature environment stress on the Qinghai-Tibet Plateau.