内蒙古荒漠草原植物水分利用特征差异及对环境因子的响应

Differences in plant water use characteristics and responses to environmental factors in the desert grassland of the Inner Mongolia

水分是干旱半干旱地区植被生长的主要限制因子,水分利用是反映植被对环境变化响应的关键生态水文过程。目前缺少对干旱半干旱区草原不同科、属植物水分利用特征差异的系统分析,且植物水分利用特征与环境因子的定量关系需要进一步研究。在内蒙古荒漠草原进行样带调查,采集7个样地0—100 cm深度土壤样品和15种植物根茎结合部(茎秆)、叶片样品,测定土壤水、植物水中δ^(2)H和δ^(18)O和植物叶片δ^(13)C的同位素,利用MixSIAR模型确定不同科、属植物水分来源比例,分析不同科、属植物水分利用来源和水分利用效率的差异,并建立植物水分来源比例及水分利用效率与各环境因子的定量关系。结果表明:(1)禾本科和菊科植物主要利用0—30 cm深度土壤水(55.63%和51.84%),其叶片δ~(13)C(-26.61‰和-27.91‰)均低于其他科(包括柽柳科、藜科和蔷薇科)(-26.36‰),且其他科主要利用60—100 cm深度土壤水(36.83%),水分利用策略更有利于在干旱条件下生存。(2)针茅属植物对0—30 cm深度土壤水的利用(55.28%)和叶片δ~(13)C(-26.38‰)高于蒿属(31%和-28.14‰),较高的水分利用效率使其在干旱环境中具有较强的生态适应性。(3)植物对不同深度土壤水的利用比例和叶片δ~(13)C对不同环境因子的响应有所差异,其中植物水分来源比例主要受年均降雨量、年均温和叶周长影响(P<0.05)。本研究揭示荒漠草原植物水分利用特征,有助于理解植物对环境变化的响应策略,同时对该地区生态系统管理提供理论依据。

Water is the main limiting factor of vegetation growth in arid and semi-arid area,and water use is a key ecohydrological process reflecting the response of vegetation to the environmental changes.At present,there is a lack of systematic analysis of the differences in water use characteristics of plants in different families and genera of grasslands in arid and semi-arid area,and the quantitative relationship between plant water use characteristics and environmental factors needs to be further studied.In this study,a transect survey was conducted in the desert steppe of the Inner Mongolia.Soil sample at a depth of 0—100 cm,junctions(stems)and leaf samples were collected from 7 plots,and the isotopes ofδ2H andδ18O in soil water and plant water and plant leafδ13 C were determined.The proportion of water sources of different families and genera plants were determined by the MixSIAR model,and the differences of water use sources and water use efficiency of plants of different families and genera were analyzed,and the quantitative relationship between the proportion of plant water sources and water use efficiency and various environmental factors were established.The results showed that Gramineae and Compositae mainly used soil water at a depth of 0—30 cm,which the absorption ratio were respectively 55.63%and 51.84%.Their leafδ^(13)C that were-26.61‰and-27.91‰were lower than those of other families(including Tamaricaceae,Chenopodiaceae,and Rosaceae),which the leafδ^(13)C was-26.36‰.The absorption ratio of other families that mainly used soil water at a depth of 60—100 cm was 36.83%and the water use strategies were conducive to survival in drought conditions.The proportion of soil water utilization at a depth of 0—30 cm by Stipa was 55.28%,and the leafδ^(13)C was-26.38‰,which were higher than that of Artemisia Linn(31%and-28.14‰).The water use strategy of Stipa made it have strongly ecological adaptability in arid environment.The response of soil water utilization ratio at different depths and leafδ^(13)C to different environmental factors were different,among which the proportions of plant water sources were mainly affected by the average annual rainfall,average annual temperature,and leaf circumference(P<0.05).This study revealed the water use characteristics of plants in desert grasslands,which was of great significance for understanding the response strategies of plants to environmental change,and it can provide the scientific basis for ecosystem management in this region.