Responses And Adaptation Strategies Of Different Life Types To Habitat Gradient Changes In Yanhe River Basin

The principle of ecological restoration must be adhered to in the process of ecological restoration on the Loess Plateau.However,it is often difficult to implement this principle,because different life types of plants often have different growth characteristics and different response and adaptation mechanisms to environmental changes.On the spatial scale,with the gradient change of habitat,the adaptation mechanism and strategies of plants to the environment will also change due to the change of plant growth restriction factors.Therefore,it is of great practical significance for the selection and planting of suitable vegetation types to analyze the traits of different life types and their environmental adaptation strategies,and to understand the response and adaptation mechanism of plants to the environment under different habitat gradients.In the process of ecological restoration on the Loess Plateau,it is necessary to comprehensively consider the factors such as plant life type,character and habitat gradient,and make a reasonable vegetation restoration scheme based on the adaptation strategies of different life types of plants.Taking Yanhe River Basin in the hilly loess region as the study area,this study quantified the variation rules of functional traits of trees,shrubs and herbaceous plants in the forest belt,forest steppe belt and steppe belt in the Yanhe River Basin by means of field vegetation survey,sample collection,character measurement and environmental factor measurement,and expounded the synergistic and tradeoff relationships among different functional traits at the life type level.The relative contribution of environmental factors to functional traits of plants at the life type level was revealed,and the response and adaptation strategies of different life types to gradient changes in habitat were explored.(1)The basic distribution of plant morphological traits and chemical traits in Yanhe River Basin is as follows: specific leaf area,specific root length,leaf tissue density,root tissue density,leaf dry matter content,root dry matter content,leaf nitrogen content,root nitrogen content and root phosphorus content have significant differences at life type level,while leaf carbon content,root carbon content and leaf phosphorus content do not have significant differences at life type level.With the worsening of climate drought from southeast to northwest,different life types of plants showed different adaptation strategies by adjusting leaf and fine root traits.The resource acquisition efficiency and nitrogen content of herb leaves and fine roots were higher,and the defense ability of arbor leaves and fine roots was stronger and carbon content was higher.(2)The correlation among plant functional traits in the Yanhe River Basin is as follows:Environmental adaptability of plants largely depends on the coordination and balance of functional traits of various organs.There were significant correlations among plant functional traits in Yanhe River Basin,and there were significant negative correlations between specific leaf area and leaf tissue density and specific root length and root tissue density,and the variation law was consistent along the habitat gradient.There were significant positive correlations between leaf nitrogen content and root nitrogen content and leaf dry matter content and root dry matter content,and the variation law was consistent along the habitat gradient.(3)The response of plants to habitat gradient in the Yanhe River Basin is as follows:water factor is the limiting factor for plant growth in the Yanhe River Basin,especially the growing season rainfall(i.e.warm season rainfall)significantly affects a series of plant characters such as specific leaf area and specific root length.The extreme climate(i.e.,the hottest average monthly temperature)significantly affects the growth and resource acquisition efficiency of different life types of plants in the Yanhe River Basin.On the one hand,the increase of temperature will aggravate the transpiration loss of plants,on the other hand,the increase of temperature difference will aggravate the drought stress of site habitat.Among soil factors,organic carbon content and cationic exchangeable capacity significantly affected plant specific root length.(4)The adaptation strategies of plants in Yanhe River Basin were as follows:Herbaceous plants had relatively low leaf tissue density and root tissue density,and relatively high specific root length,specific leaf area,leaf nitrogen content and root nitrogen content.In forest zone,forest steppe zone and steppe zone,the adaptation strategy of "rapid investment-return"(acquisition)was adopted.Tree plants had relatively high leaf tissue density,root tissue density,carbon content and relatively low specific leaf area and root length.In forest zone,forest steppe zone and steppe zone,the adaptation strategy of "slow investment-return"(conservative)was adopted.Shrubby plants showed the differentiation of adaptive strategies under habitat gradient.Shrubby plants adopted a "slow investment-return"(conservative)adaptive strategy in forest zone and forest steppe zone,while adopted a "fast investment-return"(acquisition)adaptive strategy in steppe zone.