基于环境因子对叶绿素影响的典型草原植物生活型优势研究

Dominance of different plant life forms in the typical steppe evidenced from impacts of environmental factors on chlorophyll

针对环境因子与草原植物叶绿素含量的联动是否关系到植物生活型优势的问题,该研究以锡林浩特典型草原为研究区,选取2020年7月实测的11个样地50种植物共185个牧草样品的叶绿素含量,运用相关分析、单因素方差分析、冗余分析(RDA)、逐步回归分析和通径分析等方法,系统性地分析了多环境因子对草原植物不同生活型叶绿素指标的影响,进而分析植物竞争优势形成的潜在驱动机制。研究结果表明:1)典型草原区植物叶绿素a、叶绿素b含量均与总叶绿素含量呈极显著正相关关系,相关系数分别为0.807和0.936,草原植物总叶绿素含量受叶绿素b含量的影响程度更大;2)草原植物4类生活型的叶绿素a、叶绿素b和总叶绿素含量均为小/半灌木>多年生禾草>一/二年生植物>多年生杂类草;3)环境因子对植物生活型叶绿素含量的解释程度存在差异,RDA显示环境因子对小/半灌木的叶绿素含量解释程度最大(28.0%),其次为一/二年生植物(18.3%)和多年生杂类草(17.7%),多年生禾草各项叶绿素指标的解释度最低(12.7%);4)植物生活型各叶绿素指标受多种环境因子的影响,回归分析显示小/半灌木的叶绿素b含量受到土壤有机碳含量和大气相对湿度的影响,总叶绿素含量主要受到大气相对湿度的影响,多年生杂类草叶绿素b含量主要受到地表温度的影响,一/二年生植物的叶绿素a、叶绿素b、总叶绿素含量主要受到土壤pH的影响;5)在草原生境中,通径分析的综合研究显示植物叶绿素a含量主要受到土壤环境因子的影响,植物叶绿素b和总叶绿素含量主要受到大气环境因子的影响,相比较而言,多年生禾草不易受环境因子的牵动,成为更能忍受外界环境变化的植物种类,因此,在群落演替进化中这类植物逐渐占据优势地位。

Aims This study aimed to understand whether the coupling between environmental factors and chlorophyll contents is related to the dominance of plant life forms in the grasslands.Methods In July 2020,we measured chlorophyll contents in 185 plant samples from 50 forage species of 11 sampling plots of a typical steppe in Xilinhot.Through correlation analysis,single factor analysis of variance,redundancy analysis(RDA),stepwise regression analysis and path analysis,we analyzed the effects of multiple environmental factors on indices of plant chlorophyll and the mechanism underlying the competition advantage of different plant species.Important findings 1)The contents of chlorophyll a and chlorophyll b were significantly positively correlated with that of total chlorophyll,with the correlation coefficients of 0.807 and 0.936,respectively.The contents of total chlorophyll were more affected by that of chlorophyll b.2)The contents of chlorophyll a,chlorophyll b,and total chlorophyll of the four life forms followed an order of semi-shrubs>perennial grasses>annual or biennial plants>perennial forbs.3)The variations of chlorophyll contents among plant life forms were differently explained by environmental factors.The RDA results showed that the explanatory degree of semi-shrubs was the highest(28.0%),followed by annual or biennial plants(18.3%)and perennial forbs(17.7%),and that of perennial grasses was the lowest(12.7%).4)The chlorophyll index of plant life forms were affected by various environmental factors.The chlorophyll b contents in semi-shrubs were affected by soil organic carbon content and relative air humidity,while their total chlorophyll contents were mainly influenced by relative air humidity.Chlorophyll b contents of perennial forbs were mainly restricted by surface temperature.The contents of chlorophyll a,chlorophyll b,and total chlorophyll of annual or biennial species were mainly affected by soil pH.5)Path analysis results showed that chlorophyll a contents of grasses were mainly affected by soil factors,chlorophyll b and total chlorophyll contents were mainly impacted by atmospheric factors in the grassland habitats.Comparatively,perennial grasses were not susceptible to environmental factors so that they become more tolerant to environmental changes than the other life forms.Therefore,these plants gradually became dominant during community succession and evolution.