内蒙古围封草原枯落物累积对大针茅和羊草生长发育的影响

Effects of litter accumulation on growth of Stipa grandis and Leymus chinensis in a fenced typical steppe in Inner Mongolia

围封草原枯落物累积通过改变水分和热量的再分配影响植物的生长发育。为探究不同植物种群对枯落物累积的适应性,2015—2017年在内蒙古围封典型草原设置了枯落物去除实验,对土壤温度和水分进行了原位监测,也对群落优势物种大针茅(Stipa grandis)和亚优势物种羊草(Leymus chinensis)种群的生长发育过程及种群数量特征进行了测定。结果表明:枯落物累积显著降低生长季表层和深层土壤温度(1.3—4.6℃和1.5—3.2℃),并提高表层和深层土壤水分(1.4%—10.4%和1.0%—5.0%)。枯落物累积对大针茅种群返青时间的延迟(16.9—24.2 d)显著高于羊草种群的(5.2—6.7 d),但对大针茅和羊草种群的营养生长期无显著影响。枯落物累积显著提高大针茅种群的高度但显著降低其盖度和地上生物量,引起大针茅种群的重要值显著降低(0.38→0.22)。枯落物累积显著提高羊草种群的高度、盖度和地上生物量,进而显著提高其重要值(0.16→0.28)。大针茅和羊草种群重要值排序的更替驱动围封草原植物群落演替。本研究从植物种群的角度为阐明围封草原群落结构与功能改变提供新视角,也为科学合理制定围封政策提供理论依据。

Litter accumulation affects growth of plant species by redistributing hydrothermal condition in fenced steppe ecosystems.To explore the ecological adaptations of different plant species with diverse morphological and ecological characteristics to litter accumulation,we conducted a litter removal experiment in a fenced typical steppe in Inner Mongolia during 2015—2017.Soil temperature and moisture were continuously monitored in situ.The growth and quantitative characteristic of the dominant and subdominant species(Stipa grandis and Leymus chinensis)were measured.The results were as follows.Litter accumulation significantly decreased surface and deep soil temperature(1.3—4.6℃in surface soil and 1.5—3.2℃in deep soil)but remarkably increased surface and deep soil moisture(1.4%—10.4%in surface soil and 1.0%—5.0%in deep soil).Litter accumulation delayed the returning greening day of S.grandis(16.9—24.2 days)more than that of L.chinensis(5.2—6.7 days)but had no significant effects on their vegetative period.Litter accumulation significantly increased the height of S.grandis but decreased its cover and aboveground biomass,which remarkably reduced the important value of S.grandis(0.38→0.22).Conversely,litter accumulation significantly increased the height,cover,and aboveground biomass of L.chinensis,which remarkably increased its important value(0.16→0.28).Comprehensively,the order change of important value in S.grandis and L.chinensis drove community succession in the fenced steppe.This study elucidates the changes of community structure and function in fenced steppe ecosystems from the perspective of plant population and provides the theoretical basis for scientific and rational formulation of enclosing policy.