羊草草地放牧退化演替中种群消长模型的研究

DYNAMIC POPULATION MODELS OF THE ECOLOGICAL DOMINANCE DURING THE RETROGRESSIVE SUCCESSION OF LEYMUS CHINENSIS GRASSLAND

羊草草地是东北西部及内蒙东部草原区主要的天然放牧场和割草场、具有较高的经济价值，但是由于长期过度放牧，草地已严重退化井盐碱化。本文采用数学手段，以植物种群在群落中的相对优势度为，指标，用植被在放牧退化演替系列上的空间分布序列推断其在时间上演替系列的方法，研究羊草等５种植物种群的优势度随放牧退化演替消长的规律及其数学模型。羊草按Ｄ＝１２４．２ｅ￣（－０．３５Ｔ）衰退；寸草苔和糙隐子草分别按Ｄ＝２．１３Ｔ￣（３．３）ｅ￣（－０．１５Ｔ２）和Ｄ＝１．７７Ｔ￣（３．７）ｅ￣（－０．２９Ｔ２）消长，而角碱蓬和虎尾草分别按Ｄ＝０．１１ｅ￣（１．３Ｔ）和Ｄ＝０．３８ｅ￣（０．９４Ｔ）增加。

Grasslands dominated by Leymus chinensis in the west part of the north-east China and the eastern Inner Mongolia are the main natural pasture forgrazing and hay production,and,therefore, they are highly economicallyvaluable. However,the degradation of these grassland ecosystem are verysevere, mainly due to overgrazing. In this paper,we will use matheinatical models to show the change ofthe relative dominance of plant populations in the retrogressive successionseries.In lightly and moderately grazed grasslands,Leymus chincnsis is thedominance. Its relative dominance changes with increasing grazing intensity,and this change can be described by an equation, In theentire succession series,the changes of the relative dominance of Carex duri-cscula and Clcistogenes squarrosa can be explained using models of(for C. duricscula)and (for C. squarrosa).Therelative dominance of Suaeda corniculata and Chloris virgata increases as thegrassland degrades. Their relative dominance changes can be elucidated bythe following models, D=0.11e￣(1.3T)(for S.corniculata)and D=0.38e￣(10.94T) (forC. virgata) ,respectively. Our results indicate that the shift of dominantspecies is very conspicuous during the retrogressive succession of grassland communities.