黄土高原次改林地林下植物与鼢鼠繁殖的关系

Study on the Relation between Reproduction of Zokor and Under-herbosa in the Improved Secondary Forests on the Loess Plateau

研究了黄土高原次改林林地鼢鼠繁殖参数与林下10种主要草本植物的关系,研究表明:次改初期,林下植被基本保持原次生林的特点,鼢鼠喜食的阳性植物在林内呈块状分布。林地鼢鼠雌雄比小,雌鼠怀孕率低,胎仔数少,种群繁殖能力较弱。随着鼢鼠喜食植物逐渐扩散,盖度和组成比显著增加,鼢鼠雌雄比逐渐增大,雌鼠怀孕率逐渐提高,胎仔数增加,种群繁殖能力显著增强。随着林地郁闭度的增加,鼢鼠喜食的植物逐渐从原来的生态位退出,鼢鼠种群雌雄比、雌鼠怀孕率、平均胎仔数和繁殖指数下降,繁殖能力降低,种群出现了衰退的迹象。造成鼢鼠繁殖强度变化的主要原因是林下草本植被对雌鼠平均胎仔数的影响。在林下草本植物中,影响鼢鼠繁殖强度的主要是二裂委陵菜、委陵菜和苦荬菜,其次是糙隐子草和白羊草。二裂委陵菜、委陵菜和苦荬菜的分布频度与胎仔数呈显著的正相关,达乌里胡枝子的分布频度与胎仔数呈显著负相关;二裂委陵菜和委陵菜的盖度与胎仔数呈极显著的正相关,苦荬菜、长芒草和达乌里胡枝子的盖度与胎仔数呈显著正相关,糙隐子草的盖度与胎仔数有较强的正相关性,白羊草的盖度与胎仔数呈显著的负相关。

The relationship between the reproduction of zokor and undergrowth in the improved secondary forests in loess plateau was studied based on the investigation of the data of 11-year survey.in the initial phase of the improvement if secondary forests,the undergrowth generally remained the original characteristics,and the preferable heliophilous plants of zokor were in lumpish core distribution.The female to male ratio of zokor was small;the rate of pregnancy of female zokor was low,and the average litter size was small,resulting in a weak reproduction capability of the whole population.With the proliferation of preferable plants,their coverage and components significantly increased,leading to the increases of the female to male ratio,the rate to pregnancy of female zokor,the average litter size,and the reproductive capability of the population.As the increase of canopy density of the secondary forests,the preferable plants withdrew their original niche,the zokor population degraded,evidenced by the low female to male ratio,low rate of pregnancy of female zokor,small average litter size,and weak reproductive capability.The leading factor causing the variation of reproductive capability was the influence of under-herbosa on the average litter size of zoke.The main species of under-herbosa infiuencing were Potenlilla bifurca,P.chinensis and Ixeris denticulate,next noes were Cleistogenes squarrosa,Bothriochloa ischaemum.Characteristic indices of different vegetations showed significantly different influences on the reproductive capability of zokor.There existed significantly positive correlation between average litter size of zokor and distribution frequencies of P.bifurca,P.chinensis and I.denticulate;negative correlation with distribution frequency of Lespedeza davurica;very significantly positive correlation with the coverages of P.bifurca and P.chinensis,significantly positive correlation with the coverages of I.denriculate,Stipa bungeana and L.davurica;strong positive correlation with the coverage of C.squarrosa;negative correlation with the coverage of B.ischaemu.