异针茅在不同生境下补偿生长特性及其影响因素的研究

植物的补偿生长受放牧扰动和生境资源的共同影响，但何种条件易于引起植物发生超补偿生长是长期以来争论的问题。在矮嵩草（Kobresia humilis）草甸3种生境（畜圈、牧道、封育）设置扣笼和无扣笼对比样方（不放牧和放牧处理）研究了异针茅（Stipa aliena）的补偿生长特性。结果显示，异针茅分株各部分中除根系在牧道生境为等量补偿外，叶片和花序在畜圈和牧道生境均为低补偿。异针茅的分株密度、高度以及生长分配在封育生境最高。分株各部分的相对生长率在畜圈生境最低，在牧道生境最高。典范对应分析表明，对异针茅补偿生长和相对生长率影响最大的因子是采食率。尽管畜圈生境具有良好的土壤养分和水分条件，但仍不能抵消该生境家畜重度采食和践踏对异针茅的负面影响。研究结果表明，影响异针茅分株种群补偿生长的主要因素是放牧强度，而土壤资源获得性的影响相对较小。

Research on compensatory growth of Stipa aliena and impact factors under different habitats

Grazing disturbance and resource availability can affect the compensatory growth of defoliated plants,but it is unclear which factor is the most important in inducing the over compensatory response to herbivores in a particular area.Our objectives were to examine how compensatory growth of Stipa aliena varied with different habitats in an alpine Kobresia humilis meadow and determine relative effects of these factors on compensatory growth.A field experiment was carried out at the Haibei Research Station of the Chinese Academy of Sciences from April to September 2007,which included three habitats(habitatⅠ: pen,grazed×high nutrient availability;habitatⅡ: pass pasture,grazed×low nutrient availability and habitat Ⅲ: ungrazed pasture,null defoliation ratio×low nutrient availability) with three plots per habitat.In each plot,12 quadrats(0.5 m×0.5 m) were divided into two groups(6 caged and 6 uncaged).For each group,3 of 6 quadrats were sampled in mid-June and other 3 in mid-August,respectively.We used canonical correspondence analysis(CCA) with potential impact factors selected by the forward selection procedure for the compensatory growth of S.aliena to determine the relative effects of defoliation,water and soil nutrient variables on compensatory growth.The results indicated that full compensation occurred for roots at habitat Ⅱ and low compensation was found in leaves and inflorescence at habitat Ⅰ and Ⅱ.The ramet density,height and growth allocation of the S.aliena were higher at habitat Ⅲ.The ramet relative growth rate of the species was lower at habitatⅠ and higher at habitat Ⅱ.The results of CCA showed that the most important impacted factors of compensatory growth and ramet relative growth rate of the species were defoliation ratio by grazing.Although there were higher soil nutrient and water contents at habitat Ⅰ,but still did not blot out the negative effects of heavy deflolation and trampling by domestic animals on the species.The results above suggested that the most important factors affecting the compensatory growth of S.aliena was defoliation ratio rather than soil resource availability.