小型无脊椎动物对混播草地白三叶叶片伤害程度研究

采用非破坏性的田间观测方法，以主匍匐茎的叶片伤害数，叶片伤害率和叶片伤害程度3个变量为指标，综合评价了小型无脊椎动物对多年生黑麦草与白三叶的混播草地白三叶叶片的伤害程度，系统探讨了白三叶品种类型（Alice,Retor和Gwenda)，刈割频率（高与低）及草地特征（如三叶含量，地上生物量和草层高度）对小型无脊椎动物对叶片伤害的影响。研究表明，高频率刈割的草地白三叶叶片总的伤害数及中等程度伤害的叶片数明显地高于低频率刈割处理（分别为21％和35％），另外，研究期总的叶片伤害数不同程度伤害的叶片数因白三叶品种的不同而存在着很大差异，且这种差异在春季，夏末和秋季等3个时期均十分明显，在这3个时期，在两种频率刈割下，均是品种Retor的叶片伤害数和叶片伤害率明显高于品种Alice和Gwenda，研究还表明，叶片的伤害与白三叶种群特征如白三叶含量和地上生物量存在显著的负相关，白三叶含量和地上生物量越低，则叶片的伤害数和伤害率就越高，回归模型显示，白三叶含量和地上生物量可以解释叶片的伤害数在春季，夏末，秋季各65％，59％和50％的变异，可以解释叶片伤害率在这3个时期各58％，57％和45％。

Severity of damage to Trifolium repens leaves by certain miniinvertebrate species in mixed swards

The severity of damage to white clover (Trifolium repens) leaves caused by certain miniinvertebrate species in mixed swards was assessed using the number of damaged leaves, relative leaf damage and different degrees of leaf damage in a field experiment, in which two cutting frequencies (high and low) and three clover cultivars (Alice, Retor and Gwenda) were used. The relationship between leaf damage and sward characteristics (e.g., white clover content, above-ground biomass and sward height) was determined with correlation and regression analyses. The high cutting frequency increased the number of damaged leaves and of moderately damaged leaves by 21% and 35%, respectively, compared with the low cutting frequency. The cv. Retor experienced the most severe damage by miniinvertebrates among three cultivars, both in the total number of damaged leaves and in the different damage categories. Significant differences were observed in the number of damaged leaves and relative leaf damage (as a percentage of damaged leaves relative to leaf number present) among cultivars in spring, late-summer and autumn, but did not differ during the other months. Variation in leaf damage can be associated with differences in observed characteristics of white clover population. Both the number of damaged leaves and the relative leaf damage were found to strongly negatively correlated with white clover content and above-ground biomass in spring, late-summer and autumn under each of two cutting frequencies. White clover content and biomass explained 65%, 59% and 50% of the variation in the number of damaged leaves in spring, late-summer and autumn, respectively, and 58%, 57% and 45% of the variation in relative leaf damage during these three periods.