The influence of sward management on foliage arthropod communities in a ley grassland.
The influence of different systems of grazing and silage production on the foliage fauna of a grass ley was investigated in the Irish Republic. Most arthropods were caught in 'D Vac' suction nets (up to 10 351 examples/m2) in long conserved silage swards, and least (as few as 394 examples/m2) in short swards subject to periodic heavy grazing. Immediate, non-persistent population fluctuations accompanied management-induced changes in sward height; the abundance of most groups, particularly larger insects, increased during conservation for silage, and acarine and collembolan numbers fell most under heavy grazing and following cutting. The cropping systems had no overall influence on the range of dominant taxa collected. The concept of a fauna spectrum is introduced to represent faunas containing large numbers of species and was used in a comparative analysis of treatment differences. Faunal abundance was subject to other modifying influences, notably successional increases associated with ley establishment. Atypical weather can largely override effects of cropping procedures, and principal component analysis showed that seasonality predominantly influences community structure. It is concluded that in short-term ley systems, cropping management acting within a framework of other factors limits foliage arthropod abundance by maintaining a predominantly short sward length and by modifying microclimatic conditions.<new para>ADDITIONAL ABSTRACT:<new para>The influence of different systems of grazing and silage production on the foliage fauna of perennial ryegrass/white clover swards at Celbridge, Irish Republic was studied in 1976-7. Most arthropods (10 351/m2) occurred in long conserved silage swards and least (394/m2) in swards subject to periodic heavy grazing. Abundance was related to sward ht., being less after cutting and grazing than in conserved swards. The range of spp. of the fauna was not affected by management systems.