Changes in nematode abundances and body length in response to management intensive grazing in a low-input temperate pasture

Abstract

An evaluation of changes in nematode populations in response to management was performed using a field scale experiment along a gradient of land-use intensity in the context of management intensive grazing. Four levels of decreasing intensity were measured over three growing seasons. The treatments included: 1) intensive grazing management where cows were allowed to graze for each grazing cycle, followed by routine clipping and harrowing; 2) semi-intensive grazing where cows were allowed to graze for each grazing cycle, with only one clipping event per year; 3) extensive grazing where cows were allowed to graze during every 2nd grazing cycle and no clipping or harrowing was performed; 4) stockpiling treatment where cows were permitted to graze only during the final grazing cycle, followed by clipping at the end of the season. Most indices (MI, PPI, ∑MI, and ∑MI25) resulted in significant seasonal differences; however, only familial diversity (H′) and the total number of families showed significant season by treatment interaction. Bacterivores comprised most of the nematode population with Cephalobidae being the most common family. Abundance of plant feeders was affected by season and soil moisture, whereas bacterivore abundance was associated with total organic N and soil pH. Nematode body length increased slightly in most families through time, and was associated with season, bulk density, soil moisture, and total N and C. Although omnivore numbers were highest in the extensive and semi-intensive treatments, there was a significant increase in dorylaimid body length observed in the intensive treatment through time. Increases in body length were also observed in Monhysteridae and Cephalobidae in all treatments.