Bringing forward the benefits of coarse woody debris in ecosystem recovery under different levels of grazing and vegetation density

Abstract

Restoration projects often do not effectively restore some key biological resources that take time, often centuries, to accumulate. Such resources are often characteristic of 'natural' ecosystems and are critical to successful ecosystem recovery. Deadwood or 'coarse woody debris' (CWD) is one such example. Coarse woody debris is depauperate in many of the world's ecosystems due to stand structural simplification through vegetation clearing, logging and grazing. The lag time in the natural accumulation of CWD can be a major barrier to their effective ecological restoration in the short term. We examined the effect of experimentally adding CWD, in four different treatments, on reptile abundance in temperate woodlands in south-eastern Australia - one of the most highly degraded vegetation types on the continent. We then investigated the influence that varying grazing pressure and vegetation density had on those effects. We examined three key questions: (1) Does the addition of CWD change overall reptile abundance over a 4. year period? (2) Does existing vegetation density or kangaroo grazing effect reptile response? (3) Is there evidence of high order interaction effects between CWD, kangaroo grazing and vegetation density on reptile response? Adding CWD increased reptile abundance significantly after only 4. years. The spatial pattern of CWD distribution also significantly affected reptile abundance. The location where CWD was added also was important, with open and mid-dense vegetation gaining the highest number of small skinks compared to control sites. Reduction of grazing was the most effective way of increasing small skink abundance in high density vegetation. Open areas gained most from the addition of CWD where high kangaroo grazing occurred. We conclude that adding CWD can short-cut a 100-200. year barrier to ecosystem restoration. By distributing CWD in particular patterns and places in the landscape, and in combination with different grazing levels, conservation managers can improve effectiveness of restoration programs.