Gauging environmental variation in the rejuvenation potential of disturbed natural ecosystems

摘要

"There can be no purpose more inspiring than to begin the age of restoration, reweaving the wondrous diversity of life that still surrounds us" – E.O Wilson.ududEcological restoration is an expensive, time consuming and labour intensive activity. It is therefore important to understand the potential for disturbed natural ecosystems to recover without the need for intervention. This project investigates the rate of vegetation and soil recovery from different types of disturbance at 18 sites within four major ecosystems (grassy, dry sclerophyll, wet sclerophyll, and rainforest) in Tasmania. All sites have a known disturbance history (type and age). At each site, randomly located quadrats were placed in the disturbed and control areas and the percentage cover of species, bare ground and litter estimated using a modified Braun-Blanquet scale. The pH, N, P, C of surface soils from the subset of these quadrats was measured. Topographic and climatic data were obtained at the site level. Global non-metric multi-dimensional scaling was performed on the presence/absence data for all taxa. Bray-Curtis dissimilarity matrices were produced and these were used to examine similarities and dissimilarities between disturbed and control areas. Vectors were fitted for all variables and significance determined by 1000 randomisations. Sorted tables were used to indicate the abundance and presence or absence of taxa at site and ecosystem levels. Relationships between independent variables and the mean distances between control and disturbance vegetation and soils were determined at the site level. The type of initial disturbance (superficial or severe) rather than the time since cessation of the initial disturbance or other factors was the best single predictor of the recovery of both vegetation and soil. Restoration effort should be directed towards areas that are known (as determined by site history) to have been subjected to extensive soil and vegetation disturbance.