Defining function in rangelands of the Peddie district, Eastern Cape, using Landscape Function Analysis

Abstract

Portions of natural rangeland in the Great Fish River Valley have been defined as degraded by several studies using vegetation analysis techniques. It was considered desirable that soil surface condition should also be described to provide an index of landscape function and a threshold of critical resource control. Tongway and Hindleys (1995) soil surface condition assessment technique, termed Landscape Function Analysis (LFA), was applied to rangelands in the Peddie District, Eastern Cape Province. Samples were collected across a fenceline between commercial and communal rangeland management systems. At each sample site, the LFA technique was applied, and soil samples were collected to determine major nutrient content. At the landscape organisation level, the technique yielded conclusive differences between the contrasting rangelands. The commercial site contained grass swards which would be able to control water and nutrient flow across the landscape. In the communal rangeland, vegetation cover was lower and presented weaker barriers to water and nutrient movement across the landscape. The soil surface condition index did not provide clear differences between the two sites. LFA indices provided indirect measures of these differences in landscape function. Surface soil conditions on the communal rangeland had higher organic carbon, nitrogen and phosphorus content. Following the analysis of satellite-derived vegetation indices, the commercial site had higher active green biomass (higher NDVI) and lower spatial diversity of near-infra red band (lower MSDI) than the communal site.


Keywords: soil surface assessment; nutrient content; degradation; fenceline contrasts; patches; fetches


African journal of Range & Forage Science 2001, 18(1): 53-58