THE SELECTION OF A MINIMUM SET OF KEY GRASS SPECIES FOR BIODIVERSITY CONSERVATION IN THE HIGHLAND SOURVELD OF KWAZULU-NATAL
Cobus Botha and Clement Adjorlolo
KwaZulu-Natal Department of Agriculture and Environmental Affairs, Natural Resources

 

Abstract

Landowner based biodiversity conservation initiatives in the KwaZulu-Natal Highland Sourveld require stewardship facilitators to advise on practical rangeland management. Range condition assessments are a tool employed to assess sward health and forms the basis for conservation stocking rate recommendations. This has resulted in a renewed demand for simple, accurate rangeland condition assessment techniques such as the key species method. This method can provide trends on vegetation dynamics and guide management decisions related to stocking rate over a wide range of vegetation types. The purpose of this study was to select a minimum set of key species for the moist and dry phases of the Highland Sourveld. Species composition data and range condition scores for 442 sites in the moist and 520 sites in the dry was analysed. Data sets were normally distributed for the response variable according to the Kolmogorov-Smirnov test. Forward stepwise multiple regression was used to select a minimum set of 8 species for both the moist (R2=0.96, RMSE=25.76) and the dry (R2=0.95, RMSE=26.09) phases respectively, using the training data sets. Selected species showed a 63% overlap between phases but coefficients of determination differed. Model accuracy was tested against independent data sets using Root Mean Square Error of Prediction (RMSEP) and Nash-Sutcliffe model efficiency coefficient (NSE). The Moist Highland Sourveld model yielded RMSEP of 26.16 compared to a mean of 492.8 and a NSE of 0.96. The Dry Highland Sourveld model performed similarly well with a RMSEP = 27.3 compared to a mean of 531.8 and a NSE of 0.95. A minimum set of key species was successfully selected for the Moist and Dry Highland Sourveld while not compromising the accuracy and the objectives of the technique. The selection of a single set of species representing the Highland Sourveld should further be investigated as this will widen the applicability and use in the biodiversity conservation sector.

 

Presentation Topic

THE SELECTION OF A MINIMUM SET OF KEY GRASS SPECIES FOR BIODIVERSITY CONSERVATION IN THE HIGHLAND SOURVELD OF KWAZULU-NATAL
Contact Mr Botha:
Email Cobus Botha