M Ajorlo - Faculty of Soil and Water, University of Zabol, Zabol, Iran
M.R Ebrahimian - Research Institute for Hamoun International Wetland, University of Zabol, Zabol, Iran
R.B Abdullah - Faculty of Forestry and Environment, University Putra Malaysia, Serdang, Malaysia
R.A Halim - Faculty of Agriculture, University Putra Malaysia, Serdang, Malaysia

Natural grasslands are used for communal livestock ranching by smallholders in Malaysia. Carpetgrass (Axonopus compressus (Sw.) P. Beauv) is a dominant grass in such ecosystems. Heavy stocking rate isa common problem in the majority of natural grasslands. This study aimed to quantify the response of Carpetgrass root system to grazing by cattle. Two grazing treatments, i.e., heavy stocking rate under rotational grazingfor ۲-year and no cattle grazing were selected. Root morphological traits were assessed using soil coringapproach. The soil cores were extracted directly from the center of individual grass plant to a maximum depthof ۳۰ cm using manually driven single root auger with ۸ cm diameter. Soil cores were cut into three ۱۰-cmfragments and then gently hand washed with tap water to remove all soil material. Root samples were analyzedwith WinRhizo root scanner for root length (cm), surface area (cm۲), average diameter (mm), volume (cm۳)and mass (mg). Data was compared for significant effects of grazing and soil depths using GLM procedurewith Repeated Measure analysis of variance in SPSS Statistics v۲۲.۰. Mean root length in grazed site was ۳۲%lower than that in ungrazed exclosure (P < ۰.۰۵). The total root lengths per unit area were nearly ۱۲۶ and ۱۸۶m/m۲ at the grazed and ungrazed treatments, respectively. The mean diameter of root system of heavily grazedgrass plants was ۲۵% larger than ungrazed plants (P < ۰.۰۵). Mean root volume was ۸۴% higher (P < ۰.۰۵) inheavily grazed grassland compared to ungrazed grassland. Total root mass in ۰-۳۰ cm depth were ۲۴۹ and ۱۸۰kg/ha in grazed and ungrazed sites. It should be stressed that this study was the quantification of short-term(۲-year) heavy grazing on roots at the farm scale; the actual effects of heavy grazing intensity may appear overa longer period if the same grazing treatment is continued.

Heavy grazing; root length; root diameter; root volume; root mass