Effect of Grazing Exclusion on Soil Properties and Vegetation Characteristics in Parthenium Hysterophorus L. Invaded Grassland of Hetauda, Central Nepal

Abstract

Grasslands outside Protected Areas (PAs) in Nepal are much exploited ecosystems since these areas are surrounded by heavy settlement and grazing activity in these areas is entirely human controlled rather than being natural. Intense grazing practices without any management effort are making these grasslands likely to be invaded by IAPS and deteriorating the quality of the grasslands. Therefore this study was aimed to find out the impact of grazing exclusion in a highly grazed Parthenium hysterophorus invaded grassland. Three plots of 10 m × 10 m had been fenced since 2015 in the grassland to exclude grazing for research purposes. Three plots adjacent to those permanent plots were established in 2017. Effect of grazing exclusion on soil properties, relative abundance of weed species and plant species diversity of both Above Ground Vegetation (AGV) and Below Ground Vegetation (BGV) were compared between Freely Grazed (FG) and Grazing Excluded (GE) plots. The finding demonstrated that grazing exclusion of even three years showed some noticeable difference in some of the soil physico-chemical properties and vegetation characters of FG and GE plots. Soil bulk density and organic carbon were reduced while soil pH and electrical conductivity were enhanced by grazing exclusion. However, no apparent impact of livestock exclusion was observed for soil nitrogen, phosphorus and potassium. Grazing exclusion substantially altered the species composition of the grassland and enhanced the growth of much diverse plant species in AGV of GE plots. Similarly, grazing exclusion reduced relative abundance of Parthenium hysterophorus in germinable seed bank but it has no effect in AGV. However, since grazing exclusion showed opposite effect on species diversity of AGV and BGV no conclusion could be drawn about its effect on species diversity. Therefore more studies with longer period of grazing exclusion are required to fully understand the impact of grazing exclusion on soil properties and vegetation structure of grassland in order to use it as management practice in invaded grasslands.