Effects of grazing intensity to water source on grassland condition, yield and nutritional content of selected grass species in Northwest Ethiopia

摘要

Abstract BackgroundSavanna grasslands are globally important ecosystems consisting of one of the most extensive grazing lands with unique biodiversity. The objectives of the study were to assess the effect of grazing intensity on grassland ecosystem condition, herbaceous plant biomass production, and nutritional content of selected grass species.MethodsThe study was conducted at Chagni Ranch, Northwest Ethiopia. Four transects to water source point at regular intervals of 20?m between sampling plots along transects were used for data collection. The distance between the four transects was 200?m in radius. Data were collected on grass composition, basal cover, litter cover, number of seedlings, and age distribution of dominant grasses (i.e., young, medium, or old in terms of stage of maturity), soil condition in terms of soil compaction, and soil erosion linked to the effects of trampling by grazing animals along transects (hereafter referred to as transect) to water source point. The total sample size for grass species was 160 plots. The grassland ecosystem condition, herbaceous biomass, and grass nutritional content were used as response variables linked to transect from water source point. The effects of transect on grassland ecosystem condition scores and grass nutritional content were analyzed using the analysis of variance (ANOVA).ResultsGrassland condition factors like grass composition, basal cover, litter cover, age distribution of dominant grasses, and soil condition were significantly ( P ?0.05) higher for the furthest transect to water source point than nearest transect. Out of the 28 identified herbaceous species, grasses accounted for 64.3% of the herbaceous community. Within grass species, about 55.6% were highly desirable in terms of palatability and grazing value (as most palatable species are susceptible to heavy grazing intensity). The results showed a significantly ( P ?0.05) higher proportion of perennial grasses at the furthest transect to water source point than nearest transect. The dry matter yield at the furthest transect (TD4) and third transect (TD3) were significantly ( P ?0.05) higher than the nearest transect to water source point (i.e., the first transect (TD1) and second transect (TD2)). Ash, neutral detergent fiber, acid detergent fiber, and acid detergent lignin contents of Cynodon dactylon , Sporobolus pyramidalis , and Digitaria ternata were significantly ( P ?0.05) higher at the furthest transect to water source point than nearest transect. Grazing intensity had no significant effect on the crude protein content of Cynodon dactylon and Sporobolus pyramidalis at different transects.ConclusionsThe results showed that the furthest transect to water source point were in good condition. Grass biomass production and the nutritional contents of grasses were higher for the furthest transect to water source point. The results suggested that increased grazing intensity towards water source point greatly reduced the abundance of desirable perennial grasses and the sustainability of grassland for livestock production.