Changes in grassland structure in Sierra de Organos National Park associated with a 14-year grazing exclusion

Resumen

Objective. To evaluate the effect of 14-year grazing exclusion on land cover and on the dynamics of plant functional groups in the grassland of the Sierra de Organos National Park.

Design/ Methodology/ Approach. In 2008, at the beginning of the grazing exclusion, four transects were established to measure land cover and plant functional groups. The measurements were repeated in 2010, 2012, 2014, 2018 and 2022.

Results. During the first ten years of grazing exclusion, basal cover increased by 201%, as well as by 228.7% in litter accumulation and 219% in soil cover. In other words, bare soil was significantly reduced. However, in the following period of the evaluation, basal cover and soil cover decreased, which meant an increase in bare soil. In addition, during the first decade of grazing exclusion, grasses maintained a clear dominance in the plant community. However, since 2018 those decreased, which coincided with an increase in herbaceous plants and shrubs.

Limitations/ Implications of the study. The study generated practical information applicable both in the study area and in livestock ranches in the Central-North Region of Mexico.

Findings/ Conclusions. Grazing exclusion should be limited to a period of less than ten years, since during that time the vegetation cover increases and bare soil is reduced; however, as it continued, a degradation of the pasture and the substitution of grasses for other herbaceous and shrubs were observed.