Study Site
Our study took place within a long-term grazing experiment located in Siziwang Banner (41°46’43 ”N, 111°53’42” E, elevation 1456 m) at the comprehensive experiment and demonstration center of the Inner Mongolia Academy of Agriculture and Animal Husbandry Sciences, China. The study site is a typical desert steppe ecosystem dominated by Stipa breviflora Griseb., Artemisia frigida Willd, andCleistogenes songorica (Roshev.) Ohwi. Subordinate species include Convolvulus ammannii Desr., Kochia prostrata (L.) Schrad., Caragana stenophylla Pojark. and Caragana microphylla Lam.. The soil is primarily a sandy loam texture with low nitrogen, phosphorus, and organic matter content, but high potassium. Over the course of the experiment (2004 to 2020), the average annual temperature was 3.4℃ and the average annual precipitation was 221.7 mm (the majority falling from June to August). We present the air temperature and precipitation during the growing season in which we collected data (2020) in Fig. S1.
Experimental Design
A grazing manipulation experiment was established in June 2004 in a natural grassland (~50 ha) with relatively flat terrain and relatively homogeneous vegetation and soil types. The plots were divided into three experimental blocks which each received one of four grazing treatments, control (no grazing), light grazing, medium grazing and heavy grazing (thus, there were three replicates for each treatment). Each experimental plot was 4.4 ha and constructed with iron wire fencing material. The stocking rates in each treatment were 0 (control/ no grazing), 0.91 (light grazing), 1.82 (moderate grazing, MG) and 2.71 (heavy grazing) sheep unit · (hm2A-1) -1. Each grazing plot was grazed by adult sheep from June 1 to October 1 each year. During the grazing season, the sheep were driven into the grazing area at 6:00 every day and left to forage freely until their return to the corral at 18:00.