Individual study: Effects of grazing and invasive grasses on desert vertebrates in California
Germano D.J., Rathbun G.B. & Saslaw L.R. (2012) Effects of grazing and invasive grasses on desert vertebrates in California. The Journal of Wildlife Management, 76, 670-682
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Other biodiversity: Use grazers to manage vegetation
A replicated, controlled study in 1997–2006 in scrub and grassland in central California, USA, found more ground-dwelling invertebrates in cattle-grazed plots, compared to ungrazed plots. The abundances of one of five mammals and one of three reptiles increased faster in grazed plots, compared to ungrazed plots. The abundance of one mammal species was lower in grazed plots, in some years. Less vegetation was left in grazed plots. Invertebrates: Fewer ground-dwelling invertebrates were found in grazed plots, compared to ungrazed plots, in six of nine years (data not provided). Abundances of grasshoppers did not differ between grazed and ungrazed plots (8–1,600 individuals/count). Mammals: Abundances of giant kangaroo rats Dipodomys ingens increased by 1.6 individuals/year in grazed plots, but did not increase in ungrazed plots. The changes in abundances of four other species did not differ between grazed and ungrazed plots. Heerman’s kangaroo rats Dipodomys heermanni were less abundant in grazed plots in some years (0–3 vs 0–22 individuals). Abundances of San Joaquin pocket mice Perognathus inornatus inornatus differed between grazed and ungrazed plots, but not consistently. The abundances of three other mammals did not differ between grazed and ungrazed plots. Reptiles: The abundance of blunt-nosed leopard lizards increased at a greater rate in grazed plots (6.8 vs 1.4 extra individuals/year). The change in abundances of two other species, and the overall abundances of all three species did not differ between grazed and ungrazed plots. Plants: At the end of the grazing season, less vegetation was left in grazed plots, in eight of ten years (20–2,100 vs 900–4,000 kg/ha). Methods: Four 2.6 km2 plots were established and grazed from December to leave approximately 560 kg dry matter/ha by April. Therefore, grazing intensity varied over time, and plots were not grazed at all in 2002–2004. Within each plot, a 25 ha plot was left ungrazed. Mammals were surveyed using 64 traps in each plot for six days and six nights in July–September each year. Grasshoppers and day-active lizards were surveyed visually within 9 ha grids, on ten days in May–July each year. Ground-dwelling invertebrates were monitored with pitfall traps. Vegetation was monitored on the same grids as lizards and clipped to assess biomass.