Influence of grazing intensity on performance of perennial grass mixtures in the alpine region of the Tibetan Plateau

Effects of grazing intensity on leaf photosynthetic rate (Pn), specific leaf area (SLA), individual tiller density, sward leaf area index (LAI), harvested herbage DM, and species composition in grass mixtures (Clinelymus nutans + Bromus inermis, Elymus nutans + Bromus inermis + Agropyron cristatum and Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum) were studied in the alpine region of the Tibetan Plateau. Four grazing intensities (GI), expressed as feed utilisation rates (UR) by Tibetan lambs were imposed as follows: (1) no grazing; (2) 30% UR as light grazing; (3) 50% UR as medium grazing; and (4) 70% UR as high grazing. Leaf Pn rate and tiller density of grasses increased (P < 0.05), while sward LAI and harvested herbage DM declined (P < 0.05) with the increments of GI, although no effect of GI on SLA was observed. With increasing GI, Elymus nutans and Clinelymus nutans increased but Bromus inermis and Agropyron cristatum decreased in swards, LAI and DM contribution. Whether being grazed or not, Elymus nutans + Clinelymus nutans + Bromus inermis + Agropyron cristatum was the most productive sward among the grass mixtures. Thus, two well-performed grass species (Elymus nutans and Clinelymus nutans) and the most productive mixture of four species should be investigated further as the new feed resources in the alpine grazing system of the Tibetan Plateau. Light grazing intensity of 30% UR was recommended for these grass mixtures when swards, LAI, herbage DM harvested, and species compatibility were taken into account.

Burrowing rodents as ecosystem engineers: the ecology and management of plateau zokors Myospalax fontanierii in alpine meadow ecosystems on the Tibetan Plateau

1. Plateau zokors, Myospalax fontanierii, are the only subterranean herbivores on the Tibetan plateau of China. Although the population biology of plateau zokors has been studied for many years, the interactions between zokors and plants, especially for the maintenance and structure of ecological communities, have been poorly recognized. In the past, plateau zokors have been traditionally viewed as pests, competitors with cattle, and agents of soil erosion, thus eradication programmes have been carried out by local governments and farmers. Zokors are also widely and heavily exploited for their use in traditional Chinese medicine.2. Like other fossorial animals, such as pocket gophers Geomys spp. and prairie dogs Cynomys spp. in similar ecosystems, zokors may act to increase local environmental heterogeneity at the landscape level, aid in the formation, aeration and mixing of soil, and enhance infiltration of water into the soil thus curtailing erosion. The changes that zokors cause in the physical environment, vegetation and soil clearly affect the herbivore food web. Equally, plateau zokors also provide a significant food source for many avian and mammalian predators on the plateau. Zokor control leading to depletion of prey and secondary poisoning may therefore present problems for populations of numerous other animals.3. We highlight the important role plateau zokors play in the Tibetan plateau ecosystem. Plateau zokors should be managed in concert with other comprehensive rangeland treatments to ensure the ecological equilibrium and preservation of native biodiversity, as well as the long-term sustainable use of pastureland by domestic livestock.