Liang Cunzhu

Large scale patterns of forage yield and quality across Chinese grasslands

Understanding the patterns of forage quantity and quality and investigating the factors influencing these patterns are essential for the development of animal husbandry. However, there is very little field evidence focused on these issues at a large spatial scale. In the current study, we analyzed forage quantity and quality at 177 sites distributed in all the major grassland types across China, and explored the relationship between forage quantity and quality based on consistent sampling protocols. We also investigated potential factors influencing forage quality patterns across China. Our study indicates the Tibetan grasslands had both higher quantity and quality forage than the Inner Mongolian grasslands, and alpine meadow had the best quantity and quality forage because of the meadow’s high productivity and the crude protein and nitrogen free extract content of the meadow forage. For the main vegetation formations, Kobresia tibetica meadows and Achnatherum splendens steppes had the highest quantity, while Kobresia pygmaea meadows and Kobresia humilis meadows had the best quality. We also found that although environmental factors, such as temperature and soil fertility, could affect physiological processes and so influence forage quality, the large scale patterns of change were mainly a result of the differences in vegetation types. Finally, we reported a negative relationship between forage quantity and quality: higher forage quantity means more crude fiber but less ether extract and crude protein. These findings improve our understanding on the spatial patterns of forage quantity and quality, and provide solid evidence related to the future development of animal husbandry.

Temporal and spatial heterogeneity of drought impact on vegetation growth on the Inner Mongolian Plateau

Drought frequency and intensity have increased in recent decades, with consequences for the structure and function of ecosystems of the Inner Mongolian Plateau. In this study, the Palmer drought severity index (PDSI) was chosen to assess the extent and severity of drought between 1982 and 2011. The normalised difference vegetation index (NDVI) was used to analyse the responses of five different vegetation types (forest, meadow steppe, typical steppe, desert steppe and desert) to drought. Our results show that during the last 30 years, the frequency and intensity of droughts have increased significantly, especially in summer and autumn. The greatest decline in NDVI in response to drought was observed in typical steppe and desert steppe vegetation types. Compared with other seasons, maximum decline in NDVI was observed in summer. In addition, we found that NDVI in the five vegetation types showed a lag time of 1–2 months from drought in the spring and summer. Ancillary soil moisture conditions influenced the drought response, with desert steppe showing a stronger lag effect to spring and summer drought than the other vegetation types. Our results show that drought explains a high proportion of changes in NDVI, and suggest that recent climate change has been an important factor affecting vegetation productivity in the area.

Using positive interaction ecology to explain grassland degradation induced by overgrazing

Overgrazing of grassland ecosystems in the temperate steppe region of China has resulted in serious degradation and a distinct vegetation pattern. Grassland degradation is a major concern to ecologists and has been the focus of much recent research. A lot of work has been done on grassland degradation in grassland communities but few studies have explored the mechanisms of degradation from an ecological theory perspective. Positive interaction ecology theory has become one of the major themes in ecology, particularly the Stress Gradient Hypothesis. In the following study we attempt to explain the mechanisms of grassland degradation using positive interaction ecology and provide a new perspective for recognizing grassland degradation.