The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic ...The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.展开更多
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 focu...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.展开更多
基金supported by the National Key Research and Development Program of China (2016YFC0500503)the Science and Technology Program of Inner Mongolia Autonomous Region of China (20140409, 201503001)
文摘The community assembly rules and species coexistence have always been interested by ecologists. The community phylogenetic structure is the consequence of the interaction process between the organisms and the abiotic environment and has been used to explain the relative impact of abiotic and biotic factors on species co-existence. In recent years, grassland degradation and biodiversity loss have become increasingly severe on the Mongolian Plateau, while the drivers for these changes are not clearly explored, especially whether climate change is a main factor is debated in academia. In this study, we examined the phylogenetic structure of grassland communities along five transects of climate aridity on the Mongolian Plateau, and analyzed their relations with environmental factors, with the aims to understand the formation mechanism of the grassland communities and the role of climatic factors. We surveyed grassland communities at 81 sites along the five transects, and calculated their net relatedness index(NRI) at two different quadrat scales(small scale of 1 m2 and large scale of 5 m2) to characterize the community phylogenetic structure and analyze its relationship with the key 11 environmental factors. We also calculated the generalized UniFrac distance(GUniFrac) among the grassland communities to quantify the influence of spatial distance and environmental distance on the phylogenetic β diversity. The results indicated that plant community survey using the large scale quadrat contained sufficient species to represent community compositions. The community phylogenetic structure of grasslands was significantly overdispersed at both the small and large scales, and the degree of overdispersion was greater at the large scale than at the small scale, suggesting that competitive exclusion instead of habitat filtering played a major role in determination of community composition. Altitude was the main factor affecting the community phylogenetic structure, whereas climatic factors, such as precipitation and temperature, had limited influence. The principal component analysis of the 11 environmental factors revealed that 94.04% of their variation was accounted by the first four principal components. Moreover only 14.29% and 23.26% of the variation in community phylogenetic structure were explained by the first four principal components at the small and large scales, respectively. Phylogenetic β diversity was slightly significantly correlated with both spatial distance and environmental distance, however, environmental distance had a less explanatory power than spatial distance, indicating a limited environmental effect on the community phylogenetic structure of grasslands on the Mongolian Plateau. In view of the limited effect of climatic factors on the community phylogenetic structure of grasslands, climate change may have a smaller impact on grassland degradation than previously thought.
基金supported by the National Natural Science Foundation of China (31025005 and 31021001)the Program of "One Hundred Talented People" of the Chinese Academy of Sciences (KSCX2-YW-Z-0806)
文摘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.
