| Mt. Jade Dragon, located in Northwest Yunnan, is the key area in teams of global biodiversity, and the alpine meadow in it is the focal plant community type which needs priority conservation. With the advance of tourism in Mt. Jade Dragon, its alpine meadow is suffering from increasing disturbance, which needs more attention. Meadow degradation will not only lead to species diversity reduction, but cause the shift of ecosystem function. For the purpose of researching the functional structure and diversity changing pattern during the meadow deterioration, the study carried out the field experiment in Yak Meadow Park in July2014to gain basic data. Quantitative ecology method combined with vegetation and soil data was applied to assess meadow degradation gradients. Plant functional traits including plant height, LA, SLA, LDMC, RL and SL were adopted to calculate functional diversity indexes (FRic, FEve, FDiv and RaoQ). Null model was used to identify the functional diversity changing rules.The main results are summarized as follows:The alpine meadow can be divided into four degradation gradients:no degradation, moderate degradation, middle degradation and severe degradation. Vegetation cover, height, species richness and Shannon diversity index showed the trend of decreasing along degradation gradients. With the degradation of meadow, its soil moisture content, SOM and TN decreased, while soil pH showed no significant changing pattern.Plant functional traits such as plant height, SLA, LDMC, RL and SL all decreased with the degradation of alpine meadow. FRic and RaoQ decreased along the degradation gradient, while FEve and FDiv showed the opposite trend but not significant. Species richness, FRic and RaoQ reached the maximum value in moderate degradation gradient. FRic and RaoQ reduced to minimum value in middle degradation while species richness was in severe degradation gradient with its minimum value. Species richness and Shannon diversity index had good positive correlation with FRic and RaoQ separately, and had negative correlation with FDiv. Pielou evenness index showed no significant correlation with other functional diversity indexes. The alpine meadow functional diversity in the study area was influenced by niche filtering and biotic interaction process. In the low-level degradation gradients, functional diversity was dominated by biotic interaction process, which would enhance the well-distributed of species along plant height, RL functional traits axis to fulfill the resource, and thus boost the functional diversity. With the degradation of alpine meadow, habit filtering process was increasingly strengthened, which sieved out species with the functional traits of lower height and LDMC, small SLA and RL.There were several proposals for meadow management in terms of the study conclusions. Species with lower plant height, smaller SLA, lower LDMC and shorter RL indicated high degradation environment well, thus meadow monitoring can be integrated with plant functional traits to determine degradation level. In the study, functional diversity showed significant reduction in middle degradation while species richness was still kept in high level. From the aspect of preserving functional diversity, alpine meadow degradation should be monitored at the beginning of moderate degradation and controlled under the middle degradation gradients to keep high functional diversity and species diversity. Alpine meadow was the key plant community type which had low functional redundancy, and losing species from the community will cause large extent changes of community function, which does harm to eco-health persistence. In the study, species such as Anemone trullifolia, Lamiophlomis rotata, Roscoea cautleyoides, Tibetia yunnanensis loss from the community gradually with the degradation of the meadow, and these species had good connection with community functional diversity, which hints that meadow degradation management should pay more attention to the major functional species. |
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