Aims The mature meadows(MMs)and the swamp meadows(SMs)are the two most important ecosystems in the eastern Tibetan Plateau,China.Besides their substantial differences in terms of soil water conditions and thereby the soil oxygen and nutrients,however,little is known about the differences in community composition,struc-ture,traits and productivity between these two meadows.We par-ticularly ask whether light availability mediated by physical structure heterogeneity is a key determinant of the difference in community composition and productivity between these two meadows.Methods We examined the community structure,composition,aboveground net primary productivity(ANPP),light availability in understory and the community-weighted means(CWMs)for leaf morphological and physiological traits in 12 random plots(5 m×5 m)for each of the studied habitats.Important findings The results showed that plant community in the MM had higher variation in both vertical and horizontal structure and thus had more light availability in the understory.The MM had higher spe-cies richness and greater ANPP than the SM.The CWMs of leaf morphological and physiological traits for species in the MM fea-tured a fast-growing strategy(i.e.higher height,leaf area and net photosynthesis rate and lower nitrogen:phosphorus ratio),in con-trast to those in the SM.We also found that there were significant correlations between the CWM of traits and the ANPP,indicating that some key traits in these habitats have linked to community productivity.Our study also suggests that the heterogeneity in the community structure,which affects light availability in the under-story,may play an important role in determining the community composition and productivity.In conclusion,our study revealed significant differences in community structure,composition and traits between the MM and the SM,and the light availability that related closely to community structure is the key factor to deter-mine the composition and productivity of the community of these two habitats.
Honglin LiKailiang YuDanghui XuWei LiDorjeeh TondrobGuozhen Du
Aims Plants can change in phenology and biomass allocation in response to environmental change.It has been demonstrated that nitrogen is the most limiting resource for plants in many terrestrial ecosystems.Previous studies have usually focused on either flowering phenology or biomass allocation of plants in response to nitrogen addition;how-ever,attempts to link flowering phenology and biomass allocation are still rare.In this study,we tested the effects of nitrogen addition on both flowering phenology and reproductive allocation in 34 common species.We also examined the potential linkage between flowering time and reproductive allocation in response to nitrogen addition.Methods We conducted a 3-year nitrogen addition experiment in Tibetan alpine meadow.We measured first flowering date and the repro-ductive allocation for 34 common plant species in control,low and high nitrogen added plots,respectively.one-way analysis of variance was used to examine differences of first flowering date and reproductive allocation among treatments.The relationships between the change in species first flowering date and change in reproductive allocation in response to nitrogen addition were examined by calculating Pearson correlation coefficients.Important Findings For most species,both first flowering date and reproductive alloca-tion significantly responded to nitrogen addition.Nitrogen addition significantly delayed the first flowering date and reduced the repro-ductive allocation for all graminoid species,but accelerated flower-ing and increased reproductive allocation for most forb species.We found that changes in first flowering date significantly negatively correlated with the changes in reproductive allocation over spe-cies in response to nitrogen,which indicated a positive relationship between flowering response and plant performance in reproductive allocation.species that advanced their flowering time with nitrogen addition increased their reproductive allocation,whereas those that delayed flowering time tended to decline
Zhilong ZhangKechang NiuXudong LiuPeng JiaGuozhen Du
