Browsing by Author "Hasi, Muqier"

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    Nitrogen addition amplified water effects on species composition shift and productivity increase
    (Oxford, 2021-10) Zhang, Xiaolin; Hasi, Muqier; Li, Ang; Tan, Yulian; Daryanto, Stefani; Wang, Lixin; Zhang, Xueyao; Chen, Shiping; Huang, Jianhui; Earth Sciences, School of Science
    Aims Water and nitrogen (N) are two key resources in dryland ecosystems, but they may have complex interactive effects on the community structure and ecosystem functions. How future precipitation (rainfall vs snowfall) change will impact aboveground net primary production (ANPP) is far from clear, especially when combined with increasing N availability. Methods In this study, we investigated changes in community productivity, abundance and aboveground biomass of two dominant plant functional groups (PFGs), i.e. perennial rhizome grasses (PR) and perennial bunchgrasses (PB) under the impacts of increased precipitation (rainfall vs snowfall) combined with N addition in a semiarid temperate steppe. Important Findings Summer rainfall augmentation marginally increased community ANPP, whereas it significantly increased the abundance and aboveground biomass of PR, but not those of PB. Summer rainfall addition increased the fraction of PR biomass (fPR) while decreased that of PB (fPB). Spring snow addition had no effect on aboveground biomass of either compositional PFG although it marginally increased community ANPP. Nitrogen addition significantly increased community ANPP with greater increase in PR under summer rainfall addition, indicating strong interactive effects on community ANPP largely by enhancing PR biomass. We also found a nonlinear increase in the positive effect of nitrogen addition on productivity with the increased precipitation amount. These findings indicate an amplified impact of precipitation increase on grassland productivity under the accelerated atmospheric N deposition in the future.
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    Nitrogen addition results in Medicago sativa switching nitrogen sources
    (Taylor & Francis, 2021) Wang, Yinliu; Hasi, Muqier; Bu, Dongdong; Li, Ang; Xue, Jianguo; Wang, Changhui; Tian, Qiuying; Niu, Guoxiang; Geng, Qianqian; Wang, Lixin; Huang, Jianhui; Earth Sciences, School of Science
    Background Nitrogen (N) addition may have strong impacts on legume growth and their biological N fixation (BNF), but how legume N acquisition sources respond to N inputs have yet to be comprehensively assessed.Aims We quantified the effects of N addition on the growth and BNF of Medicago sativa and to assess the response of legume N acquisition to N addition.Methods We grew M. sativa in the greenhouse under gradients of added NH4NO3 and analysed the variables that were relative to growth and BNF, such as N concentration, biomass, δ15N values, nodule number, percentage of N derived from the atmosphere (Ndfa%).Results Nitrogen addition had marginal effects on plant biomass production and foliar N concentration. Foliar δ15N value increased with increasing added N, while Ndfa% decreased. The number of nodules formed also decreased with N addition while the nitrogenase (nifH)genecopies per unit nodule mass was not significantly different with N addition.Conclusions These findings indicate that increasing mineral N availability decreases symbiotic investment into BNF, mainly by reducing nodule formation; this was found to have no significant impact on plant growth because the plant changes its N source from BNF-N to mineral N derived from the soil.