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sur le développement des zones arides et semi-arides

Titre : The Effects of Warming and Nitrogen Deposition on Litter Decomposition and Flammability in Stipa Breviflora Desert Steppe

Auteur : 李欣

Grade : Master 2022

Université : Inner Mongolia Agricultural University

Résumé partiel
Litter is not only an important component of ecosystem decomposition but also the basic material that could cause grassland fire.Here we investigated the effects of long-term warming and nitrogen（N）addition on litter decomposition and flammability for the dominant species,Stipa breviflora,in a desert steppe.We conducted a field litter bag experiment to investigate the temporal dynamics of the litter mass remaining and the stoichiometry of leaf litter carbon（C）,N,phosphorus（P）and trace elements（Fe,Ca,Mn,Na,Zn and Cu）.We also measured litter flammability in the study area.Our study will provide scientific support for grassland fire prevention and sustainable management.The main results are as follows :（1）The decomposition process of Stipa breviflora litter includes three phases:rapid decomposition stage（0～371 d）,slow decomposition rate stage（371～738 d）and accelerated decomposition rate stage（738～939 d）.In the first stage of decomposition,on the 183rd day,compared to the control,warming and N addition significantly promoted litter decomposition with significant interactions（P＜0.05）.In the second stage of decomposition,on the 559th day,N addition significantly decreased litter decomposition（P＜0.05）,but the warming effect was not significant.On the 371st day,the 738th day and the 939th day,warming and N addition did not influence litter decomposition.In the whole decomposition process,litter mass remaining was 24.3%in the control.Warming,N addition and combined warming and N addition reduced litter mass remaining by 3.7%,2.2%and 2.1%,respectively.（2）In a 3-year decomposition experiment,litter N concentration initially increased,sequently decreased and then increased with time.N addition resulted in a three-phase pattern of litter N,including increases,decreases and increases（P＜0.05）,but these effects did not occur under warming.In contrast with the N dynamics,litter C and P concentrations initially decreased and then increased with time in the control,whereas litter C showed initial increase and sequent decrease with warming and N addition（P＜0.01）.Litter mass remaining was positively correlated with litter C,P and the C/N ratio（P＜0.001）,but it was negatively associated with litter N concentration（P＜0.001）.

Mots clés : Global change ;Grassland;Litter decomposition ;Nutrient dynamics ;Flammability;

Présentation (CNKI)