Increase in medium-size rainfall events will enhance the C-sequestration capacity of biological soil crusts

作者：CuiHua Huang,Fei Peng,Itaru Shibata,Jun Luo,Xian Xue,Kinya Akashi,Atsushi Tsunekawa,Tao Wang

摘要：Biological soil crusts(BSCs)play important roles in the carbon(C)balance in arid regions.Net C balance of BSCs is strongly dependent on rainfall and consequent activation of microbes in the BSCs.The compensation-rainfall size for BSCs(the minimum rainfall amount for a positive net C balance)is assumed to be different with BSCs of different developmental stages.A field experiment with simulated rainfall amount(SRA)of 0,1,5,10,20,and 40 mm was conducted to examine the C fluxes and compensation-rainfall size of BSCs in different parts of fixed dunes in the ecotone between the Badain Jaran Desert and the Minqin Oasis.We found algae-lichen crust on the interdunes and crest,algae crust on the leeward side,and lichen-moss crust on the windward.Even a small rainfall(1 mm)can activate both photosynthesis and respiration of all types of BSCs.The gross ecosystem production,ecosystem respiration,and net ecosystem exchange were significantly affected by SRA,hours after the simulated rainfall,position on a dune,and their interactions.The rapid activation of photosynthesis provides a C source and therefore could be responsible for the increase of C efflux after each rewetting.C-uptake and-emission capacity of all the BSCs positively correlated with rainfall size,with the lowest C fluxes on the leeward side.The compensation rainfall for a net C uptake was 3.80,15.54,8.62,and 1.88 mm for BSCs on the interdunes,the leeward side,the crest,and the windward side,respectively.The whole dune started to show a net C uptake with an SRA of 5 mm and maximized with an SRA of about 30 mm.The compensation-rainfall size is negatively correlated with chlorophyll content.Our results suggest that BSCs will be favored in terms of C balance,and sand dune stabilization could be sustained with an increasing frequency of 5-10 mm rainfall events in the desert-oasis transitional zone.

发文机构：Minqin Salinization Research Station International Platform for Dryland Research and Education Arid Land Research Center

关键词：biologicalsoilcrustRAINFALLSIZEdesert-oasisECOTONECbalanceARIDregion

分类号： P[天文地球]