Biological Soil Crust Carbon Emission And Its Effects On Soil Respiration In Alpine Sandy Land

Soil respiration is the main component of terrestrial ecosystem carbon cycle, any changein soil respiration could influence the change in atmospheric CO2concentration which affectsthe global climate change in future. As an interface layer between soil and atmosphere,biological soil crust was an important part of arid and semi-arid ecosystems. Biological soilcrust could release CO2by respiration and its cover in arid and semi-arid area can reach70%orhigher, so that the contribution of biological soil crust to carbon cycle in this area could not beignored. The global climate change, particularly change in precipitation patterns could affectthe activity of biological soil crust and soil carbon cycle in arid and semi-arid ecosystem whichrestricted by water. Now no study about soil respiration, crust carbon emission and theirresponse to precipitation carried out in alpine sandy land. Thus, carrying out related research inQinghai-Tibet Plateau can fill biological soil crust gaps in carbon cycle and assess accuratelythe role of biological soil crust in carbon cycle in alpine sandy land. To discuss the carbonemission of algal crust, moss crust and moss-lichen crust and its effects on soil respiration inalpine sandy land, dynamic characteristics of biological soil crust and soil respiration and theirresponses for simulated precipitation were determined at Republican Basin in QinghaiProvince. The main conclusions from this study included:(1) Crust carbon emission rates and crust soil respiration rates had obviously temporaldynamics. The daily dynamics of crust carbon emission rates were smoothly without peak, andthe growing seasonal dynamics were bimodal. The daily and growing seasonal dynamics of thecrust soil respration rates were unimodal. The daily and growing seasonal average values ofcrust carbon emission rates were obviously smaller than those of crust soil respiraiton rates.(2) Precipitation could promote the crust carbon emission rates and crust soil respirationrates, and the precipitation played a greater role in promenting for crust carbon emission ratesthan crust soil respiraiton rates. This role was mainly reflectly in the early stage of precipitation,within the3~6minutes after precipitation, crust carbon emission rates and crust soil respiration had increased more than20-fold and3-fold, respectively. This showed that the “blowout”phenomenon of crust soil respiration rates after precipitation was caused by rapid growth ratesof crust carbon emission.(3) The biological soil crust could increase the temperature sensitivity of soil respirationon the scale of day and growing season in no precipitation conditions, and the precipitationcould alter the air temperature sensitivity of soil respiraiton. On scale of day and growingseason, the Q10values of no crust soil respiration were smaller than those of crust soilrespiraiton. After precipitation, the Q10values of no crust soil respiraiton based on airtemperature were bigger than crust soil respiraiton.(4) The effects of different types of biological soil crusts on soil respiration was different.On the scale of growing season, the effect of algal crust on soil respiraiton was weak, and themoss crust and moss-lichen crust promoted significantly the soil respiration.