不同刈割频度对大针茅草原土壤呼吸及其土壤因子的影响

摘要

The Stipa grandis steppe is a characteristically central Asian grassland.In grassland ecosystem,soil has a significant impact on plant community dynamics.The study area comprised Maodeng pasture near Xilinhaote,Inner Mongolia characterized as S.grandis steppe.We established four different mowing treatments in 2009 which were continued until 2013.Mowing frequencies were twice a year (TAY);Once a year (OAY);Once two year (OTY);No mowing (NM).Soil samples were collected to determine soil nutrient status in August 2013.Soil moisture (gravimetric),soil respiration rate and soil microbial number were measured in June,July and August,respectively.The results indicated that soil moisture of NM was the highest across all treatments.Soil organic matter content in the 20-30 cm and 30-40 cm depth bands in the TAY treatment was significantly higher than all other treatments;total soil nitrogen was also highest in the TAY treatment.There was significantly difference in soil respiration rate among cutting systems;OAY and NM produced higher soil respiration than that of remaining treatments;soil respiration was lowest in July for all systems.Soil microbial activity in NM treatments was significantly higher than in the cutting systems in both June and August.No mowing was beneficial to soil microbial activity,soil nutrients and soil respiration,but was not conducive to the growth of S.grandis.Annual mowing produced the optimal outcome in terms of productivity in the short and long term.%通过对大针茅草原土壤呼吸特性及影响因子的测定,研究3种不同刈割方式天然草地土壤呼吸特性及其影响因子,为典型草原刈割对碳收支研究提供基础理论依据.大针茅草原是亚洲中部草原亚区特有的一种草原类型.研究区设置在内蒙古锡林浩特市东部以大针茅建群的典型草原;在2009--2013年进行不同频度的刈割处理,一年两次、一年一次、两年一次(割一年休一年)、围封,在2013年8月采集测定土壤养分样品,在2013年生长季的6、7、8月进行土壤呼吸速率的测定及土壤微生物数量的测定.结果表明,围封处理下土壤含水量要高于其他刈割处理.6与8月时,围封处理下的细菌和微生物总数均显著高于刈割处理.不同频度刈割下群落的土壤呼吸速率有显著的差异,割一年休一年与围封处理显著高于其他刈割处理,且不同处理的土壤呼吸速率均在7月初为最低;土壤呼吸速率在内蒙古干旱半干旱地区与土壤含水量呈极显著正相关关系,受土壤含水量影响显著.结合生物多样性及生产利用的角度,割一年休一年为最合理的刈割频度.