植被恢复对寒旱区典型草原群落枯落物分解的影响研究

Effects of Vegetation Restoration on the Decomposition of Litter in Typical Steppe of Cold and Arid Grassland Zone

草地的不同利用方式和利用程度影响枯落物的分解过程,进而影响生态系统的物质循环和能量流动。为了解寒旱区植被恢复后草地生物地球化学循环过程,在内蒙古不同恢复年限(恢复25年、恢复12年和严重重度退化)的典型草原群落开展枯落物原位分解试验,分别于样品投放后的第15、30、45、60、75、300、330和360天回收分解袋,同时测定8个时期枯落物中氮(N)、碳(C)、磷(P)、纤维素、木质素和灰分含量并记录土壤表层温度和含水量,以确定不同恢复阶段植物群落枯落物物质损失情况。结果表明,恢复时间不同的3个群落,枯落物残留率存在显著差异(P<0.05),恢复25年群落、恢复12年群落和重度退化群落枯落物的残留率分别为31.57%、44.11%和49.63%。植被恢复对不同群落枯落物分解系数影响较小,但减少了枯落物分解时间。经过25年和12年的恢复,枯落物分解95%需要的时间分别为1465 d和1361 d,而重度退化群落为2864,植被恢复使得分解时间减少大约一半。植被恢复对枯落物中TOC含量存在显著影响(P<0.05),植被恢复可以减缓枯落物中有机碳的损失速率。经过一年的分解,重度退化群落枯落物中纤维素、木质素、和灰分的含量显著高于两个恢复群落(P<0.05)。植被恢复减少了枯落物分解过程中的难分解物质的含量。植被恢复通过改变植物枯落物中物质的组成,进而改变生物地球化学循环的速率。围封恢复可以加速草地生态系统生物地球化学循环的速率。气温是控制寒旱区草地全年枯落物分解的重要环境因素;在温度条件适宜时,水分条件的变化对枯落物分解速率有一定的影响。

The different ways and degrees of utilization about grassland affect the decomposition process of litter, and the material circulation and energy flow of the ecosystem. In order to investigate the biogeochemical cycle of grassland after vegetation restoration in cold and arid areas, in this paper, the writer performed the in situ decomposition experiments of litter in typical grassland communities with different recovery years(recovery of 25 years, recovery of 12 years and severe degradation) in Inner Mongolia. The decomposition bags were recovered on the 15 th, 30 th, 45 th, 60 th, 75 th, 300 th, 330 th and 360 th days after the sample was placed. Meanwhile, nitrogen(N), carbon(C), phosphorus(P), fiber, lignin and ash were measured in the litter of 8 periods while recorded the surface temperature and water content of the soil, to identify the loss of litter material in the plant communities at different recovery stages. The results showed that the residual rates of litter in the three communities with different recovery time were significantly different(P<0.05). The residual rates of litter in the communities with 25 years restoration, 12 years restoration and degraded communities were 31.57%, 44.11% and 49.63%, respectively. Vegetation restoration had little effect on the decomposition coefficient of litter in different communities, but reduced the decomposition time of litter. After recovery of 25 years and 12 years, the time of litter decomposition 95% respectively was 1 465 and 1 361 days, while the degraded community was 2 864 days, and vegetation restoration made the decomposition time reduce by about half. Vegetation recovery had a significant impact on the content of TOC in litter(P<0.05), and vegetation restoration could slow down the loss rate of organic carbon in litter. After one year of decomposition, the content of fiber, lignin, and ash in the degraded community litter was significantly higher than that in the two restoration communities(P<0.05). Vegetation recovery reduces the amount of refractory substances in the decomposition process of litter. Vegetation restoration changes the rate of biogeochemical cycles by altering the composition of matter in plant litter. Enclosure recovery accelerates the rate of biogeochemical cycling in grassland ecosystems. Temperature is an important environmental factor to control the decomposition of litter in the cold and arid grassland. When the temperature is suitable, the change of water condition has a certain influence on the decomposition rate of litter.