围封和放牧对退化盐碱草地 土壤碳、氮、磷储量的影响

通过时间序列上围封和放牧的对比,研究了退化盐碱草地土壤碳、氮、磷储量及其变化与放牧管理的关系。结果表明,持续放牧5、6、8年后退化草地地上生物量分别降低了10.3%、52.6%和80.7%;而围封5、6、8年后地上退化草地地上生物量分别增加了33.9%、72.4%和92.2%;地下生物量对放牧管理的响应趋势与地上生物量相同。持续放牧增加了土壤pH和容重,降低了土壤养分浓度;围封对土壤pH、容重和土壤养分浓度的作用与放牧相反。围封后,表层土壤有机碳和总磷储量逐渐增加,总氮储量先降低后增加。然而放牧下,表层土壤碳、氮、磷储量均表现为先增加后降低。由于土壤容重的降低,封育5年后,围封地土壤碳、氮、磷储量要低于放牧地。土壤碳储量的变化对地上生物量的变化响应显著,因此,地上植被的变化能作为土壤碳储量有效的指示因子。

Effects of fencing and grazing on soil carbon,nitrogen, phosphorus storage in degraded alkali-saline grassland

The relationships between grazing managements and soil carbon, nitrogen, phosphorus storage and their variations were studied in the degraded alkali-saline grassland by comparative study between fencing and grazing on time series. The results showed that aboveground biomass of degraded grassland decreased by 10.3%, 52.6% and 80.7% after 5, 6 and 8-years continuous grazing, respectively, however, the aboveground biomass of degraded grassland increased by 33.9%, 72.4% and 92.2% after 5, 6 and 8-years fencing, respectively. The underground biomass had similar response with aboveground biomass to grazing managements. Continuous grazing increased the soil pH and bulk density and reduced soil nutrient concentration whereas fencing reduced soil pH and bulk density and increased soil nutrient concentrations. With fencing, organic carbon and total phosphorus storage in surface layer soil gradually increased, however, total nitrogen storage firstly decrease and then increased. With grazing, soil carbon, nitrogen and phosphorus storage in surface layer soil all firstly increased and then decreased. After 5 years for fencing, the soil carbon, nitrogen and phosphorus storage was lower than grazing due to decreasing soil bulk density. The soil organic carbon significantly responded to aboveground biomass which suggested that the aboveground vegetation can be used as an effective indicator for soil carbon storage.