退化草原土壤健康的微生物学量化评价

Microbiological Quantitive Assessment on Soil Health in A Degraded Grassland Microbiological Quantitative Assessment on Soil Health in A Degraded Grassland

在内蒙古锡林河流域的中温型典型草原区,以围栏保护23年的羊草草原原生群落为土壤健康的控制参比样点,分析了不同退化程度下土壤的微生物生物量和呼吸作用强度等主要生物学指标,包括微生物生物量-C(Cbio)、基础呼吸量-C(CBR)、潜在呼吸量-C(CPR)、可浸提有机碳(Cext)等4个量化指标;以及代谢商(qCO2)、潜在呼吸商(CPR/Cbio)、矿化商(Cext/Cbio)、呼吸活化商(CBR/CPR)及腐殖化效率(Cext/CBR)等5个衍生系数作为土壤微生物生态生理状况的敏感性评价参数。结果表明,在放牧退化草原区,控制参比样点(Y2和Y1)表现出最高的Cbio,中等的矿化活性和低的呼吸商,显示具有良好的土壤生物学质量;轻度放牧样点(Y3)显示略低的Cbio,较高的活性和略低矿化活性;中度放牧区样点(Y4)的Cbio和腐殖化效率较低,代谢商较高,显示胁迫有所增强。重度放牧样点(Y5)的Cbio最低,矿化活性最高,呼吸商最高,显示处于明显的人为扰动或环境胁迫效应下。因此,土壤微生物生物量水平相关的参数可以作为评价土壤健康的微生物学量化指标,有潜力成为土壤生态系统预警和环境胁迫的监测指标。

The microbiological quality of soil health in different degree degraded typical grassland in Xilin river basin of Inner Mongolia was analyzed by measuring microbial biomass and respiration in the soil. The results showed that 4 basic parameters： microbial biomass-C （Cbio）, available organic-C （Cext）, basal respiration-C （CBR）, potential respiration-C （CBR）, and 5 derived parameters： metabolic quotient （CBR/Cbip; or qCO2）, respiratory activation quotient （CBR/CPR）, potential respiration quotient （CPR/Cbio）, mineralization quotient （Cext/Cbio）, and humic efficiency （Cext/CBR） could provide enough information for the evaluation of soil biological quality. The derived parameters could be used as eco-physiological quotients for assessing soil biological quality. Based on these indexes, the control sites Y2 and Y1 （fencing reserve 23 years） as ideal control sites displayed very high content of the microbial biomass and the lowest metabolic quotient among all soils, and with higher respiration and available organic carbon, they were health soil. Light grazing site Y3 （fencing reserve only 5 years） was in an average level. Moderate grazing site Y4 （nature grazing out of fencing） displayed below-average microbial biomass with rather lower basal mineralization activity and the humic efficiency was lower for lacking of the appropriate substrate in the soil. The microbes were clearly exposed to the stress effect. With the higher energetic requirements, excessive grazing Y5 site （out of fencing） displayed lower microbial biomass carbon and available organic carbon and was no better than Y4 and not healthy, Therefore, microbial parameters have showed great potential as the early warning and quantity indicators for monitoring the stresses or perturbations in soil ecosystems.