Study of Soil Microbiological Character at Different Altitudes in the Region of Dry and Hot River Valley

摘要

In this paper, soils at various altitudes in the lower reaches of the Jinshajiang River, Ningnan County, Sichuan Province, China, were selected to study the variation in characteristics of soil enzymes and soil microbial biomass and their activities at different altitudes. By laboratory testing, statistical analysis and correlation analysis, results indicated that in the dry-hot river valley region, the altitude has a significant impact on the soil microbial characteristics, including soil enzyme activities, microbial biomass, soil basal respiration intensity and substrate-induced respiration intensity (SIR). The major indicators of soil enzymes and microbial biomass exhibit an evident linear increasing trend with the rise in altitude. Soil enzymes and microbial biomass and their activities increase gradually with the reduction in dry-hot wind impact at altitudes ranging from 705-1005 m; thereafter, these indicators tend to be stable as a whole, as the altitude continues to rise and the impact of the dry-hot wind lessens. Under wet-dry cycling conditions, the main soil microbial characteristics, including soil enzyme activities, microbial biomass, soil basal respiration intensity and SIR, display an evident dry-wet seasonal change following a similar law of change; that is, the soil enzymes and microbial biomass and their activities in the dry season are significantly lower than are those in the wet season. The metabolic quotient (qCO2) in the dry season initially falls, then rises and, finally tends to be stable with the rise in altitude, whereas, in the wet season, there is no significant change in qCO2 with altitude. Further analysis shows that soil enzyme indicators, enzyme activities, soil microbial biomass and its activities in both dry and wet seasons have relatively strong correlations with soil physical and chemical properties, and, thus, can act as the indicators for soil fertility assessment. Therefore, the dry-hot wind is one of the major factors that impact soil enzymes and microbial biomass and their activities in the dry-hot river valley region along the Jinshajiang River. Technical measures should be taken, so far as is possible, during the ecological restoration to reduce the stress effects of the dry-hot wind on soil and vegetation and, thus, to promote sustainable development of regional ecological construction.