MICROBIAL RESPIRATION AND ORGANIC CARBON AS INDICATORS OF SOIL QUALITY AND NUTRIENT CYCLING IN RECLAIMED SOILS

Authors: INGRAM, L - UNIVERSITY OF WYOMING; Schuman, Gerald; STAHL, P - UNIVERSITY OF WYOMING; SPACKMAN, L - STATE OF WY-DEQ

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/22/2005
Publication Date: N/A
Citation: N/A

Interpretive Summary: Almost without exception, the evaluation of successful mined land reclamation, has been based on characteristics of the reestablished plant community. There can be little argument that the quality of the soil resource has a considerable impact on the development of the plant community but soil factors are not considered in the assessment of reclamation success. The productivity and diversity of the plant community depends on soil physical, chemical and biological properties and severe disturbance, as experienced in mining, severely impact these soil characteristics. The loss or dilution of soil organic matter (SOM) during the soil salvage and reclamation processes is important since SOM is the main pool of nutrients and energy source for soil microbial populations. Therefore, it is important that tools be developed that quickly and accurately assess soil quality as it relates to nutrient cycling in these disturbed ecosystems. Our research assessed a 3-day microbial respiration method as a tool to assess nutrient cycling and it was found to highly correlated with standardized and accepted methods such as nitrogen mineralization and microbial biomass assay methods. This research also enabled us to establish a soil organic carbon (SOC) threshold necessary in disturbed soils to ensure adequate nutrient cycling to sustain the desired plant community. We estimate that a minimum level of 0.5% SOC is necessary to ensure adequate nutrient cycling for sustainable reclamation. The 3-day microbial respiration method is simple and economical to do and will allow the mining industry and environmental regulatory agencies to make this assessment and evaluate the potential for reclamation success.

Technical Abstract: Soil quality and the ability of soil to sustain nutrient cycling in drastically disturbed ecosystems will influence the establishment and maintenance of a permanent and stable plant community. We undertook an experiment to evaluate a recently developed method to access soil quality and nutrient cycling potential for a series of reclaimed soils. The method involves correlating the three day flush of microbial respiration afer a soil is rewetted against a range of soil biological parameters. Soils were sampled from a number of reclaimed coal mines, a reclaimed uranium mine, and native, undisturbed prairie, all located in Wyoming. Soils were air-dried, re-wetted, and microbial respiration measured at three (Cmin0-3d) and 21 days (Cmin0-21d). In addition, microbial biomass carbon (MBC), nitrogen (N)-mineralization (Nmin0-21d), soil carbon (SOC) and total N was measured. Correlations between Cmin0-3d and all of the measured soil parameters in reclaimed and native soils were generally strong (r2 equal to or greater than 0.45) and highly significant (P=0.0001). Differences between reclaimed and native soils were observed with native soils exhibiting more variability, possibly due to: differences in soil homogeneity/heterogeneity, the relative lability of the substrates present; different microbial communities; and differences in soil structure properties. Correlations between Cmin0-3d and the measured soil parameters in spoil material, while significant, were less well correlated. We believe this method is a relatively fast, accurate, and economical means by which soil quality and nutrient cycling can be ascertained. We estimated that a minimum concentration of 0.89% organic matter (0.59%SOC) is necessary to sustain an adequate level of nutrient cycling in these reclaimed soils.