Submitted to: Biology and Fertility of Soils
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/27/2005
Publication Date: 4/30/2005
Citation: Fansler, S., Smith, J.L., Bolton, H. Jr., Bailey, V.L., 2005. Distribution of two C cycle enzymes in soil aggregates of a prairie chronosequence. Biology and Fertility of Soils 42: 17-23. Interpretive Summary: Soil carbon storage can be influenced by a number of factors including temperature, moisture, plant growth and soil characteristics such as texture and microbial activity. In this study we investigated the relationship between soil microorganism activity, as measured by enzyme activity, and the various crumb (aggregate) sizes of soil particles. We were looking for insights into soil carbon storage as we restore prairie lands. Interestingly we found that the native prairie soil was more similar to the agricultural soil in aggregate structure, microbial activity and carbon distribution than to either restored prairie soils. This result was probably due to the build-up of macroaggregates in the restored prairie soils from rapid plant growth in these systems. This information will be used in models of aggregate formation to better understand the mechanisms of soil carbon storage and how we can manage soil to enhance soil carbon storage.
Technical Abstract: Knowledge of the cycling and compartmentalization of soil C that influence C storage may lead to the development of strategies to increase soil C storage potentials. The objective of this study was to use soil hydrolases and soil aggregate fractionation to explore the relationship between C cycling activity and soil aggregate structure. The prairie chronosequence soils were: native prairie (NP), agricultural (AG), and tallgrass prairies restored from agriculture in 1979 (RP-79) and 1993 (RP-93). Assays for '-glucosidase (E.C. 126.96.36.199) and N-acetyl-'-glucosaminidase (NAGase, EC 188.8.131.52) activities were conducted on four aggregate size fractions (>2 mm, 1-2 mm, 250µm-1 mm, and 2- 250 µm) from each soil. There were significantly greater amounts of >2 mm aggregates in the RP-79 and RP-93 soils compared to the NP and AG soils due to rapid C accumulation from native plant establishment. Activities for both enzymes (µg PNP g-1 soil h-1) were greatest in the microaggregate (2 µm -250 µm) compared to the macroaggregate (>2 mm) fraction; however, microaggregates are a small proportion of each soil (<12%) compared to the macroaggregates (~75%). The RP soils have a hierarchal aggregate system with most of the enzyme activity in the largest aggregate fractions. The NP and AG soils show no hierarchal structure based on aggregate C accretion and significant C enzyme activity in smaller aggregates. The distribution of enzyme activity may play a role in the storage of C whereby the aggrading restored soils may be more susceptible to C loss during turnover of macroaggregates compared to the AG and NP soils with less macroaggregates.