Soil Physical, Microbial Enzyme, and Molecular Characterization of Native Prairie and Agricultural Ecosystems S.H. Anderson, R.J. Kremer, and N. Mungai Department of Soil, Environmental & Atmospheric Sciences, University of Missouri USDA-ARS Cropping Systems and Water Quality Research Unit, Columbia, Missouri Materials and Methods (cont.)  Additional soil samples were taken and essayed for energy transformation enzymes (dehyrogenase); nutrient mineralization enzymes for C (β- glucosidase), P (alkaline phosphatases), and N (β- glucosamidase); soil microbial diversity by a C substrate utilization assay; and CO 2 respiration.  Total soil DNA was extracted, quantified, and subjected to amplification (polymerase chain reaction, PCR) with known, primer DNA to detect various bacterial genotypes. Different DNA sequence combinations resulting from PCR were separated on a gel matrix using electrophoresis, visualized as a series of bands distributed over the matrix. The series of bands obtained from separating the DNA fragments resulted in genetic profiles that characterized microbial communities. Results  Soil bulk density was 32% lower for the native prairie site (TP) compared to the sites with a history of tillage (RC, PF-NP, CRP; Table 2).  Water-stable aggregates were 10 times higher for the TP site compared to the RC site. The CRP and restored prairie sites had values at 72% of the TP site (Table 2).  Saturated hydraulic conductivity values were over 35 times higher for the native prairie (TP) compared to the continuously cropped site (RC), and 2.5 times higher compared to the restored sites (PF-NP, PF- SL, CRP; Table 2). This was attributed to the greater number of macropores (> 1 mm in effective diameter) for the native prairie site.  Soil enzyme activities were consistently highest for TP and PF-SL sites (Table 3), reflecting the close relationship of SOM levels with microbial activity.  Enzyme activity values were generally lowest for soil under continuous cropping (RC) likely due to low SOM and water-stable aggregates (Table 3).  PF-NP soils were lower in dehydrogenase, glucosaminidase, and phosphatase, which may be a reflection of different microbial communities and possible different SOM quality  PF-NP soils were lower in dehydrogenase, glucosaminidase, and phosphatase, which may be a reflection of different microbial communities and possible different SOM quality.  Soil DNA content agreed closely with other indicators of soil quality (SOM, glucosidase) that are associated with microbial activity.  The site with the highest number of bands from molecular analysis of extracted soil DNA, TP with 20, appears to have the greatest bacterial diversity, while soil from RC with 10 bands had the lowest diversity. Soil from the PF and CRP sites had band numbers ranging from 12 to 16, suggesting that this ‘intermediate’ level of diversity is a characteristic response of soil undergoing restoration to its original bacterial community.  The relationship of soil organic matter (SOM) to biological activity is illustrated by strong correlations between soil DNA (representing the bacterial community) and water stable aggregates (r 2 = 0.82) and glucosidase activity (representing SOM decomposition; r 2 = 0.83). Table 1. Characteristics of ecosystems at study sites. Study Site CodeManagement SystemVegetation Tucker PrairieTPUncultivated nativeNative, warm season prairie.grasses and forbs. Prairie Fork – NewPF-NPRow crops until 1993,Little bluestem, Prairienative grasses and side-oats gramma, legumes since 1994.Indian grass. Prairie Fork – SiriceaPF-SLSame as PF-NP.Same as PF-NP with Lespedezainfestation of lespedeza. Centralia-CRPCRPManaged as CRP sinceCool season grasses 1990, no fertility.and forage legumes. Centralia-Row CropRCRotation since 1990, highSoybean (2003), fertility, minimum tillage.corn (2004). Introduction Evaluation of critical soil properties is essential in assessing the restoration of degraded prairies and old cultivated fields to ecosystems that resemble native prairies. Restoration and maintenance of soil quality is highly dependent on organic matter (SOM), an array of soil organisms and biological activity, and improved physical characteristics including water infiltration, macroporosity, aggregate stability, and bulk density.Soils managed under native ecosystems relative to agricultural row crops often have significant differences in soil physical and microbial properties. Assessment of relationships among these properties may provide useful information in how the physical environment affects microbial properties. Evaluation of critical soil properties is essential in assessing the restoration of degraded prairies and old cultivated fields to ecosystems that resemble native prairies. Restoration and maintenance of soil quality is highly dependent on organic matter (SOM), an array of soil organisms and biological activity, and improved physical characteristics including water infiltration, macroporosity, aggregate stability, and bulk density. Soils managed under native ecosystems relative to agricultural row crops often have significant differences in soil physical and microbial properties. Assessment of relationships among these properties may provide useful information in how the physical environment affects microbial properties.Objective The objective of this research was to quantify soil physical properties and soil enzyme activity, physiological and molecular characteristics for native, restored, and cultivated prairies. The objective of this research was to quantify soil physical properties and soil enzyme activity, physiological and molecular characteristics for native, restored, and cultivated prairies. Figure 1. Sites used for the study (a) Tucker Prairie, (b) Prairie Fork- new prairie, (c) Prairie Fork with sericea lespedeza infestation, (d) Centralia CRP, and (e) Centralia row crop rotation (with corn). bcde a Table 2. Soil physical and chemical properties. BulkWater-Stable Hydaulic Study SiteSOMDensity AggregatesConductivity*Porosity %g cm -3 % mm h -1 m 3 m -3 TP d** 40.8a 671a0.619a PF-NP ab 29.4b 243b0.485cd PF-SL c 28.2b 222b0.521b CRP b 30.6b 285b0.497c RC a 3.8c 17.9c0.473d *Geometric means **Means within a column followed by the same letter are not significantly different at P<0.05. Table 3. Microbial enzyme activities and DNA content for the sites. Dehydro-Glucos-Soil Study Site genase aminidaseGlucosidasePhosphataseDNA  g tpf g  g  -nitrophenol g -1 soil  g g -1 soil TP320 a*160 a 350 a 1580 a10.3 PF-NP190 c 90 c 325 ab 640 cd 8.1 PF-SL250 b150 ab 300 bc 1180 b 7.4 CRP260 b130 b 290 c 710 c 8.2 RC120 d 70 c 250 c 400 d 6.2 *Means within a column followed by the same letter are not significantly different at P<0.05. Materials and Methods  Land treatments included native, uncultivated prairie with established warm-season grasses and forbs; 10-yr-old restored prairie dominated by little bluestem (Schizachyrium scoparium),side-oats gramma (Bouteloua curtipendula), and Indian grass (Sorghastrum nutans);10-yr-old restored prairie dominated by sericea lespedeza (Lespedeza cuneata); a 14-yr-old conservation reserve program site with cool-season grasses and low density forage legumes; and a site under row crop production with the past 14 years under a corn (Zea mays)-soybean (Glycine max) rotation cropping system (Fig. 1, Table 1).  Land treatments included native, uncultivated prairie with established warm-season grasses and forbs; 10-yr-old restored prairie dominated by little bluestem (Schizachyrium scoparium), side-oats gramma (Bouteloua curtipendula), and Indian grass (Sorghastrum nutans); 10-yr-old restored prairie dominated by sericea lespedeza (Lespedeza cuneata); a 14-yr-old conservation reserve program site with cool-season grasses and low density forage legumes; and a site under row crop production with the past 14 years under a corn (Zea mays)-soybean (Glycine max) rotation cropping system (Fig. 1, Table 1).  Sampling sites were located on Mexico silt loam (fine, smectitic, mesic Aeric Vertic Epiaqualfs).  Relatively undisturbed cores (7.62 cm by 7.62 cm ) were sampled from the 0 to 10 cm depth on 12 May 2004; 3 replicate locations with 5 sub-samples per location.  Samples were evaluated for physical properties: bulk density, pore-size distributions, saturated hydraulic conductivity and water-stable aggregates. Summary This research demonstrated that soil measurements based on soil enzyme activity, physiological and molecular characteristics, and selected physical traits (water-stable aggregation, saturated hydraulic conductivity) differentiated soils managed as native prairie, restored prairie, or cultivated land. Results indicated that sites under restoration to prairie vegetation are transitional between native prairie and cultivated soils based on combined physical and microbiological analyses. The use of physiological and molecular analyses of prairie soils yielded new insights on the complex functional and structural diversity of their soil bacterial communities, which contribute to the biological characteristics of these soils.