In this study undertaken at Goose Lake Prairie State Park (1,027 ha) in northern Illinois (northeast USA), surface soil characteristics (physical, chemical and microbial properties) of three prairie restorations of varying ages were compared with undisturbed native prairie and an agricultural field.
The study sites, all in close proximity and on loamy soils, were:
i) an agriculture cropland field since the 1860s;
ii) a recent prairie restoration seeded in 1992, primarily with big bluestem Andropogon gerardii;
iii) a ‘high quality’ prairie restoration (1975) with a variety of prairie grasses and forbs;
iv) a prairie restoration (1978) on soils disturbed by a strip mine. In 1972 and 1978, reclamation measures included reshaping of spoil, spreading 15 cm of topsoil over exposed spoil, fertilizer addition and seeding with several grass and forb species.
v) a virgin prairie remnant with a diverse warm season grass and forb sward.
All prairie sites were managed by burning every three to five years.
Soil was sampled (2.2 cm diameter corer to 5 cm depth) from the sites on 21 August 1999. The following were determined: soil texture; bulk density; water-holding capacity; moisture content; organic matter; total soil carbon (C), nitrogen (N) and sulphur (S), and poly-β-hydroxybutyrate (PHB) levels. Microbial biomass was estimated as total extractable phospholipid fatty acids (PLFA), and PLFA profiles analyzed to determine microbial community composition.
Soil moisture, organic matter, total C, total N, total S, C:N ratio, water-holding capacity and microbial biomass were significantly greater in the virgin prairie and the two older (21 and 24 year) prairie restoration sites, compared with the agricultural field and the most recent restoration (begun 7 years prior to sampling). Soil bulk density was significantly greater in the agricultural field and recently restored site. Soil quality indicators and microbial communities in the restoration sites were mostly between those of the virgin prairie and the agricultural field. PHB levels and PLFA indicators of nutritional stress were significantly greater in the agricultural field and recent restoration site. Prairie age was the most important factor in determining microbial community composition.
These findings indicate that whilst the prairie restoration methods tested can improve surface soil quality, it takes many years to approach levels of virgin prairie.
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