Plant Diversity Promotes Soil Enzyme Activities in Prairie Ecosystems.

Soil enzyme activities dictate nutrient cycling, and thus are considered indicators of soil quality.  Although most soil enzymes are of microbial origin, plants can directly and indirectly impact soil enzyme activities by secreting biochemicals and altering microbial growth and enzyme synthesis.  We hypothesized that plant diversity is a key factor governing the synthesis of soil enzymes and promoting the release of enzymes to the soil environment.  In this study, below-ground soil enzyme activities and microbial properties and above-ground plant diversity and biomass in two land use systems at two different locations were evaluated.  Chronic plant stress indicators, including foliage protein contents, reducing power, as well as chlorophyll contents in a dominant plant species in these two soil ecosystems were also determined. Land use systems included native prairie (NP) and prairie under Conservation Reserve Programs (CRP).  Samples were taken twice in 2009. For each system, five replicate 1 m x 1 m quadrats were established randomly.  Within each quadrat, surface soil (0-15 cm) and plant biomass were collected and analyzed.  Across the locations between the two ecosystems, microbial biomass carbon in NP was about 1.4 fold of those in CRP, plant biomass in NP was about 2-fold of those in CRP, but number of plant species in NP was less than half of those in CRP.  Most soil enzyme activities tested were significantly higher in CRP than those in NP, which coincided with higher protein and chlorophyll contents in the foliage of the plants across these two systems.  Results suggested that plant diversity promoted soil enzyme activities in prairie soil ecosystems.