Decomposition of tall fescue (Festuca elatior var. arundinacea) and cellulose litter on surface mines and a tallgrass prairie in central Missouri, U.S.A.
In studies on decomposition of 14C-labelled and unlabelled tall fescue, and of pure cellulose litter on non-vegetated and vegetated coal surface-mine spoils and on a tallgrass prairie soil in central Missouri, losses of ash-free mass, 14C, and P from decomposing tall fescue litter were better described by double than by single exponential decay equations. Compared to other studies of litter decomposition in temperate grasslands, losses of ash-free mass from tall fescue litter were rapid. In addition, 14C-labelled tall fescue litter (initial C:N ratio 14.2) decomposed more rapidly than unlabelled tall fescue litter (initial C:N ratio 25.9), reflecting the influence of initial N content on decomposition. Decomposition of tall fescue and cellulose litter on non-vegetated mine sites was slow, probably because of low exogenous N inputs and harsh environmental conditions. Regression models of remaining ash-free mass as a function of C:N, C:P and N:P ratios increased progressively in complexity from non-vegetated mine to vegetated mine to tallgrass prairie sites, reflecting differences in the structure and function of the decomposer communities among the 3 sites. Significantly less ash-free mass, 14C and nitrogen was lost from fescue situated over very acidic (pH less than or equal to 4.5) spoil than from fescue over moderately acidic (pH more than or equal to 5.0) spoil, but transfer of 14C from decomposing litter to the spoil directly below was unaffected by either spoil pH or by the presence or absence of vegetation, and its magnitude was comparable to similar studies conducted on unmined soils. The results suggest that current reclamation practices, such as liming, fertilization, and mulching, could have conflicting effects on OM accumulation and N and dynamics in surface mine spoils.