Initial litter respiration as indicator for long-term leaf litter decomposition of Carex species

We investigated the relation between initial litter respiration and litter mass loss in the field. Thereto, we conducted a laboratory experiment on initial leaf litter respiration rates of 12 types of Carex leaf litter (a factorial combination of 4 species and 3 litter types). Water-saturated litter was incubated at a constant temperature of 20 degrees C and a relative humidity of 97%. Respiration rates were measured at 6 and 13 d after the start of the incubation. The results were compared with data from a three-year litter bag experiment in the field with the same litter types. Initial litter respiration rates were positively correlated with field-determined litter mass loss rates for periods varying from 1.5 to 36 months of incubation in the field. Litter respiration measurements performed after 6 d of incubation gave higher correlations than rates determined after 13 d of incubation. From these results we conclude that for the litter types under study, which are characterized by low lignin concentrations, initial litter respiration rates are reliable indicators for long-term litter decomposability. Thus, this quick and easy method may be a valuable tool in comparative studies of (long-term) litter decomposition rates. Initial litter respiration rates were significantly related to various litter chemistry parameters, but the patterns differed depending on whether the entire data set was considered or only the three litter types of individual species. In general, N related litter chemistry parameters explained the highest percentage of variance when the entire data set was considered, but when individual species were considered the strongest relations were generally found with P related parameters. Thus, broad-scale relations between decomposition rate and litter chemistry can be very different from small-scale comparisons. This may be one of the explanations for the fact that the relations found between decomposition rates and litter chemistry show such strong differences between studies.