Decomposition dynamic and physico-chemical of abundant species in a montane woodland in central Argentina

Abstract

Most studies on decomposition dynamics indicate that the decomposition pattern can be divided in a first rapid phase following a negative exponential model, controlled by nutrient concentration; and a second slow phase controlled by lignified carbohydrates, in which the curve acquires an asymptotic form as decomposition slows down. This pattern has been observed across different floras, but there are still contradictory evidences about which are the most accurate predictors of each decomposition phase. The objectives of this study were: (1) to determine decomposition during the two main phases throughout one year of incubation, of 20 abundant plant species from 7 contrasting plant functional types of a mountain woodland in central Argentina, and (2) to analyse the relationship of decomposition with foliar traits (both of green leaves and litter), in order to identify the more accurate predictors of the first and the second decomposition phases, as well as for annual decomposition. Decomposition was measured as the percentage of remaining dry weight (% RDW) at the end of each phase. As expected, decomposition was much slower (% RDW higher) during the second phase (70–365 days) than during the first one (0–70 days). The % RDW of the first phase was significantly and strongly associated with the % RDW of the whole incubation period. Through a stepwise multiple regression procedure we detected that the best predictors of % RDW for the first phase were the sum of recalcitrant components (lignin, cellulose and hemicellulose) of the litter with a negative relation, and specific leaf area of green leaves with a positive relation (R2 = 0.89). For the whole year incubation results were quite similar to those recorded for the first phase (R2 = 0.78). The second phase was not predicted by any of the traits measured. In general, our results agree with previous studies in which decomposition was tightly related to the physico-chemical characteristics of green leaves and litter. However, our results diverge from the idea that rapid and slow phases are controlled by labile and recalcitrant components, respectively, and suggest that more comparative studies are necessary to find a decomposition model suitable to different floras.