4 research outputs found
Litter mixture interactions at the level of plant functional types are additive.
It is very difficult to estimate litter decomposition rates in natural ecosystems because litters of many species are mixed and idiosyncratic interactions occur among those litters. A way to tackle this problem is to investigate litter mixing effects not at the species level but at the level of Plant Functional Types (PFTs). We tested the hypothesis that at the PFT level positive and negative interactions balance each other, causing an overall additive effect (no significant interactions among PFTs). Thereto, we used litter of four PFTs from a temperate peatland in which random draws were taken from the litter species pool of each PFT for every combination of 2, 3, and 4 PFTs. Decomposition rates clearly differed among the 4 PFTs (Sphagnum spp. < graminoids = N-fixing tree < forbs) and showed little variation within the PFTs (notably for the Sphagnum mosses and the graminoids). Significant positive interactions (4 out of 11) in the PFT mixtures were only found after 20 weeks and in all these combinations Sphagnum was involved. After 36 and 56 weeks of incubation interactions were not significantly different from zero. However, standard deviations were larger than the means, indicating that positive and negative interactions balanced each other. Thus, when litter mixture interactions are considered at the PFT level the interactions are additive. From this we conclude that for estimating litter decomposition rates at the ecosystem level, it is sufficient to use the weighted (by litter production) average decomposition rates of the contributing PFTs. © 2009 The Author(s)
Litter quality and interactie effects in litter mixtures: more negative interactions under elevated CO2?
1. The decomposition rate of litter mixtures can depend on interactions between compounds in the component species, i.e. in litter chemistry. Differences in litter N concentration are likely to lead to positive interaction (i.e. faster than expected decomposition) and differences in phenolic concentrations to a negative interaction. These interactions may become less positive (or more negative) when the litter is produced under elevated atmospheric C
Is there a trade-off between the plant's growth response to elevated CO2 and subsequent litter decomposability?
Under elevated levels of atmospheric C