Composition of riparian litter input regulates organic matter decomposition: Implications for headwater stream functioning in a managed forest landscape. Issue 4 (22nd January 2017)

• Record Type: Journal Article
• Authors: Lidman, Johan; Jonsson, Micael; Burrows, Ryan M.; Bundschuh, Mirco; Sponseller, Ryan A.
• Is Part Of: Ecology and evolution. Volume 7:Issue 4(2017:Mar.)
• Page Start: 1068
• Page End: 1077
• Publication Date: 2017-01-22
• Subjects: boreal -- introduced species -- land use -- litter quality -- priming effect; Ecology -- Periodicals; Evolution -- Periodicals; 577.05
• DOI: 10.1002/ece3.2726
• Languages: English
• ISSNs: 2045-7758

Abstract

Abstract: Although the importance of stream condition for leaf litter decomposition has been extensively studied, little is known about how processing rates change in response to altered riparian vegetation community composition. We investigated patterns of plant litter input and decomposition across 20 boreal headwater streams that varied in proportions of riparian deciduous and coniferous trees. We measured a suite of in‐stream physical and chemical characteristics, as well as the amount and type of litter inputs from riparian vegetation, and related these to decomposition rates of native (alder, birch, and spruce) and introduced (lodgepole pine) litter species incubated in coarse‐ and fine‐mesh bags. Total litter inputs ranged more than fivefold among sites and increased with the proportion of deciduous vegetation in the riparian zone. In line with differences in initial litter quality, mean decomposition rate was highest for alder, followed by birch, spruce, and lodgepole pine (12, 55, and 68% lower rates, respectively). Further, these rates were greater in coarse‐mesh bags that allow colonization by macroinvertebrates. Variance in decomposition rate among sites for different species was best explained by different sets of environmental conditions, but litter‐input composition (i.e., quality) was overall highly important. On average, native litter decomposed faster in sites with higher‐quality litter input and (with the exception of spruce) higher concentrations of dissolved nutrients and open canopies. By contrast, lodgepole pine decomposed more rapidly in sites receiving lower‐quality litter inputs. Birch litter decomposition rate in coarse‐mesh bags was best predicted by the same environmental variables as in fine‐mesh bags, with additional positive influences of macroinvertebrate species richness. Hence, to facilitate energy turnover in boreal headwaters, forest management with focus on conifer production should aim at increasing the presence of native deciduous trees along streams, as they promote conditions that favor higher decomposition rates of terrestrial plant litter. Abstract : We investigated how variation in riparian plant community composition, and thus variation in quality of litter input to streams, influenced in‐stream litter decomposition rates, using litter of three native and one introduced tree species. We also measured water chemistry, as this is known to influence rates of litter decomposition. Contrary to what has been shown previously, we found that litter‐input quality was the primary driver of decomposition rates, but that the main drivers differed between the native and the introduced species.