Plant-Mediated Controls on Nutrient Cycling in Temperate Fens and Bogs

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology.Abstract. This paper reports on patterns in plant-mediated processes that determine the rate of nutrient cycling in temperate fens and bogs. We linked leaf-level nutrient dynamics with leaf-litter decomposition and explored how the observed patterns were reflected in nutrient cycling at the ecosystem level. Comparisons were made among growth forms (evergreen and deciduous shrubs and trees, graminoids and Sphagnum mosses) and between mire types (fens and bogs). A literature review showed that the predominant growth form was more important as a determinant of leaf-level nutrient-use efficiency (NUE) than mire type (fen vs. bog). Evergreens had the highest N and P use efficiency. The growth form differences in NUE were mainly determined by differences in N and P concentrations in mature leaves and not by differences in resorption efficiency from senescing leaves. Sphagnum leaves had lower N and P concentrations than the other growth forms, but because of a lack of data on nutrient resorption efficiency the NUE of these mosses could not be calculated. Nitrogen use efficiency did not differ among fen and bog species, whereas bog species had a higher P use efficiency than fen species. However, a complete evaluation of mire-type or growth-form effects on NUE is only possible when data become available about nutrient resorption from senescing Sphagnum leaves. As leaf-level NUE is negatively correlated with leaf-litter nutrient concentrations, there is a direct link between NUE and litter decomposition rate. Rates of litter decomposition of Sphagnum mosses are lower than in the other growth forms, but there is still much speculation about possible reasons. The role of litter chemistry of Sphagnum mosses (including decay inhibitors and decay-resistant compounds) in de-composition especially warrants further study. The strongly deviating nutritional ecology of Sphagnum mosses clearly distinguishes fens and bogs from other ecosystems. Moreover, N and P concentrations in mature leaves from vascular plant species from fens and bogs are in almost all cases lower and leaf-level N use efficiency is higher than in species from other ecosystems, irrespective of the growth form considered.Both literature data and data from a comparative study on soil nutrient cycling in temperate fens and bogs in the United States (Maryland), The Netherlands, and Poland showed that nutrient mineralization did not differ clearly between fens and bogs. The comparative study further showed that cellulose decomposition in bogs was lower than in fens and that nutrient mineralization was higher in forested than in ...

Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

“…However, given that the total N and P concentrations were relatively low in comparison to the amount of DOC consumed during incubations (for every 1 mg C l ¡1 consumed, microbes require 40 g N l ¡1 and 8 g P l ¡1 to satisfy growth requirements using a bacterial growth eYciency of 0.4 and a bacterial molar ratio for C:N of 10 and C:P of 50), we suggest that much of the DOC consumed during incubations was not incorporated into biomass but rather was respired as CO 2 through waste respiration, as observed in Wiegner and Seitzinger (2004). Therefore, N and potentially P could have limited microbial uptake of DOC during incubations in the bog, forested wetland and upland forest soils, which is consistent with the idea that net primary production is frequently limited by N in freshwater wetlands (summarized by Aerts et al 1999) and in temperate forests (Vitousek and Howarth 1991).…”

“…The fen sites had the greatest fraction of BDOC among the soil types, which is consistent with the high protein-like Xuorescence, low C:N ratios and low aromatic C content. Minerotrophic fens have been shown to possess greater rates of primary production (summarized by Aerts et al 1999), plant litter decay and enhanced rates of nutrient cycling than in bogs. As a result, the highly productive vascular plants, either through root exudates of carbohydrates and amino acids (Eviner and Chapin 1997) or litter decay (Yano et al 2000), are likely the reason for the abundance of labile DOM present in the fen.…”

N availability and mechanisms of N conservation in deciduous and semideciduous tropical forest legume trees

“…NRE was calculated by: NRE = (N mature green -N senescent ) / N mature green × 100%, where: N mature green = N in mature green leaves, N senescent = N in senescent leaves (Pugnaire & Chapin 1993). NUE was calculated by: NUE (g of dry mass mg -1 of N) = 1 / [N mature green × (1-r)], where: N mature green = total N concentration in mature green leaves and r = NRE expressed in terms of a fraction (Aerts et al 1999). …”

“…There are indications that plants with a long leaf life span produce more organic material per unit of mineral nutrient than those with shorter leaf life spans (Chapin 1980;Aerts et al 1999). This ratio represents the nutrient use efficiency (Vitousek 1982).…”

Plant Litter Decomposition and Nutrient Release in Peatlands

“…The rate of nutrient release is not necessarily equal to the rate of mass loss because some nutrients can be immobilized by microbes and incorporated in humic compounds rather than being mineralized during mass loss [Jonasson and Shaver, 1999]. The degree of nutrient release during litter decomposition can then affect nutrient availability for plant growth and, ultimately, the structure and the functioning of plant communities [Aerts et al, 1999;Parton et al, 2007].…”