Elevated temperature may intensify the positive effects of nutrients on microbial decomposition in streams. (8th September 2014)

• Record Type: Journal Article
• Authors: Fernandes, Isabel; Seena, Sahadevan; Pascoal, Cláudia; Cássio, Fernanda
• Is Part Of: Freshwater biology. Volume 59:Number 11(2014:Nov.)
• Page Start: 2390
• Page End: 2399
• Publication Date: 2014-09-08
• Subjects: Freshwater biology -- Periodicals; Biologie d'eau douce -- Périodiques; 577.605
• DOI: 10.1111/fwb.12445
• Languages: English
• ISSNs: 0046-5070

Abstract

<abstract abstract-type="main" id="fwb12445-abs-0001"> <title>Summary</title> <p> <list id="fwb12445-list-0001" list-type="order"> <list-item> <p>Climate change scenarios predict an increase in global temperature and alterations in precipitation regimes, which may change nutrient concentrations in waterbodies. In forested streams, decomposition of allochthonous organic matter is a key ecosystem process that is affected by the quality of plant litter entering the streams and several environmental factors, including nutrient concentrations, whose interactive effects are difficult to predict.</p> </list-item> <list-item> <p>We examined the concomitant effects of increased temperature, concentration of inorganic nutrients in stream water and litter quality on leaf decomposition and activity of microbial decomposers. Leaves of alder (<italic>Alnus glutinosa</italic>) and oak (<italic>Quercus robur</italic>), representative of high and low initial N content, respectively, were immersed in a stream (NW Portugal) to allow microbial colonisation and then were exposed in microcosms to increasing concentrations of N‐NO<sub>3</sub> (0.09–5 mg L<sup>−1</sup>; six levels) and P‐PO<sub>4</sub> (0.003–0.3 mg L<sup>−1</sup>; three levels) alone or in all possible combinations. One set of microcosms was kept at 12 °C, a temperature typically found in Iberian streams in autumn, and the other set at 18 °C to simulate a warming scenario.</p> </list-item> <list-item> <p>Nitrogen immobilisation was higher in alder than in oak leaves, and increased with temperature and N concentration in stream water for both leaf species.</p> </list-item> <list-item> <p>Leaf decomposition, fungal biomass accrual and reproduction were not affected by P concentration, but overall microbial activity increased asymptotically (Michaelis–Menten kinetics) with N concentration. Increased temperature led to an increase in maximum activity of fungal decomposers and to a decrease in N concentration needed to achieve it, especially in alder leaves.</p> </list-item> <list-item> <p>Under the predicted warming scenario, leaf decomposition may become faster in streams with lower nutrient levels, especially those receiving high‐quality leaf litter.</p> </list-item> </list> </p> </abstract>