Abstract

Decomposition of plant litter is a key ecological process in streams, whose contribution to the global carbon cycle is large relative to their extent on Earth. We examined the mechanisms underlying the temperature sensitivity (TS) of instream decomposition and forecast effects of climate warming on this process. Comparing data from 41 globally distributed sites, we assessed the TS of microbial and total decomposition using litter of nine plant species combined in six mixtures. Microbial decomposition conformed to the metabolic theory of ecology and its TS was consistently higher than that of total decomposition, which was higher than found previously. Litter quality influenced the difference between microbial and total decomposition, with total decomposition of more recalcitrant litter being more sensitive to temperature. Our projections suggest that (i) warming will enhance the microbial contribution to decomposition, increasing CO2 outgassing and intensifying the warming trend, especially in colder regions; and (ii) riparian species composition will have a major influence on this process. La descomposici & oacute;n de materia vegetal es un proceso ecol & oacute;gico clave en los ecosistemas fluviales, cuya contribuci & oacute;n al ciclo global del carbono es significativa en relaci & oacute;n con su extensi & oacute;n en la Tierra. Examinamos los mecanismos que subyacen a la sensibilidad a la temperatura de la descomposici & oacute;n en r & iacute;os y proyectamos los efectos del calentamiento clim & aacute;tico sobre este proceso. Comparando datos de 41 sitios de estudio distribuidos globalmente, evaluamos la sensibilidad a la temperatura de la descomposici & oacute;n microbiana y total, utilizando hojarasca de nueve especies combinadas en seis mezclas. La descomposici & oacute;n microbiana se ajust & oacute; a la teor & iacute;a metab & oacute;lica de la ecolog & iacute;a, presentando una sensibilidad a la temperatura consistentemente mayor que la total, que a su vez fue m & aacute;s alta que la reportada previamente. La calidad de la hojarasca influy & oacute; en la diferencia entre la descomposici & oacute;n microbiana y la total, siendo la descomposici & oacute;n total de hojarascas m & aacute;s recalcitrantes m & aacute;s sensible a la temperatura. Nuestras proyecciones sugieren que (i) el calentamiento global incrementar & aacute; la contribuci & oacute;n microbiana a la descomposici & oacute;n, aumentando la emisi & oacute;n de CO2 y reforzando la presente tendencia al calentamiento, especialmente en regiones m & aacute;s fr & iacute;as; y que (ii) la composici & oacute;n de especies ribere & ntilde;as tendr & aacute; una influencia significativa en este proceso.