Soil Warming: Consequences for Foliar Litter Decay in a Spruce‐Fir Forest in Maine, USA

Abstract

AbstractIncreased rates of litter decay due to projected global warming could substantially alter the balance between C assimilation and release in forest soils, with consequent feedbacks to climate change. This study was conducted to investigate the effects of soil warming on the decomposition of red spruce (Picea rubens Sarg.) and red maple (Acer rubrum L.) foliar litter at Howland, ME. Experimentally increased Oa horizon soil temperatures (increase of 4–5°C) were maintained during the snow‐free season from 1993 through 1995 in replicated 15 by 15 m plots using heat‐resistance cables. For red maple litter, significant treatment effects included greater loss of mass (27%) and C (33%), and greater accumulation of Zn (54%) during the first 6 mo of decay in the heated plots than the control plots. After 30 mo of decay, significant treatment effects were no longer evident for red maple litter. Few treatment effects were observed for red spruce litter during the initial 18 mo of decay. However, after 30 mo of decay, significant treatment effects included greater loss of mass (19%), C (19%), N (24%), Ca (27%), Mg (12%), K (4%), Zn (60%), and cellulose (40%) in red spruce litter in the heated plots than the control plots. We conclude that a modest increase in Oa horizon soil temperature (4–5°C) can significantly increase litter decay rates and alter litter decay dynamics in this coniferous forest stand, and that these changes exhibit variations in their temporal development as a function of species and litter quality attributes.