Effects of arctic shrub expansion on biophysical vs. biogeochemical drivers of litter decomposition

摘要: Climate warming in arctic tundra may shift dominant vegetation from graminoids to deciduous shrubs, whose functional traits could, turn, alter biotic and abiotic controls over biogeochemical cycling of carbon (C) nitrogen (N). We investigated whether shrub-induced changes microclimate have stronger effects on litter decomposition nutrient release than quality quantity. In near Toolik Lake, Alaska, USA, we incubated a common substrate snow-addition experiment test snow accumulation around shrubs altered the environment enough increase rates. compared influence rate N loss by decomposing four different plant types site. used aboveground net primary production values estimated decay constant (k) our experiments calculate community-weighted mass for each Snow addition had no effect substrate, site with highest abundance lowest Species varied their rates, species same type not always following similar patterns. Community-weighted was 1.5 times greater high shrub site, only slightly decreased when adjusted soil environment, suggesting that quantity are drivers community decomposition. Our findings suggest short time scale, associated trapping unlikely turnover drive positive snow-shrub feedbacks. The mechanisms driving expansion more likely do shrub-litter feedbacks, where higher growth rates uptake allows them produce leaves, resulting larger pool faster internal nutrients.