Abstract
Microbial respiration depends on microclimatic variables and carbon (C) substrate availability, all of which are altered when ecosystems experience major disturbance. Widespread tree mortality, currently affecting pinon-juniper ecosystems in southwestern North America, may affect C substrate availability in several ways, for example, via litterfall pulses and loss of root exudation. To determine pinon mortality effects on C and water limitation of microbial respiration, we applied field amendments (sucrose and water) to two pinon-juniper sites in central New Mexico, USA: one with a recent (<1 yr), experimentally induced mortality event and a nearby site with live canopy. We monitored the respiration response to water and sucrose applications to the litter surface and to the underlying mineral soil surface, testing the following hypotheses: (1) soil respiration in a pinon-juniper woodland is water- and labile C-limited in both the litter layer and mineral soil; (2) pinon mortality reduces the C limitation of litter respiration; and (3) pinon mortality enhances the C limitation of mineral soil respiration. Litter respiration at both sites responded to increased water availability, yet surprisingly, mineral soil respiration was not limited by water. Consistent with hypothesis 2, C limitation of litter respiration was lower at the recent mortality site compared to the intact canopy site. Applications to the mineral soil showed evidence of reduction in CO
2 flux on the girdled site and a non-significant increase on the control. We speculate that the reduction may have been driven by water-induced carbonate dissolution, which serves as a sink for CO
2 and would reduce the net flux. Widespread pinon mortality may decrease labile C limitation of litter respiration, at least during the first growing season following mortality.
Keywords
litter respiration,
pinon-juniper,
ACES
Citation
Berryman, Erin; Marshall, John D.; Rahn, Thom; Litvak, Marcie; Butnor, John. 2013.Decreased carbon limitation of litter respiration in a mortality-affected pinon-juniper woodland. Biogeosciences 10:1625-1634.