Interaction of position, litter type, and water pulses on decomposition of grasses from the semiarid Patagonian steppe

Abstract

Litter lignin and nutrient content, annual rainfall, and biotic activity are not good predictors of litter decomposition in arid and semiarid ecosystems, suggesting that other factors may be important in controlling carbon turnover. We explored the relative importance of litter position (above- vs. belowground), litter type (leaf vs. root), and pulsed water events (large vs. small) on mass loss with grass species of the semiarid Patagonian steppe. In a factorial experiment of mesocosms, we incubated leaf and root litter simultaneously above- and belowground and manipulated water availability with large and small pulses. Significant interactions between position and litter type and position and pulse sizes demonstrated interactive controls on organic mass loss. Aboveground decomposition showed no response to pulse size or litter type, as roots and leaves decomposed equally rapidly under all circumstances. In contrast, belowground decomposition was significantly altered by litter type and water pulses, with roots decomposing significantly slower and small water pulses reducing belowground decomposition. The results of this mesocosm experiment support the idea that controls other than water availability may dominate aboveground mass loss, while a combination of recalcitrant litter and water penetration in the soil profile are critical factors determining belowground decomposition, which is ultimately mediated by biotic degradation.

Decomposition of 51 semidesert species from wide-ranging phylogeny is faster in standing and sand-buried than in surface leaf litters: implications for carbon and nutrient dynamics

“…As expected, the decomposition rate increased by 22.2 % in buried litter compared with surface litter. This result is consistent with most previous studies Santos et al 1984;Moorhead and Reynolds 1993;Vivanco and Austin 2006;Austin et al 2009). Generally, the buried leaf litter is exposed to a relatively cool, moist microclimate based on either our available data (Figs.…”

“…Overall, significantly greater mass loss has been reported in buried litter than in surface litter in diverse ecosystems, especially in dry regions Santos et al 1984;Moorhead and Reynolds 1993;Vivanco and Austin 2006;Austin et al 2009). This may be due to favorable temperature and moisture regimes (compared to strong microclimate fluctuations on or above the surface; see above), which benefit microbial activity in buried litter (Elkins and Whitford 1982;Moorhead and Reynolds 1993).…”

“…This may be due to favorable temperature and moisture regimes (compared to strong microclimate fluctuations on or above the surface; see above), which benefit microbial activity in buried litter (Elkins and Whitford 1982;Moorhead and Reynolds 1993). Indeed buried litter decomposition requires some soil moisture, as supplied by the larger precipitation pulses (Austin et al 2009). Santos et al (1984) asserted that some moisture may be necessary to initiate microbial activity, but above a threshold, soil organisms act independently of soil moisture.…”

Dual role of lignin in plant litter decomposition in terrestrial ecosystems

“…These correlations are much less obvious in low rainfall ecosystems, where standard indicators of litter chemistry do not predict decomposition rates and nutrient release (14)(15)(16)(17). Recent experimental evidence has shown that, in semiarid ecosystems, abiotic photodegradation can be a dominant control on decomposition of decaying plant material (18).…”

Decomposition and nitrogen transformation rates in a temperate grassland vary among co-occurring plant species

“…The difference between aboveground and belowground decomposition have been documented in other grassland systems, where a substantial difference in the magnitude of litter quality effect on decomposition was observed between leaf and root litter (Gholz et al 2000;Austin 2006, 2008;Austin et al 2009). Slow decomposition of root materials is thought to explain the greater contribution of belowground biomass than of aboveground biomass to the soil organic C pool (Johnson et al 2007).…”