Sunlight and Soil–Litter Mixing: Drivers of Litter Decomposition in Drylands

Abstract

Macroclimate has traditionally been considered the predominant driver of litter decomposition. However, in drylands, cumulative monthly or annual precipitation typically fails to predict decomposition. In these systems, the windows of opportunity for decomposer activity may rather depend on the precipitation frequency and local factors affecting litter desiccation, such as soil-litter mixing. We used a full-factorial microcosm experiment to disentangle the relative importance of cumulative precipitation, pulse frequency, and soil-litter mixing on litter decomposition. Decomposition, measured as litter carbon loss, saturated with increasing cumulative precipitation when pulses were large and infrequent, suggesting that litter moisture no longer increased and/or microbial activity was no longer limited by water availability above a certain pulse size. More frequent precipitation pulses led to increased decomposition at high levels of cumulative precipitation. Soil-litter mixing consistently increased decomposition, with greatest relative increase (+194%) under the driest conditions. Collectively, our results highlight the need to consider precipitation at finer temporal scale and incorporate soil-litter mixing as key driver of decomposition in drylands.

Photodegradation of plant litter in the Sonoran Desert varies by litter type and age

“…Explanations for these correlations include that soil may be a vector for microbes, abrade litter surfaces which could facilitate microbial colonization or leaching, or buffer temperature and moisture regimes which could enhance microbial activity Archer, 2007, 2009;Lee et al, 2014;Barnes et al, 2012Barnes et al, , 2015. It is possible that these correlations are the result of a loss in litter organic mass over time, while the ash content (i.e.…”

“…These threshold responses in shade suggest that soil film accumulation eventually fails to facilitate further decay, possibly because of the recalcitrant nature of remaining litter or because microbial inoculation is no longer limiting. Barnes et al (2012Barnes et al ( , 2015) presented a conceptual model of litter mass loss in drylands proposing that as litter ages, the relative magnitude of photodegradation would decline because soil films would reduce photodegradation. Under our experimental conditions this did not appear to be the case; rather, photodegradation increased with litter age.…”

“…Another factor that has recently been recognized to have a potentially important role in litter decomposition in arid systems is soil-litter mixing (Throop and Archer, 2007;Barnes et al, 2015). Soil particles, microbes and microbial exudates, often accumulate and form a "soil film" that adheres to litter surfaces, and this can be particularly pronounced in arid systems.…”

Moisture seasonality, soil fauna, litter quality and land use as drivers of decomposition in Cerrado soils in SE-Mato Grosso, Brazil

“…Soil cover and shade provided by canopy have been recognised as important factors controlling the microclimate in both tropical (Höfer et al, 2001) and arid ecosystems (Arriaga and Maya, 2007). The direct exposure of litter to sunlight accelerates the decay of lignin; it dehydrates the substrate and, hence, facilitates its mechanical breakdown (Austin and Ballaré, 2010;Barnes et al, 2015;Zepp et al, 1998).…”

Pulse frequency and soil‐litter mixing alter the control of cumulative precipitation over litter decomposition

“…Soil‐litter mixing (SLM) may buffer decomposers from high temperature and desiccation, thereby expanding the windows of opportunity for decomposer activity following PPT events (Barnes et al. ). This idea is supported by increased soil‐litter mixing effects under oscillating moisture conditions compared to constant moisture conditions in a laboratory study (Lee et al.…”