Labile compounds in plant litter reduce the sensitivity of decomposition to warming and altered precipitation

Abstract

SummaryTogether, climate and litter quality strongly regulate decomposition rates. Although these two factors and their interaction have been studied across species in continent-scale experiments, few researchers have studied how labile and recalcitrant compounds interact to influence decomposition, or the climate sensitivity of decomposition, within a litter type.Over a period of 3 yr, we studied the effects of warming and altered precipitation on mass loss and compound-specific decomposition using two litter types that possessed similar heteropolymer chemistry, but different proportions of labile and recalcitrant compounds.Climate treatments immediately affected the mass loss of the more recalcitrant litter, but affected the more labile litter only after 2 yr. After 3 yr, although both litter types had lost similar amounts of mass, warming (c. 4°C) and supplemental precipitation (150% of ambient) together accelerated the degradation of alkyl-carbon and lignin only in the more recalcitrant litter, highlighting the role of initial litter quality in determining whether the chemistry of litter residues converges or diverges under different climates. Our finding that labile compounds in litter reduce the climate sensitivity of mass loss and the decomposition of recalcitrant matrix is novel.Our results highlight the potential for litter quality to regulate the effect of climatic changes on the sequestration of litter-derived carbon.

Microbial community structure mediates response of soil C decomposition to litter addition and warming

“…Despite extensive work on the subject, the degree to which C chemistry alone drives the decomposition of litter and soil in response to elevated temperatures is frequently debated (Giardina and Ryan, 2000;Bol et al, 2003;Fierer et al, 2005;Knorr et al, 2005;Bauer et al, 2008;Conant et al, 2008;Craine et al, 2010;Hopkins et al, 2012;Suseela et al, 2013;Lefevre et al, 2014), as is the response of soil-C to N addition (Melillo et al, 2002;Neff et al, 2002;Auyeung et al, 2013). Part of this confusion may lie in the impact and influence of microbial community structure and function, as it has been shown as a potential driver of soil C turnover in response to N (Billings and Ziegler, 2008;Chen et al, 2014;Kaiser et al, 2014), warming (Bardgett et al, 2008;Balser and Wixon, 2009;Yuste et al, 2011;Zhou et al, 2012;Nie et al, 2013;Ziegler et al, 2013;Hopkins et al, 2014;Wei et al, 2014), and the interactive effects of N and warming (Cusack et al, 2010;Li et al, 2013).…”

Divergent responses of organic matter composition to incubation temperature

“…3). Although some studies showed greater losses of lignin at higher temperatures Suseela et al, 2013), consistent with greater temperature sensitivity of kinetically stable compounds, both increases (Derenne and Largeau, 2001) and decreases (Dignac et al, 2005;Klotzbücher et al, 2011;Thevenot et al, 2010) in lignin (or aryl C) were observed in response to decomposition. The proportional increase in lignin C with temperature in this experiment was likely driven by factors other than chemical complexity.…”

“…Recent studies have shown that starting litter chemistry and microbial community structure shape OM losses in response to temperature (Karhu et al, 2014;Suseela et al, 2013), and impact the composition of residual OM (Wallenstein et al, 2013;Wickings et al, 2012). Therefore, we hypothesized that starting OM complexity and microbial community structure, rather than temperature, would shape compositional changes in OM during incubation.…”

“…Indicators of OM quality and stability have been defined in many different ways: as residue remaining after pre-incubation (Conant et al, 2008a,b), OM with slower decomposition rates (Craine et al, 2010), older 14 C radiocarbon age (Bol et al, 2003;Hopkins et al, 2012), higher structural complexity (Fierer et al, 2005;Frey et al, 2013;Suseela et al, 2013), or by size fractionation . Recent reviews have emphasized that different indicators of stability do not provide equivalent information, highlighting, for example, that old carbon is not necessarily chemically complex carbon (Kleber et al, 2010) and that structural complexity of OM does not necessarily correspond to stability (Dungait et al, 2012).…”

Litters of photosynthetically divergent grasses exhibit differential metabolic responses to warming and elevated CO2

“…The relative peak heights were computed as the ratio of the intensity of each peak to the sum of the intensities of all selected peaks (Haberhauer and Gerzabek 1999). We conducted a principal component analysis (PCA) of the relative peak heights to interpret the DRIFT spectra (Suseela et al 2013).…”