Decay Rates, Nitrogen Fluxes, and Decomposer Communiies of Single‐ and Mixed‐Species Foliar Litter

Abstract

Decomposition rates, N fluxes, and abundances of decomposer organisms were quantified in mixed—species litterbags (containing leaves of two or three of the following tree species: Acer rubrum, Cornus florida, and Quercus prinus) and in litterbags containing leaves of a single species. Data from single—species litterbags were used to generate predicted decay rates, N fluxes, and abundances of decomposer organisms for mixed—species litterbags, against which observed values could be compared to determine if significant interaction effects occurred when litter of different species, and different resource quality, was mixed. Decay rates of mixed—species litterbags during the 1—yr study were not significantly different than predicted from decay rates of individual component species. However, there were significant interaction effects on N fluxes and abundances of decomposer organisms. In the C. florida—A. rubrum and C. florida—A. rubrum—Q. prinus litter combinations there were significantly greater initial releases of N and lower subsequent N immobilization than predicted. In the A. rubrum—Q. prinus and C. florida—A. rubrum—Q. prinus litter combinations, lengths of fungal hyphae were significantly less than predicted on at least half the collection dates. Bacterial numbers in the mixed—litter combinations were also generally less than predicted. Nematode abundances, especially fungivores, were generally greater than predicted in mixed—species litterbags until the last sample date. Observed mean abundances of nematodes over all dates were 20—30% greater than predicted. Microarthropod abundances were more variable, but tended to be lower than predicted. Our results indicate the measurement of N flux in single—species litterbags may not reflect actual N flux in the field, where leaves of several tree species are mixed together. The differences in N flux between single— and mixed—species litterbags can affect ecosystem—level estimates of N release or accumulation in decomposing litter. For example, estimates of ecosystem—level N fluxes at our field site, based on data from single—species litterbags, resulted in a 64% underestimate of N released by day 75 and a 183% overestimate of N accumulated in the litter by day 375, relative to estimates based on data from mixed—species litterbags. We suggest that the deviation of observed N fluxes in mixed—species litterbags from those predicted using single—species litterbags are the result of differences in the decomposer community, such as lower microbial and microarthropod densities and higher nematode densities, resulting when litter of varied resource quality is mixed together. Longer term studies will be needed to determine if the differences between observed and predicted decomposer communities in mixed—species litter combinations influence the latter stages of decomposition where invertebrate—microbial interactions may have a greater effect on decay rates and nutrient release.

Tree species identity mediates mechanisms of top soil carbon sequestration in a Norway spruce and European beech mixed forest

“…However, the low explanatory power of the fitted model suggests that other factors, such as output processes from the forest floor, can be important to explain C distribution in forest soils. On a given site, litter quality and its interaction with site properties are generally considered as the main factors controlling early phases of decomposition in forest ecosystems (Augusto et al 2015;Blair et al 1990). Our results provide consistent evidence of the importance of the conifer litterfall mass on the buildup of forest floor humus in forest soils (Figs.…”

Drivers of nitrogen leaching from organic layers in Central European beech forests

“…plant N uptake) of vascular plants in diverse communities. Decreased N release during decomposition seems unlikely because several studies on the relationship between plant diversity and organic matter turnover reported no or a positive e ect of plant diversity on N release (e.g., Blair et al 1990;Wardle et al 1997;Fornara et al 2009;Rosenkranz et al 2012). Lower dissolved N uxes in more diverse forests could instead have resulted from increased N demand of the vegetation as related to the greater productivity of more diverse forests (Morin et al 2011;Paquette and Messier 2011;Brassard et al 2013).…”

Biodiversity and decomposition in experimental grassland ecosystems

“…Some studies have shown a relationship between biodiversity and nutrient availability (Hooper and Vitousek 1998;Symstad et al 1998;Tilman et al 1996Tilman et al , 1997 and mineralization (Hooper and Vitousek 1998). However, litter decomposition studies have not shown consistent effects of plant species diversity on decomposition rates (Blair et al 1990;Elliott et al 1993;Fyles and Fyles 1993;Hart et al 1993;Klemmedson 1991;Knops et al 1996;Kochy and Wilson 1997;Taylor et al 1989;Williams and Alexander 1991). Four recent studies have specifically examined the effect of litter diversity on decomposition (Bardgett and Shine 1999;Finzi and Canham 1998;Hector et al 2000;Wardle et al 1997).…”