No depth-dependence of fine root litter decomposition in temperate beech forest soils

Abstract

Aims Subsoil organic carbon (OC) tends to be older and is presumed to be more stable than topsoil OC, but the reasons for this are not yet resolved. One hypothesis is that decomposition rates decrease with increasing soil depth. We tested whether decomposition rates of beech fine root litter varied with depth for a range of soils using a litterbag experiment in German beech forest plots. Methods In three study regions (Schorfheide-Chorin, Hainich-Dün and Schwäbische-Alb), we buried 432 litterbags containing 0.5 g of standardized beech root material (fine roots with a similar chemical composition collected from 2 year old Fagus sylvatica L. saplings, root diameter<2mm) at three different soil depths (5, 20 and 35 cm). The decomposition rates as well as the changes in the carbon (C) and nitrogen (N) concentrations of the decomposing fine root litter were determined at a 6 months interval during a 2 years field experiment. Results The amount of root litter remaining after 2 years of field incubation differed between the study regions (76 ± 2 % in Schorfheide-Chorin, 85 ± 2 % in Schwäbische-Alb, and 88±2 % in Hainich-Dün) but did not vary with soil depth. Conclusions Our results indicate that the initial fine root decomposition rates are more influenced by regional scale differences in environmental conditions including climate and soil parent material, than by changes in microbial activities with soil depth. Moreover, they suggest that a similar potential to decompose new resources in the form of root litter exists in both surface and deep soils

Long term decomposition: the influence of litter type and soil horizon on retention of plant carbon and nitrogen in soils

“…This finding corroborates several shorter-term (12-36 month) studies that did not find decomposition differences in a common substrate among soil horizons (Fujii and Takeda 2010) or depths (Sanaullah et al 2011;Solly et al 2015). Similarly, traditional litter decomposition studies have found that within an ecosystem or among similar ecosystems, litter type explains most of the variation in mass loss (e.g.…”

The effects of heating, rhizosphere, and depth on root litter decomposition are mediated by soil moisture

“…At depth, a lack of fresh labile carbon inputs limits the energy that microbes have to produce the enzymes they need to decompose recalcitrant carbon sources (Fontaine et al 2007). Interestingly, while Solly et al (2015) and Sanaullah et al (2011) also report similar longer term decomposition rates across depths, the dominant factors that control decomposition (e.g. abiotic vs. abiotic limitations) differed across depths.…”

“…Soil depth affects root litter decomposition rates in some studies (Rovira and Vallejo 1997;Gill and Burke 2002;Garcia-Pausas et al 2012;Berhe 2012), but not all (Weaver 1947;Sanaullah et al 2011;Solly et al 2015). Compared to topsoil, subsoil has a lower microbial biomass concentration and fungi:bacteria ratio (Stone et al 2014), lower root density and less rhizosphere volume, reduced connectivity between SOC moieties, and greater protection of organic matter by aggregates and mineral particles (Schrumpf et al 2013), all of which tend to reduce microbial activity.…”

“…Numerous studies have used the litterbag method to quantify changes in litter mass, carbon, and nutrients during decomposition (e.g., Rovira and Vallejo 1997;Silver and Miya 2001;Zhang et al 2008;Solly et al 2015). However, this approach introduces artifacts, such as restricting the physical contact of litter with the soil matrix.…”

Experimental soil warming shifts the fungal community composition at the alpine treeline

“…However, the definition of community responses to changing litter properties and the untangling of potential underlying mechanisms are complicated by the spatially heterogeneous distribution of fungi in forest soils (Lindahl et al, 2007;Davison et al, 2012;Weber et al, 2013). The spatial scale at which fungal taxa colonize litter and soil differs considerably between groups of fungi, and depends on the local physical and chemical conditions, which vary within a soil profile and depend on the plant species present (Finzi et al, 1998;Neville et al, 2002;Fierer et al, 2003;Cools et al, 2014;Clemmensen et al, 2015;Solly et al, 2015;Sterkenburg et al, 2015). Moreover, the fungal community composition is commonly stratified according to distinct functional groups occupying different soil horizons (Lindahl et al, 2007;Baldrian et al, 2012;Clemmensen et al, 2015;B€ odeker et al, 2016).…”