Biotic and Abiotic Constraints on the Decomposition of Fagus sylvatica Leaf Litter Along an Altitudinal Gradient in Contrasting Land-Use Types

Abstract

Climate change can affect the process of carbon cycling and leaf litter decomposition in multiple ways, both directly and indirectly, though the strength and direction of this relationship is often context dependent. In this experiment, we followed decomposition of a standard litter type-senescent leaves of Fagus sylvatica collected from a single location-along a 1000 m altitudinal gradient of four sites over 2.5 years. To control the edaphic conditions, we transplanted intact turf mesocosms from three different land-use types [densely wooded, sparsely wooded, and unwooded (UW) pastures] from the highest altitude site into UW pastures along the altitudinal gradient from the moist, cool high-elevation site to the dry, warm low-elevation site, using shade cloth to mimic the light conditions in the original habitats. Decomposition in the drier UW pasture mesocosms increased with altitude, likely because of higher moisture at the highest sites. Decomposition in the more mesic mesocosms from sparsely and densely wooded sites was insensitive to altitude, suggesting an overriding moisture, rather than temperature, constraint on decomposition across these sites. The functional composition of decomposer microbial communities (fungal/bacterial ratio) was similarly insensitive to altitude. Our findings bring substantial evidence for the controlling role of soil moisture on litter decomposition, as well as for the indirect effects of climate through changes in the decomposer community.

Seasonality alters drivers of soil enzyme activity in subalpine grassland soil undergoing climate change

“…In winter, in the subalpine grassland studied, water is not limiting for C-activities and so under these conditions resource availability appeared to limit SOM enzymatic activity (Brooks et al, 2005;Harrysson Drotz et al, 2009;Öquist and Laudon, 2008). Such relationships between microbial activity and abundance and WEOC/DOC content have been reported earlier (Marschner and Kalbitz, 2003;Rees and Parker, 2005), but surprisingly the WEOC degree of aromaticity normally used as a proxy of WEOC biodegradability (Marschner and Kalbitz 2003) was not found as a driver of soil enzyme activity under the climate change (Gavazov et al, 2014). The accumulation of freePOM due to lower enzyme potential activities (Fig 4.B) adds further support for fresh plant material accumulation.…”

“…The variance in soil gravimetric moisture was largely explained by our climate change manipulation (R 2 =0.53* and R 2 =0.59**; linear model for winter and summer season respectively) confirming that this variable integrates the effect of the climate change manipulation. Moreover, previous investigations of the same soil transplantation experiment revealed the prevailing soil moisture vs temperature controls on soil C turnover (Mills et al 2014) and (Gavazov et al 2014). C-enzymes potential activities were split into hydrolase enzymes (mean of ß-glucosidases, cellobiohydrolase, xylosidase, lipase) and oxidase enzyme (phenol oxidase) (Table 1).…”

Nutrient and Isotopic Dynamics of Litter Decomposition from Different Land Uses in Naturally Restoring Taihang Mountain, North China

“…The predominance of recalcitrant metabolites that are resistant to enzymatic (microbial) and environmental degradation was suspected to reduce litter mass loss in the later phase [5,10,42]. Litter decomposition can be principally divided into the early phase (before 20-40% mass loss), determined by the initial litter chemistry, while the later phase is mainly controlled by the decomposition of the lignin and the microbial community [34,50,51]; our study has demonstrated the early phase of decomposition.…”

Long‐term responses of leaf litter decomposition to temperature, litter quality and litter mixing in plateau wetlands

“…Litter decomposition can be divided into two phases, and the early phase (up to 20-40% of the total mass loss) is mainly determined by litter chemistry, while the later phase is mainly controlled by the microbial community (Berg & McClaugherty, 2008;Bray, Kitajima & Mack, 2012;Gavazov et al, 2014). Meanwhile, litter decomposition is an ecological process governed by decomposer organisms, and therefore, an increase in temperature is likely to stimulate litter decomposition by creating conditions favourable for decomposer communities and their activity (Davidson & Janssens, 2006;Chacon & Dezzeo, 2007;Cusack et al, 2009).…”

“…Environmental gradients, especially elevation gradients, have been useful in quantifying the influence of environmental conditions on ecosystem processes (Dunne et al, 2004;Malhi et al, 2010;Sundqvist, Giesler & Wardle, 2011). Elevation gradient studies represent a natural approach to evaluate the impact of climatic parameters on ecological processes (K€ orner, 2007;Gavazov et al, 2014). Furthermore, ecological field experiments along elevation gradients allow for the discrimination between direct environmental factors and other site-dependent factors, such as species traits and composition (van de Weg et al, 2009;Pellissier et al, 2010;Averill & Finzi, 2011).…”