Does moder development along a pure beech (Fagus sylvatica L.) chronosequence result from changes in litter production or in decomposition rates?

Abstract

International audienceThe development of temperate deciduous and conifers forests stands usually results in accumulation of forest floor organic matter and a shift from mull to moder humus forms. It has been suggested that an increase in nutrient uptake by trees during their rapid growth phase leads to topsoil acidification, decrease in earthworm density and thereby a decrease in litter turnover. The focus of this paper was to examine if the mull-moder shift with forest ageing results from higher leaf litter production and/or lower litter decay rates. The objectives of this research were to determine (1) changes in macro-morphological properties of humus forms, leaf litter production, litter decay rates, soil nutrients content and pH along a 130-year pure beech (Fagus sylvatica L.) chronosequence in Normandy (Northwest France), (2) if humus form varied from mull to moder with increasing stand age, and (3) if a shift from mull to moder resulted from increased litter production, decreased litter decay rates, or both. Annual litter production did not change significantly along the chronosequence (mean 2.41 t ha−1). In contrast, litter decay rates decreased significantly during the rapid growth phase of trees. In consequence, the litter turnover time (1/k) was lower in the youngest stands (20 months) compared to the oldest ones (31 months). Even in the absence of a significant pattern of variation, litter production was positively correlated with the thickness of the OF (Oi) horizon. In contrast, litter decay was strongly negatively correlated with maximum thickness of the OH (Oa) horizon, suggesting that the appearance of the humification layer was mainly due to a decrease in litter decay rate. We did not find significant changes in the main properties of the organo-mineral horizon, suggesting that soil nutrient availability may not directly affect litter dynamics. We concluded that moder development along the chronosequence resulted in decreasing litter decay rates during the aggradation phase while litter production was stable. Further studies are required to identify the ecological factors responsible for moder development along forest ageing

Biotic homogenisation and differentiation along a habitat gradient resulting from the ageing of managed beech stands

“…As a result of the decrease in the exploitation of non-timber forest products such as litter raking, and also due to the ageing of tree stands, a thicker layer of beech litter accumulates, which results in top soil acidification and lower concentrations of nutrients (Barbier et al, 2008;Trap et al, 2013). A shift from mull to moder humus form has previously been observed along the beech stand chronosequence (Trap et al, 2011). The properties of the topsoil such as moisture and nutrient loading could also be deteriorated by the fine root network of the ageing beech trees, which by the uptake of resources reduces soil water supply and nutrient availability (Barbier et al, 2008;Coomes and Grubb, 2000).…”

“…It has been shown that, along with the ageing of the beech stands, a thicker layer of beech litter has accumulated, which has resulted in top soil acidification and lower concentrations of nutrients as well as a shift from mull to moder humus observed along beech stand chronosequences (Barbier et al, 2008;Trap et al, 2011Trap et al, , 2013. Therefore, the change of soil conditions due to the ageing of the beech stands is more pronounced at less fertile sites than at more fertile ones because of the greater buffering capacity of the latter ones.…”

The Link Between Litterfall, Substrate Quality, Decomposition Rate, and Soil Nutrient Supply in 30-Year-Old Pinus massoniana Forests in the Three Gorges Reservoir Area, China

“…In our study, soil nutrient accumulation was found to be controlled by litterfall, litter quality, and decomposition rate. Furthermore, accumulation of organic materials on the forest floor resulted from an imbalance between litter production and litter decomposition rates (Trap et al, 2011). 8).…”

Influence of serpentine abundance on the vertical distribution of available elements in soils

“…Our results agree with their findings as we found here that element concentration in soil organic matter did not depend on the presence of serpentine minerals, suggesting therefore that the uptake of essential elements was only influenced by plant requirements. The decomposition of beech litter seems to be little affected by soil nutrient availability (Trap et al, 2011), but serpentinitic soils are expected to display a lower mineralization rate because of the effect heavy metals have on microbial communities (Kazakou et al, 2008). Microbial and fungal communities may however be adapted in serpentinitic areas (e.g.…”