Fine root decomposition rates do not mirror those of leaf litter among temperate tree species

Abstract

Elucidating the function of and patterns among plant traits above ground has been a major research focus, while the patterns and functioning of belowground traits remain less well understood. Even less well known is whether species differences in leaf traits and their associated biogeochemical effects are mirrored by differences in root traits and their effects. We studied fine root decomposition and N dynamics in a common garden study of 11 temperate European and North American tree species (Abies alba, Acer platanoides, Acer pseudoplatanus, Carpinus betulus, Fagus sylvatica, Larix decidua, Picea abies, Pseudotsuga menziesii, Quercus robur, Quercus rubra and Tilia cordata) to determine whether leaf litter and fine root decomposition rates are correlated across species as well as which species traits influence microbial decomposition above versus below ground. Decomposition and N immobilization rates of fine roots were unrelated to those of leaf litter across species. The lack of correspondence of above- and belowground processes arose partly because the tissue traits that influenced decomposition and detritus N dynamics different for roots versus leaves, and partly because influential traits were unrelated between roots and leaves across species. For example, while high hemicellulose concentrations and thinner roots were associated with more rapid decomposition below ground, low lignin and high Ca concentrations were associated with rapid aboveground leaf decomposition. Our study suggests that among these temperate trees, species effects on C and N dynamics in decomposing fine roots and leaf litter may not reinforce each other. Thus, species differences in rates of microbially mediated decomposition may not be as large as they would be if above- and belowground processes were working in similar directions (i.e., if faster decomposition above ground corresponded to faster decomposition below ground). Our results imply that studies that focus solely on aboveground traits may obscure some of the important mechanisms by which plant species influence ecosystem processes.

Characteristics of Fine Roots of Pinus massoniana in the Three Gorges Reservoir Area, China

“…However, there was a significantly positive correlation between fine root decomposition rate and soil temperature, which was, therefore, the major driver of fine root decomposition, similar to that found in previous studies [57,[62][63][64][65][66]. According to Cusack et al [62], precipitation-related parameters are strong predictors of litter decomposition in neotropical forests, and Hobbie et al [67] also suggested that moister soils could facilitate rapid mass loss by promoting leaching and microbial activity or a faster colonisation of decomposing material by microbes. Moreover, Zhang et al [68] and Violita et al [69] stated that the decomposition rate of roots increased with increasing internal Ca concentration in roots.…”

Effects of litter traits, soil biota, and soil chemistry on soil carbon stocks at a common garden with 14 tree species

“…in some places the moraine was within plowing depth, in others it was not). Previous studies documented that leaf and fine root chemistry, lifespan, and litter fluxes vary by as much as two-fold or more among the 14 tree species (Hobbie et al 2010;Reich et al 2005;Withington et al 2006). …”

“…In contrast, the impact of trees on the net redistribution of nutrients from soils to plants is perhaps more a function of variation in the concentrations and pools of nutrients in wood. Notably, tree species with high nutrient concentrations in leaf litter do not necessarily have high nutrient concentrations in roots (Hobbie et al 2010) or wood, so different tissues and organs of the same species can have unique effects on soil nutrient mineralization and redistribution.…”

Alterations in forest detritus inputs influence soil carbon concentration and soil respiration in a Central-European deciduous forest

“…Soil C reduced to a greater extent in a litter exclusion treatment than in a root exclusion treatment in a black cherry-sugar maple forest (Bousson Environmental Research Reserve, Pennsylvania, USA) (Bowden et al, 2013). It is not clear what controls the relative importance of aboveground and belowground litter contributions to soil C. Root and leaf litter decompose at different rates (Hobbie et al, 2010), and may produce different organic compounds that undergo different rates of chemical (Hassink, 1997) and physical (Six et al, 2002, Pronk et. al., 2013 protection.…”