Leaf litter disappearance of hardwood species of southern Québec: Interaction between litter quality and stand type

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Abstract
Leaf litter disappearance rates of ten deciduous broadleaved tree species [American basswood (Tilia americana L.), American beech (Fagus grandifolia Ehrh.), bitternut hickory (Carya cordiformis [Wang.] K. Koch.), largetooth aspen (Populus grandidentata Michx), red maple (Acer rubrum L.), red oak (Quercus rubra L.), shagbark hickory (Carya ovata [Mill.] K. Koch.), sugar maple (Acer saccharum Marsh.), white ash (Fraxinus americana L.) and yellow birch (Betula alleghaniensis Britton)] were measured in five stands of different species composition in southern Québec to determine whether the relative disappearance rates associated with earthworm activity, and the litter quality parameters predicting disappearance were constant across all stands. Pure stands of sugar maple and largetooth aspen, and three mixed stands of sugar maple with American basswood, white ash and bitternut hickory were examined. Soil pH, exchangeable Ca and Mg and available N were highest in the basswood stand. Litter disappearance from under wire mesh screens was measured around four trees of one species in each stand. There were large differences among species in N, P, K, C and tannin concentrations, tanning potential, C:N ratios and toughness of leaf litter. Species, stand type and the interaction between species and stand type all had highly significant effects on leaf litter disappearance rates. Overall, leaf litter disappearance rates in the five stands were ranked as follows: basswood > white ash = largetooth aspen > bitternut hickory = sugar maple. Basswood leaf litter disappeared the fastest and red oak leaf litter disappeared the slowest in all stands. The rankings of most other litters differed among stands. Overall the best variable to explain the rate of leaf litter disappearance was the toughness of the litter measured as the mass needed to punch a 3-mm circular hole in the leaf blade. In some stands, litter K, P and C:N ratios were also good predictors of disappearance rates. Leaf litter disappearance could be affected not only by the quality of the litter itself, but by the availability of other food sources and soil nutrients.