The American chestnut, Castanea dentata, was once the dominant species in many hardwood forests in eastern North America. The Asian pathogen Cryphonectria parasitica was introduced in 1904, killing mature chestnuts rangewide by the 1940s. Recent work has produced a new, putatively pathogen-resistant hybrid variety. Thus, the possibility exists of large-scale reintroduction to eastern American forests; but, considerable information on the ecology of the chestnut hybrid and the potential effects on the forests it would inhabit are still needed. We predicted that due to greater concentrations of precipitate tannin in C. dentata, its litter would decompose at a slower rate and contain more recalcitrant organic compounds when compared to co-occurring species. We also predicted that there would not be significant differences in the ecology of hybrid chestnut vs. pure American chestnut. In Autumn 2008, litter bags were placed in a mixed-oak forest in southeastern Ohio, containing litter from either C. dentata, C. mollissima, hybrid chestnut, Quercus alba, or Acer rubrum. Bags were collected at three-month intervals for one year, and mass loss was calculated. Leaf extracts were tested for tannins, C:N ratio, and nutrient concentrations. A carbon fractionation evaluated the relative availability of litter fractions for decomposition.
Results/Conclusions
Chestnut taxa contained more foliar precipitate tannin than Q. prinus and A. rubrum (P < 0.01), though concentrations were well within the range of species found in mixed oak ecosystems of central Appalachia. Other nutrient concentrations were also within the ranges of co-occurring species. Chestnut taxa showed significantly more rapid loss of mass (P < 0.01) and tannins (P < 0.01) than co-occurring species after three and six months, but mass loss was similar among species after 1 year (~50 %). Though precipitate tannin leached out of chestnut litter more rapidly than it did in the litter of co-occurring species; after one year, all species analyzed had lost more than 98% of their tannins. Chestnut selections contained lower concentrations of lignin than Quercus alba during the initial nine months of decomposition, but these concentrations evened out after one year. These data suggest that a reintroduction of hybrid chestnut would not lead to increased humification or an alteration in nutrient cycling regimes and ecosystem processes in Appalachian hardwood forests.
