Functional and ecosystem service differences between tree species: implications for tree species replacement

Tree species differ in their functioning at the scale of an individual tree which will result in differences in ecosystem service provision. Replacement trees for diseased trees should take account of functional differences. Globally tree species composition is changing due to species loss from pests and pathogens. The impact of this change on ecological functioning is rarely tested. Using six sites across the UK, with multiple tree species at each site, we test for functional differences between three species threatened by disease in the UK: Quercus petraea, Q. robur and Fraxinus excelsior and six other species: Acer pseudoplatanus, Castanea sativa, Fagus sylvatica, Quercus cerris, Quercus rubra, and Tilia x europaea, which have previously been suggested as ecological replacements. Differences between species were detected for all the variables measured: nitrogen mineralization, decomposition rate, total soil carbon and nitrogen, soil pH, soil temperature, and bark water holding capacity. Non-native Quercus species were only suitable replacements for native Quercus for some of the functions measured but replicating native Quercus functioning using a mixture of other species may be possible. The functioning of F. excelsior was different from most other tree species, suggesting that replicating its functioning with replacement tree species is difficult. The work highlighted that which species replaces diseased trees, even at the scale of single trees, will impact on the functions and ecosystem services provided.