Tree species composition, structure, and carbon storage in stands of urban forest of varying character in Halifax, Nova Scotia

Abstract

Characteristics of stands of urban forest in Halifax, Nova Scotia, were analyzed with regards to tree-species composition and carbon sequestration. Older stands in residential and institutional neighbourhoods are dominated by non-native species of trees, thus limiting their usefulness in terms of protection of indigenous biodiversity values. These stands do, however, provide substantial ecosystem service in terms of carbon storage, because they are dominated by relatively large trees with an almost closed canopy (averaging 83% cover), and supporting a relatively large stand biomass (averaging 131 t/ha of above-ground tree biomass). In comparison, younger residential neighbourhoods have larger frequencies of native tree species, reflecting a recent trend to preserving some natural forest as buffer strips between properties. However, the proportion of native species of trees in the younger neighbourhoods is expected to decrease with time, because non-indigenous species are the strongly dominant choice among recent plantings by homeowners. Because of recent disturbance, urban forest in younger neighbourhoods has a relatively small biomass, but this should increase with succession. Natural-forest urban parks have a tree-species composition and stand structure that are similar to that of more remote, natural forests.