For the first time, the majority of people on the planet live in urban areas and there is increased interest in managing and studying greenspace within and across cities. In New York City (NYC) 10% of the landscape is comprised of urban woodlands. Forests within the urban context can be challenging to manage due to a wide range of pressures, historic use, invasive species and limited resources. These past and current urban pressures have resulted in variable urban woodland composition and condition; however, few studies have looked at both the variation in forest community type (i.e. novel, native, successional) and indicators of healthy forests within this context. To address some of these challenges cities have established inventory, monitoring and prioritization initiatives to understand forest condition and focus management efforts. Using two large US cities (Seattle, WA and New York, NY), a combination of field data and remotely sensed data was used to characterize the distribution and condition of unique urban forest communities. Field assessment data was then used to develop a forest health and forest threat index in both cities. These condition indices and associated data can be used to guide management but also build a better understanding of urban woodland community and ecosystem dynamics across multiple scales.
Results/Conclusions
We characterized 5 unique forest groups and 30 unique forest communities; including 8 non-native forest communities in New York City. Seattle has characterized 4 unique forest groups and 12 unique forest communities; including 2 non-native forest communities. Using standardized forest health and threat indices we found 72.3% of NYC natural area forest (4,536 acres) is considered low threat, however only 3.5% (242 acres) are considered high health. Whereas in Seattle, a majority of the forest was considered high threat 51.1% (1,334 acres), and 17.7% (462 acres) were found to be high health. In NYC we found high variability in ecological indicators based on forest community including mean native seedling density (831-15,777/ha), native herbaceous cover (12-82%), soil pH (4.9-8.8) and tree canopy composition (native basal area 3.7-38.4 m2/ha) as well as complex relationships between ecological indicators of health and threat based on forest community type. Factors impacting forest condition vary by city and scale and using a similar approach to classify health and threat of forest communities we can begin to disentangle the complex ecology of urban woodlands across spatial scales which will have important conservation and scientific applications.