Developing a LIDAR-based model of complexity in old-field successional trajectories across central New York State

Background/Question/Methods

As part of a larger study to understand the impacts of simultaneous climate and land-use change on biodiversity, we are developing a landscape-level successional model for central New York based on field sampling and airborne LIDAR. This successional model will simulate future changes in vegetation structure that will, in turn, fundamentally shape wildlife habitat suitability as well as other landscape and ecosystem characteristics. The model is based on the classic ‘space-for-time’ approach, but is being coupled with regionally-extensive 30 m resolution LIDAR data, which provides a wider dataset to characterize regional successional dynamics. In summer 2011, landowner interviews and GIS analyses were used to establish a network of 32 old-fields across central New York (3–111 years post-abandonment). Fields were only selected when ages of abandonment could be established to ± 2–5 years. We established 100, 20 m diameter plots among these fields and measured vegetation using a field methodology developed specifically to couple vegetation measurement and LIDAR ground-truthing. Within each plot, the dominant vegetation layers were identified and their cover estimated. Height, composition, and spatial location of the vegetation in each layer were measured with a laser rangefinder, providing a detailed three-dimensional sampling of vegetation structure.

Results/Conclusions

Our initial analysis of the field data found dramatic differences among old-fields in vegetation structure and composition changes through time. Highly competitive herbaceous communities dominated by Solidago spp. were found to establish quickly after abandonment and remain for more than 25 years. We found some old-fields to be characteristic of young forests after only 31 years while others remained persistent shrub communities for over 50 years. Invasive shrub establishment including Rhamnus spp., Lonicera spp., and Elaeagnus spp. was widespread and represents a likely driver of divergent successional trajectories. Fraxinus americana and Acer spp. were the principle tree species found colonizing these old-fields. Trees were not found to form a distinct vegetation layer until after 10 years post-abandonment. Our preliminary modeling efforts have found that site variables including soil characteristics and field size also appear to determine successional trajectory; however, these variables are often interrelated and correlated with age since abandonment. There appear to be complex interactions between age since abandonment, invasive species, and site variables that differ among old-fields in Central New York.