Enabling continental-scale ecology through multi-decadal Landsat time series data sets

Background/Question/Methods

The National Ecological Observatory Network (NEON) is a continental-scale ecological observation platform with the goal to collect and disseminate data to understand and forecast the impacts of climate change, land use change, and invasive species on ecology. In addition to collecting in-situ and airborne data, NEON will provide access to existing satellite-derived time series data sets to enable regional to global monitoring, estimating long-term trends and forecasting, and analysis of variations due to extreme events. Temporal vegetation patterns of interest include phenological states, photosynthetic activity, and biomass estimations - variables essential as inputs for climate and carbon cycle modeling. Existing phenology products are available at moderate spatial resolutions (MODIS and AVHRR-derived products), but higher resolution products that resolve finer spatial detail are desirable. To support analysis of landscape-scale patterns and long-term phenological dynamics, the ecology community is developing new products derived from finer spatial resolution time series data sets – specifically, the long-term Landsat series. This finer spatial resolution also supports scaling efforts between in-situ and airborne measurements and the broader, regional and continental scales provided by MODIS and AVHRR.

Results/Conclusions

Recently, Landsat time series data sets have been used to characterize bark beetle and defoliator impacts on tree mortality (Meigs, et al., 2011), gradual ecosystem changes across forests and rangelands (Vogelmann, et al., 2012) and long-term average and interannual dynamics in the phenology of temperate deciduous broadleaf forests (Melaas, et al. 2013). NEON will acquire the 30+ year time series Surface Reflectance data set for each of the NEON Core and Relocatable Sites; the data will be further processed into vegetation indices (EVI, SAVI, and NDVI products), which will enable analysis at each NEON site for the types of long-term changes described in the research papers above. An example of a new phenology product, based on Melaas, et al. 2013, will be produced and assessed for a second NEON site in southern California.