Global Ecosystem Response Types Derived from the Standardized Precipitation Evapotranspiration Index and FPAR3g Series

Observing trends in global ecosystem dynamics is an important first step, but attributing these trends to climate variability represents a further step in understanding Earth system changes. In the present study, we classified global Ecosystem Response Types (ERTs) based on common spatio-temporal patterns in time-series of Standardized Precipitation Evapotranspiration Index (SPEI) and FPAR3g anomalies (1982–2011) by using an extended Principal Component Analysis. The ERTs represent region specific spatio-temporal patterns of ecosystems responding to drought or ecosystems with decreasing severity in drought events as well as ecosystems where drought was not a dominant factor in a 30-year period. Highest explanatory values in the SPEI12-FPAR3g anomalies and strongest SPEI12-FPAR3g correlations were seen in the ERTs of Australia and South America whereas lowest explanatory value and lowest correlations were observed in Asia and North America. These ERTs complement traditional pixel based methods by enabling the combined assessment of the location, timing, duration, frequency and severity of climatic and vegetation anomalies with the joint assessment of wetting and drying climatic conditions. The ERTs produced here thus have potential in supporting global change studies by mapping reference conditions of long term ecosystem changes

Global-scale mapping of changes in ecosystem functioning from earth observation-based trends in total and recurrent vegetation

Aim: To evaluate trend analysis of earth observation (EO) dense time series as a new way of describing and mapping changes in ecosystem functioning at regional to global scales. Spatio-temporal patterns of change covering 1982-2011 are discussed in the context of changes in land use and land cover (LULCC). Location: Global. Methods: This study takes advantage of the different phenological cycles of recurrent vegetation (herbaceous vegetation) and persistent vegetation (woody/shrub cover) in combining trend analyses of global-scale vegetation based on different annual/seasonal normalized difference vegetation index (NDVI) metrics. Spatial patterns of combined vegetation trends derived from the Global Inventory Modeling and Mapping Studies NDVI are analysed using land-cover information (GLC2000). Results: The direction of change in annual and seasonal NDVI metrics is similar for most global terrestrial ecosystems, but areas of diverging trends were also observed for certain regions across the globe. These areas are shown to be dominated by land-cover classes of deciduous forest in tropical/subtropical areas. Areas of observed change are found in dry deciduous forest in South America and central southern Africa and are in accordance with studies of hotspot LULCC areas conducted at local and regional scales. The results show that dense time series of EO data can be used to map large-scale changes in ecosystem functional type that are due to forest cover dynamics, including forest degradation, deforestation/reforestation and bush encroachment. Main conclusions: We show that areas characterized by changes in ecosystem functioning governed by LULCC at regional and global scales can be mapped from dense time series of global EO data. The patterns of diverging NDVI metric trends can be used as a reference in evaluating the impacts of environmental changes related to LULCC and the approach may be used to detect changes in ecosystem functioning over time