title: Trends in Global Vegetation Activity and Climatic Drivers Indicate a Decoupled Response to Climate Change.
abstract: Detailed understanding of a possible decoupling between climatic drivers of plant productivity and the response of ecosystems vegetation is required. We compared trends in six NDVI metrics (1982-2010) derived from the GIMMS3g dataset with modelled biomass productivity and assessed uncertainty in trend estimates. Annual total biomass weight (TBW) was calculated with the LINPAC model. Trends were determined using a simple linear regression, a Thiel-Sen medium slope and a piecewise regression (PWR) with two segments. Values of NDVI metrics were related to Net Primary Production (MODIS-NPP) and TBW per biome and land-use type. The simple linear and Thiel-Sen trends did not differ much whereas PWR increased the fraction of explained variation, depending on the NDVI metric considered. A positive trend in TBW indicating more favorable climatic conditions was found for 24% of pixels on land, and for 5% a negative trend. A decoupled trend, indicating positive TBW trends and monotonic negative or segmented and negative NDVI trends, was observed for 17-36% of all productive areas depending on the NDVI metric used. For only 1-2% of all pixels in productive areas, a diverging and greening trend was found despite a strong negative trend in TBW. The choice of NDVI metric used strongly affected outcomes on regional scales and differences in the fraction of explained variation in MODIS-NPP between biomes were large, and a combination of NDVI metrics is recommended for global studies. We have found an increasing difference between trends in climatic drivers and observed NDVI for large parts of the globe. Our findings suggest that future scenarios must consider impacts of constraints on plant growth such as extremes in weather and nutrient availability to predict changes in NPP and CO2 sequestration capacity.
authors.affiliation: Plant Production Systems Group, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands; PBL Assessment Agency for the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands.
authors.forename: Antonius G T
authors.initials: AG
authors.lastname: Schut
authors.affiliation: Joint Research Centre, Via Enrico Fermi 2749, I - 21027 Ispra, Italy.
authors.forename: Eva
authors.initials: E
authors.lastname: Ivits
authors.affiliation: Plant Research International, Wageningen UR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Conijn
authors.affiliation: PBL Assessment Agency for the Environment, Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands.
authors.forename: Ben
authors.initials: B
authors.lastname: Ten Brink
authors.affiliation: Section of Geography, Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen, Oster Voldgade 10, 1350 Copenhagen, Denmark.
authors.forename: Rasmus
authors.initials: R
authors.lastname: Fensholt
mesh_terms: D000465:Algorithms; D018533:Biomass; D002245:Carbon Dioxide / Q000737:chemistry; D002980:Climate; D057231:Climate Change; D003247:Conservation of Natural Resources; D016208:Databases, Factual; D017753:Ecosystem; D006813:Humidity; D016014:Linear Models; D063245:Plant Development / Q000502:physiology*; D011891:Rain; D012621:Seasons; D013472:Sunlight; D013696:Temperature; D013997:Time Factors; D014887:Weather
chemical_list: D002245:Carbon Dioxide