Abstract
Many studies already investigated the impact of climate change and
climate variability on vegetation at global and continental scales.
Using time series of remote sensing and climate data, Nemani et al.
(2003) analyzed trends in Net Primary Production in relation with
changes in climate and showed that, between 1982 and 1999, primary
productivity increased by 6% globally in response to climate change.
This study also stressed the need to take into account the spatial
variability of climatic constraints to plant growth when analyzing the
climate change impact on vegetation. Others authors described different
phenomenon linked with climate change such as increases of seasonal NDVI
amplitude and growing season duration in the Northern high latitude or
changes in circumpolar photosynthetic activities. Understanding the
interactions between climate and vegetation is also a key issue in our
PhD research. Our objective is to identify the meteorological factors
which limit the development of croplands and grasslands in relation with
their geographical localization. For that purpose, we acquired 10-daily
time series of the Normalized Difference Vegetation Index, NDVI, derived
from SPOT-VEGETATION and 7 meteorological parameters (Tmean, Tmin, Tmax,
Rain, Rad, ETP, Rain-ETP) derived from ERA40 re-analyses and the
operational ECMWF (European Centre for Medium-Range Weather Forecast)
atmospheric model. Cross-correlations between NDVI and each one of the
meteorological parameters were analysed for a set of 25 regions over
Europe and Africa: 15 agricultural regions and 10 regions covered by
grassland or savannas. Unlike others studies, we did not consider the
vegetation globally but we focussed on two types of vegetation:
croplands and grasslands. This is quite important considering the role
of phenology on the vegetation cycle and its relation with climate.
Moreover the analysis was not realised using yearly estimates but using
10-daily products. In order to avoid stationarity related issue, a
specific methodology was developed taking into account the phenological
cycle of the vegetation under consideration. Preliminary results showed
that the relation between a meteorological limiting factor, e.g.
precipitation, and NDVI can not be considered as linear during the year
or even during the growing season. Interactions must to be studied at a
smaller time scale than the growing season in order to identify properly
the limiting factors to plant growth taking into account its phenology.
Moreover the main limiting factors are variable from a region to
another. In our analysis we also considered the possibility of a delayed
response of the vegetation or a cumulated effect of meteorological
events (up to 3 months). Our methodology will be presented during the
conference and results will be discussed and illustrated by some test
cases. Reference: Nemani R.R., Keeling C.D., Hashimoto H., Jolly W.M.,
Piper S.C., Tucker C.J., Myneni R.B. and Running S.W. (2003).
'Climate-driven increases in global terrestrial net primary production
from 1982 to 1999'. Science, 300, 1560-1563.
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | EGU General Assembly 2010, held 2-7 May, 2010 in Vienna, Austria, p.11680 |
| Vol/bind | 12 |
| Sider (fra-til) | 11680 |
| Status | Udgivet - 1 maj 2010 |
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