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| Titel |
Assessing vegetation structure and ANPP dynamics in a grassland–shrubland Chihuahuan ecotone using NDVI–rainfall relationships |
| VerfasserIn |
M. Moreno-de las Heras, R. Díaz-Sierra, L. Turnbull, J. Wainwright |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 10 ; Nr. 12, no. 10 (2015-05-21), S.2907-2925 |
| Datensatznummer |
250117939
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| Publikation (Nr.) |
 copernicus.org/bg-12-2907-2015.pdf |
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| Zusammenfassung |
| Climate change and the widespread alteration of natural habitats are major
drivers of vegetation change in drylands. In the Chihuahuan Desert, large
areas of grasslands dominated by perennial grass species have transitioned
over the last 150 years to shrublands dominated by woody species, accompanied
by accelerated water and wind erosion. Multiple mechanisms drive the
shrub-encroachment process, including precipitation variations, land-use
change, and soil erosion–vegetation feedbacks. In this study, using a simple
ecohydrological modelling framework, we show that herbaceous (grasses and
forbs) and shrub vegetation in drylands have different responses to
antecedent precipitation due to functional differences in plant-growth and
water-use patterns. Therefore, shrub encroachment may be reflected in the
analysis of landscape-scale vegetation–rainfall relationships. We analyse
the structure and dynamics of vegetation at an 18 km2
grassland–shrubland ecotone in the northern edge of the Chihuahuan Desert
(McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by
investigating the relationship between decade-scale (2000–2013) records of
remotely sensed vegetation greenness (MODIS NDVI) and antecedent rainfall.
NDVI–rainfall relationships show a high sensitivity to spatial variations on
dominant vegetation types across the grassland–shrubland ecotone, and
provide biophysical criteria to (a) classify landscape types as a function of
the spatial distribution of dominant vegetation and to (b) decompose the NDVI
signal into partial components of annual net primary production (ANPP) for
herbaceous vegetation and shrubs. Analysis of remotely sensed ANPP dynamics
across the study site indicates that plant growth for herbaceous vegetation
is particularly synchronized with monsoonal summer rainfall. For shrubs, ANPP
is better explained by winter plus summer precipitation, overlapping the
monsoonal period (June–September) of rain concentration. Our results suggest
that shrub encroachment was not particularly active in this Chihuahuan
ecotone for the period 2000–2013. However, future changes in the amount and
temporal pattern of precipitation (i.e. reductions in monsoonal summer
rainfall and/or increases in winter precipitation) may enhance the
shrub-encroachment process, particularly in the face of expected upcoming
increases in aridity for desert grasslands of the southwestern USA. |
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