Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 12, issue 12
Biogeosciences, 12, 3885–3897, 2015
https://doi.org/10.5194/bg-12-3885-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 12, 3885–3897, 2015
https://doi.org/10.5194/bg-12-3885-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 26 Jun 2015

Research article | 26 Jun 2015

Growth response of temperate mountain grasslands to inter-annual variations in snow cover duration

P. Choler1,2,3 P. Choler
  • 1Univ. Grenoble Alpes, LECA, 38000 Grenoble, France
  • 2CNRS, LECA, 38000 Grenoble, France
  • 3LTER "Zone Atelier Alpes", 38000 Grenoble, France

Abstract. A remote sensing approach is used to examine the direct and indirect effects of snow cover duration and weather conditions on the growth response of mountain grasslands located above the tree line in the French Alps. Time-integrated Normalized Difference Vegetation Index (NDVIint), used as a surrogate for aboveground primary productivity, and snow cover duration were derived from a 13-year long time series of the Moderate-resolution Imaging Spectroradiometer (MODIS). A regional-scale meteorological forcing that accounted for topographical effects was provided by the SAFRAN–CROCUS–MEPRA model chain. A hierarchical path analysis was developed to analyze the multivariate causal relationships between forcing variables and proxies of primary productivity. Inter-annual variations in primary productivity were primarily governed by year-to-year variations in the length of the snow-free period and to a much lesser extent by temperature and precipitation during the growing season. A prolonged snow cover reduces the number and magnitude of frost events during the initial growth period but this has a negligible impact on NDVIint as compared to the strong negative effect of a delayed snow melting. The maximum NDVI slightly responded to increased summer precipitation and temperature but the impact on productivity was weak. The period spanning from peak standing biomass to the first snowfall accounted for two-thirds of NDVIint and this explained the high sensitivity of NDVIint to autumn temperature and autumn rainfall that control the timing of the first snowfall. The ability of mountain plants to maintain green tissues during the whole snow-free period along with the relatively low responsiveness of peak standing biomass to summer meteorological conditions led to the conclusion that the length of the snow-free period is the primary driver of the inter-annual variations in primary productivity of mountain grasslands.

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It is shown that inter-annual variations in the primary productivity of mountain grasslands are primarily governed by variations in the length of the snow-free period and to a much lesser extent by temperature and precipitation during the growing season. Meteorological variables controlling snow cover dynamics are thus of paramount importance to understand and model the amount and timing of biomass production in mountain pastures.
It is shown that inter-annual variations in the primary productivity of mountain grasslands are...
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