Quantifying snow controls on vegetation greenness

Abstract

Abstract. Snow is a key driver for biotic processes in Arctic ecosystems. Yet, quantifying relationships between snow metrics and biological components is challenging due to lack of temporally and spatially distributed observations at ecologically relevant scales and resolutions. In this study, we quantified relationships between snow, air temperature, and vegetation greenness (using annual maximum normalized difference vegetation index [MaxNDVI] and its timing [MaxNDVI_DOY]) from ground-based and remotesensing observations, in combination with physically based models, across a heterogeneous landscape in a high-Arctic, northeast Greenland region. Across the 98-km distance from the Greenland Ice Sheet (GrIS) to the coast, we quantified significant inland-coast gradients of air temperature, winter precipitation (using pre-melt snow-water-equivalent [SWE]), and snowmelt timing (using snow-free day of year [SnowFree_ DOY]). Near the coast, the mean annual air temperature was 4.5°C lower, the mean SWE was 0.3 m greater, and the mean SnowFree_DOY was 37 d later, than near the GrIS. The regional continentality gradient was eight times stronger than the south-to-north air-temperature gradient along the Greenland east coast. Across this strong gradient, the mean vegetation greening-up period (SnowFree_DOY-MaxNDVI_ DOY) varied spatially by 24-57 d. We quantified significant non-linear relationships between the vegetation characteristics of MaxNDVI and MaxNDVI_DOY, and SWE, SnowFree_DOY, and growing degree-days-sums during greening-up (Greening_GDD) across the 16-yr study period (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015). These demonstrated that the snow metrics, both SWE and SnowFree_DOY, were more important drivers of MaxNDVI and MaxNDVI_DOY than Greening_GDD within this seasonally snow-covered region. The methodologies that provided temporally and spatially distributed snow, air temperature, and vegetation greenness data are applicable to any snow-and vegetation-covered area on Earth.

Density, snow, and seasonality lead to variation in muskox (Ovibos moschatus) habitat selection during summer

“…While spring snow cover was were negatively related to marginality, and thus to habitat selectivity, we had expected snow conditions to be more close linked to the inter-annual habitat selection scale due to the large inter-annual variability in snow conditions in the area (Pedersen et al 2016). Lack of noticeable effect may have resulted from the large degree of small-scale habitat heterogeneity in the area (Pedersen et al 2018), allowing muskox to find suitable habitat in most areas irrespective the snow conditions (Beumer et al 2019). It is likely that this small-scale habitat heterogeneity is also the main driver of the increasing selection for habitat observed at the intra-annual (seasonal) scale.…”

“…It is likely that this small-scale habitat heterogeneity is also the main driver of the increasing selection for habitat observed at the intra-annual (seasonal) scale. In spring, onset of the snowmelt period varies according to local topography and habitat type (Kankaanpää et al 2018;Pedersen et al 2018), which creates a spatially heterogeneous pattern of plant emergence (Pedersen et al 2016). Hence, in spring muskox likely finds suitable forage resources throughout the census area.…”

Quantifying energetic and fitness consequences of seasonal heterothermy in an Arctic ungulate

“…These data were produced over the muskox monitoring area in Zackenberg, NE Greenland (Schmidt et al., 2015), by Pedersen et al. (2018) using MicroMet and SnowModel (Liston & Elder, 2006a, 2006b). To capture the typical snow conditions experienced by muskoxen in this area, we take the average daily values over the past 18 years (2000–2018) and use the spatial mean to get one value per day for all animals.…”

Forecasted homogenization of high Arctic vegetation communities under climate change

“…Our results also emphasize the importance of snow in explaining the distribution of plant species in the Arctic. The amount of snow governs the length of the growing season (Pedersen et al, 2018), which affects flower abundance in some species (Semenchuk, Elberling, & Cooper, 2013). Melting snow also results in higher soil moisture in summer.…”