Can a snow structure model estimate snow characteristics relevant to reindeer husbandry?

Sirpa Rasmus,Jukka Siitari,Jouko Kumpula

doi:10.7557/2.34.1.2675

Abstract

Snow affects foraging conditions of reindeer e.g. by increasing the energy expenditures for moving and digging work or, in contrast, by making access of arboreal lichen easier. Still the studies concentrating on the role of the snow pack structure on reindeer population dynamics and reindeer management are few. We aim to find out which of the snow characteristics are relevant for reindeer in the northern boreal zone according to the experiences of reindeer herders and is this relevance seen also in reproduction rate of reindeer in this area. We also aim to validate the ability of the snow model SNOWPACK to reliably estimate the relevant snow structure characteristics. We combined meteorological observations, snow structure simulations by the model SNOWPACK and annual reports by reindeer herders during winters 1972-2010 in the Muonio reindeer herding district, northern Finland. Deep snow cover and late snow melt were the most common unfavorable conditions reported. Problematic conditions related to snow structure were icy snow and ground ice or unfrozen ground below the snow, leading to mold growth on ground vegetation. Calf production percentage was negatively correlated to the measured annual snow depth and length of the snow cover time and to the simulated snow density. Winters with icy snow could be distinguished in three out of four reported cases by SNOWPACK simulations and we could detect reliably winters with conditions favorable for mold growth. Both snow amount and also quality affects the reindeer herding and reindeer reproduction rate in northern Finland. Model SNOWPACK can relatively reliably estimate the relevant structural properties of snow. Use of snow structure models could give valuable information about grazing conditions, especially when estimating the possible effects of warming winters on reindeer populations and reindeer husbandry. Similar effects will be experienced also by other arctic and boreal species.

Highlights

Semi-domesticated reindeer (Rangifer tarandus tarandus) in northern Finland live in an environment where continuously changing weather and foraging conditions signi cantly a ect populations
We used combination of meteorological observations, snow structure simulations and reports by reindeer herders to study the relevance of snow properties on reindeer herding in Muonio reindeer herding district in northern Finland
Suitability and reliability of a snow structure model SNOWPACK was evaluated on the basis of the measured snow density observations and by comparing the simulated snow characteristics to annual reproduction rate by reindeer and to observations of herders concerning the snow conditions

Summary

Introduction

Semi-domesticated reindeer (Rangifer tarandus tarandus) in northern Finland live in an environment where continuously changing weather and foraging conditions signi cantly a ect populations. Is in turn is a ected both by the amount of the main winter forage, (reindeer lichens Cladina spp.), and by the snow conditions on pastures (Skogland, 1978; Helle & Tarvainen, 1984; Kumpula, 2001). Both reindeer and its northern American relative, caribou (Rangifer tarandus), are morphologically and behaviorally adapted to Arctic ecosystems (Telfer & Kensall, 1984). The deep snow cover and late snow melt in spring can cause high winter mortality (Adamczewski et al, 1988; Kumpula & Colpaert, 2003; Helle & Kojola, 2008) and low calf production (Adams & Dale 1998; Post & Stenseth, 1999; Aanes et al, 2000; Kumpula, 2001) of both caribou and reindeer.

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