Caribou (Rangifer tarandus) rely on the short Arctic growing season to restore body condition, support the demands of lactation, and prepare for the long arctic winter, making them susceptible to even small changes in forage availability or quality. Body condition in the summer and autumn is linked to winter survival rates and fecundity in cows, critical factors in the productivity of caribou populations. Climate change predictions of warmer and wetter northern winters suggest increased snowfall over Alaska's North Slope, which has recently been verified between 1995 and 2017. However, a comprehensive analysis of how deeper snow will affect caribou forage quality is absent across Alaska. In this study, we quantify how snow depth alters the quality and seasonality of caribou forage using a long-term (24 yr) International Tundra Experiment snow depth manipulation to evaluate how winter climate change scenarios may affect tussock tundra systems in northern Alaska. Deeper snow in prior winters leads to increases in growing season leaf N and digestible protein (DP) in deciduous shrubs (Salix spp. and Betula spp.) and graminoids (Carex spp. and Eriophorum spp.), but not evergreen dwarf shrubs (Rhododendron spp. and Vaccinium spp.). Dry matter digestibility varied among species with small differences (<5%) associated with snow depth. Most striking was the discovery that deeper snow in the prior winter increased the duration of DP levels above the minimum threshold for protein gain in caribou by as much as 25 d in Salix pulchra and 6–9 d in Betula nana and Carex bigelowii in late summer and early autumn. Consequently, deeper winter snow may provide an extended window of opportunity for foraging and the accumulation of lean body mass and fat reserves which promote winter survival and successful calving the following spring and potentially improve the productivity of caribou in northern Alaska.

中文翻译：

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下雪的冬天延长了阿拉斯加北极驯鹿的优质草料的秋季供应

驯鹿 ( Rangifer tarandus) 依靠北极较短的生长季节来恢复身体状况，支持泌乳需求，并为漫长的北极冬季做准备，使它们容易受到即使是草料可用性或质量的微小变化的影响。夏季和秋季的身体状况与奶牛的冬季存活率和繁殖力有关，这是驯鹿种群生产力的关键因素。气候变化对北方冬季更暖和更潮湿的预测表明阿拉斯加北坡的降雪量增加，最近在 1995 年至 2017 年间证实了这一点。然而，阿拉斯加全境缺乏对更深的积雪将如何影响驯鹿饲料质量的综合分析。在这项研究中，我们使用长期（24 年）国际苔原实验雪深操纵来量化雪深如何改变驯鹿草料的质量和季节性，以评估冬季气候变化情景可能如何影响阿拉斯加北部的草丛苔原系统。前一个冬天更深的积雪导致落叶灌木生长季叶片氮和可消化蛋白质（DP）的增加（柳属 和Betula spp.）和禾本科植物（Carex spp. 和Eriophorum spp.），但不是常绿矮灌木（Rhododendron spp. 和Vaccinium spp.）。不同物种的干物质消化率不同，与积雪深度相关的差异很小（<5%）。最引人注目的是发现，前一个冬天更深的积雪使驯鹿的 DP 水平持续时间超过了蛋白质增加的最低阈值，在Salix pulchra 中增加了 25 天，在Betula nana和Carex bigelowii 中增加了6-9 天在夏末秋初。因此，更深的冬季积雪可能会为觅食和瘦体重和脂肪储备的积累提供更多的机会，从而促进冬季生存和第二年春天的成功产犊，并有可能提高阿拉斯加北部驯鹿的生产力。