Population Densities, Vegetation Green-Up, and Plant Productivity: Impacts on Reproductive Success and Juvenile Body Mass in Reindeer

Global warming is expected to cause earlier springs and increased primary productivity in the Arctic. These changes may improve food availability for Arctic herbivores, but may also have negative effects by generating a mismatch between the surge of high quality food in the spring and the timing of reproduction. We analyzed a 10 year dataset of satellite derived measures of vegetation green-up, population densities, calf body masses and female reproductive success in 19 reindeer (Rangifer tarandus) populations in Northern Norway. An early onset of spring and high peak plant productivity had positive effects on calf autumn body masses and female reproductive success. In addition, body masses and reproductive success were both negatively related to population density. The quantity of food available, as determined by the onset of vegetation green-up and plant productivity over the summer were the main drivers of body mass growth and reproductive success. We found no evidence for an effect of the speed of spring green-up. Nor did we detect a negative mismatch between early springs and subsequent recruitment. Effects of global warming on plant productivity and onset of spring is likely to positively affect sub-Arctic reindeer.

全球变暖预计将导致北极地区春季提前来临，同时提升区域初级生产力。此类变化或可改善北极植食动物的食物可获得性，但也可能引发负面影响：即春季优质食物大量涌现的时间与动物繁殖周期出现错配。本研究分析了挪威北部19个驯鹿（Rangifer tarandus）种群的10年数据集，该数据集包含卫星反演的植被返青期、种群密度、幼崽体重以及雌性繁殖成功率等指标。研究发现，春季提前到来与植物生产力峰值较高，均对驯鹿幼崽秋季体重及雌性繁殖成功率产生正向影响。此外，幼崽体重与繁殖成功率均与种群密度呈负相关关系。植被返青起始时间与夏季植物生产力共同决定了可获得食物总量，这是影响幼崽体重增长与繁殖成功率的核心驱动因素。本研究未发现春季返青速度存在显著影响的证据，同时也未观测到春季提前与后续种群补充之间存在负向错配效应。全球变暖对植物生产力与春季起始时间的影响，或对亚北极地区驯鹿种群产生正向作用。