Vucetich John A, Peterson Rolf O
School of Forest Resources and Environmental Science, Michigan Technological University, Houghton, MI 49931, USA.
Proc Biol Sci. 2004 Jan 22;271(1535):183-9. doi: 10.1098/rspb.2003.2589.
Long-term, concurrent measurement of population dynamics and associated top-down and bottom-up processes are rare for unmanipulated, terrestrial systems. Here, we analyse populations of moose, their predators (wolves, Canis lupus), their primary winter forage (balsam fir, Abies balsamea) and several climatic variables that were monitored for 40 consecutive years in Isle Royale National Park (544 km2), Lake Superior, USA. We judged the relative importance of top-down, bottom-up and abiotic factors on moose population growth rate by constructing multiple linear regression models, and calculating the proportion of interannual variation in moose population growth rate explained by each factor. Our analysis indicates that more variation in population growth rate is explained by bottom-up than top-down processes, and abiotic factors explain more variation than do bottom-up processes. Surprisingly, winter precipitation did not explain any significant variation in population growth rate. Like that detected for two Norwegian ungulate populations, the relationship between population growth rate and the North Atlantic Oscillation was nonlinear. Although this analysis provides significant insight, much remains unknown: of the models examined, the most parsimonious explain little more than half the variation in moose population growth rate.
对于未受人为干扰的陆地生态系统，长期同时测量种群动态以及相关的自上而下和自下而上的过程十分罕见。在此，我们分析了美国苏必利尔湖皇家岛国家公园（面积544平方公里）中驼鹿种群、其捕食者（狼，犬属灰狼）、主要冬季食物（香脂冷杉，冷杉属）以及连续40年监测的几个气候变量。我们通过构建多元线性回归模型，并计算每个因素所解释的驼鹿种群增长率年际变化比例，来判断自上而下、自下而上和非生物因素对驼鹿种群增长率的相对重要性。我们的分析表明，自下而上过程比自上而下过程解释了更多的种群增长率变化，并且非生物因素比自下而上过程解释了更多的变化。令人惊讶的是，冬季降水量并未解释种群增长率的任何显著变化。与在两个挪威有蹄类动物种群中检测到的情况一样，种群增长率与北大西洋涛动之间的关系是非线性的。尽管该分析提供了重要见解，但仍有许多未知之处：在所检验的模型中，最简约的模型解释的驼鹿种群增长率变化仅略高于一半。
