Carleton College, Department of Biology, One North College Street, Northfield, Minnesota 55057, USA.
Ecology. 2010 Feb;91(2):448-59. doi: 10.1890/08-1839.1.
Black spruce (Picea mariana) is the most abundant tree species in the boreal biome, but little is known about how climate warming may change recruitment in peatlands, especially those affected by permafrost thaw. We used results from a seven-year study in northern Manitoba, Canada, to address the following questions: (1) What is the relative importance of early life history transitions on P. mariana recruitment? (2) How are these transitions mediated by biological and environmental factors, including competition, facilitation, disease, herbivory, water table depth, and soil nutrients? (3) Do interactions among these factors create additional recruitment limitations beyond those imposed by environmental factors changing with climate warming, such as hydrology? Seed rain was measured over six years on forested permafrost plateaus and in neighboring collapse scar bogs. Seed germination and seedling survival and growth were measured over 4-5 years in collapse scars and assessed across a three-level water table treatment. Survival and growth experiments examined additional combinations of above- and belowground vascular plant competition and fertilizer addition. Results showed that failure of germination and survival on growing moss surfaces and reduced survival of seedlings in wetter microsites were primary constraints. Seed influx was significantly lower in collapse scars but likely did not limit recruitment. Biological and environmental factors mediating these life history transitions also differed in relative importance, and interactions among them tended to amplify recruitment limitation. Seedling survival was most strongly controlled by fast-growing mosses in wet microsites but also was influenced by apparent drowning in wet plots, herbivory, and loss of foliage caused by a fungal pathogen. Seedling growth was strongly controlled by water table depth, nutrient and competition levels, and fungal pathogens. Multiple, interacting factors will affect P. mariana establishment in boreal peatlands during climate warming. Generalizations about recruitment relying on few environmental gradients sensitive to climate change, such as water table, may therefore not fully capture the complexities of establishment.
黑云杉（Picea mariana）是北方生物群落中最丰富的树种，但对于气候变暖如何改变泥炭地，尤其是受永冻层融化影响的泥炭地的更新，人们知之甚少。我们利用加拿大马尼托巴省北部一项为期七年的研究结果，提出了以下三个问题：（1）在黑云杉的更新过程中，早期生活史过渡的相对重要性是什么？（2）生物和环境因素（包括竞争、促进、疾病、食草、水位深度和土壤养分）如何介导这些过渡？（3）这些因素之间的相互作用是否会在由气候变化引起的环境因素（如水文）变化之外，对繁殖产生额外的限制？在六年的时间里，我们在森林永冻高原和相邻的崩塌沼泽地测量了种子雨。在崩塌的凹痕中，我们在 4-5 年内测量了种子发芽和幼苗的存活和生长情况，并在三个水位处理水平上进行了评估。在生长的苔藓表面上发芽和存活失败以及在较潮湿的微生境中幼苗存活下降是主要限制因素。幼苗在潮湿微生境中的生长受到快速生长的苔藓的强烈控制，但也受到潮湿地段明显淹没、食草和真菌病原体导致的叶片损失的影响。幼苗的生长受水位深度、养分和竞争水平以及真菌病原体的强烈控制。在气候变暖期间，多种相互作用的因素将影响北方泥炭地黑云杉的建立。因此，仅依靠对气候变化敏感的少数环境梯度（如水位）来概括繁殖情况，可能无法完全捕捉到建立的复杂性。
