Ecological significance of plant biomass turnover

生物的分布格局在很大程度上取决于它们科普不同环境条件的能力。对于植物来说，营养物质、水和光的可用性起着重要作用。这些资源的获取得到了很好的研究，但对物种生态学同样重要的是，一旦获得，避免资源损失的能力，尽管研究较少。资源损失与叶和根的死亡率和周转率密切相关。 所描述的研究将集中在根周转。在许多生态系统中，一半以上的植物生物量在地下。然而，地下过程并不容易看到，我们的知识根周转仍然落后于地上过程，特别是在自然环境中。 有越来越多的证据表明，普遍持有的看法，短暂的特点，细根死亡率和缺乏季节性模式并不总是正确的。在北方安大略湿地，许多物种在冬季保持细根，其他物种的根在秋季同步死亡。该项目的基本假设是，这些死亡率模式可以用成本和收益来解释：北方凉爽的土壤温度降低了呼吸成本，长寿的根系对场地的抢占增加了物种的竞争力。在由于干扰而不太可能在冬季生存的栖息地中，任何生存投资都将被浪费，并且根被编程为在秋季死亡。 将评估北方湿地物种的根系死亡率模式，并将其与呼吸成本、冬季干扰的可能性和土壤温度联系起来。将调查暖冬是否会改变死亡率模式。还将评估地上死亡率模式，因为这对于正确理解根系周转模式对整个植物的意义是必要的。预期的结果不仅对我们预测物种行为的能力很重要，而且对准确预测根周转率和由此产生的碳循环和封存在湿地覆盖加拿大北部的大面积。

Distribution patterns of organisms are largely determined by their ability to cope with different environmental conditions. For plants, the availability of nutrients, water and light plays a major role. Acquisition of these resources is well studied, but equally important for the species ecology, though less studied, is the ability to avoid losses of the resources, once acquired. Resource losses are closely related to leaf and root mortality and turnover. The described research will focus on root turnover. In many ecosystems more than half of plant biomass is below ground. However, below-ground processes are not readily visible, and our knowledge of root turnover still lags behind that of above-ground processes, especially in natural environments. There is increasing evidence that the commonly held views of the ephemeral character of fine roots, and a lack of seasonal patterns in fine root mortality are not always true. In Northern Ontario wetlands many species maintain fine roots over the winter, in other species the roots die synchronously in the fall. The hypothesis underlying this project is that these mortality patterns can be explained by costs and benefits: Cool soil temperatures in the north lower the respiration costs, and site pre-emption by long-lived roots increases a species' competitive ability. In habitats with unlikely winter survival due to disturbance, any investment in survival would be wasted, and the roots are programmed to die in the fall. Root mortality patterns of northern wetland species will be assessed, and related to respiration costs, likelihood of disturbance during the winter, and soil temperatures. It will be investigated whether mild winters might change the mortality patterns. Above-ground mortality patterns will also be assessed, as this is necessary for a proper understanding of the significance of root turnover patterns for the whole plant. The expected results are not only important for our ability to predict species behaviour, but also for accurate predictions of root turnover and the resulting carbon cycling and sequestration in the wetlands which cover large areas in Canada's North.