Ecological significance of plant biomass turnover

生物体的分布模式在很大程度上取决于它们应对不同环境条件的能力。对于植物来说，养分、水分和光照的可用性起着重要作用。对这些资源的获取进行了很好的研究，但对于物种生态来说，同样重要的是一旦获得资源，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及周转密切相关。 所描述的研究将集中在根周转上。在许多生态系统中，超过一半的植物生物量在地下。然而，地下过程并不容易看到，我们对根周转的知识仍然落后于地上过程，特别是在自然环境中。 越来越多的证据表明，关于细根的短暂特性以及细根死亡缺乏季节性模式的普遍观点并不总是正确的。在安大略省北部的湿地中，许多物种在越冬时保持着良好的根部，而在其他物种中，根部在秋季同步死亡。该项目背后的假设是，这些死亡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，长期存活的根对地点的抢占提高了物种的竞争能力。在由于干扰而不太可能在冬季存活的栖息地，对生存的任何投资都将被浪费，根部被编程为在秋天死亡。 将评估北部湿地物种的根死亡模式，并与呼吸成本、冬季干扰的可能性和土壤温度有关。将对暖冬是否会改变死亡模式进行调查。地上的死亡模式也将被评估，因为这对于正确理解根周转模式对整个植物的重要性是必要的。预期的结果不仅对我们预测物种行为的能力很重要，而且对准确预测根部周转以及由此导致的加拿大北部大片湿地的碳循环和封存也很重要。

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.