Department of Ecology, Evolution & Organismal Biology, Iowa State University, Ames, Iowa, United States of America.
Department of Biology, University of Missouri-St. Louis, St. Louis, Missouri, United States of America.
PLoS One. 2014 Jun 19;9(6):e100275. doi: 10.1371/journal.pone.0100275. eCollection 2014.
Young secondary forests and plantations in the moist tropics often have rapid rates of biomass accumulation and thus sequester large amounts of carbon. Here, we compare results from mature forest and nearby 15-20 year old tree plantations in lowland Costa Rica to evaluate differences in allocation of carbon to aboveground production and root systems. We found that the tree plantations, which had fully developed, closed canopies, allocated more carbon belowground - to their root systems - than did mature forest. This increase in belowground carbon allocation correlated significantly with aboveground tree growth but not with canopy production (i.e., leaf fall or fine litter production). In contrast, there were no correlations between canopy production and either tree growth or belowground carbon allocation. Enhanced allocation of carbon to root systems can enhance plant nutrient uptake, providing nutrients beyond those required for the production of short-lived tissues such as leaves and fine roots, and thus enabling biomass accumulation. Our analyses support this deduction at our site, showing that enhanced allocation of carbon to root systems can be an important mechanism promoting biomass accumulation during forest growth in the moist tropics. Identifying factors that control when, where and for how long this occurs would help us to improve models of forest growth and nutrient cycling, and to ascertain the role that young forests play in mitigating increased atmospheric carbon dioxide.
在湿润的热带地区，年轻的次生林和人工林通常具有快速的生物量积累速度，因此会大量固定碳。在这里，我们比较了哥斯达黎加低地成熟森林和附近 15-20 年生人工林的结果，以评估碳在地上生产力和根系分配上的差异。我们发现，完全形成、树冠密闭的人工林比成熟林将更多的碳分配到地下——它们的根系中。这种地下碳分配的增加与地上树木生长显著相关，但与树冠生产（即叶子脱落或细碎屑生产）无关。相比之下，树冠生产与树木生长或地下碳分配之间均没有相关性。增强对根系的碳分配可以增强植物对养分的吸收，提供超出叶子和细根等短命组织所需的养分，从而促进生物量积累。我们的分析在我们的地点支持了这一推论，表明增强对根系的碳分配可以成为促进湿润热带森林生长过程中生物量积累的重要机制。确定控制这种情况何时、何地以及持续多长时间发生的因素将有助于我们改进森林生长和养分循环模型，并确定年轻森林在缓解大气中二氧化碳增加方面的作用。
