Why Does Forest Growth Decline with Stand Age? An Experimental Test of Carbon Acquisition and Allocation Over Stand Development

为什么森林生长会随着林龄而下降？

• 批准号: 9306356
• 负责人: James Fownes
• 金额: $ 60万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-01-15 至 1997-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9306356&HistoricalAwards=false
• 关键词: Why; Does; Forest; Growth; Decline

9306356 Fownes Why does forest growth decline with stand age? An experimental test of carbon acquisition and allocation over stand development. the overall goal of this research is to understand the production biology of even-aged forests. Biomass accumulation rates of even-aged forests typically increase at first, peak, and then decline. The conventional explanation has been that leaf area index, and thus gross while woody biomass, and thus respiration, continues to increase until relatively little photosynthate remains for new growth. However, this proposition has not been tested directly. Recent evidence, both direct estimates of stand respiration and indirect indices of growth efficiency, suggest that this explanation cannot be correct. We propose an integrated experimental test of three hypotheses: (1) that respiration does account for declining growth rate, (2) that nutrient availability decreases over time, thereby lowering leaf area, photosynthesis, or both, or (3) that the pattern is caused by shifting allocation of net production to infrequently-measured components, particularly roots. %%% The significance of the research lies in answering one of the fundamental questions in forest ecosystem biology. If the respiration hypothesis is refuted, conventional explanations of stand growth dynamics will be overthrown. Understanding the controls of stand growth and carbon allocation will be crucial for predicting the response of tropical forest to changing climate. The practical significance of the research will be in formulating a comprehensive approach to plantation management, and in answering such questions as how to optimize the plant-density/ rotation-length/ harvest-size relationship, and whether late-rotation fertilization is likely to be beneficial. The region around the experimental site is receiving serious consideration for a commercial Eucalyptus plantation industry, and results will be readily adopted into planning and management.

9306356 Fownes为什么森林生长会随着林龄的增长而下降？ 林分发展过程中碳获取与分配的试验研究。 这项研究的总体目标是了解同龄森林的生产生物学。 同龄林的生物量积累速率通常先增加，达到峰值，然后下降。 传统的解释是，叶面积指数，从而毛，而木本生物量，从而呼吸，继续增加，直到相对较少的光合作用剩下的新的增长。 然而，这一命题尚未得到直接检验。 最近的证据，直接估计林分呼吸和间接指数的增长效率，表明这种解释是不正确的。 我们提出了一个综合的实验测试的三个假设：（1），呼吸没有帐户下降的增长率，（2）养分的可用性随着时间的推移而下降，从而降低叶面积，光合作用，或两者兼而有之，或（3）的模式是由转移分配的净生产不经常测量的组件，特别是根。 这项研究的意义在于回答了森林生态系统生物学的一个基本问题。 如果呼吸假说被推翻，林分生长动态的传统解释将被推翻。 了解林分生长和碳分配的控制对于预测热带森林对气候变化的响应至关重要。 该研究的实际意义在于制定一个综合的种植园管理方法，并回答如何优化植物密度/轮伐期长度/收获量之间的关系，以及后期施肥是否可能有益等问题。 实验地点周围的区域正在接受商业桉树种植园业的认真考虑，其结果将很容易被纳入规划和管理。