Mechanisms of Patch Maintenance in Old-Growth Hemlock-Hardwood Forests

古老铁杉阔叶林斑块维护机制

• 批准号: 9423065
• 负责人: Peter Reich
• 金额: $ 29.73万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-03-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9423065&HistoricalAwards=false
• 关键词: Mechanisms; Patch; Maintenance; Old; Growth

le for toolbar execution Show multiple pages Toggle zoom-in zoom-out mode Toggles full screen2Attempts to make the document fit on one less page Moves to the next table cell Moves to the previous tablecell*Moves to the first cell in the current row)Moves 9423065 Reich Mono-dominant patches of eastern hemlock and sugar maple may persist for millennia in a stable forest mosaic pattern. This study will explore the mechanisms underlying the maintenance of this patchy mosaic, focusing primarily on feedbacks and the functional underpinnings for recruitment success. Working in mesic forests in Michigan and Wisconsin, the study will determine whether stable patch structure may be maintained by positive feedbacks between canopy properties, resource availability, differences in species ecophysiology, and population dynamics. Specifically this study will determine if these factors result in success of sugar maple recruitment beneath sugar maple, but not hemlock canopies, and of hemlock recruitment beneath hemlock, but not sugar maple. The study will also test the resource reduction/ tolerance hypothesis of community dynamics under a multiple resource, light and nitrogen scenario. In a series of field and greenhouse studies, the following hypotheses will be tested: (1) light and N availability is lower on average beneath hemlock than sugar maple canopies. (2) Small-seeded hemlock will establish beneath hemlock overstories on suitable microsites and persist due to great tolerance of combined low light and N levels. In contrast, seedlings of large seeded sugar maple can establish beneath hemlock overstories, but fail to maintain positive growth rates due to low N and light availability. (3) Hemlock seedling recruitment will fail beneath sugar maple canopies because of dense leaf litter and lack of suitable nurse logs. In contrast, greater N availability beneath sugar maple canopies enables sugar maple seedlings to maintain positive growth rates under deep shade. (4) Yellow birch will fail to establish in deep shade in either patch type and will regenerate in high resource conditions only on suitable microsites. (5) Seedling survival is a function of relative growth rate, which in turn is a function of light and N availability and of variation in seedling metabolism and allocation. The minimum light needed for survival is influenced by N availability, most in yellow birch, less in sugar maple, and least in hemlock. %%% The combination of field observations, field manipulations, and greenhouse experiments will yield a superb combination of detail to more fully understand the natural dynamics of northern forests. This project is unique in its excellent attempt to link ecosystem processes, physiological ecology and community dynamics. The results also will have direct bearing on the physiological attributes of commercially valuable tree species, such as sugar maple.

le用于工具栏执行显示多个页面切换放大缩小模式切换全屏2尝试使文档适合少一页移动到下一个表格单元格移动到上一个表格单元格 * 移动到当前行的第一个单元格）移动9423065赖希东部铁杉和糖枫的单优势斑块可能以稳定的森林镶嵌模式持续数千年。本研究将探讨维持这种不规则马赛克的机制，主要关注招聘成功的反馈和功能基础。在密歇根州和威斯康星州的中温带森林工作，研究将确定是否稳定的补丁结构可以保持冠层特性，资源的可用性，物种的生态生理学的差异，和人口动态之间的正反馈。具体来说，这项研究将确定这些因素是否会导致成功的糖枫树招聘下糖枫树，但不是铁杉树冠，铁杉招聘下铁杉，但不是糖枫树。该研究还将测试在多种资源，光和氮的情况下，社区动态的资源减少/耐受性假设。 在一系列的田间和温室研究中，将检验以下假设：（1）铁杉树冠下的光和氮的有效性平均低于糖枫树冠。(2)小种子铁杉将建立铁杉overstories下合适的微型网站，并坚持由于结合低光和N水平的大容忍。相比之下，幼苗的大种子糖枫树可以建立铁杉overstories下，但未能保持积极的增长率，由于低N和光的可用性。(3)铁杉幼苗招聘将失败糖枫树树冠下，因为密集的落叶和缺乏合适的护士日志。相比之下，更大的N可用性糖枫树树冠下，使糖枫树幼苗保持积极的增长率在深阴影下。(4)黄桦将无法建立在深阴影中的任何补丁类型，并会在高资源条件下，只有在合适的微型网站再生。(5)幼苗存活率是相对生长速率的函数，而相对生长速率又是光和氮的有效性以及幼苗代谢和分配变化的函数。 生存所需的最低光照受氮供应的影响，最在黄桦树，糖枫少，铁杉最少。 野外观察、野外操作和温室实验的结合将产生一个极好的细节组合，以更全面地了解北方森林的自然动态。该项目是独一无二的，因为它很好地尝试将生态系统过程、生理生态学和群落动态联系起来。这些结果也将直接关系到商业上有价值的树种，如糖枫的生理属性。