Litterfall along topographic gradients at lower Bisley

Litterfall (fine and coarse) due to Hurricane Hugo and subsequent fine annual litterfall inputs (1, 2 and 5 yr after Hugo) were determined for two sites (El Verde and Bisley) in the Luquillo Experimental Forest in Puerto Rico. Litter transfers into streams, riparian and upslope areas were determined within each catchment. The recovery rate of aboveground fine litterfall (leaf, fine wood <1 cm diameter, and other miscellaneous inputs) to predisturbance levels were determined 1, 2, and 5 yr after Hurricane Hugo. The amount of total litter transfers and their individual components into the riparian and upslope areas due to Hurricane Hugo varied significantly by catchments within the Luquillo Experimental Forest. At El Verde, 26-39%, 31- 35%, 14-35% and 7-12% of the total litter transfers were contributed by leaf litter, fine wood, coarse wood and fine roots, respectively. At Bisley, 28-31%, 26-29%, 33-35% and 8-10% of the litter transfers were contributed by the same categories. Differential decay rates contributed to the relative importance of fine and coarse litter inputs. The recovery of fine aboveground litterfall to pre-hurricane levels after 5 yr varied by topographic location (streams had the slowest recovery, upslope areas the highest) and catchment (El Verde: 55-77%; Bisley: 39-82% of pre-hurricane values). Support for this work was provided by grants BSR-8811902, DEB-9411973, DEB-9705814 , DEB-0080538, DEB-0218039 , DEB-0620910 , DEB-1239764, DEB-1546686, and DEB-1831952 from the National Science Foundation to the University of Puerto Rico as part of the Luquillo Long-Term Ecological Research Program. Additional support provided by the University of Puerto Rico and the International Institute of Tropical Forestry, USDA Forest Service.

本研究针对波多黎各卢奎略实验林的两个样地（埃尔韦尔德与比斯利），测定了雨果飓风引发的凋落物 (litterfall)（细粒与粗粒）输入量，以及飓风过后1、2、5年的年度细粒凋落物输入量。在每个集水区 (catchment) 内，测定了凋落物向溪流、河岸带 (riparian) 与上坡区域 (upslope area) 的迁移量；并于飓风过后1、2、5年，测定了地上细粒凋落物 (aboveground fine litterfall)（叶片、直径<1cm的细木及其他杂项输入物）恢复至扰动前水平的速率。雨果飓风引发的、输入至河岸带与上坡区域的总凋落物迁移量及其各组分，在卢奎略实验林的不同集水区间存在显著差异。在埃尔韦尔德样地，总凋落物迁移量中分别有26%~39%、31%~35%、14%~35%及7%~12%来自叶片凋落物、细木、粗木与细根；在比斯利样地，上述同类组分对凋落物迁移量的贡献占比分别为28%~31%、26%~29%、33%~35%与8%~10%。分解速率 (decay rate) 的差异决定了细粒与粗粒凋落物输入物的相对重要性。地上细粒凋落物在飓风过后5年恢复至飓风前水平的程度，因地形位置 (topographic location)（溪流区域恢复最慢，上坡区域恢复程度最高）与集水区而异：埃尔韦尔德样地为扰动前水平的55%~77%，比斯利样地为39%~82%。
本研究得到美国国家科学基金会 (National Science Foundation) 拨付给波多黎各大学的多项资助（BSR-8811902、DEB-9411973、DEB-9705814、DEB-0080538、DEB-0218039、DEB-0620910、DEB-1239764、DEB-1546686及DEB-1831952），相关资助为卢奎略长期生态研究计划的一部分。额外资助来自波多黎各大学与美国农业部林务局 (USDA Forest Service) 下属的热带林业国际研究所 (International Institute of Tropical Forestry)。