Seed Availability as a Limiting Factor in Forest Recovery Processes in Costa Rica
Seed Availability as a Limiting Factor in Forest Recovery Processes in Costa Rica
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种子供应量是哥斯达黎加森林恢复过程的限制因素
DOI：
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发表时间：
2000
期刊：
影响因子：
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通讯作者：
M. Kuzee
中科院分区：
文献类型：
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作者：
S. Wijdeven;M. Kuzee
被遗弃的牧场和次生林日益成为热带景观的显著特征。在废弃牧场上的森林再生一般很慢，实际上仅限于从外部来源的种子再生，因为农业活动改变了现场条件。我们假设，种子的可用性是一个主要的限制因素，在森林恢复废弃的牧场。通过研究位于哥斯达黎加西北部森林牧场镶嵌区的小牧场（1公顷）的种子库、种子雨和种子捕食，对这一假设进行了检验。牧草种子库中的树木种子密度（21个/m2）远低于邻近次生林种子库中的密度（402个/m2）。在五个星期内，23棵树的种子通过种子雨进入牧场。这一数字是低密度相比，发现在封闭的森林，但高于密度报告在其他研究中，几乎没有种子被发现超过20米的森林边缘。可能是小规模的牧场与附近的种子源和小规模的景观镶嵌增强了种子的传播。捕食限制了牧场的种子密度，42%的木本物种被捕食者吃掉。种子库中的种子密度低，补充受阻，再加上大量损失，严重限制了废弃牧场上的森林恢复。适度的土地利用，以及附近有种子来源的小面积空地可能会加快恢复的速度。然而，建立森林可能仍需要相当长的时间。因此，扩大现有的物种库可能是一个值得的管理策略。
Abandoned pastures and secondary forests are increasingly prominent features of tropical landscapes. Forest regrowth on abandoned pastures is generally slow and virtually limited to regeneration from seeds from external sources, since agricultural activities alter site conditions. We hypothesize that seed availability is a major limiting factor in forest recovery on abandoned pastures. This hypothesis was tested by studying the seed bank, seed rain, and seed predation in a small pasture (1 ha) situated in a forest‐pasture mosaic in northwestern Costa Rica. The tree seed density in the pasture seed bank was much lower (21/m2) than the density in the seed bank of a neighboring secondary forest (402/m2). Within a period of five weeks, 23 tree seeds entered the pasture by seed rain. This number is low compared to densities found in closed forests but higher than densities reported in other studies where virtually no seeds were found beyond 20 m from the forest edge. Possibly the small size of the pasture with seed sources nearby and the small‐scale landscape mosaic enhance seed dispersal. Predation limits the seed density in pastures, with 42% of the woody species consumed by predators. The low seed density in the seed bank, and hampered recruitment combined with significant losses, pose severe restrictions to forest recovery on abandoned pastures. Moderate land use, and small sized clearings with seed sources nearby may increase the pace of recovery. Nevertheless, forest establishment may still take a considerable time. Thus, enlarging the available pool of species may be a worthwhile management strategy.