Clark C J, Poulsen J R, Levey D J, Osenberg C W
School of Natural Resources and the Environment, University of Florida, Gainesville, Florida 32611, USA.
Am Nat. 2007 Jul;170(1):128-42. doi: 10.1086/518565. Epub 2007 May 21.
We examine the relative importance of processes that underlie plant population abundance and distribution. Two opposing views dominate the field. One posits that the ability to establish at a site is determined by the availability of suitable microsites (establishment limitation), while the second asserts that recruitment is limited by the availability of seeds (seed limitation). An underlying problem is that establishment and seed limitation are typically viewed as mutually exclusive. We conducted a meta-analysis of seed addition experiments to assess the relative strength of establishment and seed limitation to seedling recruitment. We asked (1) To what degree are populations seed and establishment limited? (2) Under what conditions (e.g., habitats and life-history traits) are species more or less limited by each? (3) How can seed addition studies be better designed to enhance our understanding of plant recruitment? We found that, in keeping with previous studies, most species are seed limited. However, the effects of seed addition are typically small, and most added seeds fail to recruit to the seedling stage. As a result, establishment limitation is stronger than seed limitation. Seed limitation was greater for large-seeded species, species in disturbed microsites, and species with relatively short-lived seed banks. Most seed addition experiments cannot assess the relationship between number of seeds added and number of subsequent recruits. This shortcoming can be overcome by increasing the number and range of seed addition treatments.
我们研究了构成植物种群丰度和分布基础的过程的相对重要性。两种相反的观点主导着该领域。一种观点认为，在某一地点定殖的能力取决于合适微生境的可利用性（定殖限制），而另一种观点则认为，补充更新受到种子可利用性的限制（种子限制）。一个潜在的问题是，定殖限制和种子限制通常被视为相互排斥的。我们对种子添加实验进行了荟萃分析，以评估定殖限制和种子限制对幼苗补充更新的相对强度。我们提出了以下问题：（1）种群在多大程度上受到种子和定殖的限制？（2）在何种条件下（例如，生境和生活史特征），物种受每种限制的程度更高或更低？（3）如何更好地设计种子添加研究，以增强我们对植物补充更新的理解？我们发现，与先前的研究一致，大多数物种受到种子限制。然而，种子添加的效果通常较小，而且大多数添加的种子未能发育到幼苗阶段。因此，定殖限制比种子限制更强。对于大种子物种、微生境受到干扰的物种以及种子库寿命相对较短的物种，种子限制更大。大多数种子添加实验无法评估添加种子的数量与后续补充更新数量之间的关系。通过增加种子添加处理的数量和范围，可以克服这一缺点。
