Spatial dynamics of a primary succession: nucleation
Spatial dynamics of a primary succession: nucleation
复制标题
初级演替的空间动力学：成核
DOI：
--
复制
发表时间：
1974
期刊：
影响因子：
--
通讯作者：
R. G. Morrison
中科院分区：
文献类型：
--
作者：
BY G. A. Yarranton;R. G. Morrison
近年来，演替过程中的空间格局变化引起了人们的极大兴趣。这种变化不仅是因为它们本身的原因，而且因为它们可能揭示演替变化的机制。Greig-Smith（1964）总结了目前公认的格局演替变异假说。他认为，变异是由持久物种的集群（通常是克隆）的建立和生长决定的。随着这些团块的扩大，并最终合并，模式的规模将增加，但不一定平稳，在高潮时达到最大值;另一方面，随着年龄的增长，传染规模的范围将增加，模式的强度将下降。Whitford（1949）、Greig-Smith（1952）、Margalef（1958）、Kershaw（1958）、Pielou（1966）和Brereton（1971）的研究支持这一观点。威廉姆斯等人（1969）研究了演替是一个渐进的过程还是分阶段的过程，即植被组成的变化率是否波动？在昆士兰州雨林的次生演替中，他们发现6年后从主要的时间变化到主要的空间变化。如果存在演替阶段，它们可能会影响空间格局的变化：格局可能因阶段而异，但过渡时期的格局也可能与阶段内的格局不同。Shafi和Yarranton（1973）已经证明了在北方森林火灾后的演替过程中不同异质性的阶段。他们发现，一个阶段可能被另一个更大同质性的阶段接替，这意味着模式的规模可能在演替的至少一部分期间减小。安德森（Anderson，1967）也注意到，在一个连续的早期，格局的规模会缩小。莫里森和雅兰顿（1973）指出，沙丘演替在不同阶段之间的过渡期，异质性最大。韦伯、特蕾西和威廉姆斯（1972）提出了一个问题，即演替过程中出现的斑块是否代表了不同的成熟阶段;莫里森和雅兰顿以及沙菲和雅兰顿（1973）都认为，不同阶段之间的过渡在地面上是不均匀的，因此情况确实如此。如果这至少被承认为一种可能性，那么它就建立了演替机制与空间格局变化之间的联系。在此推理的基础上，它被决定，详细检查地面上的植被格局之前，期间和之后的阶段过渡的演替可能不仅澄清的空间格局的顺序，但也有助于阐明演替本身的机制。莫里森（1973）曾描述过的安大略大弯曲沙丘演替被选作这样一项研究。
Changes in spatial pattern during the course of succession have attracted considerable interest in recent years. Such changes are of interest not only for their own sake, but because they may throw light on mechanisms of successional change. Greig-Smith (1964) summarized the currently accepted hypothesis of successional variations in pattern. He suggested that the variations are determined by the establishment and growth of clumps (often clones) of persistent species. As these clumps enlarge, and eventually coalesce, the scale of pattern will increase, not necessarily smoothly, to a maximum at climax; on the other hand, the intensity of pattern will decline as the range of scale of contagion increases with age. Work by Whitford (1949), Greig-Smith (1952), Margalef (1958), Kershaw (1958), Pielou (1966) and Brereton (1971) supports this view. Williams et al. (1969) have examined the question of whether succession is a gradual or stagewise process, i.e. does the rate of change of composition of the vegetation fluctuate? In a secondary succession in a Queensland rain forest they found a change from predominantly temporal to predominantly spatial variation after 6 years. If successional stages exist they are likely to influence variations in spatial pattern: patterns may differ from stage to stage but the pattern at times of transition may also differ from that within stages. Shafi & Yarranton (1973) have demonstrated stages of differing heterogeneity during a post-fire succession in the boreal forest. Their discovery that a stage may be succeeded by another of greater homogeneity implies that the scale of pattern may decrease during at least part of a succession. Anderson (1967) has also noted a decrease in the scale of pattern early in a succession. Morrison & Yarranton (1973) showed that heterogeneity is greatest during a sand dune succession at the transition between stages. Webb, Tracey & Williams (1972) raise the question of whether patches of vegetation occurring in a succession represent different stages of maturity; both Morrison & Yarranton and Shafi & Yarranton (1973) suggest that transitions from stage to stage take place heterogeneously on the ground so that this is indeed the case. If this is admitted as at least a possibility, it establishes the connection between the mechanism of succession and variations in spatial pattern. On the basis of this reasoning it was decided that detailed examination of the pattern of vegetation on the ground before, during and after a stage-to-stage transition in a succession might not only clarify the sequence of spatial pattern but also help to elucidate the mechanism of succession itself. The sand dune succession at Grand Bend, Ontario, previously described by Morrison (1973), was selected for such a study.