ALLOCATION AND THE TRANSIENT DYNAMICS OF SUCCESSION ON POOR SOILS
ALLOCATION AND THE TRANSIENT DYNAMICS OF SUCCESSION ON POOR SOILS
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DOI：
10.2307/1937382
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发表时间：
1990-06-01
期刊：
影响因子：
4.8
通讯作者：
TILMAN, D
中科院分区：
文献类型：
--
作者：
GLEESON, SK;TILMAN, D
生物量和氮素在叶、根、茎和生殖中的分配是在明尼苏达州[美国]沙地上跨越前60年次生演替的35个田间时间序列中确定的。在演替过程中，叶和根的生物量(克/平方米)增加，生殖生物量下降，茎中生物量保持不变。由于根生物量的增长速度是叶生物量的2倍，因此在演替过程中，根在总生物量中所占的比例增加，而在叶、生殖和茎中所占的比例下降。在另一项研究中，以物种为基础确定了演替过程中常见的46种物种的生物量分配。研究表明，在演替过程中，根的分配比例增加，生殖分配和茎分配的比例下降。这些变化伴随着演替过程中土壤全氮的增加和对土壤表面透光率的下降。根系分配的增加和生殖分配的减少表明，在这些养分贫乏的土壤上，演替处于短暂的定殖和竞争置换的动态中，演替后期的物种由于较高的根系分配而成为优势的氮素竞争对手。根、茎、叶和种子之间的分配权衡可能导致种子和叶分配较高的物种最初的优势，可能是因为更大的定殖率和/或最大生长速度。因此，这种演替与肥沃土壤上的演替明显不同，对肥沃土壤上的演替来说，树干分配越来越重要。这些结果与解释改良土壤早期演替模式的资源比假说相矛盾。
Biomass and nitrogen allocation to leaf, root, stem, and reproduction was determined in a 35-field chronosequence that spans the first 60 yr of secondary succession on a Minnesota [USA] sand plain. Biomass (grams per square metre) in leaf and root increased during succession, but reproductive biomass declined, and that in stem remained constant. Because root biomass increased twice as rapidly as leaf biomass, the proportion of total biomass in root increased during succession, whereas that in leaf, reproduction, and stem declined. In an additional study, biomass allocation was determined on a species-by-species basis for 46 species common at different times during succession. This study showed a similar pattern of increasing proportional root allocation and declining proportional reproductive and stem allocation during succession. These changes were accompanied by an increase in total soil nitrogen and a decrease in light penetration to the soil surface during succession. Increasing root allocation and decreasing reproductive allocation suggest that succession on these nutrient-poor soils in the transient dynamics of colonization and competitive displacement, with later successional species being superior nitrogen competitors because of higher root allocation. Allocation trade-offs between root, stem, leaf, and seed can lead to initial dominance by species with high seed and leaf allocation, presumably because of greater colonization and/or maximal growth rates. Thus, this succession differs markedly from successions on rich soils, for which stem allocation is increasingly important. These results contradict the resource ratio hypothesis as an explanation for the pattern of early succession on improverished soils.