Richardson Sarah J, Peltzer Duane A, Allen Robert B, McGlone Matt S, Parfitt Roger L
Landcare Research, PO Box 69, Lincoln, Canterbury 8152, New Zealand.
Oecologia. 2004 Apr;139(2):267-76. doi: 10.1007/s00442-004-1501-y. Epub 2004 Jan 31.
The aim of this study was to examine how shifts in soil nutrient availability along a soil chronosequence affected temperate rainforest vegetation. Soil nutrient availability, woody plant diversity, composition and structure, and woody species leaf and litter nutrient concentrations were quantified along the sequence through ecosystem progression and retrogression. In this super-wet, high leaching environment, the chronosequence exhibited rapid soil development and decline within 120000 years. There were strong gradients of soil pH, N, P and C, and these had a profound effect on vegetation. N:P(leaf) increased along the chronosequence as vegetation shifted from being N- to P- limited. However, high N:P(leaf) ratios, which indicate P-limitation, were obtained on soils with both high and low soil P availability. This was because the high N-inputs from an N-fixing shrub caused vegetation to be P-limited in spite of high soil P availability. Woody species nutrient resorption increased with site age, as availability of N and P declined. Soil P declined 8-fold along the sequence and P resorption proficiency decreased from 0.07 to 0.01%, correspondingly. N resorption proficiency decreased from 1.54 to 0.26%, corresponding to shifts in mineralisable N. Woody plant species richness, vegetation cover and tree height increased through ecosystem progression and then declined. During retrogression, the forest became shorter, more open and less diverse, and there were compositional shifts towards stress-tolerant species. Conifers (of the Podocarpaceae) were the only group to increase in richness along the sequence. Conifers maintained a lower N:P(leaf) than other groups, suggesting superior acquisition of P on poor soils. In conclusion, there was evidence that P limitation and retrogressive forests developed on old soils, but N limitation on very young soils was not apparent because of inputs from an abundant N-fixing shrub.
本研究的目的是考察沿土壤年代序列土壤养分有效性的变化如何影响温带雨林植被。通过生态系统的演替和逆行过程，对该序列上的土壤养分有效性、木本植物多样性、组成和结构，以及木本物种叶片和凋落物的养分浓度进行了量化。在这种超湿润、高淋溶的环境中，该年代序列在120000年内呈现出土壤快速发育和退化的过程。土壤pH值、氮、磷和碳存在强烈梯度，这些对植被有深远影响。随着植被从受氮限制转变为受磷限制，叶片氮磷比沿年代序列增加。然而，在土壤磷有效性高和低的土壤上均获得了表明受磷限制的高叶片氮磷比。这是因为固氮灌木输入的高氮导致尽管土壤磷有效性高，但植被仍受磷限制。随着氮和磷有效性的下降，木本物种的养分重吸收随着立地年龄的增加而增加。沿序列土壤磷下降了8倍，磷重吸收效率相应地从0.07%降至0.01%。氮重吸收效率从1.54%降至0.26%，与可矿化氮的变化相对应。通过生态系统演替，木本植物物种丰富度、植被覆盖度和树高增加，随后下降。在逆行过程中，森林变得更矮、更开阔且多样性更低，并且在组成上向耐胁迫物种转变。罗汉松科针叶树是沿序列唯一丰富度增加的类群。针叶树的叶片氮磷比低于其他类群，表明在贫瘠土壤上对磷的获取能力更强。总之，有证据表明在老龄土壤上出现了磷限制和逆行森林，但由于大量固氮灌木的输入，在非常年轻的土壤上氮限制并不明显。
