Ecole Normale Supérieure, Laboratoire d'Ecologie, UMR 7625, 46 rue d'Ulm, 75230, Paris Cedex 05, France.
Laboratoire de Biogéochimie Isotopique, UMR 7618, Université Pierre et Marie Curie, case no 120, 4 place Jussieu, 75252, Paris Cedex 05, France.
Oecologia. 2001 Apr;127(2):295-304. doi: 10.1007/s004420000598. Epub 2001 Jan 5.
We investigated total primary production and natural abundance of (13)C in soil and plants in the landscape of tiger bush, Niger. Tiger bush is viewed as a natural cyclic succession of several types of vegetation (grasses, living trees and senescent vegetation) occurring over very small areas, on soils with similar chemical and physical characteristics. Under the pioneer front, production was 130 g m(-2) year(-1) of which 23% came from C4 plants; under the thicket of mature trees, grass production was 190 g m(-2) year(-1) (all C3 grasses) and under senescent vegetation, 40 g m(-2) year(-1) of which 1.5% came from C4 plants. Total above- and belowground primary production was estimated to be 890-4880 g m(-2) year(-1) of which 0.4-0.5% was contributed by C4 plants. From 29 to 45% of the soil organic carbon originated from C4 plants even though the contribution of C4 grasses to total primary production did not exceed 0.5%. We suggest that the order in which the different sources of organic matter entered the soil could lead to the overlabelling of soil organic matter with a C4 print. Because all C4 plants are grasses located in the pioneer front of tiger bush bands, their C4 organic matter enters the soil first and fixes onto clays. The C3 organic matter enters the soil several years later and is also fixed by the clays but in a lower proportion. Therefore it is less protected from microbial activity and quickly decomposes. We postulate that the repetition of this pattern over many decades (incorporation of a pure C4 material to soil, followed by the incorporation of a C3-dominated material), leads to the overaccumulation of C4 compounds on the most protective sites.
我们研究了尼日尔虎布什景观中的土壤和植物的总初级生产力和（13）C 的自然丰度。虎布什被视为在非常小的区域上发生的几种类型植被（草、活树和衰老植被）的自然循环演替，这些植被位于具有相似化学和物理特征的土壤上。在先锋前沿，生产力为 130 g m(-2) year(-1)，其中 23%来自 C4 植物；在成熟树木的灌木丛下，草的生产力为 190 g m(-2) year(-1)（均为 C3 草），在衰老植被下，生产力为 40 g m(-2) year(-1)，其中 1.5%来自 C4 植物。估计地上和地下总初级生产力为 890-4880 g m(-2) year(-1)，其中 0.4-0.5%来自 C4 植物。尽管 C4 草对总初级生产力的贡献不超过 0.5%，但仍有 29-45%的土壤有机碳来自 C4 植物。我们认为，不同来源的有机物质进入土壤的顺序可能导致土壤有机物质被 C4 标记。由于所有 C4 植物都是位于虎布什带先锋前沿的草，它们的 C4 有机物首先进入土壤并固定在粘土上。C3 有机物在几年后进入土壤，也被粘土固定，但比例较低。因此，它较少受到微生物活动的保护，并迅速分解。我们假设，这种模式在几十年中反复出现（将纯 C4 物质掺入土壤，然后掺入以 C3 为主的物质），导致最具保护性的部位上 C4 化合物的过度积累。
