Carbon and nitrogen dynamics in ageing earthworm casts in grasslands of the eastern plains of Colombia

被引:70
作者
Decaëns, T
Rangel, AF
Asakawa, N
Thomas, RJ
机构
[1] IRD, Lab Ecol Sols Tropicaux, F-93143 Bondy, France
[2] CIAT, Unidad Suelos & Plantas, Cali 6713, Colombia
关键词
earthworms; soil fertility; soil organic matter dynamics; nitrogen dynamics; savanna;
D O I
10.1007/s003740050582
中图分类号
S15 [土壤学];
学科分类号
0903 ; 090301 ;
摘要
The effects of a large species of anecic earthworm, Martiodrilus carimaguensis Jimenez and Moreno, on soil C and N dynamics were investigated in a native savanna and a man-made pasture of the eastern plains of Colombia. We compared, across time (11 months), the total C, total N, NH4+ and NO3- contents in the earthworm casts, the underlying soil and the adjacent soil. Additional sampling of root biomass and macrofauna was performed. In the two management systems, the total C and N contents were higher in casts (4.33-7.50%) than in the bulk soil (2.81-4.08%), showing that the earthworms selected food substrates with high organic contents. In general, C contents significantly increased during cast ageing (+100%), possibly because of CO2 fixation processes, dead root accumulation and/or macrofaunal activities in casts. In fresh casts, NH4+ levels were very high (294.20-233.98 mu g g(-1) dry cast) when compared to the soil (26.96-73.95 mu g g(-1) dry soil), due to the intense mineralisation processes that occurred during the transit of soil and organic matter through the earthworm gut. During the first week of cast ageing, NH4+ levels sharply decreased, while NH3- levels showed successive peaks in the casts, the underlying soil and the adjacent soil. These results suggested the rapid production of NO3- by nitrification processes in the fresh casts, followed by diffusion to the nearby soil, first vertically, then horizontally. After 2 weeks of cast ageing, NH4+ and NO3- levels only showed slight variations, likely because of organic matter protection in stable dry casts. The root biomass was higher (1.6-4.7 times) below the old earthworm casts. The ecological significance of these results is discussed.
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页码:20 / 28
页数:9
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