institute/department: "FNWI: Institute for Biodiversity and Ecosystem Dynamics IBED" and publication year: "2008"
| Authors||A.M. Kooijman, M.M. Kooijman-Schouten, G.B. Martinez-Hernandez|
|Title||Alternative strategies to sustain N-fertility in acid and calcaric beech forests: Low microbial N-demand versus high biological activity|
|Journal||Basic and Applied Ecology|
|Faculty||Faculty of Science|
|Institute/dept.||FNWI: Institute for Biodiversity and Ecosystem Dynamics (IBED)|
|Abstract||To challenge the “conventional wisdom” that rates of net N-mineralization increase with pH, we measured net N-mineralization, respiration and/or microbial C and N in four Luxembourg beech forests with similar litter input, but different soil types, using laboratory incubation experiments. Litter input and fungal/bacterial colony ratios were also measured. To test whether the results could be explained by existing theoretical models, equations of C and N dynamics were reformulated to allow estimation of microbial growth efficiency, gross C and N release and microbial uptake, based on measured values of net N-mineralization, respiration and C:N ratios of substrate and microbes.|
Instead of an increase, net N-mineralization rates showed a significant sevenfold decrease from acid to calcaric soil in the organic layer, and a fourfold decrease in the mineral topsoil. At the same time, microbial N-demand increased with pH, as indicated by the significant decrease in net N-mineralization per unit microbe or unit C respired. These results could be explained by theoretical models. In organic layer and mineral topsoil, despite high gross N-release, net N-mineralization rates decreased with pH because of higher microbial immobilization. Increase in microbial N-demand was associated with a decrease in fungal/bacterial colony ratio: the more the bacteria, the higher the microbial N-demand.
Acid and calcaric soils seem to have different strategies to sustain ecosystem N-fertility. In calcaric soil, N-availability to the vegetation seems indeed supported by high biological activity and gross N-release, which is needed to compensate for the potentially high immobilization by bacteria. In acid soil, however, despite low gross N-release, N-availability to the vegetation may not be lower than in calcaric soil, due to high amounts of fungi and low microbial N-demand.
Use this url to link to this page: http://dare.uva.nl/en/record/301731
Contact us about this recordNotify a colleague
Add to bookbag