In:
Sciences Géologiques. Bulletin, PERSEE Program, Vol. 50, No. 1 ( 1997), p. 73-88
Abstract:
The High Resolution Biosphere Model (HRBM) has been used to pursue three objectives in this contribution to the ESCOBA project. First, validation experiments were carried out for several modules in the modular structure of the HRBM. Point data for productivity and phytomass were used to validate the productivity module. A sensitivity test demonstrated that productivity in the HRBM is mainly limited by the availability of water (precipitation). A regional study of soil organic carbon distribution was performed in collaboration with the ITE at Merlewood Research Station (Hoffstadt et al,, this volume). A second goal has been to investigate the human impact factor on the carbon cycle. The HRBM considers land-use changes and vegetation fires. In the fire module, fire probabilities are derived from climatic variables and biome type. The module has been validated against observed data for seasonal burning in West Africa (Cahoon et ai, 1992 ; Menaut et al., 1991). The HRBM predicts a maximum amount of 1.6 PgC/a from combustion of agricultural wastes in 1980. The demand for an appropriate water cycle module led us to choose an existing land surface model (SiB2, Sellers et al., 1992). We tested this model successfully using long-term point micrometeorological observations. From the response characteristics, modifications were suggested to couple SiB2 to the HRBM. Water cycle and productivity processes are linked through leaf conductance for H₂O and CO₂. The third part of our activities was intended to improve the understanding of stomatal regulation under varying climatic and CO₂ conditions. We carried out lab experiments and field campaigns in Northern Italy and Paraguay. The existence of functional types regarding the response of conductance to internal CO₂ was confirmed, and their distribution along a humidity gradient was recorded for dominating species.
Type of Medium:
Online Resource
ISSN:
0302-2692
DOI:
10.3406/sgeol.1997.1946
Language:
French
Publisher:
PERSEE Program
Publication Date:
1997
detail.hit.zdb_id:
192632-9
SSG:
13
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