Functional Ecology 2000 14, 87– 96 © 2000 British Ecological Society 87 Blackwell Science, Ltd Carbon and water exchanges of two contrasting central Siberia landscape types: regenerating forest and bog R. VALENTINI,*† S. DORE,* G. MARCHI,* D. MOLLICONE,* M. PANFYOROV,‡ C. REBMANN,‡ O. KOLLE‡ and E.-D. SCHULZE‡ *Department of Forest Science and Environment, University of Tuscia, 01100 Viterbo, Italy and ‡Max-Planck, Institute for Biogeochemistry, PO Box 100164, 07701, Jena, Germany Summary 1. In central Siberia Pinus sylvestris forests and bogs are common elements of the landscape and they show different functional behaviour in terms of energy and carbon exchanges. 2. The two ecosystems show a remarkable difference in energy dissipation, with average Bowen ratios of 0·6 and 2·9, respectively. 3. The alternation of bogs and forests with different energy partition at the surface could affect rainfall distribution and the disturbance regimes (lightening and fires) and drive the ecology of such a complex landscape. 4. During summer, water shortage and poor nutrient conditions in the soil heavily affect carbon exchange rates of the regenerating forest (– 7·7 mmol m –2 day –1 ). Con- sequently the bog becomes a significant dominant carbon sequestration element of this particular landscape with higher rates of carbon uptake (– 104·2 mmol m –2 day –1 ). Key-words: Bog, carbon balance, eddy covariance, Pinus sylvestris, regenerating forest, Siberia Functional Ecology (2000) 14, 87– 96 Introduction Forests, in terrestrial vegetation, have the maximum potential of carbon sequestration, contributing about 60% of the total net primary production of terres- trial ecosystems (Melillo et al. 1993) and play a prominent role in the global terrestrial global carbon cycle. It has been suggested that the imbalance between total carbon found in the atmosphere and fossil fuel emissions can be explained by a terrestrial sink of about 2 Gt C year –1 located in the Northern Hemisphere forest (Tans, Fung & Takahashi 1990; Schimel 1995). Siberia covers 1280 × 10 9 ha, of which 48% is for- ested. These forests constitute about 20% of total world forest and about 20% of global total net prim- ary production (Shvidenko & Nilsson 1994). The central Siberian area west of the Jenisei river, consist- ing in an alternation of Pinus sylvestris L. forests and wetlands, extends for about 2000 km to the Ural mountains and drives hydrological and carbon cycles. Rainfall distribution in the area follows a contin- ental regime and large air masses travelling from west to east are enriched by the water transpired by the terrestrial vegetation (Budiko 1982). Forest fires, pests and diseases are important natural drivers of land use/cover change. However, forest logging impacts the carbon balance of the region. About 800 × 10 3 ha are harvested annually as clearcuts, in Siberia. Nearly 85% of the clearcut operations are on a large scale and carried out with heavy equipment; these operations destroy between 50 and 80% of the existing undergrowth and disturb the carbon stored in the soil. For this reason forest resources in Siberia are deteriorating slowly but significantly, with concerns expressed for the sustain- ability of the eco-hydrological environment (Shvidenko & Nilsson 1994). Recently developments in micrometeorological theory and techniques have made the study of exchanges of carbon and energy between the bio- sphere and atmosphere more routine and reliable. In particular eddy covariance measurements allow the simultaneous measurements of water and carbon exchanges at the canopy level, integrating processes at the scale of kilometres (Baldocchi et al. 1996). This paper investigates two contrasting land-cover types, a regenerating forest and a bog, in the central Siberia region, during July 1996. The energy dissipa- tion and the effect of the dry season on carbon and water exchanges have been analysed to provide a first assessment of functional responses at landscape level. Owing to the limited period of observation, this paper has to be considered a preliminary attempt to investigate the biospheric exchanges of the Siberian landscape. †Author to whom correspondence should be addressed.