Carbon pools and ecosystem properties along a latitudinal gradient in northern Scots pine (Pinus sylvestris) forests

A significant portion of the Earth's carbon is in forested terrestrial ecos ystems. Carbon fluxes to and from these ecosystems in response to climate c hange have the potential to alter global climate. To understand how forest carbon budgets may be affected by climate, we observed patterns of carbon s torage, forest structure, and composition in Scots pine forest ecosystems a t nine sites along a northern latitudinal gradient (50-70 degrees N) crossi ng Poland, Lithuania, Latvia, Estonia, and Finland. This gradient is charac terized by a northward decline in average annual temperature (Delta = ca. 9 degrees C) and precipitation (Delta = ca. 300 mm). Total ecosystem carbon, decomposition rates, and litterfall amounts all decreased nonlinearly with increasing latitude. Plant species richness in the ground flora also decre ased with increasing latitude. However, the percent cover of lower canopy v egetation varied asystematically with respect to latitude, temperature, or precipitation. Our results are largely consistent with models and analyses indicating that northern latitude forests may respond to predicted climate changes with increased carbon sequestration. In the short term, however, th ese forests may be a source rather than a sink for atmospheric carbon as th e relative distribution of C among ecosystem components adjusts in response to changing climatic conditions. (C) 2000 Elsevier Science B.V. All rights reserved.