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Published June 2002 | Published
Journal Article Open

Trends in North American net primary productivity derived from satellite observations, 1982-1998


Net primary productivity (NPP) in North America was computed for the years 1982–1998 using the Carnegie‐Ames‐Stanford approach (CASA) carbon cycle model. CASA was driven by a new, corrected satellite record of the normalized difference vegetation index at 8‐km spatial resolution. Regional trends in the 17‐year NPP record varied substantially across the continent. Croplands and grasslands of the Central Plains and eastern Canadian forests experienced summer increases in NPP. Peak NPP trends in Alaska and western Canada occurred in late spring or early summer, suggesting an earlier onset of the growing season in these regions. Forests and woodlands of the southeastern United States showed NPP increases in spring and fall, also suggesting an increase in the length of the growing season. An analysis of climate variables showed that summer precipitation increased in the Central Plains, indicating that climate changes probably play some role in increasing NPP in this region, though intensive management of agricultural ecosystems has also increased productivity. Similarly, increased summer precipitation possibly increased NPP in eastern Canada, but another possible explanation is forest recovery after insect damage. NPP in the southeastern United States increased in the absence of climate variation. Much of this region consists of aggressively managed forests, with young stand ages and intensive silviculture resulting in increased NPP. The high latitudes of western Canada and Alaska experienced spring warming that could have increased NPP in late spring or early summer.

Additional Information

© 2002 by the American Geophysical Union. Received 22 August 2001; revised 4 February 2002; accepted 4 February 2002; published 14 May 2002. This work was funded by NASA OES grants NAG5‐9356 and NAG5‐9462 and by NASA NIP grant NAG5‐8709. VEMAP and the Ecosystem Dynamics and the Atmosphere Section, National Center for Atmospheric Research, supplied VEMAP climate data.

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Published - Hicke_et_al-2002-Global_Biogeochemical_Cycles.pdf


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October 19, 2023