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Ecological Applications, 11(2), 2001, pp. 356-370 ? 2001 by the Ecological Society of America
MEASURING NET PRIMARY PRODUCTION IN FORESTS: CONCEPTS AND FIELD METHODS
JEFFREY Q. CHAMBERS,4 DEBORAH A. CLARK,1 SANDRA BROWN,2'7DAVID W. KICKLIGHTER,3 JOHN R. THOMLINSON,5AND JIAN NI6 'Department of Biology, University ofMissouri-St. Louis; Mailing address: INTERLINK-341, P.O. Box 02-5635, Miami, Florida 33102 USA 2Department of Natural Resources and Environmental Sciences, University of Illinois, W503 Turner Hall, Urbana, Illinois 61801 USA 3The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543 USA 4National Center for Ecological Analysis and Synthesis, University of California, SantaBarbara, California 93101-3351 USA 5Institutefor Tropical Ecosystem Studies, University of Puerto Rico, P.O. Box 363682, San Juan, Puerto Rico 00936-3682 USA 6Laboratory of Quantitative Vegetation Ecology, Institute of Botany, Chinese Academy of Sciences, Xiangshan Nanxincun 20, 100093 Beijing, P.R. China
Abstract. There are pressing reasons for developing a better understanding of net primaryproduction (NPP) in the world's forests. These ecosystems play a large role in the world's carbon budget, and their dynamics, which are likely to be responding to global changes in climate and atmospheric composition, have major economic implications and impacts on global biodiversity. Although there is a long history of forest NPP studies in the ecological literature, current understanding ofecosystem-level production remains limited. Forest NPP cannot be directly measured; it must be approached by indirect methods. To date, field measurements have been largely restricted to a few aspects of NPP; methods are still lacking for field assessment of others, and past studies have involved confusion about the types of measurements needed. As a result, existing field-based estimates of forest NPPare likely to be significant underestimates. In this paper we provide a conceptual framework to guide efforts toward improved estimates of forest NPP. We define the quantity NPP* as the summed classes of organic material that should be measured or estimated in field studies for an estimate of total NPP. We discuss the above- and belowground components of NPP* and the available methods for...