Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 12/10/2007
Publication Date: 8/23/2008
Citation: Lauenroth, W.K., D.G. Milchunas, O.E. Sala, I.C. Burke, and J.A. Morgan. 2008. Chapter 12. Net primary production in the shortgrass steppe: A long-term perspective. Oxford University Press, Oxford, England. pp. 270-305. Book Chapter. Interpretive Summary:
Technical Abstract: Net primary production (NPP), the amount of carbon or energy fixed by green plants in excess of their respiratory needs, is the fundamental quantity upon which all heterotrophs and the ecosystem processes they are associated with depend. Understanding NPP is therefore a prerequisite to understanding ecosystem dynamics. Our objectives for this chapter are to describe the current state of our knowledge about the temporal and spatial patterns of NPP in the shortgrass steppe; to evaluate the important variables that control NPP; and to discuss the future of NPP in the shortgrass steppe given current hypotheses about global change. Most of the data available for NPP in the shortgrass steppe are for aboveground net primary production (ANPP), so most of our presentation will focus on ANPP and we will deal with belowground net primary production (BNPP) as a separate topic. Furthermore, our treatment of NPP in this chapter will ignore the effects of herbivory which will be covered in detail in chapter 16. Our approach will be to start with a regional-scale view of ANPP in shortgrass ecosystems and work toward a site-scale view. We will begin by briefly placing ANPP in the shortgrass steppe in its larger context of the central North American grassland region. We will then describe the regional-scale patterns and controls on ANPP, and then move to the site-scale patterns and controls on ANPP. At the site scale, we will describe both temporal and spatial dynamics and controls on ANPP as well as BNPP. We will then discuss relationships between spatial and temporal patterns in ANPP and end the chapter with a short speculative section on how future global change may influence NPP in the shortgrass steppe over the next 25 to 50 years.