Methods of Estimating Belowground Net Primary Production
Despite much recent attention over the past 30 years, belowground net primary production (BNPP) remains one of the poorest understood attributes of terrestrial ecosystems (Milchunas and Lauenroth 1992; Nadelhoffer and Raich 1992). Estimates of the ratio of BNPP to net primary production (NPP) across ecosystem types range from less than 0.20 to more than 0.80 (Bray 1963, Coleman 1976). Part of this range can be explained by differences among ecosystems, but a portion of it is the result of differences among methods. For instance, Aber et al. (1985) reported ratios of fine root production by two different methods for the same sites ranging from close to 1 to more than 10. In addition to a wide range of estimates of the importance of BNPP across ecosystem types, estimates within ecosystems also vary widely. For instance, Sims and Singh (1978) found that BNPP accounted for 24 to 87% of NPP over a range of grassland ecosystems and Vogt (1991) reported that fine root production accounted for 7 to 76% of NPP over a range of forest ecosystems. How much of this variability is the result of differences among ecosystems and how much is the result of differences among methods? While there is no agreement on the answer to this question, there is abundant evidence that all of the current methods have important strengths and limitations. The objective of this chapter is to describe the most frequently used methods to estimate BNPP and their strengths and weaknesses. The first section provides definitions of terms and descriptions of concepts. The next section describes the methods, comments on their strengths and weaknesses, and provides references in which they have been applied. The last section evaluates the degree to which uncertainty (variability) in input data influences the uncertainty of the resulting estimate of BNPP.
KeywordsFine Root Fine Root Production Ingrowth Core Dead Fine Root Belowground Carbon Allocation
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- Aerts, R.; Berendse, F.; Klerk, N.M.; Bakker, C. Root production and root turnover in two dominant species of wet heathlands. Oecologia 81:374–378; 1989.Google Scholar
- Box, G.E.P.; Hunter, W.G.; Hunter, J.S. Statistics for experimenters: An introduction to design, data analysis, and model building. New York: Wiley Sons; 1978:87–89.Google Scholar
- Brown, D.A.; Upchurch, D.R. Minirhizotrons: A summary of methods and instruments in current use. In: Taylor, H.M., ed. Minirhizotron Observation Tubes: Methods and Applications for Measuring Rhizosphere Dynamics. Madison, WI: American Society of Agronomy; 1981:15–30.Google Scholar
- Coleman, D.C. A review of root production processes and their influence on soil biota in terrestrial ecosystems. In: Anderson, J.M.; Macfadyen, A., eds. The Role of Terrestrial and Aquatic Organisms in Decomposition Processes. Proceedings of the British Ecological Society Symposium, Coleraine, N. Ireland, April 15–18, 1975. Oxford: Blackwell; 1976:417–434.Google Scholar
- Dahlman, R.C.; C.L. Kucera. Carbon-14 cycling in the root and soil components of a prairie ecosystem. Proceedings of the 2nd National Symposium on Radio-ecology, Ann Arbor, Michigan, May 15–17, 1967. Wahsington DC: U.S. Government Printing Office; 1967:652–660.Google Scholar
- Lauenroth, W.K.; Milchunas, D.G. Shortgrass steppe. In: Coupland, R.T., ed. Natural Grasslands: Introduction and Western Hemisphere. Amsterdam: Elsevier, 1992:183–226.Google Scholar
- Long, S.P.; Jones, M.B.; Roberts, M.J., eds. Primary Productivity of Grass Ecosystems of the Tropics and Sub-tropics. London: Chapman and Hall; 1992:267.Google Scholar
- O’Neill, R.V. Error analysis of ecological models. In: Nelson, D.J., ed. Radionuclides in Ecosystems. Washington, DC: U.S. Atomic Energy Commission; 1973:898–908.Google Scholar
- Smith, F.W.; Resh, S.C. Age-related changes in production and below-ground carbon allocation in Pinus contorta forests. For. Sci. 45:1–9; 1999.Google Scholar