Research at the CPER-LTER under the core topic of primary production is unique and broad in that we are addressing the production question over a range of spatial and temporal scales (Sala et al. 1987A, Lauenroth et at. 1986, Webb et al. 1983, Milchunas and Lauenroth 1987), as well as attempting to solve the very important belowground production problem (Lauenroth et al 1986, Milchunas et al. 1985, Saia et al. 1987, Singh et at. 1984).
During LTER-I, we developed a 14C dilution technique that produced accurate estimates of below-ground primary production under controlled growth-chamber experiments (Mitchunas et at. 1985). This technique can provide estimates of other important belowground processes: root exudation, belowground herbivory, and root decomposition. A field experiment using this technique was initiated in 1985. Eight 16 m2 long-term plots were labeled with a total of 75 mCi of 14C as 12CO2
Experimental objectives are to examine the partitioning of carbon into labile and structural material, respiration, and exudates, as well as root turnover and production. Plots will be sampled for 10-20 years. We will monitor surface litter and belowground root decomposition and carbon dynamics in soil aggregate. Root production ad turnover will be estimated by 14C 12C ratios, total 14C decay, and harvest methods. These data will allow us to examine how herbivory. decomposition, exudation and sloughing, and respiration affect estimates of belowground net production obtained by various methods. The short-term phase of the experiment was completed in 1986.
Publications:
Lauenroth, W.K., H.W. Hunt, D.M. Swift, and J.S. Singh. 1986. Estimating aboveground net primary production in grasslands: a simulation approach. Ecological Modelling 33:297-314.
Mulchunas, D.G., W.K. Lauenroth, J.S. Singh, CV. Cole, ana H.W. Hunt. 1985. Root turnover and production by 14C dilution: Implications of’ carbon partitioning in plants. Plant and Soil 88:353-365.
Milchunas, D.G. and W.K. Lauenroth. 1986. Three dimensional distribution of vegetation in relation to grazing and topography in the shortgrass steppe. (In prep).
Sala, O.E., W.J, Parton, L.A. Joyce, and W.K. Lauenroth. 1987A. Primary production of the Central Grassland Region of the United States: Spatial pattern and major controls. Ecology (submitted).
Saia, O.E., M.E. Biondini, and W.K. Lauenroth. 1987B. Bias in estimates of primary production: an analytical solutlon.Ecology (submitted).
Singh, J.S., W.K. Lauenroth, H.W. Hunt, and D.M. Swift. 1984. Bias and random errors in estimators of net root production: a simulation approach. Ecology 65:1760-1764.