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Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/20/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Simulation models for rangelands can be used to help manage resources, maximize returns to producers and reduce impacts on water quality. Parameters are needed for growth of woody species to allow simulation of their competition with grasses. Three attributes useful for describing and quantifying plant growth are: the potential leaf area index (LAI) or the ratio of leaf area divided by ground area; the light extinction coefficient (k) to calculate the fraction of light intercepted by leaves, using Beer's law; and the radiation-use efficiency (RUE) or amount of dry biomass produced per unit of intercepted light. Objectives in this study were to measure there for eastern red cedar and honey mesquite. Young trees were planted in the field at Temple, Texas in 1992 and measured in 1993, 1994, and 1995. Both tree species showed exponential biomass increases. RUE values were similar to values reported for other trees in the literature, but less than common values for crops. The rapid growth in 1995 was accompanied by greater leaf area and thus greater summed intercepted PAR. These values are critical for quantifying growth of these two species. Technical Abstract: Simulation models for rangelands can be used to help manage resources, maximize returns to producers and reduce impacts on water quality. Parameters are needed for growth of woody species to allow simulation of their competition with grasses. Three attributes useful for describing and quantifying plant growth are: the light extinction coefficient (k) for Beer's law; and the radiation-use efficiency (RUE). Objectives in this study were to measure LAI, k, and RUE for eastern red cedar (Juniperus virginiana L.) And honey mesquite (Prosopis glandulosa Torr. Var. Glandulosa), without competing plants. Young trees were planted in the field at Temple, Texas in early 1992 and kept free of competition from herbaceous plants. During 1993, 1994, and 1995, data were collected on biomass, leaf area, and intercepted photosynthetically active radiation (PAR) for individual trees. Both tree species showed exponential biomass increases. At the end of the 1995 growing season, mean LAI values were 1.16 for cedar and 1.25 for mesquite. Mean k values were 0.34 for mesquite and 0.37 for cedar. Radiation use efficiency for aboveground biomass was 1.60 +/- 0.17 (mean +/- standard deviation) g per MJ of intercepted PAR for cedar and 1.61 +/- 0.26 for mesquite. The rapid growth in 1995 was accompanied by greater leaf area and thus greater summed intercepted PAR. These values are critical for quantifying growth of these two species. |
