Environmental productivity indices for a Chihuahuan desert cam plant, Agave lechuguilla
Productivity of Agave lechuguilla, a commercially harvested plant that occurs over vast areas of the Chihuahuan Desert, was measured using conventional dry mass changes in the field and was predicted based on physiological responses to environmental variables in the laboratory. An environmental productivity index (EPI) was constructed as the product of indices for water status, leaf temperature, and photosynthetically active radiation (PAR). Each of these component indices was assigned a maximum value of unity when that variable was not limiting net CO/sub 2/ uptake over a 24-h period. Soil water potential, daily air and leaf temperatures, and PAR in the planes of the leaves at the field site in Coahuila, Mexico, could thus be quantitatively described in terms of their effect on net CO/sub 2/ uptake. Seasonal changes in PAR proportionally affected both the modest daytime net CO/sub 2/ uptake and the predominant nighttime net CO/sub 2/ uptake for this crassulacean acid metabolism plant, while seasonal variations in temperature had relatively small effects on net CO/sub 2/ uptake over a 24-h period. EPI was highly correlated with the number of new leaves unfolding each month in the field (r/sup 2/ = 0.83); counting unfolding leaves is a nondestructive method of estimating productivity. For the 1-yr study period EPI averaged 0.28, which led to a predicted annual dry mass gain per unit leaf area of 0.68 kg/m/sup 2/. Field measurements indicated that the actual dry mass gain was about half this value, the difference representing photosynthate needed for constructing and maintaining folded leaves, stem, and roots. The productivity of A. lechuguilla per unit ground area explored by its roots was 0.38 kg x m/sup -2/ x yr/sup -1/, which, although much less than for agricultural crops, is still much greater than the average productivity for desert ecosystems.
- Research Organization:
- Univ. of California, Los Angeles
- OSTI ID:
- 5811525
- Journal Information:
- Ecology; (United States), Vol. 67:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
09 BIOMASS FUELS
PLANT GROWTH
MEASURING METHODS
PRODUCTIVITY
BIOMASS
CARBON DIOXIDE
CORRELATIONS
DESERTS
METABOLISM
MEXICO
PLANTS
RENEWABLE RESOURCES
TEMPERATURE EFFECTS
TUMBLEWEEDS
UPTAKE
ARID LANDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DEVELOPING COUNTRIES
ENERGY SOURCES
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LATIN AMERICA
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
RENEWABLE ENERGY SOURCES
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510100* - Environment
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