Environmental productivity indices for a Chihuahuan desert cam plant, Agave lechuguilla

Journal Article · Sat Feb 01 04:00:00 EST 1986 · Ecology; (United States)

DOI:https://doi.org/10.2307/1938497· OSTI ID:5811525

Nobel, P S; Quero, E

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), Journal Name: Ecology; (United States) Vol. 67:1; ISSN ECOLA
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
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510100* -- Environment
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54 ENVIRONMENTAL SCIENCES
ARID LANDS
BIOMASS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
CORRELATIONS
DESERTS
DEVELOPING COUNTRIES
ENERGY SOURCES
GROWTH
LATIN AMERICA
MEASURING METHODS
METABOLISM
MEXICO
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
PLANT GROWTH
PLANTS
PRODUCTIVITY
RENEWABLE ENERGY SOURCES
RENEWABLE RESOURCES
RESOURCES
TEMPERATURE EFFECTS
TUMBLEWEEDS
UPTAKE