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Carbon Balance of Panicum Coloratum During Drought and Non-Drought in the Northern Chihuahuan Desert

W. B. Sisson
Journal of Ecology
Vol. 77, No. 3 (Sep., 1989), pp. 799-810
DOI: 10.2307/2260986
Stable URL: http://www.jstor.org/stable/2260986
Page Count: 12
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Carbon Balance of Panicum Coloratum During Drought and Non-Drought in the Northern Chihuahuan Desert
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Abstract

(1) The daily CO2 flux of above-ground and below-ground components of Panicum coloratum growing in the northern Chihuahuan desert was determined during a spring drought and following the autumn reproductive phase of growth. The objectives were (i) to determine the whole-plant carbon balance after a fifty-two-day drought when photosynthetic capacity was severely repressed, and (ii) to determine the whole-plant carbon balance during favourable soil-water conditions prevalent after the autumn reproductive period. (2) Water stress severely repressed diurnal photosynthetic capacity during drought. The below-ground biomass, however, consisted of suberized roots with low respiratory activity. The net result was a positive whole-plant carbon gain of 2.6 mg C g dry wt-1 day-1. (3) Precipitation, amounting to 1.12 cm, ended the fifty-two-day drought, and increased the whole-plant carbon gain approximately six-fold. (4) The mean root/shoot quotient was 1.9 during the spring drought and 0.6 in the autumn. Reproductive tissue accounted for 13-34% (mean = 22%) of the above-ground biomass in the autumn. (5) Following reproductive growth, when soil-moisture conditions were favourable, the root system comprised suberized roots, non-suberized nodal roots and other non-suberized roots. Although the last two root types had high respiration rates, their presence in low quantities and low soil temperatures resulted in below-ground respiration approximately equal to that during drought. The whole-plant carbon gain during September was 17.2 mg C g dry wt-1 day-1.

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