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Productivity and Canopy Structure in Seven Temperate Forage Grasses

L. A. Hunt and J. P. Cooper
Journal of Applied Ecology
Vol. 4, No. 2 (Nov., 1967), pp. 437-458
DOI: 10.2307/2401347
Stable URL: http://www.jstor.org/stable/2401347
Page Count: 22
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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.
Productivity and Canopy Structure in Seven Temperate Forage Grasses
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Abstract

1. Vegetative swards of the following temperate grasses were established in the glasshouse: Arrhenatherum elatius, Cynosurus cristatus, Festuca arundinacea, Festuca rubra, Lolium perenne, Phalaris tuberosa x arundinacea and Poa trivialis. Dry matter yields and rates of dry matter accumulation were measured at two levels of light interception (50-90% and >80%) and at two seasons of the year (April-May and August-September). The relationships between productivity and such features of the canopy as leaf area index, chlorophyll per unit area of leaf and of ground, foliage and leaf angle, and canopy height were examined. 2. Festuca arundinacea accumulated dry matter faster than all other species under close cutting, and than all except Lolium perenne when leniently clipped; Poa trivialis usually grew least rapidly. These differences could not be accounted for by variations in the distribution of dry matter between root and shoot, or in the proportions of senescent and dead material or mature leaf. Canopy height at 80% light interception was greater in Festuca arundinacea and Arrhenatherum elatius than in the other species and the chlorophyll content per unit of leaf and of ground was larger in Festuca arundinacea and smaller in Poa trivialis than in the other species. Net assimilation rate on a chlorophyll basis (EC) was greater for Lolium perenne than for the other species, but was not correlated with rate of dry matter accumulation. Few significant differences in mean foliage angle or leaf angle could be detected between the species and these were not related to the rate of dry matter accumulation. 3. It is concluded that among the species included in this study chlorophyll index (chlorophyll per unit of ground area) provides a useful indication of potential productivity, and that the more rapid accumulation of dry matter of Festuca arundinacea, although based in part on a larger canopy, is also associated with features such as specific leaf weight and/or chlorophyll content per unit of leaf area which may `spread' the incoming light energy over a larger photosynthetic apparatus within the individual leaf. The implications of these results in selecting for improved energy conversion by the canopy are discussed.

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