Growth of Dactylis glomerata along a light gradient in the central Appalachian region of the eastern USA: II. Mechanisms of leaf dry matter production

Microsite influences development and resource allocation of Dactylis glomerata L. (orchardgrass), a traditional pasture species with potential as an understory crop in silvopasture of humid temperate regions. An experiment using container-grown orchardgrass was conducted under field conditions to determine how open (O), shaded woodland (W) and open-to-shaded woodland transition zone (E _O, E _W) microsites influenced leaf DM production. Plants established in spring (SP) and late summer (LS) were clipped each time mean canopy height reached 20 cm. Dry matter production and allocation among structures differed, as a function of light attenuation. Specific leaf area (SLA) and photosynthetic nitrogen-use efficiency (PNUE) were associated with leaf DM production, whereas leaf N, net assimilation rate and shoot total nonstructural carbohydrates (TNC), were not. Specific leaf area was related to leaf DM of LS plants, whereas PNUE influenced leaf DM of SP plants. Stembase TNC was inversely related to relative regrowth rate (RG_RR) with RG_RR greatest and TNC the least at W. The relationship for RG_RR and TNC for SP plants growing at O and LS plants growing at W was similar. Regardless of how indices of growth are related, SP and LS plantings responded as separate populations (representing young and established plants respectively) that have different leaf DM production efficiencies. Orchardgrass was able to sustain leaf production when subjected to simultaneous stresses of shade and repeated defoliation. The LS plants growing at W respond in a manner similar to SP plants and may require management practices attuned to establishing or immature plants. The US Government’s right to retain a royalty-free, non-exclusive copyright is achnowledged.