Regeneration ecology of Chrysopogon aucheri and Cymbopogon jwarancusa in upland Balochistan: II. Dispersal, predation and soil reserves of seeds (Spikelets)
2000
Ahmad, S. (Arid Zone Research Centre, Quetta (Pakistan) Dept. of Rangeland Resources) | Call, C.A. | Schupp, E.W.
Experiments were conducted in a representative Cymbopogon- Chrysopogon grassland in upland Balochistan, Pakistan to determine how seed (spikelet) dispersal mechanism, seed (spikelet) predation, and soil seed (spikelet) bank dynamics influence the regeneration of Cymbopogon jwarancusa and Chrysopogon aucheri. Spikelet dispersal occurs primarily by wind over a 2 to 3 week period in late-June/early-July. Higher densities of spikelets fell beneath conspecifice plant canopies than the interspaces between plants. Cymbopogon jwarancusa distributed more spikelets in all microhabitats than Chryspogon aucheri. Ants (Tica verona) were the only major spikelet predator in the study area, and they have a preference for Chrysopogon aucheri spikelets over Cymbopogon jwarancusa spikelets. Lowest soil spikelet densities for both species in all microhabitats were recorded in early-April (before seedling recruitment and spikelet dispersal), whereas highest soil spikelet densities were recorded in mid-July (after seedling recruitment and spikelet dispersal). Higher soil spikelet densities were found under plant canopies than in open interspaces, and in the upper soil depth (0- 2.5 cm) than the lower soil depth (2.5-5.0 cm). In general, Cymbopogon jwarancusa had better soil spikelet reserves than Chrysopogon aucheri.
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