Year: 1975
Type: article
Abstract: Durillg a S('concl year {1872} of lO\v herb produdion, there was a significant variation of seed reserves in the upper 2 cm of soil.\Yith a doubling from F{'hruary to June and a cleBsity-indepcndent halYing by October.In Ocloher there wen~ 8 x I()" sPeds/ha (5.3 kg/ha).After favorable fall and winter rains, seed densities in Ocioher HJ73 were IO-Hi times greakr under shrubs and 2:J-27 times greater in exposed areas (together as high as !87.,5 x 10'' seeds/ha, 84.3 kg/ha).The increase invoh•cd principally the winter annual grass.F<'sluca octoflom.In 1972.when there \\"as a smaH difference in rodent density bet\veen two plots (0.8:!.0).then' was no effect of plot on seed density.In 1973.when there was a 1:17.8ratio of"rodent densiti<'.~.tht>rc '-\"as a significant effect of plot on seed densities under shrubs.From October 1073 to October 197•!. seed rcscn•<•s in vxposcd areas decreased by 20(,;. in the plot with fevi; rodents, and 40 1 ½, in the one with man>•• Consumption of seeds by rodents is probably an important factor in the decrement of seed reserves, accounting for 30 to 80r:>/4, of the decreases in this study.There is slight evidence that pocket mice difforenlially decrease the abundance of the heavier species of seed:-;.Seed density was significantly greater under shrubs than in interspaccs: density was significantly correlated vvith the size of the shrub canopy.There was a significant effect of the species of shrub on the density of total seeds.shrub seeds and seeds of the more abundant herb species, possibly due to different soil conditions created by different shrubs, and to specific differences in canopies.During years of 10\v herb production, th-e undershrub areas are a refuge of seed prod net ion by herbs.and shrub seeds form a larger portion of recruitment and future seed reserves.The difference in response of shrubs and herbs to \.Veather increasE's the stability of seed reserves.In May 1973, the density nnd biomass of herbs were significantly greater under shrubs than in interspaces.The ratio (number of herbs in May to the number of seeds the previous October) x 100, \Vas 16.8 under shrubs and 43.6 in the intcrspaccs.This minimum germination (38S;, 0\"Cr the whole habitat) may have been sufficient to account for most of till' decrease of :-;ecds in the plot with little consumption by rodents.It takes an exceptional coincidcnc<' of ('\•cnb.even in deserts, to cause a severe depletion of seed reserves.
Authors: Robert M. Chew, James F. Nelson
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
SDG: Life on land
Open Access status: green
Funder: auDA Foundation
OpenAlex ID: W1540289683