Ashe juniper seed production and germination, seedling dynamics and response of live oak/juniper

Abstract

Germination of Ashe juniper seed were compared in a controlled environment at different levels of fruit maturation, lengths of storage, and seed stratification to determine potential germination. Annual mean germination varied by an order of magnitude (3.1 % in 1993 vs. 0.3% in 1994), and the maximum occurred for seeds collected in November of each year (7.05% and 0.49%, respectively). After storing the seeds collected in 1993 and 1994 at room temperature for 24 and 6 months, respectively, mean germination significantly decreased to 0.45% and 0.20%, respectively. Cold stratification of stored seeds significantly increased mean germination to 15.6% and 13.3% in 1993 and 1994. Seedling survival was evaluated in 1995 within an Ashe juniper woodland by censusing seedlings for 1 0 months following germination. The influence of either 1) >50% graminoid foliar cover, 2) <5% cover, and 3) herbivory was evaluated. After 21 days, seedlings in caged plots had significantly higher survival than seedlings in uncaged plots. Between 49 and 105 days, the caged grass plots had the highest survival and the bare grazed plots had the least survivorship. Survival within all treatments was significantly different after 132 days. Survival significantly decreased at each collection date until June 3. Seedling recruitment within each canopy type (female and male Ashe juniper trees and live oak moftes) and zone (canopy, dripline, and grass interspace) was determined for different grazing histories. Seedling density was highest under female Ashe juniper canopies, followed by live oak and male juniper trees. Seedling density was the highest under the canopies of female Ashe juniper trees in the pastures subjected to long-term continuous grazing by goats (3.4 seedlingS/M2) . Net seedling recruitment in 1995 increased the seedling bank by 63%. Saplings (20-100 cm tall) had highest densities within the canopy zone of female trees in all grazing histories. The heavy continuous and continuous goat grazing histories had significantly shorter saplings than the exclosure and moderate pastures. Vegetation dynamics following a summer prescribed fire were tested using 24 treated and 1 0 control live oak /juniper mottes. The backfire technique was not sufficiently intense to have any significant treatment effect upon the woody species stem densities. Warm season grasses in the burned moftes had significantly lower densities in plants > 1 OCM2 basal area than those in the controls within the first year after the fire. Both functional groups (C3 and C4) were affected the second year after the fire, the largest plants (>25CM2) significantly increased densities. Growth forms (sod vs bunchgrass) did not express any significant differences due to the fire.