Survival and growth response of mesic and dry-site sources of loblolly pine seedlings to cyclic soil moisture deficit

摘要

A growth chamber study compared height, biomass, and mortality rate of 4 to 12 old pine L.) seedlings of mesic and dry-site seed sources to 7 cyclic soil moisture stress levels, averaging between -0.3 to -2.4 Soil moisture stress was monitored gravimetrically throughout each dry-down cycle until a predetermined soil moisture potential was reached; soil was then rewatered. Shoot height was measured at two-month interval, from 4 to 12 months after the emergence of the seedlings. The oven dry weight of the seedlings and their roots were used for biomass determination. Mortality was recorded every 2 months throughout the experiment. Dry-site seedlings outgrew mesic seedlings in every soil moisture stress levels. Height growth declined with increasing moisture stress for both seed sources. The most abrupt reduction in height growth occurred between the nonstressed (-0.3 seedlings and those that grew under -0.6 Dry-site source produced more shoot biomass in all soil moisture stress levels.