R. Kjelgren et La. Rupp, ESTABLISHMENT IN TREESHELTERS .1. SHELTERS REDUCE GROWTH, WATER-USE, AND HARDINESS, BUT NOT DROUGHT AVOIDANCE, HortScience, 32(7), 1997, pp. 1281-1283
We investigated water use and potential drought avoidance of Norway ma
ple (Acer platanoides L.) and green ash (Fraxinus pennsylvanica Marsh)
seedlings grown in protective plastic shelters. Gravimetric tree wate
r use and reference evapotranspiration for fescue turf(ETo) were monit
ored for 1 to 3 days during the growing season. Water use of trees was
8% to 14% of ETo in shelters vs. 29% to 40% for trees not in shelters
. Trunk diameter was affected more than whole-tree water relations by
lack of irrigation, suggesting that the nonirrigated trees were subjec
ted to only mild water stress. Shelters did not improve drought avoida
nce, as water potentials were generally more negative and trunk diamet
er increment was lower for nonirrigated trees in shelters. Maples in s
helters were affected more adversely by lack of water than were ash. H
igher temperatures in shelters also may have reduced trunk growth. Air
temperatures were 13 degrees C warmer than ambient in nonirrigated sh
elters, but only 5 degrees C warmer in irrigated shelters. Tree shelte
rs can reduce transpiration rates by over half, but benefits from redu
ced water loss may be offset by negative effects of higher air tempera
tures. Shelters reduced cold hardiness of both species, but maple was
affected more than ash.