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Gas exchange and growth of transplanted and nontransplanted, mulched and nonmulched field-grown Shumard red oak trees (Quercus shumardii Buckli.) were investigated in a semiarid climate. In Spring 2003, 12 field-grown trees were selected for uniformity. Six trees were moved with a tree spade and six trees were undisturbed. In addition, pine bark mulch was applied around three randomly selected transplant and nontransplant trees. Soil volumetric water content, predawn leaf water potential, midday stomatal conductance (g S) and leaf temperature, and growth data were collected over three consecutive growing seasons. Throughout the experiment, weekly predawn leaf water potential and g S data indicate transplanted trees with and without mulch were under greater water stress when compared with nontransplanted trees. In addition, nontransplanted trees with mulch were under greater stress when compared with nontransplanted trees without mulch. Each year, transplanted trees and nontransplanted trees with mulch had less apical growth when compared with nontransplanted trees without mulch. Although gas exchange and apical growth of transplanted trees and nontransplanted mulched trees tended to increase each growing season, by experiment termination, gas exchange and apical growth for transplanted trees and nontransplanted trees with mulch did not recover to nontransplanted, nonmulch tree levels.
Recent droughts and depleted water tables across many regions have elevated the necessity to irrigate field-grown (FG) nursery trees. At the same time, ordinances restricting nursery irrigation volume (often without regard to plant water requirements) have been implemented. This research investigated gas exchange and growth of two FG maple tree species (Acer × freemanii `Autumn Blaze' and A. truncatum) subjected to three reference evapotranspiration (ETo) irrigation regimes (100%, 60%, and 30% of ETo) in a semi-arid climate. During Spring 2002, nine containerized (11.3 L) trees of each species were field planted in a randomized block design. Each year trees were irrigated through a drip irrigation system. During the first growing season, all trees were irrigated at 100% ETo. Irrigation treatments began Spring of 2003. Gas exchange data (pre-dawn leaf water potential and midday stomatal conductance) were collected during the 2003 and 2004 growing seasons and growth data (shoot elongation, caliper increase, and leaf area) were collected at the end of each growing season. For each species, yearly data indicates irrigation regime influenced gas exchange and growth of these FG trees. However, it is interesting to note gas exchange and growth of these FG maple trees were not necessarily associated with trees receiving the high irrigation treatment. In addition, it appears the influence of irrigation volume on the growth of these FG trees is plant structure and species specific. Our data suggests irrigation of FG trees based upon local ETo measurements and soil surface root area may be a means to conserve irrigation water and produce FG trees with adequate growth. However, continued research on the influence of reduced irrigation on FG tree species is needed.
Recent droughts and depleted water tables across many regions have elevated the necessity to irrigate field-grown (FG) nursery trees. At the same time, ordinances restricting nursery irrigation volume have been implemented, often without regard to plant water requirements. This research investigated growth of seven FG tree species (Acer buergeranum, A. campestre, A. × freemanii `Autumn Blaze', A. truncatum, Quecus muehlenbergii, Q. polymorpha, and Q. robur) subjected to three reference evapotranspiration (ETo) irrigation regimes (100%, 60%, and 30% ETo) in a semi-arid climate. During Spring 2002, nine containerized (11.3 L) trees of each species were field planted in a randomized block design. Each year trees were irrigated through a drip irrigation system. During the first growing season, all trees were irrigated at 100% ETo. Irrigation treatments began Spring 2003. Growth data (shoot elongation and caliper increase) were collected at the end of the 2003 growing season. Species growth data were subjected to analysis of variance. If treatment differences were found, means were separated by Fisher's least significant difference. Shoot growth was influenced by irrigation regime for each species except A. campestre and Q. robur. For each of the five remaining species, the greatest shoot growth increase was generally not associated with the greatest irrigation regime. In a similar manner, caliper increase was influenced by irrigation regime for each species. The 100% ETo irrigation regime produced the greatest caliper increase for A. buergeranum, A. truncatum, Q. polymorpha, and Q. robur. For remaining species, the greatest caliper increase was generally not associated with the greatest irrigation regime.