Seldon, Jodelin

Profile Picture

Filters

20131
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    Effects of tree shelters and dew condensers on establishment of young tree seedlings in an arid area in Puerto Rico
    (2013) Seldon, Jodelin; Snyder, Víctor A.; College of Agricultural Sciences; Van Bloem, Skip J.; Harmsen, Eric; Department of Crops and Agro-Environmental Sciences; Vargas, María M.
    The first objective of this project was to investigate the growth and survival of seedlings of two tree species at different water levels in a greenhouse environment. The two species were the native Tabebuia heterophylla Britton and the exotic species Swietenia macrophylla King which requires more humid environments. The different water treatments were based on relative evapotranspiration (RET) demand; i.e. 1.0, 0.75, 0.50, 0.25, 0.125 and zero times the evapotranspiration demand (ETo) of the trees. Daily evapotranspiration demand ETo was determined by adding 400 ml of water to one pot in each replication block, measuring the amount percolated, and calculating ETo as the difference between these two values. For both species, 100 percent survival was possible at RET values as low as 0.50. However only 60 percent of S. macrophylla trees survived at RET = 0.25 and no trees survived at RET = 0.125. In contrast, all T. heterophylla trees survived even at RET values as low as 0.125. The second objective was to investigate the effect of tree shelters and dew condensers on the survival and early development of T. heterophylla under field conditions in a semiarid climate. T. heterophylla growth was evaluated in the field under three irrigation treatments (no irrigation, manual irrigation with 2 L of water per week, and with water supplied by a dew condenser). Each irrigation treatment was further evaluated with and without tree shelters. Treatments were imposed in a randomized complete block with 6 replications. All seedlings survived under the different experimental treatments, but growth differed among treatments. Statistically significant differences occurred between trees with and without tree shelters, but no significant effects were associated with the irrigation treatments. Trees with tree shelters exhibited greater height than those without tree shelters, but showed reduced plant diameter, biomass and number of leaves. Tree elongation, determined as the ratio of height to basal stem diameter, was significantly greater in the tree shelter treatments, but began decreasing once tree tops emerged from the tops of the tree shelters at approximately 5 to 6 months after planting. At harvest time 18 months after planting, the stems of sheltered trees were still so weak that the trees could not stand without support. Due to technical difficulties, amounts of dew condensate were not measured at Cabo Rojo. As surrogate estimates, data obtained from a one-year experiment at Rio Piedras were used. Typical volumes of water condensed on a 1 m2 surface ranged from roughly 75-150 ml/night during the summer months to 150-250 ml/night during the winter months. The major cause for seasonal fluctuations appeared to be changing night length, with longer nights allowing greater amounts of dew condensation. Based on these data and minimum water requirements for tree survival determined in the greenhouse study, the conclusion is that water produced by a 1 m2 dew condenser should be sufficient to maintain small tree seedlings alive during drought periods. This indicates the potential of dew condensers for avoiding drought failure of reforestation projects. The amount of water provided can be easily increased if necessary, by simply using larger dew condensers. The research with tree shelters confirmed the need to maintain shelters around the trees for several years, to allow sufficient trunk development for maintaining trees erect.