Performing Department
EXPERIMENT STATION
Non Technical Summary
American Samoa's forest are being degraded through anthropogenic and natural disturbances, and are frequently unable to regenerate because of invasive species. This project will provide guidelines on shade requirements/tolerances and vegetation management tactics for those wishing to conduct reforestation efforts in American Samoa, including, the National Park of American Samoa, Natural Resource Conservation Service, and private land holders.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The goal of this research project is to assess the effects of canopy cover on seedling survival and growth and determine the vegetation management requirements in stand restocking of young native Samona hardwoods. The research objectives are to: 1) test the effects of underplanting in various levels of existing canopy cover on seedling establishment and growth, 2) test the effect of polyethylene mulch used for weed control on seedling establishment and growth, and 3) compare the effects of this mulch with hand weeding of a similar-sized area.
Project Methods
Seedlings of eight Samoan hardwood trees, Calophyllum neo-ebudicum, Diospyros samoensis, Flueggea flexulosa, Intsia bijuga, Planchonella samoensis, Pometia pinnata, Syzygium inophylloides, Terminalia richii, will be propagated in the ASCC Land Grant Extension Forestry greenhouse and raised to a height of 30 to 40 cm. Propagation will require seed collection. Transplants may have to be produced by collecting wild seedlings. Seedlings will be transplanted into an existing reforestation study in the Malaeimi Valley, Tutuila, AS, in a random manner. Half of the trees will receive a 1 sq. m polyethylene mulch at the time of planting. The tree will be planted first. Then the mulch is installed over the top of it, inserting the tree through a precut incision in the center of the mulch. The mulch with then be staked to the ground with 15 cm wire staples. Half of the trees will also receive monthly weeding beginning at the time of planting. A 1 sq. m planting area will be scalped
and the tree planted in the center of that area. Treatments will be arranged so that one quarter of the trees are mulched, one quarter are weeded, one quarter have both treatments, and the remainder have none-the control. The treatments are intended to provide different forms of vegetation control. Hand weeding will provide through vegetation control of limited duration. Mulching will provide long-term consistent control of ground based vegetation but may not be effective in controlling climbers. The combined treatment will provide the best vegetation control but require a greater investment of resources. A variety of measurements will be taken during this project. Tree height and diameter at 15 cm will be measured at the time of planting, the trees tagged, and diameter measurement points marked with tree paint. Diameter is measured initially at 15 cm to avoid inflated values do to ground level stem swelling. Canopy cover will also be assessed at the time of planting using a
ceptometer at a height of 0.5 m. Tree size and canopy cover measurements will be conducted annually for the three-year duration of the study. Ceptometer height will be adjusted for annual canopy cover measurement so that the assessment is only of the canopy overtopping the seedling. Diameter-breast-height (defined as 1.37 m) will be measured when trees reach 1.5 m in height. Seedling survival will be assessed at the time of measurement. This experiment will arranged in a completely randomized design. Factors in the study are: tree species; vegetation management treatments including a control, hand weeding, mulching, and combined weeding and mulching; and percent canopy cover. The data will be analyzed using linear regression for size data, either height or diameter (at 15 or 137 cm) in m or mm, respectively and logistic regression for survival by species. Regression lines for each species will be compared to determine whether tree species have similar responses.