Avian behavior in Chinese tallow woodlands and evaluating the potential control and allelopathic interference of Chinese tallow

Date

1997-12

Journal Title

Journal ISSN

Volume Title

Publisher

Texas Tech University

Abstract

The Chinese tallow tree, (Sapium sebiferum (L)) Roxb.), has been cultivated for over 14 centuries in China for seed oil. Chinese tallow was introduced to the United States in the mid to late 1800s and has since naturalized throughout much of the southern U. S. Tallow invades a wide variety of habitats, including freshwater wetland basins, coastal prairie, mixed bottomland hardwood forests, as well as disturbed sites. It continues to expand throughout the southern U. S., but control efforts have been inconsistent. The mechanisms by which it invades are presently unknown, as are the impacts of this invasion on native biota. Therefore, we need to know how to control future tallow expansion, investigate its ecological impacts, and understand the mechanisms for its success.

During 1995 and 1996,1 studied avian behavior in Chinese tallow woodlands and evaluated potential control and allelopathic interference of Chinese tallow in the coastal prairie region of Texas. My objectives were fourfold. First, I determined total nonstructural carbohydrate (TNC) movement in Chinese tallow, and identified the period of downward translocation of photosynthate. I linked that specific physiological stage with a visible phenological stage of development in the annual cycle of tallow to determine optimal timing for control treatments. Second, I evaluated the allelopathic potential of Chinese tallow on seed germination and seedling growth and development of plant species native to the coastal prairie region of Texas. Third, I quantified avian use of and behaviors in Chinese tallow woodlands during fall migration along the Texas coast. Finally, I evaluated avian use of Chinese tallow seeds, by subjecting seeds that were fed upon by birds, to bioassay experiments to test for seed germination enhancement by bird feeding activities.

Chinese tallow root TNC trends and phenological development were monitored over an annual cycle. Six phenological stages were recorded; (1) dormancy. (2) bud break, (3) leaf development, (4) seed formation. (5) seed maturation, and (6) leaf fall. Tallow root TNC concentrations varied by phenological stage (P < 0.001), where concentrations were highest (P < 0.05) during leaf fall (60.72%) and lowest (P < 0.05) during leaf development (41.11%) and seed formation (36.71%). Chinese tallow root TNC concentrations increased during the period of seed maturation until leaf fall. If foliar applied herbicides are delivered during this period of downward translocation, effective tallow control should be observed.

I performed seed germination bioassays using black willow (Salix nigra), baldcypress (Taxodium distichum), Chinese tallow, and lettuce as test species in 2 different experimental media (i.e., aqueous extracts and substrates) prepared from fresh tallow leaves, fallen litter, and tallow woodland soil collected during 4 months to evaluate seasonal differences in allelopathic interference potential. Distilled water was used as a control for aqueous extract treatments, whereas air-dried peat was used as a control for the substrate treatments. There were varied responses by black willow, baldcypress, and lettuce seeds and seedlings exposed to tallow extract and substrate treatments. In some instances, test seeds experienced enhanced (P < 0.05) seed germination and seedling growth, but in others these responses were reduced. When exposed to its own extracts and substrate treatments. Chinese tallow showed more consistent responses. Chinese tallow control (i.e.. distilled water and substrate) treatments had reduced (P < 0.05) seed germination and seedling growth as compared to control treatments. These data suggest that tallow is not autotoxic. Tallow seed germination and seedling growth and development maybe enhanced when exposed to its own leaves, litter, and soil. Chromatographic analyses performed on the aqueous extracts support these data. No potential allelochemicals were detected during gas chromatography/mass spectrophotometry analyses. The only chemical detected during these analyses was inositol- a naturally occurring a cyclohexanehexanol. Therefore, successful tallow invasion is likely enhanced through mechanisms other than allelopathy.

Time-activity budgets were developed for black-and-white (Mniotilta varia) and yellow-rumped (Dendroica coronata) warblers. Feeding, resting, moving, maintenance, searching for food, calling while perched, and moving and calling behaviors were quantified. During 1995 and 1996, searching for food was the predominant (56.48%) activity for black-and-white warblers, whereas resting (55.89%) was the predominant activity for yellow-rumped warblers. Behavior data were also determined for other migrant, permanent resident, and winter resident birds. Migrants were observed feeding or searching for food more (P < 0.05) than either permanent or winter resident birds. These data support the hypothesis that migrant birds allocate more time to feeding and searching for food than either permanent or w inter residents birds. I collected Chinese tallow seeds that had been fed upon by yellow-rumped warblers during 1995 and subjected them to seed germination bioassays. No differences (P > 0.05) were observed for percent germination between seeds fed upon by yellow-rumped warblers (2.5%) and seed that were collected directly from Chinese tallow trees (2.5%). Bird feeding activities do not enhance tallow seed germination, but birds may still influence future tallow expansion through seed dispersal.

Description

Citation