Browsing by Author "Ostertag, Rebecca"
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Item A TEST OF HOST-TAXON, ENVIRONMENT, AND DISTANCE EFFECTS ON LEAF FUNGAL ENDOPHYTES IN METROSIDEROS ON THE ISLAND OF O‘AHU(2019-12) Sur, Gary; Ostertag, Rebecca; Sutton, Jolene; Tropical Conservation Biology & Environmental ScienceItem ARE SYMBIOTIC NITROGEN FIXATION STRATEGIES TIED TO INVASIVENESS FOR NON-NATIVE WOODY LEGUMES IN HAWAIʻI?(2020-05) Kirby, Angalee; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceItem Assessment of light quality, variability, and seedling presence in Hawaiian lowland wet forests(2015) Rosam, Jodie Ray; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceHawaiian lowland wet forest (HLWF) plant species are light-limited, yet no information exists on how the understory light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked. I measured the red-to-far-red ratio (R:FR) of light to assess light quality and quantified diurnal variability in three forest types: native-dominated, partially-invaded, and fully invaded by strawberry guava (Psidium cattleianum). I asked: (1) how does understory light quality vary relative to invasion? (2) Are there differences in light quality moving vertically among forest types? (3) Are patterns of seedling regeneration and understory light related? Native-dominated forests had the greatest light quality (highest R:FR), and Psidium cattleianum-dominated forests had the lowest. While I predicted that native seedlings would prefer high-quality light sites, all seedlings preferred medium quality environments. In invaded HLWF, native seedling regeneration is hindered, and restoration efforts should focus on non-native understory removal.Item CAN COMPOST FROM A NITROGEN-FIXING TREE, FALCATARIA MOLUCCANA, REPLACE CHEMICAL FERTILIZER AND STORE CARBON IN AGRICULTURAL SYSTEMS?(2019-05) Norton, Joanna M.; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceThe challenges of food production, invasive species control, and climate change are intersecting, as they all stem from our ongoing use of land and energy on a global scale. In East Hawai‘i, two problems involving these issues are reflective of global trends. First, an expansion of agriculture is needed here, yet upland agricultural tracts are typically troubled by inherent low fertility, physically degraded and depleted of soil carbon from tillage, and require fertilizer inputs that are environmentally costly. Second, the invasive, nitrogen-fixing tree Falcataria moluccana (albizia) is dominating landscapes and altering ecosystems with rapid-cycling carbon and nitrogen inputs. These two problems are predicted to intensify with climate change, as growing conditions in each region shift and higher temperatures and carbon dioxide levels favor fast-growing, N-fixing species. Yet each of these problems could hold a remedy for the other, using practices described in the new field of climate-smart agriculture (CSA). Hawai‘i Island presents a unique opportunity to test whether or not accumulated nutrients from F. moluccana growth can benefit agricultural systems lacking in fertility, due to the intensity and grave consequences of the F. moluccana invasion, as well as the underutilization of agricultural land and lack of food self-sufficiency in Hawai‘i. This study examined whether compost from F. moluccana can replace chemical fertilizer and store carbon in agricultural lands in East Hawai‘i. Trials were conducted over one growing season and included two crops, Zea mays (corn) and Manihot esculenta (cassava), and 4 replicates across a spectrum of East Hawai‘i farmland sites representative of varying soil conditions and land use history. Treatments included a control, a typical application of chemical fertilizer (1N nitrogen applied), two levels of F. moluccana compost (1N and 2N levels of nitrogen applied), and two levels of combinations of chemical fertilizer and compost (1N and 2N). Harvest yield results showed that the F. moluccana compost was not an adequate replacement for chemical fertilizer in the corn crops. In contrast, F. moluccana compost produced cassava yields equal to chemical fertilizer, and economic and carbon costs were also similar across treatments. Variation among locations and within locations was larger than variation due to treatment in the cassava trial, but results suggest that the compost application was more effective on more degraded farm sites. Economic and carbon costs associated with the chemical fertilizer and F. moluccana compost applications were generally not different across treatments, and a partial analysis of carbon gained or lost was also similar across treatments. The results of these field trials show that CSA using F. moluccana compost is a viable alternative to chemical fertilizer, when the site is in need of organic matter (OM), and when the crop has favorable characteristics (long-season, rooting, and/or able to grow in low fertility areas). This research was designed and completed with the partnership of invasive species managers and farmers to maximize the usefulness of the research to the local community.Item Expanding the capacity for the preservation and restoration of native forest habitats on the Island of Hawaiʻi(2021-05) Maʻa, Sebastian A.W.; Canale, Lisa K.; Miura, Lisa K.; Ostertag, RebeccaAs the native forests of Hawaiʻi Island continue to face new threats in the form of invasive species, destructive pathogens such as Rapid ʻŌhiʻa Death (ROD), and stochastic events, the need for island-wide native forest rehabilitation continues to intensify. To address these ecologic and anthropogenic issues, the County of Hawaiʻi Real Property Tax Division has expanded its Native Forest Dedication Program to provide private landowners with reduced property tax rates for dedicating their land to native forest, functional forest, or successional forest land-use designations. With Native Forest Bill 178 being recently signed into law, ordinance number 20-60 establishes a dedication process for forest preservation and restoration for private property owners who have a minimum of 2.75 acres of contiguous native forest habitat. To support this new legislation, through the work of my professional internship, new resources were created to maximize enrollment rates and the success of the individuals who are participating in this community-based native forest restoration program. Examples of the new resources created specifically for this new legislation include a native, non-native/non-invasive plant species list and an accompanying plant nursery list, a management plan template that allows landowners to develop management plans without the help of a certified natural resource management professional, and an evaluation checklist that the county will use to evaluate management plans. This new legislation, which is the first of its kind in the State of Hawaiʻi, facilitates community-based native forest restoration projects by increasing multi-stakeholder participation in the active care and management of native forest habitats throughout the County of Hawaiʻi.Item Impacts of introduced leaf-galling insects on reproduction and seedling survival of Myoporum sandwicense, a native Hawaiian tree(2017-05) Yanger, Corie Melissa; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceInsect herbivores released from biotic and abiotic controls of their native environment can have severe negative impacts on plant reproduction and survival in their introduced range. On Hawaiʻi Island, a recently introduced leaf-galling thrips species (Klambothrips myopori) has infested populations of an abundant native tree called naio (Myoporum sandwicense) causing widespread gall damage and foliage dieback. Mature trees show signs of infestation and have disappeared in some areas, yet the extent to which infestation affects naio reproduction has been unknown. Within two naio populations recently invaded by thrips, one in mesic forest and one in dry forest, I counted flowers and fruits and assessed gall damage and foliage dieback monthly for one year for naio trees with zero (0%), low (<33%), moderate (33%- 66%), and high (>66%) initial gall damage. Gall damage was defined as the percentage of gall-deformed young leaf area. Foliage dieback was defined as the percentage of necrotic leaf tissue compared to total young leaf area. At these same sites, gall damage, foliage dieback and height were recorded for naturally occurring naio seedlings over one year to determine seedling survivorship. I found that naio reproduction decreased, particularly for trees with moderate and high initial gall damage, regardless of site. Reproduction also declined drastically for trees with zero to low initial gall damage at the dry site. I used generalized linear mixed models (glmm) to identify variables that best explained observed patterns in naio reproduction, including thrips-induced gall damage and foliage dieback, tree basal area, precipitation, temperature and humidity. Results from glmms indicated that tree foliage dieback, branch foliage dieback and branch death (precipitated by thrips gall damage) were the most significant variables for explaining naio reproductive decline over time. Thrips’ gall damage and foliage dieback increased for trees with zero to low initial gall damage at the mesic site, while gall damage remained extremely low and foliage dieback was mostly low for trees with zero to low initial gall damage at the dry site. Gall damage and foliage dieback increased for trees with moderate initial gall damage at both mesic and dry sites, while gall damage and foliage dieback were high and then declined for trees with high initial foliage damage at both sites. Naio seedling survival was 34% at the mesic site and 88% at the dry site, but did not appear to be strongly related to thrips damage. At a third experimental site, I used pesticide to exclude thrips and evaluated reproductive differences in treated versus untreated naio trees of low and high initial gall damage classes. Reproduction decreased for all trees at the experimental site, and no significant difference was found in naio reproduction between treated and untreated trees. In the experiment, gall damage and foliage dieback increased for trees with low initial gall damage. Gall damage remained high and foliage dieback decreased for trees with high initial gall damage, but there was no difference in gall damage or foliage dieback between treated and untreated trees. Because I did not see a clear difference in gall damage and foliage dieback between treated and untreated trees, I think it is unlikely that the pesticide treatment was effective in excluding thrips. These results, taken as a whole across the three sites, indicate that introduced thrips have a notable negative impact on naio reproduction, and other factors are also negatively influencing naio reproduction and should be investigated. Also, further study is needed to understand dynamics of naio seedling recruitment and survival. These studies suggest that without management action, the potential for naio to replace itself through reproduction will decline.Item INTRASPECIFIC VARIATION IN HOME RANGE SIZE, OVERLAP, AND MOVEMENT BEHAVIORS OF ‘IO - THE HAWAIIAN HAWK (BUTEO SOLITARIUS)(2024-05) Durham, Amy; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceItem Invasive Plants Species Management and Lowland Wet Forest Restoration in Hawai′i(2020-05) Irish, Amanda R; Canale, Lisa K.; Ostertag, Rebecca; DiManno, Nicole; Uowolo, Amanda; Cordell, Susan; Meehan, KristinThis paper reports on two professional internships conducted as part of the Tropical Conservation Biology and Environmental Science M.S. Professional Internship program. The first was with the Big Island Invasive Species Committee (BIISC) learning about data and the metrics involved in capturing the effectiveness of control treatments. The second was working as the field crew leader with Liko Nā Pilina, a hybrid ecosystem restoration research project. These two internship opportunities were chosen based on my personal and professional interest in better understanding the landscape of invasive species management efforts.Item Quantitative Analysis of the Mesophotic Coral Ecosystem Bentos in the Northwestern Hawaiian Islands(2021-08) Knight, Laura Jean; Wiegner , Tracy N.; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceItem Seed Dispersal & Germination by Native vs. Exotic Avian Frugivores of Hawaiʻi Island(2020-06) Matsuoka, Koa; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceItem Seed Dispersal & Germination by Native vs. Exotic Avian Frugivores of Hawaiʻi Island(2020-06) Matsuoka, Koa; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceItem Understanding Ceratocystis species A: growth, morphology, and host resistance(2017-12) Luiz, Blaine; Ostertag, Rebecca; Tropical Conservation Biology & Environmental ScienceCeratocystis Wilt of ‘Ōhi‘a (Metrosideros polymorpha) is a newly discovered vascular wilt disease that has the potential to devastate native forests across the state of Hawai‘i, USA. To better understand the causal agent of the disease, C. sp. A morphology, temperature/medium dependent mycelial growth and spore production, and virulence of three isolates were assessed. In addition, individuals of four varieties of M. polymorpha from Hawai‘i Island were inoculated with C. sp. A to compare disease severity, the number of days to death of the individual, and the number of survivors. Isolates P14-1-1, P15-80, and P16-7 were all similar in morphological measurements and growth. Mycelial growth was highest at 25-30°C and on 10% V8 agar and malt yeast extract agar (MYEA) for all isolates tested. Spore production of isolate P14-1-1 was greatest at 25°C and on MYEA. Mean disease severity and mean number of days to death were not significantly different among the three isolates. Disease severity was lower in vars. incana (38.84 ± 5.08) and newellii (36.11 ± 11.01) compared to vars. glaberrima (59.17 ± 4.05) polymorpha (70.08 ± 3.64). Log mean number of days to death was higher for vars. glaberrima (3.77 ± 0.08) compared to polymorpha (3.43 ± 0.05). There were no differences in log mean number of days to death among the rest of the varieties. There was a significant relationship between variety and plant health. Vars. incana and polymorpha contributed the most to the difference, with a higher number of var. incana (11) and a lower number of var. polymorpha (0) survivors than expected.The similarities between the isolates support the hypothesis of a single recent introduction of C. sp. A and suggest that variation in pathogenicity and virulence is low within the population that exists on Hawai‘i Island. Also, the results suggest that resistance is present in M. polymorpha varieties in nature, and that var. incana may be more resistant than the other three varieties.Item ʻO KE KAHUA MA MUA, MA HOPE KE KŪKULU: INVESTIGATING THE RELATIONSHIP BETWEEN THE FUNCTIONAL TRAITS OF LEAF LITTER AND LITTER-DWELLING ARTHROPODS(2023-05) Robins, Casey Anuhea; Ostertag, Rebecca; Tropical Conservation Biology & Environmental Science