1 / 28

Limitations on Post-fire Regeneration in Māmane (Sophora chrysophylla) in Hawaii: Can Fertilization & Rhizobium Amendmen

This study examines the limitations on post-fire regeneration of Māmane in Hawaii and explores whether fertilization and Rhizobium amendments can enhance germination and growth. The findings suggest that soil properties and biotic factors may negatively impact regeneration, while fertilizer addition shows promise in improving growth.

kellykwilliams
Download Presentation

Limitations on Post-fire Regeneration in Māmane (Sophora chrysophylla) in Hawaii: Can Fertilization & Rhizobium Amendmen

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Limitations on Post-fire Regeneration in Māmane (Sophorachrysophylla) in Hawaii May 30, 2019 Please mute your phones. Audio Dial-In: 1-877-885-1087 DoDNaturalResources.net Participant Code: 713-286-7186 Twitter: @DoDNatRes

  2. Limitations on Post-fire Regeneration in Māmane (Sophorachrysophylla) in Hawaii: Can Fertilization & Rhizobium Amendments Increase Germination and Growth? Department of Defense Legacy Resource Management Program Project # 16-831 Rebecca Ostertag1, Amanda Uowolo2, Wailea Collins1, Susan Cordell2 1 University of Hawai‘i at Hilo 2 Institute of Pacific Islands Forestry, USDA Forest Service

  3. The Problem Regeneration of a dominant tree species can be limited, even under natural conditions • Examples: • Quercusrobur(pendulate oak) in central Europe (Mölder et al. 2019) • Pinussylvestris(Scots pine) in NE Spain (Vila Cabrera et al. 2012) • Pioneer trees in Guam (Caves et al. 2013) • Reasons: • Unknown biotic or abiotic factors • Anthropogenic land use practices underlie regeneration problems

  4. The Hawai‘i Example • Sophorachrysophylla(māmane) • Legume, N-fixing • Subalpine forest dominant • Exclusive food source for endangered bird, Loxioidesbailleui(Palila) • Palila restricted to the subalpine woodland on Mauna Kea on Hawai’i Island • Regeneration in some areas and not others (Photo Credit: Jack Jeffrey, USGS. Public domain.)

  5. Anthropogenic Factors

  6. PōhakuloaTraining Area • High elevation dry forest • 3% of PTA is within the Palila critical habitat designation • Dominated by māmane and naio • Wildfire in 2010 Map published by Weisseet al. 2010. Pōhakuloa Training Area (PTA) is located on the Island of Hawai‘I between Mauna Kea and Mauna Loa volcanoes. Palila critical habitat and endangered plant habitats are indicated in white. Palila are critically endangered and are limited to the slopes of Mauna Kea.

  7. Supporting DoD Missions Maintaining quality training lands Environmental stewardship of land resources; protected species Developing and testing effective procedures to improve regeneration of subalpine forests

  8. Observations at PTA • Lots of seeds but few seedlings of māmane • Fire may have transformed soil quality • Previous work: seed addition and watering did not increase regeneration

  9. Potential Amendments • Loss of nutrients from fire? • Lack of Rhizobium for N fixation? • Can we use additions to improve germination and growth?

  10. Hypotheses Can regeneration limitations be overcome with amendments? H1: Māmane germination and growth are decreased by burning Māmane germination and growth is increased by: H2A: Amendments of fertilizer H2B: Rhizobium N-fixing bacteria H3: There is a significant synergism between fertilization and Rhizobium

  11. Experimental Design 25m 5m Plot Treatments 5m Fertilizer and Rhizobium inoculum Fertilizer 5m Rhizobium inoculum Control: no fertilizer or inoculum 5m 55m Unburned Area Burned Area

  12. Analysis: Nested ANOVA Burned Unburned Control Control Rhizobium Rhizobium Rhiz*Fert Rhiz*Fert Fertilizer Fertilizer Response variables: germination, relative growth rates of height, basal diameter, volume, biomass

  13. Field Measurements

  14. Challenges Desiccation, game birds, and frost

  15. Results • Focus on greenhouse germination experiment rather than field germination • Discuss burned vs. unburned, and the effects of the treatments

  16. Greenhouse Germination Study

  17. Greenhouse Germination

  18. Field Study

  19. Effect of Site on Height

  20. Effect of Treatment on Height

  21. Effect of Site & Treatment on Height Mean height Growth rate (cm cm-1 d-1

  22. Mean Leaf Tissue % Nitrogen

  23. Mean Leaf Tissue δ15N

  24. Discussion • Germination was complicated, but suggests that fertilization • and soil properties may be have an inhibitory effect • Growth: • Burned site had increases in growth, not supporting H1. • Rhizobium addition usually did not enhance growth (H2B not supported), while fertilizer addition did (H2A supported) • Synergistic effect was not noticeable (H3) • Nutrients • N-fixation levels might be low; no evidence for fixation with Rhizobium added

  25. Discussion • Something about the biotic or abiotic characteristics of the site • or soil negatively impacts māmane regeneration • Germination is the main bottleneck • PTA soils are older than other areas, could be related to water-holding capacity, hydrophobic soils, or pathogens. • Other possibilities: soil microorganisms, hormone exudates from roots or decomposing leaves, soil pH, soil moisture

  26. Discussion • No evidence that nitrogen fixation is the problem • In nursery seedlings, Rhizobium enhances the growth and survival of māmane • Perhaps commercial Rhizobium inoculum (Guard N) is not compatible with this species • Perhaps the combination of fertilizer and Rhizobium inoculum may not be effective in water-stressed ecosystems

  27. More Questions • What is the impact of non-native game birds? • N-fixation levels? • Is the soil microbial community involved in inhibiting germination or growth?

  28. Additional Collaborators: • Faith Inman, UH • Lena Schnell and Nikhil Narahari, Colorado State University – Center • for the Environmental • Management of Military Lands • Field Help and Project Design: • KeahialakaBalaz, Hawai‘i • Community College • Nainoa Goo, RCUH • DoD Support: • Joy Anamizu • Lt. Col. Loreto V. Borce, Jr. • Other Support: • Harold Keyser, Native Nursery • Tara Holitzki and Erik Johnson, UHH Analytical Lab • Pamela Scheffler and Orlo Steele, Hawai‘i Community College Mahalo! Contact Information: Rebecca Ostertag, Department of Biology, University of Hawai‘i at Hilo, 200 W. Kawili Street, Hilo, HI 96720, USA, (808) 932-7573, ostertag@hawaii.edu

More Related