MAPPING BIOLOGICAL SOIL CRUST COVER IN THE KAWAIHAE WATERSHED A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI`I AT HILO IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE DEGREE OF MASTER OF SCIENCE IN TROPICAL CONSERVATION BIOLOGY AND ENVIRONMENTAL SCIENCE MAY 2019 By Eszter Adany Collier Thesis Committee: Ryan Perroy, Chairperson Jonathan Price Sasha Reed Keywords: sUAS, biocrust, image classification, Kohala, Hawaii, erosion, Pelekane Acknowledgements This thesis was made possible through financial support from the Hawai’i Geographic Information Coordinating Council and the Society for Conservation Biology. Access to fieldwork and data analysis equipment was generously provided by the UH Hilo Geography Department and the Spatial Data and Visualization (SDAV) lab. I would like to sincerely thank my thesis committee for contributing their time and support. Dr. Perroy’s guidance and encouragement were central to the successful completion of this thesis and I will always be grateful for his unwavering faith in my capabilities. Dr. Price taught me everything I know about landscape ecology and his wealth of knowledge about a wide variety of topics was invaluable for filling the numerous pukas that sprang up during this project. Dr. Reed’s expert knowledge of biocrusts, along with her enthusiasm for the project, was key to bringing my ideas to fruition. In addition, I’d like to thank Dr. Rebecca Ostertag and everyone who works to support the TCBES program for their tireless dedication to student mentorship. For their logistical support during my field work, I’d like to thank Cody Dwight, formerly of the Kohala Watershed Partnership, and Patti Johnson of the Parker Ranch. I’d also like to thank Dr. Corina Cerovksi-Darriau and Dr. John Stock of the United States Geological Survey for their feedback during the initial stages of this project. In addition, I’d like to thank the following people for generously sharing their knowledge and providing moral support during my research: Timo Sullivan, Kimo Melcher, and my fellow students in the 2017 TCBES cohort. I’d also like to thank my family – Zsuzsa, Istvan, Aniko and Peter – for their lifelong support of my crazy ideas, in grad school and beyond. Finally, I’d like to give special thanks to my husband, David, whose steadfast encouragement and hard work kept our ship afloat while I pursued this thesis. i Abstract Historical land use patterns on Hawai’i Island have created degraded dryland ecosystems that are at high risk for erosion. In places such as the Kawaihae watershed in leeward Kohala, the impacts of sediment deposition from the watershed have detrimentally affected coastal marine ecosystems by decreasing habitat quality and burying important cultural sites. Due to the extensive and long-term effects of erosion, it is important to understand and protect non- traditional agents that may help to hold sediments in place. Biological soil crusts are communities of photosynthetic microorganisms that grow over mineral soil in arid and semi-arid ecosystems and are known to increase soil stability. Despite their potential to mitigate erosion, the distribution of biocrusts in degraded drylands on Hawai’i Island is unknown. We mapped biocrusts in the Kawaihae watershed, a semi-arid landscape prone to erosion, using imagery collected by small unmanned aerial systems (sUAS) at three spatial resolutions (1.15, 2.05 and 2.80 cm/pixel). Using a pixel-based methodology, we produced classifications with overall accuracies ≥85% at all three resolutions. As biocrust development is associated with increasing soil stability, we also explored this relationship in the Kawaihae watershed. We identified 3 different biocrust levels of development (LOD) and conducted soil aggregate stability testing at all development levels. We found that there was a significant increase in soil stability between soils without surface biocrusts (LOD score of 0) and those with biocrusts at any development level (LOD 1-3). More highly-developed biocrusts imparted greater soil stability than less- developed biocrusts, but the impact on soil stability reached a ceiling beyond biocrust LOD 1. In addition, we applied our mapping methodology to investigate the direct impacts of biocrusts on soil loss. We overlaid our classified maps with digital surface models (DSMs) from data sets covering a 2.75-year time span. We found trends of varying soil loss between biocrust and bare soil areas, but more field work is needed to verify our results. We also explored the effects of grazing animals on biocrust cover by comparing classified images of a grazed site and a grazing- exclusion site. We found differences in biocrust coverage between the sites, including differing proportions of the land cover types present, but additional field data collection is necessary prior to drawing definitive conclusions. Overall, our project provides a new biocrust mapping methodology that could be used by researchers and land managers globally and adds insight into the role of biocrusts in erosion prevention in the Kawaihae watershed and similar arid/semi-arid landscapes. ii Table of Contents Acknowledgements ................................................................................................................i Abstract ..................................................................................................................................ii Table of Contents ...................................................................................................................iii List of Tables .........................................................................................................................v List of Figures ........................................................................................................................vi List of Abbreviations .............................................................................................................ix Chapter 1: Introduction ..........................................................................................................1 Chapter 2: Mapping biocrusts with sUAS imagery ...............................................................9 2.1: Introduction .........................................................................................................9 2.2: Methods ..............................................................................................................10 2.21: Study site ...............................................................................................10 2.22: sUAS flights ..........................................................................................10 2.23 Field data collection ..............................................................................15 2.24: Image processing ..................................................................................18 2.3: Results .................................................................................................................24 2.31: sUAS test flights ....................................................................................24 2.32: Image classification ..............................................................................28 2.4: Discussion ...........................................................................................................36 2.41: sUAS test flights ....................................................................................36 2.42: image classification ..............................................................................36 Chapter 3: Biocrusts, soil loss, and grazing animals .............................................................42 3.1: Introduction .........................................................................................................42 3.2: Methods ..............................................................................................................43 3.21: Study site ...............................................................................................43 3.22: Field data collection .............................................................................45 3.23: Imagery collection and processing .......................................................48 3.24: Image classification ..............................................................................50 3.25: Data analysis ........................................................................................53 iii 3.3: Results .................................................................................................................53 3.31: Relationship between biocrust development and soil stability .............53 3.32: Soil changes between April 2016 and January 2019 ...........................55 3.33: Biocrust cover in grazed and non-grazed sites ....................................57 3.4: Discussion ...........................................................................................................58 3.41: Biocrust development and soil aggregate stability ...............................58 3.42: Biocrusts and soil loss over time ..........................................................60 3.43: Biocrusts and grazing ungulates ..........................................................62 Chapter 4: Conclusions ..........................................................................................................66 References ..............................................................................................................................69