Vegetation Self-​​Patterning Presentation

I gave a pre­sen­ta­tion of my research on south­western plant pat­terning yesterday–this was in fact an “oral dis­ser­ta­tion defense”, according to the Masters Project Handbook. Below is a video, and the slides. I’ll hope­fully be adding more material to the research page as I get around to it, including a NetLogo imple­men­ta­tion of an existing veg­e­ta­tion model and possibly a Google Earth tour of some of the sites and data. First however I have to finish writing the non-​​oral part of the thesis.

Slides (6mb pdf)

Narrative summary of the talk:

Self-​​patterning of veg­e­ta­tion has been iden­ti­fied in dryland ecosys­tems world­wide, such as the “tiger striped” savanna of the African Sahel and the banded shrub­lands of Australia. In these water-​​limited systems plants are orga­nized into con­sis­tent spatial struc­tures by the facil­i­ta­tion of new growth in the organic shadow of existing plants. These land­scapes are the­o­rized to be more effi­cient at retaining rare rainfall, but are also expected to undergo cat­a­strophic shifts if pre­cip­i­ta­tion drops below difficult-​​to-​​predict thresholds.

No such banded systems have been iden­ti­fied in America, but I was curious if more subtle pat­terning could be hap­pening in south­western drylands which share many of the same ecosystem char­ac­ter­is­tics and display threshold response to changes in pre­cip­i­ta­tion. If a form of emergent pat­terning were occur­ring in these ecosys­tems, it would have impli­ca­tions for pre­dicting land­scape response to pending changes in climate. Focusing on piñón-​​juniper wood­lands in Arizona and New Mexico, I mapped the shapes of patches of veg­e­ta­tion from aerial pho­tographs and measured their degree of spatial pattern. Estimates of surface water movement and dis­tri­b­u­tion were devel­oped for the same sites from digital ele­va­tion models. Testing the spatial cor­re­la­tion of these land­scape char­ac­ter­is­tics indi­cated strong linkages between veg­e­ta­tion patch shape, veg­e­ta­tion density, and surface water hydrology. In sites in Arizona, these rela­tion­ships were con­sis­tent with theories of self-​​patterning, sug­gesting that this pre­vi­ously uniden­ti­fied phe­nom­enon could be occur­ring in in an American dryland landscape.

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