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Open Access Publications from the University of California

Fine-scale Environmental Variation in Mountain Landscapes: Quantitative approaches, influences on tree recruitment, and implications for scientific visualization

  • Author(s): Christianson, Danielle Svehla
  • Advisor(s): Harte, John
  • et al.
Abstract

Individual organisms respond to environmental conditions that they experience on fine spatial and temporal scales, on the order of meters and hours. For example, a tree seedling lives or dies depending on local conditions, such as freezing temperatures on a spring morning, dry soils and air in the late summer, or a gopher that finds newly grown leaf tissue tasty. The persistence of a species depends on the collective survival of individuals throughout time and at various locations in space. To be of practical use to resource managers and policy makers, tools that inform human action and non-action with regard to other species, and the ecological processes that connect us, must operate at coarse spatial (10-100s km) and temporal (years-decades) scales and be applicable to many species. A core task then is to link ecological phenomena across spatiotemporal scales.

An understanding of fine-scale environs and their influence on organisms is necessary to address this challenge, but it is lacking. A primary focus of my research is to characterize (1) the fine-scale environs (1-meter and hourly resolution) over relatively large extents (1 continuous hectare), and (2) their influence on individual organisms. I chose to study mountainous systems because fine-scale environmental descriptions in these highly complex landscapes are few. Additionally, I focused on spatiotemporal characterization of fine-scale heterogeneity as it is increasingly being used, with average conditions, to explain ecological phenomena.

In chapter 1, I systematically studied the effects of sampling designs and landscape features on a measure of fine-scale heterogeneity. I found that appropriate sampling designs can reduce error in estimating fine-scale heterogeneity on complex landscapes. In chapter 2, I report that temporal patterns in fine-scale spatial heterogeneity are consistent across four mountainous landscapes and are highly variable both daily and seasonally. For some environmental quantities, aggregated temporal metrics do not adequately represent fine-scale heterogeneity. In chapter 3, I investigated the influences of fine-scale environmental conditions on the occupancy patterns of tree seedlings. Individual tree seedlings are influenced by fine-scale abiotic and biotic environmental conditions. However, the mechanism for some biotic interactions may occur indirectly via fine-scale abiotic influences. I recommend making this distinction to enable advances in coarse-scale modeling tools. In chapter 4, I questioned how new visualizations of the natural world based on fine-scale data shape ecological practice. Such visualizations enable lively novel interactions that may lead to new insight. Ecologists should approach such practice with an understanding of how these new, often highly technical, visualizations shape knowledge generation for themselves individually and the community as a whole.

Videos for chapter 4, included as additional files, illustrate experiences in a forested study site and experiences with a digital point cloud visualization of the same study site.

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