Potential past and future tree migration responses to climate change

Morrison, Bailey Danielle

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https://hdl.handle.net/2142/102418 Copy

Description

Title

Potential past and future tree migration responses to climate change

Author(s)

Morrison, Bailey Danielle

Issue Date

2018-10-30

Director of Research (if dissertation) or Advisor (if thesis)

• Greenberg, Jonathan A.
• Fraterrigo, Jennifer

Doctoral Committee Chair(s)

Greenberg, Jonathan A.

Committee Member(s)

• Leakey, Andrew
• Punyasena, Surangi

Department of Study

School of Integrative Biology

Discipline

Ecol, Evol, Conservation Biol

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Ecology
• Biogeography
• Species Distributions
• Climate Downscale
• Species Migration
• Climate Change
• Spatial Resolution
• Climate Velocity
• Bioclimatic Niche Velocity
• Alaska
• Last Glacial Maximum
• California
• Forest Communities

Abstract

Anthropogenic climate change is leading to dramatic fluctuations of essential climate dynamics and has become a major threat to modern ecosystem services and biodiversity because of its magnitude and rate of change. Climate is a well-known key constraint of species and ecosystem functions affecting distributions, extinction risk, altered disturbance regimes, biogeochemical cycling, and other ecological responses. Specifically, the ecological responses of forest and woodland vegetation to climate change are important to understand as they are important primary producers of many goods and services on which humans depend and provide supporting and regulating services for the environment. Tree species have already been found to have altered cover, biomass, density, carbon sink capabilities, fitness, extinction, invasion of non-native species, and diversity in response to modern climate change. Many conservation approaches aim to ameliorate the negative effects of environmental change within forest communities. However, conservation strategies assume the species composition of modern communities will exist with future climate change and rely on static protected area reserves. This may cause modern conservation practices to become obsolete with climate change because climate change is a dynamic process, unlike reserve practices, and species are known to respond to climate change independent of one another and their communities. Climate surface resolution has the potential to complicate predictions of the ecological impacts of climate change since climate varies from local to global scales and this spatial variation is reflected in climate data. In Chapter 1, I investigated this issue by downscaling Last Glacial Maximum (LGM) and modern (1975-2005) 30-year averaged climate data to 60m resolution for the entire state of Alaska for 10 different climate variables, and then upsampled each variable to coarser resolutions (60m to 12km). Distributions of novel and disappeared climates were modeled to evaluate the locations and fractional area of novel and disappeared climates for each of my climate variables and resolutions. Novel and disappeared climates were primarily restricted to southern Alaska, although there were cases where some disappeared climates existed within coastal and interior Alaska. Novel and disappeared climates increased, decreased, or had no clear relationship of fractional area with the coarse climate data, however, the use of coarser climate data increased the fractional area of novel and disappeared climates due to the removal of environmental variability and climate extremes. Results from Chapter 1 reinforce the importance of downscaling coarse climate data and suggests that studies analyzing the effects of climate change on ecosystems may overestimate the effects of climate change when using coarse climate data. Once I demonstrated the importance of scale in understanding climate change, I next investigated whether high-resolution climate metrics, specifically climate velocity, were suitable predictors of a species migration response to climate change. Species have and will continue to shift their distributions in response to climate change, as species survival depends on the persistence of the suitability of a climatic niche space and their ability to keep pace with climatic changes in their realized niche. Many species are shifting their ranges in response to climate change. Climate velocity has become a commonly used index of the speeds and directions required for a species to keep pace with climate change. However, it is a simple measure of the rate at which climate is changing that disregards species-specific thresholds to their environment. In Chapter 2, using modern and LGM 60 m downscaled climate data for Alaska, I estimated the climate velocity for 8 different climate variables, as well as modeled LGM and modern distributions of white spruce using species distribution models. I then calculated the bioclimatic niche velocity of white spruce to estimate white spruce’s migration response and ability to keep pace with post-glacial climate change. Each climate velocity estimate was compared to all others, as well as to the bioclimatic niche velocity of white spruce to determine if climate velocity was a suitable predictor of a species’ migration response to climate change. I demonstrated that different climate variables yield different speeds and directions of climate, and that individual climate velocity estimates correlated poorly with the bioclimatic niche velocity as estimated for the Alaskan white spruce from the LGM to modern era. My results suggest that climate velocity alone does not provide suitable estimates of species migration responses to climate change due to climate velocity not accounting for species ecology and climatic tolerances that affect migration responses. In the previous chapter, I found evidence that bioclimatic niche velocity was a suitable approach to understanding high-resolution species migration pressures due to climate change. I then used these concepts to test if multiple species will migrate in the same direction, or independent of each other in response to climate change. Modern conservation strategies use static protected-area techniques to protect biodiversity from environmental change. However, static and stable assumptions of community dynamics assume that species will migrate with each other in response to climate change and form similar community assemblages in the future, even though it is well accepted that species respond to climate change independent of one another due to species-specific niche constraints. In Chapter 3, I calculated the bioclimatic niche direction for 72 of California’s native tree species derived from habitat suitability maps built using high-resolution downscaled climate data for the modern (1985-2015) and future (2070-2100) eras, and identified the directions of migration for each species in response to end of century climate change. Using each species’ modern habitat suitability maps, I identified and classified the different forest community types that occur throughout California during the modern era, and identified whether all the species of a community at a location displayed uniform (anisotropic) migration directions, or random (isotropic) migration directions in response to climate change. While in general, individual tree species of California displayed mean northward migration directions, a number of species were estimated to have alternative migration directions in response to climate change. A vast majority of California forest community types displayed isotropic species migration directions, indicating species will migrate independently of each other. Although all community types exhibited small amounts of anisotropic species migrations, locations where species migrate together were not clustered together throughout the community’s distributional range. My results indicated that the species that comprise California forest communities will migrate independently of each other, with the potential to create novel, no-analogue communities by the end of the 21st century. Additionally, my results suggested that current community conservation strategies should be revised and updated to reflect ecologists’ better understanding of climate change and the impact it has on species.

Graduation Semester

2018-12

Type of Resource

text

Permalink

http://hdl.handle.net/2142/102418

Copyright and License Information

Copyright 2018 Bailey Morrison

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