An examination of temporal trends, regional variation, and habitat-type differences in site-level Floristic Quality, and their implications for the use of Floristic Quality Assessment

Spyreas, Greg R.

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Description

Title

An examination of temporal trends, regional variation, and habitat-type differences in site-level Floristic Quality, and their implications for the use of Floristic Quality Assessment

Author(s)

Spyreas, Greg R.

Issue Date

2014-05-30T16:42:22Z

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

Molano-Flores, Brenda

Doctoral Committee Chair(s)

Molano-Flores, Brenda

Committee Member(s)

• Brawn, Jeffrey D.
• Dalling, James W.
• Matthews, Jeffrey W.
• Taft, John B.

Department of Study

Natural Res & Env Sci

Discipline

Natural Res & Env Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Floristic quality
• Conservation value
• Species conservatism
• Floristic Quality Assessment (FQA)
• Wetland
• Forest
• Prairie
• Grassland
• Habitat-type
• Vegetation-type
• Plant community
• Anthropogenic disturbance
• Habitat degradation
• Floral assemblage

Abstract

Floristic Quality Assessment (FQA) is a measure of site conservation value. It is premised on using an area’s plant species composition and diversity to estimate its human disturbance and degradation levels. FQA metrics are increasingly popular and influential for making land conservation, restoration, and policy decisions, as well as for scientific research. While it has been demonstrated that FQA metrics accurately measure site degradation/disturbance levels, many other FQA metric properties are unknown, especially compared to other ecological metrics. For this research, I assessed three important properties of FQA measures that are not understood: their regional patterns, their variation among different habitat-types, and their trends over time. I used site-level vegetation data from an Illinois statewide habitat monitoring program (Critical Trends Assessment Program, CTAP) to characterize FQA metric properties across regions and habitat-types. I found that forests had higher Floristic Quality values on average than wetlands. However, a separate analysis of a select group of the state’s most pristine habitats showed that the upper-range of forest Floristic Quality was equal to, or lower than, that of other habitat types. Therefore, the difference between wetlands and forests observed statewide was due to the greater relative abundance of highly degraded wetlands across the state. Across the state, Floristic Quality decreased with latitude overall, although the variation explained was not great. This relationship was stronger for forests, than wetlands, which showed a weak, quadratic latitudinal relationship. Forests were the only habitat that varied in richness, exhibiting a weak decline to the north. Temporal Floristic Quality trends were compared using a 50-year, old-field succession study. Values in all fields followed the same asymptotic pattern, reaching a peak after around 35-years. The consistency of FQA values over time show that when sites of different ages are compared with one another, an asymptotic trend in metric values should be considered the default trend that is likely over early- to mid-successional timeframes. In summary, these studies found FQA value differences among regions and habitat-types. However, there was little evidence that these differences reflect an inherent property to FQA values such that they would confound general use of these metrics. Instead, variation in Floristic Quality across habitat-types and regions was either found to be very small, or it was probably a reflection of human degradation levels across sites. Nonetheless, users must consider that some variation in FQA values could be attributable to the natural ecological characteristics of regions or habitat-types (i.e., not all variation in values was attributable to anthropogenic degradation/disturbance), and depending on users’ goals, variation may need to be accounted for. Specifically, these results highlight that site comparisons across very large latitudinal gradients, or ones that compare certain specific habitat-types with one another (e.g., upland versus floodplain forest), or ones where only very high-quality, pristine habitats are being compared, are the instances where FQA score comparisons should be done the most cautiously.

Graduation Semester

2014-05

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Copyright 2014 Greg Spyreas

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