Description

Invasion paradox, a change of direction in native-exotic richness relationships (NERRs) from negative at small scales to positive at large scales, has been shown to exist in many environments. A major explanation for these patterns is environmental heterogeneity, and to a lesser extent, species pool size. It is likely that a combination of these factors is producing these patterns and determines if and how they appear in certain environments. Beta diversity, which describes the heterogeneity of species composition among assemblages and as the scalar between local richness and regional richness (species pool size), could serve as a proxy for these factors, and therefore assess their combined influence on native-exotic richness relationships. Here, we hypothesize that the directional changes in NERRs can be explained by the degree of beta diversity among the communities being compared. We used census data from the Smithsonian Conservation Biology Institute’s Large Forest Dynamics Plot (SCBI-LFDP). Our data set consists of approximately 40,000 mapped tree stems in a 25.6 hectare plot located in Front Royal, VA. With the help of ArcGIS, we divided the plot into units of multiple sizes in order to explore the cross-scale dynamics of NERRs and beta diversity. Results show that inconsistent patterns in NERR observed across scales and across ecosystems can be partially explained by variations in the level of beta diversity and the relationship between beta diversity and scale. This hypothesis may serve as a unifying theory to explain the positive relationship between native and exotic diversity at large scales.

Location

Stewart Center 302

Start Date

11-2016

Document Type

Other

Keywords

Biodiversity, invasion, invasion paradox, biotic resistance

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Nov 1st, 12:00 AM

Analyzing the native-exotic richness relationship using native beta diversity

Stewart Center 302

Invasion paradox, a change of direction in native-exotic richness relationships (NERRs) from negative at small scales to positive at large scales, has been shown to exist in many environments. A major explanation for these patterns is environmental heterogeneity, and to a lesser extent, species pool size. It is likely that a combination of these factors is producing these patterns and determines if and how they appear in certain environments. Beta diversity, which describes the heterogeneity of species composition among assemblages and as the scalar between local richness and regional richness (species pool size), could serve as a proxy for these factors, and therefore assess their combined influence on native-exotic richness relationships. Here, we hypothesize that the directional changes in NERRs can be explained by the degree of beta diversity among the communities being compared. We used census data from the Smithsonian Conservation Biology Institute’s Large Forest Dynamics Plot (SCBI-LFDP). Our data set consists of approximately 40,000 mapped tree stems in a 25.6 hectare plot located in Front Royal, VA. With the help of ArcGIS, we divided the plot into units of multiple sizes in order to explore the cross-scale dynamics of NERRs and beta diversity. Results show that inconsistent patterns in NERR observed across scales and across ecosystems can be partially explained by variations in the level of beta diversity and the relationship between beta diversity and scale. This hypothesis may serve as a unifying theory to explain the positive relationship between native and exotic diversity at large scales.