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Replication data for: Species-specific size vulnerabilities in a competitive arena: Nutrient heterogeneity and soil fertility alter plant competitive size-asymmetries
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Brown, Charlotte; Oppon, Kenneth; Cahill Jr., James F. — 2019-04-01 This is the replication data associated with our article in our "Functional Ecology" titled "Species-specific size vulnerabilities in a competitive arena: Nutrient heterogeneity and soil fertility alter plant competitive size-asymmetries". Please see the ReadMe file for details on dataset contents.
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Data from: Rapid increases in forest understory diversity and productivity following a mountain pine beetle (Dendroctonus ponderosae) outbreak in pine forests
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Pec, Gregory J.; Karst, Justine; Sywenky, Alexandra N.; Cigan, Paul W.; Erbilgin, Nadir; Simard, Suzanne W.; Cahill Jr., James F.; Cahill, James F. — 2016-03-26 The current unprecedented outbreak of mountain pine beetle (Dendroctonus ponderosae) in lodgepole pine (Pinus contorta) forests of western Canada has resulted in a landscape consisting of a mosaic of forest stands at different stages of mortality. Within forest stands, understory communities are the reservoir of the majority of plant species diversity and influence the composition of future forests in response to disturbance. Although changes to stand composition following beetle outbreaks are well documented, information on immediate responses of forest understory plant communities is limited. The objective of this study was to examine the effects of D. ponderosae-induced tree mortality on initial changes in diversity and productivity of understory plant communities. We established a total of 110 1-m2 plots across eleven mature lodgepole pine forests to measure changes in understory diversity and productivity as a function of tree mortality and below ground resource availability across multiple years. Overall, understory community diversity and productivity increased across the gradient of increased tree mortality. Richness of herbaceous perennials increased with tree mortality as well as soil moisture and nutrient levels. In contrast, the diversity of woody perennials did not change across the gradient of tree mortality. Understory vegetation, namely herbaceous perennials, showed an immediate response to improved growing conditions caused by increases in tree mortality. How this increased pulse in understory richness and productivity affects future forest trajectories in a novel system is unknown.
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Data from: Nutrient foraging behaviour of four co-occuring perennial grassland plant species alone does not predict behaviour with neighbours
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McNickle, Gordon G.; Deyholos, Michael K.; Cahill Jr., James F.; Cahill, James F. — 2016-06-23 The spatial arrangement of nutrients and neighbours in soil influences plant growth and reproduction. Plants often respond to such stimuli through plasticity in root proliferation (root mass per soil volume), or the breadth of their root system. Here, we asked how plants adjust nutrient foraging strategies when grown alone or with neighbours. We asked (i) Does root proliferation into nutrient-rich patches when plants are grown alone predict root proliferation when plants are grown with neighbours? (ii) What factors (nutrients or neighbours) best predict the probability of root placement at different soil locations? (iii) How does the spatial distribution of nutrients alter the degree to which neighbours suppress plant growth? To answer these questions, we grew four grassland species either as individual plants or in competition, in patchy or patch-free soil, in a factorial design. We used genomic DNA to identify the spatial distribution of roots of each species when plants were grown in mixtures. The root foraging behaviour of individuals grown alone did not consistently predict behaviour in mixture. Specifically, (i) the behaviour of individually grown plants predicted behaviour of competing plants inside patches, but not in background soil. We observed over-proliferation of roots in background soil relative to what was expected from plants grown alone. (ii) Neighbours were consistently the most important variable for predicting the placement of roots in soil and caused either an increase in root system breadth, or no change relative to alone. (iii) If a species experienced growth suppression when grown in competition, individuals experienced this more severely in patchy soil compared to patch-free soil. Synthesis. Game theoretic models have predicted that under interspecific competition, over-proliferation of roots in the presence of neighbours might occur for some species but not others. Our data are consistent with these predictions but more work is needed. Nutrient foraging studies have primarily focused on plants grown alone or assumed that plants do not respond separately to neighbours and nutrients. Our data call these practices into question and contribute to a growing understanding that plants integrate information about both nutrients and neighbours when placing roots in soil.
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Replication Data for: Ice age refugium shows potential of geohistorical data to guide modern conservation efforts
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Morley, Nathaniel E. D.; Schneider, Chris L.; Cahill Jr., James F.; Sullivan, Corwin; Leighton, Lindsey R. — 2024-09-10 This repository contains the code and data required to replicate Figures 3, 4, S1, and S2 for the manuscript entitled "Ice age refugium shows potential of geohistorical data to guide modern conservation efforts." Also contains the code required to perform the Monte Carlo simulation used to calculate the probability of a refugium explaining the regional decline and recovery in spruce incidence. Manuscript summary: Many biologists regard refugia as locations that shelter a population during an environmental crisis, thus facilitating post-crisis ecological recovery. However, identifying refugia based on short-term contraction and survivorship alone is problematic as this approach fails to account for whether the species survives and recovers in the long-term. Protecting refugia that are unstable in the long-term could lead to wasted conservation efforts and the species’ extinction. Here, we present a novel method for identifying geohistorical refugia that emphasizes a population’s long-term success and post-crisis recovery. To test this method’s utility, we present a case-study using pollen data for three ecologically distinct plant taxa from lake cores over the past 20 kyr in northern Alaska, USA. Using Monte Carlo methods, we found a statistically significant decrease in spruce incidence across the study region between 13.0 – 10.0 ka. During this interval, spruce persisted at relatively high abundance in one locality that may have provided the cool, humid conditions necessary for spruce survival during an interval of warmer, drier regional climate. This locality acted as the center for post-crisis re-expansion after the warm, dry conditions passed, indicating that this location was likely a refugium. If successful geohistorical refugia can be identified, subsequent analyses should aim to identify which environmental conditions allowed the population to survive within the refugium and re-expand after the crisis, thus providing critical information for policymakers when identifying locations for successful, long-term protected areas in the face of the ongoing biodiversity crisis.

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(Author: Cahill Jr., James F.)

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