Assessing plant community composition fails to capture impacts of white-tailed deer on native and invasive plant species

Abstract

Excessive herbivory by native deer can reduce abundance of native vegetation and increase non-native vegetation, but how does the forest recover when deer are excluded or numbers are reduced? The expectation is that understory vegetation will return to a previously diverse condition, but this is not always the case. We found that community-level monitoring captured both change and lack of change in vegetation cover, height, species richness, and response of common species, but failed to capture response of uncommon species. In contrast, monitoring of target species favored by deer indicated increased plant size and reproduction when deer were reduced or excluded. We conclude that measuring individual plants (growth, flowering and reproductive success) provides a sensitive and powerful assessment of forest understory responses to deer management.

Residence time determines invasiveness and performance of garlic mustard (Alliaria petiolata) in North America

“…Decadal dynamics we describe further complicate A. petiolata impact assessments, which need to be separated from impacts of other stressors, such as white‐tailed deer ( Odocoileus virginianus ) and invasive earthworms (Didham et al ., 2007; Dávalos et al ., 2014, 2015a, b; Frelich et al ., 2019). Few such studies exist (Waller and Maas, 2013; Dávalos et al ., 2014, 2015a, b, c; Nuzzo et al ., 2017; Dávalos et al 2014, 2015a, b) but future study designs, as well as interpretation of exiting data need to be cognizant of presence and importance of other stressors and the possibility of A. petiolata invasion and decline that occur over a decadal timeframe. This limits the ability of short‐term experiments to capture long‐term impacts in the field and calls for more longitudinal research.…”

Effects of maternal source and progeny microhabitat on natural selection and population dynamics in Alliaria petiolata

“…It is important to note that we did not measure certain other factors that could affect our findings, including the degree of genetic variation in source populations, which may or may not vary across microhabitats (Stanton and Galen, ; Colautti and Lau, ). In addition, direct and indirect interactions with other organisms such as large herbivores and earthworms (Kalisz et al., ; Davalos et al., ; Nuzzo et al., ) and plant competitors (e.g., Meekins and McCarthy, ; Davalos et al., ) are known to affect garlic mustard and may influence population dynamics and trait expression. Although we controlled for some biotic interactions by planting gardens within a natural matrix of co‐occurring plants and excluding seed predation with screening over the winter, we did not experimentally evaluate the effects of other biotic factors on performance.…”

Where Is Garlic Mustard? Understanding the Ecological Context for Invasions of Alliaria petiolata

“…Deer and earthworm densities vary across sites, and the strength of their interactions and the resulting influence on garlic mustard invasion likely varies across spatial and temporal scales. A long-term comparative multisite and multistate study showed that although deer presence influences nonnative earthworm abundance, deer herbivory is the ultimate driver of native species loss (Nuzzo et al 2017 ).…”