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Brigham Young Univeristy (2018)

The responses of ants and other invertebrates to fire and rodent activity in North American deserts

Day Joshua David

Titre : The responses of ants and other invertebrates to fire and rodent activity in North American deserts

Auteur : Day Joshua David

Université de soutenance : Brigham Young Univeristy

Grade : Master of Science (MS) 2018

Résumé
Human activities are increasing the size, frequency and severity of disturbance across earth’s ecosystems including deserts. Exotic annual grasses have altered fire regimes by increasing the size, frequency, and severity of fires in these systems. Invertebrates make up a large proportion of ecosystem function and resilience. Ants are particularly good indicators of ecosystem stability. The ability of rodents to modify plant community structure post-fire, could result in rodent communities having important indirect effects on invertebrate communities. In chapter 1 we report changes in ant forager abundance and diversity with fire and rodent treatments over a three year period in the Great Basin. We found that while rodents had significant effects on the plant community in burned plots, this did not affect the ant community. Fire, however played a significant role in determining ant species richness and Shannon’s diversity index. Ant richness and diversity were reduced in burned areas compared to unburned areas. Total ant forager abundance was unaffected by fire, however, the abundance of the most common ant species, Pogonomyrmex occidentalis, increased in burned areas. The overall abundance of the other species was reduced in burned areas. We saw increases in the densities of P. occidentalis mounds in burned areas, but the average size of those discs decreased. The total area occupied by P. occidentalis mounds remained equal between burned and unburned plots. In chapter 2 we compare the abundances of different groups of invertebrates, as well as the abundances and diversity of the ant communities, between fire and rodent treatments. We then compared how those responses differed between sites in the Great Basin and Mojave deserts. In this study, we found that the abundances of most invertebrate groups remained unaffected by fire and rodent treatments. In the Great Basin, however, the abundance of flying-foragers was reduced in burned areas. At both locations, ant species richness and Shannon’s diversity were reduced in burned areas. Species richness and Shannon’s diversity were negatively correlated with invasive plant cover at both sites, and invasive plant cover was positively correlated with fire. The loss of diversity can spell losses in important ecosystem functions, and invasive grass fire cycles threaten to make these losses permanent.

Présentation

Page publiée le 9 novembre 2018, mise à jour le 10 novembre 2018