Ungulate species may have differential effects on plant community development after fire.

An interesting idea: Ungulate species may have differential effects on plant community development after fire.

Aaron Rhodes, Plant and Wildlife Sciences, Brigham Young University

Fire and herbivore disturbance drive successional cycles and ecosystem function.  While the effects of both fire and herbivory have been well studied, no disturbance acts in isolation, and the potential for interactive effects is great.  There is a current need for understanding of how fire and herbivory contribute to the regeneration and development of plant communities.

In many ecosystems, the plant community is under the pressure of herbivory from both domestic and wild ungulates. However, it is difficult to differentiate between interspecific effects on the plant community.  Competitive interactions of multiple ungulate species have the potential to change the behavior of ungulates and affect the development of plant communities.  Knowledge of these interactions and their impacts is particularly important to land managers who must balance the maintenance of native ungulate populations with sustainable land use of domestic livestock.

 This photo documents the loss of hundreds of acres of forested land because of excessive ungulate herbivory after a timber harvest.

This photo documents the loss of hundreds of acres of forested land because of excessive ungulate herbivory after a timber harvest.

A new experiment:

In 2012, we embarked on a new study whose objective is to differentiate between the effects of wildlife and livestock on forest regeneration and plant community development. We hypothesized that ungulates have strong top down effects on the trajectory of plant community development after fire. Further, the impact of each individual ungulate species is different and compounded by interactive effects of simultaneous herbivory by multiple species. Differential forage selection by herbivores can lead to shifts in plant communities due to behavioral differences in resource selection. As interspecific competition for resources increase, interactive effects may emerge. Also, we hypothesized that ungulates play a pivotal role in suppressing the reforestation of aspen forests after fire by consuming aspen basal shoots. Further, we aim to characterize the impact of each species and their relative contribution to that suppression. Ungulate herbivory could have an important role in the successional cycles of subalpine forests through their ability to suppress aspen regrowth after major disturbances. In order to differentiate between the browse impacts of deer, elk, and cattle, we constructed a set of 3 fencing types that excluded combinations of species.

  Aspen root systems generally survive major disturbances such as fire and timberharvest; they can regenerate forests by shooting up suckers as soon as weeks after the fire.

Aspen root systems generally survive major disturbances such as fire and timberharvest; they can regenerate forests by shooting up suckers as soon as weeks after the fire.

 This fence is 2 meters in height and is designed to exclude Deer, Elk, and Wildlife.

This fence is 2 meters in height and is designed to exclude Deer, Elk, and Wildlife.

 

 

 

 

 

 

 

 

 

 

 

 

 This fencing treatment excludes livestock but allows access to deer and elk who nimbly hop over it.

This fencing treatment excludes livestock but allows access to deer and elk who nimbly hop over it.

This fence allows for deer to enter the small 50cm gap at the bottom of this fence.

This fence allows for deer to enter the small 50cm gap at the bottom of this fence.

 

 

 

 

 

 

 

 

 

 

 

1. In order to quantify the differential impact of herbivory on pioneer species after fire disturbance we by constructing fences in recently burned areas. We tested for the interaction between fire and ungulate herbivory   (Can we use observational studies of plant communities and herbivore densities to get at this interaction?)

2. We characterized differences in plant community development as a function of fire and herbivory.

Questions: What are the differential impacts of ungulate species on plant community development after fire? What are the differential impacts of ungulate species on secondary succession of sub alpine forests after fire?  (Secondary questions: Does ungulate herbivory induce defense chemical production? What is the temporal variation in forage selection by ungulates?)

We are very excited about this new research project and are already beginning the analysis of the first year’s treatment effects.

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