Investigation of insect remains in lake-sediments for developing a record of past insect outbreaks
Forest insects, such as bark beetles and defoliators, have existed with their tree hosts, probably for millennia. These insect populations have fluctuated in abundance through time and their impact on forests at any particular time seems to be regulated by weather, climate, and disturbance regimes (Logan et al., 2003 [Frontiers in Ecology and the Environment 1]). Although these species are present in most western forests in low numbers, bark beetles become extremely abundant and attack healthy mature trees during outbreaks, killing vast tracts of forested land. The relationship between climate change, insect outbreaks, and fire is poorly understood, but trees injured by fire or other insect infestations seem especially vulnerable to mountain pine beetle, and conversely beetle-killed forests are the setting for the most intense forest fires in recent years.
We are attempting to develop a better understanding of the relationship between infestations of mountain pine beetle (Dendroctonus ponderosae) and the accumulation of their remains in lake sediments. Our goal is to assess the potential of such records to provide long-term information on past outbreaks. This study takes advantage of the unique opportunity offered in the Sawtooth National Recreation Area, where mountain pine beetle outbreaks are well documented for the last 50 years and where over 80% of the trees in large areas are currently dying from beetle attack. Several small lakes are located in infested areas that are suitable for paleoecological study. This fortuitous combination of circumstances allows us to address the basic questions necessary for an investigation of mountain pine beetle outbreaks in prehistoric time. Specifically, we seek to collect recent sediment from lakes in and outside of currently infested forest, determine the abundance of insect parts in these different settings, and develop an understanding of the relationship between the abundance of insect remains in the lake sediment and the location and intensity of infestations. We also are collecting short cores from two lakes to retrieve the sediments of the last few centuries. The cores are dated with the lead-210 method, which provides subdecadal resolution for the last 200 years. Periods of high insect abundance are compared against the years of known mountain pine beetle outbreak in the Sawtooth region. We consider this project to be the first phase of a larger campaign to study the relationship between past insect outbreaks and changes in climate, vegetation, and fire on times scales of centuries to millennia. This information can help provide a context for understanding current outbreaks, their ecological consequences, and their relation to other disturbances and climate change.
Long-term ecohydrologic variability in the Sawtooth region of central Idaho
The Sawtooth National Recreation Area (SNRA) of central Idaho has been severely disturbed by the recent drought and increased spring and summer temperatures. Water shortages can affect natural resources, disturbance regimes, recreational opportunities, and local livelihoods. The ecological manifestations of current drought are evident in the vast areas of beetle-killed forest, increased likelihood of catastrophic fires, and lowering of lake levels. Although water shortages are dramatic, the occurrence of such conditions in the past is poorly documented. Are current drought levels unprecedented, and if so, on what time scale? Have mountain pine beetle (Dendroctonus ponderosae) infestations occurred during other dry periods and, if so, are they always associated with large fires? Current climate projections of warming conditions in this region point to a need for more information about natural climate variability and its effects on forest health and hydrology. This study is a collaborative effort between Dr. Whitlock (Montana State University) and Dr. Pierce (Boise State University). The MSU-INRA project will examine the ecohydrological history of a small, relatively simple watershed in the SNRA to reconstruct environmental changes over the last 11,000 years. The high-resolution analysis will help determine the frequency of drought events occurring on decadal to millennial year time scales and assess the ecological response to past droughts, in terms of fire, insect outbreaks, lake-level adjustments, and vegetation changes. The BSU-INRA project will investigate modern relationships between hydrology, climate, and fire activity in the same region and provide an important calibration data set for the longer record. The recent incidence of large fires in the northwestern U.S. has been attributed to shifts in the timing of spring snowmelt and peak spring streamflow. Establishing relationships between antecedent hydrologic conditions, summer drought and fire on multiple time scales offers a powerful tool to for projecting future fire seasons. Our poor understanding of recent and past water- linkages in central Idaho limits management planning efforts that seek to consider historical range of variability. For example, we do not know the nature of ecohydrological thresholds that might greatly alter ecosystem services, including clean water, timber, habitat, recreational and economic opportunities. The study will utilize and complement research activities underway by cooperating scientists from Boise State University, Montana State University, Utah State University, and Idaho State University, who are looking at the ecology and hydrology of Sawtooth lakes, streams, and glaciers. It will also build on a USDA-funded study to examine the record of recent insect outbreaks in lake sediments in the Sawtooth region. The information obtained from this project will also provide relevant teaching materials for students, teachers, and visitors interested in understanding a region currently experiencing dynamic ecological changes.
Forest insects, such as bark beetles and defoliators, have existed with their tree hosts, probably for millennia. These insect populations have fluctuated in abundance through time and their impact on forests at any particular time seems to be regulated by weather, climate, and disturbance regimes (Logan et al., 2003 [Frontiers in Ecology and the Environment 1]). Although these species are present in most western forests in low numbers, bark beetles become extremely abundant and attack healthy mature trees during outbreaks, killing vast tracts of forested land. The relationship between climate change, insect outbreaks, and fire is poorly understood, but trees injured by fire or other insect infestations seem especially vulnerable to mountain pine beetle, and conversely beetle-killed forests are the setting for the most intense forest fires in recent years.
We are attempting to develop a better understanding of the relationship between infestations of mountain pine beetle (Dendroctonus ponderosae) and the accumulation of their remains in lake sediments. Our goal is to assess the potential of such records to provide long-term information on past outbreaks. This study takes advantage of the unique opportunity offered in the Sawtooth National Recreation Area, where mountain pine beetle outbreaks are well documented for the last 50 years and where over 80% of the trees in large areas are currently dying from beetle attack. Several small lakes are located in infested areas that are suitable for paleoecological study. This fortuitous combination of circumstances allows us to address the basic questions necessary for an investigation of mountain pine beetle outbreaks in prehistoric time. Specifically, we seek to collect recent sediment from lakes in and outside of currently infested forest, determine the abundance of insect parts in these different settings, and develop an understanding of the relationship between the abundance of insect remains in the lake sediment and the location and intensity of infestations. We also are collecting short cores from two lakes to retrieve the sediments of the last few centuries. The cores are dated with the lead-210 method, which provides subdecadal resolution for the last 200 years. Periods of high insect abundance are compared against the years of known mountain pine beetle outbreak in the Sawtooth region. We consider this project to be the first phase of a larger campaign to study the relationship between past insect outbreaks and changes in climate, vegetation, and fire on times scales of centuries to millennia. This information can help provide a context for understanding current outbreaks, their ecological consequences, and their relation to other disturbances and climate change.
Long-term ecohydrologic variability in the Sawtooth region of central Idaho
The Sawtooth National Recreation Area (SNRA) of central Idaho has been severely disturbed by the recent drought and increased spring and summer temperatures. Water shortages can affect natural resources, disturbance regimes, recreational opportunities, and local livelihoods. The ecological manifestations of current drought are evident in the vast areas of beetle-killed forest, increased likelihood of catastrophic fires, and lowering of lake levels. Although water shortages are dramatic, the occurrence of such conditions in the past is poorly documented. Are current drought levels unprecedented, and if so, on what time scale? Have mountain pine beetle (Dendroctonus ponderosae) infestations occurred during other dry periods and, if so, are they always associated with large fires? Current climate projections of warming conditions in this region point to a need for more information about natural climate variability and its effects on forest health and hydrology. This study is a collaborative effort between Dr. Whitlock (Montana State University) and Dr. Pierce (Boise State University). The MSU-INRA project will examine the ecohydrological history of a small, relatively simple watershed in the SNRA to reconstruct environmental changes over the last 11,000 years. The high-resolution analysis will help determine the frequency of drought events occurring on decadal to millennial year time scales and assess the ecological response to past droughts, in terms of fire, insect outbreaks, lake-level adjustments, and vegetation changes. The BSU-INRA project will investigate modern relationships between hydrology, climate, and fire activity in the same region and provide an important calibration data set for the longer record. The recent incidence of large fires in the northwestern U.S. has been attributed to shifts in the timing of spring snowmelt and peak spring streamflow. Establishing relationships between antecedent hydrologic conditions, summer drought and fire on multiple time scales offers a powerful tool to for projecting future fire seasons. Our poor understanding of recent and past water- linkages in central Idaho limits management planning efforts that seek to consider historical range of variability. For example, we do not know the nature of ecohydrological thresholds that might greatly alter ecosystem services, including clean water, timber, habitat, recreational and economic opportunities. The study will utilize and complement research activities underway by cooperating scientists from Boise State University, Montana State University, Utah State University, and Idaho State University, who are looking at the ecology and hydrology of Sawtooth lakes, streams, and glaciers. It will also build on a USDA-funded study to examine the record of recent insect outbreaks in lake sediments in the Sawtooth region. The information obtained from this project will also provide relevant teaching materials for students, teachers, and visitors interested in understanding a region currently experiencing dynamic ecological changes.
