Detecting and understanding disturbance is a challenge in ecology that has grown more critical with global environmental change and the emergence of research on social–ecological systems. We identify three areas of research need: developing a flexible framework that incorporates feedback loops between social and ecological systems, anticipating whether a disturbance will change vulnerability to other environmental drivers, and incorporating changes in system sensitivity to disturbance in the face of global changes in environmental drivers. In the present article, we review how discoveries from the US Long Term Ecological Research (LTER) Network have influenced theoretical paradigms in disturbance ecology, and we refine a framework for describing social–ecological disturbance that addresses these three challenges. By operationalizing this framework for seven LTER sites spanning distinct biomes, we show how disturbance can maintain or alter ecosystem state, drive spatial patterns at landscape scales, influence social–ecological interactions, and cause divergent outcomes depending on other environmental changes.
Mount St. Helens erupted on May 18, 1980 and dramatically changed the surrounding landscape. In the forty years since the eruption, scientists from the USDA Forest Service Pacific Northwest Research Station and their colleagues around the world have studied ecological recovery at the volcano, using it as a living laboratory for ecological research. Today, Mount St. Helens is the most studied volcano in the world and has changed how we understand ecological recovery and study volcanically active regions. To learn more about the scientific findings and ongoing research at Mount St. Helens, check out our Mount St. Helens webpage.
Pacific martens (Martes caurina) remain common in montane regions of the Pacific states, yet their distribution and status on the Olympic Peninsula, Washington, is uncertain. Between 1968–2008, six reliable marten detections exist; a dead juvenile female (2008) indicates martens were reproducing on the Peninsula within the last decade. To assess the status of martens, we describe carnivore surveys conducted from 1991–2008 (n = 223 stations). Additionally, we present results from three survey efforts we conducted from 2013–2016 (n = 747 stations). Although a suite of carnivore species was detected, surveys from 1991–2008 failed to detect either martens or fishers. Surveys from 2013–2016 detected reintroduced fishers, and resulted in two marten detections near Mt. Olympus, 4 km apart. A marten was photographed opportunistically near Mt. Cruiser in 2015, 44 km from Mt. Olympus. Altogether, nine reliable detections of Pacific martens were obtained between 1968 and 2016, including three since 2008. Evidence suggests martens are absent from the lower elevation regions they once occupied and occur at exceedingly low densities at higher elevations. To understand the trend in marten populations on the Peninsula and develop appropriate conservation strategies, additional broad- and fine-scale surveys using detection devices that enable the genetic identification of individuals will be needed.
An exceptionally powerful storm struck southwestern Washington in December 2007 causing large debris flows in two adjacent streams. The two affected streams had been studied prior to the storm, providing a rare opportunity to examine ecosystem recovery. We monitored the streams and their riparian zones for six years after the disturbances to determine whether recovery rates of biota, physical habitat, and water temperature differed, and if so, what factors affected resilience. Along both streams, the debris flows removed wide swaths of soil, rock, and coniferous riparian forests, widening the active channel and increasing solar exposure and summer water temperatures. Initially depauperate of vegetation, after four years red alder trees dominated the riparian plant communities. The warmer water, greater solar radiation, and unstable substrates likely contributed to variable benthic insect and tailed frog tadpole densities over time, although benthic insect communities became more similar after three years. The debris flows also decreased channel slopes and removed channel step barriers such that cutthroat trout were able to rapidly occupy habitats far upstream, but sculpins were slower to recolonize and both fish species exhibited some differences in recovery between the two streams. Crayfish were severely impacted by the debris flows; this may be due to attributes of their life history and the timing of the flows. Overall, we found that recolonizing aquatic species exhibited varying levels of resilience and recovery after the disturbances being related to the influence of physical habitat conditions, species dispersal ability, and the presence of nearby source populations.
Climate change is projected to impact ecosystem functioning, however its effect on the provision of ecosystem services is uncertain. This is particularly relevant on federal lands which harbor extensive tracts of natural vegetation. We assessed change in four ecosystem services (water runoff, groundwater recharge, carbon storage, and biodiversity) and one disservice (sediment export) in southern California between current and end-of-century (2070–2099). We used five general circulation models ranging from warmer wetter (CNRM-CM5, CCSM4) to hotter, marginally drier (IPSL-CM5A-LR) to hotter drier (FGOALS-g2, MIROC-ESM) under RCP8.5. We found greatest projected change in water runoff, from an increase of 127% under a warmer wetter GCM to a decrease of −60% under a hotter drier future. Carbon storage is projected to change the least, from an increase of 52% to a decrease of −31% across GCMs. We also determined that one-third of high biodiversity areas are threatened by high change in climatic water deficit. We estimated the current monetized annual value of sediment removal costs to be $172 million per year and the economic value of carbon storage as $7.5 billion. Understanding the impacts of climate change on ecosystem services can help develop climate-smart strategies for the sustainable management of natural resources.
Trees injured and weakened by wild or prescribed fires are susceptible to bark beetle attacks. Nonaggressive Dendroctonus valens in North American forests is often the first bark beetle to colonize fire injured pine. Although not an important contributor to post-fire mortality it does vector pathogens, and surviving diseased trees may serve as pathogen redistribution centers. Traps baited with both ethanol and monoterpene lures are known to attract D. valens, and fire injured pine are known to accumulate ethanol in tissues containing monoterpenes. The primary objective of this study was to quantify ethanol concentrations in fire injured ponderosa pine tissue near pioneering D. valens gallery entrances and compare them with levels from the unattacked side of the same tree, or their unattacked neighbors. The secondary objective was to quantify α-pinene in the same samples. Two separate but related studies were conducted, one in a June wildfire, the other in an October prescribed fire, near Bend, Oregon, USA where phloem and sapwood cores were collected for analysis by headspace gas chromatography. Wildfire damaged trees attacked by D. valens were sampled above beetle gallery entrance holes and on the opposite bole side without an entrance hole. An adjacent unattacked tree of similar size and injury was sampled at the same aspect and height. Prescribed fire damaged trees were sampled in groups of three characterized by: (1) one or more D. valens attacks with 100% crown scorch; (2) unattacked with 100% crown scorch; and (3) unattacked with ≤95% crown scorch. They were sampled above a beetle gallery entrance or equivalent positions on unattacked trees. Ethanol and α-pinene concentrations at both fires were higher in tissues above beetle entrance holes than in corresponding tissues from unattacked sides of the same tree, or adjacent trees. Ethanol concentrations in wildfire damaged trees were three or more orders of magnitude greater than in prescribed fire trees, likely a consequence of wildfire trees experiencing higher temperatures and greater heat stress indicated by injury measurements. Ethanol concentrations in stem bark char, analyzed only in the prescribed fire were two to four orders of magnitude greater than in the underlying phloem, a result of it being adsorbed and concentrated during outward diffusion. Ethanol synthesis, accumulation, and atmospheric release in combination with host monoterpenes, is proposed as the critical physiological process contributing to initial D. valens host tree and bole position selection of fire stressed ponderosa pine.
Reviewing: William J. Matthews and Edie Marsh-Matthews, Stream Fish Community Dynamics: A Critical Synthesis, 2017 Johns Hopkins University Press, 330 pp.
Community dynamics are often difficult relationships to describe because they encompass multiple taxa involved in numerous types of interactions of varying strengths, all of which may shift over space and time. Gaining insights from a suite of several long-term projects is difficult logistically and can be difficult to sustain. However, in their book Stream Fish Community Dynamics: A Critical Synthesis, Matthews and Marsh-Matthews offer a deeper understanding of warm-water fish community dynamics from a commitment to their research over their shared lifetimes.
We discuss a recent paper which evaluated the hydrologic changes resulting from a pond-and-plug meadow restoration project in the Sierra Nevada Mountains of California. In the study, measurements of streamflow into and out of the meadow suggested late-summer baseflow increased as much as five-fold when compared with prerestoration conditions. However, the volume of streamflow attributed to the restored meadow (49,000–96,000 m3 over four months) would require that 2.5–4.8 m of saturated meadow soils drain during summer months. The groundwater data from this meadow record only 0.45 m of change over this timeframe, which is less than might be expected from plant use alone (0.75 m), suggesting this restored meadow may be acting as a water sink throughout summer rather than a source.