LTER Key Research Findings

Among the many research results from LTER sites, some findings stand out as being particularly important to achieve the LTER goal of providing information to conserve, protect, and manage the nation's ecosystems. Short descriptions of key findings at each site emphasize the importance of long-term data in understanding the pace and pattern of ecological change.

Art and Nature (AND LTER)
Decades of experience with the conflicts concerning management of forests of the Pacific Northwest, especially old growth, reveal that these societal issues cannot be addressed with science alone – at their core these are issues of personal values. Towering, ancient forests and the incredible complexity of ecosystems populated by thousands of species are sources of inspiration distinctive to each...
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Old Growth (AND LTER)
Scientific, social, and economic perspectives on old-growth forests and our treatment of them have changed dramatically over the last 150 years in the Pacific Northwest. Research at the H.J.A. Andrews LTER has been central to many those changes in the last 30 years, when perceptions about old-growth shifted from an unproductive forest to be eliminated through exploitation to a valued ecosystem to...
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River Continuum (AND LTER)
The River Continuum Concept (Vannote et al. 1980) has become the dominant concept of how stream ecosystems vary from headwaters downstream to large rivers. The Andrews Forest was one of four primary sites contributing to this pioneering ecosystem paradigm in the late 1970s and early 1980s. The basic idea is that aquatic communities and ecological processes of the stream ecosystem change...
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Science and Policy (AND LTER)
A partnership between research and management at the H.J. Andrews Experimental Forest LTER has helped transform forest management and policy in the Pacific Northwest and the U.S.A. (Luoma 2006, Steel et al. 2004). This partnership has spawned new practices and policies for ecosystem management, conservation of old-growth forests, protection of forest streams, and management of dead wood in...
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Temperature Patterns in Mountain Ecosystems (AND LTER)
The basic mechanisms for how temperatures change with elevation in mountain landscapes and how temperature inversions form in valleys have been understood for many years. Under "normal" circumstances, temperatures decrease at a known rate, the "lapse rate", with elevation. Knowledge of the lapse rate allows meteorologists and scientists to extrapolate from a few measurement locations across a...
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The Ecosystem Value of Dead Wood (AND LTER)
Traditionally dead wood has been considered a wasted resource and a hazard in forested landscapes that needed to be eliminated. This all changed starting in the 1970s when Andrews scientists began to examine the many roles dead wood played in forests and streams. This included a wide range of ecological and geomorphic functions including as a habitat and food source for many terrestrial and...
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Arctic Warming (ARC LTER)
Research at the Arctic LTER site is transforming scientific understanding of how the arctic landscape will respond to climate change. Warming of the Arctic is thawing previously frozen ground (permafrost) and in some places, especially where there is buried ice, the thawed soil forms sinks and slumps called thermokarst terrain. In extreme cases this thermokarst terrain leads to complete...
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Cascade Effect (ARC LTER)
The experimental addition of low levels of phosphorus (P) to an arctic stream created a gradual transformation of the tundra stream ecosystem from a cobble-bottom stream covered with diatom-dominated biofilm to a moss-dominated bottom that hosted a different community composition of invertebrates. This transformation was not predicted and was a surprise because for the first seven or eight years...
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Food Sources (ARC LTER)
Arctic Alaska contains hundreds of thousands of lakes, almost all quite shallow. Research at the Arctic LTER on shallow lakes demonstrates that the food webs leading to fish are based mostly on primary production by bottom-dwelling algae rather than on plankton food webs. Yet, arctic fishery biologists continue to emphasize planktonic food webs and recent reviews of climate change in arctic...
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Linked Cycles (ARC LTER)
Our understanding of tundra biogeochemistry has been transformed by long term research by the ARC LTER showing that the carbon and nitrogen cycles are strongly linked and interactive at all steps in the cycle of organic matter. Changes in the arctic carbon cycle in response to climate change cannot be understood or predicted without considering carbon-nutrient interactions. The basis for the...
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Process Discovered (ARC LTER)
In the early 1990s researchers at the Arctic LTER discovered the answer to a long-standing question of why the recently measured and modeled rates of net ecosystem productivity on land were so much higher than the rates of carbon accumulation integrated over time as found in soil and peat cores. The researchers discovered that carbon dioxide and methane dissolved in groundwater in very high...
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Tracer Techniques (ARC LTER)
A tracer approach to investigation of the nitrogen (N) cycle of streams, first developed at the Arctic LTER, has transformed scientific understanding of the nitrogen cycle and food web structure in flowing waters. By adding a continuous drip of 15N-NH4 (ammonium) or 15N–NO3 (nitrate) to a stream and then sampling the downstream transport, uptake and recycling of nitrogen over distance and...
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For the People, By the People (BES LTER)
Conventional wisdom often holds that concern for the environmental is concentrated among residents of wealthier and predominantly white communities who can afford to make quality of life issues, such as environmental quality, a high priority. Poorer, ethnically mixed communities are assumed to be more preoccupied with satisfying basic needs than with protecting the environment. This conventional...
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Islands of Green (BES LTER)
Urban ecosystems offer fundamentally new habitat for both animal and plant species. While originally viewed as largely disturbed environments, urban places are emerging not as ecological disasters, but rich environments where humans interact strongly with organisms, generating new habitat and assembling new ecological communities. In Baltimore, green space is now known to harbor many species...
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Mapping Urban Lands (BES LTER)
Traditional land classifications in the US emphasized the contrast between urban or built-up versus wild or managed lands. Based on that fundamental split, urban lands have been subdivided into such categories as commercial, residential, transportation, industrial, and mixed urban. For some purposes, this relatively coarse classification is useful. However, scientists interested in the joint...
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Perceptions of Justice (BES LTER)
Twenty-five years of environmental justice scholarship shows that racial and ethnic minorities are more likely than whites to live near facilities that release toxins into the air, land, and water. Even when incomes are similar, racial and ethnic minorities are overrepresented in neighborhoods with polluting industry nearby. In Baltimore, we find an unexpected pattern -- white neighborhoods...
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River Corridors (BES LTER)
Riparian (streamside) zones are critical transition zones in the landscape, situated in between upland and aquatic ecosystems. There is a complex web of interactions between riparian zones and surrounding ecosystems that have an important influence on the movement of water and nutrients across the landscape and on biodiversity. Many nutrients are transported from upland ecosystems, especially...
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Urban Watersheds (BES LTER)
A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. The watershed approach, where the quantity and quality of water leaving a watershed is sampled is like urinalysis, where doctors monitor chemicals in the urine to assess a patient's health. The watershed approach has been applied very successfully in many LTER sites to understand...
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Adapting to Change (BNZ LTER)
Changes in climate and fire regime are already affecting rural Alaskan communities where indigenous people have historically led a subsistence lifestyle as hunters, fishers, and gatherers. Warming has changed the timing of freeze up and melting of rivers and reduced the thickness of river ice and therefore reduced the safety of winter travel and access to some hunting grounds. Increased...
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Browse Control (BNZ LTER)
Studies of the interactions between vegetation processes and mammalian herbivory have been part of BNZ LTER research for over 20 years. We have found that browsing by moose and snowshoe hares controls vegetation development and nutrient cycling at a variety of scales. Mammalian herbivores control species composition, nutrient cycling, and plant population dynamics at the stand and landscape...
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Critical Permafrost (BNZ LTER)
At least 1218 Pg (billion tons) of soil carbon (C) are stored in surface permafrost soils in boreal and arctic ecosystems, almost twice as much C than currently contained in the atmosphere (Tarnocai et al. 2009). Latitudinal gradients of soil C storage, field experiments, and laboratory incubations all show that soil C cycling in these northern ecosystems is likely to be strongly influenced by...
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Fire and Climate (BNZ LTER)
Plant ecologists working with the Bonanza Creek LTER program in Alaska have found that fire effects on soil organic layer depths is a key factor in the disruption of stable patterns of conifer dominance in the boreal forest. Plant-soil-microbial (PSM) feedbacks between vascular plants, mosses, and microbial decomposition maintain deep organic soils in black spruce forests and wetlands of Interior...
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Nutrient Sources (BNZ LTER)
Biogeochemical investigations have a long history at BNZ. These studies have demonstrated how slowly soil organic matter turn over in boreal forest soils, because of low biological activity coupled to a very short growing season. Recently, however, we have learned that nitrogen cycling in boreal forest soils continues past freeze-up and that about 40% of the annual nitrogen flux occurs during...
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Snow and Climate (BNZ LTER)
Modeling simulations over boreal Alaska have documented changes in albedo due to changes in the duration of the snow season and due to changes in the amount of young forest stands on a landscape due to changes in the fire regime. In addition, changes in the exchange of the greenhouse gases CO2 and methane have also been estimated due to changes in climate, atmospheric carbon dioxide...
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Importance of Household Decisions (CAP LTER)
Residential landscapes are a critical ecological feature of the urban ecosystem because they are widespread and are made up of highly designed and managed combinations of plants (e.g., landscaping) and animals (e.g., pets). For example, as Phoenix has urbanized, native Sonoran desert ecosystems have been replaced by an "urban oasis" that includes both lush, watered lawns and carefully managed...
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