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.
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To Be or Not to Be (GCE LTER) Why are there more organisms in some parts of the landscape than others? Are there genetic differences between populations living in one area as opposed to another? Is it because adults do better in some areas than others? Or, in marine systems, is it because there are more larvae settling from the plankton in one place than another? In the GCE-LTER study site on the Georgia coast,... Read more |
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Acid Rain (HBR LTER) Acid rain results when the combustion of fossil fuels releases sulfur dioxide and nitrogen oxides to the atmosphere. These contaminants are deposited to the Earth’s surface as precipitation, gases or particles and are called acid rain or acidic deposition. Acid rain was "discovered" in North America at Hubbard Brook through measurements of precipitation chemistry that were started in 1963. The... Read more |
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Forests that Govern (HBR LTER) The northeastern United States has been blessed with beautiful and bountiful forests that provide human society with a variety of valuable ecosystem goods and services including forest products, recreational opportunities, diverse wildlife, stable water flow, pure water quality, and sequestration of carbon. Pioneering research at Hubbard Brook, designed to elaborate ecological theory on the... Read more |
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Shifting Songbirds (HBR LTER) Forest bird populations of northeastern North America are being increasingly affected by environmental challenges, including habitat loss and degradation, forest disturbances such as ice storms, atmospheric pollutants such as acid deposition, pathogens that enhance tree mortality and climate change. To develop conservation and management plans that might mitigate such impacts, a mechanistic... Read more |
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Watersheds as Laboratories (HBR LTER) Watersheds are hydrologic units of the landscape which process water entering as precipitation, resulting in storage or loses through evapotranspiration, groundwater drainage, or stream runoff. In addition to water quantity, precipitation inputs and drainage losses transport nutrients to and from watersheds, and can be important components of nutrient dynamics of ecosystems. Small watersheds (12... Read more |
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Winter Climate Change (HBR LTER) While many from cold northern regions might welcome a bit of climate warming, the negative consequences for others -- for example, many arctic populations -- clearly counterbalance the benefits. In the northeastern United States and elsewhere, one of the ironic outcomes of winter climate warming could be an increase in the frequency of soil frost in forests; long-term observations at Hubbard... Read more |
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Envisioning the Future (HFR LTER) We are living in times of rapid social and environmental change. Scientists and policy makers urgently require analyses of multiple interacting processes in order to anticipate and adapt to future global change. Understanding future environmental change will require new approaches to synthesizing ecological and social sciences. This is no easy task. The study of coupled human and natural systems... Read more |
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Foundation Species Matter (HFR LTER) We are currently living through the sixth great extinction crisis in the Earth’s history. Ecologists and evolutionary biologists have documented that the unprecedented and rapidly accelerating loss of non-human species is the direct result of human activities: habitat conversion, over-consumption of resources, and worldwide introductions -- both deliberate and accidental -- of pests and pathogens... Read more |
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Old Forests Store Carbon (HFR LTER) Terrestrial ecosystems, especially mid-latitude forests, are accumulating carbon (2.6 Pg-C y-1) that would otherwise contribute to increasing atmospheric CO2. CO2 fertilization, forest regrowth, climate variability, and increased nutrient inputs are potential factors. Ecological theory suggests that forests older than about a century should approach equilibrium and no longer be significant carbon... Read more |
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The Power of Invasives (HFR LTER) Harvard Forest researchers have transformed the scientific understanding of biological invasion by discovering that non-native plants can disrupt the longstanding ecological relationship between native tree seedlings and their beneficial fungi by releasing chemicals belowground. With native plants suppressed, the exotic plants are able to invade forests more aggressively. The impacts of... Read more |
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Ability To Restore (JRN LTER) Desertified shrublands on degraded soils are believed to be very persistent, yet the need for services from these systems has led to numerous attempts to restore them to grassland state, often with little success. Much of the early restoration research (pre-1970s) at the JRN focused on agronomic approaches for shrub control and grass recovery. Over the decades, numerous trials of various... Read more |
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Accessible Ecology (JRN LTER) Large amounts of information have been collected, and software tools have been developed to understand and predict dynamics of ecological systems. However, much of the data and tools remain inaccessible to a broad audience beyond the initial scientists, data collectors, and software developers. The Jornada has been developing tools and activities designed to make scientific knowledge... Read more |
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Expanding Deserts (JRN LTER) Desertification is the shift from perennial grasslands to shrublands that occurs globally to impact nearly 40% of the Earth’s land surface and a fifth of the world’s human population. Desertification results from interactions between human activities (such as livestock overgrazing) and prolonged drought. However, these broad-scale drivers are insufficient to explain variability in dynamics at... Read more |
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Heterogeneity and Nonequilibrium Dynamics (JRN LTER) Much of ecological research in terrestrial systems focuses on detailed understanding of local processes, such as competition for limiting resources, on fine-scale dynamics of individual plots that are extrapolated to broad-scale patterns of ecosystem types and biomes. Although this perspective can explain short-term dynamics at fine scales of plants and patches in drylands, landscape-scale... Read more |
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Tipping Points (JRN LTER) Tipping points resulting in state changes (or regime shifts) have been documented in many ecosystem types around the world, and are particularly important in dryland ecosystems, including those of the southwestern US. Dryland state changes include the conversion of agriculturally productive grasslands to unproductive shrublands, conversion to dominance by invasive species, or the loss of... Read more |
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Agriculture and Climate Change (KBS LTER) Since 1992 scientists at the KBS LTER site have studied fluxes of the major, naturally occurring greenhouse gases -- carbon dioxide (CO2), methane, and nitrous oxide -- in a variety of cropped and natural ecosystems. A 2010 update of research originally published in 2000 continues to show how different cropping strategies can have markedly different effects on greenhouse gas fluxes from both... Read more |
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Diverse Landscapes Curtail Crop Pests (KBS LTER) The soybean aphid Aphis glycines, an invasive insect pest, is the greatest threat to soybean production in the United States. First detected in the United States in 2000, this East Asian pest has spread rapidly through the Midwest and costs growers about $30 million to $50 million per year in reduced yield. By 2005, farmers had responded with a 20-fold increase in insecticide use,... Read more |
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Minimizing Nitrogen Pollution (KBS LTER) Through a variety of long-term studies, KBS LTER research has significantly advanced scientific understanding of nitrogen cycling in cropping systems as well as in the broader landscape. Agricultural landscapes commonly have excessive concentrations of nitrate (an especially mobile form of nitrogen) in ground and surface waters due to fertilizer applications in excess of what the crops can use.... Read more |
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Soil Microbes and Agriculture (KBS LTER) Microbes in terrestrial environments are important catalysts of global carbon and nitrogen cycles, including the production and consumption of greenhouse gases in soil. Some microbes produce the greenhouse gases carbon dioxide (CO2) and nitrous oxide (N2O) while decomposing organic matter in soil. Others consume methane (CH4) from the atmosphere, thus helping to mitigate climate... Read more |
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Climate variability and change (KNZ LTER) Climate is a critical driver of grassland structure and function. Grasslands occur in areas that are prone to occasional drought and are characterized by highly variable patterns of rainfall, both between (inter-annually) and within (intra-annually) years. North American grasslands were formed by climate changes originating during the Miocene-Pliocene transition, and their present day... Read more |
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Fire and Grazing (KNZ LTER) Understanding the ecological effects of fire and grazing in grasslands is an important aspect of research at the Konza Prairie (KNZ) LTER site. The tallgrass prairies of North America were shaped by natural disturbances that included periodic fires and the activities of ungulate grazers, and these remain important processes in tallgrass prairie and other grasslands around the world. In order to... Read more |
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Grassland stream ecology (KNZ LTER) Grasslands and wooded grasslands cover around 40% of the Earth’s terrestrial surface and more than ¼ of global runoff originates from these systems. Yet, surprisingly little is known about the ecology and unique properties of streams that link grasslands to downstream habitats. Understanding the ecology and ecosystem services provided by small headwater streams in the Great Plains region is... Read more |
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Restoring Grasslands (KNZ LTER) Restoration ecology seeks to repair the diversity and dynamics of ecosystems degraded by human activities. Restoration studies in tallgrass prairie have become a core part of the Konza Prairie LTER (KNZ) program over the last decade, and are particularly timely because human activities have resulted in widespread loss and degradation of tallgrass prairie and other temperate grasslands. Here we... Read more |
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Woody plant encroachment (KNZ LTER) Predicting how ecosystems will respond to forecast environmental changes and to evaluate the consequences of those responses is a major challenge for ecologists today. One of the most prevalent contemporary land-cover changes is woody plant encroachment into grasslands and increased cover of shrubs and trees in grasslands and savannas. Causes of increased woody plant abundance may vary in... Read more |
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Hurricanes, Humans, and Future Ecosystems (LUQ LTER) Ecosystems are increasingly subjected to combined natural and human disturbances. Since 1990 in Puerto Rico we have been studying human and hurricane disturbance and their interactions in a tropical forest. The work takes place on the 16-ha Luquillo Forest Dynamics Plot (LFDP) in the Luquillo Mountains. Part of the plot was logged or farmed up until the 1930s (Fig. 1). On the rest of the plot... Read more |
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