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Light Environment in Hemlock Removal Experiment at Harvard Forest since 2003
The impending loss of hemlock trees due to hemlock woolly adelgid (Adelges tsugae) infestation is expected to lead to changes in the light environment of the forest understory. These changes will both drive succession and will themselves be altered by successional processes. The light reaching the forest floor is measured using hemispherical canopy photographs. Photographs were taken in summer of 2003 and in December 2004 and May 2005 (both deciduous-tree leaf-off condition), prior to the application of the logging and girdling treatments, and then in September 2005 (deciduous tree leaf-on condition) after logging and girdling. Subsequent photographic series will be taken annually in spring (leaf-off) and summer/fall (leaf-on).
Air and Soil Temperature in Hemlock Removal Experiment at Harvard Forest since 2004
The impending loss of hemlock trees due to hemlock woolly adelgid (Adelges tsugae) infestation is expected to lead to changes in the temperature regime of the forest understory. These changes will both drive succession and will themselves be altered by successional processes. Air temperature (1 m above forest floor) and soil temperature (at 10 cm depth) are measured at 1-minute intervals (hourly averages, minimum, and maximum are stored) using thermistors connected to Campbell 21-X dataloggers. Temperature measurements began 60-120 days prior to applications of the logging and girdling treatments, and will continue for the duration of the study.
Ant Diversity and Vegetation Composition in Hemlock Removal Experiment at Harvard Forest 2006
Ants comprise a considerable amount of animal biomass in terrestrial ecosystems and play major roles in ecological processes ranging from seed dispersal to soil turnover. Invasion by the hemlock woolly adelgid will transform late-successional hemlock forests into earlier successional mixed hardwood-white pine forests or red-maple wetlands. Understanding how ant assemblages vary in different habitat types allows for predictions of how hemlock decline could alter the composition of ant assemblages, with implications for a wide range of ecosystem processes. An ongoing study at the Simes Tract of Harvard Forest is documenting the effects of invasion and land-use history on ant biodiversity. Surveys from 2003 to 2005 focused on ant structure in hemlock and hardwood microhabitats in the Harvard Forest Hemlock Removal Experiment, in which hemlock forest response to deforestation by the hemlock woolly adelgid (Adelges tsugae) and to selective logging is being examined (Ellison et al. 2005). In the summer of 2006, we surveyed a greater range of microhabitat types with two objectives. First, to collect rare or elusive species in hemlock and hardwood stands that may have gone uncollected in previous years. Second, to sample forest communities not included in previous years - white pine, swamp, and rocky slope - for ant species unique to these microhabitats. We found fourteen newly documented species of ants in the Simes Tract - nine of which were in an open, swamp. Aphaenogaster rudis and Camponotus pennsylvanicus were the only ant species found in all microhabitat types. In a canonical correspondence analysis, A. rudis and C. pennsylvanicus were associated most strongly with hemlock stands and low species richness of understory plants.
Deer and Moose Browsing in Hemlock Removal Experiment at Harvard Forest 2008
Hemlock decline in New England is caused by direct and indirect effects of invasion of the hemlock woolly adelgid. Direct damage from the insect is causing gradual mortality of hemlock, and widespread harvesting of hemlock in advance of mortality, in contrast, causes immediate mortality and removal of biomass from the site. Although both processes affect thousands of acres of forest annually we have only a limited understanding of their effects on forest ecosystem function and productivity and the nature of the subsequent forest community. We anticipate that harvesting will yield different consequences than gradual mortality from the insect. Therefore we designed an experiment to simulate these contrasting impacts, by logging or girdling hemlock stands. Results from the experimental treatments will be compared to the changes observed in forests that are being infested by the adelgid, and can also be included in integrated analyses of a suite of large experiments that form a core component of the Harvard Forest LTER program. Deer and moose foraging can play a key role in shaping forest regeneration after disturbance in temperate forest. In 2008, we initiated a browsing survey of woody stems in the Simes hemlock removal experiment plots. There are regular moose sightings in the study area, and moose pellets are commonly found within the plots. Also, extensive browsing of tree regeneration in the logged plots was noted starting in 2007. Sampling of the 8 study plots was completed in Summer 2008. The next sampling is tentatively scheduled for Summer 2013.
Coarse Woody Debris in Hemlock Removal Experiment at Harvard Forest since 2005
The woody detritus survey is designed to measure coarse woody detritus that includes snags, logs, and stumps, and to estimate fine woody detritus which includes smaller pieces of downed wood. To capture both standing and downed wood, we based our survey around two main types of methods, the line intercept method and the fixed radius plot method. Surveys have been completed for 2005, 2007, 2009, 2011, 2013, 2015, 2017, and 2021.
Overstory Vegetation in Hemlock Removal Experiment at Harvard Forest since 2003
Hemlock decline in New England is caused by direct and indirect effects of invasion of the hemlock woolly adelgid. Direct damage from the insect is causing gradual mortality of hemlock. Widespread harvesting of hemlock in advance of mortality, in contrast, causes immediate mortality and removal of biomass from the site. Although both processes affect thousands of acres of forest annually we have only a limited understanding of their effects on forest ecosystem function and productivity and the nature of the subsequent forest community. We anticipate that harvesting will yield different consequences than gradual mortality from the insect. Therefore, we designed an experiment to simulate these contrasting impacts, by logging or girdling hemlock stands. Results from the experimental treatments will be compared to the changes observed in forests that are being infested by adelgid and can also be included in integrated analyses of a suite of large experiments that form a core component of the Harvard Forest LTER program.
Litterfall in Hemlock Removal Experiment at Harvard Forest since 2005
Hemlock decline in New England is caused by direct and indirect effects of invasion of the hemlock woolly adelgid. Direct damage from the insect is causing gradual mortality of hemlock, and widespread harvesting of hemlock in advance of mortality, in contrast, causes immediate mortality and removal of biomass from the site. Although both processes affect thousands of acres of forest annually we have only a limited understanding of their effects on forest ecosystem function and productivity and the nature of the subsequent forest community. We anticipate that harvesting will yield different consequences than gradual mortality from the insect. Therefore we designed an experiment to simulate these contrasting impacts, by logging or girdling hemlock stands. Results from the experimental treatments will be compared to the changes observed in forests that are being infested by the adelgid, and can also be included in integrated analyses of a suite of large experiments that form a core component of the Harvard Forest LTER program.
20-Year Root Mass in Chronic Nitrogen Amendment Experiment at Harvard Forest 2008
Forests typically respond to nitrogen additions with increased productivity, hence a long-held paradigm was that chronic additions of anthropogenically-derived atmospheric deposition would have positive ecosystem effects. However, twenty years of work at the Harvard Forest Chronic N Deposition plots, and in other forest ecosystems as well, has shown that that this simplistic view is incomplete. For example, enhanced ammonium uptake increases soil acidity, leading to mobilization of aluminum, and loss of nutrient cations (e.g. Mg2+, Ca2+, and K+ ) all of which influence root mass, turnover, and activity. To address long-term impacts of N additions on forest root mass, we removed O-horizon (forest floor) samples from the Chronic N hardwood and red pine stands to quantify the total mass of roots. We found that long term N additions had contrasting results in the two forests. In the hardwood plots, total root mass (less than 2mm) increased from 0.167 + 0.026 (S.E.) kg m-2 in the control plot to 0.434 + 0.170 kg m-2 in the high N plots. In contrast, in the red pine stand, roots declined from 0.074 + 0.011 (S.E.) kg m-2 in the control plot to 0.031 + 0.016 kg m-2 in the high N plots. These data are in agreement with data for aboveground productivity at the Chronic N plots, which show stimulated growth in the hardwoods and severe growth declines and enhanced mortality in the pine stand.
Autumnal Litter Input in DIRT Litter Manipulation Experiment at Harvard Forest 2008
Climate change will alter forest ecosystem productivity, changing the quantity and quality of detrital inputs to soil and altering rates of soil organic matter (SOM) accumulation and stabilization. To examine changes in forest soil SOM pools, we have used the Detritus Input and Removal Treatments (DIRT) Project to alter organic matter input rates and sources (roots, leaves) to soils, allowing us to measure contributions of organic matter sources to long-term SOM storage at five temperate forests (Harvard Forest, HJ Andrews, Bousson (PA) Experimental Forest (BEF), U. Michigan Biological Station (UMBS), Síkfokut ILTER, Hungary). Organic matter inputs are altered by excluding or adding leaf inputs, or by excluding roots from forested plots. Soil respiration partitioning at HF, BEF, and UMBS shows that soil fertility controls the allocation of C to above- and belowground tissue. At UMBS, glacial outwash sandy soils are extremely low in N, and C released from root respiration plus root litter decomposition is 87% of total soil respiration. Conversely, at the N-rich BEF site, total belowground sources of CO2 are only 61% of soil respiration, with 47% attributed to root litter. These data suggest that at BEF, leaf litter, comprising only 39% of soil respiration, would be a more important source of long-term SOM than root litter. However, soil chemistry and radiocarbon data have shown us that long-term soil C storage is complex. The year 2010 represents the 20-year anniversary of the initiation of DIRT treatments at the Harvard Forest (2010), and we are therefore planning to conduct systematic sampling campaigns for a comprehensive study of changes in SOM quality after long-term manipulation of inputs. One objective is to quantify how 20 years of litter input alterations have affected SOM quantity and quality at the surface (0-20 cm) and deeper in the soil profile (20-100 cm). To uderstand these changes, we need to quantify the quantity and quality of aboveground litter inp
Root and Mycorrhizal Respiration at Harvard Forest Soil Warming Experiments 2007-2008
Soil heating typically causes large initial increases in soil respiration, with the enhancement lessening over time. This transient response is attributed to rapid decomposition of labile soil C compounds in the first years of heating, but the potential role of changes in root and mycorrhizal respiration is not well understood. To assess the degree to which root respiration adjusts to warmer soil temperature regimes, specific root respiration rates (nmol CO2/g/s) are being measured in three soil warming experiments at Harvard Forest. Soils in the experiments had been heated since 1991, 2003 and 2006. Respiration rates for fine roots (less than 1 mm) from control and heated plots were measured both at a common reference temperature of 18 deg C and at the ambient soil temperature of the measurement date for the control and heated (+ 5 deg C) treatments. Mycorrhizal respiration is being assessed through the use of hyphal ingrowth bags which allow determination both mycorrhizal hyphal biomass and respiration rate. Changes in mycorrhizal community composition are also being investigated. Specific questions we will address include: Does rapid temperature acclimation occur in roots of large perennial woody plants? How do root biomass, root N concentration, and root respiration rates adjust to long-term changes in soil temperature and moisture and concomitant changes in N availability? How is mycorrhizal biomass and activity influenced by the effects of warmer soil temperatures on host C balance and soil N availability? How do the short- and long-term responses of roots and mycorrhizae to warming and associated changes in soil nutrient cycling affect soil CO2 efflux and C availability for aboveground NPP? Are the interrelationships between warmer soil temperature regimes and C fluxes to and from roots and mycorrhizae adequately described by current ecophysiological models?
Soil Arthropods in Hemlock Removal Experiment at Harvard Forest 2008
In eastern North American forests, eastern hemlock (Tsuga canadensis) is a foundation species. As hemlock is lost from forests due to the invasive hemlock woolly adelgid (Adelges tsugae) and pre-emptive salvage logging, the structure of assemblages of species associated with hemlock is expected to change. We manipulated hemlock canopy structure at hectare scales to investigate the effects of hemlock death on assemblages of ants, beetles, and spiders in a New England forest. Relative to reference hemlock stands, both in situ death of hemlock and logging and removal of hemlock altered composition and diversity of beetles and spiders, and logging increased the species richness and evenness of ant assemblages. Species composition of ant assemblages in disturbed habitats was non-random relative to the regional species pool, but we found no evidence that interspecific competition shaped the structure of ant, beetle or spider assemblages, in either manipulated or intact forest stands. Environmental filtering by hemlock appears to maintain low levels of species richness and evenness in forest stands, suggesting that the loss of hemlock due to the hemlock woolly adelgid or human activities will not likely lead to extirpations of ant, beetle, or spider species at local scales.
Barre Woods Soil Warming Experiment at Harvard Forest since 2001
Two of the major results of our original soil warming study were that: (1) warming stimulated the decay of a labile soil carbon pool; and (2) it also increased the availability of inorganic nitrogen to plants. Because of the small size of the original warming plots an important question we have not been able to answer conclusively is: Has the increase in available nitrogen led to an increase in carbon storage in the vegetation? And if yes, how much? In a systems context an additional question is: What is the balance between the carbon lost from the soil and the carbon stored in the vegetation in response to soil warming? We are now addressing these important questions with a new warming experiment in the Barre Woods area of the Harvard Forest. The Barre Woods site was chosen because of its similarities to the Prospect Hill site - stand age, tree species composition, and soil type. There is no evidence of a plow horizon at the Barre Woods site, though surrounding stone walls indicate past use as pastureland. Historical records indicate the site was destroyed during the 1938 hurricane and then regrew naturally. During the summer and fall of 2001 we buried 3.4 miles of heating cable in a 30 x 30m plot. Cables were buried at a 10cm depth, spaced 20cm apart. A second 30 x 30m area was delineated to serve as the control plot. Results from the original soil warming experiment confirmed that the soil disturbance associated with the installation of heating cables has had no effect on soil temperatures and only minor and variable impacts on soil moisture. In April 2002, we began a one-year period of baseline measurements before turning on the heat in the new megaplot. These measurements included nitrogen mineralization, trace gas fluxes (CO2, CH4, N2O), tree growth (dendrometer bands), an understory species survey, canopy foliage analysis (C:N, NIR), and lysimetry. Thermistors were installed in both plots to begin tracking soil temperatures. The baseline measurements have con
Vegetation Response in Simulated Hurricane Experiment at Harvard Forest since 1990
Wind disturbance profoundly shapes temperate forests but few studies have evaluated patterns and mechanisms of long-term forest dynamics following major windthrows. In 1990, we initiated a large hurricane simulation experiment in a 0.8 ha manipulation (pulldown) and 0.6 ha control area of a maturing Quercus rubra-Acer rubrum forest in New England. We toppled 276 trees in the pulldown, using a winch and cable, in the northwesterly direction of natural treefall from major hurricanes. Eighty percent of canopy trees and two-thirds of all trees greater than 5 cm dbh suffered direct and indirect damage. We used twenty years of measurements to evaluate the trajectory and mechanisms of forest response after intense disturbance. Based on the patch size and disturbance magnitude, we expected pioneer tree and understory species to drive succession. The first decade of analyses emphasized tree seedling establishment and sprouting by damaged trees as the dominant mechanisms of forest recovery in this extensive damaged area. However, despite 80% canopy damage and 8000 m2 patch size, surviving overstory and advance regeneration controlled longer-term forest development. Residual oaks make up 42% of stand basal area after 20 years. The new cohort of trees, dominated by black birch advance regeneration, contributes 30% of stand basal area. There were shifts in understory vegetation composition and cover, but few species were gained or lost after 20 years. Stand productivity rebounded quickly (litterfall recovered to pre-disturbance levels in six years), but we predict that basal area in the pulldown will lag behind the control (which gained 6 m2/ha over 20 years) for decades to come. This controlled experiment showed that although the scale and intensity of damage were great, abundant advance regeneration, understory vegetation, and damaged trees remained, allowing the forest to resist changes in ecosystem processes and invasion by new species.
Fuel Loading in Simulated Hurricane Experiment at Harvard Forest since 1993
Wind disturbance profoundly shapes temperate forests but few studies have evaluated patterns and mechanisms of long-term forest dynamics following major windthrows. In 1990, we initiated a large hurricane simulation experiment in a 0.8 ha manipulation (pulldown) and 0.6 ha control area of a maturing Quercus rubra-Acer rubrum forest in New England. We toppled 276 trees in the pulldown, using a winch and cable, in the northwesterly direction of natural treefall from major hurricanes. Eighty percent of canopy trees and two-thirds of all trees greater than 5 cm dbh suffered direct and indirect damage. An enormous input of dead wood was one result of the manipulation. Many perceive an increased risk of wildfire after trees are blown down, but this depends on the amount, size, and persistence of the dead wood inputs.
Ant Mesocosm Experiment in Harvard Forest Lath Houses 2011-2012
Direct and indirect consequences of global warming on ecosystem functions and processes mediated by invertebrates remain understudied but are likely to have major impacts on ecosystems in the future. Among animals, invertebrates are taxonomically diverse, responsive to temperature changes, and play major ecological roles which also respond to temperature changes. We used a mesocosm experiment to evaluate impacts of two warming treatments (+3.5 and + 5 °C, set points) and the presence and absence of the ant Formica subsericea (a major mediator of processes in north-temperate ecosystems) on decomposition rate, soil movement, soil respiration, and nitrogen availability. Replicate 19-Litre mesocosms were placed outdoors in lath houses and continuously warmed for 30 days in 2011 and 85 days in 2012. Warming treatments mimicked expected temperature increases for future climates in eastern North America. In both years, the amount of soil displaced and soil respiration increased in the warming and ant presence treatments (soil movement: 73 to 119%; soil respiration: 37 to 48% relative to the control treatments without ants). Decomposition rate and nitrogen availability tended to decrease in the warmest treatments (decomposition rate: -26 to -30%; nitrate availability: -11 to -42%). Path analyses indicated that ants had significant short term direct and indirect effects on the studied ecosystem processes. These results suggest that ants may be moving more soil and building deeper nests to escape increasing temperatures, but warming may also influence their direct and indirect effects on soil ecosystem processes.
Root Exudation Simulation Experiment in a Red Oak Stand at Harvard Forest 2011
Root exudation is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates (“exudate mimics”) containing C alone or C in combination with N (C:N ratio of 10) through microlysimeter “root simulators” into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was
Baseline Plant Abundances on Garlic Mustard Experiment Plots at Harvard Forest 2013
This is a five year project that investigates the reassembly of soil fungi and native plants in forests affected by biological invasion. The experiment brings together regional land managers to create comparative eradications of garlic mustard at nine distinct sites along a natural climate and nitrogen deposition gradient in New England. This dataset represents baseline plant abundances from 2013 at nine study plots in Harvard Forest. Species richness, Shannon diversity, and Pielou’s evenness were not different between invaded and non-invaded plots at Harvard Forest.
Red Maple Seedling Soil Warming Experiment in Harvard Forest Lath House 2015
Microhabitat environmental conditions are an important filter for seedling establishment, controlling the availability of optimal recruitment sites. Understanding how tree seedlings respond to warming soil temperature is critical for predicting population recruitment in the future hardwood forests of northeastern North America, particularly as environmental conditions and thus optimal microhabitat availabilities change. We examined the effect of 5˚C soil warming during the first growing season on germination, survival, phenology, growth, and stem and root biomass allocation in Acer rubrum (red maple) seedlings. While there was no effect of soil warming on germination or survival, seedlings growing in warmer soils demonstrated significantly accelerated leaf expansion, delayed autumn leaf senescence, and an extended leaf production period. Further, seedlings growing in warmer soils showed larger leaf area, stem and root structures at the end of the first growing season, with no evidence of biomass allocation tradeoffs. Results suggest A. rubrum seedlings can capitalize on soil warming by adjusting leaf phenology and leaf production, resulting in a longer period of carbon uptake and leading to higher overall biomass. The absence of growth allocation tradeoffs suggests A. rubrum will respond positively to increasing soil temperatures in northeastern forests, at least in the early life stages.
Foliar and Soil Chemistry at Harvard Forest Chronic Nitrogen Amendment Experiment 1995-2009
The aim of the chronic N study at Harvard Forest is to increase our understanding of ecosystem nitrogen dynamics in response to elevated nitrogen inputs. In recent, nitrogen deposition in the Northeastern United States has been 10 to 20 times above historic background levels which could possibly saturate the retention capacity of a forest ecosystem. Long-term elevated N deposition typically leads to an increase in the concentration of total foliar N, with or without similar changes in the important base elements such as Ca, Mg and K. This increase in leaf N content also leads to significant shifts in the internal partitioning of N within the leaf. For example, in conifers, N deposition has been shown to significantly increase leaf N present in the form of free amino acids such as arginine. Little is known about N partitioning for hardwoods under these conditions. These changes in N partitioning are possibly connected to leaf function. The present study was conducted to experimentally test whether the alterations in N partitioning do occur due to long-term N deposition and if so do they have a positive or a negative effect on photosynthetic capacity and biomass production. A possible decoupling of the relationship between foliar N and photosynthetic rate may occurs under these conditions. The treatment plots used in this study are part of the Chronic Nitrogen Amendment Study at the Harvard Forest LTER site (42.5°N, 72°W). The site has a temperate climate with monthly temperatures ranging from -7°C in January to 20°C in July. Average annual precipitation is 110 cm (http://harvardforest.fas.harvard.edu). The site averages approximately 8 kg ha-1 year-1 of total N deposition. As reported earlier, the land-use history of the pine and hardwood stands used in this study is very different. Two adjacent stands were chosen for the study: an even-aged red pine (Pinus resinosa Ait.) stand and a 50-year-old mixed hardwood stand that had regenerated naturally after clearcutting i
Understory Removal Experiment at Harvard Forest 1956-2018
In 1956, Ernie Gould and colleagues established an experiment to test whether removing understory trees will accelerate the growth of the residual overstory. The motivation for the experiment was the suggestion that the understory uses growth materials that would otherwise be available for the main canopy crop trees, and that if the understory were removed the development of the crop trees would be accelerated. In Tom Swamp Compartment I, a 300’ by 400’ rectangular plot was established in a closed-canopy hardwood forest, and every tree >2 inches dbh was mapped, measured and assigned to the overstory or understory. In half of the plot, all understory trees and woody shrubs were cut. Wood and brush were removed from the study area. Sprouts that emerged were killed by spraying with 2-4-5-T and kerosene in 1956 and 1958. Diameter growth measurements of the remaining trees (overstory in the treated area; overstory and understory in the control) were repeated in 1960, 1966, 1969, and 1975 as part of the original experiment. The control portion of the plot was measured in 2003 and 2018. This data set contains tree measurements from the control portion of the site for 1956, 1969, 1975, 2003, and 2018. Additional measurements are available on paper data sheets in the Harvard Forest Document Archives (Research File HF 1956-03). Results of the understory removal experiment are reported in Kelty and Gould (1987).
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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DANDI Archive for NWB datasets
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International Brain Laboratory public data
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OpenNeuro
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