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80 results for “removal experiment”
Ants and Ecosystem Function in Hemlock Removal Experiment at Harvard Forest 2006-2014
Eastern hemlock (Tsuga canadensis) is a foundation species in eastern North American forests. Hemlock stands host unique assemblages of flora and fauna, and the structure of these assemblages is expected to change as hemlock declines due to infestation by the hemlock woolly adelgid (Adelges tsugae) and is removed by pre-emptive salvage logging. A 2003 survey of hemlock stands in central Connecticut and Massachusetts showed that ant species richness and abundance is substantially greater in logged and adelgid-infested hemlock stands than it is in intact hemlock stands (see HF065) and we hypothesized that we would see similar changes in ant species diversity following application of treatments in the Hemlock Removal Experiment at the Simes Tract (see HF118). We further hypothesized that because ants are known to modulate ecosystem function in other habitats that observed changes in ant species diversity would be accompanied by changes in ecosystem processes including soil respiration rate and nitrogen availability. In April 2006, we established a set of sub-plots in all eight canopy manipulation plots of the Hemlock Removal Experiment. In each canopy manipulation plot, we installed two ant exclosure plots, two disturbance control plots, and two control plots. Ant species richness and abundance, as well as effectiveness of the exclosures, is monitored with pitfall traps monthly during the summer. Soil nitrogen availability is measured using resins that are collected every three months, and soil respiration is measured bi-weekly during the growing season.
Plant community responses to functional group and species removals along biodiversity experiment vegetation transects at the Jornada Basin LTER site, 1997-2002
This dataset contains vegetative cover data of plots that have had various plant functional groups or species experimentally removed at the Jornada Basin LTER site in southern New Mexico, USA. This data was collected with the objective to distinguish the differential effects of plant community biomass, functional groups, and biodiversity within functional groups on ecosystem and plant community function. To make these distinctions, treatments were established by the selective removal of plant species or functional groups within experimental plots. There are eight treatments: control (C, no removals); four functional group removal treatments (PG, perennial grass removed; S, shrubs removed; SSh, subshrubs removed; Succ, succulents removed), and three species richness manipulation treatments. Richness manipulations included a simplified treatment (Simp), where only the single most abundant species of each growth form is preserved and all other species in the growth form are removed, a reduced‐Larrea treatment (rL), where the Larrea is assumed to be the dominant and is removed while minority components remain, and a reduced-Prosopsis treatment (rP), where Prosopis rather than Larrea is removed as the shrub dominant. Following treatments, vegetative data was collected by sampling each plot along three transects twice a year (Spring and Fall) for 5 years from 1997-2002 (no data collected in 1998). This data set consists of the date of collection, plot number, treatment type, transect number, quadrat number, species codes, two diameters, height, condition, count, record IDs, and error codes. This study is complete.
Borrichia removal experiment at Dean Creek marsh on Sapelo Island, Georgia between 1995 and 2001
To examine the effect of Borrichia on Batis and Sarcocornia sp., I completely clipped all vegetation from six 0.5 x 0.5 m quadrats in a mixed stand of the three species at the Dean Creek marsh in June 1995. Six additional plots were left unmanipulated as controls. Removal and control plots were fully interspersed. I clipped Borrichia from the removal plots every 6 months but allowed other plant species to re-colonize.
Seed Bank in Hemlock Removal Experiment at Harvard Forest 2004-2015
The impending loss of hemlock trees due to hemlock woolly adelgid (Adelges tsugae) infestation prompted the need to identify species of plants able to colonize areas where hemlock has been removed. We investigated species present in the seed bank (in 2004 and 2010), the seedling bank (in 2004 and 2010), and seed rain (from 2005-2015) in the Harvard Forest Hemlock Removal Experiment. In 2004, Kelley Sullivan and Aaron Ellison determined the distribution of seeds buried in the soil in the six hemlock and two hardwood stands, before canopy treatments were applied (data files hf105-01, hf105-02). In 2010, Elizabeth Farnsworth and Aaron Ellison examined the distribution of plant species present five years after the simulated hemlock removal experiment was performed and six years after the baseline, pre-treatment study of the seedbank (data files hf105-03, hf105-04, hf105-05). In the 2010 study, we hypothesized that the composition of the seed and seedling banks and seed rain would diverge among the two treatments and the controls, based on the differential impacts of harvesting versus adelgid attack on the standing vegetation. We further hypothesized that the older (deeper) strata of the seedbanks of the treatment plots would have been exhausted over time, thus yielding poor germination relative to the top strata that continually receive seed rain. Identical methods of characterizing the composition of the seedbank and the aboveground vegetation at seedbank core locations were applied in both 2004 and 2010. Additional comparisons were made with long-term data collected on overall plant species composition in the Simes plots (datasets HF 106, HF126), and with data on seed rain (data file hf105-05). This study provides a unique temporal documentation of changes in the seedbank, seed rain, and vegetation under conditions of a changing overstory.
Understory 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, 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 are 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.
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.
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.
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).
Salamander Response in Hemlock Removal Experiment at Harvard Forest 2003-2005
Despite reductions in prices, pre-emptive salvage logging of eastern hemlock stands has increased since the arrival of eastern hemlock woolly adelgid (Adelges tsugae, HWA) into this region. The microenvironmental changes associated with eastern hemlock loss have been found to be even more severe than when stands are lost to logging due to HWA infestation. This study assessed the effects of a commercial logging operation on two 90m x 90m (0.8 ha) plots, conducted in the winter of 2004-2005, on eastern redback salamander (Plethodon cinereus) relative abundance within the Simes tract at Harvard Forest. Over the past seven seasons (fall 2003 - fall 2005; excluding winter) I have been monitoring eastern redback salamander relative abundance using artificial cover objects (ACOs). The objectives of this study were 1) to assess whether logging has an impact on redback relative abundance at a plot level 2) to assess whether logging in isolated plots has an impact on relative abundance throughout the entire Simes tract 3) to assess whether redback relative abundance is stable over two years. Redback relative abundance in spring 2005 was 660% lower than in spring 2004 in logged plots, while in unlogged plots there was a 4% increase in redback relative abundance in spring 2005 versus spring 2004 (one-way ANOVA; df = 7, F = 6.21, p less than 0.05). Between fall 2004 and spring 2005 redback relative abundance decreased by 727% in the logged plots, compared to only a 29% decrease in unlogged plots (one-way ANOVA; df = 7, F = 10.51, p less than 0.05). Plots adjacent to logged plots had a significantly higher increase in redback relative abundance in spring 2005 versus spring 2004 than those not adjacent to the logged plots (one-way ANOVA; df = 5, F = 8.64, p less than 0.05). There was no significant difference in redback relative abundance in all plots in spring 2004 versus spring 2005 (one-way ANOVA; df = 15, F = 0.20, p = 0.665), or in fall 2004 versus spring 2005 (one-way ANOVA;
Synthesis of Hemlock Removal Experiment at Harvard Forest 2003-2019
In 2023, we synthesized the data from 6 Harvard Forest Hemlock Removal Experiment datasets (HF054, HF106, HF107, HF125, HF126 and HF161) to discern differences between the girdling and logging treatments from 2004-2019. Forest insect outbreaks cause large changes in ecosystem structure, composition, and function. Humans often respond to insect outbreaks by conducting salvage logging, which can amplify the immediate effects, but it is unclear whether logging will result in lasting differences in forest structure and dynamics when compared with forests affected only by insect outbreak. We used 15 years of data from an experimental removal of Tsuga canadensis (L.) Carr. (Eastern hemlock), a foundation tree species within eastern North American forests, and contrasted the rate, magnitude, and persistence of response trajectories between girdling (emulating mortality from insect outbreak) and timber harvest treatments.
Community and Ecosystem Impacts in Hemlock Removal Experiment at Harvard Forest 2003-2020
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 creates a contrasting disturbance. 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 have designed an experiment to simulate the impact of both in order to contrast them. To simulate some of the effects of the adelgid (e.g., progressive mortality, retention of the wood on the site) we are girdling all hemlocks in a hemlock-dominated stand. In the adjacent area we are conducting a commercial harvesting of hemlock. Results from both 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.
Dendrochronological Record in Hemlock Removal Experiment at Harvard Forest 2004-2006
As part of the long-term goal of reconstructing the stand and land-use history of the Simes Tract at Harvard Forest, trees were cored from the 8 hemlock and hardwood plots in the Hemlock Removal Experiment. Cores were sanded and growth was measured. The data were used for the 2006 senior thesis (Division III paper) of Peter Bettman-Kerson at Hampshire College ("Dendrochronological reconstruction of historical disturbances in a hemlock forest at the Harvard Forest, Petersham, MA"). This dataset is the raw growth data for 230 trees sampled across the 8 plots.
Biomass removal at the initiation of a biodiversity experiment at the Jornada Basin LTER site in 1995
This dataset contains data on vegetation biomass removed from treatment plots during the establishment of a biodiversity experiment at the Jornada Basin LTER site in southern New Mexico, USA. In fall of 1995, various combinations of plant functional groups or species were experimentally removed from 25 x 25 meter plots with the objective to distinguish the differential effects of plant community biomass, functional groups, and biodiversity within functional groups on ecosystem and plant community function. Eight different treatments were established with selective removal of species or functional groups: control (C, no removals); four functional group removal treatments (PG, perennial grass removed; S, shrubs removed; SSh, subshrubs removed; Succ, succulents removed), and three species richness manipulation treatments. Richness manipulations included a simplified treatment (Simp), where only the single most abundant species of each growth form is preserved and all other species in the growth form are removed, a reduced‐Larrea treatment (rL), where the Larrea is assumed to be the dominant and is removed while minority components remain, and a reduced-Prosopsis treatment (rP), where Prosopis rather than Larrea is removed as the shrub dominant. The amount of plant material removed during the establishment of these treatments was recorded for later use as covariate or measure of disturbance. Removed fresh material was weighed in the field by species, then converted to dry mass using a subset of removed plot vegetation that was oven-dried and weighed in the lab. Variables in this file summarize the dry mass of plants removed by growth form (functional group, i.e. shrub, subshrub, perennial grass, succulent), and by total live dry mass, for each plot in the biodiversity experiment. Also provided are masses of dead material collected from plots (same groups as live material removed for each treatment) and total dry mass, live plus dead. Species-level data are available upo
Plant species-level responses to functional group and species removals in biodiversity experiment plots at the Jornada Basin LTER site, 1999
This dataset contains individual species size data in vegetation plots that have had various plant functional groups or species experimentally removed at the Jornada Basin LTER site in southern New Mexico, USA. This data was collected with the objective to distinguish the differential effects of plant community biomass, functional groups, and biodiversity within functional groups on ecosystem and plant community function. To make these distinctions, treatments were established by the selective removal of plant species or functional groups within experimental plots. There are eight treatments: control (C, no removals); four functional group removal treatments (PG, perennial grass removed; S, shrubs removed; SSh, subshrubs removed; Succ, succulents removed), and three species richness manipulation treatments. Richness manipulations included a simplified treatment (Simp), where only the single most abundant species of each growth form is preserved and all other species in the growth form are removed, a reduced‐Larrea treatment (rL), where the Larrea is assumed to be the dominant and is removed while minority components remain, and a reduced-Prosopsis treatment (rP), where Prosopis rather than Larrea is removed as the shrub dominant. In 1999, this pilot study attempted to assess individual species responses of representative individuals in these treatments. Ten randomly selected individuals of eight plant species were measured in each experimental plot, and this dataset reports volumetric data (diameters and height) for each. The study was designed as an individual-based complement to the transect data in EDI dataset knb-lter-jrn.210121001 but was not continued past 1999. This dataset is complete.
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