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86 results for “hemlock”
Stream Periphyton Response to Hemlock Mortality in Central Massachusetts 2006
The Hemlock Wooly Adelgid (HWA) invasion is expected to cause widespread mortality of eastern hemlock [Tsuga canadensis (L.) Carriere] throughout much of New England. Light levels in streams with hemlock riparian zones are anticipated to increase as hemlock are replaced by deciduous trees. We sought to: 1) quantify differences in light reaching streams with hemlock and deciduous riparian zones, 2) determine if increases in light result in higher periphyton biomass, and 3) explore the role of macroinvertebrate grazing on periphyton biomass as light increases in an attempt to help predict stream ecosystem responses to hemlock mortality. Light measurements were taken along 100-800m stream reaches with riparian zones of healthy hemlock and deciduous trees in MA and CT in order to document an integrated light profile for each stream. In addition, a 2 x 2 factorial experimental design with five replicates was executed on a deciduous reach of Egypt Brook in central MA, in which light (high light vs. low light) and grazing (high grazing vs. low grazing) were manipulated. Light measurements were significantly higher for streams with deciduous riparian zones than hemlock riparian zones. Controlled shading reduced chlorophyll a, while excluding grazing yielded inconclusive results. Periphyton biomass in Egypt Brook was found to be light limited, and grazing did not suppress periphyton biomass. As hemlocks die, in-stream light will be significantly augmented, and periphyton biomass will increase. A challenge for stream ecologists will be to incorporate multiple physical, chemical, and biological controls on biota in order to fully understand how regional hemlock mortality will alter stream periphyton biomass.
Tree-ring measurements from permanent plot in old-growth hemlock-hardwood forest, Huron Mts., MI
This package includes tree growth-ring widths for increment cores collected from a long-term 'macroplot' established in old-growth hemlock-northern hardwoods forest at the Huron Mts. of northern MI. Tree demographic monitoring data for the entire ca. 3.0 ha macroplot are available in the EDI package edi.1416.1. In 1994 and 1995, increment cores were taken for all 'core-able' trees greater than ~ 10 cm diameter for a subsection of the macroplot about 1 ha in area, along with some additional Tsuga canadensis trees beyond that 1 ha section. Cores are NOT cross-dated. See Methods for more details. This data-package may be cross-referenced to the demographic data in edi.1416.1 using stem numbers.
Tree-ring measurements from permanent study plot in old-growth hemlock-hardwood forest, Dukes RNA, Hiawatha NF, Marquette Co., MI
This package includes tree growth-ring widths for increment cores collected from a long-term 'macroplot' established in old-growth hemlock-northern hardwoods forest at the Dukes Research Natural Area/Dukes Experimental Forest in the Hiawatha National Forest in Marquette Co., MI. Tree demographic monitoring data for the entire ca. 3.0 ha macroplot, from 1992 to 2019, are available in the EDI package edi.1526.1. In 1993, 1994 and 1995, increment cores were taken for all 'core-able' trees greater than ~ 10 cm diameter for a subsection of the macroplot about 1 ha in area. Trees that were obviously badly rotten and hollow or steeply leaning were not cored. Cores are not cross-dated. See Methods for more details. This data-package may be cross-referenced to the demographic data in edi.1526.1 using stem numbers.
Ant Assemblages in Hemlock Removal Experiment at Harvard Forest since 2003
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. As part of the Hemlock Removal Experiment at the Simes Tract, we annually monitor ant species composition and abundance.
Tree Seed Dispersal in Hemlock Removal Experiment at Harvard Forest 2005
Throughout the northeast, the hemlock woolly adelgid (Adelges tsugae) threatens eastern hemlock (Tsuga canadensis) through direct mortality resulting from infestation followed by defoliation and indirect mortality in the form of pre-emptive logging. The efficacy of regeneration of vegetation following hemlock decline depends upon advance regeneration of seedlings and saplings, seed dispersal, and recruitment. In this study, we investigated (1) whether the basic parameters of height of release and wind velocity affected seed dispersal distance and (2) tested the fit of a basic ballistic model of seed dispersal to empirical data in areas both with and without canopies. We collected empirical data from seed dropping and seed rain experiments at Harvard Forest. Height and wind velocity only affected seed dispersal distance in open areas. Predicted values of dispersal distance generated by the basic ballistic model did not provide a good fit to observed dispersal data. Poor fits of the ballistic model to the data were due to the model’s inability to account for rare, long distance dispersal events. More complex models with additional parameters are necessary to model non-localized seed dispersal.
Stream Macroinvertebrates in Hemlock and Deciduous Watersheds at Harvard Forest 2005-2007
Tsuga canadensis (Eastern Hemlock) is a common forest species that is declining throughout its range in the eastern United States because of the invasion of an non-native forest pest, Adelges tsugae (Hemlock Woolly Adelgid). This pest kills infected trees, and over time, infected stands are replaced by deciduous forests. The conversion of forests from Hemlock to deciduous species is predicted to impact the hydrology, chemistry, and biology of associated headwater streams. In this study, we examined the macroinvertebrate communities of two adjacent headwater streams with differing Hemlock influence in central Massachusetts. Abundance, taxa richness, diversity, and unique taxa were generally greater in the deciduous stream. Differences in the distribution of functional feeding groups were observed: the Hemlock stream had a greater percentage of collector-gatherers while the deciduous stream had a greater percentage of shredders and predators. These findings suggest that macroinvertebrate communities in streams draining Hemlock and deciduous watersheds may differ in structure and function, and that anticipated Hemlock mortality may impact the region’s stream ecology.
Canopy LiDAR Measurements in Hemlock Removal Experiment at Harvard Forest 2005
As the ecological functioning of a forest stand is often related to the spatial organization of the canopy, we used a portable canopy LiDAR (PCL; Parker et al. 2004) to measure volumetric canopy structure in the simulated HWA management treatments. In September and October 2005, prior to leaf abscission, we set up 16 parallel transects spaced 2 meters apart in the 900 m2 (30 x 30 m) interior of each of the eight treatment plots. The orientation of the transects were either north-south or east-west to minimize the difficulty of traversing the stand. The distances to canopy surfaces more than1 m above the ground along the transects were recorded with the PCL. Assuming a constant horizontal sampling rate, the continual height measures were binned into 1 m intervals. From these measures, vertical canopy profiles, canopy openness, canopy rugosity, and other metrics related to the three-dimensional structure of the canopy can be derived. These canopy measures will be repeated minimally at 5 and 15 year intervals to develop an understanding of early structural dynamics and micrometeorological consequences associated with the simulated HWA treatments. (Parker, G.G., D.J. Harding, and M.L. Berger. 2004. A portable LIDAR system for rapid determination of forest canopy structure. Journal of Applied Ecology 41, 755-767).
Soil Respiration in Hemlock Removal Experiment at Harvard Forest 2003-2009
Soil respiration (SR) is a combination of autotrophic (root respiration) and heterotrophic (microbial respiration). As a combination of these two belowground processes, separating their relative contributions to SR from is difficult. The hemlock removal experiment provided an opportunity to look at these two components of SR. Girdling and logging result in the death and/or removal of aboveground biomass (trees) and subsequently death of root biomass. As a result the measured respiration in these treatment plots should then be comprised primarily of the microbial respiration component of SR. By measuring SR in control plots, and taking the difference with girdled and logged plots, we may determine the relative contribution of root and microbial respiration.
Sapwood Temperatures in Hemlock Trees at Harvard Forest HEM Tower 1997-1998
Sapwood temperatures in four large hemlocks, 130-200 years old and about 40 to 90 cm basal diameter and 25 to 29 m tall, were measured in order to estimate sapwood respiration in these trees as part of a physiological model for hemlock forest carbon exchange. As expected, sapwood temperature varied most in small branches and least in the main bole of the tree near the ground. An additional finding from these measurements is that sapwood begins to freeze at -1 to -2 degrees C, as shown by a stabilization and in some cases an increase of about 1 degree C in sapwood temperature when air temperature cooled continuously to below this temperature range.
Inorganic Nitrogen Pools and Tree Composition in Hemlock Removal Experiment at Harvard Forest 2007-2009
This study assessed how the change in leaf litter input and environmental conditions, from that of hemlock stands to earlier successional deciduous stands, will affect inorganic nitrogen availability at the interface of the mineral soil and LFH horizons. In early October 2007 we exchanged 0.5 x 0.5 m "loaves" of LFH horizons from hemlock and deciduous stands between forest types, while keeping control plots in the original forest stands. Inorganic nitrogen outputs from the litter loaves were monitored for 20 months using ion-exchange resins, removing and replacing the resins three times at 5 - 8 month intervals. Results indicated that there were differences between the control hemlock and deciduous loaves - NO3 and NH4 availability were higher in deciduous stands. However, the transfer of litter loaves from one stand type to another did not reveal changes in nutrient availability due to a shift in habitat. Rather, the methodology of moving litter loaves to a new site caused greater changes in nutrient availability, particularly over the summer months.
Stand and Community Response to Hemlock Woolly Adelgid in Southern New England since 1995
Hemlock woolly adelgid (HWA), Adelges tsugae, an introduced aphid-like insect from Asia, is expanding its range across the northeastern United States through the range of Tsuga canadensis (eastern hemlock) and can severely reduce or eliminate this important late-successional species. As part of a study investigating stand- and landscape-level forest dynamics resulting from HWA infestation, we examined initial community response of eight T. canadensis stands in south-central Connecticut and then continued to monitor these stands every other year. Our major objectives were to assess mortality patterns in T. canadensis, evaluate subsequent changes in stand microenvironment, and relate these and stand composition to initial patterns of regeneration, understory response, and community reorganization. Tsuga canadensis damage varied broadly across the study area ranging from near zero to greater than 95 % mortality. All size and age classes sampled were attacked by HWA, although smaller trees exhibited higher mortality rates than larger trees. All remaining T. canadensis sampled in seven of the eight stands were infested with HWA and over 90 % suffered at least 50 % foliar loss. Since 1995, overstory and understory mortality has risen 5 to 15 % per year to overall values of 50 to 99%. There has been no sign of tree recovery and the health and vigor of remaining trees deteriorated in all infested stands. Results suggest that trees on some sites can remain alive for over 10 years following initial infestation and remain standing for 6 to 8 years following mortality. Substantial accumulations of downed woody debris have developed in stands with severe HWA damage. Canopy gaps created by HWA damage significantly increased the amount of light reaching the forest floor and resulted in rapid understory vegetation responses. Prolific Betula lenta (black birch) establishment occurred in stands with moderate to severe T. canadensis mortality. In addition, opportunistic herbaceous spe
Snowpack in Hemlock, Hardwood, and Open Sites at Harvard Forest 2008-2014
Sub-forest canopy meteorological forcing and snowpack properties can profoundly influence the winter ecology. 3/4 inch graduated PVC snow stakes and web cams were installed at three Harvard Forest (HF) sites including: mixed-hardwood at the Little Prospect Hill (LPH) Eddy Flux Tower, near the Hemlock walk-up tower, and at the open area behind Shaler Hall. Web cameras connected to a laptop at the three sites provided daily images of snowpack surface depth. Snow density profiles were recorded during weekly to monthly site visits from December 2008 to April 2014. Gaps in the datasets were primarily caused by laptop malfunctions and lack of site visits necessary to maintain equipment and to obtain density measurements of the snowpack. There were no site visits to record snowpack properties during the 2011-2012 snow season, a year of unusually low snowfall. These datasets would prove useful for research related to snow ecology and hydrology projects at Harvard Forest.
Monitoring Amphibians in the Declined Hemlocks at Harvard Forest 2013-2014
Disturbances such as outbreaks of nonnative insects and pathogens can devastate unique habitats and directly reduce biodiversity. The foundation tree species Tsuga canadensis (eastern hemlock) is declining due to infestation by the nonnative insect Adelges tsugae (hemlock woolly adelgid). The decline and expected elimination of hemlock from northeastern US forests is changing forest structure, function, and assemblages of associated species. We assessed changes in occupancy, detection probability, and relative abundance of two species of terrestrial salamanders, Plethodon cinereus (eastern red-back salamander) and Notopthalmus viridescens viridescens (eastern red-spotted newt), in the experimental removal of T. canadensis at Harvard Forest. Four treatments (logging, girdling, hemlock control and hardwood control) have been applied and replicated in eight 0.81-ha plots. Salamanders were sampled under cover boards and using visual encounter surveys in June-July of 2013 and 2014. Removal of the hemlock canopy increased occupancy of P. cinereus but significantly reduced its estimated detection probability and abundance. Estimated abundance of N. v. viridescens also declined dramatically after canopy manipulations. Our results suggest that ten years after hemlock loss due to either the adelgid or pre-emptive salvage logging, and 50-70 years later when these forests have become mid-successional mixed deciduous stands, that the abundance of these salamanders likely will be less than 50% of their abundance in current, intact hemlock stands.
Hemlock Woolly Adelgid and Elongate Hemlock Scale Surveys in Connecticut and Massachusetts 1997-2011
In the eastern USA, eastern hemlock (Tsuga canadensis) is the host plant for two invasive insect species - hemlock woolly adelgid (Adelges tsugae) and elongate hemlock scale (Fiorinia externa). We observed the density of adult hemlock woolly adelgid and elongate hemlock scale on eastern hemlock branches on five occasions over 14 years at 142 stands across a latitudinal transect encompassing 7,500 km2 in Connecticut and Massachusetts to assess whether there is a difference in the response to abiotic conditions (winter temperature, summer temperature, summer precipitation) between the two species, and whether the distribution and abundance of each insect species is dependent on biotic interactions with the co-occurring insect species.
Red-backed Salamanders as Indicators of Hemlock Forest Health at Harvard Forest 2014
Species that react quickly to ecological changes are useful indicators for assessing forest health. Red-backed salamanders (Plethodontid cinereus) may be used as an indicator species in declining hemlock forests, allowing for assessment of soil quality and forest health. We hypothesized that decline of hemlock stands due to the effect of hemlock woolly adelgid would negatively impact the abundance of red-backed salamanders by altering soil quality. In the Hemlock Removal Experiment at Harvard Forest, eight-0.8ha plots were treated either with girdling to simulate adelgid invasion, logging to simulate preemptive logging strategies, no treatment in hemlock areas, or no treatment in hardwood areas. Within these treatments in June and July of 2014, P. cinereus relative abundance was determined from coverboard surveys. Soil quality was determined from core samples. Bulk density, pH, carbon-nitrogen ratio, moisture, soil temperature, and litter depth were measured, and ordination was used to create an index of soil quality from these. There was a significant correlation between plot treatment and soil quality (p less than 0.05). Temperature, CN ratio, and pH influenced a strong significant negative correlation between soil quality and salamander abundance (pless than 0.05). Soil quality affected by hemlock decline influenced salamander abundance. These data suggest that we could gain an understanding of forest health and soil quality by examining salamander abundance. Assessing adelgid invasion can be difficult and objective, whereas salamander abundances are easily measured; therefore, we suggest that salamander abundances could be useful in assessing the health of hemlock forest ecosystems.
Soil Carbon in a Hemlock Stand Infected by Hemlock Woolly Adelgid at Harvard Forest since 2015
The main objective of this research is to study changes in soil carbon stocks (soil C, root biomass) and fluxes (soil respiration) in a hemlock stand that is currently infested by the hemlock woolly adelgid, and where trees are declining in vigor and dying off. Soil respiration is measured throughout the growing season using an automated system, which produces a long-term, high-temporal-resolution series of soil respiration over multiple locations. Soil carbon stocks and root biomass are estimated by sampling soil in multiple locations throughout the hemlock stand following the sampling design used by Serita Frey at Harvard Farm (“Conant plots”). The large number of samples will be used to determine how many should be resampled in the future to be able to determine if any difference in soil C content or root biomass is statistically significant. Soil and roots will be sampled every 5 to 10 years to evaluate the trends in soil carbon stocks during and after the decline of hemlock caused by the hemlock woolly adelgid infestation.
Structure of Ant Communities in Declining Hemlock Stands at Harvard Forest 2003
In biomass and ecological dominance, ants are the most important invertebrate taxon in terrestrial ecosystems and they can alter significantly fundamental processes and dynamics of soil ecosystems. Relative to deciduous stands, hemlock stands are depauperate in ant species that are linked to differences in rates of soil turnover and nutrient mineralization between these forest types. In both hemlock and deciduous stands, we will document ant species richness and abundance; assess their role in soil nutrient cycling; determine temporal trajectories of ant community assembly as hemlock declines following woolly adelgid infestation, and is subsequently replaced by birch; and discover how these trajectories influence nutrient availability during this transition. For more details see: Ellison, A. M., J. Chen, D. Dz, C. Kammerer-Burnham, and M. Lau. 2005. Changes in ant community structure and composition associated with hemlock decline in New England. Pages 280-289 in B. Onken and R. Reardon, editors. Proceedings of the 3rd Symposium on Hemlock Woolly Adelgid in the Eastern United States. US Department of Agriculgure - US Forest Service - Forest Health Technology Enterprise Team, Morgantown, West Virginia.
Plot-based vegetation data for a large tract of old--growth hemlock-northern hardwood forest, Marquette Co., Michigan: 1988
In 1987-88 members of the Burton V. Barnes lab at University of Michigan conducted a landscape inventory of portions of the Huron Mountain Club lands (primarily, the self-declared 'Reserved Area') in Powell Township, northern Marquette County, MI. The data-set deposited here, collect under direction of Philip E. Stuart (then a graduate student in the lab) focuses on the ca. 1200 ha of old-growth, mesic hemlock-northern hardwood forests within the larger property. 313 plots (450 m^2) were established at nodes of an approximately 10 chain (~192 m) grid that fell within these forest types. The data-set includes canopy tree measurements, ground-layer cover estimates (for a subpplot), and a number of soil and topographic variables (measured directly and derived). A description of the study and results is published in Simpson et al. 1990. Occasional Papers of the Huron Mountain Wildlife Foundation Number 4, with associated maps.
Permanent plot data for old-growth white pine - hemlock - hardwood forests in the Huron Mountains, Marquette County, Michigan: 2006-2022
This study was initiated by Dr. Dennis A. Riege with a focus on the role of white pine (Pinus strobus) in old-growth mixed white pine-hemlock-northern hardwood forests. Study areas within the lands of the Huron Mt. Club were selected for prominent presence of canopy white pine. Several permanent study plots, totaling about 3.3 ha, were established, with all trees >5 cm diameter at breast height (dbh) identified, mapped and measured. Initiatl establishment was from 2006-2008. All plots were remeasured in 2011, 2016 and 2021-22. Mortality and new recruits were documented in remeasurements. Reference coordinates for each plot are included in 'Methods'. Data tables in this package include all of these measurements. Additional information, including maps of downed logs, is included in material included under 'other entities'.
Ant Assemblages in Hemlock Removal Experiment at Harvard Forest since 2003 (Reformatted to the ecocomDP Design Pattern)
This data package is formatted as an ecocomDP (Ecological Community Data Pattern). For more information on ecocomDP see https://github.com/EDIorg/ecocomDP. This Level 1 data package was derived from the Level 0 data package found here: https://pasta.lternet.edu/package/metadata/eml/knb-lter-hfr/118/33. The abstract below was extracted from the Level 0 data package and is included for context: 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. As part of the Hemlock Removal Experiment at the Simes Tract, we annually monitor ant species composition and abundance.
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