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Litterfall, Biomass and Productivity in CRUI Land Use Project at Harvard Forest 1996-1997

Prior agricultural land use often plays an important role in the present condition of forests. This research was conducted to find any productivity differences among previously plowed, pastured, and woodlot sites. There are six sites, two from each of the land use types. With this research we wanted to estimate the productivity for each of the six stands and test the hypothesis that rates of annual aboveground biomass and annual litter fall in recovering forests would decline in the order woodlot - pastured - plowed. Twenty-five trees, of various diameters and species, were cored at each site. The cores were analyzed and the radial growth was calculated for the most recent 5 and 10 year intervals. Biomass increments were also calculated for the same time span using published allometric equations. Aboveground woody productivity was calculated for diameter classes within species and semi-log relationships of productivity per diameter were used to calculate the productivity of all trees in the stand that were not cored. Site-specific and species-specific equations were used. Litter fall was estimated by collecting litter from ten traps each in the six stands. Litter was sorted by species and reported on a dry matter basis. Red oaks and red maples were the major contributors of biomass and litter fall in all six of the stands, accounting for about seventy percent of the total aboveground biomass. Although woodlots had higher total biomass there was not a significant difference in productivity across the six sites. The range of productivity including both litter fall and aboveground woody production was from 7524-9014 Kg/ha. This fell into the range for temperate forests according to results published by the International Biological Program. Production per unit biomass was greater in the plowed stand and least in the woodlots.

Herbaceous Species in CRUI Land Use Project at Harvard Forest 1996

Forests recovering from agricultural legacies differ in many ways that influence the landscape distribution, local abundance, and dispersion of herbaceous populations, as well as patterns of species associations within the herbaceous stratum. We recorded the presence/absence of 10 herbaceous species on a 1 x 1 m resolution in a 30 x 50 m permanent plot grid in six land use legacy sites (2 plowed, 2 pastured, 2 permanent woodlot) in summer 1996 to test predictions about herbaceous species abundance, richness, dispersion patterns, patterns of association, and their relationships to forest structure, microclimates, and soil resources. The 10 species chosen differed in several ways (evergreen vs. deciduous, stature, clonal architecture, affinity for disturbed vs. undisturbed forests) that allowed us to probe the impacts of prior disturbance and current resource patterns (light, water, nutrients) on the spatial patterns of individual species and species associations.

Mapped Trees in CRUI Land Use Project at Harvard Forest 1996-2006

Numerous variables related to land use disturbance and recovery processes influence forest composition, structure, and growth. We measured forest communities in six sites that were formerly plowed, pastured, or continuously forested woodlots in Prospect Hill to test predictions about species composition, stand structure, and productivity in response to agricultural land use legacies. A permanent 30 x 50 m plot gridded in 5 x 5 m sub-plots was established in each of the 6 sites. All trees at least 2.5 cm DBH (diameter at breast height, 1.3 m) were mapped visually in the field, marked with an aluminum tag, and their DBH recorded in summer 1996. Individual boles of multi-stemmed trees were measured separately and a composite single DBH was calculated. Standing dead trees were also mapped and their DBH recorded as well. The 1996 data were used to determine above ground woody biomass using allometric equations for individual trees. The permanent plots were re-surveyed ten years later in fall 2006. The status of each tree mapped in 1996 was recorded (alive, dead standing, dead fallen, forked) and DBH’s were re-measured. Additional trees that grew across the 2.5 cm DBH threshold during the ten-year period were mapped and their DBH’s measured. Composite diameters and above ground woody biomass were determined for forked trees as in 1996. The 2006 re-measurements were used to analyze changes in species composition, stand structure (density, diameter distribution), and mortality patterns among species and size classes, and to calculate net changes in above ground woody biomass across the ten-year period.

Tree Seedlings in CRUI Land Use Project at Harvard Forest 1996

Forests recovering from agricultural legacies differ in many ways that influence tree seed dispersal and seedling establishment patterns. We recorded the number of seedlings (less than 0.5 m tall) of all tree species on a 1 x 1 m resolution across six land use legacy sites (2 plowed, 2 pastured, 2 permanent woodlot) in summer 1996 to test several predictions about seedling abundance, diversity, and dispersion patterns, and their relationships to forest structure, microclimates, and soil resources.

Herbaceous Community Composition in CRUI Land Use Project at Harvard Forest 1996

Patterns of vascular plant species richness were investigated in six land use legacy sites (2 formerly plowed, 2 formerly pastured, and 2 permanent woodlot) in Prospect Hill to test predictions about the effects of disturbance, light and soil resources, and forest floor environmental heterogeneity on community composition. The occurrence of vascular taxa was recorded in each of the 60 5 m x 5 m contiguous plots within the 30 m x 50 m permanently gridded study plot in each land use legacy site in June 1996. Identification was made to species in most cases. Woodlots showed higher average species richness at the site level (53) than either pastured (52 species) or plowed (49) sites. However woodlots also show greater spatial variation in richness at the 5 m x 5 m resolution than either the plowed or pastured sites (in that order) as represented by the range, standard deviation, and coefficient of variation. Seasonally-averaged light levels at 50 cm are approximately twice as high in the plowed and pastured sites as in the woodlots, but the woodlots show significantly greater soil organic matter, carbon, nitrogen and water-holding capacity than the post-agricultural sites. These results suggest that soil resources may be more important than light in fostering higher herbaceous stratum richness. However, woodlot richness is also affected by the presence of taxa that are slow to re-colonize heavily disturbed sites (e.g., Epigaea repens) and to distinctive microsites that are less common in the plowed or pastured sites in the Harvard Forest system (e.g., exposed boulders). The greater spatial variation in woodlot richness is strongly influenced by both substrate diversity and by scattered hemlock trees, which substantially depress the herb stratum in localized patches.

openCC0Nov 2023View details →

Dynamics of Old-Growth Forests on Wachusett Mountain in Princeton MA 1996-1997

One of the largest old-growth forests in southern New England was recently "discovered" on the exposed upper slopes of Wachusett Mountain, one of the most heavily used recreational areas in Massachusetts, less than 50 miles from urban Boston. Presettlement and early post-settlement data suggest that most of the area's forests were comprised of a mixture of Quercus rubra and northern hardwood species. Individual species abundances and recruitment dynamics in the four stands exhibit highly variable spatial and temporal patterns across sites that differ in aspect and exposure. Three uneven-aged hardwood stands contain Quercus rubra in the largest size classes, various amounts of Fagus grandifolia, Acer and Betula species in the middle size classes and dense thickets of Acer pennsylvanicum, Acer spicatum, and Hamamelis virginiana in the small size classes. Several individuals of Q. rubra, B. lenta, and B. alleghaniensis are at or very near the maximum longevity known for these species. Of particular significance is the presence of Q. rubra exceeding 250 - 300 years of age. A Tsuga canadensis stand contains unimodal size and age distributions, with trees less than 60-cm dbh and 100 to 300 years old. Widespread Quercus rubra recruitment occurred on all sites from the 1600s through the early 1800s, when it dropped precipitously except for scattered individuals on more open talus sites, and was replaced by either Tsuga or Acer and Betula species. The historical change in recruitment from Quercus to more shade-tolerant species evidently was driven by a change in disturbance regime from an early period when fire was a major factor controlling forest dynamics to a period over the last two centuries when hurricanes (1815 and 1938), frequent wind, ice, and snow damage, but no fire, are documented. The asynchronous nature of tree-ring releases and suppression and the relatively low amount of coarse woody debris corroborate this interpretation. Chronic canopy damage through time p

Radiocarbon Measurements at Harvard Forest 1996-2010

Long-term datasets on soil C stocks, radiocarbon content, and CO2 efflux from the Harvard forest, MA were applied to the ForCent model to examine soil C dynamics over long term timescales and under warming and nitrogen amendments. The objective was to determine if manipulations of soil temperature and nitrogen supply affect the relative age of respired soil C substrates. Heating of the soil increased decomposition of all soil C pools, the absolute amount of increased decomposition from the older pools was not large enough to make a difference in 14C composition of respired C from model results. Further the high spatial variation observed in 14C from temperature and nitrogen amendments made it difficult to detect changes in respired C sources over this short a study period.

Physiological Model of CO2 Exchange by Hemlock Forests at Harvard Forest 1996-2000

A physiological model of carbon (C) exchange for a mature hemlock forest was developed, with separate component models for net photosynthesis (Pn), leaf respiration (Rl) , woody tissue respiration (Rw) and soil respiration (Rs). The model estimated that about 1.2 Mg C/ha was stored above and below ground between November 1, 1997 and October 31, 1998. This was generally a wet year with a wet and cloudy summer, except during August, which probably influenced the model output significantly. The whole-forest C exchange model estimated that most C storage in the forest occurred in spring. Warm temperatures with high soil moisture caused whole-forest respiration to exceed Pn during the summer, leading to a net C loss from the ecosystem. Leaf-level light-saturated Pn reached a maximum at about 20 deg C, then remained stable up to about 30 deg C, but at lower light levels Pn decreased above 20 deg C. This contributed to the lack of carbon storage during the summer, when the warmest days reached 30 to 32 deg C. Soil respiration was estimated at 60 to 75% of total ecosystem respiration, and during summer Rs increased exponentially with soil temperature with a Q10 of 3.8, so that from July through September, monthly Rs alone was 73 to 88% of total canopy Pn (Estimated monthly Rs ranged from 1.14 to 1.68 Mg/ha and estimated monthly Pn was 1.29 to 2.06 Mg/ha in July through September). A second major control on carbon storage by the hemlock forest was daily minimum temperature in spring and fall. There was no measurable Pn after daily minimum temperatures of -5 deg C or lower, although no effect of minimum temperature on Pn was observed for temperatures above 0 deg C.

CFCs and Radiatively Important Trace Species at Harvard Forest EMS Tower 1996-2005

Measurements of 13 ozone-depleting and/or greenhouse gases are taken above the forest canopy at Harvard Forest, downwind of the New York City - Washington, D. C. corridor, every 25 minutes using a four-channel gas chromatographic system called FACTS (Forest and Atmosphere Chromatograph of Trace Species). The species measured are H2, CO, CH4, methyl chloroform (CH3CCl3), chloroform (CHCl3), carbon tetrachloride (CCl4), CFC-11 (CCl3F), CFC-12 (CCl2F2), CFC-113 (C2Cl3F3), halon-1211 (CBrClF2), perchlorethylene (C2Cl4), nitrous oxide (N2O), and sulfur hexafluoride (SF6). Observations began in January 1996 and are continuing.

openCC (other)Oct 2025View details →

Data of predation on mussels from an LTREB project in the Gulf of Maine, USA, from 1996 to 2021.

Experimental clearings in macroalgal (Ascophyllum nodosum) stands were made in 1996 to determine if mussel beds and macroalgal stands on protected intertidal shores in New England represent alternative community states. Uncleared control plots and four sizes of circular clearings (1m, 2m, 4m and 8m in diameter), which mimicked ice scour events, were established in A. nodosum stands at 12 sites on Swan’s Island, Maine, USA. This dataset reports mussel predation on clumps of 15 mussels (Mytilus edulis) using mesh bags placed in the centers of clearings and controls. Mussel mortality was monitored in 1996, 1999, 2000, 2003, 2004, 2007 and then annually from 2010 to 2021. Causes of death were attributed to dogwhelks (Nucella lapillus), crabs (Carcinus maenas and Cancer spp.) or unknown causes. Presence and activities (e.g., drilling) of dogwhelks was also recorded. The standardized identifiers (Bay, Site, Plot) allow integration with related Environmental Data Initiative packages on community composition and recruitment of mussels, barnacles and rockweeds. Research was funded by NSF's LTREB program.

openCC (other)Feb 2023View details →

Plant biomass in heath tundra experimental plots, 1996, Arctic LTER, Toolik Lake, Alaska.

Plant biomass in arctic heath experimental plots. Plots set up in 1989 with nitrogen, phosphorus, nitrogen plus phosphorus and a shade treatment were harvested for above ground biomass. Root mass was also measured on a smaller subsample.

Soil Respiration at Harvard Forest HEM and LPH Towers 1996-2007

Soil respiration, including both CO2 produced during decomposition of organic matter in soil and surface litter, and CO2 produced during respiration of living roots, is a major component of forest-atmosphere carbon exchange, typically comprising 60 to 80% of whole-forest respiration. Soil respiration data can explain a major part of a forest ecosystem’s response to changing climate, and help in evaluating the accuracy of nighttime eddy flux data as estimates of whole-ecosystem respiration measurements. Soil respiration in the footprint areas of the Harvard Forest Hemlock and Little Prospect Hill eddy flux towers has shown generally similar responses to soil temperature and precipitation as soil respiration near the EMS flux tower (see data set HF006), but also some differences. Soil respiration at the Hemlock tower site has been lower than at the other tower sites during very wet summer weather, but higher during dry summer periods. Average estimated annual total soil respiration has been close to the same for all three tower footprint areas, however. There has been some evidence of lower soil respiration in the parts of the Little Prospect Hill tower footprint with lowest soil moisture (those with a high slope position, 100 m from the tower), as compared with other sites during very dry summer periods, but such periods have been very rare during the period of data collection. Soil respiration measured near the Little Prospect Hill tower in summer has also been higher than ecosystem respiration as estimated from nighttime carbon flux measured by an eddy covariance system. This indicates that during some nighttime periods, CO2 is being removed from the volume of air below the eddy flux system by a route other than through the top of the forest canopy near the flux tower, possibly by downslope advection, even under conditions when it initially appeared that atmospheric turbulence was high enough to prevent removal of CO2 by these other mechanisms.

Linking Community Dynamics and Ecosystem Function at Harvard Forest 1996-2000

Human activities are effecting profound changes in the structure and function of natural ecosystems. A comprehensive understanding of current ecosystem dynamics and future responses to global change requires an integrated investigation of ecological processes at many levels of organization. My thesis research addressed this goal by examining interactions between community- and ecosystem-level dynamics in mixed conifer broad-leaved forests in eastern North America. I addressed the nature of canopy-seedling feedbacks in mixed forests by relating seedling regeneration patterns in contrasting stand types to understory conditions (EXPERIMENT 1), and by directly manipulating resource availability to separate the individual effects of particular resources (EXPERIMENT 2). To investigate how nitrogen deposition will influence future forest composition, I examined the impact of increased nitrogen availability on regeneration of both coniferous and broad-leaved tree species under both closed canopy (EXPERIMENT 3) and simulated gap (EXPERIMENT 4) conditions. Future changes in forest composition might then influence whole-ecosystem productivity. I used two scaling approaches (leaf-level aggregation, EXPERIMENT 5; whole-tree sap flow, EXPERIMENT 6), I examined how the dominant coniferous and broad-leaved species in mixed temperate forests differed in their contributions to canopy-level photosynthesis.

Ecology and Biogeography of a Northern Caddisfly in Cape Cod MA 1996-2002

We have documented a large population of a rarely collected northern caddisfly, Phanocelia canadensis (Banks) (Trichoptera: Limnephilidae), on Cape Cod, Massachusetts. This species' range is generally considered to be centered in northern Canada, although there are individual records of adults from eastern Maine and New Hampshire, and a single adult was collected from Sherborn, Massachusetts, in the 1920s. The scarcity of this species in collections may reflect true rarity, with populations sparsely but widely distributed across the northern part of the continent. Alternately, it may reflect a sampling bias, in that the larvae of this species were unknown until the late 1980s, adults are diurnal and fly late in the fall, and larvae occur in wetlands and are closely associated with Sphagnum, from which they make their cases. We have carried out an in-depth habitat comparison of sites in which we found or did not find larvae on Cape Cod in seven years of intensive sampling. Habitat characteristics distinguishing wetlands with and without Phanocelia include dominance by Sphagnum sp., shrub cover, and low pH. We are currently searching in similar habitats across the state for additional populations.

openCC (other)Nov 2022View details →

North Temperate Lakes LTER: Lake District Revenues 1992 - 1996

Lake District revenues record one of the primary means of action available to lake districts. These districts are a form of special purpose district created by the state of Wisconsin in the early 1970s to address the specific problems of lake mangement not being addressed by existing governmental capacities. These districts are by statute granted the authority to levy property taxes, special assessments, special charges and delinquent charges against property owners within their geographic boundaries. This fund-raising authority gives to lake districts a capacity not only to raise substantial funds but to do so consistently over time, thereby alloting to them a practical capacity not readily available to other groups (such as lake associations) involved in lake management. Data are from years 1992 - 1996. Sampling Frequency: annually Number of sites: 190

openCC (other)Nov 2022View details →

Zooplankton of Small Lakes and Wetland Ponds in Wisconsin - North Temperate Lakes LTER 1996

We sampled zooplankton communities from 54 small water bodies distributed throughout Wisconsin to evaluate whether a snap-shot of zooplankton community structure during early spring could be used for the purpose of differentiating lakes from wetlands. We collected a single set of zooplankton and water chemistry data during a one-month time window (synchronized from south to north across the state) from an open water site in each basin as a means to minimize and standardize sampling effort and to minimize cascading effects arising from predator-prey interactions with resident and immigrant aquatic insect communities. We identified 53 taxa of zooplankton from 54 sites sampled across Wisconsin. There was an average of 6.83 taxa per site. The zooplankton species were distributed with a great deal of independence. We did not detect significant correlations between number of taxa and geographic region or waterbody size. There was a significant inverse correlation between number of taxa and the concentration of calcium ion, alkalinity and conductivity. One pair of taxa, Lynceus brachyurus and Chaoborus americanus, showed a significant difference in average duration of sites of their respective occurrence. All other pairs of taxa had no significant difference in average latitude, waterbody surface area, total phosphorus, total Kjeldahl nitrogen, alkalinity, conductivity, calcium ion, sulfate, nitrate, silicate or chloride. Taxa were distributed at random among the sites - there were no statistically significant pairs of taxa occurring together or avoiding each other. Multivariate analysis of zooplankton associations showed no evidence of distinct associations that could be used to distinguish lakes from wetlands. Zooplankton community structure appears to be a poor tool for distinguishing between lakes and wetlands, especially at the relatively large scale of Wisconsin (dimension of about 500 km). The data suggest that a small body of water in Wisconsin could be classified

openCC (other)Dec 2022View details →

Little Rock Lake Experiment at North Temperate Lakes LTER: Nutrients 1996 - 2000

The Little Rock Acidification Experiment was a joint project involving the USEPA (Duluth Lab), University of Minnesota-Twin Cities, University of Wisconsin-Superior, University of Wisconsin-Madison, and the Wisconsin Department of Natural Resources. Little Rock Lake is a bi-lobed lake in Vilas County, Wisconsin, USA. In 1983 the lake was divided in half by an impermeable curtain and from 1984-1989 the northern basin of the lake was acidified with sulfuric acid in three two-year stages. The target pHs for 1984-5, 1986-7, and 1988-9 were 5.7, 5.2, and 4.7, respectively. Starting in 1990 the lake was allowed to recover naturally with the curtain still in place. Data were collected through 2000. The main objective was to understand the population, community, and ecosystem responses to whole-lake acidification. Funding for this project was provided by the USEPA and NSF. Parameters characterizing the nutrient chemistry of the treatment and reference basins of Little Rock Lake are measured at one station in the deepest part of each basin at the top and bottom of the epilimnion, mid-thermocline, and top, middle, and bottom of the hypolimnion. These parameters include total nitrogen, total dissolved nitrogen, nitrate, ammonia, total phosphorus, total dissolved phosphorus, dissolved reactive phosphorus, bicarbonite-reactive filtered and unfiltered silica, dissolved reactive silica, total inorganic carbon, dissolved inorganic carbon, total organic carbon, dissolved organic carbon, and total particulate matter. Sampling Frequency: varies - Number of sites: 2