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Xylem Embolism Formation, Refilling and Water Storage in Tree Trunks at Harvard Forest 2012

Trunks of large trees play an important role in whole-plant water balance but technical difficulties have limited most hydraulic research to small stems, leaves and roots. To investigate the dynamics of water-related processes in tree trunks, such as winter embolism refilling, xylem hydraulic vulnerability, and water storage, volumetric water content (VWC) in the main stem was monitored continuously using frequency domain moisture sensors in adult Betula papyrifera trees from early spring through the beginning of winter. An air injection technique was developed to estimate hydraulic vulnerability of the trunk xylem. Trunk VWC increased in early spring and again in autumn concurrent with root pressure during both seasons. Diurnal fluctuations and a gradual decrease in trunk VWC through the growing season were observed, which, in combination with VWC increase after significant rainfall events and depletion during periods of high water demand, indicate the importance of stem water storage in both short-and long-term water balance. Comparisons between the trunk air injection results and conventional branch hydraulic vulnerability curves showed no evidence of “vulnerability segmentation” between the main stem and small branches in B. papyrifera. Measurements of VWC following air injection, together with evidences from air injection and xylem dye perfusion, indicate that embolized vessels can be refilled by active root pressure but not in the absence of root pressure. The precise, continuous and non-destructive measurement of wood water content using frequency domain sensors provides an ideal way to probe many hydraulic processes in large tree trunks that are otherwise difficult to investigate.

Tree Inventories for Validating Terrestrial Lidar Measurements at Harvard Forest 2007-2014

Our objective is to improve the measurements of canopy structure and biomass of a forest stand and detect their annual changes via a ground-based laser scanning technology, also known as terrestrial lidar (TLS). A TLS instrument utilizes lasers to scan an environment, measure 3D locations of objects encountered by lasers and detect intensities of laser lights scattered by those objects back to the TLS instrument. TLS have shown abilities and is being further explored to retrieve stem diameter, stem count density, stand height, leaf area index, foliage profile, foliage area volume density, aboveground biomass and other useful forest structural parameters rapidly and accurately. Three TLS instruments used in this project include: (1) the Echidna (R) Validation Instrument (EVI), built by CSIRO Australia; (2) Dual-Wavelength Echidna® Lidar (DWEL), built by Boston University, University of Massachusetts, Lowell, University of Massachusetts, Boston and CSIRO Australia; (3) Compact Biomass Lidar (CBL), built by University of Massachusetts, Boston. To validate the forest structural parameters retrieved using these TLS instruments, we set up a one-ha (100 m by 100 m) forest site and collected tree inventory data including: tree location, tree species, DBH, tree height and crown dimension since 2007 with a two-year gap of 2008 and 2009. Lidar data are available from the ORNL DAAC (http://dx.doi.org/10.3334/ORNLDAAC/1045).

Whole-Tree Nonstructural Carbohydrate Budgets in Five Species at Harvard Forest 2014

We measured nonstructural carbohydrate (NSC) concentrations throughout the year in the branches, stemwood, and roots of five temperate tree species. These NSC concentrations were used in two ways. First, we scaled up concentrations to the whole-tree level using allometric equations and compared NSC storage between these five species to determine the size and seasonal fluctuation of whole-tree total NSC budgets as well as the contribution of individual organs. Second, for four of these species, we assessed the radial patterns and seasonality of NSC concentrations in the stemwood based on contrasting wood anatomy (ring-porous vs. diffuse-porous).

Hemlock Mapped Tree Plot at Harvard Forest since 1990

Most of the central New England landscape was cleared for agriculture in the mid-19th century and then naturally reforested into "secondary forests" with the abandonment of agricultural land. Some sites, often poorly drained, remained forested, but were usually subjected to intensive fuelwood cutting or logging and are termed "primary forests." The Hemlock Woodlot was never cleared for agriculture, but has a history of cutting and natural disturbance. The hemlock woodlot is located in the center of Harvard Forest's Prospect Hill Tract, adjacent to a spruce-blackgum swamp. Soils are moist and rocky, with a thick organic layer. Hemlock dominates tree species composition (62% by basal area), with hardwoods and scattered large white pine comprising the remainder. Most of the trees are 100-150 years old, with a few hemlock trees up to 230 years old. While the site was never cleared for agriculture, it was logged several times and chestnut blight removed a chestnut-dominated overstory in the 1910s. The 0.72 ha stem-mapped plot is at the center of a 4-ha hemlock-dominated forest. This plot serves as a major reference site and is part of a network of hemlock forests that are being intensively sampled as the hemlock woolly adelgid arrives.

Lyford Mapped Tree Plot at Harvard Forest since 1969

Permanent forest plots provide an empirical understanding of forest change over time, and are an invaluable part of forestry and ecological research. Walter Lyford began measurements of a 2.88 ha red oak-red maple forest on the Prospect Hill Tract of Harvard Forest in 1969. All trees over 2 inches (5 cm) were mapped on very large-scale (1 inch = 5 feet) hand-drawn maps, and included live and dead trees, stumps, windthrows and other features such as stone walls, boulders, soil moisture and a damage boundary from the 1938 hurricane. All living and dead trees have been re-located and measured (diameter at breast height, canopy class for live trees; condition, decay class, diameter, bole length and stem orientation for fallen dead trees) in 1969, 1975, 1987-1992, 2001, and 2011. In 2001, the original, hand-drawn maps were digitized using ArcView GIS. From 1969 to 2011, red oak (Quercus rubra) increased its dominance of the stand’s total basal area from 52% to 60%; however, red maple (Acer rubrum) has become relatively less abundant, decreasing from 30% to 23%. While red oak and red maple continue to account for the majority of the basal area in the stand, the secondary species experienced a dramatic increase in relative abundance of individuals in the stand; yellow birch (Betula alleghaniensis), black birch (Betula lenta), American chestnut (Castanea dentata), American beech (Fagus grandifolia), witch hazel (Hamamelis virginiana), eastern white pine (Pinus strobus), and eastern hemlock (Tsuga canadensis) have increased from comprising 25% of the individuals in the stand in 1969 to comprising 52% in 2011. The total biomass of living individuals is increasing linearly (R2=0.99, p=0.0002), which implies that the stand has not yet experienced an age-induced decrease in biomass accumulation.

Age of Nonstructural Carbohydrates in Four Tree Species at Harvard Forest 2015

We estimated the mean age of sugars within and between different organs of four temperate tree species using the radiocarbon (carbon-14) bomb spike approach. Radial patterns of carbon-14 in the stemwood and coarse roots showed that sugars tended to became older when moving towards the pith.

Gene Expression and Tree Growth in the CTFS-ForestGEO Plot at Harvard Forest 2017-2019

Major goals in ecosystem ecology have been to scale from leaves to canopies and to determine whether individual-level, intra-species and inter-specific variation is critical for models projecting ecosystem processes now and in the future. The project is important in that it examines these issues in detail considering genotypes and levels of gene expression all the way up to canopy level CO2 flux. Ecological genomics and transcriptomics are nascent fields that have been primarily restricted to model species in natural and (mostly) controlled environments. To date, we have very few studies of non-model organisms in nature and/or studies of functional genomics through space and time. The research is producing extraordinarily rich datasets regarding the gene expression of trees across populations, through space in each population, across the growing season and across years and linking this information to growth and gas exchange. It will, therefore, provide tremendous insights into how much variation exists in nature thereby guiding sampling designs in future ecological 'omics projects. More importantly, it will provide unusually detailed phenotypic information for important non-model species that have large impacts on the CO2 flux of eastern US forests.

openCC0May 2024View details →

Overstory Mapped Tree Plots at Harvard Forest since 1990

These plots were established and mapped in 1990 for an experiment designed to study the effects of selective overstory tree mortality. The planned manipulation was to kill and leave standing one species in each of four plots, to simulate mortality by a species-specific pathogen. This manipulation was never done, for logistical reasons and because the appearance of the hemlock woolly adelgid provided a more pressing "natural" experiment to study; however, the plots are maintained and have been used in other studies. There are four 50m x 50m plots, located in a mixed hardwood forest (red oak and maple species are major components), north of the experimental hurricane. Tree data from the control plot of the experimental hurricane study could be added to this set for some analyses, since all the plots are in the same general area and forest type, and similar types of measurements were made on all of these trees. Tree diameter and condition were re-surveyed in these plots in Autumns 2003, 2013 and 2023, and saplings growing into the "tree" size class of greater than or equal to 5cm diameter were measured, tagged and mapped.

Nonstructural Carbon, Phenology and Wood Formation in Three Tree Species at Harvard Forest 2017-2019

This data set comprises various observations and measurements across the 2017 to 2019 growing season for seven red maple (Acer rubrum), eight red oak (Quercus rubra), and six white pine (Pinus strobus) in the Prospect Hill Tract of Harvard Forest. The observations include spring and fall leaf phenology and basic allometry, such as diameter at breast height and height. For the leaf phenology, we followed the protocol from John O’Keefe (HF003). Measurements include wood growth data from weekly microcores and a three time characterisation of growing season nonstructural carbon concentrations (soluble sugars and starch) for stems and leaves. Additionally, stem CO2 efflux was measured once a month for the 2018 growing season and weekly for the 2019 growing season.

PhenoCam Images and Canopy Phenology at the Harvard Forest Witness Tree since 2014

The PhenoCam Network uses imagery from digital cameras to track vegetation phenology and seasonal changes in vegetation activity in diverse ecosystems across North America and around the world. Imagery is uploaded to the PhenoCam server at the University of New Hampshire, where it is made publicly available in near-real time, every 30 minutes from sunrise to sunset, 365 days a year. The data are processed using simple image analysis tools to yield a measure of canopy greenness, from which phenological metrics are extracted, characterizing the start and end of the growing season. These transition dates have been shown to align well with on-the-ground observations of tree phenology at Harvard Forest (HF003). Long-term PhenoCam data can be used to track the impact of climate variability and change on the rhythm of the seasons. This dataset contains one mid-day image for each camera. Please see the PhenoCam Network website (https://phenocam.nau.edu/webcam/) for more information and additional images.

openCC0Jan 2024View details →

Visual Counts of Tree Reproduction near NEON plots at Harvard Forest since 2020

Mast seeding, a resource pulse that has cascading effects in the environment, is a measure that can provide insight into forest dynamics. When masting data is collected in sequential years it can provide information on how tree populations are responding to climatic and environmental variables, and can also be used to relate to other indices, such as seed-eating animal species. The objective of this study is to quantify the yearly seed production of mast seeding tree species at Harvard Forest which are located near National Ecological Observatory Network (NEON) plots. This project is part of larger NEON-enabled project examining mast seeding on a continental scale at 25 NEON sites in the United States, which uses mast seeding records in conjunction with NEON collected data products like mammal box-trapping, tick drags, and bird point counts. Data collected on mast seeding can be linked to these other indices at regional and continental scales.

Juvenile Tree Responses to Soil Warming at Harvard Forest since 1995

The main goal of this study is to assess eastern tree species’ growth, survivorship, and phenological responses to soil warming in order to forecast future changes in forest succession and carbon dynamics. From 2003 through 2010, we determined that shade-tolerant, normally slower-growing species benefitted most from warming. We are continuing to study species-species responses to investigate the duration of and mechanisms behind species- and functional group responses to climate warming. Monitoring long-term demographic and physiological responses of juvenile trees with and without soil warming will allow us to model future eastern tree species successional shifts under warmer climate conditions.

Witness Tree Data in Southern New England and Long Island 1640-1999

Early surveyors' witness-tree records from initial land divisions are often used to reconstruct the vegetation at the time of European settlement and before extensive Euro-American land use. The following description of methods comes from the published paper (Hall, B., G .Motzkin, D. R. Foster, M. Syfert and J. Burk. 2002. Three hundred years of forest and land-use change in Massachusetts, USA. Journal of Biogeography 29, 1319-1335): "Following methods described more fully in Cogbill et al. (2002), we used early surveyors' tree records from initial land divisions in each town to reconstruct the vegetation at the time of European settlement and before extensive Euro-American land use. All available original 17th - early 19th century survey records located at the state archives and individual town halls were examined and colloquial or common names of marker trees were noted... With few exceptions, only surveys that occurred within 80 years of town settlement were gathered in order to limit the potential influence of European land use on species composition."

Hydraulic Pathways in Leaves of Temperate Trees at Harvard Forest 2002

The transport of water, sugar and nutrients in trees is restricted to specific vascular pathways, and thus organs may be relatively isolated from one another (=sectored). Strongly sectored leaf-to-leaf pathways have been shown for the transport of sugar and signal molecules within a shoot, but not previously for water transport. The hydraulic sectoriality of leaf-to-leaf pathways was determined for current year shoots of six temperate deciduous tree species (three ring-porous: Castanea dentata, Fraxinus americana and Quercus rubra, and three diffuse-porous: Acer saccharum, Betula papyrifera and Liriodendron tulipifera). Hydraulic sectoriality was determined using dye staining and a hydraulic method. In the dye method, leaf blades were removed, and dye was forced into the most proximal petiole. For each petiole we counted the vascular traces shared with the proximal petiole. For other shoots, measurements were made of the leaf-area specific hydraulic conductivity for leaf-to-leaf pathways (kLL). In five of six species patterns of sectoriality reflected phyllotaxy; both the sharing of vascular bundles between leaves and kLL were higher for orthostichous than non-orthostichous leaf pairs. Species-differences in leaf-to-leaf sectoriality were determined as the proportional differences between non-orthostichous vs. orthostichous leaf pairs in their staining of shared vascular bundles and in their kLL; for the six species these two indices of sectoriality were strongly correlated (R2 = 0.94; P less than 0.001). Species varied 8-fold in their kLL-based sectoriality, and ring-porous species were more sectored than diffuse-porous species. Differential leaf-to-leaf sectoriality has implications for species-specific coordination of leaf gas exchange and water relations within a branch, especially during fluctuations in irradiance, water and nutrient availability.

openCC (other)Dec 2024View details →

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.

openCC (other)Apr 2025View details →

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.

openCC (other)May 2025View details →

Dataset on tree diversity metrics and aboveground carbon storage in Southeastern U.S. oak-pine forests, 2009–2019

This dataset contains measurements of tree structural and taxonomic diversity, stand attributes, and aboveground carbon storage from mixed oak-pine forests in Florida, Georgia, and Alabama, located in the southeastern United States. Data were collected from 946 mixed oak-pine, and 7224 longleaf-slash pine and oak-pine Forest Inventory and Analysis (FIA) plots respectively spanning the years 2009 to 2019. Variables include aboveground carbon, aboveground biomass, tree density, basal area, stand age, and diversity metrics such as Shannon indices for tree species and diameter-based structural classes. Functional diversity metrics—including functional dominance and functional divergence—are also included. These data were used to support a published study examining the interactive effects of diversity metrics on carbon storage using structural equation modeling. The geographic coverage represents humid subtropical forest regions of the southeastern U.S.

openCC (other)Jul 2025View details →

CO2 and CH4 fluxes from living and standing dead trees in Howland Research Forest, Maine USA, 2024

Methane (CH4) is the second-largest contributor to human-induced climate change, with significant uncertainties in its terrestrial sources and sinks. Tree stems, both living and dead, play crucial roles in forest ecosystem CH4 and carbon dioxide (CO2) flux dynamics, yet much remains unknown regarding the environmental drivers of fluxes. We measured CH4 and CO2 fluxes from 51 living trees (Picea rubens, Tsuga canadensis, Acer rubrum) along an upland-to-wetland gradient at Howland Research Forest, a net annual sink of CH4, in Maine USA. We also measured CH4 and CO2 fluxes from six standing dead red spruce stems (snags). We measured fluxes every two weeks throughout the growing season (April to November 2024) and at three heights (for a subset of red spruce stems) to capture a range of environmental conditions.

openCC (other)Aug 2025View details →

Data for: Simulated postfire tree regeneration suggests reorganization of Greater Yellowstone forests during the 21st century

Tree regeneration underpins forest resilience, but how postfire tree regeneration will change with future climate and fire regimes is difficult to anticipate. Areas of sparse and failed postfire tree regeneration have been documented in western US forests, but how future recovery pathways will unfold is uncertain. We conducted a simulation study in the Greater Yellowstone Ecosystem (GYE; United States) using a process-based model, iLand, to ask how rates, composition, and spatial patterns of postfire tree regeneration vary with 21st-century climate. Subalpine forest and fire dynamics were simulated through 2100 under four climate scenarios, 2 × 2 factorial of aridity (wet and dry) and temperature (warm and hot), in five GYE landscapes. We tallied postfire tree seedling density by species in simulated fires (> 400 ha) at five years postfire. This data set contains three data sets to reproduce analyses for changes rates of regeneration, proportion of burned cells with regeneration failure, and postfire reorganization pathways. We include the data and R scripts used for these three analyses in the publication associated with these data.