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Sap Flow of Northern Red Oak Trees Under Ecosystem Warming at Harvard Forest 2011
Over the next century, air temperature increases up to 5 °C are projected for the northeastern USA. Because evapotranspiration dominates water loss from terrestrial ecosystems, tree ecophysiological response to warming will have important consequences for forest water budgets. We measured growing season sap flow rates in mature northern red oak (Quercus rubra L.) trees in a combined air (up to 5.5 °C above ambient) and soil (up to 1.85 °C above ambient at 6-cm depth) warming experiment at Harvard Forest, MA, USA. Principal components analysis found air and soil temperatures had the largest effects on sap flow. On average, each 1 °C increase in temperature increased sap flow rates by approximately 1100 kg H2O m-2 sapwood area day-1 throughout the growing season and by 1200 kg H2O m-2 sapwood area day-1 during the early growing season. Reductions in the number of cold winter days correlated positively with increased sap flow at night during the early growing season (a decrease of 100 heating-degree-days was associated with a sapflow increase of approximately 5 kg H2O m-2 sapwood area day-1). Soil moisture declined with increased treatment temperatures, and each soil moisture percentage increase resulted in an increase in sap flow of approximately 360 kg H2O m-2 sapwood area day-1. At night, soil moisture correlated positively with sap flow rate. These results demonstrate that warmer air and soil temperatures in winter and throughout the growing season lead to increased sap flow rates, which could affect forest water budgets throughout the year.
Extracellular Enzyme Activity in Rhizosphere Soil at Harvard Forest and Pisgah State Forest 2010
The exudation of carbon (C) by tree roots stimulates microbial activity and the production of extracellular enzymes in the rhizosphere. Here, we investigated whether the strength of rhizosphere processes differed between temperate forest trees that vary in soil organic matter (SOM) chemistry and associate with either ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi. We measured rates of microbial and extracellular enzyme activity, and nitrogen (N) availability in samples of rhizosphere and bulk soil influenced by four temperate forest tree species (i.e., to estimate a rhizosphere effect). The magnitude of the rhizosphere effects could not be easily characterized by mycorrhizal associations or SOM chemistry. Ash had the lowest rhizosphere effects and beech had the highest rhizosphere effects, representing one AM and one ECM species, respectively. Hemlock and sugar maple had equivalent rhizosphere effects on enzyme activity. However, the form of N produced in the rhizosphere varied with mycorrhizal association. Enhanced enzyme activity primarily increased amino acid availability in ECM rhizospheres and increased inorganic N availability in AM rhizospheres. These results show that the exudation of C by roots can enhance extracellular enzyme activity and soil-N cycling. This work suggests that global changes that alter belowground C allocation have the potential to impact the form and amount of N to support primary production in ECM and AM stands.
Social Network Survey of Forest Landowners in New Hampshire and Vermont 2010
Forests provide invaluable services, and nationally a significant portion of them are owned by millions of individual, private decision makers. Butler (2008) reports that the vast majority of owners (92%, representing 87% of all family forest lands) make management decisions for their land on their own, with a very small minority relying on the advice of professional foresters. Nationally, Butler (2008) goes on to report that 4 % of family forest owners (representing 17% of family forest land) have a professionally prepared management plan for their lands. It is clear that family forests are important, yet millions of owners are apparently not making decisions on the basis of professional advice. Our goal was to improve our understanding of who landowners seek information from when making decisions about their forestland. More specifically, our objective was to explore the possible role of egocentric social networks that landowners may rely upon for information when making a decision. Can we estimate their composition, the possible role of professionals, and the nature of the relationships, in terms of involvement, helpfulness, and trust? Finally, we explored landowner egocentric networks in two similar and adjacent states (Vermont and New Hampshire) that have different programmatic approaches to reaching landowners. Do these result in different ways that landowners acquire information? Using two different approaches through a mail survey methodology, we assessed the extent to which private woodland owners are connected to other people, the degree to which they are considered information sources, and the nature of their decision making behavior. Respondents consistently report valuable connections to non-professionals. They similarly report nominal contact to public foresters, whose role is to inspire prudent forest stewardship on privately held lands. This minimal contact is consistent in two different states with rather different programmatic goals (e.g., educatio
Warming Effects on Microbial Structure and Decomposition at Harvard Forest 2011
Because microorganisms are sensitive to temperature, ongoing global warming is predicted to influence microbial community structure and function. We used large-scale warming experiments established at two sites near the northern and southern boundaries of US eastern deciduous forests to explore how microbial communities and their function respond to warming at sites with differing climatic regimes. Soil microbial community structure and function responded to warming at the southern but not the northern site. However, changes in microbial community structure and function at the southern site did not result in changes in cellulose decomposition rates. While most global change models rest on the assumption that taxa will respond similarly to warming across sites and their ranges, these results suggest that the responses of microorganisms to warming may be mediated by differences across the geographic boundaries of ecosystems.
Root Exudation Simulation Experiment in a Red Oak Stand at Harvard Forest 2011
Root exudation is thought to increase the activity of microbes and the exoenzymes they synthesize, leading to accelerated rates of carbon (C) mineralization and nutrient cycling in rhizosphere soils relative to bulk soils. The nitrogen (N) content of microbial biomass and exoenzymes may introduce a stoichiometric constraint on the ability of microbes to effectively utilize the root exudates, particularly if the exudates are rich in C but low in N. We combined a theoretical model of microbial activity with an exudation experiment to test the hypothesis that the ability of soil microbes to utilize root exudates for the synthesis of additional biomass and exoenzymes is constrained by N availability. The field experiment simulated exudation by automatically pumping solutions of chemicals often found in root exudates (“exudate mimics”) containing C alone or C in combination with N (C:N ratio of 10) through microlysimeter “root simulators” into intact forest soils in two 50-day experiments. The delivery of C-only exudate mimics increased microbial respiration but had no effect on microbial biomass or exoenzyme activities. By contrast, experimental delivery of exudate mimics containing both C and N significantly increased microbial respiration, microbial biomass, and the activity of exoenzymes that decompose low molecular weight components of soil organic matter (SOM, e.g., cellulose, amino sugars), while decreasing the activity of exoenzymes that degrade high molecular weight SOM (e.g., polyphenols, lignin). The modeling results were consistent with the experiments; simulated delivery of C-only exudates induced microbial N-limitation, which constrained the synthesis of microbial biomass and exoenzymes. Exuding N as well as C alleviated this stoichiometric constraint in the model, allowing for increased exoenzyme production, the priming of decomposition, and a net release of N from SOM (i.e., mineralization). The quantity of N released from SOM in the model simulations was
Temperature Sensitivity of Microbial Activity in Three Forest Soils at Harvard Forest 2010-2011
We evaluated possible seasonal variation in the temperature sensitivity of microbially mediated soil fluxes related to decomposition (net N mineralization, net nitrification, proteolysis, the maximum velocity (Vmax) of proteolysis, microbial respiration, and the Vmax of four soil exo-enzymes) across forests dominated by eastern hemlock (Tsuga canadensis), white ash (Fraxinus americana), and red oak (Quercus rubra) in Harvard Forest. We asked two simple questions: (1) do temperature sensitivities vary across forest types or different steps of the decomposition process, and (2) do temperature sensitivities display plasticity on a seasonal time frame?We observed substantial variation in temperature sensitivities (Q10 and R10 values) across the different fluxes and forest types. The ash soils exhibited the strongest temperature sensitivities and the mineral-N fluxes exhibited higher temperature sensitivities relative to the proteolytic fluxes or microbial respiration. The Vmax of soil exo-enzymes varied considerably in an interactive manner across forests and time, and the response of some enzymes was consistent with the thermal plasticity. The enzymatic kinetic properties Vmax and Km (half-saturation constant) were strongly correlated with slopes that differed across enzymes, reflecting an enzyme-specific tradeoff between maximum catalytic rate and substrate-binding efficiency. Generally, Q10 values were largely constant, but R10 values varied in a manner consistent with distinct seasonal plasticity. There was a consistent seasonal shift in R10 values coincident with snowmelt, suggesting that the time following snowmelt is a particularly interesting and dynamic period of microbial activity in these temperate forests.
Long-Term Impacts of the Hemlock Woolly Adelgid on Forest Carbon at Harvard Forest 2008-2011
The abundance of eastern hemlock (Tsuga canadensis) in eastern US forests has declined since the 1950s owing to the introduction of the non-native insect, hemlock woolly adelgid (HWA, Adelges tsugae). In southern New England, eastern hemlock is being replaced by the deciduous tree species, black birch (Betula lenta). To date there is little understanding of whether hemlock loss will fundamentally alter ecosystem C balance and component fluxes. In this study, we use a comparative approach to study potential changes in C fluxes and storage and N cycling associated with HWA-induced hemlock decline and replacement. The stands include primary- and secondary-growth hemlock forests (230 and 132 years old, respectively), recently disturbed stands (5 and 18 years old) that now have rapidly growing black birch saplings, and a mature black birch stand of age similar to the second-growth hemlock stand. We addressed the question of whether the quantity and distribution of C pools in black birch forests are the same as those found in the hemlock stands they replace and, if so, over what time scales. We found that if HWA did not infest hemlock stands in central MA, C stocks in these secondary stands could still increase by at least 30% over a period of 100 years. Girdling, intended to simulate HWA infestation, resulted in a large transfer of C from live biomass to coarse woody debris five years after treatment, but had little effect on total ecosystem C content. A former hemlock stand killed by HWA and now dominated by black birch saplings also had a large pool of highly decayed CWD and a rapidly aggrading C pool in live biomass. C pools in biomass in a mature, secondary growth black birch stand 135 years since pastureland abandonment were as large as those in a primary-growth hemlock stand 235 years of age. We also found that aboveground net primary production was higher in the aggrading black birch stand and significantly so at 18-years post-HWA compared to the secondary-hemlock
Eastern Massachusetts Flowering Phenology 1852-2013
Climate change has resulted in major changes in the phenology of some species but not others. Long-term field observational records provide the best assessment of these changes, but geographic and taxonomic biases limit their utility. Plant specimens in herbaria have been hypothesized to provide a wealth of additional data for studying phenological responses to climatic change. However, no study to our knowledge has comprehensively addressed whether herbarium data are accurate measures of phenological response, and thus applicable to addressing such questions. We compared flowering phenology determined from field observations (years 1852-1858; 1875; 1878-1908; 2003-2006; 2011-2013) and herbarium records (1852-2013) of 20 species from New England, USA. Earliest flowering date estimated from herbarium records faithfully reflected field observations of first flowering date and substantially increased the sampling range across climatic conditions. Additionally, although most species demonstrated a response to inter-annual temperature variation, long-term temporal changes in phenological response were not detectable. Our findings support the use of herbarium records for understanding plant phenological responses to changes in temperature, and also importantly establish a new use of herbarium collections: inferring primary phenological cueing mechanisms of individual species (e.g., temperature, winter chilling, photoperiod). These latter data are lacking from most investigations of phenological change, but are vital for understanding differential responses of individual species to ongoing climate change.
Foundation Species Revisited: Citation Analysis of Ellison et al. 2005
Ecologists and environmental scientists often prioritize research efforts with conservation importance. Dominant, widespread, or locally abundant species at low risk of extinction receive relatively little attention unless they are invasive. Native foundation species create habitats and environmental conditions that support many associated species and modulate local-scale ecosystem processes, but the generally high local or regional abundance of foundation species may lead to less research about them. We used citation analysis (2005-2014) to examine research following from a suggestion to identify and study foundation species while they were still common and not threatened. We explored the use and expanding definition of the foundation species concept, as well as the trajectory and ecological focus of research on foundation species throughout the world in 378 papers published in this nine-year span. Contemporary authors who cite key papers defining a foundation species pay little attention to its actual definition and species studied in this context rarely were identified as foundation species. Although functions and roles of foundation species, such as creating unique microclimates or supporting dependent species, are being studied, less research is focused on identifying them before they are threatened or lost from the ecosystem that they otherwise define. Invasive species were identified as the most common threat to foundation species. Our citation analysis and synthesis provides a new conceptual framework linking identification of and research about foundation species with their functional roles and our ability to manage emerging threats to them.
Soil Temperature and Water Content in Macrosystems Biodiversity Project at Harvard Forest 2011-2012
Patterns of biodiversity, such as the increase toward the tropics and the peaked curve during ecological succession, are fundamental phenomena for ecology. Such patterns have multiple, interacting causes, but temperature emerges as a dominant factor across organisms from microbes to trees and mammals, and across terrestrial, marine, and freshwater environments. However, there is little consensus on the underlying mechanisms, even as global temperatures increase and the need to predict their effects becomes more pressing. The purpose of this project is to generate and test theory for how temperature impacts biodiversity through its effect on biochemical processes and metabolic rate. A combination of standardized surveys in the field and controlled experiments in the field and laboratory measure diversity of three taxa -- trees, invertebrates, and microbes -- and key biogeochemical processes of decomposition in seven forests distributed along a geographic gradient of increasing temperature from cold temperate to warm tropical. Readings of soil temperature and soil moisture were taken with HOBO sensors from November 2011 to November 2012. These sensors were installed at five experimental tree growth plots installed by the Enquist Lab (PI, Brian Enquist) from the University of Arizona as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Soil Chemistry and Moisture in Macrosystems Biodiversity Project at Harvard Forest 2012
Patterns of biodiversity, such as the increase toward the tropics and the peaked curve during ecological succession, are fundamental phenomena for ecology. Such patterns have multiple, interacting causes, but temperature emerges as a dominant factor across organisms from microbes to trees and mammals, and across terrestrial, marine, and freshwater environments. However, there is little consensus on the underlying mechanisms, even as global temperatures increase and the need to predict their effects becomes more pressing. The purpose of this project is to generate and test theory for how temperature impacts biodiversity through its effect on biochemical processes and metabolic rate. A combination of standardized surveys in the field and controlled experiments in the field and laboratory measure diversity of three taxa -- trees, invertebrates, and microbes -- and key biogeochemical processes of decomposition in seven forests distributed along a geographic gradient of increasing temperature from cold temperate to warm tropical. Soil chemistry (TN, TC, NH4-N, NO3-N, and pH) and moisture measurements were taken from soil cores from an array of 21 1m2 subplots and processed by the University of Oklahoma Institute for Environmental Genomics as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Soil Bacteria and Archaea in Macrosystems Biodiversity Project at Harvard Forest 2012
Patterns of biodiversity, such as the increase toward the tropics and the peaked curve during ecological succession, are fundamental phenomena for ecology. Such patterns have multiple, interacting causes, but temperature emerges as a dominant factor across organisms from microbes to trees and mammals, and across terrestrial, marine, and freshwater environments. However, there is little consensus on the underlying mechanisms, even as global temperatures increase and the need to predict their effects becomes more pressing. The purpose of this project is to generate and test theory for how temperature impacts biodiversity through its effect on biochemical processes and metabolic rate. A combination of standardized surveys in the field and controlled experiments in the field and laboratory measure diversity of three taxa -- trees, invertebrates, and microbes -- and key biogeochemical processes of decomposition in seven forests distributed along a geographic gradient of increasing temperature from cold temperate to warm tropical. This field experiment focused on soil microbes. DNA was extracted and purified from soil cores from an array of 21 1m2 subplots. The V4 region of the 16S rRNA genes for bacteria and archaea were amplified and sequenced using Illumina MiSeq by the University of Oklahoma Institute for Environmental Genomics as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Soil Invertebrate Species in Macrosystems Biodiversity Project at Harvard Forest 2012
Leaf litter invertebrates and soil microbes were sampled in an array of 21 1m2 subplots by the Kaspari Ant Lab at the University of Oklahoma as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Tree Growth in Macrosystems Biodiversity Project at Harvard Forest 2011-2013
Patterns of biodiversity, such as the increase toward the tropics and the peaked curve during ecological succession, are fundamental phenomena for ecology. Such patterns have multiple, interacting causes, but temperature emerges as a dominant factor across organisms from microbes to trees and mammals, and across terrestrial, marine, and freshwater environments. However, there is little consensus on the underlying mechanisms, even as global temperatures increase and the need to predict their effects becomes more pressing. The purpose of this project is to generate and test theory for how temperature impacts biodiversity through its effect on biochemical processes and metabolic rate. A combination of standardized surveys in the field and controlled experiments in the field and laboratory measure diversity of three taxa -- trees, invertebrates, and microbes -- and key biogeochemical processes of decomposition in seven forests distributed along a geographic gradient of increasing temperature from cold temperate to warm tropical. This dataset contains annual growth measurements of trees along a series of transects using the measures of diameter at breast height and/or diameter and ground height at the five Gentry plots set up at Harvard Forest. These plots were set up by the Enquist Lab (PI, Brian Enquist) from the University of Arizona as part of a macrosystems biodiversity and latitude project supported by the National Science Foundation under Cooperative Agreement DEB#1065836.
Age and Size of Smith Firs at Treeline in Tibet 1700-2013
The most widespread response to global warming among alpine treeline ecotones is not an upward shift, but an increase in tree density. However, the impact of increasing density on interactions among trees at treeline is not well understood. Here, we test if treeline densification induced by climatic warming leads to increasing intraspecific competition. We mapped and measured the size and age of Smith fir trees growing in two treelines located in the southeastern Tibetan Plateau. We used spatial point-pattern and codispersion analyses to describe the spatial association and covariation among seedlings, juveniles, and adults grouped in 30-year age classes from the 1860s to the present. Effects of competition on tree height and regeneration were inferred from bivariate mark-correlations. Since the 1950s, a rapid densification occurred at both sites in response to climatic warming. Competition between adults and juveniles or seedlings at small scales intensified as density increased. Encroachment negatively affected height growth and further reduced recruitment around mature trees. We infer that tree recruitment at the study treelines was more cold-limited prior to 1950 and shifted to a less temperature-constrained regime in response to climatic warming. Therefore, the ongoing densification and encroachment of alpine treelines could alter the way climate drives their transitions towards subalpine forests.
Correction Factors for Dissolved Organic Carbon Extracted from Soil in New England 2012-2013
Oxidizable dissolved organic carbon (DOC) is regularly measured in environmental samples using a colorimetric method with Mn(III)-pyrophosphate as the oxidizing agent. It is simpler to use and has a much higher throughput than the commonly used dichromate oxidation and combustion methods. Here, we demonstrate that the method often leads to an underestimation or overestimation of the concentration of common organic compounds in solutions. To our knowledge, no published study has taken this fact into account when analyzing DOC data. Hence, we compared Mn(III)-pyrophosphate-based results with measurements performed with a total organic carbon combustion analyzer for samples of organic and mineral soil horizons of two temperate deciduous forests (Harvard Forest, Hubbard Brook), of organic soil horizon of a primary growth hemlock stand (Harvard Forest), and of a peatland (Caribou Bog) located in New England, USA. The Mn(III)-pyrophosphate method consistently underestimated DOC concentration in soil extracts. We present correction factors for the different types of soil studied. By employing correction factors, we find the method can be an inexpensive, accurate, and high throughput tool to measure DOC in environmental samples.
Bird Communities in Forest Openings at Harvard Forest 2014-2015
Currently, many of the most severely declining neotropical migrants in the northeastern United States are disturbance dependent, early-successional species. Much of their decline is attributed to loss of suitable habitat. Large clearcuts (>5.0 ha) are widely considered to be optimal habitat for most shrubland bird species. However, it is well documented that certain species are capable of breeding within significantly smaller patches of habitat (less than 2.0 ha), which are most commonly created through group selection harvest cuttings. The goal of this research is to determine habitat characteristics translatable to habitat value for shrubland birds for use in conservation programs to maximize biological value. This research will provide an assessment of the value of forest openings for shrubland birds, helping to define the suitability of forest canopy openings for specific bird species. This project will describe the conservation value of shrubland openings deemed too small to sustain full suites of specialist shrubland birds by providing threshold patch area values for individual species able to use these smaller patches.
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.
Prospect Hill Forest Plots at Harvard Forest 2013
Northern temperate forests function as an important carbon sink in the global carbon budget. Eddy covariance and plot-based measurements indicate that the Harvard Forest carbon sink is substantial and that the rate of carbon sequestration has increased over the past 20 years. A synthesis effort is underway to better understand how forest development, response to disturbance, and dominant tree species drive the patterns and mechanisms of forest carbon dynamics at the Harvard Forest. The goal of this project is to sample and analyze forest carbon stocks and dynamics across a suite of permanent plots established in 1937 and re-measured in 1992 in order to understand how and why forest carbon stocks have changed between 1937 and 2013. Data from this suite of plots will give spatial and temporal context to a synthesis of detailed, site-specific permanent forest plot studies. Other goals, such as vegetation biodiversity, and a more detailed study of root patterns in soils and belowground carbon distribution, are of strong interest but not addressed in detail in this sampling effort.
Baseline Plant Abundances on Garlic Mustard Experiment Plots at Harvard Forest 2013
This is a five year project that investigates the reassembly of soil fungi and native plants in forests affected by biological invasion. The experiment brings together regional land managers to create comparative eradications of garlic mustard at nine distinct sites along a natural climate and nitrogen deposition gradient in New England. This dataset represents baseline plant abundances from 2013 at nine study plots in Harvard Forest. Species richness, Shannon diversity, and Pielou’s evenness were not different between invaded and non-invaded plots at Harvard Forest.
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These curated guides explain access requirements, typical timelines, costs, and reuse considerations for widely used research datasets.
Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.