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7,355 results for “soils”
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.
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.
Red Maple Seedling Soil Warming Experiment in Harvard Forest Lath House 2015
Microhabitat environmental conditions are an important filter for seedling establishment, controlling the availability of optimal recruitment sites. Understanding how tree seedlings respond to warming soil temperature is critical for predicting population recruitment in the future hardwood forests of northeastern North America, particularly as environmental conditions and thus optimal microhabitat availabilities change. We examined the effect of 5˚C soil warming during the first growing season on germination, survival, phenology, growth, and stem and root biomass allocation in Acer rubrum (red maple) seedlings. While there was no effect of soil warming on germination or survival, seedlings growing in warmer soils demonstrated significantly accelerated leaf expansion, delayed autumn leaf senescence, and an extended leaf production period. Further, seedlings growing in warmer soils showed larger leaf area, stem and root structures at the end of the first growing season, with no evidence of biomass allocation tradeoffs. Results suggest A. rubrum seedlings can capitalize on soil warming by adjusting leaf phenology and leaf production, resulting in a longer period of carbon uptake and leading to higher overall biomass. The absence of growth allocation tradeoffs suggests A. rubrum will respond positively to increasing soil temperatures in northeastern forests, at least in the early life stages.
Foliar and Soil Chemistry at Harvard Forest Chronic Nitrogen Amendment Experiment 1995-2009
The aim of the chronic N study at Harvard Forest is to increase our understanding of ecosystem nitrogen dynamics in response to elevated nitrogen inputs. In recent, nitrogen deposition in the Northeastern United States has been 10 to 20 times above historic background levels which could possibly saturate the retention capacity of a forest ecosystem. Long-term elevated N deposition typically leads to an increase in the concentration of total foliar N, with or without similar changes in the important base elements such as Ca, Mg and K. This increase in leaf N content also leads to significant shifts in the internal partitioning of N within the leaf. For example, in conifers, N deposition has been shown to significantly increase leaf N present in the form of free amino acids such as arginine. Little is known about N partitioning for hardwoods under these conditions. These changes in N partitioning are possibly connected to leaf function. The present study was conducted to experimentally test whether the alterations in N partitioning do occur due to long-term N deposition and if so do they have a positive or a negative effect on photosynthetic capacity and biomass production. A possible decoupling of the relationship between foliar N and photosynthetic rate may occurs under these conditions. The treatment plots used in this study are part of the Chronic Nitrogen Amendment Study at the Harvard Forest LTER site (42.5°N, 72°W). The site has a temperate climate with monthly temperatures ranging from -7°C in January to 20°C in July. Average annual precipitation is 110 cm (http://harvardforest.fas.harvard.edu). The site averages approximately 8 kg ha-1 year-1 of total N deposition. As reported earlier, the land-use history of the pine and hardwood stands used in this study is very different. Two adjacent stands were chosen for the study: an even-aged red pine (Pinus resinosa Ait.) stand and a 50-year-old mixed hardwood stand that had regenerated naturally after clearcutting i
Effects of Warming on Soil Microbial Communities at Harvard Forest 2011
As Earth’s climate warms, soil carbon pools and the microbial communities that process them may change, altering the way in which carbon is recycled in soil. In this study, we used a combination of metagenomics and bacterial cultivation to evaluate the hypothesis that experimentally raising soil temperatures by 5°C for 5, 8, or 20 years increased the potential for temperate forest soil microbial communities to degrade carbohydrates. Warming decreased the proportion of carbohydrate-degrading genes in the organic horizon derived from eukaryotes and increased the fraction of genes in the mineral soil associated with Actinobacteria in all studies. Genes associated with carbohydrate degradation increased in the organic horizon after 5 years of warming but had decreased in the organic horizon after warming the soil continuously for 20 years. However, a greater proportion of the 295 bacteria from 6 phyla (10 classes, 14 orders, and 34 families) isolated from heated plots in the 20-year experiment were able to depolymerize cellulose and xylan than bacterial isolates from control soils. Together, these findings indicate that the enrichment of bacteria capable of degrading carbohydrates could be important for accelerated carbon cycling in a warmer world.
Effects of Warming on Soil Biogeochemistry at Harvard Forest 2014-2015
More than two decades of experimental soil warming in the Prospect Hill tract of the Harvard Forest has revealed non-linear soil respiration (HF005) and soil carbon loss patterns (Melillo et al., Science, 2017). The datasets here were collected to evaluate how the quantity and quality of soil carbon has been affected by 5C warming, and to assess the role that altered extracellular enzyme allocation may play in this. We collected soils over the 2014 growing season, after 23 years of soil warming. We confirmed previous results that warming had depleted the soil of organic matter, and this was accompanied by an overall decrease in microbial biomass particularly apparent in the forest floor in the fall. Using pyrolysis-GCMS, we found that the relative abundance of soil organic matter compound classes was unaffected by warming in the upper organic horizon (“forest floor”). However, lipids increased in relative abundance to the detriment of polysaccharides and lignin in the upper mineral soil, where warming had depleted soil mineral surfaces of organic matter. Despite these changes in soil organic matter quantity and quality, the potential extracellular enzyme activity per gram of soil was unaffected by warming treatment under common lab conditions. However, under in-situ temperature conditions, warming increased enzyme activity per unit microbial biomass, indicating heated plot microbes get better return on their enzyme investment than those in control plots.
Geogenic Gases in a Red Wood-Ant Nest and Soil in the Neuwied Basin, Germany 2016
Geochemical tracers of crustal fluids (CO2, He, Rn) provide a useful tool for the identification of buried fault structures. We acquired geochemical data during 7 months of continual sampling to identify causal processes underlying correlations between ambient air and degassing patterns of three gases (CO2, He, Rn) in a nest of red wood ants (Formica polyctena; “RWA”) and the soil at Goloring in the Neuwied Basin, a part of the East Eifel Volcanic Field (EEVF). We explored whether temporal relations and degassing rhythms in soil and nest gas concentrations could be indicators of hidden faults through which the gases migrate to the surface from depth. In nest gas, the coupled system of CO2-He and He concentrations exceeding atmospheric standards 2-3 fold suggested that RWA nests may be biological indicators of hidden degassing faults and fractures at small scales. Equivalently periodic degassing infradian rhythms in the RWA nest, soil, and three nearby mineral springs suggested NW-SE and NE-SW tectonic linkages. Because volcanic activity in the EEVF is dormant, more detailed information on the EEVF’s tectonic, magmatic, and degassing systems and its active tectonic fault zones are needed. Such data could provide additional insights into earthquake processes that are related to magmatic processes at the lower crust.
Phenology and Vegetation Growth in Prospect Hill Soil Warming Experiment at Harvard Forest 1992-1993
As the mean annual temperature of northeast North America rises as a component of global climatic change, it is important to understand how the predominant vegetation of the region will be affected. Existing experimental and correlative evidence from field sites suggests that temperature rise will significantly modify soil processes, nutrient availability, and plant growth. We investigated the responses of temperate deciduous forest vegetation to artificial soil warming at 20 sampling dates during the 1992 and 1993 growing season. We explored whether soil warming measurably altered growth and the temporal dynamics of leaf and fruit production in 26 species of three contrasting plant growth forms (herbaceous perennials, shrubs, and canopy trees). We hypothesized that soil warming would exert differential effects on emergence, phenology, leaf expansion rates, growth, photosynthesis, and vegetative and sexual reproduction among species, with implications for changing community structure in these forests. Timing of leaf emergence and flower production was not affected by treatment in saplings; however, mature trees and shrubs leafed out slightly earlier and in larger numbers in heated plots. Soil warming significantly enhanced relative growth in stem diameters of woody plants, especially shrubs, in 1992. This effect was less pronounced in 1993. Species richness was lower in heated plots than in intact control plots in both years; disturbed but unheated control plots showed the lowest species richness of all plots. Changes in relative abundance of herbaceous species from 1992 to 1993 were not significantly affected by treatment. Rank abundances of species were more stable between years in the heated and disturbance-control plots than in the intact plots. Total density of herbaceous species was highest in heated plots during April and May of both years, reflecting greatly accelerated emergence of two dominant species, Maianthemum canadense and Uvularia sessilifolia, due t
Soil Microbial Community Effects on Quercus Rubra Seedling Survival at Harvard Forest 2016-2017
Feedbacks between plants and their soil microbial communities often drive negative density dependence in tropical forests, but their importance for tree demographics in temperate forests remains unclear. Additionally, the relative contribution of intraspecific seedling competition and soil pathogens to density-dependent patterns has rarely been assessed. We assessed how the soil microbial community influenced Quercus rubra seedling survival by growing seedlings in a greenhouse inoculated with soil collected from beneath conspecific and heterospecific mature trees. We found that seedlings grown with soil from beneath conspecific adults had a higher mortality rate than seedlings grown with soil from beneath heterospecific adults; therefore adult plant-soil feedbacks decrease seedling survival in Q. rubra.
Impacts of Deer and Moose on Soil Carbon, Soil Respiration, and Root Biomass at Harvard Forest since 2017
Over the past decade, several deer and moose exclosures have been built at Harvard Forest to study the effect of ungulate browsing on tree regeneration, species diversity, and composition. We built on the existing infrastructure to study the impacts of deer and moose browsing on soil carbon stocks (soil C, root biomass) in regenerating forests.
Soil Carbon and Nitrogen at the Harvard Farm at Harvard Forest since 2015
These data represent baseline soil bulk density and total soil carbon and nitrogen concentrations for the three grazing treatments at Harvard Farm: hay (no grazing), rotational grazing, and intensive grazing. These samples were collected at the beginning of the study, so any differences across plots or treatments are due to inherent soil variability at the site rather than the treatments themselves. These data were collected to establish the starting conditions with which to compare potential treatment effects at later sampling dates.
Leaf and Soil Nitrogen Following Lymantria dispar Defoliation in Central Massachusetts 2018-2019
In this study we investigated relationships between ecosystem nitrogen (N) cycling and tree defoliation during a recent 2015-2018 irruption of invasive Lymantria dispar caterpillars, which can cause tree stress and sometimes mortality following multiple years of defoliation. Nitrogen is a critical nutrient that limits the growth of caterpillars and plants in temperate forests. We assessed the associations between N concentrations, soil solution inorganic N availability, and defoliation intensity by L. dispar at the scale of individual trees in the Amherst, MA area and forest plots in the Quabbin Reservoir area.
Effects of Soil Warming on Bacterial Degradation of Carbohydrates at Harvard Forest 2011
As Earth’s climate warms, soil carbon pools and the microbes that process them may change, altering the way in which carbon is recycled in soil. We used bacterial cultivation to evaluate the hypothesis that experimentally raising soil temperatures by 5°C for 20 years increased the potential for temperate forest soil microbial communities to degrade carbohydrates. A greater proportion of the 295 bacteria from 6 phyla (10 classes, 14 orders, and 34 families) isolated from heated plots in the 20-year experiment were able to depolymerize cellulose and xylan than bacterial isolates from control soils. These findings indicate that the enrichment of bacteria capable of degrading carbohydrates could be important for accelerated carbon cycling in a warmer world. Data for the isolates from the Harvard Forest culturing project is archived at https://osf.io/ahb2v/.
Effects of Soil Warming and Substrate Complexity on Microbial Carbon Use Efficiency at Harvard Forest 2017
Soil microbial carbon use efficiency (CUE) is a combination of growth and respiration, which may respond differently to climate change depending on physical protection of soil carbon (C) and its availability to microbes. In a mid-latitude hardwood forest in central Massachusetts, 27 years of soil warming (+5 ◦C) has resulted in C loss and altered soil organic matter (SOM) quality, yet the underlying mechanisms remain unclear. Here, we hypothesized that long-term warming reduces physical aggregate protection of SOM, microbial CUE, and its temperature sensitivity. Soil was separated into macroaggregate (250–2000 μm) and microaggregate (less than 250 μm) fractions, and CUE was measured with 18O-enriched water in samples incubated at 15 and 25 ◦C for 24 h. We found that long-term warming reduced soil C and nitrogen concentrations and extracellular enzyme activity in macroaggregates, but did not affect physical protection of SOM. Long-term warming showed little effect on CUE or microbial biomass turnover time because it reduced both growth and respiration. However, CUE was less temperature sensitive in macroaggregates from the warmed compared to the control plots. Our findings suggest that microbial thermal responses to long-term warming occur mostly in soil compartments where SOM is less physically protected and thus more vulnerable to microbial degradation.
Carbon Cycle Dynamics in Soil Warming Experiments at Harvard Forest 2019
Microbes are responsible for cycling carbon (C) through soils, and predicted changes in soil C stocks under climate change are highly sensitive to shifts in the mechanisms assumed to control the microbial physiological response to warming. Two mechanisms have been suggested to explain the long-term warming impact on microbial physiology: microbial thermal acclimation and changes in the quantity and quality of substrates available for microbial metabolism. Yet studies disentangling these two mechanisms are lacking. To resolve the drivers of changes in microbial physiology in response to long-term warming, we sampled soils from 13- and 28-year-old soil warming experiments in different seasons. We performed short-term laboratory incubations across a range of temperatures to measure the relationships between temperature sensitivity of physiology (growth, respiration, carbon use efficiency, and extracellular enzyme activity) and the chemical composition of soil organic matter. We observed apparent thermal acclimation of microbial respiration, but only in summer, when warming had exacerbated the seasonally-induced, already small dissolved organic matter pools. Irrespective of warming, greater quantity and quality of soil carbon increased the extracellular enzymatic pool and its temperature sensitivity. We propose that fresh litter input into the system seasonally cancels apparent thermal acclimation of C-cycling processes to decadal warming. Our findings reveal that long-term warming has indirectly affected microbial physiology via reduced C availability in this system, implying that earth system models including these negative feedbacks may be best suited to describe long-term warming effects on these soils.
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.
Effect of Warming on Thermal Adaptation of Soil Microbial Growth Traits at Harvard Forest 2013-2023
Adaptation of soil microbes due to warming from climate change has been observed, but it remains unknown what microbial growth traits are adaptive to warming. We studied bacterial isolates from the Harvard Forest Long-Term Ecological Research site, where field soils have been experimentally heated to 5ºC above ambient temperature with unheated controls for thirty years. We hypothesized that Alphaproteobacteria from warmed plots have (1) less temperature sensitive growth rates; (2) higher optimum growth temperatures; and (3) higher maximum growth temperatures compared to isolates from control plots. We made high-throughput measurements of bacterial growth in liquid cultures over time and across temperatures from 22-37ºC in 2-3ºC increments. We estimated growth rates by fitting Gompertz models to the growth data. Temperature sensitivity of growth rate, optimum growth temperature, and maximum growth temperature were estimated by the Ratkowsky 1983 model and a modified Macromolecular Rate Theory (MMRT) model. To determine evidence of adaptation, we ran phylogenetic generalized least squares tests on isolates from warmed and control soils. Our results showed evidence of adaptation of higher optimum growth temperature of bacterial isolates from heated soils. However, we observed no evidence of adaptation of temperature sensitivity of growth and maximum growth temperature. Our project begins to capture the shape of the temperature response curves, but illustrates that the relationship between growth and temperature is complex and cannot be limited to a single point in the biokinetic range.
Soil Warming Plus Nitrogen Addition Experiment at Harvard Forest since 2006
Climate warming and N deposition are occurring on a global scale with unknown long-term effects on soil microbial communities and the biogeochemical processes they perform. Few studies have examined the interactive effects of elevated temperatures and N additions on soil microbial community structure and function. The overall objective of this study is to investigate whether warming and N additions restructure microbial communities and alter the response of soil C pools to these two stressors. A related study is examining the interactive effects of warming and N additions on plant and ant diversity. This research is being carried out at the Soil Warming x Nitrogen Addition Study at the Harvard Forest which includes four treatments: control, warming (heating to 5 deg C above ambient), warming x N, and N additions only (addition of 50 kg N/ha/yr). Soil respiration measurements have been made monthly since the beginning of the experiment in 2006. In 2010 and 2011, two different methods were compared: static chamber measurements and instantaneous field IRGA assessments. Soil samples (~0-10 cm) have been sampled annually for total C and N, N mineralization, and microbial community composition. Most recently, soils were collected in October 2011 from across the entire profile (0-50 cm) to access potential changes in soil C and N pools with depth. First, 20 x 20 cm forest floor samples were collected. Mineral soils were then collected in 10 cm depth increments to ~50 cm. Samples are currently being analyzed for total C and N, microbial biomass and community composition and fungal gene expression (transcriptomics). Additionally, long-term incubations are being conducted to measure labile and recalcitrant C fractions. Additional soil physical (texture) and chemical (pH, inorganic N) are being measured. Field season measurements of soil respiration indicate that both warming and N additions continue to stimulate CO2 flux, with warming treatments having a stronger effect on re
Prospect Hill Soil Warming Experiment at Harvard Forest since 1991
The soil warming experiment was installed on the Prospect Hill tract in 1991 to allow us to investigate the effects of a 5 deg C temperature increase on soil processes fundamental to the global cycling of carbon and nitrogen. The experiment is located in an even-aged mixed hardwood forest. Six replicates of three treatments, Heated (resistance heating cables buried at 10cm and maintained at a 5 deg C differential from the control plots), Disturbance Control (cables installed but not powered) and Control treatments make up the randomized block design. The temperature differential is maintained with monitoring at five minute increments by an automated thermistor network in the plots, wired to a multiplexer and a datalogger in the control shed. In the plots, measurements of trace gasses (CO2, N2O and CH4), nitrogen mineralization, soil moisture and soil water chemistry have allowed us to quantify changes in the soil system. Ten years of elevated soil temperatures at the Harvard Forest soil warming experiment suggest that there are limits to a positive feedback to the global warming cycle. After many early years of increased CO2 fluxes from the warmed plots, years nine and ten have revealed no significant differences in releases of CO2 between the heated and control plots. Nitrogen mineralization has shown a large response to warming as well, with twice the rate of N mineralized in years 1-4, followed by a gradual decrease in rates to about the 40% level in 1998. Resumption of mineralization measurements in 2001 reveals a continued decrease in mineralization rates. Field results from the soil warming experiment indicate that only a small fraction of the soil carbon in this mid-latitude forest ecosystem will be lost to the atmosphere in response to warming. We find that a 5 deg C warming of the soil for a decade results in a loss of about 11% of the carbon stored in the top 60 cm of soil, with most of this loss occurring in the first four to five years. By the end of the
Trace Gas Fluxes and Soil N Dynamics in Simulated Hurricane Experiment at Harvard Forest 1989-1991
This study examined the fluxes of greenhouse gases between soils and the atmosphere in the Simulated Hurricane Experiment. The abstract from the published paper (see Methods) is reproduced below. "Fluxes of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) between soils and the atmosphere were measured monthly for one year in a 77-year-old temperate hardwood forest following a simulated hurricane blowdown. Emissions of CO2 and uptake of CH4 for the control plot were 4.92 MT C ha-1 y-1 and 3.87 kg C ha-1 y-1, respectively, and were not significantly different from the blowdown plot. Annual N2O emissions in the control plot (0.23 kg N ha-1 y-1) were low and were reduced 78% by the blowdown. Net N mineralization was not affected by the blowdown. Net nitrification was greater in the blowdown than in the control, however, the absolute rate of net nitrification, as well as the proportion of mineralized N that was nitrified, remained low. Fluxes of CO2 and CH4 were correlated positively to soil temperature, and CH4 uptake showed a negative relationship to soil moisture. Substantial resprouting and leafing out of downed or damaged trees, and increased growth of understory vegetation following the blowdown, were probably responsible for the relatively small differences in soil temperature, moisture, N availability, and net N mineralization and net nitrification between the control and blowdown plots, thus resulting in no change in CO2 or CH4 fluxes, and no increase in N2O emission."
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Allen Brain Atlas
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DANDI Archive for NWB datasets
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International Brain Laboratory public data
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OpenNeuro
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