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openCC (other)Jun 2025View details →

Tree seedling abundance mediated by local neighborhood effects and microsite conditions

Tree recruitment across elevational gradients is shaped by myriad factors, including abundance of nearby conspecific adults and abiotic establishment conditions. We measured seedling abundance and overstory basal area for six tree species that dominate northern temperate and montane boreal forests on mountains in the northeastern United States. Data were collected on elevational transects spaced at 100m-intervals of elevation on ten mountains. Associated environmental variables, including vegetation cover, substrate, microclimate, and light environment, were also collected.

Effects of Prey Availability on Sarracenia Physiology at Harvard Forest 2005

Allometric relationships exist between maximal mass-based net photosynthetic rates, leaf mass per unit area, and foliar Nitrogen (N) and Phosphorus (P) content, which hold across a diverse spectrum of over 2500 plant species worldwide. Carnivorous plants depart from this spectrum because they dedicate substantial leaf area to capturing prey, from which they derive N and P under very nutrient-limiting situations. We conducted a manipulative feeding experiment to test whether morphological and physiological allometric relationships of carnivorous plants when nutrients are not limiting are more similar to allometric relationships of non-carnivorous plants. We examined the effects of prey availability on photosynthetic rate (Amass), chlorophyll fluorescence, growth, architecture, and foliar nutrient and chlorophyll content of ten pitcher plant (Sarracenia) species. We tested the hypothesis that increased prey availability would stimulate Amass of one or more leaves, increase photosynthetic N- and P-use efficiencies (PNUEN, PNUEP), increase relative biomass allocation to photosynthetically efficient, non-predatory phyllodes rather than pitchers, increase overall plant biomass, and reduce stress-related chlorophyll fluorescence. This is the first multi-species, controlled feeding experiment using realistic prey treatments, measuring these physiological parameters directly, and elucidating mechanisms of nutrient stoichiometry and allometry in carnivorous plants. Increased prey availability increased chlorophyll content, Amass and photosystem efficiency (the Fv/Fm ratio) across the 10 Sarracenia species. These increases were most evident in younger leaves, as older leaves rapidly translocated nutrients to newer, growing tissues. Better-fed plants produced a significantly higher proportion of phyllodes than controls. Higher prey availability was associated with lower N:P ratios, and a shift from P- to N-limitation. PNUEP was significantly enhanced by supplementary feeding, w

Effects of Warming on Tree Species Recruitment at Harvard Forest and Duke Forest since 2009

Climate change is restructuring forests of the United States, although the details of this restructuring are currently uncertain. Rising temperatures of 2 to 8 deg C and associated changes in soil moisture will shift the competitive balance between species that compete for light and water, changing their abilities to produce seed, germinate, grow, and survive. We are using large scale experiments to determine the effects of warming on the most sensitive stage of species distributions, i.e., recruitment, in mixed deciduous forests in southern New England and in the Piedmont region of North Carolina. Two questions organize our proposed research: (1) Might temperate tree species near the "warm" end of their range in the eastern United States decline in abundance during the coming century due to projected warming? and (2) Might trees near the "cool" end of their range in the eastern United States increase in abundance, or extend their range, during the coming 100 years because of projected warming? To explore these questions, we are exposing seedlings to air and soil warming experiments in two eastern deciduous forest sites; one at the Harvard Forest (HF) in central Massachusetts, and the other at the Duke Forest (DF) in the Piedmont region of North Carolina. We focus on tree species common to both Harvard and Duke Forests (such as red, black, and white oaks), those near northern range limits (black oak, tulip poplar), and those near southern range limits (yellow birch, sugar maple). At each site, we plant seeds in common gardens established in temperature-controlled, open-top chambers. The experimental design is replicated and fully factorial and involves three temperature regimes (ambient, +3 deg C and +5 deg C) and two light regimes (closed forest canopy (low light) and gap conditions (high light)). Measured variables include Fall/Spring responses to temperature and mid-Summer responses to low soil moisture. This research will advance our understanding of how the abu

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.

Effects of Acorn Production on White-Footed Mouse Populations at Harvard Forest 1997-1999

Recently several authors have documented fluctuations in the abundance of white-footed mice (Peromyscus leucopus noveboracensis) with fluctuations in acorn production (Elkinton et al. 1996, Ostfeld et al. 1996, Wolff 1996, Jones et al. 1998). Acorns are the major food source of white-footed mice during winter and are extensively cached. They are also food for many other species as well; over 100 species of birds and mammals feed on acorns (Van Dersal 1940). A large mast crop in fall usually correlates with a large mouse population the following summer, whereas a poor crop correlates with low population numbers. One experimental study supplementing acorns on forest plots demonstrated a concomitant increase in white-footed mice populations (Jones et al. 1998). It has been hypothesized that a large mast crop increases overwinter survival and may allow continued reproduction during the winter months, which results in a larger population the following year. We have four objectives in monitoring acorn abundance at Harvard Forest: 1) test for correlation of estimates of acorn production with estimates of overwinter survival probabilities and abundance of white-footed mice using mark-recapture statistical models (HF054), 2) document annual variation in acorn abundance and quality, which compliments a program at Harvard Forest documenting changes in woody plant phenology with climatic variation (HF003), 3) test hypotheses concerning the correlation of acorn production with environmental factors such as temperature, rainfall, and weevil infestation, and 4) provide data for inter-site comparisons, such as to test for synchrony in production at various scales across the landscape. We estimate acorn production with timed visual surveys following methods adapted from Koenig et al. (1994). Individual tagged trees on two small mammal trapping plots are surveyed each year by two observers. Detailed methods are described in the metadata.

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.

Effect of Prey Availability on Sarracenia Purpurea Stoichiometry at Belvidere Bog, Vermont 2002

The carnivorous pitcher plant Sarracenia purpurea receives nutrients from both captured prey and atmospheric deposition, making it a good subject for the study of ecological stoichiometry and nutrient limitation. We added prey in a manipulative field experiment and measured nutrient accumulation in pitcher-plant tissue and pitcher liquid, as well as changes in plant morphology, growth, and photosynthetic rate. Prey addition had no effect on traditional measures of nutrient limitation (leaf morphology, growth, or photosynthetic rate). However, stoichiometric measures of nutrient limitation were affected, as the concentration of both N and P in the leaf tissue increased with the addition of prey. Pitcher fluid pH and nitrate concentration did not vary among treatments, although dissolved oxygen levels decreased and ammonia levels increased with prey addition. Ratios of N:P, N:K, and K:P in pitcher-plant tissues suggest that prey additions shifted these carnivorous plants from P limitation under ambient conditions to N limitation with the addition of prey.

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.

Effects of Forest Fragmentation on Carbon Sequestration and Respiration at Harvard Forest since 2016

Forest loss/fragmentation can have profound impacts on the terrestrial carbon (C) cycle by reducing forest uptake of carbon dioxide (CO2; the primary driver of anthropogenic climate change) through photosynthesis and C storage in forest biomass. Relative to intact rural forests, trees growing in forest fragments within developed landscapes typically experience conditions that can enhance growth such as warmer and longer growing seasons (i.e. urban heat island effect) and greater light and nutrient availability (e.g., nitrogen deposition) as well as conditions that can hinder growth such as increased exposure to damaging pollutants such as ozone and higher rates of disturbance. Our research quantifies the impact of fragmentation on C uptake and respiration near forest edges. In 2016 six 600‐m2 plots were installed along forest edges at the HF, measuring 20 m along the forest edge and extending 30 m into the forest perpendicular to the forest edge. Plot biomass was mapped and tree cores were taken in all trees >10cm diameter. The plots were installed at multiple edge aspects and adjacent land cover types (three meadows, two pastures, and one road). Within each plot, a pair of polyvinyl chloride soil respiration collars 20 cm in diameter × 7 cm tall and located 10 m apart was inserted approximately 2 cm into the soil at four distances from the edge (0, 10, 20, and 30m). Each plot had n = 8 collars for a total of n = 48 collars. Following installation, collars were left in the soil for at least 2 weeks to equilibrate. Air temperature, relative humidity, soil temperature, and soil moisture were logged along the center plot transect.

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.

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.

openCC (other)Jan 2025View details →

The effects the mode of delivery of microcystin-LR has on rusty crayfish (Faxonius rusticus) behavior and physiology

Microcystin is a deadly toxin produced during algal blooms. The cells release MCLR which can cause significant neurological and behavioral damage to organisms exposed to the toxin. MCLR can exist in the water column and in the sediment and through normal ecological processes move between those two states or location. Given the location of the toxin, it is possible that MCLR in the sediment could have different adverse effects on organisms as opposed to when the toxin is in the water column. We tested that idea using crayfish that were exposed to either nothing, a vehicle to carry the mclr, and mclr. In addition, the toxin and vehicle were dosed either in the water column or in the sediment. Behavioral and physiological measures were taken after 4 days of exposure, The results indicate that at both the behavioral and physiological level, the location of the toxin has different adverse effects.

openCC (other)Jan 2025View details →

Effects of inoculation of restored and remnant prairie soils on growth, nodulation, and root colonization of three prairie legumes

In this dataset, we present legume biomass, nodule number, and % root colonization of three species of prairie legumes (Amorpha canescens, Lespedeza capitata, and Dalea purpurea) when inoculated with soil from one of 6 remnant or 10 restored prairies in southwest Michigan, USA. Plants were grown for 10 weeks in a growth chamber.

openCC (other)Mar 2025View details →

Soil nitrogen availability vs. acidification: effects on soil respiration, heterotrophic respiration, and soil physicochemical properties in mixed temperate forests in central New York, USA (2019-2022)

In 2011, an experimental nitrogen x pH manipulation study was initiated in mixed temperate forests in central New York, USA to disentangle the often-confounded roles of nitrogen (N) and soil pH in driving various ecosystem processes. This data package contains soil physicochemical properties (soil pH, resin available nitrogen), soil temperature, in situ soil respiration, and heterotrophic respiration measured from laboratory incubations of soils collected from experimental plots. Soil pH was measured both pre-treatment (2009-2010) and after 8 and 11 years of experimental treatment. All other properties were measured between 9 and 12 years after treatment initiation.

openCC0Mar 2025View details →

The interactive effects of nitrate and road salt on benthic algal assemblages in an artificial stream experiment

To investigate and quantify the multi-tiered responses of benthic algal assemblages to the impacts of road salt and nitrate, we created artificial flow-through streams with terracotta vessels with nutrient diffusing substrates (NDS) containing varying concentrations of both salt (0-7500 mg/L) and nitrate (0-5.9 mg/L) and incubated for 56 days during the summer. This work was done at the University of Michigan Biological Station's stream research facility. The streams and algae were sampled on day 7, 14, 28, and 56. The algae pigments were quantified via a fluoroprobe and diatoms were quantified with counts on slides. Finally, both 13s and 16s DNA sequencing was performed on all of the samples.

openCC (other)Jun 2025View details →

Perry et al. (2025) Data Package: Effects of diluted bitumen and remediation methods on lower trophic levels within boreal lake enclosures. Data were collected during 2019 at the IISD Experimental Lakes Area in Northwestern Ontario.

This data package corresponds to a research study by Perry et al. (2025) titled "The effects of diluted bitumen, the shoreline cleaner Corexit EC9580A, and bio-stimulation on the lower food web of a boreal lake, with a focus on natural phytoplankton communities." The study examines the effect of controlled spills of diluted bitumen and two remediation methods on lower trophic levels (phytoplankton, periphyton, zooplankton). The study was undertaken within shoreline enclosures within Lake 260 at the IISD Experimental Lakes Area during 2019. In addition to primary oil recovery using sorbent pads, the two secondary remediation methods: 1) enhanced monitoring natural recovery (eMNR) that included the biostimulation of microbial communities via a slow release nutrient fertilizer, and 2) a shoreline washing agent (SWA or SCA; Corexit 9580) used to increase oil removal from affected shorelines. This data package includes the response of perphyton and zooplankton.