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Long term response of arctic tussock tundra to thermal erosion features: A modeling analysis. Tussock tundra nitrogen fertilized simulation

The Multiple Element Limitation (MEL) model is used to simulate the recovery of Alaskan arctic tussock tundra to thermal erosion features (TEFs) caused by permafrost thaw and mass wasting. TEFs could be significant to regional carbon (C) and nutrient budgets because permafrost soils contain large stocks of soil organic matter (SOM) and TEFs are expected to become more frequent as climate warms. These simulations deal only with recovery following TEF stabilization and do not address initial losses of C and nutrients during TEF formation. To capture the variability among and within TEFs, we simulate a range of post-stabilization conditions by varying the initial size of SOM pools and nutrient supply rates. This file contains the results for 25 years of tussock tundra under nitrogen fertilization conditions.

Long term response of arctic tussock tundra to thermal erosion features: A modeling analysis. Tussock tundra nitrogen and phosphorus fertilization simulation

Long term response of arctic tussock tundra to thermal erosion features: A modeling analysis. Tussock tundra phosphorus fertilization simulation

Long term response of arctic tussock tundra to thermal erosion features: A modeling analysis. Tussock tundra shade house simulation

openCC (other)Feb 2023View details →

Ecosystem-level Carbon dioxide fluxes in two long-term experimental wet sedge tundra sites near Toolik Lake, AK, ARC LTER 1994.

Ecosystem-level Carbon dioxide fluxes were measured in two long-term experimental wet sedge tundra sites near Toolik Lake, AK. Experimental treatments at each site included factorial nitrogenXphosphorus, greenhouse and shade house and were begun in 1985 (Sag site) or in 1988 (Toolik sites). Fluxes were measured on quadrats that were later sampled for biomass and leaf area.

openCC (other)Dec 2025View details →

Late season thaw depth measured in the Arctic Long Term Ecological Research (ARC LTER) moist acidic tussock experimental plots at Toolik Field station, Alaska Arctic 1993 to 2025

Late season thaw depth was measured in the Arctic Long Term Ecological Research (ARC LTER) experimental plots (1981 Moist Acidic Tussock, 1989 Moist Acidic Tussock, 2006 Low Fertilization Moist Acidic Tussock, 1989 Moist Non-acidic Tussock, 1989 Moist Non-acidic Non-tussock and 1989 Wet Sedge tundra) at Toolik Lake, Alaska using a steel thaw probe. Note: for 2017-2018 only 1989 Moist Non-Acidic Tussock Tundra and 2006 Low fertilization Moist Acidic Tussock Tundra were measured. For other sites it has become difficult to distinguish rocks from frozen soil with a steel thaw probe. Starting in 2023 weekly thaw depth measurements were made throughout the growing season in the 2006 Low fertilization Moist Acidic Tussock Tundra experiment.

openCC (other)Oct 2024View details →

Soil biogeochemical variables collected on the Arctic Long Term Ecological Research (ARC LTER) experimental plots in moist acidic and dry heath tundra, Arctic LTER, Toolik Field Station, Alaska 2017.

**Note: Versions 1 and 2 had the wrong data files.** Soil nutrients (total Carbon and Nitrogen, inorganic nutrients (ammonium ion (NH4), nitrate anion (NO3-), phosphate anion (PO43-)); organic nutrients (extractable organic carbon (EOC), extractable total nitrogen (ETN), extractable organic phosphorus (EOP)), microbial biomass, and extracellular enzyme activity on soils sampled from the Arctic LTER Dry Heath (organic soils only) and Moist Acidic Tundra (organic and mineral soils) herbivore exclosures and control plots at Toolik Lake, AK in July 2017.

openCC (other)Aug 2024View details →

Above ground plant, belowground stem and root biomass in Arctic Long-term Ecological Research's 2006 moist acidic tussock tundra experimental sites, 2012, Toolik Lake, Alaska.

Above ground plant, belowground stem and root biomass was measured in moist acidic tussock tundra experimental sites established in 2006 by the Arctic Long-term Ecological Research site (ARC-LTER. Control plots and plots amended with three different levels of nitrogen(N) and phosphorus(P), F10 (10 g/m2 N and 5 g/m2 P); F5 (5 g/m2 N and 2.5 g/m2 P); F2 (2 g/m2 N and 1 g/m2 P), were sampled.

openCC0Jan 2022View details →

Long-term monitoring and research of the ecology of the Tres Rios constructed treatment wetland, Phoenix, Arizona, USA, ongoing since 2011

# Project Description In order to better understand the water, nutrient and treatment dynamics of aridland constructed treatment wetlands, we have developed datasets tracking primary productivity (aboveground and belowground), nutrient and water budget dynamics, soils, and aquatic metabolism at the Tres Rios wetlands, operated by the City of Phoenix Water Services Department, since July 2011. The 3-cell Tres Rios Wetlands were completed in 2010 and are associated with the 91st Avenue Wastewater Treatment Plant, the largest in Phoenix. This project is focused on the largest of the three wetlands treatment cells which was the first to be planted and became operational in Summer 2010. The wetland cells are bounded by roads (the "shoreline"), and the system we study is 42 ha in size, approximately half of which is open water and half of which is fringing vegetated marsh. Water depth is relatively consistent across the marsh (approximately 25cm) and effluent inflow to the cell varies seasonally from 95,000 to over 270,000 m3 d-1. Measurements are taken along two gradients representing the two hydraulic pathways of the system: The whole-system, from inflow to outflow, within the vegetated marsh itself. # Abstract Constructed treatment wetlands (CTW) provide cost effective and ecosystem-service based solutions to the problem of urban wastewater treatment. They are a particularly attractive option for water reuse in arid cities, where water resources are scarce, and understanding CTW function in these environments is critical to facilitating sustainable water use practices. Although CTW are well established and studied in mesic climates, how they function in and respond to hot, arid climates is comparatively not well understood. Specifically, large atmospheric water losses via evaporation and plant transpiration comprise a much larger component of the whole-system water budget than in mesic climates. Additionally, given the primary role that emergent macrophytes play in nit

openCC0Nov 2024View details →

High-frequency, long-term measurements of water quality and chlorophyll in the Tempe Town Lake, Tempe, Arizona, USA, ongoing since 2018

Constructed in 1997, the Tempe Town Lake is a small reservoir that transforms a section of the typically-dry Salt River bed into a 224-acre lake in the heart of Tempe, Arizona. To accommodate the river when it flows, the lake features hydraulically-operated steel gates that allow water to pass through the system unimpeded. The lake has been a remarkable success as a community amenity and as a driver of economic growth in the area around the lake. The lake provides an ideal model system for the many artificial lakes constructed in arid-land cities owing to management decisions, such as draining, that affect their operation and ecology. At the same time, dramatic shifts in hydrology and chemistry when the lake is transformed to a flowing river and back into a Lake during and after floods, provide opportunities to study the system's dynamic evolution to new limnological steady states. The CAP LTER began measuring water quality, including temperature, pH, conductivity, dissolved oxygen, dissolved organic carbon (DOC), and total dissolved nitrogen (TDN) in the lake starting 2005. Initially, these data were collected through a mix of hand-held meters and analyses of water samples collected during regular visits to the lake (e.g., see [knb-lter-cap.630](https://portal.edirepository.org/nis/mapbrowse?scope=knb-lter-cap&identifier=630)). In summer 2018, the CAP LTER installed a *in situ* datasonde to measure water quality, including optical dissolved organic carbon characteristics, at high temporal resolution (~ 30 minutes). After a brief period during which data were collected both with the datasonde, and by hand-held meters and analyses of water samples, the project transitioned to collecting data exclusively with the datasonde. The data presented here reflect readings captured by the datasone.

openCC (other)Apr 2022View details →

Daily porewater salinity, conductivity, and temperature measurements from the GCE-LTER Seawater Addition Long-Term Experiment (SALTEx) Project

The Georgia Coastal Ecosystems LTER Seawater Addition Long-Term Experiment (SALTEx) is a large-scale field experiment designed to simulate saltwater intrusion in a tidal freshwater wetland to predict how chronic (Press) and acute (Pulse) salinization will affect this and other tidal freshwater ecosystems. Six porewater well samples were collected four days per week from six treatment plots using a peristalsis pump. Salinity and conductivity were measured from the samples using a handheld conductivity/salinity meter. In addition, water delivery treatments were conducted four days per week after porewater samples were collected.

Long-term Dynamics of Vegetation and Environment in Central Massachusetts 1000-2000

Historical and ecological data from north-central Massachusetts suggest that widespread and intensive human disturbance after European settlement led to a shift in forest composition and obscured regional patterns of species abundance. A paleoecological approach was required to place recent forest dynamics in a long-term context. Pollen and charcoal data from 11 small lakes in north-central Massachusetts were used to reconstruct local vegetation dynamics and fire histories across the region over the past 1000 years. The sites are located across an environmental gradient. Paleoecological data indicate that prior to European settlement, there was regional variation in forest composition corresponding to differences in climate, substrate, and fire regime. Oak, chestnut and hickory were abundant at low elevations, whereas hemlock, beech, sugar maple, and yellow birch were common at high elevations. Fire appears to have been more frequent and/or intense at lower elevations, maintaining high abundances of oak, and archaeological data suggest Native American populations were greater in these areas. A change in forest composition at higher elevations, around 550 years before present, may be related to the Little Ice Age (a period of variable climate), fire, and/or activity by Native Americans, and led to regional convergence in forest composition. After European settlement, forest composition changed markedly in response to human disturbance and there was a sharp increase in rates of vegetation change. Regional patterns were obscured further, leading to homogenization of broad-scale forest composition. There is no indication from the pollen data that forests are returning to pre-European settlement forest composition, and rates of vegetation change remain high, reflecting continuing disturbance to the landscape, despite regional reforestation.

Long-term Stand Dynamics in Central Massachusetts 1500-2000

The long-term impact of human land-use is among the most important factors influencing the development of vegetation in New England, a region which experienced extensive agricultural clearance in the 19th century and subsequent reforestation during this century. We employed stand-level pollen stratigraphies and tree-ring chronologies to examine the post-settlement dynamics of hemlock stands which have never been pastured or plowed, representing among the least disturbed parts of the central Massachusetts landscape. Although the sites are currently dominated by large Tsuga canadensis individuals and give the impression of great age and stability, our results indicate that they have dynamic developmental histories driven by exogenous disturbance factors, including logging, forest pathogens, catastrophic wind disturbance, and fire. Sites containing pre-settlement pollen assemblages indicate stand compositions at this time which were substantially different from each other and from modern assemblages. Pollen assemblages similar to those of modern stands were not established in any of our sites until the 20th century and the mechanisms by which these assemblages arose was considerably different in each stand, indicating great flexibility of forest response to a variety of disturbance types.

Long-Term Field Research Sites at Harvard Forest since 1937

The Harvard Forest is an iconic field station, hosting hundreds of field-based studies since it was founded in 1907. Site-based, long-term research increased sharply starting in 1988, when Harvard Forest became a Long-Term Ecological Research Site. This dataset documents the locations of most long-term research studies initiated since 1988; a few studies that began earlier and are still active are also included. Short-term studies, or studies that focus on sampling individual organisms, are not included.

openCC0Aug 2024View details →

Effects of Long-Term Soil Warming on Ecosystem Function at Harvard Forest 2019

Across biomes, soil biodiversity promotes ecosystem functions. However, whether this relationship will be maintained within ecosystems under climate change is uncertain. Here, using two long-term soil warming experiments, we investigated how warming affects the relationship between ecosystem functions and bacterial diversity across seasons, soil horizons, and warming duration. Soils were sampled from these warming experiments located at the Harvard Forest Long-Term Ecological Research (LTER) site, where soils had been heated +5°C above ambient for 13 or 28 years at the time of sampling. We assessed seven measurements representative of different ecosystem functions and nutrient pools. We also surveyed bacterial community diversity. We found that ecosystem function was significantly affected by season, with autumn samples having a higher intercept than summer samples in our model, suggesting a higher overall baseline of ecosystem function in the fall. The effect of warming on bacterial diversity was similarly affected by season, where warming in the summer was associated with decreased bacterial evenness in the organic horizon. Despite the decreased bacterial evenness in the warmed plots, we found that the relationship between ecosystem function and bacterial diversity was unaffected by warming or warming duration. Our findings highlight that season is a consistent driver of ecosystem function as well as a modulator of climate change effects on bacterial community evenness.

openCC0Nov 2024View details →

Effects of Long-Term Soil Warming on Microbial Yield, Acquisition, and Stress Traits at Harvard Forest 2014

Soil microbial traits drive ecosystem functions. This relationship can explain why microbial functional diversity is typically positively correlated with ecosystem function. However, microbial adaptation to climate change related warming stress can shift microbial traits with direct implications for carbon cycling in the soil. Here, we investigated how long-term warming affects the relationship between microbial trait diversity and ecosystem function. Soils were sampled after 24 years of +5\degree C warming alongside unheated control soils from the Harvard Forest Long-Term Ecological Research site. Ecosystem function was estimated from six different enzyme activities and microbial biomass. This data was coupled with metatranscriptomics sequencing, where reads were assigned to yield, acquisition, or stress trait categories. We found that in organic horizon soils, warming decreased the richness of acquisition-related traits. In the mineral soils, we observed that heated soils exhibited a negative relationship with the richness of acquisition related traits. These results suggest that the microbial communities exposed to long-term warming is shifting away from a resource acquisition life history strategy.

Long-Term Decomposition Plots at Harvard Forest 1990-2009

Mass loss (estimated by decreases in density) and total nitrogen content (TKN) is measured in decaying logs (1.2 m long and diameter range: 6-50 cm) and sticks (10-30 cm long and diameter less than 5 cm) of red pine (Pinus resinosa Ait.) and red maple (Acer rubrum L.) Logs and sticks were collected from freshly cut trees and placed on the forest floor in a red pine plantation (pine only) or a nearby red maple dominated deciduous forest (maple only) in the Prospect Hill tract. Maple logs and sticks lost density faster than did pine. Total Kjeldahl Nitrogen is measured as a percent of organic matter in red pine and red maple logs. N content differed significantly according to state of decay (p=0.002) but not between species. Total organic phosphorus in Kjeldahl digests is measured as a percent of organic matter in red pine and red maple logs. P content differed significantly according to state of decay (p=0.0008) but not between species.

Long-term Vegetation Dynamics on the Massachusetts Coast from 2000 BP to Present

We use a retrospective approach to reconstruct the past distribution of fire in New England and to investigate the important drivers of this pattern across the period of European arrival to North America. Our study sites are in New England, and range from pitch pine and oak forests of coastal Massachusetts, pine and hardwood forests of central Massachusetts, and northern hardwood and spruce fir forests of northern Massachusetts and Vermont. We collected sediment profiles from 18 lakes across the study area to assess fossil charcoal and pollen abundance over the past 1000 years and including the time period of European arrival and settlement. Based on presettlement pollen composition, our study sites are divided into three vegetation types: 1) pitch pine and oak, 2) oak, pine, and hardwood, and 3) northern hardwoods. The abundance of presettlement charcoal in these lakes is closely related to climate and the composition of surrounding vegetation. Charcoal is most abundant in pitch pine forests and least common in northern hardwood and spruce forests. Following the arrival of Europeans, charcoal abundance increases, at most sites substantially, and vegetation composition changed in a direction of either greater dominance by pitch pine or white pine, depending on whether the forests were located in the southern or northern part of New England. The major factor influencing the distribution of fire across New England is climate, which has a direct effect on the physical conditions conducive to fire ignition and spread and an indirect effect on fire through its control on the distribution of vegetation at this spatial scale. We find evidence that other factors exert some control over local fire regimes as well including landforms and their impact on vegetation composition, firebreaks, and prevailing winds. Native Americans likely influenced the local occurrence of fire, but their impact on regional fire regimes in New England is not apparent from this or other studies. Ho

Long-term Vegetation Dynamics in Southwestern New Hampshire from 13000 BP to Present

The paleoecological record allows contemporary ecologists to put current phenomena into the context of a longer time-frame, thereby providing the opportunity to evaluate the importance of slowly operating processes, past cyclic or unusual events, disturbance regimes, and historically constrained phenomena. We briefly outline the environmental history of the Quaternary, discuss the spatial and temporal resolution of the paleoecological evidence for biotic change, and summarize data relevant to such current issues as the nature of the biotic community, the role of disturbance, stability versus rapid change, evolutionary theory, explanations of species diversity, and refugia theory. Finally, we offer examples of the utility of paleoecological techniques for ecologists and environmental scientists.