Search for: All records

Abstract. Although the negative consequences of increased nitrogen (N) supply for plant communities and soil chemistry are well known, most studies have focused on mesic grasslands, and the fate of added N in arid and semi-arid ecosystems remains unclear. To study the impacts of long-term increased N deposition on ecosystem N pools, we sampled a 26-year-long fertilization (10 g N m−2 yr−1) experiment in the northern Chihuahuan Desert at the Sevilleta National Wildlife Refuge (SNWR) in New Mexico. To determine the fate of the added N, we measured multiple soil, microbial, and plant N pools in shallow soils at three time points across the 2020 growing season. We found small but significant increases with fertilization in soil-available NO3--N and NH4+-N, yet the soil microbial and plant communities do not appear to be taking advantage of the increased N availability, with no changes in biomass or N content in either community. However, there were increases in total soil N with fertilization, suggesting increases in microbial or plant N earlier in the experiment. Ultimately, the majority of the N added in this multi-decadal experiment was not found in the shallow soil or the microbial or plant community and is likely to have been lost from the ecosystem entirely. 

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. 

This dataset contains physical soil characteristics, PLFA based microbial community composition, extracellular enzymatic activity, nitrate and ammonium activity, and phosphorus availability in various phosphorus pools (Biologically Based Phosphorus, potassium sulfate, Olsen-P). Soils were collected from two depths (0-2cm, 2-30 cm), four microhabitats (grass, shrub, biocrust, interspace), and four landforms (alluvial flat, alluvial fan remnant, erosional scarplet, fan piedmont – see coordinates) within the Jornada Experimental Range in July 2021 to answer questions about how these variables change across these spatial scales in drylands. This project was a collaboration between researchers at New Mexico State University and The University of Texas at El Paso as part of the Drylands Critical Zone Thematic Cluster within the Critical Zone Network. This dataset is complete. 

We conducted a manipulative experiment to quantify the impact of small mammal herbivores on the plant community of the tundra at three sites near Toolik Lake, Alaska. At each site we set up grazing fences in July of 2018 to simulate different levels of small mammal herbivore (vole and lemming) activity. Each site had 3 treatment plots and a control plot: 1) Exclosure treatments (EX) were 8 meter (m) x 8m square mesh fences 2) control plots (CT) were 8m x 8m unfenced plots marked with pin flags at corners 3) press treatments (PR) were 20m x 20m square mesh fences stocked with 4 tundra voles (Microtus oeconomus) every summer except for 2024 and 4) pulse treatments (PU) where we stocked the fence with 4 voles in 2018 and then removed and excluded voles from 2019 onward. At each site in each plot we collected relative abundance of plant species and ground cover in 8 1 square meter (m2) plots once each year (except in 2020). 

We conducted a manipulative experiment to quantify the impact of small mammal herbivores on the belowground biogeochemistry of the tundra at three sites near Toolik Lake, Alaska. At each site we set up grazing fences in July of 2018 to simulate different levels of small mammal herbivore (vole and lemming) activity. Each site had 3 treatment plots and a control plot: 1)Exclosure treatments (EX) were 8 meter (m) x 8m square mesh fences 2) control plots (CT) were 8m x 8m unfenced plots marked with pin flags at corners 3) press treatments (PR) were 20m x 20m square mesh fences stocked with 4 tundra voles (Microtus oeconomus) every summer except for 2024 and 4) pulse treatments (PU) where we stocked the fence with 4 voles in 2018 and then removed and excluded voles from 2019 onward. At each site we collected temperature measurements using iButton data loggers from the soil surface, the soil organic layer, and the soil mineral layer every 4 hours from 2018 - 2024. iButton loggers were removed and replaced after soil thaw every summer. 

We conducted a manipulative experiment to quantify the impact of small mammal herbivores on the belowground biogeochemistry of the tundra at three sites near Toolik Lake, Alaska. At each site we set up grazing fences in July of 2018 to simulate different levels of small mammal herbivore (vole and lemming) activity. Each site had 3 treatment plots and a control plot: 1)Exclosure treatments (EX) were 8 meter (m) x 8m square mesh fences 2) control plots (CT) were 8m x 8m unfenced plots marked with pin flags at corners 3) press treatments (PR) were 20m x 20m square mesh fences stocked with 4 tundra voles (Microtus oeconomus) every summer and 4) pulse treatments (PU) where we stocked the fence with 4 voles in 2018 and then removed and excluded voles from 2019-2022. At each site we collected 10 thaw depth measurements along a transect from each treatment. 

Abstract Retrogressive thaw slumps (RTS)—thermal erosion of soil and vegetation after ground ice thaw—are increasing. Recovery of plant biomass after RTS is important for maintaining Arctic carbon (C) stocks and is regulated by nutrient availability for new plant growth. Many RTS are characterized by verdant shrub growth mid-succession, atypical of the surrounding nutrient-limited tundra. Here, we investigated the potential for internal and external sources of nitrogen (N) and phosphorus (P) to support mid-successional shrub growth at three Alaskan RTS chronosequences. We assessed patterns of soil and microbial CNP, soil NP cycling rates and stocks, N inputs via biological N₂-fixation, and thaw leachate over time after disturbance. We found a clear transfer of P stocks from mineral to organic soils with increasing site age, yet insufficient N from any one source to support observed shrub growth. Instead, multiple mechanisms may have contributed to mid-successional shrub growth, including sustained N-cycling with reduced plant biomass, N leaching from undisturbed tundra, uninvestigated sources of N₂-fixation, and most promising given the large resource, deep mineral soil N stocks. These potential mechanisms of N supply are critical for the regulation of the Arctic C cycle in response to an increasingly common climate-driven disturbance. 

Soil and plant sampling analysis under small mammal-built structures and controls sites from near the Team Vole fences: Nome, Toolik, Utqiagvik, AK 2018-2020.