Geology topics

Edmund E. Grote

Publications and source records attributed to Edmund E. Grote.

10 recordsLinked to original sources

USGS2026

Understanding the links between functional performance and environment in cold desert ecosystems through the flagship biocrust forming moss Syntrichia caninervis

Background and aims Biocrust communities shape the soil surface in drylands, regulating important ecosystem properties. Despite this, few works address key functional attributes in these poikilohydric photosynthetic communities, including the length of metabolic activity in the field and its relationship with microclimate. We aim to disentangle the links between functional performance of a keystone biocrust species and environment in drylands, in order to better understand ecosystem functioning and services provided to the soil by these organisms. Methods We developed a 23 months monitoring experiment using very high resolution measurements of chlorophyll a fluorescence and microclimate in the field, comparing habitats with soils of different particle size composition and microclimatic conditions for the flagship biocrust moss Syntrichia caninervis on the Colorado Plateau, Utah, USA. Results While growing in soils of different composition did not impair the functional performance of the species, the sun/shade plasticity did affect key physiological attributes. Our results quantified a strategy based on avoidance of the most extreme environmental conditions, where metabolic activity only occur during 19.9% of the total time monitored. Relative humidity was the best microclimatic predictor of metabolic activity, and the annual length of metabolically active periods showed strong convergences with other drylands of the world. Conclusions These results collectively suggest a strong control of the environment over the ecosystem services provided by biocrusts. Our results include evidence for an improved understanding of the plasticity of S. caninervis to its variety of habitats, and its response to potential threats under different climate change scenarios.

Utah↗

USGS2024

Trajectories and tipping points of piñon–juniper woodlands after fire and thinning

Piñon–juniper (PJ) woodlands are a dominant community type across the Intermountain West, comprising over a million acres and experiencing critical effects from increasing wildfire. Large PJ mortality and regeneration failure after catastrophic wildfire have elevated concerns about the long-term viability of PJ woodlands. Thinning is increasingly used to safeguard forests from fire and in an attempt to increase climate resilience. We have only a limited understanding of how fire and thinning will affect the structure and function of PJ ecosystems. Here, we examined vegetation structure, microclimate conditions, and PJ regeneration dynamics following ~20 years post-fire and thinning treatments. We found that burned areas had undergone a state shift that did not show signs of returning to their previous state. This shift was characterized by (1) distinct plant community composition dominated by grasses; (2) a lack of PJ recruitment; (3) a decrease in the sizes of interspaces in between plants; (4) lower abundance of late successional biological soil crusts; (5) lower mean and minimum daily soil moisture values; (6) lower minimum daily vapor pressure deficit; and (7) higher photosynthetically active radiation. Thinning created distinct plant communities and served as an intermediate between intact and burned communities. More intensive thinning decreased PJ recruitment and late successional biocrust cover. Our results indicate that fire has the potential to create drier and more stressful microsite conditions, and that, in the absence of active management following fire, there may be shifts to persistent ecological states dominated by grasses. Additionally, more intensive thinning had a larger impact on community structure and recruitment than less intensive thinning, suggesting that careful consideration of goals could help avoid unintended consequences. While our results indicate the vulnerability of PJ ecosystems to fire, they also highlight management actions that could be adapted to create conditions that promote PJ re-establishment.

Colorado↗

USGS2023

Droughting a megadrought: Ecological consequences of a decade of experimental drought atop aridification on the Colorado Plateau

Global dryland vegetation communities will likely change as ongoing drought conditions shift regional climates towards a more arid future. Additional aridification of drylands can impact plant and ground cover, biogeochemical cycles, and plant-soil feedbacks, yet how and when these crucial ecosystem components will respond to drought intensification requires further investigation. Using a long-term precipitation reduction experiment (35% reduction) conducted across the Colorado Plateau and spanning ten years into a 20+ year regional megadrought, we explored how vegetation cover, soil conditions, and growing season nitrogen (N) availability are impacted by drying climate conditions. We observed large declines for all dominant plant functional types (C 3 and C 4 grasses and C 3 and C 4 shrubs) across measurement period, both in the drought treatment and control plots, likely due to ongoing regional megadrought conditions. In experimental drought plots, we observed less plant cover, less biological soil crust cover, warmer and drier soil conditions, and more soil resin-extractable N compared to the control plots. Observed increases in soil N availability were best explained by a negative correlation with plant cover regardless of treatment, suggesting that declines in vegetation N uptake may be driving increases in available soil N. However, in ecosystems experiencing long-term aridification, increased N availability may ultimately result in N losses if soil moisture is consistently too dry to support plant and microbial N immobilization and ecosystem recovery. These results show dramatic, worrisome declines in plant cover with long-term drought. Additionally, this study highlights that more plant cover losses are possible with further drought intensification, and underscore that, in addition to large drought effects on aboveground communities, drying trends drive significant changes to critical soil resources such as N availability, all of which could have long-term ecosystem impacts for drylands.

Global Change Biology↗

USGS2021

Climatic controls on soil carbon accumulation and loss in a dryland ecosystems

Arid and semiarid ecosystems drive year-to-year variability in the strength of the terrestrial carbon (C) sink, yet there is uncertainty about how soil C gains and losses contribute to this variation. To address this knowledge gap, we embedded C-depleted soil mesocosms, containing litter or biocrust C inputs, within an in situ dryland ecosystem warming experiment. Over the course of one year, changes in microbial biomass and total soil organic C pools were monitored alongside hourly measurements of soil CO 2 flux. We also developed a biogeochemical model to explore the mechanisms that gave rise to observed soil C dynamics. Field data and model simulations demonstrated that water exerted much stronger control on soil biogeochemistry than temperature, with precipitation events triggering large CO 2 pulses and transport of litter- and biocrust-derived C into the soil profile. We expected leaching of organic matter would result in steady accumulation of C within the mineral soil over time. Instead, the size of the total organic C pool fluctuated throughout the year, largely in response to microbial growth: increases in the size of microbial biomass were negatively correlated with the quantity of C residing in the top 2 cm, where most biogeochemical changes were observed. Our data and models suggest that microbial responses to precipitation events trigger rapid metabolism of dissolved organic C inputs, which strongly limit accumulation of autotroph-derived C belowground. Accordingly, changes in the magnitude and/or frequency of precipitation events in this dryland ecosystem could have profound impacts on the strength of the soil C sink.

Utah↗

USGS2019

Manufacturing simple and inexpensive soil surface temperature and gravimetric water content sensors

Quantifying temperature and moisture at the soil surface is essential for understanding how soil surface biota respond to changes in the environment. However, at the soil surface these variables are highly dynamic and standard sensors do not explicitly measure temperature or moisture in the upper few millimeters of the soil profile. This paper describes methods for manufacturing simple, inexpensive sensors that simultaneously measure the temperature and moisture of the upper 5 mm of the soil surface. In addition to sensor construction, steps for quality control, as well as for calibration for various substrates, are explained. The sensors incorporate a Type E thermocouple to measure temperature and assess soil moisture by measuring the resistance between two gold-plated metal probes at the end of the sensor at a depth of 5 mm. The methods presented here can be altered to customize probes for different depths or substrates. These sensors have been effective in a variety of environments and have endured months of heavy rains in tropical forests as well as intense solar radiation in deserts of the southwestern U.S. Results demonstrate the effectiveness of these sensors for evaluating warming, drying, and freezing of the soil surface in a global change experiment.

Journal of Visualized Experiments↗

USGS2018

Patterns of longer-term climate change effects on CO2 efflux from biocrusted soils differ from those observed in the short term

Biological soil crusts (biocrusts) are predicted to be sensitive to the increased temperature and altered precipitation associated with climate change. We assessed the effects of these factors on soil carbon dioxide (CO 2 ) balance in biocrusted soils using a sequence of manipulations over a 9-year period. We warmed biocrusted soils by 2 and, later, by 4 °C to better capture updated forecasts of future temperature at a site on the Colorado Plateau, USA. We also watered soils to alter monsoon-season precipitation amount and frequency and had plots that received both warming and altered precipitation treatments. Within treatment plots, we used 20 automated flux chambers to monitor net soil exchange (NSE) of CO 2 hourly, first in 2006–2007 and then again in 2013–2014, for a total of 39 months. Net CO 2 efflux from biocrusted soils in the warming treatment increased a year after the experiment began (2006–2007). However, after 9 years and even greater warming (4 °C), results were more mixed, with a reversal of the increase in 2013 (i.e., controls showed higher net CO 2 efflux than treatment plots) and with similarly high rates in all treatments during 2014, a wet year. Over the longer term, we saw evidence of reduced photosynthetic capacity of the biocrusts in response to both the temperature and altered precipitation treatments. Patterns in biocrusted soil CO 2 exchange under experimentally altered climate suggest that (1) warming stimulation of CO 2 efflux was diminished later in the experiment, even in the face of greater warming; and (2) treatment effects on CO 2 flux patterns were likely driven by changes in biocrust species composition and by changes in root respiration due to vascular plant responses.

Biogeosciences↗

USGS2017

The concurrent use of novel soil surface microclimate measurements to evaluate CO2 pulses in biocrusted interspaces in a cool desert ecosystem

Carbon cycling associated with biological soil crusts, which occupy interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO 2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the ‘mantle of fertility’), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report a multi-sensor approach to simultaneously measuring temperature and moisture of this biocrust surface layer (0–2 mm), and the deeper soil profile, concurrent with automated measurement of surface soil CO 2 effluxes. Our results illuminate robust relationships between biocrust water content and field CO 2 pulses that have previously been difficult to detect and explain. All observed CO 2 pulses over the measurement period corresponded to surface wetting events, including when the wetting events did not penetrate into the soil below the biocrust layer (0–2 mm). The variability of temperature and moisture of the biocrust surface layer was much greater than even in the 0–5 cm layer of the soil beneath the biocrust, or deeper in the soil profile. We therefore suggest that coupling surface measurements of biocrust moisture and temperature to automated CO 2 flux measurements may greatly improve our understanding of the climatic sensitivity of carbon cycling in biocrusted interspaces in our study region, and that this method may be globally relevant and applicable.

Biogeochemistry↗

USGS2015

Observations of net soil exchange of CO 2 in a dryland show experimental warming increases carbon losses in biocrust soils

Many arid and semiarid ecosystems have soils covered with well-developed biological soil crust communities (biocrusts) made up of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface. These communities are a fundamental component of dryland ecosystems, and are critical to dryland carbon (C) cycling. To examine the effects of warming temperatures on soil C balance in a dryland ecosystem, we used infrared heaters to warm biocrust-dominated soils to 2 °C above control conditions at a field site on the Colorado Plateau, USA. We monitored net soil exchange (NSE) of CO 2 every hour for 21 months using automated flux chambers (5 control and 5 warmed chambers), which included the CO 2 fluxes of the biocrusts and the soil beneath them. We observed measurable photosynthesis in biocrust soils on 12 % of measurement days, which correlated well with precipitation events and soil wet-up. These days included several snow events, providing what we believe to be the first evidence of substantial photosynthesis underneath snow by biocrust organisms in drylands. Overall, biocrust soils in both control and warmed plots were net CO 2 sources to the atmosphere, with control plots losing 62 ± 8 g C m −2 (mean ± SE) over the first year of measurement and warmed plots losing 74 ± 9 g C m −2 . Between control and warmed plots, the difference in soil C loss was uncertain over the course of the entire year due to large and variable rates in spring, but on days during which soils were wet and crusts were actively photosynthesizing, biocrusts that were warmed by 2 °C had a substantially more negative C balance (i.e., biocrust soils took up less C and/or lost more C in warmed plots). Taken together, our data suggest a substantial risk of increased C loss from biocrust soils with higher future temperatures, and highlight a robust capacity to predict CO 2 exchange in biocrust soils using easily measured environmental parameters.

Arizona, Colorado, New Mexico, Utah↗

USGS2010

Carbon, water, and energy fluxes in a semiarid cold desert grassland during and following multiyear drought

The net exchanges of carbon dioxide, water vapor, and energy were examined in a perennial Colorado Plateau grassland for 5 years. The study began within a multiyear drought and continued as the drought ended. The grassland is located near the northern boundary of the influence of the North American monsoon, a major climatic feature bringing summer rain. Following rain, evapotranspiration peaked above 8 mm d -1 but was usually much smaller (2-4 mm d -1 ). Net productivity of the grassland was low compared to other ecosystems, with peak hourly net CO 2 uptake in the spring of 4 (mu or u)mol m -2 s -1 and springtime carbon gain in the range of 42 + or - 11 g C m -2 (based on fluxes) to 72 + or - 55 g C m -2 (based on carbon stocks; annual carbon gain was not quantified). Drought decreased gross ecosystem productivity (GEP) and total ecosystem respiration, with a much larger GEP decrease. Monsoon rains led to respiratory pulses, lasting a few days at most, and only rarely resulted in net CO 2 gain, despite the fact that C 4 grasses dominated plant cover. Minor CO 2 uptake was observed in fall following rain. Spring CO 2 uptake was regulated by deep soil moisture, which depended on precipitation in the prior fall and winter. The lack of CO 2 uptake during the monsoon and the dependence of GEP on deep soil moisture are in contrast with arid grasslands of the warm deserts. Cold desert grasslands are most likely to be impacted by future changes in winter and not summer precipitation.

Colorado Plateau↗

USGS2010

Carbon exchange in biological soil crust communities under differential temperatures and soil water contents: Implications for global change

Biological soil crusts (biocrusts) are an integral part of the soil system in arid regions worldwide, stabilizing soil surfaces, aiding vascular plant establishment, and are significant sources of ecosystem nitrogen and carbon. Hydration and temperature primarily control ecosystem CO 2 flux in these systems. Using constructed mesocosms for incubations under controlled laboratory conditions, we examined the effect of temperature (5–35 °C) and water content (WC, 20–100%) on CO 2 exchange in light (cyanobacterially dominated) and dark (cyanobacteria/lichen and moss dominated) biocrusts of the cool Colorado Plateau Desert in Utah and the hot Chihuahuan Desert in New Mexico. In light crusts from both Utah and New Mexico, net photosynthesis was highest at temperatures >30 °C. Net photosynthesis in light crusts from Utah was relatively insensitive to changes in soil moisture. In contrast, light crusts from New Mexico tended to exhibit higher rates of net photosynthesis at higher soil moisture. Dark crusts originating from both sites exhibited the greatest net photosynthesis at intermediate soil water content (40–60%). Declines in net photosynthesis were observed in dark crusts with crusts from Utah showing declines at temperatures >25 °C and those originating from New Mexico showing declines at temperatures >35 °C. Maximum net photosynthesis in all crust types from all locations were strongly influenced by offsets in the optimal temperature and water content for gross photosynthesis compared with dark respiration. Gross photosynthesis tended to be maximized at some intermediate value of temperature and water content and dark respiration tended to increase linearly. The results of this study suggest biocrusts are capable of CO 2 exchange under a wide range of conditions. However, significant changes in the magnitude of this exchange should be expected for the temperature and precipitation changes suggested by current climate models.

New Mexico, Utah↗