Kyungsoo Yoo

• PhD
• Professor at University of Minnesota

Cryoturbation in high-latitude soils is crucial for the long-term cycling of elements, but the rates of soil motion are poorly constrained. Here, we test whether the rate of frost creep, soil erosion and vertical soil mixing in frost boils can be estimated using short-lived radionuclides (137Cs and 210Pb). We find a small-scale variation in 137Cs a...

Exotic earthworms are invading forests in North America where native earthworms have been absent since the last glaciation. These earthworms bioturbate soils and may enhance physical interactions between minerals and organic matter (OM), thus affecting mineral sorption of carbon (C) which may affect C cycling. We quantitatively show how OM-mineral...

Hardwood forests of the Great Lakes Region have evolved without earthworms since the Last Glacial Maximum, but are now being invaded by exotic earthworms introduced through agriculture, fishing, and logging. These exotic earthworms are known to increase soil mixing, affect soil carbon storage, and dramatically alter soil morphology. Here we show, u...

Interactions between organic carbon (OC) and minerals represent a critical mechanism for stabilizing organic matter in soils. Because both mineral weathering and plant productivity are negatively affected by soil erosion, mineral-associated organic carbon (MOC) chemistry is also expected to vary with erosion intensity. Here we show that MOC chemist...

Soils and agriculture are inextricably linked, in the past as well as today. The Pacific islands, which often represent organized gradients of the essential soil-forming factors of substrate age and rainfall, represent excellent study systems to understand interactions between people and soils. The relationship between soil characteristics and indi...

Agricultural practices modify the environment, and that modified environment is, in turn, inherited by subsequent generations. Humans are not the only animals that transform the environment, however, and humans often use ecosystems that depend on the engineering and services of other animals for maintained functionality. In this way, non-human anim...

Mineral specific surface area (SSA) increases as primary minerals weather and restructure into secondary phyllosilicate, oxide, and oxyhydroxide minerals. SSA is a measurable property that captures cumulative effects of many physical and chemical weathering processes in a single measurement and has meaningful implications for many soil processes, i...

Exchange plays a number of roles within societies, including the provisioning of necessary and prestige resources. The elucidation of these different roles requires documenting how different kinds of material were used and how these resources became distributed. These studies are particularly prominent in Polynesia, especially the Sāmoan archipelag...

Northern hardwood forests in formerly glaciated areas had been free of earthworms until exotic European earthworms were introduced by human activities. The invasion of exotic earthworms is known to dramatically alter soil physical, geochemical, and biological properties, but its impacts on soil microbiomes are still unclear. Here we show that the i...

Over the last decade, an increasing number of studies have used soundscapes to address diverse ecological questions. Sound represents one of the few sources of information capable of providing in situ insights into processes occurring within opaque soil matrices. To date, the use of soundscapes for soil macrofauna monitoring has been experimentally...

Mineral specific surface area (SSA) is generated as primary minerals weather and restructure into secondary phyllosilicate, oxide, and oxyhydroxide minerals. SSA is a measurable property that captures cumulative effects of many physical and chemical weathering processes in a single measurement and has meaningful implications to many soil processes,...

Successful settlement on Polynesian islands required the alteration of environments, and such alteration produced extensive cultural landscapes. While some of the characteristics of these landscapes are well-established, what drives the spatial and temporal structure of these settlements is not clear across the entire region. Here, we present data...

Northern hardwood forests in formerly glaciated areas had been free of earthworms until exotic European earthworms were introduced by human activities. The invasion of exotic earthworms is known to dramatically alter soil physical, geochemical, and biological properties, but its impacts on soil microbiomes are still unclear. Here we show that the i...

Soils form at the intersection of the lithosphere, biosphere, atmosphere, and hydrosphere and thus are the location where the fluxes of minerals, water and solutes, and organic matter occur. The directions and sizes of these fluxes, and their sensitivities to environmental forcings, determine the soil's mass and composition, as well as its temporal...

Stone and earthen architecture is nearly ubiquitous in the archaeological record of Pacific islands. The construction of this architecture is tied to a range of socio-political processes, and the temporal patterning of these features is useful for understanding the rate at which populations grew, innovation occurred, and social inequality emerged....

Non‐native, invasive earthworms are altering soils throughout the world. Ecological cascades emanating from these invasions stem from rapid consumption of leaf litter by earthworms. This occurs at a midpoint in the trophic pyramid, unlike the more familiar bottom‐up or top‐down cascades. These cascades cause fundamental changes (“microcascade effec...

Physical and chemical interactions between soil organic matter (OM) and minerals is one of the primary mechanisms for stabilizing OM in terrestrial ecosystems. Focusing on OM association with mineral surfaces, this study sought to examine mineral-associated OM from the perspectives of both mineral surface characteristics and organic matter chemistr...

Meteoric beryllium‐10 (¹⁰Bem, t1/2 = 1.4 Myr) is a cosmogenic radionuclide that remains largely underutilized for deriving hillslope‐scale estimates of erosion on uplands under conditions of land use change. We applied two different models for estimating erosion rates from observed ¹⁰Bem concentrations (a one‐dimensional model predicting vertical p...

The interaction of soil organic matter (SOM) and minerals is a critical mechanism for retaining SOM in soil and protecting soil fertility and long-term agricultural sustainability. The chemical speciation of carbon (C) and nitrogen (N) in mineral-associated SOM can be sensitive to both anthropogenic management practices and landscape positions, but...

Climate and topography have been widely recognized but studied separately as important factors controlling soil organic carbon (SOC) dynamics. Subsequently, the significance of their interplay in determining SOC storages and their pools is not well understood. Here we examined SOC storages and SOC-mineral interactions along two hillslope transects...

The interactive effects of climate and topography on the composition, distribution and storage of soil organic carbon (SOC) remain unclear. This is particularly true for pyrogenic carbon (PyC) which is considered long-lasting in soil environments. With a goal to characterize how PyC responds to climate-dependent erosion and deposition processes, tw...

Steep soil-mantled hillslopes are thought to be important sources of sediments and organic carbon (OC) to rivers. Minerals in these sediments may protect OC from decomposition, yet the significance of such interactions in steep upland soils remains poorly constrained particularly in relation to erosion rates. We examined a tributary basin draining...

Phosphorus (P) is an essential nutrient for life. Deficits in soil P reduce primary production and alter biodiversity.A soil P paradigm based on studies of soils that form on flat topography, where erosion rates are minimal,indicates P is supplied to soil mainly as apatite from the underlying parent material and over time is lost viaweathering or tra...

It is now well established that European earthworms are re-shaping formerly glaciated forests in North America with dramatic ecological consequences. However, few have considered the potential invasiveness of this species assemblage in the European arctic. Here we argue that some earthworm species (Lumbricus rubellus, Lumbricus terrestris and Aporr...

Most hillslope studies examining the interplay between climate and earth surface processes tend to be biased towards eroding parts of landscapes. This limitation makes it difficult to assess how entire upland landscapes, which are mosaics of eroding and depositional areas, evolve physio-chemically as a function of climate. Here we combine new soil...

We present a statistical model of soil and rock weathering in deep profiles to expand the capacity to assess weathering to heterogeneous bedrock types, which are common at the earth's surface. We developed the Weathering Trends (WT) model by extending the fractional mass change calculation (tau) of the geochemical mass balance model in two importan...

Soils form at the intersection of the lithosphere, biosphere, atmosphere, and hydrosphere and thus are the location where the fluxes of minerals, water and solutes, and organic matter occur. The directions and sizes of these fluxes, and their sensitivities to environmental forcings, determine the soil's mass and composition, as well as its temporal...

The empirical quantification of rates of material movement in cryoturbated soils has lagged behind the physical and chemical characterisation of these materials. We applied a novel suite of elemental (C, Hg), stable isotope (13C) and radioisotope (137Cs, 210Pb, 14C, 10Be) tracers in conjunction with analytical and numerical models to constrain the...

Biogeoscience is a rapidly growing interdisciplinary field that aims to bring together biological and geophysical processes. This book builds an enhanced understanding of ecosystems by focusing on the integrative connections between ecological processes and the geosphere, hydrosphere and atmosphere. Each chapter provides studies by researchers who...

The delineation and mapping of eroded phases of existing soil series has been an important activity throughout the history of soil survey activities in the United States, with implications for land management, crop production and the estimation of historical sediment losses and fluxes. An analysis of the SSURGO database shows that 462,979 km2 of er...

The ridgelines of mountain ranges are a source of geomorphic information unadulterated by the arrival of sediment from upslope. Studies along ridgecrests, therefore, can help identify and isolate the controls on important regolith properties such as thickness and texture. A 1.5-km section of ridgeline in the Sierra Nevada (CA) with a tenfold decrea...

Assessing how vegetation controls hillslope soil processes is a challenging problem, as few abiotic landscapes exist as observational controls. Here we identify five avenues to examine how actively eroding hillslope soils and processes would differ without vegetation, and we explore some potential feedbacks that may result in land-scape resilience...

The characteristics of the sediment transported by rivers (e.g. sediment flux, grain size distribution – GSD) dictate whether rivers aggrade or erode their substrate. They also condition the architecture and properties of sedimentary successions in basins. In this study, we investigate the relationship between landscape steepness and the grain size...

The time minerals spend in the weathering zone is crucial in determining soil biogeochemical cycles, solid state chemistry and soil texture. This length of time is closely related to erosion rates and can be modulated by sediment transport, mixing rates within the soil and the temporal evolution of erosion. Here we describe how time length can be a...

Background/Question/Methods Earthworms are arguably the best known soil bioturbator, yet their impacts on soil biogeochemistry are difficult to quantify separately from their role in physically mixing soils. In glaciated regions of North America, forests have evolved without native earthworms since the last glacial retreat. However, earthworms ha...

Many geomorphic studies assume that bedrock geology is not a first-order control on landscape form in order to isolate drivers of geomorphic change (e.g., climate or tectonics). Yet underlying geology may influence the efficacy of soil production and sediment transport on hillslopes. We performed quantitative analysis of LiDAR digital terrain model...

Chemical weathering affects hillslope form through dissolution and mineral transformations that lower the surface. In addition, mineral transformations affect the rheology, hydrology, and nutrient cycling of soils, all of which alter the geomorphic processes sculpting landscapes. Soil rheology is altered by the weakening of rocks from chemical weat...

Erosion rates dictate the morphology of landscapes, and therefore quantifying them is a critical part of many geomorphic studies. Methods to directly measure erosion rates are expensive and time consuming, whereas topographic analysis facilitates prediction of erosion rates rapidly and over large spatial extents. If hillslope sediment flux is nonli...

Erosion in soil-mantled landscapes affects soil thickness, which modulates the production of soil. Soil thickness and erosion rate, combined with soil mixing processes, control the time particles spend in the soil. This time strongly influences both the physical and chemical characteristics of soil particles. There is increasing recognition that lo...

Non-native European earthworms are invading previously earthworm-free hardwood forests in the northern Great Lakes Region. Whereas earthworms' impacts on soil morphology and geochemical properties have been well documented in agricultural settings, the role of earthworms in biogeochemical cycles of undisturbed forests remains poorly understood. The...

In order to quantify land use impacts on the magnitude and landscape distribution of soil organic carbon (SOC) we are applying terrain attributes calculated from LiDAR-derived digital elevation models to predict SOC in the upper 1.5 m of soil at grassland and agricultural sites situated on loess soils in southeastern Minnesota. We developed separat...

Approximately 1200-2000 petagrams (Pg-1015 g) of carbon are stored in the Earth's soil as soil organic matter (SOM), representing two times the amount of carbon stored in the Earth's vegetation and atmosphere combined. SOM significantly influences several essential ecosystem services including nutrient cycling, mitigation of soil erosion, and stora...

We are investigating the impact of exotic earthworms on the rate of nutrient and ion release from soil chemical weathering along an ~200 m invasion chronosequence in a northern Minnesota sugar maple forest. The earthworms belong to three ecological groups that represent different feeding and burrowing behaviors, all of which were introduced from Eu...

The human alteration of agricultural landscapes is one of the most important factors in pedologic and geomorphic change, and can influence hydrology and aquatic chemistry at large scales. Most of the Midwestern Corn Belt that is currently dominated by subsurface tile drainage (such as southern Minnesota) was historically prairie and wetland which h...

Improving Chesapeake Bay water quality requires reducing nutrient and sediment loading from watershed sources. After entering stream channels, sediment and nutrients are often exchanged between the water column and storage compartments along river valleys, increasing the time for water quality improvements to be observed downstream. Along a 2.43 km...

Landscapes evolve through time, both in terms of their geomorphology and their geochemistry. Past studies have highlighted that topography suffers from the problem of equifinality: the topographic configuration of landscapes can be the result of many different, yet equally plausible, erosion histories. In hillslope soils the properties and chemistr...

Generation and transport of sediment across hillslopes and rivers are closely tied to mechanisms that produce and remove weathered material; in uplands this production and transport controls the thicknesses of weathering profiles. These processes, by controlling the residence time of minerals in the weathering profiles, further regulate the interac...

The efficiency with which sediment is transported on soil-mantled hillslopes is controlled by climate and lithology. In this study we perform quantitative analysis of airborne Light Detection and Ranging (LiDAR) digital terrain models (DTMs) to investigate the topographic signature of two distinct lithologies in the Feather River catchment in north...

Over geologic timescales, the weathering of silicate rocks has helped to maintain a mostly habitable planet, and it is clear that understanding rates of chemical weathering is key to accurately interpreting past changes in climate and seawater chemistry. However, the mechanisms that drive changes in weathering rates through time are incompletely de...

The interactions of organic matter and minerals contribute to the capacity of soils to store C. Such interactions may be controlled by the processes that determine the availability of organic matter and minerals, and their physical contacts. One of these processes is bioturbation, and earthworms are the best known organisms that physically mix soil...

Minnesota forested soils have evolved without the presence of earthworms since the last glacial retreat. When exotic earthworms arrive, enhanced soil bioturbation often results in dramatic morphological and chemical changes in soils with negative implications for the forests’ sustainability. However, the impacts of earthworm invasion on geochemical...

How and how fast do hillslope soils form as the landscape's morphology changes over time? Here results are shown from an ongoing study that simultaneously examines the morphologic and geochemical evo-lution of soil mantled hillslopes that have been exposed to distinctively different denudation history. In Northern Sierra Nevada, California, the aut...

Critical Zone (CZ) research investigates the chemical, physical, and biological processes that modulate the Earth's surface. Here, we advance 12 hypotheses that must be tested to improve our understanding of the CZ: (1) Solar-to-chemical conversion of energy by plants regulates flows of carbon, water, and nutrients through plant-microbe soil networ...

In natural ecosystems, bioturbation is an essential component of soil formation, whereas tillage drives soil mixing in agricultural soils. Yet soil mixing is commonly neglected in modeling soil organic carbon (SOC) as it responds to land use changes. Here, in order to determine mixing-driven carbon fluxes, we combine a mass balance model with measu...

Streams, rivers, lakes, and other inland waters are important agents in the coupling of biogeochemical cycles between continents, atmosphere, and oceans. The depiction of these roles in global-scale assessments of carbon (C) and other bioactive elements remains limited, yet recent findings suggest that C discharged to the oceans is only a fraction...

One of the central tenets in geomorphology is that a chemical denudation rate is limited by the total denudation rate, which controls how fast minerals are exposed to reactive environments of the earth's surface. Though the mineral supply rate has been routinely tied to tectonic uplifts, in soil mantled landscapes, organisms such as earthworms may...

When deciphering the history and future of landscape morphology, we focus on the evolution of ground surface elevation. A convenient unit to study this particular problem is the volume per area per time, which is often the unit that is used to present physical and total denudation rates. This unit, however, needs to be combined with the bulk densit...

Rates of erosion can control the morphology of entire landscapes. Methods to quantify erosion are expensive and time consuming, but potentially these rates may be predicted rapidly over large spatial extents using topographic metrics. In landscapes with similar vegetation, climate and geology, mean basin slope has been shown to be linearly correlat...

The rate of chemical weathering reactions can vary spatially on eroding hillslopes due to variations in both fluid and mineral residence times. The chemistry of soil in eroding landscapes is not simply a function of local weathering rates, but rather is the result of the integrated weathering of minerals as they move downslope. Thus if solid state...

We broadly agree that the interactions of organic matter and minerals contribute to soils' capacity to store carbon. Such interactions may be controlled by the processes that determine the availability of organic matter and minerals and their physical contacts. One of these processes is bioturbation, and earthworms are the best known organisms that...

The distribution and stability of soil organic carbon (SOC) pools at the landscape scale is dependent upon a number of factors including vegetation inputs and rates of soil loss or accumulation. In order to create a broader framework with which to characterize the size and stability of SOC pools across the landscape, we are combining deep profile m...

When hillslopes respond to incision triggered by tectonic uplift, there is a competition between chemical and physical processes in shaping the landscape. We are studying a tributary basin of the Middle Folk Feather River (FR) in Sierra Nevada CA, where an incision signal is still propagating throughout the basin. Soils were sampled along 3 hillslo...

There is an ever increasing need to make pedology a process-oriented and quantitative scientific discipline. Key tools in this effort are tracers that help quantify the direction and rates of various pedogenic processes over time-scales beyond the reach of field studies. Though not commonly acknowledged, several atmospheric pollutants could be idea...

1] Linking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic. In laboratory studies, collections of minerals are exposed to the same weathering environment over a fixed amount of time. In natural soils, minerals enter, are mixed within, and leave the soil via erosion and dissolution/leaching...

Hillslope topography and soil thickness respond to changes in river incision or deposition. For example, accelerated river incision leads to a wave of steepening and soil thinning that begins at the channel and moves upslope [1]. Because of the coupled response of topography, soil thickness and channel incision or deposition rates, it may be possib...

The size distribution, abundance and durability of coarse sediment supplied by hillslopes to channels fundamentally influences channel morphodynamics, including the rate of river incision into bedrock. However, little is known about how hillslope boundary conditions such as erosion rate, climate and lithology, affect the production of bedload-sized...

Tectonically driven changes in channel incision rates lead to changes in hillslope erosion rates that propagate upslope. In an effort to understand how these changes affect soil geochemistry, this study theoretically and empirically integrates sediment transport and chemical weathering. Here, we focus on a tributary basin of the Middle Folk Feather...

In the last decade, modeling and mechanistic studies of organic carbon (OC) turnover in soils and sediments have converged on one key finding - that organic matter (OM) complexation to fine minerals is a critical factor to stabilizing and sequestering carbon. However, OC production and mineral production are typically spatially separated (Fig. 1)....

The generation of sediment and its transport occurs within and at the boundaries of colluvial soils. Models that predict the evolution of soil mantled landscapes are most commonly based on statements of mass conservation that quantify mass fluxes (i.e., sediment transport) and mass sources (e.g., soil production) within colluvial soil. Traditionall...

The cycles of carbon (C) and minerals are largely considered independently. However, there is a growing consensus that C complexation onto mineral surface is critical in protecting C from decomposition and thus lengthening C turnover time. To create C-mineral complexes, physical contact must occur between organic matter and minerals, yet production...

Though earthworms may appear ubiquitous and native where they are found, this is not true in the Glaciated areas of North America. After the glacial retreat, earthworms were not able to catch up with the northward expansion of forests. Subsequently, these forests in the glaciated areas have developed without native earthworm species over the past s...

a b s t r a c t a r t i c l e i n f o Keywords: weathering erosion soil geochemistry hillslope processes sediment transport channel incision Hillslopes have been intensively studied by both geomorphologists and soil scientists. Whereas geomorphologists have focused on the physical soil production and transport on hillslopes, soil scientists have be...

A positive relationship between the mean annual precipitation (MAP) and soil organic carbon (SOC) is found in most surveys covering the subarctic and boreal region. In this paper we assess mechanisms behind variable SOC pools in dry tundra soils developed along a 50 km long subarctic precipitation (snow) gradient in northern Sweden. Lead 210 is use...

Differences in chemical weathering extent and character are expected to exist across topographic escarpments due to spatial gradients of climatic and/or tectonic forcing. The passive margin escarpment of south-eastern Australia has a debated but generally accepted model of propagation in which it retreated (within 40 Ma) to near its current positio...

Thawing of permafrost and a subsequent accelerated loss of mercury from the soil constitute a possible threat to the quality of high-latitude surface waters. In this paper we estimate the export of mercury generated by a thawing palsa mire in northern Sweden, by assessing net mercury storage changes along thermokarst erosion gradients. Lower mercur...

During the erosion of soil mantled landscapes, minerals experience weathering that can be broadly divided into two stages. First, mineral weathering in saprolite begins after the passage of a downward propagating weathering front. During this stage weathering proceeds in the absence of significant physical disturbance, but the relative position of...

The morphology of landscapes is the result of a combination of climatic and tectonic forcing, integrated over time. Here we examine the ability of a landscape to preserve evidence of transient climate and tectonics. Using simplified numerical models that nonetheless capture the salient transient behavior of soil mantled landscapes, we examine i) ov...

We present a mathematical model that integrates geochemical and geomorphic processes responsible for soils' elemental and mineralogical evolution on diverse landforms: eroding to depositional to level grounds. This new model combines a hillslope sediment mass balance and a soil geochemical mass balance. We model soils as the sum of a physically dis...

There is an ever increasing need to make pedology a process-oriented and quantitative scientific discipline. Key tools in this effort are tracers that help quantify the direction and rates of various pedogenic processes over time-scales beyond the reach of field studies. Though not commonly acknowledged, several atmospheric pollutants could be idea...

Virtually all soil chronosequence studies have equated the degreeof mineral weathering with the soil age, which is equal to thetime since the cessation of erosion or deposition. The primaryminerals from the parent material, however, enter the soil asthe weathering front propagates downward and are depleted viachemical weathering. The residence time...

Understanding the genesis of hillslope soils is challenging. They are the products of geomorphic, hydrologic, and geochemical processes that are interacting among themselves and are affected by the soils they shape. Our goal is to mechanically and quantitatively integrate the soil production and transport, chemical weathering of minerals, and solut...

Most soil biogeochemistry studies treat the soils and their inorganic and organic constituents as physically immobile. Those soil materials, however, are in perpetual motion due to the conversion of bedrock to soils, colluvial transport, and vertical mixing by various biophysical perturbations of the soils. Subsequently, a soil is continuously repl...

Based on laboratory studies, chemical weathering rates in the critical zone (CZ) have been considered to be a function of temperature and the chemistry of CZ pore waters. Because the rate of soil water flow through the critical zone determines, in part, the chemistry of the pore water, this control on chemical weathering rates could be considered h...

1] We developed a process-oriented hillslope soil mass balance model that integrates chemical and physical processes within hillslope soils. The model explicitly factors that soil chemical weathering at any hillslope position is related to the flux of soil eroded from upslope as well as soil production from underlying bedrock. The model was merged...

Long-term impact that land use change exerts on soil elemental pool is evaluated in the Coastal Plain in northern Delaware. Two soil profiles of forest and agricultural land, which are in close proximity but under different land use types at least for last hundred years, are studied. The forest soil is used as a reference soil unaffected by agricul...

On soil covered landscapes, geomorphic processes are synonymous with soil forming processes. Whereas soil formation is a time dependent process by definition, steady state assumptions have been made to hillslope soil mass balances incorporating soil production, sediment (=soil) transport, and more recently soil chemical weathering. Among the many a...

Significant portions of the global soil organic carbon (SOC) pool must reside on sloping terrains where the spatial distribution of SOC reflects the combined effects of geomorphic processes and biological C cycling. Using a newly developed soil C mass balance model that explicitly includes soil production and sediment transport, we investigated the...

Burrowing organisms assist in shaping earth surfaces and are simultaneously affected by the environment they inhabit; however, a conceptual framework is not yet available to describe this feedback. We introduce a model that connects the population density of soil-burrowing animals to sediment transport via energy. The model, combined with available...

1] Little is known about the role of vegetated hillslope sediment transport in the soil C cycle and soil-atmosphere C exchange. We combined a hillslope sediment transport model with empirical soil C measurements to quantify the erosion and temporal storage of soil organic carbon (SOC) within two grasslands in central California. The sites have cont...

On most soil-mantled hillslopes, slope-dependent sediment transport is primarily driven by biological processes and, at steady-state, the eroded soil is replaced by production from the underlying saprolite. We are investigating how soil production, weathering, and transport change as precipitation and biological activity decrease to near zero value...

Chemical weathering drives biogeochemical cycles from local to global scales, and has the power to regulate the earth's climate on geological time scales. However, little is known of the spatial variation in weathering on hillslopes, and the mechanisms behind those variations. This study addresses the topographic control on soil chemical weathering...

We compiled new and published data on the natural abundance N isotope composition (delta15N values) of soil and plant organic matter from around the world. Across a broad range of climate and ecosystem types, we found that soil and plant delta15N values systematically decreased with increasing mean annual precipitation (MAP) and decreasing mean ann...