Soil Frost Depth Research Articles

Assessment of Frost Depth and Frost Heave in Romania

The investigation of extreme weather and climate events has gained momentum in the last few decades, spurred in part by political involvement. However, not enough attention has been paid to the historical recorded data of climate monitoring. An accurate estimate of maximum soil frost depth is an important factor in determining construction costs and structures’ foundations, and designers also need reliable information about local meteorological parameters. In this study, the calculations of the parameters for the city of Arad are presented as an example. An updated Romanian frost depth map and a new Romanian freeze–thaw cycle (FTC) map are needed since recent climate studies have documented an increase in global and regional surface temperatures, with the greatest shift in warming occurring over the last three decades. This trend is particularly pronounced when comparing the 1990–2020 period with earlier periods, which could be indicative of broader climate change trends. It is important to note that these conclusions are based solely on the provided statistical parameters and do not take into account other potential factors influencing temperature trends in the region. The results from this investigation could be used to achieve a reduction in frost disasters and the formulation of policies and measures for the adaptation of geotechnical/structural design for Romanian territory. They may also support the development of maps that help to visualize and understand the evolving climate patterns in the region, including changes in frost depth and the frequency of freeze–thaw cycles, which are important for various sectors such as agriculture, construction, and infrastructural planning. Given the documented increase in global and regional surface temperatures, updating such maps will also provide valuable information for policymakers, researchers, and stakeholders on how to adapt to ongoing climate change and its impacts on the Romanian region.

How Soil Freezes and Thaws at a Snow-Dominated Forest Site in the U.S.—A Synthetic Approach Using the Soil and Cold Regions Model (SCRM)

The freeze–thaw process controls several hydrologic processes, including infiltration, runoff, and soil erosion. Simulating this process is important, particularly in cold and mountainous regions. The Soil and Cold Regions Model (SCRM) was used to simulate, study, and understand the behavior of twelve homogenous soils subject to a freeze–thaw process, based on meteorological data at a snow-dominated forest site in Laramie, WY, USA, from 2010 and 2012. The relationships of soil pore size, soil particle contact, and meteorological data were varied. Our analysis of the model compared simulations using metrics such as soil frost depth, days with ice, and maximum ice content. The model showed that the freeze–thaw process was strongest in the period with a shallow snowpack, with particle packing within the soil profile being an important factor in this process; that soil texture and water content control soil thermal properties; and that water movement towards the freezing front was especially important in fine-textured soils, where water and ice were concentrated in the upper layers. Based on these results, future research that combines a broader set of soil conditions with an extended set of field meteorology and real soil data could elucidate the influence of soil texture on the thermal properties related to soil frost.

Simulations of Soil Water and Heat Processes for No Tillage and Conventional Tillage Systems in Mollisols of China

Soil water and temperature are important factors to reflect variations in soil heat and water flows especially for tillage systems. The objective of this study was to evaluate the performance of the CoupModel in predicting the effect of tillage practices on soil water and heat processes for conventional tillage (CT) and no-tillage (NT) systems with straw mulching on semi-arid and high-latitude Mollisols of northeast China. This model was calibrated and evaluated in a three-year tillage experiment from 2009 to 2011 in a field experiment station, using field measurements of daily soil temperature and water storage in profiles for CT and NT separately. The results showed that under the model, soil temperatures were well simulated at 0–90 cm soil depths for CT, as indicated by R2 ≥ 0.97, the nRMSE = 27.5–38.7% and −1.02 °C ≤ ME ≤ −0.31 °C, and soil water storage at 0–130 cm soil depth (R2 = 0.01–0.06, the nRMSE = 19.6–37.1%, 13.3 mm ≤ ME ≤ 28.2 mm) was simulated with more uncertainty. “Moderate to good agreements” were achieved for NT. In general, the temporal and spatial variations of soil temperature and water for NT were well simulated by CoupModel. Although NT decreased soil evaporation—thus improving soil water content, especially in the root zone soil—and lowered the soil frozen depths, it reduced the soil temperatures, which could influence crop growth. It was concluded that the CoupModel proved to be a functional tool to predict soil heat and water processes for CT and NT systems in high-latitude seasonal frost conditions of Mollisols in China to estimate the soil temperature, water, energy balance, and frost depth dynamics in relatively complex systems that combined plant dynamics with tillage and/or no tillage covered with straw mulching in the soil surface.

Controlling soil frost depth in winter soil to improve physical soil properties, suppress nitrogen leaching, and improve onion field productivity in cold regions

Controlling soil frost depth in winter soil to improve physical soil properties, suppress nitrogen leaching, and improve onion field productivity in cold regions

THE LOW TEMPERATURE INFLUENCE ON THE DEEP EXCAVATION SUPPORTING SYSTEM

The practical experience to dig an excavation shows that this process is extended in time and can last for several months engulfing different seasons. An additional accounting of processes occurring in excavation shoring and surrounding soil body during wintertime, when the air temperature drops below zero, is important in such circumstances. This paper describes the results of a field survey of shoring of a deep excavation, soil body and buildings of a surrounding development as the air temperature was changing during the 2020-2021 winter. The survey was performed by monitoring the horizontal and vertical positions of structures using inclinometers and tacheometers. The heaving properties of the clay soil positioned at the excavation digging level were determined in laboratory conditions. The soil frost depth was determined by a numerical simulation of temperature distributions in the "atmosphere-excavation-soil body" system. All this helped understand the nature of the processes observed. The observation results showed that, as the temperature was decreasing, the excavation shoring structures moved into the excavation to a distance of up to 8 mm, and the surrounding development buildings shrank by up to 5 mm. The laboratory study results showed in this context that soils bordering on the shoring structures and foundations of surrounding buildings were not heaving. Thereupon, the strains, which were registered in this actual situation, can not be explained by the frost-heaving phenomenon. The observed strain can be explained by shrinkage of the sprung structure material resulting from a decreasing mean daily air temperature. This effect was confirmed by test results and several surveys presented in the paper. Based on the study conclusions practical guidelines were formulated for excavation digging with consideration to seasonal air temperature fluctuations causing shrinkage and expansion of sprung structures in the shoring structures of excavation of any depth.

Effects of snow and climate on soil temperature and frost development in forested peatlands in minnesota, USA

Black spruce (Picea mariana) peatlands play important ecologic and economic roles in the temperate-boreal region of North America, providing a valuable timber resource while also performing important ecosystem functions. Climate models project decreases in the amount of snowfall received throughout the temperate-boreal region by 2100, as average wintertime temperatures increase. We used a paired-plot experimental design to assess the effect of snow removal on soil temperature and frost development at six forested peatland sites in northern Minnesota, USA, during the three winters from 2017 to 2020. Treatments consisted of 1) removal of snow throughout the winter, or 2) ambient snow cover conditions. During the three years of the study, there was a significant effect of snow removal by mid-winter that continued into late winter and spring, where removal of snow increased soil frost depth compared to plots with ambient snow cover treatment. Soil temperatures in the removal plots were highly responsive to air temperature fluctuations to depths of 20 cm or more, whereas the ambient snow cover soils exhibited little fluctuation and maintained temperatures near or above 0° C for much of the winter season. We found that each cumulative freezing degree day resulted in an average of 0.36 cm of soil frost development in snow removal plots, as compared to 0.07 cm depth in the ambient treatment plots. Soils were significantly colder through much of the summer growing season in the removal treatment compared to the ambient treatment, with detectable soil frost in the soil profile as late as mid- to late-June. These results indicate that predicted changes in wintertime precipitation may result in increased development of soil frost in forested peatland systems, although some of this effect may be offset by predicted concurrent increases in air temperature. We did not measure indicators of biological activity, but the large and prolonged reduction in soil temperature with snow removal is likely to depress biological activity throughout the growing season and the many ecosystem functions it influences. Because of the role that soil temperature and frost play on the hydrologic and ecological processes of peatlands, as well as the crucial role of soil frost in peatland forest management, findings of this study provide important insight into the potential effects of altered winter conditions on these expansive and ecologically important ecosystems.

Effects of snow compaction ‘yuki-fumi’ on soil frost depth and volunteer potato control in potato–wheat rotation system in Hokkaido

ABSTRACT Emergence of unharvested potatoes that survived during winter becomes source for nematodes and diseases, causing serious weed problems in rotational crop fields. Herein, we describe frost killing of unharvested potatoes in potato–wheat rotation fields using snow compaction ‘yuki-fumi’ under multiple climate conditions. The effect of snow compaction in controlling volunteer potato over winter wheat was verified in 17 farm fields in Hokkaido, Japan from 2015–16 to 2017–18. A reduction in the temperature of soil under ‘yuki-fumi’ was slower than that under snow removal ‘yuki-wari’, which was used in previous studies. However, snow compaction achieved a substantial reduction in volunteer potato sprouting in most of the experimental sites. The sprouting of volunteer potatoes was reduced in snow-compaction blocks with soil temperatures below −3°C. For winter wheat sowing in potato–wheat rotation, the soil is tilled to a shallower depth than that for other crops, and thus, unharvested potato tubers are not pushed down during field preparation for wheat sowing. Consequently, even if the soil temperature drops slightly, snow compaction can regulate the sprouting of volunteer potatoes. Snow compaction did not exert any apparent influence on wheat growth and grain yield. At some sites with a deeper snowpack, development of soil frost and reduction in soil temperature did not progress with continued snow compaction owing to fallen snow. We validated the usefulness of snow compaction as a countermeasure to control volunteer potatoes in snowy regions.

Soil erosion and radiocesium migration during the snowmelt period in grasslands and forested areas of Miyagi prefecture, Japan.

This study aimed to examine the influence of snowmelt on soil erosion processes in mountainous landscapes in the Miyagi prefecture of Japan. The investigated slopes had different expositions and were covered with grasslands and forests. The snowpack thickness, soil frost depth, volume of surface runoff, physicochemical properties of the soil and sediments, cesium composition of the snow and meltwater, and air dose rate were determined. In mid-February, snow cover reached its maximum thickness (100-179cm). In the forest, the snow depth was always lower by 15-20cm. The soil did not freeze in winter in any of the plots. Surface runoff was observed only in the grassland plots and depended on the slope aspect. The total volume of surface runoff ranged from 31 to 52mm and snowmelt soil losses ranged from 2 to 9kgha-1 DM. Radiocesium concentrations in runoff samples ranged from 0.1 to 8.4BqL-1, below the standard limit for drinking water in Japan (10BqL-1). The average organic matter content of the sampled sediments was 0.4%, higher than that in the surface soil. The silt fraction in sediments became dominant for particle size distribution, and the activity concentration of total radiocesium was, on average, 250Bqkg-1. The air dose rate was always lower than the maximum permissible level (0.2μSvh-1) and varied from 0.02 to 0.09μSvh-1 in winter, and from 0.08 to 0.13μSvh-1 at times of the year without snow.

Strong seasonal connectivity between shallow groundwater and soil frost in a humid alpine meadow, northeastern Qinghai-Tibetan Plateau

The freeze-thaw cycle in the active soil layer plays a crucial role in cold-region hydrological processes, yet the effect of vertical water migration caused by the soil frost on shallow groundwater remains poorly quantified. The shallow groundwater level (GWL), soil frost depth and main environmental controls were monitored in a humid alpine meadow on the northeastern Qinghai-Tibetan Plateau from 2012 to 2017. GWL fluctuated with two seasonal maxima and minima during soil frost-centric year from November to October. GWL declined remarkably from the strong peak (3.9 ± 0.2 m, Mean ± S.D.) in mid-January to the strong minimum (4.8 ± 0.1 m) in mid-May, and then increased to the second peak (4.2 ± 0.2 m) in late August. This seasonal variability in GWL was mainly attributed to the freeze-thaw processes of the lower layer soil frost from November to late June both at a ∼45-day delay, respectively. The clear increasing GWL from mid-November to mid-January was probably related to the melted upper layer soil frost, which was detained in subsoil layers because of the high thermal isolating effect in topsoil Mattic Epipedon (dense organic-rich turf) and the associated negative subsoil profile temperature gradient from mid-May to late August. The seasonal N-type in GWL was thus hysteretically determined by the soil freeze-thaw processes and the related subsoil profile temperature gradient. Annually, GWL was significantly correlated with air temperature (R2 = 0.88, P = 0.003, N = 6), suggesting the shallow groundwater recharges would be weakened under the warming scenario. Annual GWL was not directly connected with annual precipitation (P = 0.81), likely owing to the high water holding capacity of the topsoil Mattic Epipedon and the similarity between precipitation input and evapotranspiration loss. This critical buffering function of the topsoil Mattic Epipedon in vertical moisture movement should be taken into consideration when modeling regional water dynamics in humid alpine meadows.

The 10-Year Return Levels of Maximum Wind Speeds under Frozen and Unfrozen Soil Forest Conditions in Finland

Reliable high spatial resolution information on the variation of extreme wind speeds under frozen and unfrozen soil conditions can enhance wind damage risk management in forestry. In this study, we aimed to produce spatially detailed estimates for the 10-year return level of maximum wind speeds for frozen (>20 cm frost depth) and unfrozen soil conditions for dense Norway spruce stands on clay or silt soil, Scots pine stands on sandy soil and Scots pine stands on drained peatland throughout Finland. For this purpose, the coarse resolution estimates of the 10-year return levels of maximum wind speeds based on 1979–2014 ERA-Interim reanalysis were downscaled to 20 m grid by using the wind multiplier approach, taking into account the effect of topography and surface roughness. The soil frost depth was estimated using a soil frost model. Results showed that due to a large variability in the timing of annual maximum wind speed, differences in the 10-year return levels of maximum wind speeds between the frozen and unfrozen soil seasons are generally rather small. Larger differences in this study are mostly found in peatlands, where soil frost seasons are notably shorter than in mineral soils. Also, the high resolution of wind multiplier downscaling and consideration of wind direction revealed some larger local scale differences around topographic features like hills and ridgelines.

The effect of a freeze–thaw cycle on dissolved nitrogen dynamics and its relation to dissolved organic matter and soil microbial biomass in the soil of a northern hardwood forest

Recent global warming models project a significant change in winter climate over the next few decades. The decrease in snowpack in the winter will decrease the heat insulation function of the snowpack, resulting in increased soil freeze–thaw cycles. Here, we examined the impact of winter freeze–thaw cycles on year-round dissolved nitrogen (N) and carbon (C) dynamics and their relationship with dissolved organic matter and microbial biomass in soil by conducting an in situ experimental reduction in snowpack. We investigated dissolved inorganic N (NH4+ and NO3−), dissolved organic N (DON), dissolved organic carbon (DOC), inorganic N leaching, soil microbial biomass, and microbial activities (mineralization and nitrification) in the surface soil of a northern hardwood forest located in Japan. Experimental snowpack reduction significantly increased the number of soil freeze–thaw cycles and soil frost depth. The NH4+ content of the surface soil was significantly increased by the amplified soil freeze–thaw cycles due to decreased snowpack, while the soil NO3– content was unchanged or decreased slightly. The gravimetric soil moisture, DON and DOC contents in soil and soil microbial biomass significantly increased by the snowpack removal in winter. Our results suggest that the amplified freeze–thaw cycles in soil increase the availability of DON and DOC for soil microbes due to an increase in soil freezing. The increases in both DON and DOC in winter contributed to the enhanced growth of soil microbes, resulting in the increased availability of NH4+ in winter from net mineralization following an increase in soil freeze–thaw cycles. Our study clearly indicated that snow reduction significantly increased the availability of dissolved nitrogen and carbon during winter, caused by increased soil water content due to freeze–thaw cycles in winter.

Effects of a snow-compaction treatment on soil freezing, snowmelt runoff, and soil nitrate movement: A field-scale paired-plot experiment

A frozen soil layer may impede snowmelt infiltration, resulting in a large amount of runoff that influences the soil water balance and anion movement in the soil profile. To examine the relationships among soil frost depth, snowmelt runoff, and nitrate leaching in agricultural fields, we measured both the snowmelt runoff for three winters and other environmental factors including the soil frost depth and nitrate content in a ∼10,000 m2 field. We divided the field into two subplots: one was maintained in a natural snow cover condition (the control plot), and the snow cover was compacted on the other plot (the treated plot) to enhance the development of the soil frost depth. In all three winters, soil frost depths in the control plot were <0.2 m and very little runoff was observed during the snowmelt period. In contrast, the soil frost depth became >0.4 m and a large amount of snowmelt runoff was observed in the treated plot. The depth of the peak nitrate concentration after the snowmelt period was shallower in the treated plot compared to the control plot. Moreover, a significant linear relationship was observed between (1) the amount of nitrate in the 0–0.3 m depth after the snowmelt period and (2) the total amount of snowmelt infiltration calculated by subtracting the amount of snowmelt runoff from the amount of snowmelt water. These results suggest that snow compaction can be a promising technique to develop a uniform soil frost depth in large-scale fields, which consequently controls the soil water and nutrient movement in the soil layer.

Planned snow compaction approach (yuki-fumi) contributes toward balancing wheat yield and the frost-kill of unharvested potato tubers

Snow compaction implements the thermal conditions compatible with both killing volunteer potatoes and good wheat growth. To reveal how soil freezing regulates volunteer potatoes without preventing the growth of winter wheat, we conducted experiments in a wheat field in Hokkaido, Japan (42°53′N, 143°05′E), from winter 2013 to summer 2017. Owing to the enhanced thermal conductivity of snowpack during cold periods, different timings and frequencies of snow compaction allowed us to target different soil temperatures and frost depths. In most years and blocks, snow compaction achieved soil frost depth >0.3 m and killed all potato tubers, but in 2016–17, soil frost depth was <0.3 m in DC, and 7% of potatoes sprouted. These findings indicate that snow compaction before a heavy snowpack can effectively kill tubers. Wheat grain yield did not differ among treatments except in 2013–14. Deep soil freezing did not always reduce the wheat yield, but delayed snowmelt and thus delayed growth enhanced the likelihood of plants experiencing higher air temperature at the early spike development stage. Although changes in yield components such as culm length and spikelet density were associated with varietal responses to temperature, warm conditions in 2014 reduced the dry matter and shortened the grain-filling period, resulting in a greater decrease in yield. Furthermore, rapid hard freezing and direct physical impact may have caused much greater injury to wheat under a shallow snowpack in 2013–14. Thus, our findings indicate that proper snow compaction can balance wheat production and kill unharvested potatoes in crop rotation, and except for hot summer, gentle procedure of grain-filling could compensate the grain weight even in less spring growth.

A High‐Resolution Land Model With Groundwater Lateral Flow, Water Use, and Soil Freeze‐Thaw Front Dynamics and its Applications in an Endorheic Basin

AbstractHuman water regulation, groundwater lateral flow, and the movement of frost and thaw fronts (FTFs) affect soil water and thermal processes, as well as energy and water exchanges between the land surface and atmosphere. Reasonable representation of these processes in land surface models is very important to improving the understanding of land‐atmosphere interactions. In this study, mathematical descriptions of groundwater lateral flow, human water regulation, and FTFs were synchronously incorporated into a high‐resolution community land model, which is then named the Land Surface Model for Chinese Academy of Sciences (CAS‐LSM). With a series of atmospheric forcings and high‐resolution land surface data from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) program, numerical simulations of the period 1981–2013 using CAS‐LSM with 1‐km resolution were conducted for an endorheic basin, the Heihe River Basin in China. Compared with observations, CAS‐LSM reproduced the distributions of groundwater, evapotranspiration, and permafrost reasonably and well matched the temporal changes in ground temperature, heat fluxes, and FTFs. Results illuminate the temporal and spatial characteristics of frozen soil and the changes in the land‐atmosphere exchange of carbon, water, and energy. The permafrost and seasonally frozen soil were distinguished. In the seasonally frozen areas, the maximum soil frost depth increased by 0.65 mm/year within natural areas and decreased by 2.12 mm/year in human‐dominated areas. The active layer thickness increased 8.63 mm/year for permafrost. In the permafrost zone evapotranspiration and latent heat flux increased, and the sensible heat flux declined. In the human‐dominated areas water use raised the latent heat flux and reduced the sensible heat flux, net ecosystem exchange, and streamflow recharging to the eco‐fragile region in the lower reaches. Results suggested that the land surface model CAS‐LSM is a potential tool for studying land surface processes, especially in cold and arid regions experiencing human interventions.

Increased Soil Frost Versus Summer Drought as Drivers of Plant Biomass Responses to Reduced Precipitation: Results from a Globally Coordinated Field Experiment

Reduced precipitation treatments often are used in field experiments to explore the effects of drought on plant productivity and species composition. However, in seasonally snow-covered regions reduced precipitation also reduces snow cover, which can increase soil frost depth, decrease minimum soil temperatures and increase soil freeze–thaw cycles. Therefore, in addition to the effects of reduced precipitation on plants via drought, freezing damage to overwintering plant tissues at or below the soil surface could further affect plant productivity and relative species abundances during the growing season. We examined the effects of both reduced rainfall (via rain-out shelters) and reduced snow cover (via snow removal) at 13 sites globally (primarily grasslands) within the framework of the International Drought Experiment, a coordinated distributed experiment. Plant cover was estimated at the species level, and aboveground biomass was quantified at the functional group level. Among sites, we observed a negative correlation between the snow removal effect on minimum soil temperature and plant biomass production the next growing season. Three sites exhibited significant rain-out shelter effects on plant productivity, but there was no correlation among sites between the rain-out shelter effect on minimum soil moisture and plant biomass. There was no interaction between snow removal and rain-out shelters for plant biomass, although these two factors only exhibited significant effects simultaneously for a single site. Overall, our results reveal that reduced snowfall, when it decreases minimum soil temperatures, can be an important component of the total effect of reduced precipitation on plant productivity.

Effects of snow removal on soil labile nitrogen in a subalpine spruce forest of western Sichuan, China

Warming-induced decrease in seasonal snow cover has a great potential to affect soil nitrogen cycle in alpine cold forest ecosystems. In this study, a wooden-shelter method was used to remove the snow accumulation. Soil nitrogen pools and mineralization rates in the snow removal and control plots were measured synchronously in three critical periods (early snow cover, deep snow cover and snow cover melting) in a subalpine spruce forest of western Sichuan, China. Seasonal snow cover kept soil from cold air temperature. Snow removal decreased average and minimum soil temperatures (5 cm) by 0.33 and 1.17 ℃, respectively. In addition, snow removal caused a positive effect on soil frost depth and freeze-thaw cycle. There was a significant dynamic in soil labile nitrogen pool among different periods. Snow removal on average increased NH4+-N, NO3--N and dissolved organic nitrogen (DON) contents by 38.6%, 23.5% and 57.3%, respectively, over the winter. Moreover, snow removal increased soil net nitrification and mineralization rates in the snow co-ver melting period. Overall, warming-induced decrease in snow cover could stimulate winter soil nitrogen cycle of subalpine forests.

Optimum soil frost depth to alleviate climate change effects in cold region agriculture

On-farm soil frost control has been used for the management of volunteer potatoes (Solanum tuberosum L.), a serious weed problem caused by climate change, in northern Japan. Deep soil frost penetration is necessary for the effective eradication of unharvested small potato tubers; however, this process can delay soil thaw and increase soil wetting in spring, thereby delaying agricultural activity initiation and increasing nitrous oxide emissions from soil. Conversely, shallow soil frost development helps over-wintering of unharvested potato tubers and nitrate leaching from surface soil owing to the periodic infiltration of snowmelt water. In this study, we synthesised on-farm snow cover manipulation experiments to determine the optimum soil frost depth that can eradicate unharvested potato tubers without affecting agricultural activity initiation while minimising N pollution from agricultural soil. The optimum soil frost depth was estimated to be 0.28–0.33 m on the basis of the annual maximum soil frost depth. Soil frost control is a promising practice to alleviate climate change effects on agriculture in cold regions, which was initiated by local farmers and further promoted by national and local research institutes.

Hydrologic flowpaths during snowmelt in forested headwater catchments under differing winter climatic and soil frost regimes

Changes in hydrologic flowpaths have important impacts on the timing, magnitude and hydrochemistry of run-off during snowmelt in forested catchments, but how flowpaths are affected by variation in winter climate and the irregular presence of soil frost remains poorly understood. The depth and extent of soil frost may be expected to increase as snowpack decreases or develops later because of climate change. In this study, we used end-member mixing analysis to determine daily contributions of snow, forest floor soil water and groundwater to stream run-off during snowmelt under different soil frost regimes resulting from interannual and elevational variation at the Hubbard Brook Experimental Forest in New Hampshire, USA. We observed greater routing of run-off through forest floor flowpaths during early snowmelt in 2011, when the snowpack was deep and soil frost was minimal, compared with the early snowmelt in 2012 under conditions of deep and extensive soil frost. The results indicate that widespread soil frost that penetrated the depth of the forest floor decreased the flow signal through the shallowest subsurface flowpaths, but did not reduce overall infiltration of melt waters, as the contribution from the snow-precipitation end-member was similar under both conditions. These results are consistent with development of granular soil frost which permits vertical infiltration of melt waters, but either reduces lateral flow in the forest floor or prevents the solute exchange that would produce the typical chemical signature of shallow subsurface flowpaths in streamwater. Copyright © 2016 John Wiley & Sons, Ltd.

Standing corn residue effects on soil frost depth, snow depth and soil heat flux in Northeast China

Abstract 1 Standing corn residue has been proven to reduce wind erosion in Northeast China, but how standing corn residue affects soils during winter remained unclear. Our objective was to compare soil frost depth associated with two zero-tillage methods [i.e., chopping corn stalks into small sections then spread them on soil (hereafter referred to as ‘CCR’) and standing corn residue (hereafter referred to as ‘SCR’)]. Frost tubes were used to determine soil frost depth, and soil heat flux plates were used to measure soil heat flux 8-cm beneath the soil surface. Compared with CCR treatment, SCR reduced maximum soil frost depth significantly ( p

Contrasting effects of winter snowpack and soil frost on growing season microbial biomass and enzyme activity in two mixed-hardwood forests

Winter is recognized as an important time for microbial activity that influences biogeochemical cycles. The onset of the winter snowpack in temperate hardwood ecosystems has been and will continue to be delayed over the next century. The decline in snowpack results in more soil freeze–thaw events and lower winter soil temperatures. Understanding microbial responses to varying snowpack conditions is important to understanding the effect of climate change on forest ecosystems. To this end, we removed snow to simulate a thinner, more ephemeral snowpack at two sites in the northeastern US, Harvard Forest (MA) and Hubbard Brook Experimental Forest (NH). We then measured microbial and exoenzyme activity in soils following snowmelt and three additional time points across the growing season. We found that microbial and exoenzyme activity were both positively correlated with the depth and duration of the snowpack at each site. The depth and duration of soil frost were negatively correlated with microbial biomass, exoenzyme activity and respiration, but only at Harvard Forest and not at Hubbard Brook. At both sites the changes in microbial and exoenzyme activity were transient and did not persist into the growing season past tree leaf-out. While it is possible that reductions in the snowpack and changes to microbial activity in the early spring may lead to asynchrony in the phenology of microbial relative to plant activity, it is at present uncertain whether and over what time scale this asynchrony may affect other forest ecosystem processes.