Changes In Soil Cover Research Articles

ИЗМЕНЕНИЕ ПОЧВ И ПОЧВЕННОГО ПОКРОВА ЕЛОВЫХ ЛЕСОВ ПОСЛЕ СПЛОШНОЛЕСОСЕЧНЫХ РУБОК

ИЗМЕНЕНИЕ ПОЧВ И ПОЧВЕННОГО ПОКРОВА ЕЛОВЫХ ЛЕСОВ ПОСЛЕ СПЛОШНОЛЕСОСЕЧНЫХ РУБОК

Soil Greenhouse Gas Emissions in Response to Corn Stover Removal and Tillage Management Across the US Corn Belt

In-field measurements of direct soil greenhouse gas (GHG) emissions provide critical data for quantifying the net energy efficiency and economic feasibility of crop residue-based bioenergy production systems. A major challenge to such assessments has been the paucity of field studies addressing the effects of crop residue removal and associated best practices for soil management (i.e., conservation tillage) on soil emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). This regional survey summarizes soil GHG emissions from nine maize production systems evaluating different levels of corn stover removal under conventional or conservation tillage management across the US Corn Belt. Cumulative growing season soil emissions of CO2, N2O, and/or CH4 were measured for 2–5 years (2008–2012) at these various sites using a standardized static vented chamber technique as part of the USDA-ARS’s Resilient Economic Agricultural Practices (REAP) regional partnership. Cumulative soil GHG emissions during the growing season varied widely across sites, by management, and by year. Overall, corn stover removal decreased soil total CO2 and N2O emissions by -4 and -7 %, respectively, relative to no removal. No management treatments affected soil CH4 fluxes. When aggregated to total GHG emissions (Mg CO2 eq ha−1) across all sites and years, corn stover removal decreased growing season soil emissions by −5 ± 1 % (mean ± se) and ranged from -36 % to 54 % (n = 50). Lower GHG emissions in stover removal treatments were attributed to decreased C and N inputs into soils, as well as possible microclimatic differences associated with changes in soil cover. High levels of spatial and temporal variabilities in direct GHG emissions highlighted the importance of site-specific management and environmental conditions on the dynamics of GHG emissions from agricultural soils.

Mapping key agricultural sources of dust emissions within the Lake Simcoe airshed

A decline in water quality attributed to excessive inputs of phosphorus has been observed in Lake Simcoe over the past few decades. Various studies have estimated that 25–50% of the total phosphorus entering the lake is from atmospheric deposition. Bare soil exposure in the spring due to lack of vegetative cover, along with soil disturbance related to agricultural activities, results in higher susceptibility to wind erosion and dust emission. This study introduces the new concept of Dust Response Units (DRUs), which combine soil type and land use to determine the dust emission susceptibility based on the hourly variation of wind speed and monthly changes in soil cover due to crop growth. The Wind Erosion Prediction System (WEPS) was used to determine dust emission suppression factors for a combination of 11 different soils and 6 dominant agricultural land uses, totaling 66 different DRUs in the Lake Simcoe airshed. Employing a widely used dust emission model and applying these dust emission suppression factors resulted in the identification of high risk DRUs. Twelve of the potential 66 DRUs were determined to contribute 85% of the total crop dust emissions within the Lake Simcoe airshed, including sand, loam, sandy loam, and loamy sand soils combined with row crop, mixed, and hay and pasture land management operations. This study demonstrates a new method to map high priority areas for targeted implementation of dust control best management practices that could be useful in agricultural areas both within and beyond the Lake Simcoe airshed

Twenty-five years of changes in soil cover on Canadian Chernozemic (Mollisol) soils, and the impact on the risk of soil degradation

Huffman, T., Coote, D. R. and Green, M. 2012. Twenty-five years of changes in soil cover on Canadian Chernozemic (Mollisol) soils, and the impact on the risk of soil degradation. Can. J. Soil Sci. 92: 471–479. Agricultural soils that are covered by vegetation or crop residue are less susceptible to degradation by wind and water erosion, organic matter depletion, structural degradation and declining fertility. In general, perennial crops, higher yields, reduced tillage and continuous cropping provide more soil cover than annual crops, lower yields, intensive tillage, residue harvesting and fallowing. This study presents a model for estimating the number of days in a year that the soil surface is protected and demonstrates its application on the Canadian prairies over the period from 1981 to 2006. Over the 25-yr study period, the average soil cover on Canadian prairie soils increased by 4.8% overall. The improvement came primarily as a result of widespread adoption of no-till and a decline in the use of summerfallow, but the gains were offset to a great deal by a shift from higher-cover crops such as wheat, oats and barley to more profitable but lower-cover crops such as canola, soybeans and potatoes. The implication of these trends is that, even though protection of prairie agricultural soils has improved over the past 25 yr, soil cover could decline dramatically over the next several decades if crop changes continue, the adoption of conservation tillage reaches a peak and residue harvesting for biofuels becomes more common.

Lateglacial to early Holocene multiproxy record from Loch Assynt, NW Scotland

A core, recovered from a water depth of 53m in Loch Assynt, North-West Scotland, has yielded a 9m sequence comprising two distinct units, an upper, organic-rich unit (Unit I, ca. 6m) overlying a sequence of laminated clays, silts and sands (Unit II, ca. 3m). The upper unit is essentially Holocene in age based upon three bulk AMS radiocarbon dates while a fourth radiocarbon date from Unit II confirms a late-glacial age for that interval and supports a broadly linear age–depth relationship. Distinct variations in the magnetic susceptibility record of the lower unit can be visually correlated to major changes in the Greenland ice core (GISP2), this together with pollen evidence supports the radiocarbon dating suggesting an age of approximately 11,000 to around 17,000cal. BP for Unit II, with evidence for the Younger Dryas (Loch Lomond) stadial and the Bolling–Allerød climatic phases. Variations in the magnetic susceptibility record of the late-glacial sediments are thought to relate to climatically driven changes in soil cover and erosion rates. The multiproxy record from Loch Assynt indicates relatively continuous, sub-aqueous sedimentation during the last ∼17,000 years, providing an approximate age for the initiation of modern Loch Assynt and supporting recent dates of moraine retreat lines in the Loanan Valley from about 14–15 ka BP. Pollen and chironomid sampling provides further insights to the history of this relatively deep water body and compliment existing high-resolution palaeo-precipitation records for the mid to late Holocene interval from speleothem archives within the loch catchment.

Structure and composition of bacterial and fungal community in soil under soybean monoculture in the Brazilian Cerrado

Soybean is the most important oilseed cultivated in the world and Brazil is the second major producer. Expansion of soybean cultivation has direct and indirect impacts on natural habitats of high conservation value, such as the Brazilian savannas (Cerrado). In addition to deforestation, land conversion includes the use of fertilizers and pesticides and can lead to changes in the soil microbial communities. This study evaluated the soil bacterial and fungal communities and the microbial biomass C in a native Cerrado and in a similar no-tillage soybean monoculture area using PCR-DGGE and sequencing of bands. Compared to the native area, microbial biomass C was lower in the soybean area and cluster analysis indicated that the structure of soil microbial communities differed. 16S and 18S rDNA dendrograms analysis did not show differences between row and inter-row samples, but microbial biomass C values were higher in inter-rows during soybean fructification and harvest. The study pointed to different responses and alterations in bacterial and fungal communities due to soil cover changes (fallow x growth period) and crop development. These changes might be related to differences in the pattern of root exudates affecting the soil microbial community. Among the bands chosen for sequencing there was a predominance of actinobacteria, y-proteobacteria and ascomycetous divisions. Even under no-tillage management methods, the soil microbial community was affected due to changes in the soil cover and crop development, hence warning of the impacts caused by changes in land use.

Structure and composition of bacterial and fungal community in soil under soybean monoculture in the Brazilian Cerrado.

Soybean is the most important oilseed cultivated in the world and Brazil is the second major producer. Expansion of soybean cultivation has direct and indirect impacts on natural habitats of high conservation value, such as the Brazilian savannas (Cerrado). In addition to deforestation, land conversion includes the use of fertilizers and pesticides and can lead to changes in the soil microbial communities. This study evaluated the soil bacterial and fungal communities and the microbial biomass C in a native Cerrado and in a similar no-tillage soybean monoculture area using PCR-DGGE and sequencing of bands. Compared to the native area, microbial biomass C was lower in the soybean area and cluster analysis indicated that the structure of soil microbial communities differed. 16S and 18S rDNA dendrograms analysis did not show differences between row and inter-row samples, but microbial biomass C values were higher in inter-rows during soybean fructification and harvest. The study pointed to different responses and alterations in bacterial and fungal communities due to soil cover changes (fallow x growth period) and crop development. These changes might be related to differences in the pattern of root exudates affecting the soil microbial community. Among the bands chosen for sequencing there was a predominance of actinobacteria, γ-proteobacteria and ascomycetous divisions. Even under no-tillage management methods, the soil microbial community was affected due to changes in the soil cover and crop development, hence warning of the impacts caused by changes in land use.

The change in soil cover on the exposed bed of the Aral Sea

Desiccation of the Aral Sea has led to the formation of new soil cover on the exposed seabed. Investigation of the newly formed dry land is very important since it is a source of dust storms and salts transferred to long distances. A soil map of the exposed seabed for 2000 has been produced on the basis of the map for the year 1990 (Institute of Soil Science, Uzbekistan), satellite images, and selected field observations of groundwater table. During the period 1990–2000, the sea recessed 20–32 km, thus changing the soil cover characteristics. The maps of soil cover with the detailed information on soil textures, the characterization of soil types, the soil formation trends, and the changes in soil types during the sea recession process are available. Attention has been paid to erosion tendencies and susceptibility to dust and salt transfers. As a whole, the soil cover was formed as a result of the replacement of excessive wetlands (salt-marsh), located in the form of strip along the sea, by hydromorphic and semi-hydromorphic, semi-automorphic and automorphic soils. The drying seabed has complicated lithological and morphologic composition. The territory of the exposed seabed is characterized by different hydrological conditions. Groundwater depth varies from 0.5 to 10 m. With the shore's recession, the water storage groundwater is approaching the surface. With general tendency towards desertification, the initial soil cover changes. The soils that did not reach the complete genetic formation, under the influence of quickly changing hydrogeological conditions, are transformed into the other types and subtypes. Often, while becoming dry, they are self-destructed and change into sands. Currently, the following types of soils are observed on the exposed seabed: automorphic solonchaks, semi-automorphic solonchaks, semi-hydromorphic solonchaks, hydromorphic solonchaks, desert sandy soils, sands.

Landscape fragmentation and soil cover changes on south- and north-facing slopes during ecosystems recovery: an analysis from multi-date air photographs

A quantitative analysis is presented, of soil and vegetation patch patterns from air photographs of three dates (1956, 1976 and 1990). Relationships between changes in soil cover and landscape fragmentation are assessed for north- and south-facing slope units in the semi-arid zone of Israel undergoing recovery following severe overgrazing and woodcutting phases. Soil loss accompanied by an increase in rock fragment exposure, and an increase in soil erodibility due to a decrease in aggregate size and organic matter content are the two main characteristics of soil changes in this area. Changes in both of these characteristics are highly correlated with soil brightness properties as recorded from aerial photographs. The methodology developed combines image processing techniques, enabling differentiation between soil and vegetation patches, with raster Geographical Information Systems (GIS) techniques, allowing patch distribution, fragmentation and form to be analyzed. Expansion of vegetation patches and contraction of soil patches were found to follow similar lines of spatial pattern evolution when parameterized according to their size, form and density. Assessment of temporal changes in soil and vegetation patch composition indicated that there is a phase difference of 12 years between the processes taking place on the two slope units. Hypothetical descriptions of soil patch fragmentation and vegetation patch expansion processes between 1920 and 2010 were formulated following the analysis of data between 1956 and 1990. Evidence of soil brightness changes provided indications for the continuation of soil loss, mainly in large patches (a few thousands of square meters in size) undergoing relatively slow fragmentation.

Regional measurements and modeling of windblown agricultural dust: The Columbia Plateau PM10 Program

The Columbia Plateau PM10 Program [CP3] is a multi‐investigator study of windblown dust in the Pacific Northwest with an emphasis upon the role of agricultural lands in regional dust storms. Ambient measurements of PM10 within the source areas of the central basin of Washington during several autumn dust periods show that typical background concentrations [nonwind‐event periods] decrease from an average of 34 μg m−3 in early fall to 10 μg m−3 in late fall. During wind events, ambient concentrations at downwind urban receptors can exceed 500 μg m−3 on an hourly basis, with 24 hour averaged values as high as 300 μg m−3. Particle counts during wind events are enhanced by as much as a factor of 5 for particle sizes greater than 5 μm, and also for sizes between 1 and 5 μm compared to nonwindy periods. Analysis of the synoptic conditions which exist during these dust storms showed a common situation where a surface low is moving rapidly across British Columbia while a surface high is positioned in the Great Basin of Nevada. A regional windblown dust air quality model, developed for the CP3 study, predicts large dust plumes stretching across eastern Washington with maximum concentrations in the source regions exceeding 10,000 μg m−3. Total mass emissions during a storm are estimated to equal 100 Gg dy−1, which represents about 1% of recent estimates of the global annual dust emission rate. In the initial applications of the model, available PM10 observations are used to calibrate the dust emission algorithm. Changes in the dust constant for two modeled events are consistent with changes in soil cover and accumulated precipitation between an early fall event and a late fall event. The estimated fluxes are in a range similar to those in the literature but appear to be much less than estimated from global modeling of recently disturbed soils.