Effect Of Landscape Position Research Articles

Effects of landscape position on perennial biomass and food crop performance in buffer areas

AbstractDue to the environmental consequences of annual‐dominated cropping systems, there is an increasing need to identify agronomic strategies that incorporate perennial crops. One strategy for increasing perennial cover is through the targeted use of annually harvested perennial food and bioproduct crops in buffer strips, which has the potential to create new revenue streams for farmers and substantially mitigate agricultural nutrient pollution from conventional cropping systems. As buffers are typically installed on marginal land, it is critical to understand how landscape position influences the success of perennial crops. The objectives of this study were to determine the relatively early influence of landscape position on the productivity of a variety of perennial crops and their subsequent soil nutrients and soil water storing capabilities. In this experiment, nine perennial (alfalfa, alsike clover, indiangrass, switchgrass, big bluestem, prairie cordgrass, intermediate wheatgrass, high‐diversity polyculture, low‐diversity polyculture) and two annual (corn, soybean) crops were planted across two landscape positions (hillslope and deposition). Plant biomass, plant tissue nitrogen, soil moisture, and soil NO3‐N and NH4‐N were measured and compared at two different locations in Minnesota. Overall, the polyculture mixes, and to some extent intermediate wheatgrass, performed the best with respect to biomass production while also providing ecosystem services across most soil by landscape position combinations tested in this study. However, there were some important findings specific to each soil and landscape position combination, mainly oriented toward biomass production. We also observed temporal patterns in soil moisture and depth‐related patterns in soil N reductions. This study presents an opportunity to optimize the use of perennial crops on marginal agricultural lands for improved environmental and economic benefit.

Dynamics of soil quality in a conserved landscape in the highland sub humid ecosystem, Northwestern Ethiopia

Several studies have assessed the dynamics of soil quality induced by soil and water conservation (SWC), but many showed disagreement over the efficacy of SWC interventions in the Ethiopian highlands. This study used a before and after soil and water conservation practices (SWCP) comparison approach to evaluate the effect of SWCP on soil quality dynamics. Fifty-four composite and 10 undisturbed soil samples were collected in 2012 (before SWCP) and 2022 (after SWCP). Statistical mean, analysis of variance, and principal component analysis were applied to test the significant differences among treatments. The findings demonstrated that SWCP has significantly improved most of the soil quality indicators such as soil organic matter, total nitrogen, available phosphorous, pH, total porosity, field capacity, and available water, and reduced the value of bulk density and coarse fragments. The interaction effect of landscape position and types of structures provided statistically significant results for soil organic matter, total nitrogen, magnesium, calcium, and base saturation. Soil and stone-faced soil bunds treated at lower landscapes were superior in improving soil quality attributes. The soil quality indexing showed, the overall soil quality improvement as a result of SWCP was about 32.15%. The level of improvement for different SWCPs was 32% for stone faced soil bunds and 33% for soil bunds. The findings revealed that SWCP implementation can improve soil quality. Soil organic matter is a key biological quality component that contributed 25% to the soil quality index and highly impacted soil physicochemical properties. We suggest additional assessment of best and integrated land management practices to ensure further improvement in soil quality, crop productivity, and ecosystem services in the subhumid ecosystems.

Assessing the Agronomic Subfield Variability by Sentinel-2 NDVI Time-Series and Landscape Position

Optimizing crop yield is one of the main focuses of precision farming. Variability in crop within a field can be influenced by many factors and it is necessary to better understand their interrelationships before precision management methods can be successfully used to optimize yield and quality. In this study, NDVI time-series from Sentinel-2 imagery and the effects of landscape position, topographic features, and weather conditions on agronomic spatial variability of crop yields and yield quality were analyzed. Landscape position allowed the identification of three areas with different topographic characteristics. Subfield A performed the best in terms of grain yield, with a mean yield value 10% higher than subfield B and 35% higher than subfield C, and the protein content was significantly higher in area A. The NDVI derived from the Sentinel-2 data confirms the higher values of area A, compared to subfields B and C, and provides useful information about the lower NDVI cluster in the marginal areas of the field that are more exposed to water flow in the spring season and drought stress in the summer season. Landscape position analysis and Sentinel-2 data can be used to identify high, medium, and low NDVI values differentiated for each subfield area and associated with specific agronomic traits. In a climate change scenario, NDVI time-series and landscape position can improve the agronomic management of the fields.

Topographic effects on soil microclimate and surface cover crop residue decomposition in rolling cropland

Rolling hill topography is common in agricultural land throughout the Southeastern United States. In areas of complex topography, downslope movement of soil nutrients and water can lead to nutrient losses and soil degradation, as well as spatial yield variability. Additionally, differences in the accumulation of water, slope aspect, and crop biomass production can lead to disparate conditions of soil moisture and soil temperature throughout a given field. Winter cover crops can reduce erosion and mitigate nutrient losses, while also potentially providing a source of nitrogen (N) to the subsequent cash crop as the cover crop residue decomposes. However, given that moisture and temperature at the soil surface are primary controls on residue decomposition, topographic heterogeneity may lead to variable rates of cover crop breakdown and N return to the system. We investigated the effect of landscape position on soil volumetric moisture and temperature at 5 cm depth, and the decomposition and N release rate of two cover crop residues, a sole-seeded cereal rye (Secale cereale L.) cover crop, and a cereal rye/crimson clover (Trifolium incarnatum) mixture over two maize (Zea mays L.) growing seasons in Lexington, KY. We found differences in soil moisture and soil temperature across landscape positions, with backslope positions tending to be the warmest and driest positions, and toeslope positions tending to be wettest. However, we did not observe significant differences in decomposition or residue N release rate among landscape positions or cover crop treatments. Our results emphasize the inherent variability present in abiotic factors in rolling hill cropland but indicate that cover crop residue persistence and N release are relatively consistent among landscape positions.

Landscape Position Effects on Magnetic Properties of Soils in the Agricultural Land Pechenigy, Ukraine

Landscape Position Effects on Magnetic Properties of Soils in the Agricultural Land Pechenigy, Ukraine

Effects of landscape positions on soil physicochemical properties at Shenkolla Watershed, South Central Ethiopia

BackgroundUnderstanding the effects of landscape positions on soil physicochemical properties is crucial for improving the soil productivity and to ensure the environmental sustainability. Three land use types forest land, grazing land and cultivated land all within upper, middle and lower landscape positions were selected to determine the effects of landscape positions, land use types and their interaction effects on soil physicochemical properties. Twenty seven soil samples were collected from lower landscape, middle landscape and upper landscape positions at the depth of 0–20 cm in nine replications. In addition, undisturbed soil samples were taken using core sampler from each land use type under upper, middle and lower landscape positions for the ascertainment of bulk density and water retentive capacity. The analysis of variance (ANOVA) was applied to determine variations in soil parameters among landscape positions and land use types. A Generalized Linear Models (GLMs) analysis was conducted to determine the influence of independent (fixed) factors, on the soil properties (response variables). Treatment means comparison was determined using the Least Significant Difference (LSD) at 0.05 level of significances.ResultsThe result indicated that among the soil properties sand (p < 0.001), silt (p < 0.001), clay (p < 0.001), bulk density (p < 0.01), water holding capacity at FC (p < 0.001), water retention at PWP (p < 0.01), Available water content (AWC) (p < 0.01), soil reaction (pH) (p < 0.05), Soil organic carbon (SOC%) (p < 0.01), Total nitrogen (TN%) (p < 0.01), available phosphorus (p < 0.05) and CEC (p < 0.001) have shown a significant variation among the landscape categories. Similarly, variation of sand (p < 0.001), silt (p < 0.001), clay (p < 0.001), bulk density (p < 0.01), water holding capacity at FC (p < 0.001), water retention at PWP (p < 0.001), Available water content (AWC) (p < 0.01), soil reaction (pH) (p < 0.01), SOC (p < 0.01), TN (p < 0.001) available phosphorus (AP) (p < 0.001) and CEC (p < 0.001) were also statistically significant among the land use types. Moreover, lower landscape position and forest land had high mean value of SOC, TN, AP, CEC, EB (exchangeable bases), and available micronutrients, whereas upper landscape position and intensively cultivated land had low mean value of SOC, TN, AP, CEC, EB (exchangeable bases), and available micronutrients.ConclusionLandscape positions, land use types and interaction effects of landscape position and land use types (LSP * LU) significantly affected soil properties. Soil with best quality was found in lower landscape position and forest land, while less quality of soil was found in upper landscape position and cultivated land. Thus, efforts should be made to improve the quality of soil under upper landscape position and cultivated land using biological and physical soil conservation measures.

A landscape approach to nitrogen cycling in urban lawns reveals the interaction between topography and human behaviors

Lawns are a common ecosystem type in human-dominated landscapes which can have negative impacts on water quality due to fertilizer applications, but also host a range of ecosystem services. While many studies have addressed water and nitrogen (N) dynamics in lawns, few have considered how topography interacts with human behaviors to control these dynamics. Our overarching objective was to determine if mesoscale topography (hillslopes within lawns) interacts with human behavior (fertilizer use) influencing patterns of N mobilization and removal in lawns. To that end, we measured several hydrobiogeochemical characteristics associated with N dynamics along topographic gradients in fertilized and unfertilized residential and institutional lawns. We found topographic gradients affect the hydrobiogeochemistry of lawns, with significant effects of landscape position (top versus toe slope versus bottomland swales), but with direction and strength of the effect often varying among different lawn types (exurban versus suburban front yards versus suburban backyards versus institutional). Fertilizer application did not affect the hydrobiogeochemical properties of lawns. Rather, results from this study suggest lawns in suburban front yards were at greatest risk of N mobilization due to a complex suite of characteristics including proximity to impervious surfaces, swales with low saturated infiltration rates, and potential vulnerability to N deposition from vehicles. This study highlights the need to consider landscape controls of water and N fluxes and how they interact with human behaviors to better understand how these landscapes function. These results contribute to the emerging understanding of the structure, function and environmental impacts of lawns.

No biotic homogenisation across decades but consistent effects of landscape position and pH on macrophyte communities in boreal lakes

It has been predicted that spatial beta diversity shows a decreasing trend in the Anthropocene due to increasing human impact, causing biotic homogenisation. We aimed to discover if vascular aquatic macrophyte communities show different spatial patterns in beta diversity in relation to land use and environmental characteristics in different decades from 1940s to 2010s. We aimed to discover if spatial structures differ between species‐, phylogeny‐ and functional‐based beta diversity. We used presence–absence data of aquatic macrophytes from five decades from small boreal lakes. We utilized generalised dissimilarity modelling to analyse spatial patterns in beta diversity in relation to environmental gradients. We found that lake elevation and pH were the most important variables in each decade, while land use was not particularly important in shaping beta diversity patterns. We did not find signs of a decreasing trend in spatial beta diversity in our study area during the past 70 yr. We did not find signs of either biotic homogenisation or biotic differentiation (taxonomic, phylogenetic or functional). Vascular aquatic macrophyte communities showed only slightly different beta diversity patterns in relation to human impact across decades. The patterns of different facets of beta diversity diverged only slightly from each other. Lake position in the landscape, reflecting both natural connectivity and lake characteristics, explained the patterns found in beta diversity, probably because our study area has faced only modest changes in land use from 1940s to 2010s when compared globally. Our study highlights the fact that biotic homogenisation is not an unambiguous process acting similarly at all spatial and temporal scales or in different environments and different organism groups.

Cover Crops and Landscape Position Effects on Nitrogen Dynamics in Plant-Soil-Water Pools

Nitrogen dynamics and water quality benefits deriving from the use of cover crops (CCs) are mostly incurred from plot-scale studies without incorporating large-scale variability that is induced by landscape positions. Our understanding of how topography affects the N response in CC systems is limited. The objectives of this study were to evaluate the effects of topography (shoulder, backslope, and footslope) and CCs (cereal rye, Secale cereale L. and hairy vetch, Vicia villosa L.) on nitrogen (N) uptake, soil inorganic N content (nitrate-N, NO3-N and total N, TN), and N leaching in watersheds that were planted with or without CCs. The crop rotation in CC watersheds was corn (Zea mays L.)-cereal rye-soybean (Glycine max L.)-hairy vetch whereas control watersheds had corn-no CC-soybean-no CC rotation. Data from the watersheds was collected for three cash crop seasons and three CC seasons from 2015 to 2018. Nitrogen uptake of hairy vetch in CC watersheds was 110.9, 85.02, and 44.89 kg ha−1 higher at the shoulder, backslope, and footslope positions, when compared to shoulder, backslope, and footslope positions of no CC watersheds. About 12 to 69% reduction in soil solution NO3-N and TN was observed with cereal rye CC when compared to no CCs watersheds. However, reductions in soil solution N concentrations were only seen at the footslope position where the hairy vetch reduced NO3-N and TN concentrations by 7.71 and 8.14 mg L−1 in CC watersheds compared to no CC watersheds. During the corn and soybean growing seasons, similar reductions in soil solution N concentration were only seen at the footslope position in the CC watersheds. The excessive N at footslope positions of CC watersheds may have been fixed in CC biomass, immobilized, or lost through denitrification stimulated by higher water availability at the footslope position. The results of this research can help farmers and stakeholders to make decisions that are site-specific and topographically driven for the management of CCs in row-cropped systems.

Effect of Landscape Position on the Concentration and Distribution of Soil Carbon Fractions at Busby Forest in Central Missouri

We quantified the concentrations and distribution of different soil carbon fractions – total carbon (TC), recalcitrant C measured as nonhydrolyzable carbon (NHC) and labile organic carbon measured as hydrolyzable carbon (HC), hot-water soluble C (HWC) and cold-water soluble C (CWC) at Busby forest in central Missouri. The forest soil contained large concentrations of soil organic carbon (SOC) (ranging from 26,700 to 85,000 mg C kg-1 soil); NHC (12,500 to 47,000 mg C kg-1 soil); HC (2,000 to 6,100 mg C kg-1 soil); HWC (700 to 1,550 mg C kg-1 soil); and CWC (280 to 520 mg C kg-1 soil). Soil C fractions were correlated with each other and with total organic C with correlation coefficients (r) ranging from 0.48 to 0.87. Among these correlations, NHC was significantly correlated with TC (p = 0.0027, r = 0.63), suggesting that a higher proportion of C is in the recalcitrant fraction, consequently, promoting C sequestration in these soils. Our results also showed that more than half (51.25%) of total organic C can be stabilized in the NHC fraction in these soils. Accumulation of C in the NHC fraction reflects C stabilization and sequestration in these forest soils. This information is very important for soil C modeling, as more studies attempt to include soil C fractions.

Extent to which pH and topographic factors control soil organic carbon level in dry farming cropland soils of the mountainous region of Southwest China

Soil organic carbon (SOC) in agricultural land is influenced greatly by indeterminate human activity, making it difficult to understand the spatial pattern of SOC. Soil pH and topographic conditions are key indices in the Chinese Soil Genetic Classification System (CSGCS) and manage some critical factors that control the dynamics of SOC either directly or indirectly. To identify the extent to which pH and topographic factors control SOC levels in dry farming cropland soils of the mountainous region of Southwest China, we compared the differences along topographic gradients, and analysed the contribution of different factors in determining SOC status using analysis of variance (ANOVA) and linear regression. Our results indicated the SOC levels ranged from 10.46g•kg−1 to 37.60g•kg−1 and were significantly correlated with soil pH, landscape position, slope and elevation (p<0.05). On a large scale, the combined effects of landscape position and elevation contributed to fluctuating SOC levels along the elevation gradient. SOC levels slightly, but significantly, decreased from base to summit. The difference of SOC levels along a 200m elevation gradient exhibited statistical significance (p<0.05). A slope range, from 0 to 42°, was categorized into three groups, namely, 5° to 15°, 15° to 30° and others. The slope range 15° to 30° had significantly greater SOC values than the other groups. These variables could all together explain approximately 40% of total variation in SOC, of which approximately 70% was attributable to soil pH, suggesting soil pH plays a key role in forming the spatial pattern of SOC levels in dry farming cropland soils of the mountainous region of Southwest China. The combined effect of landscape position and elevation could further explain 7.3% of SOC variation, which is more apparent than the effect of elevation alone.

Seasonal and inter‐annual variability in litter decomposition and nitrogen availability in a mid‐Appalachian watershed

AbstractThe role that microclimates play on soil decomposition is poorly understood. Though litter decomposition is controlled by climate and substrate quality at coarse spatial scales, at the watershed scale, microclimates mediated by forest structure and landscape position can influence decomposition rates and in turn affect nitrogen cycling. To evaluate the effects of landscape position and vegetation heterogeneity on decomposition, we employed a two‐year litterbag study (2011–2013) using yellow birch leaf litter across the Weimer Run watershed, a cool, humid watershed located near Davis, West Virginia. From our results, we created a spatially explicit empirical model that we tested against both a single‐pool and three‐pool decomposition model, each based on climate and derived from the Long‐Term Intersite Decomposition Experiment Team. Initial litter decomposition varied by elevation, with greater rates of decomposition at locations lower in the watershed. Decomposition rates differed by elevation, except during the first winter of the study. No differences in decomposition rates were seen among elevation levels when snowfall was below average for the first winter (2011–2012). During the second winter (2012–2013), elevation levels showed separation in decomposition rates, with higher elevations exhibiting lower decomposition rate. This suggests important controls on decomposition exerted by the presence or absence of snow, inter‐annual climate variability, and the interaction of both with topography. Our empirical model showed greater rates of decomposition during early stages of decomposition (&lt;12 months), but converged with the three‐pool decomposition model after 20 months. Plant available nitrogen differed by vegetation cover, largely driven by greater availability of nitrate (NO3−) beneath areas of canopy closure in the forest. Controls on decomposition and nitrogen cycling within the Weimer Run watershed vary spatially by elevation and vegetation cover and are subject to complex interactions and differ from standard models of decomposition. The effect of the inter‐annual variance of snow depth on litter decomposition is of note and an important consideration moving forward. Climate‐based models of decomposition greatly underestimate initial rates of decomposition, potentially leading to under‐accounting and compounded uncertainty.

Growth dynamics of black spruce (Picea mariana) in a rapidly thawing discontinuous permafrost peatland

AbstractHigh‐latitude warming has led to radical changes in abiotic conditions influencing forest growth. In the North American boreal forest, widespread declines in forest productivity (particularly in western regions) and changing climate‐growth relationships have been documented. Previous studies have proposed that this decline can be attributed to drought stress as increasing temperatures may cause evapotranspirative demand to exceed available moisture. We used tree ring studies to document growth dynamics of black spruce, one of the most dominant boreal tree species, in a boreal peatland experiencing rapid permafrost thaw. We specifically look at how changing permafrost conditions influence growth. Growth of black spruce at this site has declined steadily since the mid‐1900s and exhibited a shift from positive responses to temperature pre‐1970 to predominantly negative responses in recent decades, despite precipitation increasing over time at this site. Our results show that there is no apparent effect of landscape position or rate of lateral permafrost thaw on growth trends of black spruce, despite gradients in soil moisture and active layer thickness across the mosaic of wetlands and drier permafrost plateaus at this site. However, this does not imply no effect of permafrost thaw on growth; our results support growing evidence that vertical permafrost thaw (i.e., active layer thickening) is causing drought stress in these slow‐growing, shallow‐rooted trees. To our knowledge, this study is the first to investigate permafrost as a driver of within‐site variability in growth‐climate responses, and we provide insight into the widespread growth declines and divergence of climate‐growth relationships in high‐latitude forests.

Crop, Tillage, and Landscape Effects on Near‐Surface Soil Quality Indices in Indiana

Core Ideas Soil quality scores were highest in perennial grass systems, followed by a soybean‐dominated rotation, followed by a corn‐based rotation. No‐till crop production had no higher soil quality score than chisel–disk tillage but the uncultivated perennial grass system scored higher than both. In this crop production‐dominated region, soil quality is driven by biological properties like soil C and β‐glucosidase activity and physical properties like bulk density and macroaggregate stability. Soil quality is a critical link between land management and water quality. We aimed to assess soil quality within the Cedar Creek Watershed, a pothole‐dominated subwatershed within the St. Joseph River watershed that drains into the Western Lake Erie Basin in northeastern Indiana. The Soil Management Assessment Framework (SMAF) with 10 soil quality indicators was used to assess inherent and dynamic soil and environmental characteristics across crop rotations, tillage practices, and landscape positions. Surface physical, chemical, and nutrient component indices were high, averaging 90, 93, and 98% of the optimum, respectively. Surface biology had the lowest component score, averaging 69% of the optimum. Crop rotation, tillage, and landscape position effects were assessed using ANOVA. Crop selection had a greater impact on soil quality than tillage, with perennial grass systems having higher values than corn (Zea mays L.) or soybean [Glycine max (L.) Merr.]. Furthermore, soybean rotations often scored higher than corn rotations. Uncultivated perennial grass systems had higher overall soil quality index (SQI) values and physical, chemical, and biological component values than no‐till or chisel–disk systems. Chisel–disk effects on overall and component SQI values were generally not significantly different from no‐till management except for a few physical indicators. Toe‐slopes had higher physical, biological, and overall SQI values than summit positions but toe‐slope values were not significantly different from those of mid‐slope positions. This work highlights the positive effects of perennial grass systems, the negative effects of corn‐based systems, and the neutral effects of tillage on soil quality.

Standard survey designs drive bias in the mapping of upland swamp communities

AbstractVegetation maps are critical biodiversity planning instruments, but the classification of vegetation for mapping can be strongly biased by survey design. Standardization of survey design across different vegetation types is therefore increasingly recommended for vegetation mapping programs. However, some vegetation types have complex small‐scale vegetation patterns that are important in characterizing these vegetation types, and standard designs will often not capture these patterns. The objective of this paper was to investigate the magnitude of potential map bias that results from survey design standardization and recommend approaches to deal with this bias. We surveyed upland swamps of the Greater Blue Mountains World Heritage Area Australia using two contrasting survey designs, including the standard 400 m2 single quadrat design recommended and used by authorities. We then derived a classification for these swamps and tested the effect of survey design on this classification, species richness and the type of species detected (obligate or facultative swamp species). Species richness and species type were not significantly different among survey techniques. However, more than 40% of swamps clustered differently among survey designs. Thus, one of the 10 derived communities (which is floristically consistent with a previously mapped endangered community) was indistinct, and some individual swamps misclassified using the standard survey design. An effect of landscape position on swamp floristic patterns and a significant trend for high similarity scores among swamps surveyed with multiple small quadrats compared to the standard survey design was also determined. Australian upland swamps are classified at the global scale as shrub‐dominated wetlands, and complex floristic patterns have been recorded in shrub‐dominated wetlands in both northern and southern hemispheres. We therefore advocate either multiple survey designs or different survey standards for upland swamp communities and other vegetation types that have complex floristic patterns at small scales.

Long-term cultivation and landscape position effects on aggregate size and organic carbon fractionation on surface soil properties in semi-arid region of Iran

ABSTRACTThis study was carried out to investigate the effects of long-term cultivation and landscape position on organic carbon content and soil aggregation. Sampling sites were determined based upon land use at the end of 50 years soil use and management, cultivated/annual wheat cropping and grazed pasture, and landscape position in Chaharmahal-va-Bakhtiary province, southwest Iran. Soil samples were collected from the 0–5 cm and 5–15 cm depths in two adjacent fields that have the same slope and aspect. The soil was silty clay at the summit and footslope positions, and was a silty clay loam at the backslope. Wet-sieving analysis and aggregate-size fractionation methods were used to separate the samples into three aggregate fractions (i.e., 2–4.75, 0.25–2, and 0.053–0.25 mm). The treatments were arranged in a factorial design. Land use significantly affected the water-stable aggregate fractions, so that the wet soil stability of the macroaggregates (i.e., 2–4.75 mm) was higher in the pasture, whereas it was greater for the meso-aggregates (i.e., 0.25–2 mm) in the cultivated soils. Cultivation decreased both the wet-aggregate stability and percent of macroaggregates whereas long-term pasture enhanced aggregation. Soil organic carbon (SOC) content within aggregates and primary particles was also significantly influenced by landscape position, land use, and the depth of sampling. The SOC content was higher in clay than those in silt and sand contents. The SOC content decreased as depth increased in all fractions. In general, the highest and lowest wet-stable aggregates were observed on the footslope and backslope positions, respectively.

Soil Quality of a Mature Alley Cropping Agroforestry System in Temperate North America

Long-term effects of alley cropping on soils in the temperate zone are not widely known. Management, landscape, and soil depth effects on soil physical and biological properties were examined in a silver maple (Acer saccharinum L.) no-till corn (Zea mays L.)- soybean (Glycine max L.) rotation established in 1990 in northeast Missouri. Soils from crop alleys and tree rows were collected along transects traversing upper to lower landscape positions at three depths. Fluorescein diacetate hydrolase (FDA), β-glucosidase, β-glucosaminidase, and dehydrogenase activities were measured. Soil bulk density, aggregate stability, carbon (C), nitrogen N), and enzyme activities decreased with soil depth in alley and tree rows except for glucosaminidase. Soil physical and biological parameters did not differ significantly between alley and tree row. Landscape position effects were not significant for management or depth. Tree establishment improves soil quality in the crop alley as the system matures with improvements extended throughout the soil profile.

Comparison of Corn Transpiration, Eddy Covariance, and Soil Water Loss

Sap flow gages are used to estimate plant transpiration (an indirect form of soil water loss), but relatively few studies compare transpiration with other measures of soil water loss. The purpose of this study was to compare two landscape positions for transpiration (T) from sap flow measurements, soil water changes estimated by daily neutron probe readings, and evapotranspiration (ET) determined via eddy covariance and associated microclimate measurements. Monitoring at backslope and toeslope positions occurred for 2 wk during the corn (Zea mays L.) early reproductive stage. Evaporation from soil (E) and potential ET were calculated from microclimate measurements. The T from sap flow measurements plus calculated soil E was significantly higher at the backslope position than the toeslope position. Grain yields were within 3% (9020 vs. 8774 kg ha−1) for the toeslope and backslope positions. At the backslope position, crop development was delayed at the milk stage and leaf area index was larger compared with corn at the toeslope position. For July 18th through August 4th, the water table was 0.65 to 0.85 m deep at the toeslope position but 1.70 to 2.28 m deep at the backslope position. Higher water table depths at the toeslope position would supply extra water during dry times compared with the backslope position but could also have caused low temperature stress early in the season. The backslope faced south and could have experienced higher wind speed causing water stress during dry periods. The mid to late 2011 growing season was dry enough to detect landscape position effects.

Water and Dissolved Carbon Fluxes in an Eroding Soil Landscape Depending on Terrain Position

Leaching of dissolved C in arable hummocky ground moraine soil landscapes is characterized by a spatial continuum of more or less erosion‐affected Luvisols, Calcaric Regosols at exposed positions, and Colluvic Regosols in depressions. Our objective was to estimate the fluxes of dissolved C in four differently eroded soils as affected by erosion‐induced pedological and soil structural alterations. In this model study, we considered landscape position effects by adapting the water table as the bottom boundary condition and erosion effects by using pedon‐specific soil hydraulic properties. The one‐dimensional vertical water movement was described with the Richards equation using HYDRUS‐1D. Solute fluxes were obtained by combining calculated water fluxes with concentrations of dissolved organic and inorganic C (DOC and DIC, respectively) measured from soil solution extracted by suction cups at biweekly intervals. In the 3‐yr period (2010–2012), DOC fluxes in the 2‐m soil depth were similar at the three non‐colluvic locations with −0.8 ± 0.1 g m−2 yr−1 (i.e., outflow) but were 0.4 g m−2 yr−1 (i.e., input) in the depression. The DIC fluxes ranged from −10.2 g m−2 yr−1 for the eroded Luvisol, −9.2 g m−2 yr−1 for the Luvisol, and −6.1 g m−2 yr−1 for the Calcaric Regosol to 3.2 g m−2 yr−1 for the Colluvic Regosol. The temporal variations in DOC and DIC fluxes were controlled by water fluxes. The spatially distributed leaching results corroborate the hypothesis that the effects of soil erosion influence fluxes through modified hydraulic and transport properties and terrain‐dependent boundary conditions.

Biomass yield from planted mixtures and monocultures of native prairie vegetation across a heterogeneous farm landscape

Farms in the glaciated tallgrass prairie region of North America are topographically heterogeneous with wide-ranging soil quality. This environmental heterogeneity may affect choice and placement of species planted for biomass production. We designed replicated experiments and monitored farm-scale production to evaluate the effects of landscape position, vegetation type, and year on yields of monocultures and mixtures. Research was conducted on a 262-ha South Dakota working farm where cropland had been replanted with a variety of native grassland types having biofuel feedstock potential. Vegetation type (diverse mixture or switchgrass [Panicum virgatum L.] monoculture) and year interacted to influence yield in replicated experiments (p<0.10). Mean annual switchgrass yield above a stubble height of 10cm was 9.3Mgha−1 in two replicated experiments, and was greater than yield of mixtures (7.3Mgha−1) in 6 of 7 year×vegetation type combinations. Landscape position interacted with year and vegetation type to influence yield (p<0.10). Variability was generally greatest at the lowest landscape position. On the farm's larger fields (0.4–46ha), three-year mean yields of switchgrass monocultures cut at ground level (12.7Mgha−1) were also greater than yields of mixtures (9.7Mgha−1) but both were less than prairie cordgrass (Spartina pectinata Link) monoculture yield (13.2Mgha−1) in a restored wetland. A combination of prairie monocultures and mixtures, strategically placed across a farm landscape, could offer a balance of productivity, ecosystem services, and income with potential as biofuel feedstock and other income streams (hay, seed, beef).