Slope Position Research Articles

Tree Radial Growth Responses to Climate and Reservoir Impoundment in Valleys in Southwestern China

Southwestern China is a critical biodiversity hotspot area, and many large hydroelectric projects have been established in the valleys in the region. Tree growth in the valleys will be affected by both regional climate and reservoir impoundment. However, it remains unknown whether the radial growth of trees in the valleys has a common response pattern to the regional climate, and it is also unclear whether the response of radial growth to reservoir impoundment can be detected. In this study, we developed tree-ring width chronologies of Pinus yunnanensis Franch. collected at 11 sites with vertical and horizontal gradients to three hydroelectric reservoirs in three riverine valleys in southwestern China. We analyzed the radial growth responses to the regional climate from 1986 to 2017 by correlation with instrumental meteorological data. Tree growth responses to reservoir impoundment were investigated through spatial and temporal comparisons using the change in the Euclidean distance and difference test. We also distinguished their responses at tree-ring sites without influenced by reservoir impoundment including two sites in the valleys and seven sites at high elevations. The results showed that the climate conditions in May and the dry season before the growth season significantly limit the radial growth in the valleys, which is different to that at high-elevation areas in southwestern China. Growth variations in the valleys are related to elevations and the trees in similar slopes positions exhibit similar responses. For trees in the low slope positions, both variance and mean values of radial growth are affected by reservoir impoundment. Trees at relatively low sites (i.e., sites M2, R2, L2), rather than the trees close to the reservoirs (i.e., sites M1, R1, L1), respond more sensitively to reservoir impoundment.

Effects of slope and tree position on soil properties in a temperate deciduous forest

Effects of slope and tree position on soil properties in a temperate deciduous forest

Comparative Analysis of Machine Learning-Based Predictive Models for Fine Dead Fuel Moisture of Subtropical Forest in China

The moisture content of fine dead surface fuel in forests is a crucial metric for assessing its combustibility and plays a pivotal role in the early warning, occurrence, and spread of forest fires. Accurate prediction of the moisture content of fine dead fuel on the forest surface is a critical challenge in forest fire management. Previous research on fine surface fuel moisture content has been mainly focused on coniferous forests in cold temperate zones, but there has been less attention given to understanding the fuel moisture dynamics in subtropical forests, which limits the development of regional forest fire warning models. Here, we consider the coupled influence of multiple meteorological, terrain, forest stand, and other characteristic factors on the fine dead fuel moisture content within the subtropical evergreen broadleaved forest region of southern China. The ability of five machine learning algorithms to predict the moisture content of fine dead fuel on the forest surface is assessed, and the key factors affecting the model accuracy are identified. Results show that when a single meteorological factor is used as a forecasting model, its forecasting accuracy is less than that of the combined model with multiple characteristic factors. However, the prediction accuracy of the model is improved after the addition of forest stand factors and terrain factors. The model prediction ability is the best for the combination of all feature factors including meteorology, forest stand, and terrain. The overall prediction accuracy of the model is ordered as follows: random forest > extreme gradient boosting > support vector machine > stepwise linear regression > k-nearest neighbor. Canopy density in forest stand factors, slope position and altitude in terrain factors, and average relative air humidity and light intensity in the previous 15 days are the key meteorological factors affecting the prediction accuracy of fuel moisture content. Our results provide scientific guidance and support for understanding the variability of forest surface fuel moisture content and improved regional forest fire warnings.

Changes in soil aggregate stability and aggregate-associated carbon under different slope positions in a karst region of Southwest China

Soil aggregates are crucial for reducing soil erosion and enhancing soil organic carbon sequestration. However, knowledge regarding influences of different slope positions on compositions and carbon content for different soil aggregates is limited. Soil samples were collected from various slope positions including dip slope, anti-dip slope and valley depression in the Longtan karst valley of Southwest China. Contents of macroaggregate (> 0.25 mm), microaggregate (0.053–0.25 mm) and silt and clay fraction (< 0.053 mm), and aggregate-associated carbon contents under the three slope positions were measured. Compared to the anti-dip slope, the mean weight diameter under the dip slope and valley depression decreased by 28.48 % and 58.79 %, respectively, while the geometric mean diameter decreased by 39.01 % and 62.57 %, respectively. The mean carbon content in silt and clay fraction was 27.59 % and 21.00 % lower than the macroaggregate- and microaggregate-associated carbon content, respectively. Under the valley depression and dip slope, soil organic carbon contents in bulk soil (37.67 % and 10.36 %, respectively), microaggregate (37.56 % and 4.95 %), and silt and clay fraction (39.99 % and 12.84 %, respectively) were significantly lower than those under the anti-dip slope. However, the difference in macroaggregate-associated carbon content among the three slope positions was not significant. The silt and clay fraction was the major contributor to soil carbon pool in bulk soil in the study area because of its high content. Compared to the anti-dip slope, contribution of macroaggregates to soil carbon pool under the dip slope and valley depression decreased by 25.53 % and 47.95 %, respectively, whereas the contribution of silt and clay fraction increased by 22.68 % and 42.66 %, respectively. These results suggested that the anti-dip slope surpassed both the dip slope and valley depression in carbon sequestration and soil and water conservation in karst regions.

Assessment of Quality, Fungal Population and Diversity, of Irrigation Water in Selected Areas of Minna, Niger State, Nigeria

Water samples were collected at 3 slope positions (upper, middle and lower) from four locations practising irrigation agriculture in Minna as follows; Fadikwe, Mechanic village in keterin-gwari, Soje-A in kpakungu and Bali in Chanchaga and fitted to a Completely Randomized Design (CRD) having slope positions as replicates for each treatment. Water sampling, Physical and chemical properties and Fungi population and diversity were determined using standard methods. Data generated were subjected to Analysis of Variance (ANOVA) and means were separated using Least Significance Differences (LSD) and Duncan Multiple Range Test. Result obtained revealed that Chanchaga irrigation water recorded the highest fungi population of 1.6 x 107 CFU/ml why fungi diversity was the least at Chanchaga. The presence of _Geotrichum species_ (2.33 x 106CFU/ml), _Candida tropicalis_ (4.33 x 106CFU/ml) and _Torulopsis glabrata_ (1.67 x 106CFU/ml) in water obtained from Mechanic village may be due to the presence of hydrocarbons in the oil polluting the water. They are potential degraders of crude oil hydrocarbons. They may therefore be responsible for the value of Biochemical Oxygen Demand of 261 mg/l recorded at Mechanic village. The Biochemical Oxygen Demand values of 342 mg/l and 360.00mg/l recorded at Fadikwe and Soje A respectively may be due to the presence of _Aspergillus niger.Aspergillus niger_ is a utility biological indicator of level of degradation of pollutant. These values were however higher than the Food and Agriculture organisation (FAO) standards for irrigation water. Further studies should however be carried out to investigate the bioremediating potentials of the fungi species identified in irrigation water obtained from Chanchaga.

From science to practice: The AGSUS protocol for monitoring and certification of sustainable soil management and carbon sequestration

Sustainable soil management is indispensable for achieving the UN Sustainable Development goals and soil carbon sequestration for climate change mitigation has gained importance in recent years, yet there are few examples of projects carried out to this purpose, and protocols that facilitate this task. Here we present a monitoring system that relies on sampling soils in the field, as opposed to a modeling approach. The high spatial variability of SOC was addressed by requiring that the participating farms divide their land according to management zones, based on soil type, slope position and land use history, and the sampling density was established as one sampling point per one hundred hectares, while for environments smaller than 500 ha minimum of five points must be used. These points are georeferenced and will be revisited for annual monitoring of sustainable soil management, and every five years for soil sampling for SOC, texture, bulk density, pH, electric conductivity (if indicated), and available phosphorus determinations. The monitoring of sustainable soil management will be carried out through a visual evaluation of 12 soil quality parameters, as described in the handbook published by the AGSUS group. The data obtained from the visual evaluation and the soil analyses (bulk density, particle size fractions, C content, and pH) in the baseline monitoring of Argentinean and Brazilian farms during 2022 were analyzed for the relation between visual evaluation score and the means of these soil parameters. The organic matter indicator (OMI)was calculated by the formula OMI = OM/clay plus silt*100. The data base contained visual soil evaluation scores at 80 georeferenced sampling points, representing 12 farms located in different agroecological zones of the Argentinean Pampas, and 47 sampling points on two farms in Mato Grosso, Brazil. Our results showed a relationship between the VE (Visual Evaluation) score and SOC contents of the soils, especially when these were expressed in relation to their fine mineral particles as with the OMI for the soils of the Argentinean Pampa and the Brazilian Mato Grosso. The OMI showed differences between the three VE scores ranging from 4.7 to 6.7 and from 3.1 to 5.1 in the 0–0.1 m and 0.1–0.2 m depths, respectively. Relationships between the VE score and SOC, OMI, Sand, Silt and Clay plus Silt were only found for the 39 cases of VE “moderate” score in Pampas soils, whereas for the 39 cases of “good” scores no significant relations were encountered. These soils had high SOC and OMI, indicating that they are healthy soils, near saturation level, with low C sequestration potential.

Soil Fertility Assessment and Mapping under Different Land Use Types along Toposequence at Danka Watershed in Dinsho Districts of Bale Highland Oromia, Southeastern Ethiopia

Soil fertility assessment and mapping bases, to increase fertilizer usage efficiency, decision-makers, planners, and soil management in undulating slopes farming of Ethiopian highlands like Bale Highland. The study aimed to assess and map soil fertility status along toposequence under different land use types at the Danka watershed of Dinsho District Bale Highland, Southeastern Ethiopia. Following the initial reconnaissance field survey, 54 composite soil samples were prepared from the three land use types (natural forest, grazing, and cultivated) at three slope positions lower (0 - 10%), middle (10 - 15%), and upper (15 - 30%) at a soil depth of 0 to 20 cm. Finally, the laboratory results were interpolated using the IDW interpolation technique in ArcGIS software 10.5 for the soil fertility status map and further analyzed using R software 4.1.1 Version for mean separation. The study findings indicate that the soil texture class of the study was loam to clay loam, clay loam, and clay to clay loam at the upper, middle, and lower slope positions, respectively. The finding revealed that the values varied from 5.81 – 6.66, 2.07 – 6.25%, 0.13 – 0.71%, 2.83 – 17.56 gm/kg, and 14.04 -38.80 cmol (+)/kg) for the soil pH, organic matter, total nitrogen, available phosphorus, and CEC, respectively. In this study, most of the soil fertility status of the Danka watershed was as follows: natural forest &gt; grassland &gt; cultivated land use types and lower slope &gt; middle slope &gt; upper slope positions. In conclusion, the main factors contributing to the area's declining soil fertility status were monocropping, total crop residue removal, soil erosion, nutrient leaching, and inadequate soil management. The results of the current study offer the basis for the work of farmers, planners, decision-makers, and other agriculture-related stakeholders. Integrated soil fertility management with biophysical soil conservation measures is advisable for cultivated land at all slope positions. Further, a study on slope position-based crop response fertilizer rating for agricultural precision and ensuring food security is recommended in undulating fields of the Danka watershed.

Effects of Slope Position on Soil Physicochemical Properties of Cultivated Land Use Type in Danka Watershed of Dinsho District, Bale Highland, Oromia, Southeast Ethiopia

Quantify and understand soil nutrient loss under different undulating topography farming bases for site-specific management and targeted fertilizer application rates. The study aimed to assess the effect of slope positions on soil physicochemical properties at the Danka watershed of Dinsho District Bale Highland, Southeastern Ethiopia. Consequent to the reconnaissance survey, soil samples were taken from the cultivated land use type in three replications at three different soil depths (0-0, 20-40, and 40-60 cm) and three slope positions (upper, middle, and lower), analyzed follow standard laboratory procedure and further analyzed using R software 4.1.1 version. The results showed soil physicochemical properties were significantly (P ≤ 0.05) influenced by the interaction between slope positions and soil depth. The results of soil physical properties varied from 1.29 -1.73 g cm-3, 2.47 – 2.74 g cm-3, 47.80 - 36.75%, 10.78 – 15.11%, 12.76 – 18.16%, and 4.06 – 8.16% bulk density, particle density, total porosity, FC, PWP, and AWHC, respectively. Selected soil chemical properties varied from 5.91 - 6.45, 0.64 - 3.20%, 0.04 - 0.25%, 1.14 - 5.60 gm/kg, and 10.24 - 37.24 cmol (+)/kg) soil pH, organic matter, total nitrogen, available phosphorus, and CEC, respectively. The values of exchangeable bases were concentration increased from the upper slope position toward the lower slope position and with increased soil depth. Soil micronutrients were increased with increased slope and decreased with increased soil depth. The lowest slope position had relatively better soil nutrient contents than other slope positions. It is advised that integrated soil fertility management, biophysical soil and water conservation, and slope-based, site-specific fertilizer rating for advance agricultural precision and ensure food security.

Performance of Cocoa Fruit (Theobroma cacao L.) at Different Slope Positions in a Wet Tropical Climate

Performance of Cocoa Fruit (Theobroma cacao L.) at Different Slope Positions in a Wet Tropical Climate

Soil water percolation and nutrient fluxes as a function of topographical, seasonal and soil texture variation in Central Amazonia, Brazil

AbstractUnderstanding soil water dynamics and transport of nutrients is challenging in tropical rainforests due to the uniqueness of several properties related to soils, vegetation and seasonality that make relating patterns found in temperate environments to tropical sites difficult. We address the need for better edaphic characterization in tropical environments by investigating soil water percolation rates and chemistry across topographic, soil texture and seasonal gradients in a mature tropical rainforest in Central Amazonia, Brazil. We utilized a passive wick flux meter (e.g., drainage lysimeter) to directly measure real‐time percolation fluxes at 60‐cm depth, and to sample a suite of chemical species across plateau, slope and valley topographic positions. We found percolation flux volume and chemical exports generally increase with decreasing elevation and clay content, which was lowest in the valley. Daily percolation flux was observed to be 2.39 ± 0.44 in plateau, 3.01 ± 0.50 in slope and 6.16 ± 0.83 mm in valley. Most solutes were present in small amounts of &lt;1 mg L−1, such as PO₄3−, Fe2+/Fe3+ and Mn2+; however, NO3− concentrations were &gt;20 mg L−1, even exceeding 100 mg L−1 in the valley. Based on additional isotopic analysis, we speculate high NO3− concentrations are partially an artefact of root decomposition following installation of the flux meters. The empirical relationships we show among percolation volume and nutrient exports under varying topographies and soil textures can improve Earth System Model performance by better constraining ecohydrological relationships to nutrient fluxes, which can in‐turn better illuminate the important factors that govern their behaviour.

Effects of conventional soil and water conservation measures on soil moisture of sloping land in the loess region

ABSTRACT Traditional soil conservation measures were widely recognized for their excellent ability to promote rainwater infiltration in the loess region. However, little is known about how these measures affect the soil moisture variations under natural rainfall conditions. To compare their effects on soil water content, four different treatments were conducted at runoff plots, i.e., super absorbent polymer amendment (SCR), ridge–furrow rainwater harvesting with plastic mulching (CRP), the same measure with CRP but without mulching (CRN), and flat planting (FSN, control), soil moisture at multiple slope positions and depths were periodically measured. The results showed that in the top 0- to 30-cm soil, SCR and CRN relatively greatly varied with time, yet CRP and FSN changed less. The mean soil water content of these treatments generally followed the pattern of CRN &amp;gt; SCR &amp;gt; CRP &amp;gt; FSN. Responding to a heavy rainfall event, the recharge and depletion rates of soil water storage generally showed similar patterns of SCR &amp;gt; CRN &amp;gt; CRP &amp;gt; FSN in the topsoil, yet in the deeper soil they followed the patterns of CRP &amp;gt; CRN &amp;gt; FSN &amp;gt; SCR. It suggested that SCR and CRN could improve the water accumulation and infiltration performances in the topsoil, and thus may be more suitable for rain-fed crop planting on sloping farmlands of the loess region.

Plant survival and growth in bioretention cells under a cold climate

Urbanization coupled with climate change results in significant stormwater management challenges. In this context, the use of green infrastructures such as bioswales and bioretention systems to intercept, slow down and filter runoff has been increasing in North America in recent years. However, little data is available on the selection of optimal plant species adapted to cold climates, their optimal positioning in the swale and intra and inter-seasonal variation in plant growth. A field experiment was conducted during three growing seasons from July 2020 to August 2022 in a proximal suburb of Québec City, Canada, to monitor the survival rate. Growth (height and plant area), and floridity (number of flower buds and flower stems) of 22 plant species in 48 cold climate bioretention cells located along streets. The study aimed to understand the influence of planting position (margin: upper position, usually dryer; slope; middle position, fluctuating water conditions; bottom: lower position, usually moister) on species development, in order to identify the species most and least adapted to the different moisture conditions. Results showed that survival was generally high (> 86%) and was not affected by position within the bioretention cells. However, for most species, plant area increased, and height decreased at the margin compared to the slope position, while floridity only increased at the margin for four species (Heliopsis helianthoides (L.) Sweet, Coreopsis verticillata L., Hemerocallis ‘Stella Supreme” L., Verbena hastata L.). Seven species (Campanula carpatica Jacq “Alba”, Hesperis matronalis L., Osmundastrum cinnamomeum (L.) C. Presl, Rudbeckia hirta L., Verbena hastata L., Cerastium tomentosum L., Athyrium filix-femina (L.) Roth ex Mertens) exhibited lower survival and growth rates over time than the others. Overall, 15 out of 22 species performed well in the bioretention cells with minimum maintenance over the course of the experiment. Results also showed that plant area at the end of the growing season was much more influenced by position in the bioretention cells than were height or floridity, while survival was not influenced by this factor. A better knowledge of plant interactions in varying spatial distribution over time can contribute to improving and potentially maximizing bioretention performance.

Accuracy and sensitivity of soil erosion estimation using 137Cs technology: A statistical perspective

Random spatial variation of the 137Cs inventory is the principal contributor to uncertainty in soil erosion estimation using 137Cs technology. A statistically sound sampling design is imperative for obtaining reliable soil erosion estimations. The objectives of this study are to: 1) characterize the effect of sample size on the estimates of mean inventories; 2) evaluate the sensitivity of the estimated soil redistribution to sample size using a new 137Cs model; 3) compare erosion detection limits among five conversion models; and 4) assess three spatial interpolation methods. Two small watersheds were sampled in an irregular grid design, and 30 samples were taken on a reference site. A moving window scheme was used to compute the 7-point and 11-point means of 137Cs inventories. The Welch’s modified t-test was used to test the mean estimates and to compute the detection limits for the replicated samples. Five models were selected to convert 137Cs inventories to soil redistribution rates. Since most single samples without replication yielded insignificant test results, the 137Cs technique cannot be used to estimate soil erosion at a single point due to random spatial variation. With 30 reference samples, 7 replicate samples on the sampling site provided reliable estimations of 137Cs inventories and soil redistribution. The spatial patterns of the estimated 137Cs inventories and soil redistribution became more regular and systematic as sample size increased, which agreed increasingly well with topography and surface hydrology. Replicate samples can be taken from each landform element or slope position where the erosion rate is expected to be uniform. Alternatively, a systematic grid sampling scheme can be used, and the nearest neighbors can be treated as replicates to calculate moving averages. The Type I and II errors with replicated samples showed that all sampling positions should be included in calculating watershed or area mean erosion rates even though the Type I errors indicated insignificant redistribution rates for some samples. Due to the lack of spatial autocorrelation, spline and inverse distance weighting methods performed better than kriging for interpolation. Detection limits and magnitudes of soil redistribution varied substantially with conversion models, depending on their sensitivities to changes in 137Cs inventories.

Arbuscular mycorrhizal fungal interactions bridge the support of root-associated microbiota for slope multifunctionality in an erosion-prone ecosystem.

The role of diverse soil microbiota in restoring erosion-induced degraded lands is well recognized. Yet, the facilitative interactions among symbiotic arbuscular mycorrhizal (AM) fungi, rhizobia, and heterotrophic bacteria, which underpin multiple functions in eroded ecosystems, remain unclear. Here, we utilized quantitative microbiota profiling and ecological network analyses to explore the interplay between the diversity and biotic associations of root-associated microbiota and multifunctionality across an eroded slope of a Robinia pseudoacacia plantation on the Loess Plateau. We found explicit variations in slope multifunctionality across different slope positions, associated with shifts in limiting resources, including soil phosphorus (P) and moisture. To cope with P limitation, AM fungi were recruited by R. pseudoacacia, assuming pivotal roles as keystones and connectors within cross-kingdom networks. Furthermore, AM fungi facilitated the assembly and composition of bacterial and rhizobial communities, collectively driving slope multifunctionality. The symbiotic association among R. pseudoacacia, AM fungi, and rhizobia promoted slope multifunctionality through enhanced decomposition of recalcitrant compounds, improved P mineralization potential, and optimized microbial metabolism. Overall, our findings highlight the crucial role of AM fungal-centered microbiota associated with R. pseudoacacia in functional delivery within eroded landscapes, providing valuable insights for the sustainable restoration of degraded ecosystems in erosion-prone regions.

Characteristics of spatial and temporal variability in the distribution of biological soil crusts on the Loess Plateau, China.

Biological soil crust (biocrust) is widely distributed on the Loess Plateau and plays multiple roles in regulating ecosystem stability and multifunctionality. Few reports are available on the distribution characteristics of biocrust in this region, which limits the assessment of its ecological functions. Based on 388 sampling points in different precipitation zones on the Loess Plateau from 2009 to 2020, we analyzed the coverage, composition, and influencing factors of biocrust across different durations since land abandonment, precipitation levels, topography (slope aspect and position), and utilization of abandoned slopelands (shrubland, forest, and grassland). On this base, with the assistance of machine learning and spatial modeling methods, we generated a distribution map of biocrust and its composition at a resolution of 250 m × 250 m, and analyzed the spatial distribution of biocrust on the Loess Plateau. The results showed that the average biocrust coverage in the woodlands and grasslands was 47.3%, of which cyanobacterial crust accounted for 25.5%, moss crust 19.7%, and lichen crust 2.1%. There were significant temporal and spatial variations. Temporally, the coverage of biocrust in specific regions fluctuated with the extension of the abandoned durations and coverage of cyanobacterial crust, while moss crust showed a reverse pattern. In addition, the coverage of biocrust in the wet season was slightly higher than that in the dry season within a year. Spatially, the coverage of biocrusts on the sandy lands area on the Loess Plateau was higher and dominated by cyanobacterial crusts, while the coverage was lower in the hilly and gully area. Precipitation and utilization of abandoned land were the major factors driving biocrust coverage and composition, while slope direction and position did not show obvious effect. In addition, soil organic carbon content, pH, and texture were related to the distribution of biocrust. This study uncovered the spatial and temporal variability of biocrust distribution, which might provide important data support for the research and management of biocrust in the Loess Plateau region.

Characterization Of Soils Derived From Sandstone In Effraya - Etung Local Government Area Of Cross River State, Nigeria

Pedological characterization of soils derived from sandstone in Effraya - Etung Local Government Area of Cross River State, Nigeria was studied with the view to suggesting appropriate management strategies. Three representative profile pits were dug in the summit, middle slope and valley bottom positions and the location of each profile was recorded with the aid of German Etrax 2000 GPS meter. The profile pits were described according to Soil Survey Staff. The soils were well drained in the summit and middle slope to poorly drained at the valley bottom and the soil color varied from very dark grayish brown to dark brown and also from yellowish brown to dark yellowish brown within the different horizons. Mean values of 65%, 23% and 12% were obtained in the surface soils for sand, silt and clay respectively while the textural class ranged from loamy sand to sandy loam in the surface and predominantly sandy clay loam in the subsurface soils. Bulk density and particle density had mean values of 1.2g/cm3 and 2.45g/cm3 with total porosity mean value of 48.5% for surface soils respectively. The strongly acidic soils were low in total nitrogen, organic carbon, available phosphorus, and exchangeable bases. CEC in the soils was moderately high with low ECEC while base saturation was below 50%. These results show that the soils are low in fertility and thus will require management practices such as liming, mulching, return of crop residues, and also planting of acid tolerant crops may be recommended for improved crop production.&#x0D; &#x0D;

Age of Soil and Water Conservation Practices on Selected Soil Properties along the Toposequence of Gerado Watershed, Habru District, Eastern Amhara, Ethiopia

The government of Ethiopia through community participation has widely implemented soil and water conservation (SWC) measures, especially in the highlands of Ethiopia. However, the effects of these practices on the physicochemical properties of soils have not been well assessed and documented in the study area. Thus, this experiment was conducted to evaluate the effects of SWC practice on selected soil physicochemical properties. Treatments were nonconserved land, 3- and 9-year-old soil conservation practices under three slope positions, namely, lower slope (0–8%), middle slope (9–15%), and upper slope (&gt;15%) positions, and at two soil depths (0–20 and 20–40 cm) with three replications. Accordingly, 54 composite soil samples were collected and analyzed based on standard procedures. The results showed that the age of soil and water conservation practice, topography, and soil depths significantly affected most of the soil properties. Conserving the watershed for nine years improved the subsoil clay content from 37.1 to 46.3%, subsoil soil moisture content from 13.38 to 24.61%, surface total nitrogen content from 18.1 to 81%, available phosphorus content from 13.1 to 33.5 mg kg−1, surface organic carbon from 0.28 to 2.83%, soil carbon stock from 9.26 to 35.59 t ha−1, and surface cation exchange capacity from 21.5 to 57.4 Cmolec kg−1. Therefore, maintaining soil and water conservation practices for long periods can improve soil properties. However, planting different grasses, with the existing physical structures is needed to increase soil nutrient and carbon stock.

Spatial stratified heterogeneity analysis of field scale permafrost in Northeast China based on optimal parameters-based geographical detector.

Affected by global warming, the permafrost in Northeast China (NEC) has been continuously degrading in recent years. Many researchers have focused on the spatial and temporal distribution characteristics of permafrost in NEC, however, few studies have delved into the field scale. In this study, based on the Optimal Parameters-based Geographical Detector (OPGD) model and Receiver Operating Characteristic (ROC) test, the spatial stratified heterogeneity of permafrost distribution and the indicating performance of environmental variables on permafrost in NEC at the field scale were analyzed. Permafrost spatial distribution data were obtained from the Engineering Geological Investigation Reports (EGIR) of six highways located in NEC and a total of 19 environmental variables related to heat transfer, vegetation, soil, topography, moisture, and ecology were selected. The H-factors (variables with the highest contribution in factor detector results and interaction detector results): slope position (γ), surface frost number (SFN), elevation (DEM), topographic diversity (TD), and annual snow cover days (ASCD) were found to be the major contributors to the distribution of permafrost at the field scale. Among them, γ has the highest contribution and is a special explanatory variable for permafrost. In most cases, interaction can improve the impact of variables, especially the interaction between H-factors. The risk of permafrost decreases with the increase of TD, RN, and SBD, and increases with the increase of SFN. The performance of SFN to indicate permafrost distribution was found to be the best among all variables (AUC = 0.7063). There is spatial heterogeneity in the distribution of permafrost on highways in different spatial locations. This study summarized the numerical and spatial location between permafrost and different environmental variables at the field scale, and many results were found to be informative for environmental studies and engineering construction in NEC.

Toposequence effect on soil properties and suitability rating for selected crops in Northern Guinea Savanna, Nigeria

A toposequence at Giwa, Kaduna State was studied with the aim of assessing the effect of topography on soil properties and suitability ratings for rainfed rice, cowpea, and tomato. Three slope positions namely, lower slope (LS), middle slope (MS) and upper slope (US) were delineated, and their properties were assessed. Results indicated that soils on all locations were very deep (167 – 192 cm) with occurrence of plinthite at subsurface of MS and US. Slope position of the soils was noted to influence morphological, physical and chemical properties. Content of silt and sand fractions, available water content and moisture retention at field capacity were all significantly influenced by slope. Melanization, braunification, plinthization and argilluviation were some pedogenetic process notable in the soils. Suitability studies revealed that 29.12% of the area was moderately suitable (S2) for rice cultivation with limitations of climate, soil physical property and fertility, while 70.88% of the area were marginally suitable (S3), with an additional limitation in wetness. For cowpea, 68.13% of the soils were S2 with limitations in fertility, while MS was highly suitable (S1). Tomato was rated S2 for the entire area with general limitations in climate and fertility. Suitability for rice increased down the slope from US, while that of cowpea and tomato increased along the slope from LS to US. This effect was attributed to distribution of nutrient and water, as preconditioned by topography. Management practice suggests the use of LS for rice, while MS and US may be rotated for cultivating tomato and cowpea.

Identification, Prioritization and Mapping of Major Constraints and Potentials in the Medo Watershed the Case of West Arsi District in Central Rift Valley Area of Ethiopia

The concentration to characterize the biophysical and socio-economic features in the integrated watersheds is to identify and prioritize production constraints for designing appropriate research and development interventions. The objective of this study was to assess the current biophysical of characteristics of Medo watershed, West Arsi Zone of Oromia, Ethiopia. To do so relevant data and tools were used; ArcGIS, Microsoft Excel sheet and fundamental formulae were applied for the analysis are some. The results of the study indicated that the major land use types in the watershed are agricultural land covering 50%, vegetation (shrubs, forests and, plantations) covering 24% and settlement covering 16% out of the total land use. Slope gradient of Medo watershed ranges from zero to more than 20 and the slope gradient of 2-5 and 5-10 cover the greatest in area coverage representing 201 ha and 170 ha respectively. We can also observe that about 8% out of the total area is subjected to severe erosion. Sandy clay loam was the dominant soil textural classes in the surface soils and Phaeozems, Retinols and Andosols are the dominant soil types, which cover 57%, 36% and 7% of the sub-watershed area for lower, middle, and upper slope positions, respectively. Mean annual rainfall of the area ranges from 960.09 mm at lower part of the watershed to the 1304.93 mm at upper part of the watershed. Accordingly, Medo sub-watershed is laid in majority of at sub humid agro ecological zone. An assessment of the trees within the landscape of watershed showed some remnant natural forests and a wide variety of shrubby vegetation is encountered at all landscapes. About 40 percent of the watershed, is under high to extremely severe soil loss values (&gt;45 ton per hectare per year). The baseline study also identified that those natural resources degradation such as land, and or/ soil fertility, reduction, and recent changes in the areas’ weather condition in line of climate change prevailing in current years are few of the many factors that are contributing to the land and crop productivity reductions in the area. Therefore, prioritizing the identified problem and preparing intervention of different technologies and development plans to solve the problems by taking into consideration the existing opportunities of the watershed.