Drainage Class Research Articles

Influence of site and soil properties on the DRIFT spectra of northern cold-region soils

We investigated the influence of site characteristics and soil properties on the chemical composition of organic matter in soils collected from a latitudinal transect across northern cold-region through analysis of diffuse reflectance Fourier transform mid infrared (DRIFT) spectra of bulk soils. The study included 119 soil samples collected from 28 sites including tundra, boreal forest, grassland, and coastal rainforest ecosystems. Organic, mineral, and cryoturbated soil horizons, both seasonally and perennially frozen, representing a variety of depths and edaphic conditions were examined. The amount and chemical composition of organic matter, as well as site and soil properties, exerted a strong influence on the DRIFT spectra. The spectra were highly sensitive to the extent of organic matter decomposition, enabling the ordination of organic (Oi, Oe and Oa) horizons. Differences in absorbance intensity for several spectral bands indicated that Oi horizons contained greater abundance of relatively fresh residues, phenolic-OH compounds, aliphatic compounds, and carbohydrates. In contrast, Oa horizons had a greater presence of amide groups, aromatics, CC bonds, carboxylates and carboxylic acids. Another significant factor differentiating these horizons was the incorporation of clays and silicates into the Oa horizons. Calculated ratios of characteristic spectral bands showed a clear trend of increasing decomposition from Oi to Oe to Oa. The DRIFT spectra were related to many site/soil attributes including land cover type, parent material, and associated factors, such as permafrost presence/absence, drainage class, horizon depth, bulk density, cation exchange capacity, and pH. A single DRIFT spectral band was identified that might be used in future studies to quickly estimate the organic carbon, total nitrogen, and carbon:nitrogen ratios of northern soils. Our results demonstrate that the information contained in DRIFT spectra of soil integrates the quantity and chemical composition of soil organic matter with soil properties and highlights the potential for using this information to assess the degradation state of organic matter stored in northern cold-region soils.

Soil protection for a sustainable future: options for a soil monitoring network for Ireland

AbstractThe increased recognition of the importance of soil is reflected in the UN Post‐2015 Development Agenda with sustainable development goals that directly and indirectly relate to soil quality and protection. Despite a lack of legally binding legislation for soil protection, the European Commission remains committed to the objective of soil protection. However, the achievement of a legally binding framework for soil protection relies on the implementation of a soil monitoring network (SMN) that can detect changes to soil quality over time. As beneficiaries do not pay for the provision of soil information, the options for soil monitoring are limited. The use of existing data sets should be considered first. Using Ireland as an example, this research explored the opportunities for a SMN for Ireland considering three existing national data sets. The options for a SMN are considered in terms of their spatial and stratified distribution, the parameters to be measured and an economic analysis of the options proposed. This research finds that for Ireland, either a 10 or a 16 km2 grid interval stratified by land use and drainage class offers the best potential in relation to the spatial distribution of existing data sets to reflect local data at a national level. With existing data, the stratified SIS data using the 16 km2 grid offers the best value for money, with baseline costs for analysis, excluding field costs, of between €706 481 and €2.8 million. Acknowledging the impossibility of measuring all parameters with ideal frequency, this study proposes a two‐tier system for optimized monitoring frequency. Parameters must anticipate future policy requirements. Finally, the implementation of a SMN must be accompanied by standardized methods, defined thresholds and action mandates to maintain soil quality within allowable limits.

Physiographic factors underlie rates of biomass production during succession in Great Lakes forest landscapes

Biomass production in living trees is the basis of numerous forest ecosystem functions and services. However, rates of and controls on biomass production vary widely across temperate forests, particularly over successional timescales of decades and centuries. Biomass production in temperate forests is most often interpreted within the context of biotic or top-down controls, such as species composition or disturbance. However, there is need to investigate how bottom-up physiographic factors, such as landform attributes, drainage, and soil properties mediate biomass production. In order to investigate patterns, controls, and potentials for biomass production across spatial levels ranging from individual ecosystems, to landscapes, to entire regions, we synthesized long-term forest inventory datasets from the United States Great Lakes region, placed them in the context of a hierarchical ecological unit classification, and tested the influence of physiographic factors on biomass production rates and temporal trajectories across ecological levels. Key findings include: 1) At nearly all ecological levels, physiographic controls (e.g., soil texture, drainage class, water table depth) on soil moisture status are significant predictors of variation in biomass production rates, with mesic sites accumulating biomass more rapidly than xeric sites, which, in turn accumulate biomass more rapidly than hydric sites. 2) Aboveground live biomass can apparently continue to accumulate through 2–3 centuries of succession, exceeding 300–400Mgha−1 on mesic sites throughout the region. 3) Stand age distributions indicate that hydric sites are harvested least often, while the high production rates of mesic sites suggest they are most appropriate for frequent harvesting. 4) Median, 1st-quartile, and 3rd-quartile growth rates of individual ecosystems, landscapes, and ecoregional subsections and sections reveal ecological units in which forests may vary in their potential for increases or decreases in biomass production, e.g., due to management interventions, climate change, or disturbances. Specifically, some units have tightly constrained distributions, suggesting little capacity for change in production rates relative to observed medians, while other units have wide variation in biomass production rates, indicating the potential for relatively large increases or decreases in production. Altogether, the results of this analysis show that physiography exerts widespread, bottom-up controls on biomass production across the region of study, and can be used in spatially explicit frameworks to understand ecosystem functioning and inform scientific forest management.

Denitrification potential in the subsurface environment in the Manawatu River catchment, New Zealand: Indications from oxidation-reduction conditions, hydrogeological factors, and implications for nutrient management

A sound understanding of the effects of hydrogeological factors on loss, transport and transformation of farm nutrients is essential for predicting their impacts on ecosystem health of receiving waters. We assessed the potential of groundwater to attenuate nitrate through denitrification, and the distribution of this potential across the Tararua Groundwater Management Zone (GWMZ) in the Manawatu River catchment, New Zealand. We combined a number of methods in an unprecedented manner to confirm findings and obtain supporting evidence for the features that determine the subsurface denitrification characteristics. Our results showed that the denitrification characteristics of groundwater varied considerably in the Tararua GWMZ. The southern part of the Tararua GWMZ contained mainly oxic groundwater with low potential to denitrify, whereas the middle and northern parts of the Tararua GWMZ contained reduced groundwater with high denitrification potential. The hydrogeological features that influence denitrification potential in groundwater were identified as soil texture and drainage class, and the aquifer material or rock type. Low dissolved oxygen levels and nitrate concentrations were found in groundwater where the combinations of soil and rock types had poor drainage characteristics as opposed to higher concentrations in groundwater under well-drained soils and rocks (e.g. gravels). Intensive pastoral farming over well-drained soils and rocks showed high nitrate concentration in groundwater. This spatial variability in denitrification potential of groundwater offers a targeted management of nutrients runoff and leaching from pastoral lands to reduce their impacts on receiving surface waters.

Pyrogenic carbon distribution in mineral topsoils of the northeastern United States

Due to its slow turnover rates in soil, pyrogenic carbon (PyC) is considered an important C pool and relevant to climate change processes. Therefore, the amounts of soil PyC were compared to environmental covariates over an area of 327,757km2 in the northeastern United States in order to understand the controls on PyC distribution over large areas. Topsoil (defined as the soil A horizon, after removal of any organic horizons) samples were collected at 165 field sites in a generalised random tessellation stratified design that corresponded to approximately 1 site per 1600km2 and PyC was estimated from diffuse reflectance mid-infrared spectroscopy measurements using a partial least-squares regression analysis in conjunction with a large database of PyC measurements based on a solid-state 13C nuclear magnetic resonance spectroscopy technique. Three spatial models were applied to the data in order to relate critical environmental covariates to the changes in spatial density of PyC over the landscape. Regional mean density estimates of PyC were 11.0gkg−1 (0.84Ggkm−2) for Ordinary Kriging, 25.8gkg−1 (12.2Ggkm−2) for Multivariate Linear Regression, and 26.1gkg−1 (12.4Ggkm−2) for Bayesian Regression Kriging. Akaike Information Criterion (AIC) indicated that the Multivariate Linear Regression model performed best (AIC=842.6; n=165) compared to Ordinary Kriging (AIC=982.4) and Bayesian Regression Kriging (AIC=979.2). Soil PyC concentrations correlated well with total soil sulphur (P<0.001; n=165), plant tissue lignin (P=0.003), and drainage class (P=0.008). This suggests the opportunity of including related environmental parameters in the spatial assessment of PyC in soils. Better estimates of the contribution of PyC to the global carbon cycle will thus also require more accurate assessments of these covariates.

Soil type, soil slope and topsoil depth relationships on a Co. Cavan Drumlin

The soils of a 100 ac (40 ha) drumlin in Co. Cavan were accurately mapped with respect to soil type, soil slope and topsoil depth. The results show that at least 5 contrasting soil Orders/Great Groups occur in close proximity to one another and that representatives of nearly all conventional units of soil slope and soil drainage classes were encountered. The relationships between soil type, soil slope and topsoil depth are discussed and the problem of showing intricate soil patterns on published maps is highlighted.

Underestimation of boreal forest soil carbon stocks related to soil classification and drainage

Soil organic carbon (C), accumulated over millennia, comprise more than half of the C stored in boreal and temperate forest landscapes. We used the Norwegian national forest inventory and soil survey network (n = 719, no deep organic soils) to explore the validity of a deterministic model representation of this pool (Yasso07). We statistically compared simulated and measured soil C stocks and related differences (measured – simulated) to site factors (drainage, topography, climate, vegetation, C-to-N ratio, and soil classification). Median C stocks were 5.0 kg C·m−2 (model) and 14.5 kg C·m−2 (measurements). Soil C differences related to site factors (r2 of 0.16 to 0.37). For Brunisols, Gleysols, and wet Organic soils, differences related primarily to topographic wetness. For Regosols, Podzols, and Dystric Eluviated Brunisols, they related to climate, profile depth, and, in some cases, drainage class and site index. We argue that soil moisture regimes in our study area overrule tree productivity effects in the determination of soil C stocks and present conditions for soil formation that the model cannot (and does not explicitly) account for. These are processes such as humification and podsolization that involve eluviation and illuviation of dissolved organic C (DOC) with sesquioxides to form spodic B horizons and carbon enrichment due to hampered decomposition in frequently anoxic conditions.

Impacts of water regime and land-use on soil CO2 efflux in a small temperate agricultural catchment

Within the context of climate change, it is necessary to improve our mechanistic understanding of processes that release CO2 to the atmosphere. This study was designed to investigate spatial variation of soil CO2 efflux (FCO2) at the landscape (catchment) scale, which has received less attention so far in comparison to more homogeneous, smaller areas. More specifically, this study investigated the impacts of water regime, land-use and crop rotation on FCO2 in a small temperate agricultural catchment. FCO2 was measured manually with closed dynamic chambers over a 1 year period (36 weekly to bi-weekly measurement dates) at 22 sites that were selected to represent most of the diversity of drainage classes, soil types and land-uses in a small catchment in North-Western France. FCO2 was modelled empirically at each site as a function of soil temperature and soil water content. As a secondary step, impacts of water regime, land-use and crop rotation on heterotrophic respiration (HR) were also sought, with HR being estimated empirically as a fraction of FCO2 on the basis of partitioning coefficients taken from the literature. Results showed that water regime, land-use and crop rotation all had significant impacts on FCO2 on an annual scale. Poorly-drained sites emitted less CO2 than well-drained and moderately-well drained sites, which could be explained by reduced soil CO2 production and/or limitations in soil transport in more saturated environments. In addition, larger annual FCO2 were measured on grasslands compared to croplands (wheat and maize crops), which is likely due to the presence of larger amounts of available soil carbon and nutrients and to the presence or denser rooting systems. Due to the literature-based determination of partitioning coefficients, the results related to HR estimates were affected by more uncertainties than those related to FCO2 but they showed that the water regime tended to impact them similarly as FCO2, while HR was likely less affected by land-use. Altogether, the results of this study, performed at scale of a small agricultural temperate catchment, confirm that specific patterns of FCO2 result from varying soil CO2 production and transport processes, resulting from complex interactions between soil environment characteristics (soil carbon content, water regime,…) and land-use/crop rotations.

Landscape Effects of Wildfire on Permafrost Distribution in Interior Alaska Derived from Remote Sensing

Climate change coupled with an intensifying wildfire regime is becoming an important driver of permafrost loss and ecosystem change in the northern boreal forest. There is a growing need to understand the effects of fire on the spatial distribution of permafrost and its associated ecological consequences. We focus on the effects of fire a decade after disturbance in a rocky upland landscape in the interior Alaskan boreal forest. Our main objectives were to (1) map near-surface permafrost distribution and drainage classes and (2) analyze the controls over landscape-scale patterns of post-fire permafrost degradation. Relationships among remote sensing variables and field-based data on soil properties (temperature, moisture, organic layer thickness) and vegetation (plant community composition) were analyzed using correlation, regression, and ordination analyses. The remote sensing data we considered included spectral indices from optical datasets (Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and Landsat 8 Operational Land Imager (OLI)), the principal components of a time series of radar backscatter (Advanced Land Observing Satellite—Phased Array type L-band Synthetic Aperture Radar (ALOS-PALSAR)), and topographic variables from a Light Detection and Ranging (LiDAR)-derived digital elevation model (DEM). We found strong empirical relationships between the normalized difference infrared index (NDII) and post-fire vegetation, soil moisture, and soil temperature, enabling us to indirectly map permafrost status and drainage class using regression-based models. The thickness of the insulating surface organic layer after fire, a measure of burn severity, was an important control over the extent of permafrost degradation. According to our classifications, 90% of the area considered to have experienced high severity burn (using the difference normalized burn ratio (dNBR)) lacked permafrost after fire. Permafrost thaw, in turn, likely increased drainage and resulted in drier surface soils. Burn severity also influenced plant community composition, which was tightly linked to soil temperature and moisture. Overall, interactions between burn severity, topography, and vegetation appear to control the distribution of near-surface permafrost and associated drainage conditions after disturbance.

Investigation of the relationship between landform classes and electrical conductivity (EC) of water and soil using a fuzzy model in a GIS environment

Abstract. Soil genesis is highly dependent on landforms as they control the erosional processes and the soil physical and chemical properties. The relationship between landform classification and electrical conductivity (EC) of soil and water in the northern part of Meharloo watershed, Fars province, Iran, was investigated using a combination of a geographical information system (GIS) and a fuzzy model. The results of the fuzzy method for water EC showed 36.6 % of the land to be moderately land suitable for agriculture; high, 31.69 %; and very high, 31.65 %. In comparison, the results of the fuzzy method for soil EC showed 24.31 % of the land to be as not suitable for agriculture (low class); moderate, 11.78 %; high, 25.74 %; and very high, 38.16 %. In total, the land suitable for agriculture with low EC is located in the north and northeast of the study area. The relationship between landform and EC shows that EC of water is high for the valley classes, while the EC of soil is high in the upland drainage class. In addition, the lowest EC levels for soil and water are in the plains class.

Interspecific Differences of the Capacities on Excessive Soil Moisture Stress for Upland Crops in Converted Paddy Field

The interspecific estimation for tolerance capacities of upland crop species to excessive soil water stress in paddy field is significant in agricultural practices. Most of upland crops can be damaged by either excessive soil water or capillary rise of the water table during rainy season in paddy fields. The major objective of this study was to evaluate water stress of upland crops under different drainage classes in converted paddy field. This experiment was carried out in poorly drained soil (PDS) and imperfectly drained soil (IDS) of alluvial sloping area located at Toero-ri, Bubuk-myeon, Miryang-si, Gyeongsangnam-do. The soil was Gagog series, which was a member of the fine silty, mixed, nonacid, mesic family of Aeric Endoaquepts (Low Humic-Gley soils). Two drainage methods, namely under Open ditch drainage methods (ODM) and, Closed pipe drainage methods (PDM) were installed within 1-m position at the lower edge of the upper paddy fields. The results showed that sum of excess water days (SWD30), which was used to represent the moisture stress index, was 42 days (the lowest) in the PDM compared with 110 days in the ODM. Most of upland crops were more susceptible to excessive soil water during panicle initial stage on more PDS than on IDS. Yield of upland crops in the PDM was continuously increased by the rate of 15.1% on sorghum, 15.4% foxtail millet, 53.6% proso millet, 49.6% soybean and 47.9% adzuki bean as compared in the ODM. The capacity for tolerance by excessive soil water based on yield of each upland crop in the poorly drained sloping paddy fields was the order of sorghum, soybean, foxtail millet, proso millet and adzuki bean. Therefore, Sorghum is relatively tolerant to excessive soil water conditions and, may be grown successfully in converted paddy field.

Linking the Depth-to-Water Topographic Index to Soil Moisture on Boreal Forest Sites in Alberta

The depth-to-water (DTW) index is defined as the cumulative slope along the least-cost pathway from any cell in the landscape to the nearest flow channel. The flow channel network is determined by the flow initiation area selected, allowing the representation of various geological and topographical attributes of the landscape. We used data from 125 plots across five locations in the boreal forest of Alberta, Canada, to evaluate the following: the relationships between soil attributes and DTW; the optimal flow initiation area; and models to map the spatial variation of soil properties. Soil moisture regime (SMR), drainage class, and depth-to-mottles were strongly related with DTW, whereas soil nutrient regime, organic matter thickness, soil texture, and coarse fragment content exhibited weak and inconsistent relationships with DTW. A flow initiation area of 2 ha yielded the best representation for SMR, drainage class, and depth-to-mottles. DTW, flow accumulation (FA) and local slope were combined in a linear model to estimate and map SMR, whereas only DTW and FA were used to model drainage and depth-to-mottles. These results suggest that the DTW index can capture soil properties closely influenced by the water table but cannot characterize site and soil factors, which are also determined by parent material, climate, and vegetation.

Harmonized soil property values for broad-scale modelling (WISE30sec) with estimates of global soil carbon stocks

Soils play a key role in providing a range of ecosystem services. Quality-assessed soil information, with quantified uncertainty levels, is needed to address a range of global issues. Traditional mapping methods, which recognize that soil classes are “important carriers of soil information”, were used to prepare an updated harmonized dataset of derived soil properties for the world at a nominal resolution of 30 by 30arc sec (WISE30sec). The map unit composition was determined using an overlay of the Harmonized World Soil Database, with minor corrections, and the Köppen–Geiger climate zones map as categorical co-variate. Property estimates for the respective component soil units were derived using taxonomy-based transfer rules that draw on a statistical analysis of some 21,000 soil profiles. Best estimates (mean±standard deviation) for twenty soil properties were calculated for seven depth intervals (up to 2m depth or less when thinner): organic carbon content, total nitrogen, C/N ratio, pH(H2O), CECsoil, CECclay, effective CEC, total exchangeable bases (TEB), base saturation, aluminium saturation, calcium carbonate content, gypsum content, exchangeable sodium percentage (ESP), electrical conductivity, particle size distribution (content of sand, silt and clay), proportion of coarse fragments (>2mm), bulk density, and available water capacity (−33 to −1500kPa); also the dominant soil drainage class. Coefficients of variation tend to be large. WISE30sec may be used for applications at a broad scale (<1:1M) upon consideration of the underlying data lineage, generalizations, and the associated uncertainties. As an example, the database was used to calculate the global soil organic carbon (SOC) stock to 2m depth. Some 30% (607±87PgC) of this stock (2060±215PgC) is held in the Northern Circumpolar Region, which is considered most sensitive to climate change.

Factors influencing organic-horizon carbon pools in mixed-species stands of central Maine, USA

The overall goal of this study was to evaluate the correlation of multiple abiotic and biotic factors with organic-horizon (O-horizon) carbon (C) content on the Penobscot Experimental Forest in central Maine, USA. O-horizon samples were collected and their associated depths were recorded from stands managed with a range of silvicultural and harvesting treatments (i.e., selection, shelterwood, and commercial clearcut) and an unmanaged control. The overall mean for O-horizon C content from all samples was 25.6±16.1Mgha−1 (mean±SD). The samples were used to develop a pedotransfer function for predicting O-horizon C content from O-horizon depth (R2=0.47, RMSE=1.6Mgha−1) so that an average of O-horizon C content could be calculated for permanent sample plots on which abiotic and biotic factors were quantified. O-horizon depth measurements recorded along transects on permanent sample plots were used to calculate plot average O-horizon C content. There were no significant differences in average predicted O-horizon C content among selection, shelterwood, and commercial clearcut treatments. However, variation in predicted O-horizon C content between stands where the same treatment was applied was statistically significant and was likely due to the timing of harvests and abundance of dead wood buried within O horizons. Depth to redoximorphic features, cartographic depth to water table or saturated zone, drainage class, fine woody debris mass, downed woody debris volume, tree basal area, and the relative basal area of conifer species were not significant predictors of predicted O-horizon C content at the plot level. When the individual predicted values of O-horizon C content were modeled, within-plot variation accounted for 83.8% of the variance. Bryophyte mass, which was predicted from bryophyte cover, only explained 1.2% of the variation in O-horizon C content at the microsite level. These results highlight the sizeable variability in O-horizon C content within and among these mixed-species stands with various forest management and natural disturbance histories.

Effects of disturbance on understory succession in upland and lowland boreal forests and implications for woodland caribou (Rangifer tarandus caribou)

Boreal forest development is influenced by both natural and anthropogenic disturbances that alter stand structure and nutrient cycling over decadal timescales. The effects of disturbance on boreal forests is likely to be modified by soil moisture, given that disturbance severity, vegetation structure and plant productivity vary between upland and lowland forest stands. Future changes in boreal vegetation dynamics are predicted to have consequences for a range of ecosystem services including climate feedbacks and wildlife management. Here, as part of a broader study on habitat use and forage of woodland caribou, we investigated the effects of soil drainage class (upland vs. lowland), disturbance (wildfire vs. timber harvest), and stand age on understory plant species richness, cover, biomass, productivity, and foliar C/N. Due to faster nutrient turnover rates in upland soils, we predicted that understory vegetation in uplands would be more productive, biodiverse and nutrient-rich than in lowlands. We also expected disturbance to lead to greater changes in understory vegetation in uplands, given that both fire and timber harvesting tend to be more severe in drier ecosystems. Our results showed that plant understory characteristics varied primarily between soil drainage classes, with few differences between stands recovering from wildfire or timber harvesting. Contrary to our predictions, lowland understory vegetation had greater total understory plant species richness, aboveground net primary productivity, and foliar C/N compared to upland understory vegetation. We also found no difference in total understory vegetation percent cover, productivity or foliar C/N between burned and harvested stands. Understory net primary productivity decreased with time following disturbance in uplands but increased nonlinearly with stand age in lowlands. Greater productivity in lowlands was attributed primarily to evergreen shrubs, though graminoids also were more productive in lowlands than in uplands. Our study has implications for the threatened woodland caribou with respect to the nutritional aspects of their habitat selection. Our results suggest that the commonly held assertion that, by selecting lowlands, caribou face a trade-off between lower predation risk and lower forage quality may be incorrect and requires further examination.

Total and Labile Phosphorus Concentrations as Influenced by Riparian Buffer Soil Properties.

Riparian buffers can act as a phosphorus (P) source under active stream bank erosion. Using soil and landscape variables (soil series, drainage class, organic matter, and pH) to index P concentrations could improve P loss risk tools for buffers. The objectives of this study were (i) to determine if soil properties could predict total and labile P concentrations within a 10-ha riparian buffer and (ii) to quantify the degree of spatial dependence of P and related properties. Soil samples were taken in 15-cm increments to a depth of 60 cm using a grid ( = 71) from an established riparian buffer along the Rock River in Vermont. Total soil P (TP), plant-available P determined by Modified Morgan extraction (MM-P), pH, soil organic matter (SOM), soil texture, and select cations were measured. We found that TP (152-1536 mg P kg) and MM-P (0.4-14.6 mg kg) ranged widely, with distinct differences between soil series. Mean TP and MM-P were greater in alluvial and glaciolacustrine soils compared with glacial till. Across all samples, MM-P was weakly related to soil properties; however, total labile P (orthophosphate + organic P measured by ICP) and unreactive labile P (ICP-P - colorimetric-P) could both be predicted by SOM ( = 0.59 and 0.73, respectively). Strong spatial dependence was found for P and related properties as revealed by geospatial analyses. Results show that P availability in the buffer was strongly related to soil genesis and support site-specific approaches for P loss risk evaluation in buffers.

A note on the Hybrid Soil Moisture Deficit Model v2.0

Abstract The Hybrid Soil Moisture Deficit (HSMD) model has been used for a wide range of applications, including modelling of grassland productivity and utilisation, assessment of agricultural management opportunities such as slurry spreading, predicting nutrient emissions to the environment and risks of pathogen transfer to water. In the decade since its publication, various ad hoc modifications have been developed and the recent publication of the Irish Soil Information System has facilitated improved assessment of the spatial soil moisture dynamics. In this short note, we formally present a new version of the model (HSMD2.0), which includes two new soil drainage classes, as well as an optional module to account for the topographic wetness index at any location. In addition, we present a new Indicative Soil Drainage Map for Ireland, based on the Irish Soil Classification system, developed as part of the Irish Soil Information System.

Interspecific variation in resistance of two host tree species to spruce budworm

Woody plants regularly sustain biomass losses to herbivorous insects. Consequently, they have developed various resistance mechanisms to cope with insect attack. However, these mechanisms of defense and how they are affected by resource availability are not well understood. The present study aimed at evaluating and comparing the natural resistance (antibiosis and tolerance) of balsam fir (Abies balsamea [L.] Mill.) and white spruce (Picea glauca [Moench) Voss] to spruce budworm, Choristoneura fumiferana (Clem.), and how drainage site quality as a component of resource availability affects the expression of resistance over time (6 years). Our results showed that there are differences in natural resistance between the two tree species to spruce budworm, but it was not significantly affected by drainage quality. Balsam fir exhibited higher foliar toxic secondary compounds concentrations than white spruce in all drainage classes, resulting in lower male pupal mass, survival and longer male developmental time. This, however, did not prevent spruce budworm from consuming more foliage in balsam fir than in white spruce. This response suggests that either natural levels of measured secondary compounds do not provide sufficient toxicity to reduce defoliation, or spruce budworm has developed compensatory mechanisms, which allow it to utilize food resources more efficiently or minimize the toxic effects that are produced by its host's defensive compounds. Larvae exhibited lower pupal mass and higher mortality in rapidly drained and subhygric sites. Drainage class also affected the amount of foliage destroyed but its impact varied over the years and was probably influenced by climatic variables. These results demonstrate the complexity of predicting the effect of resource availability on tree defenses, especially when other confounding environmental factors can affect tree resource allocation and utilization.

Soil morphology as an indicator for assessment of drainage system efficiency in sugarcane cultivated lands, South Khuzestan, Iran

Land drainage is an operation which increases land production and ensures sustainable land use. Soil scientists attempt to arrive a scientific procedure for assessing the efficiency of drainage system, among the correlation between soil morphological characteristics, mainly soil color and redoximorphic features and water table behavior. The aims of this study were investigating the efficiency of drainage system through soil morphological and micromorphological characteristics and judge about the existence of episaturation or endosaturation, in Khuzestan sugarcane cultivated lands after years of artificial drainage. 5 pedons were dug and characterized based on their morphological and micromorphological features. The characteristics of redoximorphic features showed no considerable differences in drainage class between artificial drained field and virgin land. The only contrast was shallower ground water table in virgin lands. 4 pedons were classified as somewhat poorly drained and one as well drained. These drainage classes show that despite the existence of artificial drainage system, the problems haven’t been eliminated yet. All pedons showed horizons with low chroma colours in deeper horizons and different types of redoximorphic feature. Micromorphological observations proved that the lands were involved in Endosaturation due to high ground water level.

CHARACTERIZATION AND CLASSIFICATION OF FLOODPLAIN SOILS IN THE PORTO ALEGRE METROPOLITAN REGION, RS, BRAZIL

ABSTRACTIn the Porto Alegre metropolitan region (PAMR) there are a significant proportion of floodplain soils, mainly Planosols and Gleysols, in relation to upland soils. This study aimed to evaluate the morphological, chemical and physical characteristics, and to classify floodplain soils in the PAMR. Six soil profiles were evaluated under different sedimentary lithologies and drainage classes, and samples were collected for chemical and physical analyzes. Two orders of mineral soils (Planosols and Gleysols) and one order of organic soil (Organosols) were identified. The soils were moderately deep to deep and stratified. In mineral soils hue ranged between 7.5YR and 2.5Y, with the occurrence of Bg, Btg or Cg gley horizons, while in organic soil the colors were neutral. Sand and silt were the predominant particle sizes according to the origin sedimentary deposits. The organic carbon content was negatively related to soil density and positively related to soil specific surface area and with soil cation exchange capacity. Soil chemical characterization showed expressive variation in bases, aluminum and sodium saturation. Ki index and Fe(CBD)/Fe(H2SO4) ratio indicated a low soil weathering degree. The different sedimentary lithologies and the soil hydromorphism degree were the main factors related to differences in morphological, physical and chemical characteristics of soils in the PAMR.