Seasonal Waterlogging Research Articles

Using stomatal conductance capacity during water stress as a tool for tree species selection for urban stormwater control systems

Improving our understanding of how different tree species function in urban stormwater management systems is important, as tree pits may provide a temporary reservoir for stormwater and as trees have the potential to actively reduce stormwater runoff by transpiration. While urban tree planting pits are increasingly used for short-term water storage during stormwater runoff events, this storage can have negative effects on both tree vitality and water removal capacity, since stress from waterlogging result in stomatal closure. However, sensitivity to water stress varies by species. It is therefore important to determine which tree species can maintain long-term vitality and continued transpiration even under water stress, and thus are suitable for such locations. Here, we studied how nine different tree species, varying in expected tolerance to water stress, were affected by short-term and seasonal waterlogging, in a greenhouse experiment. The seedlings (Magnolia x loebneri, Tilia tomentosa, and Sorbus torminalis – low water logging tolerance; Cercidiphyllum japonicum, Rhamnus cathartica, and Fraxinus ornus – medium water logging tolerance; Quercus palustris, Acer saccharinum, and Fraxinus pennsylvanica – high water logging tolerance) were exposed to two days, five days and seasonal waterlogging. The treatments reflected best practice (optimal), suboptimal and total lack of tree pit drainage, using Swedish standards. Stomatal conductance and leaf water potential were determined regularly over a period of 71 days, and morphological adjustments were registered. Four of the species were affected already after two days of waterlogging, with reduced stomatal conductance either during the waterlogging or immediately after, and only the most waterlogging tolerant species were unaffected by the five-day treatment. However, all plants survived waterlogging for almost 30 days before the estimated permanent wilting was reached in some plants. We suggest that tree species selection for stormwater management systems should consider the species’ capacity to maintain high stomatal conductance during waterlogging, as there were clear differences between species. The effectiveness of the selected species could have an important impact on the stormwater management capacity of cities, as well as on other aspects of ecosystem service delivery from urban trees.

Underground trees inhabit varied environmental extremes across the Afrotropics.

Geoxyles, a distinctive feature of Afrotropical savannas and grasslands, survive recurrent disturbances by resprouting subshrub branches from large below-ground woody structures. Underground trees are a type of geoxyle that independently evolved within woody genera of at least 40 plant families in Africa. The environmental limits and determinants of underground tree biogeography are poorly understood, with the relative influence of frost and fire debated in particular. We aim to quantify variability in the niche of underground tree species relative to their taller, woody tree/shrub congeners. Using occurrence records of four Afrotropical genera, Parinari (Chrysobalanaceae), Ozoroa (Anacardiaceae), Syzygium (Myrtaceae) and Lannea (Anacardiaceae), and environmental data of nine climate and disturbance variables, the biogeography and niche of underground trees are compared with their open and closed ecosystem congeners. Along multiple environmental gradients and in a multidimensional environmental space, underground trees inhabit significantly distinct and extreme environments relative to open and closed ecosystem congeners. Niche overlap is low among underground trees and their congeners, and also among underground trees of the four genera. Of the study taxa, Parinari underground trees inhabit hotter, drier and more seasonal environments where herbivory pressure is greatest. Ozoroa underground trees occupy relatively more fire-prone environments, while Syzygium underground trees sustain the highest frost frequency and occur in relatively wetter conditions with seasonal waterlogging. Lannea underground trees are associated with the lowest temperatures, highest precipitation, and varying exposure to disturbance. While underground trees exhibit repeated convergent evolution, varied environments shape the ecology and biogeography of this iconic plant functional group. The multiplicity of extreme environments related to fire, frost, herbivory and waterlogging that different underground tree taxa occupy, and the distinctiveness of these environments, should be recognized in the management of African grassy ecosystems.

Seasonal Waterlogging Variation in the Sylhet City Corporation Area, Bangladesh- an Integrated Geospatial Approach

Waterlogging is considered a severe environmental hazard in the Sylhet city corporation (SCC) area of northeast Bangladesh adversely affects the local socio-economic development. The integrated geospatial approach presents a worthy alternative to the conventional mapping of waterlogged surface areas. The remote sensing-based water index technique was used for delineating pre-monsoon and post-monsoon waterlogged areas of SCC in 2020 and 2021. Seasonal deviations of the waterlogging were determined by overlaying the waterlogged sites emanated from the pre-monsoon and post-monsoon periods under the GIS environment. Results show that waterlogged areas for pre-monsoon and post-monsoon seasons in 2020 are 2.25 sq. km and 4.12 sq. km, respectively, whereas 2.22 sq. km and 3.90 sq. km in 2021. Hence, the seasonal variations in waterlogged areas in 2020 and 2021 are 1.87 sq. km and 1.68 sq. km, respectively. This analysis also demonstrates that waterlogging in SCC is utterly driven by the high seasonal variations that mainly depend on the amount of rainfall besides the local flood-prone geologic settings and climate change.

The other side of tropical forest drought: do shallow water table regions of Amazonia act as large-scale hydrological refugia from drought?

Tropical forest function is of global significance to climate change responses, and critically determined by water availability patterns. Groundwater is tightly related to soil water through the water table depth (WT), but historically neglected in ecological studies. Shallow WT forests (WT < 5 m) are underrepresented in forest research networks and absent in eddy flux measurements, although they represent c. 50% of the Amazon and are expected to respond differently to global-change-related droughts. We review WT patterns and consequences for plants, emerging results, and advance a conceptual model integrating environment and trait distributions to predict climate change effects. Shallow WT forests have a distinct species composition, with more resource-acquisitive and hydrologically vulnerable trees, shorter canopies and lower biomass than deep WT forests. During 'normal' climatic years, shallow WT forests have higher mortality and lower productivity than deep WT forests, but during moderate droughts mortality is buffered and productivity increases. However, during severe drought, shallow WT forests may be more sensitive due to shallow roots and drought-intolerant traits. Our evidence supports the hypothesis of neglected shallow WT forests being resilient to moderate drought, challenging the prevailing view of widespread negative effects of climate change on Amazonian forests that ignores WT gradients, but predicts they could collapse under very strong droughts.

Climate change shifts forward flowering and reduces crop waterlogging stress

Climate change will drive increased frequencies of extreme climatic events. Despite this, there is little scholarly information on the extent to which waterlogging caused by extreme rainfall events will impact on crop physiological behaviour. To improve the ability to reliably model crop growth and development under soil waterlogging stress, we advanced the process-basis of waterlogging in the farming systems model Agricultural Systems Production Systems sIMulator. Our new mathematical description of waterlogging adequately represented waterlogging stress effects on the development, biomass and grain yield of many commercial Australian barley genotypes. We then used the improved model to examine how optimal flowering periods (OFPs, the point at which long-term abiotic stresses are minimal) change under historical and future climates in waterlogging-prone environments, and found that climate change will reduce waterlogging stress and shift forward OFP (26 d earlier on average across locations). For the emissions scenario representative concentration pathway 8.5 at 2090, waterlogging stresses diminished but this was not enough to prevent substantial yield reduction due to increasingly severe high temperature stress (−35% average reduction in yield across locations, genotypes and sowing dates). It was shown that seasonal waterlogging stress patterns under future conditions will be similar to those occurring historically. Yield reduction caused by waterlogging stress was 6% and 4% on average across sites under historical and future climates. To adapt, both genotypic and management adaptations will be required: earlier sowing and planting waterlogging tolerant genotypes mitigate yield penalty caused by waterlogging by up to 26% and 24% under historical and future climates. We conclude that even though the prevalence of waterlogging in future will diminish, climate change and extreme climatic events will have substantial and perverse effects on the productivity and sustainability of Australian farms.

不同积水生境对河南黄河湿地植物多样性的影响

湿地作为水陆交替的过渡地带，承担着重要的生态服务功能，湿地植物是生态功能作用发挥的基础。不同积水生境与湿地植物物种组成和分布关系密切。黄河流域是国家的重要生态屏障，湿地面积广阔，河南黄河湿地作为黄河湿地的重要组成部分，其积水生境对植物多样性的影响尚不清晰。为研究河南黄河湿地植物的多样性现状以及积水生境对其植物多样性的影响，采用样方和样线相结合的方法对河南省7个黄河湿地自然保护区中的湿地植物进行调查，共设置样方981个。重点分析了不同积水生境湿地植物的主要群系和物种组成，研究了各生境物种多样性和群落多样性特征（α多样性），对比了的不同积水生境植物物种组成相似性和群落间相似程度（β多样性），明确了各生境的植物物种排序和指示种。结果表明：（1）河南黄河湿地植物群系以草本群系为主，共发现188种湿地植物，分属56科，138属；（2）不同积水状况湿地植物物种丰富度大小依次为：季节性积水 > 永久性积水 > 间歇性积水 > 季节性水涝，主要群系总数与物种丰富度趋势表现一致；（3）不同积水生境湿地植物的物种组成存在显著差异，季节性积水和永久性积水生境中植物物种组成相似性和群落间相似程度最高，各积水生境均有明显的优势种和指示种。河南黄河湿地积水生境在不同流段差异显著，不同积水生境下植物多样性和主要植物群系有明显区别，进行湿地生态建设时，建议优先保护季节性积水生境，减少季节性水涝生境的产生，以达到维持物种多样性，发挥湿地最大生态价值的目的。;As a transitional zone between land and water, wetland plays an important role in ecological services. Wetland plants are the basis of ecological function. The composition and distribution of plant species are closely related to different water habitats. The Yellow River basin is an important ecological barrier for the country, and the wetland area is vast. The Yellow River wetland in Henan is an important part of the Yellow River wetland. However, the effects of waterlogged habitats on plant diversity are still unclear. In order to study the plant diversity of the Yellow River wetland in Henan Province and the influence of waterlogging habitats on its plant diversity, we utilized the method of combining quadrat and transect to investigate wetland plants in seven Yellow River wetland nature reserves in Henan Province. In these reserves, a total of 981 quadrats were set for investigation. This research focused on analyzing the composition of main flora and species of wetland plants in different waterlogging habitats. Therefore, we studied the characteristics of species diversity and community diversity (α diversity) in different habitats, and compared the similarity of plant species composition and degree of similarity between communities (β diversity) in different waterlogging habitats. Moreover, the sequence and indicator species of plant species in the seven habitats were also clearly identified. The results show that:(1) Herbaceous flora is the main flora in Henan Yellow River wetland. A total of 188 species of wetland plants, belonging to 138 genera and 56 families, were found. (2) Under different standing water conditions, the plant species richness was in the order of seasonal ponding > permanent ponding > intermittent ponding > seasonal waterlogging. In addtion, the total number of major communities was consistent with the trend of species richness. (3) There are significant differences in plant species composition among different waterlogging habitats. The similarity of plant species composition and communities between seasonal ponding and permanent ponding habitats was the highest. There were obvious dominant species and indicator species in each waterlogging habitat. The hydrological habitats of the Yellow River wetland in Henan province were significantly different in different flow segments. There are obvious differences of plant diversity and main plant groups in different waterlogging habitats in the Yellow River wetland in Henan province. Under the circumstances, we suggest giving priority to the protection of seasonal ponding habitats and reducing the occurrence of seasonal waterlogging habitats during wetland ecological construction, so that we can achieve the purpose of maintaining species diversity and giving full play to the maximum ecological value of wetlands.

Evaluation of Eucalyptus Clones Under Seasonal Waterlogging Conditions in South-Western Punjab

Eucalyptus is widely planted genus in many continents due to its rapid growth, several uses and good adaptability to climates and soil types. This study was based on nine Eucalyptus clones/progenies (C-413, C-3020, C-2135, C-7, C-2045, C-411, C-526, C-316 and seedlings) planted at farmers field experiencing seasonal waterlogging. The experiment was planted following randomized block design with plot size of 12 trees replicated four times. The survival of Seedlings, C-7, C-413, C-526 and C-316 was better and varied from 78.3 to 88.3 percent. Significant differences were found for tree height and diameter at age of 2 and 4 year, and volume index at age of 4 year. The tree height and diameter at breast height at 4 year age varied from 5.93 to 6.76 m and 56.4 to 87.6 mm, respectively. The relative ranking on basis of volume index was C-413&gt;C-316&gt;C-411&gt;C-7&gt;C-526. Clones C-413, C-316, C-7 and C-526 were promising based on adaptability and growth traits.

The impact of seasonal waterlogging on the depth-wise distribution of major and trace metals in the soils of the eastern Ganges basin

In the Ganges River basin, studies related to the depth-wise distribution of major and trace metals in these floodplain soils (seasonally waterlogged and non-water logged) have been limited thus far. This research attempts to address this gap in the current literature by geochemical and geostatistical analyses and assessment of soil pollution. Significant concentrations of major and trace metals in these soils could greatly impact the health of local communities. Soil samples were collected in the eastern Ganges basin from a shallow seasonally waterlogged (SWL) site and a shallow non-waterlogged (SNWL) site up to 3 m below ground level (mbgl) and a deep seasonally waterlogged (DWL, up to 14 mbgl) site. The soils were analysed to determine soil texture and the concentration of major oxides and trace metals with increasing depth. The average concentration of trace metals (Ba, Rb, V, Cr, Ni, As, Pb, Ga, Co, Cs, Nb, W) and major oxides (Al2O3, Fe2O3, K2O, MgO) are higher in the SWL soil than the SNWL soil. A higher concentration of metals generally occurred in the upper soil layers due to the adsorption of elements by the silt and clay fractions. Soil pollution assessment indicated that W, As, Sb and Cu are enriched in both the waterlogged and non-waterlogged soils, while Sn is enriched in the SNWL soil profile only. The values obtained for the geochemical indices, which were geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF) and pollution load index (PLI), were relatively higher in the top layers for the SWL and DWL sites. Based on effects range-low (ERL) and effects range-median (ERM) values, the possibility of adverse biological effects caused by the metals is highest for Ni in the DWL site, Cr and Ni in the SWL site and Cu in the SNWL site. Pearson’s correlation and principal component analysis (PCA) justify the role of soil texture, phyllosilicates, Fe-Mn oxyhydroxides and carbonates in the occurrence and distribution of metals in these soils. Seasonal waterlogging facilitates the dissolution and precipitation of oxides, hydroxides, carbonates and adsorption/desorption processes, leading to the accumulation and retention of more trace metals in the soil. This study implies that the silt and clay present in the vadose zone may act as a filter to protect local groundwater aquifers from metal contamination. This work provides insights on the behaviour of major and trace metals in the soil depth profile of seasonally waterlogged floodplain soil that is used for local agriculture.

A study on the groundwater of Peenya industrial area and its related elements in Bengaluru region of Karnataka State, India

Abstract Groundwater samples were collected from the Peenya Industrial area of Bengaluru, India to test its quality, elemental composition and inherent bacterial population. Further analysis was done using GIS Based Geostatistical techniques to study the level of groundwater and to generate various maps of lineament, digital elevation, geomorphology, soil erosion, salt affected areas and water logging in this region. Physical and chemical parameters such as Total Dissolved Solids, pH, temperature, BOD, COD, metal ions present in the water samples were studied along with predominant microbial constituents. The Total Dissolved Solids and Total Hardness were far beyond the maximum concentration levels. Further analysis of the isolated bacteria was done using staining methods and biochemical tests. The results obtained showed that the area under study had wells ranging from shallow to deep heights of 30 to 80 meters, with a wide variety of 10-400 LPM; whereas the lineament map suggested that the area was bound with parallel ridges and joints. The geographical data represented pediplain complexes, anthropogenic terrains and water bodies. The area was found to go through a seasonal water logging and the soil loss was due to sheet erosion and rill erosion. It was also observed that the groundwater was contaminated with heavy metals such as lead, chromium etc. along with a diversified bacterial population.

Vertical drains to minimize duration of seasonal waterlogging in Eastern Ganges Basin flood plains: a field experiment

In the Ganges basin, 8268.6 km2 of irrigation command area is waterlogged following monsoon rains. In this study, vertical drain (VD) (L × D, 7 × 1 m) filled with drainage gravel (6.5 m) and coarse sand (0.5 m) is installed in farmer’s agricultural field to minimize the duration of seasonal waterlogging and tested in Mukundpur village, Vaishalli District, Bihar, India. At the experimental site, inundation of rainfall and runoff from surrounding areas along with the seepage from an earthen canal start in September and remain till February, every year which prevents timely planting of wheat in November-end/December. Drainage due to percolation and recharge to groundwater is constrained by 6.4-m thick clay layer, below 0.5-m root-zone, and the groundwater level, which rises to the surface level. VDs were installed to provide a path and allow inundated water to recharge the aquifer, as groundwater level recedes. Groundwater level drop, floodwater infiltration rate, groundwater discharge, and VD capability were estimated through field data. Results show that VDs connected the floodwater to groundwater and transferred the floodwater to the aquifer when groundwater level started to recede. The site was fully drained by the end of December, permitting farmers to plant wheat in January providing cool nights at germination, thus increasing yields.

Non-destructive Phenotyping to Identify Brachiaria Hybrids Tolerant to Waterlogging Stress under Field Conditions.

Brachiaria grasses are sown in tropical regions around the world, especially in the Neotropics, to improve livestock production. Waterlogging is a major constraint to the productivity and persistence of Brachiaria grasses during the rainy season. While some Brachiaria cultivars are moderately tolerant to seasonal waterlogging, none of the commercial cultivars combines superior yield potential and nutritional quality with a high level of waterlogging tolerance. The Brachiaria breeding program at the International Center for Tropical Agriculture, has been using recurrent selection for the past two decades to combine forage yield with resistance to biotic and abiotic stress factors. The main objective of this study was to test the suitability of normalized difference vegetation index (NDVI) and image-based phenotyping as non-destructive approaches to identify Brachiaria hybrids tolerant to waterlogging stress under field conditions. Nineteen promising hybrid selections from the breeding program and three commercial checks were evaluated for their tolerance to waterlogging under field conditions. The waterlogging treatment was imposed by applying and maintaining water to 3 cm above soil surface. Plant performance was determined non-destructively using proximal sensing and image-based phenotyping and also destructively via harvesting for comparison. Image analysis of projected green and dead areas, NDVI and shoot biomass were positively correlated (r ≥ 0.8). Our results indicate that image analysis and NDVI can serve as non-destructive screening approaches for the identification of Brachiaria hybrids tolerant to waterlogging stress.

Pedosphere Degradation due to Seasonal Water Logging in Southwestern Punjab

Introduction of irrigated agriculture has turned some basin lands seasonally waterlogged. Seasonally waterlogged soils remain poorly understood particularly in relation to the changes in pedosphere and pedogenic pathways. Present investigation evaluated changes in the pedosphere and its implications in pedogenic pathways of these seasonal waterlogged soils. Five soil profiles along the central transit of the waterlogged area of the southwestern Punjab (74°30′–74°45′E longitude and 30°03′75″–30°33′07″N latitude) were studied. On seasonal water logging, the present land depicts shift of matrix colour from yellowish brown to olive brown, decay in the thickness and strength of structured B-horizons, increase in exchangeable Na and soluble salts in the surface horizons, fall of exchangeable divalent cations to exchangeable-Na ratio and an increase in the mobility of citrate–bicarbonate–dithionite extractable free Fe and Mn. Seasonal water logging resulted in two phases of degeneration, deterioration of structured B-horizon and the dispersion of clays and soluble salts and their inconsistent downward movements with water table front. The operating soil process is incipient hydromorphism.

A Micromorphological Assessment of Anthropogenic Features in Pre-Columbian French Guiana Dark Soils (FGDS): First Results

In order to document site formation processes at microscale and to characterise pre-Columbian French Guiana dark soils (FGDS), micromorphology was performed on three sites. For the first time it was possible (i) to microscopically characterise pre-Columbian Anthrosols in different physical contexts and (ii), to identify anthropogenic features associated with past human occupation. Microfeatures of the Holocene alluvial terrace of the lower Maroni River witnessed (i) several episodes of clay enrichment and/or redistribution, (ii) seasonal waterlogging, and (iii), post-depositional biological activity. Clay en- richment and organic matter inputs together with biological activity processes might have alternated, probably in relation to vegetal cover and/or anthropogenic activities. On top of the alluvial terrace, bio- turbated dark layers are enriched in fine brown organic matter and charcoals. Cumulic soil development was favoured when successive sediment inputs due to episodic flooding and/or overland flow was pos- sible (Chemin Saint Louis site). On a lateritic hill, under rainforest, at the MC87 ring-ditched mountain (Montagnes Couronnees or Crowned Mountain), microscale identification of yellowish unburnt oxic B horizon aggregates together with anthropogenic features related to fire such as charcoals and burnt soil fragments (rubefied and dark brown aggregates) stress that lateritic soil acted as support for activities in the enclosure, and as reworked material in the ditch. These components could result from clearance for settlement, agricultural management and cultivation, or domestic activities. The obtained results allow first comparisons to be drawn between pre-Columbian FGDS and Brazilian dark earths (BDE). Except a similarity in colour, the former is revealed to be less rich in anthropogenic components with an absence of phosphatic elements such as bones.

Tropical tree water use under seasonal waterlogging and drought in central Cambodia

Summary In central Cambodia, rapid growing non-endemic species are planted for future timber production. However, less is understood about the impact of the introduction of non-endemic species on the transpiration characteristics of the forest, which has been composed of native species that adapted to the highly seasonal environments. Sap flux of two native and one non-endemic tree species in central Cambodia was measured to reveal its seasonal trends and variability in the Monsoon Asia region. Measurements were carried out in a 10- to 15-year-old forest in the dry and rainy seasons that were defined by differing rainfall patterns. The seasonal trend in depth to water table differed from that of rainfall; groundwater table depth reached zero late in the rainy season and increased gradually after the onset of the dry season. The ratio of sap flux to an equilibrium evaporation condition of the native species, Popel ( Shorea roxburghii ), showed a sharp decline at the end of the dry season, whereas that of a non-endemic species, eucalyptus ( Eucalyptus camaldulensis ), decreased in the mid rainy season while Tbeng ( Dipterocarpus obtusifolius ) did not show a clear trend. The ratio of sap flux to an equilibrium evaporation was negatively correlated with the depth to water table in Popel, but was positively correlated in eucalyptus, possibly because of the negative effects of flooding. In addition to the large seasonal variation, intra-species variation in sap flux was also large and was a major controlling factor for tree-level water uptake at this young forest site in both dry and rainy seasons. In conclusion, the transpiration characteristics of this forest were species-specific and were controlled more by the fluctuating depths to groundwater rather than the onset of the rainy/dry seasons defined by rainfall events.

Microbial Activity and Culturable Bacterial Diversity in Sediments of the Great Rann of Kachchh, Western India

The Great Rann of Kachchh, a vast expanse of salt desert in Western India is a unique hostile ecosystem posing an extreme environment to life forms due to high salt content, hyper-arid climate, seasonal water logging and extremes of temperature. In the virtual absence of natural vegetation, soils and sediments of Rann of Kachchh are microbially dominated ecosystems. In the present study microbial activity and the diversity of cultivated heterotrophic bacteria were investigated in the sediments collected along a 5-m exposed section at Khadir Island in the Great Rann of Kachchh. Microbial activity (as an index of sediment enzymes) was found to be high in the middle of the section (200-280 cm). Dehydrogenase (DHA), substrate-induced DHA and alkaline phosphatase activities revealed the oligotrophic nature of the basal portion (320-480 cm). Abundant bacterial isolates obtained from different depths were found to be clustered in 12 different phylogenetic groups by amplified ribosomal DNA restriction analysis. 16S rRNA gene sequencing revealed the dominant bacterial ribotypes to be affiliated to Firmicutes (Families Bacillaceae and Staphylococcaceae) and Actinobacteria (Family Brevibacteriaceae) with minor contribution of Proteobacteria (Families Phyllobacteriaceae and Bartonellaceae), pointing their endurance and adaptability to environmental stresses. Statistical analysis indicated that sediment organic carbon, salinity, total available nitrogen and total available phosphorous are most likely critical determinants of microbial activity in the Khadir Island sediments.

Occurrence of iron and associated bacterial populations in soils of a forested subtropical coastal catchment

Iron (Fe) biogeochemistry is potentially of environmental significance in plantation-forested, subtropical coastal ecosystems where soil disturbance and seasonal water-logging may lead to elevation of Fe mobilization and associated water quality deterioration. Using wet-chemical extraction and laboratory cultivation, we examined the occurrence of Fe forms and associated bacterial populations in diverse soils of a representative subtropical Australian coastal catchment (Poona Creek). Total reactive Fe was abundant throughout 0–30 cm soil cores, consisting primarily of crystalline forms in well-drained sand soils and water-logged loam soils, whereas in water-logged, low-clay soils, over half of total reactive Fe was present in poorly-crystalline forms due to organic and inorganic complexation, respectively. Forestry practices such as plantation clear-felling and replanting, seasonal water-logging and mineral soil properties significantly impacted soil organic carbon (C), potentially-bioavailable Fe pools and densities of S-, but not Fe-, bacterial populations. Bacterial Fe(III) reduction and abiotic Fe(II) oxidation, as well as chemolithotrophic S oxidation and aerobic, heterotrophic respiration were integral to catchment terrestrial Fe–C cycling. This work demonstrates bacterial involvement in terrestrial Fe cycling in a subtropical coastal circumneutral-pH ecosystem.

Ecosystem response to soil biogeochemical behavior during the Late Cretaceous and early Paleocene within the western interior of North America

Paleosol properties are routinely characterized by whole-rock geochemistry, compromising the interpretation of important biogeochemical information in deep time. As a consequence, we employ a new pedotransfer function approach to the characterization of paleosols and apply this methodology to Late Cretaceous (Campanian and Maastrichtian) and early Paleocene (Danian) landscapes from the Dawson Creek study area of the western interior to: (1) reconstruct collodially based physical and chemical soil properties, and (2) assess climate and soil biogeochemical controls on evolving terrestrial ecosystems. Nine paleoseries (i.e., pedotypes) characterize the range of soil properties within the fluvial stratigraphic succession, which includes Entisols, Inceptisols, and Vertisols. All soils had optimal water-holding potential as inferred from low bulk densities, whereas poorly drained and colonizing landscapes likely suffered from poor aeration during seasonal water logging. Even with high water-holding capacity, Maastrichtian soils experienced seasonal moisture stress because of lower rainfall than Campanian and Danian soils. Fertility levels were sufficient for the growth of most plants judging from high cation exchange capacity and base saturation, negligible aluminum toxicities because of nonacid pH, and limited salinity and sodicity from relatively low exchangeable sodium and soluble salts in solution. Unlike warm-temperate and forested paleosols with neutral pH from the Campanian and Danian, subtropical and alkaline paleosols from the Maastrichtian apparently supported a woodland plant formation adapted to low availability of iron and manganese, which were fixed with calcium in carbonate, and low availability of phosphorous because it formed insoluble compounds with iron and manganese. Carbon, nitrogen, phosphorous, and sulfur cycling through microbially mediated mineralization of soil organic matter was limited from low litter inputs in both early and midsuccessional ecosystems, particularly in woodland soils. Results do not reveal demonstrable changes in soil characteristics through the K-T transition.

Geotechnical and environmental problems related to shales in the Abakaliki area, Southeastern Nigeria

Six (6) samples of shale and five (5) water samples from hand-dug wells and boreholes, from different locations within the Abakaliki shale formation, have been assessed to evaluate the impact of the shale formation to the geotechnical and hydrogeo-environmental problems prevalent in the Abakaliki area (Southeastern Nigeria). Results indicated that the shale samples have Atterberg limits that might be considered moderate to high; while Liquid Limit (LL) ranged from 49 – 54, the Plasticity Index (PI) ranged from 34 – 38. These relatively high LL and PI suggested presence of expansive clays, some swelling of the shale on moisture influx and high compressibility. Natural moisture content (with mean value of 20%) was also significantly high. Hydrochemical analyses, on the other hand, revealed that the water samples had comparatively high content of ions and dissolved particles; Ca2+ ranged from 8.0 – 134.0 mg/l, Mg2+ ranged from 0.2 – 3.3 mg/l, HCO-3ranged from 21.8 – 1176.1 mg/l and total dissolved solids ranged 56.9 – 1415.0 mg/l. Dissolution of soluble minerals (predominantly calcite and other rock salts) contained in the shale might likely be responsible for the release of these particles. Geotechnical behaviours of the shale and hydrogeochemical characteristics of water samples from the shale formation, thus, provided insights into the probable causes of seasonal waterlogging, consistent poor groundwater quantity and quality, structural and foundation problems that are prevalent in the Abakaliki area. Key words: Abakaliki shale, dissolution, environmental problems, geotechnical analysis, groundwater quality, structural failure.

Intra-specific variation for response to salt and waterlogging in Acacia ampliceps Maslin seedlings

Salinity is a major form of land degradation worldwide, with seasonal or temporary waterlogging often being an associated issue. Acaciaampliceps is a highly salt-tolerant small tree, naturally-occurring in north-western Australia, which produces abundant biomass with potential for fuelwood and fodder. We investigated the extent of variation amongst provenances and families of A. ampliceps for seedling response to salt and waterlogging. Seven-week old seedlings from 27 families (seven provenances, grouped into two regions), were treated in sand-filled pots in a glasshouse with either mixed salt (S) solutions (150 mol m−3 for 14 days, 300 mol m−3 for 33 days), waterlogging (W) or combined salt (S) and waterlogging (SW). Only 3% of seedlings died, mostly from the combined salt × waterlogging treatment. Seedlings from the Kimberley region had significantly greater height and shoot biomass than those from the Pilbara. Within these regions, Wave Hill (seedlot 14631) and Halls Creek (15738) provenances had the best growth. Height growth was reduced similarly for S- and W-treated plants, whereas that of SW-treated plants was reduced much more. Salt and waterlogging caused shoot dry weight reduction at harvest of 41 and 46%, respectively, with a slight interaction between salt and waterlogging; SW treated plants were most affected. Generally there were relatively small differences in the growth response of provenances and families to salt, but larger (often highly significant) variation in response to waterlogging. Genotypic variation for shoot and phyllode water content and phyllode number in response to salt and waterlogging was generally small. The good agreement found at the provenance level between seedling growth in this experiment and growth of young trees on saline land in a trial in Pakistan suggests that glasshouse screening may be a useful means for selecting potential provenances for field evaluation.

Structure and species richness in wetland continua on sandy soils in subtropical and tropical Australia

AbstractNet photosynthetic fixation of wetland plant communities is confined to the period of the year when the surface soil is not waterlogged and is thus well aerated. In the open‐structured vegetation continuum across freshwater wetlands on sandy soils in subtropical and tropical Australia, the sum of the foliage projective covers (FPCs) of the overstorey and understorey strata remains constant, while that of the overstorey decreases to zero as seasonal waterlogging (and anaerobic conditions) in the surface root systems increases. Density and height of the overstorey trees – of only one or two species – and species richness (number of species per hectare) in the understorey decreases along this waterlogging gradient. Melaleuca paperbark trees, possessing surface roots with cortical aerenchyma, may form a closed‐forest at the edge of the wetland continuum wherever there is a continuous flow of aerated water. As global warming progresses, an increase in air temperature in the atmosphere flowing over and through the wetland continuum during the short period of annual foliage‐growth will affect the combined FPCs of overstorey and understorey strata, as well as the leaf‐specific weights of all leaves throughout the plant community. With a reduction in net photosynthetic fixation, species richness of the plant community will slowly decline.