Recording relative water table depth using PVC tape discolouration: Advantages and constraints in fens

Question: Recognizing water table dynamics in wetlands is crucial for understanding species‐environment relationships, ecosystem function and changes during restoration. The PVC tape discolouration method enables spatially and temporally extensive studies of reductive conditions associated with long‐term water table dynamics in peat soils. The reliability of the method has been verified only for ombrotrophic bogs, even though wide usage can be expected in minerotrophic fens. Location: T?reboň basin, Czech Republic. Methods: Using data from 49 plots in six poor and moderately rich fens, we correlated the directly measured lowest, highest and mean water table depths and the same variables indicated by discolouration of PVC tape attached to green bamboo stakes installed vertically in the soil profile. Results: The depth to the first sign of PVC discolouration was highly correlated with the directly measured position of the highest water table, the correlation between the depth of complete discolouration and the directly measured position of the lowest water table was poorer. The accuracy of the minimum water table measurement depended on the depth of the peat layer. Surprisingly, the depth at which the green bamboo stakes turned brown correlated highly with the minimum water table. Conclusions: The PVC tape discolouration method reliably indicates water table maxima in fens, but minima are not accurately indicated. The depth of the green bamboo discolouration is suggested as a new alternative indicator of the minimum water table, even in fens and mineral soils. Combining both methods enables efficient monitoring of water table dynamics at a large number of mire sites.     

Ecodesign of PVC packing tape using life cycle assessment

Purpose

Polymer materials play an important role in the improvement and quality of life. However, due to their persistence in the environment, polymer materials may be harmful to the ecosystems. According to the European Directive on Packaging and Packaging Waste, management of these wastes should include prevention of their generation as a priority. The main motivation for employing ecodesign of a product is to reduce both raw material consumption and waste generation through a good initial design.

Methods

In this study, life cycle assessment (LCA) was applied to the design of printed PVC plastic packing tape in order to reduce its environmental impact. LCA software GaBi4.4^® was used to determine the PVC packing tape life cycle stage with the highest environmental impacts.

Results and discussion

LCA results showed that PVC film manufacture was the stage with the highest impact. It was therefore reasonable to assume that packing tape manufactured with material other than PVC could have reduced environmental impact, and LCA was used to evaluate this hypothesis. When using Kraft paper or polypropylene plastic packing tape, the weighted impacts were reduced by 36.3 and 39.9 %, respectively.

Conclusions

PVC plastic packing tape has been redesigned with the aim of reducing waste and raw material consumption. LCA results showed that a suitable option for reducing life cycle environmental impact is to use alternative film materials. Kraft paper and polypropylene plastic packing tape were found to give lower values of almost all environmental impact indexes and normalized and weighted impacts.     

Effects of snow-load and shading by vascular plants on the vertical growth of hummocks formed by Sphagnum papillosum in a mire of northern Japan

The growth of hummock Sphagnum species in bogs depends on hydrological and climatic conditions, with different hummock morphologies being found across geographical regions. We investigated how plant shade and winter snow-load regulate the growth pattern and height of Sphagnum papillosum hummocks in a cool-temperate bog in Japan. Hummocks were subjected to four treatments across 2?years (1 hummock per treatment per year): no treatment (control), snow-load-free (S), vascular plant trimming (T), and snow-load-free and vascular plant trimming in combination (S&T). Further, the effects of vascular plant cover and snow -load on the vertical growth and height of hummocks were examined. Annual growth rates of S. papillosum were higher for the control (34?C41?mm) than S&T treatment, and were intermediate for separate S and T treatments. In contrast to vascular plant-growing hummocks, vascular plant-trimmed hummocks showed a negative correlation between water-table depth (measured from the capitulum to the water-table) and Sphagnum growth. Hence, in summer, shading by vascular plants may prevent desiccation and facilitate the growth of Sphagnum. Snow-loaded hummocks were weighed down by 3?C11?cm. After snowmelt, the shoots continued to grow within the water-table depth range that allowed growth. Hence, heavy winter snow-loads may depress the surfaces of hummocks closer to the water-table, which stimulates Sphagnum growth, resulting in the recovery of hummock height. Thus, the water stress caused by summer desiccation is critical in regulating the upper limit of hummock height in bogs subject to dry summer conditions and heavy winter snowfall.     

Water relations and growth responses of Uniola paniculata (sea oats) to soil moisture and water-table depth

Summary This study examined the water relations and growth responses of Uniola paniculata (sea oats) to (1) three watering regimes and (2) four controlled water-table depths. Uniola paniculata is frequently the dominant foredune grass along much of the southeastern Atlantic and Gulf coasts of the United States, but its distribution is limited in Louisiana. Throughout most of its range, U. paniculata tends to dominate and be well adapted to the most exposed areas of the dune where soil moisture is low. Dune elevations in Louisiana, however, rarely exceed 2 m, and as a result the depth to the water table is generally shallow. We hypothesized that if U. paniculata grows very near the water-table, as it may in Louisiana, it will display signs of water-logging stress. This study demonstrated that excessive soil moisture resulting from inundation or shallow water-table depth has a greater negative effect on plant growth than do low soil moisture conditions. Uniola paniculata's initial response to either drought or inundation was a reduction of leaf (stomatal) conductance and a concomitant decrease in leaf elongation. However, plants could recover from drought-induced leaf xylem pressures of less than-3.3 MPa, but prolonged inundation killed the plants. Waterlogging stress (manifested in significantly reduced leaf stomatal conductances and reduced biomass production) was observed in plants grown at 0.3 m above the water table. This stress was relieved, however, at an elevation of 0.9 m above the water table. As the elevation was increased from 0.9 to 2.7 m, there were no signs of drought stress nor a stimulation in growth due to lower soil moisture. We concluded that although U. paniculata's moisture-conserving traits adapt it well to the dune environment, this species can grow very well at an elevation of only 0.9 m above the water table. Field measurements of water-table depth in three Louisiana populations averaged about 1.3 m. Therefore, the observed limited distribution of U. paniculata along the Louisiana coast apparently cannot be explained by water-logging stress induced by the low dune elevations and the corresponding shallow water-table depth.     

Local environmental correlates of variability in the organic soils of moorland and alpine vegetation,Mt Sprent,Tasmania

Abstract Data on soils, vegetation and environment were collected between 510 and 1050m a. s. l. on Mt Sprent, southwestern Tasmania, traversing the Gymnoschoenus sphaerocephalus sedgeland-alpine vegetation boundary. One or more of the following horizons were found in almost all soil pits (downwards from the surface to the bed rock) fibric peat, hemic peat, sapric peat, organic sand, sand and clay. Mean total soil depth, mean organic soil depth, mean humification of the soil surface horizon, pH and mean organic content of the surface horizon all decline with altitude, while the redness of the soil and the mean depth of the mineral and gravel layers increase. At four intensively studied sites at 620, 850, 930 and 1040 m the relationships between phytosociological, topographic and water-table variables, and soil characteristics were determined. The pH of the topsoil was significantly positively related to water-table depth at three sites, but there were no other relationships between local environmental variation and soil characteristics that were consistent between most of the four sites, despite a large number of locally significant relationships. The alpine and sedgeland soils differ most markedly in colour, number of horizons and degree of humification of the surface horizon. The vegetation at each site was separated into communities along a drainage gradient. The mesoscale differences in soils seem most likely to be attributable to a vegetation productivity gradient.     

Ecological gradients in some Sphagnum mires in the south-eastern Alps (Italy)

Abstract. Vegetation was sampled at 170 plots in five mires in the Italian Alps to characterize the distribution of plant species along the main environmental gradients. Water-table depth, water pH, electrical conductivity, Ca-, Mg-, K- and Na-concen-trations in soil pore water, shade intensity, and distance from the mire margin were determined at each plot. At mire margins the water table was deeper than in the mire expanse, and K-, Ca- and Mg-concentrations, and conductivity were higher. The first and by far most important axis of a DCCA-ordination was interpreted as a gradient of water-table depth, in relation to the distance from the mire margin, whereas the second axis was mainly associated with water pH.     

棉红铃虫性信息素应用技术研究

1986-1993年在棉红铃虫（Pectinop hora gossypiella Saunders）发生中密度、高密度区应用红铃虫性信息素2％微胶囊、2%改进微胶囊、塑料纤维夹片、PVC胶带、聚乙烯塑料管,采用干扰交配方式进行防治技术的研究。经过22个年次试验结果表明：在红铃虫发生中密度地区以自然沟,沟渠为界．5—8公顷连片棉田为使用单位,所用剂型均能有效控制红铃虫的为害。青铃活虫、籽棉含虫量、僵瓣花比常规农药防治区减少70—80%以上。在高密度区．试验区四周需有100公尺以上隔离带．使用PVC胶带剂型．在越冬代始蛾对时施挂一次,干扰交配时间可达三个月以上．性信息素释放稳定,控制青铃活虫、籽棉含虫量与使用4—5次菊酯农药的效果相当。     

Production and microtopography of bog bryophytes: response to warming and water-table manipulations

Boreal peatlands, which contain a large fraction of the world's soil organic carbon pool, may be significantly affected by changes in climate and land use, with attendant feedback to climate through changes in albedo, fluxes of energy or trace gases, and soil carbon storage. The response of peatlands to changing environmental conditions will probably be dictated in part by scale-dependent topographic heterogeneity, which is known to interact with hydrology, vegetation, nutrients, and emissions of trace gases. Because the bryophyte community can contribute the majority of aboveground production in bogs, we investigated how microscale topography affects the response of bryophyte species production and cover to warming (using overhead infrared lamps) and manipulations of water-table height within experimental mesocosms. We removed 27 intact peat monoliths (2.1-m² surface area, 0.5-0.7 m depth) from a bog in northern Minnesota, USA, and subjected them to three warming and three water-table treatments in a fully crossed factorial design. Between 1994 and 1998, we determined annual production of the four dominant bryophyte taxa within three microtopographic zones (low, medium, and high relative to the water table). We also estimated species cover and calculated changes in topography and roughness of the bryophyte surface through time. Total production of all bryophytes, and production of the individual taxa Polytrichum strictum, Sphagnum magellanicum, and Sphagnum Section Acutifolia, were about 100% greater in low microtopographic zones than in high zones, and about 50% greater in low than in medium zones. Production of bryophytes increased along the gradient of increasing water-table heights, but in most years, total production of bryophytes was negatively correlated with height above the set water table only for the wettest water-table treatment. Although bryophyte production was unaffected by the warming treatments, the bryophyte surface flattened in proportion to the degree of warming. These results indicate that production of bryophytes is driven most strongly by the absolute and relative height of the bryophyte surface above the water table. Predicted changes in water-table height commensurate with changes in surface temperature may thus affect both production and superficial topography of bryophyte communities.     

The effect of an intermittent water-table gradient on soil and xylem nitrate in cotton

Summary Cotton (Gossypium hirsutum cv Deltapine 61) was grown in a sloping plot of soil in the field to examine the effect of a gradient of water-table depth on soil nitrate availability and plant uptake during two periods of the growing season. Before the water-table was imposed NO₃ was less concentrated at the lower end of the sloping plot. This was attributed to slow denitrification at microsites within the soil at the lower end which was wetter than further up the plot. At flooding NO₃ disappeared only slowly due to a carbon substrate limitation to denitrification in the soil. This loss occurred primarily in areas where the water-table was high and oxygen concentration in the soil solution was low. Plant NO₃ uptake, assessed by measuring the concentration in the xylem, parallelled the distribution of NO₃ in the soil solution. Under high water-tables xylem NO₃ levels fell but it was not possible to say whether this was due to impaired root function or to the reduced concentration of NO₃ observed in the soil solution. At intermediate water-table depths where soil NO₃ availability remained high xylem NO₃ concentration fell relative to the well drained control plants, suggesting that flooding had damaged the root system.Manufactured by Merck. Mention of commerical names does not imply endorsement by either CSIRO or USDA.     

Plant niches along the water-table gradient on an ombrotrophic mire expanse

The vegetation within an ombrotrophic mire expanse m SE Norway is studied m detail Presence/absence of species and depth to the water table are recorded for 6976 plots (4x4 cm) The cumulative probability distributions along the water-table gradient are calculated for 24 species, and Inter-transect variability tested Shifts in realised depth to the water table (niche shifts) are frequent for most species It is concluded that interactions are of minor importance for species in the field layer The Sphagnum spp possess some attributes indicating equilibrium, while others indicate ongoing competition The patchy distribution of hepatics and lichens depend on chance and successional stage, and coexistence within these guilds depend on creation of new naked peat patches     

Correlation of chlorophyll a and total carotenoid concentrations with coral bleaching from locations on the Pacific coast of Mexico

Diving campaigns were undertaken to study the bleaching phenomenon in the Mexican Central Pacific and to catalogue the degree to which bleaching affected three coralline reefs (la Boquita, Carrizales, and Tenacatita). Bleaching evaluations of Pocillopora capitata were conducted by assessing the concentrations of chlorophyll a and total carotenoids from samples along submarine transect lines. We identified that the Reffs Boquita and Tenacatita locations were predominantly composed of bleached and pale coral populations. The concentrations of chlorophyll a within the areas of the different populations were greater at sites of greater depth compared with those at the surface. In contrast, the total carotenoid concentrations in normal pigmented coral at greater depth were significantly higher (P?<?0.05) compared with both levels of discolouration at both depths. The chlorophyll a/total carotenoid ratios in these populations are discussed as a potential mechanism responsible for the poor condition of these corals as a result of environmental stress.     

Responses of photosynthesis,dry mass and carbon isotope discrimination in winter wheat to different irrigation depths

Photosynthetica - In order to test the effects of irrigation depth on winter wheat photosynthesis, four treatments were applied in a field experiment using PVC growth tubes (identical amounts of...     

Is oxygen involved in beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) red heartwood formation?

European beech (Fagus sylvatica) facultatively develops red heartwood, which decreases the value of its timber and is difficult to predict in standing trees. According to current theory, the absence of oxygen prevents discolouration in the wood of uninjured trees, and red heartwood forms when oxygen enters the stem through injuries. This theory requires that oxygen concentrations in uncoloured wood are generally very low, and that oxygen can diffuse several metres in the centre of a stem, bypassing the respiring sapwood. Oxygen concentrations measured at different depth in stems with and without red heartwood varied strongly and were generally depleted relative to the air, but rarely close to 0. Concentrations in red heartwood were somewhat, though not significantly higher than in the inner wood of trees without red heartwood. The colour of wood exposed to different oxygen concentrations changed strongly at higher concentrations, but concentrations in standing stems are generally high enough for discolouration. Model calculations suggested that only massive injuries that kill most sapwood at an entry point would allow high amounts of oxygen to penetrate to the core, in which case it may diffuse several metres in the axial direction without being consumed by respiring sapwood. However, given the relatively high diffusion in axial direction, oxygen should spread within a few days, not several years as the development of red heartwood appears to take. These measurements and calculations suggested that, while oxygen is required for beech red heartwood discoloration, it is not the only factor involved but could act by affecting the activity of micro-organisms.     

Quantifying the effect of testate amoeba decomposition on peat-based water-table reconstructions

Testate amoebae are a widely-used tool for palaeohydrological reconstruction from peatlands. However, it has been observed that weak idiosomic siliceous tests (WISTs) are common in uppermost peats, but very rarely found as subfossils deeper in the peat profile. This taphonomic problem has been noted widely and it has been established that WISTs disaggregate and/or dissolve in the low pH condition of ombrotrophic peatlands. Here we investigate the effect of this taphonomic problem on water-table reconstructions from thirty European peatlands through the comparison of reconstructions based on all taxa and those with WISTs removed. In almost all cases the decomposition of WISTs does not introduce discernible bias to peatland water-table reconstructions. However, some discrepancy is apparent when large abundances of Corythion-Trinema type are present (9−12 cm deviation with 50–60% abundance of this particular taxon). We recommend that WISTs should be removed before carrying out water-table reconstructions, and that the minimum count of testate amoebae per sample should exclude WISTs to ensure the development of robust reconstructions.     

Four Biofuel Species’ Responses to Periodic Flooding and High Water Tables on a Florida Histosol

Rising energy costs, decreasing soil depth, and best management practices that require on-farm water retention have led to interest in flood-tolerant bioenergy crops for production in the Everglades Agricultural Area (EAA) of Florida. Information on the effects of high water tables on sugarcane (Saccharum spp. L.) is available; however, little is known about the bioenergy crops elephant grass (Pennisetum purpureum Schumach.), energycane (Saccharum spp. L.), and giant reed (Arundo donax L.). The objective of this study was to evaluate the role of water-table depth on the yields, morphology, physiology, and early season growth of these three bioenergy species in relation to sugarcane. The species were grown in a greenhouse and subjected to three water management strategies, ?40 or ?16 cm constant water-table depths, and bi-weekly flooding with drainage to ?40 cm. The experiment was conducted in plant-cane, first-ratoon, and successive plant-cane crop cycles.       Periodic flooding relative to a ?40 cm constant water table significantly reduced dry weights and leaf area index and increased aerenchyma development. Averaged among crops, dry weight declined by 32, 49, 37, and 52% while leaf area index (LAI) decreased by 31, 50, 46, and 57% for giant reed, elephant grass, energycane, and sugarcane, respectively, in response to flooding. Aerenchyma proportional area of the stalk increased by 52, 90, and 95% for elephant grass, energycane, and sugarcane, respectively, but aerenchyma in giant reed decreased by 11%. High yields and stalk populations for all water tables were observed in energycane and elephant grass. These two species show potential for bioenergy production in the EAA. Field trials are recommended to confirm production scale yield.     

Ecosystem Respiration in a Cool Temperate Bog Depends on Peat Temperature But Not Water Table

Ecosystem respiration (ER) is an important but poorly understood part of the carbon (C) budget of peatlands and is controlled primarily by the thermal and hydrologic regimes. To establish the relative importance of these two controls for a large ombrotrophic bog near Ottawa, Canada, we analyzed ER from measurements of nighttime net ecosystem exchange of carbon dioxide (CO₂) determined by eddy covariance technique. Measurements were made from May to October over five years, 1998 to 2002. Ecosystem respiration ranged from less than 1 μmol CO₂ m⁻² s⁻¹ in spring (May) and fall (late October) to 2–4 μmol CO₂ m⁻² s⁻¹ during mid-summer (July-August). As anticipated, there was a strong relationship between ER and peat temperatures (r² = 0.62). Q₁₀ between 5° to 15°C varied from 2.2 to 4.2 depending upon the choice of depth where temperature was measured and location within a hummock or hollow. There was only a weak relationship between ER and water-table depth (r² = 0.11). A laboratory incubation of peat cores at different moisture contents showed that CO₂ production was reduced by drying in the surface samples, but there was little decrease in production due to drying from below a depth of 30 cm. We postulate that the weak correlation between ER and water table position in this peatland is primarily a function of the bog being relatively dry, with water table varying between 30 and 75 cm below the hummock tops. The dryness gives rise to a complex ER response to water table involving i) compensations between production of CO₂ in the upper and lower peat profile as the water table falls and ii) the importance of autotrophic respiration, which is relatively independent of water-table position.     

Cyanobacteria cause black staining of the National Museum of the American Indian Building, Washington, DC, USA

Microbial deterioration of stone is a widely recognised problem affecting monuments and buildings all over the world. In this paper, dark-coloured staining, putatively attributed to microorganisms, on areas of the National Museum of the American Indian Building, Washington, DC, USA, were studied. Observations by optical and electron microscopy of surfaces and cross sections of limestone indicated that biofilms, which penetrated up to a maximum depth of about 1?mm, were mainly composed of cyanobacteria, with the predominance of Gloeocapsa and Lyngbya. Denaturing gradient gel electrophoresis analysis revealed that the microbial community also included eukaryotic algae (Trebouxiophyceae) and fungi (Ascomycota), along with a consortium of bacteria. Energy-dispersive X-ray spectroscopy analysis showed the same elemental composition in stained and unstained areas of the samples, indicating that the discolouration was not due to abiotic chemical changes within the stone. The dark pigmentation of the stone was correlated with the high content of scytonemin, which was found in all samples.     

Reseating of ecological gradients. II. The effect of scale on symmetry of species response curves

Response curves are presented for 15 species of vascular plants, bryophytes, and lichens relative to the water-table gradient in a boreal Norwegian mire. The gradient is scaled in two ways; position of median water-table in cm below the surface of the bottom layer, and in units of compositional turnover (rescaled by DCA). The two scalings produce quite different curves above the maximum water-level, which corresponds to median water-level 10–14 cm below the surface of the bottom layer. The significant drop in compositional turnover above this level can be ascribed to vertical differences in water-table having a lesser effect on plants in aerated hummocks than on plants in temporarily water-logged hollows. Skewness of response curves was reduced by gradient rescaling, most strongly after removal of influence of other gradients. It is argued that response curves will generally be Gaussian if: (1) the response is with respect to a dominant ecological factor, (2) the range of variation along the gradient is sufficient, (3) the distribution of samples is adequate, and (4), the gradient is scaled in units of compositional turnover.