Tomas Thierfelder

Towards a framework for predicting impacts of land-use on recharge: 1. A review of recharge studies in Australia

This work investigated the potential for developing generic relationships from measurements of recharge made in previous studies that would allow the assessment of the impact of land-use change on recharge. Forty-one studies that measured recharge from across Australia were reviewed to generate a database. Studies were characterised on the basis of broad soil type (sand or non-sand), land-use/vegetation (annual, perennial, or trees), and annual rainfall. Attempts to develop quantitative recharge relationships met with limited success because of the limited geographical coverage of the studies, lack of details on the study sites, and high variability in the data. Nevertheless, the following relationships for annual vegetation were statistically valid: Ln(recharge) = –19.03 + 3.63 ln(rainfall) [for sandy soils]; F(1, 96) = 149.03; R 2 = 0.60 Ln(recharge) = –12.65 + 2.41 ln(rainfall) [for non-sandy soils]; F(1,151) = 46.87; R 2 = 0.23 The low degree of explanation of rainfall for the annual × non-sand data suggests that it is likely that soil structure becomes more important for higher clay content soils. Recharge under trees was negligible compared with that under annuals. These relationships should not be used in areas such as those where: preferential pathway flow is the dominant recharge mechanism, rainfall is summer dominant, lateral hydraulic gradients are high, water holding capacities are very low, or there are fresh, high-yielding aquifers. Collectively, the results show that: (1) rainfall explains a significant proportion of the observed recharge variation; (2) there is a significant difference between mean recharge under trees and annual vegetation; (3) there is a significant difference between mean recharge under annual vegetation on sand soils and non-sand soils; (4) the land-use groups had a greater influence on recharge than the broad soil groups used in this study; (5) there is a lack of annual recharge measurements under perennial pastures/crops, under trees in high rainfall zones (i.e. >600 mm/year) and in areas of summer dominant rainfall; (6) across a broad range of locations, recharge is higher under shallow-rooted annual vegetation than deep-rooted vegetation; and (7) the estimator of Zhang et al. (1999) for ‘excess water’ may provide a useful indication of the upper limit to the long-term average recharge measurements. Large variation in the data resulted from disparity in the recharge techniques used, the coarse soil categories used, failure to account for land management factors, and complications due to macropores and shallow water tables. It is proposed that the value of the information presented here may be enhanced in future studies by incorporating information from qualitative studies, particularly paired-site studies, and by drawing information from unsaturated zone and groundwater modelling studies, particularly comparisons of different land-uses at similar locations. Furthermore, the results of this study can be used to identify gaps in knowledge and, hence, target areas for future research such as annual recharge measurements beneath perennial vegetation. Additional keywords: dryland salinity, groundwater management, deep drainage.

Ecosystem change and stability over multiple decades in the Swedish subarctic: complex processes and multiple drivers

The subarctic environment of northernmost Sweden has changed over the past century, particularly elements of climate and cryosphere. This paper presents a unique geo-referenced record of environmental and ecosystem observations from the area since 1913. Abiotic changes have been substantial. Vegetation changes include not only increases in growth and range extension but also counterintuitive decreases, and stability: all three possible responses. Changes in species composition within the major plant communities have ranged between almost no changes to almost a 50 per cent increase in the number of species. Changes in plant species abundance also vary with particularly large increases in trees and shrubs (up to 600%). There has been an increase in abundance of aspen and large changes in other plant communities responding to wetland area increases resulting from permafrost thaw. Populations of herbivores have responded to varying management practices and climate regimes, particularly changing snow conditions. While it is difficult to generalize and scale-up the site-specific changes in ecosystems, this very site-specificity, combined with projections of change, is of immediate relevance to local stakeholders who need to adapt to new opportunities and to respond to challenges. Furthermore, the relatively small area and its unique datasets are a microcosm of the complexity of Arctic landscapes in transition that remains to be documented.

Inferring the location of catchment characteristic soil moisture monitoring sites. Covariance structures in the temporal domain

Information shortage is a fundamental constraint in catchment hydrology that severely affects the possibilities for secure inference of the generic hydrologic landscape, as well as for secure validation of physically deduced distributed models. The introduction of databases with high enough spatiotemporal resolution to properly reflect generic hydrological catchment characteristics may therefore be considered as an inferential breakthrough. The work presented here is part of a project where observations from such an Australian catchment (the Tarrawarra) are utilised to estimate the discrepancy for individual soil moisture monitoring sites in reflecting generic catchment characteristics. With low enough discrepancy, observation sites may be considered as catchment characteristic soil moisture monitoring (CASMM) sites, thus capturing unbiased catchment characteristics and being well suited to represent the catchment in a monitoring effort. In this particular study, covariance structures in the temporal domain are inferred in order to enable subsequent enquiries regarding CASMM discrepancies. This is accomplished with ARMAX filters applied to the conditional auto- and cross-covariance structures that connect observations of soil moisture to the temporal variation of meteorology. The results suggest that weekly observations of Tarrawarra soil moisture are quite consistent realisations of first order auto-regressive processes, which means that the present state of soil moisture is generally acquired through the past week. With auto-correlative effects filtered out, cross-correlative meteorological effects on Tarrawarra soil moisture are identified and generally represented by the present weeks accumulation of rainfall, the present weeks accumulation of global radiation, and the previous weeks maximum wind speed. After successive filtering of conditional cross-correlative effects, residual time-series observations may be considered as temporally independent, and therefore are well suited for subsequent inferences regarding covariance structures in the spatial domain. Since the exclusion of auto-correlative effects is necessary for unambiguous model interpretation, the estimated cross-correlative parameters should reflect the true nature of underlying physical processes.

The creosote content of used railway crossties as compared with European stipulations for hazardous waste.

Through the history of railways, wooden crossties impregnated with potentially hazardous creosote tar have supported the rails. With impregnated crossties having a lifespan of approximately 50 years, their creosote content is considered as quite safely stored while in dug-down usage. This situation of relative safety does, however, change into acute risk upon replacement and destruction. Carrying a highly flammable content, creosote crossties discharge a pulse of carcinogenic PAH compounds if burnt as ordinary waste. Safe destruction is therefore required if concentrations exceed a critical limit stipulated by the European Union. Since safe destruction is a process of considerable expense, there is a tendency among financial stakeholders to underestimate the creosote content of used railway crossties. In order to actually test whether concentrations generally exceed the critical limit, a set of used creosote ties was therefore sampled while still situated in the railway embankment. With a standard sum of sixteen PAH compounds used as an expression of their total creosote content, the generic concentration was formally inferred and found to significantly exceed the critical limit. The same applies to the fraction of seven carcinogenic PAH compounds, that alone exceed the stipulated limit for hazardous waste. It was also found that the material of railway embankments, whether or not the crossties were used in switches and/or railway yards, and sample depth within the crossties, has a significant effect on creosote concentrations. Regardless of the status of these factors, the concentrations significantly exceed the critical limit that defines hazardous waste within the European Union.

Time lag between peak concentrations of plasma and salivary cortisol following a stressful procedure in dairy cattle.

BackgroundMeasurement of salivary cortisol has been used extensively as a non-invasive alternative to blood sampling to assess adrenal activity in ruminants. However, there is evidence suggesting a considerable delay in the transfer of cortisol from plasma into saliva. Previous studies in cattle have used long sampling intervals making it difficult to characterise the relationship between plasma and salivary cortisol (PLCort and SACort, respectively) concentrations at different time points and determine whether or not such a time lag exist in large ruminants. Therefore, the objective of this study was to characterise the relationship between plasma and salivary cortisol and determine if there is a significant time lag between reaching peak cortisol concentrations in plasma and saliva across a 4.25 h time-period, using short sampling intervals of 10-15 min, following social separation in dairy cattle.Five cows were separated from their calves at 4 days after calving, and six calves were separated from a group of four peers at 8 weeks of age. Following separation, the animals were moved to an unfamiliar surrounding where they could not see their calves or pen mates. The animals were catheterised with indwelling jugular catheters 1 day before sampling. Blood and saliva samples were obtained simultaneously before and after separation.ResultsIn response to the stressors, PLCort and SACort increased reaching peak concentrations 10 and 20 min after separation, respectively. This suggested a 10 min time lag between peak cortisol concentrations in plasma and saliva, which was further confirmed with a time-series analysis. Considering the 10 min time lag, SACort was strongly correlated with PLCort (P < 0.0001).ConclusionsSalivary cortisol correlates well with plasma cortisol and is a good indicator of the time-dependent variations in cortisol concentrations in plasma following acute stress. However, there is a time lag to reach peak cortisol concentrations in saliva compared to those in plasma, which should be considered when saliva samples are used as the only measure of hypothalamic-pituitary-adrenal axis response to stress in cattle.

Impact of stroke on anterior–posterior force generation prior to seat-off during sit-to-walk

Force generation during sit-to-walk (STW) post-stroke is a poorly studied area, although STW is a common daily transfer giving rise to a risk of falling in persons with disability. The purpose of this study was to describe and compare strategies for anterior-posterior (AP) force generation prior to seat-off during the STW transfer in both subjects with stroke and in matched controls. During STW at self-selected speed, AP force data were collected by 4 force plates, beneath the buttocks and feet from eight subjects with stroke (>6 months after onset) and 8 matched controls. Subjects with post-stroke hemiparesis and matched controls generated a similar magnitude of total AP force impulses (F(1,71)=0.67; p=0.42) beneath buttocks and feet prior to seat-off during STW. However, there were significant group differences in AP force impulse generation beneath the stance buttock (i.e. the non-paretic buttock in the stroke group), with longer duration (F(1,71)=8.78; p<0.005), larger net AP impulse (F(1,71)=6.76; p<0.05) and larger braking impulse (F(1,71)=7.24; p<0.05) in the stroke group. The total braking impulse beneath buttocks and feet was about 4.5 times larger in the stroke group than in the control group (F(1,71)=8.84; p<0.005). An intra- and inter-limb dys-coordination with substantial use of braking impulses was demonstrated in the stroke group. This motor strategy differed markedly from the smooth force interaction in the control group. These results might be important in the development of treatment models related to locomotion post-stroke.

Functional microbial diversity of the railway track bed.

Railways constitute relatively unexplored microbial habitats. Little is known about the amounts, activities or distributions of microorganisms and their associated heterotrophic capabilities on railway embankments. The aim of this study was to investigate the microbiology of two Swedish railway tracks in order to fill some of the gaps in the available information. We estimated microbial biomass by means of substrate-induced respiration, microbial activity as basal respiration (BR) and as a kinetically derived parameter (r) hypothesised to correspond to the active fraction of the microbial biomass. It was confirmed that the microbial biomass and activity were low as compared with agricultural soils and that their distributions were distinctly positively skewed. Spatial Kriging revealed that covariance structures were sustained on a scale smaller than the employed sampling grid (<1 m). Substrate richness (SR), as measured with Biolog ECO plates, was used as a quantitative measure of functional diversity. SR correlated to microbial activity and SIR, indicating that functional traits were lacking where the microbial biomass was low or less active. The dependence of microbial activities on basic soil characteristics were inferred by separately designed general linear models. Water content was found to be the most important factor moderating basal respiration and functional diversity, whereas the organic matter content was identified as the most important covariate for SIR. Multivariate analysis of the carbon source utilisation patterns of the Biolog plates with equivalent average well-colour development revealed homogenous substrate utilisation among samples. This indicates that the microbial functional potential is randomly distributed in the railway track bed. In combination, our findings imply that the ecosystem functionality of railway embankments may be seriously hampered as compared with agricultural soils. This has consequences for the risk assessment of herbicides applied to railways.

Country characteristics and non-indigenous species

This paper presents an econometric test of two hypotheses underlying the occurrence of non-indigenous species (NIS) at the global scale: openness of recipient nations which allows for international trade to act as a vector of NIS, and habitat fragmentation in recipient nations which facilitates establishment of introduced NIS. Explorative econometric methods have been utilised that combine the analysis of dimensionality with subset variable selection and multiple linear regression. Both NIS hypotheses are thereby supported, although slightly different in the cases of the mainland and island nations. It is concluded that expressions of openness have a larger impact on the number of NIS per unit territorial area in the mainland nations, whereas biota variables play a more dominant role in the case of the island nations. It is also concluded that different expressions of NIS occurrence affect the result, where NIS per area unit facilitates excellent explanatory performance.

Beyond K-means: Clusters Identification for GIS

Clustering is an important concept for analysis of data in GIS. Due to the potentially large amount of data in such systems, the time complexity for clustering algorithms is critical. K-means is a popular clustering algorithm for large-scale systems because of its linear complexity. However, this requires a priori knowledge of the number of clusters and the subsequent selection of their centroids. We propose a method for K-means to find automatically the number of clusters and their associated centroids. Moreover, we consider recursive extension of the algorithm to improve visibility of the results at different levels of abstraction, in order to support the decision-making process.

Ban of a broad-spectrum insecticide in apple orchards: effects on tortricid populations, management strategies, and fruit damage

The objective of this study was to investigate the effects of the ban of Gusathion® (azinphosmethyl) as insecticide in Swedish apple orchards on tortricid moth population density and tortricid-induced crop damage. In addition, the effects on growers’ management strategies, such as choice of spraying dates and alternative insecticide combinations, were studied. Populations of Adoxophyes orana, Archips podana, Archips rosana, Cydia pomonella, Pandemis heparana, Hedya nubiferana, and Spilonota ocellana were monitored using sex-pheromone traps during the four consecutive seasons of 2008–2011, with annual crop damage estimates made prior to harvest. Azinphosmethyl was banned after 2008. Significantly increasing population densities were observed in A. orana, A. podana, C. pomonella, and H. nubiferana, whereas correspondingly increasing crop damage was observed only in the case of C. pomonella. The growers’ management strategies, with respect to number and timing of spray applications, did not change during the study period although the insecticides available after the ban were less persistent and more specific, i.e., either with primarily ovicidal or larvicidal effect. Analysis of a broad range of factors showed that temperatures during winter and spring, number and timing of insecticide applications, and usage of azinphosmethyl in 2008 were important factors affecting population size and the damage caused by the tortricid species studied.