Pollution impacts on bird population density and species diversity at four non-ferrous smelter sites

Non-ferrous smelters pose a potential hazard for breeding bird populations, but comprehensive analyses of the impacts on bird population densities around smelter sites are currently lacking. We measured with point counts bird population densities around four smelter sites in Russia (Monchegorsk, Karabash and Revda) and Finland (Harjavalta) to explore the relationships between bird population density/species diversity and exposure level quantified by the potentially bioavailable copper concentrations in forest litter. Total bird densities, bird biomasses and species diversities decreased in the vicinity of all three Russian smelters. In Harjavalta, there were no pollution-related trends in total bird density or biomass, although species diversity (species number and Shannon’s index) decreased towards the pollution source. In general, the four smelters showed negative effects on bird populations in decreasing order of impact as follows: Monchegorsk > Karabash > Revda > Harjavalta, reflecting the amount of current and past emissions and consequent habitat change at each site. Our results suggest that around copper–nickel and copper smelters the pollution impact on bird diversity is accelerated when the litter copper level exceeds 1000 μg/g. However, even though bird densities and diversities reflected the exposure levels in our study, they were not associated with litter copper concentrations in a strictly dose-dependent manner, indicating that copper itself is not a primary cause for the changes in bird communities, but rather the combined effect of multiple pollutants on birds and especially on the resources necessary for breeding, such as food and suitable habitat.     

Global food security,biodiversity conservation and the future of agricultural intensification

There is vigorous debate about the potential for reforestation to offset losses in biodiversity associated with tropical deforestation, but a scarcity of good data. We quantified developmental trajectories following active restoration (replanting) of deforested pasture land to tropical Australian rainforest, using 20 different bird community indicators within chronosequences of multiple sites. Bird species composition in restored sites (1–24 years old) was intermediate between that of reference sites in pasture and primary rainforest. Total species richness was much less sensitive to land cover change than composition indicators, because of contrasting species-specific response patterns. For example, open-country (grassland/wetland) bird species declined in richness and abundance with increasing site age, while rainforest-dependent species increased. Results from two different landscapes (uplands and lowlands) were remarkably consistent, despite differing bird assemblages. After 10 years, restored sites averaged about half the number of rainforest-dependent bird species typical of rainforest. Mean values at around 20 years overlapped with the “poorest” rainforest reference sites, but projections suggest that >150 years are required to reach mean rainforest levels, and high variability among sites means that many were not on track towards ever achieving a rainforest-like bird community. Regional rainforest endemics were half as likely to occupy older revegetated sites as non-endemic rainforest-dependent species. Between-site variability and slow colonisation by regional endemics strongly constrain the potential of rainforest restoration to offset the biodiversity impacts of tropical deforestation. The results also mean that ongoing monitoring of biodiversity is an essential part of restoration management.     

Soil moisture effects on infectivity and persistence of the entomopathogenic nematodes Steinernema scarabaei,S. glaseri,Heterorhabditis zealandica,and H. bacteriophora

We tested the effect of soil moisture on the performance of four entomopathogenic nematodes species that have recently shown promise for the control of white grubs, i.e., Heterorhabditis bacteriophora, H. zealandica, Steinernema scarabaei, and S. glaseri. Experiments for all four nematodes were conducted in sandy loam, for S. scarabaei also in loamy sand and silt loam. Infectivity was tested by exposing third-instar Japanese beetle, Popillia japonica, to nematodes in laboratory experiments and determining nematode establishment in the larvae and larval mortality. Nematode infectivity was the highest at moderate soil moistures (−10 to −100 kPa), and tended to be lower in wet (−1 kPa) and moderately dry (−1000 kPa) soil. In dry soil (−3000 kPa), only S. scarabaei showed some activity. S. scarabaei was active from −1 to −3000 kPa in all soil types but the range of highest activity was wider in loamy sand (−1 to −1000 kPa) than in loamy sand and silt loam (−10 to −100 kPa). Persistence was determined in laboratory experiments by baiting nematode-inoculated soil with larvae of the greater wax moth, Galleria mellonella. For both Heterorhabditis spp. persistence was short at −10 kPa, improved slightly at −100 kPa, significantly at −1000 kPa, and was the highest at −3000 kPa. Both Steinernema spp. persisted very well at −10 kPa. However, S. glaseri persistence was the shortest at −10 kPa but did not differ significantly at −100 to −3000 kPa, whereas S. scarabaei persistence was not affected by soil moisture. Our observations concur with previous observations on the effect of soil moisture on entomopathogenic nematodes but also show that moisture ranges for infectivity and persistence vary among species. Differences among species may be based on differences in size and behavioral and physiological adaptations.     

Enzyme activities and diuron persistence in soil amended with vermicompost derived from spent grape marc and treated with urea

Mineral fertilizers, organic amendments, and pesticides are inputs commonly used in conventional farming practices. The aim of this study was to evaluate the effects of single or combined applications of spent grape marc-vermicompost, urea, and/or diuron on soil-enzyme activities and the persistence of this herbicide in soils with low organic carbon content. The application of vermicompost enhanced dehydrogenase (DHase) enzyme activity over time but altered soil urease activity to a very limited extent. The reduction in diuron concentrations and the increase in DHase activity indicated that the soil microorganisms were capable of degrading the ureic herbicide. Treatment with vermicompost and diuron had a stimulatory effect on soil microbial activity. On the whole, the application of diuron and urea to the vermicompost-amended soil raised DHase and urease activity to maximum levels (>3 μg INTF g^?1 h^?1 and >47 μg NH₄⁺ g^?1 h^?1, respectively). The application of urea to the unamended and vermicompost-amended soil decreased diuron persistence from 18.8 and 33 d to 12.5 and 15 d, respectively. Our findings show that although vermicompost additions reduce diuron availability, this boosts diuron degradation when combined with urea. These additions, under different soil management conditions, minimize the bioavailability and persistence of diuron and consequently the risk of leaching and seepage into aquifers. Compared with untreated soils, these types of treated soils could also improve agricultural sustainability and the quality of the environment.     

The effectiveness of conservation measures to enhance nest survival in a meadow bird suffering from anthropogenic nest loss

The main reason for meadow bird declines is supposed to be the intensification of grassland management with earlier first harvest dates and more frequent harvests, resulting in high nest destruction rates. To increase productivity of meadow bird populations in intensified grassland areas a delay of mowing date and individual nest protection measures have been proposed. However, for ground-nesting songbirds such as the whinchat (Saxicola rubetra) the effectiveness of such measures remains widely unknown. In particular, if nest predation rate is high, measures to protect nests from agricultural destruction alone might be questionable. Here, we quantify whinchat nest survival of (1) unprotected nests situated in early mown meadows, (2) protected nests situated in early mown meadows, and (3) nests situated in late mown meadows. Analyses considered the fact that successful and unsuccessful nests are not found with equal probabilities. Periods of reduced nest survival were associated with mowing periods in the different types of meadows. In early mown meadows nest survival rates were low (S < 0.1), and both conservation measures, individual nest protection and delayed mowing, resulted in significantly increased nest survival rates (S > 0.7). Individual nest protection cannot avoid changes in habitat quality of intensively managed meadows, and therefore is only suitable as small-scale and short-term measure to increase nest success until a high portion of late mown meadows is established. Thus, we suggest that a combination of the two measures applied to intensified grassland fields should be provided to maintain viable sizes of endangered meadow bird populations.     

Survival and persistence of genetically modified Sinorhizobium meliloti in soil

Studies were conducted to evaluate the survival and persistence of Sinorhizobium meliloti 104A14 and two acid phosphatase-negative mutants in Kirkland (fine, mixed, thermic Udertic Paleustolls) silt loam soils with various fertility levels, and to assess the impact of inoculation on nodule occupancy and soil microbial community structure in the inoculated alfalfa (Medicago sativa L.) rhizosphere. Recovery of the inoculated strains was 100% (in the order of 10⁸ cells g⁻¹ soil) immediately following inoculation to soils, but decreased from 10⁸ cells g⁻¹ soil to undetectable levels in a nutrient-poor soil within 32 days. In a nutrient-rich soil, approximately 2–3% (4.7–7.43×10⁶ cells g⁻¹ soil) of the mutants and 23% (5.84×10⁷ cells g⁻¹ soil) of the wild-type inocula persisted for more than 64 days. Survivability and persistence of the wild-type S. meliloti were significantly greater than that of the genetically modified acid phosphatase negative mutants in all the soils tested. The persistence and nodule occupancy of the introduced S. meliloti in sterile and non-sterile soils were also tested for two repeated alfalfa growth periods in the same plant growth units, with a 1 month interval in between and no additional inoculation for the second period. Nodule occupancy of the introduced S. meliloti in non-sterile soils ranged from 30 to 60% for the first period and 85 to 100% for the second period. Our results suggest that survival and persistence of S. meliloti was enhanced by alfalfa cultivation and increased soil fertility, but impaired by mutation of acid phosphatase genes regardless of phosphorus nutritional levels. Moreover, inoculation with genetically modified S. meliloti strain 104A14 promoted indigenous bacterial growth in soil (increased bacterial population from 1.4×10⁶ to 4.3×10⁶ cells g⁻¹ soil), but not the growth of fungi and yeast. However, inoculation of the wild-type S. meliloti or genetically modified mutants did not result in significant changes in microbial community structure as indicated by EP indices and ratios of r/K strategists.     

Estimation of evaporation using a dual-beam surface layer scintillometer and component energy balance measurements

A dual-beam surface layer scintillometer (SLS), for the estimation of sensible heat flux density H for a path length of 101 m, was used in a mixed grassland community in the eastern seaboard of South Africa for 30 months. Measurements also included Bowen ratio (BR) and eddy covariance (EC) estimates of H. Acceptable SLS data between 0600 h and 1800 h, judged by the percent of error-free 1 kHz data exceeding 25% and an inner scale of turbulence exceeding 2 mm, showed little seasonal variation and was consistently high—between 86.7% and 94.8%. An analysis of the various Monin–Obukhov similarity theory (MOST) empirical dimensionless stability functions used for estimating H from the SLS measurements showed percent differences in H that varied from ?30% to 28% for neutral to unstable conditions, respectively and for stable continuous conditions the differences in H were within 60 W m^?2 with much larger differences for stable sporadic conditions. The good agreement in measurements of H over an extended period for the SLS, BR and EC methods demonstrates the applicability and robustness of the SLS method and the associated MOST empirical functions used for estimating H for a range of canopy heights, stability conditions and diurnal and seasonal weather conditions. Furthermore, there was no evidence for an underestimation in EC sensible heat compared to SLS and BR measurements, which implies that any lack of energy balance closure points to possible latent energy EC underestimation or due to energy fluxes not included in the shortened energy balance if the net irradiance and soil heat flux components are correct. A sensitivity analysis was used to determine the relative importance of the SLS data inputs of air temperature, atmospheric pressure, beam path length and beam height on H estimates. Worst-case errors in air temperature, atmospheric pressure, beam path length and beam height resulted in errors in H within 1.0%, 1.3%, 3.0% and 4.0%, respectively. Overall, the worst-case total percent error in SLS-estimated H is within 5.3% and the typical percent error is within 3.9%. Accounting for the error in net irradiance and soil heat flux measurements, the seasonal variation in the error in daily evaporation estimated as a residual of the energy balance is generally less than 0.2 mm (0.49 MJ m^?2) in winter when the daily evaporation was about 1 mm (2.45 MJ m^?2) and typically less than 0.4 mm (0.98 MJ m^?2) when the evaporation exceeded 4 mm (9.8 MJ m^?2). Soil heat flux density measurements can contribute significantly to the overall error.     

Climatic trends associated with summerfallow in the Canadian Prairies

The Canadian Prairies have undergone important land use changes over the past 150 years. Beginning in the early 20th century, a significant portion of agricultural land was under summerfallow primarily to conserve soil moisture. The area under fallow grew to over 11 Mha, which constitute about 25% of Canada's cultivated land, and mostly remained at that level until 1975, subsequent to which improved land management practices led to significant reductions in areas under summerfallow. By 2001 summerfallow area had been reduced to 5.4 Mha, and future projections expect it to fall to 3.5 Mha. Numerous modeling studies and observations have shown that land use change can have a significant impact on regional and local climate. In the Canadian Prairies, these effects would likely be seen during the mid-June to mid-July period, when agricultural crops undergo rapid foliar expansion and substantial transpiration, thus contributing to significantly higher latent heat fluxes. Observations of 1976–2000 climate trends in the black, dark brown and brown soil zones of the Canadian Prairies showed that there have been substantial reductions in maximum temperature (1.7 °C decade⁻¹), diurnal temperature range (1.1 °C decade⁻¹) and solar radiation (1.2 MJ m⁻² decade⁻¹), as well as a corresponding increase in precipitation (10.3 mm decade⁻¹) during the mid-June to July period. These findings are in opposition to trends that would be expected from climate change from an enhanced greenhouse effect, and suggest that there is substantial correspondence between reductions in summerfallow and changes in climate in the agricultural regions of the Canadian Prairies.     

Impact of abundant Pheidole ant species on soil nutrients in relation to the food biology of the species

Impact of Pheidole sp., reportedly important in insect pest suppression in agroecosystems was studied on supporting agroecosystem services. This tropical ant species was found to be common and abundant in agroecosystems, with a high nest density and preference for the central, crop-growing zone of annual cropping systems. Physico-chemical characteristics of the debris soil were examined from nests located by the roadside and within two managed ecosystems. The debris soil had significantly higher concentrations of total C, N, P and NO₃-N along with higher water-holding capacity and moderate-sized soil particles in comparison to the control soil. The pH of the Pheidole sp. debris soil was shifted towards reduced alkaline conditions. Results reveal that annually, 2.44 kg/ha C, 0.071 kg/ha P, 0.628 kg/ha N and 0.009 kg/ha NO₃-N are added to the soil through the accumulation of organic refuse at the nest rim. This contributes to soil nutrient enhancement and is suggested to enhance ecosystem productivity. The high nutrient content of nest debris soil is linked to the predominance of arthropod carcasses (93.7% of the total organic refuse) in the refuse piles derived from the animal-based food (70.3%) brought to the nests by the foragers. Plant-based food was 29.6% (seeds, leaves, roots, etc.) of the total indicating a minor role of Pheidole sp. as a seed harvester. The results suggest an important role of Pheidole sp. in regulating the soil nutrients as an ecosystem engineer.     

Coupling effects of depth of film-bottomed tillage and amount of irrigation and nitrogen fertilizer on spring wheat yield

The crop cultivation with film-bottomed tillage may benefit more, but little is known about the coupling effects of depth of film-bottomed tillage (DFBT) and amount of irrigation and nitrogen (N) fertilizer on spring wheat yield. A field quadratic regression orthogonal design experiment was conducted to determine the effects of DFBT, irrigation and N fertilization on seed yield of spring wheat (Triticum aestivum L.) in the Hexi Corridor, China from 2002 to 2005. Five levels of irrigation (143, 165, 225, 285, and 306 mm), five levels of N (45, 70, 140, 210, and 235 kg N ha⁻¹) and five DFBT (46, 60, 70, 80, and 94 cm) were investigated. Irrigation (44 mm ≤ irrigation ≤ 300 mm), DFBT (46 cm ≤ DFBT ≤ 80 cm), and N (≤160 kg N ha⁻¹) significantly increased wheat yield. DFBT, N and irrigation had a positive effect on wheat yield, in the order: irrigation > N > DFBT. The coupling between DFBT × N and, between N × irrigation had a synergistic effect on spring wheat yield. The coefficient of DFBT × irrigation was negative showing the coupling of DFBT × irrigation had a reciprocal inhibition or substitution effect. The findings suggest that spring wheat should be irrigated with 300 mm of water, with an application of 160 kg N ha⁻¹ and a 70 cm DFBT in the arid climate and sandy soil areas of China, to obtain the highest wheat yield with maximum economic benefit. The assessment with respect to N fertilizer use efficiency, environmental pollution need further research.     

Implications of input estimation,residue quality and carbon saturation on the predictive power of the Rothamsted Carbon Model

Effects of fertilisation and cropland management on soil organic carbon (SOC) dynamics can be assessed best in long-term experiments. Using data from the long-term fertilisation experiment in Puch, Germany (part of the series “Internationale Organische Stickstoff Dauerversuche”, IOSDV), we tested the performance of the Rothamsted Carbon Model 26.3 (RothC). The objectives of this work were: (i) quantify the C-input and the efficiency of SOC stabilisation, (ii) test the performance of different input estimates on predictive power of the RothC and (iii) test implementations of residue quality and C-saturation on model predictions. The experiment is a full-factorial strip design, the factors being “organic amendment” and “level of N-fertiliser”. Each treatment was replicated three times. The crop rotation is silage maize–winter wheat–winter barley. Five levels of the factor “organic amendment” were considered: (i) CON: no organic amendment; (ii) SLU: slurry application (on average 0.8 Mg C ha^? 1 year^? 1); (iii) FYM: application of farmyard manure (30 to 40 Mg ha^? 1 fresh mass every third year to maize, on average 1.0 Mg C ha^? 1 year^? 1); (iv) STR: straw incorporation after harvest of wheat and barley (depending on straw yield on average 0.7 to 2.2 Mg C ha^? 1 year^? 1); (v) STSL: slurry application plus straw incorporation (on average 1.1 to 2.4 Mg C ha^? 1 year^? 1). All treatments (including CON) were combined with five different levels of N-fertilisation (N0 to N4), whereas N0 was nil N application and N4 averaged 177 kg N ha^? 1 year^? 1. N-rates increased gradually and differed depending on the crop. Starting values for SOC stocks (Mg ha^? 1) were measured in 1983 as a mean among N-rates for organic amendment treatments (CON: 42; SLU: 39.8; FYM: 40.5; STR 39.8; STSL: 40.5). SOC stocks (0–25 cm) in 2004 (35.5 to 46.6 Mg C ha^? 1) were in the order STSL > FYM = SLU > STR = CON (p ≤ 0.001). However, slightly different starting values indicated a higher loss of SOC after 21 years in the CON (11–14%) compared to the STR treatments (1–10%). Effect of N-rate was not significant. The observed relation between change of SOC and C-input was quadratic (Y_O = ? 13.4 + 7.5x ? 0.9x²; R² = 0.74, p ≤ 0.001), which contrasted the linear relationship predicted by RothC (Y_P = ? 12.9 + 5.5x; R² = 0.97, p ≤ 0.0001). Serious deviation between observed and predicted relationship occurred above C-inputs of 2.5 Mg C ha^? 1 year^? 1. Mechanistic explanation (e.g. C-saturation or increased mineralisation by N-fertilisation) for the observation needs further exploration, but implication on regional estimates for C-accumulation for different cropland management scenarios is obvious: potential gain in SOC storage by increasing C-inputs may be overestimated, at least under conditions of the Puch site. Independent model predictions (i.e. no parameter adjustment and independent estimation and measurement of C-input) were successful for treatments without straw incorporation (CON, SLU, FYM). Using a regression between crop yields and crop residue input yielded better results than using a constant belowground-to-aboveground biomass ratio. SOC stocks of treatments STR and STSL were seriously overestimated by the model. Using a higher decomposability of crop residue improved result only marginally and required the change of a standard parameter. Using a simple implementation of C-saturation improved predictions for STR and STSL but failed to simulate dynamics in all other treatments. Overall, our results showed that it is important to recognise that relation between SOC change and C-input is not necessarily linear. However, the RothC model predicted SOC dynamics well at lower input levels. Observation that a regression equation for input estimation is superior to a constant biomass ratio for modelling purposes has to be tested further. An implementation of residue quality or saturation capacity in the RothC model may be promising for a better mechanistic understanding of SOC dynamics. However, this requires careful calibration and will increase the number of parameters to be fitted.     

Single and mixture toxicity of gold nanoparticles and gold(III) to Enchytraeus buchholzi (Oligochaeta)

The ecotoxicity of gold nanoparticles (Au-NPs), gold(III) and their mixtures was assessed in the potworm Enchytraeus buchholzi after 14-day bioassays. The worms were exposed at 20 °C in OECD artificial soil to 0, 9.37, 18.7, 28.1 and 37.5 mg/kg Au-NPs or Au(III) and 0, 9.37 + 9.37, 18.7 + 18.7, 28.1 + 28.1, 37.5 + 37.5 mg Au-NPs + Au(III)/kg. The results indicated that the range of Au-NPs concentrations used in the present study was not deleterious to the survival and reproduction of E. buchholzi. Au(III) showed no significant effect on survival but was significantly deleterious to reproduction in the highest treatment (p ≤ 0.01). A 14-day EC50_Au(III) = 35.5 mg/kg was estimated for effects on reproduction. Au-NPs/Au(III) mixtures essentially caused the same effects as Au(III) except for 18.7 mg Au(III)/kg vs. 18.7 + 18.7 mg Au-NPs + Au(III)/kg where the mixture treatment was significantly more toxic to reproduction (p < 0.02). Mixture results suggested a seemingly additive effect between Au-NPs and Au(III), although the conventional toxic unit approach could not be used to ascertain this conclusively because of the lack of Au-NPs toxicity. The order of toxicity between Au-NPs, Au(III) and their mixtures was Au-NPs = Au(III) = Au-NPs/Au(III) for survival and Au-NPs < Au(III) ≤ Au-NPs/Au(III) for reproduction.     

Solar global UVB (280–315 nm) and UVA (315–380 nm) radiant fluxes and their relationships with broadband global radiant flux at an eastern Mediterranean site

The depletion in the concentration of ozone layer in the stratosphere may significantly increase the UV radiant flux levels (mainly the UVB, 280–315 nm) reaching the earth's surface. These modifications have raised concern among scientists and policy makers during the last two decades so that numerous field experiments have been conducted illustrating deleterious UVB effects on both ecosystems and human beings. This study aiming to explore the UV radiant flux levels in the eastern Mediterranean basin, hourly measurements of global UVB (G_uvb), UVA (G_uva) and broadband (G_h) radiant fluxes collected at Athalassa, Cyprus (35°N, 33°E, 165 m above MSL) from 1 January 2004 to 31 December 2006, during a joint research project between the Athens University and the Meteorological Service of Cyprus, are employed. These data were used to determine temporal variability of the UV radiant components further addressing their dependence on several atmospheric parameters.The analyses of hourly UVB and UVA values indicated significant diurnal variation of these radiant fluxes during daylight hours. The seasonal variation of the ratios obtained from hourly correlations ranged from 0.0299 ± 0.003 (winter) to 0.0311 ± 0.002 (autumn) with an annual mean of 0.0309 ± 0.003 for (G_uva/G_h), and from 0.00160 ± 0.0003 (winter) to 0.00168 ± 0.0003 (autumn) with an annual mean of 0.00164 ± 0.0003 for (G_uvb/G_h). The hourly ratio (G_uva/G_h) increased from 0.0306 ± 0.003 to 0.0318 ± 0.003 as sky conditions changed from clear to overcast; the hourly (G_uvb/G_h) ratio also increased from 0.00162 ± 0.0003 to 0.00170 ± 0.0004, as sky conditions changed from clear to overcast skies. Several atmospheric parameters such as sky clearness (?), brightness (Δ) and path length (sin h) were found to cause changes to both G_uva/G_h and G_uva/G_h ratios. The present data set indicated also a seasonal contribution of the aerosol extinction on these radiometric ratios. Finally, the inverse correlation between ozone and the UVB radiant flux by means of daily G_uvb/G_uva ratio has been verified for the Athalassa's environment.     

Detection of water stress in an olive orchard with thermal remote sensing imagery

An investigation of the detection of water stress in non-homogeneous crop canopies such as orchards using high-spatial resolution remote sensing thermal imagery is presented. An airborne campaign was conducted with the Airborne Hyperspectral Scanner (AHS) acquiring imagery in 38 spectral bands in the 0.43–12.5 μm spectral range at 2.5 m spatial resolution. The AHS sensor was flown at 7:30, 9:30 and 12:30 GMT in 25 July 2004 over an olive orchard with three different water-deficit irrigation treatments to study the spatial and diurnal variability of temperature as a function of water stress. A total of 10 AHS bands located within the thermal-infrared region were assessed for the retrieval of the land surface temperature using the split-window algorithm, separating pure crowns from shadows and sunlit soil pixels using the reflectance bands. Ground truth validation was conducted with infrared thermal sensors placed on top of the trees for continuous thermal data acquisition. Crown temperature (T_c), crown minus air temperature (T_c − T_a), and relative temperature difference to well-irrigated trees (T_c − T_R, where T_R is the mean temperature of the well-irrigated trees) were calculated from the ground sensors and from the AHS imagery at the crown spatial resolution. Correlation coefficients for T_c − T_R between ground IRT sensors and airborne image-based AHS estimations were R² = 0.50 (7:30 GMT), R² = 0.45 (9:30 GMT) and R² = 0.57 (12:30 GMT). Relationships between leaf water potential and crown T_c − T_a measured with the airborne sensor obtained determination coefficients of R² = 0.62 (7:30 GMT), R² = 0.35 (9:30 GMT) and R² = 0.25 (12:30 GMT). Images of T_c − T_a and T_c − T_R for the entire field were obtained at the three times during the day of the overflight, showing the spatial and temporal distribution of the thermal variability as a function of the water deficit irrigation schemes.     

Impact of high cadmium and nickel soil concentration on selected physiological parameters of Arundo donax L.

The purpose of this study was to investigate the effects of high cadmium and nickel soil concentrations on selected physiological parameters of Arundo donax L. A 2-year pot experiment was held in the field and the pots were irrigated with aqueous solutions of Cd and Ni in concentrations of 5, 50 and 100 ppm, against the control (tap water). At the end of the cultivation periods the pots soil was divided into three equal zones and total and NH₄OAc extractable Cd and Ni concentrations were determined. The top zone exhibited the highest metal content. Cadmium and nickel total concentrations at the end of the experiment were up to 973.8 mg kg⁻¹ and 2543.3 mg kg⁻¹ respectively, while NH₄OAc extractable Cd was up to 291.7 mg kg⁻¹ and Ni up to 510.3 mg kg⁻¹. Stomatal conductance ranged between 0.3 and 0.8 mol CO₂ m⁻² s⁻¹, intercellular CO₂ concentration ranged between 212.9 and 243.0 ppm CO₂, stomatal resistance between 0.6 and 1.3 s cm⁻¹, chlorophyll content (SPAD values) between 46.3 and 57.0 and chlorophyll fluorescence (F_v/F_m) ranged between 0.8 and 0.9. All studied physiological parameters did not show statistically significant differences among control and heavy metal treated plants for both years; therefore, high soil cadmium and nickel concentration did not inhibit stomatal opening and did not affect the function of the photosynthetic machine of A. donax plants.     

Mapping to inform conservation: A case study of changes in semi-natural habitats and their connectivity over 70 years

Intensification of human activities has caused drastic losses in semi-natural habitats, resulting as well in declining connectivity between remaining fragments. Successful future restoration should therefore increase both habitat area and connectivity. The first steps in a framework for doing so are addressed here, which involve the mapping of past habitat change. We present a method which is unique in: the large area covered (2500 km²), the high resolution of the data (25 × 25 m), the long period assessed (70 years), and a system for translation of land use maps into Broad Habitat Types using soil surveys.We digitised land use maps from the 1930s for the county of Dorset in southern England. The resulting map was compared to the UK Land Cover Map of 2000. For our example area, land use shifted dramatically to more intensive agriculture: 97% of all semi-natural grasslands were converted into agriculturally-improved grassland or arable land as were large proportions of the heathlands and rough grasslands (?57%). The other important driver of change was afforestation (+25%). The larger habitat areas became fragmented, with average fragment size of different habitats falling by 31–94%. Furthermore, the connectivity between fragments dropped drastically, by up to 98%.Analyses such as those presented here not only quantify the scale and pattern of habitat loss, but are important to inform land-use planning to restore biodiversity by both increasing the available habitat and facilitating dispersal among habitat fragments. We discuss the possible steps for such a framework.     

Comparing net ecosystem exchange of carbon dioxide between an old-growth and mature forest in the upper Midwest,USA

Old-growth forests are often assumed to exhibit no net carbon assimilation over time periods of several years. This generalization has not been typically supported by the few whole-ecosystem, stand-scale eddy-covariance measurements of carbon dioxide exchange in old-growth forests. An eddy-flux tower installed in a >300-year-old hemlock–hardwood forest near the Sylvania Wilderness, Ottawa National Forest, MI, USA, observed a small annual carbon sink of CO₂ of −72 ± 36 g C m⁻² year⁻¹ in 2002 and −147 ± 42 g C m⁻² year⁻¹ in 2003. This carbon sink was much smaller than carbon sinks of −438 ± 49 g C m⁻² year⁻¹ in 2002 and −490 ± 48 g C m⁻² year⁻¹ in 2003 observed by a nearby flux tower in a 70-year-old mature hardwood forest (Willow Creek, WI). The mature forest had vegetation similar to the old-growth site prior to European settlement. Both sites had slightly larger carbon sinks in 2003, which was a drier and cooler year than 2002. However, the difference in sink strength between the two years was smaller than the uncertainty in the results arising from missing and screened data. Both sites also had significant systematic errors due to non-representative fluxes during certain micrometeorological conditions, which required careful screening. The difference in sink strength between the two sites was driven mainly by greater ER at the old-growth site (965 ± 35 g C m⁻² year⁻¹ in 2002 and 883 ± 69 g C m⁻² year⁻¹ in 2003) compared to the mature site (668 ± 21 g C m⁻² year⁻¹ in 2002 and 703 ± 17 g C m⁻² year⁻¹ in 2003). GEP was lower at the old-growth site (1037 ± 47 g C m⁻² year⁻¹ in 2002 and 1030 ± 41 g C m⁻² year⁻¹ in 2003) compared to the mature site (1106 ± 47 g C m⁻² year⁻¹ in 2002 and 1192 ± 51 g C m⁻² year⁻¹ in 2003), especially in 2003. Observations also suggested that growing season ER had greater interannual variability at the old-growth site. These results imply that old-growth forests in the region may be carbon sinks, though these sinks are smaller than mature forests, mostly likely due to greater ER.     

Relationships between soil pH and microbial properties in a UK arable soil

Effects of changing pH along a natural continuous gradient of a UK silty-loam soil were investigated. The site was a 200 m soil transect of the Hoosfield acid strip (Rothamsted Research, UK) which has grown continuous barley for more than 100 years. This experiment provides a remarkably uniform soil pH gradient, ranging from about pH 8.3 to 3.7. Soil total and organic C and the ratio: (soil organic C)/(soil total N) decreased due to decreasing plant C inputs as the soil pH declined. As expected, the CaCO₃ concentration was greatest at very high pH values (pH > 7.5). In contrast, extractable Al concentrations increased linearly (R² = 0.94, p < 0.001) from below about pH 5.4, while extractable Mn concentrations were largest at pH 4.4 and decreased at lower pHs. Biomass C and biomass ninhydrin-N were greatest above pH 7. There were statistically significant relationships between soil pH and biomass C (R² = 0.80, p < 0.001), biomass ninhydrin-N (R² = 0.90, p < 0.001), organic C (R² = 0.83, p < 0.001) and total N (R² = 0.83, p < 0.001), confirming the importance of soil organic matter and pH in stimulating microbial biomass growth. Soil CO₂ evolution increased as pH increased (R² = 0.97, p < 0.001). In contrast, the respiratory quotient (qCO₂) had the greatest values at either end of the pH range. This is almost certainly a response to stress caused by the low p. At the highest pH, both abiotic (from CaCO₃) and biotic Co₂ will be involved so the effects of high pH on biomass activity are confounded. Microbial biomass and microbial activity tended to stabilise at pH values between about 5 and 7 because the differences in organic C, total N and Al concentrations within this pH range were small. This work has established clear relationships between microbial biomass and microbial activity over an extremely wide soil pH range and within a single soil type. In contrast, most other studies have used soils of both different pH and soil type to make similar comparisons. In the latter case, the effects of soil pH on microbial properties are confounded with effects of different soil types, vegetation cover and local climatic conditions.     

Difference in spatiotemporal patterns of wildlife road-crossings and wildlife-vehicle collisions

Human–wildlife conflicts like wildlife–vehicle collisions pose major challenges for the management and conservation of mobile wildlife in human-dominated landscapes, particularly when large species are involved. Mitigation measures to reduce risk of collisions may be based on information given by wildlife movement and collision data. To test whether movement and collision data indicate different spatiotemporal risk zones, we predicted year-around probabilities of road-crossings of GPS-marked female moose (Alces alces) (n = 102), and compared them with spatiotemporal patterns of police recorded moose-vehicle collisions (n = 1158). Probability of moose road-crossings peaked in May, June, and between mid November and the beginning of January, i.e. during moose migration. Moose-vehicle collisions were more likely during autumn and winter. Comparing environmental attributes of crossing and collision sites showed significant differences. The likelihood of collisions increased with the abundance of human-modified areas and higher allowed speed, and was lower on forest roads. We found that animal movement data alone are insufficient to predict collision risk zones, while analyses of collision data alone overestimate the collision risk in certain habitats. Our findings suggest that higher collision risk is largely due to low light and poor road surface conditions rather than to more animal road-crossings. This suggests that efforts to reduce wildlife collisions should focus on driver attitudes and road conditions rather than animal movement, and any efforts to model the collision risk will require actual collision data, and not just movement data.