Life cycle traits of the parthenogenetic earthworm Octolasion cyaneum (Savigny, 1826)

This laboratory-based study provides baseline life cycle data for the obligatory parthenogenetic earthworm Octolasion cyaneum. Singleton and twin hatchlings were cultured individually with biomass, survival and reproductive condition recorded at 4-weekly intervals during a complete year. After maturation, cocoon production, masses and incubation time were also recorded along with viability and number of hatchlings per cocoon. Individual mean mass of singletons was significantly (P < 0.05) greater than twins at the outset (0.042 and 0.025 g respectively) and remained so until week 52 (2.22 and 1.96 g respectively). Singletons matured more rapidly than twins (24 vs. 32 weeks respectively) and produced more cocoons than twins (3.2 and 2.2 coc worm⁻¹ (4 weeks)⁻¹ respectively). Approximately 20% of all viable cocoons produced twins. Singleton hatchlings weighed significantly (P < 0.05) more than twin hatchlings (0.032 and 0.018 g respectively) but there was no significant difference (P > 0.05) between mean masses of singleton (mean masses 0.033 and 0.032 g) or twin (0.017 and 0.018 g) hatchlings produced by singleton and twin parents. The likelihood that a cocoon contained twins or a singleton was not influenced by the singleton/twin status of the parent. There was no significant difference (P > 0.05) in the incubation times of cocoons produced by singletons and twins (129 and 128 days respectively).     

Responses of small rodents to habitat restoration and management for the imperiled Florida Scrub-Jay

Debate about the relative merits of single-species management versus more comprehensive approaches has intensified in recent years. In east-central Florida, USA, land managers use prescribed burns and mechanical cutting to manage and restore scrub habitat to benefit the imperiled Florida Scrub-Jay (Aphelocoma coerulescens). However, these land-management techniques may affect non-target taxa, especially the threatened southeastern beach mouse (Peromyscus polionotus niveiventris). We evaluated the collateral effects of single-species land management by trapping P. p. niveiventris and other small rodents in eighteen land-management compartments at Cape Canaveral Air Force Station, Florida during 2004–2005. Compartments were managed using either prescribed burns (N = 5), mechanical cutting (N = 6), checkerboarding (cut and uncut lanes alternating and overlapping, followed by a prescribed burn, N = 4) or left unburned and uncut for >50 year (N = 3). P. p. niveiventris was significantly more abundant in compartments managed with prescribed burns (mean ± SE: 4.2 ± 0.7 individuals/transect) than those managed with cutting alone (1.0 ± 0.3) or not managed for >50 y (0.2 ± 0.1 individuals/transect). In contrast, the cotton mouse (Peromyscus gossypinus) tended to be more abundant in compartments managed with mechanical cutting alone (2.6 ± 0.4 individuals/transect) compared to the other three management strategies (prescribed burns; 1.5 ± 0.4; checkerboarding, 1.1 ± 0.3; not managed, 1.6 ± 0.4 individuals/transect) but these differences were not statistically significant. Abundances of P. p. niveiventris and Florida Scrub-Jay breeding groups were positively correlated (r = 0.655), suggesting that both listed species benefit from similar management techniques. Thus, the mosaic of burned and cut patches used to improve habitat for the Florida Scrub-Jay also benefits an endemic, non-target species. Single-species management may benefit multiple species when restoration improves their shared habitat, which in this case is an endangered, fire-dependent ecosystem: Florida scrub.     

Kinetics of acid phosphatase in calcium chloride extractable soil organic matter

The aim of this work was to compare the kinetic parameters of acid phosphatase (EC 3.1.3.2.) extracted from two forest soils under oak or pine. Soil was extracted with 4 mM CaCl₂ and the extract was divided into two fractions by filtration: one >0.2 μm containing microbial cells and soil particulates, and the other <0.2 μm containing fine particles and dissolved organic compounds of soil. The >0.2 μm fraction had higher K_m (0.26–0.82 vs. 0.12–0.39) and V_max (0.07–0.79 vs. 0.06–0.16) values than the <0.2 μm fraction, indicating a higher enzyme-substrate affinity and smaller amount of enzyme in fine particles and dissolved organic matter.     

Amphibian production in forested landscapes in relation to wetland hydroperiod: A case study of vernal pools and beaver ponds

Many amphibian species are plastic in their selection of breeding sites and use both short- and longer-hydroperiod wetlands. Understanding which wetland types are most important to amphibian production is critical for focusing conservation efforts. We compared reproduction of wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) and production of wood frog juveniles between seasonal (vernal pools) and semi-permanent (beaver-created ponds) wetlands in the central Adirondack region of the northeastern United States. In 65 seasonal wetlands and 37 semi-permanent wetlands over 3 years, densities of wood frog egg masses were similar, but seasonal wetlands contained 4× as many spotted salamander egg masses as did semi-permanent wetlands. For wood frogs, survival to metamorphosis and juvenile production were an order of magnitude higher in semi-permanent wetlands. Models of wood frog production linked to the climatic record predicted that, depending on annual variation in rainfall and survival to metamorphosis, semi-permanent wetlands may produce annually 1.2–23× the number of wood frogs that seasonal wetlands produce within the study area. Models incorporating variation in demographic traits throughout the range of wood frogs suggest that higher survival to metamorphosis in beaver ponds and higher clutch densities in vernal pools strongly influence metamorph production on a regional basis. Semi-permanent wetlands make major contributions to amphibian production in our region and may also be an important source of colonists to seasonal wetlands following periods of drought. Protection of wetlands along the landscape-level continuum of hydroperiod therefore may be critical for maintaining and restoring amphibian populations.     

Integrated approach of metal removal and bioprecipitation followed by fungal degradation of organic pollutants from contaminated soils

This study reports the assessment of a novel process combining sequential treatments of a historically contaminated soil from the ACNA site (Cengio, Savona, Italy), a decommissioned industrial area. The soil was leached with 0.5 M citric acid leading to a removal of metals in the following order: Pb (74.2%) > Cu (72.6%) > Zn (40.2%) > Ni (55.7%) > Cd (41.5%) > Cr > (21.7%) Co > (19%) Fe (8.2%) with a concomitant low removal of organic contaminants (12%). The leachate was then incubated with the metal-resistant Klebsiella oxytoca strain BAS-10, capable of using residual citrate to produce an iron gel that co-precipitated metals. Concomitantly, the leached solid waste was bioaugmented with the autochthonous isolate of Allescheriella sp. DABAC 1 leading to a complete degradation of several organic contaminants, including trichlorobenzene, naphtalene, dichloroaniline and pentachloroaniline. The overall removals of organic contaminants by the fungus were 44.3% and 63.8% in non-leached and leached soil.     

Phosphorus release during decomposition of crop residues under conventional and zero tillage

Field experiments were conducted at Fort Vermilion (58°23′N 116°02′W), Alberta, to determine phosphorus (P) release patterns from red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and monoculture wheat (Triticum aestivum) residues in the 7th and 8th years of conventional and zero tillage. Phosphorus contained in crop residues ranged from 1.5 kg ha⁻¹ in pea to 9.2 kg ha⁻¹ in clover GM, both under zero tillage. The patterns of P release over a 52-week period sometimes varied with tillage, i.e., a greater percentage of GM residue P was released under conventional tillage than under zero tillage in the first 2–10 weeks of residue placement. Wheat residues resulted in net P immobilization under zero tillage, but the amounts immobilized were less than 1 kg ha⁻¹. When net P mineralization occurred, the percentage of P released ranged from 24% of wheat P under conventional tillage to 74% of GM P under conventional tillage. The amounts of P released were 0.4 kg ha⁻¹ from wheat, 0.8 kg ha⁻¹ from canola, 0.4 kg ha⁻¹ from pea and 5.1–5.6 kg ha⁻¹ from clover GM residues. Therefore, only GM residues recycled agronomically significant amounts of P for use by subsequent crops in rotation. Phosphorus release was positively correlated with residue P concentration and negatively correlated with C/P and lignin/P ratios.     

Influence of temperature and drought on seasonal and interannual variations of soil, bole and ecosystem respiration in a boreal aspen stand

Continuous half-hourly measurements of soil (R_s) and bole respiration (R_b), as well as whole-ecosystem CO₂ exchange, were made with a non steady-state automated chamber system and with the eddy covariance (EC) technique, respectively, in a mature trembling aspen stand between January 2001 and December 2003. Our main objective was to investigate the influence of long-term variations of environmental and biological variables on component-specific and whole-ecosystem respiration (R_e) processes. During the study period, the stand was exposed to severe drought conditions that affected much of the western plains of North America. Over the 3 years, daily mean R_s varied from a minimum of 0.1 μmol m⁻² s⁻¹ during winter to a maximum of 9.2 μmol m⁻² s⁻¹ in mid-summer. Seasonal variations of R_s were highly correlated with variations of soil temperature (T_s) and water content (θ) in the surface soil layers. Both variables explained 96, 95 and 90% of the variance in daily mean R_s from 2001 to 2003. Aspen daily mean R_b varied from negligible during winter to a maximum of 2.5 μmol m⁻² bark s⁻¹ (2.2 μmol m⁻² ground s⁻¹) during the growing season. Maximum R_b occurred at the end of the aspen radial growth increment and leaf emergence period during each year. This was 2 months before the peak in bole temperature (T_b) in 2001 and 2003. Nonetheless, R_b was highly correlated with T_b and this variable explained 77, 87 and 62% of the variance in R_b in the respective years. Partitioning of R_b between its maintenance (R_bm) and growth (R_bg) components using the mature tissue method showed that daily mean R_bg occurred at the same time as aspen radial growth increment during each growing season. This method led, however, to systematic over- and underestimations of R_bm and R_bg, respectively, during each year. Annual totals of R_s, R_b and estimated foliage respiration (R_f) from hazelnut and aspen trees were, on average, 829, 159 and 202 g C m⁻² year⁻¹, respectively, over the 3 years. These totals corresponded to 70, 14 and 16%, respectively, of scaled-up respiration estimates of R_e from chamber measurements. Scaled R_e estimates were 25% higher (1190 g C m⁻² year⁻¹) than the annual totals of R_e obtained from EC (949 g C m⁻² year⁻¹). The independent effects of temperature and drought on annual totals of R_e and its components were difficult to separate because the two variables co-varied during the 3 years. However, recalculation of annual totals of R_s to remove the limitations imposed by low θ, suggests that drought played a more important role than temperature in explaining interannual variations of R_s and R_e.     

Interpreting the dependence of soil respiration on soil temperature and water content in a boreal aspen stand

Continuous half-hourly measurements of soil CO₂ efflux made between January and December 2001 in a mature trembling aspen stand located at the southern edge of the boreal forest in Canada were used to investigate the seasonal and diurnal dependence of soil respiration (R_s) on soil temperature (T_s) and water content (θ). Daily mean R_s varied from a minimum of 0.1 μmol m⁻² s⁻¹ in February to a maximum of 9.2 μmol m⁻² s⁻¹ in mid-July. Daily mean T_s at the 2-cm depth was the primary variable accounting for the temporal variation of R_s and no differences between Arrhenius and Q₁₀ response functions were found to describe the seasonal relationship. R_s at 10 °C (R_s10) and the temperature sensitivity of R_s (Q_10Rs) calculated at the seasonal time scale were 3.8 μmol m⁻² s⁻¹ and 3.8, respectively. Temperature normalization of daily mean R_s (R_sN) revealed that θ in the 0–15 cm soil layer was the secondary variable accounting for the temporal variation of R_s during the growing season. Daily R_sN showed two distinctive phases with respect to soil water field capacity in the 0–15 cm layer (θ_fc, 0.30 m³ m⁻³): (1) R_sN was strongly reduced when θ decreased below θ_fc, which reflected a reduction in microbial decomposition, and (2) R_sN slightly decreased when θ increased above θ_fc, which reflected a restriction of CO₂ or O₂ transport in the soil profile.Diurnal variations of half-hourly R_s were usually out of phase with T_s at the 2-cm depth, which resulted in strong diurnal hysteresis between the two variables. Daily nighttime R_s10 and Q_10Rs parameters calculated from half-hourly nighttime measurements of R_s and T_s at the 2-cm depth (when there was steady cooling of the soil) varied greatly during the growing season and ranged from 6.8 to 1.6 μmol m⁻² s⁻¹ and 5.5 to 1.3, respectively. On average, daily nighttime R_s10 (4.5 μmol m⁻² s⁻¹) and Q_10Rs (2.8) were higher and lower, respectively, than the values obtained from the seasonal relationship. Seasonal variations of these daily parameters were highly correlated with variations of θ in the 0–15 cm soil layer, with a tendency of low R_s10 and Q_10Rs values at low θ. Overall, the use of seasonal R_s10 and Q_10Rs parameters led to an overestimation of daily ranges of half-hourly R_s (ΔR_s) during drought conditions, which supported findings that the short-term temperature sensitivity of R_s was lower during periods of low θ. The use of daily nighttime R_s10 and Q_10Rs parameters greatly helped at simulating ΔR_s during these periods but did not improve the estimation of half-hourly R_s throughout the year as it could not account for the diurnal hysteresis effect.     

Earthworms of different functional groups affect the fate of the Bt-toxin Cry1Ab from transgenic maize in soil

The fate of the insecticidal Cry1Ab protein from crop residues (leaves and roots) of the transgenic maize variety MON810 was studied in the presence and absence of two earthworm species (Lumbricus terrestris, Aporrectodea caliginosa; separate incubations) in soil microcosms. The recombinant Cry1Ab protein was quantified using a highly sensitive ELISA. Control microcosms received corresponding non-transgenic plant material. All earthworms survived in the microcosms over a period of 5 weeks, irrespective of whether they received MON810 or non-transgenic plant material. Weight loss was observed for both earthworm species, independent of the plant material or transgenic modification. A strong decline of immunoreactive Cry1Ab in plant residues (mean initial concentration approx. 5000 ng g⁻¹) of MON810 was observed in all treatments, but in microcosms with earthworms this decline was significantly higher with less than 10% of the initial Cry1Ab concentration remaining after 5 weeks. Cry1Ab concentrations in casts were only 0.1% of those found in remaining plant material of the respective microcosms. No immunoreactive Cry1Ab proteins were found in earthworm tissues (threshold of detection: 0.58 ng g⁻¹ fresh weight). No further decline was found for Cry1Ab concentrations in casts of A. caliginosa during a subsequent period of 3 months of incubation in bulk soil (<0.1 ng g⁻¹) after removal of the earthworms from the microcosms, while in casts of L. terrestris the concentration decreased from 0.4 to below 0.1 ng g⁻¹. In conclusion, this study demonstrates that earthworms enhance the decline of immunoreactive Cry1Ab proteins from maize residues.     

The distribution of volatile isoprenoids in the soil horizons around Pinus halepensis trees

We measured the terpene concentration in pentane and water extracts from soil horizons (litter, organic, top and low mineral) and from roots growing in top and low mineral horizons on a distance gradient from Pinus halepensis L. trees growing alone on a grassland. Terpene concentrations in pentane were higher than in water extracts, although β-caryophyllene showed relatively high solubility in water. The litter and roots were important sources of terpenes in soil. Alpha-pinene dominated in roots growing in both “top” (A1) and “low” (B) mineral horizons (123 ± 36 μg g⁻¹ or 14 ± 5 mg m⁻²) and roots in low mineral horizon (270 ± 91 μg g⁻¹ or 7 ± 2 mg m⁻²). Beta-caryophyllene dominated in litter (1469 ± 331 μg g⁻¹ or 2004 ± 481 mg m⁻²). Terpene concentration in soil decreased with increasing distance to the trunk. This is likely to be related to changes in litter and roots type on the distance gradient from pine to grass and herbs. The relative contributions of all compounds, except α-pinene, were similar in the mineral soils and litter. This suggests that litter of P. halepensis is probably the main source of major terpene compounds. However, long-term emissions of α-pinene from P. halepensis roots might also contribute to α-pinene concentrations in rhizosphere soils.     

Evaluation of NASA satellite- and assimilation model-derived long-term daily temperature data over the continental US

Agricultural research increasingly is expected to provide precise, quantitative information with an explicit geographic coverage. Limited availability of daily meteorological records often constrains efforts to provide such information through use of simulation models, spatial analysis, and related decision support tools. The Prediction Of Worldwide Energy Resources (NASA/POWER) project at the NASA Langley Research Center provides daily data globally for maximum and minimum temperatures and other weather variables on a 1° latitude–longitude grid. The data are assembled from a range of products derived from satellite imagery, ground observations, windsondes, modeling and data assimilation. Daily temperature data from NASA/POWER for 1983 to 2004 for the continental US were compared with data of 855 individual ground stations from the National Weather Service Cooperative Observer Program (COOP). Additionally, a wheat (Triticum aestivum L.) simulation model was used to compare predicted time to anthesis using the two data sources. Comparisons of daily maximum temperatures (T_max) gave an r²-value of 0.88 (P < 0.001) and root-mean-squared error (RMSE) of 4.1 °C. For minimum temperature (T_min), the r²-value was 0.88 (P < 0.001) and RMSE, 3.7 °C. Mean values of T_max, and T_min from NASA/POWER were, respectively, 2.4 °C cooler and 1.1 °C warmer than the COOP data. Differences in temperature were least during summer months. When data were aggregated over periods of 8 days or more, the RMSE values declined to below 2.7 °C for T_max and T_min. Simulations of time to anthesis with the two data sources were also strongly correlated (r² = 0.92, P < 0.001, RMSE = 14.5 d). Anthesis dates of winter wheat regions showed better agreement than southern, winter-grown spring wheat regions. The differences between the data sources were associated with differences in elevation, which in large part resulted from NASA/POWER data being based on mean elevations over a 1° grid cells vs. COOP data corresponding to the elevation of specific stations. Additional sources of variation might include proximity to coastlines and differences in observation time, although these factors were not quantified. Overall, if mountainous and coastal regions are excluded, the NASA/POWER data appeared promising as a source of continuous daily temperature data for the USA for research and management applications concerned with scales appropriate to the 1° coordinate grid. It further appeared that the POWER data could be improved by adjusting for elevation (lapse rate) effects, reducing seasonal bias, and refining estimation of actual maximum and minimum temperatures in diurnal cycles.     

Net ecosystem productivity of boreal aspen forests under drought and climate change: Mathematical modelling with Ecosys

The net ecosystem productivity (NEP) of boreal aspen is strongly affected by comparative rates of annual potential evapotranspiration (E_a) and precipitation (P_a). Changes in E_a versus P_a during future climate change will likely determine changes in aspen NEP and consequently the magnitude of the carbon sink/source of a significant part of the boreal forest. We hypothesize that the effects of E_a versus P_a on aspen NEP can be modelled with a soil–root–canopy hydraulic resistance scheme coupled to a canopy energy balance closure scheme that determines canopy water status and thereby CO₂ uptake. As part of the ecosystem model ecosys, these schemes were used to model diurnal declines in CO₂ and latent heat (LE) exchange during a 3-year drought (2001–2003) at the Fluxnet-Canada Research Network (FCRN) southern old aspen site (SOA). These declines were consistent with those measured by eddy covariance (EC) at SOA, except that ecosystem CO₂ effluxes modelled during most nights were larger that those measured by EC or gap-filled from other EC measurements. Soil CO₂ effluxes in the model were close to, but sometimes smaller than, those measured by automated surface chambers at SOA. Diurnal declines in CO₂ exchange during the drought caused declines in annual NEP in the model, and in gap-filled EC measurements (model versus EC in g C m⁻²: 275 versus 367 ± 110 in 2001, 82 versus 144 ± 43 in 2002 and 23 versus 104 ± 31 in 2003). Lower modelled NEP was attributed to the larger modelled CO₂ effluxes. Ecosys was then used to predict changes in aspen net biome productivity (NBP = NEP − C lost from disturbance) caused by 6-year versus 3-year recurring droughts during 100-year fire cycles under current climate versus climate change projected under the IPCC SRES A1B scenario. Although NBP was adversely affected during recurring 6-year droughts under current climate, it recovered quickly during non-drought years so that long-term NBP was maintained at 4 g C m⁻² year⁻¹. NBP rose by 10, 108 and 126 g C m⁻² year⁻¹ during the first, second and third centuries under climate change with recurring 3-year droughts, indicating a gradual rise in sink activity by boreal aspen. However recurring 6-year droughts during climate change caused recurring negative NBP (C losses), gradually depleting aspen C reserves and eventually causing dieback of the aspen overstory during the third century of climate change. This dieback was followed by a large decline in NBP.We conclude that NBP of boreal aspen will rise gradually under current projections of climate change, except under prolonged (e.g. 6 years) recurring droughts, which would eventually cause aspen to die back and substantial amounts of C to be lost.     

Stemflow in three shrubs and its effect on soil water enhancement in semiarid loess region of China

Stemflow of three semiarid shrubs (Tamarix ramosissima, Caragana korshinskii and Reaumuria soongorica) and its effect on soil water enhancement were evaluated during the growing season of 2004 and 2005 in the semiarid loess region of China. The results indicated that stemflow averaged 2.2%, 3.7% and 7.2% of the bulk precipitation for T. ramosissima, R. soongorica and C. korshinskii, respectively. Individual stemflow increased in a linear function with increasing rainfall depth, while it tended to increase with rain intensity when rain intensity was less than 2 mm h⁻¹, but showed an opposite trend when rain intensity was greater than 2 mm h⁻¹.The relationship between funnelling ratios and rainfall suggested that there existed a rainfall depth threshold of 11 mm for C. korshinskii and 17 mm for both T. ramosissima and R. soongorica. Funnelling ratios positively increased with increasing rainfall depth before the rainfall depth threshold values had been reached but showed a decreasing trend after the rainfall depth threshold. Average funnelling ratios were 153.5 ± 66.2, 53.2 ± 25.7 and 24.8 ± 15.3 for C. korshinskii, R. soongorica and T. ramosissima, respectively, indicating canopy architecture of the three shrubs was an effective funnel to channel stemflow to the root area, and C. korshinskii showed greater potential to use stemflow water in the arid conditions. For individual rainfall events the wetting front depths in the rooting zone around the stems of the shrubs were 1.2–4.5, 1.4–3.8 and 1.4–2.8 times deeper than that in the bare area outside canopy for C. korshinskii, T. ramosissima and R. soongorica, respectively; correspondingly, soil water content was also significantly higher in the root area around the shrub stem than that in the area outside the shrub canopy. This confirms that shrub stemflow conserved in the deep soil layers may be an available moisture source for plant growth under arid conditions.     

Phenylpyrazoles impact on Folsomia candida (Collembola)

Effects of the broad-spectrum insecticide fipronil were investigated on a non-target insect living in the soil, the springtail Folsomia candida Willem. Fipronil induced a significant reduction in juvenile production (PNEC = 250 μg kg⁻¹ dry soil), which seemed to be linked with an impact on the first stages of springtail development: juveniles and 7-day-old adults. These young organisms have a thinner integument, a smaller mass body and a weaker detoxification efficiency and were more sensitive than adults (14 days old) to fipronil and phenylpyrazole derivatives. Contact toxicity for juveniles was measured (LC₅₀(96 h)) giving the following values: fipronil, 450 μg l⁻¹; sulfone-fipronil, 430 μg l⁻¹; sulfide-fipronil, 160 μg l⁻¹. F. candida organisms were able to avoid contaminated food because phenylpyrazoles decreased food appetency. However, F. candida could bioaccumulate fipronil through trans-tegumental penetration (BAF_96 h = 160) and its high biotransformation rate inside springtail bodies (1 ng fipronil metabolized day⁻¹ individual⁻¹) was suspected to increase this process. Under natural conditions, phenylpyrazoles risk assessment on springtails seems to be weak due to their capacity of avoiding high contaminated zones and their biochemical tolerance to this class of insecticides.     

Sorptive interaction between goethite and strongly reducing organic substances from anaerobic decomposition of green manures

Strongly reducing organic substances (SROS) and iron oxides exist widely in soils and sediments and have been implicated in many soil and sediment processes. In the present work, the sorptive interaction between goethite and SROS derived from anaerobic decomposition of green manures was investigated by differential pulse voltammetry (DPV). Both green manures, Astragalus sinicus (Astragalus) and Vicia varia (Vicia) were chosen to be anaerobically decomposed by the mixed microorganisms isolated from paddy soils for 30 d to prepare different SROS. Goethite used in experiments was synthesized in laboratory. The anaerobic incubation solutions from green manures at different incubation time were arranged to react with goethite, in which SROS concentration and Fe(II) species were analyzed. The anaerobic decomposition of Astragalus generally produced SROS more in amount but weaker in reducibility than that of Vicia in the same incubation time. The available SROS from Astragalus that could interact with goethite was 0.69 ± 0.04, 0.84 ± 0.04 and 1.09 ± 0.03 cmol kg⁻¹ as incubated for 10, 15 and 30 d, respectively, for Vicia, it was 0.12 ± 0.03, 0.46 ± 0.02 and 0.70 ± 0.02 cmol kg⁻¹. One of the fates of SROS as they interacted with goethite was oxidation. The amounts of oxidizable SROS from Astragalus decreased over increasing incubation time from 0.51 ± 0.05 cmol kg⁻¹ at day 10 to 0.39 ± 0.04 cmol kg⁻¹ at day 30, but for Vicia, it increased with the highest reaching to 0.58 ± 0.04 cmol kg⁻¹ at day 30. Another fate of these substances was sorption by goethite. The SROS from Astragalus were sorbed more readily than those from Vicia, and closely depended upon the incubation time, whereas for those from Vicia, the corresponding values were remarkably less and apparently unchangeable with incubation time. The extent of goethite dissolution induced by the anaerobic solution from Vicia was greater than that from Astragalus, showing its higher reactivity.     

Distribution of earthworms and influence of soil properties across a successional sand dune ecosystem in NW England

An investigation of earthworms across a sand dune system in NW England examined species distribution and abundance with respect to soil physico-chemical conditions and management. Replicated 0.1 m² quadrats were examined every 50 m along 700 m transects across areas of vegetation succession and samples were then taken every 10 m where earthworms were first encountered. A translocation of Aporrectodea longa assessed the ability of this species to live in soils with a high sand content and laboratory work examined growth, maturation and survival of this species in soils with increasing proportions of sand (0–100%). Nine earthworm species were found on the dunes, but none in yellow dunes where organic matter (OM) content was <1%. Dendrobaena octaedra and Lumbricus rubellus were located 300 m from the strand line in grey dunes with an OM content of 3.9%. Allolobophora chlorotica and Lumbricus castaneus occurred within a wet dune slack at 340 m (OM content 11%). In areas of human disturbance (dune car park), A. longa, Aporrectodea caliginosa and Lumbricus terrestris were present, and in soil below pine trees L. castaneus and L. rubellus were present in litter. Laboratory growth of A. longa demonstrated significant (p < 0.05) increases in growth (2–2.75 g) with 25 and 50% sand compared with 0, 75 and 100% over 24 weeks and a greater rate of maturation. Initial results show earthworm colonisation to be influenced by dune successional stage. Laboratory findings suggested A. longa could exist in higher sand content areas but experimental design needs development. The translocation was unsuccessful. Future investigations could examine soil properties more closely and undertake monitoring on site throughout the year.     

Numerical and behavioral responses of waterfowl to the invasive American mink: A conservation paradox

A behavioral response is usually the first adaptation of animals to environmental changes such as the introduction of an alien invasive species, and it seems to be the most important factor in reducing the negative impact of new predators on naive prey. This study examined changes in the abundance and behavior of breeding coots (Fulica atra) and great crested grebes (Podiceps cristatus) in response to invasion of the Mazurian Lakeland (NE Poland) by American mink (Neovison vison), first recorded here in 1984. Feral mink densities varied from 1.0 to 14.6 individuals per 10 km of shoreline. Mink were responsible for the losses of 17–58% of experimental clutches (artificial nests containing chicken eggs) that were deployed. Mink destroyed more experimental clutches than other predators; the effects of mink predation were similar in reeds and on the bank. Radio-tracking showed that mink avoided lake banks near human settlements. Mink have markedly affected the breeding distribution of both species and caused a greater than 20-fold decline in coot numbers. For coots and grebes breeding distribution and nesting success were positively associated with built-up areas along lake shores and also with whether the birds were breeding in colonies. Increased brood survival of coots and grebes near human settlements is a paradox in the sense that a man-made habitat change has provided refuge from an alien predator.     

Ant-induced soil modification and its effect on plant below-ground biomass

Lasius flavus is a dominant mound-building ant species of temperate grasslands that significantly modifies soil parameters. These modifications are usually the result of workers’ activities such as food accumulation and nest construction. An alternative hypothesis that could explain changes in soil is colony founding in areas of higher soil fertility.In our study we investigated several soil parameters sampled in 10 ant nests and adjacent (control) plots in mountain grassland in Slovakia. The alternative hypothesis was tested by comparing occupied and abandoned mounds. While we found increased concentrations of available P and K in the nests, concentrations of total C, total N, Ca²⁺ and Mg²⁺ were lower there. We propose that differences found between the soil of nests and control plots are entirely a product of ant activity during mound occupancy and not due to initial soil differences during nest establishment. This was confirmed by the comparison of occupied and abandoned nests in which the soil fertility of abandoned nests was similar to conditions in the surrounding soil.Along with the modification of soil chemistry, we recorded changes in soil physical properties and the vertical distribution of nutrients. Ant nests were characterized by the dominance of 0.02–0.1 mm particles and lower bulk density. In the same habitat, nutrient concentrations did not change along the vertical gradient in contrast to control plots where soil nutrients decreased and bulk density increased with depth. Root biomass followed the vertical pattern observed with nutrients: in control plots, most roots were concentrated in the uppermost layer (0–3 cm), whereas they were evenly distributed along the vertical gradient in the nests. We also found that rhizome internodes of Agrostis capillaris were thinner and longer in plants from the mounds. Changes in soil physical properties, vertical distribution of nutrients and root biomass in the nests are most probably a consequence of mounding and soil mixing (bioturbation), which has been less reported on in ant-soil studies.     

Magnetic properties of the urban soils in Shanghai and their environmental implications

To study the feasibility of using magnetic techniques for monitoring soil pollution in Shanghai, magnetic properties and heavy metals in the topsoils in an urban site (Songnan Town) and a less-urbanized agricultural site (Luojing Town) in Baoshan District, Shanghai, were studied. Compared with the background, magnetic signals of the urban topsoils are extremely enhanced with magnetic susceptibility (χ_lf) from 127.3–1959 × 10^− 8 m³ kg^− 1; while those of the agricultural topsoils are only slightly increased. However, both the urban and agricultural topsoils contain few pedogenic SP grains, as indicated by their low χ_fd% (< 3.6%). Ratios of χ_arm/SIRM, χ_arm/χ_lf and SIRM/χ_lf indicate that the grain size of magnetic minerals in the urban topsoils is significantly coarser than that in the background and the agricultural topsoils. Furthermore, the urban topsoils show low coercivity and magnetic soft behaviors, as indicated by higher SOFT%, lower HARD%, higher IRM_300 mT/SIRM (close to 1) and lower IRM_− 200 mT/SIRM (close to − 1). It suggests that the urban topsoils have received some coarse ferrimagnetic particles. Heavy metals are highly enriched in the magnetic fractions of the topsoils. Geochemical properties of the magnetic fraction of the urban topsoils are significantly different from those of the agricultural topsoils, further indicating that the extra magnetic minerals accumulated in the urban topsoils are neither inherited from soil parent materials nor from pedogenic processes, but originate from anthropogenic activities. The significant correlations between heavy metals and χ_lf, χ_arm, SIRM, SOFT and HIRM of the topsoils in the district indicate that the magnetic techniques can be used for monitoring soil pollution in Shanghai. The soils with χ_lf from 39–50 × 10^− 8 m³ kg^− 1 in the district are tentatively defined as “slightly polluted soils”; those with χ_lf > 50 × 10^− 8 m³ kg^− 1 are defined as “polluted soils”.     

Vulnerability of ground-nesting waterbirds to predation by invasive American mink in the Cape Horn Biosphere Reserve, Chile

Biological invasions constitute one of the most important threats to biodiversity. This is especially true for “naïve” birds that have evolved in the absence of terrestrial predators in island ecosystems. The American mink (Mustela vison) has recently established a feral population on Navarino Island (55°S), southern Chile, where it represents a new guild of terrestrial mammal predators. We investigated the impact of mink on ground-nesting coastal waterbirds with the aim of deriving a vulnerability profile for birds as a function of different breeding strategies, habitat, and nest characteristics. We compared rates of nest survival and mink predation on 102 nests of solitary nesting species (Chloephaga picta, Tachyeres pteneres), on 361 nests of colonial birds (Larus dominicanus, Larus scoresbii, Sterna hirundinacea), and on 558 artificial nests. We calculated relative mink and bird densities at all nest sites. Nests of colonial species showed the highest nest survival probabilities (67-84%) and no predation by mink. Nest survival rates for solitary nesting species were lower (5-20%) and mink predation rates higher (10-44%). Discriminant analyses revealed that mink preyed upon artificial nests mainly at shores with rocky outcroppings where mink were abundant. High nest concealment increased the probability for predation by mink. Conservation planning should consider that invasive mink might severely affect the reproduction success of bird species with the following characteristics: solitary nesting, nesting habitat at rocky outcrop shores, and concealed nests. We recommend that work starts immediately to control the mink population with a priority in the nesting habitats of vulnerable endemic waterbirds.