Female biased mortality caused by anthropogenic nest loss contributes to population decline and adult sex ratio of a meadow bird

Meadow breeding birds such as the whinchat Saxicola rubetra have been declining due to increased farming intensity. In modern grassland management, the first mowing and the bird’s breeding cycle coincide, causing high nest destruction rates and low productivity of grassland bird populations. However, it is virtually unknown whether the mowing process directly affects adult survival by accidentally killing incubating females. We studied adult survival of an Alpine whinchat population during two breeding seasons using either colour-ringing or radio-tracking of 71 adults. Assessing territories, mowing phenology and nest destruction from 1988 to 2007 allowed changes in the factors associated with female mowing mortality to be estimated. Adult survival over 5-day-periods was Φ = 0.986, but during the period of mowing female survival was strongly reduced (Φ = 0.946). As a result, 80.6% of the males, but only 68.4% of the females survived the breeding season. Mowing undoubtedly killed two of 20 radio-tagged females when they were laying or incubating. In the 20-year period, an increasing proportion of nests were destroyed before the chicks hatched and this change was associated with an increased distortion of the adult sex ratio. Modelling the population growth rate showed that including the additional effect of mowing on female mortality resulted in a 1.7 times faster local population decline. These results are consistent with the hypothesis that the extinction of whinchat populations in the lowlands of central Europe was caused not only by habitat degradation and low productivity, but also by increased man-made female mortality.     

An outline of soil nematode succession on abandoned fields in South Bohemia

Secondary succession of nematodes was studied in 1–48-year-old abandoned fields on cambisols in South Bohemia, Czech Republic, and compared with cultivated field and sub-climax oak forests. Bacterivores were the predominant group in the cultivated field whereas in forests root-fungal feeders (mainly Filenchus) were almost as abundant as bacterivores. The total abundance of nematodes in the cultivated field averaged 868 × 10³ ind m⁻². During the first three years of succession the abundance practically did not change (775 × 10³ ind m⁻²), the fauna was still similar to that in cultivated field but the biomass increased mainly due to Aporcelaimellus. Then the abundance increased up to 3731 × 10³ ind m⁻² in 7–8-year-old abandoned fields, plant parasites (Helicotylenchus) dominated and the fungal-based decomposition channel was activated. Later the abundance stabilised at between 1086 and 1478 × 10³ ind m⁻² in 13–25-year-old successional meadow stages with high population densities of omnivores and predators. The total abundance of nematodes was low in the 12–13-year-old willow shrub stage (594 × 10³ ind m⁻²), increased in the 35–48-year-old birch shrub stage (1760 × 10³ ind m⁻²) and the nematode fauna developed towards a forest community. The diversity and maturity of nematode communities generally increased with the age of abandoned fields but the highest values were in meadow stages (81–113 species, 57–68 genera, MI 2.73–3.30). The development of meadow arrested succession towards forests or diverted succession towards a waterlogged ecosystem. The succession of nematodes was influenced by the method of field abandonment (bare soil vs. legume cover, mowing) that affected the formation of either a shrub or meadow stage, and by the soil water status. The composition of the nematode fauna indicated that the soil food web could recover faster from agricultural disturbance under successive meadows than under shrubs.     

Habitat use and activity patterns of larval and adult Cantharis beetles in arable land

Generalist predators play a key role in agriculturally and environmentally sustainable systems of pest control. A detailed knowledge on their ecology, however, is needed to improve management practices to maximize their service of pest control. The present study examines the habitat use and activity patterns of larval and adult Cantharis beetles that are abundant predators in arable land. Laboratory experiments revealed that sixth instar larvae of Cantharis fusca and Cantharis livida significantly preferred high relative humidity levels of 85–90% to lower ones. This can explain their preference for meadows over fields due to the more favorable microclimatic conditions in the former habitats. Surface activity of sixth instar Cantharis larvae during autumn, winter and early spring occurred at soil temperatures above 0 °C. However, no correlation between surface activity and soil temperature, air temperature or relative humidity was found above 0 °C. Catches of sixth instar Cantharis larvae within fenced pitfall traps were higher in a meadow (Mean ± S.D.; 13.8 ± 7.63 individuals m⁻²) than in a field (4.60 ± 2.89 individuals m⁻²). Mark-recapture density estimations for sixth instar larvae indicated mean densities of 25.9 ± 5.63 (field) and 42.8 ± 16.0 individuals m⁻² (meadow). The same pattern was found for adult emergence rates in the field (0.17 ± 0.39 adults m⁻²) and meadow (1.83 ± 1.17 adults m⁻²) as well as for adult densities in the vegetation (field 4.89 ± 3.62 adults 60 m⁻²; meadow 12.5 ± 11.2 adults 60 m⁻²). It is concluded that especially in winter elements that provide plant cover should be incorporated in arable fields to enhance larval cantharid population densities and to attract them from their prime grassland habitats into arable sites.     

Terrestrial habitat requirements of nesting freshwater turtles

Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of > 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m for Malaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6–98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (<200 m zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys, Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings.     

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.     

Invasive alien goldenrods negatively affect grassland bird communities in Eastern Europe

Invasive alien plants constitute a major threat to local biodiversity. Moreover, their appearance often coincides with land use change. Many endangered groups of organisms suffer from habitat loss, which is often a consequence of the invasion of alien plants. This paper examines how invasive alien goldenrods Solidago spp. affect the richness of endangered grassland bird species and numbers of breeding pairs in abandoned meadows in southern Poland. Meadows invaded by goldenrods (n = 15) had lower bird species richness and a lower number of breeding pairs than meadows in which goldenrods were absent (n = 15). Two important factors positively influencing bird species richness were meadow area and shrub density (the latter only in meadows without goldenrods). Moreover, both the index of potential food density (number of butterflies) and plant species richness were much lower in meadows invaded by goldenrods than in meadows without these plants. Urgent action aimed at preventing the invasion of alien goldenrods in abandoned meadows is needed and such measures should involve regular mowing. Our results also highlight the fact that land abandonment in Central and Eastern Europe is not necessarily as beneficial for biodiversity as it is commonly believed and it may even lead to a decrease in the populations of several bird species in the agricultural landscape.     

Accounting for variability in soil microbial communities of temperate upland grassland ecosystems

This study aimed to determine the factors which regulate soil microbial community organisation and function in temperate upland grassland ecosystems. Soil microbial biomass (C_mic), activity (respiration and potential carbon utilisation) and community structure (phospholipid fatty acid (PLFA) analysis, culturing and community level physiological profiles (CLPP) (Biolog^®)) were measured across a gradient of three upland grassland types; Festuca–Agrostis–Galium grassland (unimproved grassland, National Vegetation Classification (NVC) — U4a); Festuca–Agrostis–Galium grassland, Holcus–Trifolium sub-community (semi-improved grassland, NVC — U4b); Lolium–Cynosurus grassland (improved grassland, NVC — MG6) at three sites in different biogeographic areas of the UK over a period of 1 year. Variation in C_mic was mainly due to grassland type and site (accounting for 55% variance, v, in the data). C_mic was significantly (P<0.001) high in the unimproved grassland at Torridon (237.4 g C m⁻² cf. 81.2 g C m⁻² in semi- and 63.8 g C m⁻² in improved grasslands) and Sourhope (114.6 g C m⁻² cf. in 44.8 g C m⁻² semi- and 68.3 g C m⁻² in improved grasslands) and semi-improved grassland at Abergwyngregyn (76.0 g C m⁻² cf. 41.7 g C m⁻² in un- and 58.3 g C m⁻² in improved grasslands). C_mic showed little temporal variation (v=3.7%). Soil microbial activity, measured as basal respiration was also mainly affected by grassland type and site (n=32%). In contrast to C_mic, respiration was significantly (P<0.001) high in the improved grassland at Sourhope (263.4 l h⁻¹m⁻² cf. 79.6 l h⁻¹m⁻² in semi- and 203.9 l h⁻¹m⁻² unimproved grasslands) and Abergwyngregyn (198.8 l h⁻¹m⁻² cf. 173.7 l h⁻¹m⁻² in semi- and 88.2 l h⁻¹m⁻² unimproved grasslands). Microbial activity, measured as potential carbon utilisation, agreed with the respiration measurements and was significantly (P<0.001) high in the improved grassland at all three sites (A₅₉₀ 0.14 cf. 0.09 in semi- and 0.07 in unimproved grassland). However, date of sampling also had a significant (P<0.001) impact on C utilisation potential (v=24.7%) with samples from April 1997 having highest activity at all three sites. Variation in microbial community structure was due, predominantly, to grassland type (average v=23.6% for bacterial and fungal numbers and PLFA) and date of sampling (average v=39.7% for bacterial and fungal numbers and PLFA). Numbers of culturable bacteria and bacterial PLFA were significantly (P<0.001) high in the improved grassland at all three sites. Fungal populations were significantly (P<0.01) high in the unimproved grassland at Sourhope and Abergwyngregyn. The results demonstrate a shift in soil microbial community structure from one favouring fungi to one favouring bacteria as grassland improvement increased. Numbers of bacteria and fungi were also significantly (P<0.001) higher in August than any other sampling date. Canonical variate analysis (CVA) of the carbon utilisation data significantly (P<0.05) differentiated microbial communities from the three grassland types, mainly due to greater utilisation of sugars and citric acid in the improved grasslands compared to greater utilisation of carboxylic acids, phenolics and neutral amino acids in the unimproved grasslands, possibly reflecting substrate availability in these grasslands. Differences in C_mic, activity and community structure between grassland types were robust over time. In addition, broad scale measures of microbial growth and activity (C_mic and respiration) showed little temporal variation compared to measures of soil microbial community structure, which varied quantitatively with respect to environmental variables (temperature, moisture) and plant productivity, hence substrate supply.     

Testing the stability of carbon pools stored in tussock sedge meadows

Tussocks formed by Carex stricta are a relatively large carbon (C) pool in sedge meadows, but the stability of organic matter in these ecosystems is not well understood. We initiated year-long incubation experiments (22.5 °C) to evaluate the CO₂ and CH₄ production potentials of sedge meadow substrates under field moist and inundated treatments from five sites in the Upper Midwest, USA (4 reference, 1 restored). C mineralization potentials decreased with depth (tussocks > underlying soil), and were positively correlated with macro-organic matter content and negatively with lignin. Across sites, C stored in tussocks and soil at the restoration was the least stable, suggesting that the restoration of C-storage function may take decades. Mineralization potentials were similar between field moist and inundated treatments, but inundation resulted in higher methane production, accounting for 24–51% of total carbon mineralized from tussocks. In the field however, C. stricta tussocks emitted less methane (393 ± 76 mg CH₄ m⁻² d⁻¹) than tussock interspaces (1362 ± 371 mg CH₄ m⁻² d⁻¹) early in the growing season; we suggest that tussock tops oxidized methane produced from deeper anoxic horizons. Our results highlight the importance of considering how microtopography modulates greenhouse gas flux from wetlands and suggests that the C stored in the older, more decomposed C. stricta tussock sedge meadow substrates (both within and between sites) is relatively stable.     

Tallgrass prairie management and bird nest success along roadsides

The attributes of roadside vegetation, an important bird habitat in grassland ecosystems, have been shown to affect bird abundance, distribution composition, and diversity, yet there are relatively few works on reproductive success of birds nesting along roadsides. Because roadsides are linear habitats, management at the landscape scale can affect nest success in roadsides through bottom-up and top-down effects. In northeastern Oklahoma tallgrass prairie is subjected annually to prescribed spring fires. In the short term fires can alter both arthropod abundance and predator access to nests. We explored effects of burning on bird nest success with a five-year study along roads that traversed tallgrass prairie habitat. Using data from ∼1400 nests of 23 species, we generated nest survival curves for groups of altricial species defined by nest substrate (ground, shrub, tree, or culvert). We then determined if these curves were affected by management practice (spring burning), food abundance (arthropod biomass), and habitat attributes (tree density and height). Nest substrate had a large effect on nest success: despite their shorter nest exposure period, ground nests were least successful and culvert nests were most successful. An increase in arthropod biomass following burning was possibly the cause for the increased nest success in burned plots, regardless of substrate, suggesting bottom-up control. Tree height and nest height were correlated positively with nest success, whereas tree density had no effect. Conversely, nest predation rates were correlated negatively with nest success, with ground nests experiencing the highest predation, culvert nests the lowest. Our results suggest that burning may increase nest success through bottom-up processes, but some species may not benefit from the increase in food abundance as a result of a concomitant increase in predation.     

Earthworm activity alters geogenic arsenic and soil nutrient dynamics

Environmental pollution due to arsenic (As) has been well studied and most investigations have focused on inorganic As coming from industrial areas. However, the natural rock-borne contamination of this metalloid has been underestimated and few studies focusing on annelids have addressed the question of geogenic As distribution in earthworm biogenic structures. Our study concentrated on the earthworm drilosphere and investigated the distribution of As in surface-casts and burrow-linings. In this context, we assumed that the concentration of geogenic As should differ in biogenic structures (faeces, burrow-linings) compared to non-ingested soil. To test our hypothesis, microcosms in controlled conditions were filled with soil containing 157 mg As kg^?1 from a geogenic origin. The soil was collected from a meadow in the Jura Mountains. The earthworm Aporrectodea giardi was selected because of its natural presence in the meadow and its anecic behaviour.We found that while earthworm surface-casts were enriched in carbon, nitrogen and available phosphorus compared to non-ingested soil, no enrichment was found for geogenic arsenic. The coarse sand fraction contained 3.5 times more As than silt and clay fractions but no significant difference existed between surface-casts and non-ingested soil. Iron was shown to be the main mineral bearing phase for As and predominated in the coarse sand fraction. No retention effect of organic matter on geogenic arsenic was observed. In conclusion, it appeared that geogenic As did not affect biological components and environmental aspects. These findings are particularly encouraging considering that most of the environments at an altitude of 1330 m in the Jura Mountains have exposed rocks, especially on meadows that are regularly grazed by cattle.     

Beetles community structures under different reclamation practices

Differences in beetle community structures between not re-cultivated over 60 years old forest and 10 years old re-cultivated meadow and shrubs were compared. On each locality there were arranged three replicates of 10 pitfall trap rows. Mean abundance of beetles was significantly greater on old forest stand than re-cultivated meadow. However no significant differences between localities in species richness and non parametric index of diversity (Shannon H′) were recorded. Rank–abundance curves for newly established communities best fits to geometric model of distribution (r = 0.98, P < 0.001) which is characteristic for species poor communities, where a single environmental resource is extremely important, meanwhile old stand, without any reclamation practice is best fitted to lognormal distribution model (r = 0.99, P < 0.001) which is typical for more stable and well developed communities. Principal component analysis for log (N + 1) transformed matrix of abundances described well 60% of the total variance. Two clear groups of species transects were derived: one concentrated assemblages of both reclaimed and newly established communities and the second one old non reclaimed forest stands. Significant feature of trophic guild structure in all three communities is the lowest abundance of decomposers meanwhile predators predominate on non re-cultivated old sites and herbivores on reclaimed young stands.     

Effects of bioenergy crop cultivation on earthworm communities—A comparative study of perennial (Miscanthus) and annual crops with consideration of graded land-use intensity

Energy crops are of growing importance in agriculture worldwide. This field study aimed to investigate earthworm communities of different intensively cultivated soils during a 2-year period, with special emphasis on annual and perennial energy crops like rapeseed, maize, and Miscanthus. These were compared with cereals, grassland, and fallow sites. Distribution patterns of earthworm abundance, species, and ecological categories were analysed by constrained ordination procedures (redundancy analysis; CANOCO) using a set of environmental variables as predictors, such as CN value of harvest residues, SOC and N_t content, soil pH, soil texture, and land-use intensity. The latter was determined by principal component analysis using average soil coverage and intensity of tillage, weed control, and fertilisation as input variables. It was clearly found that land-use intensity was the dominant regressor for earthworm abundance and total number of species. The diversity of earthworm communities was especially enhanced and showed a more balanced species composition in extensively managed soils under grassland, fallow, and Miscanthus. For the total number of species, Miscanthus (5.1 ± 0.9) took a medium position and neither differed significantly from intensively managed rapeseed (4.0 ± 0.9), cereals (3.7 ± 1.1), and maize sites (3.0 ± 1.4), nor from grassland (6.8 ± 1.5) and fallow (6.4 ± 1.0) sites. Total earthworm abundance ranged between 355 (±132) and 62 (±49) individuals m⁻² in fallow and maize sites, respectively.Interestingly, Miscanthus had quite positive effects on earthworm communities although the CN value of harvest residues was very high. It is recommended that Miscanthus may facilitate a diverse earthworm community even in intensive agricultural landscapes.     

Effect of low-intensity grazing on the species-rich vegetation of traditionally mown subalpine meadows

Subalpine meadows, which traditionally were mown every other year, are particularly rich in plant species, especially forbs. Near Davos (Switzerland) we compared the vegetation of mown sites with that of sites grazed for up to 50 years by non-lactating cows. We recorded an overall mean of 51.5 plant species per 4×4 m plot. Among grazed sites, evenness decreased with time since conversion to grazing (−0.11 in 50 years; P<0.05), suggesting progressive vegetation change, which may eventually result in the loss of species. Ground cover by forbs tended to be higher in mown than in grazed sites (by 7.2%; P<0.1). The proportion of not-clonally colonising perennial species decreased after conversion to grazing (−7.72%; in 50 years, P<0.05), while the cover by graminoid species increased (+14.2% in 50 years; P<0.1). More intensively grazed sites had a lower cover of dwarf shrubs and higher cover of legume species (P<0.05). Because grazing negatively affects both botanical richness and agricultural quality, mowing of traditionally mown subalpine meadows should be maintained, and recently grazed meadows should be reconverted to mowing.     

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.     

The effect of organic matter on the structure of soils of different land uses

In this study, the soil structure of two soils (Haplic Chernozem and Eutric Fluvisol) of different land uses (forest, meadow, urban and agro-ecosystem – consisted of four crop rotations) in Slovakia was compared. The soil aggregate stability was determined with a dependence on the chemical composition of plant residues. The quantity and quality of the organic matter was assessed through the parameters of the C and N in size fractions of dry-sieved and water-resistant aggregates. The soil structure of the forest ecosystem was evaluated as the best of all of forms of land use. Differences in the soil structure under the grass vegetation of a meadow (natural conditions) and urban ecosystem were also recorded. The agro-ecosystem was characterised by a higher portion (55.95%) of the most valuable (agronomically) water-resistant aggregate size fraction of 0.5–3 mm. Values of the carbon management index showed that the larger water-resistant aggregates were, the greater were the changes in the organic matter (r = ?0.680, P < 0.05). In addition, a smaller content of dry-sieved aggregates of the 3–5 mm size fraction was observed with higher contents of soil organic carbon (SOC) (r = ?0.728, P < 0.05) and labile carbon (C_L) (r = ?0.760, P < 0.05); there were also greater changes in the soil organic matter and vice versa, higher contents of SOC (r = 0.744, P < 0.05) and C_L (r = 0.806, P < 0.05) greater contents of dry-sieved aggregates of size fraction 0.5–1 mm. The soil structure of agro-ecosystem was superior at a higher content of cellulose (r = ?0.712, P < 0.05) in the plant residues. The higher content of cellulose and hemicellulose in the plant residue of a previous crop was reflected in a smaller C_L content in the water-resistant aggregates (r = ?0.984, P < 0.05). A correlation was observed between a high content of lignin in the plant residue and a smaller SOC content in the water-resistant aggregates (r = ?0.967, P < 0.05). Lastly, a higher content of proteins in the plant residues (r = 0.744, P < 0.05) supported a greater content of dry-sieved aggregates of the 0.5–1 mm size fraction.     

The effect of two ant species Lasius niger and Lasius flavus on soil properties in two contrasting habitats

Ants significantly change the soil environment within the nest. The aim of this study is to contribute to ecology and thus the importance of two ant species Lasius niger and Lasius flavus in a post-mining landscape near the town of Sokolov in northwest Bohemia where both species are common. Chemical (total C, N, and available P) and microbiological parameters (respiration, cellulose decomposition and direct counts of bacteria) were investigated in both ant species in two different habitats: a tertiary clay heap after brown coal mining with a weakly developed organic layer and semi natural meadows with well developed organic horizons. Total C and N in the L. flavus mound was lower than in the surrounding soil in both stands, the same was true for total N in L. niger on the heaps. L. niger nests in both sites were significantly enriched by available P. A litter bag test with cellulose indicated lower decomposition in the ant nest in comparison with the surrounding soil. Respiration seems to be limited by lower soil moisture in the nest. However, microbial respiration, even in suitable moisture conditions, did not differ between the nest and soil (on heaps) or nest respiration was significantly lower (in L. flavus nests in the meadow). In meadow soil both species had a lower bacteria count than the surrounding soil, but the L. niger nest on the heap had higher bacterial numbers. Both species significantly alter soil conditions, although the effect on selected parameters is variable. Moreover, the result with lower nest moisture and lower decomposition rate in ant mounds indicates that soil moisture should be the next important factor limiting soil processes inside ant mounds.     

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.     

Soil genesis and heterogeneity of phosphorus forms and carbon below mounds inhabited by primary and secondary termites

Termite activities are known to significantly influence small-scale soil properties in tropical savannas. The lateral and vertical extent of the alterations to the nest's surrounding, and particularly resulting impacts on diagnostic soil horizons remain largely unresolved until today. We examined the effects of mound-building termites on soil genesis and constitutive chemical soil properties in and below their nests. Two transects to a soil depth of 100 cm were dug below three younger mounds of Cornitermes silvestrii (the primary nest builder), three older mounds in which C. silvestrii had died out and which were secondarily colonized mainly by Nasutitermes kemneri, and three reference sites in the Brazilian Cerrado. The samples were characterized by standard procedures for soil classification; in addition, phosphorus extractions were conducted on selected samples using NaHCO₃ for labile P forms, and concentrated HCl for stable P forms. This data set was then used to build calibration models for the prediction of labile and stable inorganic (P_i) and organic (P_o) P forms, as well as for contents of organic carbon (OC), for the remaining samples applying mid-infrared spectroscopy in combination with partial least squares regression (MIRS-PLSR). We can show that the termite influence on the soil was sufficiently large to change diagnostic characteristics of the soils under termite mounds. The MIRS-PLSR predictions were suitable for quantifying organic carbon and most of the labile and stable phosphorus fractions. They showed an enrichment of OC, NaHCO₃-P_o and NaHCO₃-P_i contents in nests inhabited by primary and secondary termites by factors of 1.6–2.0 and 1.4–1.5, respectively. The soils surrounding the nests had higher contents of OC and NaHCO₃-P under both nest types vertically down to 30 cm below the lower nest border, and OC and NaHCO₃-P_i contents were elevated at minimum to a lateral distance of 60 cm away from the nest border. As the pattern of HCl_conc-P_i, which comprised 95% of total P, showed no variations, we conclude that the higher NaHCO₃-P_i amount was formed in termite nests by changing the availability of the more stable HCl_conc-P_i. In contrast to the contents, the OC and NaHCO₃-P stocks below the mounds inhabited by primary termites were comparable to those inhabited by secondary ones, because the bulk density of the secondarily inhabited nests was elevated. This was due to a transport of clay-rich material from the subsurface argic horizons into the nests. Here, the secondary termites even reverted the lessivation observed in the reference soils and under mounds inhabited by primary termites, thus causing the soil types to change from Alisols and Acrisols to the properties of Umbrisols.     

Earthworm density and biomass in relation to plant diversity and soil properties in a Palouse prairie remnant

Earthworms are important soil animals in grassland ecosystems and are considered to be important to soil quality. The overall impact of earthworms on soil properties and plant diversity, however, depends on earthworm species, functional group and the type of ecosystem. The primary purpose of this study was to document the relationship among earthworms, key soil properties and native and exotic plant diversity in the little studied, Palouse prairie grassland (Idaho, USA). A secondary objective was to determine the effectiveness of three methods commonly used to sample earthworms. A hillslope characterized by Palouse prairie vegetation, well-expressed, hummocky (mounded) topography and known to support both exotic and native earthworm species was selected for study. The hillslope was divided into three zones [annual-dominated (AD), mixed (MX) and perennial-dominated (PD)] based on characteristics of the inter-mound plant communities described in previous research. Total earthworm biomass in the MX zone (53.5 g m⁻²) was significantly greater than in the PD zone (14.7 g m⁻²) (P = 0.0384), but did not differ from the AD zone. Earthworm density ranged from 52 to 81.1 individuals m⁻² but was not significantly different across zones. Total C and N at 0 to 10 and 30 to 50 cm depths were significantly greater in the AD and PD zones as compared to the same depths in the MX zone. Soil textural class was silt loam within all zones and the soil silt fraction was positively correlated with total exotic earthworm density (R = 0.783, P = 0.0125) and biomass (R = 0.816, P = 0.0072). Native earthworms were only found in the zone with the greatest total and native plant diversity (PD). Total soil C and N were not correlated to earthworm density, but soil total C and N were significantly negatively correlated with exotic plant density, which indicates that invasive plants may be decreasing soil total C (R = −0.800) and N (R = −0.800). Calculated earthworm densities using data from the electroshocker were generally lower than those based on the hand-sorting method. Electroshocking, however, created lower disturbance and was the only method that resulted in the collection of the deep-burrowing, native species Driloleirus americanus.