Distribution Of Burrows Research Articles

3D characterisation of earthworm burrow systems in natural soil cores collected from a 12-year-old pasture

To link earthworm burrow distribution with the spatial variability of soil functions, accurate mapping of their spatial burrowing patterns is required. Eight natural soil cores (25 cm in diameter; up to 60 cm long) were collected from a pasture in spring 2001–2003. Earthworm populations were sampled on the first date and the anecic species Nicodrilus giardi was found to be dominant (55% of the average density of 101 worms m −2). Soil cores were imaged using medical X-ray tomography equipment. These tomography images served as a basis for 3D reconstructions generated using specifically written software. Finally, the reconstructed burrow systems were measured and analysed using mathematical morphological approaches. The 3D reconstructions thus derived showed dense systems of interconnected burrows. A number of burrows extending vertically from the top to the bottom of the cores, but most were short, disconnected burrows. These two classes of burrows could not be linked with the activity of a particular species. In addition to the visual appraisal of the burrow system shape, structural parameters such as burrow volume, burrow wall surface area, burrow length density, topology and burrow angles were computed from the 3D reconstructions. Total burrow length density ranged from 687 to 1212 m m −3. Burrow volume density represented less than 2.5% of total soil volume and ranged from 13.3 × 10 3 to 24.2 × 10 3 cm 3 m −3. Inspite of the apparently high continuity of burrows, only 9–43% of the volume was connected to the soil surface. Total burrow wall area ranged from 7721 to 12764 cm 2 m −3 while surface-connected burrow wall surface area ranged from 1069 to 7237 cm 2 m −3. The drilosphere volumes (i.e. a 2 mm thick sheath around burrows) were estimated to range from 44.9 × 10 3 to 52.9 × 10 3 cm 3 m −3. Earthworm activity was found to vary throughout the year as revealed by changes in burrowing patterns. The burrow systems in spring 2001 were denser than that in others years, and the burrow systems in spring 2003 appeared to be partially re-filled close to the surface. This temporal variability demonstrates that it is virtually impossible to obtain true replicates of burrow systems of a given earthworm community without knowing (1) which burrows were created by which species and (2) the burrows age. However, the accurate description and quantification of earthworm burrow systems using powerful image processing tools allows a detailed discussion of the potential impact of earthworms on soil functions under natural conditions.

The Effects of Livestock on California Ground Squirrels (Spermophilus beecheyii)

Understanding the impacts of livestock grazing on wildlands is important for making appropriate ecosystem management decisions. Using livestock exclosures, we examined the effects of moderate cattle grazing on the abundance of California ground squirrels (Spermophilus beecheyii Richardson) and the spatial distribution of active burrows within their colonies in grassland and blue oak (Quercus douglasii Hook. Arn.) savanna habitats in the coastal range of California over a 3-year period (1991-1994). Overall, relative population densities of California ground squirrels declined significantly throughout the experiment, but did not differ between grazed and ungrazed colonies or between habitats. There was also no significant interaction between these 2 factors. The spatial distribution of burrows, as measured by the mean nearest neighbor distance of active entrances within a colony, did not differ significantly between grazed and ungrazed colonies or between habitats, nor was the interaction significant. Thus, low to moderate levels of cattle grazing did not appear to have a strong effect on the population dynamics of California ground squirrels, and grazing may be compatible with maintenance of ground squirrel populations. Based on multivariate analysis of variance of 1994 data, live plant cover, native plant cover, and standing biomass were lower where the number of burrows was higher on grazed colonies but were little affected on ungrazed colonies. Ground squirrels may increase the impact of livestock grazing and thus reduce the capacity of the land to support other activities. However, it is clear that the effects of livestock grazing are complex and that detailed studies of potential mechanisms by which grazing impacts California ground squirrel populations are necessary.

Effects of cattle grazing on ecology and habitat of Columbia Basin pygmy rabbits ( Brachylagus idahoensis)

Dramatic declines in the endangered Columbia Basin pygmy rabbit, a genetically unique population of small, burrowing rabbits in Northwestern United States, are likely the combined results of habitat degradation and fragmentation, disease, and predation. A critical component of pygmy rabbit habitat includes big sagebrush ( Artemisia tridentata), which constitutes 82–99% of their winter diet and 10–50% of their summer diet. Sagebrush also forms the bulk of hiding cover around burrow sites. Across the range of pygmy rabbits, sagebrush habitat is grazed extensively by cattle. However, grazing has unknown effects on pygmy rabbits inhabiting the remaining, fragmented shrub-steppe habitat. We evaluated the effects of four grazing treatments on the distribution of pygmy rabbit burrows, diets of pygmy rabbits, and quality and quantity of vegetation at Sagebrush Flat in central Washington. Ungrazed areas contained significantly more burrows per unit area than did grazed areas. Vegetation composition and structure differed little among treatments in early summer before annual grazing by cattle. However, cattle grazing in late summer through winter removed about 50% of the grass cover, and reduced the nutritional quality (e.g., increased fiber and decreased protein) of the remaining grass. Although pygmy rabbits ate <2% grasses in winter, grasses and forbs comprised 53% of late summer diets. Because these endangered rabbits avoided grazed areas, removing cattle grazing from key habitat locations may benefit efforts to restore this rabbit in Washington.

大阪府泉南の海岸埋め立て部における陸ガニの生息状況と環境特性との関係に関する研究

In this study, we researched the habitat of terrestrial crabs, which migrate to the seaside to disperse their eggs in reproduction season, by marking the distribution of burrows and the number of the crab. The eggs hatch at the same time as they are dispersed. The larvae go down to the sea to grow up and after a while, they come back to the same habitat. Therefore, they need the area where the coastal forest, beach and the sea are unified to feel the tidal cycle and migrate safely from the forest to the sea. From this survey, we investigated the relationships between the habitat and environmental characteristics, which are topographic and conditions. As a result, the crabs tend to dig burrows on steep sides which are more than 50% slope in the forest or near the water. Moreover, their habitats are separated each other by the effect of the distance from the water. In conclusion, it would be a good way to protect the habitat that corridors such as rivers or creeks to connect the coastal forests and the sea, and to link each other are built in this area. Moreover, it would be another effective plan to distribute water places like small ponds or springwater in every 50m along the forest.

X-ray tomographic and hydraulic characterization of burrowing by three earthworm species in repacked soil cores

To test the assumption that different earthworm species make differently-structured burrow systems that can affect water permeability, the burrow systems made by adults of three earthworms species ( Lumbricus terrestris, Nicodrilus giardi and Octalasion lacteum) were studied in repacked soil cores (20 cm diameter by 40 cm high) under controlled conditions of temperature and humidity. Five core were used for each species and one adult earthworm was incubated per soil core over 21 days. Three-dimensional reconstruction (skeletons and volumetric images) of the burrow systems was performed and characterized after computer analysis of the 2D-slices from X-rays tomography. Total burrow length, number of burrows, branching rate, connectivity, burrow continuity, mean verticality and mean sinuosity of the burrows were measured from the skeletons. Differences were found between species in burrow characteristics: only one vertical and continuous burrow with large diameter for L. terrestris; long and complex burrow systems with branching burrows for N. giardi and O. lacteum. Moreover, 3D volume reconstruction of burrow systems enabled determination of the total volume, the distributed burrow volume as a function of depth and, using the tools of mathematical morphology, the pore size distribution of burrows. Results showed that the burrow volume of N. giardi was the highest; the three species had a unimodal pore size distribution centered on 8, 7 and 5 mm in diameter for L. terrestris, N. giardi and O. lacteum, respectively. Saturated hydraulic permeability was measured for each core and predicted using a water flow model. Significant differences between species were found, the burrow systems made by N. giardi being the most efficient for water flow. Differences in hydraulic properties between species resulted mainly from the difference in burrow continuity, the presence of openings at the soil surface and the burrow depth penetration.

Simulating surface and subsurface initiation of macropore flow

Initiation of macropore flow either from the soil surface or from a saturated soil layer at depth is a first order control on water flow in macropores and water transfer from macropores into the surrounding soil matrix. Nevertheless, these initiation processes have not been well documented. We surveyed surface topography at four field sites with permanent grass vegetation with grid spacing of 10 cm and applied Kriging to derive the spatial correlation structure. We then simulated the water flux into macropores based on different combinations of surveyed surface micro-topographies, spatial earthworm burrow distributions, and the soil properties, to examine more fully the role of macropore drainage area (MDA) on macropore flow initiation. The spatial distributions of the earthworm burrows were derived from horizontal soil sections extracted from each study profile. The MDA was calculated for different sets of surface topography and macropore density using a flow accumulation algorithm. The resulting MDA of each macropore was used to calculate the total relative MDA, which is equal to the proportion of overland flow draining into macropores, and the MDA probability distribution. The results showed that the macropore density primarily controlled the total MDA and that surface micro-topography strongly influenced the probability distribution of the MDA. Only a few macropores contributed significantly to the total macropore flow whereas the majority of macropores received little water; a phenomenon especially pronounced for a rough surface topography and for a low soil surface gradient. The simulated probability distribution of subsurface initiation was very different from the distribution derived for surface initiation; more symmetrical, less variable and slightly influenced by the roughness and the gradient of the interface between the saturated and the low permeable soil layer. We conclude that the different amount of water supplied to each macropore further alters the percolation depth and transport of solutes in macroporous soils and should be considered for modelling infiltration in macroporous soils.

The influence of macrofaunal burrow spacing and diffusive scaling on sedimentary nitrification and denitrification: An experimental simulation and model approach

The influence of burrow spacing on nitrification and denitrification was simulated experimentally using sediment plugs of different thicknesses immersed in aerated seawater reservoirs. Different plug thicknesses mimic different distances between oxygenated burrow centers and produce similar changes in aerobic–anaerobic reaction balances as a function of diffusive transport scaling. The thicknesses used were roughly equivalent to transport scales (interburrow spacing) that could be produced by burrow abundances of ~400 to 50,000 m-2, depending on burrow lumen radii (e.g., 0.05–1 cm). Following the exposure of anoxic sediment plugs to aerated water, an efficient aerobic nitrification zone was established within the first ~2–3 millimeters of sediment. At pseudo-steady state, the thinnest plug (2 mm) simulating highest burrow density, was entirely oxic and the denitrification rate nil. Denitrification was stimulated in anoxic regions of the thicker plugs (5, 10, and 20 mm) compared to the initial value in experimental sediment. Maximum nitrification rates and the highest denitrification/nitrification ratio between oxic nitrification and adjacent denitrification zones occurred for the intermediate plug thickness of 5 mm. Of the oxic/anoxic composites, the thickest plug showed the least efficient coupling between nitrification/denitrification zones (lowest denitrification/nitrification ratio). Both the thickness of the oxic layer and the total net remineralization of dissolved inorganic N varied inversely with plug thickness. A set of diffusion–reaction models was formulated assuming a range of possible nitrification kinetic functions. All model forms predicted optimal nitrification–denitrification and ammonification–denitrification coupling with relative oxic–anoxic zonation scales comparable to intermediate plug thicknesses (5–6 mm). However, none of the commonly assumed kinetic forms for nitrification could produce the observed NO-3 profiles in detail, implying that natural sediment populations of nitrifiers may be less sensitive to O2 than laboratory strains. Our experimental and model results clearly show that rates of N remineralization and the balance between stimulation/inhibition of denitrification are highly dependent on sedimentary biogenic structure and the particular geometries of irrigated burrow distributions.

Sampling marine pore waters for Mn, Fe, U, Re and Mo: modifications on diffusional equilibration thin film gel probes

Pore water metal profiles are important for identifying redox horizons and understanding trace metal geochemical cycling. The challenges of pore water sampling for trace metals are minimizing disturbance, especially at the sediment–water interface, and minimizing oxidation during sampling. We are investigating diffusional equilibration in thin films (DET) probes for obtaining pore water profiles. Our goal is to use probes for redox-sensitive trace metals U, Re and Mo, in addition to Mn and Fe, in coastal marine areas. Initial solution equilibration tests and laboratory core incubation experiments suggest that equilibration times for probes in sediments are approximately 24–48 h. Control tests suggest that the incubation does not alter the redox conditions in the pore waters. Pore water profiles from cores sampled by slicing, centrifuging and filtering (in a nitrogen atmosphere) and from probes are similar. Two modifications on the gel probe design were tested to determine their impact. (1) PVC wedges were attached to the backs of probes to increase the contact between sediments and the probe surface and to reduce the risk of forming channels along the probe surface, which might allow vertical pore water transport. Lower Fe concentrations were measured from probes without PVC wedges, but other metal profiles were similar. (2) A modified face frame was removed from the front of a probe, to reduce disturbance of the sediments during insertion and to increase the contact between the sediments and probe surface. Probes with modified face frames did not have increasing U and Mo concentrations with depth, whereas two of the three probes without face frames did have increasing concentrations. Increasing U and Mo concentrations at depth may be reflecting the influence of irrigating burrows and their supply of oxygen to reduced sediments, which could oxidize previously reduced metals. The distribution of burrows is heterogeneous and resulting profiles would also be expected to be heterogeneous in their response. Differences between probe profiles and sliced/centrifuged profiles are examined to gain insight into possible sampling artifacts. Peaks in the Re sliced/centrifuged profiles suggest a large Re flux to the overlying waters, which is neither calculated from probe profiles nor measured in benthic chamber samples. It is possible that heterogeneity at the sampling site in Buzzards Bay resulted in these differences; however, it is also possible that centrifugation releases Re from pore structures that would not be measured with less intrusive sampling methods, such as gel probes or benthic chambers.

Topographic distribution and daily activity of the European ground squirrel population in Bugacpuszta, Hungary

Factors affecting the population density and daily pattern of activity of the European ground squirrelSpermophilus citellus (Linnaeus, 1766) were studied in two habitats of the Kiskunsag National Park, Hungary. One habitat was dominated by sandy and the other by salty grassland. Population densities were estimated by counting ground squirrel burrow entrances in sample areas with different microhabitat characteristics. Three categories (elevated, level and depressed) were used to describe the spatial distribution of burrows according to microtopography. Daily activity was evaluated by counting the ground squirrels visible on the surface and registering their alarm calls. The highest proportion of ground squirrel holes was found on elevations in the two habitats. Ground squirrels showed a similar daily activity pattern in different areas and in the same season in consecutive years. The daily activity consisted in a morning peak, a midday pause and a less regular afternoon activity period. Human activity had no direct effect on the daily activity pattern. Emission of alarm calls peaked in June, when litters emerge from the maternal burrows.

Distribution of Badger (Meles Meles), Fox (Vulpes Vulpes) and Raccoon Dog (Nyctereutes Procyonoides) Burrows in Different Habitats and Soil Types of Lithuania

Distribution of badger (Meles meles), fox (Vulpes vulpes) and raccoon dog (Nyctereutes procyonoides) burrows in different habitats and soil types of Lithuania was investigated after surveying 371 pre-selected 1×1-km squares. Analysis of burrow distribution within habitats and soils was made applying digitised habitat data. Statistical data were analysed applying a generalised linear model with Poisson distribution and a logarithmic link function. Badger setts were found in 10, raccoon dog burrows in 11 and fox earths in 15 habitat types. The tendencies were similar for all the three species. Burrowing mammals avoided open or wet places and preferred to dwell in burrows that had been dug out in habitats providing cover. Badgers avoided digging setts in sandy soils but showed tendency to dig setts in sandy loam. Foxes liked to dwell in burrows dug out in soils of very high permeability. Raccoon dogs showed a tendency to avoid burrows dug out in soil of very low permeability.

Mantis shrimps Rissoides desmaresti in Tremadog Bay, North Wales

In 1999 divers discovered a population of the burrowing mantis shrimp Rissoides (Meiosquilla) desmaresti (Crustacea: Stomatopoda) east of the St Tudwal's Islands, North Wales. This species has only sporadically been recorded in UK waters and commonly occurs in the Mediterranean. In summer 2000 the burrow morphology and distribution of these shrimps in the area east of the St Tudwal's Islands was investigated. Burrows were found at ten of the 15 sites investigated in a survey area measuring ∼18 km2. Burrow density varied from one to 11 burrows per 100 m2. The burrows were always recorded in sediments consisting of a mixture of mud, sand and gravel but were not present at sites with a high proportion of mud (&gt;70%) or sandy sediments with very little mud ([les ]2%). Resin casts of six burrows revealed that these have a simple elongated U-shape, with an average length of ∼450 mm and depth of ∼160 mm. The average diameter of the burrow entrance was 19±2 mm and the diameter of the burrow along the horizontal section varied between 18 and 38 mm with a distinct constriction part way along.

Bioirrigation modeling in experimental benthic mesocosms

Burrow irrigation by benthic infauna affects chemical mass transfer regimes in marine and estuarine sediments. The bioirrigation facilitates rapid exchange of solutes between oxygenated overlying water and anoxic pore water, and thus promotes biogeochemical reactions that include degradation of sedimentary organic matter and reoxidation of reduced species. A comprehensive understanding of chemical mass transfer processes in aquatic sediments thus requires a proper treatment of bioirrigation. We investigated bioirrigation processes during early diagenesis using laboratory benthic mesocosms. Bioirrigation was carried out in the mesocosms by Schizocardium sp., a funnel-feeding enteropneust hemichordate that builds and ventilates a U-shaped burrow. Interpretation of the laboratory results was aided by a two-dimensional multicomponent model for transport and reactions that explicitly accounts for the depth-dependent distribution of burrows as well as the chemical mass transfers in the immediate vicinity of burrow walls. Our study shows that bioirrigation significantly affects the spatial distributions of pore water solutes. Moreover, bioirrigation promotes burrow walls to be the site of steep geochemical gradients and rapid chemical mass transfer. Our results also indicate that the exchange function, a, widely used in one-dimensional bioirrigation modeling, can accurately describe the bioirrigation regimes if its depth attenuation is coupled to the depth-dependent distribution of burrows. In addition, this study shows that the multicomponent 2D reaction-transport model is a useful research tool that can be used to critically evaluate common biogeochemical assumptions such as the prescribed depth dependencies of organic matter degradation rate and C/N ratio, as well as the lack of macrofaunal contribution of metabolites to the pore water.

Burrowing activity in the sand‐bubbler crab, Dotilla fenestrata (Crustacea, Ocypodidae), inhabiting a mangrove swamp in Kenya

AbstractSeveral species of crabs belonging to the family Ocypodidae are burrowers; they inhabit tropical sandy and muddy shores, including mangrove swamps, exposed to extreme conditions of intertidal areas. Dotilla fenestrata, the only East African representative of the subfamily Scopimerinae, exhibits high flexibility in its burrowing activity. Only part of the population has an exclusively burrow‐orientated activity, whereas most individuals form dense aggregations or droves, that during the phase of diurnal low water move away from the normal distribution zone. Burrows are built according to two different architectural designs, the feeding‐trench burrow and the igloo, which then constitute their territory. A resident will lose a contest for the burrow when the attacker is larger. When the ground is uncovered at low tide, emergence can be delayed or even fail to occur, and some crabs remain buried during the entire low water period. Only 50+ of crabs remain faithful to the original burrow, while the others either leave it to occupy an empty one or dig a new burrow, or join the wandering drove. The spatial distribution of burrows from the high water neap level (our reference point) to the sea, differs during both spring and neap tides, and both diurnal and nocturnal tides. The differences may be due partly to the change of physical conditions, such as drainage and substrate grade (although within a mangrove swamp these do not follow a consistent gradient), but mostly may be related to the trade‐off between the benefits and costs of living at different intertidal levels. With its burrowing and feeding activity leading to the re‐deposition of excavated and pseudofaecal pellets, Dotilla plays a role as a sediment mover in this very specialized habitat. The results obtained from this study are compared with those reported in other ocypodids.

Lunar synchrony in the reproduction of the Moluccan Megapode Megapodius wallacei

The Moluccan Megapode Megapodius wallacei uses heat generated by the sun to incubate its eggs. It buries the eggs deep in the sand of sun‐exposed beaches and open sandy areas on islands in the Moluccas, Indonesia. The eggs are laid at night and left to incubate for two to three months without parental care. We present evidence that the Moluccan Megapode exhibits lunar synchrony in the timing of egg‐laying, its spatial distribution of egg burrows and in its behaviour at communal nesting grounds. More Moluccan Megapodes visit the nesting grounds on bright nights than during the new moon. Data collected on the spatial distribution and depth of egg burrows also exhibit lunar periodicity. On moonlit nights, the birds excavate burrows in communal groups and spend longer at the nesting ground digging deeper burrows. Lunaphilia and lunar periodicity of reproduction are rarely documented in birds. We discuss possible explanations for these behaviours in the Moluccan Megapode.

Spatial distribution and habitat preference of the endangered tarantula, Brachypelma klaasi (Araneae: Theraphosidae) in Mexico

Brachypelma, a genus of nine endangered tarantula species in Mexico, is the only group of spiders included in Appendix II of CITES, owing to habitat degradation and illegal trafficking. However, while the majority of the nine species of Brachypelma are thought to be threatened, little is known of their ecology and distribution. Brachypelma klaasi is the rarest species, occurring in a few isolated populations on the Pacific coast of Mexico. We present an analysis of population distribution and micro-habitat requirements of B. klaasi over different spatial scales within the biological reserve at Chamela, Jalisco as part of a wider ecological study of the endangered Brachypelma group. Burrows and dispersing spiders were confined to a southern area of the reserve covering approximately 0.5 km2. Within this area, burrows were not aggregated at lower spatial scales (24–216 m2), unlike other related species. Also, there was no evidence that intra-specific interactions (either positive or negative interactions) influenced the distribution of burrows. Distribution of burrows at low spatial scales was related to low afternoon temperatures and high humidity in mid-summer. These abiotic factors may influence the survival and development of eggs and spiderlings, and appear to be more important in governing the distribution of B. klaasi than are food resources or intra-specific interactions. We discuss how these findings may facilitate the re-introduction of captive-bred individuals of B. klaasi and other Brachypelma species.

Paleohydrologic and Stratigraphic Significance of Crayfish Burrows in Continental Deposits: Examples from Several Paleocene Laramide Basins in the Rocky Mountains

ABSTRACT Paleocene crayfish burrows are present locally in great abundance in the Greater Green River, Hanna, Wind River, and Piceance basins of Wyoming and Colorado. In the Washakie sub-basin of the Greater Green River Basin, burrows are found in (1) lenticular, cross-bedded sandstones of fluvial-channel origin, (2) massive sandstones and mudrocks of floodplain origin that surround and interfinger with the cross-bedded sandstones, and (3) thin, sandy ironstone beds of overbank and crevasse-splay origin. The burrows, which represent crayfish activity in proximal to distal floodplain settings, are assigned to Camborygma symplokonomos, C. eumekenomos, and C. litonomos on the basis of their architectural morphologies. C. araioklados is not present. Crayfish burrows are part of pedogenically modified channel and overbank deposits. In all the basins studied, burrows are abundant only in non-coal-bearing rocks. The presence of elongate burrows indicates that the landscape was imperfectly drained (on a seasonal basis), and the burrow depths suggest the paleo-water table was 1-4+ m below the paleosurface. Swampy conditions prevailed in areas where carbonaceous shales and coals formed, and thus crayfish did not construct deep burrows. The crayfish burrows and associated lithologies suggest a warm, humid, wet-seasonal climate. In the eastern Washakie Basin, the vertical and lateral distribution of burrows and their abundance reflect changes in the paleohydrologic regime over space and time. Burrow depth and overall abundance decreases towards local basin lowlands, where they are rare. The paleohydrologic regime coupled with a progressively less seasonal climate through time allowed the formation of the Cherokee coal zone in the late Paleocene. In an otherwise lithologically homogeneous, non-variegated deposits, stratigraphically significant surfaces may be indicated only by the tops of burrowed intervals and by other types of paleosols. The tops of burrowed intervals represent paleosurfaces of varying environmental stability on which there are different frequency and magnitude of sedimentation events. Immature cumulative paleosols characterized by less intensely burrowed beds or bedsets record higher sedimentation rates. More intensely burrowed beds or bedsets reflect the activity of many generations of crayfish; hence, the tops of these layers record longer durations of exposure and pedogenic modification with infrequent or no sedimentation. Paleosols represented by burrowed intervals, in conjunction with sandstone and mudrock stacking patterns, can be used to identify significant stratigraphic surfaces, such as parasequences and sequence boundaries, in fully continental environments.

A Semiquantitative Field Method for Evaluating Bioturbation on Bedding Planes

Amount of bioturbation on bedding planes records the relationship between physical and chemical depositional conditions and biological activity. We propose a simple and easy-to-use method for field estimation of horizontal disruption using bedding-plane bioturbation indices that allow rapid generation of large data sets. Photographs of a representative subset of observations can be evaluated in the laboratory using image analysis and statistical analysis programs, providing a check on accuracy and potentially yielding additional information on the size, shape, and distribution of burrows and bioturbated patches. Extent of bioturbation on bedding planes can be integrated with other sedimentologic and ichnologic characteristics to interpret the infaunal community paleoecology and to reconstruct the history of the depositional, erosional, and burrowing events. Furthermore, use of the bedding-plane bioturbation indices and ichnofabric indices on vertical surfaces facilitates comparison of the extent of bioturbation through time, within and between facies, and across and between basins. It therefore enhances recognition of significant changes in physical processes, chemical conditions, and biological activity, and is a powerful tool in identifying long-term biological trends.

The role of earthworm burrows in pesticide transport from ploughlands

Macropores including earthworm burrows are thought to be major pathways for the transport of pesticides to ground and surface waters. We recorded the size and distribution of earthworm burrows over a year in an arable field at ADAS Rosemaund, Hereford and Worcester, UK. We collected material from their linings to analyse their chemical properties. We show that: i. the population of burrows recovers quickly after cultivation and is at or near its maximum during the period when most pesticides are applied; ii. the linings of earthworm burrows contain more organic carbon than the soil matrix and may have an enhanced pesticide adsorption potential; and iii. wormcasts have similar composition to burrow‐linings and show enhanced pesticide adsorption coefficient in line with their organic carbon content. Using the Damkoehler number suggests earthworm burrows are effective pollutant conduits. This has important implications for modelling pesticide movement through soils.

The interaction between plant roots and earthworm burrows in pasture

The distribution of burrows made by earthworms entering a soil with an established root system was measured in a field experiment, using vertically inserted mini-rhizotrons. Different root distributions were established by having pure swards of one of four pasture species (Ryegrass, Chicory, White clover and Lucerne) and different quantities of roots were maintained by cutting the sward to different heights. When plant roots are present before earthworms are active in the soil, the number and distribution of earthworm burrows is affected by both the quantity of roots and the plant species. Aporrectodea caliginosa and Lumbricus rubellus have more superficial burrows, and A. longa and L. terrestris deeper burrows in the soil profile. As earthworm burrows become established, a small proportion of plant roots explore the burrows. We suggest that the interaction between plant roots is two-way, with plant roots tending to determine the distribution of earthworms burrows and some plant roots tending to follow burrows.

Distribution and abundance of burrows formed by Lumbricus terrestris L. and Aporrectodea caliginosa Sav. in the soil profile

The distribution of burrows made by Lumbricus terrestris L. and Aporrectodea caliginosa Sav. was studied on an unploughed field. The positions of earthworm burrows were mapped in 9 horizontal planes to a depth of 80 cm in a pit of 70 by 40 cm. Burrow diameter and presence of plant roots growing in burrows were also recorded. Burrows on six of the nine planes were considered as two-dimensional point patterns and analyzed as spatial point processes. A three-dimensional image was constructed for burrows formed by L. terrestris. The total number of burrows ranged between 180 and 1260 m −2 at depths of 80 and 30 cm, respectively. The majority of burrows were evidently formed by A. caliginosa. The smallest size class (2–3 mm) of burrows was dominant at depths between 8 and 40 cm. Deeper in the soil profile, the proportion of larger burrows increased markedly. Burrows formed by L. terrestris appeared to be non-branching, and extended vertically beyond 80 cm. In all soil layers studied, burrow distribution was found to be completely random. The proportion of burrows containing plant roots was between 18 and 60%, at depths of 80 and 15 cm, respectively.