Distribution Of Burrows Research Articles

Spatial Association of Lemming Burrows with Landforms in the Swedish Subarctic Mountains: Implications for Periglacial Feature Stability

Burrowing mammals often have considerable geomorphological impacts, and their tunneling activities may decrease the stability of landforms. We document the spatial distribution of Norwegian lemming burrows in a subarctic alpine meadow to determine the preferred locations for burrow entrances and to examine the potential for burrowing to decrease the stability of periglacial landforms at the site. Burrow entrances were disproportionately common into the base and sides of landforms (>68% of burrows), probably reflecting the lower energetic cost of moving soil horizontally, rather than vertically, out of burrows. Most burrow entrances (>60%) were also located under large rocks, which probably improve burrow stability by providing a firm ceiling to the entrance. Field observations show that these burrows are relatively stable, as only 3% were associated with any signs of increased erosion or landform instability. Therefore, in contrast to some previous studies, and despite burrowing being concentrated on landforms, we suggest that these rodents have little direct impact on landform integrity at this site.

GIS analysis of the spatial relationship between plateau pika burrow distribution and vegetation distributional patterns

GIS analysis of the spatial relationship between plateau pika burrow distribution and vegetation distributional patterns

Linking invertebrate burrow distributions (neoichnology) to physicochemical stresses on a sandy tidal flat: implications for the rock record

AbstractInvertebrate burrow distributions (neoichnology) across a modern tidal flat are presented as an analogue for interpreting the ichnology of palaeo‐tidal‐flat successions. Burrow distributions are linked to physical and chemical (physicochemical) stresses to establish the main controls on the distribution of biosedimentary structures. Across the tidal flat, there is clear heterogeneity in both the diversity of traces and the intensity of burrowing. This heterogeneity reflects a myriad of physicochemical stresses, with the sedimentation rate dominating burrow distributions. Across all substrates, the total area occupied by organisms rarely exceeds 3% of the tidal‐flat surface, and is commonly <1%; this equates to a bioturbation index value of one. To reach bioturbation index values of two to six, sediments must be available to biogenic reworking and/or recolonization. With an increasing sedimentation rate, substrates are rapidly buried and re‐exposed, which limits the time when a substrate is available to colonization. For palaeo‐ichnological studies, this research presents several key results. (i) Burrow cross‐cutting relationships in tidal‐flat successions commonly reflect natural heterogeneities in the areal distribution of infaunal communities, rather than infaunal tiering. (ii) Ichnofabric analysis of palaeo‐tidal flats with a high sedimentation rate would yield fabrics that reflect heterogeneities in the areal distribution of infaunal communities rather than variability in the physicochemical stresses of the environment. (iii) The composite trace‐fossil assemblage of tidal flats cannot be attributed to a single ichnofacies, but instead comprises elements typical of multiple ichnofacies. (iv) The main controls on trace assemblages across tidal flats in fully marine settings are sedimentological and include the sedimentation rate and, to a lesser extent, grain size.

Resource Selection by Black-Footed Ferrets in South Dakota and Montana

The black-footed ferret (Mustela nigripes), once extinct in the wild, remains one of the most critically endangered mammals in North America despite 18 years of reintroduction attempts. Because black-footed ferrets are specialized predators of prairie dogs (Cynomys sp.), a better understanding of how black-footed ferrets select resources might provide insight into how best to identify and manage reintroduction sites. We monitored ferret resource selection at two reintroduction sites with different densities of prairie dog populations-one that contained a high density of prairie dogs (Conata Basin, South Dakota) and one that was lower (UL Bend, Montana). We evaluated support for hypotheses about ferret resource selection as related to the distribution of active burrows used by black-tailed prairie dogs (Cynomys ludovicianus), interactions between ferrets, and habitat edge effects. We found support for all three factors within both populations; however, they affected ferret resource selection differently at each site. Ferrets at Conata Basin tended to select areas with high prairie dog burrow density, closer to the colony edge, and that overlapped other ferret ranges. In contrast, ferrets at UL Bend tended not to select areas of high active prairie dog burrow density, avoided areas close to edge habitat, and females avoided areas occupied by other ferrets. The differences observed between the two sites might be best explained by prairie dog densities, which were higher at Conata Basin (119.3 active burrows per ha) than at UL Bend (44.4 active burrows per ha). Given the positive growth of ferret populations at Conata Basin, management that increases the density of prairie dogs might enhance ferret success within natural areas. To achieve long-term recovery of ferrets in the wild, conservationists should increasingly work across and outside natural area boundaries to increase prairie dog populations.

Kausale und funktionale Aspekte der Verteilung von Uferschwalbenbruten (Riparia riparia L.)

For breeding, sand martins dig burrows in sandy cliffs. The distribution of burrows and broods is non-random in different respects. The study deals with proximate factors responsible for this feature and with the question, whether differences in breeding success are correlated with differences in the distribution of burrows and broods. A series of field experiments shows that characteristics of the cliff (upper and/or lower limit, existing burrows, ledges) and of the conspecifics (social attraction, defence of burrows) influence the birds' selection of a burrow-site and that site-attachment is also involved. Birds in the highest burrows suffer less predation by a beech marten; the breeding success is correlated with the length of the burrows and with the synchronisation of broods in the sub-colonies.

Likelihood of burrow flow in Canadian agricultural lands

Summary Indicators of risk of water contamination (IROWCs) by agricultural contaminants are developed to assess sustainability of agriculture. Burrow flow (BF) is part of the transport hydrology algorithm used in IROWCs since it is a key pathway for sub-surface contaminant transport. The objectives of this study were to develop a methodology for predicting the likelihood of BF occurrence in agricultural soils across Canada at the landscape scale, and to determine its variation over a 25-year period (1981–2006). The BF algorithm considers the influence of climate, soil properties, and soil management on the likely frequency of BF and distribution of burrows (B) made by Lumbricus terrestris L. Nova Scotia, Prince Edward Island, Ontario, Quebec, followed by New Brunswick, had the highest likelihood of BF due to favourable humidity, sufficient heat, medium-textured soils, and strong runoff during the growing season and spring thaw. Alberta and Saskatchewan are too dry to favour BF. Areas with high risk of BF fall within locations of high potential for lateral flow due to shallow soils, or to the presence of tile drainage, which may connect BF pathways to important water bodies such as the Great Lakes and the St-Lawrence River. Sensitivity analyses on threshold values used in the BF algorithm indicated that Manitoba is the most sensitive province to changes in precipitation, Quebec to temperature, Prince Edward Island to soil depth, and Ontario to manure application. The BF algorithm can be used as a simple tool to predict the likelihood of water and contaminant transport along earthworm burrows with data available across Canada. It will be upgraded with new data (e.g. climate change) and with an improved algorithm after statistical analyses and correlations with actual water quality data.

Home‐range size and spatial organization of black‐footed ferrets Mustela nigripes in South Dakota, USA

AbstractEffective conservation planning for endangered species depends on an understanding of space use patterns. Black‐footed ferrets Mustela nigripes depend on prairie dogs Cynomys sp. as prey and use their burrow systems for shelter. The availability of areas with high densities of active prairie dog burrows is the major factor thought to affect their selection of sites and resources. However, we have little knowledge about how the spatial distribution of active prairie dog burrows might influence the spatial organization and home‐range size of ferrets. We monitored the movements of black‐footed ferrets on a black‐tailed prairie dog C. ludovicianus colony in South Dakota to document ferret space use patterns. Home ranges of female ferrets were 22.9 ‐ 95.6 ha in size (x̄ = 56.3 ha, SE = 19.7, N = 6), while male ferret home ranges were on average more than twice as large as those of females (x̄ = 128.3 ha, SE = 68.5, N = 3). The home‐range size of female ferrets was correlated with mean active prairie dog burrow utilization distribution (UD) value within ferret home ranges, where home‐range size decreased as active prairie dog burrow UD value increased (r2 = 0.974, P < 0.001, N = 6). Ferret space use overlapped more extensively than previously reported, with up to 43% UD overlap between a ferret and the nearest adjacent ferret of the same sex. Areas of overlap tended to have higher active prairie dog burrow UD values, suggesting that the spatial distribution of active prairie dog burrows influenced both home‐range size and the amount of space use overlap between ferrets. These findings emphasize the potential influence of resource distribution on carnivore sociobiology and the importance of considering that distribution in assessing habitat for the reintroduction of specialized species.

Fine-scale environmental heterogeneities of tidal creeks affect distribution of crab burrows in a Chinese salt marsh

Tidal creeks are an important structure of salt marshes in estuarine ecosystems, providing valuable ecosystem services to wildlife in the estuary. To determine the effects of environmental heterogeneities within tidal creeks on the features of crab burrows, we divided a typical creek section into four parts (i.e., microhabitats): bottom, slope, edge and flat, investigated the distribution of crab burrows and sediment properties on creek sections in the Yangtze River estuary, and compared the burrow distribution in tidal creeks with that in non-creek areas. Our results showed that from the creek bottom to flat soil water content declined ( F 3, 60 = 93.8, p < 0.001), and the variations of other sediment physical and chemical properties associated with the change of soil water content were significant among the microhabitats on the creek sections ( p < 0.001 for pH, conductivity, and grain size). No crab burrows were found at the creek bottom. The burrows on the slope were smaller in size ( p < 0.001 for burrow opening diameter) while the density was higher than that at the edge and on the flat ( F 2, 45 = 31.2, p < 0.001). Moreover, although the correlations between burrow distribution and sediment properties varied among the microhabitats on the creek sections, crabs generally selected relatively solid sediments to build their burrows. On the slope, there was a significantly negative relationship between burrow density and soil water content ( r 2 = 0.53, p < 0.001). At the edge, the correlation between total burrow opening area and soil water content was significantly negative ( r 2 = 0.44, p < 0.002). The density of small crab burrows (<10 mm) was greater, but that of large burrows (>10 mm) was lower in tidal creeks than in non-creek habitats. Therefore, sediment properties showed a gradual transition from hydrophytic to terrestrial environments on the creek section, which caused significant differences of burrow distribution among the microhabitats. The creeks of tidal salt marshes could affect ecological processes and functioning through affecting crab burrows.

Infaunal burrow ventilation and pore-water transport in muddy sediments

The ventilation of burrows by tube-dwelling benthos is understood to be important in determining rates of exchange of solutes between the sediment and overlying water. However, few models have attempted to link the burrow ventilation behavior of tube-dwelling organisms with their geochemical consequences. The classic cylinder model of bioirrigation in muddy sediments (Aller, R.C., 1980. Quantifying solute distributions in the bioturbated zone of marine sediments by defining an average microenvironment. Geochimica et Cosmochimica Acta 44, 1955–1965) links pore-water processes and burrow sizes and distributions in the sediment by assuming that burrows are fully flushed. The equivalence between the cylinder model and the more commonly used one-dimensional non-local exchange model depends upon this assumption. However, this assumption has seldom been tested in the field. We have extended the cylinder model of bioirrigation to include burrow ventilation activities of organisms. Burrow ventilation is modeled as a simple non-local exchange of burrow water with overlying water. Model simulations indicate that burrow ventilation has a large effect on vertical profiles and fluxes of solute tracers. We collected data on burrow geometry in the field by CT-scanning freshly collected sediment cores. At the same study sites, we measured activity profiles of 222Rn, a naturally occurring radionuclide tracer of pore-water transport. With model geometry independently constrained, we tested the model by comparing our model-predicted profiles with measured profiles. Our results demonstrate that burrows in the field are not fully flushed. Our estimated burrow ventilation rates compare favorably with previous laboratory measurements. The inclusion of realistic burrow ventilation in this pore-water transport model strongly affects modeled solute profiles and fluxes. We demonstrate how model parameters can be determined from field samples and present a model that more realistically simulates pore-water transport processes in muddy sediments.

Effect of Bioirrigation on Sediment−Water Exchange of Methylmercury in Boston Harbor, Massachusetts

Coastal marine sediments are important sites of methylmercury (MMHg) production, and dissolved efflux provides an important source of MMHg to near-shore, and possibly offshore, water columns and food webs. We measured the flux of MMHg across the sediment-water interface at four stations in Boston Harbor that span a range of infaunal population densities and bioirrigation intensities. At each station we carried out total MMHg flux measurements using core incubations and collected near-surface pore waters to establish MMHg gradients for diffusive flux calculations. The flux cores were also imaged by CT scanning to determine the distribution of infaunal burrows, and pore-water sulfide and 222Rn profiles were measured. Total MMHg fluxes, measured using core incubations, ranged from -4 to 191 pmol m(-2) d(-1), and total MMHg fluxes were strongly correlated with burrow densities at the stations. Estimated diffusive fluxes, calculated based on MMHg concentration gradients below the sediment-water interface, were much lower than total fluxes at three of the stations, ranging from 2-19 pmol m(-2) d(-1). These results indicate that MMHg exchange may be significantly enhanced over molecular diffusion in bioturbated sediments. Furthermore, burrow density provides a strong predictor of total MMHg flux. Pore-water exchange of both dissolved MMHg and 222Rn, a naturally occurring pore-watertracer, increased across the range of observed burrow densities, suggesting that the presence of burrows enhances both MMHg production and flux.

Circannual rhythm in spatial distribution of burrows of freshwater crab, Barytelphusa cunicularis (Westwood, 1836)

Ecologists use a number of techniques to quantify and statistically analyse patterns of spatial distribution. The present study deals with the temporal distribution and nature of the burrows of the crab Barytelphusa cunicularis, found at Maroda Sector, Bhilai, India. All the burrows present in an area of 112 m2 were examined, during a span of 24 consecutive months. The number and pattern of burrows were observed every month in the study area. The data were subjected to nearest neighbour analysis. Rn values were computed to ascertain whether the distributions are clustered, random or regular. The burrows are considered more randomly spaced when Rn gets closer to 1.0. Time series data on Rn values, number of the total, single- and double-mouthed burrows were analysed by cosinor rhythmometry. The pattern of burrow distributions becomes more random in the early September with a spread between the beginnings of July and November. The timing of the peak in the burrows follows the peak in Rn values suggesting a post-reproductive increase in burrowing activities. The chronobiological analyses of Rn values add a new dimension to the interpretation of spatial distribution of crab burrows. This paper documents rhythm as an ecological phenomenon.

Notes on the structure and the use of Neosarmatium meinerti and Cardisoma carnifex burrows in a Kenyan mangrove swamp (Decapoda Brachyura)

Burrow distribution and morphology were investigated in Neosarmatium meinerti and Cardisoma carnifex, two species sharing the same environment in a Kenyan mangrove swamp. Burrow structure and occupation ratio were also analysed. The sizes and shapes of the burrows are consistently variable in both the species. Most of the burrows have a simple linear shape, that in few cases can be complicated by the presence of bends, rooms and accessory branches. Bends are due to obstacles found while digging the burrows, the rooms and the accessory branches are probably used to store food. In accordance with the fact that C. carnifex is larger than N. meinerti, the burrows of the two species significantly differ in terms of both diameter and volume. For N. meinerti burrows there is a strong correlation between the carapace width and the entrance size, and with the volume, but not with the linear length. Thus length is not related to crab size but varies depending on the substrate, the presence of roots and the depth of the sea water level. An interesting finding is that some crab burrows are occupied by the fish Acentrogobius simplex as a temporary refuge, probably aiding its survival in shoal periods.

Population traits of the burrowing toad Rhinella fernandezae (Gallardo, 1957) (Anura, Bufonidae)

Size distribution, sex ratio and use of burrows of the burrowing toad Rhinella fernandezae were studied in Buenos Aires province, Argentina. Two sites separated by approximately 300 m were studied: one was a road next to a swamp, and the other a garden of a country house located further from the swamp. We identified toad burrows, and individuals were sexed, measured and given an individual mark. Burrows were examined in subsequent months after the first sampling to assess the presence of toads. We found significant differences in the size distribution between areas, being the proportion of juveniles greater at the site next to the swamp where the reproduction of the species was observed. This result may suggest that the site located near to the swamp functions as a source habitat of individuals that migrate to the other site, where recruitment would be very scarce. Sex proportion of adults did not differ from 1:1 in neither the total population nor in each site, suggesting that there was not differential mortality by sex. Some toads changed burrows throughout the study period, but there were not differences in the frequency of change between adults and juveniles.

Distribution of northern pocket gopher burrows, and effects on earthworms and infiltration in a prairie landscape in Alberta, Canada

The prairie pothole region of North America is characterized by hydrologically closed depressions that seasonally fill with water and provide critical early season habitat for migratory waterfowl. Infiltration of snowmelt and rainfall in the uplands and under these depressions, controls the lateral input of water to the depressions. Relationships between soil infiltrability and land use, topography, northern pocket gopher burrowing, and endogeic earthworm abundances were studied in a prairie pothole region near Calgary, Alberta. An alfalfa field and an adjacent grassland area were divided into upland, transitional, and depressional zones. Gopher mound distribution and area was measured in each land-use area and each topographic zone, earthworm abundance was estimated by excavation, and infiltration was measured by a ring infiltrometer. Depressional areas in the grassland contained fewest mounds, averaging 0.2 mounds per 25 m 2. Conversely, the depressional areas in the alfalfa contained 9.2 mounds per 25 m 2. Transitional zones in the alfalfa and grassland averaged 4.6 and 6.9 mounds per 25 m 2, respectively. In the transition zones in the two land-use areas, earthworms were Aporrectodea trapezoides and Aporrectodea tuberculata. Worm density in soil not under gopher mounds averaged 250 worms m −3 in the grassland and 82 worms m −3 in the alfalfa. Under gopher mounds, there were 860 worms m −3 in the grassland and 49 worms m −3 in the alfalfa. However, the effects of gopher and earthworm burrowing on water infiltration rates were unclear. Gopher burrowing activity appeared to have no effect on infiltration rates in either area.

Breeding habitat of the Cook's Petrel (Pterodroma cookii) on Little Barrier Island (Hauturu): implications for the conservation of a New Zealand endemic

Cook's Petrel (Pterodroma cookii), a trans-equatorial migrant endemic to the New Zealand archipelago, is today endangered and restricted to island habitats at the northern and southern extents of its former range. To improve the limited knowledge of the breeding habitat of this species, we combined an island-wide survey, the mapping capabilities of geographic information systems, and logistic and autologistic analyses to examine burrow distribution and habitat use of the world's largest population of Cook's Petrel, on Little Barrier Island (Hauturu). Our results show that, on this island, Cook's Petrel breeds predominantly above 300 m above sea level, on steeper slopes, closer to ridge tops, and in unmodified forest habitats with low and open canopies and greater numbers of large stems compared to the available terrain and habitat. Within these habitats above 300 m, densities of burrows are 0.04 burrows m−2. Through comparisons with habitat data from two low-altitude colonies, we conclude that the current distribution of this population is a result of habitat selection and historical human-mediated impacts. We suggest that mature forest habitats, close proximity to ridge tops, and steep slopes are key habitat requirements for this species. A large amount of suitable habitat is available for Cook's Petrel on Little Barrier Island and the recent removal of introduced predators is expected to result in an expansion of this population. The results of the current study provide useful information to aid in the restoration of former colony sites on other islands and the New Zealand mainland.

The ghost crab Ocypode quadrata (Fabricius, 1787) as a potential indicator of anthropic impact along the Rio Grande do Sul coast, Brazil

The aim of this study is to compare the density and vertical distribution of ghost crab Ocypode quadrata burrows at three beaches with different degrees of anthropic impact. In order to achieve this, 12 1 m 2 quadrants were laid out at random daily on each beach, over a 100 m wide strip stretching from the dunes to the waterline, in order to estimate the density of the burrows. The results showed that the density of O. quadrata burrows was lower at beaches with higher anthropic impact – Tramandaí and Harmonia. Jardim do Éden beach, which suffers little impact, had the highest density of burrows. Vertical distribution of the burrows at Tramandaí beach was restricted by the presence of a strip which cars drive along. The burrows along this beach tended to be distributed over a strip where there are kiosks which offer protection from the traffic. At Jardim do Éden and Harmonia beaches, vertical distribution of the burrows was affected only by the dynamics of the rise and ebb of the waterline, caused by two storm events. The results showed that the density of ghost crab O. quadrata burrows is a tool of quick and easy use in diagnosing anthropic impact in coastal areas.

Cost of foraging in the subterranean rodentCtenomys talarum: effect of soil hardness

Subterranean burrows provide inhabitants with shelter, a relatively stable thermal environment, and potentially access to food resources. However, one cost of living in such burrows is the energetically expensive mode of locomotion. Soil hardness and the physiological capabilities of animals are likely important factors that affect the cost of burrow construction, and hence, distribution of burrows. We assessed the effect of soil hardness on the cost of digging by captive individual Ctenomys talarum Thomas, 1898 in soft soils. Digging metabolic rate (DMR) was higher in harder soil than in softer soil (408.30 ± 51.35 mL O2·h–1vs. 267.59 ± 20.97 mL O2·h–1, respectively). In C. talarum, a higher soil hardness augments DMR by increasing, in terms of the cost of burrowing model, the costs of shearing and of pushing the removed soil. Additionally, these costs differ between C. talarum and other subterranean species (e.g., Thomomys bottae (Eydoux and Gervais, 1836)), depending on soil hardness and digging mode. Thus, the relationship between digging cost and soil hardness appears to be one of the most important factors that affect burrowing efficiency in subterranean rodents.

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.

Burrow morphology, biometry, age and growth of piddocks (Mollusca: Bivalvia: Pholadidae) on the south coast of England

Biometry and growth of three piddock species Pholas dactylus, Barnea candida and B. parva, from chalk and clay substrata were investigated between 1999 and 2000 at five low shore locations along the south coast of England. Piddock burrow shape was significantly different (P<0.01) amongst the locations. Burrows at Lyme Regis showed the largest (height/maximum diameter) ratio (4.86±2.00) whilst those at Compton the lowest (3.73±1.62). Using the method of Bhattacharya, the population structure of P. dactylus, B. candida and B. parva was separated into eight, three and five modal size classes, respectively. Age and shell growth were determined from the number and spacing, respectively, of annual growth lines present in acetate peel replicas of shell sections. The von Bertalanffy growth (VBG) equation fitted the size at age data obtained for P. dactylus and B. candida (L∞ and K were 79.3±13.8 mm and 0.0011±0.22 and 29.6±1.5 mm and 1.17±0.47, respectively) whilst the size at age data for B. parva were linearly related and did not fit the assumptions of the VBG equation. Male and female gonads were mature and piddocks competent to spawn between June and September 1999, with settlement of juveniles observed between November 1999 and February 2000. A significant relationship between burrow aperture diameter and age of the occupant piddock was established for the three species. Burrow morphology and spatial distribution of burrows were influenced by substratum hardness and population density. Based on estimates at Lyme Regis, piddocks are capable of removing up to 41% of the shore substratum to a depth of 85 mm over their lifespan (12 years), significantly compromising the structural stability of the soft rock shores they inhabit and contributing to bioerosion.

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.