Microbiological characterization of the structures built by earthworms and ants in an agricultural field

The genesis and architecture of the structures built by ants and earthworms differ markedly, suggesting that—in addition to having different physical and chemical properties—the resident microbial community should also have unique properties. We characterized the inorganic N, biomass C, C mineralization rate, and functional diversity of the microbial communities of earthworm casts, earthworm burrow soil, ant mounds, and bulk soil from an agricultural field. Mound soil was most enriched in inorganic N and had the lowest pH, moisture content, and C mineralization rate. Functional diversity was evaluated by determining the ability of microorganisms to grow on 31 substrates using Biolog^®EcoPlates in combination with a most probable number (MPN) approach. Casts had MPNs that were one to two orders of magnitude higher than burrow, mound and bulk soil for most substrates. Casts also had the highest MPNs for particular substrate guilds relative to bulk soil, followed by mound and burrow soil. Indices of substrate diversity and evenness were highest for casts, followed by burrow, mound, and bulk soil. Differences in the type of habitat provided by the structures built by ants and earthworms result in the differential distribution of nutrients, microbial activity, and metabolic diversity of soils within an agricultural field that affect soil fertility and quality.     

1500万毒价/ml D型肉毒杀鼠素在新疆地区防治草原鼠害的研究

采用1.5ml/hm2、2.25ml/hm2、3ml/hm2三个浓度梯度的1500万毒价/ml D型肉毒梭菌毒素对新疆的主要草地害鼠进行灭治,其矫正灭洞率分别为:84.18±1.86%、86.65±2.34%、87.33±2.21%.均取得较好效果,且各浓度梯度无显著差异(P＞0.05).D型肉毒梭菌毒素适口性好,无二次中毒现象,可在新疆广泛使用.     

Rodent burrow network dynamics under human‐induced landscape transformation from desert to steppe in Kalmykian rangelands

Rodents play an important role in rangelands through the engineering of extensive burrow systems, which provides key habitats for many animal and plant species. We have analyzed the long‐term variation in the abundance and distribution of rodent burrows in grazing ecosystems of southern Russia (Kalmykia) under the landscape change from desert to steppe caused by the drastic reduction of livestock after the collapse of the USSR in the early 1990s. We conducted burrow surveys in the “desert” (1980) and “steppe” (2017) periods on 19 3‐km transects. We found considerable changes in burrow abundance and distribution, as well as evidence of desert habitat fragmentation and isolation caused by the expansion of tall‐grass communities. Burrows of the open‐dwelling diurnal ground squirrel (Spermophilus pygmaeus), the dominant and the keystone species during the “desert” period, almost completely disappeared from the rodent burrow network by 2017, indicating significant habitat loss. In contrast, the burrows of the folivorous social vole (Microtus socialis) which was rare in the 1980s, became abundant and ubiquitously distributed. The burrow density of the desert‐dwelling psammophilous midday gerbil (Meriones meridianus) decreased, while the distances between occupied patches increased, indicating desert habitat fragmentation and loss of population connectivity. Burrows of the folivorous tamarisk gerbils (M. tamariscinus) were recorded only sporadically in both 1980 and 2017. The observed changes in the rodent burrow network, the key component of grazing ecosystems, correlate with rodent species ecology and can have long‐term and important consequences for ecosystem functioning.     

A non-destructive method for the morphological assessment of earthworm burrow systems in three dimensions by X-ray computed tomography

Summary Earthworm burrows of endogeic species (Allolobophora caliginosa, Octolasium cyaneum) in artificially packed soil columns were examined using X-ray computed tomography. By means of digital image processing, it was possible to reconstruct and visualize the burrow system in three dimensions. The reconstruction revealed morphological features of the burrows which were not obvious from two-dimensional section images.     

Assessment of earthworm burrowing efficiency in compacted soil with a combination of morphological and soil physical measurements

Summary Column experiments were carried out to quantify the effect of earthworms on compacted soil. The earthworms (Lumbricus terrestris) were able to burrow into soil which was artificially compacted to a pore volume as low as 40%; they may also penetrate an artificial plough pan deep in the soil. The effect of the burrowing activity of Lumbricus terrestris was quantified by measuring hydraulic conductivities and infiltration rates through the whole soil column (19 cm wide, 40 cm long). Morphological parameters, mainly the vertically projected burrow depth, were correlated with the saturated hydraulic conductivity. The amount of casts deposited by Lumbricus terrestris on the soil surface increased with the degree of soil compaction. The bulk density of casts was always less than that of the original soil.     

新疆维吾尔自治区应用C·肉毒杀鼠素灭鼠试验报告

Ｃ·肉毒杀鼠素（下称毒素）０．１％浓度毒饵，对新疆的主要害鼠大沙鼠和黄兔尾鼠进行灭治，校正灭洞率分别为９７．４％和９０．２％，均可取得良好效果。常用农药０．５％甘氟毒饵的灭治效果分别为９８．５％和６７．１％。因此，毒素能够代替甘氟在新疆草地灭鼠中应用；以小麦和草颗粒作载体与０．１％毒素拌制毒饵，灭杀大沙鼠和黄兔尾鼠灭洞率分别为９８．２％、９９．３％和９０．２％、９１．７％，两种载体均可使用；新疆草地的害鼠四月份正值数量低峰期，废弃洞数量很大，有效洞率大沙鼠为９．３７％、黄兔尾鼠为１４．７０％。     

A method of extracting earthworms from cores of soil with minimum damage to the soil

 Lumbricid earthworms have often been shown to increase the growth of plants. The earthworms and plants were generally grown together in the same soil, although sometimes earthworms were reluctant to enter the soil. It was not possible to isolate the mechanism for the increased growth, as no method was available to extract the earthworms with no damage to the soil before the plants were grown. A method is described which enabled Aporrectodea caliginosa, but not A. trapezoides, to enter all cores, and which extracted A. caliginosa from the cores probably with minimum damage to the soil. Received: 20 October 1998     

Fluorine contamination of soils and earthworms (Lumbricus spp.) near a site of long-term industrial emission in southern Germany

Summary The F contamination of soils and Lumbricus spp. around a site of long-term industrial emission in southern Germany was examined. Among total, water extractable, and HCl-soluble fractions, the latter most appropriately characterized anthropogenic F accumulation. Based on the HCl-soluble fractions from 88 sampling sites, a contamination map consisting of three zones was established. F accumulation in the calcareous soils of the area was restricted to the top 40–50 cm and can be explained by precipitation as CaF₂. Earthworms (Lumbricus spp.) collected from the different zones reflected the F contamination well in the significant correlations found between total F in earthworms with and without gut and the corresponding soils. The bioaccumulation of F in earthworms is obvious, and may become hazardous for the earthworms themselves and for other animals feeding on contaminated soil and/or its fauna. A significantly higher F value was recorded in the linings of earthworm tubes than in the corresponding soil. F translocation by earthworm burrowing may be a mechanism of subsoil contamination.