Altitudinal changes in collembolan communities were studied by sampling soil microarthropods along 3 a gradient from 950 to 2150m a.s.l., under a wide range of forest vegetation types. A multivariate 4 method showed that most changes in species composition followed changes in soil chemistry, humus 5 forms and vegetation. A transition from mull to mor humus, with concomitant soil acidification, was 6 observed with increasing elevation. It was observed that at a given elevation changes in soil acidity 7 occurring in the course of forest dynamics exerted the same effects than altitude, thus soil acidity 8 explained better the composition of collembolan communities. Densities and local diversity of 9Collembola were observed to increase with soil acidity, which can be explained by i) physiological 10 adaptations to acid soils inherited from palaeozoic times and ii) more habitat and food resources when 11 organic matter accumulates at the top of the soil profile. 12 13 14

Keywords: Collembola/physical factors/agricultural practices. 1.INTRODUCTION:Soil animals promote the decomposition of organic matter by comminuting litter, The present experiment was conducted to study the Collembolan population of agricultural fields in which three crops (jute, paddy rice and wheat) were cultivated and supplemented with graded doses of N, P, and K fertilizers. Treatments were also designed to estimate the effects of organic manure and herbicides. 2.MATERIALS AND METHODS:Experimental plots were selected at the Jute Agricultural Research Institute (I.C.A.R.), Barrackpore, West Bengal, India (22°46'N, 88°24'E), in a long-term (15-yr) fertilizer experiment. In this experiment, three croppping systems using jute, paddy rice and wheat succeeded round the year. Nine different treatments (Table I) were replicated four times using a randomised block design. Soil samples were collected from experimental plots at monthly intervals for three consecutive years. Plot size was 20m x 10m.The soil was alluvium from the Gangetic plain. Fertilizer sources for NPK treatment were urea, superphosphate and potassium chloride, respectively. The three crop rotations consisted of two cereals, paddy rice (Oryza sativa L.) and wheat (Triticum aestivum L.) and one fibre crop, jute (Corchorus olitorius L.). Jute was sown in April and harvested in July. Paddy rice was transplanted in August and harvested in November. Wheat was sown in December and harvested in March. 4Hand weeding and hoeing were done at monthly intervals after sowing or transplanting. A herbicide was used for weed control in treatment 7. Soil samples were collected from all replicated plots at monthly intervals. Samplers were 9cm long and with a cross sectional area of 28cm 2 . Three cores were taken from each plot, at each time. Tullgren funnel extractors were used for collecting soil microarthropods.The extraction time was five days. Soil temperature, surface humidity and soil moisture were recorded each month from all replicated plots under each treatment.After extraction, animals were mounted in polyvinylalcohol and identified to the species or to the genus level under a phase contrast microscope. In the absence of a comprehensive account of Indian springtails, half of the species could only be identified at the genus level.Data pooled over three years for each experimental plot were used for the calculation of Spearman rank correlation coefficients, a posteriori comparisons among means using t-tests or non-parametric Kolmogorov-Smirnov tests according to normality of residuals [32] and correspondence analysis [16]. For correspondence analysis, data were transformed using refocusing (mean fixed to 20) and reweighting (variance fixed to 1) and variables were doubled in higher and lower values according to Ponge and Delhaye [28]. The latter procedure allowed to display changes in population densities. Each variable was thus represented by two points (higher and lower values) which were symmetrical around the origin. The farther these points were from the...

Soil life supports the functioning and biodiversity of terrestrial ecosystems. Springtails (Collembola) are among the most abundant soil arthropods regulating soil fertility and flow of energy through above- and belowground food webs. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset representing 2470 sites, we estimate the total soil springtail biomass at 27.5 megatons carbon, which is threefold higher than wild terrestrial vertebrates, and record peak densities up to 2 million individuals per square meter in the tundra. Despite a 20-fold biomass difference between the tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the changes in temperature with latitude. Neither springtail density nor community metabolism is predicted by local species richness, which is high in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation and resource limitation in soil communities. Contrasting relationships of biomass, diversity and activity of springtail communities with temperature suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting soil functioning.

International audienceLaboratory experiments were conducted using intact collembolan communities, exposed to Madit D-(R) a phenylurea herbicide (active ingredient isoproturon). Effects were investigated using two distinct humus types, an acid Dysmoder and a neutral Eumull. Within two weeks, no effect of the herbicide was displayed by the Eumull population, while the Dysmoder population was stimulated. When animals were able to escape from the herbicide through a perforated wall separating two compartments filled with natural soil, the behavior of collembolan communities exhibited interactive (non-additive) effects of humus type and herbicide application. The combination of an acid soil (supposedly providing greater tolerance to organic pollutants) with a neutral soil, increased biodiversity of Collembola, but caused the disappearance of some acido-sensitive species, pointing to complex relationships between pesticides, soils and soil organisms. Parallel experiments with single species demonstrated that at the recommended dose Madit D-(R) may cause avoidance effects, but no toxicity

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