Total Number Of Invertebrates Research Articles

BIOLOGICAL ACTIVITY OF GREY FOREST SOILS OF THE STARODUB AND BRYANSK OPOLIE AGROECOSYSTEMS

The main indicators of biological activity of grey forest soils of the Starodub and Bryansk Opolie in natural ecosystems, regular and intensive agroecosystems, including radioactively contaminated ones, were determined year by year. It is established that the radioactivity of the soils in the natural ecosystem catena of the Starodub Opolie is practically identical. In agroecosystems the radionuclides in soil catenas are redistributed. They are accumulated in the agrohorizons of soil cavities. In the natural ecosystem the total number of invertebrates and the absolute number of earthworms are higher in grey forest soils, having the second humus horizon cavities, than in the grey forest soils of the neighboring low ridge. In both soils of opolie the earthworms predominate among invertebrates, accounting for about 81 % of their total number. Radioactive contamination reduces the number of earthworms less than the intensification of crop cultivation technologies. In the grey forest soil of the regular agroecosystem, this figure is reduced by 56%, and in the grey forest soil with the second humus horizon by 76 %. In intensive agroecosystems the number of earthworms is reduced less, by 39 and 23 %, respectively. The biomass of the microbiota is significantly greater in the grey forest soils with the second humus horizon of the soil cavities than in the grey forest soils of the neighboring low ridge. Radioactive contamination of these soils reduces microbiota biomass less than intensification of crop cultivation technologies. In the grey forest soils of the agroecosystem, this figure is reduced by 50%, and in the grey forest soil with the second humus horizon by 61 %. In the intensive agroecosystem the biomass of microbiota decreases less intensively, by 30 and 46 %, respectively. In the incubation experiment on the grey forest soils of the Bryansk Opolje it is marked that soil enrichment with organic matter activates the soil microbiota more than 2 times. To a lesser extent, soil respiration increases with NPK application. This figure rises more than 5 times with the combined use of straw and NPK. In the field experiment, the cultivation of winter wheat in the crop rotation after annual grasses and mineral fertilization at the rate of NeoPeoKm+Neo activated the soil microbiota by 75-76 %. The biological cultivation technology on the background of the aftereffect of dung, straw and green manure without mineral fertilization causes a decrease in soil respiration and cellulolytic activity, as compared with the intensive technology.

Influence of the herbaceous layer and litter depth on the spatial distribution of litter macrofauna in a forest plantation

The litter invertebrate community consists of species from different size, trophic and taxonomic groups. The distribution of the animal population of the litter horizon depends upon many factors, especially the content of the phytocoenosis, the projective herbaceous plant cover, moisture, litter thickness and the soil texture. This article analyses the variability of the main characteristics of litter invertebrate communities (total number, number of species, diversity according to the Shannon–Wiener and Pielou indices) on plots with different herbaceous plant composition and cover in plantations of Robinia pseudoacacia L. in the South steppe zone of Ukraine (territory of the “Tiligulsky” Regional Landscape Park). The taxonomic structure of the litter communities in the Robinia plantation was dominated by predatory groups of invertebrates (Carabidae, Aranea, Formicidae). The abundance of Julidae, Isopoda, Silphidae and Staphylinidae was relatively low. The studied forest plots were characterized by the simplified size structure of the litter macrofauna. The absence of species with body length of 16–20 mm and length over 20 mm indicates damage to the most significant trophic chains. The forest belt studied is in a highly disturbed condition, the plots being dominated by steppe species of herbaceous plants. The analyzed factors (diversity and extent of cover of herbaceous plants) do not determine the structure of the litter macrofauna community but affect it indirectly: a slight increase in the total number of invertebrates was observed in areas with minimal and maximum number of species of herbaceous plants. The relationship between the abundance of invertebrates and the percentage of herbaceous plant cover is manifested insignificantly. We noted a tendency for the number of invertebrate species to decrease along the gradient of herbaceous plant cover due to the concentration of dominant predatory species which exterminate other trophic groups of macrofauna.

Macroinvertebrate identity, not diversity, differed across patches differing in substrate particle size and leaf litter packs in low order, tropical Atlantic forest streams

Mac roinvertebrate identity, not diversity, differed across patches differing in substrate particle size and leaf litter packs in low order, tropical Atlantic forest streams The size of streambed sediment particles is an important determinant of habitat complexity for stream-dwelling invertebrates. In tropical streams we tested if, at the patch scale, sandy substrates were poorer in organisms and taxa when compared with larger grain-size substrates in three experiments: (a) sampling patches with coarse and fine substrates and leaf packs in eight low-order streams, (b) manipulating substrate size at the patch scale in a low-order stream and (c) sampling coarse and fine sediment patches in a larger river. We also investigated the abundance of aquatic hyphomycete conidia in these streams to relate shredder abundance with the presence of fungal decomposers, given that tropical streams are frequently reported as being poor in shredders. In the three experiments, there were consistently no differences in terms of the family richness or total number of invertebrates across the substrate types, but taxa identity differed across substrates. Invertebrate numbers and taxa were positively correlated with current velocity. Macroinvertebrate densities (150-300 individuals/m 2 ) were lower than those reported in the literature (500->1500 individuals/m 2 ), but the number of taxa was high (37 families observed, 52 estimated). Shredders comprised 13% of all individuals and 11% of all taxa. The low number of shredders contrasted with the presence of aquatic hyphomycete spores in stream waters and in leaves sampled from the streams. We concluded that the high number of taxa and low number of individuals buffer changes in substrate, allowing the presence of invertebrates even in the less-favorable substrates (sand). Although litter and aquatic hyphomycetes were present in these streams, shredders were poorly represented; this raises the question as to why litter consumers are scarce when resources are abundant in forested tropical streams.

Utilisation of agri-environment scheme habitats to enhance invertebrate ecosystem service providers

The impact of habitat management (project-managed, farmer-managed or organic), quantity (proportion of uncropped land) and spatial configuration of habitats (arranged as strips or blocks) on the density and biomass of invertebrate functional groups was studied at the farm (100-ha block) and plot scale. At the farm scale, invertebrate abundance and biomass per unit area of uncropped land, responded positively to the presence of project-managed habitats for a number of invertebrate groups (including parasitoids and chick food). The abundance of different invertebrate functional groups varied considerably between habitat types; no single habitat provided the highest densities of all groups, suggesting that a diversity of habitats is beneficial for ecosystem service delivery. Grassy habitats supported the highest densities of predatory invertebrates, wild bird seed the most parasitoids and annual plant habitats the highest levels of chick food for farmland birds. Vegetation characteristics influenced total invertebrate biomass and levels of chick food, but not the total number of invertebrates or the abundance of those providing biocontrol.

Reduced Densities of the Invasive Wasp,Vespula vulgaris(Hymenoptera: Vespidae), did not Alter the Invertebrate Community Composition ofNothofagusForests in New Zealand

Invasive common wasps (Vespula vulgaris L.) are predators of invertebrates in Nothofagus forests of New Zealand. We reduced wasp densities by poisoning in three sites over three y. We predicted an increase in the number of invertebrates and a change in the community composition in sites where wasps were poisoned (wasps removed) relative to nearby sites where wasps were not poisoned (wasps maintained). Wasp densities were significantly reduced by an average of 58.9% by poisoning. Despite this reduction in wasp densities, native bush ants (Prolasius advenus Forel) were the only taxa that was significantly influenced by wasp removal. However, contrary to our predictions there were more ants caught in pitfall traps where wasps were maintained. We believe that the higher abundance of these ants is probably because of the scarcity of honeydew in wasp-maintained sites and compensatory foraging by ants in these areas. Otherwise, our results indicated no significant effects of reduced wasp densities on the total number of invertebrates, or the number of invertebrate families, observed in pitfall or Malaise traps. An analysis of community composition (permutational multivariate analysis of variance) also indicated no significant difference between wasp-removed or wasp-maintained communities. The most parsimonious explanation for our results is that although we significantly reduced wasp numbers, we may not have reduced numbers sufficiently or for a sufficiently long period, to see a change or recovery in the community.

Farmland bird invertebrate food provision in arable crops

Invertebrates are an essential food source for most farmland birds yet their relative abundance and biomass in the most commonly grown arable crops are poorly understood. Dvac suction sampling was used to determine the abundance, biomass and community composition of those invertebrate groups considered important in the diet of farmland birds for the commonest arable crops. Approximately 40 fields were sampled at the edge and mid‐field over 2 years in three different locations in England. In cereals, the fauna was primarily comprised of Araneae (10%), Coleoptera (30%) and Hemiptera (58%), whereas the oilseed rape fauna was dominated by Coleoptera (65%) and peas and potatoes by Hemiptera (89%). Beans contained a high proportion of Coleoptera (39%) and Hemiptera (49%). Aphididae were the most abundant family (20–86% of total), although in oilseed rape and beans, Chrysomelidae, Curculionidae and Nitidulidae formed ca 20% of the fauna. Aphids only formed a small proportion (7%) of the total biomass, except in peas (32%). Instead, Araneae, Carabidae, Heteroptera, Homoptera and Tipulidae formed much larger and more equal proportions. The highest abundance and biomass of invertebrates were recorded in cereals and least in potatoes. The Grey Partridge chick‐food index in all crops was only a half or less of the level required to ensure that chick survival is sufficient to maintain numbers of this red‐listed species. The total number of invertebrates, their biomass, diversity and the Grey Partridge chick‐food index were higher at the crop edge compared to mid‐field. Conservation measures are needed to help reverse the long‐term declines of invertebrates on farmland, which should include developing further invertebrate‐rich, agri‐environment scheme options and management techniques to encourage invertebrates considered important as bird food within arable crops.

The Distribution of Benthic and Hyporheic Macroinvertebrates from the Heads and Tails of Riffles

The spatial distribution of benthic (up to 0.05 m depth) and hyporheic (0.25 and 0.5 m depth) macroinvertebrates from downwelling zones at the heads of riffles and upwelling zones at the tails of riffles was examined in two studies on a 4th order chalk stream in Dorset, England. In the first study, differences in benthic and hyporheic macroinvertebrate community composition between the head and tail of a single riffle were investigated. In the second study, a replicated design involving eight riffles was used to compare benthic and hyporheic macroinvertebrate community composition both between heads and tails of the same riffles and between riffles. In the first (single riffle) study there were significantly higher mean numbers of benthic invertebrates and families at the riffle head (715 individuals and 13.8 families per 0.0225 m2) compared to the tail (192 individuals and 8.7 families). ANOSIM analysis also showed that the community structure of head and tail benthic samples was significantly different. In the second (replicated riffle) study, there were also significantly more benthic invertebrates at riffle heads (\(\bar{x}\) = 594 per 0.0225 m2) compared to tails (\(\bar{x}\) = 417 per 0.0225 m2), although this was not the case for families, and community structure also differed significantly between riffle heads and tails. In contrast, in the hyporheic zone, there were no significant differences between the total numbers of invertebrates in the riffle heads and tails, or between riffles, although a significant difference in family richness between riffle head and tail samples was identified in the first study. Community analysis revealed progressively poorer separation of riffle head and tail samples at 0.25 m and 0.5 m hyporheic depths. Whilst being able to identify clear differences in benthic communities from riffles heads and tails, the physically heterogeneous nature of the riffle habitats studied made it difficult to account for the consistent differences in macroinvertebrate communities observed with the physical variables measured.

Responses of benthic invertebrates and their avian predators to the experimental removal of macroalgal mats

A field experiment investigating the effects of algal removal on benthic invertebrates and estuarine birds was carried out during September and October 2001. A randomized block experimental design was employed and three treatments were used: sites with algal cover maintained, when necessary by the addition of algae, sites with algal cover removed and control sites that were not manipulated in any way. Total invertebrate numbers increased during the experiment, but species varied in their response to the different treatments. Although Hydrobia ulvae showed the greatest increase in cleared sites after two months, there was no significant difference between treatments. Corophium volutator showed significant colonization of cleared sites during the experimental period, and numbers of Phyllodocemaculata also increased in the cleared sites. Results showed that while more sedentary benthic infauna are less capable of adjusting to the affects of algal clearance, more mobile epifauna and polychaetes show an ability to disperse to cleared sites in a relatively short period of time. Wading birds, however, did not enter the study site in any abundance during the experiment. Black-headed gulls (Larus ridibundus) were significantly more abundant in cleared sites than in algal cover-maintained or control sites when foraging.

Moose, Trees, and Ground-Living Invertebrates: Indirect Interactions in Swedish Pine Forests

The role of moose in structuring the boreal forest ecosystem has been studied extensively in recent years. This research has focused mainly on the effects of moose on vegetation and soil dynamics. However, the extent to which these effects influence animal communities has received little attention. We studied how invertebrate assemblages on the forest floor of two Swedish pine forests were affected by the presence of moose. Our approach was to trap invertebrates using pitfall traps in unbrowsed exclosures and browsed reference plots, estimate the percentage cover of herb-layer plants, measure the height and density of tree species, and measure the accumulation of leaf litter. The effect of moose on tree strata differed between the two areas. In Sunnas, where the stand was a mixture of deciduous trees and pines, the main effect of moose was to eliminate most of the deciduous trees from the canopy. Here the amount of deciduous leaf litter was ten times higher in unbrowsed exclosures compared with browsed plots. The stands on the dry sites in the other area, Furudal, were almost pure pine. Here, moose browsing reduced the density of taller pines, but increased the number of pine saplings. At Sunnas, the herb-layer plant cover did not differ between browsed and unbrowsed plots. However, there was a difference between exclosures and browsed plots in terms of the ground-dwelling invertebrate assemblage. Number of individuals of most invertebrate groups that differed between exclosures and browsed plots were higher in unbrowsed plots and the total number of invertebrates was also higher in unbrowsed plots, but diversity of invertebrate fauna was higher in browsed plots. At Furudal both the vegetation and invertebrate assemblages differed between browsed and unbrowsed plots. Browsed plots had a higher cover of ground lichens, while unbrowsed plots had more mosses. Among the invertebrate taxa that differed between treatments, the number favored by browsing and the number disfavored by browsing were roughly equal, and diversity was not affected by moose. We suggest that by affecting the density and composition of tree species, moose indirectly influenced the structure of invertebrate communities. At Sunnas, the reduction in the amount of deciduous leaf litter was probably the key effect. Vegetation was not affected much, but the differences in litter layer composition had affected the microclimate on the forest floor while also providing an important additional trophic resource and habitat for ground-dwelling invertebrates. At Furudal the main effect of moose was to reduce the density of the pine canopy, thus increasing the amount of light penetrating to the forest floor. As a consequence, the floral composition and microclimate was altered which, in turn, affected the invertebrate fauna.

An update on the quantification of stream drift

The reliable quantification of stream drift is of vital importance for all drift studies. Although variation between drift samples is smaller than between benthic samples, some six to seven replicates have been considered necessary by ALLAN & RUSSEK (1985) to obtain a precision of 95 %-confidence limits within 50 % of the mean. While a review of drift studies published during the last twelve years showed that many researchers have probably used too few replicates to allow a reliable quantification of stream drift, it may be often unnecessary to use as many as six or seven. In the present study conducted in a Swiss river, we analysed data from 24 drift samples taken on six different occasions during three studies conducted in winter, spring, and summer. In each season, drift was sampled twice. The 95 %-confidence limits obtained with just four replicates were within the 50 %-boundary on all six sampling occasions for the total number of invertebrates and the five relatively most common taxa in spring and summer. In the two winter collections, taxon-specific confidence limits were outside 50% of the mean in five cases out of ten. However, overall drift densities in winter were low, and all but one of the taxa with high variation between replicates were quite rare in actual numbers. A similar or even better statistical precision may be possible in other rivers, because the higher number of replicates recommended by ALLAN & RUSSEK (1985) may have been partly due to collecting some of their replicate samples during periods of low overall drift. When studying the drift of rare taxa, however, actually more than six to seven replicates may be required to generate reasonable estimates of their drift densities. We suggest that researchers conduct more pilot studies in their individual study systems to determine the appropriate number of replicates needed, since this has been rarely done in the past.

Disturbance by aquatic plant management in streams: Effects on benthic invertebrates

The effect of aquatic plant removal on benthic invertebrates and their habitat was studied in two macrophyte-rich streams of the Swiss Plateau. In each stream, habitat conditions (macrophyte biomass, current velocity, water depth) and invertebrate densities were monitored in a control reach and in a reach where plants were removed by cutting. Biological samples were taken and physical parameters measured on three dates before and six dates after plant removal in both reaches. Responses to plant removal were similar in both streams; macrophyte cutting initially decreased mean plant biomass (ca. 85%) and total number of invertebrates (ca. 65%). Variation between replicates was, however, higher in one of the streams, causing fewer effects on plants and invertebrates to be statistically significant. Plant cutting affected mainly taxa that used macrophytes as habitat (e.g. Simuliidae, Chironomidae), whereas highly mobile taxa (e.g. Ephemeroptera) and taxa living on or within the bed sediments (e.g. Trichoptera, Bivalvia) were less affected. Taxa that decreased after plant removal recovered within 4‐6 months, although recovery of macrophytes was quite different in both streams. Invertebrate recovery also seemed to be seasonally dependent, with cutting having a less severe impact during summer than spring. Our results suggest that macrophytes in streams should be removed only in summer, preferably leaving some plant beds to act as refugia for phytophilous invertebrates. © 1998 John Wiley & Sons, Ltd.

Response of soil and leaf litter microarthropods to forest application of diflubenzuron

The objective of this study was to assess the effects of forest application of diflubenzuron (Dimilin®), a gypsy moth suppressant, on nontarget invertebrates in litter and soil on the forest floor. Four experimental watersheds (two treatment and two reference) in the Fernow Experimental Forest, West Virginia, were sampled for two years before and one year after application of diflubenzuron (70 g ha−1, AI). Soil and leaf litter arthropods were monitored before and after application using soil cores and litter bag colonization samplers. Frequency analysis, BACIP, and ANOVA were used to analyse the data for diflubenzuron treatment effects. During the 36 month study, soil core samples were dominated by mites (49%) and springtails (28%). A total of 19 taxonomic groups were suitable for statistical analysis. We detected no significant treatment effects based on total organism counts or counts by trophic categories (p < 0.05). There were no significant treatment effects for populations of major taxonomic groups, except for Araneae (spiders). Analysis of leaf litter bags also showed no significant differences in total numbers of invertebrates or in trophic categories between treated and reference watersheds during the 12 month post-treatment study. Density of one species of springtail (Sminthurus purpurescens) and springtails as a group were significantly lower in treated watersheds. High variation was associated with both soil core and leaf bag samples; because of this variation, a significance level of 0.05 should be considered very conservative. Long-term trends in soil biota were evident, demonstrating the need for well-established pre-treatment baseline data for pesticide impacts on soil organisms

Benthic assemblages in Utah headwater streams with and without trout

In a series of high-gradient streams along the Wasatch Front in northern Utah, perlid stoneflies were more abundant in benthic samples from 14 fishless streams than in 9 similar streams which contained trout. Smaller-bodied perlodid stoneflies were more abundant in samples from streams containing trout. Herbivorous insect abundances varied substantially within groups of streams containing and lacking trout; multivariate analysis of variance using the six most abundant herbivorous taxa indicated no significant difference between the two groups of streams. Similarly, total numbers of invertebrates did not differ between streams with and without fish. Sites above and below the upstream limit of trout in three streams showed patterns in invertebrate abundances similar to that seen at the whole-stream scale. Trout may have no effect on the overall density of stream benthos because of their negative direct effects on invertebrate predators.

Effects of Suction-Dredge Gold Mining on Benthic Invertebrates in a Northern California Stream

Abstract The effects on benthic invertebrates of mining with two suction dredges were investigated in 1983 by using artificial-substrate samplers in Big East Fork Creek, a tributary to Canyon Creek in northern California. The samplers were placed in Big East Fork Creek above and below the dredge site and in Canyon Creek above and below the confluence of Big East Fork Creek. The effects of dredging on invertebrates varied with taxa and were site-specific at the level of dredging during the study. Total numbers of invertebrates that colonized samplers and their diversity indices did not differ significantly between Big East Fork and Canyon creeks or above and below dredges in either creek. Numbers of invertebrates peaked earlier in samplers below the dredges. In Big East Fork Creek, shredders were more abundant above than below dredges, whereas gatherers were more abundant below dredges. Filterers rapidly colonized samplers below dredges and were later displaced by siltation. Shredders were more abundant ab...

The Effects of Conservation Management of Reed Beds. I. The Invertebrates

1. A replicated experiment was done in plots in a stand of reed (Phragmites australis) which were cut, burnt or left unmanaged. Invertebrates in the soil were sampled by heat extraction and hand-sorting, and those above ground by water traps, dissection of reed stems and in situ counting. 2. Only a few families showed differences between treatments, and this number declined with time after treatment. After 1 year, no soil invertebrates and only a few families of above-ground invertebrates showed any significant treatment effects. 3. Most treatment effects were between the unmanaged control and both cut and burnt plots. A significant difference between cut and burnt treatments was recorded for only one family, with numbers lower in the cut plots. 4. Total number of invertebrates, species-richness, species diversity and evenness showed no relationship with treatment. 5. Many soil invertebrates were more abundant in drier parts of the reed bed, but there was no similar effect on above-ground invertebrates.

Short term biotic response before and during the treatment of an acid mine drainage with sodium carbonate

The lower portion of Upper Three Runs, a woodland stream in central Pennsylvania, receives acid drainage from a strip mine. In 1974, the effect of this input on pH and benthic invertebrates was studied by Tomkiewicz & Dunson (1977). We sampled the same stations in 1986 and then treated the mine drainage with sodium carbonate for seven days in an effort to evaluate the short term colonization response of brook trout (Salvelinus fontinalis) and invertebrates. No differences in the pattern of pH and invertebrate distribution was found between the 1974 and 1986 results, although pH values and invertebrate densities were higher in 1986. Total number of invertebrates and number of taxa colonizing bricks during three pre-treatment time periods (8, 10, 18 days) did not differ from the single treatment period (7 days). However, two species of Baetis (Ephemeroptera: Baetidae) did increase in the treatment section during sodium carbonate application. The number of brook trout also increased in the treatment section, as compared to one pre-treatment estimate. These results indicate that motile species are able to respond within seven days, whereas, longer treatment may be required to produce community wide responses.

The use of benthic invertebrate data for evaluating impacts of urban runoff

The benthic macroinvertebrate population of a stream in an urbanized watershed was compared to the benthos in a rural stream. Using buried samplers, no significant difference between streams was found in total numbers of invertebrates, indicating no long term loss of colonization potential in the urban stream. Classifying the benthos in functional family groupings (based on Cummins, 1973) showed the rural stream to have nearly twice the functional diversity of the urban stream. The benthos of the urban stream was dominated by a few groups of invertebrates which could adapt to the erosional/depositional nature of the substrate and could utilize transient, low quality food sources. The density of invertebrates was adequate to support a coho salmon and cutthroat trout population in the urban stream. Apparently, the salmonids feed on available benthos and do not select specific benthic trophic groups. An evaluation of six similarity coefficients using cluster analysis showed that only the Canberra Metric index was able to represent the raw data according to known data associations.

Macroinvertebrate drift in the upper Wye catchment, Wales

Drift samples collected at five sites in the upper catchment of the River Wye yielded 99 taxa (excluding Chironomidae and Simuliidae). Significantly fewer taxa were collected from a site on the impounded River Elan (W4) compared with nearby River Wye sites. Mean daily density of drifting macroinvertebrates ranged from 6.3 × 10-2 to 782.9 × 10-2m-3, with greatest densities during the summer months, and Ephemeroptera, Coleoptera and Diptera generally comprised the greatest proportion of animals collected. Chironomids formed a considerable proportion of collections at W4 and the relative abundance of ephemeropterans, coleopterans and trichopterans was generally significantly less at W4 than at other sites. Estimates of the total numbers of invertebrates drifting past each site varied from 8.3 × 103 to 1 373.1 × 103day-1. Total numbers drifting were significantly related to estimates of total benthic density and similar relationships were established for some major taxonomic groups and some species.