Enchytraeid numbers,biomass and respiratory metabolism in a beech woodland - Wytham Woods,Oxford

Summary The mean annual population density of enchytraeids in the litter and upper 6 cm of soil was found to be 14,590 m^-2. Mean individual weights approximated 116, 158 and 151 g wet wt. in the litter, 0–3 cm and 3–6 cm strata respectively. The mean biomass was estimated to be 1.908 g wet wt m^-2. Vertical migration was shown to occur, the upward migration in late Autumn was a response to temperatures in the litter being temporarily higher than those of the 0–3 cm stratum. As a result of upward vertical migration and possibly recruitment, numbers reached a maximum in the litter during Winter. On an annual basis the litter, 0–3 and 3–6 cm strata contained 41.43, 46.44 and 12.12% respectively of the extracted enchytraeids. The equivalent biomass values were 33.18, 52.46 and 14.36%. Total numbers and biomass revealed a general picture of high values in late Autumn to Winter which gradually decreased through Spring and Summer except for a minor peak in May–June. The annual oxygen consumption of the enchytraeids approximated 4.285 l O₂ m^-2 yr^-1 (20.461 kcal85.610 kJ) and accounted for 1.63% of the total soil metabolism. A production/biomass (P/B) ratio of 4.93 was estimated as was a net population efficiency of 32%. For this site the contribution by enchytraeids to total soil respiration is about one-third that of the earthworms and an order of magnitude greater than that of the nematodes.     

Phenology and intensity of phyllophage attack on Fagus sylvatica in Wytham Woods, Oxford

ABSTRACT.

• 1 Overwintering beech buds began to swell in early April and bud-break occurred in early May. Most phyllophage attacks were initiated during the 21 day period of leaf growth but additional attacks occurred up to 46 days from bud break.
• 2 An average beech tree, with a top height of 24 m and a d.b.h. of 110 cm, bore 420 345 leaves (17% in the upper canopy, 27% in the upper middle canopy, 27% in the middle canopy, 18% in the lower middle canopy and 11% in the lower canopy).
• 3 Damage by phyllophages was greatest in the lower canopy; some 75—85% of the leaves were attacked in this stratum and damage amounted to 35% of the total phyllopage damage to the trees.
• 4 The major agents of damage in the lower canopy were adult P. argentatus, larval R. fagi and lepidopteran macrophages. Adult R. fagi concentrated their feeding in the upper canopy.
• 5 Allowing for damage expansion due to leaf growth the percentages of the total leaf area actually removed, or seriously damaged, by phyllophages were calculated to be 3.43–4.00% in 1978 and 2.37–2.74% in 1979.

     

Earthworm numbers,biomass and respiratory metabolism in a beech woodland-Wytham Woods,Oxford

Summary The mean annual population density of earthworms was found to be 164.6 m^-2 during a period of detailed study between October 1971 and September 1972. In a year of less detailed study between November 1972 and October 1973 the population density was 117.5 m^-2 (139.8 m^-2 when the type of extraction method was allowed for). Mean biomass densities in the two years of investigation were 41.0 g preserved wet wt m^-2 (1971–1972) and 38.6 (possibly 39.2) g preserved wet wt m^-2 (1972–1973).Comparison of the Brogden's Belt population and biomass densities with those reported from other woodlands indicates that soil type is more important than leaf litter type in determining the numerical abundance of earthworms. Population densities are lower in beechwoods on mor soils, mor soils also support significantly fewer species. As with numbers, mean biomass density in beechwoods on mor soils was significantly lower than that occurring in beechwoods on mull soils; the latter, in turn, being lower than those found in mixed deciduous woods on mull soils. Unlike population density biomass density is influenced by both soil and litter type, this is discussed by reference to mean body weights and food quality as reflected by tannin, nitrogen and carbohydrate content.The annual respiratory metabolism of the Brogden's Belt earthworms was calculated to be between 10.7 and 13.41 O₂ m^-2 a^-1, which is equivalent to between 4.1 and 5.1% of the total soil metabolism. A production/biomass ratio of 0.49–0.58 was estimated, as was a net population efficiency of 22%.     

Changes in the ground flora in Wytham Woods,southern England from 1974 to 1991 – implications for nature conservation

Abstract. The ground flora (vascular plants < 2 m high, excluding trees and shrubs) was recorded in 1974 and 1991 from 163 permanent 10 m x 10 m plots arranged on a systematic grid across Wytham Woods, near Oxford (UK). The Woods cover about 320 ha, are predominantly deciduous, but of varying ages and management types. The total number of species found (173, 167 respectively), the mean richness per plot (16.7, 17.2) and the breakdown of the species list between different species types (ancient woodland indicators, other woodland species, non‐woodland species) showed no significant differences between 1974 and 1991, but mean ground cover declined from 80% to 64%. Ancient woodland indicators as a group showed less change between the years than species associated with the open glades and grassland patches in the wood. Some species increased in frequency across the woodland including Arum maculatum, Brachypodium sylvaticum, Deschampsia cespitosa and Poa trivialis; while others such as Ajugareptans, Angelica sylvestris and Circaea lutetiana declined. Mean cover of Rubus fruticosus per plot declined from 35% to 6% and of Mercurialis perennis from 32 to 24%. More species were lost from plantations than from semi‐natural stands. The results are based on only two times, so inferences on possible causes must be drawn with caution. However the results are consistent with the effects of (1) the changing conditions associated with stand growth, particularly in the plantations, and (2) an increase in browsing/grazing by deer. No evidence was found for an effect of changing soil nitrogen levels on the vegetation. Changes in the ground flora as well as the woody layers, and in managed as well as unmanaged stands should be monitored, if nature conservation objectives are to be met.     

The variation in population densities of fleas in house martin nests in Leicestershire

Abstract. 1. Five species of flea were recorded from 150 nests taken from house eaves in Leicestershire. Three species, C.hirundinis, C.farreniand C.rusticus , were associated with nests used for breeding by martins in the year of collection whilst C.gallinae and C.fringillae were associated with nests used by sparrows.
2. Analysis of the three species of martin fleas with various characteristics of the structure and location of the nest revealed that all three species favoured the presence of nest lining consisting of feathers or grass (or the two combined) in preference to straw or to no nest lining.
3. Both C.hirundinis and C.rusticus showed a preference for the texture of the surface to which the nest was attached, the former preferring nests attached to plain brick, or pebble-dashed surfaces, whilst the latter preferred pebble-dash to stone. Both also showed a relation with the height of the nest above ground level.
4. The numbers of C.hirundinus showed a strong positive correlation with those of C.farreni and C.rusticus , which were not correlated with each other.
5. Lastly, the number of nests collected that had been used by house sparrows and contained C.gallinae and C.fringillae was too small to allow us to reach any conclusion about their preferences.     

The stoat Mustela erminea population decline in northern Belarus and its consequences for weasels Mustela nivalis

Abstract

In northern Belarus, we have documented a decline in the local stoat Mustela erminea population following the naturalisation of the American mink Mustela vison. The most likely cause is the reduction in the density and distribution of the main prey of stoats, the riparian voles (the water vole Arvicola terrestris and the root vole Microtus oeconomus), due to excessive predation by mink. Since the stoat population has declined, the number of weasels Mustela nivalis in marshlands has increased and their mean body mass has increased, correlated with the higher number and mean weights of rodents available for weasels in marshland compared with forest habitats.     

The use of weasels for natural control of mouse and vole populations in a coastal coniferous forest

Summary Nectar-feeding frequently occurs in male and female tabanids. 53% of the 7,002 females and 69% of the 2,436 males reacted positively to cold anthrone. Although there are seasonal fluctuations in rates of blood and nectar-feeding, the acquisition of sugars may be essential for tabanid survival during the summer. Differences in blood-feeding rates among the species may indicate different blood-sucking habits.This work is a part of Ph.D. thesis carried out at the Institut für Allgemeine und Spezielle Zoologie, Justus-Liebig-Universität Gießen     

Bayesian population dynamics of interacting species: great gerbils and fleas in Kazakhstan

We propose a discrete-time Bayesian hierarchical model for the population dynamics of the great gerbil-flea ecological system. The model accounts for the sampling variability arising from data originally collected for other purposes. The prior for the unknown population densities incorporates specific biological hypotheses regarding the interacting dynamics of the two species, as well as their life cycles, where density-dependent effects are included. Posterior estimates are obtained via Markov chain Monte Carlo. The variance of the observed density estimates is a quadratic function of the unknown density. Our study indicates the presence of a density-dependent growth rate for the gerbil population. For the flea population there is clear evidence of density-dependent over-summer net growth, which is dependent on the flea-to-gerbil ratio at the beginning of the reproductive summer. Over-winter net growth is favored by high density. We estimate that on average 35% of the gerbil population survives the winter. Our study shows that hierarchical Bayesian models can be useful in extracting ecobiological information from observational data.     

The epizootiological role of the population organization of the stock of fleas on the long-tailed suslik in a natural focus of plague in Tuva

Spatial location of epizootic events in the Tuva plague focus is determined at a considerable degree by the population structure of the flea Citellophilus tesquorum--the main plague microbe vector. Within the enzootic territory occupied by five populations of the long-tailed ground squirrel (Citellus undulatus) there are six populations of C. tesquorum. Each population of fleas has a corresponding autonomic plague focus. Various conditions for the microbe life activity in these populations are recovered. The circulation of the microbe is closely connected with certain intrapopulation groupings of fleas--the nuclei of populations.     

Live fast--die young. The life history of stoats and weasels

Rarely seen but endowed with a larger-than-life reputation, stoats and weasels are among our most common and yet most enigmatic predators. They are the world's smallest carnivores and they spend much of their short lives in a frenetic search for prey. Their quicksilver behaviour and 'burn-out not fade-away' lifestyle provide many puzzles for biologists and conservationists alike.     

Neosomy in fleas, and the sessile life-style

Fleas arc basically free-living parasites, and the sessile life-style is an evolutionary 'after-thought'. The specializations described are somewhat similar in the various neosomes, only they have been developed within restraints imposed by the family 'strait-jacket' and the contrasting characters and habits of different hosts.