bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of noise stress on EFS‐mediated cholinergic and inhibitory NANC responses in tracheae from normal and sensitized guinea‐pigs
Authors: Breschi M.C. , Nieri P. , Lazzeri N. , Martinotti E.
Published: November 2003

1 The aim of the present research was to study the cholinergic and inhibitory non‐adrenergic‐non‐cholinergic (NANC) responses obtained with electrical field stimulation (EFS) of tracheal tissues from sham‐ and noise‐exposed guinea‐pigs. A comparison was also made between normal and ovalbumin (OA)‐sensitized animals.

2 In proximal tracheae pretreated with indomethacin (3 μM), propranolol (1 μM), α‐chymotrypsin (2 U ml−1) and L‐NAME (0.1 mM), frequency‐dependent responses to EFS (0.1 ms width; 20 V, 0.1‐‐100 Hz, 15 s train duration) were obtained, both contractile and relaxing in nature. The contractile responses were abolished by atropine (1 μM), and did not vary significantly between sham‐ and noise‐exposed guinea‐pigs, or between normal and sensitized animals. The NANC relaxing responses, present in spite of the pre‐treatment of the tissues with L‐NAME and α‐chymotrypsin, and almost completely abolished by tetrodotoxin (TTX) treatment (10 μM), appeared to be enhanced in noise‐exposed guinea‐pigs, with respect to sham‐exposed animals, but only when the animals were not OA‐sensitized.

3 In distal tracheae contracted with histamine (10 μM), the study of the whole inhibitory NANC response (pre‐treatment with propranolol, but not with α‐chymotrypsin and L‐NAME), which was mainly TTX‐sensitive, revealed a statistically non‐significant difference between sham‐ and noise‐exposed guinea‐pigs, both normal and OA‐sensitized. When distal tracheae were preincubated with α‐chymotrypsin (2 U ml−1) and L‐NAME (0.1 mM), in addition to propranolol, a significant residual inhibitory NANC response to EFS was observed. Surprisingly, in this case, similarly to the evidence obtained in proximal tracheae, a significantly enhanced response was revealed in noise‐exposed guinea‐pigs with respect to sham‐exposed animals.

4 The noise‐induced enhancement of the relaxant response disappeared when the tissues were pretreated with the A2 purinergic antagonist 3,7‐dimethyl‐1‐propargylxanthine (DMPX, 1 μM), while it persisted in the presence of the A1 antagonist 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX, 10 nM).

5 The above data indicate that, while not modifying the cholinergic and the whole inhibitory NANC response to EFS, noise stress selectively influences an inhibitory component of the NANC system in guinea‐pig trachea with a mechanism probably involving an enhanced neurally mediated release of adenosine, which relaxes the smooth muscle via A2 receptors. This effect appears to be lacking or masked in sensitized guinea‐pigs.
Acetylcholinesterase histochemistry and functional characterization of the muscarinic receptor mediating the contraction of the bovine oesophageal groove
Authors: Barahona M. V. , Sánchez‐Fortún S. , San Andrés M. D. , Ballesteros E. , San Andrés M.
Published: November 2003

1 By using acetylcholinesterase (AChE) histochemistry and invitro isometric techniques, we have studied the presence and distribution of AChE‐positive nerves, as well as the effects of muscarinic cholinoceptor agonists and selective antagonists, in the bovine oesophageal groove.

2 AChE‐positive nerves and cells were distributed widely on the oesophageal groove floor. These fibres originated from adventitial ganglia containing bodies with high AChE activity and were shown grouped as large adventitial nerve bundles.

3 Both in the presence and absence of physostigmine, acetylcholine (ACh) induced concentration dependent contractions of bovine oesophageal groove strips. The rank order of the pD2 values for muscarinic agonists was: oxotremorine‐M (7.37) = carbachol (7.14) > acetylcholine plus physostigmine (6.46) > bethanechol (5.42) > McN‐A‐343 (4.45) > acetylcholine (4.06).

4 Hexamethonium (10−6–10−4M), a nicotinic receptor blocker, did not affect the carbachol concentration–response curve, which was significantly inhibited by the muscarinic antagonist, atropine (10−9–10−8M).

5 The preferential muscarinic antagonists pirenzepine (M1), 11‐(2(‐(diethyl‐amino)methyl)‐1‐piperidinylacetyl)‐5,‐11‐dihydro‐6H‐pyrido(2,3‐b)‐(1,4)‐benzodiazepine‐6‐one (AF‐DX 116) and methoctramine (M2), 4‐diphenyl‐acetoxy‐N‐methyl‐piperidine methiodide (4‐DAMP) and p‐fluoro‐hexahydrosiladiphenidol (p‐F‐HHSiD) (M3) and tropicamide (M4) evoked rightwards displacements in a parallel manner of the carbachol control curve, and there was no decrease of the maximum response with the highest concentration of antagonist utilized. The muscarinic antagonist affinities, expressed in terms of pA2 values, were: atropine (9.51) = 4‐DAMP (9.32) > p‐F‐HHSiD (7.78) > tropicamide (7.40) > pirenzepine (6.91) = AF‐DX 116 (6.88) = methoctramine (6.71). This muscarinic antagonist profile suggests that an M3 receptor is involved in the carbachol induced contraction.

6 The present results suggest that a rich network of AChE‐ positive fibres is present in the oesophageal groove floor, where they form a nerve trunk and thinner branches accompanying blood vessels and sometimes around ganglia. The muscarinic cholinergic contraction of the bovine oesohageal groove seems to be mediated via activation of an M3 postsynaptic muscarinic receptor.
The peripheral NK‐1/NK‐2 receptor antagonist MDL 105,172A inhibits tachykinin‐mediated respiratory effects in guinea‐pigs
Authors: Kudlacz E.M. , Knippenberg R.W. , Shatzer S.A. , Kehne J.H. , McCloskey T.C. , Burkholder T.P.
Published: November 2003

1 Stimulation of sensory nerves causes release of tachykinins, including substance P (SP) and neurokinin A (NKA), which produce a variety of respiratory effects via NK‐1 and NK‐2 receptors, respectively. Hence, development of a compound which could potently and equivalently antagonize both receptors was pursued.

2 MDL 105,172A ((R)‐1‐[3‐(3,4‐dichlorophenyl)‐1‐(3,4,5‐trimethoxybenzoyl)‐3‐pyrrolidinyl]‐4‐phenyl‐piperidine‐4‐morpholinecarboxamide) exhibited high affinity for NK‐1 (4.34 nm) and NK‐2 (2.05 nm) receptors. In vitro, the compound antagonized SP (pA2 = 8.36) or NKA (pA2 = 8.61)‐induced inositol phosphate accumulation in tachykinin monoreceptor cell lines.

3 In anaesthetized guinea‐pigs, MDL 105,172A inhibited SP‐induced plasma protein extravasation (ED50 = 1 mg kg−1, i.v.) and [β‐Ala8]NKA 4–10‐induced bronchoconstriction (ED50 = 0.5 mg kg−1, i.v.) indicating NK‐1 and NK‐2 antagonism, respectively.

4 Capsaicin was used to elicit respiratory effects in anaesthetized and conscious guinea‐pigs; the latter were inhibited by MDL 105,172A following i.v. (ED50 = 1 mg kg−1) or oral (ED50 = 20 mg kg−1) adminstration. Hence, MDL 105,172A can inhibit pulmonary responses to tachykinins released endogenously in the airways.

5 At doses up to 200 mg kg−1, p.o., MDL 105,172A failed to inhibit repetitive hind paw tapping induced by i.c.v. GR 73632, an NK‐1 selective agonist, in gerbils, whereas CP‐99,994 (0.87 mg kg−1, s.c.) completely ablated the effect. These data suggest that MDL 105,172A does not penetrate the central nervous system (CNS) and its tachykinin antagonism is restricted to the periphery.

6 MDL 105,172A is a non‐peptide, potent, equivalent antagonist of NK‐1 and NK‐2 receptors. Its ability to inhibit both exogenously administered as well as endogenously released tachykinins support its use in examining the role of sensory neuropeptides in diseases associated with neurogenic inflammation including asthma.
Vasoconstriction of rat renal interlobar arteries by noradrenaline and neuropeptide Y
Authors: Chen H. , Bischoff A. , Schäfers R. F. , Wambach G. , Philipp T. , Michel M. C.
Published: November 2003

1 We have studied the contractile effects of noradrenaline and neuropeptide Y given alone and in combination on isolated rat renal interlobar arteries.

2 Noradrenaline contracted proximal and distal intrarenal microvessels in a concentration dependent manner, with similar potency (EC50≈ 550 nM), but maximum effects were greater in the proximal than in the distal vessel segments (≈ 10 and 6 mN, respectively).

3 The noradrenaline‐induced contraction was inhibited by low prazosin concentrations (3‐‐10 nM) but not by 1 μM yohimbine indicating involvement of α1‐ but not α2‐adrenoceptors. The α1A‐adrenoceptor‐selective antagonists, 5‐methylurapidil and tamsulosin, had high potency (apparent affinities of ≈ 8 nM and 57 pM, respectively) while the α1D‐adrenoceptor‐selective antagonist, BMY 7378, had only low potency (apparent affinity ≈ 300 nM). The α1B‐adrenoceptor‐alkylating agent, chloroethylclonidine (10 μM for 30 min at 37°C), had no inhibitory effects. The Ca2+ entry blocker, nitrendipine (300 nM), reduced the potency and maximal effects of noradrenaline.

4 Neuropeptide Y (1‐‐100 nM) also contracted interlobar arteries in a concentration dependent manner, with greater effects in the proximal than in the distal segments, but maximal effects were only small in either segment (<2 mN). In addition, neuropeptide Y also potentiated the response to noradrenaline, i.e. lowered its EC50 but this enhancement was also small.

5 We conclude that noradrenaline contracts rat interlobar arteries by an α1A‐adrenoceptor; its co‐transmitter, neuropeptide Y, affects the response only marginally in this vascular bed.
Effects of esmolol on 35 GHz microwave‐induced lethal heat stress
Authors: Jauchem J. R. , Ryan K. L. , Lovelace J. D. , Frei M. R.
Published: November 2003

1 The purpose of this study was to examine effects of the β1‐adrenoreceptor antagonist esmolol (infused at 2 or 4 mg kg−1 body wt min−1) on heart rate, blood pressure, respiratory rate, localized body temperature changes, survival times, and lethal body temperatures that occur during the exposure of anesthaetized rats to 35 GHz microwaves.

2 Forty Sprague–Dawley rats, anaesthetized with ketamine, were exposed to 35 GHz microwaves at a level that resulted in heating and death. During irradiation, a continuous increase in heart rate and a biphasic response in blood pressure (initial increase followed by a decrease) were observed in all groups of animals.

3 Esmolol caused a significant dose‐dependent decrease in blood pressure, relative to saline‐treated animals, but only a small attenuation of the heat‐induced rise in heart rate. In experiments in which esmolol was infused and microwave exposure was continued until death, drug‐treated animals survived for significantly shorter periods and died at significantly lower body temperatures. The change in survival may have been related to the lower blood pressure due to esmolol treatment.
The effects of bromoacetylalprenololmenthane on the responses to isoprenaline of the left ventricle from normo‐, prehyper‐ and hypertensive rats
Authors: Doggrell S. A. , Mistry D. N. , Henderson C. J.
Published: November 2003

1 We have studied the effects of bromoacetylalprenololmenthane (BAAM), a very slowly reversible β‐adrenoceptor antagonist, on the responses of the left ventricle of 5 and 22 week old Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) to isoprenaline. At 5 weeks the SHRs were prehypertensive and at 22 weeks they had hypertension‐induced hypertrophy of the left ventricle.

2 The mean potency of isoprenaline on the left ventricle from 5 week old WKY was similar to that obtained on left ventricles from 22 week old WKY, and 5 and 22 week old SHRs.

3 Following treatment of the left ventricle with BAAM at 10−6m for 30 min, there was a parallel rightward shift of the isoprenaline concentration–response curves. Treatment with a higher concentration of BAAM (10−5m) caused non‐parallel rightward shifts of the concentration–response curves, with a depression of the isoprenaline maximum responses. These data were used to derive affinity (KA) values for isoprenaline. The mean isoprenaline KA value on the left ventricle from 5 week old WKY was 2.44 × 10−6m, and similar KA values were obtained on the left ventricles from 22 week old WKY and 5 and 22 week old SHRs. On all the left ventricles tested, isoprenaline produced a half maximal response by occupying less than 1%, and a near maximal response by occupying about 5% of the available β1‐adrenoceptors.

4 This study has shown that there are no differences in the cardiac responses to isoprenaline at β1‐adrenoceptors, isoprenaline KA values or the β1‐adrenoceptor reserve for isoprenaline on the SHR left ventricle in prehypertension or in the early stages of hypertension‐induced hypertrophy.
Chronic terbutaline treatment desensitizes β‐adrenergic inhibition of lymphocyte activation in healthy volunteers
Authors: Werner C. , Poller U. , Brodde O.‐E.
Published: November 2003

1 A substantial body of evidence has accumulated that β‐adrenoceptor mediated increases in human lymphocyte cyclic AMP can inhibit activation of resting lymphocytes. The aim of this study was to determine whether this effect might desensitize during chronic β‐adrenoceptor agonist treatment. We assessed the effects of 2 weeks treatment with the β2‐adrenoceptor agonist terbutaline (3 × 5 mg day−1 p.o.) on isoprenaline‐induced inhibition of concanavalin A‐evoked lymphocyte activation in nine healthy male volunteers. Lymphocyte activation was determined by [3H]‐thymidine incorporation (as a measure of proliferation), and inositol phosphate formation was assessed in [3H]‐myo‐inositol prelabelled lymphocytes in the presence of 10 mm LiCl.

2 Terbutaline treatment caused a significant reduction in isoprenaline (1 nm– 10 μm)‐induced increases in lymphocyte cyclic AMP content; the maximal increase was 14 ± 3 pmol/106 cells before and 7 ± 2 pmol/106 cells (n= 9, P < 0.05) after terbutaline treatment.

3 The mitogen concanavalin A (Con A, 1–32 μg ml−1)‐induced increase in inositol phosphate formation was significantly enhanced after terbutaline treatment (max. increase before treatment: 255 ± 25% above basal; after treatment 453 ± 16% above basal; n= 9, P < 0.001), while isoprenaline (1 nm– 10 μm)‐induced inhibition of Con A (16 μg ml−1)‐evoked increases in inositol phosphate formation was significantly reduced after the terbutaline treatment (max. inhibition before treatment: 22 ± 4%; after treatment 9 ± 1%, n= 9, P < 0.01).

4 Con A (1.25 – 10 μg ml−1)‐induced increases in [3H]‐thymidine incorporation into the lymphocytes (as a measure of proliferation) was not affected by the terbutaline treatment. On the other hand, isoprenaline (1 nm– 1 μm)‐induced inhibition of Con A (5 μg ml−1)‐evoked lymphocyte proliferation (max. inhibition: 33 ± 7%, n= 9) was almost completely abolished after the terbutaline treatment.

5 We conclude that chronic treatment with terbutaline desensitizes lymphocyte β2‐adrenoceptors and, therefore, the inhibitory effect of cyclic AMP on lymphocyte activation.
Generic distribution patterns in subsaharan African Rubiaceae (Angiospermae)
Authors: Robbrecht Elmar
Published: November 2003

A survey of the distribution of the Rubiaceae from subsaharan African (continental part: 1,900 species in 164 genera; Madagascar: 675 species in 83 genera) is given. Genera are classified in nine major distribution patterns, most of which are further subdivided. General statistics of the data are given, and the patterns are discussed in the light of (i) the phytogeographical literature relating to tropical Africa and (ii) existing evolutionary hypotheses on the Rubiaceae.
Large scale patterns and trophic structure of southern African rocky shores: the roles of geographic variation and wave exposure
Authors: Bustamante Rodrigo , Branch George
Published: November 2003

In this study we revise the biogeographic delimitation, and large‐scale patterns of community structure of the intertidal rocky shores of southern Africa. We use binary (presence/absence) and per‐species biomass data collected at fifteen localities and thirty‐seven different rocky sites, encompassing the shores of southern Namibia, South Africa and southern Mozambique. Multivariate analyses revealed that the shores of southern Africa (south of 25°) can be divided into three main biogeographic provinces: the west coast or Namaqua province, the south coast or Agulhas province and the east coast or Natal province. The biomass structure of the intertidal rocky shores communities of southern Africa varied at a large scale, corresponding to biogeographic differences, while local‐scale variation accorded with the intensity of local wave action. The average biomass of west coast communities was on average significantly greater than that of the south and east provinces. At a local scale, the community biomass on exposed shores was an order of magnitude greater than on sheltered shores, within all biogeographic provinces. Semi‐exposed shores exhibited intermediate average biomass. The trophic structure of these communities varied significantly with wave action: autotrophs, filter‐feeders and invertebrate predators were more prevalent on wave exposed than sheltered shores, whereas grazers were more abundant on sheltered and semi‐exposed shores. Exposed shores were consistently dominated by far fewer species than semi‐exposed and sheltered shores, independently of biogeographic differences. Within all biogeographic provinces semi‐exposed and sheltered shores were more diverse than exposed shores. West coast intertidal communities therefore had high levels of biomass, but were consistently species‐poor. Several working hypotheses that could explain these large and small‐scale patterns are presented.
Biogeography of Banksia in southwestern Australia
Authors: Lamont Byron , Connell S.W.
Published: November 2003

Comprehensive new data bases on the taxonomy, distribution, ecology and climate of Banksia (Proteaceae) were used to study the biogeography of the sixty endemic species in southwestern Australia. They occur at the wettest coastal tip, with up to 1.5 m rainfall p.a., 1500 km along the north coast, 1000 km along the south coast and up to 450 km inland to the desert margin, with as low as 0.2 m rainfall p.a. The largest areas (sum of 30´ lat.×30´ long. grid cells) containing banksias were under much more arid climates than those with highest species density. Species density was usually lowest at the climatic extremes. Two nodes of species richness and ten floristic groups, each with a characteristic climate, landscape, vegetation and soil types and suite of indicator and endemic species, were recognized. A case is made for resurrecting the Lesueur (northern node) and Stirling (west portion of the southern node) phytogeographic districts, together with separating the West (east portion of the southern node) from the East Eyre district. These species‐rich areas coincide with nutrient impoverished sands and laterite associated with dissected uplands having low, highly sclerophyllous vegetation. The distribution of strongly serotinous species and those with persistent florets is consistent with greater reliance on fire for creating suitable recruitment conditions with increasing aridity. The distribution of needle‐leaved species is only partly explained by their superior drought tolerance. A preliminary transplant trial with two Banksia species showed that their distribution was only partly restricted by their current climatic profile.
Reserve mass and dispersal investment in relation to geographic range of plant species: phylogenetically independent contrasts
Authors: Edwards Will , Westoby Mark
Published: November 2003

Recent studies have reported conflicting evidence about correlations between seed size and plant species geographic range sizes. Using phylogenetically independent contrasts (PICs) within genera, we found no consistent differences in reserve mass between species with similar dispersal morphology and «wide» versus «narrow» geographic ranges. There was also no tendency within genera for broad ranged species to be those that allocate a larger percentage of the resources invested in each diaspora to dispersal structures. PICs were also constructed between species having a tenfold difference in seed size. In these PICs, the larger seeded species often occupied a greater number of regions than species with smaller seed sizes. This result was generated primarily through the comparison of species from different genera, families or higher level taxa which differed not only in seed mass but also in dispersal modes and growth forms. Finally, comparing species within Acacia and Eucalyptus having similar seed size but different dispersal modes, we found that bird dispersal (in Acacia) and possession of a wing for wind dispersal (in Eucalyptus) was associated with wider geographic range compared to lower‐investment dispersal modes. Taken together, these comparisons indicate that seed size is not itself important as a factor influencing breadth of geographic range. Dispersal mode and growth form may have an influence, however, and seed size differences may be associated with contrasts in dispersal mode or growth form.
Influence of edaphic specialization on pteridophyte distribution in neotropical rain forests
Authors: Tuomisto Hanna , Poulsen Axel Dalberg
Published: November 2003

The abundance of terrestrial pteridophytes was studied in eight sites in Western Amazonia, all representing lowland tropical rain forest in non‐inundated terrain (tierra firme). In each site, a sample plot ranging from 0.25 ha to 1.00 ha in area was inventoried and all terrestrial pteridophytes were recorded. In total, 27,000 individuals representing sixty‐four species were encountered, with each plot having between fourteen and thirty‐three species. The plots represented a gradient from nutrient‐poor sandy soils to relatively fertile clay soils, and it was found that their floristic compositions clearly correlated with the differences in the soils. Two‐thirds of the species were restricted either to poor, intermediate or rich soils, while less than a tenth were found growing on all soil types. Analyses of species lists from another twenty neotropical localities supported the result that some pteridophyte species associate, whereas other species are never found growing together. The floristic similarities among sites showed no relationship to the geographical distances between them, but rather reflected similarities in soils. It is concluded that pteridophytes are good indicators of such ecological conditions, and that when interpreting biogeographical patterns in the neotropical rain forests, it is important to take into account the distribution of edaphically different habitats.
Spatial pattern of diversity in a tropical rain forest in Malaysia
Authors: He Fangliang , Legendre Pierre , LaFrankie James
Published: November 2003

The diversity of trees (species richness, abundance and Shannon diversity) in a tropical rain forest of Malaysia has been studied from the point of view of its spatial organization in order to formulate hypotheses about the origin of the observed spatial patterns. The question that motivated this study is whether tropical forests communities are in a state of equilibrium or non‐equilibrium. Three aspects have been examined: (1) changes in diversity were studied with respect to sampling area and sampling designs. A minimum area of 5–10 ha is recommended by the species–area curves, while 2–5 ha seem appropriate based on the Shannon diversity–area curves. Different sampling designs significantly affect the species–area curves. The power function, which can be derived under the equilibrium assumption, is not appropriate to fit the observed diversity–area curves. (2) The spatial features of diversity variables were then studied. Variograms showed that there are dominant short‐range effects (around 150 m), obvious anisotropic distribution, and high random variation in the diversity data. (3) Partitioning the variation of the diversity measures into environmental (topographic) and spatial components indicated that the spatial organisation of that community was mostly unpredictable. There may be many processes controlling the formation of the spatial patterns in the tropical rain forest. Unidentified causes, affecting mainly the small‐scale processes (<20 m), seem responsible for the large amount of undetermined variation in the diversity data sets. The study suggests that the Pasoh forest of Malaysia may not be in a state of equilibrium.
The size and composition of the hymenopteran fauna of Costa Rica
Authors: Gaston Kevin , Gauld Ian , Hanson Paul
Published: November 2003

An intensive survey of the hymenopteran fauna of Costa Rica provides an opportunity to explore the size and composition of a species‐rich insect order in a large tropical region. A working estimate of the richness of the fauna is 20,000 species. This is consistent with some published estimates of the numbers of species of Hymenoptera worldwide, but at odds with suggestions that all insect species number several tens of millions. Sixty‐one families of Hymenoptera have been collected in Costa Rica, and the numbers of species per unit area is more than twice that of most of the other regions for which data are available. The Costa Rican fauna has higher proportions of egg parasitoids and of eusocial species, and a lower proportion of primary phytophages than that of the British Isles.
Biodiversity and vegetation of small‐sized inselbergs in a West African rain forest (Taı, Ivory Coast)
Authors: Porembski Stefan , Szarzynski Jörg , Mund Jan‐Peter , Barthlott Wilhelm
Published: November 2003

The vegetation of small granitic rock outcrops (geomorphologically small‐sized inselbergs) which do not reach the canopy was studied in the Taı rain forest (southwestern Ivory Coast) under aspects of species diversity and phytogeographical affinities. Rock outcrops form edaphically arid (due to absent or very sparse soil cover) and microclimatologically xeric (i.e. low air humidity, temperature regularly exceeding 50°C) islands with cryptogamic crusts, succulents and poikilohydric vascular plants as characteristic elements of their vegetation which differs totally from the surrounding forest. Altogether sixty‐six species of vascular plants out of twenty‐nine families occur, the number of species correlates positively with inselberg size. Compared with large inselbergs the microclimatic attributes of small‐sized rock outcrops are less pronounced. This is accompanied by a decrease of typical inselberg taxa (i.e. species mainly occurring on inselbergs). Low beta diversity between inselbergs indicates deterministic influences as important regulators of species composition. Annual Poaceae and Cyperaceae are richly represented. It can be hypothesized that inselbergs may represent natural growing sites of widely distributed tropical weeds today. Inselbergs might provide habitat resources for savanna elements in rain forest zones.
Seasonal dynamics of Mediterranean pasture seed banks along environmental gradients
Authors: Ortega M. , Levassor C. , Peco B.
Published: November 2003

The size and dynamics of seed banks were studied in grazed and ungrazed Mediterranean pastures at different altitudes and topography positions. The soil samples were collected in autumn and spring and the seed banks composition was determined by greenhouse germination over a 9‐month period. The percentage of bare ground and the presence of new seedlings were recorded monthly from October to July in the field. A fall in seed density and species richness in the banks and a tendency for seeds to remain in the banks were linked to a rise in altitude. Germination in lower pastures mainly occurred in October in the numerous gaps left by the summer drought. At higher altitudes, the scarcity of gaps and the harsh climate led to an autumn–spring segregation of germination. On a local scale, the low slope positions and the ungrazed plots had a larger number of persistent seed bank species and a lower percentage of bare ground where seeds could germinate than their respective plots in the upper positions and grazed plots. A higher seed density in ungrazed than grazed plots was only detected in the three highest plots. No seed bank species richness trend was detected. In populations of the same species in different types of environments, the seasonal variation of seed numbers was environment‐dependent for the majority of the species. In general, perennial grassland and its related low gaps availability appear to favour persistent seed banks.
Distribution of C3 and C4 grasses along an altitudinal gradient in Central Argentina
Authors: Cabido Marcelo , Ateca Norma , Astegiano Marta , Anton Ana
Published: November 2003

The distribution pattern of C3 and C4 grasses was studied in eight sites located between 350 m and 2100 m along an altitudinal gradient in Central Argentina. Of 139 taxa fifty‐nine are C3 and eighty C4. Species of the C3 tribes (Stipeae, Poeae, Meliceae, Aveneae, Bromeae and Triticeae) and C3 Paniceae species increase in number at higher elevations; only one C3 species was found below 650 m. C4 Aristideae, Pappophoreae, Eragrostideae, Cynodonteae, Andropogoneae and Paniceae increase at lower altitudes. The floristic crossover point is at about 1500 m; the ground cover cross‐over point is at about 1000 m. Analysis of the relationships between % C4 species along the gradient and nine climatic and environmental variables showed the highest correlation with July mean temperature, but all temperature variables show highly significant correlations with % C4. Correlation with annual rainfall is lower but also significant. These results are consistent with previous research showing the relative importance of C4 grasses as temperature increases. C3 species make a high contribution to relative grass coverage below the C3/C4 floristic crossover point but are rare below 1000 m.
Fire history and composition of the subalpine forest of western Colorado during the Holocene
Authors: Fall Patricia
Published: November 2003

Pollen and plant macrofossils from the Keystone Ironbog are used to document changes in species composition and the dynamics of the subalpine forest in western Colorado over the past 8000 years. Modern pollen spectra (particularly pollen influx), plant macrofossils, observations on modern species composition, and quantified densities and mean basal areas of forest trees are used to interpret the paleoecology of the forest. From 8000 to 2600 years ago the fen was surrounded by a subalpine forest. However, unlike the modern subalpine forest where Abies lasiocarpa (Hooker) Nuttall is slighlty more abundant than Picea engelmannii (Parry) Engelmann, these Holocene forests had a greater dominance of P. engelmannii, perhaps reflecting a summer wet climate like that of the modern southern Rocky Mountains and Colorado Plateau. Mesic conditions promoted a dense understory of Sphagnum moss, forbs, grasses, and shrubs which periodically burned with long (centennial) return‐interval and stand‐replacing fires. Populus tremuloides Michaux was the dominant successional forest tree 8000–6400 and 4400–2600 years ago, with Picea engelmannii and Abies lasiocarpa becoming reestablished within a couple hundred years. A subalpine meadow or grassland covered the fen for about 2000 years between 6400 and 4400 years ago. Over the past 2600 years a stable, non‐successional Pinus contorta (Douglas) spp latifolia (Engelmann) Critchfield forest grew around the fen. This forest stand had a relatively sparse understory. The persistence of Pinus contorta at this elevation (2920 m) probably reflects a shift to drier climatic conditions, perhaps coupled with a change in fire regime to relatively frequent (decadal) surface fires. Following fire Pinus contorta became reestablished at least within 200 years, but the subalpine Picea engelmannii‐Abies lasiocarpa forest never regenerated at this elevation
The ecology and distribution of lichens in tropical deciduous and evergreen forests of northern Thailand
Authors: Wolseley P. A. , Aguirre‐Hudson B.
Published: November 2003

During three years of research on epiphytic lichen communities as indicators of environmental change in northern Thailand plots were set up in a range of forest types between 400 and 1600 m in 1991/2 and revisited in 1993. Other areas were visited in 1993 and collections made in a wider range of geographical, altitudinal and vegetation conditions in Thailand. From this data factors influencing the distribution of lichens in a monsoon climate are outlined and characteristic components of the lichen flora given at family, generic and where possible specific level. Dominant taxa of the montane forests include hygrophilous macrolichens of the ‘Lobarion’ that are also a characteristic component of old growth fagaceous forests in Europe, whereas the evergreen forests are dominated by moisture‐dependent crustose taxa with a trentepohlioid photobiont, and the deciduous dipterocarp forests by often brightly coloured xerophytic lichens with a trebouxioid photobiont. Taxa are proposed as indicators of forest type including those that are indicators of old‐growth forests and of disturbance. Quantitative recording of selected taxa at genus and species level is suggested to estimate rates of change in monsoon forests in southeast Asia.
Fire in tropical dry forests: corticolous lichens as indicators of recent ecological changes in Thailand
Authors: Wolseley P. A. , Aguirre‐Hudson B.
Published: November 2003

The distribution of lichens in lowland deciduous and evergreen forests in Thailand is used to interpret recent changes in the distribution of these forests. The role of fire in changing the forest structure, microclimate and species content is discussed. Characteristic corticolous lichen communities of dry deciduous and moist evergreen forests are described, as well as changes in the composition of the flora following fire events. Where frequent fires have altered the forest rates of change in forest type are suggested using lichen data from randomly selected trees in forest plots, and growth rates of sampled species in quadrats. The disjunct nature of the lichen floras in lowland deciduous and evergreen forests is discussed, their origin and use in interpreting changes in forest types in monsoon climates over long periods of time.
Larger seeds in tropical floras: consistent patterns independent of growth form and dispersal mode
Authors: Lord Janice , Egan Judy , Clifford Trevor , Jurado Enrique , Leishman Michelle , Williams Dick , Westoby Mark
Published: November 2003

Many species of tropical moist forests have large seeds compared to those found in temperate floras. This could be attributed to a prevalence of woody growth forms, or adaptation to dispersal by vertebrates, or the dense shade of a closed canopy, rather than to an intrinsic tropical v. temperate difference. We compared tropical v. temperate seed mass data at two geographic scales; firstly within Australia between tropical, subtropical and temperate open woodlands, then between six tropical and temperate datasets from five continents. Within Australia we found that seed mass increased with decreasing latitude in ten out of eleven growth form‐dispersal mode combinations: only wind‐dispersed graminoids showed no significant effect. While the pattern of generally larger seeds in the tropical flora was associated with tropical families tending to have larger seeds than temperate families, we also found that tropical species had larger seeds than temperate cofamilials. As a preliminary test of the generality of these findings we included a further four tropical and temperate data sets in a second analysis. Average tropical seed masses were larger than temperate seed masses in all testable growth form‐dispersal mode combinations, and statistically larger in five out of seven cases: unassisted, vertebrate‐ and wind‐dispersed woody species, and unassisted and vertebrate‐dispersed forbs. No difference was found for wind‐dispersed forbs or for graminoids lacking dispersal structures. That an effect was found in these combinations rules out explanations based solely on characteristics of tropical v. temperate dispersers, although this may be a contributing factor. Instead we suggest that some aspect of tropical systems, for example higher metabolic costs of seedling production, has selected for a general increase in seed mass among tropical taxa.
Mammals of Australian islands: factors influencing species richness
Authors: Burbidge Andrew , Williams Matthew , Abbott Ian
Published: November 2003

Distribution patterns of indigenous non‐volant terrestrial mammals on 257 Australian islands were examined in relation to environmental parameters and the effects of human‐induced disturbance during prehistoric and historic times on island species numbers. Species occurrence for individual species, for taxonomic and trophic groups, and for all species together was related to environmental parameters using regression analysis and the extreme‐value function model. Patterns of occurrence were examined separately within three major biogeographic regions derived by pattern analysis. The number of species known to have occurred on these islands during historic times was adequately predicted from area alone. No statistically significant improvement in predicted species number was gained by including island elevation, mean annual rainfall, isolation from the mainland or the number of potentially competing species present on the island. Similarly, no single factor other than area was found to influence consistently the presence of individual species. We conclude that the occurrence of indigenous non‐volant terrestrial mammal species on these islands indicates a relictual rather than equilibrial fauna. Visitation by Aboriginal people during prehistoric times did not significantly increase mammal extinctions on islands. Examination of patterns of species richness for a given area on a regional basis showed that islands in and around Bass Strait and Tasmania (Bass Region) were the most species‐rich, islands off the northern coasts were slightly less rich, and islands off the south western coasts had fewest species. This is in contrast to the usual latitudinal gradient in species richness patterns. However, islands off the northern and eastern coasts had an overall greater number of different species. When considered in relation to the number of different species of mammals occurring within each region, islands of a given size in Bass Region typically bore a higher proportion of this species pool than other regions. The Bass Region was found to be particularly rich in macropoid herbivores and dasyurid carnivores and insectivores. Analyses indicated that there is a very strong relationship between the presence of exotics as a whole and the local extinction of native mammals. Many mammal species formerly widespread on the Australian mainland are now restricted totally to islands (nine species) or are threatened with extinction on the mainland and have island populations of conservation significance (ten species). In all, thirty‐five islands protect eighteen taxa of Australian threatened mammals. The land‐use and management of these islands is of considerable importance to nature conservation. The introduction of exotic mammals to these islands should be prevented; any introductions that occur should be eradicated immediately.
The use of the land survey record to reconstruct pre‐European vegetation patterns in the Darling Downs, Queensland, Australia
Authors: Fensham R. , Fairfax R.
Published: November 2003

The Darling Downs is an extremely arable district in south eastern Queensland that has lost the majority of its native vegetation cover to agriculture. Vegetation references from land survey charts produced during the late 19th and early 20th century aided the reconstruction of the original vegetation patterns in the Darling Downs. Nearly 5000 references to vegetation were located for the study area and formed the basis of a vegetation map. The survey plans contain reference to seventy‐three plant names which could generally be aligned to existing species, the majority of which are trees. The surveyors also referred to vegetation structure with terms such as ‘open’, ‘shrubby’ and ‘dense’. The ambiguous use of some references and the lack of adequate coverage of surveyor's charts for some sections of the study area did not allow for the production of an accurate and comprehensive map using the survey record in isolation. An iterative process evolved where (i) a working map of the vegetation was produced from the survey record; (ii) the map was ground‐truthed with existing remnants and ambiguities in surveyors’ terminology clarified; (iii) for gaps in the record, hypotheses concerning eradicated vegetation were erected from knowledge of the environmental correlates of existing remnants; and (iv) these hypotheses were tested from areas where the survey record is comprehensive. Some vegetation types cannot be distinguished reliably on the basis of their physical environment and the distinction between these types for mapping was reliant on either the evidence from the survey record or remaining paddock trees. These processes enabled relatively accurate mapping of the pre‐European vegetation of the study area at 1:100,000 scale. Comparison of the survey record and the vegetation of existing remnants suggests that overstorey composition and understorey density have changed little during European management within remnants.
Effects of seasonal migration on the latitudinal distribution of west Palaearctic bird species
Authors: Newton I. , Dale L.
Published: November 2003

This paper examines seasonal changes in the latitudinal distribution of birds (excluding seabirds) that breed in the western Palaearctic. Some resident species occupy ranges that span less than 5° of latitude year‐round, while some migrant species range over more than 120° of latitude during the course of a year. Among migrant species of land and freshwater habitats, the latitudinal spans of breeding and wintering ranges are correlated. In general, species that breed over a narrow span of latitude also winter over a narrow span of latitude, and vice versa. Among both groups, for any given span of breeding range, species that winter partly in Eurasia and partly in Africa winter over a wider latitudinal span than those that winter entirely within Eurasia or entirely within Africa. Among coastal birds, there is no correlation between the latitudinal spans of breeding and winter areas; most shorebird species breed over a narrow span of (northern) latitude and winter over a wide span distributed linearly along coastlines. Several migration patterns can be distinguished, from complete overlap of breeding and wintering ranges in year‐round residents, through partial separation of summer and winter ranges, to complete separation of summer and winter ranges in different geographical regions. In some such species, the gap between breeding and wintering ranges spans up to 55° of latitude (6000 km).
Probability of describing an Australian scarab beetle:(r)influence of body size and distribution
Authors: Allsopp P. G
Published: November 2003

Dates of description for species within a group are broad and it is often assumed that recently described animal species are relatively smaller. This may be because small animals are more easily overlooked. Here, I explore the relationships between dates of description of Australian scarab beetles and their body size, extent of occurrence and the particular areas in which a species occurs. The extent of occurrence and the particular areas in which a species occurs are the best predictors of the date of description. Wide‐ranging species occurring in the south east of Australia were generally described first. However, the amount of variation explained by these relationships varies between groups of the beetles. Body size is a poor indicator of the date of description. Understanding these relationships is important in collecting representative samples of the fauna.
Rangeland vegetation dynamics and moisture availability in Tunisia: an investigation using satellite and meteorological data
Authors: Wellens Jane
Published: November 2003

Improved knowledge of the interactions between regional climatic patterns and vegetation dynamics are necessary for predicting the future impacts of climate change on vegetation and biogeochemical processes. This paper describes how Normalized Difference Vegetation Index (NDVI) images generated from Advanced Very High Resolution Radiometer (AVHRR) satellite data were used to investigate the dynamics of rangeland vegetation in Tunisia. The NDVI images provided information about intra‐ and inter‐annual variations in vegetation over nine growing seasons (1983–1992). Comparison of the NDVI data with field‐collected ecological parameters for nine individual field sites indicated a strong relationship between the NDVI and percentage vegetation cover. The relationship between biomass measurements and NDVI was, however, less strong. Rainfall and NDVI data for each field site were compared, and significant relationships were found between the two. These indicated that there was a delay in the vegetation response to rainfall. In addition, the NDVI data showed that the vegetation at some of the field sites remained active throughout the summer although there was no rainfall during this period. TuMERT (Tunisian Model to Estimate Rangeland Transpiration), a simple water‐balance model, was developed to estimate the amount of rainfall available for use by the vegetation during transpiration. The estimates of actual transpiration derived from TuMERT were found to be more strongly correlated with the AVHRR‐NDVI measurements than the rainfall data.
Students modelling environmental issues
Authors: Kurtz dos Santos A.C. , Thielo M.R. , Kleer A.A.
Published: November 2003

This work is based on a Brazilian project that aims to promote the use of a semi‐quantitative tool with students (11 ‐ 18 years old) in topics about local environmental problems. The paper presents the VISQ program, a network to analyse models, a set of tasks and three examples of models made by students. Results suggest that the VISQ program is suitable for use in Environmental Education as while working with the proposed tasks students thought at a system level becoming aware of some local environmental issues.
An interactive systemfor learning rotational dynamics
Authors: Dhillon A. S.
Published: November 2003

The paper outlines an interactive problem‐solving system based, to an extent, on constructivism. It takes the prior knowledge of students into account and allows them to initiate and control the interaction. The rationale for the program and the methods used to obtain the data informing the program development are detailed. Insight into the program is provided through a discussion of its features and internal structure. The program evaluation which was done through students using it for the solution of two problems and through student feedback using questionnaires and interviews, shows the potential and the need for an expansion of the system.
Selecting communication media for distributed communities
Authors: Heeren E. , Lewis R.
Published: November 2003

Within the 'Virtual Mobility and Distributed Laboratories' project three naturalistic case studies of distributed research communities were conducted with a focus on the communication media used. The findings provide insight into relationships between the different media that the communities selected, and the different activities to which these media contributed. It is suggested that these findings are also relevant for distributed groups in which collaborative learning is the primary aim. A framework is presented for understanding and recommending selections of media for particular kinds of tasks, which is derived by integrating Media‐richness Theory and Activity Theory. This framework indicates how task/media fit may be achieved while taking into account the evolving character of activities in a distributed community. Some implications of the framework for collaborative distance learning are highlighted.