Aggressive behaviour in Montagu’s harrier Circus pygargus during the courtship period

Aggressive behaviour of Montagu’s harrier was observed during the pre-laying period in the 1992–1995 seasons on the calcareous marshes of Chelm in Eastern Poland. In total, 435 flights performed by 24 pairs of individually marked harriers were analysed. All flights were performed in relation to the territory of defence. Males performed 61% of aggressive interactions while females performed 39%. Intraspecific and interspecific aggression comprising direct attacks (58%), escorts (13%), pursuits (28%) and “mirror behaviour” (1%) were described for the first time. Interspecific aggressive behaviour occurred only near territory boundaries. The main intruders were marsh harriers Circus aeruginosus breeding on the same marshes. Occasionally, harriers attacked curlews Numenius arquata, short-eared owls Asio flammeus, magpies Pica pica, hooded crows Corvus corone cornix, common buzzards Buteo buteo or hobbies Falco subbuteo. Four cases of communal mobbing were observed. Three to five males from the neighbourhood attacked the intruders together. Intraspecific aggressive behaviour was observed in the pair territory, near the boundary or at a distance of up to 100 m from the defended area. Aggressive interactions performed by both sexes were more frequent towards birds of the same sex. Females defended their territories more aggressively against females. Similarly, males were more aggressive against males. All cases of aggressive behaviour were observed near harrier territories. Aggressive relations between birds outside breeding territories or when foraging around marshes were not observed.     

Play behaviour and active training of Montagu’s harrier (Circus pygargus) offspring in the post-fledging period

Play bouts and active training of juveniles by Montagus harrier (Circus pygargus) adults in the post-fledging period were observed. Fledglings often played with prey and with a variety of inanimate objects such as bits of moss, regurgitated pellets, sticks and a wad of hay. Inanimate objects selected for play were, in length, very similar to the common vole (Microtus arvalis), which is the most common prey of the species during their breeding period. Some recently fledged individuals were trained to capture invertebrate prey by adults demonstrating techniques for the fledglings and thus develop their hunting skills. Training sessions took place only in the foraging areas of the adult birds.     

Collision risk of Montagu’s Harriers Circus pygargus with wind turbines derived from high-resolution GPS tracking

Flight behaviour characteristics such as flight altitude and avoidance behaviour determine the species-specific collision risk of birds with wind turbines. However, traditional observational methods exhibit limited positional accuracy. High-resolution GPS telemetry represents a promising method to overcome this drawback. In this study, we used three-dimensional GPS tracking data including high-accuracy tracks recorded at 3-s intervals to investigate the collision risk of breeding male Montagu's Harriers Circus pygargus in the Dutch–German border region. Avoidance of wind turbines was quantified by a novel approach comparing observed flights to a null model of random flight behaviour. On average, Montagu's Harriers spent as much as 8.2 h per day in flight. Most flights were at low altitude, with only 7.1% within the average rotor height range (RHR; 45–125 m). Montagu's Harriers showed significant avoidance behaviour, approaching turbines less often than expected, particularly when flying within the RHR (avoidance rate of 93.5%). For the present state, with wind farms situated on the fringes of the regional nesting range, collision risk models based on our new insights on flight behaviour indicated 0.6–2.0 yearly collisions of adult males (as compared with a population size of c. 40 pairs). However, the erection of a new wind farm inside the core breeding area could markedly increase mortality (up to 9.7 yearly collisions). If repowering of the wind farms was carried out using low-reaching modern turbines (RHR 36–150 m), mortality would more than double, whereas it would stay approximately constant if higher turbines (RHR 86–200 m) were used. Our study demonstrates the great potential of high-resolution GPS tracking for collision risk assessments. The resulting information on collision-related flight behaviour allows for performing detailed scenario analyses on wind farm siting and turbine design, in contrast to current environmental assessment practices. With regard to Montagu's Harriers, we conclude that although the deployment of higher wind turbines represents an opportunity to reduce collision risk for this species, precluding wind energy developments in core breeding areas remains the most important mitigation measure.     

Seasonal and spatial variation in the diet of brown trout (Salmo trutta L.) in the subarctic River Laxá, north-east Iceland

This study examines seasonal and spatial patterns in the diet composition, stomach fullness and condition of a landlocked population of brown trout (2.5–61.3 cm) in the lake-fed River Laxá in NE-Iceland. The stomach contents consisted predominantly of benthic invertebrates, such as blackfly larvae Simulium vittatum (58%), chironomids (24%) and the freshwater snail Radix peregra (7%). The seasonal and spatial patterns of S. vittatum in the stomach contents were consistent with published studies on the life cycle and production of S. vittatum in the River Laxá. Close to the Lake Myvatn outlet (0–16 km), S. vittatum constituted 63% of the stomach content volume, and exhibited two peaks (i.e., generations) in its seasonal contribution to the stomach contents, whereas further downstream (16–35 km) S. vittatum constituted 45% of the volume and showed only clear evidence of one generation. Seasonal fluctuations in S. vittatum availability appear to affect the stomach fullness and the condition factor of the trout, especially close to the lake outlet where the fluctuations are pronounced.     

The fertility of women Poland in the period of trasformation of the political and economics system (the 80’s and 90’s)

Wielkopolska (western Poland) is a region, with good reason, called the main food base of Poland. All indices of agricultural production have always been there (since 19th century) much higher than elsewhere in the country (Ratajczak 1977/1978, Buszko 1984, Gorzelak 1989, Czyzewski et al. 1992; table 1). Such a situation had a beneficial effect on the amount of the income generated by a family of Wielkopolska and, thus, decided on its better financial status. Additionally, rural inhabitants of this region have always been characterised by a more advantageous educational structure in comparison with people of other Polish villages. Generally, it is easy to detect the relationship between the life standard, the level of education and family planning. The aim of this paper is to assess fertility of women from villages of Wielkopolska in the period of transformation of the political and economic system in Poland.     

The role of Apodemus mice and Microtus voles in the diet of the Tengmalm’s owl in Central Europe

Based on a long-term dataset (1999–2010), we investigated how the availability of main prey affects the breeding density and food ecology of the Tengmalm’s owl (Aegolius funereus) in the Czech Republic. In particular, we assessed the role of Microtus voles and Apodemus mice in the diet, based on the main predictions of the optimal diet theory that the diet composition depends on the availability of the main prey. We found that (i) the Tengmalm’s owl exhibited no numerical response to the availability of Microtus voles and Apodemus mice in the field; (ii) the availability of Apodemus mice in the field positively affected their proportion in the diet (26 %), and despite a high proportion of Microtus voles in the owls’ diet (47 %), no relationship was found between their availability in the field and proportion in the diet; (iii) the proportion of Apodemus mice was negatively correlated to the proportion of Microtus voles, Sorex shrews and birds in the diet, but no similar relationship was detected for Microtus voles; (iv) the reproductive output of Tengmalm’s owls was positively correlated to the proportion of Apodemus mice in the diet, as well as to Apodemus mice and Microtus vole availability in the field; and (v) diet diversity and diet overlap were not significantly affected by the abundance of Apodemus mice and Microtus voles. Therefore, the validity of these main optimal diet theory predictions was not confirmed, especially for Microtus vole prey, due to an opportunistic choice between Apodemus mice and Microtus voles. We suggest that the reproductive output of nocturnal raptors in Central Europe may be less dependent on Microtus vole supply than that of their northern counterparts.     

Seasonal variation of leaf respiration and the alternative pathway in field-grown Populus × canadensis

The temperature response of plant respiration varies between species and can acclimate to changing temperatures. Mitochondrial respiration in plants has two terminal oxidases: the cytochrome c oxidase (COX) and the cyanide-resistant alternative oxidase (AOX). In Populus × canadensis var. italica, a deciduous tree species, we investigated the temperature response of leaf respiration via the alternative and cytochrome pathways, as well as seasonal changes in these pathways, using the oxygen isotope fractionation technique. The electron partitioning through the alternative pathway (τ(a) ) increased from 0 to 30-40% with measurement temperatures from 6 to 30°C at all times measured throughout the growing season. τ(a) at the growth temperature (the average temperature during 3 days prior to sampling) increased from 12 to 29% from spring until late summer and decreased thereafter. Total respiration declined throughout the growing season by 50%, concomitantly with decreases in both AOX (64%) and COX (32%) protein abundances. Our results provide new insight into the natural variability of AOX protein abundances and alternative respiration electron partitioning over immediate and seasonal timescales.     

Density-dependent regulation of population size in colonial breeders: Allee and buffer effects in the migratory Montagu’s harrier

Expanding populations offer an opportunity to uncover the processes driving spatial variation in distribution and abundance. Individual settlement decisions will be influenced by the availability and relative quality of patches, and by how these respond to changes in conspecific density. For example, conspecific presence can alter patch suitability through reductions in resource availability or territorial exclusion, leading to buffer effect patterns of disproportionate population expansion into poorer quality areas. However, conspecific presence can also enhance patch suitability through Allee effect processes, such as transmission of information about resources or improved predator detection and deterrence. Here, we explore the factors underlying the settlement pattern of a growing population of Montagu’s harriers (Circus pygargus) in Spain. The population increased exponentially between 1981 and 2001, but stabilised between 2001 and 2004. This population increase occurred alongside a remarkable spatial expansion, with novel site use occurring prior to maximum densities in occupied sites being reached. However, no temporal trends in fecundity were observed and, within sites, average fecundity did not decline with increasing density. Across the population, variance in productivity did increase with population size, suggesting a complex pattern of density-dependent costs and benefits. We suggest that both Allee and buffer effects are operating in this system, with the benefits of conspecific presence counteracting density-dependent declines in resource availability or quality.     

Seasonal and sexual variation in diel activity rhythms of pine martenMartes martes in the Białowieża National Park (Poland)

From 1991–1996, the activity rhythms of 14 radio-collared pine martensMartes martes (Linnaeus, 1758) (6 males and 8 females) were studied in the pristine deciduous and mixed forests of the Białowieża National Park. Tracking data (5823 h) indicated that the activity rhythms of pine martens varied between sexes and seasons. In spring, male activity peaked at 20.00–00.00 h, whereas in summer and autumn-winter, activity was bimodal, peaking at 18.00–22.00 h and 02.00–04.00 h. Female activity in spring was more evenly distributed than that of males, but in summer their activity peaked at 20.00–00.00 h, while in autumn-winter females had a bimodal rhythm with peaks at 18.00–20.00 h and 02.00–06.00 h. In breeding females, activity rhythms changed in the course of pregnancy and nursing. On average, martens started their activity 73±209 (SD) min before sunset and finished 87±245 min after sunrise. Females became active earlier than males but both sexes terminated activity at the same time. For both males and females the daily activity rhythm was not related to the diurnal course of temperature.     

Seasonal variations in the composition of Holstein cow’s milk and temperature–humidity index relationship

A retrospective study on seasonal variations in the characteristics of cow’s milk and temperature–humidity index (THI) relationship was conducted on bulk milk data collected from 2003 to 2009. The THI relationship study was carried out on 508 613 bulk milk data items recorded in 3328 dairy farms form the Lombardy region, Italy. Temperature and relative humidity data from 40 weather stations were used to calculate THI. Milk characteristics data referred to somatic cell count (SCC), total bacterial count (TBC), fat percentage (FA%) and protein percentage (PR%). Annual, seasonal and monthly variations in milk composition were evaluated on 656 064 data items recorded in 3727 dairy farms. The model highlighted a significant association between the year, season and month, and the parameters analysed (SCC, TBC, FA%, PR%). The summer season emerged as the most critical season. Of the summer months, July presented the most critical conditions for TBC, FA% and PR%, (52 054±183 655, 3.73%±0.35% and 3.30%±0.15%, respectively), and August presented higher values of SCC (369 503±228 377). Each milk record was linked to THI data calculated at the nearest weather station. The analysis demonstrated a positive correlation between THI and SCC and TBC, and indicated a significant change in the slope at 57.3 and 72.8 maximum THI, respectively. The model demonstrated a negative correlation between THI and FA% and PR% and provided breakpoints in the pattern at 50.2 and 65.2 maximum THI, respectively. The results of this study indicate the presence of critical climatic thresholds for bulk tank milk composition in dairy cows. Such indications could facilitate the adoption of heat management strategies, which may ensure the health and production of dairy cows and limit related economic losses.     

Seasonal variation and diet quality among Spanish people aged over 55 years

There is evidence supporting the importance of a healthy diet; however, there are few studies analyzing the seasonal variation of food intake. The present study was aimed to evaluate seasonal variation of food and energy intake in Spanish elderly also to investigate diet quality based on the Healthy Eating Index (HEI) score. From a cross-sectional study, 28 individuals (39% males) aged over 55 years volunteered for a longitudinal follow-up. Dietary assessment was evaluated through 24-h dietary recalls. Energy and nutrient intake were calculated using DIAL software. Furthermore, diet quality was measured using HEI. Data was analyzed considering the interaction of sex, age, fitness status, and body composition. Cereals intake was significantly lower in summer than in winter and autumn (both p?<?0.05); whereas, drinks intake was significantly higher in summer than in winter, spring, and autumn (all p?<?0.01). Daily energy intake was significant higher in spring than in summer, and in autumn than in summer (p?<?0.05), and energy intake from lunch was also statistically higher in spring than in summer (p?<?0.01). The HEI was classified as good; however, a negative and significant association was observed between HEI and cholesterol, alcohol, and monounsaturated fatty acids intake (p?<?0.01). Cereals and drinks intake and total daily energy intake changed according to seasons. This should be considered in nutritional studies. Diet quality seems not to be affected by these seasonal changes, and HEI did not show a good association with the majority of foods and macro- and micronutrients.     

Seasonal Dynamics of the Airborne Bacterial Community and Selected Viruses in a Children’s Daycare Center

Children’s daycare centers appear to be hubs of respiratory infectious disease transmission, yet there is only limited information about the airborne microbial communities that are present in daycare centers. We have investigated the microbial community of the air in a daycare center, including seasonal dynamics in the bacterial community and the presence of specific viral pathogens. We collected filters from the heating, ventilation, and air conditioning (HVAC) system of a daycare center every two weeks over the course of a year. Amplifying and sequencing the 16S rRNA gene revealed that the air was dominated by Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes that are commonly associated with the human skin flora. Clear seasonal differences in the microbial community were not evident; however, the community structure differed when the daycare center was closed and unoccupied for a 13-day period. These results suggest that human occupancy, rather than the environment, is the major driver in shaping the microbial community structure in the air of the daycare center. Using PCR for targeted viruses, we detected a seasonal pattern in the presence of respiratory syncytial virus that included the period of typical occurrence of the disease related to the virus; however, we did not detect the presence of adenovirus or rotavirus at any time.     

School’s Out: Seasonal Variation in the Movement Patterns of School Children

School children are core groups in the transmission of many common infectious diseases, and are likely to play a key role in the spatial dispersal of disease across multiple scales. However, there is currently little detailed information about the spatial movements of this epidemiologically important age group. To address this knowledge gap, we collaborated with eight secondary schools to conduct a survey of movement patterns of school pupils in primary and secondary schools in the United Kingdom. We found evidence of a significant change in behaviour between term time and holidays, with term time weekdays characterised by predominately local movements, and holidays seeing much broader variation in travel patterns. Studies that use mathematical models to examine epidemic transmission and control often use adult commuting data as a proxy for population movements. We show that while these data share some features with the movement patterns reported by school children, there are some crucial differences between the movements of children and adult commuters during both term-time and holidays.     

No diurnal variation of classical and candidate biomarkers of Alzheimer’s disease in CSF

Background

Cerebrospinal fluid (CSF) biomarkers have gained increasing importance in the diagnostic work-up of Alzheimer’s disease (AD). The core CSF biomarkers related to AD pathology (Aβ42, t-tau and p-tau) are currently used in CSF diagnostics, while candidate markers of amyloid metabolism (Aβ38, Aβ40, sAPPα, sAPPβ), synaptic loss (neurogranin), neuroinflammation (YKL-40), neuronal damage (VILIP-1) and genetic risk (apolipoprotein E) are undergoing evaluation. Diurnal fluctuation in the concentration of CSF biomarkers has been reported and may represent a preanalytical confounding factor in the laboratory diagnosis of AD. The aim of the present study was to investigate the diurnal variability of classical and candidate CSF biomarkers in a cohort of neurosurgical patients carrying a CSF drainage.

Method

Samples were collected from a cohort of 13 neurosurgical patients from either ventricular (n?=?6) or lumbar (n?=?7) CSF drainage at six time points during the day, 1–7 days following the neurosurgical intervention. Concentrations of the core biomarkers were determined by immunoassays.

Results

Although absolute values largely varied among subjects, none of the biomarkers showed significant diurnal variation. Site of drainage (lumbar vs. ventricular) did not influence this result. The different immunoassays used for tau and Aβ markers provided similar results.

Conclusion

Time of day at CSF collection does not ultimately affect the concentration levels of classical and candidate AD biomarkers. Similar trends were found when using different immunoassays, thus corroborating the consistency of the data.

     

Seasonal morphophysiological variations in the prostatic complex of the Tarabul’s gerbil (Gerbillus tarabuli)

Gerbillus tarabuli is a nocturnal Saharan rodent which has an annual reproductive cycle characterized by the reproductive activity in spring and a long phase of sexual quiescence in other seasons. We describe the morphology and hormonal regulation of the prostatic complex of this rodent in the two periods, based on anatomical, histological, morphometric, and immunohistochemical analyses. The organisation of this prostatic complex is similar to that reported for Meriones unguiculatus, but different from the prostate of Psammomys obesus, the rat, and the mouse. In addition to the anterior lobes, ventral lobes, and dorsal lobes, the prostatic complex of Gerbillus tarabuli, also includes dorsolateral lobe. Each lobe is composed of a fibro-muscular stroma surrounding a glandular epithelium. Dorsolateral lobes are easily distinguishable by their big volume. The prostate grows and regresses cyclically throughout the year. During the resting season, ventral lobes and anterior lobes showed atrophy, with a significant decrease in both epithelial height and supranuclear area size, and a strong thickening of the fibro-muscular compartment. In dorsal lobes, the epithelial and stromal compartments atrophied and regenerated simultaneously, whereas in dorsolateral lobe the thickness of the epithelium, the supranuclear zone and the stroma increased during resting period. Furthermore, seasonal variations were observed in the distribution and expression of both androgen receptors, and estrogens receptors. Expression patterns of all receptors were lobe-specific. In conclusion, both androgens and estrogens are involved in the homeostasis and regulation of the prostate in Gerbillus tarabuli. Dorsolateral lobe seems to be controlled by a different mechanism than other lobes.     

Conservative treatment in Scheuermann’s kyphosis: comparison between lateral curve and variation of the vertebral geometry

Background

Conservative treatment in the Scheuermann’s kyphosis obtain, during skeletal growth, remodelling of the deformed vertebras. In a previous paper on Scheuermann’s kyphosis, we have studied the geometry variations of all vertebrae included in the curve, before and after the treatment.

The purpose of this study was to confirm the effectiveness of conservative treatment in Scheuermann’s kyphosis and was to evaluate and compare the variation of the vertebral geometry with the curve trend in Cobb degrees, before and after conservative treatment.

Methods

From a consecutive series of patients, we selected 90 patients with thoracic Scheuermann’s kyphosis, treated using anti-gravity brace: 59 male, 31 female. The mean age at the beginning of the treatment was 14 years.

Radiographical measurements were performed on radiographs from a lateral projection, at the beginning (t1) and at the end of the treatment (t5). Vertebral geometry modifications at t1 and t5 were analysed according to the following parameters and evaluated by three independent observers: Anterior wedging angle (ALFA) of the apex vertebra and Posterior wall inclination (APOS) of the limiting lower vertebra. The curve was measured in Cobb degrees.

Results

The results from our study showed that of the 90 patients with a thoracic curve mean value of Cobb degrees was 57.8 ± 6.0 SD at t1 and 41.3 ± 5.6 SD at t5. The differences between t1(angle at baseline) and t5 (end of treatment) were calculated for Cobb, ALFA and APOS angle and were respectively −16.4 ± 4.5, −6.4 ± 1.4 and −2.7 ± 1.2; tested with paired t-test were significative (p < 0.01). The results of the regression analysis to test the relationship between the three measures for the kyphosis (Cobb degree, ALFA and APOS) showed that the best association was between Cobb t5 and ALFA t5 (p < 0.01) and Cobb t1 and APOS t1 (p < 0.01). No significative association was found between the difference between ALFA and APOS.

Conclusion

We sustain that using new parameters to study vertebral remodelling allows us to reach a better comprehension of Scheuermann spine response to anti-gravity brace treatment. Furthermore, the evaluation of the ALFA angle of the apex vertebra confirms to be more reliable than Cobb’s angle because it cannot be affected by the radiological position.

     

Seasonal variations in the energy budget of Elliot’s pheasant (Syrmaticus ellioti) in cage

This study aimed to discuss the energy budget of Elliot’s pheasant Syrmaticus ellioti in different seasons, with life and health, good growth and normal digestion of Elliot’s pheasant as the tested objects, The energy budget of Elliot’s pheasant was measured by daily collection of the trial pheasants’ excrement in the biological garden of Guangxi Normal University from March 2011 to February 2012. The results showed that the gross energy consumption, metabolic energy and excrement energy varied by season, increasing as temperature decreased. There was significant difference in gross energy consumption, metabolic energy, excrement energy between adults and nonages. There was also a trend that food digestibility of pheasants increases as temperature increases. In the same season, the food digestibility of adults was better than that of nonages. Throughout spring, summer, autumn and winter, the metabolic energy of 4-year adults were 305.77±13.40 kJ/d, 263.67±11.89 kJ/d, 357.23±25.49 kJ/d and 403.12±24.91 kJ/d, respectively, and the nonages were 284.86±17.22 kJ/d, 284. 66±15.16 kJ/d, 402. 26±31.46 kJ/d and 420. 30±31.98 kJ/d, respectively. The minimum metabolic energies were 247.65±21.81 g, 265.86±26.53 g, respectively for each group, detected between 4-year adults and 1-year nonages. Further study is needed to determine whether 29.6 C is the optimal temperature for the Elliot’s pheasant.     

Geographical and within-population variation in the globeflower–globeflower fly interaction: the costs and benefits of rearing pollinator’s larvae

Interspecific interactions can vary within and among populations and geographical locations, and this variation can influence the nature of the interaction (e.g. mutualistic versus antagonistic) and its evolutionary stability. Globeflowers are exclusively pollinated by flies whose larvae feed only on their seeds. Here we document geographical variability in costs and benefits in globeflowers in sustaining their pollinating flies throughout the range of this arctic-alpine European plant over several years. A total of 1,710 flower heads from 38 populations were analysed for their carpel, egg and seed contents. Individual and population analyses control for the confounding influences of variation in both: (1) population traits, such as fly density and egg distribution among flower heads; and (2) individuals traits, such as carpel and egg numbers per flower head. Despite considerable variation in ecological conditions and pollinator densities across populations, large proportions (range 33–58%) of seeds are released after predation, with a benefit-to-cost ratio of 3, indicating that the mutualism is stable over the whole globeflower geographical range. The stability of the mutualistic interaction relies on density-dependent competition among larvae co-developing in a flower head. This competition is revealed by a sharp decrease in the number of seeds eaten per larva with increasing larval number, and is intensified by non-uniform egg distribution among globeflowers within a population. Carpel number is highly variable across globeflowers (range 10–69), and flies lay more eggs in large flowers. Most plants within a population contribute to the rearing of pollinators, but some pay more than others. Large globeflowers lose more seed to pollinator larvae, but also release more seed than smaller plants. The apparent alignment of interests between fly and plant (positive relationship between numbers of seeds released and destroyed) is shown to hide a conflict of interest found when flower size is controlled for.     

Role of zinc and copper ions in the pathogenetic mechanisms of Alzheimer’s and Parkinson’s diseases

Disbalance of zinc (Zn²⁺) and copper (Cu²⁺) ions in the central nervous system is involved in the pathogenesis of numerous neurodegenerative disorders such as multisystem atrophy, amyotrophic lateral sclerosis, Creutzfeldt-Jakob disease, Wilson-Konovalov disease, Alzheimer’s disease, and Parkinson’s disease. Among these, Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the most frequent age-related neurodegenerative pathologies with disorders in Zn²⁺ and Cu²⁺ homeostasis playing a pivotal role in the mechanisms of pathogenesis. In this review we generalized and systematized current literature data concerning this problem. The interactions of Zn²⁺ and Cu²⁺ with amyloid precursor protein (APP), β-amyloid (Abeta), tau-protein, metallothioneins, and GSK3β are considered, as well as the role of these interactions in the generation of free radicals in AD and PD. Analysis of the literature suggests that the main factors of AD and PD pathogenesis (oxidative stress, structural disorders and aggregation of proteins, mitochondrial dysfunction, energy deficiency) that initiate a cascade of events resulting finally in the dysfunction of neuronal networks are mediated by the disbalance of Zn²⁺ and Cu²⁺.     

Can spatial variation and inter-annual variation in precipitation explain the seed density and species richness of the germinable soil seed bank in a tropical dry forest in north-eastern Brazil?

The interaction between microhabitat and inter-annual variation in precipitation has an important role on the dynamics of the seed bank and can play a crucial role in survival and maintenance of plant populations in semi-arid environments. We hypothesized that the type of microhabitat and the inter-annual variability in precipitation can explain the richness and density of the seed bank in a semi-arid region in Brazil. The study was conducted in an area of tropical dry forest with shrub-tree physiognomy, locally called caatinga. We collected 35 soil samples in three distinct microhabitats, at the end of rainy and dry seasons, respectively, over three years, totalling 630 samples. The seed bank (richness and seed density) were determined by seedling emergence method. Over the three years, 79 species emerged from the seed bank, 64, 45 and 42 in riparian, non-riparian and rocky microhabitats, respectively. We recorded differences in species richness and average density between microhabitats and between years, with significant statistical interaction between them. Inter-annual precipitation explained 48% and 5% of the variation in richness and seed density, respectively. Spatial variation explained 7% of the species richness and 31% of the density. Our results show that the interaction between spatial variation and precipitation has an important role on the spatial and temporal heterogeneity of the richness and density of seed banks in dry environments.