Sex-related differences in leaf traits in an androdioecious shrub under contrasting levels of soil salinity

This study explores whether male and hermaphrodite plants of Phillyrea angustifolia (Oleaceae) show physiological and structural differences at the leaf level under severe water stress driven by drought and soil salinity. Leaf traits were measured in summer, at the height of the summer drought period, in male and hermaphrodite plants from two adjacent sites under contrasting soil salinity levels. Male plants from the saline site had significantly higher leaf proline content compared to males from the nonsaline site. By contrast, leaf proline levels were similarly low in hermaphrodite plants from both sites. On the other hand, hermaphrodite plants from the saline site had higher leaf stomatal frequency than hermaphrodites from the nonsaline site, whereas this parameter did not differ for male plants across sites. Such differences could be interpreted as the result of two different solutions to the same selective pressure in the androdioecious shrub P. angustifolia.     

Gonad development and fatty acid composition of Patella depressa Pennant (Gastropoda: Prosobranchia) populations with different patterns of spatial distribution, in exposed and sheltered sites

The present study examines the effect of shore exposure on the feeding performance (assessed by fatty acid analyses of the whole body) and gonad condition (stage of development and gonad somatic index, GSI) of Patella depressa populations. Male and female limpets were collected at exposed and sheltered sites, during winter and summer. The population at the exposed site was at a more advanced stage of gonad development, with a higher dispersion of gonad stages, both in winter and summer. Additionally, limpets from the exposed site, particularly the males, presented a higher GSI than the corresponding stage in the sheltered site. The quantitatively most important fatty acids were the saturated fatty acids (SFA) 16:0, 14:0, and 18:0, the monounsaturated fatty acids (MUFA) 18:1(n−7), 18:1(n−9), 16:1(n−7) and 20:1(n−9) and the polyunsaturated fatty acids (PUFA) 20:5(n−3) and 20:4(n−6). Females had a significantly higher fatty acid methyl esters (FAME) content (in summer and winter) and higher amounts of SFA and MUFA (in summer), which points to a higher degree of storage of neutral lipids in this sex. Male and female limpets at the exposed site had a significantly higher FAME, SFA, MUFA, PUFA and highly unsaturated fatty acids (HUFA) content than the corresponding sex in the sheltered site in summer. In addition, an inversion in the eicosapentaenoic acid (EPA)/arachidonic acid (ARA) and (n−3)/(n−6) ratios was observed in the sheltered site, as a result of the significantly higher levels of ARA and (n−6) fatty acids and lower amounts of EPA and (n−3) fatty acids found in the sheltered limpets. A high variability among patches in the fatty acid composition in the exposed site was found in winter, possibly related to the aggregation of limpets at this time. The differences found between limpets from the exposed and sheltered sites suggest qualitative and quantitative differences in their diets. Additionally, the results show that the spatial aggregation strategy adopted by limpets in sites of great wave and wind exposure does not affect their feeding and reproductive success, at least in the site examined here. In fact, more developed gonads, a higher GSI and an elevated FAME content was found in the exposed population. Possible factors are suggested and discussed to explain these observations.     

Longitudinal changes in the benthic bacterial community of the Mahoning River (Ohio, U.S.A.)

To examine spatial differences in bacterial communities along the Mahoning River in Northeast Ohio (USA), sediment samples were collected on two dates from three sites. Downstream portions (sites 2 and 3, in this study) of the Mahoning River have been highly impacted by human activities. Two approaches were used to characterize the bacterial community: fluorescent in situ hybridization (FISH) with taxon specific probes and denaturing gradient gel electrophoresis (DGGE). Bacterial numbers (per g ash free dry mass), based on staining with DAPI (4′, 6-diamidino-2-phenylindole) or FISH with Domain Bacteria, Acinetobacter calcoaceticus or Pseudomonas putida-specific probes, were higher at the most upstream site (site 1) compared to the more disturbed downstream sites (sites 2 and 3). In addition, the number of bands based on DGGE was higher at the upstream site (site 1) compared to the two downstream sites (2 and 3) during spring. However, in summer, the number of bands was similar among sites and the most upstream (1) and the middle site (2) had the same average number of bands. In spring, the percent similarity (based on the presence/absence of bands) among the three sites was relatively low compared to summer. In general, differences in the bacterial community were found among the sites with differing levels of anthropogenic disturbance but varied between the two dates examined.     

The role of summer precipitation and summer temperature in establishment and growth of dwarf shrub <Emphasis Type="Italic">Betula nana</Emphasis> in northeast Siberian tundra

It is widely believed that deciduous tundra-shrub dominance is increasing in the pan-Arctic region, mainly due to rising temperature. We sampled dwarf birch (Betula nana L.) at a northeastern Siberian tundra site and used dendrochronological methods to explore the relationship between climatic variables and local shrub dominance. We found that establishment of shrub ramets was positively related to summer precipitation, which implies that the current high dominance of B. nana at our study site could be related to high summer precipitation in the period from 1960 to 1990. The results confirmed that early summer temperature is most influential to annual growth rates of B. nana. In addition, summer precipitation stimulated shrub growth in years with warm summers, suggesting that B. nana growth may be co-limited by summer moisture supply. The dual controlling role of temperature and summer precipitation on B. nana growth and establishment is important to predict future climate-driven vegetation dynamics in the Arctic tundra.     

Distribution and seasonality ofLegionella pneumophila in colling towers

The numbers of presumptiveLegionella pneumophila cells in waters and sediments of nine different cooling towers located on the same site in the northeastern United States were determined at approximately monthly intervals for 18 months. All systems received makeup water from the same source and received the same chemical treatments. PresumptiveL. pneumophila were found in both water and sediment samples from all systems on all sampling dates. An important result of this study was the finding that tower sediments represent large reservoirs ofL. pneumophila. The only correlation between levels of presumptiveL. pneumophila and any of the physical, chemical, or operating characteristics evaluated was with winter shutdown and drainage followed by a nonoperational period. These systems showed a definite seasonal response with the highest levels of presumptiveL. pneumophila found in the summer and fall. Systems operated year round showed relatively constant numbers ofL. pneumophila in both water and sediments.     

The annual gametogenic cycle of the sea anemone Metridium senile from the Gulf of Maine

A year-long study was conducted to quantify the reproductive cycle of the clonal sea anemone, Metridium senile, an important member of the benthic community in the Gulf of Maine (GOM). M.senile is an abundant sessile invertebrate that forms identifiable clonal aggregations that are maintained by pedal laceration but individuals can also reproduce sexually. Specimens were collected monthly from a shallow (< 10 m) subtidal site and the reproductive cycle of male and female anemones was described on a seasonal basis using histological preparation of the gonads and light microscopy. Gametogenesis was determined for both sexes and showed that females undergo spawning during the seasonal transition from summer to fall, while males have mature sperm within testicular cysts in the winter, spring, and summer. Environmental data recorded at the study site shows that the spawning period occurs during a period of peak water temperature (August-September), and rapid gametogenesis occurs during periods of high food availability (April). The low percentage of reproductively mature anemones and the dominance of asexual reproduction in this population are believed to be the result of the high flow regime at this site.     

Seasonal Ecology and Behavior of an Endangered Rainforest Frog (Litoria rheocola) Threatened by Disease

One of the most devastating wildlife diseases ever recorded is chytridiomycosis, a recently emerged amphibian disease that is caused by the chytrid fungus Batrachochytrium dendrobatidis. Understanding, predicting, and managing the impacts of chytridiomycosis on any amphibian species will require detailed information on its ecology and behavior because this pathogen is transmitted by contact with water or other individuals, and pathogen growth rates are thermally sensitive. The common mistfrog (Litoria rheocola) is an endangered tropical rainforest frog that has declined due to chytridiomycosis. We tracked L. rheocola during the winter (cool/dry) and summer (warm/wet) seasons at a low- and high-elevation site. We found that seasonal differences in environmental temperatures and frog behavior should render this species most vulnerable to B. dendrobatidis during cooler months and at higher elevations, which matches observed patterns of infection prevalence in this species. During winter, frogs moved shorter distances than during summer, and they spent less time in vegetation and more time in the stream, which should increase exposure to aquatic B. dendrobatidis zoospores. At a low-elevation site (40 m ASL), estimated body temperatures were within the optimal range for B. dendrobatidis growth (15-25°C) most of the time during winter, but they reached temperatures above this threshold frequently in summer. At a higher elevation (750 m ASL), estimated body temperatures were within the range most favorable for B. dendrobatidis year-round, and did not exceed 25°C, even during summer. Our study provides the first detailed information on the ecology and behavior of L. rheocola and suggests ecological mechanisms for infection dynamics that have been observed in this endangered species.     

Observations on post-fire black morel ascocarp development in an Israeli burnt forest site and their preferred micro-sites

Morchella species ascocarps (morels) are sought-after edible mushrooms that exhibit pyrophilous behavior, proliferating in fire-affected soils of certain types of forests. The factors governing fruiting in this habitat are poorly understood. An observational approach was used to determine the spatial distribution on preferred micro-sites of black morel fruiting in a forest after a summer fire, subjected to different post-fire forestry management activities. Clearing the burnt tree stumps from the site, compaction of the burnt soil by heavy machinery (bulldozers) and covering the soil with chopped wood created preferred micro-sites for black morel fruiting. Fewer fruit bodies developed on untouched burnt soil, and almost none on non-burnt soil at the same site. These observations enhance understanding the ecological principles underlying the distribution and abundance of morel ascocarp development in natural habitats; such an understanding could contribute to conservation and management of morel fruiting in the wild.     

Age validation of juvenile Notothenia rossii at Potter Cove, South Shetland Islands, using mark-recapture data

Among all validation methods of age determination in fish, release of known age and marked specimens gives the most reliable information. We carried out a tag-recapture experiment on Notothenia rossii at Potter Cove, to validate, for first time for this species using this method, the principle of annual deposition of an annulus in scales and otoliths. Of 132 juvenile specimens (TL = 22.1–38.1 cm) tagged and released in successive years from 2004 to 2010, 7 were recaptured at the same site after periods of 1–13 months. In scales of five specimens recovered after 10–13 months, one extra annulus was laid down, exhibiting an additional winter zone of closely spaced sclerites. Consistently, the same analysis in two individuals marked and recaptured during the same summer, after 1–3 months at liberty, did not show the deposition of an additional annulus. All the fish tagged or recaptured during the experiment period (December to March) showed in their scales an edge zone of widely spaced sclerites, in agreement with the known pattern of growth in summer. Likewise, an analysis in selected specimens showed good consistency between the numbers of sclerites deposited in scales and the time of fish release. The comparative analysis between scales taken at recapture and otoliths of the same individual allowed a simultaneous counting of the annuli with complete correspondence. The growth in length of fish ranged from 0.5 to 6.1 cm, depending on the time of release.     

Seasonal Variations in Survival of Indicator Bacteria in Soil and Their Contribution to Storm-water Pollution

Survival of a fecal coliform (Escherichia coli) and a fecal streptococcus (Streptococcus faecalis var. liquifaciens) was studied through several years at shaded and exposed outdoor soil plots. Death rates for both organisms were calculated for the different seasons at both sites. The 90% reduction times for the fecal coliform ranged from 3.3 days in summer to 13.4 days in autumn. For the fecal streptococcus, 90% reduction times were from 2.7 days in summer to 20.1 days in winter. During summer, the fecal coliform survived slightly longer than the fecal streptococcus; during autumn, survival was the same; and in spring and winter the fecal streptococcus survived much longer than the fecal coliform. Both organisms were isolated from storm-water runoff collected below a sampling site when counts were sufficiently high in soil. Isolation was more frequent during prolonged rains, lasting up to 10 days, than during short rain storms. There was evidence of aftergrowth of nonfecal coliforms in the soil as a result of temperature and rainfall variations. Such aftergrowth may contribute to variations in bacterial count of storm-water runoff which have no relation to the sanitary history of the drainage area.     

Summer mortality in the hazel dormouse (Muscardinus avellanarius) and its effect on population dynamics

In the period 2000–2012, 38.3 % of 950 marked overwintered hazel dormice (Muscardinus avellanarius) were not recaptured at a study site in Lithuania in autumn. As adult dormice are sedentary, it is presumed that those dormice not recaptured died between late April and August. The highest total number of dormice captured for the last time was recorded in May and the lowest in August. The total summer mortality was significantly higher in females (42.5 %) than in males (34.6 %), but it did not depend on dormouse age or body weight. Tawny owl (Strix aluco) is the main known dormouse predator in Lithuania, and likely, it has the highest impact on summer mortality of M. avellanarius. Over the years, the total summer mortality of adult dormice ranged from 27 % to 52 %. The increased summer mortality resulted in decreased total dormouse population density and particularly decreased density of adult females in summer. Decreased densities led to more intensive breeding in the dormouse population, specifically breeding by young-of-the-year females, a pattern that is not common for this species. The number of breeding cases by young-of-the-year females was inversely related to the density of adult overwintered females in summer and to the number of breeding cases of these females. Breeding by young-of-the-year females was the main factor in the restoration of decreased population density in summer. Lithuanian populations of M. avellanarius are unique in their high proportion of breeding cases by young-of-the-year females amongst all populations investigated in the entire species distributional range.     

Scavenging in Antarctica: Intense variation between sites and seasons in shallow benthic necrophagy

The response of scavengers to a feeding cue at Adelaide Island, West Antarctic Peninsula was investigated using a baited video camera system. Fourteen experimental deployments, each lasting 72 h were conducted at two contrasting sites during the winter and summer of 2005. The rate of bait consumption varied between sites but not between seasons, and was low in comparison with studies at lower latitudes and greater depths. At the Hangar Cove site, the nemertean Parborlasia corrugatus was out-competed at the bait and displaced by the lysianassid amphipod Cheirmedon femoratus during winter. However, C. femoratus did not feed on the bait during summer, allowing P. corrugatus to monopolise the feeding opportunity. At the South Cove site the asteroid Odontaster validus dominated the bait in both seasons but sporadic feeding by the nototheniid fish Notothenia coriiceps considerably affected consumption rates during two of the six deployments. Scavengers were attracted to the bait in very high numbers and opportunistic necrophagy seems to be a successful strategy in an environment that is intensely disturbed by ice.     

Changes in water relations for Acacia ancistrocarpa on natural and mine-rehabilitation sites in response to an experimental wetting pulse in the Great Sandy Desert

Vegetation plays an essential role in mine-site rehabilitation as it serves to reduce erosion and extract moisture from the soil cover, thus minimising deep drainage to potentially hazardous materials below. Plant water-use patterns and root development are likely to be impacted where subsoils are physically and/or chemically inhospitable and close to the surface, particularly in arid and semi-arid environments where pulses of rainfall are infrequent and interspersed with long dry periods. The aim of this investigation was to determine how plant water relations of the woody shrub species Acacia ancistrocarpa (Maiden and Blakely) were affected by a summer wetting pulse on a degraded mine-rehabilitation site and a pristine natural site in the Great Sandy Desert of north-western Australia. At both the natural and rehabilitation sites, 20 m³ of water was applied to emulate an 80-mm rainfall event comparable with cyclones that occur during the summer wet season. We found that plants responded with significant increases in stomatal conductance, leaf water potential and sap-flow in lateral roots within three days of irrigation at the natural site and two days at the rehabilitation site. At the rehabilitation site this response occurred despite the fact that sinker roots were stunted by impeding physical properties of the mine-waste material. Sap-flow velocity, using the heat ratio method, in lateral and primary sinker roots was close to zero at night and positive during the day for trees at both sites during the dry period before the irrigation. These data indicate hydraulic redistribution was not occurring between the primary sinker and lateral roots at night, and water was transported along the laterals towards the crown, despite the fact they were in dry soil. Excavations revealed that lateral roots extended up to 6 m and displayed secondary sinker roots accessing water from deeper soil layers, even from mine-waste material. These morphological traits likely improved the water relations and survival of A. ancistrocarpa at the rehabilitation site. Considering these traits and the rapid pulse responsiveness of this species, we recommend A. ancistrocarpa for future rehabilitation projects at this and other mine-sites in the region.     

Tree-ring patterns and climate response of Mediterranean fir populations in Central Greece

Central Greece is the distribution common area of the endemic fir species Abies cephalonica and Abies borisii-regis. Forests fires and fir decline are some of the problems both species encountered during the past decades, with these problems being exacerbated lately by climate change. The present research investigates tree-ring patterns and climate responses of three fir populations along a latitudinal gradient in Central Greece. All three populations were homogeneous in their dendrometric, silvicultural and site characteristics but were phenotypically different. The analysis of tree-ring widths site chronologies revealed that 59% of their variability interprets common tree-ring patterns whereas another 25% interprets their differences as they appear from a south to north direction. This variability in tree-ring widths is proportional to the variability observed for precipitation, temperature and drought from a south to north direction in this region. The tree-ring to climate relationships revealed that the main climatic factor affecting fir tree-ring width is late spring and summer precipitation to which is positively correlated. Also, tree-ring widths were positively affected by the temperatures of the October and April before the growing season. However, June drought adversely affected tree-ring widths of the northern site while it positively affected them at the beginning of the spring season, especially for the southern site and in September for the northern sites. All dendrochronological statistics, tree-ring patterns and climate-growth relationships show a south to north trend following the climatic and phenotypic (species) variation observed to the same direction for fir populations in Central Greece.     

The ecophysiology of some marine nematodes from Bermuda: Seasonal aspects

In the winter of 1976 the horizontal and vertical distribution, temperature tolerance and oxygen consumption at three experimental temperatures were determined for several species of nematodes inhabiting a low-energy beach in Bermuda. The results are compared with those of previous summer investigations carried out on the same beach.The three most abundant species of nematodes on the beach, Steineria sterreri Ott, Trefusia schiemeri Ott and Theristus floridanus Wieser & Hopper show distinct patterns of distribution as well as distinct survival-time curves when upper lethal temperature is plotted against exposure time. No seasonal resistance adaptation to high temperature occurs in Steineria sterreri and Trefusia schiemeri, the two species for which comparative summer data are available.Theristus erectus, which dominated the flat in summer, is much more heat tolerant than T. Floridanus which replaced it in winter. Oxygen consumption at 15°C is twice as high in T. Floridanus as in Trefusia schiemeri whereas at 22° and 30°C both species consume approximately the same amount of oxygen. T. Schiemeri is capable of seasonal adaptation of Q_O2 inasmuch as it consumes just about as much oxygen in winter at 22°C as in summer at 30°C.The seasonal data support the suggestion that on a subtropical low-energy beach the metabolic capacities of many meiofauna species are closely adjusted to the micro-environment in which they live.     

Responses of pigmentation and δ13C in Qilian juniper to cold and drought stresses under natural conditions in the Qilian Mountains,China

The seasonal changes of pigments and stable carbon isotope composition (δ¹³C values) were investigated in needles of Qilian juniper (Sabina przewalskii Kom.) from two typical sites, one drier and the other wetter, in the Qilian Mountains, China. The anthocyanins and rhodoxanthin content from both sites were much higher in winter than in summer. Plant needles contained more carotenoids and xanthophylls in winter at the wetter site, while no seasonal difference appeared at the drier site. However, lower chlorophyll content and higher proline and δ¹³C were observed at the drier site. Average tree height was shorter at the drier site trees than at the wetter site. Our results suggested that under natural conditions, pigmentation in S. przewalskii may serve to improve the energy balance of the photosynthetic apparatus under cold and drought stresses. Proline and δ¹³C could be used as drought indicators for S. przewalskii.     

Anatomical characteristics and hydrologic signals in tree-rings of oaks (Quercus robur L.)

Key message

Anatomical characteristics and hydrologic signals in tree-rings of oaks from areas with regular flooding may vary, even within the same forest stand, and largely depend on the micro-environmental conditions.

Abstract

Q. robur decline in European floodplain forests in recent years seems to be strongly associated with the deteriorating hydrological regime. We investigated the influence of the Krka River flow on tree-ring patterns of Q. robur from the Krakovo floodplain forests (Slovenia) to assess the effect of micro-location conditions on hydrological signals in wood-anatomical characteristics. We selected two groups of Q. robur trees growing at nearby locations with different hydrological conditions, resulting in frequent autumn and spring flooding at the wetter site (=W oaks) but no flooding at the other, drier site (=D oaks). We found differences between the two groups in the anatomical structure of tree-rings; however, ring width proved to be the main variable determining the anatomical structure of oak wood. D and W oaks responded differently to the Krka River flow in the studied period. Radial growth of D oaks was negatively influenced by spring flow, but positively influenced by minimum summer flow. In W oaks, ring width was positively correlated with mean summer flow. Thus, environmental information stored in wood-anatomical features may vary, even within the same forest stand, and largely depends on the micro-environment. Reduced wood increments of D oaks suggest that growth conditions are less favourable, implying a link between the health state of oaks from lowland forest and hydrological conditions. Trees intended for hydrological reconstruction must therefore be carefully selected to avoid the possibility of error and potential loss of information. Anatomical characteristics and hydrological signals in tree-rings of oaks from areas with regular flooding may vary, even within the same forest stand, and largely depends on the micro-environmental conditions.     

Germination and anchorage ofEnteromorpha spp. in sediments of the Wadden Sea

Large quantities of filamentous green algae (Enteromorpha spp.) have regularly occurred on muddy and sandy tidal flats in Königshafen, on the island of Sylt (North Sea), since 1979 — covering the sediments in thick mats during the summer months. While spores ofEnteromorpha were encountered in both mud and sand, germling formation was restricted to sand. However, mud snails (Hydrobia ulvae Pennant) were overgrown with smallEnteromorpha filaments in both habitats, about 50% of them at a muddy site and 20% at a sandy one. Filaments, several cm in length and still adhering to the snails, became tangled into clusters. At the sandy site, with abundantArenicola marina L., these clusters slid into the feeding funnels of lugworm burrows; the importance of this secondary anchorage is demonstrated by a field experiment. We suggest that the primary and secondary attachment ofEnteromorpha filaments provided by benthic fauna is an essential step in the development of green algal mats on sedimentary tidal flats.     

Climate–growth relationships of silver fir (Abies alba Mill.) in marginal populations of Central Italy

This study is part of a LIFE+ project on marginal mountain ecosystem conservation. In five mixed European beech-silver fir forests of Central Italy (Tuscany and Marches), classified as priority habitats of the Natura 2000 Network, we analysed the climate–growth relationships of silver fir (Abies alba Mill.) along an altitudinal gradient. The aims of this study were: (i) to identify the main spatial patterns in the frequency domain of both silver fir growth and climate variables in five different sites and (ii) to detect the overall climate sensitivity of the target species through time.Multivariate analysis displayed groups of chronologies with similar growth patterns for each frequency band-pass, discriminating for altitude and geographical location. The spectral density of climate variables at seasonal scale displayed common spatial patterns during late-spring and summer months. In stands where fir grows in optimal conditions, the most significant growth responses to climate were the positive influence of late-spring and summer precipitations of the previous year and the negative effect of summer temperatures of both previous and current year, although decreasing during the last decades. On the other hand, the site at lowest altitude shows a low and not very consistent climate sensitivity as compared to the preferred altitudes. At the highest site (1375 m asl) the positive effect of previous year spring–summer precipitation and summer temperature of both previous and current year disappears.Results suggest that in the studied areas a water-use increase in summer is a possible response of silver fir to the significant reduction of spring precipitation and general temperature increase throughout the 20th century.These findings provide additional information on silver fir responses to climate variability at different altitudes, useful for calibrating silvicultural treatments to apply for conservation of sensitive ecosystems and of tree species in mountain areas.     

Effect of climatic variability on δ13C and tree-ring growth in piñon pine (Pinus edulis)

Understanding the response of long-lived species to natural climatic variability at multiple scales is a prerequisite for forecasting ecosystem responses to global climate change. This study investigated the response of piñon pine (Pinus edulis) to natural climatic variability using information on physiology and growth as recorded in leaves and tree rings. δ¹³C of annual leaf cohorts (δ¹³C_leaf) and tree rings (δ¹³C_ring) were measured at an ecotonal/xeric site and a mid-range/mesic site. Ring width indices (RWI) were used to estimate annual growth of individual trees. Relationships between seasonal and annual climate parameters and δ¹³C and growth were investigated. δ¹³C–climate relationships were stronger for δ¹³C_leaf than for δ¹³C_ring especially at the xeric site. The mean monthly maximum summer temperatures over May through September (summer T _max) had the strongest influence on δ¹³C_leaf. There was a strong negative relationship between RWI with summer T _max and a strong positive relationship between RWI with October to October precipitation (water–year PPN) at both sites. This suggests that piñon pine populations could be vulnerable to decreased growth and, perhaps mortality, in response to warmer, drier conditions predicted by models of global climate change.