Variability In Ecological Conditions Research Articles

High-Frequency Variability of Bacterioplankton in Response to Environmental Drivers in Red Sea Coastal Waters.

Autotrophic and heterotrophic bacterioplankton are essential to the biogeochemistry of tropical ecosystems. However, the processes that govern their dynamics are not well known. We provide here a high-frequency assessment of bacterial community dynamics and concurrent environmental factors in Red Sea coastal waters. Weekly sampling of surface samples during a full annual cycle at an enclosed station revealed high variability in ecological conditions, which reflected in changes of major bacterioplankton communities. Temperature varied between 23 and 34°C during the sampling period. Autotrophic (Synechococcus, 1.7–16.2 × 104 cells mL−1) and heterotrophic bacteria (1.6–4.3 × 105 cells mL−1) showed two maxima in abundance in spring and summer, while minima were found in winter and autumn. Heterotrophic cells with high nucleic acid content (HNA) peaked in July, but their contribution to the total cell counts (35–60%) did not show a clear seasonal pattern. Actively respiring cells (CTC+) contributed between 4 and 51% of the total number of heterotrophic bacteria, while live cells (with intact membrane) consistently accounted for over 90%. Sequenced 16S rRNA amplicons revealed a predominance of Proteobacteria in summer and autumn (>40%) and a smaller contribution in winter (21–24%), with members of the Alphaproteobacteria class dominating throughout the year. The contribution of the Flavobacteriaceae family was highest in winter (21%), while the Rhodobacteraceae contribution was lowest (6%). Temperature, chlorophyll-a, and dissolved organic carbon concentration were the environmental variables with the greatest effects on bacterial abundance and diversity patterns.

Managing emerging threats to spotted owls

ABSTRACTThe 3 spotted owl (Strix occidentalis) subspecies in North America (i.e., northern spotted owl [S. o. caurina], California spotted owl [S. o. occidentalis], Mexican spotted owl [S. o. lucida]) have all experienced population declines over the past century due to habitat loss and fragmentation from logging. Now, the emerging influences of climate change, high‐severity fire, and barred owl (Strix varia) invasion also appear to be synergistically and differentially affecting population trends of each subspecies. Our objective was to review the existing literature on the spotted owl to describe historical and emerging threats and whether those threats have been adequately examined for each subspecies. Using 527 publications from a Web of Science search of the literature from 1900–2015, we statistically evaluated the emphasis placed on each subspecies regarding 4 influences: mechanical tree removal, fire, climate change, and barred owl invasion. There were 98 papers that explicitly examined the effects of ≥1 of these influences. Most of these papers were focused on the northern spotted owl, and for all 3 subspecies, most papers examined short‐term effects only. We used our results to identify significant information gaps relative to historical and emerging threats. Commercial timber harvesting remains a potential threat for all 3 spotted owl subspecies, but effects from forest thinning may be increasing because of the heightened emphasis on fuels reduction and forest restoration treatments on public lands. Owl response to mechanical tree removal, especially forest thinning, remains understudied. Climate change also may threaten all 3 subspecies. Changes in climate likely affect survival and reproduction of spotted owls and their prey, and alter habitat availability by affecting disturbance regimes and vegetation composition and succession, but little empirical information is available describing specific responses to climate change. The literature on response to high‐severity fire is sparse for some subspecies, primarily short‐term in nature, and not consistent. Barred owl invasion is a major threat to the northern spotted owl and the California spotted owl but does not currently threaten the Mexican spotted owl. Rigorous research on the response of spotted owls to all factors influencing population change, particularly for the Mexican spotted owl, is needed. The most useful information for predicting owl response to these threats stems primarily from long‐term studies of owl demography. The lack of such studies within the range of the Mexican spotted owl greatly limits our understanding of its population dynamics and our ability to predict the effects of various threats on Mexican spotted owl populations. For all 3 subspecies, we encourage long‐term studies of their responses to threats, using uniquely marked owls across large spatial extents to account for spatiotemporal variability in ecological conditions within and among subspecies. © 2018 The Wildlife Society.

Migration and wintering strategies in vulnerable Mediterranean Osprey populations

A broad range of migration strategies exist in avian species, and different strategies can occur in different populations of the same species. For the breeding Osprey Pandion haliaetus populations of the Mediterranean, sporadic observations of ringed birds collected in the past suggested variations in migratory and wintering behaviour. We used GPS tracking data from 41 individuals from Corsica, the Balearic Islands and continental Italy to perform the first detailed analysis of the migratory and wintering strategies of these Osprey populations. Ospreys showed heterogeneous migratory behaviour, with 73% of the individuals migrating and the remaining 27% staying all year round at breeding sites. For migratory individuals, an extremely short duration of migration (5.2 ± 2.6 days) was recorded. Mediterranean Ospreys were able to perform long non‐stop flights over the open sea, sometimes overnight. They also performed pre‐ and post‐migratory trips to secondary sites, before or after crossing the sea during both autumn and spring migration. Ospreys spent the winter at temperate latitudes and showed high plasticity in habitat selection, using marine bays, coastal lagoons/marshland and inland freshwater sites along the coasts of different countries of the Mediterranean basin. Movements and home‐range areas were restricted during the wintering season. The short duration of trips and high levels of variability in migratory routes and wintering grounds revealed high behavioural plasticity among individuals, probably promoted by the relatively low seasonal variability in ecological conditions throughout the year in the Mediterranean region, and weak competition for non‐breeding sites. We stress the importance of considering the diversity in migration strategies and the particular ecology of these vulnerable populations, especially in relation to proactive management measures for the species at the scale of the Mediterranean region.

Concurrent validity of footswitches analysis for the measurement of temporal gait parameters

The GAITRite ® system, according to the published data, appears to be an easy to use and validated device for gait analysis. However, it only allows acquisitions on short distances in a nonecological environment. In addition to this device, it could be interesting to use new embarked evaluation tools. The main aim of this study was to examine the concurrent validity of temporal parameters recorded by the portable Zero Wire, AURION ® footswitch system in comparison to the GAITRite ® mat. In a single center prospective study, 40 healthy subjects were included. Each subject had to walk at three different speeds (slow, normal, max) and temporal gait parameters were recorded at the same time by each system. To measure the validity of the footswitch system, we calculated inter class correlation coefficient (ICC) for each temporal parameter (step and cycle time, cadence, % of stance, % of single support, % of swing). Gait parameters recorded at maximum gait velocity showed the best concordance between the two assessments, with a majority of parameters demonstrating a very good validity (ICC > 0.91). At slow speed, the analysis revealed excellent results for gait cadence and step and cycle times, whereas validity was good (ICC > 0.71) to moderate (ICC > 0.51) for the other parameters. The validity profile was a little worse at normal speed, especially for % of swing and % of stance. The Zero Wire, AURION ® , portable footswitch system, is a valid for temporal gait parameters assessment, particularly considering raw parameters. It provides the opportunity to assess gait parameters and variability in ecological conditions, particularly in dual-task gait protocols.

Mesoscale Variation in Snag and Hardwood Densities and Sizes in Old-Growth Forests in Western Oregon

Abstract Snags and hardwoods contribute to biological, structural, and functional diversity in old-growth forests. In the US Pacific Northwest, only general knowledge about regional patterns is available to determine target density of snags and hardwood trees. To investigate their variability at relevant scales for silviculture, we examined snag and hardwood densities and sizes in 20 old-growth units in northern and southern aspects in the Coast Range and the Willamette Valley foothills of Oregon. Snag densities varied largely between subregions and aspects, with aspect affecting densities more than subregion. In the Coast Range, snag density was 2.8 times greater on northern aspects than on southern aspects, whereas in the Willamette Valley foothills snag density was 1.4 times greater on northern aspects than on southern aspects. Density of snags larger than 101.6 cm in diameter was very low. Hardwood densities were also greater on northern aspects than on southern aspects. The negative exponential distribution of hardwood density frequency by size classes could be explained by cohort growth under a wide range of competitive pressures or repeated-recruitment events. Aspect and subregion should be taken into account when defining management targets. Allowing for flexibility at these smaller spatial scales would better reflect the variability in ecological conditions and land use history that led to the development of old-growth stands.

Variable Helper Effects, Ecological Conditions, and the Evolution of Cooperative Breeding in the Acorn Woodpecker

The ecological conditions leading to delayed dispersal and helping behavior are generally thought to follow one of two contrasting scenarios: that conditions are stable and predictable, resulting in young being ecologically forced to remain as helpers (extrinsic constraints and the habitat saturation hypothesis), or that conditions are highly variable and unpredictable, leading to the need for helpers to raise young, at least when conditions are poor (intrinsic constraints and the hard life hypothesis). We investigated how variability in ecological conditions influences the degree to which helpers augment breeder fitness in the cooperatively breeding acorn woodpecker (Melanerpes formicivorus), a species in which the acorn crop, territory quality, and prior breeding experience all vary in ways that have important effects on fitness. We found that the relationship between ecological conditions and the probability that birds would remain as helpers was variable but that helpers generally yielded greater fitness benefits when ecological conditions were favorable, rather than unfavorable, for breeding. These results affirm the importance of extrinsic constraints to delayed dispersal and cooperative breeding in this species, despite its dependence on a highly variable and unpredictable acorn crop. Our findings also confirm that helpers can have very different fitness effects, depending on conditions, but that those effects are not necessarily greater when breeding conditions are unfavorable.

Challenges of Socio-economically Evaluating Wildfire Management on Non-industrial Private and Public Forestland in the Western United States

Non-industrial private forests (NIPFs) and public forests in the United States generate many non-market benefits for landholders and society generally. These values can be both enhanced and diminished by wildfire management. This paper considers the challenges of supporting economically efficient allocation of wildfire suppression resources in a social cost-benefit analysis framework when non-market values are important. These challenges include substantial gaps in scientific understanding about how the spatial and temporal provision of non-market values are affected by wildfire, the limited utility of benefit transfer in wildfire assessment, a lack of studies that have estimated marginal willingness-to-pay to conserve non-market values, violation of consumer budget constraints, and the infeasibility of valuing indigenous cultural heritage. These challenges present serious impediments to adapting price-based decision-support tools to accommodate non-market values and support decision-making consistent with contemporary federal wildfire policy. Departure from the historic range and variability of ecological conditions is proposed as a complementary framework to support wildfire management decisions when non-market values are important on NIPF and public forestland.

Landscape patterns as indicators of ecological change at Fort Benning, Georgia, USA

This research examined landscape indicators that signal ecological change in both intensely used and lightly used lands at Fort Benning, Georgia. Changes in patterns of land cover through time affect the ecological system by altering the proportion and distribution of habitats for species that these cover types support. Landscape patterns, therefore, are important indicators of land-use impacts, past and present, upon the landscape. This analysis of landscape pattern began with a landscape characterization based on witness tree data from 1827 and the 1830s and remotely sensed data from 1974, 1983, 1991, and 1999. The data from the early 1800s, although coarse, were useful in characterizing the historical range of variability in ecological conditions for the area. The steps for the analysis involved the creation of a land-cover database and a time series of land-cover maps, computation of landscape metrics, and evaluation of changes in those metrics over time as evidenced in the land-cover maps. We focused on five cover types (bare/developed land, deciduous forest, mixed forest, pine forest, and non-forest vegetated land), for they reveal information important to resources management at Fort Benning. An examination of land-cover class and landscape metrics, computed from the maps, indicated that a suite of metrics adequately describes the changing landscape at Fort Benning, Georgia. The most appropriate metrics were percent cover, total edge (km), number of patches, descriptors of patch area, nearest neighbor distance, the mean perimeter-to-area ratio, shape range, and clumpiness. Identification of such ecological indicators is an important component of building an effective environmental monitoring system.

Predicting time‐specific changes in demographic processes using remote‐sensing data

Summary Models of wildlife population dynamics are crucial for sustainable utilization and management strategies. Fluctuating ecological conditions are often key factors influencing both carrying capacity, mortality and reproductive rates in ungulates. To be reliable, demographic models should preferably rely on easily obtainable variables that are directly linked to the ecological processes regulating a population. We compared the explanatory power of rainfall, a commonly used proxy for variability in ecological conditions, with normalized differential vegetation index (NDVI), a remote‐sensing index value that is a more direct measure of vegetation productivity, to predict time‐specific conception rates of an elephant population in northern Kenya. Season‐specific conception rates were correlated with both quality measures. However, generalized linear logistic models compared using Akaike's information criteria showed that a model based on the NDVI measure outperformed models based on rainfall measures. A predictive model based on coarse demographic data and the maximum seasonal NDVI value was able to trace the large variation in observed season‐specific conception rates (Range 0–0·4), with a low median deviation from observed values of 0·07. By combining the model of season‐specific conception rates with the average seasonal distribution of conception dates, the monthly number of conceptions (range 0–22) could be predicted within ±3 with 80% confidence. Synthesis and applications. The strong predictive power of the normalized differential vegetation index on time‐specific variation in a demographic variable is likely to be generally applicable to resource‐limited ungulate species occurring in ecologically variable ecosystems, and could potentially be a powerful factor in demographic population modelling.

Patch level variation of bark beetle attack (Col., Scolytidae) on snapped and uprooted trees in Norway spruce primeval natural forest in endemic condition: proportions of colonized surface and variability of ecological conditions

Abstract: From two snapped and five uprooted trees, 452 samples were obtained. Ips typographs, Jps amitinus, Dryocoetes spp., Hylurgops palliaus, Hylurgops glabratus, Pityogenes chalcographus, Polygraphus polygraphus, P. subopacus, Pityophthorus pityographus, Xyloterus lineatus and Xilechinus pilosus were present. Single and multiple linear regression were used for assessing the influence of insolation and host factors on the proportion of bark attacked by individual species, on the proportion of bark attacked by all bark beetle groups taken together and on the number of bark beetle groups present on individual trunks. Results show that the proportion of bark colonized by I. typographus is related to the connection of the trunk to roots and to insolation. The proportion of bark attacked by all species together was a function of trunk dimensions. Shaded trunks are attacked only by shade and moisture preferring species, while trunks exposed to higher levels of solar insolation are attacked by higher temperature preferring species on the sunny parts and by shade and moisture preferring species on shady parts.

Basic loci in cultivation of certain crops in the past and modern times

In 1968 H. Brücher asked: "Gibt es Genzentren?" He proposed a negative answer, but was wrong. The geographical distribution of the majority of crops is not even over all parts of their areas. There are loci of great abundance and regions of small plantations. The abundance of individuals in the large plantation is a factor favouring the display of genetic variability (an increase of the mutation number). The variability of ecological conditions, the antiquity of cultivation and the possibility of interspecific hybridization in such loci promote genetic variability; but a uniformity of ecological conditions and strong selection (natural or artificial) can eliminate new genotypes arising and preserve the homogeneity of the initial populations. Therefore loci of great genetic variability (Genzentren) exist only in conditions favourable for agriculture (with weak natural selection) and in conditions of a primitive consumer agriculture (without strong artificial selection). Loci of genetic variability can be observed in the following regions of a past or existing plantation abundance: in the ancient primary regions of domestication of certain plants; in the regions of ancient large scale cultivation around the primary domestication centers; and in the secondary loci of abundance in conditions favourable for agriculture where certain crops migrated from their primary cultivation regions. Certain loci of abundance (ancient and modern) have no noticeable genetic variability in their different crops, which are relatively uniform there. Such loci of abundance without genetic variability are either disposed at the periphery of the area of the particular crop, with worse natural conditions than in the rest of the area (control by strong natural selection), or are new loci of abundance in conditions of commercial agriculture (control by regular plant-breeding).All loci of polymorphism (Genzentren) are undoubtedly a temporary historical phenomenon. The absence of regular plant breeding was an indispensable condition for the rise of genetic variability loci in the regions of plantation abundance of certain crops. In modern times plant breeding becomes an inevitable component of commercial agriculture. Thus new loci of abundance have no great genetic variability and ancient centres of polymorphism of different crops now go to ruin, giving place to plantations of the few best varieties. Loci of genetic variability are now a relic of the past, while loci of abundance with the few best varieties conform with the economics of modern world agriculture, which aspires to cultivate each crop in the regions where its production cost will be lower and to avoid areas with an expensive product.