Large scale and regional demographic responses to climatic changes in Europe during the Final Palaeolithic.

Spatial confinement to a home range is theorized to be a more energetically efficient method of acquiring resources than random searching due to spatial memory. Intraspecific studies that have compared home range size at different population densities have found that home ranges shrink as population density increases. This negative trend could be due to increased conspecific competition via population density increase or due to correlations between resource density and population density. We use the 10-year population cycle of snowshoe hares (Lepus americanus) and individual-level food-add experiments as a case study to assess whether the mechanism of the relationship between home range size and population density is related to competition from increased conspecific density or confounds between population density and resource density. Over six winters (1 December-31 March) and a 50-fold change in population density, we estimated weekly home range sizes (n = 464; 90% minimum convex polygons) of 88 radio-collared hares, of which 26 were food-supplemented. We found a negative relationship between home range size and population density in controls; home ranges decreased by 2.5 ha as hare density increased from 0.24 to 1.2 hare/ha. Food-supplemented hares showed a more negative response to population density than controls (4.0 ± 0.56 ha decrease per 1 hare/ha increase). Our results suggest that the negative trend between home range size and population density is not due to confounds between population and resource density. Likely, there is a trade-off between resource acquisition and some other density-driven constraint when foraging at high densities, which we suggest is a reduction in resource sharing to minimize competition and maintain resource familiarity at high densities.

Studying the change in population distribution and density can provide important basis for regional development and planning. The spatial patterns and driving factors of the change in population density in China were not clear yet. Therefore, using the population census data in 2000 and 2010, this study firstly analyzed the change of population density in China and divided the change in all 2353 counties into 4 types, consisting of rapid increase, slow increase, slow decrease and rapid decrease. Subsequently, based on the partial least square (PLS) regression method, we recognized the significant factors (among 11 natural and social-economic factors) impacting population density change for the whole country and counties with different types of population change. The results showed that: (1) compared to the population density in 2000, in 2010, the population density in most of the counties (over 60%) increased by 21 persons per km2 on average, while the population density in other counties decreased by 13 persons per km2. Of all the 2353 counties, 860 and 589 counties respectively showed rapid and slow increase in population density, while 458 and 446 counties showed slow and rapid decrease in population density, respectively. (2) Among the 11 factors, social-economic factors impacted population density change more significantly than natural factors. The higher economic development level, better medical condition and stronger communication capability were the main pull factors of population increase. The dense population density was the main push factor of population decrease. These conclusions clarified the spatial pattern of population change and its influencing factors in China over the past 10 years and could provide helpful reference for the future population planning.

This paper provides the first paleolimnological studies performed in the upper Kama basin (Perm region). These yielded a detailed pollen record characterizing the changes in the natural conditions of the transition from the periglacial environment of the Late Glacial period to the interglacial conditions of the Holocene between 14.15 and 10.0 cal ka BP. It was found that open birch woodland with larch existed in the Allerød period (14.15–12.7 сal ka BP) and was replaced by larch forest-steppe during the Younger Dryas (12.7–11.5 cal ka BP). The spread of spruce began in the early Holocene between 11.5 and 10.7 cal ka BP, whereas open larch and spruce woodlands became dominant between 10.7 and 10.0 cal ka BP. Quantitative palaeoclimatic reconstruction reveals that the average temperature of the warmest month (July) and the annual precipitation were considerably lower than modern values. The average July temperature increased from 10 to 16ºС between 14.15 and 12.7 cal ka BP. Then, small fluctuations within 1ºС occurred between 12.7 and 10.0 cal ka BP. The average annual precipitation was 200-300 mm below modern values between 14.15 and 10.7 cal ka BP and reached them only after 10.7 cal ka BP.

Recent investigations of the Eastern Mediterranean Sea carried out during the GECO cruise with RV Urania provided a substantial number of new cold-water coral (CWC) records, including branching and solitary scleractinian species. These new sites are located along steep escarpments and on topographic highs along the margins of Crete, Karpathos, and Rhodes. The majority of the corals represent fossil occurrences, predominantly Late Pleistocene assemblages. Our research documents that the Eastern Mediterranean Basin has been colonized by CWC at favorable times during the Last Glacial, in particular during the Younger Dryas. Schizocyathus fissilis is reported for the first time for the Mediterranean, while the finding of Ceratotrochus magnaghii represents the first record for the Eastern Mediterranean. Various coral facies occur on the southerly island slopes of Crete, Karpathos, and Rhodes, including hardgrounds and loose skeletal sediments. Hardgrounds occur on steep topographies between ca. 500 and 1,700 m, and can conveniently be subdivided as (1) Neopycnodonte-Desmophyllum framestone, (2) Desmophyllum-Caryophyllia framestone, (3) Madrepora-Lophelia rudstone, (4) Pelagic mudstone and wackestone, and (5) Siliciclastic-carbonate conglomerate and breccia. Unconsolidated skeletal sediments containing corals mainly occur on gentler topographic situations between ca. 140 and 600 m and can be subdivided as: (A) Lophelia-Madrepora rubble, (B) Dendrophyllia rubble, (C) Stenocyathus rubble, (D) Caryophyllia calveri rubble, and (E) fine-grained sediment with octocoral axes. Many of these facies types are also present in the western part of the Mediterranean and have fossil representatives from the Pleistocene to the Recent. Radiocarbon dating (AMS-14C) reveals Younger Dryas ages between 12.4 and 12.0 ka cal BP for Lophelia pertusa and Madrepora oculata. Desmophyllum dianthus occurs during the Last Glacial Maximum (21.8 ka cal BP) and the Younger Dryas (11.7 ka cal BP), as well as during the Late Holocene and subrecent times (4.4–0.6 ka cal BP). Caryophyllia sarsiae occurs during the Late Glacial (15.5 ka cal BP), while Caryophyllia calveri occurs during the Early Preboreal (10.8 ka cal BP). The ages for the framework-constructing corals L. pertusa and M. oculata are coherent with their temporal predominance during the Younger Dryas in other parts of the Mediterranean.

Evidence for a Younger Dryas glacial advance in the Andes of northwestern Venezuela

The peopling of Amazonia: Chrono-stratigraphic evidence from Serranía La Lindosa, Colombian Amazon

Last glacial–Holocene geochronology of sediment cores from a high-altitude Tibetan lake based on AMS 14C dating of plant fossils: Implications for paleoenvironmental reconstructions

Late glacial and Holocene climate in the Kunlun Pass region (northern Tibetan Plateau) inferred from a multi-proxy lake record

ABSTRACTConcentrated food sources are used frequently in white‐tailed deer (Odocoileus virginianus) management and research, but because such food sources are easily defended, aggressive interactions among deer may influence their effectiveness. The objectives of this study were to determine if deer population density or season affect 1) the order or degree of social dominance among different age and sex groups of white‐tailed deer, 2) the rate at which aggressive interactions occur, 3) the severity of interactions, and 4) the extent to which subordinate groups avoid dominant groups. We conducted our study in South Texas using 2 sets of 3, 81‐ha enclosures managed at varying deer population densities. We captured aggressive interactions using digital trail‐cameras placed at sites with spatially concentrated food. We found that bucks ≥2 years of age were dominant over all other age and sex groups in ≥87% of their interactions regardless of deer density or season. The odds of a buck dominating over a doe increased by 10% (95% CI = 0–21%) for each additional deer/km2 during summer, but density had little effect in any other season. Yearling bucks were dominant in 81% (95% CI = 51–100%) of their interactions with does during spring, whereas during other seasons we found no clear order to the dominance hierarchy. Social dominance between yearling bucks and does was not affected by population density. The rate of aggressive interactions increased by 2% (95% CI = 1–3%) for each additional deer/km2 and did not differ by season. Ten percent (95% CI = 6–14%) of interactions involved more violent behaviors that we characterized as severe; this percentage did not change with population density or season. At all population densities, during all seasons, does avoided bucks at sites with concentrated food; however, the degree of avoidance declined with increasing deer density in all seasons except spring. Our results indicate that as population density increases, so do social pressures that may limit access of subordinate age and sex groups to concentrated food sites. Therefore, concentrated food sites are not equally accessible to all age and sex groups of deer and the effectiveness of such sites in deer management and research may become increasingly limited as population density increases. © 2013 The Wildlife Society.

This paper explores the relationship between public transit mode share and population density. It critically reviews the long-held belief that an increase in population density (compact built form) will result in an increase in public transit ridership. The research developed a longitudinal data set of travel behavior, transit supply, and proxies of built form for 1996 and 2016 for the City of Toronto. The data set is spatially disaggregated at the Traffic Analysis Zone (TAZ) level such that the TAZs that divide the City into 480 mutually exclusive and collectively exhaustive zones. The paper found that a cross-sectional analysis of population density and transit mode share captures mostly the contemporaneous relationship between the two and does not, by default, lend credence to the argument that if the density increases over time at a place, it will subsequently result in higher public transit ridership. Such a question will require a longitudinal analysis where the impact of a change in public density over time is examined to determine its impact, if any, on transit ridership. Using Linear Mixed Models for longitudinal data, the paper found that the contemporaneous relation between density and transit mode share holds, but the change in population density over time does not automatically correlate with an increase in transit ridership

High-rise apartment houses have technical and economic advantages in areas with dense population. Their placement in the central part of the city allows increasing the number of living space in the limited territory, to bring population to the place of employment and reduce pendular migration. But increase in population density leads to psychological problems: level of a stress, fatigue increases, the number of phobias grows, infectious diseases extend quicker. These problems can be solved at resettlement of inhabitants to the suburb. However such decision leads to aggravation of a transport problem and the pulsing increase in population density in the downtown and on its suburb. To solve a transport problem, it is necessary not to increase the square of the cities. Therefore in the suburbs is also used high-rise construction. But high-rise residential districts on the suburb of the city get own social problems which are capable to destroy all advantages of high-rise construction.

Transformation of regional vegetation driven by climate change during the last deglacial–early Holocene at Chaohu Lake, eastern China: New pollen insights

Objective. Prior studies of automated external defrillator placement strategies for public access defibrillation (PAD) have addressed only the venue of out-of-hospital cardiac arrest (OOHCA) in large urban areas. This study evaluates the relationship between population density and the incidence and location of OOHCA. Methods. This study was a retrospective analysis of 624,199 Georgia state emergency medical services patient care reports (PCRs) in 2000. The PCR categorized these cardiac arrests by county into 12 location options. Counties were divided into population densities of <100, 100–400, 400–1,000, and >1,000 persons per square mile. The incidence of cardiac arrest for each location type was calculated for each population density group. Results. The <100 density group had only 21.77% of the state's population but 30.96% of the state's cardiac arrests, whereas the >1,000 density group had 35.46% of the population but only 23.55% of the cardiac arrests (p < 0.0001). The relative risk (95% confidence interval) for OOHCA in the <100 density group compared with the >1,000 density group was 2.14 (2.00, 2.29). The percentage of OOHCAs that occurred in the home for each population density group was: <100 persons per square mile, (67.67%); 100–400 persons per square mile, (68.83%); 400–1,000 persons per square mile, (65.75%); and >1,000 persons per square mile (62.09%) (p = 0.0001). Conclusions. There are variations in incidence and location of OOHCA based on population density in Georgia. As population density increases, the incidence percentage of OOHCAs decreases. However, as population density increases, there is an increase in the percentage of cardiac arrests occurring outside the home, where more OOHCAs could potentially benefit from PAD.

In 1962, the Kansas Fish and Game Commission initiated an investigation to determine the effect of semiannual releases of pen-raised bobwhite quail (Colinus virginianus) on population densities of native wild quail populations, on availability of birds to hunters, and on hunter success.Stocking during spring resulted in 7% fewer birds in the fall population on the stocked area than on the control area. Stocking during fall resulted in 14% more birds, at the time hunting season began, on the stocked area than on the control area. Neither of these differences were statistically significant, and it is concluded that there was no significant difference attributable to stocking between population densities of stocked and control areas. On the stocked area, however, there was a significant net increase of 25% in population density between the fall census period and the preseason census period. It is concluded that the density-depressing influence of spring stocking combined with the density-elevating influence of fall stocking, on the stocked area, produced a significant increase, attributable to stocking, between the population density preceding fall release and the population density preceding the hunting season. It is further concluded that in the comparison of preseason population densities for the treatment and control areas, the depressing effect of spring stocking and the elevating effect of fall stocking resulted in a treatment-area population that was significantly larger than that found on the unstacked control area.Some pen-raised birds established themselves as a part of the population on the stocked area, but there was not a proportional increase in population density. There were fewer native quail on the area when treated with semiannual stocking than when under control condition. The difference in density of native birds between stocked and control areas was not statistically significant. Stocking significantly increased hunter success by 30% and 35% on areas in Cherokee and Linn Counties, respectively, but the number of coveys flushed per hour was not significantly increased by stocking pen-raised quail.

Mixotrophic organisms are increasingly recognized as important components of ecosystems, but the factors controlling their nutrition pathways (in particular their autotrophy–heterotrophy balance) are little known. Both autotrophy and heterotrophy are expected to respond to density‐dependent mechanisms but not necessarily in the same direction and/or strength. We hypothesize that the autotrophy–heterotrophy balance of mixotrophic organisms might therefore be a function of population densities. To investigate this relationship, we sampled mixotrophic jellyfish holobionts (host, Mastigias papua etpisoni; symbiont, Cladocopium sp.) in a marine lake (Palau, Micronesia) on six occasions (from 2010 to 2018). Over this period, population densities varied ~100 fold. We characterized the nutrition of the holobionts using the δ13C and δ15N signatures as well as C:N ratios. δ13C values increased and δ15N values decreased with increasing population densities (respectively, R2 = 0.86 and 0.70, P &lt; 0.05). Although less distinct, C:N ratios increased with increasing population densities (R2 = 0.59, 0.1 &gt; P &gt; 0.05). This indicates that the autotrophy–heterotrophy balance tends toward autotrophy when population densities increase. We propose that the availability of zooplanktonic prey is the main driver of this pattern. These results demonstrate that the autotrophy–heterotrophy balance of mixotrophic jellyfishes can be tightly regulated by density‐dependent mechanisms.