Journal articles on the topic 'Tree Population dynamic'
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1
Isaacson, S., S. Rachmilevitch, J. E. Ephrath, S. Maman, and D. G. Blumberg. "MONITORING TREE POPULATION DYNAMICS IN ARID ZONE THROUGH MULTIPLE TEMPORAL SCALES: INTEGRATION OF SPATIAL ANALYSIS, CHANGE DETECTION AND FIELD LONG TERM MONITORING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 21, 2016): 513–15. http://dx.doi.org/10.5194/isprs-archives-xli-b7-513-2016.
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High mortality rates and lack of recruitment in the acacia populations throughout the Negev Desert and the Arava rift valley of Israel have been reported in previous studies. However, it is difficult to determine whether these reports can be evidence to a significant decline trend of the trees populations. This is because of the slow dynamic processes of acaia tree populations and the lack of long term continuous monitoring data. We suggest a new data analysis technique that expands the time scope of the field long term monitoring of trees in arid environments. This will enables us to improve our understanding of the spatial and temporal changes of these populations. <br><br> We implemented two different approaches in order to expand the time scope of the acacia population field survey: (1) individual based tree change detection using Corona satellite images and (2) spatial analysis of trees population, converting spatial data into temporal data. The next step was to integrate the results of the two analysis techniques (change detection and spatial analysis) with field monitoring. This technique can be implemented to other tree populations in arid environments to help assess the vegetation conditions and dynamics of those ecosystems.
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Isaacson, S., S. Rachmilevitch, J. E. Ephrath, S. Maman, and D. G. Blumberg. "MONITORING TREE POPULATION DYNAMICS IN ARID ZONE THROUGH MULTIPLE TEMPORAL SCALES: INTEGRATION OF SPATIAL ANALYSIS, CHANGE DETECTION AND FIELD LONG TERM MONITORING." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 21, 2016): 513–15. http://dx.doi.org/10.5194/isprsarchives-xli-b7-513-2016.
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High mortality rates and lack of recruitment in the acacia populations throughout the Negev Desert and the Arava rift valley of Israel have been reported in previous studies. However, it is difficult to determine whether these reports can be evidence to a significant decline trend of the trees populations. This is because of the slow dynamic processes of acaia tree populations and the lack of long term continuous monitoring data. We suggest a new data analysis technique that expands the time scope of the field long term monitoring of trees in arid environments. This will enables us to improve our understanding of the spatial and temporal changes of these populations. <br><br> We implemented two different approaches in order to expand the time scope of the acacia population field survey: (1) individual based tree change detection using Corona satellite images and (2) spatial analysis of trees population, converting spatial data into temporal data. The next step was to integrate the results of the two analysis techniques (change detection and spatial analysis) with field monitoring. This technique can be implemented to other tree populations in arid environments to help assess the vegetation conditions and dynamics of those ecosystems.
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Beloiu, Mirela, and Carl Beierkuhnlein. "Differences in the Spatial Structure of Two Pinus cembra L. Populations in the Carpathian Mountains." Forests 10, no. 4 (April 11, 2019): 326. http://dx.doi.org/10.3390/f10040326.
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Pinus cembra L. is a key species of high elevation forest ecosystems in Europe. However, in most mountain ranges, its importance has declined considerably. Remnant populations are often isolated and their dynamics and functioning are not well understood. Here, we apply novel approaches in pattern analysis to two P. cembra populations in the Carpathian Mountains in order to identify commonalities and divergences in their spatial structure and dynamics. Four study sites (1.2 ha each) were investigated within the treeline ecotone in two protected areas that differ in terms of protection status. Based on height and diameter, the individuals were classified into three size-classes: sapling, intermediate and adult trees. Spatial distribution and interactions between tree sizes were analyzed using point pattern analysis. The overall structure of all trees was aggregated at a small distance and regular at a greater distance in the population from the Natura 2000 site (p = 0.002), while in the National Park population it was a random pattern. However, the general patterns do not apply to tree size classes and the relationship among them. In the Natura 2000 site, there was no correlation, all the trees were mixed, regardless of their size. In the National Park, the sapling and intermediate were strongly clustered (p = 0.001), but the adult trees were spatially separated from all juveniles, forming patches at a lower elevation. In both areas, spatial patterns indicate the dynamics of the P. cembra population. Whereas in the National Park population, there is evidence of an upward shift, which cannot be confirmed in Natura 2000, where size classes are completely mixed and the dynamic does not translate into an expansion of the population area. The spatial differences between the two populations indicate that conservation strategies need to be developed more individually to support the regeneration of these isolated populations.
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Möller, Simon, Louis du Plessis, and Tanja Stadler. "Impact of the tree prior on estimating clock rates during epidemic outbreaks." Proceedings of the National Academy of Sciences 115, no. 16 (April 2, 2018): 4200–4205. http://dx.doi.org/10.1073/pnas.1713314115.
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Bayesian phylogenetics aims at estimating phylogenetic trees together with evolutionary and population dynamic parameters based on genetic sequences. It has been noted that the clock rate, one of the evolutionary parameters, decreases with an increase in the sampling period of sequences. In particular, clock rates of epidemic outbreaks are often estimated to be higher compared with the long-term clock rate. Purifying selection has been suggested as a biological factor that contributes to this phenomenon, since it purges slightly deleterious mutations from a population over time. However, other factors such as methodological biases may also play a role and make a biological interpretation of results difficult. In this paper, we identify methodological biases originating from the choice of tree prior, that is, the model specifying epidemiological dynamics. With a simulation study we demonstrate that a misspecification of the tree prior can upwardly bias the inferred clock rate and that the interplay of the different models involved in the inference can be complex and nonintuitive. We also show that the choice of tree prior can influence the inference of clock rate on real-world Ebola virus (EBOV) datasets. While commonly used tree priors result in very high clock-rate estimates for sequences from the initial phase of the epidemic in Sierra Leone, tree priors allowing for population structure lead to estimates agreeing with the long-term rate for EBOV.
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Needham, Jessica, Cory Merow, Chia-Hao Chang-Yang, Hal Caswell, and Sean M. McMahon. "Inferring forest fate from demographic data: from vital rates to population dynamic models." Proceedings of the Royal Society B: Biological Sciences 285, no. 1874 (March 7, 2018): 20172050. http://dx.doi.org/10.1098/rspb.2017.2050.
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As population-level patterns of interest in forests emerge from individual vital rates, modelling forest dynamics requires making the link between the scales at which data are collected (individual stems) and the scales at which questions are asked (e.g. populations and communities). Structured population models (e.g. integral projection models (IPMs)) are useful tools for linking vital rates to population dynamics. However, the application of such models to forest trees remains challenging owing to features of tree life cycles, such as slow growth, long lifespan and lack of data on crucial ontogenic stages. We developed a survival model that accounts for size-dependent mortality and a growth model that characterizes individual heterogeneity. We integrated vital rate models into two types of population model; an analytically tractable form of IPM and an individual-based model (IBM) that is applied with stochastic simulations. We calculated longevities, passage times to, and occupancy time in, different life cycle stages, important metrics for understanding how demographic rates translate into patterns of forest turnover and carbon residence times. Here, we illustrate the methods for three tropical forest species with varying life-forms. Population dynamics from IPMs and IBMs matched a 34 year time series of data (albeit a snapshot of the life cycle for canopy trees) and highlight differences in life-history strategies between species. Specifically, the greater variation in growth rates within the two canopy species suggests an ability to respond to available resources, which in turn manifests as faster passage times and greater occupancy times in larger size classes. The framework presented here offers a novel and accessible approach to modelling the population dynamics of forest trees.
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Shen, Yong, Louis S. Santiago, Lei Ma, Guo-Jun Lin, Ju-Yu Lian, Hong-Lin Cao, and Wan-Hui Ye. "Forest dynamics of a subtropical monsoon forest in Dinghushan, China: recruitment, mortality and the pace of community change." Journal of Tropical Ecology 29, no. 2 (February 18, 2013): 131–45. http://dx.doi.org/10.1017/s0266467413000059.
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Abstract:Structure and demographics in many tropical forests is changing, but the causes of these changes remain unclear. We studied 5 y (2005–2010) of species turnover, recruitment, mortality and population change data from a 20-ha subtropical forest plot in Dinghushan, China, to identify trends in forest change, and to test whether tree mortality is associated with intraspecific or interspecific competition. We found the Dinghushan forest to be more dynamic than one temperate and two tropical forests in a comparison of large, long-term forest dynamics plots. Within Dinghushan, size-class distributions were bell-shaped only for the three most dominant species and reverse J-shaped for other species. Bell-shaped population distributions can indicate a population in decline, but our data suggest that these large and long-lived species are not in decline because the pattern is driven by increasing probabilities of transition to larger size class with increasing size and fast growth in saplings. Spatially aggregated tree species distributions were common for surviving and dead individuals. Competitive associations were more frequently intraspecific than interspecific. The competition that induced tree mortality was more associated with intraspecific than interspecific interactions. Intraspecific competitive exclusion and density-dependence appear to play important roles in tree mortality in this subtropical forest.
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Scire, Jérémie, Joëlle Barido-Sottani, Denise Kühnert, Timothy G. Vaughan, and Tanja Stadler. "Robust Phylodynamic Analysis of Genetic Sequencing Data from Structured Populations." Viruses 14, no. 8 (July 27, 2022): 1648. http://dx.doi.org/10.3390/v14081648.
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The multi-type birth–death model with sampling is a phylodynamic model which enables the quantification of past population dynamics in structured populations based on phylogenetic trees. The BEAST 2 package bdmm implements an algorithm for numerically computing the probability density of a phylogenetic tree given the population dynamic parameters under this model. In the initial release of bdmm, analyses were computationally limited to trees consisting of up to approximately 250 genetic samples. We implemented important algorithmic changes to bdmm which dramatically increased the number of genetic samples that could be analyzed and which improved the numerical robustness and efficiency of the calculations. Including more samples led to the improved precision of parameter estimates, particularly for structured models with a high number of inferred parameters. Furthermore, we report on several model extensions to bdmm, inspired by properties common to empirical datasets. We applied this improved algorithm to two partly overlapping datasets of the Influenza A virus HA sequences sampled around the world—one with 500 samples and the other with only 175—for comparison. We report and compare the global migration patterns and seasonal dynamics inferred from each dataset. In this way, we show the information that is gained by analyzing the bigger dataset, which became possible with the presented algorithmic changes to bdmm. In summary, bdmm allows for the robust, faster, and more general phylodynamic inference of larger datasets.
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Widyati, E., M. Siarudin, and Y. Yonky Indrajaya. "The Dynamic of Functional Microbes Community Under Auri (Acacia auriculiformis Cunn. Ex Benth) Agroforestry System." Jurnal Manajemen Hutan Tropika (Journal of Tropical Forest Management) 28, no. 2 (August 9, 2022): 119–27. http://dx.doi.org/10.7226/jtfm.28.2.119.
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Microbes are important rhizosphere constituents for providing nutrients in the soil. This study analyzes the dynamic of soil functional microbes' populations on land managed as an agroforestry (AF) system. The AF system consists of a 2-years old auri tree combined with several crops, i.e., wild grasses, peanuts (Arachis hypogaea), pigeon pea (Cajanus cajan), and maize (Zea mays). Soil samples were collected from each rhizosphere and then analyzed for their chemical properties such as N, P, K, pH, and C organic contents. The population of functional microbes was observed by isolation of the non-symbiotic N-fixer microbes (BNF), the cellulose-degrading microbes (CDM), and the phosphate solubilizing microbes (PSM) in their selective media. The total soil sugars were also tested for root exudates. The results showed that in an auri agroforestry system, the kind of crops determines the content of the soil organic material that is turned-offer into the soil. This affects the population structure and functional microbial abundance in the rhizosphere. Furthermore, microbial colonization in the rhizosphere affects plants in producing root exudates. Then, root exudates shape the structures of the microbial community, as well as an influence among inhabitants in defining mineralization of soil organic matter, nutrient availability, and trees performance.
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Woziwoda, Beata, Katarzyna Pawicka, and Grzegorz J. Wolski. "Charakterystyka lasu grądowego z jodłą w rezerwacie „Jamno”." Biuletyn Szadkowski 12 (December 30, 2012): 127–43. http://dx.doi.org/10.18778/1643-0700.12.07.
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The “Jamno” nature reserve was established to protect the forest community with European silver fir Abies alba Mill. on the northern border of natural occurrence of this tree species in Poland. The results of current phytosociological studies (done in 2011) show that the oak-hornbeam forest – “Tilio-Carpinetum calamagrostietosum” association with “Abies alba”, exist within reserve. The present structure and species composition of studied community is determined by spontaneous changes of tree stand. The different proportion of silver fir in shrub and tree stand layers indicate the dynamic changes within this species population.
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Sinsin, Tudal E. M., Fouad Mounir, and Ahmed El Aboudi. "Conservation, valuation and sustainable development issues of the Argan Tree Biosphere Reserve in Morocco." Environmental & Socio-economic Studies 8, no. 1 (March 1, 2020): 28–35. http://dx.doi.org/10.2478/environ-2020-0004.
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AbstractThe argan tree is a multi-purpose tree (fruit tree, medicinal, cosmetic, and pastoral plant) found in the semi-arid and arid regions of North Africa. It is under strong human pressure such as the impact of population growth, crop expansion, overgrazing, and wood and fruit exploitation that are also the main causes of desertification in the rest of the world. Over the years, interest in this beneficial tree and demand for its products have increased: especially with the increase in the price of argan oil, which is now one of the most expensive and much in demand oils in the world. This increase has led to many socio-political, economic and cultural changes at the national, regional and local levels, especially in farming behaviour and the habits of the local population. This bibliographic research was therefore conducted in order to analyse the various changes and their consequences on the planning, conservation, and management methods implemented in the argan tree area and their effects on the habits of the local population in order to ensure the sustainability of the Argan Tree Biosphere Reserve in Morocco. Indeed, the aims of this study were, firstly, to analyse the change dynamic of argan forest area in the ABR; and secondly, to investigate the impact of various socio-political, economic and cultural changes resulting from increased prices of argan oil on planning, conservation, and management methods of argan tree ecosystem and on the habits of the local population.
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Shegelski, Victor A., Erin O. Campbell, Kirsten M. Thompson, Caroline M. Whitehouse, and Felix A. H. Sperling. "Source and spread dynamics of mountain pine beetle in central Alberta, Canada." Canadian Entomologist 153, no. 3 (February 24, 2021): 314–26. http://dx.doi.org/10.4039/tce.2020.83.
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AbstractThe mountain pine beetle (Dendroctonus ponderosae Hopkins) (Coleoptera: Curculionidae) is a significant destructive force in the pine forests of western Canada and has the capacity to spread east into a novel host tree species, jack pine (Pinaceae). New populations have been documented in central Alberta, Canada, but the source populations for these outbreaks have yet to be identified. In this study, we use genetic data to identify parent populations for recent outbreak sites near Slave Lake, Lac La Biche, and Hinton, Alberta. We found the northern population cluster that entered Alberta near Grande Prairie was the source of the most eastern established population near Lac La Biche, and the range expansion to this leading-edge population has been too rapid to establish evidence of population structure. However, some dispersal from a population in the Jasper and Hinton area has been detected as far north and east as Slave Lake, Alberta. We also identified two potential source populations for the current outbreak in Hinton: most beetles appear to be from Jasper National Park, Alberta, but some also originated from the northern population cluster. These findings demonstrate the dynamic dispersal capabilities of mountain pine beetle across the Alberta landscape and the potential hazard of increased dispersal to newly established leading-edge populations.
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Eliades, Nicolas-George, Filippos Aravanopoulos, and Andreas Christou. "Mediterranean Islands Hosting Marginal and Peripheral Forest Tree Populations: The Case of Pinus brutia Ten. in Cyprus." Forests 9, no. 9 (August 24, 2018): 514. http://dx.doi.org/10.3390/f9090514.
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Mediterranean islands have served as important Tertiary and glacial refuges, hosting important peripheral and ecologically marginal forest tree populations. These populations, presumably harboring unique gene complexes, are particularly interesting in the context of climate change. Pinus brutia Ten. is widespread in the eastern Mediterranean Basin and in Cyprus in particular it is the most common tree species. This study evaluated genetic patterns and morphoanatomical local adaptation along the species geographical distribution and altitudinal range in Cyprus. Analysis showed that the Cyprus population of P. brutia is a peripheral population with high genetic diversity, comprised of different subpopulations. Evidence suggests the presence of ongoing dynamic evolutionary processes among the different subpopulations, while the most relic and isolated subpopulations exhibited a decreased genetic diversity compared to the most compact subpopulations in the central area of the island. These results could be the consequence of the small size and prolonged isolation of the former. Comparing populations along an altitude gradient, higher genetic diversity was detected at the middle level. The phenotypic plasticity observed is particularly important for the adaptive potential of P. brutia in an island environment, since it allows rapid change in local environmental conditions.
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Luo, Xian Hai, and Liang Zhen Li. "Dynamics Automatic Design of Planar Linkage Mechanism Based on Genetic Program." Advanced Materials Research 396-398 (November 2011): 2447–51. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.2447.
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Regarded planar linkage mechanism kinematic target and execution of kinematic pair constraint reaction restrictions as the quantitative objectives, established the comprehensive dynamic design fitness function with the distance between a kinematics target and execution of a set of practical movement points, and the difference between actual constraint reaction of kinematic pair and its limit. According to multi-branch tree expression and random configuration method to create mechanical initial population, driven by the fitness function, made the mechanical population evolution towards the target requirements by the use of copy, crossover and mutation operators of genetic program. In the evolutionary process, inserted kinematics and dynamics automatic analysis technique, design examples indicated that using a genetic program can search parallel in different mechanical configuration space, dimension space and inertia space, automatically searched to such kinds of mechanisms approximate kinematics target and dynamics requirements, thus fulfilling the dynamics automatic design.
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Moore, Caitlin E., Jason Beringer, Bradley Evans, Lindsay B. Hutley, Ian McHugh, and Nigel J. Tapper. "The contribution of trees and grasses to productivity of an Australian tropical savanna." Biogeosciences 13, no. 8 (April 26, 2016): 2387–403. http://dx.doi.org/10.5194/bg-13-2387-2016.
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Abstract. Savanna ecosystems cover 20 % of the global land surface and account for 25 % of global terrestrial carbon uptake. They support one fifth of the world's human population and are one of the most important ecosystems on our planet. Savanna productivity is a product of the interplay between trees and grass that co-dominate savanna landscapes and are maintained through interactions with climate and disturbance (fire, land use change, herbivory). In this study, we evaluate the temporally dynamic partitioning of overstory and understory carbon dioxide fluxes in Australian tropical savanna using overstory and understory eddy covariance measurements. Over a 2-year period (September 2012 to October 2014) the overall net ecosystem productivity (NEP) of the savanna was 506.2 (±22 SE) g C m−2 yr−1. The total gross primary productivity (GPP) was 2267.1 (±80 SE) g C m−2 yr−1, of which the understory contributed 32 %. The understory contribution was strongly seasonal, with most GPP occurring in the wet season (40 % of total ecosystem in the wet season and 18 % in the dry). This study is the first to elucidate the temporal dynamics of savanna understory and overstory carbon flux components explicitly using observational information. Understanding grass productivity is crucial for evaluating fuel loads, as is tree productivity for quantifying the tree carbon sink. This information will contribute to a significant refinement of the representation of savannas in models, as well as improved understanding of relative tree-grass productivity and competition for resources.
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Moore, C. E., J. Beringer, B. Evans, L. B. Hutley, I. McHugh, and N. J. Tapper. "The contribution of trees and grasses to productivity of an Australian tropical savanna." Biogeosciences Discussions 12, no. 23 (December 7, 2015): 19307–50. http://dx.doi.org/10.5194/bgd-12-19307-2015.
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Abstract. Savanna ecosystems cover 20 % of the global land surface and account for 25 % of global terrestrial carbon uptake. They support one fifth of the world's human population and are one of the most important ecosystems on our planet. Savanna productivity is a product of the interplay between trees and grass that co-dominate savanna landscapes and are maintained through interactions with climate and disturbance (fire, land use change, herbivory). In this study, we evaluate the temporally dynamic partitioning of overstory and understory carbon dioxide fluxes in Australian tropical savanna using overstory and understory eddy covariance measurements. Over a two year period (September 2012 to October 2014) the overall net ecosystem productivity (NEP) of the savanna was 506.2 (±22 SE) g C m−2 yr−1. The total gross primary productivity (GPP) was 2267.1 (±80 SE) g C m−2 yr−1, of which the understory contributed 32 %. The understory contribution was strongly seasonal, with most GPP occurring in the wet season (40 % of total ecosystem in the wet season and 18 % in the dry). This study is the first to elucidate the temporal dynamics of savanna understory and overstory carbon flux components explicitly using observational information. Understanding grass productivity is crucial for evaluating fuel loads, as is tree productivity for quantifying the tree carbon sink. This information will contribute to a significant refinement of the representation of savannas in models, as well as improved understanding of relative tree-grass productivity and competition for resources.
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Vinceti, Barbara, Marlène Elias, Rashid Azimov, Muhabbat Turdieva, Sagynbek Aaliev, Farhod Bobokalonov, Evgeniy Butkov, et al. "Home gardens of Central Asia: Reservoirs of diversity of fruit and nut tree species." PLOS ONE 17, no. 7 (July 28, 2022): e0271398. http://dx.doi.org/10.1371/journal.pone.0271398.
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Central Asia is an important center of origin for many globally valued fruit and nut tree species. Forest degradation and deforestation are cause for concern for the conservation of these valuable species, now confined to small remnant populations. Home gardens have the important function of sustaining household food consumption and income generation, and can potentially play a critical role in conserving diversity of fruit and nut trees. These systems have been very poorly documented in the scientific literature. This study contributes to filling this gap by describing the diversity of fruit and nut trees in home gardens of Kyrgyzstan, Uzbekistan, and Tajikistan, examining their dynamic flow of planting material and its sources, understanding their future prospects, and looking at significant differences between the three countries. Home gardens show a similar portfolio of the most abundant tree species (apple, apricot, walnut, pear, and plum). Although the diversity of tree species and varieties recorded is significant, small population sizes can limit future possibilities for this diversity to thrive, given the pressure on natural stands and on habitats where the preferred species are found. Furthermore, the selection of species and varieties to be planted in home gardens is increasingly influenced by market opportunities and availability of exotic material. Some of the most abundant tree species recorded are represented largely by exotic varieties (apple, pear), while others (e.g., apricot, walnut, plum) are still mainly characterized by traditional local varieties that are not formally registered. Home gardens continue to play a critical role in rural livelihoods and in national economies, and many rural inhabitants still aspire to maintain them. Thus, home gardens should be integrated in national research and extension systems and closely linked to national conservation efforts. Changes and possible declines in the diversity they host, their health status, and resilience should be carefully monitored.
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Kornienko, Vladimir Olegovich, and Svetlana Anatolyevna Prikhodko. "A new methodological approach to evaluation of mechanical resistance of green plantings in urban environments." Samara Journal of Science 7, no. 2 (June 15, 2018): 72–77. http://dx.doi.org/10.17816/snv201872114.
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The trees growing in urban environments are exposed to the highest pressure of negative exogenous factors and, consequently, many tree species come to the critical age and become hazardous. A complex approach to evaluate the condition of green plantings under the technogenous load using visual, instrumental, biomechanical etc. methods allows timely and reliable identification of hazardous trees. For this purpose, we developed a new methodology of determining the hazardous degree of trees in residential areas. This method is based on the accounts of tree mechanical hardiness evaluation and up-to-date instrumental research data to be used by municipal services employed in plantings monitoring and care. The main parameters are: age, diameter of the base, diameter at height, trunk girth at the base, trunk girth at a height of 1,3 m, the height of the tree, the angle of inclination of the trunk, the vital status score for Saveleva, morphological damage to the trunk, the description of the crown architectonics, the presence of morphogenetic and exogenous damage to the leaf blade, the population of the trunk pests, the presence of hollows, the wind feature and the loading of this site, the mode of visiting the territory (recreational load), the direction of possible fall, percentage of sound rot, modulus of elasticity of wood, density of wood, the ratio of biomass to critical mass, mechanical resistance to static and dynamic loads according to calculations on biomechanics. In the case study of a model tree (London plane) the applicability of this approach to landscaping practices is shown.
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Khandu, Yeshey, Anan Polthanee, and Supat Isarangkool Na Ayutthaya. "Ecological Dynamics and Regeneration Expansion of Treeline Ecotones in Response to Climate Change in Northern Bhutan Himalayas." Forests 13, no. 7 (July 6, 2022): 1062. http://dx.doi.org/10.3390/f13071062.
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The alpine treeline ecotones are an early indicator of vegetation’s response to changes in climate, and the advancement of diffuse treeline ecotones has been associated with mean annual warming temperatures. However, the knowledge of how tree demographic size, age and population distribution, and regeneration decrease with increasing elevation and mean annual temperature remain fragmentary in Bhutan. There was no explanation of how treelines migrate in response to the climate. Therefore, the objectives of this study were to investigate tree demographic size and age and population distribution, as well as the regeneration expansion of treeline ecotones of Abies densa trees in response to climate change. Demographic data from thirty transect bands from treeline ecotones and reconstructed mean annual temperatures from tree-rings were used. Regression analysis was used to establish a relationship between elevation/temperature and demographic tree size and age, as well as to determine recruitment frequency distributions and whether these could be driven by climate change. The tree demography indicated that the treeline ecotone in our sampling site is temperature limited. Hence, cooler temperatures at higher elevations should drive decreases in basal diameter, age and recruitment frequencies. From the dendroecological analysis, the diffuse treeline ecotones appear to be climbing on average 1.00 m per year in Northern Bhutan. We also found that the recruitment frequency has increased over recent years (1850–2017), as temperatures continue to rise. The thermal treeline ecotones will be likely to serve as a line of bioclimatic reference against which other zones of bioclimate can be defined. With documented responses of treeline ecotones toward mean annual temperatures, the expectation is that additional warming will continue to influence regeneration expansion in the future. This dynamic response of treeline ecotones towards the climate acts as an indicator of climate change. Information about climbing treelines and altered ecotones should be a vital part of the material for decision makers to consider, to assess impacts and threats to Himalayan alpine biota.
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Zhou, Tong, Xiao-Juan Huang, Shou-Zhou Zhang, Yuan Wang, Ying-Juan Wang, Wen-Zhe Liu, Ya-Ling Wang, Jia-Bin Zou, and Zhong-Hu Li. "Population Demographic History of a Rare and Endangered Tree Magnolia sprengeri Pamp. in East Asia Revealed by Molecular Data and Ecological Niche Analysis." Forests 12, no. 7 (July 16, 2021): 931. http://dx.doi.org/10.3390/f12070931.
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Quaternary climate and environment oscillations have profoundly shaped the population dynamic history and geographic distributions of current plants. However, how the endangered and rare tree species respond to the climatic and environmental fluctuations in the subtropical regions of China in East Asia still needs elucidation. In this study, we collected 36 natural populations of an endangered and rare tree species Magnolia sprengeri Pamp. in subtropical China to determine the demographic history, and modeled the changes of geographic distributions of this species in East Asia based on the MaxEnt ecological niche analyses. In addition, we sequenced three maternally inherited chloroplast DNA fragments (matK, trnH-psbA, and rbcL) for all the natural populations which covered the whole geographic distributions of M. sprengeri. Population genetic analysis showed that the endangered tree species have a low level of chloroplast DNA diversity. However, the genetic variation contribution within populations was greater than that among populations (FST = 0.276), which demonstrated a high level of genetic differentiation. Interestingly, some unique chloroplast DNA haplotypes and higher genetic variations were identified in the Qinling-Daba Mountains, Central China, and Tianmu Mountains of Zhejiang province, East of China in East Asia. Combining with the species distribution modeling, we speculated that these areas might be the potential glacial refugia for the endangered plant M. sprengeri. Phylogeographic analysis demonstrated that the geographic factors (e.g., mountains, rivers, and other isolation barriers) had little effect on the genetic divergence among populations. Ecological niche modeling further revealed that the natural populations of M. sprengeri did not experience significant geographic distribution changes from the last glacial maximum to the present time. These findings are in line with the analysis results of the multimodal mismatch patterns of the chloroplast DNA variations. To protect the endangered species M. sprengeri, in situ and ex situ conservation strategies should be formulated for the natural populations with higher genetic variations.
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Pacala, Stephen W., Charles D. Canham, and J. A. Silander Jr. "Forest models defined by field measurements: I. The design of a northeastern forest simulator." Canadian Journal of Forest Research 23, no. 10 (October 1, 1993): 1980–88. http://dx.doi.org/10.1139/x93-249.
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We introduce a new spatially explicit model of forest dynamics. The model is constructed from submodels that predict an individual tree's growth, survival, dispersal, and recruitment, and submodels that predict the local availability of resources. Competition is entirely mechanistic; plants interfere with one another only by depleting resources. We also describe maximum likelihood methods for estimating each of the submodels from data collected in the field. Over the past two years, we collected the necessary data for the dominant tree species in the Great Mountain Forest (Norfolk, Conn.). We report estimates of submodels for each species, and show that the calibrated population dynamic model predicts the structure and dynamics of natural forests. Finally, we contrast our model with the JABOWA–FORET family of forest models.
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Di Filippo, Alfredo, Michele Baliva, Michele Brunetti, and Luca Di Fiore. "Long-Term Tree-Ring Response to Drought and Frost in Two Pinus halepensis Populations Growing under Contrasting Environmental Conditions in Peninsular Italy." Forests 12, no. 3 (March 6, 2021): 305. http://dx.doi.org/10.3390/f12030305.
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Pinus halepensis dominates coastal to mountain areas throughout the Mediterranean Basin. Its growth plasticity, based on polycyclic shoot formation and dynamic cambial activity, and tolerance to extreme drought and exceptional frosts, allows it to colonize a vast array of environments. We used tree-rings from codominant pines to compare lifespan, growth rates, age and size distribution in a typical coastal (i.e., prolonged drought, occasional low-intensity fires) vs. inland hilly (i.e., moister conditions, recurrent frosts) population. BAI trends, growth-limiting climate factors and tree-ring anatomical anomalies were analyzed considering the differences in climate and phenology obtained from multispectral satellite images. The species maximum lifespan was 100–125 years. Mortality was mainly due to fire on the coast, or heart-rot in the inland site. Populations differed in productivity, which was maintained over time despite recent warming. Site conditions affected the growing season dynamics, the control over ring formation by summer drought vs. winter cold and the frequency of anatomical anomalies. Recurrent frost rings, associated with temperatures below −10 °C, occurred only at the inland site. Pinus halepensis confirmed its remarkable growth plasticity to diverse and variable environmental conditions. Its ability to survive extreme events and sustain productivity confirmed its adaptability to climate change in coastal areas as well as on Mediterranean mountains.
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Tan, Siqiao, Yu Liang, Ruowen Zheng, Hongjie Yuan, Zhengbing Zhang, and Chenfeng Long. "Dynamic Prediction of Chilo suppressalis Occurrence in Rice Based on Deep Learning." Processes 9, no. 12 (December 1, 2021): 2166. http://dx.doi.org/10.3390/pr9122166.
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(1) Background: The striped rice stem borer (SRSB), Chilo suppressalis, has severely diminished the yield and quality of rice in China. A timely and accurate prediction of the rice pest population can facilitate the designation of a pest control strategy. (2) Methods: In this study, we applied multiple linear regression (MLR), gradient boosting decision tree (GBDT), and deep auto-regressive (DeepAR) models in the dynamic prediction of the SRSB population occurrence during the crop season from 2000 to 2020 in Hunan province, China, by using weather factors and time series of related pests. (3) Results: This research demonstrated the potential of the deep learning method used in integrated pest management through the qualitative and quantitative evaluation of a reasonable validating dataset (the average coefficient of determination Rmean2 for the DeepAR, GBDT, and MLR models were 0.952, 0.500, and 0.166, respectively). (4) Conclusions: The DeepAR model with integrated ground-based meteorological variables, time series of related pests, and time features achieved the most accurate dynamic forecasting of the population occurrence quantity of SRSB as compared with MLR and GBDT.
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Röhr, David L., Felipe Camurugi, Gustavo B. Paterno, Marcelo Gehara, Flora A. Juncá, Guilherme F. R. Álvares, Reuber A. Brandão, and Adrian A. Garda. "Variability in anuran advertisement call: a multi-level study with 15 species of monkey tree frogs (Anura, Phyllomedusidae)." Canadian Journal of Zoology 98, no. 8 (August 2020): 495–504. http://dx.doi.org/10.1139/cjz-2020-0018.
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Understanding the variability of acoustic signals is a first important step for the comprehension of the evolutionary processes that led to current diversity. Herein, we evaluate the variability of the advertisement call of the phyllomedusid species from the genera Phyllomedusa Wagler, 1830 and Pithecopus Cope, 1866 at different levels: intra-individual, intra-population, inter-population, intra-species, and inter-specific. An analysis of coefficients of variation showed a continuum of variability between the acoustic parameters analyzed, from static to highly dynamic. The majority of the variation was attributed to the inter-specific level, while call parameters at the intra-individual level varied the least. However, each parameter behaved differently with call interval being the most variable across all levels. Most temporal acoustic parameters were affected by environmental temperature, while pulse rate and dominant frequency were strongly influenced by body size. Only pulse rate was correlated to the geographic distance between populations, while all parameters presented a significant phylogenetic signal. Based on these results, we discuss the possible importance of different evolutionary forces and the usage of vocalizations for taxonomic purposes.
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Vaughan, Timothy G., Gabriel E. Leventhal, David A. Rasmussen, Alexei J. Drummond, David Welch, and Tanja Stadler. "Estimating Epidemic Incidence and Prevalence from Genomic Data." Molecular Biology and Evolution 36, no. 8 (May 6, 2019): 1804–16. http://dx.doi.org/10.1093/molbev/msz106.
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Abstract Modern phylodynamic methods interpret an inferred phylogenetic tree as a partial transmission chain providing information about the dynamic process of transmission and removal (where removal may be due to recovery, death, or behavior change). Birth–death and coalescent processes have been introduced to model the stochastic dynamics of epidemic spread under common epidemiological models such as the SIS and SIR models and are successfully used to infer phylogenetic trees together with transmission (birth) and removal (death) rates. These methods either integrate analytically over past incidence and prevalence to infer rate parameters, and thus cannot explicitly infer past incidence or prevalence, or allow such inference only in the coalescent limit of large population size. Here, we introduce a particle filtering framework to explicitly infer prevalence and incidence trajectories along with phylogenies and epidemiological model parameters from genomic sequences and case count data in a manner consistent with the underlying birth–death model. After demonstrating the accuracy of this method on simulated data, we use it to assess the prevalence through time of the early 2014 Ebola outbreak in Sierra Leone.
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Rico, Yessica, M. Ángel León-Tapia, Marisol Zurita-Solís, Flor Rodríguez-Gómez, and Suria Gisela Vásquez-Morales. "Influence of Pleistocene climatic oscillations on the phylogeography and demographic history of endemic vulnerable trees (section Magnolia) of the Tropical Montane Cloud Forest in Mexico." PeerJ 9 (September 28, 2021): e12181. http://dx.doi.org/10.7717/peerj.12181.
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The Tropical Montane Cloud Forest (TMCF) is a highly dynamic ecosystem that has undergone frequent spatial changes in response to the interglacial-glacial cycles of the Pleistocene. These climatic fluctuations between cold and warm cycles have led to species range shifts and contractions-expansions, resulting in complex patterns of genetic structure and lineage divergence in forest tree species. In this study, we sequenced four regions of the chloroplast DNA (trnT-trnL, trnK5-matk, rpl32-trnL, trnS-trnG) for 20 populations and 96 individuals to evaluate the phylogeography, historical demography, and paleodistributions of vulnerable endemic TMCF trees in Mexico: Magnolia pedrazae (north-region), M. schiedeana (central-region), and M. schiedeana population Oaxaca (south-region). Our data recovered 49 haplotypes that showed a significant phylogeographic structure in three regions: north, central, and south. Bayesian Phylogeographic and Ecological Clustering (BPEC) analysis also supported the divergence in three lineages and highlighted the role of environmental factors (temperature and precipitation) in genetic differentiation. Our historical demography analyses revealed demographic expansions predating the Last Interglacial (LIG, ~125,000 years ago), while Approximate Bayesian Computation (ABC) simulations equally supported two contrasting demographic scenarios. The BPEC and haplotype network analyses suggested that ancestral haplotypes were geographically found in central Veracruz. Our paleodistributions modeling showed evidence of range shifts and expansions-contractions from the LIG to the present, which suggested the complex evolutionary dynamics associated to the climatic oscillations of the Pleistocene. Habitat management of remnant forest fragments where large and genetically diverse populations occur in the three TMCF regions analyzed would be key for the conservation of these magnolia populations.
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Aliyu, Muhammad, Murali M, Abdulsalam Y. Gital, and Souley Boukari. "Efficient Metaheuristic Population-Based and Deterministic Algorithm for Resource Provisioning Using Ant Colony Optimization and Spanning Tree." International Journal of Cloud Applications and Computing 10, no. 2 (April 2020): 1–21. http://dx.doi.org/10.4018/ijcac.2020040101.
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Resource provisioning is the core function of cloud computing which is faced with serious challenges as demand grows. Several strategies of cloud computing resources optimization were considered by many researchers. Optimization algorithms used are still under reckoning and modification so as to enhance their potentials. As such, a dynamic scheme that can combine several algorithms' characteristics is required. Quite a number of optimization techniques have been reassessed based on metaheuristics and deterministic to map out with the challenges of resource provisioning in the Cloud. This research work proposes to involve the ant colony optimization (ACO) population-based mechanism by extending it to form a hybrid meta-heuristic through deterministic spanning tree (SPT) algorithm incorporation. Extensive experiment conducted in the cloudsim simulator provided an efficient result in terms of faster convergence, and makespan time minimization as compared to other population-based and deterministic algorithms as it significantly improves performance.
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Wong, Chi Wah, Chen Chen, Lorenzo A. Rossi, Monga Abila, Janet Munu, Ryotaro Nakamura, and Zahra Eftekhari. "Explainable Tree-Based Predictions for Unplanned 30-Day Readmission of Patients With Cancer Using Clinical Embeddings." JCO Clinical Cancer Informatics, no. 5 (February 2021): 155–67. http://dx.doi.org/10.1200/cci.20.00127.
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PURPOSE Thirty-day unplanned readmission is one of the key components in measuring quality in patient care. Risk of readmission in oncology patients may be associated with a wide variety of specific factors including laboratory results and diagnoses, and it is hard to include all such features using traditional approaches such as one-hot encoding in predictive models. METHODS We used clinical embeddings to represent complex medical concepts in lower dimensional spaces. For predictive modeling, we used gradient-boosted trees and adopted the shapley additive explanation framework to offer consistent individualized predictions. We used retrospective inpatient data between 2013 and 2018 with temporal split for training and testing. RESULTS Our best performing model predicting readmission at discharge using clinical embeddings showed a testing area under receiver operating characteristic curve of 0.78 (95% CI, 0.77 to 0.80). Use of clinical embeddings led to up to 23.1% gain in area under precision-recall curve and 6% in area under receiver operating characteristic curve. Hematology models had more performance gain over surgery and medical oncology. Our study was the first to develop (1) explainable predictive models for the hematology population and (2) dynamic models to keep track of readmission risk throughout the duration of patient visit. CONCLUSION To our knowledge, our study was the first to develop (1) explainable predictive models for the hematology population and (2) dynamic models to keep track of readmission risk throughout the duration of patient visit.
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He, Chunmei, Shihong Jia, Ying Luo, Zhanqing Hao, and Qiulong Yin. "Spatial Distribution and Species Association of Dominant Tree Species in Huangguan Plot of Qinling Mountains, China." Forests 13, no. 6 (May 31, 2022): 866. http://dx.doi.org/10.3390/f13060866.
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The spatial distribution pattern and population structure of trees are shaped by multiple processes, such as species characteristics, environmental factors, and intraspecific and interspecific interactions. Studying the spatial distribution patterns of species, species associations, and their relationships with environmental factors is conducive to uncovering the mechanisms of biodiversity maintenance and exploring the underlying ecological processes of community stability and succession. This study was conducted in a 25-ha Qinling Huangguan forest (warm-temperate, deciduous, broad-leaved) dynamic monitoring plot. We used univariate and bivariate g(r) functions of the point pattern analysis method to evaluate the spatial distribution patterns of dominant tree species within the community, and the intra- and interspecific associations among different life-history stages. Complete spatial randomness and heterogeneous Poisson were used to reveal the potential process of community construction. We also used Berman’s test to determine the effect of three topographic variables on the distribution of dominant species. The results indicated that all dominant species in this community showed small-scale aggregation distribution. When we excluded the influence of environmental heterogeneity, the degree of aggregation distribution of each dominant species tended to decrease, and the trees mainly showed random or uniform distribution. This showed that environmental heterogeneity significantly affects the spatial distribution of tree species. Dominant species mainly showed positive associations with one another among different life-history stages, while negative associations prevailed among different tree species. Furthermore, we found that the associations between species were characterized by interspecific competition. Berman’s test results under the assumption of complete spatial randomness showed that the distribution of each dominant species was mainly affected by slope and convexity.
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Ortiz-Quijano, Adriana Beatriz, Arturo Sánchez-González, Lauro López-Mata, and José Villanueva-Díaz. "Population structure of Fagus grandifolia subsp. mexicana in the cloud forest of Hidalgo State, Mexico." Botanical Sciences 94, no. 3 (September 8, 2016): 483. http://dx.doi.org/10.17129/botsci.515.
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The highest densities and largest areas of <em>Fagus grandifolia</em> subsp. <em>mexicana</em> in Mexico grow in the cloud forest of the state of Hidalgo. Although this taxon is endangered, there is little information about its population structure. This study provides data on the structure of heights, diameters and ages of <em>Fagus</em> in three populations in Hidalgo. Additionally, information was obtained on the structure of the beech forests, whose canopy is dominated by <em>Fagus</em>. At each locality, three to five 400 m<sup>2</sup> sample plots, depending on the size of the respective forest, were randomly selected. Within each plot, density and basal area of each species of tree and shrub with diameter greater than 2.5 cm (1.30 m) were estimated. At the species level, populations are dynamic, with a high percentage of young individuals; however, at one of the localities, changes have occurred in the last decade due to anthropogenic activity, and the structure of sizes and diameters in the youngest age categories has changed. Diameter was a good indicator of the age of the trees. At the community level, the dominance of <em>Fagus</em> and other species differed between localities, which is probably related to the degree of disturbance. Population and community structure are related and could be considered as indicators of changes in environmental conditions in the recent past and today.
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Bauerle, Taryn L., and Michela Centinari. "Assessment of Root System Development among Four Ornamental Tree Species through Time via X-ray Computed Tomography." HortScience 49, no. 1 (January 2014): 44–50. http://dx.doi.org/10.21273/hortsci.49.1.44.
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Tree root systems are inherently dynamic in their distribution within a soil volume. Analysis of tree root system space occupation through time can improve not only our implicit understanding of a virtually hidden portion of a plant, but influence future management decisions through a more thorough understanding of root placement within a soil volume. We compared root standing crop populations of four ornamental tree species including Acer rubrum L. ‘Franksred’ (Acer), Carpinus betula L. ‘Columnaris’ (Carpinus), Gleditsia tricanthos L. var. inermis ‘Skycole’ (Gleditsia), and Quercus rubra L. ‘Rubrum’ (Quercus) grown in a nursery mix substrate within large 57-L containers using an X-ray computed tomography (CT) approach through time. Individual root identification was performed manually on two-dimensional slices of CT scans. Our data show high variation in species total root number through time with Carpinus exhibiting the largest root population throughout the study period. However, species exhibited differences in root distribution patterns as exemplified by the shallow and horizontally more uniform rooting pattern of Acer in comparison with the highly plastic root distribution in space through time in Gleditsia. Root frequencies within 1-mm root diameter class distributions shifted by species with the most drastic differences found between high frequencies of relatively small diameter roots in Acer vs. pronounced shifts in dominate root diameter size class as found in Gleditsia and lesser so in Carpinus during a growing season. Our findings demonstrate differences in whole tree root systems space occupation non-destructively through time and highlight a disparity in how species fill a container volume during growth.
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Zambrano-Navea, Castor, Fernando Bastida, and Jose L. Gonzalez-Andujar. "A cohort-based stochastic model of the population dynamic and long-term management of Conyza bonariensis in fruiting tree crops." Crop Protection 80 (February 2016): 15–20. http://dx.doi.org/10.1016/j.cropro.2015.10.023.
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Yao, Liangjin, Yuanke Xu, Bo Jiang, Chuping Wu, Weigao Yuan, Jinru Zhu, Tingting Li, and Zhigao Wang. "Competition Restricts the Growth, Development, and Propagation of Carpinus tientaiensis: A Rare and Endangered Species in China." Forests 12, no. 4 (April 17, 2021): 503. http://dx.doi.org/10.3390/f12040503.
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The protection and propagation of rare and endangered species are key to the preservation of their population development; however, due to the scarcity of individuals, the potential effects and status of rare and endangered species in the whole forest ecosystem are still poorly understood. Using data from a 60 × 140 m forest dynamic monitoring sample of the Carpinus tientaiensis (Betulaceae) species in Zhejiang of Southeast China. We assessed the population distribution and diameter at breast height (DBH) structure of the Carpinus tientaiensis species, which was a rare and endangered species, as well as intra- and interspecific correlation with other species. The results show that saplings (1 cm ≤ DBH < 5 cm) and juveniles (5 cm ≤ DBH < 10 cm) were more aggregated than larger individuals (DBH ≥ 20 cm) of Carpinus tientaiensis. The DBH size structure of all the trees shows an obvious inverted “J” distribution. With an increase in the DBH size category, the number of individuals gradually decreases. Due to the diffusion limitation, the spatial distribution patterns of all the tree individuals and roof geese in the sample land are increased at a small spatial scale, and as the spatial scale increases, the degree of aggregation decreases gradually. The relationship between different diameter stages of the population of Carpinus tientaiensis showed a consistent general trend. The spatial distribution of individuals with a large diameter on a small scale was significantly positively correlated (p < 0.001). With an increase in the scale, there was no significant correlation (p > 0.05) between individuals with a large diameter and individuals with a small diameter. There was no significant correlation (p > 0.05) between the population of Carpinus tientaiensis and other species in the sample, and the strong unidirectional competition of other species in the sample can be seen by the competition index. We found that interspecific competition restricts the growth and expansion of Carpinus tientaiensis, and it has adopted different ecological strategies to coexist with a population of common tree species occupying a similar living space.
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Gaire, N. P., M. Koirala, D. R. Bhuju, and H. P. Borgaonkar. "Treeline dynamics with climate change at the central Nepal Himalaya." Climate of the Past 10, no. 4 (July 4, 2014): 1277–90. http://dx.doi.org/10.5194/cp-10-1277-2014.
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Abstract. Treeline shifting in tandem with climate change has widely been reported from various parts of the world. In Nepal, several impacts of climate change on the physical environment have been observed, but study on the biological impacts is lacking. This dendrochronological study was carried out at the treeline in the high mountain slope of Kalchuman Lake (3750–4003 m a.s.l.) area of Manaslu Conservation Area in the central Nepal Himalaya to explore the impact of climate change on the treeline dynamic. Two belt transect plots (size: 20 m wide, > 250 m long) were laid which included treeline as well as tree species limit. Ecological mapping of all individuals of dominant trees Abies spectabilis and Betula utilis was done and their tree cores were collected. Stand character and age distribution revealed an occurrence of more matured B. utilis (max. age 198 years) compared to A. spectabilis (max. age 160 years). A. spectabilis contained an overwhelmingly high population (89%) of younger plants (< 50 years) indicating its high recruitment rate. Population age structure along the elevation gradient revealed an upward shifting of A. spectabilis at the rate of 2.61 m year-1 since AD 1850. The upper distribution limit of B. utilis was found to be stagnant in the past few decades. An increment in plant density as well as upward shifting in the studied treeline ecotones was observed. The temporal growth of A. spectabilis was correlated negatively with the monthly mean and minimum temperature of June to September of the current and previous year. The regeneration of A. spectabilis, on the other hand, was positively correlated with August precipitation and monthly maximum temperature of the month of the current year. The growth and regeneration of A. spectabilis was more sensitive to maximum and minimum temperature rather than average temperature. The growth of the B. utilis was mainly limited by moisture stress during the pre-monsoon season. As these two species presented species-specific responses to climate change with differential pattern in regeneration condition, much wider differences are anticipated in their population status as climate continues to change throughout the century.
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Goldschmidt, Eliezer E. "Carbohydrate Supply as a Limiting Factor for Citrus Fruit Growth and Productivity." HortScience 32, no. 3 (June 1997): 550E—551. http://dx.doi.org/10.21273/hortsci.32.3.550e.
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Carbohydrates fulfill several roles in plants; as building stones, as a source of energy, and also, as recently demonstrated, as modulators of gene expression. Primary, photosynthetic production of carbohydrates (as well as their release from tree reserves) is linked with the carbohydrate-consuming processes through complex feedback and feedforward regulatory loops. With horticultural productivity as the goal, maximum resources must be diverted toward reproductive processes. Persistence of viable vegetative structures must be secured, however, to enable the function of tree systems and ensure the tree's potential for future years. Thus, in the carbohydrate resource allocation of fruit trees, a delicate balance must be maintained between the vegetative and reproductive needs. Flowering, fruit set, and fruit enlargement have been identified as three distinct, critical stages within the annual course of yield formation in citrus. While each of these stages has its own, salient developmental features, all require considerable amounts of energy and their occurrence is dependent, at least to some extent, on the availability of carbohydrates. Whereas flower bud differentiation may require only a threshold level of carbohydrates, floral development and anthesis consume large amounts of carbohydrates due to the very large number of flowers per tree and their high rates of respiration. Fruit set is more closely linked to carbohydrate levels. Fruitlet abscission acts as a self-thinning, feedback mechanism to adjust the tree's fruit population to the carbohydrate supply. This mechanism does not operate properly in certain mandarin cultivars, resulting in alternate bearing. The acquisition of fruit size appears to be most directly correlated with the availability of photosynthate. Elimination of alternative sinks by extreme thinning and girdling brings about tremendous increases in fruit size. The fruit's vascular system also expands in response to the increase in photosynthate availability. A dynamic model has been constructed to provide a quantitative analysis of citrus trees' carbon balance during the annual productivity cycle.
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Zhao, Ji, Yi Fu, and Juan Mei. "An improved dynamic cooperative random drift particle swarm optimization algorithm based on search history decision." Journal of Algorithms & Computational Technology 14 (January 2020): 174830262097353. http://dx.doi.org/10.1177/1748302620973537.
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A novel dynamic cooperative random drift particle swarm optimization algorithm based on entire search history decision (CRDPSO) is reported. At each iteration, the positions and the fitness values of the evaluated solutions in the algorithm are stored by a binary space partitioning tree structure archive, which leads to a fast fitness function approximation. The mutation is adaptive and parameter-less because of the fitness function approximation enhancing the mutation strategy. The dynamic cooperation between the particles by using the context vector increases the population diversity helps to improve the search ability of the swarm and cooperatively searches for the global optimum. The performance of CRDPSO is tested on standard benchmark problems including multimodal and unimodal functions. The empirical results show that CRDPSO outperforms other well-known stochastic optimization methods.
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Gaire, N. P., M. Koirala, D. R. Bhuju, and H. P. Borgaonkar. "Treeline dynamics with climate change at Central Nepal Himalaya." Climate of the Past Discussions 9, no. 5 (October 28, 2013): 5941–76. http://dx.doi.org/10.5194/cpd-9-5941-2013.
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Abstract. Global climate change has multidimensional impacts with several biological fingerprints, and treeline shifting in tandem with climate change is a widely observed phenomenon in various parts of the world. In Nepal several impacts of climate change on physical environments have been observed. However, studies on the biological impacts are lacking. This dendrochronological study was carried out at the treeline ecotone (3750–4003 m a.s.l.) in the Kalchuman Lake (Kal Tal) area of the Manaslu Conservation Area in central Nepal Himalaya with the aim to study the dynamic impact of climate change at the treeline. The study provides an insight into regeneration and treeline dynamics over the past 200 yr. Two belt transect plots (size: 20 m wide, >250 m long) were laid covering forest line, treeline as well as tree species Abies spectabilis and Betula utilis was done and their tree-cores were collected. Stand character and age distribution revealed an occurrence of more matured B. utilis (max. age 198 yr old) compared to A. spectabilis (max. age 160 yr). A. spectabilis contained an overwhelmingly high population (89%) of younger plants (<50 yr) indicating its high recruitment rate. Population age structure along an elevation gradient revealed an upward shifting of A. spectabilis at the rate of 2.61 m yr−1 since 1850 AD. The upper distribution limit of B. utilis was found stagnant in the past few decades. An increment in plant density as well as upward shifting in the studied treeline ecotones was observed. Thus, two species presented species-specific responses to climate change and much wider differences anticipated in their population status as climate continues to cha spectabilis correlated negatively with the mean monthly temperature of May–August of the current year and with September of the previous year. The regeneration of A. spectabilis, on the other hand, was positively related with May–August precipitation and January–April temperature of the current year. The reconstructed average summer temperature (May–August) using tree ring data revealed alternate period of cool and warm period with warming in the 2nd half of the 20th century. Further palynological and geochronological studies of sediments of the Kalchuman Lake would advance our understanding of past climatic trends and dynamics of the associated treeline and vegetation in the area.
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Yanchuk, Alvin D. "A quantitative framework for breeding and conservation of forest tree genetic resources in British Columbia." Canadian Journal of Forest Research 31, no. 4 (April 1, 2001): 566–76. http://dx.doi.org/10.1139/x00-133.
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Over the last decade, forest tree breeders have become aware of the need for gene conservation, but have struggled with methods that would meaningfully integrate breeding and conservation populations. Gene Namkoong has provided the most guidance in this area by defining the role of in- and ex-situ populations in forest tree gene resource management and, particularly, the need for this to be dynamic in time and space. However, once conservation plans for individual species in British Columbia were considered, it became clear that more quantitative structure was needed to provide a framework for attaining practical management objectives. This paper attempts to provide such a framework and show how breeding and conservation populations can be integrated into a continuum of genetic resources. First, capturing only one copy of an allele is likely not satisfactory to meet conservation objectives, and sampling targets should be set higher (e.g., 20) so as to avoid potential problems of inbreeding at later stages in the program. Second, there seems to be a large problem with conserving very low frequency alleles that are recessive, but this occurs in nature as well. Third, in situ populations should be large enough and in a state to persist on their own over several generations, so the more recent effective population size numbers proposed by Lynch (1996) (i.e., ~1000) need to be considered. Fourth, while breeding populations of moderate size (~80) will contain adequate amounts of quantitative genetic variation, they will also contain 20 copies of dominant alleles at frequencies of ~0.20 or higher. Fifth, maintaining and rejuvenating strategic ex-situ test populations now seems to be the only way to conserve low- to mid-frequency alleles that will (i) be reduced in progressive breeding populations by drift and, (ii) over time, not be in desirable genetic backgrounds in in situ populations. Sixth, any reliance on locating mutants in production populations seems generally remote and cannot be relied upon except in a very few situations, although mutation will be important in breeding and in reserves in situ.
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Polo-Cavia, Nuria, José Miguel Oliveira, Alberto José Redondo Villa, and Rafael Márquez. "Background colour matching in a wild population of Alytes obstetricans." Amphibia-Reptilia 37, no. 3 (2016): 253–60. http://dx.doi.org/10.1163/15685381-00003050.
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The capacity for physiological colour change has long been described in anuran amphibians. Camouflage against predators seems to be the most relevant function of dynamic changes in skin colour of frogs, but key aspects such as the rate at which these changes occur, or the specific colour components involved are not completely clear. Whereas most research on the topic has been reported on tree frogs in laboratory conditions, studies in other anurans or in the field are much scarcer. Here we show a potentially plastic, adaptive response in coloration of common midwife toads, Alytes obstetricans, from a population of central Portugal, whose pigmentation varied with their natural backgrounds. Using quantitative image analysis, we compared hue, saturation and brightness of dorsal skin coloration of toads and the colour of the area of ground immediately around them. We found a positive correlation between coloration of toads and background colour for the three components of the colour. As well as other anuran species, A. obstetricans might adjust skin coloration to match the surrounding environment, thus benefitting from short-term reversible crypsis strategies against predators. A less supported hypothesis would be that toads accurately select matching backgrounds to improve concealment as an antipredatory strategy.
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Lin, Du, Bo Shen, Yurong Liu, Fuad E. Alsaadi, and Ahmed Alsaedi. "Genetic algorithm-based compliant robot path planning: an improved Bi-RRT-based initialization method." Assembly Automation 37, no. 3 (August 7, 2017): 261–70. http://dx.doi.org/10.1108/aa-12-2016-173.
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Purpose The purpose of this paper is to improve the performance of the genetic algorithm-based compliant robot path planning (GACRPP) in complex dynamic environment by proposing an improved bidirectional rapidly exploring random tree (Bi-RRT)-based population initialization method. Design/methodology/approach To achieve GACRPP in complex dynamic environment with high performance, an improved Bi-RRT-based population initialization method is proposed. First, the grid model is adopted to preprocess the working space of mobile robot. Second, an improved Bi-RRT is proposed to create multi-cluster connections between the starting point and the goal point. Third, the backtracking method is used to generate the initial population based on the multi-cluster connections generated by the improved Bi-RRT. Subsequently, some comparative experiments are implemented where the performances of the improved Bi-RRT-based population initialization method are compared with other population initialization methods, and the comparison results of the improved genetic algorithm (IGA) combining with the different population initialization methods are shown. Finally, the optimal path is further smoothed with the help of the technique of quadratic B-spline curves. Findings It is shown in the experiment results that the improved Bi-RRT-based population initialization method is capable of deriving a more diversified initial population with less execution time and the IGA combining with the proposed population initialization method outperforms the one with other population initialization methods in terms of the length of optimal path and the execution time. Originality/value In this paper, the Bi-RRT is introduced as a population initialization method into the GACRPP problem. An improved Bi-RRT is proposed for the purpose of increasing the diversity of initial population. To characterize the diversity of initial population, a new notion of breadth is defined in terms of Hausdorff distance between different paths.
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Wang, Danping, Kunyuan Hu, Lianbo Ma, Maowei He, and Hanning Chen. "Multispecies Coevolution Particle Swarm Optimization Based on Previous Search History." Discrete Dynamics in Nature and Society 2017 (2017): 1–22. http://dx.doi.org/10.1155/2017/5193013.
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A hybrid coevolution particle swarm optimization algorithm with dynamic multispecies strategy based on K-means clustering and nonrevisit strategy based on Binary Space Partitioning fitness tree (called MCPSO-PSH) is proposed. Previous search history memorized into the Binary Space Partitioning fitness tree can effectively restrain the individuals’ revisit phenomenon. The whole population is partitioned into several subspecies and cooperative coevolution is realized by an information communication mechanism between subspecies, which can enhance the global search ability of particles and avoid premature convergence to local optimum. To demonstrate the power of the method, comparisons between the proposed algorithm and state-of-the-art algorithms are grouped into two categories: 10 basic benchmark functions (10-dimensional and 30-dimensional), 10 CEC2005 benchmark functions (30-dimensional), and a real-world problem (multilevel image segmentation problems). Experimental results show that MCPSO-PSH displays a competitive performance compared to the other swarm-based or evolutionary algorithms in terms of solution accuracy and statistical tests.
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Tang, Yi, and Xin Jun Wang. "Effects of Grazing on Reproductive Allocation of Elm in Horqin Sandy Land, Northeastern China." Advanced Materials Research 937 (May 2014): 554–58. http://dx.doi.org/10.4028/www.scientific.net/amr.937.554.
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Grazing, one of the most important disturbance in Northern China, influenced vegetation restoration on the aspects of population survival, community structure and landscape patterns. However, effects of grazing on elm trees (Ulmus pumila), the key species in climax community in Horqin Sandy Land, were not fully understood, especially on the aspects of reproductive allocation. Reproductive allocation was vital to affect seed production, which determined the number of seed source used for recruitment. Furthermore, recruitment regulated the population dynamic even to the community structure. To estimate effects of grazing on elm trees reproductive allocation, a field experiment was conducted in Wulanaodu, southern of Horqin Sandy Land. Elm trees suffering grazing with intensities were classified with diameter in breast (DBH). Current-year shoots, leaves and seeds in each tree mentioned above, were selected and measured in the laboratory respectively. The dry weight of them considered as biomass allocated to reproductive and vegetative growth. Our results showed that the reproductive allocation of early-matured and over-matured trees were 25.17% and 35.91% separately in closed land and were 42.48% and 60.03% in light grazed land correspondingly, indicating the reproductive allocation of early-matured and over-matured trees in closed land was significant lower than in grazed land (P<0.05). Meanwhile, matured trees devoted 71.15% of required resource to reproduction in closed land, and this ratio was 67.34% and 71.75% in light and heavy-grazed land, indicating the difference of reproductive allocation was not significant between the grazed and closed lands (P>0.05). Furthermore, matured trees devoted 71.75% of resource to seeds and the corresponding ratio was 60.03% and 42.48% in over-matured trees and early-matured trees, indicating matured trees significantly devoted more resource to reproduction than over-matured trees and early-matured trees (P<0.05). It is suggested that grazing improved the ratio of biomass allocation to reproduction.
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Scherstjanoi, M., J. O. Kaplan, E. Thürig, and H. Lischke. "GAPPARD: a computationally efficient method of approximating gap-scale disturbance in vegetation models." Geoscientific Model Development Discussions 6, no. 1 (February 15, 2013): 1021–84. http://dx.doi.org/10.5194/gmdd-6-1021-2013.
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Abstract. Models of vegetation dynamics that are designed for application at spatial scales larger than individual forest gaps suffer from several limitations. Typically, either a population average approximation is used that results in unrealistic tree allometry and forest stand structure, or models have a high computational demand because they need to simulate both a series of age-based cohorts and a number of replicate patches to account for stochastic gap-scale disturbances. The detail required by the latter method increases the number of calculations by two to three orders of magnitude compared to the less realistic population average approach. In an effort to increase the efficiency of dynamic vegetation models without sacrificing realism, and to explore patterns of spatial scaling in forests, we developed a new method for simulating stand-replacing disturbances that is both accurate and 10-50x faster than approaches that use replicate patches. The GAPPARD (approximating GAP model results with a Probabilistic Approach to account for stand Replacing Disturbances) method works by postprocessing the output of deterministic, undisturbed simulations of a cohort-based vegetation model by deriving the distribution of patch ages at any point in time on the basis of a disturbance probability. With this distribution, the expected value of any output variable can be calculated from the output values of the deterministic undisturbed run at the time corresponding to the patch age. To account for temporal changes in model forcing, e.g., as a result of climate change, GAPPARD performs a series of deterministic simulations and interpolates between the results in the postprocessing step. We integrated the GAPPARD method in the forest models LPJ-GUESS and TreeM-LPJ, and evaluated these in a series of simulations along an altitudinal transect of an inner-alpine valley. With GAPPARD applied to LPJ-GUESS results were insignificantly different from the output of the original model LPJ-GUESS using 100 replicate patches, but simulation time was reduced by approximately the factor 10. Our new method is therefore highly suited rapidly approximating LPJ-GUESS results, and provides the opportunity for future studies over large spatial domains, allows easier parameterization of tree species, faster identification of areas of interesting simulation results, and comparisons with large-scale datasets and forest models.
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Li, Kevin, John H. Vandermeer, and Ivette Perfecto. "Disentangling endogenous versus exogenous pattern formation in spatial ecology: a case study of the ant Azteca sericeasur in southern Mexico." Royal Society Open Science 3, no. 5 (May 2016): 160073. http://dx.doi.org/10.1098/rsos.160073.
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Spatial patterns in ecology can be described as reflective of environmental heterogeneity (exogenous), or emergent from dynamic relationships between interacting species (endogenous), but few empirical studies focus on the combination. The spatial distribution of the nests of Azteca sericeasur , a keystone tropical arboreal ant, is thought to form endogenous spatial patterns among the shade trees of a coffee plantation through self-regulating interactions with controlling agents (i.e. natural enemies). Using inhomogeneous point process models, we found evidence for both types of processes in the spatial distribution of A. sericeasur . Each year's nest distribution was determined mainly by a density-dependent relationship with the previous year's lagged nest density; but using a novel application of a Thomas cluster process to account for the effects of nest clustering, we found that nest distribution also correlated significantly with tree density in the later years of the study. This coincided with the initiation of agricultural intensification and tree felling on the coffee farm. The emergence of this significant exogenous effect, along with the changing character of the density-dependent effect of lagged nest density, provides clues to the mechanism behind a unique phenomenon observed in the plot, that of an increase in nest population despite resource limitation in nest sites. Our results have implications in coffee agroecological management, as this system provides important biocontrol ecosystem services. Further research is needed, however, to understand the effective scales at which these relationships occur.
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Gao, Yilong, Zhiqiang Xie, Xinyang Liu, Wei Zhou, and Xu Yu. "Integrated scheduling algorithm based on the priority constraint table for complex products with tree structure." Advances in Mechanical Engineering 12, no. 12 (December 2020): 168781402098520. http://dx.doi.org/10.1177/1687814020985206.
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Aiming at the existing intelligent optimization algorithms for solving the integrated scheduling problem of complex products with tree structure, there are problems of missing optimal solutions when designing encoding methods or generating infeasible offspring while designing evolutionary operators, an integrated scheduling algorithm based on the priority constraint table is proposed in this paper. A novel encoding method based on the dynamic priority constraint table is developed, which can guarantee the feasibility and completeness of the initial population individuals. For the legitimacy of the generated offspring individuals, two new different crossover and mutation methods are designed separately. The introduced evolutionary operators can avoid the detection and repairment of the infeasible individuals. An insertion-based greedy decoding method is also developed. In addition, based on the critical operations, a local search strategy is presented to enhance the search ability for the superior solutions. The feasibility and superiority of the proposed algorithm is verified by comparative experiments.
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Argles, Arthur P. K., Jonathan R. Moore, Chris Huntingford, Andrew J. Wiltshire, Anna B. Harper, Chris D. Jones, and Peter M. Cox. "Robust Ecosystem Demography (RED version 1.0): a parsimonious approach to modelling vegetation dynamics in Earth system models." Geoscientific Model Development 13, no. 9 (September 7, 2020): 4067–89. http://dx.doi.org/10.5194/gmd-13-4067-2020.
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Abstract. A significant proportion of the uncertainty in climate projections arises from uncertainty in the representation of land carbon uptake. Dynamic global vegetation models (DGVMs) vary in their representations of regrowth and competition for resources, which results in differing responses to changes in atmospheric CO2 and climate. More advanced cohort-based patch models are now becoming established in the latest DGVMs. These models typically attempt to simulate the size distribution of trees as a function of both tree size (mass or trunk diameter) and age (time since disturbance). This approach can capture the overall impact of stochastic disturbance events on the forest structure and biomass – but at the cost of increasing the number of parameters and ambiguity when updating the probability density function (pdf) in two dimensions. Here we present the Robust Ecosystem Demography (RED), in which the pdf is collapsed onto the single dimension of tree mass. RED is designed to retain the ability of more complex cohort DGVMs to represent forest demography, while also being parameter sparse and analytically solvable for the steady state. The population of each plant functional type (PFT) is partitioned into mass classes with a fixed baseline mortality along with an assumed power-law scaling of growth rate with mass. The analytical equilibrium solutions of RED allow the model to be calibrated against observed forest cover using a single parameter – the ratio of mortality to growth for a tree of a reference mass (μ0). We show that RED can thus be calibrated to the ESA LC_CCI (European Space Agency Land Cover Climate Change Initiative) coverage dataset for nine PFTs. Using net primary productivity and litter outputs from the UK Earth System Model (UKESM), we are able to diagnose the spatially varying disturbance rates consistent with this observed vegetation map. The analytical form for RED circumnavigates the need to spin up the numerical model, making it attractive for application in Earth system models (ESMs). This is especially so given that the model is also highly parameter sparse.
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Yan, Xinqing, and Zhouping Yin. "QTDFS-ALOHA." International Journal of Applied Logistics 1, no. 1 (January 2010): 67–82. http://dx.doi.org/10.4018/jal.2010090205.
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Proposed protocols work clumsily in resolving the collisions occurred in dense RFID tag environment. QTDFS-ALOHA, a hybrid protocol which combines the query tree protocol and the dynamic frame slot ALOHA protocol, is proposed. In each frame of this protocol, only tags in the active set are allowed to answer in randomly selected slots. Afterwards, the population of tags in the active set is estimated. According to the identification accuracy required, the protocol may choose to continue the identification of the active set with delicately calculated frame length, or to divide the active set into multiple subsets using some binary prefix strings and identify each subset subsequently in the following frames. This process is performed recursively for all tag sets until the required accuracy is achieved. Proposed tag population estimation methods are summarized and evaluated. Numeric simulation verifies that this hybrid protocol outperforms other frame slot ALOHA based protocols.
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Chebbah, Dahlia, Nohal Elissa, Denis Sereno, Omar Hamarsheh, Anthony Marteau, Julie Jan, Arezki Izri, and Mohammad Akhoundi. "Bed Bugs (Hemiptera: Cimicidae) Population Diversity and First Record of Cimex hemipterus in Paris." Insects 12, no. 7 (June 25, 2021): 578. http://dx.doi.org/10.3390/insects12070578.
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Cimex lectularius and C. hemipterus are blood-sucking insects with a long history of presence in human communities. We investigated the molecular diversity of the bed bug population of Paris and its suburb cities using cytochrome oxidase 1 (CO1) sequencing. A total of 1211 specimens belonging to different life stages were collected from 62 infested human dwellings in Paris (13 out of 20 arrondissements) and the surrounding cities (18 cities). Morphological determination and COI sequencing of 132 specimens demonstrated C. lectularius as the predominant species and, surprisingly, the presence of C. hemipterus in four infested areas of Paris and its suburb cities. Neighbor-joining tree and network analyses depicted the presence of two C. lectularius populations. Most samples from Paris and its suburb cities clustered in a major clade. The second population encompasses specimens from Paris (arrondissements 11 and 19) and its suburb cities (e.g., Bobigny, Pantin, and Montreuil) that clustered with Hungary, Czechia, and Finland. This is the second evidence for C. hemipterus infestation in France and the third in Europe, which challenges the classic pattern of C. hemipterus dispersion and implies sympatric occurrence of C. lectularius and C. hemipterus. Since Paris is one of the most popular tourist destinations in the world, our observations shed light on bed bugs’ dispersal dynamic and may help future vector control strategies.
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Nacheski, Sterja, Irena Papazova-Anakieva, Stanislava Lazarevska, and Blagoj Shurbevski. "Dynamics of populations of pine processionary moth (Thaumetopoea pityocampa) in the Republic of North Macedonia during the period 2007-2017." Silva Balcanica 21, no. 1 (June 30, 2020): 77–82. http://dx.doi.org/10.3897/silvabalcanica.21.e54605.
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This study presents results for the dynamic of the populations of the pine processionary moth (Thaumetopoea pityocampa) during the period 2007-2017 and the impact of reducing factors in the Repub-lic of North Macedonia. The population density was determined by the number of larval nests both per tree and per hectare that varied during the research period. The number of individuals went up between 2007 and 2010, while during the following years it rapidly decreased. Since 2011, an overall prograding trend has been recorded in the several subsequent years. This could be explained by the huge number of individuals from the previous years that were in a diapause. The abundance of pest populations continued to grow in 2016 as no measures were taken. During the winter of 2016/2017, the impact of the extremely low temperatures on pest mortality was monitored in 2016-2017 generation. The density of the populations came to latency due to the very large number of dead larvae of second and third larval stages. We recorded a 100% mortality of larvae in plantations of Pinus nigra in the regions near Prilep, Sveti Nikole, Shtip, Kochani and Negotino Villages.
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O'Halloran, Aisling M., Peter Hartley, David Moloney, Christine McGarrigle, Rose Anne Kenny, and Roman Romero-Ortuno. "Informing patterns of health and social care utilisation in Irish older people according to the Clinical Frailty Scale." HRB Open Research 4 (May 18, 2021): 54. http://dx.doi.org/10.12688/hrbopenres.13301.1.
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Background: There is increasing policy interest in the consideration of frailty measures (rather than chronological age alone) to inform more equitable allocation of health and social care resources. In this study the Clinical Frailty Scale (CFS) classification tree was applied to data from The Irish Longitudinal Study on Ageing (TILDA) and correlated with health and social care utilisation. CFS transitions over time were also explored. Methods: Applying the CFS classification tree algorithm, secondary analyses of TILDA data were performed to examine distributions of health and social care by CFS categories using descriptive statistics weighted to the population of Ireland aged ≥65 years at Wave 5 (n=3,441; mean age 74.5 (SD ±7.0) years, 54.7% female). CFS transitions over 8 years and (Waves 1-5) were investigated using multi-state Markov models and alluvial charts. Results: The prevalence of CFS categories at Wave 5 were: 6% ‘very fit’, 36% ‘fit’, 31% ‘managing well’, 16% ‘vulnerable’, 6% ‘mildly frail’, 4% ‘moderately frail’ and 1% ‘severely frail’. No participants were ‘very severely frail’ or ‘terminally ill’. Increasing CFS categories were associated with increasing hospital and community health services use and increasing hours of formal and informal social care provision. The transitions analyses suggested CFS transitions are dynamic, with 2-year probability of transitioning from ‘fit’ (CFS1-3) to ‘vulnerable’ (CFS4), and ‘fit’ to ‘frail’ (CFS5+) at 34% and 6%, respectively. ‘Vulnerable’ and ‘frail’ had a 22% and 17% probability of reversal to ‘fit’ and ‘vulnerable’, respectively. Conclusions: Our results suggest that the CFS classification tree stratified the TILDA population aged ≥65 years into subgroups with increasing health and social care needs. The CFS could be used to aid the allocation of health and social care resources in older people in Ireland. We recommend that CFS status in individuals is reviewed at least every 2 years.
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Chaturvedi, Pankaj, Arjun Singh, Atanu Bhattacharya, Vidisha Tuljapurkar, Deepa Nair, Devendra Chaukar, and Rajesh Dikshit. "Population-level Outcomes of Early Thyroid Cancers: A Need to Revisit Current Practice." Rambam Maimonides Medical Journal 13, no. 2 (April 26, 2022): e0008. http://dx.doi.org/10.5041/rmmj.10467.
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Background: Early thyroid cancers have excellent long-term outcomes, yet the word “cancer” draws unnecessary apprehension. This study aimed to define when the recommendations for observation and surveillance may be extended to early thyroid cancers at the population level. Methods: Non-metastasized thyroid cancers ≤40 mm diameter were identified from the 1975–2016 Surveillance, Epidemiology and End Results (SEER) database. Causes of death were compared across demographic data. Disease-specific outcomes were compared to the age-adjusted healthy United States (US) population. Survival estimates were computed using Kaplan–Meier and compared using the Cox proportional hazard model. Dynamic benchmarks impacting disease-specific overall survival were determined by decision tree modeling and tested by the Cox model. Results: Of the 28,728 thyroid cancers included in this study, 98.4% underwent some form of thyroid-specific treatment and were followed for a maximum of 10.9 years. This group had a 4.3% mortality rate at the end of follow-up (10.9 years maximum), with 13 times more deaths attributed to competing risks rather than thyroid cancer (stage T1a versus stage T1b, P=1.000; T1 versus T2, P<0.001). Among the untreated T1a or T1b tumors, the risk of disease-specific death was 21 times lower than death due to other causes. There was no significant difference between T1a and T1b tumors nor across sex. The age-adjusted risk of death for the healthy US population was higher than the population with thyroid cancer. Dynamic categorization demonstrated worsening outcomes up to 73 years, uninfluenced by sex or tumor size. For patients over 73 years of age, only tumors >26 mm impacted outcomes. Conclusion: Based on the current data, T1a and T1b nodules have similar survival outcomes and are not significantly impacted even when left untreated. Multi-institutional prospective studies are needed to confirm these findings so that current observation and surveillance recommendations can be extended to certain T1 thyroid nodules.