Pattern avoidance in forests of binary shrubs

We investigate pattern avoidance in permutations satisfying some additional restrictions. These are naturally considered in terms of avoiding patterns in linear extensions of certain forest-like partially ordered sets, which we call binary shrub forests. In this context, we enumerate forests avoiding patterns of length three. In four of the five non-equivalent cases, we present explicit enumerations by exhibiting bijections with certain lattice paths bounded above by the line y = lx, for some l in Q+, one of these being the celebrated Duchon’s club paths with l = 2/3. In the remaining case, we use the machinery of analytic combinatorics to determine the minimal polynomial of its generating function, and deduce its growth rate

Proofs of Conjectures about Pattern-Avoiding Linear Extensions

After fixing a canonical ordering (or labeling) of the elements of a finite poset, one can associate each linear extension of the poset with a permutation. Some recent papers consider specific families of posets and ask how many linear extensions give rise to permutations that avoid certain patterns. We build off of two of these papers. We first consider pattern avoidance in $k$-ary heaps, where we obtain a general result that proves a conjecture of Levin, Pudwell, Riehl, and Sandberg in a special case. We then prove some conjectures that Anderson, Egge, Riehl, Ryan, Steinke, and Vaughan made about pattern-avoiding linear extensions of rectangular posets.Comment: 9 pages, 2 figure

Pattern Avoidance in Task-Precedence Posets

We have extended classical pattern avoidance to a new structure: multiple task-precedence posets whose Hasse diagrams have three levels, which we will call diamonds. The vertices of each diamond are assigned labels which are compatible with the poset. A corresponding permutation is formed by reading these labels by increasing levels, and then from left to right. We used Sage to form enumerative conjectures for the associated permutations avoiding collections of patterns of length three, which we then proved. We have discovered a bijection between diamonds avoiding 132 and certain generalized Dyck paths. We have also found the generating function for descents, and therefore the number of avoiders, in these permutations for the majority of collections of patterns of length three. An interesting application of this work (and the motivating example) can be found when task-precedence posets represent warehouse package fulfillment by robots, in which case avoidance of both 231 and 321 ensures we never stack two heavier packages on top of a lighter package.Comment: 17 page

Edges effects on seed predation by rodents in deciduous forests of northern Switzerland

Seed predation by rodents affects plant population dynamics and it mayrespond to changes in vegetation structure at forest edges. This studyinvestigates the magnitude and direction of a potential edge effect intemperatedeciduous forests, and it seeks possible explanations based on predatorabundance and vegetation structure. The study was conducted at twelve forestedges in northern Switzerland; in six sites all shrubs at the forest edge wereremoved, whereas the other sites maintained a structurally rich shrub layer. Ineach site three transects were laid out from the edge towards the forestinterior. In six plots along these transects (at 1, 3, 6, 12, 25, 50m) we studied seed removal from experimental dishes, rodentabundance in live-traps and four characteristics of the vegetation structure.For both woody seed species (Prunus avium,Viburnum lantana) predation was significantly higher nearthe forest edge in the structurally rich sites; in the other sites no suchgradient was found. Selectively accessible dishes revealed that rodents werethemain predators, whereas predation by insects or molluscs was not observed.Abundance of rodents (Apodemus flavicollis, A.sylvaticus, Clethrionomys glareolus) washighestunder dense shrubs close to the forest edge. In the structurally rich sitesthere was a clear gradient of decreasing shrub cover from the edge towards theforest interior; a weaker gradient was observed in the structurally poor sites.We conclude that high shrub cover near the forest edge is the main determinantfor edge effects in seed predation, and edges without a shrub belt show no sucheffec

Direct and indirect effects of climate on demography and early growth of Pinus sylvestris at the rear edge: changing roles of biotic and abiotic factors

Global change triggers shifts in forest composition, with warming and aridification being particularly threatening for the populations located at the rear edge of the species distributions. This is the case of Scots pine (Pinus sylvestris) in the Mediterranean Basin where uncertainties in relation to its dynamics under these changing scenarios are still high. We analysed the relative effect of climate on the recruitment patterns of Scots pine and its interactions with local biotic and abiotic variables at different spatial scales. Number of seedlings and saplings was surveyed, and their annual shoot growth measured in 96 plots located across altitudinal gradients in three different regions in the Iberian Peninsula. We found a significant influence of climate on demography and performance of recruits, with a non-linear effect of temperature on the presence of juveniles, and a positive effect of precipitation on their survival. Abundance of juveniles of P. sylvestris that underwent their first summer drought was skewed towards higher altitudes than the altitudinal mean range of the conspecific adults and the optimum elevation for seedlings¿ emergence. At local level, light availability did not influence juveniles¿ density, but it enhanced their growth. Biotic interactions were found between juveniles and the herb cover (competition) and between the number of newly emerged seedlings and shrubs (facilitation). Results also highlighted the indirect effect that climate exerts over the local factors, modulating the interactions with the pre-existing vegetation that were more evident at more stressful sites. This multiscale approach improves our understanding of the dynamics of these marginal populations and some management criteria can be inferred to boost their conservation under the current global warming.Funding was provided by the Spanish Ministry for Innovation and Science with the grant Consolider-Montes (CSD2008_00040), and the European Union with the projects BACCARA (CE: FP7-226299, 7FP) and FunDivEUROPE (CE: FP7-ENV-2010. 265171).Peer Reviewe

Landscape factors influencing habitat and crop selection by wild boar in Sweden

The wild boar population has increased rapidly during the last two decades in the southern and central parts of Sweden. This rise in population size has caused severe damages to agricultural fields through their foraging behavior. Thus, there is a need for improved knowledge about landscape factors influencing habitat selection which will help in the proper management of wild boar hence reducing the losses they cause in the agricultural sector. The main aim of this study is to evaluate landscape factors influencing wild boar selection of various habitats and crop fields in south-central Sweden. Eleven wild boar were fitted with GPS/GSM-collars to record movement among different habitats and crops. Data were analyzed using QGIS (version 3.10.0), R studio (version 3.6.2), and Microsoft Excel software. Descriptive statistics show that wild boar have a high preference for clear-cuts, agricultural fields, and deciduous forests, but show a lower preference for other kinds of open land. Wild boar tended to avoid growing and mature coniferous forests and open wetlands during summer but had a high preference for crop fields with oat, spring wheat, spring barley, and mixed crops. A binary logistic model revealed a significant influence of distance to feeding stations on the selection of different habitats and crop fields with both positive and negative effects. Distance to main roads also significantly influenced the proportion of selection of habitats and crop fields with both positive and negative correlation on the proportion of wild boar selection. As a general conclusion, feeding stations and roads influenced the selection of different habitats and crop fields differently. Further, wildlife management strategies on wild boar should be improved to consider both time and space to reduce damages on agricultural fields

Ecological indicators as tools to monitor the effects of climate change on Tropical dry forest

As terras secas (hiper-áridas, áridas, semi-áridas e sub-húmidas secas) cobrem cerca de 47% do globo terrestre e abrigam cerca de 39% da população mundial. Ocorrem maioritariamente em países menos desenvolvidos, mais pobres e altamente dependentes dos recursos naturais. A necessidade de antecipar os impactos das alterações climáticas nas terras secas é indiscutível devido à sua alta vulnerabilidade a alterações climáticas e ambientais (tendo como consequência a desertificação), já que ambas constituem importantes ameaças para a biodiversidade e para a prestação de serviços de ecossistema essenciais para o bem-estar humano. Métricas de diversidade (taxonómicas e funcionais) são usadas de forma complementar para monitorizar a resposta dos ecossistemas ao clima. Assim, o principal objetivo desta tese é identificar potenciais indicadores ecológicos, baseados métricas taxonómicas e funcionais, que possam ser usados como ferramentas para monitorizar os efeitos das alterações climáticas na Floresta tropical seca. A Caatinga, um dos ecossistemas mais diversos das Florestas Neotropicais sazonalmente secas, mas também dos mais vulneráveis às alterações climáticas no Brasil foi a área estudada. O índice de aridez foi considerado uma variável adequada para avaliar os efeitos das alterações climáticas na vegetação. Para este estudo, utilizamos um banco de dados muito rico com informações sobre a ocorrência de cerca de 1 000 espécies de plantas neste ecossistema, obtida a partir de dados provenientes de diferentes fontes, recolhidos com diferentes metodologias e esforços de amostragem no espaço e ao longo do tempo. Aplicando uma metodologia de reamostragem, a abundância de espécies de plantas foi estimada ao longo de um gradiente espacial de clima. Tais informações são essenciais para avaliar a resposta das métricas de diversidade, especialmente aquelas que requerem dados de abundância, como métricas funcionais. Foram estudadas 13 características funcionais da planta (CFP), que determinam as respostas das espécies ao meio ambiente e permitem avaliar a resposta das métricas ao clima. Das 13 CFP estudadas, oito responderam à aridez, que por sua vez afetou a estrutura funcional da vegetação da Caatinga. A análise de agrupamento com base nos 13 CFP foi usada para agrupar espécies em sete grupos funcionais principais que respondem à aridez. Os grupos caracterizados pela presença de defesas químicas e via fotossintética CAM (metabolismo ácido das crassuláceas) foram aqueles cuja abundância relativa aumentou mais com o aumento da aridez. Assim, estes foram propostos como indicadores ecológicos para rastrear os efeitos a aridez na estrutura funcional da comunidade vegetal. Com base nos resultados descritos anteriormente, foi feita uma análise global de métricas complementares de diversidade para avaliar a suscetibilidade da comunidade de plantas, do ponto de vista taxonómico e funcional, ao longo do gradiente de aridez. Em locais mais áridos, verificou-se uma maior diversidade funcional suportada por algumas espécies de plantas (baixa riqueza de espécies) com funções únicas, sugerindo baixa resiliência. Em contraste, locais menos áridos mostraram menor diversidade funcional, mas maior redundância funcional entre as espécies. No geral, as conclusões deste trabalho apoiam o uso de métricas complementares de diversidade vegetal como indicadores ecológicos de alerta dos impactos das mudanças climáticas no ecossistema da Caatinga. Além disso, a resposta da comunidade vegetal ao longo do gradiente espacial do clima fornece indicações sobre possíveis alterações ao longo do tempo sob um aumento da aridez global, contribuindo para melhorar as previsões sobre os efeitos das alterações climáticas. Como as projeções não são muito animadoras, é fundamental que conservemos e restauremos taxonómica e funcionalmente estas florestas secas, a fim de mitigar os impactos negativos previstos das alterações climáticas no ecossistema da Caatinga.Drylands (hyper-arid, arid, semi-arid and dry sub-humid areas) cover about 47% of global land surface and harbour about 39% of the world´s population, encompassing the least developed countries, poorest and highly dependent on natural resources. The need to anticipate the impacts of climate change on drylands is indisputable due to their high vulnerability to climate and environmental changes (leading to desertification), as both disturbances are key threats to biodiversity and to ecolosystem services delivery, essential to human well-being. Diversity metrics (taxonomic and functional) are complementarily used to monitoring ecosystems’ response to climate. With this in mind the main aim of this thesis was to identify potential ecological indicators based on both taxonomic and functional plant diversity metrics, to be used as tools to monitor the effects of climate change on Tropical dry forest. Caatinga, one of the most diverse ecosystems in Neotropical seasonally dry forests, and more vulnerable to climate change in Brazil, was used as a case study. The aridity index was considered as an adequate variable to assess the effects of climate change on vegetation. In this study, a very rich database with information on the occurrence of around 1 000 plant species in this ecosystem was used. It contained data derived from different sources, collected with different sampling methodologies and sampling efforts in space and over time. By applying a re-sampling methodology, plant species abundance was estimated along a spatial climate gradient. This information is essential to assess the response of diversity metrics, especially those that require abundance data, such as functional metrics. Thirteen plant functional traits (PFT) were studied, which determine species’ responses to the environment, and allow to assess the response of functional metrics to climate. Of the 13 PFT studied, eight responded to aridity, which affected the functional structure of Caatinga vegetation. Clustering analysis based on the 13 PFT was used to group species into seven main functional groups responding to aridity. Functional groups with the presence of chemical defense and CAM (crassulacean acid metabolism) photosynthetic pathway were those whose relative abundance increased most with increasing aridity. Thus, they were proposed as ecological indicators to track aridity effects on the plant community functional structure. Based on the previously described results, a global analysis of complementary diversity metrics was made to assess the susceptibility of the plant community, from a taxonomic and functional point of view, along the aridity gradient. In more arid sites, there was a higher functional diversity supported by a few plant species (low species richness) with unique functions, suggesting low resilience to environmental change. Contrastingly, less arid sites showed lower functional diversity but higher functional redundancy among species. Overall, this work’s findings support the use of complementary plant diversity metrics as warning ecological indicators of climate change impacts on the Caatinga ecosystem. In adition, the response of the plant community along the spatial climate gradient provides indications on how it might change over time under a global aridity increase, contributing to improve predictions on the effects of climate change. As projections are not very encouraging, it is crucial that we taxonomically and functionally conserve and restore these dry forests in order to mitigate the predicted negative impacts of climate change in the Caatinga ecosystem.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq - bolsa: 206444/2014-1)Ministério do Desenvolvimento Regional junto ao Projeto de Integração do Rio São Francisco (PISF

Short-term effects of wildfire on Sierra Nevada bighorn sheep habitat ecology

We studied changes in vegetation and habitat selection by endangered Sierra Nevada bighorn sheep (Ovis candensis sierrae; hereafter Sierra bighorn) for 2 years following wildfire on winter ranges in eastern California. We hypothesized that wildfire would change both forage availability and predation risk. Green forage biomass on Sierra bighorn winter ranges rebounded quickly from wildfire. Within 2 years green forage biomass was equal in burned and unburned areas, although total forage biomass was greater in unburned areas. Plants in the burn had 3% greater crude protein but equivalent digestibility and phenology. Forage composition in burned areas was forb dominated compared with unburned areas that were shrub dominated. Visibility, a measure of predation risk, was 9% greater in burned areas at a 5 m radii compared with unburned areas. We found no change in fecal nitrogen between Sierra bighorn in burned and unburned areas but there was a shift to higher diet composition of forbs in the burn. We evaluated Sierra bighorn resource selection using seasonal resource selection functions that included spatiotemporal models of forage biomass and spatial models of predation risk by cougars (Puma concolor), the main predator of Sierra bighorn. In the first year post-wildfire, Sierra bighorn increased selection for new growth herbaceous biomass in response to the reduced biomass caused by wildfire. While wildfire initially reduced total forage biomass it also created pockets of the highest new forb biomass in areas of high cougar use. These pockets attracted Sierra bighorn causing an increase in overlap with cougars in winter 2008. Sierra bighorn showed consistent selection to be near escape terrain and remained closer to escape terrain in areas of high cougar use compared to areas with low cougar use. By spring 2008 and winter and spring of 2009 Sierra bighorn strongly selected total forage biomass where cougar use was low and in areas of high cougar use, Sierra bighorn avoided total forage biomass. As a result Sierra bighorn overlap with cougar use was reduced. We advise management to consider the effects of fire on both forage availability and predation when implementing prescribed burns to benefit ungulates

Effects of Nonnative Plants on Space-Use in Eastern Box Turtles

Introduction of nonnative plants outside their natural range has caused widespread reduction in the abundance and diversity of native plant species. Nonnative plants typically form dense, often monotypic, thickets that affect the ability of animals to find food, reproduce, avoid predation risk, and thermoregulate. By doing so, nonnative plants have the potential to displace resident animals from areas otherwise suitable as animal habitat. However, limited studies have investigated whether resident animals avoid areas dominated by nonnative plants. This study investigated impacts of nonnative plants on eastern box turtles (Terrapene carolina carolina), a species that has been declining throughout their range. To determine if eastern box turtles avoid nonnative plants, I estimated habitat selection based on GPS fixes recorded for 16 individuals (6 males and 10 females) in an urban forest. Specifically, I determined if nonnative plants are avoided when turtles establish their home range (i.e., second order selection) and when they use their home ranges (i.e., third order selection). For females, the density of four of the six most common nonnative plant species was lower in turtle locations than available locations across the study area (i.e., second order selection) and those within home ranges (i.e., third order selection). For males, the density of only one nonnative plant species was lower in turtle locations than available locations across the study area (i.e., second order selection), and none of the species were different between turtle locations and available locations within their home ranges (i.e., third order selection). These results suggests that eastern box turtles avoid some (but not all) species of nonnative plants and that females are more sensitive to nonnative plants than males. The displacement of animals from highly invaded areas represents a functional loss of habitat. The reduction in available habitat area may lead to reduction in carrying capacity of invaded areas, and therefore, may have long-term impacts on population persistence