Detecting Climate Driven Changes in Chlorophyll-a Using High Frequency Monitoring: The Impact of the 2019 European Heatwave in Three Contrasting Aquatic Systems

The frequency of heatwave events in Europe is increasing as a result of climate change. This can have implications for the water quality and ecological functioning of aquatic systems. We deployed three spectroradiometer WISPstations at three sites in Europe (Italy, Estonia, and Lithuania/Russia) to measure chlorophyll-a at high frequency. A heatwave in July 2019 occurred with record daily maximum temperatures over 40 °C in parts of Europe. The effects of the resulting storm that ended the heatwave were more discernable than the heatwave itself. Following the storm, chlorophyll-a concentrations increased markedly in two of the lakes and remained high for the duration of the summer while at one site concentrations increased linearly. Heatwaves and subsequent storms appeared to play an important role in structuring the phenology of the primary producers, with wider implications for lake functioning. Chlorophyll-a peaked in early September, after which a wind event dissipated concentrations until calmer conditions returned. Synoptic coordinated high frequency monitoring needs to be advanced in Europe as part of water management policy and to improve knowledge on the implications of climate change. Lakes, as dynamic ecosystems with fast moving species-succession, provide a prism to observe the scale of future change.

Seasonal Variations in the Biodiversity, Ecological Strategy, and Specialization of Diatoms and Copepods in a Coastal System With Phaeocystis Blooms: The Key Role of Trait Trade-Offs

Although eutrophication induced by anthropogenic nutrient enrichment is a driver of shifts in community composition and eventually a threat to marine biodiversity, the causes and consequences on ecosystem functioning remain greatly unknown. In this study, by applying a trait-based approach and measuring niche breadth of diatoms and copepods, the drivers and underlying mechanisms of the seasonal species succession of these ecological communities in a coastal system dominated in spring by Phaeocystis blooms were explored. It is suggested that the seasonal succession of diatoms and copepods is the result of several trade-offs among functional traits that are controlled by the seasonal abiotic and biotic pressure encountered by the plankton communities. The results of this study highlight that a trade-off between competition and predator, i.e., weak competitors are better protected against predation, plays an important role in promoting plankton species richness and triggers the Phaeocystis bloom. As often observed in eutrophicated ecosystems, only the biotic homogenization of the copepod community and the shift in the diet of copepods toward Phaeocystis detrital materials have been detected during the Phaeocystis bloom. The diatom and copepod communities respond synchronously to fluctuating resources and biotic conditions by successively selecting species with specific traits. This study confirms the key role of competition and predation in controlling annual plankton succession.

Temporal and Spatial Signaling Mediating the Balance of the Plankton Microbiome

The annual patterns of plankton succession in the ocean determine ecological and biogeochemical cycles. The temporally fluctuating interplay between photosynthetic eukaryotes and the associated microbiota balances the composition of aquatic planktonic ecosystems. In addition to nutrients and abiotic factors, chemical signaling determines the outcome of interactions between phytoplankton and their associated microbiomes. Chemical mediators control essential processes, such as the development of key morphological, physiological, behavioral, and life-history traits during algal growth. These molecules thus impact species succession and community composition across time and space in processes that are highlighted in this review. We focus on spatial, seasonal, and physiological dynamics that occur during the early association of algae with bacteria, the exponential growth of a bloom, and also during its decline and recycling. We also discuss how patterns from field data and global surveys might be linked to the actions of metabolic markers in natural phytoplankton assemblages. Expected final online publication date for the Annual Review of Marine Science, Volume 14 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Mapping Vegetation Species Succession in a Mountainous Grassland ecosystem using Landsat and Sentinel-2 data

Vegetation species succession and composition are significant factors determining the rate of ecosystem biodiversity recovery after being disturbed and subsequently vital for sustainable and effective natural resource management and biodiversity. The succession and composition of grasslands ecosystems worldwide have significantly been affected by accelerated environmental changes due to natural and anthropogenic activities. Therefore, understanding spatial data on the succession of grassland vegetation species and communities through mapping and monitoring is essential to gain knowledge on the ecosystem and other ecosystem services. This study used a random forest machine learning classifier on the Google Earth Engine platform to classify grass vegetation species with Landsat 7 ETM+ and ASTER multispectral imager (MI) data resampled with the current Sentinel-2 MSI data to map and estimate the changes in vegetation species succession. The results indicate that ASTER IM has the least accuracy of 72%, Landsat 7 ETM+ 84%, and Sentinel-2 had the highest of 87%. The result also shows that other species had replaced four dominant grass species totaling about 49 km 2 throughout the study.

Friends in All the Green Spaces: Weather Dependent Changes in Urban Mosquito (Diptera: Culicidae) Abundance and Diversity

Mosquitoes (Diptera: Culicidae) are universally recognized as troublesome pests and vectors of various pathogens and parasites. Understandably, the species makeup and diversity of individual populations depends on local and broad scale environmental trends, especially on temperature and hydrological variations. Anthropogenic landscapes make for unique habitats, but their effect on insects likely varies across climatic regions. The aim of this study was to investigate the diversity and seasonal patterns of urban mosquitoes in the boreal region. Specimens were collected with an insect net from May to September during three years and determined to species or species group level. Weather information was added to each data point and results analyzed using multivariate regression models. Fieldwork yielded 1890 mosquitoes from four genera. Both abundance and the effective number of species (ENS) significantly decreased during the study period. The number of collected mosquitoes had a negative correlation with wind speed and temperature, latter of which exhibited a negative association with humidity. Species succession followed predictable patterns, but with some variation between years. Still, Culex pipiens/Culex torrentium were the most abundant throughout the study. Importantly, all dominant species were known disease vectors. Our work showed that higher temperatures could result in fewer mosquitoes in boreal towns.

DESEMPENHO DE Lactuca sativa (ALFACE) DIANTE DO AUMENTO DA DENSIDADE DE CULTIVOS CONSORCIADOS EM HORTAS AGROFLORESTAIS

Lactuca sativa (ALFACE) PERFORMANCE DURING INCREASE IN THE DENSITY OF INTERCROPPED IN AGROFOREST GARDENSRENDIMIENTO DE Lactuca sativa (ALFACE) DURANTE EL AUMENTO DE LA DENSIDAD DE LOS CULTIVOS INTERCALADOS EN LOS JARDINES AGROFORESTALESRESUMOFoi realizado um experimento para verificar se a consorciação de um número crescente de cultivos olerícolas, escolhidos de acordo com a lógica da sucessão de espécies no espaço ao longo do tempo, afetaria a produção de matéria seca de Lactuca sativa (alface) em hortas agroflorestais. O delineamento experimental foi em delineamento em blocos casualizados, com um fator em três níveis, e quatro repetições. A eficiência dos consórcios foi estimada pela matéria seca de L. sativa. Os resultados mostraram que o aumento do número de espécies consorciadas e consequente densidade de plantio não influenciou o parâmetro avaliado. Isto evidencia uma vantagem cultural conferida pelos consórcios sucessionais testados, uma vez que foram conduzidos sem a aplicação de insumos sintéticos e tóxicos, além de se obter uma produção de alimentos de qualidade diferenciada dos convencionais e prestar serviços ecossistêmicos de regulação. Não houve perdas produtivas para L. sativa decorrentes do adensamento dos cultivos.Palavras-chave: Agrofloresta; Sucessão Ecológica; Agricultura Sintrópica.ABSTRACTAn experiment was carried out to verify if the intercropping of a growing number of vegetables, chosen according to the logic of species succession over time, would affect the production of dry matter of Lactuca sativa (lettuce) in agroforestry gardens. The experimental design was a randomized complete block design with one factor at three levels and four replications. Consortium efficiency was estimated by L. sativa dry matter. The results showed that the increase of the number of intercropping species and consequent planting density did not influence the evaluated parameter. This evidences a cultural advantage conferred by the successional consortiums tested, since without the application of synthetic and toxic inputs, besides obtaining a production of quality differentiated of food conventional and providing ecosystem regulation services. There were no productive losses for L. sativa due to the densification of crops.Keywords: Agroforestry; Ecological Succession; Syntropic Agriculture.RESUMENSe llevó a cabo un experimento para verificar si el cultivo intercalado de un número creciente de verduras, elegidos de acuerdo con la lógica de sucesión de especies a lo largo del tiempo, afectaría la producción de materia seca de Lactuca sativa (lechuga) en jardines agroforestales. El diseño experimental fue un diseño de bloques completos al azar con un factor en tres niveles y cuatro repeticiones. La eficiencia del consorcio fue estimada por la materia seca de L. sativa. Los resultados mostraron que el aumento del número de especies intercaladas y la consiguiente densidad de siembra no influyeron en el parámetro evaluado. Esto evidencia una ventaja cultural conferida por los consorcios sucesionales probados, ya que se realizaron sin la aplicación de insumos sintéticos y tóxicos, además obtener producción de alimentos de calidad diferenciada de los convencionales y la prestación de servicios de regulación del ecosistema. No hubo pérdidas productivas para L. sativa debido a la densificación de los cultivos.Palabras clave: Agroforestería; Sucesión Ecológica; Agricultura sintrópica.

Parastā oša Fraxinus Excelsior L. destrukcija Latvijā: audžu sukcesija un oša atjaunošanās = Dieback of common ash Fraxinus Excelsior L. in Latvia: species succession and ash regeneration

The area of common ash forest is only 1–2% of the total forest area in Europe and 0.3% in Latvia. Prior to dieback, ash was an economically and still is ecologically highly important tree species. In Eastern Europe since the beginning of the 1990s, and a decade later throughout Central and Western Europe, rapid dieback of ash stands caused by an unknown reason was observed. In 2006 the causal agent of ash dieback – an anamorphic fungus Hymenoscyphus fraxineus (species name later refined) was determined. In Latvia, intensive dieback of ash stands has been observed since 2000. The aim of the thesis was to assess the dieback dynamics of common ash Fraxinus excelsior L. stands and determine the main factors affecting susceptibility of the trees, as well as future succession and potential regeneration of the affected common ash stands in Latvia. In Latvia, The area of young ash stands decreased by 4.4 times during 2000–2015. The ten-year-inventory (2005–2015) revealed that the overall mortality of ash was 6.9% and standing volume of ash stands decreased by 171 m3 ha–1. The obtained results indicated that regeneration of ash saplings in ash young stands as well as in mature stands was lower than in in the pre-dieback times, but regeneration was still successful. Furthermore, survival and health condition of ash saplings was relatively poor, as only ca. ⅓ of individuals were healthy, and the health condition decreased with aging. Overgrowth of ash stands with shrub species has begun, suggesting formation of broadleaved stands with a small admixture of ash in the future. We found that, susceptibility to ash dieback is significantly affected by morphometric parameters of ash trees and stands, site conditions and meteorological factors. In Latvia, ash dieback was present in ash stands of all ages and composition, yet some individual and regional differences were observed. Lower susceptibility to ash dieback was observed for older/larger dimensions trees, mixed stands on well-drained and dry mineral soils, stands thinned more intensively, and in the eastern part of Latvia. The findings of the thesis are applicable for the planning of ash stand management, assessment of the existing situation, for the designation of additional genetic resource forests, as well as provide basic information for future studies.

A Middle Pleistocene steppe bison find within the Dürnstein Castle (Wachau, Lower Austria)

In the course of foundation works in the Dürnstein Castle cervical and front leg bones of a large Bison priscus bull were discovered in fluvial sediments. The small city of Dürnstein with its medieval centre is part of the UNESCO Wachau Cultural Landscape and is built mainly on Palaeozoic basement rocks. The find location is completely overbuilt, but remnants of fluvial sediments on the bones together with the altitude of the site approximately 17 m above the Danube point to a Middle Pleistocene fluvial aggradation level not younger than ca. 240,000 years, and the maximum age is 400,000 years. The fossil bearing location is interpreted as a small sandy bay of the Pleistocene Danube, protected from later degradation and erosion. Morphometric comparisons and taphonomic analyses of the bones allow the reconstruction of a scenario in which the bison probably had drowned in a flood and its carcass was buried quickly before destruction by scavengers or erosion. The study includes a comparison with bison specimens of an unpublished small megafaunal assemblage from adjacent Krems-Kreuzbergstraße. Processing marks on parts of these bones point to an anthropogenic Middle Palaeolithic influence and translocation. In addition, a tentative chronological sketch of the regional Bison species succession (B. menneri, B. schoetensacki, B. priscus) from the Early to the Late Pleistocene is presented.