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Nutrient addition to a white sand tropical forest results in greater growth of saplings of canopy tree species than understorey specialist tree species
No full textIn tropical rain forest understories, canopy tree saplings coexist with understorey specialist trees, in a highly competitive environment for light, space, and soil nutrients. To investigate the impact of increasing nutrient pollution from human activity, we assessed differences between canopy trees saplings and understory specialists in their crown structures, allometries, and growth rates in response to experimental nutrient fertilization. In a nutrient-poor white sand forest in Sabah, Malaysian Borneo we measured tree size and crown dimensions for understorey specialists and canopy tree saplings (≤ 10 cm diameter) before and after experimental fertilization with nitrogen and calcium carbonate. Results showed that saplings of canopy species were taller than understorey specialists for a given stem diameter, but crown allometries were similar. Three years of fertilization did not affect allometric relationships between diameter and tree height or crown dimensions, suggesting that these allometries are stable and resource-independent. However, relative crown radius growth rate and crown volume growth rate for canopy tree saplings were three times faster after N + CaCO3 fertilization when compared to controls, demonstrating canopy tree saplings’ crown plasticity to maximize access to light. This study highlights different strategies employed by canopy and understorey species in the competitive forest understorey. Canopy saplings showed greater crown plasticity, investing added soil nutrients into crown expansion for enhanced light interception. Nitrogen deposition could thus advantage canopy species through increased competition with understory specialists resulting in potential species loss. The stability of the allometric relationships, when forests are subjected to nitrogen deposition supports their use for biomass estimation
Beyond agriculture: land use thresholds governing pesticide mixture risks in megacity surface waters
No full textGrowing concerns have emerged regarding the risks of pesticide mixtures in surface water ecosystems, yet the mechanisms through which human activities, especially land use patterns, affect these risks remain inadequately studied. This research presents an innovative approach, combining multi-scale land use analysis with pesticide risk assessment, quantifying relationships between mixed pesticide ecological risks and land use patterns. Findings indicate that the impacts of urban land use on pesticide ecological risks surpass the traditionally recognized agricultural effects, demonstrating significant spatial scale-dependent effects. Generalized additive model analysis reveals that 1−3 km and 2−3 km buffer zones represent the critical ranges where urban land use and cropland, respectively, have significant impacts on pesticide risks. Non-parametric change point analysis determined critical land use thresholds triggering significant ecological risk increases: 10−25% for cropland and 10−30% for urban areas. These discoveries provide crucial quantitative foundations for landscape planning and pesticide risk management. The results not only challenge traditional views of agricultural activities as primary pesticide sources but also provide new perspectives for pesticide pollution control and water quality management in large cities
The genome sequence of the red-barred tortrix moth, Ditula angustiorana (Haworth, 1811)
Get PDFWe present a genome assembly from a female specimen of Ditula angustiorana (Red-barred Tortrix; Arthropoda; Insecta; Lepidoptera; Tortricidae). The genome sequence has a total length of 468.36 megabases. Most of the assembly (99.83%) is scaffolded into 31 chromosomal pseudomolecules, including the W and Z sex chromosomes. The mitochondrial genome has also been assembled, with a length of 16.19 kilobases
Instrument design and performance of the first seven stations of RNO-G
Get PDFThe Radio Neutrino Observatory in Greenland (RNO-G) is the first in-ice radio array in the northern hemisphere for the detection of ultra-high energy neutrinos via the coherent radio emission from neutrino-induced particle cascades within the ice. The array is currently in phased construction near Summit Station on the Greenland ice sheet, with 7 stations deployed during the first two boreal summer field seasons of 2021 and 2022. In this paper, we describe the installation and system design of these initial RNO-G stations, and discuss the performance of the array as of summer 2024
Metapopulation distribution shapes year‐round overlap with fisheries for a circumpolar seabird
Get PDFAlthough fisheries bycatch is the greatest threat to many migratory marine megafauna, it remains unclear how population exposure to bycatch varies across the global range of threatened species. Such assessments across multiple populations are crucial for understanding variation in impacts and for identifying the management bodies responsible for reducing bycatch. Here, we combine extensive biologging data from white‐chinned petrel ( Procellaria aequinoctialis ) populations (representing >98% of their global breeding population) with pelagic and demersal longline and trawl fishing effort to map the global distribution and fisheries‐overlap hotspots for the most bycaught seabird in the Southern Hemisphere. We tracked the year‐round movements of 132 adults in 2006–2018 and examined spatial overlap among seven populations comprising three genetically distinct groupings (metapopulations). Foraging areas during the nonbreeding season were more concentrated than during breeding, with birds from all populations migrating to continental shelf or upwelling zones, but with low spatial overlap among metapopulations. Fisheries overlap differed more among than within metapopulations, underlining that these should be considered separate management units. Overlap with pelagic longline fisheries was greatest for Indian Ocean populations, and from the fleets of South Africa, Japan, Taiwan, and Spain, off southern Africa and in the High Seas. Overlap with demersal longline and trawl fisheries was greatest for Indian and Atlantic Ocean populations, within the Exclusive Economic Zones of South Africa, Namibia, and Argentina, and with the South Korean demersal longline fleet in the High Seas. The high overlap with South Korean longliners in the southwest Atlantic Ocean is of particular concern as demersal fishing in this region is not covered by any Regional Fisheries Management Organization (RFMO). We also identified fisheries‐overlap hotspots within RFMOs where there are no seabird‐bycatch mitigation requirements (1.5%–53.1% of total overlap within the area of competence of each RFMO), or where current mitigation regulations need to be strengthened. Our recommendations are that management bodies target the high‐priority fisheries we have identified for improved bycatch monitoring, mandatory best‐practice bycatch mitigation, and close monitoring of compliance, given the conservation concerns for white‐chinned petrels and other threatened seabirds
Seasonal ecophysiology of two páramo species: the dominance of light over water limitations
Get PDFDry and rainy seasons in many ecosystems differ significantly in cloudiness, precipitation, and incident sunlight. These seasonal variations can influence photosynthesis by altering light availability and water stress. This study examines whether light availability or water stress is the primary limiting factor for photosynthesis in páramo plants during the dry and rainy seasons. We measured photosynthetic carbon gain per unit leaf area ( A n ), stomatal conductance ( g s ), chlorophyll fluorescence (ϕPSII), and leaf water potentials, in two dominant páramo species, Espeletia grandiflora and Chusquea tessellata , across both seasons. Photosynthetic light-response curves were generated for each species, and statistical analyses assessed the relative influence of environmental factors such as light, temperature, and vapor pressure deficit on An. Contrary to our expectations, An was higher in the dry season despite increased water stress, suggesting that light availability is a stronger driver of carbon assimilation. However, light-response curves showed that Espeletia grandiflora exhibited higher potential carbon uptake during the dry season, while C. tessellata had greater uptake during the rainy season. Statistical analyses indicated that light was the primary factor influencing A n in both seasons, though temperature and vapor pressure deficit also played a role for C. tessellata in the rainy season. The combination of high solar radiation and elevated leaf temperatures in the dry season facilitated greater carbon assimilation, particularly in E. grandiflora . In contrast, the cloudier conditions of the rainy season limited photosynthesis despite reduced water stress. Although C. tessellata exhibited high A n during the dry season, it appeared vulnerable to high radiation and desiccation. These findings emphasize that cloud cover and light availability, rather than water stress alone, are key drivers of páramo plant carbon uptake, with important implications for predicting climate change effects in high-altitude ecosystems
Analysis of the seasonal and solar effect on the vertical magnetic transfer function at Eskdalemuir Observatory, Scotland
Get PDFGeomagnetic observations at Eskdalemuir observatory in Southern Scotland reveal reduced amplitudes in the vertical component variations compared with the horizontal components for periods of less than an hour. A subsurface high conductivity feature has previously been suggested to account for this anomaly. However, past studies have overlooked the effect of seasonal source changes and impact of solar activity on external geomagnetic field variations. The vertical magnetic transfer function —referred to as the tipper —relates temporal variations in the vertical magnetic field to those in the horizontal magnetic field and is sensitive to lateral electrical conductivity contrasts in the subsurface. Quantifying the seasonal variations in the tipper helps to identify times when external field variations minimally bias tipper estimates, thereby providing a more accurate representation of subsurface conductivity. Ionospheric current systems, particularly during geomagnetic storms, may violate the plane wave assumption underlying tipper estimation at mid-latitudes. This may allude to a more complex source geometry responsible for magnetic field variations. Our study quantifies and proposes a correction for space weather-driven external field contributions to observations for periods shorter than 1 hr. Using high-quality digital magnetic field data with a 1-min sampling rate from 2001 to 2019, we estimate the tipper at Eskdalemuir, revealing seasonal differences that increase with periods between 1000 s and 10 000 s. After finding that tipper estimates during the 2016 time-series are least affected by seasonal effects, we used 1-s time-series and a simple empirical model to quantify the daily variability of the tipper. The model consists of annual and semi-annual terms plus a term proportional to either the F 10.7 cm solar flux or geomagnetic Ap index. Neither model fits the data to within the expected error, but the model that uses Ap has better fit. Tipper estimates from temporary site deployments are affected by these seasonal external variations, and we correct those obtained at sites near Eskdalemuir during a recent field experiment using this model
The geomagnetic and geoelectric response to the May 2024 geomagnetic storm in the United Kingdom
Get PDFThe “Gannon” geomagnetic storm of 10 −12 May 2024 was the first extreme storm of the solar cycle 25 and the largest storm in more than 20 years. The auroral electrojet, driven by a strong negative interplanetary magnetic field exceeding −50nT, moved towards the equator in the evening of the 10th May reaching the latitudes of central and southern England (below 54N) for several hours. Widespread sightings of the aurora were observed across the country, and rapid variations of the magnetic field were recorded in the United Kingdom (UK). Here we present the geomagnetic and geoelectric data recorded during the storm in the UK together with models of ground effects and images of auroral displays around the country. We compare the May 2024 storm with geomagnetic data from the September 2017, October 2003, March 1989 as well as September 1859 Carrington event to demonstrate the differences in magnitude, timings and latitudinal extent between these events. We use the geomagnetic observations, and a ground electric field model based on magnetotelluric data combined with the high-voltage power grid network information to estimate geomagnetically induced currents (GICs) at substation level during the storm. The highest modelled GICs exceeded 60 A in substations in southwest and east−central England as well as northern Wales. Substation GICs modelled in higher latitude stations in Scotland exhibited lower values because the leading edge of the auroral oval rapidly moved to lower latitudes. The “Gannon” storm compared to historical storms on a global scale in terms of the aa* index, ranks third since 1868, after March 1989 and September 1941. However locally, the maximum magnetic field rate of change suggests it is closer to a 1−in−30 years event. Hence, there was relatively little impact on grounded technology in the United Kingdom
Where and when the mesopelagic carbon budget balances, if at all
Get PDFThe ocean biological carbon pump (BCP) transports organic matter from the surface to the deep ocean. Accurately quantifying the efficiency of the BCP is essential for understanding potential climate feedbacks and entails measuring the flux of organic material in and out of the mesopelagic layer (approximately 100–1,000 m). Observational estimates are often restricted to measuring the BCP efficiency over short timescales. Here we use an ocean biogeochemical model to diagnose where, and on what timescales, the mesopelagic is sufficiently in steady state that balancing the carbon budget may be possible. For the majority of the ocean the sources and sinks of organic carbon in the mesopelagic do not balance on timescales shorter than 1 year. Assuming steady state risks falsely inferring the existence of missing processes or the magnitudes of known ones to close the budget and will lead to incorrect estimates of the strength of the BCP
Is Britain divided by an Acadian suture?
No full textThe Appalachian−Caledonide orogen records protracted Paleozoic convergence during Iapetus Ocean closure. Grampian−Taconian arc-continent collision at the Laurentian margin and subduction polarity reversal were followed by Ordovician to Silurian subduction-accretion beneath the Laurentian margin, culminating in continental collision in the Scandinavian Caledonides, and soft collision along the Solway−Navan−Silvermines line in Britain and Ireland. Laurentia-derived detrital zircon crossed this boundary, commonly regarded as the main Iapetus suture, upon collision at ca. 430 Ma. Calc-alkaline magmatism continued into the Devonian on both sides of the supposed suture, producing the “trans-suture suite” of magmatic rocks that extend south as far as a boundary, here termed the Ynys Môn line, separating the Lakesman terrane from the Monian belt of North Wales. South of this line, Laurentia-derived detritus is absent from Silurian samples, but appears in Emsian Old Red Sandstone. Laurentia-derived detritus was held up at the Ynys Môn line for at least 12 Myr. This boundary is interpreted as a previously unrecognized suture, recording obliquely sinistral north-dipping subduction of a remaining tract of Iapetus, leading to magmatism north of the boundary and eventual Acadian collision
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