Size Class Distribution Research Articles

Water holding capacity, aggregation, respiration, and chemical character of acid soil amended rice straw biochar enriched with different volumes of liquid extract (sap) of Kappapychus alvarezii

The quality of acidic soil is determined by organic C content produced from rice straw biochar in agriculture. In this context, liquid extract from Kappapychus alvarezii (K-sap) is used as a biochar enrichment agent. Therefore, this research aimed to (i) analyze the character of K-sap enriched rice straw biochar with different volumes, as well as (ii) evaluate the impact on soil water holding capacity, size class distribution, aggregate stability index, respiration rate, and acidic soil chemical characters. The treatment tested was the volume of K-sap kg-1 biochar, namely (i) without biochar, (ii) 0 mL, (iii) 500 mL, (iv) 1,000 mL, and (v) 1,500 mL. Each treatment was repeated three times and placed according to a randomized block design procedure. The area covered by K-sap, pore size, and amorphous degree increased while the pore volume of the biochar surface decreased. The addition of 1,000 mL of K-sap kg-1 biochar released a new peak number associated with the aliphatic and aromatic groups. The K-sap enriched biochar increased the proportion of soil aggregate size of 1-2 mm, water holding capacity, carbon storage, pH, total N, available P and K, exchangeable base cations as well as base saturation. Meanwhile, the concentration of Al3+ and H+ were decreased in the acidic soil solution. The results showed that the performance of rice straw biochar, K-sap volumes, soil chemical quality, water holding capacity, and ability to store carbon of the acidic soil was improved by adding K-sap volume.

Endemic Prunus species in the high Himalayas, Eastern Nepal, seeking conservation

Prunus species play an important role in preserving the Nepal's unique identity; such as three endemic species of Prunus, Prunus topkegolensis, Prunus jajarkotensis, and Prunus taplejungnica, represent the country's local area. An ecological and social survey of P. topkegolensis and P. taplejungnica was conducted. To analyze these species' regeneration status and population structures, the density of seedlings, saplings, and adult trees were compared, and created a diameter size class diagram. The Wilcoxon signed-rank test was used to compare the average values of seedlings, saplings, and adult trees between two species. To determine the ethnobotanical importance of a species, the relative frequency of citation (RFC) was calculated for various use categories. We classified both species as trees as the average diameter at breast height (DBH) of P. topkegolensis was 19.55 ± 14.66 cm with an average height 5.05 ± 2.28 m, while that of P. taplejungnica was 14.5 ± 7.93 cm with an average height of 4.89 ± 1.66 m. P. topkegolensis had an average 32 ± 31 adult trees, 16 ± 15 saplings, and 21 ± 18 seedlings per 0.1 ha, while P. taplejungnica had 12 ± 5 adult trees, 2 saplings, and 6 ± 4 seedlings per 0.1 ha. The number of seedlings and saplings at the plot level differed significantly between species (W = 75.5, p- = 0.05, and W = 84, p = 0.01, respectively). Both had humped-shaped diameter at breast height size class distribution. However, P. taplejungnica had a more apparent hump-shaped diameter at breast height distribution than P. topkegolensis, indicating that P. taplejungnica has more unsustainable regeneration issues. P. taplejungnica was locally recognized as a separate species from P. rufa, whereas P. topkegolensis was not. P. topkegolensis have seven different use categories, with wood and fuel wood being the most frequently cited, with RFC value 1. Rapid vulnerability assessment (RVA) showed both species are having high conservation threats. In situ conservation measures are suggested to address the issue of poor regeneration and disturbances.

Assessing structure, spatial patterning, and size class distribution of miombo woodland species along a precipitation gradient

Our study investigates the intricate ecological mechanisms shaping miombo woodlands across a rainfall gradient in Zimbabwe. We comprehensively analysed vegetation structure, tree morphology, and spatial patterning across three distinct ecological regions characterized by varying mean annual precipitation (MAP). Results reveal that taller and larger trees are prevalent in the more humid site, while higher tree density is observed in the drier site. The spatial analysis highlights a significant aggregation of adult miombo species across all sites, with juveniles exhibiting a propensity to cluster around adult trees. These findings underscore the pivotal role of ecological gradients, such as precipitation, in shaping miombo woodland structure. However, the absence of clear spatial patterns across the rainfall gradient suggests that precipitation may have less influence on the spatial distribution of miombo trees. Understanding these complex ecological dynamics is essential for developing targeted conservation and management strategies that align with the unique attributes of miombo woodlands, critical ecosystems within the African landscape particularly vulnerable to global climate change.

Commercial maize hybrids have smaller root systems after 80 Years of breeding

Roots have gained attention for their role in improving plant function in high-stress environments and providing ecosystem services such as soil organic carbon storage. An important step in breeding for enhanced root phenotypes is understanding how root traits have changed historically due to selection for yield and other aboveground traits. However, among the few era panel studies focused on roots, there are conflicting findings about how breeding has altered traits such as root system length and biomass, while other traits such as root depth distribution, root size class distribution, and tissue quality remain largely unexplored. Our aim was to assess breeding-driven changes in root traits that are relevant to resource acquisition and soil carbon sequestration. We grew twelve maize (Zea mays L.) hybrids from the Corteva/Pioneer ERA panel, spanning from 1936 to 2014, in 1.5 m deep mesocosms. At the eight-leaf stage, intact root systems were imaged and analyzed using a custom root phenotyping platform, and roots and shoots were subjected to carbon and nitrogen analysis and Diffuse Reflectance FTIR to assess variation in tissue composition. We found that the newest hybrids produced 40% less root biomass and 36% less root length than the oldest hybrids, with declines of 0.024 g year−1 (s.e.: 0.005, p < 0.01) and 0.86 m year−1 (s.e.: 0.23, p < 0.01) with no changes in maximum rooting depth, which averaged 113 cm (±5.62). , and no directional shifts in chemical composition. We also found a decline in the root-to-shoot ratio from 0.58 g g−1 to 0.46 g g−1 (s.e.: 0.0006, p < 0.05). Our results suggest that selection for yield has indirectly decreased root system size over 80 years of maize breeding. Smaller root systems of modern hybrids may contribute to the higher optimum plant populations and higher yields of modern maize hybrids.

Assessing Microplastics and Nanoparticles in the Surface Seawater of Venice Lagoon-Part I: Methodology of Research.

Microplastics (MPs) and nanoplastics (NPs) both represent significant concerns in environmental sciences. This paper aims to develop a convenient and efficient methodology for the detection and measurement of MPs and nanoparticles from surface seawater and to apply it to the water samples collected from the UNESCO site of Venice and its lagoon, more precisely in the Venice-Lido Port Inlet, Grand Canal under Rialto Bridge, and Saint Marc basin. In this study, MPs were analyzed through optical microscopy for their relative abundance and characterized based on their color, shape, and size classes, while the concentration and the mean of nanoparticles were estimated via the Nanoparticle Tracking Analysis technique. Bulk seawater sampling, combined with filtration through a cascade of stainless-steel sieves and subsequent digestion, facilitates the detection of MPs of relatively small sizes (size classes distribution: >1 mm, 1000-250 μm, 250-125 μm, 125-90 μm, and 90-32 μm), similar to the size of MPs ingested by marine invertebrates and fishes. A protocol for minimizing interference from non-plastic nanoparticles through evaporation, digestion, and filtration processes was proposed to enrich the sample for NPs. The findings contribute to the understanding of the extent and characteristics of MPs and nanoparticle pollution in the Venice Lagoon seawater, highlighting the potential environmental risks associated with these pollutants and the need for coordinated approaches to mitigate them. This article is based on scientific research carried out within the framework of the H2020 In-No-Plastic-Innovative approaches towards prevention, removal and reuse of marine plastic litter project (G.A. ID no. 101000612).

Spatial distribution of woody plants in relation to mistletoe-infected Vachellia karroo trees in a semi-arid African savanna

By increasing resource heterogeneity, mistletoe-infected trees can restructure plant community processes and distribution patterns. No information is available on how mistletoe-infected Vachellia (Acacia) karroo trees within V. karroo dominated stands are spatially distributed, and on how they influence the spatial patterns of their surrounding conspecifics and heterospecifics. Each woody plant was stem mapped using a cartesian plane (x, y) within three 50×50 m plots located in V. karroo dominated stands in a semi-arid savanna, South West Zimbabwe. Pair correlations g(r) were used for the univariate analysis and Poisson process null models were applied to quantify and detect overall departure from randomness. For the bivariate analysis, pair correlations g12(r) under the null model of independence were used, whilst the mark correlation function (kmm(r)) was used to analyse the correlation of tree canopy area and mistletoe infection intensity. For each plot, size class distributions, based on tree height and basal stem diameter displayed negative J curves, with steep negative regression slopes across the size classes, clearly indicating a strongly recruiting population of V. karroo. The univariate patterns of all trees (infected and non-infected) were consistent with a random pattern, which is attributed to unsystematic mistletoe seed dispersal by birds. The univariate analysis of all woody plants (adults and juveniles) exhibited aggregation at small spatial scales due to the high abundance of clustered seedlings and saplings. At small spatial scales, understory woody plants (both conspecifics and non-conspecifics) were positively associated with mistletoe-infected trees due to mistletoephily which is the facilitation (or nurse protégé interactions) within the more resource-rich mistletoe-infected tree subcanopies. These results provide strong evidence suggesting that the variations in spatial pattern modification by mistletoe-infected trees could further increase spatial heterogeneity in this semi-arid savanna. As such, by increasing heterogeneity, mistletoe-infected trees can increase the resilience of semi-arid savannas in the face of perturbations and stochastic events.

Karakteristik Biologi dan Kelimpahan Rajungan (Portunus pelagicus) di Sekitar Perairan Sumenep

The high demand for the crab export market has resulted in the crab commodity experiencing a decline and leading to exploitation. Prediction of crab stocks in Sumenep Regency is minimal due to a need for further information regarding crab data. This study aims to determine the biological characteristics of the blue swimming crab (Portunus pelagicus), limiting blue swimming crab (Portunus pelagicus), and water quality characteristics around Sumenep. Research methods is observation methods or directly contact fishermen. Data collection included blue swimming crab biology, including morphometric aspects, which consisted of measurements of carapace width, carapace length, weight, and level of gonadal maturity. Data collection for water quality parameters used the insitu method at each research location. The results of this study were variations in the morphometric characters of the crabs in the distribution of the carapace width of the male crabs found in class 121-138 mm, as many as 137 individuals, while the female crabs were found in class 121-138 mm as many as 136 individuals, the distribution of size class based on the length of the female crab in class 60 .42-68.42mm as many as 112 people. The size class distribution of male crabs was mainly found in the 51.42-59.42mm class of 96 individuals; the distribution of size classes based on the weight in male crabs in the 126-157 gram class was 65 individuals. The size class of female swimming crabs was found in the 158-189 gram class; as many as 67 individuals applied for crabs around Sumenep. Based on the crab data collection at the first location, Talango was 289 ind/700 cm2, the second location was Tanjung Saronggi, 65 and/700 cm2, and in the third location, Gili Genting, there was as much as 104 ind/700 cm2. The waters of Tanjung Saronggi are a location that has more male crabs than female crabs. The air quality characteristics around Sumenep waters are categorized as optimal for blue swimming crab habitat.

A diatom extension to the cGEnIE Earth system model – EcoGEnIE 1.1

Abstract. We extend the ecological component (ECOGEM) of the carbon-centric Grid-Enabled Integrated Earth system model (cGEnIE) to include a diatom functional group. ECOGEM represents plankton community dynamics via a spectrum of ecophysiological traits originally based on size and plankton food web (phyto- and zooplankton; EcoGEnIE 1.0), which we developed here to account for a diatom functional group (EcoGEnIE 1.1). We tuned EcoGEnIE 1.1, exploring a range of ecophysiological parameter values specific to phytoplankton, including diatom growth and survival (18 parameters over 550 runs) to achieve best fits to observations of diatom biogeography and size class distribution as well as to global ocean nutrient and dissolved oxygen distributions. This, in conjunction with a previously developed representation of opal dissolution and an updated representation of the ocean iron cycle in the water column, resulted in an improved distribution of dissolved oxygen in the water column relative to the previous EcoGEnIE 1.0, with global export production (7.4 Gt C yr−1) now closer to previous estimates. Simulated diatom biogeography is characterised by larger size classes dominating at high latitudes, notably in the Southern Ocean, and smaller size classes dominating at lower latitudes. Overall, diatom biological productivity accounts for ∼20 % of global carbon biomass in the model, with diatoms outcompeting other phytoplankton functional groups when dissolved silica is available due to their faster maximum photosynthetic rates and reduced palatability to grazers. Adding a diatom functional group provides the cGEnIE Earth system model with an extended capability to explore ecological dynamics and their influence on ocean biogeochemistry.

Fire responses of flora in a sclerophyll–rainforest vegetation complex in the Nightcap Range, North Coast, New South Wales

Context Species fire responses were investigated in a mixed sclerophyll–rainforest ecosystem in the Nightcap Range, North Coast, New South Wales. Aims To examine rates of seedling recruitment and resprouting in functional and phytogeographic components of wet sclerophyll forest (WSRf), and adjacent open forest (OF) and rock outcrop shrubland (RO). Methods Species resprouting and seedling recruitment traits (fire responses) were recorded in 45 stem plots and 225 seedling subplots in WSRf, OF and RO. Species fire responses were classified, community fire-response spectra compiled and rates of seedling recruitment and resprouting in WSRf examined in relation to primary fire response, growth-form, habitat and broad functional and phytogeographic species groupings. Species size-regenerative class distribution was used to analyse population structure, fire impact, regeneration and recruitment in resprouter species that comprised most of the mesic-Gondwanan element of the WSRf flora. Key results WSRf, OF and RO habitats had distinctively different fire-response spectra. In WSRf, there was a high proportion of mesophyll resprouter species of Gondwanan origin with nil or very low seedling recruitment, a distinct component of mesophyll seeders of Indo-Malayan origin, as well as sclerophyll seeders and resprouters that also comprised most of the OF and RO floras. Resprouters comprised 75% of the WSRf flora, 50% OF and 10% pavement shrubland. Continuous size-class distributions indicated recruitment between fire events in the majority of mesophyll resprouters in WSRf. Lower total seedling density appeared to reflect inherent species traits and less canopy disturbance by fire. Large sclerophyll species forming the unburnt canopy of WSRf had very low seedling recruitment. Conclusions Different habitats (WSRf, OF and RO) and functional and phytogeographic clades in WSRf display distinctive patterns of resprouting and seedling-recruitment fire response. Fire responses of species that maintain species population and community composition are governed by fire regime, habitat variables and inherent species traits. Implications The distinctive fire-response spectrum of WSRf appears to be a direct consequence of the overlap of ‘new’ and ‘old’ floras in this broad vegetation type.

Spatiotemporal Variability in Phytoplankton Size Class Modulated by Summer Monsoon Wind Forcing in the Central Arabian Sea

AbstractThe Arabian Sea is an area of intense ocean‐atmospheric coupling that impacts its physicochemical, and biological processes. During the summer monsoon (June‐September), in the central Arabian Sea, a low‐level atmospheric jet blows parallel to the Arabian Peninsula causing open ocean upwelling in the north and downwelling in the south of the jet axis. High wind speeds are witnessed in the jet axis which advect nutrients from the Somali coast. Consequently, hydrography and physicochemical parameters show high spatial variability. In this dynamic region, phytoplankton size class distribution, directly controlled by nutrient supply, can be modulated by monsoon wind variability via upwelling, advection, and entrainment, however, has not been investigated recently. We studied phytoplankton size class related to atmospheric forcing, hydrography, and nutrient stoichiometry in August 2017 and 2018 along 64°E (11°N–21°N). Chemical taxonomy‐based analysis (CHEMTAX and manual) revealed that in the north, upwelling‐driven nutrient enrichment supported microphytoplankton, mostly diatoms contributing ∼50% to phytoplankton biomass. A stronger upwelling due to higher wind forcing in 2018 compared to 2017 resulted in an enhanced nutrient supply as well as an increased contribution of diatoms. Prymnesiophytic nanophytoplankton distribution was linked to mixed layer depths with insignificant spatial variability (20%–30%). Conversely, in the nutrient‐poor southern region, zeaxanthin and DV‐Chla containing picocyanobacteria and prochlorophytes contributed &gt;50% to the total phytoplankton biomass and were associated with high temperatures. Likely, increasing warming and related changes in monsoon intensity might directly influence phytoplankton size classes impacting trophic transfer and carbon cycling.

Impact of 2015–2016 El Niño on phytoplankton size class distribution during the summer and winter monsoon in the Arabian Sea

ABSTRACT Phytoplankton community response to extreme climate variability has an important effect on the regional marine ecosystem. The 2015–2016 El Niño event has been the strongest El Niño event on record of the century, which has a high chance of impacting the most productive ecological zone like the Arabian Sea. In this study, we investigated the influence of the 2015–2016 El Niño on the seasonal pattern and its impact on the phytoplankton size class (PSC) distribution in the Arabian Sea based on monthly satellite PSC observations and physical observations from various sources from 2003 to 2019. Results showed that the 2015–2016 El Niño event influenced the physical drivers and consequently weakened the monsoonal pattern that led to the enhancement or inhibition of specific PSC in the Arabian Sea. During the 2015 summer monsoon, the intensity of summer upwelling was weaker than normal, which caused a reduction in the abundance of microplankton to ~8% and an increase in the abundance of picoplankton to ~12%. Similarly, during the 2016 winter monsoon, the weakening of convective mixing and the formation of warm core eddy led to a reduction in the abundance of microplankton to ~6% and an increase in the abundance of picoplankton to ~9%. However, the nanoplankton distribution was observed stable with no significant response to the extreme physical condition due to its ubiquitous nature. The effect of the 2015–2016 El Niño event altered the physical conditions and associated specific PSC distribution in the Arabian Sea. Notably, the distinct response of each PSC to the changing climate and their environmental adaptation was identified in this study. Our results indicated that the phytoplankton community structure and associated marine ecosystem are sensitive to the effects of climate change.

Size class, sex ratio, and spatial distribution of four populations of Pimelea microcephala subsp. microcephala under different long-term rainfall regimes

The separation of sexes in dioecious plants enables males and females to adopt different strategies to balance reproduction and growth, but can also lead to female susceptibility due to their high reproductive burden. Understanding if a dioecious species is susceptible or adaptable in the face of worsening abiotic conditions would be useful for revegetating habitats under climate change. Our study compared four populations of the Australian native shrub, Pimelea microcephala subsp. microcephala (n = 885) across an annual rainfall gradient of ∼250–400 mm to understand the impact of decreasing rainfall on size classes, growth metrics, sex ratio, the proportion of juveniles and spatial distributions. We found that irrespective of site rainfall, male and female plants achieved similar sizes. The populations exhibited four size classes, defined by height, diameter and sex, but not site rainfall (unpaired group method with arithmetic mean cluster analysis, p < .05). Spatially, populations reflected the clumped distribution of overlying canopy cover, and did not demonstrate niche partitioning between sexes. The lack of population variation with rainfall indicates that the species may be suitable for arid zone revegetation in arid regions with declining rainfall. Conservation management of the species should include maintaining canopy tree cover to encourage seed dispersal.

Distribution, population structure and microhabitat profile of Euphorbia bupleurifolia

Many South African succulent Euphorbia spp. are threatened by anthropogenic activities such as habitat loss and illegal harvesting. However, only a few species have been studied in sufficient detail to aid their conservation through the development of effective management plans. This study documents the distribution, abundance, and population biology of the formerly widespread Euphorbia bupleurifolia, a species endemic to the Eastern Cape and KwaZulu-Natal provinces of South Africa. Until recently, the status of wild populations of this species was largely unknown. Searches for plants in each of the 31 previously recorded localities revealed that only nine populations (29 %) still had plants in 2018, indicating a contraction of the distribution, with the species apparently now ranging from Makhanda to Port Edward. Population size and structure, flowering, microhabitat requirements and various other factors, including potential threats and disturbances, were quantified for the nine populations. Complete counts were conducted, and the diameters of plants were measured and canopy areas calculated. Population sizes varied from one (effectively extinct) to 675 plants (with a total of 1724 plants recorded across all populations). Measurements of cultivated plants at the Walter Sisulu National Botanical Garden established that the onset of reproduction can be expected for a plant with a canopy area of 2.63 cm2, and annual growth rates of 0.55±8.37 cm2 are possible. Bell-shaped size class distribution (SCD) patterns were dominant, which is attributed to an adult persistence population survival strategy. Unsustainable harvesting, inappropriate fire frequencies as well as habitat loss and degradation remain a threat to the species. Euphorbia bupleurifolia persists mostly in sites with low vegetation biomass, high bare ground cover and minimal overstorey shade. This study highlights the drastic decline of a Least Concern species, formally considered widespread (i.e. common), and provides baseline demographic data, which may be employed in future monitoring and management of the remaining populations, to improve the conservation of E. bupleurifolia. Intensified field surveys involving citizen science programmes (e.g. CREW) and subsequent uplisting of the species to a higher Red List threat category is recommended.

Rhynchostreon oyster assemblages across the Central European region: Three types of environment and an alternative view in the intraspecific variability of Rhynchostreon suborbiculatum (Lamarck, 1801)

The morphological variability in Rhynchostreon suborbiculatum (Lamarck, 1801) is a well-known phenomenon in the Cretaceous palaeobiology. The current study focuses on two morphotypes differentiated by the presence/absence of radial ribs on the apical part of the left valve, while the fusion of palaeoecological and morphological results allows the study of the evolution of R. suborbiculatum under specific environmental conditions. Based on analyses of grain size, concentration of major oxides and oyster taphonomy in five Cenomanian–Turonian oyster-bearing localities, three habitats that differ in substrate, energy level and salinity regime were recognised: the dynamic Cenomanian nearshore environment (environment B), the Turonian hemipelagic environment (environment C) and the Cenomanian–Turonian marginal marine environment influenced by river dynamics (environment A). An analysis of the size distribution and morphotype structures of three palaeopopulations of R. suborbiculatum shows lithofacial dependence in morphotype distribution, indicating substrate granularity and level of environmental energy. The higher prevalence of ribbed morphs in smaller size classes as well as in fine-grained deposits suggests that apical ribbing is an adaptive trait with a stabilising effect, especially during the early growth stages or when colonising low-energy environments with very soft substrates. The distribution of the large size classes, combined with the shell thickness and vaulting, suggest that the compensation provided by the ribs is insufficient in high energy environments, where strong waves, turbulent flow, and higher sedimentation rates are the main selection pressures. Thus, other adaptations, such as body size and massiveness of the shell, become more critical for the survival of individuals.

Nursery upweller type has minimal impact on subsequent grow-out of Eastern oysters (Crassostrea virginica)

Demand for oysters in the premium half-shell market drives the need for research to optimize and improve oyster aquaculture production methods. After setting, oysters are typically maintained in nursery upwellers that provide nutrients and oxygen while removing waste. They remain in the nursery until they are large enough to be deployed in aquaculture gear. Land-based upweller systems include silo and bottle upwellers, with bottles requiring less space and maintenance. However, it is unknown if upweller type influences oyster growth, shape, or survival after field deployment. This study reared Eastern oysters, Crassostrea virginica, to 2 mm in silo or bottle upwellers and deployed them to floating bags for a six-week grow-out period. Oysters were sampled initially, then size graded, counted, and redeployed every two weeks. Changes in growth parameters, quality ratios, survival, and hinge backbend deformity prevalence were determined after six weeks. Initially, silo-reared oysters were larger than those reared in bottles, likely due to the need for flow rate optimization and/or the tumbling action that breaks the fragile growing edge of the shell. Despite these initial differences, there were minimal size differences between upweller types after six weeks of growth in the field. There were no significant differences in survival, hinge backbend abnormality prevalence, or size class distribution between upweller types. These results indicate that upweller choice has minimal impact on the grow-out phase of oyster production and both systems are acceptable for Eastern oyster production in the northern Gulf of Mexico.

Early-melting snowpatch plant communities are transitioning into novel states

Snowpatch plant community distribution and composition are strongly tied to the duration of long-lasting snow cover in alpine areas; they are vulnerable to global climatic changes that result in warmer temperatures and longer growing seasons. We used a revisitation study to quantify early-melting snowpatch floristic and functional diversity change in southern Australia, and document shrub size-class distributions over time to detect evidence for their encroachment into snowpatches, a key prediction with climatic change. Early-melting snowpatch vegetation has declined in areal extent, changed in species composition, and shrub and tussock grass cover has increased, but changes in functional trait diversity were less clear. Species gains, particularly by non-clonal species, accounted for most of the floristic change observed. Shrub recruitment was ongoing by most shrub species. Biotic differentiation is occurring; many early-melting snowpatches are transitioning to a novel state with changed composition and taller vegetation structure, but there is little evidence for species loss having occurred. Given enough time, however, the long-term loss of species is likely (i.e. biotic homogenisation) if taller shrubs outcompete short-statured snowpatch species. Our results provide evidence that this alpine ecosystem is forming a novel community with an uncertain future.

Water column distribution of zooplanktonic size classes derived from in-situ plankton profilers: Potential use to contextualize contaminant loads in plankton

Pollution is one of the main anthropogenic threats to marine ecosystems. Studies analysing the accumulation and transfer of contaminants in planktonic food webs tend to rely on samples collected in discrete water bodies. Here, we assessed the representativeness of measurements at the chlorophyll-a maximum layer during the MERITE-HIPPOCAMPE cruise for the entire water column by investigating the vertical distribution of particles and plankton obtained by in-situ optical profilers at nine stations across the Mediterranean Sea. We identified specific conditions where the interpretation of results from contaminant analyses can be improved by detailing plankton size structure and vertical distributions. First, the presence of higher than usual plankton concentrations can result in sampling issues that will affect biomass estimation within each size class and therefore bias our understanding of the contaminant dynamics. Secondly, the presence of an unsampled water layer with high zooplankton biomass might imply non-resolved contaminant pathways along the trophic structure. This study lays the basis for optimizing sampling strategy in contaminant studies.

Insights from analyzing local ecological knowledge and stand structure for guiding conservation actions for the endangered tropical tree Pterocarpus erinaceus. Poir

Sustainable management and conservation of multipurpose tree species in their natural habitats is crucial, given their vulnerability to climate change and increasing human activities. This can be achieved by harnessing insights from local ecological knowledge (LEK) and classical ecological approaches to support biodiversity conservation efforts. Using forest inventory data from 126 plots and information from a semi-structured survey of 234 households, we investigated LEK (perception on population trend, causes, and conservation attitudes toward the species) and population ecology (tree density, size class distribution – SCD, structural diversity, and stability) of the endangered rosewood Pterocarpus erinaceus Poir. along a climate gradient in Benin (Sudanian (SZ), Sudano-Guinean (SGZ) and Guinean (GZ)). The results indicated that local communities were aware of the decline of P. erinaceus populations, although variations were observed with respect to ethnicity and age. The protection of the species regeneration by the communities in the GZ (63 %) probably led to the high regeneration rate (90 %) of P. erinaceus in this zone. Tree density declined from the SZ to GZ (2 and 1.23 times lower in SGZ and GZ compared to SZ), but variation in the mean diameter at breast height showed the opposite pattern (1.98 and 1.90 times lower in SGZ and SZ than in GZ). The SCD in the SGZ exhibited a bell-shaped pattern, while the populations in the SZ and GZ showed an inverted J-shaped distribution. Pruning intensity was 6.60 to 35.25 times higher in the SZ than in the SGZ and GZ, respectively, where regeneration rates were low, reflecting the potential negative effects of pruning on regeneration. Furthermore, P. erinaceus demonstrated tolerance for mixed-species stands (mingling of 40 % to 75 %), indicating an opportunity to integrate it into agroforestry systems with other species. This research highlights the impacts of human activity and climate conditions on P. erinaceus populations and informs on potential management actions needed for the conservation of the species.

Vegetation description around the savanna flux measurement site at Benfontein Nature Reserve, South Africa

A flux tower with eddy covariance instruments was recently erected at Benfontein Nature Reserve (BNR) outside of Kimberley. An understanding of the landscape within the flux tower footprint, in this case natural vegetation, is necessary to interpret the data collected by the eddy covariance instruments. The tower was erected as part of the Expanded Freshwater and Terrestrial Environmental Observation Network (EFTEON) infrastructure initiative to establish long-term monitoring platforms focused on socially relevant terrestrial landscapes and their coupled hydrological systems. We sought to describe the vegetation within the flux tower footprint to set a baseline of the vegetation in the landscape at the inception of the long-term monitoring of flux measurements at BNR. Woody vegetation was surveyed in five square 1 ha plots while the herbaceous layer was sampled across 105 circular plots following the Socio-Ecological Observatory for Southern African Woodland (SEOSAW) protocol. Woody vegetation was quantified in terms of abundance, diversity and biomass, together with Size Class Distribution (SCD) methods to describe the woody vegetation structure. The herbaceous layer was described by species count, basal cover, biomass, and diversity which was assessed using the Shannon-Weiner Diversity Index. Five tree species, dominated by Vachellia erioloba, were found in the plots. Recruits (0 and 1 m tall) were significantly more abundant than large trees (1.2–9.5 m high). The SCD for the woody vegetation yielded a Type IIIa curve i.e. populations missing one or more size classes, for all tree species except Ziziphus mucronata which yielded a Type IIIb curve representing a population missing small sized trees. The herbaceous layer was diverse, consisting of 10 grass and 32 forb species. Schmidtia pappophoroides was the dominant grass species in terms of count, basal cover and aboveground biomass. Herbaceous biomass was two times higher than that of woody vegetation, with the North plot contributing the highest biomass for herbaceous and woody vegetation. The results indicate that the vegetation around the flux tower represents a wooded grassland, which is a type of a savanna. These vegetation data will contribute to the interpretation of data collected by the flux tower instruments now and in the future. Furthermore, long-term data collection in this reserve is needed to capture the woody vegetation dynamics and its interaction with the herbaceous layer.

Environmental DNA (eDNA) removal rates in streams differ by particle size under varying substrate and light conditions

The use of environmental DNA (eDNA) as a sampling tool offers insights into the detection of invasive and/or rare aquatic species and enables biodiversity assessment without traditional sampling approaches, which are often labor-intensive. However, our understanding of the environmental factors that impact eDNA removal (i.e., how rapidly eDNA is removed from the water column by the combination of decay and physical removal) in flowing waters is limited. This limitation constrains predictions about the location and density of target organisms after positive detection. To address this question, we spiked Common Carp (Cyprinus carpio) eDNA into recirculating mesocosms (n = 24) under varying light (shaded versus open) and benthic substrate conditions (no substrate, bare substrate, and biofilm-colonized substrate). We then collected water samples from each mesocosm at four time points (40 min, 6 h, 18 h, and 48 h), and sequentially filtered the samples through 10, 1.0, and 0.2 μm filters to quantify removal rates for different eDNA particle sizes under varying light and substrate conditions. Combining all size classes, total eDNA removal rates were higher for mesocosms with biofilm-colonized substrate compared to those with no substrate or bare (i.e., no biofilm) substrate, which is consistent with previous findings linking biofilm colonization with increased eDNA removal and degradation. Additionally, when biofilm was present, light availability increased eDNA removal; eDNA levels fell below detection after 6–18 h for open mesocosms versus 18–48 h for shaded mesocosms. Among size classes, larger particles (>10 μm) were removed faster than small particles (1.0–0.2 μm). These results suggest that changes in the distribution of eDNA size classes over time (e.g., with downstream transport) and with differing environmental conditions could be used to predict the location of target organisms in flowing waters, which will advance the use of eDNA as a tool for species monitoring and management.