Ecological Processes Research Articles

Aggregating taxa and the influence of scale: Potential concerns for analysis of stability using functional measures

AbstractA functional group approach to analyzing ecological processes calls for aggregating species populations' data (e.g., biomass, abundance) into larger functional units. This method offers a more direct insight into the coarse community and ecosystem dynamics than a species level. Since aggregation changes the scale of analysis, it is reasonable to expect that the results and inferences will also change. To gauge the nature and size of this effect, we examined two sets of communities using the same methodology at taxonomic and functional levels. We asked how asynchrony among constituent populations stabilizes the regional biomass or abundance in two systems: zooplankton in North American temperate lakes and rock pool invertebrates in Jamaica. We aggregated species into pairs by organism size for the functional level analysis because it correlates well with life history traits. We hypothesized that taxonomical and functional level analyses would yield different pictures and inferences. We analyzed asynchrony among local populations, metapopulations, and populations of different species at different locations. We found that in lakes, different asynchrony classes contributed to the stabilization of the regional metric than in the rock pools. We further found that aggregation of taxa into functional units changed the pattern of differences between lakes and rock pools revealed by taxonomical analysis and that each set of communities responded differently to species lumping. While aggregating taxa leads to different results, the taxonomic and functional lenses add new insights to the biological interpretation of mechanisms stabilizing communities when interpreted jointly. Specifically, population asynchrony—a known stabilizing factor—can provide complementary stabilizing mechanisms when seen through taxonomic and functional lenses. Without exposing these modes, inferences about abundance/biomass/richness stabilizing contributions arising from asynchrony will remain tenuous. Exposing these modes offers a path for significant breakthroughs in linking local, spatial, and functional structures to multispecies system dynamics.

Migratory singers dynamically overlap the signal space of a breeding warbler community.

Migratory species inhabit many communities along their migratory routes. Across taxa, these species repeatedly move into and out of communities, interacting with each other and locally breeding species and competing for resources and niche space. However, their influence is rarely considered in analyses of ecological processes within the communities they temporarily occupy. Here, we explore the impact of migratory species on a breeding community using the framework of acoustic signal space, a limited resource in which sounds of species within communities co-exist. Migrating New World warblers (Parulidae, hereafter referred to as migrant species) often sing during refueling stops in areas and at times during which locally breeding warbler species (hereafter breeding species) are singing to establish territories and attract mates. We used eBird data to determine the co-occurrence of 19 migrant and 11 breeding warbler species across spring migration in SW Michigan, generated a signal space from song recordings of these species, and examined patterns of signaling overlap experienced by breeding species as migrants moved through the community. Migrant species were present for two-thirds of the breeding season of local species, including periods when breeding species established territories and attracted mates. Signaling niche overlap experienced by individual breeding species was idiosyncratic and varied over time, yet niche overlap between migrant and breeding species occurred more commonly than between breeding species or between migrant species. Nevertheless, the proportion of niche overlap between migrant and breeding warblers was similar to overlap among breeding species. Our findings showed that singing by migrant species overlapped the signals of many breeding species, suggesting that migrants could have unexplored impacts on communication in breeding species, potentially affecting song detection and song evolution. Our study contributes to a growing body of research documenting the impacts of migratory species on communities and ecosystems.

Abstract PR003: Multi-drug adaptive therapy protocol in vitro: An exercise in optimization for neuroblastoma

Abstract From initiation, invasion, dissemination to local and distant progression, relapse, recurrence to metastasis – clinico-pathological development of cancer follows the ecological processes of a multi-species niche construction. Ecological interactions result in adaptive changes that are driven by Darwinian evolution. This can be observed in the heterogeneity of tumor cells and their differential response to therapy. Some tumor cells are sensitive to treatment and can be eliminated by therapy, while others are resistant and can survive and proliferate under therapy. Adaptive therapy is a novel approach that leverages the competitive dynamics between sensitive and resistant cells, by dynamically adjusting the therapy dose and schedule based on biomarkers of tumor burden. In this study, we propose a multi-drug adaptive therapy protocol that uses two drugs with orthogonal mechanisms of action, meaning that they target different pathways or processes in the cancer cells. We investigate how to optimize the switching time between the two drugs, based on the personalized response to therapy and the evolutionary trade-offs between resistance and fitness and describe a corresponding real-time in vitro protocol. We performed experiments using two human neuroblastoma cell lines, sknbe2c and lan1, which exhibit distinct resistance profiles to different therapies, have different genetic profiles and show different growth patterns. We chose the combination of cisplatin and vincristine as the drugs of interest, since they are part of the Rapid COJEC protocol, which is a standard multidrug regimen for treating high-risk neuroblastomas in children. We monitored the drug treatment effects using noninvasive real-time microscopy based on cellular holography, which allows us to capture the morphological and behavioral changes of the cells. We fitted the treatment response curves with a stochastic diffusion equation that incorporates evolutionary mechanisms such as speciation, cost-dependent predator-prey interaction and drift, to model the dynamics of drug resistance and sensitivity. Unlike conventional therapy, which follows a fixed schedule and dose, adaptive therapy uses biomarkers of tumor burden, such as imaging or circulating tumor cells, to guide the timing and intensity of treatment. We propose a stochastic model that predicts the optimal switching time between two drugs based on the personalized response to therapy, which is inferred from Bayesian updating of the model parameters. This results in a patient-specific response model that accounts for the uncertainty and variability in the data. Assuming that a reliable and sensitive measure of tumor burden is available, we demonstrate how our model can be used to design a customized multi-drug adaptive therapy protocol for each patient. We are currently testing the efficacy of our protocol over other conventional protocols, and we plan to translate it to patient derived xenograft mouse models of neuroblastoma in the future. Citation Format: Subhayan Chattopadhyay, Jenny Karlsson, David Gisselsson. Multi-drug adaptive therapy protocol in vitro: An exercise in optimization for neuroblastoma [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Translating Cancer Evolution and Data Science: The Next Frontier; 2023 Dec 3-6; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_2):Abstract nr PR003.

Urban Rats ( Rattus norvegicus ) through a One Health Lens: Social and Ecological Factors Promote Opportunities for Urban Leptospirosis in Rats, Dogs, and People

Abstract Living in cities creates One Health challenges because urban environments can promote pathogen transmission in wildlife and human-wildlife interactions with commensal species such as rats. In this study, we examined social and ecological processes that lead to an elevated risk of leptospirosis, a fatal rat-associated disease transmitted through Leptospira interrogans bacteria in urine. We examined rat and human factors associated with (1) human exposure to rat urine in the home environment, (2) the presence of rats carrying L. interrogans on the block, and (3) environmental conditions associated with rat infection. We surveyed residents and trapped rats on the same 16 blocks in four neighbourhoods in Chicago. Survey respondents were more likely to observe rat urine in their homes if they had lower incomes. Blocks where rats were carrying L. interrogans had higher rat abundance and respondents with higher incomes, who reported dogs dying from leptospirosis, children playing in yards with rat waste, flooded yards, and gardens with rat burrows. Rats were more likely to be infected with L. interrogans if they were trapped on a block with more accessible garbage and if they were older. Our results highlight that rat presence alone does not determine the risk of close contact with rat-associated pathogens; socio-economics can affect an individual’s ability to exclude animals from living spaces. In addition, improved waste management may help mitigate disease risks for humans, wildlife, and domestic animals. We also discuss opportunities for public education about rat-associated zoonoses and lessons learned about meaningful community engagement in One Health work. Information © The Authors 2024

Offspring sex ratio increases with paternal reproductive success in a colony of southern elephant seals

AbstractIn polygynous species, male reproductive success is often determined by their ability to dominate female harems. Harem‐holders sire a disproportionate number of offspring. Male dominance tends to correlate with age, but intense competition and early male mortality limit most males from achieving high social status. To maximize reproductive success despite low rank, offspring sex ratio adjustment may have evolved, favoring the sex with higher fitness. If traits influencing dominance are heritable and confer reproductive advantages, we expect fathers with higher reproductive success to produce more sons, as they are more likely to become dominant. In contrast, subordinate males with lower success may benefit from siring more daughters. We tested this hypothesis on a colony of southern elephant seals breeding on the Kerguelen Archipelago. We used genetic markers to link the paternity of 540 pups to 58 breeding males. We found that the probability of siring a son increases from 43% to 54% with paternal relative reproductive success, supporting the offspring sex ratio adjustment hypothesis. Given that various factors influence sex ratio in a population, future studies should tease apart these ecological processes (e.g., paternal dominance, maternal condition, local density, or adult sex ratio) and investigate how they interact with each other.

Stochastic and deterministic assembly processes of microbial communities in relation to natural attenuation of black stains in Lascaux Cave.

Community assembly processes are complex and understanding them represents a challenge in microbial ecology. Here, we used Lascaux Cave as a stable, confined environment to quantify the importance of stochastic vs deterministic processes during microbial community dynamics across the three domains of life in relation to an anthropogenic disturbance that had resulted in the side-by-side occurrence of a resistant community (unstained limestone), an impacted community (present in black stains), and a resilient community (attenuated stains). Metabarcoding data showed that the microbial communities of attenuated stains, black stains, and unstained surfaces differed, with attenuated stains being in an intermediate position. We found four scenarios to explain community response to disturbance in stable conditions for the three domains of life. Specifically, we proposed the existence of a fourth, not-documented yet scenario that concerns the always-rare microbial taxa, where stochastic processes predominate even after disturbance but are replaced by deterministic processes during post-disturbance recovery. This suggests a major role of always-rare taxa in resilience, perhaps because they might provide key functions required for ecosystem recovery.IMPORTANCEThe importance of stochastic vs deterministic processes in cave microbial ecology has been a neglected topic so far, and this work provided an opportunity to do so in a context related to the dynamics of black-stain alterations in Lascaux, a UNESCO Paleolithic cave. Of particular significance was the discovery of a novel scenario for always-rare microbial taxa in relation to disturbance, in which stochastic processes are replaced later by deterministic processes during post-disturbance recovery, i.e., during attenuation of black stains.

Monospecific mangrove reforestation changes relationship between benthic mollusc diversity and biomass: Implication for coastal wetland management

Anthropogenic causes are overtaking natural factors to reshape patterns of biodiversity and ecosystem functioning. Mangrove reforestation aimed at reversing losses of mangroves has been conducted worldwide for several decades. However, how reforestation influences the link between ecological processes that shape community diversity and the consequent effects on ecosystem functions such as biomass production is less well known. Here we used data collected before and after mangrove planting to examine the effects of reforestation on molluscan species richness and biomass production by testing the changes in species richness, compositional similarities, distance-decay effects (community similarity decreases with increasing geographical distance) in metacommunity across a regional scale of 480 km (23–27 °N) in southeast Chinese coasts. Additionally, we further detected the impact of landscape configuration caused by different intensities of reforestation on the mollusc community. After the mangrove reforestation, mollusc species richness and biomass increased significantly. The increases in species richness and biomass of mollusc community were mediated by reducing distance-decay effect, indicating an increase in relationship strength between species richness and biomass might be associated with a decrease in distance-decay effect with rising mangrove habitat. We highlight the importance of considering the effects of anthropogenic changes on the relationship between biodiversity and ecosystem functioning. Quantifying the distance-decay effect of these influences enables management decisions about coastal restoration to be based upon ecological mechanisms rather than wishful thinking or superficial appearance.

Mapping the susceptibility of reefs to rubble accumulation across the Great Barrier Reef

Disturbance-induced rubble accumulations are described as “killing fields” on coral reefs as coral recruits suffer high post-settlement mortality, creating a bottleneck for reef recovery. The increasing frequency of coral bleaching events, that can generate rubble once coral dies, has heightened concerns that rubble beds will become more widespread and persistent. But we currently lack the tools to predict where rubble is most likely to accumulate. Here, we developed a modelling framework to identify areas that are likely to accumulate rubble on forereef slopes across the Great Barrier Reef. The algorithm uses new high-resolution bathymetric and geomorphic datasets from satellite remote sensing. We found that 47 km of reef slope (3% of the entire reef surveyed), primarily in the southern region, could potentially reach 50% rubble cover. Despite being statistically significant (p < 0.001), the effects of depth and aspect on rubble cover were minimal, with a 0.2% difference in rubble cover between deeper and shallower regions, as well as a maximum difference of 0.8% among slopes facing various directions. Therefore, we conclude that the effects of depth and aspect were insufficient to influence ecological processes such as larval recruitment and recovery in different coral communities. Maps of potential rubble accumulation can be used to prioritise surveys and potential restoration, particularly after major disturbances have occurred.

The interior climate and its microclimatic variation of temperate forests in Northern Patagonia, Argentina

Knowledge on mesoclimatic zonation and microclimatic variations within mountain forest ecosystems is crucial for understanding regional species turnover and effects of climate change on these systems. The temperate mountain forests in the Andean region of South America are among the largest and contiguous natural deciduous forest areas in the world. Due to their pronounced disturbance regime and different successional stages, a climatic zonation combined with the characterisation of its microclimatic variation is important to identify thresholds of species occurrences.We used micro-loggers to measure air temperature and relative humidity for one year at 40 measurement locations along longitudinal and elevation gradients in mountain forests in Northern Patagonia, Argentina. Our results unveil mesoclimatic patterns within these forests characterised by variations in temperature and vapour pressure deficit along the elevational gradient in general, but also at different times of the year. For example, Austrocedrus chilensis and Nothofagus dombeyi forests differed mainly by temperature and its diurnal range in the warmest months of the year. Also, differences between forest stands and gaps were more pronounced in the warmest months of the year and at lower elevations, with up to 2.5 K higher temperatures in the second half of the day in gaps. We found clear indications that shrubland of Nothofagus antarctica representing a successional stage after disturbances alters the mesoclimatic pattern, favouring forest fire ignition. Such mesoclimatic variations have a major influence on tree species turnover and ecological processes within these forest ecosystems.The findings contribute to our understanding of the complex interplay between topography, climate, and vegetation in shaping the spatial patterns of species occurrences.

The vertebrate bone hypothesis: Understanding the impact of bone on vertebrate stoichiometry

Abstract Understanding how animals store and recycle nutrients is a major question in ecological stoichiometry, a field that applies mass‐balance to ecological and physiological processes. However, ecological stoichiometry has thus far failed to accurately predict elemental demand and release in vertebrates. Because they invest in bone, a tissue mineralized with calcium phosphate, vertebrates are phosphorus (P) rich, allowing them to uniquely impact P cycling. Nonetheless, bone's impact goes further than merely changing vertebrate body elemental content. We propose a potential guiding hypothesis for vertebrate P stoichiometry called the ‘Vertebrate Bone Hypothesis (VBH)’. The VBH has three components: (1)Bone strongly impacts vertebrate whole‐body %P and N:P. (2) Bone is a P storage tissue that acts in elemental homeostasis. (3)Bone does not have constant elemental content. To characterize this hypothesis, we integrate bone physiology with stoichiometric principles, and we systematically review quantitative bone measurements to showcase cryptic diversity in vertebrate P content. Finally, we apply the characteristics of the VBH to ontogeny and reproduction, both of which impact bone physiology and elemental demand, to demonstrate the context dependency of bone's stoichiometric impact. Read the free Plain Language Summary for this article on the Journal blog.

Not just crop or forest: an integrated land cover map for agricultural and natural areas

Due to the key role surrounding landscape plays in ecological processes, a detailed characterization of land cover is critical for researchers and conservation practitioners. Unfortunately, in the United States, land cover data are split across thematic datasets that emphasize agricultural or natural vegetation, but not both. To address this gap, we merged two datasets, the LANDFIRE National Vegetation Classification (NVC) and USDA-NASS Cropland Data Layer (CDL), to produce integrated ‘Spatial Products for Agriculture and Nature’ (SPAN). Our workflow leveraged strengths of the NVC and the CDL to create detailed rasters comprising both agricultural and natural land-cover classes. We generated SPAN annually from 2012–2021 for the conterminous United States, quantified agreement and accuracy of SPAN, and published the complete computational workflow. In our validation analyses, we found that approximately 5.5% of NVC agricultural pixels conflicted with the CDL, but we resolved most conflicts, leaving only 0.6% of agricultural pixels unresolved in SPAN. These ready-to-use rasters characterizing both agricultural and natural land cover will be widely useful in environmental research and management.

Carbonate budgets induced by coral restoration of a Great Barrier Reef site following cyclone damage

Coral carbonate production is fundamental to reef accretion and, consequently, the preservation of essential reef ecosystem services, such as wave attenuation and sustained reef biodiversity. However, the unprecedented loss of coral reefs from anthropogenic impacts has put these valuable ecosystem services at risk. To counteract this loss, active rehabilitation of degraded reef sites has accelerated globally. A variety of restoration practices exist, tailored to local site needs and reef types. For sites where there is a significant unconsolidated substrate, Mars Assisted Reef Restoration System (MARRS, or “Reef Stars”) has been utilised to contribute toward rubble stabilisation and reef accretion. However, the effect of the Reef Stars on the local carbonate budgets and structural complexity has not been assessed. For that purpose, we assess coral cover and reef complexity through a census-based approach to identify the contribution of carbonate producers and eroders alongside studying coral skeletal properties to estimate current carbonate budgets on a rehabilitated site compared to natural unrehabilitated reef and rubble patches on the mid-Great Barrier Reef. Our research identified positive ecological processes and ecological functions such as increased carbonate budget, coral cover and structural complexity at the restored site compared to the non-intervened reef and rubble patches. In general, no impacts on skeletal rigour relative to this active reef restoration were found for two key coral species and the Acropora rubble for most of the skeletal traits. However, Pocillopora damicornis hardness seemed to decrease on the restored site compared to the other sites, demonstrating different performances of coral species during restoration activities that should be considered to maximise return-on-effort of restoration activities. Overall, our data demonstrate that consideration of carbonate budgets is important for measuring success of coral restoration initiatives and that coral restoration can be a relevant tool to recover lost local carbonate budgets.

Mean landscape‐scale incidence of species in discrete habitats is patch size dependent

AbstractAimA pervasive negative relationship between the species richness of an assemblage and the mean global range size of the species it contains has recently been identified. Here, we test for an effect of habitat patch size on the mean landscape‐scale incidence (estimating local range size) of constituent species independent of variation in richness.LocationGlobal.Time PeriodContemporary.Major Taxa StudiedVarious.MethodsWe devised a new standardized patch‐scale metric, Mean Species Landscape‐scale Incidences per Patch (MSLIP). Positive values indicate a patch contains more widespread (high‐incidence) species than expected relative to their frequency in the landscape; negative values indicate the presence of more narrow‐range (low‐incidence) species. For 202 metacommunity datasets (archipelagos, habitat islands and fragments) we regressed MSLIP on patch size, testing four hypotheses: (i) no effect (zero slope), (ii) more widespread species in smaller patches (negative slope), (iii) more narrow‐range species in smaller patches (positive slope), (iv) a composite effect (curvilinear/unimodal).ResultsThere was a generally negative curvilinear relationship between MSLIP and patch size, consistent with smaller and larger patches respectively containing more high‐ and low‐incidence species than expected. At intermediate patch sizes, mean species incidence approximates that of the overall landscape. Relative richness mediated this relationship; species‐rich sites of any size increasingly favoured low‐incidence species, species‐poor sites high‐incidence species. Results were consistent for taxonomic groups, and metacommunity types, except aquatic habitat islands.Main ConclusionsThe dependence of mean species incidence on both patch size and relative richness has implications for biodiversity and community assembly theory, or when seeking to understand ecological processes sensitive to species composition (e.g., ecosystem functioning, trophic web structures). We propose the ‘patch size where the MSLIP regression intersects zero’ as a benchmark distinguishing smaller from larger patches, with the expectation small patches preferentially support more high‐incidence and large patches more low‐incidence species.

Distinct Contributions of Climate Change and Anthropogenic Activities to Evapotranspiration and Gross Primary Production Variations over Mainland China

In recent decades, China has experienced substantial climate change and significant vegetation greenness due to the extensive implementation of artificial ecological restoration programs. However, the quantitative contributions of climatic and anthropogenic drivers to the national variations in associated evapotranspiration (ET) and gross primary productivity (GPP) over China at different climate zoning sub-regions remain unclear. Based on the analysis of climate factor and vegetation disturbance trends created by anthropogenic activities, this study constructed a remote sensing-based ecological model consisting of Penman–Monteith–Leuning (PML) and light use efficiency (LUE) components. The proposed model simulated the spatiotemporal changes in ET and GPP between 1999 and 2018 over China. The contributions of climatic factors and anthropogenic activities to ET and GPP variations were quantitatively calculated by ridge regression. The results show that (1) both interannual ET and GPP markedly increased, by 1.32 mm yr−1 and 8.01 g C m−2 yr−1, respectively; (2) vegetation changes due to anthropogenic disturbance made the dominant contribution to GPP variations over China, while the dominant factor influencing ET changes differed by sub-region due to the joint effects of vegetation and climate; (3) temperature and precipitation positively affected ET, while wind speed, humidity, and solar radiation negatively contributed to ET in most parts of Mainland China. These findings may provide a workable, scientific reference for further ecological restoration decision-making processes in China.

Defining the roles of local precipitation and anthropogenic water sources in driving the abundance of Aedes aegypti, an emerging disease vector in urban, arid landscapes

Understanding drivers of disease vectors’ population dynamics is a pressing challenge. For short-lived organisms like mosquitoes, landscape-scale models must account for their highly local and rapid life cycles. Aedes aegypti, a vector of multiple emerging diseases, has become abundant in desert population centers where water from precipitation could be a limiting factor. To explain this apparent paradox, we examined Ae. aegypti abundances at > 660 trapping locations per year for 3 years in the urbanized Maricopa County (metropolitan Phoenix), Arizona, USA. We created daily precipitation layers from weather station data using a kriging algorithm, and connected localized daily precipitation to numbers of mosquitoes trapped at each location on subsequent days. Precipitation events occurring in either of two critical developmental periods for mosquitoes were correlated to suppressed subsequent adult female presence and abundance. LASSO models supported these analyses for female presence but not abundance. Precipitation may explain 72% of Ae. aegypti presence and 90% of abundance, with anthropogenic water sources supporting mosquitoes during long, precipitation-free periods. The method of using kriging and weather station data may be generally applicable to the study of various ecological processes and patterns, and lead to insights into microclimates associated with a variety of organisms’ life cycles.

Revegetated riparian areas are dominated by weeds, and lack structural diversity and natural recruitment: lessons for restoration practice

Riparian areas can be highly biodiverse and provide critical ecosystem services. However, they are frequently subject to anthropogenic impacts such as land clearing, agricultural use, and urban development. Restoration of riparian areas via revegetation commonly improves the health of waterways and surrounding areas, but vegetation outcomes are rarely assessed. Our study compared 10 to 14‐year‐old revegetation to remnant vegetation in riparian areas of south‐eastern Australia to determine if species composition, vegetation structure, and ecosystem function (plant recruitment) differed. We also assessed if the amount of surrounding native vegetation, browsers (including deer, rabbits, and macropods), or soil characteristics influenced native woody plant recruitment at revegetated sites. While native and exotic woody species richness did not differ, native woody plants were less abundant and exotic woody plants twice as abundant at revegetated sites. The ground layer of revegetated sites was dominated by weeds, whereas remnant sites largely comprised native herbaceous plants and leaf litter. Tree heights and tree canopy cover were similar in revegetated and remnant areas, although shrubs and ferns were lacking in revegetation. Native woody plant recruitment was lower at revegetated sites and was negatively associated with browser presence. Our results suggest that while revegetation may have similar species richness and tree cover as remnant areas, weeds often dominate and important structural components such as shrubs and ferns, and ecological processes such as plant recruitment, are lacking. Better consideration of all vegetation strata, reduced browsing pressure and weed control are likely to achieve better revegetation outcomes.

Biodiversity of network modules drives ecosystem functioning in biochar-amended paddy soil.

Soil microbes are central in governing soil multifunctionality and driving ecological processes. Despite biochar application has been reported to enhance soil biodiversity, its impacts on soil multifunctionality and the relationships between soil taxonomic biodiversity and ecosystem functioning remain controversial in paddy soil. Herein, we characterized the biodiversity information on soil communities, including bacteria, fungi, protists, and nematodes, and tested their effects on twelve ecosystem metrics (including functions related to enzyme activities, nutrient provisioning, and element cycling) in biochar-amended paddy soil. The biochar amendment augmented soil multifunctionality by 20.1 and 35.7% in the early stage, while the effects were diminished in the late stage. Moreover, the soil microbial diversity and core modules were significantly correlated with soil multifunctionality. Our analysis revealed that not just soil microbial diversity, but specifically the biodiversity within the identified microbial modules, had a more pronounced impact on ecosystem functions. These modules, comprising diverse microbial taxa, especially protists, played key roles in driving ecosystem functioning in biochar-amended paddy soils. This highlights the importance of understanding the structure and interactions within microbial communities to fully comprehend the impact of biochar on soil ecosystem functioning in the agricultural ecosystem.

Factors influencing space-use and kill distribution of sympatric lion prides in a semi-arid savanna landscape.

Understanding lions' (Panthera leo) space-use is important for the management of multi-species wildlife systems because lions can have profound impacts on ecosystem-wide ecological processes. Semi-arid savanna landscapes are typically heterogeneous with species space-use driven by the availability and distribution of resources. Previous studies have demonstrated that lions select areas close to water as encounter rates with prey are higher and hunting success is greater in these regions. Where multiple lion prides exist, landscape partitioning is expected to follow a despotic distribution in which competitively superior prides occupy high-quality areas while subordinates select poorer habitats. In this study, Global Positioning System collar data and logistic regression were used to investigate space-use and hunting success among 50% of lion prides at Malilangwe Wildlife Reserve, Zimbabwe. Our findings show that lion space-use was driven by surface water availability and that home range selection was socially hierarchical with the dominant pride occupying habitat in which water was most abundant. In addition, we found that the effect of shrub cover, clay content and soil depth on kill probability was area specific and not influenced by hierarchical dominance. Where multiple lion prides are studied, we recommend treating prides as individual units because pooling data may obscure site and pride specific response patterns.

Optimizing nitrogen application position to change root distribution in soil and regulate maize growth and yield formation in a wide-narrow row cropping system: pot and field experiments.

The wide-and narrow-row cropping technology used for maize has the advantages of protecting cultivated soil and improving the population structure in maize fields. However, the relationship between nitrogen application position and root interactions has not been determined. Through pot and field experiments, we evaluated the effects of two nitrogen application positions ((narrow row nitrogen application (RC) and wide row nitrogen application (RN)) and two nitrogen application regimens ((high nitrogen(HN) and low nitrogen(LN)) on root growth and yield composition of wide-narrow row maize during the flowering and harvest stages. In field experiments, RC increased the biomass, length and surface area of competing roots (narrow-row roots, CR) at the flowering stage. The yield and agronomic efficiency of N(AEN) and partial factor productivity of N(PFPN) were increased by RN compared to RC under HN, However, the AEN under LN was significantly lower; There was no significant effect on maize growth and biomass allocation at the same level of application of N. At the flowering stage, the results of CR and non-competing roots (wide-row roots, NCR) was consistent under pot experiments and the field experiments, and the yield under RN was also higher than that under RC, although the difference was not significant. Furthermore, according to the principal component analysis and correlation analysis, the competing roots were the main factor influencing yield and AEN. In conclusion, our study showed that RN is a useful fertilization method to improve overall productivity. All in all, how roots coordinate neighbors and nitrogen spatial heterogeneity is a complex ecological process, and its trophic behavior deserves further study.

The oceanic mixed layer changes along with the state transition of the Beaufort Gyre

Recent state transition of the Beaufort Gyre has drawn great interest in the Arctic research community, but how the upper ocean hydrographic structure varies with this transition remains poorly understood. The upper ocean mixed layer plays an important role in climatic and ecological processes. Therefore, we analyze the Ice-Tethered Profiler (ITP) observations over the last two decades (2004–2022) to investigate the long-term trend of the mixed layer in the Arctic Ocean’s Beaufort Gyre (BG) from an observational perspective. Results show that the linear trend of the BG surface mixed layer depth (MLD) before and after 2015 has changed significantly, characterized by the vanishing or even reversal of the significant deepening trend. This transition is most pronounced in winter. The BG winter mixed layer is significantly cooler, saltier and denser in the mid-transition period (2013–2017) compared to the pre-transition period (2004–2012), but becomes significantly warmer, fresher and lighter in the post-transition period (2018–2022). The transition feature of the depth of maximum buoyancy frequency in the upper BG is similar to that of MLD, while this maximum decreases significantly in both the mid- and post-transition period when compared to their previous period. The deepening signal of MLD is propagated eastward, which coincides with the recent transition of BG position and freshwater distribution. Mechanism analysis further reveals that the reversal of winter MLD trend before and after 2015 may be due to changes in surface wind stirring and Ekman pumping. This study extends the investigation of the recent state transition of BG considering the upper hydrographic structure.