Biology subjects

Hector, A.

Publications and source records attributed to Hector, A..

15 recordsLinked to original sources

bioRxiv2026

Still Lost in Definitions: How Resilience Is Used in Ecology

Resilience is a central concept in ecology and environmental policy, yet its meaning and quantification remain inconsistent across subfields. Clarifying how resilience is defined and measured across the subfields of ecology is therefore a critical step towards delivering coordinated efforts to strengthen resilience research. Here, we analyse 594 studies published between 1977 and 2025 to determine how resilience is quantified across ecological contexts. Using large language models to extract structured data and conditional inference forests to assess predictors of metric choice, we show that resilience is most commonly ([~]25%) quantified using recovery rate and recovery degree, but no single metric dominates. Crucially, study attributes like organisational level, methodological approach, and disturbance regime explain only a small fraction of variation in metric selection. Despite this apparent inconsistency, more than 90% of studies draw from a shared set of six quantitative dimensions of resilience. This combination of weak constraint and latent convergence suggests that resilience metrics function as a flexible but implicitly standardised toolkit rather than as context-specific constructs. We argue that this hidden structure provides a foundation for a unified, multidimensional resilience framework that can support synthesis across ecological systems and improve the translation of resilience science into conservation and policy.

ecology↗

bioRxiv2025

Current estimates of population resilience do not predict resilience to directional environmental shifts

Natural systems worldwide are exposed to gradual changes imposed by directional environmental shifts, known as ramp disturbances. However, contemporary assessments of population resilience focus on the resistance and recovery of systems following one-off (i.e., pulse) disturbances. Thus, our current perception of demographic resilience overlooks the potential impacts of the cumulative effects of ramp disturbances on population dynamics. Simulating 50-year ramp disturbance scenarios upon the survival and fecundity dynamics of 511 populations across 344 species, we illustrate non-linear patterns in how directional environmental shifts will reshape the resilience of natural populations. Accordingly, existing estimates of population resilience are not robust against a backdrop of ongoing and continuous environmental change. Instead, we demonstrate the need to quantify how the relative partitioning of energetic resources across survival vs. fecundity informs population resilience. Our findings challenge the use of well-established approaches in forecasting population resilience to ongoing global change.

ecology↗

bioRxiv2024

Variation in precipitation drives differences in interactions and short-term transient instability between grassland functional groups: a stage-structured community approach

Climate change is expected to increase the frequency and severity of precipitation extremes, causing droughts and flooding. Consequently, grassland communities are forecasted to become increasingly unstable. To predict grassland responses, we need empirical information together with models that reliably extrapolate community dynamics from those observations. However, such prediction is challenging because community models typically simulate long-term (asymptotic) performance, and thus potentially neglect their short-term (transient) performance. Here, we use data from a precipitation experiment performed over eight years to model both short- and long-term responses of three functional groups - grasses, legumes, and non-leguminous forbs - to precipitation extremes. We use multi-functional-group Integral Projection Models and pseudospectral theory, to track grassland community dynamics. We show that the percentage-cover-stage-structure of functional groups shapes their transient instability, and that inter-functional-group interactions are competitive under increased precipitation but facilitative under decreased precipitation. IPMs and pseudospectra enable forecasting of how functional-group-stage-structure drives responses to climatic extremes.

ecology↗

bioRxiv2024

Tree diversity reduces pathogen damage in temperate forests: a systematic review and meta-analysis

Diversifying planted forests to reduce the risks associated with large scale disturbances, such as pathogens, is a major aim of sustainable forest management. Previous meta-analyses have shown that insect pest damage is lower in mixed forest stands compared to monocultures, but the same has not been shown for pathogens. Here, we provide the first systematic review and meta-analysis specifically testing the effects of tree species diversity on pathogen damage. Relevant studies were retrieved using bibliographic databases and internet searches, as well as previously unpublished data sets contributed by stakeholders. We found that more diverse forest stands overall had significantly lower pathogen damage, and that this result was most pronounced in temperate forests for which the most studies were available. Although in some cases tree diversity had a strong effect, this was not universal and was influenced neither by pathogen specialism, nor by the presence of alternative hosts in stands. Instead, we found that tree neighbour identity rather than species richness emerged as a crucial variable impacting pathogen damage in mixed stands. Neighbour identity effects reported in studies were far-ranging, including impacts on the microclimate of stands. Future work should focus on mechanistic explanations that could underpin neighbour identity effects in mixed forests. We suggest the use of the disease triangle as a tool for considering the multiple factors that can influence pathogen damage in mixed forest stands.

ecology↗

bioRxiv2024

No enhancement of soil carbon persistence by sheep grazing in a long-term calcareous grassland experiment

Soils hold a globally important carbon pool that is generally more persistent than the carbon stored in plant biomass. However, this carbon is becoming increasingly vulnerable to disturbances such as soil warming, fire, and erosion. Managing land to increase soil carbon sequestration and persistence may therefore improve long-term soil carbon storage and contribute to climate change mitigation. It has been hypothesized that grazing by large herbivores may enhance the persistence of soil carbon by increasing the amount of soil organic matter forming more stable associations with mineral particles (mineral-associated organic matter). We compared sheep-grazed and ungrazed plots within the Gibson Grazing and Successional Experiment located in the Upper Seeds calcareous grassland in Wytham Woods, Oxfordshire, using organic matter fractionation to estimate the surface (0-5 cm) carbon stocks in the mineral-associated and particulate organic matter fractions. Counter to predictions, after 35 years sheep grazing had not increased mineral-associated organic matter carbon stocks relative to ungrazed plots. We hypothesize that this indicates the saturation of mineral surfaces in both grazed and ungrazed treatments and the inability of grazing to increase soil nitrogen stocks and decrease pH to levels conducive for mineral-associated carbon sequestration. Only one of twelve soil properties examined showed statistically detectable responses to grazing: spring-grazing increased the C:N ratio in the mineral-associated organic matter. While the number of tests performed (24) means this may be a false-positive result, if genuine it would be consistent with a more direct pathway from plant exudates to mineral-associated organic matter formation due to compensatory growth in response to spring-grazing. Overall, the results of this long-term experiment do not support the hypothesis that grazing can improve the persistence of the soil carbon pool.

ecology↗

bioRxiv2024

Electrocorticographic and Astrocytic Signatures of Stearoyl-CoA Desaturase Inhibition in the Triple Transgenic Mouse Model of Alzheimer's Disease

The symptomatology of Alzheimers disease (AD) includes cognitive deficits and sleep disturbances. Recent findings suggest the involvement of dysfunctions in lipid metabolism, such as oleic acid build-up, in the brain of AD patients and animal models. In addition, the inhibition of stearoyl-CoA desaturase (SCD), a lipid-converting enzyme, was shown to restore memory in triple transgenic (3xTg)-AD mice. In the brain, astrocytes regulate the synthesis of specific lipids. Alterations in astrocytes and their function were reported in AD patients and animal models, and astrocytes have been implicated in the regulation of sleep. However, the relationship between sleep disturbances, astrocytes and lipid metabolism remains to be explored in AD. This project thus aimed at assessing whether the inhibition of SCD restores sleep in 3xTg-AD mice, and whether this associated with modifications in astrocytic function. Wild-type (WT) and 3xTg-AD female mice (4-months old) received intracerebroventricular infusion of a SCD inhibitor (SCDi) or vehicle for 28 days, and a 24-hour electrocorticographic (ECoG) recording was conducted post-treatment. Post-mortem brain slices were stained for the astrocytic markers glial fibrillary acidic protein (GFAP) and 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) to perform cell counting and/or morphological evaluation in the hippocampus, lateral hypothalamus and thalamus. The results indicate that the reduced time spent awake and increased time spent in slow wave sleep (SWS) in 3xTg-AD mice was not restored by the SCDi treatment. Similar observations were made concerning the increased number of wake and SWS bouts in 3xTg-AD mice. Rhythmic and scale-free ECoG activity were markedly altered in 3xTg-AD mice for all wake/sleep states, and SCDi significantly altered these phenotypes in a different manner in mutant mice in comparison to WT mice. GFAP- and ALDH1L1-positive cell densities were elevated in the hippocampus and lateral hypothalamus/thalamus of 3x-Tg-AD mice, respectively, and SCDi rescued the increase in the CA1 region in particular. Overall, these findings suggest that the multiple wake/sleep alterations in 3xTg-AD mice are not substantially restored by targeting lipid metabolism using SCD inhibition, at least for the targeted age window, but that this treatment can revert hippocampal changes in astrocytes. This work will benefit the understanding of the pathophysiology related to AD and associated sleep disturbances.

neuroscience↗

bioRxiv2023

Seabird traits and seasonality modulate nutrient dynamics of terrestrial and marine habitats on atolls

Marine nutrients underpin productivity and functioning of oceanic island ecosystems. Seabirds represent a primary source of marine nutrients. In tropical regions, some of the largest seabird populations nest on atolls, yet there is limited information available on seabird contributions to atoll ecosystem nutrient dynamics. To investigate the spatial and seasonal dynamics of seabird contributions, we assessed seabird colonies of different taxa, including red-footed boobies and terns, nesting on separate islands of Farquhar Atoll, Seychelles. We assessed nutrient concentrations of guano, soil, coastal plants and nearby seagrass in seabird colonies and at a control island with no seabirds, during the wet and dry seasons. Sooty terns contributed the highest quantities of nutrients, estimated at 71.2 N tonne.yr-1 and 52.2 P tonne.yr-1. Seabird-derived nutrient transfer occurred year-round from seabird colonies to soil, coastal plants and seagrass. Soil macro- and inorganic nutrients were higher in the high-density, ground-nesting tern colony and during the dry season, coinciding with the breeding period of sooty terns. Both red-footed booby and tern colonies maintained high nitrogen levels (%N) in coastal plants year-round, while phosphorus levels (%P) did not differ between islands or seasons. Seabird-derived nitrogen reversed nitrogen limitation (log C:N) of seagrass during the dry season. We provide the first insights into seabird nutrient contributions to atoll ecosystems in Seychelles, with recommendations for seabird conservation to boost and support atoll and island ecosystem resilience. Our results from a relatively undisturbed atoll serve as a baseline with which more impacted atolls and future changes can be assessed.

ecology↗

bioRxiv2023

Experimental drought reduces the productivity and stability of a recovering calcareous grassland

O_LIGrasslands comprise 40% of terrestrial ecosystems and are globally important for food production, carbon storage, and other ecosystem services. However, grasslands in many areas are becoming increasingly exposed to extreme wet and dry periods resulting from global temperature increases. C_LIO_LITherefore, understanding how grasslands will respond to climate change is a pressing issue for managing changes to biodiversity and ecosystem service provision. C_LIO_LIHere, we use experimental manipulations of precipitation (50% increase and 50% decrease of growing-season precipitation) to investigate the resistance of the diversity and productivity of a calcareous grassland community recovering from historical agricultural conversion. C_LIO_LIWe found that decreasing growing season precipitation led to reductions of mean productivity (25 % decrease in peak above-ground biomass) and its temporal stability (54 % increase in biomass variance across years). However, the grassland community composition was resistant to the precipitation manipulations, with no clear difference in community compositional turnover, dissimilarity, or biodiversity indices. Furthermore, the precipitation manipulations had no effect on the path of ongoing (30 year) recovery of grassland plant diversity from the period of previous agricultural conversion. C_LIO_LIWhile the diversity of this calcareous grassland was resistant to precipitation extremes (at least in the short term), sustained reductions in growing-season precipitation reduced productivity and its temporal stability demonstrating that different properties of grasslands can vary in their responses to changes in precipitation. C_LI

ecology↗

bioRxiv2023

Experimentally induced drought and growing season stage modulate community-level functional traits in a temperate grassland

O_LIExtreme precipitation events are expected to become more intense and frequent with climate change. This climatic shift may impact the structure and dynamics of natural communities and the key ecosystem services they provide. Changes in species abundance under these extreme conditions are thought to be driven by functional traits, morpho-physiological characteristics of an organism that impact its fitness. Future environmental conditions may, therefore, favour different functional traits to those in present-day communities. C_LIO_LIHere, we measure functional traits on 586 vascular plants in a temperate grassland where precipitation has been experimentally manipulated for six years. We calculated community-weighted means of five functional traits (plant height, leaf dry matter content, leaf thickness, specific leaf area, and leaf phosphorus concentration) and compared community-weighted means between three levels of precipitation: drought (-50%), irrigated (+50%), and control. Additionally, we contrasted treatments at two different timings along the growing season: mid-season and late-season. C_LIO_LIWe expected altered community-weighted means for traits associated with a conservative use of water that will result from increased summer stress-induced intraspecific variability in the mid-season and from community composition changes in the late-season, after the field is cut, a common management action across most European grasslands. C_LIO_LIIn the drought treatment, we found significantly lower community-weighted mean plant height and leaf dry matter content. However, we only observed these differences after the mid-season cut. We also observed an increase in leaf phosphorus concentration in the drought treatment before the mid-season cut. A combination of changes in community composition and intraspecific variation contributed to these differences, with community composition being more important after the cut. Species with higher height, leaf dry matter content, and lower leaf thickness showed a more pronounced abundance decline at the drought plots. We observed no changes in functional traits community-weighted means in the irrigated treatment compared to those in control and drought treatments. C_LIO_LISynthesis. Our results suggest how the functional trait composition of grassland communities may shift under climate change-induced drought, stressing the interacting effects with growing season stages. C_LI

ecology↗

bioRxiv2022

Logging alters tropical forest structure, while conversion reduces biodiversity and functioning

The impacts of degradation and deforestation on tropical forests are poorly understood, particularly at landscape scales. We present an extensive ecosystem analysis of the impacts of logging and conversion of tropical forest to oil palm from a large-scale study in Borneo, synthesizing responses from 82 variables categorized into four ecological levels spanning a broad suite of ecosystem properties: 1) structure and environment, 2) species traits, 3) biodiversity, and 4) ecosystem functions. Responses were highly heterogeneous and often complex and non-linear. Variables that were directly impacted by the physical process of timber extraction, such as soil structure, were sensitive to even moderate amounts of logging, whereas measures of biodiversity and ecosystem functioning were generally resilient to logging but more affected by conversion to oil palm plantation. One-Sentence SummaryLogging tropical forest mostly impacts structure while biodiversity and functions are more vulnerable to habitat conversion.

ecology↗

bioRxiv2022

Positive effects of tree diversity on tropical forest restoration in a field-scale experiment

Experiments under controlled conditions have established that ecosystem functioning is generally positively related to levels of biodiversity, but it is unclear how widespread these effects are in real-world settings and whether they can be harnessed for ecosystem restoration. We used a long-term, field-scale tropical restoration experiment to test how the diversity of planted trees affected recovery measured across a 500 ha area of selectively logged forest using multiple sources of satellite data. Replanting with species rich mixtures of tree seedlings that had higher phylogenetic and functional diversity accelerated restoration rates. Our results are consistent with a positive relationship between biodiversity and ecosystem functioning in the lowland dipterocarp rainforests of SE Asia and demonstrate that using diverse mixtures of species can enhance initial recovery after logging.

ecology↗

bioRxiv2022

Flexible estimation of biodiversity with short-range multispectral imaging in a temperate grassland

O_LIImage sensing technologies are rapidly increasing the cost-effectiveness of biodiversity monitoring efforts. Species differences in the reflectance of electromagnetic radiation have recently been highlighted as a promising target to estimate plant biodiversity using multispectral image data. C_LIO_LIHowever, these efforts are currently hampered by logistical difficulties in broad-scale implementation and their use in characterizing biodiversity at different spatial scales. C_LIO_LIHere, we investigate the utility of multispectral imaging technology from commercially available unmanned aerial vehicles (UAVs, or drones) in estimating biodiversity metrics at short-range (<10 m image recording height) in a temperate calcareous grassland ecosystem in Oxfordshire, UK. We calculate a suite of moments (coefficient of variation, standard deviation, skew, kurtosis) for the distribution of radiance from multispectral images at five wavelength bands (Blue 450{+/-}16 nm; Green 560{+/-}16 nm; Red 650{+/-}16 nm; Red Edge 730{+/-}16 nm; Near Infrared 840{+/-}16 nm) and test their effectiveness at estimating ground-truthed biodiversity metrics from in-situ botanical surveys for 37 - 1 m x 1 m quadrats. C_LIO_LIWe find positive associations between the average coefficient of variation in spectral radiance and both the Shannon-Weiner and Simpsons biodiversity indices. Furthermore, we find that the average coefficient of variation in spectral radiance is consistent and highly repeatable, across sampling days and recording heights. Positive associations with biodiversity indices hold irrespective of the image recording height (2-8 m), but we report reductions in estimates of spectral diversity with increases to UAV recording height. UAV imaging reduced sampling time by 16-fold relative to in-situ botanical surveys. C_LIO_LISynthesis - We demonstrate the utility of multispectral radiance moments as an indicator of grassland biodiversity metrics at high spatial resolution using a widely available UAV monitoring system at a coarse spectral resolution. The use of UAV technology with multispectral sensors has far-reaching potential to provide cost-effective and high-resolution monitoring of biodiversity in complex environments. C_LI

ecology↗

bioRxiv2022

Higher aboveground carbon stocks in mixed-species planted forests than monocultures - a meta-analysis

Natural forest is declining globally as the area of planted forest increases. Planted forests are often monocultures, despite results suggesting that higher species richness improves ecosystem functioning and stability. To test if this is generally the case, we performed a meta-analysis of available results. We assessed aboveground carbon stocks in mixed-species planted forests vs (a) the average of constituent species monocultures, (b) the best constituent species monoculture, and (c) commercial species monocultures. We investigated whether any advantage of mixtures over monocultures was positively related to species richness, as well as potential mechanisms driving differences in carbon stocks between mixtures and monocultures. The meta-analysis dataset included 79 comparisons from 21 sites. Carbon stocks in mixed planted forests were higher than the average of stocks in monocultures of their constituent species, containing on average 70% more carbon. Mixed planted forests also out-performed commercial monocultures, containing on average 77% more carbon. There was c.25% more carbon in mixed planted forests relative to the best performing monocultures, although this difference was not statistically significant. Overyielding was highest in four-species mixtures (richness range 2-6 species). More data providing better coverage of richness and age gradients (study sites aged 3.5-28 years) is needed to increase confidence in these results. None of the potential mechanisms we examined (nitrogen-fixer present vs absent; native vs non-native/mixed origin; tree diversity experiment vs forestry plantation) consistently explained variation in the diversity effects. This suggests that our findings are driven by a combination of small (statistically insignificant) effects from these sources or further unidentified mechanisms or some combination of the two. We conclude that increasing tree species richness in planted forests can increase carbon stocks while bringing other potential benefits associated with diversification. However, implementation will depend on the balance of these benefits relative to the operational challenges and costs of diversification.

ecology↗

bioRxiv2020

Biotic and abiotic drivers of soil microbial functions across tree diversity experiments

AimSoil microorganisms are essential for the functioning of terrestrial ecosystems. Although soil microbial communities and functions may be linked to the tree species composition and diversity of forests, there has been no comprehensive study of how general potential relationships are and if these are context-dependent. A global network of tree diversity experiments (TreeDivNet) allows for a first examination of tree diversity-soil microbial function relationships across environmental gradients. LocationGlobal Major Taxa StudiedSoil microorganisms MethodsSoil samples collected from eleven tree diversity experiments in four biomes across four continents were used to measure soil basal respiration, microbial biomass, and carbon use efficiency using the substrate-induced respiration method. All samples were measured using the same analytical device in the same laboratory to prevent measurement bias. We used linear mixed-effects models to examine the effects of tree species diversity, environmental conditions, and their interactions on soil microbial functions. ResultsAcross biodiversity experiments, abiotic drivers, mainly soil water content, significantly increased soil microbial functions. Potential evapotranspiration (PET) increased, whereas soil C-to-N ratio (CN) decreased soil microbial functions under dry soil conditions, but high soil water content reduced the importance of other abiotic drivers. Tree species richness and phylogenetic diversity had overall similar, but weak and context-dependent (climate, soil abiotic variables) effects on soil microbial respiration. Positive tree diversity effects on soil microbial respiration were most pronounced at low PET, low soil CN, and high tree density. Soil microbial functions increased with the age of the experiment. Main conclusionsOur results point at the importance of soil water content for maintaining high levels of soil microbial functions and modulating effects of other environmental drivers. Moreover, overall tree diversity effects on soil microbial functions seem to be negligible in the short term (experiments were 1-18 years old). However, context-dependent tree diversity effects (climate, soil abiotic variables) have greater importance at high tree density, and significant effects of experimental age call for longer-term studies. Such systematic insights are key to better integrate soil carbon dynamics into the management of afforestation projects across environmental contexts, as todays reforestation efforts remain focused largely on aboveground carbon storage and are still dominated by less diverse forests stands of commercial species.

ecology↗

bioRxiv2017

Strong positive biodiversity-productivity relationships in a subtropical forest experiment

Forest ecosystems contribute substantially to global terrestrial primary productivity and climate regulation, but, in contrast to grasslands, experimental evidence for a positive biodiversity-productivity relationship in highly diverse forests is still lacking1. Here, we provide such evidence from a large forest biodiversity experiment with a novel design2 in subtropical China. Productivity (stand-level tree basal area, aboveground volume and carbon and their annual increment) increased linearly with the logarithm of tree species richness. Additive partitioning3 showed that increasing positive complementarity effects combined with weakening negative selection effects caused a strengthening of the relationship over time. In 2-species mixed stands, complementary effects increased with functional distance and selection effects with vertical crown dissimilarity between species. Understorey shrubs reduced stand-level tree productivity, but this effect of competition was attenuated by shrub species richness, indicating that a diverse understorey may facilitate overall ecosystem functioning. Identical biodiversity-productivity relationships were found in plots of different size, suggesting that extrapolation to larger scales is possible. Our results highlight the potential of multi-species afforestation strategies to simultaneously contribute to mitigation of climate change and biodiversity restoration.

ecology↗