Biology subjects

Milcu, A.

Publications and source records attributed to Milcu, A..

8 recordsLinked to original sources

bioRxiv2026

Severe warming alters biomass allocation and enhances ecosystem respiration in an alpine grassland: evidence from a short-term mesocosm experiment

Background and aims Alpine ecosystems are highly sensitive to climate change, with rising temperatures threatening ecosystem structure and function. This study examined the short-term responses of alpine grassland ecosystems (Mont Blanc, Italy) to projected climate scenarios using an Ecotron mesocosm experiment. Methods Ecosystem monoliths were exposed to current (~420 ppm CO2) and future CO2; concentrations (~550 and ~800 ppm) under RCP 4.5 and RCP 8.5 scenarios, incorporating changes in temperature, precipitation, humidity, and radiation. CO2; fluxes (NEP, GPP, Reco), soil chemistry, vegetation coverage, above- and belowground biomass, and plant functional traits were assessed throughout the experiment. Results Alpine grassland ecosystems withstood moderate warming (RCP 4.5), while under severe warming (RCP 8.5), GPP, vegetation cover and biomass increased with a shift toward aboveground allocation, although daytime NEP remained stable as gains were offset by higher Reco, with no detectable water and nutrients limitations. On a diel basis, higher GPP was offset by enhanced Reco, indicating a potential towards net C loss. Salix herbacea exhibited functional trait adjustments-higher LMA and Na, and elevated delta15N-reflecting greater leaf longevity, water-use efficiency, and altered nitrogen metabolism, suggesting potential community reorganization. Conclusion Over a single growing season, alpine ecosystems appeared relatively stable under moderate warming. However, under the more severe RCP 8.5 scenario, biomass allocation shifted toward greater aboveground and reduced belowground investment, leading to altered C fluxes that, if sustained over the long-term, could drive the ecosystem C balance from a sink to a source. Responses were plant species-specific, indicating uneven acclimation within the community.

plant biology↗

bioRxiv2025

Resource economics of tree communities control soil food web multifunctionality in European forests

Plants affect terrestrial ecosystem functioning by performing the primary production that energetically sustains heterotrophic organisms1, and by shaping the microenvironment2. However, the influence of plant diversity and community composition on ecosystem functioning through their effects on energy flow into food webs has been little studied3,4, especially for soil food webs that channel most of the plant-derived energy1,5. Applying a food web energetics approach6,7, we show that the resource economics of dominant tree species control soil food web multifunctionality across European forests. Specifically, tree communities dominated by resource acquisitive species promoted faster rates of multiple soil trophic functions simultaneously than did those dominated by resource conservative species. This was primarily driven by their production of plant litter with higher nutritional quality and their warmer forest microclimate, leading to a higher metabolic activity of soil organisms8. Tree species mixing had rather weak and negative effects on soil food web multifunctionality, mostly due to a shift in the resource-based energy channeling from living plant fine roots to litter and a cooling effect on the forest microclimate. Tree diversity effects were largely outweighed by community compositional effects, which were of similar magnitude to the effects of biogeographic differences among locations. Our findings emphasize the importance of plant functional traits related to resource economics as drivers of plant community effects on soil food web functioning5,9 and highlight the consequences that climate-driven shifts in tree community composition could have for forest soil functioning.

ecology↗

bioRxiv2023

Earthworms and plants can decrease soil greenhouse gases emissions by modulating soil moisture fluctuations and soil macroporosity in a mesocosm experiment

Earthworms can stimulate microbial activity and hence, greenhouse gas (GHG) emissions from soils. However, the extent of this effect in the presence of plants and soil moisture fluctuations, which are influenced by earthworm burrowing activity, remains uncertain. Here we report the effect of earthworms (without, anecic, endogeic, both) and plants (with, without) on GHG (CO2, N2O) emissions in a 3 month-greenhouse mesocosm experiment simulating a simplified agricultural context. The mesocosms allowed for water drainage at the bottom to account for the earthworm engineering effect on water flow during two drying-wetting cycles. N2O cumulative emissions were 34.6 and 44.8% lower when both earthworm species and only endogeic species were present, respectively, and 19.8% lower in presence of plants. The presence of the endogeic species alone or in combination with the anecic species slightly reduced CO2 emissions by 5.9% and 11.4% respectively, and plants presence increased emissions by 6%. Earthworms, plants and soil water content interactively affected weekly N2O emissions, an effect controlled by increased soil dryness due to drainage via earthworm burrows and mesocosm evapotranspiration. Soil macroporosity (measured by X-ray tomography) was affected by earthworm species-specific burrowing activity. Both GHG emissions decreased with top soil macropore volume, presumably due to reduced moisture and microbial activity. N2O emissions decreased with macropore volume in the deepest layer, likely due to fewer anaerobic microsites. Our results indicate that, under experimental conditions allowing for plant and earthworm engineering effects on soil moisture, earthworms do not increase GHG emissions and that endogeic earthworms may even reduce N2O emissions.

ecology↗

bioRxiv2023

Natural genetic variation underlying the negative effect of elevated CO2 on ionome composition in Arabidopsis thaliana

The elevation of atmospheric CO2 leads to a decline in the plant mineral content, which might pose a significant threat to food security in the coming decades. To date, very few genes have been identified as having a role in the negative effect of elevated CO2 on plant mineral composition. Yet, several studies have shown a certain degree of diversity in the ionomes response to elevated CO2, associated with genotypic variation. This suggests the existence of genetic factors controlling the effect of CO2 on ionome composition. However, no large-scale studies have been carried out to date to explore the genetic diversity of the ionome responses to elevated CO2. Here, we used six hundred Arabidopsis thaliana accessions, representing geographical distributions ranging from worldwide to regional and local environments, to analyze the natural genetic variation underlying the negative effect of elevated CO2 on the ionome composition in plants. We show that the growth under elevated CO2 leads to a global and important decrease of the ionome content whatever the geographic distribution of the population. We also observed a high range of genetic diversity in the response of the ionome composition to elevated CO2, and we identified sub-populations, showing effects on their ionome ranging from the most pronounced to resilience or even to a benefit in response to elevated CO2. Using genome-wide association mapping on the response of each mineral element to elevated CO2 or on integrative traits, we identified a large set of QTLs and genes associated with the ionome response to elevated CO2. Finally, we demonstrate that the function of one of these genes is associated to the negative effect of elevated CO2 on the plant mineral composition. This resource will contribute to understand the genetic mechanisms underlying the negative effect of elevated CO2 on plant mineral nutrition, and could help towards the development of crops adapted to a high-CO2 world.

plant biology↗

bioRxiv2020

Microhabitat and ectomycorrhizal effects on the establishment, growth and survival of Quercus ilex L. seedlings under drought

The success of tree recruitment in Mediterranean Quercus ilex forests is threatened by the increasing intensity, duration and frequency of drought periods. Seedling germination and growth are modulated by complex interactions between abiotic (microhabitat conditions) and biotic factors (mycorrhiza association) that may mitigate the impacts of climate change on tree recruitment. To better understand and anticipate these effects, we conducted a germination experiment in a long-term precipitation reduction (PR) field experiment where we monitored seedling establishment and survival, micro-environmental conditions and ectomycorrhizal (ECM) colonization by different mycelia exploration types during the first year of seedling growth. We hypothesized that (i) the PR treatment decreases seedling survival relative to the control with ambient conditions, (ii) the underlying mechanisms for seedling survival are better understood with detailed information of microhabitat water and light availability irrespective of the PR treatment, (iii) the PR treatment will favour the development of ECM exploration types with drought-resistance traits such as differentiated rhizomorphs. Contrary to our first hypothesis, seedling survival was lower in control plots with overall higher soil moisture. Micro-site light and soil moisture conditions were better predictors of seedling survival and growth than the plot-level PR treatment, confirming our second hypothesis. Furthermore, in line with our third hypothesis, we found that ECM with longer extramatrical mycelia were more abundant in the PR treatment plots and were positively correlated to survival, which suggests a potential role of this ECM exploration type in seedling survival and recruitment. Although summer drought was the main cause of seedling mortality, our study indicates that drier conditions in spring can increase seedling survival, presumably through a synergistic effect of drought adapted ECM species and less favourable conditions for root pathogens.

ecology↗

bioRxiv2019

Plant traits are poor predictors of long-term ecosystem functioning

Earth is home to over 350,000 vascular plant species1 that differ in their traits in innumerable ways. Yet, a handful of functional traits can help explaining major differences among species in photosynthetic rate, growth rate, reproductive output and other aspects of plant performance2-6. A key challenge, coined "the Holy Grail" in ecology, is to upscale this understanding in order to predict how natural or anthropogenically driven changes in the identity and diversity of co-occurring plant species drive the functioning of ecosystems7, 8. Here, we analyze the extent to which 42 different ecosystem functions can be predicted by 41 plant traits in 78 experimentally manipulated grassland plots over 10 years. Despite the unprecedented number of traits analyzed, the average percentage of variation in ecosystem functioning that they jointly explained was only moderate (32.6%) within individual years, and even much lower (12.7%) across years. Most other studies linking ecosystem functioning to plant traits analyzed no more than six traits, and when including either only six random or the six most frequently studied traits in our analysis, the average percentage of explained variation in across-year ecosystem functioning dropped to 4.8%. Furthermore, different ecosystem functions were driven by different traits, with on average only 12.2% overlap in significant predictors. Thus, we did not find evidence for the existence of a small set of key traits able to explain variation in multiple ecosystem functions across years. Our results therefore suggest that there are strong limits in the extent to which we can predict the long-term functional consequences of the ongoing, rapid changes in the composition and diversity of plant communities that humanity is currently facing.

ecology↗

bioRxiv2018

Functional composition rather than species richness drive carbon gain and allocation in experimental grasslands

Numerous experiments have shown positive diversity effects on plant productivity, but little is known about related processes of carbon gain and allocation. We investigated these processes in a controlled environment (Montpellier European Ecotron) applying a continuous 13CO2 label for three weeks to 12 soil-vegetation monoliths originating from a grassland biodiversity experiment (Jena Experiment) and representing two diversity levels (4 and 16 sown species). Plant species richness did not affect community- and species-level 13C abundances neither in total biomass nor in non-structural carbohydrates (NSC). Community-level 13C excess tended to be higher in the 16-species than in the 4-species mixtures. Community-level 13C excess was positively related to canopy leaf nitrogen (N), i.e. leaf N per unit soil surface. At the species level shoot 13C abundances varied among plant functional groups and were larger in legumes and tall herbs than in grasses and small herbs and correlated positively with traits as leaf N concentrations, stomatal conductance and shoot height. The 13C abundances in NSC were larger in transport sugars (sucrose, raffinose-family oligosaccharides) than in free glucose, fructose and compounds of the storage pool (starch) suggesting that newly assimilated carbon is to a small portion allocated to storage. Our results emphasize that the functional composition of communities is key in explaining carbon assimilation in grasslands.

ecology↗

bioRxiv2017

Does circadian regulation lead to optimal gas exchange regulation?

Optimal stomatal theory is an evolutionary model proposing that leaves trade-off Carbon (C) for water to maximise C assimilation (A) and minimise transpiration (E), thereby generating a marginal water cost of carbon gain ({lambda}) that remains constant over short temporal scales. The circadian clock is a molecular timer of metabolism that controls A and stomatal conductance (gs), amongst other processes, in a broad array of plant species. Here, we test whether circadian regulation contributes towards achieving optimal stomatal behaviour. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature and vapour pressure deficit over 48 hours. We observed a significant and self-sustained circadian oscillation in A and in stomatal conductance (gs) which also led to a circadian oscillation in{lambda} . The lack of constant marginal water cost indicates that circadian regulation does not directly lead to optimal stomatal behaviour. However, the temporal pattern in gas exchange, indicative of either maximizing A or of minimizing E, depending upon time of day, indicates that circadian regulation could contribute towards optimizing stomatal responses. More broadly, our results add to the emerging field of plant circadian ecology and show that molecular controls may partially explain leaf-level patterns observed in the field.

ecology↗