Evidence of region‐wide bat population decline from long‐term monitoring and Bayesian occupancy models with empirically informed priors

Strategic conservation efforts for cryptic species, especially bats, are hindered by limited understanding of distribution and population trends. Integrating long‐term encounter surveys with multi‐season occupancy models provides a solution whereby inferences about changing occupancy probabilities and latent changes in abundance can be supported. When harnessed to a Bayesian inferential paradigm, this modeling framework offers flexibility for conservation programs that need to update prior model‐based understanding about at‐risk species with new data. This scenario is exemplified by a bat monitoring program in the Pacific Northwestern United States in which results from 8 years of surveys from 2003 to 2010 require updating with new data from 2016 to 2018. The new data were collected after the arrival of bat white‐nose syndrome and expansion of wind power generation, stressors expected to cause population declines in at least two vulnerable species, little brown bat (Myotis lucifugus) and the hoary bat (Lasiurus cinereus). We used multi‐season occupancy models with empirically informed prior distributions drawn from previous occupancy results (2003–2010) to assess evidence of contemporary decline in these two species. Empirically informed priors provided the bridge across the two monitoring periods and increased precision of parameter posterior distributions, but did not alter inferences relative to use of vague priors. We found evidence of region‐wide summertime decline for the hoary bat ( = 0.86 ± 0.10) since 2010, but no evidence of decline for the little brown bat ( = 1.1 ± 0.10). White‐nose syndrome was documented in the region in 2016 and may not yet have caused regional impact to the little brown bat. However, our discovery of hoary bat decline is consistent with the hypothesis that the longer duration and greater geographic extent of the wind energy stressor (collision and barotrauma) have impacted the species. These hypotheses can be evaluated and updated over time within our framework of pre–post impact monitoring and modeling. Our approach provides the foundation for a strategic evidence‐based conservation system and contributes to a growing preponderance of evidence from multiple lines of inquiry that bat species are declining.     

Surface‐water availability governs survival of an amphibian in arid mountain streams

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The Arabidopsis root stele transporter NPF2.3 contributes to nitrate translocation to shoots under salt stress

In most plants, constitutes the major source of nitrogen, and its assimilation into amino acids is mainly achieved in shoots. Furthermore, recent reports have revealed that reduction of translocation from roots to shoots is involved in plant acclimation to abiotic stress. NPF2.3, a member of the NAXT (nitrate excretion transporter) sub‐group of the NRT1/PTR family (NPF) from Arabidopsis, is expressed in root pericycle cells, where it is targeted to the plasma membrane. Transport assays using NPF2.3‐enriched Lactococcus lactis membranes showed that this protein is endowed with transport activity, displaying a strong selectivity for against Cl^?. In response to salt stress, translocation to shoots is reduced, at least partly because expression of the root stele transporter gene NPF7.3 is decreased. In contrast, NPF2.3 expression was maintained under these conditions. A loss‐of‐function mutation in NPF2.3 resulted in decreased root‐to‐shoot translocation and reduced shoot content in plants grown under salt stress. Also, the mutant displayed impaired shoot biomass production when plants were grown under mild salt stress. These mutant phenotypes were dependent on the presence of Na⁺ in the external medium. Our data indicate that NPF2.3 is a constitutively expressed transporter whose contribution to translocation to the shoots is quantitatively and physiologically significant under salinity.     

Variation in morphological and reproductive characteristics of females of Anolis nebulosus (Squamata: Dactyloidae) from island and mainland populations near the Pacific Coast of Mexico

We present a comparative analysis of the morphological and reproductive characteristics of adult female Anolis nebulosus, an arboreal lizard found on both mainland and insular habitats near the Pacific Coast of Mexico. Females from San Pancho Island were larger in all measured morphological variables than females from Biological Field Station Chamela (BFSCH) on the mainland, and those also reproduced at smaller body size (snout‐vent length, SVL: range = 35–44,  = 39 mm) than females on San Pancho Island (range = 40–47,  = 43 mm). Egg mass and egg volume were also greater on San Pancho Island, but clutch frequency was higher on BFSCH during breeding season; in this place, one egg every 8 days over a period of 4 months (123 days) versus one egg every 10 days over a period of 4 months (130 days) on San Pancho Island. Thus, we conclude that certain characteristics related to reproduction (e.g. size at sexual maturity, egg mass and egg volume) in A. nebulosus with populations inhabiting islands and mainland, vary primarily in accordance with female SVL. These variations are most likely a response to the different pressures where A. nebulosus inhabits on environments the islands and mainland near the Pacific Coast of Mexico.     

Pyric‐carnivory: Raptor use of prescribed fires

Fire is a process that shaped and maintained most terrestrial ecosystems worldwide. Changes in land use and patterns of human settlement have altered fire regimes and led to fire suppression resulting in numerous undesirable consequences spanning individual species and entire ecosystems. Many obvious and direct consequences of fire suppression have been well studied, but several, albeit less obvious, costs of alteration to fire regimes on wildlife are unknown. One such phenomenon is the response of carnivores to fire events—something we refer to as pyric‐carnivory. To investigate the prevalence of pyric‐carnivory in raptors, we monitored 25 prescribed fires occurring during two different seasons and across two different locations in tallgrass prairie of the central United States. We used paired point counts occurring before and during prescribed fires to quantify the use of fires by raptors. We found a strong attraction to fires with average maximum abundance nearly seven times greater during fires than prior to ignitions (before:  = 2.90, SE = 0.42; during:  = 20.20; SE = 3.29) and an average difference between fire events and immediately before fires of 15.2 (±2.69) raptors. This result was driven by Swainson's hawks (Buteo swainsoni), which were the most abundant (n = 346) of the nine species we observed using fires. Our results illustrate the importance of fire as integral disturbance process that effects wildlife behavior through multiple mechanisms that are often overshadowed by the predominant view of fire as a tool used for vegetation management.     

Different fates of deposited and in a temperate forest in northeast China: a 15N tracer study

Increasing atmospheric reactive nitrogen (N) deposition due to human activities could change N cycling in terrestrial ecosystems. However, the differences between the fates of deposited and are still not fully understood. Here, we investigated the fates of deposited and , respectively, via the application of ¹⁵NH₄NO₃ and NH₄¹⁵NO₃ in a temperate forest ecosystem. Results showed that at 410 days after tracer application, most was immobilized in litter layer (50 ± 2%), while a considerable amount of penetrated into 0–5 cm mineral soil (42 ± 2%), indicating that litter layer and 0–5 cm mineral soil were the major N sinks of and , respectively. Broad‐leaved trees assimilated more ¹⁵N under NH₄¹⁵NO₃ treatment compared to under ¹⁵NH₄NO₃ treatment, indicating their preference for –N. At 410 days after tracer application, 16 ± 4% added ¹⁵N was found in aboveground biomass under treatment, which was twice more than that under treatment (6 ± 1%). At the same time, approximately 80% added ¹⁵N was recovered in soil and plants under both treatments, which suggested that this forest had high potential for retention of deposited N. These results provided evidence that there were great differences between the fates of deposited and , which could help us better understand the mechanisms and capability of forest ecosystems as a sink of reactive nitrogen.     

Leaf chlorophyll content as a proxy for leaf photosynthetic capacity

Improving the accuracy of estimates of forest carbon exchange is a central priority for understanding ecosystem response to increased atmospheric CO₂ levels and improving carbon cycle modelling. However, the spatially continuous parameterization of photosynthetic capacity (Vcmax) at global scales and appropriate temporal intervals within terrestrial biosphere models (TBMs) remains unresolved. This research investigates the use of biochemical parameters for modelling leaf photosynthetic capacity within a deciduous forest. Particular attention is given to the impacts of seasonality on both leaf biophysical variables and physiological processes, and their interdependent relationships. Four deciduous tree species were sampled across three growing seasons (2013–2015), approximately every 10 days for leaf chlorophyll content (Chl_Leaf) and canopy structure. Leaf nitrogen (N_Area) was also measured during 2014. Leaf photosynthesis was measured during 2014–2015 using a Li‐6400 gas‐exchange system, with A‐Ci curves to model Vcmax. Results showed that seasonality and variations between species resulted in weak relationships between Vcmax normalized to 25°C () and N_Area (R² = 0.62, P < 0.001), whereas Chl_Leaf demonstrated a much stronger correlation with (R² = 0.78, P < 0.001). The relationship between Chl_Leaf and N_Area was also weak (R² = 0.47, P < 0.001), possibly due to the dynamic partitioning of nitrogen, between and within photosynthetic and nonphotosynthetic fractions. The spatial and temporal variability of was mapped using Landsat TM/ETM satellite data across the forest site, using physical models to derive Chl_Leaf. TBMs largely treat photosynthetic parameters as either fixed constants or varying according to leaf nitrogen content. This research challenges assumptions that simple N_Area– relationships can reliably be used to constrain photosynthetic capacity in TBMs, even within the same plant functional type. It is suggested that Chl_Leaf provides a more accurate, direct proxy for and is also more easily retrievable from satellite data. These results have important implications for carbon modelling within deciduous ecosystems.     

RISK OF POPULATION EXTINCTION FROM FIXATION OF NEW DELETERIOUS MUTATIONS

The fixation of new deleterious mutations is analyzed for a randomly mating population of constant size with no environmental or demographic stochasticity. Mildly deleterious mutations are far more important in causing loss of fitness and eventual extinction than are lethal and semilethal mutations in populations with effective sizes, N_e, larger than a few individuals. If all mildly deleterious mutations have the same selection coefficient, s against heterozygotes and 2s against homozygotes, the mean time to extinction, , is asymptotically proportional to for 4N_es > 1. Nearly neutral mutations pose the greatest risk of extinction for stable populations, because the magnitude of selection coefficient that minimizes is about ? = 0.4/N_e. The influence of variance in selection coefficients among mutations is analyzed assuming a gamma distribution of s, with mean and variance . The mean time to extinction increases with variance in selection coefficients if is near ?, but can decrease greatly if is much larger than ?. For a given coefficient of variation of , the mean time to extinction is asymptotically proportional to for . When s is exponentially distributed, (c = 1) is asymptotically proportional to . These results in conjunction with data on the rate and magnitude of mildly deleterious mutations in Drosophila melanogaster indicate that even moderately large populations, with effective sizes on the order of N_e = 10³, may incur a substantial risk of extinction from the fixation of new mutations.     

The effect of O2 and pressure on thiosulfate oxidation by Thiomicrospira thermophila

Microbial sulfur cycling in marine sediments often occurs in environments characterized by transient chemical gradients that affect both the availability of nutrients and the activity of microbes. High turnover rates of intermediate valence sulfur compounds and the intermittent availability of oxygen in these systems greatly impact the activity of sulfur‐oxidizing micro‐organisms in particular. In this study, the thiosulfate‐oxidizing hydrothermal vent bacterium Thiomicrospira thermophila strain EPR85 was grown in continuous culture at a range of dissolved oxygen concentrations (0.04–1.9 mM) and high pressure (5–10 MPa) in medium buffered at pH 8. Thiosulfate oxidation under these conditions produced tetrathionate, sulfate, and elemental sulfur, in contrast to previous closed‐system experiments at ambient pressure during which thiosulfate was quantitatively oxidized to sulfate. The maximum observed specific growth rate at 5 MPa pressure under unlimited O₂ was 0.25 hr^?1. This is comparable to the μ_max (0.28 hr^?1) observed at low pH (<6) at ambient pressure when T. thermophila produces the same mix of sulfur species. The half‐saturation constant for O₂ () estimated from this study was 0.2 mM (at a cell density of 10⁵ cells/ml) and was robust at all pressures tested (0.4–10 MPa), consistent with piezotolerant behavior of this strain. The cell‐specific was determined to be 1.5 pmol O₂/cell. The concentrations of products formed were correlated with oxygen availability, with tetrathionate production in excess of sulfate production at all pressure conditions tested. This study provides evidence for transient sulfur storage during times when substrate concentration exceeds cell‐specific and subsequent consumption when oxygen dropped below that threshold. These results may be common among sulfur oxidizers in a variety of environments (e.g., deep marine sediments to photosynthetic microbial mats).     

Optimizing Water Exchange Rates and Rotational Mobility for High‐Relaxivity of a Novel Gd‐DO3A Derivative Complex Conjugated to Inulin as Macromolecular Contrast Agents for MRI

Thanks to the understanding of the relationships between the residence lifetime τ_M of the coordinated water molecules to macrocyclic Gd‐complexes and the rotational mobility τ_R of these structures, and according to the theory for paramagnetic relaxation, it is now possible to design macromolecular contrast agents with enhanced relaxivities by optimizing these two parameters through ligand structural modification. We succeeded in accelerating the water exchange rate by inducing steric compression around the water binding site, and by removing the amide function from the DOTA‐AA ligand [1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid mono(p‐aminoanilide)] ( L ) previously designed. This new ligand 10[2(1‐oxo‐1‐p‐propylthioureidophenylpropyl]‐1,4,7,10‐tetraazacyclodecane‐1,4,7‐tetraacetic acid ( L ₁ ) was then covalently conjugated to API [O‐(aminopropyl)inulin] to get the complex API ‐(GdL ₁ )x with intent to slow down the rotational correlation time (τ_R) of the macromolecular complex. The evaluation of the longitudinal relaxivity at different magnetic fields and the study of the ¹⁷O‐NMR at variable temperature of the low‐molecular‐weight compound ( GdL ₁ ) showed a slight decrease of the τ_M value ( = 331 ns vs.  = 450 ns for the Gd L complex). Consequently to the increase of the size of the API ‐(GdL ₁ )x complex, the rotational correlation time becomes about 360 times longer compared to the monomeric GdL ₁ complex (τ_R = 33,700 ps), which results in an enhanced proton relaxivity.     

Species turnover (β‐diversity) in ectomycorrhizal fungi linked to uptake capacity

Ectomycorrhizal (EcM) fungal communities may be shaped by both deterministic and stochastic processes, potentially influencing ecosystem development and function. We evaluated community assembly processes for EcM fungi of Pseudotsuga menziesii among 12 sites up to 400 km apart in southwest British Columbia (Canada) by investigating species turnover (β‐diversity) in relation to soil nitrogen (N) availability and physical distance. We then examined functional traits for an N‐related niche by quantifying net fluxes of , and protons on excised root tips from three contrasting sites using a microelectrode ion flux measurement system. EcM fungal communities were well aligned with soil N availability and pH, with no effect of site proximity (distance–decay curve) on species assemblages. Species turnover was significant (β_1/2 = 1.48) along soil N gradients, with many more Tomentella species on high N than low N soils, in contrast to Cortinarius species. Ammonium uptake was greatest in the spring on the medium and rich sites and averaged over 190 nmol/m²/s for Tomentella species. The lowest uptake rates of were by nonmycorrhizal roots of axenically grown seedlings (10 nmol/m²/s), followed by Cortinarius species (60 nmol/m²/s). EcM roots from all sites displayed only marginal uptake of nitrate (8.3 nmol/m²/s). These results suggest uptake capacity is an important functional trait influencing the assembly of EcM fungal communities. The diversity of EcM fungal species across the region arguably provides critical belowground adaptations to organic and inorganic N supply that are integral to temperate rainforest ecology.     

Changes in interspecies association patterns of Atlantic bottlenose dolphins,Tursiops truncatus,and Atlantic spotted dolphins,Stenella frontalis,after demographic changes related to environmental disturbance

Animal populations can be affected by environmental disturbances in many ways including demographic and behavioral changes. This can affect interspecies associations for regularly interacting sympatric species, like bottlenose and spotted dolphins in the Bahamas (observed since 1985 and interspecies associations analyzed since 1993). After two hurricanes in 2004 each species lost roughly 30% of their respective communities resulting in differing social structure and behavioral changes. During mixed species encounters (MSE) group sizes for spotted dolphins ( = 14.1 ± 9.2) were significantly larger than bottlenose dolphins ( = 6.0 ± 7.3; F = 11.74, df = 1, P < 0.001), however, t‐tests revealed no differences between aggressive vs. affiliative encounters. Sexual/aggressive behavior regularly seen previously was not observed posthurricanes and aggressive encounters were greatly reduced. Generally results were similar to prehurricane data including high resightings of spotted dolphins with male alliances prevalent (including new juvenile alliances seen only posthurricane), and individualized bottlenose participation with few male alliances. However temporal associations varied compared to prehurricane. Interspecies association and behavior patterns were altered and likely affected by the changes in intraspecies association patterns following the hurricanes. However both species still participated in MSE, suggesting this is an important component of their ability to coexist as sympatric species.     

Leghemoglobin is nitrated in functional legume nodules in a tyrosine residue within the heme cavity by a nitrite/peroxide‐dependent mechanism

Protein tyrosine (Tyr) nitration is a post‐translational modification yielding 3‐nitrotyrosine (NO₂–Tyr). Formation of NO₂–Tyr is generally considered as a marker of nitro‐oxidative stress and is involved in some human pathophysiological disorders, but has been poorly studied in plants. Leghemoglobin (Lb) is an abundant hemeprotein of legume nodules that plays an essential role as an O₂ transporter. Liquid chromatography coupled to tandem mass spectrometry was used for a targeted search and quantification of NO₂–Tyr in Lb. For all Lbs examined, Tyr30, located in the distal heme pocket, is the major target of nitration. Lower amounts were found for NO₂–Tyr25 and NO₂–Tyr133. Nitrated Lb and other as yet unidentified nitrated proteins were also detected in nodules of plants not receiving and were found to decrease during senescence. This demonstrates formation of nitric oxide (˙NO) and by alternative means to nitrate reductase, probably via a ˙NO synthase‐like enzyme, and strongly suggests that nitrated proteins perform biological functions and are not merely metabolic byproducts. In vitro assays with purified Lb revealed that Tyr nitration requires  + H₂O₂ and that peroxynitrite is not an efficient inducer of nitration, probably because Lb isomerizes it to . Nitrated Lb is formed via oxoferryl Lb, which generates nitrogen dioxide and tyrosyl radicals. This mechanism is distinctly different from that involved in heme nitration. Formation of NO₂–Tyr in Lb is a consequence of active metabolism in functional nodules, where Lb may act as a sink of toxic peroxynitrite and may play a protective role in the symbiosis.     

Estimators for QST and coalescence times

Comparisons of to can provide insights into the evolutionary processes that lead to differentiation, or lack thereof, among the phenotypes of different groups (e.g., populations, species), and these comparisons have been performed on a variety of taxa, including humans. Here, I show that for neutrally evolving (i.e., by genetic drift, mutation, and gene flow alone) quantitative characters, the two commonly used estimators have somewhat different interpretations in terms of coalescence times, particularly when the number of groups that have been sampled is small. A similar situation occurs for estimators. Consequently, when observations come from only a small number of groups, which is not an unusual situation, it is important to match estimators appropriately when comparing to .     

A new proposal for measurement of the adjusted mean crowding through consideration of size variability in habitat units

The mean crowding has previously been measured under the assumption that all quadrats or habitat units have the same size, even though the actual habitat units such as seeds or leaves are generally variable in size. A new index, ‘adjusted mean crowding’, which is adjusted for this variability can be given as where Q is the total number of habitat units in the whole area, x_j the number of individuals in the jth habitat unit, and a_j is defined as the ‘relative size’ of the jth habitat unit, i.e. a_y=y_y/(∑y_j/Q) where y_j is the actually measured size of the jth habitat unit. It is expected that and for the uniform distribution and the random distribution ‘per unit size’, respectively. The comparison between and regressions ( analysis) for the egg distribution pattern of Callosobruchus chinensis or C. maculatus proved that the regression is biased by a positive correlation between the egg number per seed and seed size rather than by a density-dependent change in the ovipositional behavior.     

Biophysical analysis of the dynamics of calmodulin interactions with neurogranin and Ca2+/calmodulin‐dependent kinase II

Calmodulin (CaM) functions depend on interactions with CaM‐binding proteins, regulated by . Induced structural changes influence the affinity, kinetics, and specificities of the interactions. The dynamics of CaM interactions with neurogranin (Ng) and the CaM‐binding region of /calmodulin‐dependent kinase II (CaMKII_290−309) have been studied using biophysical methods. These proteins have opposite dependencies for CaM binding. Surface plasmon resonance biosensor analysis confirmed that and CaM interact very rapidly, and with moderate affinity ( ). Calmodulin‐CaMKII_290−309 interactions were only detected in the presence of , exhibiting fast kinetics and nanomolar affinity ( ). The CaM–Ng interaction had higher affinity under ‐depleted ( and k ₋₁ = 1.6 × 10⁻¹s⁻¹) than ‐saturated conditions ( ). The IQ motif of Ng (Ng₂₇₋₅₀) had similar affinity for CaM as Ng under ‐saturated conditions ( ), but no interaction was seen under ‐depleted conditions. Microscale thermophoresis using fluorescently labeled CaM confirmed the surface plasmon resonance results qualitatively, but estimated lower affinities for the Ng ( ) and CaMKII_290−309( ) interactions. Although CaMKII_290−309 showed expected interaction characteristics, they may be different for full‐length CaMKII. The data for full‐length Ng, but not Ng₂₇₋₅₀, agree with the current model on Ng regulation of /CaM signaling.     

Exploring a Pool‐seq‐only approach for gaining population genomic insights in nonmodel species

Developing genomic insights is challenging in nonmodel species for which resources are often scarce and prohibitively costly. Here, we explore the potential of a recently established approach using Pool‐seq data to generate a de novo genome assembly for mining exons, upon which Pool‐seq data are used to estimate population divergence and diversity. We do this for two pairs of sympatric populations of brown trout (Salmo trutta): one naturally sympatric set of populations and another pair of populations introduced to a common environment. We validate our approach by comparing the results to those from markers previously used to describe the populations (allozymes and individual‐based single nucleotide polymorphisms [SNPs]) and from mapping the Pool‐seq data to a reference genome of the closely related Atlantic salmon (Salmo salar). We find that genomic differentiation (F_ST) between the two introduced populations exceeds that of the naturally sympatric populations (F_ST = 0.13 and 0.03 between the introduced and the naturally sympatric populations, respectively), in concordance with estimates from the previously used SNPs. The same level of population divergence is found for the two genome assemblies, but estimates of average nucleotide diversity differ ( ≈ 0.002 and  ≈ 0.001 when mapping to S. trutta and S. salar, respectively), although the relationships between population values are largely consistent. This discrepancy might be attributed to biases when mapping to a haploid condensed assembly made of highly fragmented read data compared to using a high‐quality reference assembly from a divergent species. We conclude that the Pool‐seq‐only approach can be suitable for detecting and quantifying genome‐wide population differentiation, and for comparing genomic diversity in populations of nonmodel species where reference genomes are lacking.     

Effect of initial soil properties on six‐year growth of 15 tree species in tropical restoration plantings

In restoration plantings in degraded pastures, initial soil nutrient status may lead to differential growth of tropical tree species with diverse life history attributes and capacity for N₂ fixation. In 2006, we planted 1,440 seedlings of 15 native tree species in 16 fenced plots (30 × 30 m) in a 60‐year‐old pasture in Los Tuxtlas, Veracruz, Mexico, in two planting combinations. In the first year, we evaluated bulk density, pH, the concentration of organic carbon (C), total nitrogen (N), ammonia (), nitrate (), and total phosphorus (P) in the upper soil profile (0–20 cm in depth) of all plots. The first two axes of two principal component analyses explained more than 60% of the variation in soil variables: The axes were related to increasing bulk density, , , total N concentration, and pH. Average relative growth rates in diameter at the stem base of the juvenile trees after 6 years were higher for pioneer (45.7%) and N₂‐fixing species (47.6%) than for nonpioneer (34.7%) and nonfixing species (36.2%). Most N₂‐fixing species and those with the slowest growth rates did not respond to soil attributes. Tree species benefited from higher pH levels and existing litter biomass. The pioneers Ficus yoponensis, Cecropia obtusifolia, and Heliocarpus appendiculatus, and the N₂‐fixing nonpioneers Cojoba arborea, Inga sinacae, and Platymiscium dimorphandrum were promising for forest restoration on our site, given their high growth rates.     

Nitrate or ammonium: Influences of nitrogen source on the physiology of a green alga

In freshwaters, algal species are exposed to different inorganic nitrogen (N_i) sources whose incorporation varies in biochemical energy demand. We hypothesized that due to the lesser energy requirement of ammonium ()‐use, in contrast to nitrate ()‐use, more energy remains for other metabolic processes, especially under CO₂‐ and phosphorus (P_i) limiting conditions. Therefore, we tested differences in cell characteristics of the green alga Chlamydomonas acidophila grown on or under covariation of CO₂ and P_i‐supply in order to determine limitations, in a full‐factorial design. As expected, results revealed higher carbon fixation rates for ‐grown cells compared to growth with under low CO₂ conditions. ‐grown cells accumulated more of the nine analyzed amino acids, especially under P_i‐limited conditions, compared to cells provided with . This is probably due to a slower protein synthesis in cells provided with . In contrast to our expectations, compared to ‐grown cells ‐grown cells had higher photosynthetic efficiency under P_i‐limitation. In conclusion, growth on the N_i‐source did not result in a clearly enhanced C_i‐assimilation, as it was highly dependent on P_i and CO₂ conditions (replete or limited). Results are potentially connected to the fact that C. acidophila is able to use only CO₂ as its inorganic carbon (C_i) source.     

Differential responses of two wetland graminoids to high ammonium at different pH values

Enhanced soil ammonium () concentrations in wetlands often lead to graminoid dominance, but species composition is highly variable. Although is readily taken up as a nutrient, several wetland species are known to be sensitive to high concentrations or even suffer toxicity, particularly at low soil pH. More knowledge about differential graminoid responses to high availability in relation to soil pH can help to better understand vegetation changes. The responses of two wetland graminoids, Juncus acutiflorus and Carex disticha, to high (2 mmol·l^?1) versus control (20 μmol·l^?1) concentrations were tested in a controlled hydroponic set up, at two pH values (4 and 6). A high concentration did not change total biomass for these species at either pH, but increased C allocation to shoots and increased P uptake, leading to K and Ca limitation, depending on pH treatment. More than 50% of N taken up by C. disticha was invested in N‐rich amino acids with decreasing C:N ratio, but only 10% for J. acutiflorus. Although both species appeared to be well adapted to high loadings in the short term, C. disticha showed higher classic detoxifying responses that are early warning indicators for decreased tolerance in the long term. In general, the efficient aboveground biomass allocation, P uptake and N detoxification explain the competitive strength of wetland graminoids at the expense of overall biodiversity at high loading. In addition, differential responses to enhanced affect interspecific competition among graminoids and lead to a shift in vegetation composition.