Land Use Alters the Drought Responses of Productivity and CO<Subscript>2</Subscript> Fluxes in Mountain Grassland

Climate extremes and land-use changes can have major impacts on the carbon cycle of ecosystems. Their combined effects have rarely been tested. We studied whether and how the abandonment of traditionally managed mountain grassland changes the resilience of carbon dynamics to drought. In an in situ common garden experiment located in a subalpine meadow in the Austrian Central Alps, we exposed intact ecosystem monoliths from a managed and an abandoned mountain grassland to an experimental early-summer drought and measured the responses of gross primary productivity, ecosystem respiration, phytomass and its components, and of leaf area index during the drought and the subsequent recovery period. Across all these parameters, the managed grassland was more strongly affected by drought and recovered faster than the abandoned grassland. A bivariate representation of resilience confirmed an inverse relationship of resistance and recovery; thus, low resistance was related to high recovery from drought and vice versa. In consequence, the overall perturbation of the carbon cycle caused by drought was larger in the managed than the abandoned grassland. The faster recovery of carbon dynamics from drought in the managed grassland was associated with a significantly higher uptake of nitrogen from soil. Furthermore, in both grasslands leaf nitrogen concentrations were enhanced after drought and likely reflected drought-induced increases in nitrogen availability. Our study shows that ongoing and future land-use changes have the potential to profoundly alter the impacts of climate extremes on grassland carbon dynamics.     

Is intensity of plant root mycorrhizal colonization a good proxy for plant growth rate,dominance and decomposition in nutrient poor conditions?

Questions

Mycorrhizae may be a key element of plant nutritional strategies and of carbon and nutrient cycling. Recent research suggests that in natural conditions, intensity of mycorrhizal colonization should be considered an important plant feature. How are inter‐specific variations in mycorrhizal colonization rate, plant relative growth rate (RGR ) and leaf litter decomposability related? Is (arbuscular) mycorrhizal colonization linked to the dominance of plant species in nutrient‐stressed ecosystems?

Location

Teberda State Biosphere Reserve, northwest Caucasus, Russia.

Methods

We measured plant RGR under mycorrhizal limitation and under natural nutrition conditions, together with leaf litter decomposability and field intensity of mycorrhizal colonization across a wide range of plant species, typical for alpine communities of European mountains. We applied regression analysis to test whether the intensity of mycorrhizal colonization is a good predictor of RGR and decomposition rate, and tested how these traits predict plant dominance in communities.

Results

Forb species with a high level of field mycorrhizal colonization had lower RGR under nutritional and mycorrhizal limitation, while grasses were unaffected. Litter decomposition rate was not related to the intensity of mycorrhizal colonization. Dominant species mostly had a higher level of mycorrhizal colonization and lower RGR without mycorrhizal colonization than subordinate species, implying that they were more dependent on mycorrhizal symbionts. There were no differences in litter decomposability.

Conclusions

In alpine herbaceous plant communities dominated by arbuscular mycorrhizae, nutrient dynamics are to a large extent controlled by mycorrhizal symbiosis. Intensity of mycorrhizal colonization is a negative predictor for whole plant RGR . Our study highlights the importance of mycorrhizal colonization as a key trait underpinning the role of plant species in carbon and nutrient dynamics in nutrient‐limited herbaceous plant communities.

     

Spatial heterogeneity in species composition constrains plant community responses to herbivory and fertilisation

Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change – fertilisation and herbivore loss – are affected by species pool size and spatial compositional heterogeneity. Fertilisation led to higher rates of local extinction, whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.     

Independent suboesophageal neuronal innervation of the defense gland and longitudinal muscles in the stick insect (Peruphasma schultei) prothorax

This study investigates the neuroanatomy of the defense gland and a related muscle in the stick insect Peruphasma schultei with axonal tracing and histological sections. The gland is innervated by three neurons through the Nervus anterior of the suboesophageal ganglion (SOG), the ipsilateral neuron (ILN), the contralateral neuron (CLN) and the prothoracic intersegmental neuron (PIN). The ILN has a large soma which is typical for motoneurons that cause fast contraction of large muscles and its dendrites are located in motor-sensory and sensory neuropile areas of the SOG. The CLN might be involved in the coordination of bilateral or unilateral discharge as its neurites are closely associated to the ILN of the contralateral gland. Close to the ejaculatory duct of the gland lies a dorsal longitudinal neck muscle, musculus pronoto-occipitalis (Idlm2), which is likely indirectly involved in gland discharge by controlling neck movements and, therefore, the direction of discharge. This muscle is innervated by three ventral median neurons (VMN). Thus, three neuron types (ILN, CLN, and PIN) innervate the gland muscle directly, and the VMNs could aid secretion indirectly. The cytoanatomy of motorneurons innervating the defense gland and neck muscle are discussed regarding the structure and functions of the neuropile in the SOG. As a basis for the neuroanatomical study on the defense gland we assembled a map of the SOG in Phasmatodea.     

Shifts in priming partly explain impacts of long‐term nitrogen input in different chemical forms on soil organic carbon storage

Input of labile organic carbon can enhance decomposition of extant soil organic carbon (SOC) through priming. We hypothesized that long‐term nitrogen (N) input in different chemical forms alters SOC pools by altering priming effects associated with N‐mediated changes in plants and soil microbes. The hypothesis was tested by integrating field experimental data of plants, soil microbes and two incubation experiments with soils that had experienced 10 years of N enrichment with three chemical forms (ammonium, nitrate and both ammonium and nitrate) in an alpine meadow on the Tibetan Plateau. Incubations with glucose–¹³C addition at three rates were used to quantify effects of exogenous organic carbon input on the priming of SOC. Incubations with microbial inocula extracted from soils that had experienced different long‐term N treatments were conducted to detect effects of N‐mediated changes in soil microbes on priming effects. We found strong evidence and a mechanistic explanation for alteration of SOC pools following 10 years of N enrichment with different chemical forms. We detected significant negative priming effects both in soils collected from ammonium‐addition plots and in sterilized soils inoculated with soil microbes extracted from ammonium‐addition plots. In contrast, significant positive priming effects were found both in soils collected from nitrate‐addition plots and in sterilized soils inoculated with soil microbes extracted from nitrate‐addition plots. Meanwhile, the abundance and richness of graminoids were higher and the abundance of soil microbes was lower in ammonium‐addition than in nitrate‐addition plots. Our findings provide evidence that shifts toward higher graminoid abundance and changes in soil microbial abundance mediated by N chemical forms are key drivers for priming effects and SOC pool changes, thereby linking human interference with the N cycle to climate change.     

Inside Back Cover: Development of a 3‐dimensional tissue lung phantom of a preterm infant for optical measurements of oxygen—Laser‐detector position considerations (J. Biophotonics 3/2018)

The picture depicts the different 3d‐printed organs, thorax, lungs, heart and bone. Assembled it is used as an optical phantom of a preterm infant for performing percutaneous optical measurements of the gas content in the lungs. In order to simulate the optical properties of the tissue, the heart and thorax can be filled with liquid phantoms, a mixture of Intralipid and Indian Ink. Further details can be found in the article by Jim Larsson et al. ( e201700097 ).

     

Dynamic L-type CaV1.2 channel trafficking facilitates CaV1.2 clustering and cooperative gating

L-type Ca_V1.2 channels are key regulators of gene expression, cell excitability and muscle contraction. Ca_V1.2 channels organize in clusters throughout the plasma membrane. This channel organization has been suggested to contribute to the concerted activation of adjacent Ca_V1.2 channels (e.g. cooperative gating). Here, we tested the hypothesis that dynamic intracellular and perimembrane trafficking of Ca_V1.2 channels is critical for formation and dissolution of functional channel clusters mediating cooperative gating. We found that Ca_V1.2 moves in vesicular structures of circular and tubular shape with diverse intracellular and submembrane trafficking patterns. Both microtubules and actin filaments are required for dynamic movement of Ca_V1.2 vesicles. These vesicles undergo constitutive homotypic fusion and fission events that sustain Ca_V1.2 clustering, channel activity and cooperative gating. Our study suggests that Ca_V1.2 clusters and activity can be modulated by diverse and unique intracellular and perimembrane vesicular dynamics to fine-tune Ca²⁺ signals.     

Hidden in the Arabian Mountains: Multilocus phylogeny reveals cryptic diversity in the endemic Omanosaura lizards

An increase in studies in the Hajar Mountains from the southeastern Arabian Peninsula has revealed a high richness of endemic evolutionary lineages with many cryptic taxa. Omanosaura is the only lacertid lizard genus endemic to the Hajar Mountains, with two species O. cyanura and O. jayakari distributed throughout this mountain range. The phylogenetic relationships and genetic diversity between and within these species have been poorly studied. In this study, we collected mitochondrial (12S, cytb, and nd4) and nuclear (cmos and mc1r) sequences for 25 specimens of Omanosaura, including 15 individuals of O. jayakari and 10 of O. cyanura. We performed phylogenetic analyses based on network reconstruction, maximum likelihood and Bayesian inference to estimate the relationships and intraspecific genetic diversity of these species. We estimated the time of divergence between the two species in the Miocene, around 8.5 million years ago. Omanosaura jayakari shows little genetic diversity, while O. cyanura presents two differentiated lineages. These are reciprocally monophyletic at mitochondrial and nuclear genes and present a high genetic distance between them. These two lineages are associated with the geographic features of the Hajar Mountains, with one lineage distributed in the northernmost part of the Hajar Mountains and the other in the rest of the western Hajars, the Jebel Akhdar, and the eastern Hajars. This geographic relationship has been recovered previously in other reptile taxa and is generally associated with high levels of local genetic diversity. Our results suggest the existence of cryptic diversity within O. cyanura and support a general biogeographic pattern of high diversity and endemism in the northern Hajar Mountains that certainly deserves additional research in the future.     

Phenolic and flavonoid production and antimicrobial activity of <Emphasis Type="Italic">Gymnosporia buxifolia</Emphasis> (L.) Szyszyl cell cultures

Gymnosporia buxifolia (Celastraceae) is a well-known traditional medicinal plant used to treat various diseases. The aim of the study was to quantify the total phenolic and flavonoid content of cell biomass of G. buxifolia developed in vitro using plant growth regulators (PGRs), phloroglucinol (PG) and an antagonist of cytokinin activity 6-(2-hydroxy-3-methylbenzylamino) purine (PI55). The antibacterial activity of calli was also evaluated. The accumulation of phenolic contents and its antibacterial activity in the cell biomass varied between the treatments as well as the mother plant. Generally, a higher accumulation of phenolic contents translated to improved activity against selected pathogenic bacteria. This was apparent in biomass derived from solid and liquid MS media containing combinations of 5 µM PG, 1.5 µM benzyladenine (BA) or meta-topolin (mT) with or without 1 µM picloram (Pic) and 5 µM PG or PI55, 1 µM BA with or without 0.5 µM Pic respectively. The choice of PGRs, PG and PI55 treatments used during in vitro cell culture systems influenced the therapeutic potential of G. buxifolia. Our results indicate that the cell biomass from suspension and/or solid culture of G. buxifolia could be promising as antibacterial agents with possible applications in the pharmaceutical industry.     

Analysis of the effect of plant growth regulators and organic elicitors on antibacterial activity of <Emphasis Type="Italic">Eucomis autumnalis</Emphasis> and <Emphasis Type="Italic">Drimia robusta</Emphasis> ex vitro-grown biomass

The effects of plant growth regulators (PGRs) and organic elicitors (OEs) on in vitro propagation of Eucomis autumnalis was established. Three-year-old ex vitro grown plants from organogenesis of E. autumnalis and somatic embryogenesis (previously reported protocol) of Drimia robusta were investigated for antibacterial activity. In vitro propagation from leaf explants of E. autumnalis was established using different PGRs and OE treatments for mass propagation, biomass production and bioactivity analysis to supplement the use of wild plant material. Prolific shoots (16.0?±?0.94 shoots per explant) were obtained with MS (Murashige and Skoog in Physiol Plant 15:473–497, 1962) medium containing 100 mg l^?1 haemoglobin (HB), 10 µM benzyladenine (BA) and 2 µM naphthaleneacetic acid (NAA). The shoots were rooted effectively with a combination of 2.5 µM indole-3-acetic acid and 5.0 µM indole-3-butyric acid. The plantlets were successfully acclimatized in a vermiculite-soil mixture (1:1 v/v) in the greenhouse. Three-year-old ex vitro-grown E. autumnalis and D. robusta plants derived via organogenesis and somatic embryogenesis respectively exhibited antibacterial activity and varied with PGR and OE treatments, plant parts and bacteria. The leaves of E. autumnalis ex vitro-derived from a combination of HB, BA and NAA followed by the individual treatments of BA and HB gave the best antibacterial activities (<?1 mg ml^?1: minimum inhibitory concentration from 0.098 to 0.78 mg ml^?1) against all tested pathogenic bacteria (Bacillus subtilis, Enterococcus faecalis, Micrococcus luteus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa). The bulbs of D. robusta ex vitro-derived from solid culture with 10 µM picloram, 1 µM thidiazuron and 20 µM glutamine exhibited good antibacterial activity against E. faecalis, M. luteus and S. aureus when compared with other treatments and mother plants. The ex vitro-grown E. autumnalis and D. robusta biomass produced with PGRs along with OE treatments confirmed a good potent bioresource and can be used as antibacterial agents. The in vitro plant regeneration of E. autumnalis and D. robusta protocols and ex vitro plants could be used for conservation strategies, bioactivity and traditional medicinal use.