Warmer and drier conditions associated with ongoing climate change will increase abiotic stress for plants and mycorrhizal fungi in drylands worldwide, thereby potentially reducing vegetation cover ...and productivity and increasing the risk of land degradation and desertification. Rhizosphere microbial interactions and feedbacks are critical processes that could either mitigate or aggravate the vulnerability of dryland vegetation to forecasted climate change.We conducted a four-year manipulative study in a semiarid shrubland in the Iberian Peninsula to assess the effects of warming (~2.5ºC; W), rainfall reduction (~30%; RR) and their combination (W+RR) on the performance of native shrubs (
) and their associated mycorrhizal fungi.Warming (W and W+RR) decreased the net photosynthetic rates of
shrubs by ~31% despite concurrent increases in stomatal conductance (~33%), leading to sharp decreases (~50%) in water use efficiency. Warming also advanced growth phenology, decreased leaf nitrogen and phosphorus contents per unit area, reduced shoot biomass production by ~36% and decreased survival during a dry year in both W and W+RR plants. Plants under RR showed more moderate decreases (~10-20%) in photosynthesis, stomatal conductance and shoot growth.Warming, RR and W+RR altered ectomycorrhizal fungal (EMF) community structure and drastically reduced the relative abundance of EMF sequences obtained by high-throughput sequencing, a response associated with decreases in the leaf nitrogen, phosphorus and dry matter contents of their host plants. In contrast to EMF, the community structure and relative sequence abundances of other non-mycorrhizal fungal guilds were not significantly affected by the climate manipulation treatments.
Our findings highlight the vulnerability of both native plants and their symbiotic mycorrhizal fungi to climate warming and drying in semiarid shrublands, and point to the importance of a deeper understanding of plant-soil feedbacks to predict dryland vegetation responses to forecasted aridification. The interdependent responses of plants and ectomycorrhizal fungi to warming and rainfall reduction may lead to a detrimental feedback loop on vegetation productivity and nutrient pool size, which could amplify the adverse impacts of forecasted climate change on ecosystem functioning in EMF-dominated drylands.
The metabolic diversity of microbial communities is fundamental for the multiple soil functions mediated by microorganisms. Community level physiological profiles (CLPPs) based on sole C source ...oxidation have been used as a fast and reproducible tool to study soil microbial functional diversity because the utilisation of available carbon is the key factor governing microbial growth in soil. Our aim was to assess the phylogenetic affiliation of the microorganisms responsible for C consumption after inoculating Biolog™ plates. For this purpose, two semi-arid Mediterranean forest soils with significantly different patterns of C consumption and microbial community structure were used. Following the inoculation of the Biolog plates, suspensions from seven wells were sampled after 1, 2 and 7 d of incubation. DNA was extracted and the microbial communities analysed by polymerase chain reaction followed by denaturing gradient gel electrophoresis (PCR–DGGE) and sequencing of excised bands.
Despite major differences in the microbial communities of the soils studied, their DGGE banding patterns after incubation were similar for all the analysed C source suspensions. Microorganisms belonging to β-Proteobacteria (Ralstonia sp. and Burkholderia sp.) and α-Proteobacteria (Rhizobium sp.) were dominant. These opportunists had a competitive advantage under the conditions at which the CLPPs were analysed.
This study reveals that significantly different CLPP patterns can be generated on the basis of only 3–4 genera, as reflected by PCR–DGGE analysis. Also for this reason, CLPPs based on incubations of soil suspensions should just be used as a screening method and always be accompanied by other techniques for community analysis.
Same nurse but different time Navarro-Cano, Jose A.; Goberna, Marta; Valiente-Banuet, Alfonso ...
Functional ecology,
11/2016, Letnik:
30, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Summary
Plant facilitation assembles functionally contrasted communities in dry lands. Nurse plants are often early colonizers with xerophytic traits that were mostly selected during the dry ...Quaternary (Quaternary syndrome), while beneficiary plants tend to be late‐successional species with mesophytic traits that evolved mainly during the more humid Tertiary (Tertiary syndrome). Integrating plant facilitation within the community assembly theory requires a better understanding of the ontogenetic development of the nursing abilities that benefit functionally contrasted species.
We assessed whether the same nurse plant facilitates species with Quaternary and Tertiary syndromes in an ecosystem under severe abiotic stress conditions imposed by aridity and gypsum soil toxicity. We hypothesized that both functional types find suitable microsites for seedling establishment underneath the same nurse but their optimal regeneration niches are temporally segregated along the ontogenetic development of the nurse.
We carried out a sowing experiment along a 40‐year ontogenetic gradient of the nurse shrub Ononis tridentata. Seeds from five Tertiary and five Quaternary species were sown and seedling emergence monitored.
While the nurse age did not affect the seedling emergence of Quaternary species, it significantly increased that of Tertiary species. These results were corroborated for elder ontogenetic stages in non‐manipulated plants in the field. Juveniles of Quaternary species were able to grow beneath nurse plants along their whole ontogenetic gradient excepting beneath Ononis seedlings, while Tertiary species were only facilitated by mature nurses.
Synthesis. Our results show that plant nursing abilities evolve ontogenetically in a different way for beneficiary Quaternary and Tertiary plant lineages. The finding of a plant species that plays a role as key assembler of early‐ and late‐successional species in plant dynamics broadens the scope of facilitation in the community assembly theory.
A lay summary is available for this article.
Lay Summary
Two different case studies concerning potential overload situations of anaerobic digesters were investigated and mathematically modelled by means of the Anaerobic Digestion Model No. 1 (ADM1). The ...first scenario included a digester failure at a municipal WWTP which occurred during revision works of the upstream digester within a two-step digestion system when the sludge was directly by-passed to the 2nd-step reactor. Secondly, the non-occurrence of a highly expected upset situation in a lab-scale digester fed with cattle manure was investigated. ADM1 was utilized to derive indicators which were used to investigate the relationship between digester stability and biomass population dynamics. Conventional design parameters such as the organic loading rate appeared unsuitable for process description under dynamic conditions. Indicators reflecting the biokinetic state (e.g.
F
net/
M
net or the VFA/alkalinity ratio) are more adequate for the assessment of the stability of reactors in transient situations.
Phylogenetic diversity enhances ecosystem functioning but restoration ecology has not taken advantage of this knowledge. We propose plant facilitation as a mechanism to promote phylogenetic diversity ...in restoration practices. We planted three functionally different species (Gypsophila struthium, Sedum album, and Limonium sucronicum) in a degraded gypsum ecosystem in Spain and found that after 7 years, the species with nurse traits (G. struthium) survived longer and facilitated the establishment of new species forming phylogenetically diverse neighborhoods. These facilitation‐driven phylodiverse communities may potentially produce a cascade of benefits on ecosystem functioning.
The aim of this study was to design a microarray targeting methanogens found in anaerobic digesters, and to apply this chip together with a cloning approach to investigate the methanogenic community ...present in an anaerobic digester. Oligonucleotide probes were designed based on sequence differences in the 16S rRNA genes in order to target microorganisms
in situ. For microarray hybridisations, DNA was subjected to PCR amplification of the 16S rRNA gene and Cy5-labeled. The microarray was tested with pure cultures, and of the 1854 individual probe-target hybridisation reactions performed, there were only 28 false positive (1.5%) and 16 false negative signals (0.86%). The sensitivity of the array was also tested, and it was found that when 0.4
pg of DNA from a pure culture was subjected to PCR amplification, signals above the detection limit were obtained. Also, the application of 25
ng of PCR product from a pure culture to an array resulted in detectable signals. The ANAEROCHIP was hybridised with DNA from an anaerobic sludge. Strong hybridisation signals were obtained for
Methanoculleus, and weaker signals, in decreasing order, were obtained for
Methanosarcina,
Methanobacterium,
Methanobrevibacter, and
Methanosphaera. In order to check the results obtained with the microarray, the archaeal community structure of the same digester was analysed by 16S rRNA gene cloning and sequencing. Community structure was determined by restriction digestion of almost 200 clones and by sequencing of the 15 different resulting patterns.
Methanoculleus was the dominant (84.1%) microorganism in the anaerobic sludge, and
Methanobrevibacter (5.8%),
Methanobacterium (3.7%),
Methanosarcina (2.1%),
Methanosphaera (1.6%), an uncultured archaeon (1.6%) and
Methanothermobacter (1%) were also detected. These results showed the microarray to be a suitable tool for studying methanogenic communities in sludge.
► Organic wastes from different origins were bioconverted into four vermicomposts. ► Vermicomposts’ chemical features and microbial functional diversity were explored. ► Response of the ...vermicomposts’ microbiota to three pesticides was investigated. ► The vermicompost’ chemical features affected its microbial functional diversity. ► Functional diversity of the microbiota was related with its response to pesticides.
The relationships between vermicompost chemical features, enzyme activities, community-level physiological profiles (CLPPs), fungal community structures, and its microbial respiratory response to pesticides were investigated. Fungal community structure of vermicomposts produced from damaged tomato fruits (DT), winery wastes (WW), olive-mill waste and biosolids (OB), and cattle manure (CM) were determined by denaturing gradient gel electrophoresis of 18S rDNA. MicroResp™ was used for assessing vermicompost CLPPs and testing the microbial response to metalaxyl, imidacloprid, and diuron. Vermicompost enzyme activities and CLPPs indicated that WW, OB, and DT had higher microbial functional diversity than CM. The microbiota of the former tolerated all three pesticides whereas microbial respiration in CM was negatively affected by metalaxyl and imidacloprid. The response of vermicompost microbiota to the fungicide metalaxyl was correlated to its fungal community structure. The results suggest that vermicomposts with higher microbial functional diversity can be useful for the management of pesticide pollution in agriculture.
AbstractThe full-scale start-up of a novel BIO4GAS digester system, a highly economic, small-scale biogas plant was monitored for 6 months. The digester was loaded with cattle manure, and a new slow ...temperature increase strategy (12–37°C at 0.25°C d−1) was tested, rendering a daily methane yield of 289±148 mL g−1 volatile solids. Stable biogas production, pH, and high reduction of volatile fatty acids (from 5.2 to 0.6 g L−1) indicated a well working process. The prokaryotic community was monitored by cloning and quantitative real-time PCR of the 16S rRNA gene. Archaeal diversity decreased at the taxonomic class level, whereas the bacterial community was affected only up to the family level. A shift from hydrogenotrophic methanogens toward a consortium dominated by metabolically versatile methanogens occurred with Methanosarcina outcompeting Methanobrevibacter under the changing conditions of volatile fatty acid concentrations. Main bacterial phyla (Firmicutes, Bacteroidetes, and Proteobacteria) did not change during the start-up; however, minor populations of cellulose-degraders (Ruminococcaceae), syntrophic fatty acid oxidizers (Syntrophomonas), and acetogens (Sedimentibacter) established. The results provide experimental evidence of a dynamic archaeal community and a relatively stable bacterial community during dramatic environmental changes of a successful reactor start-up.
The acclimatization of methanogens to two-phase olive mill wastes (TPOMW) was investigated in pilot fermenters started up with cattle excreta (37C) and after changing their feed to excreta plus TPOMW ...(37C or 55C) or TPOMW alone (37C) until a steady state was reached (28 days). Methanogenic diversity was screened using a phylogenetic microarray (AnaeroChip), and positive targets were quantified by real-time PCR. Results revealed high phylogenetic richness, with representatives of three out of the four taxonomic orders found in digesters. Methanosarcina dominated in the starting excreta (>96% of total 16S rRNA gene copies; over 45 times more abundant than any other methanogen) at high acetate (0.21 g liter-1) and ammonia N concentrations (1.3 g liter-1). Codigestion at 37C induced a 6-fold increase of Methanosarcina numbers, correlated with CH4 production (rPearson = 0.94; P = 0.02). At 55C, the rise in temperature and H2 partial pressure induced a burst of Methanobacterium, Methanoculleus, Methanothermobacter, and a group of uncultured archaea. The digestion of excreta alone resulted in low but constant biogas production despite certain oscillations in the methanogenic biomass. Unsuccessful digestion of TPOMW alone was attributed to high Cu levels inducing inhibition of methanogenic activity. In conclusion, the versatile Methanosarcina immediately adapted to the shift from excreta to excreta plus TPOMW and was responsible for the stimulated CH4 production at 37C. Higher temperatures (55C) fostered methanogenic diversity by promoting some H2 scavengers while yielding the highest CH4 production. Further testing is needed to find out whether there is a link between increased methanogenic diversity and reactor productivity.
In this study, 16S rRNA gene primers were designed to complement the suite of already available PCR primers for the detection of different methanogens involved in biogas production through anaerobic ...digestion by SYBR Green real-time PCR. Primers designed for use in TaqMan real-time PCR for the organisms
Methanosaeta
,
Methanosarcina
, and
Methanoculleus
have been described previously; however, we found that (i) the Methanoculleus primers were not specific to members of the genus and that (ii) the Methanosarcina primers did not work specifically with SYBR Green real-time PCR. Thus, we designed new primers for these and other methanogens, and we optimized SYBR Green real-time PCR assays. Primers were tested by end-point and real-time PCR, and they were found to work specifically and sensitively. Application of these primers will allow the detection and quantification of Methanoculleus, Methanosarcina,
Methanothermobacter
, and a group of yet uncultured archaea from anaerobic habitats.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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