Esteban, Genoveva

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Biological Diversity and Ecosystem Function in SoilWebsite: http://www.nmw.ac.uk/soilbioSoilBiodiversityNERC Thematic ProgrammeNewsletter - Issue number 7 May 2001Photo: S BucklandSOIL BIODIVERSITY:The Second Phase The main themes: Quantification of C flows in the soil and the role of the diversity faunal groups. The use of C isotope signals from 13CO2labelled inputs was to be a key component of the experimental method. Bidders were told that 13CO2  signals would beprovided.  A contract supervised by NERC would deliver the labelled CO2 with the necessary flexibility to vary the datesover the remaining years. Proposals which focus on aspects of the N pathways would be considered, but the emphasis is onC, and the functional groups and processes controlling its fluxes. Development of model theory and an overarching conceptual model into which mathematical sub-models could be placed.Models linking C flows and the inter-relationships with functional diversity, possibly linking the size and activity of populationswith soil architecture will require the development of new model theory and approaches.  A key goal of the model developmentwill be to reduce the number of parameters, while retaining a realistic representation of the critical processes and pathways. Resilience of key processes and the controlling organisms to stress/disturbance and the role of diversity in the relevantgroups of biota in determining resilience. Opportunities exist for relaxing the existing treatments and for imposing newperturbations on the soil biota. Proposals in this area were asked to address functional and taxonomic aspects of biodiversity,either in the field or laboratory. Strategic studies related to the requirements of the user community, if possible largely funded by appropriate users. Projectsto address questions of strategic importance, eg the influence of diversity of functional groups on rates of degradation ofchemical compounds; the influence of stresses on the capacity of soils to degrade pollutants or contaminants; also thedevelopment of indicators of soil sustainability, sensitivity or resilience. Studies could be funded by relevant users. Areas ofthe Sourhope site could be used for additional treatments, for example specific contaminants. Studies filling gaps in understanding the functional diversity of specific groups of organisms in the Sourhope soil. In thiscontext, a number of small Research Grants (up to £35,000), may be awarded. No further PhD studentships are envisaged.The Steering Committee met after the Warwick University discussions to define the second phase ofthe Programme. The main aim was to quantify functional groups of biota in C transfers in the soil,emphasising interactions, eg linkages between fungi and collembola or between bacteria, protozoa andworms. Studies should sit in an explicit modelling framework and provide output data to fit intomathematical models of  segments of the food web.Fruits of the FieldBasidiomes collected at the 2000 sampling showing the completerange of species morphologyBasidiome diversity at SourhopeUnder a threatening September sky and with waterproofs at theready, Janie Pryce Miller, Professor Roy Watling, Dr MikeRichardson and I entered the Sourhope field site.  The reason wewere there was to survey,  collect and isolate the autumn-fruitingbasidiomycete fungi.  With Roy Watling and Mike Richardson asidentification experts, we scanned each plot at the field site forany basidiomycete fruiting bodies (basidiomes).  All basidiomyceteswere identified in situ, except for difficult cases which werecollected and given to Roy Watling for further study. Arepresentative selection of species was taken for immediateisolation from spores in the laboratory at the Sourhope fieldstation.Compared with the species kindly collected in autumn 1999 byDr Sarah Buckland, there were greater numbers of species andindividuals recorded in 2000.  There were also differences in thefive most common species recorded between the two collections.In 1999 the five most common species collected were, indescending order: Nolanea staurospora (36 basidiomes),Camarophyllus niveus (11),  Psilocybe semilanceata (11),  Clavulinopsishelvola (10) and Hygrocybe laetea (7).  By contrast, in 2000 thefive most common species collected were: Psilocybe semilanceata(307), Galerina clavata (167), Clavulinopsis fusiformis (133), Nolaneastaurospora (96) and Mycena aetites (60).  All species that occurredin the top five of 1999 were also present in the 2000 samples.The species found in both years were typical of fungal assemblagesin acidic grasslands.  Galerina clavata is common in damp areasand was noted upon collection to be concentrated around thefurrows of the site, where there is likely to be an increase in soilmoisture.   A further collection is planned in September 2001.As part of our project “Biodiversity of root feeders and theirimpact on soil microbial communities” we are studying whetherthere are interactions between the large root-feeding insects (suchas tipulids and chafer grubs) and arbuscular mycorrhizal (AM)fungi.  One of our original hypotheses was that these insectsconsume large quantities of root and disturb the mycorrhizalmycelium through burrowing.  Therefore their presence may serveto reduce fungal colonization.  Reducing their numbers with aninsecticide should therefore lead to an increased level ofmycorrhizal colonization.  We have recorded AM colonizationlevels in the control and biocide plots at Sourhope since June1999.  At the start of the experiment, there was no difference incolonization levels of Agrostis capillaris between treatments withthe control plots having a level 1.33 times that of the biocide.However, by October 2000, this situation had changed and levelsin the control plots were four times that of the biocide plots.Applying insecticide has not increased  AM abundance andappears to have decreased it.Our thoughts have therefore turned to other organisms presentin the soil, which might be affected by the biocide, and whichmight affect AM fungi.  The obvious candidate is the Collembola,as one of us (Gange 2000) thinks that these organisms canincrease AM colonization, through their preferential feeding onnon-mycorrhizal fungi in the rhizosphere, thus reducing fungalcompetition and allowing AM fungal growth.  If this is so, thenadding a biocide should reduce Collembola numbers and therebydecrease AM abundance.  Collembola appear to be more evenlydistributed over the site (relatively speaking!) than larger insectsand are certainly more numerous.  We are therefore now thinkingthat the most important subterranean herbivores are at the micro,rather than macro scale.   When we get back on site, we will starttesting this idea  in  Sourhope Collembolan communities …….Gange, A.C. (2000) Arbuscular mycorrhizal fungi, collembola and plantgrowth. TREE 15, 369-72.Amanda Currie, Alan Gange & Phil MurrayGraham Burt-Smith has been appointed to take over from SarahBuckland this month.  The two will work together during May onsite maintenance and Sarah will remain in summer to carry onwith her research under the Macaulay Institute award.  Grahamhas been based in Sheffield carrying out environmental surveys,but has previous experience in banking, which may be useful ineking out the NERC grant money.  His PhD was carried out onone of the LTER sites in the USA, so he has experience of longterm sites.It would be premature to say goodbye to Sarah Buckland at themoment, but as most of you will know by now she has retired assite manager.  She has done a fantastic job of co-ordination andsucceeded in keeping everyone happy.  We wish her well for thefuture.Vegetation changes in responseto biocide effect on soil faunaNew Sourhope site managerPhotograph: Lewis DeaconRichard Scott, Programme ManagerLewis DeaconKing’s College Londonand CEH Merlewood10 cmAt CEH Windermere, in collaboration with the University ofGlasgow (Prof. Keith Vickerman) and CEH Merlewood (Dr HelainaBlack), we are studying protozoan diversity and its role in carbonand nitrogen turnover in Sourhope soils.  Within the variousresearch areas of this project, there is one devoted to thetaxonomy of ciliated protozoa (CEH-Windermere).  Ciliates arefascinating single-celled organisms characterised by having a real“mouth” which they use to ingest particles ranging in size frombacteria to other organisms as big as themselves.  So far,  wehave found one hundred and four species of ciliates in re-hydratedsoil samples from Sourhope.  One of these species, Psilotrichaacuminata, is particularly interesting.It was first discovered in 1859 by a priest examining some rain-soaked manure on a farm in Germany, but it has never, untilnow, been described in detail.  It belongs to a group known ashypotrichs, referring to the groups of cilia (the ‘cirri’,  arrows tosome of them in Figure 1) scattered across the ventral surface ofthe organism and used mainly for crawling on particles.  Themouth is also on the ventral side (M on the dividing specimen ofFigure 2).As our investigations show, the ciliate is not just ‘anotherhypotrich’ (of which a few are described every year).  Indeed,Psilotricha acuminata is probably the ‘missing-link’ between twolarge families of hypotrichs.  The unknown identity of the commonancestor has been tormenting hypotrich taxonomists for sometime.  The features that give our species the status of missing linkare the morphology of the ciliature (typical of the Euplotidae)and the morphogenesis during cell division (distinctive of theOxytrichidae).  In the past, several hypotheses have been offeredfor the identity of the common ancestor of both families, and inall cases the hypothetical ciliate would have had the featureswhich we have now been able to demonstrate in Psilotrichaacuminata.  Further research into the natural history and celldivision processes of this ciliate will help to illuminate theevolutionary history of the hypotrichs.  The full re-description ofPsilotricha acuminata is currently in press with the Journal ofEukaryotic Microbiology.Braving the autumn monsoon season, most of the members ofthe Programme arrived to report research findings to date andto discuss the questions to be tackled in the second phase ofresearch.  The Programme manager emphasized in the buildupto the meeting the importance to NERC of the application ofresearch to the user community.  A panel of users was presentand reflected to the meeting on the relevance of the SoilBiodiversity Programme to their needs.  Prof John Lawton attendedin his triple role as Programme author, PI and NERC ChiefExecutive.  He gave a challenging summary of the meeting whichgenerated a lively discussion.Some of the PDRAs and PhD students who attended felt thatthe format, with over 80 people in the meeting room, held in theluxury of the Scarman House conference centre, inhibited theirfull participation.Generally, apart from the cost of attendance, the meeting was asuccess and set  the scene well for Steering Committee to draftthe objectives for the second phase of research.The Committee decided to create a service contract for theprovision of the 13CO2  pulse and set five main categories underwhich awards would be invited (see front page article). Richard ScottWarwick University meeting ofaward holders November 2000A microbial missing-link found atSourhopeRestrictions affecting access to farmland have meant thatresearchers have not been able to access Sourhope since theFoot & Mouth outbreak began in February.A  case at Hownam near Jedburgh has brought Sourhopeperilously close to the outbreak and into an area with tighterrestrictions.  For this reason special arrangements have beenmade for samples to be provided by MLURI site staff, under thedirection of the PIs.A detailed workplan has been produced by the Site managershowing the dates set aside for the samples for each project.(Link to 2001 F&M workplan is on the News page of the SoilBiodiversity web site  www.nmw.ac.uk/soilbio).At the time of writing the disease appears to be declining andhopefully the access restrictions will be lifted later in the year.Meantime teams must plan to work with the assistance ofSourhope staff who will strive to cope   with the extra demands.Foot and MouthRichard ScottFigure 1:  The cilliated protozoonPsilotricha acuminata (approx. 70µmlong).  Arrows to some of  the cirri.Figure 2:  Specimen undergoingbipartition showing two mouths (M),one for each daughter cell.Genoveva F. Esteban, CEH-WindermereWebsite: http://www.nmw.ac.uk/soilbioDATES FOR THE DIARYPhase one of the Ecotron experiment investigated the effects ofmanipulated soil faunal diversity on ecosystem functioning.  Wereported the arduous task of setting up this experiment in issue5 of this newsletter; here we provide an update on what hashappened since.   The first phase ran for nine months until earlyNovember 2000.  This was followed by a busy interim periodthat, among other activities, included a 13C  pulse chaseexperiment.  The Ecotron study tests the hypothesis that morediverse soil communities retain more carbon, as well as providinga mechanistic understanding of how they do it.  Phase two of theexperiment started after the model communities were N-perturbedin mid-December.The initial nine months went to plan.  The Ecotron Team and the19 collaborators are currently analysing data  amassed in phaseone.  We undertook a 14C study to see if communities of differentsoil biota diversities metabolise C of different ages. This workwas done with the NERC Radiocarbon Laboratory at East Kilbride.The 14C samples are currently being analysed at the NSFAccelerator Mass Spectrometry (AMS) facility in Arizona, USA.Between the two experimental phases Nick Ostle and Phil Inesonbrought SID to the Ecotron.  The chambers were pulsed with13CO2 in early November; little did we realise what we hadcommitted ourselves to.  On top of massive amounts of 13Csampling we frantically collected both final harvest data for PhaseOne as well as the baseline data for Phase Two.  Even now weEcotron scientists shudder as we think back to those long bleakdays in November.  The pulse-labelled samples are being analysedat Merlewood by the 15N-SIF team as we write this report.Ecotron – the story continues...That team, the Ecotron team and associated collaborators willmass balance the work and determine trophic relationships.  Amodelling approach, in collaboration with Bill Hunt of the NREL,will aid interpretation of the data, as well as developing andtesting specific hypotheses only feasible with a model.Phase Two of the Ecotron experiment is a nine-month perturbationstudy.  The resistance and resilience of our establishedcommunities comprising the three biota treatments (micro-fauna,micro- and meso-fauna, and micro-, meso- and macro-fauna) arebeing followed subsequent to N fertilisation. Just prior tofertilisation, each of the 15 Ecotron communities were dividedinto discrete halves with a stainless steel sheet.NH4NO3 fertiliser was applied (quantityequivalent to 240 kg N ha-1as atSourhope) to one half of each communityacross two days.  The unperturbed halffunctions as the control.  The Ecotron SoilBiodiversity experiment is scheduled forfinal harvest at the start of August 2001.That is when those 16 tonnes of soil weso laboriously transferred from Sourhope to Silwood will bethrown out of the window into an awaiting skip!Steering Committee meeting26/27th June 2001   -   York UniversityBritish Soil Science Society3-5 September 2001   -   Durham University(meeting opportunity for PI’s - old and new)Programme Meeting28-30 January 2002   -   Stirling UniversityGeorge Tordoff & Till EggersImperial College, LondonProgramme ManagerMr Richard ScottSoil Biodiversity ProgrammeCentre for Ecology & HydrologyMerlewood Research StationGrange-over-SandsCumbria  LA11 6JU,  UK.Tel: 015395 36041 (direct line)32264 (switchboard)Fax: 015395 35343 (direct line)E-mail: soilbio@ceh.ac.ukEditor(to whom copy should be sent)Miss Rebecca Pinder

A microbial missing-link found at Sourhope

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A microbial missing-link found at Sourhope

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