Structure and Function of Terrestrial Biotic Communities

An analysis of bedrock and associated soils was conducted at a series of coastal localities in East Antarctica as well as further inland in the Prince Charles Mountains. Protozoans and micrometazoans were extracted from soil samples and an assessment made of their ecological relations with each other and with soil characteristics.Mineral soils, regardless of topographic elevation and proximity to the coast, were characterised by large gravel fractions (fragments of underlying bedrock) and minimal clay fractions, implying that these soils were predominantly the products of physical weathering, with little chemical alteration. Only where humans, dogs or birds contributed organic matter were there elevated concentrations of nitrogen, phosphorus or organic matter.Generally, mineral nitrogen did not seem to have resulted from microbial mineralisation, but at some sites there was evidence that atmospheric nitrate had been concentrated by sublimination of snow. Water-soluble and dilute acid-soluble phosphorous concentrations were surprisingly high for such organically poor soils. There was a sufficiently large labile pool of common macronutrients to sustain the autotrophic activity likely to occur within the bounds of prevailing temperatures and moisture; thus nutrients are not likely to be limiting for these soil communities.There was a limited fauna. Flagellates were rare and ciliates occurred only in the coastal areas sampled, whereas amoebae were found over a greater geographic and elevational span. Micrometazoans such as rotifers, tardigrades and nematodes were more common in coastal soils than in those further inland, but occurred in soils over most of the naturally occurring range of soil moistures, acidities, nutrient levels, electrolyte levels and organic contents. Exceptions were the exclusion of rotifers from alkaline soils with high nutrient levels, and the tendency of nematodes to be absent from soils with low pH. Tardigrades were found at almost all levels of soil characterisitcs.The occurrence of these metazoan phyla under such a range of environments probably resulted from their known capacity to alternate between endurance of inclement conditions in a state of deep dormancy (anhydrobiosis), and taking advantage of ephemeral favourable conditions by temporarily resuming metabolic activity. The conditions measured in soils containing micrometazoans may merely indicate thise conditions these animals can survive while dormant, not those under which active animals can carry out vital processes. In some localities there were positive associations between various taxon-pairs of metazoans and protozoans, whereas at others their occurrences seemed to be random with respect to each other.The fields for this dataset are:siteconductivitybedrock typequartzgarnetpyroxenehomblendebiotiteK-feldsparplagioclaseothercatalogue numbermaterialUSDA texture class% dry weight% volumecolour (munsell)Total N(micro grams g-1)Minimum N (KCl) NH3-N(micro grams g-1)Minimum N (KCl) NH4-N(micro grams g-1)Dilute acid sol. P(micro grams g-1)loss on ignition (%)amoebaeciliatestardigradesnematodesassociationsrotiferssamplesgranitic gneissAmphibolite (B4)Quartz sandstone (J1)Garnet Pegmatite (W3)>19.05mm19.05-11.13mm11.13-9.60mm9.60-5.66mm5.66-4.76mm4.76-4.00mm4.00-2.80mm2.80-2.00mmless than 2.00mm2.00 mm- 212 micro meters212 micro meters- 20 micro meters20 micro meters - 2 micro metersless than 2 micro metersmont.verm.chlor.IlliteKaol.Int. K:Isepiol.int MIint I:CInt M:CSample codepH KCI (1:5)pH H20 (1:5)micro siemens cm-1(1:5)Water- Sol. P(1:5)(micro grams mL-1)Water- Sol. K(1:5)(micro grams mL-1)Water Sol. K(1:5)(micro grams g-1)Ngrand totalvariablescorrelation with elevationcorrelation without elevationRHOPcorrelations of:soil moistureorganic matter (LOI)water soluble PAcid soluble Pexchangeable Kwater soluble K (wt)nitrate Nammonia Nsoil moisture and organic matterSoil moisture and soluble Psoil moisture and acid-soluble Psoil moisture and pH (water)soil moisture and pH (KCl)organic matter and acid-soluble Porganic matter and total Norganic matter and pH (water)organic matter and pH (KCl)soluble P and acid-soluble Psoluble P and total Nsoluble P and pH (water)soluble P and pH (KCl)acid-soluble P and total Nacid-soluble P and pH (water)acid-soluble P and pH (KCl)Total N and pH (water)Total N and pH (KCl)pH (water) and pH (KCl)coastalPCMobservedexpectedX2 (X squared)+/-