The salt content of the soil was found by means of Mohr's titration, and though it fluctuated rather erratically it did show a tendency to be more salt in summer (3.5% on 8/1/53 in air-dried soil) and less salt in winter (only 1.2% on 10/7/52). This agrees with the results of Evans (1953) working on halophytic vegetation at Lake Ellesmere, New Zealand, although his highest values in summer were about 6%. It was found that only the spring tides came over the salt meadow, while the highest springs reached the inland edge of the ecotone.

Soil

The organic content of the soil to a depth of 20 cm was examined, below which there is almost pure sand. From a typical sod 25 sq cm in area and 20 cm deep, all the plants and live roots were separated out. The organic content of the remaining soil was found by drying and incineration. 25.5% dry weight of the soil was organic matter. Vertical distribution of organic matter including plant material was found to be:

The Biome. For the purposes of sampling extraction and counting of organisms, it was found convenient to divide the organisms in this way:

1. Soil Microbiota. Dilution techniques were used, giving a mean result for 26/6/53 of 25,000 moulds and 968,000 bacteria (aerobic heterotrophs) and yeasts per cc of soil. On an area basis these are per square metre 255,000,000 moulds, and 9,880,000,000 bacteria and yeasts.

For protozoa, diatoms and algae, these methods were highly unsatisfactory owing to the very large amount of fine organic matter in this soil. For the protozoa, experiments indicated merely their rarity on the salt meadow, an average result being 2,500 protozoa per sq m.

2. Soil Microfauna. A cylindrical brass sampler was used for taking soil samples, 1 sq cm in area and 10 cm deep. Each sample consisted of 5 such borings. Seasonal samples were taken to a depth of 10 cm because experiments on vertical distribution of the soil microfauna showed that most of the fauna was present in the upper 10 cm of turf.

For extraction of the fauna the funnel technique of Overgaard (1948) was used, but five large funnels were used instead of nine small ones, the shredded soil being placed in wire gauze trays, 7 cm in diameter. The electric light was adjusted to keep the temperature constant at 30° C. After 15 hours in the apparatus, 10 ccs were run off from each funnel, and, after being centrifuged

and heated, stored in Goodey's fixative. To facilitate counting, the supernatant liquid was poured off, and lactophenol + a few drops of lactophenol cotton blue were added, and the tube allowed to stand for at least an hour. It was found that all of the microfauna except for one species of harpacticoid, stained readily by this method, and could then be easily counted.

The efficiency of this time for extraction was tested by running the apparatus as usual for 15 hours, then tapping off 10 ccs from each funnel, and running it for a further 13 ½ hours. It was found to have this efficiency:

Only 1 rotifer was found, so that no conclusions have been drawn about them. Overgaard estimated 90% efficiency for nematodes and rotifers from moss samples.

3. Mesofauna. For full-time arthropod members of the community, bucket-sampling was found to give consistent results. Cylindrical samplers (10 cm in height × ½ sq dm in area), made from galvanised iron, had one end sharpened and toothed into a cutting edge. 1 cm from this edge, a band of thick wire was soldered around the cylinder, so that the effective depth of the sampler was 1 cm. Over the blunt end of the sampler a square of dentist's rubber dam was fastened with a rubber band. To sample: the cylinder, complete with the rubber over the blunt end, was forced into the ground up to the level of the wire. The soil was cut round and then cut off flush with the sharp end of the sampler. A second rubber dam was fastened over the sharp end, and the cylinder carried home with vegetation uppermost. Five such samples were taken each time.

Samples were taken to a depth of 1 cm. Experiments showed that most of the mesofauna occurred in this layer:

This does not, unfortunately, include caterpillars of the moth, Scoparia tetracycla Meyr, which did not occur in the experimental samples but are found commonly on the salt meadow, burrowing to a depth of about 8 cm.

The apparatus for extraction of the mesofauna was a modified version of Salmon's hotplate + funnel method. Instead of the hotplate at 80° C. (Salmon, 1946), an electrically heated waterbath was used. The temperature at the bottom of the tank, whose under surface was in contact with the inverted samples (soil surface uppermost), was raised in 1 ¾ hours to 65° C., and was maintained at this temperature for 15 hours, by which time no more animals came down. The waterbath was a convenient method of subjecting samples from three different areas to the same extraction conditions. The air-gap (Haarlov, 1947) was not allowed for as ants and spiders easily escaped. However, sometimes oligochaetes lay on the sides of the funnel. These were washed through with alcohol, or, if too desiccated, were merely counted and added to the number in the jar. Macfadyen (personal communication) suggests that the use of vertical-sided samplers, without funnels but with the air-gap, overcomes many of these difficulties.

The high temperature was used partly to hasten extraction of the animals and partly because of Salmon's success with high temperature funnels. The last seasonal sampling was just being done when Macfadyen's paper describing his low-temperature funnels appeared (1953). Trials were then made with lower temperatures on the salt meadow mesofauna. It was found that the low temperature, 35° C. for seven days, was certainly very much more efficient in extracting coccids and mites, and probably also for collemboles and dipterous larvae, although these groups are so erratically distributed on the salt meadow that only by taking a large number of samples could this be proved. However, in spite of its shortcomings, the method described here has been used consistently throughout the work in this study so that all the results are comparable, though probably too low.

Some idea of which were the most active animals of the mesofauna was gained by the use of Fichter alcohol pitfall traps (Fichter, 1941). This apparatus was successful throughout the year in the grassy meadow, but was flooded out at times by the tide covering the salt meadow. Therefore, although it does give some information about the active animals of the community, its results cannot be used quantitatively. Sweeping with a special net with one flat side (20 cm in length), and a long handle, was attempted in order to sample flying and jumping animals rarely caught in the bucket samples. However, the weather and tide did not often permit successful sweeping to be carried out, and qualitative but no quantitative information was gained.

Van der Drift (1950) seems to be the only other worker using automatic extraction methods to have studied nematodes and rotifers as well as the arthropod fauna, and has also used trapping techniques. His study also was carried out on the simplest most uniform community available to him, the litter of a beech forest floor. This is strictly speaking only part of the beech forest community, and he did not examine the trees themselves.

4. Macrofauna. Visual observations were made on the birds and mammals. Black-backed gulls, Larus dominicanus Lichtenstein, pied oystercatchers, Haematopus ostralegus finchi Martens, pied stilts, Himantopus himantopus leucocephalus Gould, bar-tailed godwit, Limosa lapponia baueri Naumann, and rarely red-billed gulls, Larus novaehollandiae scopulinus Forster, were occasionally present on the meadow feeding and sheltering behind Leptocarpus and Scirpus nodosus when there was a very strong wind and a high tide. A flock of banded dotterel, Charadrius bicinctus Jardine and Selby winters on the area.

Harrier hawks, Circus approximans gouldi Bonaparte, frequent the area, and up to 20 have been seen roosting there at night. At times flocks of redpolls, Carduelis flammea cabaret (P. L. S. Mueller), and starlings, Sturnus vulgaris Linn., feed in this region. Two larks, Alauda arvensis Linn. had territory in the grassy meadow, and up to a dozen at a time have been seen feeding on the salt meadow.

Rabbits, Oryctolagus caniculus (Linn.), with burrows further inland, used the salt meadow for feeding and the hummocks for defecating. They are, however, not often seen actually on the salt meadow by day, but do frequent it by night Stoats. Mustela erminea Linn., are common in the district, and twice were actually seen capturing rabbits on the area. Hedgehogs, Erinaceus europaeus Linn., occur on the salt meadow and in the grassy meadow.

appear until the true salt meadow is reached and Salicornia has almost disappeared. Cotula appears at 105 m from the water's edge, while Salicornia and Samolus are last seen at 115 m. The salt meadow, in this part, extends from 100 m to 120 m. Cotula prefers the better-drained upper region and also the hummocks. There is an ecotone from approximately 120 m to 140 m in which salt meadow plants give way to grassy meadow plants, and in which Poa caespitosa and Scirpus nodosus occur. In the grassy meadow, no Selliera is seen beyond 140 m, while Cotula and Scirpus are last seen at 150 m. The vegetation of the grassy meadow consists of the grasses Holcus lanatus Linn., Holcus mollis Linn., Anthoxanthum odoratum Linn. and Agrostis sp, with the herbs, Centaurium umbellatum Gilib., Odontites viscosa Linn., Leontodon hispidus Linn., Acaena sanguisorbae Valh., Lagenophora petiolata Hook., Trifolium repens Linn., Helichrysum filicaule Hook., Hydrocotyle novae-zelandiae D. C. Prodr., Hydrocotyle sp., Cerastium sp., Gunnera monoica (Raoul) var. albocarpa (T. Kirk), Gunnera mixta (T. Kirk).

Animals of the Transect. Six sampling stations were chosen. Those at 10 m, 50 m, and 80 m were in the Salicornia zone, the ones at 110 m in the salt meadow, 130 m in the ecotone, and 170 m in the grassy meadow.

Sampling at each of these stations was done on 9/4/53 and 15/11/53 (Fig. 2). On the first occasion, five ½ sq dm samples and two 10 cc samples were taken at each of the stations. The soil microfauna was given the usual extraction treatment, while the mesofauna was given only three hours in the funnels as the apparatus could take samples from only three stations at a time. However, on the second occasion 5 microfaunal samples as well as 5 mesofaunal samples were taken at each station, because the original kite of the microfauna had shown irregularities that would probably be smoothed out by more extensive sampling. Also on this occasion the ground was very wet, and it was felt advisable to leave the mesofaunal samples for 15 hours in the funnels Thus while the actual numbers of animals extracted on the two occasions are not comparable, their distributions along the transect are.

The crab, Helice crassa Dana, runs about on the surface in the Salicornia region and digs winding burrows, averaging 30 cm in depth. Its distribution was examined by quadrating methods. On 2/7/53, the numbers of open crab holes were recorded per square metre at every metre along the transect until no more crab holes were found. The last was found at 93 m inland. It was found that the number of open crab holes per square metre varied inversely with the height above sea-level, while the percentage of Salicornia per square metre bore only a general inverse relationship to the height above sea level.

Caterpillars of the moth, Scoparia tetracycla and larvae of the weevil, Dryopais variabilis Broun, were not taken in the ordinary samples owing to the depth of their burrows. Their occurrence was studied by means of special samples at every 5 metres between 85 m and 135 m. Both caterpillars and weevil larvae occurred right throughout the salt meadow and ecotone, the averages being 45 caterpillars and 14 weevil larvae per sq m. No apparent change in numbers with height above sea level was seen, probably because the slope was too slight within the distance sampled. Occasional caterpillar burrows have been found lower down in the Salicornia zone. The inhabitants seem to be able to tolerate periodic covering by the tide by having a winding silk-lined burrow in which enough air can be enclosed to last until the burrow is uncovered again. The burrow is lined

with thicker silk when the animal pupates. Weevil larvae also are found well down in the Salicornia zone.

The kite diagrams for 9/4/53 and 15/11/53 (Fig. 2) show the area traversed by the transect to be divisible into 5 zones.

1. Lower Salicornia zone, which is much the wettest of all zones, and includes the 10 m and 50 m sampling stations. There is a peak in the population numbers of the Hermanniid mite, and in dolichopodid larvae and crabs. There is also a small peak (composed mostly of adults) in the population of the amphipod, Orchestia chiliensis Milne-Edwards. It is particularly interesting that at the 50 m station both the haplotaxid oligochaete, Pelodrilus bipapillatus Michaelson and nereid polychaetes were present, burrowing in the soil.

2. Upper Salicornia zone, including the 80 m sampling station where Salicornia is greatly admixed with Selliera, Samolus and Scirpus cernuus. The peaks of the coccid, Trionymus sp., and harpacticoid populations occur here. In addition to the mesofauna that was present in the previous zone, there are hymenoptera and Thysanoptera, but field observations show that these are really present right along the transect. The components of the microfauna remain the same. Experiments, with Evans and Guild's (1947) potassium permanganate method of extracting earthworms from the soil, showed that nereids are present here also along with oligochaetes.

3. Salt Meadow. Here are the peaks of the staphylinid, Carpelimus sp., the amphipod, Orchestia chiliensis, and the more terrestrial dipterous larvae. Most nematodes also seem to prefer this zone. Polychaetes are no longer present. Dolichopodid larvae do occur here commonly and psocoptera occasionally, although Table I does not show this.

4. Tussock-ecotone. A uropodinad mite has its peak here. In this region aquatic dolichopodid and other brachycerous larvae are no longer present. The soil microfauna is noticeably diminishing and the mesofauna is increasing. The first appearance of truly terrestrial animals is striking—pselaphid beetles, jassid bugs, ants, isopods and the only record of a pseudoscorpion.

5. Grassy Meadow. Collemboles (in April), oligochaetes, some of the oribatids and other mites, and also rotifers (mostly Rotaria macrura Ehrenberg) reach peaks in their population numbers in this zone. The halophilic staphylinid, Carpelimus sp., and the amphipod, O. chiliensis, are no longer present. There have been two records from the alcohol pitfall trap of Talorchestia tumida

Fig. 3.—Kite diagrams showing the horizontal distribution of the total mesofauna compared with that of the total microfauna on 9/4/53 and 15/11/53.

Chilton, a more terrestrial amphipod. Here the mesofauna is at its maximum and the soil microfauna (apart from the oligochaetes) has decreased considerably.

The most striking thing about this transect is the wide overlap of marine and terrestrial animals. In the lower Salicornia zone there are collemboles, coleoptera, cyclorrhaphous larvae, Hemiptera, lepidopterous larvae, mites, spiders and oligochaetes occurring along with amphipods, polychaetes and crabs, while in the ecotone amphipods, O. chiliensis, are still present with a more completely terrestrial fauna. All the animals must either be able to adapt themselves to or be widely tolerant of the varying conditions of water and salinity.

Kite diagrams (Fig. 3) show the distribution of the total mesofauna and total microfauna. It is clear that the soil microfauna is greatest in the rich organic upper Salicornia and salt meadow regions, and the mesofauna is greatest in the grassy meadow with the tallest vegetation.

Overgaard Nielsen (1949) states that hydrophilous nematodes thrive best in a wet soil, and concerning aerophilous nematodes, “As long as water films are present an increase of the water content will favour the activity of nematodes. However, when the soil becomes permanently waterlogged probably the nutritional conditions are impoverished on account of the reduction of water-air interfaces with a consequent reduction of microbiological activity.” It seems likely, therefore, not only that most of the nematodes will on analysis turn out to be hydrophilous, but also that in this highly organic but waterlogged soil, they may feed largely on decaying organic matter. A number of specimens have been observed with brown gut contents. Overgaard (1948b), working on the fauna of moss, however, maintains that “the current opinion that nematodes feed on decaying organic matter cannot be confirmed.” He also points out (1949) that arthropods, being typically aerophilous animals, should “have their maximum activities at the time and in places where nematodes are inactive (in the transitional period—I would add, or zone—between moist and dry it is of course possible for both groups to maintain their activities).” This seems to support these results—the arthropods having their maximum abundance in the drier grassy meadow, while the soil microfauna and arthropods are both active in the transitional salt meadow zone.

The only similar transect of which I am aware is that of Weis-Fogh (1947-48), but his was only 12 metres long and was not influenced by the tide. He demonstrated that there was a change in species composition of the fauna from constantly moist to temporarily dry regions.

to young animals from November to February, with the highest population, 3,600 per sq m, in mid-January.

Coccids, Trionymus sp. Large coccids occurred in decreasing numbers until late November, when very small ones appeared. The peak period was from December to March, with a maximum of 9,040 per sq m in early February. Very young coccids were present from late November until January, and by the end of the sampling period the population was a mixture of large and half-grown animals.

Mites show a general increase in numbers from the beginning of October until the end of March. Most are present throughout the year, but the active Erythraeid shows clear seasonal variation, having been caught only from mid-October until the end of February. The alcohol pitfall trap results and general field observations bear this out, indicating a maximum in their population in January.

Staphylinids, Carpelimus sp. (Fig. 4). These animals show an interesting seasonal variation, in that there appear to be two breeding periods, one in spring and one in autumn. There are two peaks of larvae, one October-November and the other February-March, the maximum number being 4280 per sq m in early February. The adult population was approximately 2000 per sq m until November, it dropped to approximately 300 per sq m until the end of January and rose to a fairly constant level of approximately 4000 per sq m from February until June, with a peak of 5600 in mid-May. The period in November, December and January, when the numbers of both adults and larvae dropped to such a low level, was in no way peculiar as regards weather conditions, and the numbers

Fig. 4.—Seasonal changes in the population of the staphylinid, Carpelimus sp., in the salt meadow (below) compared with those of Bro. Larsen (1949) for Atheta and Tachinus in a salt marsh in Denmark (above). The solid lines represent adults, and the broken lines larvae.

of other animals did not show a similar drop. This graph was compared with that of Bro. Larsen (1949) for the staphylinids, Atheta and Tachinus, from dried creeks on the Tipperne Peninsula, Denmark. Her work shows a single peak of larvae and a single peak of adults. It seems likely that this was due to a much more rigorous climate than that of New Zealand. Here, the seasonal change in physical factors, particularly temperatures, was within such a small range that two broods would be possible.

Collembola. This population curve was very erratic indeed, possibly for two reasons. When the tide comes over the meadow a large portion of the springtail population floats and when the water retreats a tidemark of springtails is left. Whether or not this tidemark was happened upon when sampling would produce enormous irregularities. Secondly, Dr. Salmon tells me that another factor to complicate the picture is that on warm summer days, springtails swarm, and eggs are laid and hatch within two or three days. Thus sudden fluctuations in the springtail population occur. and sampling should be done every day for a week or more to detect these changes.

Weevils, Dryopais variabilis. These are present in small numbers throughout the year as shown by seasonal and pitfall collections. They seem to live in greater numbers on the tops of the hummocks than on the flat, and also occur in the Salicornia zone. Too few adults were ever caught for their population to show seasonal fluctuations.

Moths, Scoparia tetracycla. Larvae are present in burrows in the soil right throughout the winter. Pupae were not found until November, and adults were emerging in December and January.

Spiders, Micryphantids, though relatively few in number, appear to show a peak period from the beginning of December until the end of April. Lycosids, carrying egg cocoons, have been observed in October, and the pitfall trap in the grassy meadow showed a large population of lycosids with a large proportion of young ones during December and January.

Hymenoptera. The seasonal variations of some of the Hymenoptera was indicated only by the alcohol pitfall trap, which caught the largest numbers in January and February.

It seems that temperature may be the most important physical factor of those measured, which influences breeding in the arthropods. When the graph of the whole arthropod population is compared with that of vegetation temperature (Fig. 5) it is seen that there is a general temperature increase from the beginning of October until the end of April, with a peak period from mid-November until late March. The population curve has an overall increase from early October to the end of March, with a peak period from early January until early March. There are no great extremes of temperature, and no great extremes in population numbers.

It is realised, however, that for any real knowledge of population dynamics insects must be bred in the laboratory so that the lengths of the various stages of the life cycle can be correctly determined, and that each species must be thoroughly examined in each stage of its life cycle, as Borutzky (1939, a and b) has done with Chironomus plumosus, Tanypus, Corethra and oligochaetes in Lake Beloie.

3. The Microfauna. The graph of the total soil fauna (Fig. 5) shows many irregularities, shown also in the separate groups themselves. These may be

In Fig. 6 the solid lines indicate food relationships, actually observed in this community. The broken lines represent assumed relationships based on observations of similar groups in other communities or ones mentioned in the literature. For example, Overgaard (1947) divides nematodes into four dietary groups and Bro. Larsen (1952) found salt-marsh staphylinids eating algae and burrowing in the surface soil. In this study the gut contents of many staphylinids were examined and nothing recognisable was found. Some contained brownish material, and it is assumed that they were eating humus.

∧₁, the producer organisms, is represented in this community by the four salt meadow plants, as well as by autotrophic bacteria, diatoms and algae.

Of the consumer organisms, which are dependent upon the ∧₁ level, there are several trophic levels:

Fig. 6.—Foodweb of the salt meadow community showing trophic levels. The producer organisms are enclosed in boxes, and succeeding trophic levels are enclosed in succeeding concentric circles. Solid lines represent known relationships and broken lines assumed relationships.

∧₂, the animals feeding directly on the plants. There are several groupings within this level as most of the herbivores of this community appear to feed selectively on a particular part of the plant, for instance, rabbits on leaves and redpolls on seeds. On the other hand, some members of the community appear to feed on more than one part of the plants. In their burrows, Scoparia caterpillars have been seen with only leaves of all plants. However, the soil is so dense that roots and even stems and humus must have been eaten in making the burrow, as only a pile of sandy earth is found at the mouth of the burrow. Coccids also probably feed on creeping stems as well as on roots. In this trophic level, animals with complex life histories may change, during their life cycle, the part of the plant on which they feed, and may even change from one trophic level to another (see next trophic level, ∧3). Lepidoptera in their larval stages feed on leaves and probably also on stems and roots, but in their adult stage they feed on the nectar of flowers. In this level, animals that feed on humus mostly live in the thin layer of loose surface soil. On the tops of the hummocks the soil is better drained, and more burrowing and humus feeding animals seem to live there.

∧3, the secondary consumers, are the primary carnivores. Besides the animals normally looked upon as carnivores such as stoats, harrier hawks and other birds, spiders and certain mites, this level includes parasites of herbivorous animals such as rabbit nematodes, springtail nematodes and parasitic hymenopterous larvae. However, where one large carnivore feeds upon numbers of smaller prey, numbers of small parasites generally infest one large host.

As already noted, animals may, during their life cycle, change from one trophic level to another, as do the parasitic Hymenoptera. These have been found in adult form feeding upon flowers. It has only been assumed that their larvae are parasitic. It has been assumed that the possible hosts are coccids and caterpillars. Thus these animals would belong to the ∧3 level as larvae and to the ∧2 level as adults.

A ∧4 level of secondary carnivores and parasites of primary carnivores has been found. The harrier hawk acts as a secondary carnivore when it eats dotterel, and probably as a tertiary carnivore if it eats the skink, Lygosoma smithii Gray, which eats spiders, but the skink has so far been found only on the grassy meadow and so has not been included in this food web.

Parasites of a primary carnivore have been found in the form of the ecto-and endoparasites of the banded dotterel. An interesting problem is found here: the dotterel appears to feed exclusively upon amphipods, while wintering in the inlet. It has a Hymenolepidid cestode parasitic in its intestine in fairly large numbers. If this cestode passes its larval stage in the amphipod, there is another instance of an animal which passes from one trophic level to another during its life history, but both stages this time are parasitic, that is, its larval stage belongs to ∧3 and its adult stage to ∧4.

The dead plants and animals will pass back to form humus so that most of the organic matter goes back into the ecosystem again. This is due to the activity of heterotrophic bacteria, which are present at every level from ∧2 to ∧_{n + 1}.

However, some material from this community will not pass back into the cycle again as it has been removed by such animals as the harrier hawk, rabbit or stoat, which have wide ranges and may put material removed from one such small community back into another. Also, animals which feed in other communities

this pyramid, which has been constructed for the fauna of 1 sq m. However, the largest animals shown on the pyramid, from 3 to 9 mm in length, are all large herbivores or debris eaters, except for the lycosid spiders.

It is also clear that there is a group of small carnivores in each of the three smaller size ranges: certain mites in the 0-1 mm Erythraeid mites and micryphantid spiders in 1-2 mm, and Oncholaimus in 2-3 mm group. Thus it does not seem to be true for this community that carnivores are predominantly at the apex of the pyramid, and herbivores at the base. Each size range seems to have its own large number of herbivores and smaller number of carnivores, although carnivores probably feed on herbivores in adjacent size ranges as well.

“Biomass” or weight of a species population per unit area has been used by authors dealing with animals only. In this paper, the terms “zoomass” and “phytomass” are used because both kingdoms are being considered, and the term “biomass” is reserved for the total weight of living material per unit area in the community.

The separate species zoomasses were determined for the mesofauna by direct weighing of a counted number of animals. The wet weight was obtained by weighing the animals after gently drying their outsides between blotting paper. Most workers give dry weight of animals, but wet weight has here been used because

the weight of the soil microfauna could be calculated only as wet weight. Weights of nematodes were estimated by the Overgaard Nielsen (1949) method. Several nematodes of each group, mounted in lactophenol, were measured for length, using a camera lucida and micrometer slide, and also the diameter of the nematode halfway down the oesophagus. After measurement the volume was calculated and the weight using his estimation of the specific gravity of a nematode = 1. This method was also used for oligochaetes and harpacticoids. Their specific gravity was assumed to be approximately the same as that of nematodes. Rotifers and harpacticoid nauplii were too few for any direct calculations to be done. Their average weights were therefore assumed to be the same as that of Group 2 nematodes. The weight of a bacterium is assumed to be. 000, 000, 001 mg. From average wet weights of one animal of each species or group and the records of numbers per square metre, the species zoomasses were calculated.

In Fig. 7, by means of a three dimensional histogram, the pyramid of numbers, plotted on the horizontal axes, is compared with the zoomasses of the corresponding size groups, plotted on the vertical axis. The date selected was 5/2/53, when the mesofauna reached its maximum. It seems to indicate that somewhat of a

Fig. 7.—Three-dimensional diagram showing the relationship of size group zoomasses to the Pyramid of Numbers on 5/2/53. The horizontal axes show the size groups and the numbers of animals in each—i.e., the Pyramid of Numbers, while the vertical axis shows the zoomasses of the animals in each size group. The animals in the size group are: 0-1 mm, harpacticoids and their nauplii, nematodes, other mites; 1-2 mm, Collembola, Thysanoptera, Hymenoptera, Coccids, Micryphantids, Erythraeid mites, nematodes; 2-3 mm, Staphylinids and their larvae, nematocerous larvae, other Hemiptera, Oncholaimus and other nematodes; 3-4 mm, cyclorrhaphous larvae; 4-5 mm, none; 5-6 mm, weevils, oligochaetes, other brachycerous larvae; 6-7 mm, dolichopodid larvae, lycosids; 7-8 mm, amphipods; 8-9 mm, lepidopterous larvae.

Overgaard concludes from a comparison of these results with others he obtained from his own work and that of Weis-Fogh that “microarthropods (mites and collemboles) constitute a larger weight than nematodes in raw humus and probably most organic soils, while in mineral soil the opposite is found.” However, although the salt meadow soil is highly organic it is peculiar in being peaty, and thus too dense to support a larger weight of microarthropods than nematodes. Thus my results directly oppose his.

Unfortunately van der Drift (1950) gives his results in a diagram from which numbers cannot be deduced readily, and he calculated the species volumes, not zoomasses. Thus his results are not comparable.

Total Biomass.—An approximate total biomass has been worked out for the salt meadow. It is not a complete biomass because no figures have been obtained for the algae, diatoms or fungi. There are indications that the numbers of these are small, and that the error brought about due to neglecting them will be well within the range of approximation already accepted. For reasons already given the figures for bacteria and protozoa could hardly be more approximate.

Therefore, approximate total biomass = 1,712 g per sq m.

Weight of Organic Matter per Square Metre. For an approximate idea of the weight of organic matter in animals, the organic content of amphipods was determined, from the loss of weight on incineration of the air-dried animals. Thus 78.83% dry weight of amphipods is organic matter. It has been assumed that this percentage of organic matter is constant for invertebrates, so that the weight of animal organic matter has been calculated from this.

Live plants and their roots were sorted from the soil, and by incineration, the weight of live plant organic matter was found. The remainder of the soil was incinerated, giving an estimate of dead organic matter + animal organic