18. BRYOPHYTE AND LICHEN ECOLOGY AT SWANSON. - T.C. Chambers. History of the Swanson Area: This is fully discussed in an article by C.B. Trevarthen in this volume. To save unnecessary repetition readers are referred to his maps. Ecological Nomenclature; R.G. Robbins was the first investigator in N.Z. to employ quantitative as well as qualitative methods in the study of our Bryophyte communities. In Europe and U.S.A. bryophytes and lichens have been included in many investigations on higher plant comm• unities but they have been seriously neglected in N.Z. Various terms have been used by overseas investigators of bryophyte communities, e.g. 'societies', 'clans', 'colonies', 'families', 'associations', 1assoc- iules' etc. Professor Lippmaa (1934-35) introduced a new approach— the unistratal association concept in which the layers (synusiae) are regarded as separate associations. At the Amsterdam Botanical Cong• ress Du Rietz and Gams proposed to name these "one-layered associations" - Unions - and Lippmaa accepted this. The term Union admirably fits the bryophyte component of a plant community. Sirgo (Estonia) first used this term and it has since been more extensively used by Cain and his associated in U.S.A. and by Robbins and Butler* in N.Z. In the present investigation a Union has been looked upon as a unistratal community dominated by one or more species having high cover and high frequency and generally being of similar or related life form. Methods; The size of the quadrat used in the analyses was 0.1 sq. metres, which is the most usual size in bryo-ecological investigations. An oblong quadrat was used 20 cms. X 50 cms., which Robbins found was slightly better than the square for some of his work at Woodhill. AS the bryophyte community at Swanson is fairly homogeneous, due largely to the vegetative reproduction of the moss plants, it is likely that the oblong quadrat would get a better sample. Probably, any shape would be efficient providing sufficient quadrats were studied. In the field work a species list for the quadrat and the coverage classes were noted as follows: Class X Species covering less than 1% of quadrat. If 1 ti ti 1 to 5% " It 2 tt ti 5 to 25% " II 3 ti H 25 to 50% " II 4 ti ti 50 to 75$ " II 5 it it 75 to100% " AS the quadrats were small accurate estimates of coverage were possible. Prom the species list for each quadrat, besides noting coverage, frequency was also calculated. The bryophytes in the first two phanerogamic communities discussed were investigated from both qualitative and quantitative aspects. The other communities mentioned have only been considered qualitatively. 1. Leptospermum Associes on eastern side of Stream: The average height of the scrub is about 18 feet and is never less than 10 feet, Leptospermum scoparium is dominant with fewer plants of L. ericoides. The most striking feature of this scrub is the almost complete terres• trial carpet of bryophytes and lichens. A series of quadrats was made in this area and the results analysed.*" Dicranoloma billardieri is the dominant moss and from both statistical results and field observations this forms a Dicranoloma billardieri Union—the major terrestrial bryo• phyte association in the area. Very often the Dicranoloma is assoc• iated with lichens of the genus Cladonia, particularly with 0. floerk- iana and this forms the Dicranoloma billardieri - Cladonia Union. In * N.J. Butler (Wellington) interpreted the Union as "a homogeneous unistratal community with a special habitat preference and dominated by one or more species of the same life form." * See Table I. 19. the small hollow on the northern side of the hut, milk moss (Leucobryum candidum) plays an important part in the bryophyte community, forming a Dicranoloma billardieri - Leucobryum Union. The terrestrial mosses here do not form such a complete carpet as in the previously mentioned Unions. In Great Britain a closely related species, L. glaucum, is an indicator of acid conditions. It is possible that L. candidum in N.Z. grows in a similar habitat. If this is true it might partly account for the poorer bryophyte cover in this area. Another factor which must be taken into consideration is that a number of dicot, shrubs have become established and the leaf fall from these appears to retard bryophyte growth. In the Dicranoloma - Cladonia Union the following species are locally-dominant in small patches and thus form facies of the Union: Ptychomnion aciculare, Thuidium furfurosum, Hypnum cupressiforme Leucobryum >'and:,;:11 m, Cladonia (species b).~ Ptychomnion aciculare is more abundant in the tea-tree near the stream than around the hut. It seems 'unlikely that this is caused by moisture conditions, as in other parts of the Waitakere Ranges this moss is often abundant in ridge veg• etation and probably in these parts forms a true Ptychomnion aciculare Union. There seems to be little doubt that the terrestrial bryophytes function as a seed bed for regeneration of forest trees. The sponge• like nature of the moss carpet makes it a great potential water storage organ of the forest. 'This is, no doubt, a big factor in assisting the establishment of these seedlings which later in the succession of the forest will dominate the area. The following species are common in the Dicranoloma - Cladonia Union: 1• Agathis australis 9. Knightia excelsa. 2. Dacrydium cupressinum 10. Olearia 1 furfuracea. 3. Phyllocladus trichomanoides. 11. 0. cunninghamii. 4. Podoparous_totara. 1 2. Pomaderris _e i 5. Meiicytibiss ramiflorus. 13• No^hopar^x aro^r•e um. 6. Gen 3. op torn a ligustrifolium. 14. Pseudopanax crassifolium. 7• Suttonia salicina. 1 5. Coprosma see,, 8. Suttonia australis. Besides those p .ants, ferns are quite numerous scattered^ partic- ularly BJLej3jraum B. fraseri. Gleichenia circinata, G_, cunnjng- hamii, Paesia 0 tendo is also The brans it ion from this scrub to the grassy area around the hut is interesting (see transect),* . The Dicranoloma gradually gives way to Hypnum cupressiforme and Thuidium furfurosum which in the less shaded par' gives way to Campylopus int. flexus which in turn gives way to gri f i ! I Campylopus- Campylopus introflexus Dicranoloma* Dicran• grass Hypnum- Thuidium. oloma . Teatree Open clearing scrub Dicranoloma 10 high. Belt transect showing billardieri. transition from Hypnum cupressiforme. Leptospermum scrub to Thuidium furfurosum. grassy clearing in front Campylopus introflexus. of hut. Grasses. 3are ground. 20. 2. leptospermum associes on trio ridge at the southern end cf the property. In contrast wi tia that around tae hut this veget• ation almost completely lacks a bryophyte flora. The Leptospermum can:py is very open. There is a very dense herbaceous layer made up mainly of Schoenus tendo, Gleichenia cunninghamii and G. circinata with scattered clumps of Gahnia xanthocarpa and Astelia trinervia. Beneath this few bryophytes can survive and probably the regeneration of phanerogams is retarded. The moss Sematophyllum amoenum is occasional on dead twigs, bases :f trunks and on the ground. a few small plants cf Dicranoloma are also present mainly at tae edges of tracks. a comparison of the bryophytes in the tea-tree around the hut with those on the ridge boars out the following statement by P.W. Richards : "Owing te their small size and restricted growth mosses are always at a great disadvantage in competition with vascular plants and it is roughly true to say that any factor which checks growth of herbaceous plants favours moss vegetation." It also bears cut another of his statements: "That such small and comparatively slow growing plants should te able te produce important changes in their habitats is mainly due to the fact that they are social organ• isms and only those species with well-marked social habit have per• ceptible reactions." . 3. Leptospermum-Kauri associes on the northern end cf the ridge : In complete contrast with Leptospermum at the southern end of the ridge this area has a bryophyte community in some respects very sim• ilar to that found around the hut. It possesses an almost complete carpet of bryophytes and lichens right to the bases of the tree trunks. The kauris are at the advanced ricker stage and the Leptospermum is gradually being eliminated. Phyllocladus, Olearia and Knightia are all abundant. Together with these there is a large well-established population cf the alien Hakea. Schoenus tendo, while fairly abun• dant, is not successful in crowding cut tae bryophytes as on the southern end of the ridge. The main terrestrial bryophyte community is the Dicranoloma billardieri Union. In places large cushions of Dicranoloma over 1 ft. in depth possibly mark the sits of old burnt or fallen logs and stumps but there are no traces cf rotten wood beneath the cush• ions to prove this point. In several localised patches there are large white areas where Cladonia floerkiana has become the sole dom• inant and in other areas it forms a Dicraneloma-Claicnia Union like that in the Leptospermum around the nut. (see Table II). The litter on the forest floor is mainly Kauri leaves and twigs but under low growing shrubs such as Olearia furfuracea there is more slow decaying leaf litter ana no bryophytes or lichens at all. While the extra shade may have some influence, the presence of slew decaying leaves and possibly their toxic effect as they decomposed, all helped to eliminate the bryophytes although the list point needs further investigation. There are numerous seedlings growing in the Pi crane Jorna• Cladonia Union. These include Agathis australis, Phyllocladus trichomanoides, Leucopogon fascicularis, Olearia cunninghamii, Senecio kirkii, Knightia excelsa anei Hakea acicularis. The average depth of the bryophyte carpet is. six inches - on the average 3 inches deeper than that around the hut.