by
L.A.J. Thomson
Tree Seed Centre, Division of Forest Research, CSIRO
P.O. Box 4008, Canberra, ACT 2600 Australia
and
M.L. Merwin
International Tree Crops Institute
P.O. Box 888, Winters, California, U.S.A.
ABSTRACT
Seed was collected from native stands of Eucalyptus camaldulensis Dehnh. (river red gum) in western Victoria, Australia. Collecting locations included the Wimmera River, Outlet Creek, Yarriambiack Creek, Avon River, Richardson River and the southwest Wimmera Lakes. The collection was undertaken to intensively sample E. camaldulensis provenances in this region which includes Lake Albacutya, a seed source that has exhibited superior growth over a range of sites in Mediterranean climate zones. A total of 252 individual trees were sampled in 21 provenances, 12 widely separated trees per provenance, distributed from the headwaters to the terminal lakes of each river system.
This seed will be available from the CSIRO Tree Seed Centre for field trials to investigate genetic variation within E. camaldulensis, and to identify individuals and provenances capable of fast growth and tolerant of various stresses (drought, waterlogging, salinity, low temperatures). The CSIRO Tree Seed Centre and the U.S. Forest Service (through Dr. F.T. Ledig) will coordinate research results of trials undertaken at the provenance and individual tree levels, respectively.
INTRODUCTION
Eucalyptus camaldulensis Dehnh. (river red gum) is one of the most commercially important eucalypt species outside Australia. It is also a highly variable species, e.g. the growth rate and stem form of individual trees vary considerably both within and between provenances, or localities of seed origin (Jacobs, 1981).
In Mediterranean climate zones, the Lake Albacutya (Victoria) provenance has exhibited superior growth on a wide range of sites compared to other temperate sources of E. camaldulensis (Lacaze, 1970, 1978; Karschon, 1974; Ledig, 1983). However, with the exception of some lakes near Lake Albacutya (i.e. Lake Coorong and Lake Agnes) and some sites along the Murray River, few other Victorian populations of river red gum have been evaluated in provenance trials (Grunwald and Karschon, 1977; El-Lakany, 1983). Early research results suggest that there may be only minor differences in performance of red gum from different lakes in northwestern Victoria (L. Thomson, unpublished data).
Prior to developing strategies for the improvement of traits of commercial forestry importance in temperate zone E. camaldulensis, it is desirable to determine the pattern of genetic variation in this species in western Victoria, especially in the Lake Albacutya region.
This report describes seed collections of E. camaldulensis undertaken in western Victoria, from the headwaters to the terminal lakes of the Wimmera River/Outlet Creek, Yarriambiack Creek and Avon/Richardson River systems, and the southwest Wimmera Lakes. The collections were undertaken within the framework of the on-going cooperative seed collection programme between CSIRO and FAO's Forestry Department.
The objectives were to collect seed for use in field trials to:
obtain information on the nature of variation (within and between populations) for important forestry characteristics (survival, growth and form);
identify superior individuals/populations capable of fast growth and tolerant of various stresses (e.g. drought, waterlogging, salinity, low temperatures) for use in plantations and breeding programmes; and
identify the most suitable habitats or sites for future seed collections of temperate E. camaldulensis.
In regard to the latter objective, Lake Albacutya and some nearby lakes are located in state or national parks so that their potential for use as commercial seed collection sites is limited.
RESULTS AND DISCUSSION
Seed collections were timed to coincide with the recent maturation of fruits resulting from the spring-summer 1984 flowering, and were undertaken during the period of 14 May to 11 June 1985. Seed was collected from 21 provenances located from the headwaters to the terminal lakes of the Wimmera River/Outlet Creek, Yarriambiack Creek and Avon/Richardson River systems, and the southwest Wimmera Lakes (see Figure 1 and Table 1).
Seed was collected from 252 trees comprising twelve trees per provenance. Within a provenance the basic criteria for selecting seed trees were: (1) presence of mature seed capsules; (2) separation between selected trees of not less than 100 m, and preferably 200–300 m; and (3) a representative sampling of trees occupying different habitats (soils and landscape positions). Capsule-bearing branches and branchlets were cut from each tree with either a pole pruning saw or hand secateurs, and bundled in calico collecting sheets.
Stem diameter at breast height (dbh) and canopy height was measured for each tree. Trees were classified on the basis of age, form and stand density. Soil type, slope, flooding regime and associated vegetation were also recorded and the positions of seed trees mapped. Bulk soil samples were obtained by combining four subsamples per provenance, except at the saline sites of the Lowan Salt Lake Valley where soil samples were taken beneath the canopy of each seed tree. Soil samples were dried, ground and sieved (2 mm mesh) prior to analysis for pH and salinity as electrical conductivity (EC) in a 1:5 soil/water extracts.
Individual seedlots were tested in the laboratory for germination and viability. A total of over 48 kg of E. camaldulensis seed was collected; the average viability of each seedlot ranged from 254 to 759 viable seeds per gram.
Substantial differences in microclimate, soils, flooding regime and other environmental factors were observed within some of the sampled provenances of E. camaldulensis. Natural selection may have operated to produce individuals and populations of E. camaldulensis adapted to survival in particular ecological niches, e.g. margins of fresh or saline lakes, seasonal watercourses and sand dunes. Parental phenotypes exhibited diverse growth forms and morphological characteristics of buds and fruits, both within and between populations.
FIGURE 1
EUCALYPTUS CAMALDULENSIS COLLECTING SITES IN WESTERN VICTORIA
TABLE 1 - SEEDLOT SUMMARY
| Serial No. | CSIRO Seedlot No. | Locality | Lat. (deg. S) | Long. (deg. E) | Elev. (M) | Soil ECa (mS cm-1) | ||
| 1a | 15021 | Wimmera R./Elmhurst | 37 | 13 | 143 | 16 | 310–340 | 0.16 |
| 1b | 15022 | Wimmera R./Glenorchy | 36 | 55 | 142 | 40 | 160–180 | 0.30 |
| 1c | 15023 | Wimmera R./Pimpinio | 36 | 35 | 142 | 00 | 100 | 0.12 |
| 2a | 15024 | L. Hindmarsh SE shore | 36 | 08 | 141 | 48 | 75 | 0.04b |
| 2b | 15025 | L. Hindmarsh NW shore | 35 | 57 | 141 | 52 | 75 | 1.91 |
| 2c | 15026 | Outlet Creek | 35 | 49 | 141 | 56 | 75 | 0.28 |
| 3a | 15027 | L. Albacutya S shore | 35 | 48 | 141 | 58 | 70 | 0.15 |
| 3b | 15028 | L. Albacutya E shore | 35 | 46 | 142 | 00 | 70 | 0.28 |
| 3c | 15029 | L. Albacutya N shore | 35 | 42 | 141 | 57 | 70–75 | 0.04 |
| 4a | 15030 | Wyperfeld N.P. lakes | 35 | 35 | 142 | 03 | 55–60 | 0.13 |
| 4b | 15031 | Lake Agnes | 35 | 26 | 141 | 57 | 45 | 0.08 |
| 4c | 15032 | Wirrengren Plain | 35 | 24 | 141 | 53 | 45 | 0.09 |
| 5a | 15033 | Yarriambiack Ck./ Warracknabeal | 36 | 20 | 142 | 24 | 110 | 0.09 |
| 5b | 15034 | Yarriambiack Ck./Brim | 36 | 04 | 142 | 25 | 95 | 0.33 |
| 5c | 15035 | Lake Coorong | 35 | 44 | 142 | 23 | 75 | 0.10 |
| 6a | 15036 | Lowan Selt Lake Valley (Nonsaline) | 36 | 50 | 141 | 50 | 130–140 | 0.10 |
| 6b | 15037 | Lowan Salt Lake Valley (Saline) | 36 | 50 | 141 | 50 | 130–140 | 0.76c |
| 6c | 15038 | Minimay/Bringalbert | 36 | 47 | 141 | 21 | 130–135 | 0.07 |
| 7a | 15039 | Avon R. headwaters | 36 | 52 | 143 | 11 | 220–310 | 0.21 |
| 7b | 15040 | Avon R./Richardson R. | 36 | 33 | 142 | 55 | 120 | 1.51 |
| 7c | 15041 | Lake Buloke | 36 | 17 | 142 | 58 | 100 | 1.53 |
| a Electrical conductivity in 1:5 soil water extract | ||||||||
| b For subpopulation on Wimmera River at Jeparit. EC - 1.20 mS cm-1 | ||||||||
| c Average of soil samples at 12 individual trees (range 0.09–1.86 mS cm-1) | ||||||||
Serial numbers are also indicated in figure 1.
E. camaldulensis relies on seasonal flooding and/or a high water-table for its survival in areas of low rainfall. However, there may be differences in selection pressure for drought tolerance between individuals and populations due to differences in flooding regimes, soil type and climate. Taking into account these environmental factors it is possible that individuals within the following provenances may produce more drought tolerant progeny: Wyperfeld National Park Lakes (4A), Lake Agnes (4B), Wirrengren Plain (4C) and Yarriambiack Creek (5A,B).
It appeared that trees in several provenances were subject to a high selection pressure for salinity tolerance, i.e. those provenances where soil EC is high (EC> 0.4 mS cm-1): Wimmera River/Jeparit (2A), NW Lake Hindmarsh (2B), Lowan Salt Lake Valley (6N), Avon/Richardson Rivers (7B) and Lake Buloke (7C).
Trees in the two provenances at relatively higher elevations, Wimmera River/Elmhurst (1A) and Avon River headwaters (7A), are probably subject to the greatest selection pressure for frost tolerance. Nevertheless, severe winter frosts (e.g. 1983–85) may occur in northwestern Victoria and seedling progeny of trees in provenances such as Wyperfield National Park Lakes (4A), Lake Agnes (4B) and Wirregren Plain (4C) may also exhibit a high level of cold or frost tolerance.
There was great variation both between and within collection sites in the size of seed crops on different trees. From discussions with local apiarists and foresters it would appear that heavy seed crops are produced on a biennial basis. Based on viability measurements of all 252 seedlots, there was an apparent correlation between seed viability per unit mass of seed and chaff and the visually-assessed density of the red gum stand (Figure 2).
FIGURE 2
Average viability of seed and chaff collected from 252 E. camaldulensis trees classified according to stand density
The causal basis of this relationship cannot be deduced as many factors affect seed viability. However, it is suggested that seed collections may be most profitably carried out in denser stands of E. camaldulensis for two reasons. Firstly a greater quantity of viable seed may be collected per unit of time spent collecting. Secondly, the probability of outcrossing is greater in denser stands and hence a lower proportion of seed is likely to be selfed. (Due to the nature of regeneration in riverine E. camaldulensis, neighbouring trees are less likely to be closely related in this species than in other Eucalyptus spp., e.g. E. obliqua, where marked “neighbourhood” effects have been observed (Brown et al., 1975). Selfing may have considerable deleterious consequences in Eucalyptus (Eldridge and Griffin, 1983)).
Seed from these collections will be available from the CSIRO Tree Seed Centre for investigations of genetic variation within E. camaldulensis, and to identify provenances and individuals capable of fast growth and tolerance of drought, salinity and/or frost. The Tree Seed Centre will coordinate international trials of provenances of E. camaldulensis from Western Victoria. Dr. F.T. Ledig of the Institute of Forest Genetics, U.S. Forest Service, plans to establish progeny trials at five sites in California in 1986 or -87.
ACKNOWLEDGEMENTS
Financial support for this seed collection was provided for the Tree Seed Centre through the U.S.D.A. Forest Service (Dr. F.T. Ledig, U.S.F.S., P.S.W., Berkeley, California). The cooperation of the National Parks Service of the Victorian Department of Conservation, Forests and Lands in permitting collections of E. camaldulensis in state and national parks is gratefully acknowledged. The authors wish to thank the following individuals for their practical assistance to the successful completion of seed collections: T. O'Sullivan, “Pine Plains”, Patchewollock; J. McQueen, “Kyllachy”, Natimuk; and Barry Sutton, Victorian Dept. of Conservation, Forests & Lands Nursery, Wail.
REFERENCES
Brown, A.H.D., Matheson, A.C. and Eldridge, K.G. 1975 Estimation of the mating systems of Eucalyptus obliqua L'Herit. using allozyme polymorphisms. Aust. J. Bot. 23:931–949.
Eldridge, K.G. and Griffin, A.R. 1983 Selfing effects in Eucalyptus regnans. Silvae Genetica 32:216–221.
El-Lakany, M.H. 1983 Provenance/site interaction in irrigated plantations of Eucalyptus camaldulensis. Silvicultura (São Paulo) 31:450–451.
Grünwald, C. and Karschon, R. 1977 Further observations on the effect of seed origin on coppice regeneration in Eucalyptus camaldulensis Dehn.. Leaflet No. 61, Divn. of Forestry, Agric. Res. Org., Israel.
Jacobs, M. 1981 Eucalyptus for Planting. 2nd ed.. Forestry Series No. 11, FAO, Rome, 677 pp.
Karschon, R. 1974 The relation of seed origin to growth of Eucalyptus camaldulensis Dehn. in Israel. Israel J. Agric. Res. 23(3–4):159–173.
Lacaze, J.F. 1970 Etude de l'Adaptation Ecologique des Eucalyptus. In: Documents, 4th Sess. Medit. For. Res. Comm.. FAO Jt. Subcomm. Medit. Forestry Problems, Ankara. FO:SCMI/FR 70/2/10. FAO, Rome.
Lacaze, J.F. 1978 Study of ecological adaptation of Eucalyptus: Study of provenances of Eucalyptus camaldulensis. In: Progress and Problems of Genetic Improvement of Tropical Forest Trees. Proc. Joint Workshop IUFRO WPs 52.02.08 & 52.03.01 (Eds. D.G. Nikles, J. Burley and R.D. Barnes). Vol. II, pp. 979–994.
Ledig, F.T. 1983 Eucalypt improvement for California: progress and plans. In: Proceedings of a workshop on Eucalyptus in California, June 14–16, 1983, Sacramento, California. Gen. Tech. Rep. PSW-69, U.S.D.A. Forest Service, Pacific Southwest Forest & Range Experiment Station, pp. 115–120.
1 Manuscript received December 1985.
