Camaldulensis Dehnh Research Articles

Abkhandari (Aquifer management): a green path to the sustainable development of marginal Drylands

Recurrent droughts and occasional floods are the facts of life in drylands. The presence of innumerable societies in deserts is the living proof that even the extremely dry environments are livable; the secret is how to adapt to the situation. Floodwater management, the most important art of sedentarized desert dwellers, is the secret of living with deserts. Floodwater irrigation alone, or in combination with the artificial recharge of groundwater (ARG), has sustained the Persians for millennia. The scientists at the Kowsar Floodwater Spreading and Aquifer Management Research, Training and Extension Station in the Gareh Bygone Plain have been working since January 1983 to revive this ancient art and upgrade it to the level of science. A summary of important findings is provided as follows: Debris cones and coarse alluvial fans are the best places for the ARG as they provide the potential aquifer for groundwater storage. The recharged water may be used for irrigation on the lower lying, fine alluvium; Flood is not a proverbial curse but a blessing in disguise, and the turbid floodwater is the best resource for the sustainable development of drylands; Translocation of fine clay minerals eventually makes the vadose zone impermeable. Planting deep-rooted, drought-resistent trees and shrubs, and introducing sowbugs (Hemilepistus shirazi Schuttz) are reliable methods to increase infiltration rate and the saturated bydraulic conductivity of the ARG systems; The moving sand stabilization is best achieved by spreading turbid floodwater onto them. Establishing of living windbreaks and planting of fodder trees and shrubs turn a sand menace into a verdant pasture; The 10 year average of native forage yield in the ARG systems has been 445 kg·ha−1·year−1 as o:osed to 92 kg·ha−1·year−1 for the control. At 4×4 m2 spacing,Atriplex lentiformis (Torr.) Wats. can annually yield 1500 kg ha−1 of dry matter and su:ort 3 heads of sheep; The stem- and fuel wood yield of 18 year oldEucalyptus camaldulensis Dehnh. in the ARG system have been 4,684 and 781 kg·ha−1·year−1, respectively. The mean annual carbon sequestration of this tree has been 2.975 tons per ha; Up to 80% of the diverted floodwaters reach the unconfined aquifer. As evaporation practically wastes large volumes of water in surface reservoirs, storing water underground is logical in deserts; The high evaporation rate, the large sediment load, the environmental hazards, the undesirable social costs, the long time needed for the different phases of study, and the very large price tag make dam building the mosthydro-illogical choice in deserts where the ARG is practicable; Each 5.5 ha of the irrigated farm provides income for a family of 7.64 member and 0.38 employment o:ortunities for a farm hand. On average, 4-ha of an ARG system provides one full time job for irrigation farmers. The benefit: cost ratio for this project is 22; The number of wells in the area affected by the ARG activities has increased 10-fold to 130 wells, the irrigated area has increased 8-fold to 1,193 ha, and 345 job o:ortunities have been created in 4 villages that surround the Station.

Distribution of Accumulated Aluminum and Changes in Cell Wall Polysaccharides in Eucalyptus camaldulensis and Melaleuca cajuputi under Aluminum Stress

Distribution of aluminum (Al) within plant components and Al-induced changes in cell wall polysaccharides in root tips of Eucalyptus camaldulensis Dehnh. seedlings were compared with those of Melaleuca cajuputi Powell. In E. camaldulensis, 0.5 mM Al (pH 4.2 for 40 d) reduced plant dry weight by 50%, increased callose concentration in the root tips and induced leaf necrosis. In comparison with M. cajuputi, Al concentrations were higher in roots and leaves of E. camaldulensis on both a fresh weight basis and in the cell sap, but were lower in the cell wall. Al increased pectin, hemicellulose and cellulose concentration in the cell walls of E. camaldulensis root tips. Al-induced leaf necrosis and growth reduction in E. camaldulensis is discussed in the context of potentially toxic concentrations of Al in plant tissue and changes in polysaccharide content which could reduce water and nutrient uptake and cell wall extensibility in roots.

Water-use efficiency and carbon isotope discrimination of Acacia ampliceps and Eucalyptus camaldulensis at different soil moisture regimes under semi-arid conditions

Acacia ampliceps Maslin and Eucalyptus camaldulensis Dehnh. were grown for one year in lysimeters at three soil moisture regimes: 100 % (well-watered), 75 % (medium-watered) and 50 % (low-watered) of total plant available water. Biomass yield of both species increased with increase in soil moisture. Water-use efficiency (WUE) of E. camaldulensis decreased and that of A. ampliceps increased markedly with decrease in available soil moisture. A. ampliceps showed 4 − 5 times more biomass yield than E. camaldulensis grown at similar soil moisture. A. ampliceps showed almost 5, 9 and 12 times higher WUE than E. camaldulensis under low-, medium- and well-watered treatments, respectively. Significant negative correlation of δ13C with WUE (r = −0.99) was observed in A. ampliceps. In contrast, δ13C of E. camaldulensis showed a significant positive correlation with WUE (r = 0.82).

Productivity and suitability analysis of social forestry woodlot species in Dhaka Forest Division, Bangladesh

Reforestation efforts in Bangladesh need information on the biophysical performance and social suitability of potential species. We investigated the biophysical and social suitability of three species, Acacia auriculiformis Benth (Leguminosae, Mimosaceae), Acacia mangium Willd., and Eucalyptus camaldulensis Dehnh. (Myrtaceae) in 8-year-old monoculture plantations for reforestation of woodlots in Dhaka Forest Division, Bangladesh. The prevailing site conditions of the study area were suitable for all three species. Seven regression models were tested to find the best-fit model for volume and productivity calculation of each species. A simple linear regression model as a function of height ( h) and diameter at breast height (dbh), i.e. V = b 0 + b 1 (dbh + dbh 2 + dbh 2 × h) was selected to compute volume and productivity for all three species. Survival, average height, productivity, and gross revenue earned from A. mangium were greatest, followed by A. auriculiformis; both were substantially higher than E. camaldulensis. Local people preferred A. auriculiformis most, followed by A. mangium and finally E. camaldulensis. However, the discrepancy between the productivity/revenue projections and local perception index suggests that there should be sufficient attention paid to both the interests and objectives of implementing agencies, as well as the needs and preferences of rural communities in selecting suitable species for future woodlot establishment in the same site. Therefore, the findings of this study serve as a benchmark for more in-depth investigation regarding preferences, and gaining an historical perspective on how a more secure market might affect local people's choice of species.

Acúmulo de nutrientes na parte aérea, na serapilheira acumulada sobre o solo e decomposição de filódios de <i>Acacia mangium</i> Willd.

O acúmulo de N, P, K, Ca e Mg nos tecidos da parte aérea e na serapilheira acumulada sobre o solo, bem como a velocidade de decomposição de filódios e a eficiência de uso de nutrientes (CUB) da Acacia mangium Willd (mangium) foram avaliados num povoamento localizado em Seropédica, RJ. A espécie apresentou elevada eficiência de uso dos nutrientes, acumulando, aos cinco anos, grande quantidade de biomassa em sua parte aérea (135 t.ha-1) e contendo: 544,9 kg.ha-1 de N; 281,7 kg.ha-1 de Ca; 242,9 kg.ha-1 de K; 47 kg.ha-1 de Mg e 35,2 kg.ha-1 de P. Na serapilheira acumulada sobre o solo (12,7 t.ha-1), foram encontradas reservas significativas dos nutrientes (251,0; 5,7; 14,6; 102,7 e 22,7 kg.ha-1 de N, P, K, Ca e Mg respectivamente). A constante de decomposição (k) foi estimada em 0,00165 g.g-1.dia-1 e o tempo de meia vida dos filódios em 421 dias. A acumulação de serapilheira pode ser positiva no sentido de constituir reserva de nutrientes para cultivos em sucessão, mas também pode representar uma desvantagem, por servir como combustível em áreas sujeitas a queimadas.

Photosynthetic gas exchange, growth and biomass allocation of two Eucalyptus and three indigenous tree species of Ethiopia under moisture deficit

The effects of water deficit on growth, biomass allocation and gas exchange of Cordia africana Lam., Croton macrostachyus Del., Eucalyptus camaldulensis Dehnh, Eucalyptus globulus Labill. and Millettia ferruginea (Hochst.) Baker seedlings were studied under glasshouse conditions for 104 days. Plants were subjected to four watering regimes, viz. control (well-watered), mild-, moderate- or severe-water-deficit conditions corresponding to 25, 50, or 75% of the control moisture level, respectively. Well-watered plants produced about 4–6 times higher biomass compared to severely water deficient plants. All species had comparable biomass production under sufficient water or mild water deficit. However, the eucalypts produced more biomass than the deciduous species under severe water deficit. C. africana and C. macrostachyus invested more biomass to root unlike the other species. Increased water supply increased biomass allocation to leaves in M. ferruginea and the eucalypts whereas it increased biomass allocation to roots in C. macrostachyus. Water deficit reduced predawn and midday leaf water potentials in all the studied species with large decline at the midday in the eucalypts. Water deficit had marked effect on leaf relative water content (RWC) in C. macrostachyus and C. africana in which severely stressed plants had greatly reduced RWC than the controls during both predawn and midday. M. ferruginea maintained high predawn and midday RWC under all treatment conditions. Both stomatal conductances and photosynthetic rates declined in response to increasing water stress, however, the reductions followed different patterns for the different species. Water losses from C. macrostachyus and C. africana leaves were about 2–3 times those of E. camaldulensis and E. globulus across all the treatments. Water stress reduced whole plant water use efficiencies (WUE WL) from 5 ± 0.9 to 2 ± 0.6 g dry mass kg −1 water depending on the species. WUE WL of C. africana and C. macrostachyus were lower compared to the other species in all treatments. M. ferruginea showed superior water stress avoidance as evidenced by its high tissue water potential, RWC and photosynthetic rate under severe water deficit.

Seed Source Variation in Growth Performance of Eucalyptus camaldulensis Dehnh. of Australian Origin in India

Abstract Results of a provenance trial of Eucalyptus camaldulensis Dehnh. laid out in 2001 at Seothi (30° N Lat., 76° E Long. and 250 m altitude) Haryana, a semi-arid region of India are reported and discussed. Six seed sources from Australia viz. Laura River, Emu Creek, Degrey River, Wiluna, Kennedy River, Morehead River were evaluated from nursery stage (3 months) to field performance (2 year). Two sources viz. E.tereticornis (Helenvele, Qld) and FRI-4 a local seed source were used as control (check material). Significant differences between the seed sources at nursery stage were observed for collar diameter (P < 0.05) and number of leaves (P < 0.01). At age 2 years, significant differences between the seed sources (P < 0.05) were observed for height and field survival. The two seed sources viz. Emu Creek Petford, QLD and Laura river, QLD ranked first and second for height and survival at this age. Results indicate that genetic differences exist between the sources of E. camaldulensis. None of the traits assessed (viz. height, collar diameter, number of leaves, number of branches and survival) was found to correlate with any of the geographical coordinates of the site (latitude, longitude and altitude). There were fair differences between phenotypic and genotypic coefficient of variability. Heritability values were fairly high for height and clear bole length in comparison to collar diameter, number of branches and survival. The relative performance of these provenances was fairly consistent throughout the period of observation. The two sources viz. Laura river, QLD and Emu Creek Petford, QLD are recommended for potential source for plantation programme under semi-arid conditions.

Influence of FA resin and Linseed oil preservatives on mechanical properties of Heartwood of Eucalyptus camaldulensis Dehnh.

Eucalyptus camaldulensis Dehnh. called as River Red Gum, is a medium to large hardwood found adjacent to most of the inland rivers of mainland Australia. The durability of the wood is low compared to other hardwoods. There has been an increased interest in treatment of hardwoods with preservatives for wood protection and increasing the life of treated wood. Several studies were conducted on use of preservatives for hardwoods. This study was taken up to find out the influence of Resin and Linseed oil preservative treatments on the wood quality in heartwood of Eucalyptus camaldulensis. Wood samples treated with FA resin had higher values for MOE and MOR, which were 17.5 GPa and 124.7 MPa respectively, compared to Linseed oil treated samples. The results indicated that the uptake of Furfuryl Alcohol (FA) resin was 13.0 l m-3 and that of Linseed oil was 9.7 l m-3. From the study it may be inferred that the mechanical properties of heartwood of Red Gum (Eucalyptus camaldulensis) could be enhanced by FA resin treatment for two hours.

Ecohydrology and Environmental Change to Lake Albacutya and Wyperfeld Park in North‐Western Victoria, Australia

AbstractLake Albacutya is a well‐known intermittent lake in north‐western Victoria. The lake is near the termination of the Wimmera River. From time‐to‐time the lake fills and flow passes down Outlet Creek into Wyperfeld National Park. The wetlands associated with the lake have a high biodiversity value and are named in international treaties. This paper examines the hydrologic factors associated with lake filling and flow into Wyperfeld. The lake has filled approximately six times since 1880 and has partially filled on other occasions. Examination of rainfall data from 1875 at Horsham gave no indication of long term rainfall decline, and showed that rainfall at Horsham can be viewed as representative of rainfall in the Wimmera River catchment. However a double‐mass analysis showed that the relationship between the Wimmera River flow and rainfall has varied from 1890 to the present. Examination of data associated with six fillings of Lake Albacutya suggested that filling is a two‐year event requiring at least 550 GL of flow passing Horsham over the two years immediately associated with the flood. A simple model based on rainfall and this threshold reproduced observed characteristics of the data reasonably well. This suggested that the flooding frequency of Lake Albacutya has dropped from about one in 25 years in the natural state to a substantially lower frequency under current river conditions. The results also suggested that because of changes in the Wimmera River the last filling and flood into Wyperfeld in 1976 was far smaller than it would otherwise have been. This is consistent with field mapping of the flood in relation to River Red Gum (Eucalyptus camaldulensis Dehnh.) stands. Analysis of the health of these stands showed major dieback with the severity of this being roughly proportional to the distance from the 1976 flood boundaries. An examination of values associated with the lake and adjoining Wyperfeld National Park suggested that biodiversity and economic values are and will be compromised by the reduction in flooding. In particular, an internationally‐known provenance of Red Gum is at risk, and bird‐breeding opportunities have diminished.

Role of exudation of organic acids and phosphate in aluminum tolerance of four tropical woody species.

Responses of Melaleuca leucadendra (L.) L., Melaleuca cajuputi Powell, Acacia auriculiformis A. Cunn. ex Benth. and Eucalyptus camaldulensis Dehnh. to aluminum (Al) toxicity at low pH are poorly understood. We investigated effects of low pH and exudation of ligands by roots on Al tolerance of these species. Seedlings were grown hydroponically in nutrient solutions at pH 4.2 or 3.5 containing AlCl3 at concentrations ranging from 0 to 4 mM Al. The presence of 4 mM Al at pH 3.5 depressed growth in all species. Growth depression was greatest in E. camaldulensis, least in A. auriculiformis. In the low Al treatment (0.5 mM Al), roots of M. cajuputi tended to have the highest Al concentration among species, whereas in the 4 mM Al treatment, the highest Al concentration was found in roots of E. camaldulensis. Aluminum application enhanced root exudation of citrate in all species, with the enhancement in M. cajuputi, M. leucadendra and A. auriculiformis being similar and much greater than in E. camaldulensis. Exudation of oxalate and phenolic compounds was greater in E. camaldulensis than in the other species. The presence of Al enhanced phosphate exudation in all species, particularly in A. auriculiformis. Acacia auriculiformis was tolerant to low pH, probably because the presence of an unknown substance increased the pH. Application of 0.38 mM Al alleviated the toxicity of the pH 3.5 treatment in E. camaldulensis and M. cajuputi, whereas low pH alleviated Al toxicity in A. auriculiformis. We conclude that exudation of ligands such as citrate and phosphate only partly accounts for interspecific differences in Al tolerance among the tropical woody plants studied, whereas the reciprocal alleviation of Al toxicity and low pH differed considerably among the species.

Clay Translocation in the Artificial Recharge of a Groundwater System in the Southern Zagros Mountains, Iran

The shortage of water in Iran and most countries in the arid and semiarid zones is approaching the critical stage. Because about 60% of the water used in Iran is supplied by underground resources and natural recharge cannot replace the amount of water exploited, artificial recharge of groundwater (ARG) is actively pursued in this country. Desiltation of turbid floodwaters in sedimentation basins is a prerequisite for ARG. It is executed close to the heads of alluvial fans on an extensive area in Iran. Because the sediment removal efficiency of sedimentation basins is not 100%, downward migration of some clay particles, both in sedimentation basins and recharge ponds, causes the gradual impermeability and eventual clogging of the vadose zone and reduces the economic life of the recharge systems. Coarse-grained alluvium beneath 2 sedimentation basins, one in operation for 13 years and the other for 11 years, was sampled down to a depth of 7.5 m. Sampling was repeated in a control area outside and adjacent to the ARG system. X-ray diffraction patterns clearly show the presence of illite, chlorite, kaolinite, smectite, and sepiolite. Single laths and bundles of laths of palygorskite–sepiolite, a well-formed 6-sided and a pseudohexagonal flake of kaolinite, and smectite particles with smooth, wavy edges are clearly seen in the transmission electron micrograph. The order of clay mineral accumulation at a depth of 7.5 m was as follows: sepiolite > palygorskite > chlorite. The relatively high concentration of sepiolite may indicate its neoformation in the rooting zone of river red gum (Eucalyptus camaldulensis Dehnh.).

Tree-root systems and herbaceous species-characteristics under tree species introduced into grazing lands in subhumid Cameroon

The effect of tree species on the characteristics of the herbaceous stratum, during the first five years of a fallow, was evaluated in the North of Cameroon (average annual temperature 28.2 °C, total annual rainfall 1050 mm). Treatments included a natural grazed herbaceous fallow, a natural ungrazed herbaceous fallow and three planted tree fallows (Acacia polyacantha Willd. ssp. campylacantha (Hochst. ex A. Rich.), Senna siamea Lam. and Eucalyptus camaldulensis Dehnh.), which were protected against grazing. Because tree species influenced light interception in different ways, as well as having different root patterns, they had different effects on the herbaceous stratum in terms of species composition and biomass. The grazed herbaceous fallow maintained the greatest species richness. Protection against grazing or the introduction of tree species associated with the absence of grazing induced both a progressive evolution to a particular species composition. The ungrazed herbaceous fallow consisted mainly of Andropogon gayanus Kunth, which provided the greatest biomass (8 t dry matter ha–1 at the end of the fallow period). E. camaldulensis provided little shade and the lowest fine root mass in the top layer allowing the growth of A. gayanus and thus a greater herbaceous biomass (3.5 t DM ha–1) than that found under the other tree species. Under the heavy shade of A. polyacantha, the herbaceous stratum consisted mainly of annual Pennisetum spp. (2.2 t DM ha–1) and showed the greatest N concentration (1.3%), probably due to N2 fixation by the tree species. After the fourth year, despite the relatively open tree canopy, S. siamea, which showed the highest fine root mass, had a strong depressive effect on the herbaceous stratum.

Comparative growth, biomass production, nutrient use and soil amelioration by nitrogen-fixing tree species in semi-arid Senegal

Survival, biomass production, nutrient use and fertility of soil were examined in experimental stands of 10-year-old N-fixing indigenous Acacia nilotica (L.) Del. (eight provenances), A. senegal (L.) Willd. (one provenance), Acacia tortilis (Forsskal) Hayne (six provenances), Acacia raddiana syn A. tortilis (Forssk.) Hayne ssp. raddiana (Savi) Brenan (three provenances) and exotic N-fixing A. holosericea A. Cunn. ex G. Don (one provenance), A. cowleana Tate (one provenance), Acacia aneura F. Muell. ex Benth. (twelve provenances), Prosopis juliflora (Sw.) DC. (one naturalised provenance), Prosopis cineraria (L.) Druce (five provenances) and P. chilensis (Molina) Stuntz (two provenances) growing on a coastal site in semi-arid Senegal. Similar data were obtained for the non-N-fixing fast-growing exotic species Azadirachta indica Adr. Juss. and Eucalyptus camaldulensis Dehnh. of the same age that were growing on adjacent plots. P. juliflora produced more biomass than the other species and showed the greatest potential for use as a multipurpose tree. A. aneura showed the greatest potential for fodder production and despite its small stature, it ranked second for biomass among the N-fixing species. Of the indigenous species, A. nilotica was the most efficient user of non-renewable elements in biomass production. A. raddiana seemed profligate in its consumption of both N and P in wood production. E. camaldulensis was efficient in its use of N in wood but its wood contained large concentrations of P and K. A. aneura, P. juliflora and A. nilotica had the smallest concentrations of P in wood. A. raddiana and A. indica contained large concentrations of K in their wood in contrast to A. aneura and A. nilotica which were the most efficient users of K in wood production. There were few significant differences in fertility in soils beneath the differing tree species. Nevertheless, plots containing P. juliflora and P. cineraria tended to be the most fertile. Soil beneath A. indica was more fertile than soil beneath some N-fixing species. The extent of removal of plant nutrients in biomass suggests that without inputs of nutrient elements, harvest of wood and foliage is unlikely to be sustainable at the measured rate of production for more than two tree rotations of 10 years duration.

Genetic variation in Eucalyptus camaldulensis Dehnh. for growth and stem straightness in a provenance–family trial on saltland in Pakistan

In an Eucalyptus camaldulensis Dehnh. provenance–family trial established on a moderately saline–sodic site in Pakistan, 114 families (from 14 Australian provenances) and six Pakistani seedlots were evaluated for survival, growth and stem form, up to the age of 60 months. Significant differences were found among provenances and families-within-provenances for all parameters. The provenance from De Grey river (WA) performed best, with 18 of the 25 families having very fast growth rates. Overall survival, at 60 months, was 74% (provenance mean range of 89% (Wiluna) to 28% (Vic.)). Overall mean height at age 60 months was 8.7 m (provenance mean range of 10.2 m (De Grey river) to 4.6 m (Vic.)). Overall mean diameter at breast height (DBH) was 6.7 cm with provenance mean range from 9.2 cm (De Grey river) to 3.4 cm (Vic.). Stem straightness (scored qualitatively on a four point scale of 1–4 with four as the straightest stem) for most of the provenances was good to very good with a trial mean value of 3.2. Within-provenance individual tree heritability estimates obtained for height, DBH and stem straightness at age 60 months were 0.14, 0.11 and 0.15, respectively (assuming a coefficient of relationship of 0.3 for open-pollinated families of E. camaldulensis). Covariate analyses showed that variations in soil salinity across the trial site had little influence on comparison between means of provenances or of families-within-provenances. Based on this experiment, we believe that there is good potential to genetically improve growth of E. camaldulensis in breeding programs for saline soils in Pakistan.

Nuclear RFLP variation in Eucalyptus camaldulensis Dehnh. from northern Australia.

Eucalyptus camaldulensis Dehnh. is the most widely planted eucalypt in the tropics. Natural populations are riparian and sampling strategies for breeding programmes have assumed that gene flow among drainage basins is limited. RFLP variation, within and among 31 populations from river systems across northern Australia, was analysed to test this hypothesis. To allow comparisons within and between river systems, trees were sampled from up to three populations per river system. Allele frequencies were correlated with longitude for more than half the 33 RFLP loci surveyed. Genetic identity was greatest between populations in closest geographic proximity, irrespective of river system, suggesting that sampling strategies for breeding programmes should be based on geographic distance rather than river system. The level of genetic variation was similar throughout the geographic range examined (mean H(E) = 0.49). However, there was evidence of a barrier to gene flow between populations in the east and west of the species range. The RFLP data support morphological evidence of hybridisation between E. camaldulensis and E. tereticornis Sm. in several populations in northeast Queensland and the genetic divergence of E. camaldulensis subsp. simulata Brooker and Kleinig.

New genus and two new species of gall midge (Diptera: Cecidomyiidae) damaging buds on Eucalyptus in Australia

AbstractTwo new gall midges whose larvae damage leaf and branch buds of eucalypts in Australia are described and a new genus, Eucalyptodiplosis Kolesik (Cecidomyiidi: Cecidomyiini) is erected to contain them. The infested buds are deformed and do not develop further. Eucalyptodiplosis germinis Kolesik was found on Eucalyptus cosmophylla F. Muell. and Eucalyptus camaldulensis Dehnh. in natural bush vegetation in South Australia. Eucalyptodiplosis mcintyrei Kolesik is a potential pest of Eucalyptus grandis Hill ex Maiden in plantation forests in New South Wales with the potential to cause economically significant damage in young tree plantations. The basic biology of the midges is described and a key to adults of currently known Australian genera of the supertribe Cecidomyiidi is presented.

Effect of NaCl and high pH on seedling growth of 15 Eucalyptus camaldulensis Dehnh. provenances

Eucalyptus camaldulensis Dehnh. is a moderately salt-tolerant Australian tree species widely used in farm forestry, often in salt-affected landscapes. In a glasshouse experiment, E. camaldulensis seedlings from 15 wide-ranging Australian seed sources (provenances), were cultured in sand-filled pots and treated for 57 days with control (no added NaCl in tap water, neutral pH), saline (150 mol m−3 NaCl, stepped high pH (pH 7.6 to 9.5) and combined NaCl and high pH solutions. Significant differences were found among provenances in height and shoot dry weight. Differences in provenance response to treatment were found for dry weight but not for height. Reductions in shoot dry weight due to NaCl and high pH ranged from 42.9% to 82.0% and 4.3% to 51.7% respectively. Provenances from Lake Hindmarsh-SE (Victoria) and Lake Albacutya-N (Victoria) had relatively high tolerance to both stresses whereas those from Lake Albacutya-S (Victoria), Lowan Valley (Victoria), Silverton (New South Wales) and Katherine (Northern Territory) had low tolerance to both stresses. Provenances from De Grey River and Fitzroy River (Western Australia) were most tolerant of high pH. The performance of these provenances in this experiment generally accorded well with that in saline field environments.

Analysis of respiratory metabolism correlates well with the response of Eucalyptus camaldulensis seedlings to NaCl and high pH.

Growth of sand-cultured Eucalyptus camaldulensis Dehnh. (river red gum) seedlings from six wide-ranging provenances was reduced in the presence of 150 mM NaCl, a high pH of 9.5, and combined NaCl and high pH, compared with no applied NaCl and neutral pH. Effects of these stress conditions on respiration rates and substrate carbon conversion efficiencies of rapidly-expanding leaf tissue were measured with calorespirometric techniques. Growth rates were calculated from respiration parameters. Respiration rate, measured as metabolic heat production rate (q), showed no consistent trend with either NaCl or high pH, whereas the rate measured as CO2 production rate (R CO2) was generally lower with both treatments. The ratio of heat lost per mole of CO2 produced [q/(R CO2)] was consistently increased by both stresses. Stress causes a larger fraction of metabolic energy produced by aerobic metabolism to be lost as heat, relative to non-stressed controls. Consequently, a larger fraction of photosynthetic product in stressed seedlings must be metabolized to CO2 per mole of C incorporated into biomass. Our results indicate that 0.42 mol substrate C is converted to CO2 per mole C incorporated into biomass for control plants, compared with 0.96 mol for plants treated with combined NaCl and high pH. Respiratory responses to treatment varied with provenance. Specific growth rates, calculated from repiratory parameters (q and RCO2) of stressed E. camaldulensis seedlings, generally paralleled experimentally-determined reduced growth (dry weight) of these seedlings. Thus, measurements of leaf respiration allow calculation of growth inhibition caused by NaCl and high pH stress. However, we could not discriminate among provenances in this experiment with only one level of NaCl and pH.

River Red Gum ( Eucalyptus camaldulensis Dehnh.) organic matter as a carbon source in the lower Darling River, Australia

The Darling River, in New South Wales, Australia, is a large semi-arid system with a highly variable flow regime, characterised by unpredictable events of flooding and drought. In large lowland rivers like the Darling, lateral (river-floodplain) interactions can greatly influence both physical and biological components of the system. The floodplain and riparian zone of the Darling River is dominated by River Red Gum (RRG), Eucalyptus camaldulensis. The large amount of organic matter they produce accumulates on the floodplain and on benches within the channel, and is subject to alternate periods of flooding and drying as a result of highly variable flows. This paper examines the effect of alternate periods of flooding and drying on the processing of E. camaldulensis organic matter. Results of the 6-month in situ field study, together with results from laboratory experiments comparing dissolved organic carbon (DOC) release from various RRG litter types, suggest that RRG leaves provide the most bio-available source of carbon to the system, while bark may be more important as a habitat for invertebrates and other fauna. Laboratory experiments exploring the effect of drying and re-flooding on litter breakdown and release of DOC suggested that the majority of DOC was released from RRG leaves in the first 24 h of inundation. Also, upon drying and re-flooding of the leaves, a smaller but significant release of DOC occurred. However, an alternative wet/dry cycle did not affect weight loss of the leaf litter. Results of the field and lab experiments suggest that RRG leaves represent an important source of carbon to the Darling River, with inputs being influenced by the highly variable flow regime.

Elastic and osmotic adjustments in rooted cuttings of several clones of Eucalyptus camaldulensis Dehnh. from southeastern Australia after a drought

Summary Eucalyptus camaldulensis Dehnh., considered as a drought tolerant species, was examined in relation to some mechanisms linked to drought tolerance (cell-wall elastic adjustment and osmotic adjustment) and to the intraspecific variation related to those features. Rooted cuttings of five clones obtained from three different provenances from Australia (Gilgandra: 106, 109; Lake Albacutya: 119, 125; Condamine: 105) were gradually submitted to a water limitation regime. Water stress curtailed relative leaf area growth rate, pre-dawn relative water content (RWC) and noon stomatal conductance (gs) in all clones. Shoot water parameters were estimated at the end of the drought period by pressure-volume (P–V) analysis through a repeat pressurization method. The curves obtained were analyzed by Schulte’s P–V Curve Analysis Program. Drought decreased very significantly the osmotic potential at full turgor (χπFT) and at the turgor loss point (χπTLP), with a significant clone effect: 105 had the lowest values (–2.12±0.04 MPa and –2.39±0.05 MPa). Osmotic adjustment (OA) on average was 0.34±0.02 MPa. Drought increased maximum bulk modulus of elasticity (ɛMAX) by 6.60.7 MPa. There were no clonal differences in either OA or elastic adjustment.Water stress increased significantly turgor potential at full turgor (χFT), and differences between control and stress plants show that the OA recorded did not fully account for the positive changes in turgor of stressed plants. Drought decreased shoot turgid mass/dry mass ratio (TM/DM), again with a significant clone effect: 105 had the lowest value (2.66±0.11). Reduced shoot TM/DM combined with increases in ɛMAXduring stress were indicative of cell wall adjustment, reduced turgor-loss volumes and tightening of the cell walls around the protoplasts, suggesting a cell size reduction. No effects were observed on RWC at the turgor loss point. A regression model that considered ɛMAX and χπFT explained best the response patterns of stressed plants. The mechanisms observed in Eucalyptus camaldulensis that delay growth while maintaining turgor and water uptake allow us to consider it as a dehydration postponement species.