Eucalyptus camaldulensis

River regulation has led to a decline in the condition of Australia’s dominant riverine tree species, Eucalyptus camaldulensis Dehnh., in the Murray-Darling Basin.  A quantitative method of assessing the condition of these important riparian forests is required for effective monitoring and management.  A range of stand structural, morphological and physiological variables was measured in stands of contrasting condition along the Murray River in southeastern Australia.  Percentage live basal area, plant area index and crown vigour were found to be reliable, objective indicators of stand condition.  Little difference was detected in the physiological performance of trees in terms of water potential and chlorophyll fluorescence among stands of good and poor condition.

The nomenclature of Eucalyptus camaldulensis Dehnh. (Myrtaceae) has been muchdiscussed since modern studies suggested that Dehnhardt, the author of the species, employed this name for a plant different from that indicated today with this named. A recent work carried out by a multidisciplinary approach based on examination of illustrations and herbaria specimens as well as on consultation of documents in historical archives, showed that Dehnhardt’s original description applies to the taxon currently indicated as E. camaldulensis subsp. camaldulensis. In order to support this previous conclusion, a DNA barcoding analysis was carried on both historical specimens and cultivated and wild material of E. camaldulensis. Results confirmed that there is no substantial taxonomical difference between the plant on which Dehnhardt established E. camaldulensis and the plants now indicated by this name.

Acacia mangium Willd., Eucalyptus spp., Tectona grandis L.f. (teak), Hevea brasiliensis (Willd. ex Adr. Juss.) Müll. Arg. (rubber), Paraserianthes falcataria (L.) I.C.Nielsen, and Gmelina arborea Roxb. (yemane) are the main tropical hardwood plantation species in South-east Asia. The occurrence of heart rot in acacias has received widespread attention but root rot is the most damaging disease of acacia plantations. Eucalypts face a different disease threat where outbreaks of leaf and shoot blights are most destructive. Teak, on the other hand, faces few disease threats although it has many insect pests. Since the 1980s, rubber has gained popularity as a source of timber (rubberwood or heveawood) and timber clones have recently been developed. The pathology of rubber is well understood and documented but the disease susceptibility of the new timber clones is currently unknown. In P. falcataria plantations gall rust appears to be an emerging threat. Yemane plantations in some parts of...

Forest dieback is a worldwide problem that is likely to increase with climate change and increasing human demands for resources.  Eucalyptus camaldulensis forests are an acute example of forest dieback, with 70% of the Victorian Murray River floodplain in some state of dieback.  If we are to halt dieback in these floodplain forests, we need to understand what makes stands susceptible to dieback.  Forest diebacks are often related to stand structure, with dieback more severe in senescent or high-density stands.  We determined whether certain stand structures make these forests more susceptible to dieback.  We undertook an extensive survey of 176 stands across 100 000 ha of forest, covering the range of stand condition on this floodplain.  Large and small trees (20, 40, 80 and 120 cm diameter) showed a similar reduction in the probability of being alive with decreasing stand condition.  A slight improvement in stand condition was found at higher densities and basal areas, which may reflect the higher productivity or younger age of these stands.  Stand condition was moderately, positively correlated with longitude, with stand condition being higher in the east of the Murray River floodplain where flooding frequencies are currently higher.  This suggests that dieback of these floodplain forests would be more effectively mitigated by increased water availability through flooding than by altering stand structure.

Water is the main limiting factor for the development of agricultural species and forest species. In Chile more than ¾ of the land surface corresponds to arid and semiarid areas. Several studies have shown that species of the genus Eucalyptus, have a wide potential in the tolerance to limited rainfall. For this reason, we evaluate the effect of water availability in some responses of three species of Eucalyptus: Eucalyptus globulus, Eucalyptus camaldulensis and Eucalyptus cladocalyx. The plants were subjected to three levels of water availability, defined as: no stress, moderate stress and severe stress. The plants were kept under semi-controlled environments and responses were evaluated during two cycles of drying at the end of each cycle, plants were rehydrated for one week. The results indicate that E. camaldulensis had higher physiological plasticity with respect to the values of stem water potential, stomatal conductance, photosynthesis (with E. cladocalyx) and chlorophyll fluo...

1. Regulation of rivers for human demands has led to extensive forest dieback on many floodplains.  If these important ecosystems are to be maintained under future drier climates, we need accurate tools for predicting forest dieback.  In the absence of spatially explicit flooding histories for many floodplains, changes in groundwater conditions may be a good indicator of water availability and, therefore, an important environmental indicator.
2. Eucalyptus camaldulensis forests of Australia are an acute example of forest dieback, with 70% of the Victorian Murray River floodplain dying back.  We quantified the relationship between forest dieback and ground water across this extensive floodplain (ca 100 000 ha of forest over 1500 km of river length).
3. A combination of extensive ground surveys, remotely sensed data and modelling methods was used to predict forest dieback at the time of the survey and in the past.  This approach provides a valuable tool for accurately monitoring forest condition over large spatial scales.  Forest dieback was estimated to have increased from 45% to 70% of the floodplain between 1990 and 2006.
4. Accurate groundwater data (depth and salinity) over a 20-year period were obtained for 289 bores and summarised using non-linear regression.  Groundwater depth and salinity were strong predictors of stand condition.  This suggests that changes in groundwater conditions could be used to signal areas vulnerable to forest dieback and prioritize the limited water available for managed flooding.
5. In the upper Murray, where ground water is predominantly fresh (< 15 mS cm-2), dieback increased with increasing groundwater depth.  In contrast, the condition of stands in the lower Murray improved with increases in groundwater depth due its high salinity (> 30 mS cm-2).  These regional differences in response of the same tree species to groundwater conditions show that our understanding of the drivers of forest dieback is best achieved at spatial and temporal scales representative of the problem.