Role of plant functional traits in determining vegetation composition of abandoned grazing land in north-eastern Victoria, Australia

Question: In the Northern Hemisphere, species with dispersal limitations are typically absent from secondary forests. In Australia, little is known about dispersal mechanisms and other traits that drive species composition within post-agricultural, secondary forest. We asked whether mode of seed dispersal, nutrient uptake strategy, fire response, and life form in extant vegetation differ according to land-use history. We also asked whether functional traits of Australian species that confer tolerance to grazing and re-colonisation potential differ from those in the Northern Hemisphere. Location: Delatite Peninsula, NE Victoria, Australia. Methods: The vegetation of primary and secondary forests was surveyed using a paired-plot design. Eight traits were measured for all species recorded. ANOSIM tests and Non-metric Multi-dimensional Scaling were used to test differences in the abundance of plant attributes between land-use types. Results: Land-use history had a significant effect on vegetation composition. Specific leaf area (SLA) proved to be the best predictor of response to land-use change. Primary forest species were typically myrmecochorous phanerophytes with low SLA. In the secondary forest, species were typically therophytes with epizoochorous dispersal and high SLA. Conclusions: The attributes of species in secondary forests provide tolerance to grazing suggesting that disturbance caused by past grazing activity determined the composition of these forests. Myrmecochores were rare in secondary forests, suggesting that species had failed to re-colonise due to dispersal limitations. Functional traits that resulted in species loss through disturbance and prevented re-colonisation were different to those in the Northern Hemisphere and were attributable to the sclerophyllous nature of the primary forest

Conversion of native forest to exotic Pinus radiata plantation: Response of understorey plant composition using a plant functional trait approach

This study aimed to determine the response of native plant species to changed growing conditions, especially increased shade, following establishment of exotic Pinus radiata plantation on cleared native eucalypt forest. In the Northern Hemisphere, species tolerant to shading are typically herbaceous perennials, with large seeds, no obvious mechanism of seed dispersal, and spread by clonal means. We investigated whether life form, mode of seed dispersal, leaf area, specific leaf area (SLA), nutrient uptake strategy, seed mass, fire response, plant height, and clonal spread differed between understorey species of pine plantation and native forest. Further, we asked whether plant functional traits that confer tolerance to stress through shading differ from those in other floras. The study was conducted on the Delatite Peninsula in north-eastern Victoria, Australia. Vegetation of adjacent native forest and pine plantation were surveyed using eight 7 m × 7 m plots per site, randomly located within five paired sites. Differences in plant traits between land-use types were tested by Non-metric Multi-dimensional Scaling (NMDS), analysis of similarity (ANOSIM) and paired t-tests. Cluster analysis of the nine plant traits was used to define emergent groups, with differences between land-use types examined by ANOSIM and indicator species analysis. There was a significant change in the composition of understorey vegetation following conversion to pine plantation that included a decline in the richness of native species. NMDS of plant attributes showed a clear separation of native forest from pine plantation with land use strongly correlated in ordination space (r2 = 0.611). Cluster analysis produced seven emergent groups of plant functional traits for 78 identified plant species. Phanerophytes split into two groups (myrmecochorous trees and shrubs; myrmecochorous shrubs), perennial herbs into four groups (upright herbs, myrmecochorous herbs, barochorous herbs, flat rosette herbs) with one group representing therophytes and anemochorous perennials. Perennial herbs with intermediate SLA and clonal spread were tolerant of the shaded conditions in pine plantation while the two groups of phanerophytes and the myrmecochorous herbs were largely excluded. Shared traits of excluded emergent groups included those that provided an over-riding adaptation to mineral nutrient stress, including myrmecochory, low SLA, ectomycorrhizal and ericoid mycorrhizal associations and N2-fixation. These plant traits could not provide tolerance to stress through shading, which is better explained by the open canopied nature of the native forest

Restoration potential of native forests after removal of conifer plantation: A perspective from Australia

This study investigates whether undertaking a rotation of pine plantation on abandoned farmland facilitates the return of native species. Plant functional traits were used as a means of assessing the effects of land-use change on vegetation. We explored the relationships among plant traits, time since harvesting and environmental variables for the vegetation found in Pinus radiata plantations after clear-felling. Vegetation was monitored 1-3. years following harvesting and repeated eight years later. We compared species richness, composition and traits to those in reference native forest and abandoned farmland. There was a significant temporal shift in attribute associations of harvested plantations towards those in native forest and a move away from plant attributes common to the pre-plantation use of abandoned farmland. Cluster analysis produced ten emergent groups of plant functional traits for 144 plant species. After harvesting, attribute associations were typical of therophytes and included high specific leaf area (SLA), small stature, arbuscular or non-mycorrhizal associations and small, wind-dispersed seed. These were predominantly introduced species that were dominant in abandoned farmland. The repeat survey identified an obvious decrease in therophytes and an increase in species with low SLA, ant dispersal, large seed and ectomycorrhizal associations. This was largely due to an increase in native Myrmecochorous shrubs. Similar attributes were also shared by Ericoid heaths but these species failed to recolonise harvested sites. Relationships among plant traits of species and environmental variables changed over time with a greater proportion of the variance in attribute associations explained by prevailing site conditions (e.g. type of ground cover, edaphic properties) with increasing time since harvesting. There were no relationships among plant attribute associations and stem density or basal area of planted overstorey species suggesting that planting of tubestock seedlings of native overstorey species does not effectively promote the development of native vegetation. The persistence of introduced grasses in areas of former plantation, recruitment failure of native species and a ready supply of introduced species from surrounding land uses suggest that additional rehabilitation measures will be required to promote the return of a fuller complement of native species

Do generalisations of global trade-offs in plant design apply to an Australian sclerophyllous flora?

Functional-trait analysis at a global scale has found evidence for evolutionary specialisation of species into those designed to acquire resources rapidly and those designed to conserve resources. The present study aimed to determine whether such a trade-off exists in sclerophyllous vegetation in Australia. We measured 10 traits for 167 plant species. The first axis of a principal components analysis represented a trade-off between resource acquisition and resource conservation, consistent with global trends. Common traits shared by resource-conservative species included low specific leaf area (SLA), resprouting, ant-dispersal, and ericoid mycorrhizal and ectomycorrhizal associations. These attributes were typical of 3 of 13 functional groups produced by cluster analysis (eucalypts, ant-dispersed shrubs, ericoid heaths) that had the lowest SLA, and were almost exclusively native shrubs and trees. Resource-acquisitive species had high SLA, a small stature, annual life cycle, arbuscular mycorrhizal or non-mycorrhizal associations, and small, wind-dispersed seeds. These attributes are similar to those identified for species with a ruderal strategy and were typical of the functional groups representing wind-dispersed composites, AM annuals and non-mycorrhizal annuals that had the highest SLA and were dominated by introduced species. Comparable trait associations have been found in other studies, suggesting that similar processes drive plant design at a global scale. However, there were some patterns specific to the flora studied that were attributable to adaptations to suit the nutrient-poor soils and arid conditions typical of the Australian environment

Deforestation strongly affects soil seed banks in eucalypt forests: Generalisations in functional traits and implications for restoration

We examined the potential role of the soil seed bank in restoration of an open eucalypt forest community following land-use change involving clearing of native eucalypt forest for grazing and subsequent abandonment, and for establishment of Pinus radiata plantation. We used plant functional traits responsive to disturbance and other traits associated with the capacity to re-colonise and form persistent seed banks as a means of assessing the effects of land-use change on soil seed banks. The soil seed bank and corresponding extant vegetation was surveyed within four replicated paired sites of fragmented native forest and abandoned farmland, and native forest and pine plantation. There was a significant difference in the composition of the soil seed bank for both land-use changes. Non-metric Multi-dimensional Scaling of plant attributes showed a clear separation of samples according to land-use type and between seed bank and extant vegetation. Cluster analysis of plant functional traits produced eight emergent groups. Phanerophytes were classified as either Ant-dispersed shrubs and herbs, Ericoid heaths or Eucalypts, perennial herbs were either Vertebrate-dispersed species, Barochorous annuals and herbs or Small-seeded hemicryptophytes and the remaining species were Wind-dispersed species or Small-seeded annuals. Small-seeded annuals dominated the soil seed banks and native phanerophytes with low specific leaf area, resprouting, ant-dispersal, large seed, and ericoid mycorrhizal and ectomycorrhizal associations formed a minor component of the soil seed bank for all land-use types. Sørensen Similarity between the vegetation and soil seed bank was low across all land-use types and was explained by the dominance of annuals in the soil seed bank and perennial species in the extant vegetation. Indicator species analysis revealed an increase in Wind-dispersed species, Barochorous species and Small-seeded annuals in the soil seed bank relative to extant vegetation. Trait associations include a therophyte life form (of predominantly introduced species) with high specific leaf area, small round seed, a seeder fire response, and arbuscular or non-mycorrhizal associations. Underlying axes in trait variation indicate seed banks were dominated by traits associated with the rapid acquisition of resources or the ability to respond rapidly to disturbance that provided for large and persistent stores of introduced ruderal species. In contrast, species excluded from the seed bank shared traits associated with the conservation of resources or ability to withstand environmental stress and were typical of native phanerophytes. These generalisable patterns in plant traits make it unlikely that eucalypt communities can be restored from the native soil seed bank alone

Surfactant protein A (SP-A) binds to phosphatidylserine and competes with annexin V binding on late apoptotic cells

The role of surfactant protein A (SP-A) in the recognition and clearance of apoptotic cells is well established, but to date, it is still not clear which surface molecules of apoptotic cells are involved in the process. Here we present evidence that phosphatidylserine (PS) is a relevant binding molecule for human SP-A. The binding is Ca2+-dependent and is not inhibited by mannose, suggesting that the sugar-binding site of the carbohydrate recognition domain (CRD) of SP-A is not involved. Flow cytometry studies on apoptotic Jurkat cells revealed apparent inhibition of annexin V binding by increasing concentrations of SP-A in late apoptotic but not early apoptotic cells, and this was consistent for Jurkat cells and neutrophils. Supporting these data, confocal microscopy results show a co-localisation of annexin V and SP-A in late apoptotic but not early apoptotic cells. However, we cannot conclude that this inhibition is exclusively due to the binding of SP-A to PS on the cell surface, as annexin V is not wholly specific for PS and SP-A also interacts with other phospholipids that might become exposed on the apoptotic cell surface. <br/