Barbara Bowen

Pollen dispersal is the step in higher plant mating systems over which the parent plant has the least control as it is dependent on the vagaries of weather conditions (anemophily) or animal behaviour (animal pollinator activity). While many families have passive release from the anther the Proteaceae has a diversity of pollen dispersal methods. Flowers from a range of species in the Proteaceae, covering the majority of genera from each of the four main subfamilies, were examined to determine how pollen is dispersed and to gain an overall view of how male function varies within the family. This provides a basis for predicting the degree of the six likely fates of pollen released in this family. Only one group (subfamily Persoonioideae) and four genera in one other subfamily (Proteoideae) dispense pollen directly from the anthers onto a flower visitor. Five genera in the Proteoideae have explosive pollen release, while Symphionema may require vibration to release the pollen. All the remaining Proteoideae genera, the single species of Bellendenoideae, and all genera of the Grevilleoideae (except Sphalmium) have a pollen presenter where pollen is dispersed from the style of the flower. Ancestral Proteaceae were likely to have been insect pollinated and had relatively small flowers. Taxa with explosive pollen release may have evolved early in the family and may have been more abundant early in the fossil record. However, the taxa with pollen presenters became much more abundant throughout the Tertiary when many developed robust gynoecia that can accommodate larger vertebrate pollinators.

The black-flanked rock-wallaby (Petrogale lateralis lateralis) is a threatened species, once widespread throughout Western Australia but now restricted to disjunct populations including those of Cape Range National Park. It is a herbivore with a foraging range restricted to rocky outcrops and, as such, may be impacted by competition for resources from other native or introduced herbivores. This study compared the diet of the black-flanked rock-wallaby with those of co-occurring species, the euro (Macropus robustus erubescens) and the feral goat (Capra hircus), from two gorges at Cape Range National Park, to determine whether there is overlap in dietary niches. Diet composition was determined using microhistological analysis of faecal pellets in comparison with reference plant material. The black-flanked rock-wallaby diet consisted predominately of browse/forbs with some variation across seasons (63% in summer months 74% in winter months) this overlapped significantly with the diet of goats (Schoener Index: 0.79-0.88), but not euros (SI: 0.41-0.57), whose diet consisted predominantly of grasses (72-78%). There was, however, a significant overlap in the consumption of plants with stellate hairs for all three herbivores (SI: 0.89-0.98). Dietary overlap between rock-wallabies and goats may indicate a mechanism for competition, supporting continuing measures for reduction of goat numbers in Cape Range National Park.

The ancient Gondwanan family Proteaceae has its greatest speciation in fire-prone environments of Australia. Fire response is either by seedling recruitment from parent plants that succumb to fire (obligate seeders), or survival and resprouting from protected buds (resprouters). Starch is the main source of energy for resprouting and in roots is restricted to parenchyma tissue. This study compared the size and distribution of storage parenchyma and the magnitude of starch reserves in roots of several proteaceous species from different genera in relation to their fire response and taxonomy. Cross-sections (2 μm) of roots of 51 resprouter and 42 seeder species from 12 genera were stained for starch. Areas of cortex and ray parenchyma along with starch grain density were measured using image analysis software (Assess 2.0) and comparable samples of root tissue were assayed chemically for starch. Starch, where present, predominated in ray and cortex tissue with a greater percentage in resprouters (13.4 ± 1.03) than seeders (1.8 ± 0.26); these results correlated significantly with the chemical assay for starch (r = 0.93, P < 0.0001). Resprouters also had more storage parenchyma (56.9 ± 1.72%) than seeders (41.9 ± 1.91%) mostly due to broader rays (17.5 ± 1.22%) compared with seeders (8.2 ± 0.16%). Percentage of cortex tissue was similar for seeders and resprouters (39.4 ± 2.24 and 33.7 ± 2.04 respectively). Anatomical preferences for storage site were consistent within genera and broad suprageneric groupings. This study shows that histological analysis of root starch is a reliable predictor of resprouting capacity in Proteaceae and that patterns of storage tissue within genera, together with the persistence of parenchyma devoid of starch in seeders, are consistent with response to fire and suggests homoplastic evolution of this response within the family.

Fires are features of ecological communities in much of Australia; however, very little is still known about the potential impact of fire on plant diseases in the natural environment. Phytophthora cinnamomi is an introduced soil-borne plant pathogen with a wide host range, affecting a large proportion of native plant species in Australia and other regions of the world, but its interaction with fire is poorly understood. An investigation of the effects of fire on P. cinnamomi activity was undertaken in the Stirling Range National Park of south-western Australia, where fire is used as a management tool to reduce the negative impact of wildfires and more than 60% of the park is infested with, and 48% of woody plant species are known to be susceptible to, P. cinnamomi. At eight sites confirmed to be infested with P. cinnamomi, the proportion of dead and dying susceptible species was used as a proxy for P. cinnamomi activity. Subset modelling was used to determine the interactive effects of latest fire interval, average fire interval, soil water-holding capacity and pH on P. cinnamomi activity. It was found that the latest and average fire interval were the variables that best explained the variation in the percentage of dead and dying susceptible species among sites, indicating that fire in P. cinnamomi-infested communities has the potential to increase both the severity and extent of disease in native plant communities.

This study investigates whether tree decline in Eucalyptus gomphocephala (tuart) is associated with the functional diversity of soil bacterial communities. We selected 12 sites with different stages of decline and assessed crown health [Crown density (CD), Foliage transparency (FT), Uncompacted live crown ratio (ULCR), Crown dieback ratio (CDR) and Epicormic index (EI)] and soil bacterial functional diversity based on Biolog EcoPlates™ incubation [Average well colour development (AWCD), Shannon diversity (H'), richness (S) and Shannon evenness (E)]. Crown health indices differed between sites with EI being the most robust indicator of decline in crown health followed by CDR and CD (P<0.05). Soil bacterial indices collected at 0-10 and 20-30. cm soil depth between December (summer, dry season) and May (autumn, start of wet season) differed between sites (P<0.05), and significant relationships between crown health indices, except ULCR, and all soil bacterial indices were observed. Principle component analysis (PCA) showed that a decrease in the utilization of carbohydrates, carboxylic acids, amino acids and amines by the soil bacterial communities correlated to sites with poor crown health, indicating some changes in physiological responses of bacterial groups with declining tree health. Using stepwise regression analyses, in the 0-10. cm soil layer in December, itaconic acid had a 46% contribution to the EI. Carboxylic acids, including itaconic acid, have a strong ability to solubilize soil minerals in calcareous soil, and these possibly increased the availability of soil mineral nutrients in the healthier sites compared to the declining sites, particularly in the dry season. In addition, lack of soil water in the declining sites limited soil bacterial diversity and was positively correlated with EI in the 0-10. cm soil layer in December. In conclusion, soil bacterial functional diversity has a strong relationship with tuart decline and the importance of soil microbes in tuart ecosystem health must be considered in the future.

Management interventions are needed to reverse the decline of Tuart (Eucalyptus gomphocephala) woodland in the Yalgorup area of south-west Western Australia where the largest intact remaining example of this ecosystem is located. Although the cause of the decline is uncertain and several factors may be involved, management action should not be withheld because the decline process is not fully understood. We contend that the reduction in fire frequency over the last 50 years has led to an increase in understorey density, particularly of Western Australian Peppermint (Agonis flexuosa), resulting in greater competition for resources, which may in turn have increased the susceptibility of healthy woodland to decline. In contrast to Tuart regeneration, which is usually tied to fire, Western Australian Peppermint can establish readily in unburnt woodland. Further, once Western Australian Peppermint seedlings develop to the lignotuberous stage, they can resprout vigorously after fire. Therefore, a combination of fire and the physical removal of understorey in sites where this species has formed extensive thickets is required to: (i) provide an opportunity for regeneration of Tuart in both healthy and declining stands; (ii) improve the chances of sustained recovery of Tuart trees in declining stands; and (iii) ensure heterogeneity in the vegetation at multiple scales, a recognized strategy for conserving biodiversity and increasing ecosystem resilience. We propose that this approach may also be relevant to other tree decline syndromes in southern Australia. However, fostering community support for active intervention using thinning and fire in conservation reserves and staging the operations within an experimental framework will be important for such action to gain both the social and scientific acceptance necessary for it to be applied widely.

Stirlingia latifolia R. Br. is a proteaceous undershrub that is widespread in open woodlands and heathlands of the south-west botanical province of Western Australia where it is subject to frequent fires, both natural and the result of fuel-reduction burns. Shoots are completely destroyed by fire but regenerate rapidly by resprouting numerous new shoots from the root crown. Flowering is strongly triggered by fire with only sparse flowering in fire-free periods. A study was undertaken to compare regrowth and flowering in populations of S. latifolia burnt in summer or autumn with populations burnt in spring as well as in unburnt population. Post-fire flowering was recorded in 92% of plants burnt in summer/autumn compared with 73% of plants burnt in spring and less than 3% in populations that had not been burnt for more than 2 years. Plants burnt in summer/autumn resprouted an average of 8.5 shoots from their root crown, of which 93% developed an inflorescence. In contrast, spring-burnt plants averaged only 5.9 shoots per plant with only 64% of these bearing an inflorescence. Ability to produce flowers was found to be related to plant age, with young individuals producing fewer or no inflorescences following spring burns in comparison with the more prolific flowering of similarly aged individuals following summer/autumn burns. Summer/autumn-burnt plants also produced significantly longer inflorescence-bearing shoots bearing a greater numbers of flower heads than those burnt in spring. Possible explanations for these results are given in the present report.

Banksia prionotes Lindley is a fire-sensitive, fast-growing tree of nutrient-impoverished deep sands of south-western Australia. Its root system is dimorphic, comprising proteoid root-bearing, lateral roots absorbing superficially concentrated nutrients during the wet winter season and a single main sinker (tap) root extending down to the water table. Shoot extension commences in early summer coincident with drying of topsoil and ceases at the end of summer upon initiation of inflorescences and resting buds. Shoot growth utilises nutrients accumulated the previous and earlier wet seasons and current photosynthate formed at the expense of ground water abstracted by the sinker root. Rooting morphologies of differently aged trees are described and yearly changes in dry matter distribution between leaves, trunk and parts of root systems are related to dry matter gain and foliage area. The seasonality of nutrient uptake by proteoid, lateral and sinker roots and nutrient translocation in shoots is assessed by xylem and phloem sap analyses. Specific hydraulic conductivities of xylem of sinker roots are considerably higher than in lateral roots and higher again than in trunk xylem. The differences involved relate to vessel lengths and diameters and proportional transectional areas devoted to conducting tissues. Seasonal changes in dependence on ground water as opposed to recent rain are estimated using deuterium : hydrogen natural abundance ratios of water extracted from xylem of lateral roots, tap root and trunk. Relationships between water stress and timing and progress of extension growth of shoots are studied using carbon isotope natural abundance ratios of new leaf dry matter and abscisic acid levels in xylem and phloem sap.

Stirlingia latifolia, a common shrub of Banksia woodlands of SW Australia, is a highly successful resprouter species recovering from fire by multiple sprouting of new shoots from its upper root stock. in comparison with the congeneric fire-sensitive (obligate seeder) species Stirlingia tenuifolia it exhibits a low shoot:root dry weight ratio and high concentrations of stored starch in the cortical tissue of its roots. The relationship between root reserves of starch and development of newly sprouting shoot material following fire is examined in S. latifolia after spring and summer burns. During the initial 2-5 month period after fire, levels of stored starch in the roots fall by 50-75%, followed by a slow increase as plants reproduce and the attainment of pre-fire starch levels by 1·5-2 years after the fire. Starch reserves of roots can be further reduced by shading the regenerating shoots to limit their input of photosynthates and almost totally eliminated by monthly removal of successive flushes of new shoots over a 10-12 month period. New shoots continue to sprout until all the starch is eliminated. The data are discussed in relation to the fire-induced reproduction of S. latifolia and its ability to thrive in very frequently burnt habitats.Copyright 1993, 1999 Academic Press

Juvenile (2–4 years old) plants of a taxonomically diverse range of dicotyledonous species were examined following recruitment from seed in recently burnt habitats in S.W. Australia. Obligate seeder species (those succumbing to fire) had on average, an almost threefold greater total plant d. wt and more than a fourfold greater shoot: root d. wt ratio than comparably-aged, cohabiting, resprouter species (those capable of surviving fire). Starch was generally much more concentrated in root dry matter of resprouters than seeders, and both categories exhibited greater starch storage capacity in roots than shoots. Members of the Myrtaccae were exceptional in not showing a greater root starch reserve in resprouter than in seeder species. and in carrying as high, or higher, starch levels in shoots as in roots. Anatomical investigations on roots provided instances of zero starch storage, storage, only in rays or in cortex, in rays and in xylem parenchyma, in rays and in cortex, or in all three locations. High starch ratings of resprouter roots related mostly to higher starch grain packing density at storage sites, but in certain instances these also reflected proportionally greater areas of tissue specifically devoted to storage. Dry matter of shoots of both seeders and resprouters generally contained higher levels of N, P, K, Ca and Mg than that of roots, but there was no significant evidence of elements being more concentrated in resprouters than in seeders.