Acacia Species - Native Plants in Australia - Literature review Example

Literature Review: Native Plants in Australia (Acacia Species) Name Institution Introduction The Acacia species is one of the dominant vegetations in Australia. Common species based on seedlot orders are A. mangium, A.auriculiormis, A.aulacocarpa, A.mearnsii and A.melanoxylon (Griffin, Midgley, Bush, Cunningham & Rinaudo, 2011). Globally, Acacia species comprise 40 percent of tree plantations in sub-tropics and tropics. The species grows well in land that is not sufficient for food production (Griffin et al., 2011). Different literature was reviewed on Acacia species in Australia including Western Australia. The outcome of the review is categorized into uses of Acacia, salinity tolerance and clearance in Western Australia. Search Process Online databases and journals that were used include Elsevier, Wiley, Research Gate, Oxford Journals, BMC Biology, the Journal of Medicinal Plants Research, Functional Plant Biology, Journal of Vegetation Science and the International Journal of Agriculture and Biology. Search terms used for the review were salinity, nutrient composition, Acacia species, wood fuel, salt tolerance, clearance, and wood production. Inclusion criteria included articles with the words Acacia species in the titles, articles published after 2006 and peer-reviewed studies. Criteria for exclusion included articles that discussed other species similar to Acacia such as Eucalyptus, opinion-based articles or studies published before 2006. Twenty-one articles were identified from the search. Only eleven articles were selected for the review. Uses of Acacia, Food Industry and Distribution Griffin et al. (2011) conducted a study on the international use of acacias including future prospects. Their study referred to Australian Tree Seed Center (ATSC) database to establish the taxa, scale of use and location of Australian species. Their study established that Australia species have global uses because the species grows in subtropics and tropics (Griffin et al., 2011). The study revealed that Australian acacia species have been traditionally used for fiber crops and fuel wood in Australia. The biological characteristics of Acacia species make them ideal for crop planting. Firstly, Acacia species are ideal crop plants because their seed is sold cheaply in the country. Secondly, the seedlings of Acacia species can be raised easily and quickly because they grow relatively with little input. Lastly, Acacia species are ideal crop plans because they can grow in variety of environments especially areas that are not adaptable for food crop production. The species adapt to areas with limited nutrients and water. Griffin et al. (2011) agreed with Midgley and Breadle (2007) that Australian Acacias are useful for pulp wood, fuelwood, tannin and solid wood. Acacia mangium (A.mangium) and Acacia auriculiformis (A.auriculiformis) produce pulp in Southeast Asia. The species are used for wood chip production and export of hardwood chips from Brazil and Vietnam. Countries in South America, Central America and Southeast Asia grow Acacias in plantations for pulp production and export to India and China. Acacia plants are used for furniture production. Midgley and Breadle (2007) reported that Acacia melanoxylon is used for producing furniture in Southeast Asia, Chile, South Africa and New Zealand. The demand for these species in furniture production has increased over the years due to the decline in forest logs and the increased awareness of Acacias for light construction, plywood, flooring and furniture. In addition, the high density of Acacia hybrids such as A.auriculiformis and mangium hybrid make it useful for making products that require strength. Tannin production is the third use for Australian acacias. The A.mearnsii species is a persistent tree that is suitable for tannin extraction. The Australian species is grown in Brazil and South Africa for tannin production and export. Studies show that South Africa exports 75% of tannin that is extracted from the Australian acacia species (Griffin et al., 2011). Australia acacias are used for fuelwood, poles and food. The Aboriginals use some acacia seeds for food while West Africans produce the species for seed crops. The seed crops are used for firewood, nitrogen fixation, building poles and wind breaks (Griffin et al., 2011). In Australia, the seeds of Acacia saligna, A.aneura, A.victoriae and A.stenophylla are used for stock fodder and reserve for drought fodder. Developing countries use Acacia species for fuelwood while species such as A.tumida and A.saligna are used as windbreaks since they thrive well in soils with high pH and sandy soils. Ratnayake and Joyce (2010) observed that acacias are used for floral displays, horticulture and fragrances. A.dealbata produces flowers for the perfume industry whereas hybrids of the same species are used as floral displays and ornamentals in Australia and the Europe. Horticultural uses include foliage, landscaping and commercial gardening. Some Acacia species have medicinal uses. A study by Ali et al. (2012) reveals that Acacia nilotical Lam found in subtropical and tropical countries is commonly used for medicine. The species can be used to treat different ailments because of anti-oxidant properties such as phenols, oleosins, alkaloids, essential oils, terpenes and phenolic glycosides. As a result, different parts such as leaves, bark, seeds, roots and fruits/flowers provide anti-cancer, vasoconstrictor, anti-diabetic, anti-mutagenic, anti-platelet agregator, anti-fungal, anti-asthmatic and anti-plasmodial properties. The roots have anti-cancer properties and can be used to treat tuberculosis while the leaf can treat diarrhea, ulcers and Alzheimer’s disease. The gum contains astringent and emollient properties while the seeds have antiplasmodial properties. The pods have anti-hypertensive, anti-fertility and anti-diarrheal properties while the stem bark has anti-bacterial, diuretic and nutritive properties for treating toothaches, skin diseases, hemorrhage and leucoderma. The bark of the trunk is used to treat bronchitis, bleeding piles, dysentery, diarrhea and common colds. A.nilotica also has anti-bacterial and antioxidant properties as well as inhibitory activity against human immunodeficiency virus (HIV) and hepatitis C virus (Ali et al., 2012). Salinity Tolerance in Different Species Saline soils are predominant in arid and semi-arid areas that have insufficient rainfall for leaching. This salinity is a problem for agriculture, pasture and forestry because high salt concentrations affect plant growth. Excessive salt content saline soils kills growing plants, suppresses shoot growth and retards seedling growth and germination (Hardikar & Pandey, 2008). This is because high salt concentrations reduce the soil’s osmotic potential and access to salt water for plants. However, some Australian acacia species have been found to grow successfully in saline soil such as A.stenophylla and A.maconochieana. Diouf et al. (2007) observed that A.seyal was tolerant to saline environments. Their study revealed that the Acacia species can tolerate temporary flooding, alluvial soils, clay soils and rocky soils. It performs well on non-saline and saline soils. From the article, A.seyal performs well in saline soils because it can enter symbiosis with vesicular arbuscular mycorrhizal fungi and legume-nodulating bacteria found in the rhizosphere. The species can achieve nodulation when suspended in highly saline soils as well as alkaline soils. This is because the plant can establish a symbiotic relationship with natural rhizobial populations in the soil environments (Diouf et al., 2007). Hardikar and Pandey (2008) observed that Acacia Senegal species is tolerant to saline conditions. Their study on the species’ response to saline showed that the growth of seedlings takes longer in saline soils compared to non-saline soils. Seed germination also decreased significantly with high salt stress. Root and stem elongation was also retarded as soil salinity increased while dry weight decreased as salt concentrations increased. The study reported that the water content of taproots, leaves and stems decreased significantly as salt concentrations in soil increased. There was a significant decrease in water potential, potassium content, sodium content and concentrations of calcium, magnesium nitrogen and phosphorous when salt concentrations were increased. Although the results show that salt stress affects plant growth, A.senegal was shown to have a higher survival rate in saline soils. Similar findings were observed by Abari, Nars, Hojjati and Bayat (2011). They reported that A.oerfata and A.tortilis seedlings had lower germination rate in saline conditions. Their findings showed that the seedlings decreased in germination speed and percentage as salt stress was increased. With regards to germination speed and percentage, A.oerfata had a better response to salt stress to imply that this species has a higher salt tolerance compared to A.tortilis. Thrall, Bever and Slattery (2008) agree on the host-soil symbiotic relationship between Acacia plants and rhizobia. Their laboratory study investigated the interaction of Acacia and rhizobia in saline soils. The laboratory results revealed that the growth of rhizobial isolates declined as salt tolerance increased. The results also show that salt-tolerant Acacias are not as responsive to rhizobial inoculations compared to salt-sensitive hosts. This implies that Acacias have lower dependence on symbiosis for salt adaptation. To improve the salt tolerance of Acacia species, Soliman, Shanan, Massoud and Swelim (2012) proposed that co-inclulation with a combination of Sinorhizoblum terangae (R) with arbuscular micorrhizal fungi (AMF). Their research showed that salt stress continued to increase calcium and sodium content while reducing potassium, phosphorous and nitrogen content. From their article, the salt-tolerance of Acacia saligna can be improved by applying bio-inoculants (AMF+R). These bio-inoculants help the species to make osmotic adjustments so that it can adapt to saline soils. III. Clearance in Australia and Western Australia Land clearance is a challenge for Australia. According to Bradshaw (2011), developed country has undergone significant changes in the use of land due to human settlement and transformation of forest structure. Forest cover has decreased significantly over the years. Historically, vegetation and forests were cleared for agricultural use. Clearance rates increased after the Crown Lands Alienation Act was passed. The Act influenced the rapid clearance of vegetation for unrestricted settlement. Rapid deforestation in New South Wales and Western Australia occurred in the 19th and 20th centuries in favor of industrial development such as wheat development. Fifty percent of land in Western Australia was cleared for agricultural development in mid-20th century. This reduced native vegetation cover to 7 percent from 90 percent (Bradshaw, 2011). The demand for agricultural produce and cattle grazing areas intensified land clearance activities. These activities had a negative effect on the ecosystem. Agricultural activities contributed to forest degradation and deforestation. Ajani (2008) and Bradshaw (2011) agree that agricultural use of land has reduced forest cover by 38 percent and has severely degraded the remaining forest cover. Presently, fifty percent of Australia’s forest is severely degraded or cleared. This clearance has affected the function of forest ecosystem because forests are more isolated and occupy smaller areas. Consequently, the isolation of native vegetation has had a negative effect on biodiversity such as making animal and plant species more extinct. Human activities such as logging have altered up to 80 percent of Acacia and eucalyptus trees. The deforestation of Acacia forests and other native vegetation species has had a negative effect on climate. Clearance of native vegetation for agricultural use has increased the amount of greenhouse gases released to the atmosphere. This has resulted in higher carbon emissions and higher temperatures in Australia. Rapid changes in temperature and rainfall patterns in Australia are evidence of carbon emissions in Australia (Ajani, 2008).As a result, Australia has implemented protections for forests to prevent further fragmentation, degradation, or compromise of biodiversity. Ajani (2008) recommends that there is a need to control the deforestation and fragmentation of forests. Conclusion Eleven articles were considered for the review. Three themes were identified: Acacia uses, salinity and clearance of Australia and Western Australia. Four articles established that Australian Acacias are useful for fuelwood, pulpwood, tannin, solid wood, ornamental designs, and medicinal benefits. Five articles established that salinity affects the germination and plant growth rate of Acacia plants. The authors agreed that salinity affected plant growth and that Acacia species were tolerant in salt stress conditions. Lastly, two studies explain the negative effect of forest clearance on climate and forest cover. The studies revealed that the clearance of Australian forest or native vegetation for agricultural uses contributed to degradation, deforestation, isolation of forest cover, higher greenhouse gas emissions, and climate change. All of the articles provided valuable insight into Australian Acacia species. References Abari, A., Nasr, M., Hojjati, M., & Bayat, D. (2011). Salt effects on seed germination and seedling emergence of two Acacia species. African Journal of Plant Science, 5(1), 52-56. Ajani, J. (2008). Australia’s transition from native forests to plantations: The implications for woodchips, puplmills, tax breaks and climate change. Agenda, 15, 21-28. Ali, A., Akhtar, N., Khan, B., Khan, M., Rasul, A., Uz-Zaman, S., Khalid, N., Waseem, K., Mahmood, T., & Ali, L. (2012). Acacia nilotica: A plant of multipurpose medicinal uses. Journal of Medicinal Plants Research, 6(9), 1492-1496. Diouf, D., Samba-Mbaye, R., Lesueur, D., Ba, A., Dreyfus, B., Lajudie, P., & Neyra, M. (2007). Genetic diversity of Acacia seyal Del. Rhizobial populations indigenous to Senegalese soils in relation to salinity and pH of the sampling sites. Microbial Ecology, 54, 553-566. Bradshaw, C.J. (2012). Little left to lose: Deforestation and forest degradation in Australia since European colonization. Journal of Plant Ecology, 5(1), 109-120. Hardikar, S., & Pandey, A. (2008). Growth, water status and nutrient accumulation of seedlings of Acacia Senegal (L.) Willd. In response to soil salinity. Anales de Biologia, 30, 17-28. Griffin, A., Midgley, S. J., Bush, D., Cunningham, P., & Rinaudo, A. (2011). Global uses of Australian acacias- The trends and future prospects. Diversity and Distributions, 17, 837-847. Midgley, S., & Beadle, C. (2007). Tropical acacias an expanding market for solid wood. Acacia Utilization and Management: Adding Value: Proceedings of a Blackwood Industry Group Workshop, Victoria: Rural Industries Research and Development Corporation. Ratnayake, K., & Joyce, D. (2010). Native Australian acacias: Unrealized ornamental potential. Chronica Horticulturae, 50, 19-22. Soliman, A., Shanan, N., Massound, O., & Swelim, D. (2012). Improving salinity tolerance of Acacia saligna (Labill.) plant by arbuscular mycorrhizal fungi and Rhizobium inoculation. African Journal of Biotechnology, 11(5), 1259-1266. Thrall, P., Bever, J., & Slattery, F. (2008). Rhizobial mediation of Acacia adaptation to soil salinity: Evidence of underlying trade-offs and tests of expected patterns. Journal of Ecology, 96(4), 746-755. Read More