Patchiness in Natural Environments: Examining the Mistletoe-Host Relationship - Term Paper Example

tсhinеss in Natural Еnvirоnmеnts : Ехаmining Thе Mistlеtое-Hоst Rеlаtiоnshiр Date: Affiliation: Раtсhinеss in Natural Еnvirоnmеnts: Ехаmining thе Mistlеtое-Hоst Rеlаtiоnshiр Introduction Mistletoes are native flowering plants which grow as parasites or semi-parasites on the branches of trees and the shrubs. In Australia, they mainly occur in almost every woody plant and the number of the woody plants around determines their population. Mistletoes are believed to use particular trees as the hosts and they include the following-wattles, Sennas, She Oaks, Eucalyptus, Tea-Trees, Haekas, Emu Bushes, Quandongs among others. They usually live in an intimate relationship with other organisms which are in the plant community including their plant hosts, pollinators and the seed dispersal agents. The mistletoes are used as a source of food by some animals especially the birds and vertebrates. Mistletoes are known to occur naturally in the native forests, but previous studies show they can exist in partial woodlands, edges of forests and the roadsides (Tuner, 1991). The study into control of mistletoe on the red box, Eucalyptus polyanthemos affirms that mistletoes contribute to the reduced diameter of growth of the tree as a result of the replacement of the crown by the mistletoe foliage. Moreover, loss of the basal area increment in trees that are not treated with the2:4-D herbicide was 26%.the trees that had the larger number of the mistletoe plants exhibited the greater reduction in the height and the diameter in general. Research postulates that loss of growth and death of trees in hardwood and the softwood forests in north America exceed 3 billion board feet annually and that translates to 7080,000m3 annually. This loss appears to be a huge loss and, therefore, the mistletoe is a threat to the forest. The mess is caused by a different group of plants that have different methods of seed dispersal on the trees in a different order that grows in the Northern Hemisphere, but the magnitude of thee parasitism on the host trees on that continent is not indicated. However, in Australia, there are no comparable figures to indicate the degree of damage the mistletoe has done on the Australian forests (Rast, 1996). However, considering, the effects of the tree to the American forest, it is also important to note that it has also caused significant damage on the Australian forests and woodlands. Therefore, it is paramount for the study to how the range that the “parasite” have affected the trees. Further investigation is necessary to reveal the predisposing factors of the trees to the parasitism by the mistletoes. However, it is noted that the incidence of infestation in the eucalyptus trees by the Anyema Spp in the Northern Victoria has been increasing with the increase in age. The older the tree gets the more it becomes attacked by the mistletoe and this posed as a challenge to the forests. The mistletoes are considered to be the hemi-parasites or the epi-parasites; the host plant is usually disadvantaged since the mistletoe depends on the host for food, minerals and water. Some species, a swelling is usually formed where haustoria of the mistletoe plant is connecting with the xylem tissues of the host tree and later the extremities of the branch beyond the mistletoe ends up dying off. Mistletoe tissues are known to have high osmotic pressure compared to the host plant and, therefore, they tend to draw for more water from the host plant therefore making it weak (Russell, 2007). The mistletoe has been posing as a great challenge today owing the fact that it is causing destruction to trees hence prompting need to address the issue. The decline of the number of trees in Australia have contributed to increasing in the mistletoe, for example, the trees have reduced in the last century due to human settlement, the remaining trees are set in woodland and this gives a chance for the mistletoe to continue dispersing day in day out. It means that with scattered trees each and every tree will be affected by the menace. Moreover, the natural control agents are absent and this makes the presence of the mistletoe to dominate. Many of the animals which relied on mistletoe as source of food have been displaced and others dead and this has contributed to further increase. For example, possums were the feeders of the mistletoe leaves and they were poisoned along with rabbits by the strychnine. The decreases of the feeders have translated to the drastic increase of the plant and that means increased in the level of damage. The mistletoe has caused a considerable decrease in old, in the old trees. For most parts, the young trees are not helping in replacement since the livestock and animals are eating up the small trees. The trees have continued becoming rarer in the landscape and the seed supply that allows regeneration have also decreased therefore leading to ultimate decrease. Considering the challenges that are brought out by the presence of mistletoe, it is paramount to carry out a study that will explain the extent of damage under the following objectives (Tuner, 1991). To examine the population and distribution of mistletoes in a given portion of forest To examine the competitive advantage of the plant that makes it survive in host plants To examine the main predators of the plant and the extent of consumption Methods The study of took place in Daintree rain forest with supervision and assistance from the forest rangers. The area is a national rain forest though some parts of the forest have experience logging for quite some time and, therefore, the trees are scattered. The area under study was around one square kilometer and it was further divided into ten sections of around hundred square meters (Watson, 2011). The ten sections were studied into detail to ensure the data received was accurate. The random method was used where transect was randomly positioned and the trees within transect were determined. The trees were classified according to species and whether the mistletoes invested them or not. Many species of trees were recorded on the basis of location and whether they were infested with mistletoes. The study was successful and it depicted that there is a certain tree which is heavily affected by mistletoes while others were not affected or they were affected in minor cases. More also, it was noted that those trees that were located in the areas that logging had taken place were more affected compared to those which were in areas where logging had not taken place. Logging leads to aeration and such environment favors dispersal of the mistletoe seeds. Moreover, transect were used in the thickets and it was noted that the trees that were located in the thickets were not heavily invested compared to those in the woodlands. The situation can be explained by the fact that the open area is prone high chances of dispersal and the same time there are no animals that can feed on mistletoe(Watson, 2011). In order to examine the competitive ability of the mistletoe plant which makes it survive in the host plant, the area of the host was determined and the strategic position of the mistletoe was decided. The mistletoe plant was proved to have tastes in the crown and especially the parts that are facing the sun directly. The sun is essential for the plant carryout photosynthesis and it was noted that the plants were doing well where the sun was sufficient. In this relation, the plants were noted to survive well in the sections of the tree that were facing the sun. However, in the thickets, the plant was not doing very well (Tuner, 1991). Moreover, the tissue of the plant was taken and that of the host plant was to determine whether, the tissues were specialized to live on the host plant. In an attempt to determine the main feeders of the plant, some hidden cameras were positioned in strategic places and it was noted that possums were the main feeders of the plants. Moreover, there were some honeyeater birds which were feeding on the plants and that also acted as feeders of the plant. Results It was noted that mistletoe normally infests those plants trees which are well aerated and at the same which are facing the sun. From the table below, is affirmative that eucalyptus trees are the most affected trees and it is as a result of their place. Initially in the methods, it was reported that frequent logging occasioned the area and this contributed to high infestation. The high infestation in these trees was attributed to high cases of logging that provided enough light for germination and dispersal. Taking into account that most of the eucalyptus is planted after logging, the case of infestation must increase. The location of the mistletoe in relation to the tree was also noted be influenced by the agents of dispersal (Russell, 2007). Moreover, it was noted that the osmotic pressure of the Mistletoe cell is much higher compared to that of the host plant and a result; it can draw water and minerals from the plant. Therefore, the reduced in width of the crown that culminates in reduced board feet is attributed to the case of physiological adaptation of the parasitic mistletoe. Type of tree No of trees sampled No of trees infested with mistletoe Percentage of infested trees Infested with mistletoe The degree of infestation Location of the mistletoe Osmotic pressure of the cell of mistletoe in relation to host(H:M) Sennas 10 5 50% yes Fairly infested On the trunk 2:3 She Oaks 10 4 4% yes Fairly infested On the trunk 3:4 Tea-Trees 8 0 0% no No infestation No part noted 2:3 Emu Bushes 7 0 0% no No infestation No part noted 2:5 Quandongs 5 4 8% yes Intensely infested Longitudinal branches and the trunk 2:4 , Eucalyptus 10 10 100% yes Intensely infested Longitudinal branches and the trunk 2:3 Haekas, 7 6 85% yes Intensely infested Longitudinal branches and the trunk 2:5 Total no of trees 57 40 nil nil nil Discussion After through research, there is a design that was noted as far as distribution of the mistletoe was concerned. For example, it was noted that in the woodlands especially where logging had taken place, many mistletoes were reported and this can be explained by the ability of the mistletoe to thrive in well aerated and lighted areas. For example, it is possible for the mistletoe to grow and thrive in woodlands because such areas are well aerated and sunlight isa enough. However, the people of the mistletoe in the thickets is much lower because light and enough air is not readily available. According to the above given report, it is evident that the people of the mistletoes follows a heterogeneous design and that is why on finds that some areas have high population of the mistletoes while other sections do not have at all. The reason behind the distribution is light and availability of aeration. Excessive heat leads to wilting and finally death of the plant (Russell, 2007). The heterogeneous pattern in the distribution, in the landscape and be explained using the biotic and biotic factors. The biotic factors which affect the distribution of the mistletoe include feeders and predators. As posited above, the main feeders of the mistletoe plant are the possums and some nectar feeding birds which have considerably reduced in the past few decades. The possum has reduced since the loggers and other people who are settling in the nearby areas have been poisoning, therefore, reducing them. This has considerably led to increased mistletoe since there are no eliminating agents. This explains why many types of mistletoe do not infest the trees in the thickets since the feeders and agents of dispersal are not many. Moreover, the vectors are many in the woodlands compared to the interior of the thickets and they enhance pollination hence the increase in such areas (Russell, 2007). Moreover, some of abiotic factors such as light, water and minerals have also affected the distribution in one way or the other. For example, the mistletoe cannot adapt and survive in areas where light is limited. It depends on light for photosynthesis and, therefore, it must thrive in an area with enough light. Water is paramount in every organism and plants which grow in areas with minimal rain do not support mistletoes. Minerals are important in growth and development mistletoes in areas that were fertile, it was noted that mistletoe had increased in number since the minerals are vital for the growth. Moreover, minerals are used in enhancing the cell osmotic pressure and, therefore, it is paramount for the minerals to be present in the soil. The soil determines what to grow. Fertile soils ensure that many types of mistletoe are growing in that particular region compared to soils that are not fertile (Watson, 2011). The position of the tree determines whether the mistletoes will grow or will not grow, if the tree is positioned in an area which has sufficient light, water and minerals, is obvious the plant must grow. For instance, in those areas where the water and minerals were not enough, there were some trees but they were not as much as that of the areas that had good conditions to favor goodness. In conclusion, it is evident that the mistletoe is a major parasitic plant it has caused considerable damage in the environment and more especially in the woodlands. Many board feet of wood and especially in North America and Australia have been destroyed and this has caused alarm in the environment. Control and management of the plant is paramount to ensure that sustainability of the environment is enhanced. References MacRaild, L. M. (2008). Ecology of mistletoe parasitism in rural landscapes: a multi-scale perspective. London: Oxford University Press. Rast, M. (1996). A G.I.S. based study of mistletoe in the Clare Valley and Southern Flinders Ranges, South Australia: a report to the Ministers of the S.A. Dept. of Environment and Natural Resources, the S.A. Dept. of Housing and Urban Development and the S.A. Dept. of Ag. Adelaide, S. Aust.: Dept. of Environment and Natural Resources. Russell, R. (2007). The first aerial parasites in the sandalwood order (Santalales): molecular phylogenetic and biogeographic investigations. London: Oxford University Press. Start, A. N. (2011). Fire responses and survival strategies of mistletoes (Loranthaceae) in an arid environment in Western Australia. Australian Journal of Botany, 59(6), 533. Tuner, R, .J. (1991), Mistletoe in Eucalypt Forest-A resource for Birds, South Wales: Forestry Commission of New South Wales Watson, D. (2011). Mistletoes of Southern Australia. Victoria: CSIRO Pub.. Read More