Decomposition Rate & Replanted Forest on Motutapu Island
Motutapu Island that is sometimes simply called Motutapu is an island belonging to the Hauraki Gulf Maritime Park. As for the geographic features characteristic for the sacred or sanctuary island, Motutapu Island can be contrasted to the neighboring island called Rangitoto that is covered with forests while Motutapu Island lacks forests and is covered in grassland and wet meadows (Bain & Dunford, 2006, p. 148). As the Geology section of the official website of The Motutapu Restoration Trust (2009) suggests, there occurred a volcanic eruption about six hundred years ago and the island of Rangitoto is its product. However, the fact of special interest for the present research is that the same volcanic eruption caused Motutapus covering with fertile, friable, it attractive for cultivation by Maori, hence the great fertile potential of the soil of the island (The Motutapu Restoration Trust, 2009, para.1). However, it is known that there are very few areas on the Island that are covered with forests. This is why a major fifty-year community project aimed at the restoration of Motutapus Island is of great interest for the present research since it can be regarded as the research in the framework of this Community restoration program.
Decomposition of plant litter is directly connected with the formation of soil organic matter (Breemen & Buurman, 2002, p. 85). Since there is a direct connection between the restoration of forests and the structure of the soil, it is necessary to conduct research analyzing the differences of soil structure in the areas of forest that differ from one another by the age of plants.
Literature Review
On the whole, very little scientific research devoted to botanical features or soil study of Motutapu Island has been conducted. Esler (1980) perused research of botanical features of Motutapu and neighboring regions. The value of this research is in the fact that the author has presented an outline of vegetation and flora on the island under consideration, concluding that Motutapu is predominantly pasture with extensive riparian swamps, degenerate relics of native forest, and very minor areas of scrubland (Esler, 1980, p. 15). Research of great importance for the nature of Motutapu Island and, consequently, for the present study, is the conservation vision for the islands Rangitoto and Motutapu, conducted by Miller, Craig, and Mitchell (1994). The researchers offer a strategy of restoration of the state of functioning native ecosystems by means of revegetation of large areas of Motutapu Island and the reintroduction or translocation of native fauna (Miller et al., 1994, p. 65). The study delineates the ultimate aims of planting strategy as a recreation of habitat on the farmed areas, protection and enhancement of the existing vegetation, and protection and enhancement of archeological and cultural sites (Miller et al., 1994, p. 76). Also, this research is of great use as it offers geological information about the soil of the island, defining it as soil with a high nutrient status and an and fauna (Miller et al., 1994, p. 76). However, the research focused on the soil of Motutapu is too concise, hence the topicality of the present study.
Decomposition is one of the processes of great importance for the formation of soil. Kricher (1999) calls it one of natures most fundamental processes, singling out fungi and bacteria as principal actors of the process of decomposition (p. 47). Breemen and Buurman (2002) state that soil organic matter is generally considered to be dead organic material that is present in the soil and offer the analysis of living organic matter consisting of humus and they pay special attention to the decomposition of fresh organic matter, derived from living organisms, plants and animals (p. 85). The significance of the decomposition process is shown by Swift, Heal, and Anderson (1979) who analyze the interrelation of three subsystems within an ecosystem: plant subsystem, the herbivore subsystem, and the decomposition subsystem, which ensure the integrity of the whole ecosystem by means of energy transferring (p. 5). The researchers considered the amount of detritus entering the decomposition system and they offered the method of calculation based on special attention to the above-ground input of plant detritus direct to the decomposition subsystem, which is plant litterfall (Swift et al., 1979, p. 13).
Among the factors influencing the speed and rate of decomposition, Nollet (2006) mentions the availability and stability of light, exposure to air, different temperature, and moisture. The same factors will be included in the present study. As for the studies of decomposition rates, valuable research was conducted by Krasny (2003), who offered the comparison of decomposition rates in soil with and without earthworms and comparison of decomposition rates in litter and mineral soil, wetland and forest soil, and at varying temperatures and moisture contents (p. 123). This research has proved the dramatic effect of earthworms on decomposition in forest soils and the researcher has also mentioned the necessity of analysis of additional factors, such as weight of worms, their species, soil moisture, temperature (Krasny, 2003, p. 123). Taking into consideration the whole amount of scientific literature studied, it is possible to state that the review of literature of the topic has created the ground and the main directions for the present research that will be offered in the following subsections.
Justification/Benefits
As the review of literature suggests, the study of decomposition rates of forest soil is of vital importance for ecology. The present research will produce benefit that may be considered in two dimensions: theoretical one and practical one. The shortage of specialized literature on the soils of Motutapu and scrubland soils of the island, in particular, is the evidence of the novelty of the current research. As for the theoretical topicality of the study, it can be proven by similar research in the field. Cuevas & Medina (1988) studied the dynamics of leaf litter decomposition in Amazonian forests, and Ewel (1977) successfully studied litter fall and leaf decomposition in a tropical forest succession in Guatemala. However, nowadays there is no similar research of the interrelation of forest succession and decomposition rates on Motutapu Isalnd.
As for the practical application of the findings of the study of decomposition rate changes beneath replanted forests on Motutapu Island, it will help to show the importance of biodiversity to ecosystem health. The importance of this matter has been proven by Townsed et al. (2003) who mention the declining of global biodiversity as an issue of vital importance and the significance of data on decomposition rates as the sign of critical importance of biodiversity for the health of ecosystem (p. 382). Thus, the findings of the study can help to make Motutapuan ecosystem healthier. Also, Berg and Staaf (1980) conducted related research of decomposition rate and chemical changes of Scots pine needle litter for the purpose of the provision of data for simulation models of nutrient transfers in soil (p. 363). Thus, the findings of the present research may be useful for composition of the model of Motutapuan ecosystem. Besides, if King et al. (2002) have established that changes in species evenness of litter produce no effect on decomposition process (p. 1959). The present research will identify the existence of changes of decomposition processes depending on the age of the plants under analysis.
Methodology
The main method of the current research is the qualitative analysis of the leaf litter collected in the region under study. The sample will consist of four transects, each twenty meters long, starting from the upper edge of the forest proceeding towards the centre down the valley. The first transect will include the seedlings of one year old, the second will , the third will give the data pertaining to , while the fourth transect will enable the researchers to collect data about .
The tools applied for the collection of data during the study are leaf litter bags of two types, fine litter bags and coarse litter bags set on the six points of each transect. Thus, the total number of litter bags is thirty six and the number seems sufficient and optimal. The choice of the litter bags of two types will give additional opportunities for the analysis.
The initial analysis of sample leaves of Coprosma Robusta of total number of eighty will be performed. The leaves will be dried under 70o C for 24 hours and the constant K will be calculated for the subsequent measurement of decomposition rates of leaf litter in the studied transects.
Relying of the existing research of decomposition rate reviewed in the previous subsection of the present research proposal, such factors influencing decomposition will be taken into account: light, soil temperature, moisture, pH, and litter weight. Invertebrate abundance will be analyzed quantitatively and qualitatively by means of weighing. A point quarter centered stick will be also placed on each transect point. Four species will be identified on the trees nearest to each corner.
The total time period of the experiment will cover about three months (March, 5-6th May, 9th).
Contribution
The present experimental research can be beneficial for the Community restoration project of Motutapus cultural and natural landscape (Department of Conservation, undated, para. 12). Hence nation-wide importance of the research. The usefulness of decomposition process for the formation of soil has become a proven fact already. The findings of the study will identify the highest decomposition rates in certain parts of replanted forest. They will contribute to the process of identification of the measures necessary to increase the fertility of the soils of scrubland. Intensified fertility will stimulate the growth and development of forests on Motutatu Island. Consequently, the research will make its contribution to the implementation of the restoration project. As the influence of such factors as light, moisture, invertebrate abundance, etc., will be studied, the optimal areas for planting native trees will be determined and may be put into practice. The research will also make it possible to predict the intensity of growth of scrubland on Motutapu Island.
