In this study we evaluate and compare different invasive species management scenarios in order to investigate a cost-effective management strategy over space and time. Cost effectiveness matters because budget constraints limit the area that can be treated to mitigate the risk of invasion in any given year. The spatial nature of invasive species spread makes it important to effectively allocate budget resources to control spread over space and time. We develop and use a simulation model to examine and compare the effect of various management strategies on the pattern and extent of invasive species spread, as well as management costs. Our model is based on a biological model that captures the dynamic and spatial aspect of invasion, integrated with a spatially explicit dynamic decision tool. Our model explicitly integrates the tradeoff between management intensity and management cost, and quantifies this tradeoff, which is important information for allocating management efforts efficiently and effectively over space and time.

Black pine is very widely distributed in Turkey, with most stands managed by periodic harvesting to meet domestic wood demand. However, scientific knowledge about the spatial structure of stands after thinning is lacking. To correct this deficiency, 12 pure black pine stands in the Alaçam Mountains between 61 and 95 years of age were investigated. The stands were mapped according to spatial tree distribution and thinning grades were determined by both number of trees per hectare and basal area. The numbers of trees in the stands were between 590 and 2163 (before thinning) and between 269 and 1422 (after thinning). Spatial-structure analyses were carried out before and after thinning using a pair correlation function. Graphical illustrations were extracted and visually assessed. In addition, the total areas below and above the theoretical line (g=1) of the pair correlation functions were calculated, and the effects of thinning on these were determined. No change was observed in the slightly thinned sample stands (17, 35, 38, and 56) and only slight changes in the moderately thinned stands (18, 21, 49. and 53). The most striking differences were detected in the intensively thinned stands (59, 68, 76, and 78). Regular areas have increased in parallel with increased thinning applications. In other respects; clustered areas did not decrease along with the increased thinning. The pair correlation function provides a comprehensive explanation of the effects of thinning on stand spatial structure.

Numerous studies have confirmed Altitudinal gradients and physical environment as the major factors that affect species richness and distribution. The world's biodiversity are not evenly distributed due to the variations in biogeographically conditions. The West African tropical rain forest ecosystem host about two- thirds of the earth's biodiversity however, little information is known about this rich biodiversity especially the factors that link species richness and distribution. In this study, the richness and distribution of amphibians were investigated. In this regard, systematic sampling was used as a method to determine amphibian species richness and distribution along the three levels of elevation. Litter levels were also recorded to determine the effect of litter levels as ecological variable on amphibian's richness and distribution. The instruments used include GPS, ruler, a hundred meter line tape and compass. The result reveals a significant variation of amphibian's richness and diversity along elevational gradient. However there was a negative relationship between amphibian species and litter levels along the lower, middle and upper elevational levels.