Quiz 21: Landscape Ecology

Landscape ecology is the study of structure of landscape, processes influenced by the landscape, and changes in landscape over the time. Landscape is made up of different types of ecosystems. The study of an ecosystem is called ecosystem ecology. It involves study of the interactions between the biotic and abiotic components of the ecosystem. An ecosystem is made up of a community. A community is a group of species occurring in a geographical area and interacting with each other. Thus, the scale of study increases from the community to an ecosystem and finally to the landscape. The study of a forest may be carried out differently by a community ecologist, an ecosystem ecologist and a landscape ecologist. An ecosystem ecologist may have following queries: • Abiotic components of the forest ecosystem • Biotic components or the species of plants and animals in the forest ecosystem • Interactions between the biotic and abiotic components of the ecosystem • Productivity of the ecosystem • Decomposition and nutrient cycling in the ecosystem A community ecologist may have following queries: • Community structure and the trophic levels • Types of food chains and food webs in the forest • Ecological succession over a period of time • Species abundance and diversity A landscape ecologist may have following queries on the forest: • Shape, size, number, and location of the forest patches in the landscape • Origin of the forest landscape, changes in the landscape over time due to natural and man-made processes • Composition of the forest landscape • Effect of landscape structure on the populations of species

Mann-Whitney test is a statistical test that ranks the observations of two populations and uses the ranks for statistical analysis. The amount of organic matter or detritus in streams flowing through the deciduous and the coniferous forest can be compared by the Mann-Whitney test. The rejection of null hypothesis depends on the comparison between the calculated value and the critical value of the Mann-Whitney statistic. However, any conclusions made on the basis of this test have to be verified by proper ecological studies. This is because the test is based on the rank or order of the observations and not on the actual value of the observation. Also, the sampling of detritus was done from two streams, one from the deciduous and another from the coniferous forest. The sample should include a sufficient number of streams from each forest patch to make accurate conclusions. Hence, one cannot make precise conclusions regarding the variability in amount of detritus found in the streams flowing through the deciduous and coniferous forest patches.

The relationship between patch perimeter and patch area influences the patch structure in a landscape. Long perimeter and a small area is a characteristic of an elongated patch. Such patches have a longer edge compared to the interiors. Similarly, increase in patch area increases the patch interiors decreasing the edge. The edges of habitats with different ecosystems on either side have been referred to as ecotones. The proportion of species living in the ecotones depends on the area of the habitat patch enclosed by the ecotones. A smaller area with a large perimeter leads to longer ecotones thus increasing the proportion of inhabitant species such as birds. Thus elongated habitats possess more ecotones compared to a circular patch. A habitat patch with a larger area has a large interior and comparatively less edge. Hence such areas have more species of birds associated with forest interiors.