PEATLAND SPECIES PREFERENCES - AN OVERVIEW OF OUR CURRENT KNOWLEDGE-BASE

The autecology of several peatland plant species has been studied on a wide variety of gradients that include elevation relative to the wate r table, surface water chemistry, mire margin to mire expanse, shade, and climate. The accuracy with which species' realized niches are defi ned and the ability to predict community structure as conditions chang e along gradients vary considerably between studies. Many studies have quantified species niche dimensions along individual gradients, and a lthough they have the ability to predict species abundance and distrib ution, they do not account for synergistic effects between gradients. Other methods analyze two gradients simultaneously producing rectangle s and ellipsoids, but these methods have limited predictive ability. A variety of ordination techniques are often used to analyze species pr eferences along several gradients simultaneously. However, with the ex ception of Detrended Canonical Correspondence Analysis, these methods have limited predictive ability because gradients are defined as ordin ation axes and it is difficult to analyze each gradient individually. Species response surfaces calculated along several gradients simultane ously offer a more accurate definition of species' realized niche dime nsions. Response surfaces can be used to predict baseline community st ructure along several gradients, but they do not integrate such biotic factors as competition and succession, as well as such disturbances a s fire, pollution, and peat harvesting.