We examine modern pollen, vegetation and climate relationships for the arcto-boreal region of North America using isopollen maps, scatter diagrams and response surfaces. These analyses are based on an array of 1119 modern pollen sites extending from Alaska to Greenland (excluding the Pacific-Cordillera region of western North America) and north of $42\ circ N$ latitude. The pollen sum consists of thirty-one taxa selected for their abundance on the modern landscape or significance as indicators of particular vegetation types. Response surfaces were calculated using a locally weighted-average procedure in order to display the percentages of the various taxa as a function of one to three climate variables. The isopoll maps accurately reflect taxa abundance and range limits, although the actual percentage at these limits may vary. Pollen of the major boreal taxa have optima at $10-20\ circ C$ and dry (Pinus), moist (Abies) and intermediate (Picea) values of precipitation. Monospecific pollen taxa and those where the species have similar ecologies show a simple climate optimum, whereas pollen taxa with several species, such as Betula, show multiple optima. Each boreal taxon, even those with similar ranges, has a unique surface, suggesting that community level responses to climatic change, whether past or future, are likely to be complex and variable throughout North America.
