CORRELATION OF SOIL DEVELOPMENT AND LANDSCAPE POSITION WITH FALL LEAF COLORS

Fall leaf color change is a spectacular and economically important event in the Eastern United States. During leaf death, or senescence, the green pigment chlorophyll is degraded and “unmasks” the underlying orange carotenoids and yellow xanthophylls. Unlike yellow and orange pigments however, red anthocyanins are newly synthesized during fall leaf senescence. The biological function of this energy-expending production of red pigments is debated and poorly understood. It has been anecdotally observed that yellow-senescing species tend to inhabit floodplains, while red-senescing species tend to inhabit upland areas. In this study we hypothesize that soil properties are related to anthocyanin production. In order to test this hypothesis, we quantify the proportion of red-senescing and yellow-senescing species along a topographic transect across a floodplain to an adjacent valley divide in the UNC-Charlotte nature preserve in Charlotte, North Carolina. We also describe a soil catena along this transect and correlate soil properties with the amount of anthocyainin production in two species: Liquidambar styraciflua and Acer rubrum as determined by collecting leaf samples during senescence. Our results indicate a higher proportion of red-senescing species in upland areas that are characterized by soils with well-developed Bt horizons overlying saprolite. We document a higher proportion of yellow-senescing species in footslope and levee landscape positions. Soils in these areas are characterized by relatively weakly-developed cummulic B horizons that suggest episodic sediment deposition. Anthocyanin production within both L. styraciflua and A. rubrum was positively correlated with soil nutrient availability along our transect. The results from this study indicate that anthocyanin production within a species is likely dependent upon soil nutrient availability, which varies throughout the landscape as a function of geomorphic processes.