PARENT SESSION
Poster Session #19: Nutrient Cycling.
Tuesday, August 7, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
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Yuccas as islands of fertility in Great Plains grasslands.
Mendoza, Arlene1, Wedin, David2, 1 2
ABSTRACT- Although yuccas (Yucca glauca) are abundant in northern Great Plains grasslands, their effects on soil carbon (C) and nitrogen (N) have received little attention. We studied two yucca populations in western Nebraska, one in sand hills prairie, the other on silty clay loam with mixed grass prairie. The population density and size distribution of yucca clumps were measured at each site. At the sand hills site, yuccas comprised 9.5% of the vegetative cover and 50% of aboveground biomass, while at the mixed grass site, values were 12.3% and 73%. Soil samples were collected under yuccas and in adjacent grassland, and analyzed for mineral N (NO3 and NH4), total carbon (C), and soil isotopic C (13C/12C) signature. Total soil C increased 22%, NH4 25%, and NO3 280% under yucca clumps compared to adjacent grassland (averages across both soil types). Because yuccas are C3, soil C derived from them has a unique signature in these C4-dominated grasslands. Carbon isotopic analysis suggest that 26% of the soil C under yuccas at the mixed grass site and 17% at the sand hills site has a yucca origin. Thus, the effect of yuccas in these two grassland types (increased N availability and soil organic matter) is similar to that reported for trees and shrubs in other semi-arid grasslands and savannas.
KEY WORDS: yucca, grassland, nitrogen, carbon