No short-term change in soil properties following four-fold litter addition in a Costa Rican rain forest
We experimentally manipulated forest floor litter to investigate the influence of litter quality and quantity on soil properties over the short-term (weeks to months) in a wet tropical forest in NE Costa Rica. The study included old growth forest on high fertility soils, old growth forest on low fertility soils, and secondary forest on intermediate fertility soils. Forest floor litter was removed from a 16 m2 area and added to an adjacent 4 m2 area in March 2003, resulting in a one to four-fold increase in the annual litter input to the forest floor. We created three addition, three removal and three control plots per forest type. We measured treatment effects on variation in soil moisture, temperature, pH, and Bray-1 P (plant available) over a 5-month period that captured the dry-wet season transition. Litter manipulation had no effect on any of the soil properties measured during the 5-month study period. Significant variability through time and a similar temporal pattern across the three forest stands suggest that climatic variability is driving short-term patterns in these soil properties rather than seasonal inputs of litter. In general, soils were warmer, drier and more basic with higher available P during dry season months. Even in wet tropical forests, small variability in climate can play an important role in soil dynamics over periods of weeks to months. Although litter manipulation did not influence soil properties over the 5-month study period, a longer lag may exist between the timing of litter inputs and the influence of that litter on soil properties, especially plant available P.
KeywordsBray-1 P La Selva Litter manipulation pH Phosphorus Seasonality Soil moisture Temperature
We would like to thank Deborah A. Clark and David B. Clark for providing site-level data for the two old growth sites included in this study. This research was funded by the Andrew W. Mellon Foundation and the University of Virginia. Support for the Carbono Project plots and the long-term litterfall measurements in them was provided by the National Science Foundation (DEB-9629245), the Andrew W. Mellon Foundation, and Conservation International's team Initiative.
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