Soil Properties beneath Ceanothus and Pine Stands in the Eastern Sierra Nevada
- Dale W. Johnson
Soils and soil solutions were collected from adjacent ceanothus (Ceanothus velutinus Dougl.) and Jeffrey pine (Pinus jeffreyi Grev. & Balf) stands in Little Valley, Nevada. It was hypothesized that excessive N fixation by ceanothus, like red alder (Alnus rubra Bong.), causes accelerated nitrification, NO−3 leaching, and soil acidification. This hypothesis was not supported. Comparisons of soils from five paired ceanothus-pine plots showed that ceanothus soils not only had greater C and N concentrations, but also greater cation-exchange capacity, base saturation, and exchangeable Ca2+, Mg2+, and K+ than pine soils. There were no significant differences in extractable P or SO2−4 overall, although there were differences at some sites. Extractable P levels were quite high relative to more humid forest soils, whereas extractable SO2−4 levels were very low. Soil solutions from ceanothus, pine, and a riparian mountain alder (Alnus tenuifolia Nutt.) stand were characterized by low NO−3 concentrations, circumneutral pH, and high base cation, HCO−3, SO2−4, Cl−, and Si concentrations. The chemical composition of nearby streamwaters was similar to that of soil solutions with respect to NO−3, pH, HCO−3, and base cation and Si concentrations. Streamwater SO2−4 and Cl− concentrations (≈ 3–17 µmolc L−1) were more than an order of magnitude lower than those in soil solutions (≈ 150–270 µmolc L−1), however, indicating that soils adjacent to the stream had little influence on its chemistry. Thus, the NO−3 pulse (from <1 to ≈ 30 µmolc L−1) measured in both streamwaters and ceanothus soil solutions during snowmelt most likely originated from the melting snowpack.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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