Soil biological P cycling becomes increasingly important during soil and ecosystem development, which are known to be influenced by soil forming factors. However, the majority of studies examining the impact of single soil forming factor rather the interactive impacts of multiple soil forming factors on biological P cycling, led to poor understandings on the biological P cycling in landscapes where various drivers of soil P cycling operate simultaneously. The interactive impacts of lithology and climate on biological P cycling were comprehensively evaluated using lithological and climatic gradients in the California Sierra Nevada and southern Cascades. Soils (0-5 cm and 5-15 cm depth) from twelve combinations of three parent materials (andesite, basalt, granite) and four climatic zones encompassing a wide range of MAP (330 - 1400 mm) and MAT (5.0 - 17.0 oC) were collected and analyzed for resin P (Presin), organic P (Po), microbial biomass P (Pmic) and total P (Pt), potential activities of acid phosphomonoesterase (ACP), alkaline phosphomonoesterase (ALP), and phosphodiesterase (PDE), as well as soil properties related to P cycling (pH, pedogenic secondary minerals, organic carbon [OC]).
Results/Conclusions
When grouped by lithology, correlations among Pmic and phosphatases and with edaphic and climatic variables (MAP, MAT) were lithologically specific. When grouped by biome, ACP and ALP but not PDE activities were most strongly related to OC. Lithology influenced Pmic, ACP and ALP activities more than climate, but the opposite was observed for PDE. This could be due to the different origins of these phosphatases given distinct plant species among the climatic zones. This study demonstrates that lithological and climatic influences on phosphatase activities and the relationships among phosphatase activities and soil variables (e.g., OC) depend on interactions of pedogenic factors of lithology and climate. Additionally, OC, Presin, and Po may not necessarily be the best predictors of phosphatase activities as is commonly proposed. Lithologic effects, as well as pedogenic minerals such as nanocrystalline Fe/Al-(hydr)oxides and aluminosilicates that integrate lithology and climate are proposed to enable a more comprehensive assessment of biological P cycling sensitive to large-scale ecosystem context.