Seasonal variations in phosphorus fractions in semiarid sandy soils under different vegetation types |
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Authors: | Qiong Zhao De-Hui Zeng Zhi-Ping Fan Zhan-Yuan Yu Ya-Lin Hu Jianwei Zhang |
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Institution: | aDaqinggou Ecological Station, Institute of Applied Ecology, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, Liaoning 110016, China;bUSDA Forest Service, Pacific Southwest Research Station, 3644 Avtech Parkway, Redding, CA 96002, USA |
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Abstract: | We investigated the seasonal patterns of soil phosphorus (P) fractions under five vegetation types – Ulmus macrocarpa savanna, grassland, Pinus sylvestris var. mongolica plantation, Pinus tabulaeformis plantation, and Populus simonii plantation – in the southeastern Keerqin Sandy Lands of China. The measured P fractions (0–20 cm depth) included: soil total P (TP), total organic and inorganic P (TPo and TPi), bicarbonate extractable organic and inorganic P (BPo and BPi), microbial biomass P (MBP), and in situ resin-adsorbed P (resin-P). Soil TP and TPo concentrations in the savanna and grassland were significantly lower in summer than in spring and autumn. However, they were relatively stable in three forest plantations. Soil labile P fractions showed a significant seasonal pattern under all vegetation types with the peak in summer, except soil MBP that was constant in the savanna and grassland and BPo that decreased over time in the savanna. This pattern of labile P fractions was attributed to a combination of seasonal climatic changes, low P availability, as well as the biological controls of soil P transformation in the study area. Litter decomposition played a key role in soil P availability. The monthly resin-P released from litter decomposition in summer was 2.6–7.4 times greater than in other seasons, and was 1.7–3.4 times of that in the 10 cm depth soil. Concentrations of soil P fractions were obviously affected by vegetation type. The savanna had the highest total P and MBP concentrations and the P. tabulaeformis plantation had the highest BPi and resin-P among all vegetation types. Among forest plantations, P. simonii plantation had the highest total P and MBP. These results suggest that U. macrocarpa savanna is the best system conserving soil nutrient (particularly P) stocks and microbial activity, followed by the grassland and P. simonii plantation, while the pine plantations are the worst. |
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Keywords: | Forest plantations Litter decomposition Savanna Semiarid region Soil P dynamics |
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