Effects of Pinus sylvestris var. mongolica afforestation on soil phosphorus status of the Keerqin Sandy Lands in China |
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| Authors: | Q Zhao DH Zeng DK Lee XY He ZP Fan YH Jin |
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| Institution: | aInstitute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;bGraduate University of Chinese Academy of Sciences, Beijing 100039, China;cDepartment of Forest Sciences, Seoul National University, Seoul 151-921, Republic of Korea |
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| Abstract: | Few studies have considered the effects of afforestation on soil phosphorus (P) status in semiarid regions such as the Keerqin Sandy Lands in China, though plantations have been widely established on P-deficient sandy soils to control wind-induced desertification. Phosphorus fractions and acid phosphomonoesterase (AP) activities were compared in the rhizosphere and bulk soils (0–5 and 5–20 cm) under Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) plantations of different ages (15, 22, and 30 years old) and in bulk soils under grasslands to understand soil P behavior with Mongolian pine plantation development and to find out major factors controlling soil P cycling. Stand age and rhizosphere processes had similar effects on the soil P fractions. Labile inorganic P and phosphate absorbed on aluminum and iron oxides were not affected by stand age and rhizosphere processes. Rhizosphere effects of Mongolian pine accelerated the mineralization of organic P by increasing microbial and AP activities. Soil P properties in bulk and rhizosphere soils changed similarly with plantation development. In the first 15 years after afforestation, total organic P, calcium phosphate, labile organic P, microbial biomass P (MBP) concentrations, and AP activities were reduced sharply. About 73% of the reduction in total P came from mineralization of organic P and 24% came from solubilization of calcium phosphate. From 15 to 22 years onward, soil total organic P and calcium phosphate decreased gradually and labile organic P, MBP, and AP activities increased greatly, whereas total inorganic P remained constant. The results suggest that soil P pool was depleted with Mongolian pine plantation development, especially in the early stage. As the dominant form of soil P, organic P was the main source of available P and associated biological processes controlled soil P cycling under Mongolian pine plantations. To ensure sustainability of pine plantations, it is imperative that soil fertility is conserved by adding fertilizer, thinning, and protecting litterfall. |
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| Keywords: | Rhizosphere effects Mineralization of organic phosphorus Soil phosphorus depletion |
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