Abstract: In 2004,a field investigation was made on the mycorrhizal infection rate,spore density,soil available phosphorus content,and soil phosphatase activity in the Guoqing No.1 (Citrus unshiu)/trifoliate orange (Poncirus trifoliata) and Guoqing No.4 (C.unshiu)/trifoliate orange (P.trifoliata) plantations,aimed to approach the correlations between the arbuscular mycorrhizal fungal growth on citrus roots and the available phosphorus content and phosphatase activity in rhizosphere soil.The results showed that the annual variation of mycorrhizal infection rate and spore density in the test plantations was in “Λ” shape,while that of soil available phosphorus content and neutral phosphatase activity was in “V” shape.The mycorrhizal infection rate was significantly positively correlated with spore density (P<0.01),and negatively correlated with soil available phosphorus content (P<0.01),indicating that higher spore density and lower soil available phosphorus content could accelerate the mycorrhizai infection on citrus roots.The pore density was significantly negatively correlated with soil available phosphorus content (P<0.01) while positively correlated with soil total and neutral phosphatase activity (P<0.01),suggesting that soil available phosphorus could inhibit the increase of spore density,while soil total and neutral phosphatase activity could stimulate it.The mineralization of soil organic phosphorus in citrus plantations was mainly depended on soil neutral phosphatase activity.

Key words: participatory appraisal, livelihood strategy, agriculture- animal husbandry ecotone, land use