Comparison of plant phosphorus content and soil inorganic phosphorus classification characteristics between karst and non-karst forests

【Objective】To compare phosphorus content in leaves，roots，litters of plants and soil phosphorus content and inorganic phosphorus classification characteristics in karst and non-karst forests in the Lijiang River basin of Guangxi and to provide scientific reference for understanding the phosphorus cycle of karst forests and promoting restoration of degraded karst forest ecosystem.【Method】Sample plots were set up in karst and non-karst forests in the Lijiang River basin. Plant leaves，roots and litters were collected to determine phosphorus content，soil samples were collected to determine content of total phosphorus，available phosphorus and each component of inorganic phosphorus and analyze physical and chemical properties such as soil pH，water content，carbon content and nitrogen content. The correlation between plant phosphorus and different soil components was analyzed，the difference in phosphorus between karst and non-karst forests was determined and the main reasons were studied.【Result】The contents of total carbon，total nitrogen，dissolved organic carbon，dissolved nitrogen，and carbon to nitrogen ratio in karst forest soil were significantly lower than those in nonkarst forest soil（P<0.05，the same below）；phosphorus content in roots and litters of plants in karst forest（0.03% and 0.04%）were significantly lower than those in non-karst forest（0.05% and 0.11%）；total phosphorus content and available phosphorus content in karst forest soil were 231.0 and 2.2 mg/kg，respectively，which were significantly lower than those of non-karst forest soil（total phosphorus 609.0 mg/kg and available phosphorus 9.3 mg/kg）；ferron-bounded phosphorus（Fe-P），occluded phosphorus（O-P）and calcium-bounded phosphorus（Ca-P）were all significantly different between the two types of forest；inorganic phosphorus in karst forest soil was mainly Fe-P，while the inorganic phosphorus in non-karst forest soil was mainly O-P；phosphorus content in leaves of karst and non-karst forest plants were significantly correlated with the content of soil available phosphorus and aluminum-bounded phosphorus（Al-P）；and the phosphorus content in roots were significantly or extremely significantly（P<0.01）correlated with the content of soil total phosphorus，available phosphorus，Fe-P，O-P and Ca-P；while the phosphorus concentrations in litters were extremely significantly negatively correlated with the content of soil total phosphorus and available phosphorus，and were significantly positively correlated with Fe-P.【Conclusion】The differences in soil total and available phosphorus content and inorganic phosphorus classification between karst and non-karst forests in the Lijiang River basin may affect soil phosphorus acquisition and absorption in karst and non-karst forests vegetation，thus leading to variations of phosphorus content in plant leaves， roots and litters.