Lead distribution and cycling in forest-rice agroforestry systems in Northern Hunan

In hilly regions of southern China, rice plants are often cultivated with forests to make up of a forest-rice agroforestry system, where the forests are often occupied in upper parts and the rice paddy fields in lower parts.... [ view full abstract ]

In hilly regions of southern China, rice plants are often cultivated with forests to make up of a forest-rice agroforestry system, where the forests are often occupied in upper parts and the rice paddy fields in lower parts. In this present study, the distribution and dynamic characteristics of Pb were investigated in two types of forest-rice agroforestry systems and one rice paddy system (without forests, as a control) in Taoling Forest Farm, Human Province of China from late May to early September in 2012. The main objectives of this study were to examine transport patterns of Pb in different components of hydrological process and to calculate input-output budgets of Pb in the forest-rice systems. The results showed that (1) Of the total amount of Pb input into the systems by precipitation, about 30.5%~47.3% of them was retained in forests, -6.9%~-7.5% was in ponds, 17.8%~21.2% was in rice paddy-fields, and the rest was exported from the systems through rice paddy field water, rice-straw and rice-grain harvestings; (3) Because of the difference of canopy density of forests between the forest-rice agroforestry systems, the Mixed forests-rice paddy system exhibited the highest capacity to retain the Pb , the next was Pine forests-rice paddy system, and the control site had the minimum value of capacity. It seemed that the retaining capacity of Pb was positively related to the canopy density of forests. The canopy density of forests and different forest types affected distribution, transport and output of Lead in the forest-rice agroforestry systems.