Seasonal Variation And Environmental Implication Of Dissolved Organic Carbon In Fruit Garden Soils Of Karst And Non-Karst Area, Maocun, Guilin, China

Soil dissolved organic carbon (DOC) is an important soil carbon pool and is active organic carbon pool in soil and aquatic environment. Because of its specialties of instability and the environmental sensitivity, DOC has been the research focus of the global carbon cycling. As the biggest carbon pool in the world, karst terrain covers 12% the world area and approximately 1/3 land of China. And karst terrain occupies 6.1×10⁷ billion tC, is 99.55% of the whole world carbon pool.Take three kinds of tree in Karst area and non-Karst area (Castanea mollissima, Ginkgo biloba, Prunuspersica) for study objects. We study the seasonal change of the soil dissolved and its effects on trees.The content of soil dissolved carbon is higher in autumn and summer than that in winter and spring. Thereinto, the max DOC is located Castanea mollissima, top soil (0-20cm) in Karst area, up to 195.40mg·kg^-1, the min DOC is located Ginkgo biloba, subsoil (20-50cm) in Karst area, only 4.70 mg·kg^-1. And double apices in all samples.Both top soil and subsoil are the same change law. After all, the content of DOC in top soil is higher than that in subsoil. And according to different tree, Castanea mollissima is the max, Prunuspersica is the rain in Karst area, Ginkgo biloba is the max, Prunuspersica is the min in non-Karst area. The content of Doc in Karst area is 1.4 times more than non-Karst area.DOC and pH has the relation of negative (r0.05=-0.515, n=66 in Karst area, r0.05=-0.017, n=66 in non-Karst area), Soil organic carbon, total nitrogen, available nitrogen has the positive relation with DOC both in Karst area and non-Karst area. But the total phosphorous, available phosphorous, total potassium, available potassium, total calcium, available calcium are reverse with DOC in Karst area. But in non-Karst area, one impact is negative, that is available phosphorous, and the others are positive. Dissolution in summer and autumn is higher than that in winter and spring. Because of high temperature, soil respiration, rainwater, and the organic acid from leaves and the mineralization of soil organic matter, the dissolution of the test stone is vast. Microorganism is activity because of high temperature and a plenty of rain. Soil CO2 and rainfall are the reason of the dissolution. The dissolution in non-Karst area is 2.26 times than that in Karst area. The average in non-Karst area is 75.18mg per piece, and 33.31mg per piece in Karst area.