The Effects Of Fire On Water Quality And Soil Physic-chemical Properties

Soil hydro-physical and chemical properties under Betula platyphylla forest, Larix gmelini forest and Betula platyphylla - Larix gmelini mixed forest on Songling of Great Xing'an Mountain during the same year of high intensity fire were studied.and the concentration changes of ions (Ca²⁺,SO₄^2- , Na⁺, Mg²⁺, NO₃^-, F^-, Fe, K⁺, Cl^-, Br^-) were measured in burned and unburned streams in Songling forest region from May to Oct, show as a result:Results show that the most ions flux were higher in burned stream than that in unburned stream during the sampling period, and the greatest concentrations of most ions transported from burned stream occurred in July. After fire, the most amplitude chemical ion was Ca²⁺, whose average concentration was 5.50 mg/ L more than that in unburned stream, and the total concentration of every chemical ion presents a trend Ca²⁺>SO₄^2->Na⁺>Mg²⁺>NO₃^->F^-and the average concentration of Fe, K⁺, Cl^-, Br^- had decreased. SO₄^2- had the largest loss among these anions, and followed by NO₃^-. Overall, the increase degree of cation was greater than that of anion after burning.In the three type forests, soil properties of 0-10 cm soil layer were better than 10-20cm soil layer, and fire did not change the pattern with deepth, but increased the difference obviously. These properties included soil bulk density, soil porosity, soil moisture capacity and soil water storage capacity. Comparement of three forest types, in unburned forest, soil aeration of Betula platyphylla forest was better than Larix gmelini forest, while in burned forest, soil aeration of the latter was better than that of the former forest type. Soil average moisture capacity of Larix gmelini forest was higher than that of Betula platyphylla forest, while soil average water storage capacity of the former was lower than that of the latter forest type. Overall, soil properties, such as soil organic matter, soil moisture capacity and soil water storage capacity of Betula platyphylla and Larix gmelini forest were better than that of Betula platyphylla - Larix gmelini mixed forest. The high intensity fire increased the soil bulk density, and decreased soil average porosity and soil moisture capacity for the three type forests.In the burned and unburned three type forests, soil pH, soil organic matter, soil N , soil P, soil K had the same variation trend with increasing soil depth, i e, soil pH, soil organic matter, soil nutrient increased. Fire did not change the pattern with deepth, but decreased the difference obviously. After fire, soil pH decreased, while soil available P increased in the three type forests. The soil average organic matter, soil average N and soil average total P decreased in Betula platyphylla forest and Larix gmelini forest, and that increased in Betula platyphylla -Larix gmelini mixed forest. The soil average K increased in Betula platyphylla forest and Larix gmelini forest, and that decreased in Betula platyphylla - Larix gmelini mixed forest.Comparement of three forest types, in burned and unburned forests the soil properties of Larix gmelini forest was better than that of Betula platyphylla forest, and Betula platyphylla forest was better than Betula platyphylla - Larix gmelini mixed forest, and these properties include pH, soil organic matter, soil nutrient. But the chemical properties had improved after fire.