Physicochemical properties and water holding capacity of forest soil in Liaohe upstream

The difference in soil physicochemical properties between forest types determines forest soil quality, water and soil conservation function to a certain extent, and is the key to soil quality evaluation and forest ecological function improvement.However, similar research is still lacking in Liaohe upstream.In this study, five typical forest types including pure forest of Pinus tabulaeformis, Larix gmelinii, Pinus sylvestris, mixed coniferous forest and mixed conifer with broad leaf forest were selected to conduct field survey and soil sample collection.A total of 14 physicochemical properties were measured, the differences among different forest types were compared, and the soil quality evaluation indexes were constructed.The results showed that the soil physicochemical properties in different forest types were significantly different.The maximum moisture content (36.6%), capillary water storage capacity (34.3%) and field water holding capacity (34.3%) of Pinus sylvestris forest were significantly higher than those of other forest types.The Pinus sylvestris forest was with the best soil physical properties, and good soil porosity and water holding capacity; while for the soil of Pinus tabulaeformis forest, the alkali hydrolysable nitrogen (85.2 mg · kg^-1), total phosphorus(0.18 mg · kg^-1), available phosphorus (26.9 mg · kg^-1), total porosity (43.9%) and water content (10.7%) were significantly lower than those of other forest types.The Pinus tabulaeformis forest was with poor soil nutrient status with poor fertility and low soil porosity.The soil quality index (SQI) values of the five forest types were relatively low, ranging from 0.11 to 0.76.Among them, 58.6% of the soil quality was medium or above, which was in the order of Pinus sylvestris forest (0.52)>Larix gmelinii forest (0.45) >Pinus tabulaeformis forest (0.44)>mixed coniferous forest (0.42)>mixed conifer with broad leaf forest (0.41).Therefore, it would be feasible to adjust and improve the physicochemical properties of forest soil based on key species.When evaluating the soil-related ecological service functions of forest types in Liaohe upstream in the future, forest types differences are needed to be fully considered.As for coniferous species, it is recommended to give priority to Pinus sylvestris, Larix gmelinii should be used appropriately and Pinus tabulaeformis should be restricted.In terms of forest types, mixed conifer and broad leaf forest are advocated, especially pine and oak mixed forests.