The dynamic and thermodynamic characteristics of soil reactions catalyzed by soil enzymes under long-term fertilization in Loess Plateau Theoretical Investigation on Structure and Property of Abietic Acids in Rosin Thermodynamic and Kinetic Parameters for Adsorption of Nitrobenzene by Bamboo-Charcoal Water Storage, Sediment Reduction and Hydraulic Parameters as Affected by Vegetation on Earth Roads in the Gully Area of the Loess Tableland