Evaluation of Multiple Forest Service Based on the Integration of Stand Structural Attributes in Mixed Oak Forests

In order to understand forest services at stand level through the integration of structural attributes, forest structures in three main stand types were analyzed based on various structural attributes relating to the services of habitat conservation, timber production and soil water conservation in Loess Plateau, China. Forty sample plots with similar site and environment conditions were established in three types of oak stands. Twenty-two indexes such as stand density, mean DBH, mean height, etc., were selected to analyze the relationship between structural attributes and forest service. With a core set of structural attributes selected by principal component analysis, the link between the service and structural attributes and the compatibility between each service was analyzed using correlation analysis. The results show that the oak-broadleaf mixed forest has the highest structural complexity index (SCI), indicating the best habitat conservation among others, while the oak-pine mixed forest and pure oak forest have the highest timber value in different scenarios of timber price, indicating the largest potential for timber production. Little differences were found between stand types regarding the indicators for soil water conservation. The structural attributes that had a positive correlation with habitat conservation (e.g., number of shrub species, species richness of canopy layer, the proportion of broadleaves and snag density) were identified to be negative for timber production; while the attributes that had a positive correlation with timber production (e.g., stand density and proportion of pine and oaks) were found to be negative for habitat conservation. The results of the trade-off analysis showed that timber production tends to be conflicting with the other two non-timber forest services. In order to enhance the provisioning of multiple services, it was suggested to implement the interventions that could balance these services, such as structural retention and single-tree selective logging. This study could contribute to the theoretical base for the decision making in the multi-purpose sustainable management of oak forests in China.