Many Spatial Decision Support Systems (SDSSs) have been developed for environmental and natural resources decision-making in recent years. However, an important limitation of the SDSS applications is that they are not interoperable. Several issues prevent the further development of SDSS applications such as the incapability of sharing and reusing existing heterogeneous data and geoprocessing. This paper proposed a framework of web services-based interoperable SDSSs using geospatial semantic technologies such as ontology, web services and service-oriented architecture for decision-making. The proposed interoperable SDSS enables decision-makers to reuse and integrate geospatial data and geoprocessing from heterogeneous sources across the Internet. Based on the proposed framework, a prototype to assist in protective boundary delimitation for Lunan Stone Forest Conservation has been implemented to demonstrate how ontology-based web services and the services-oriented architecture (SOA) contribute to the development of interoperable SDSSs.