The goal of this thesis is to provide an adaptable protocol stack architecture for data fusion applications. Towards the goal, this thesis presents the design of SensorStack, that addresses three key issues. First, towards network-level adaptability, how to dynamically adapt the placement of a fusion application task graph on the network? We have designed a distributed role assignment algorithm and implemented in the context of DFuse, a framework for distributed data fusion. Second, towards node-level adaptability, how to facilitate cross-layering on a node to foster agile adaptation of a node's behavior commensurate with the network-level changes? SensorStack provides information exchange service (IES) as a framework for cross-module information exchange. Finally, towards tying the network and node level adaptability together, control data published in IES needs to be shared across the network. SensorStack uses a probabilistic broadcast based dissemination service (IDS) for control data. We implement SensorStack in TinyOS and Linux to validate the SensorStack design, and use simulation experiments to investigate its network performance. Experiments demonstrate the utility of adaptability in SensorStack to increase application longevity.