This paper proposes an effective subtree merging based data collection algorithm for wireless sensor networks (WSNs), named as SMDC algorithm, which can be applied in a new kind of applications in WSNs, i.e., area query application. The SMDC algorithm can prevent unnecessary energy consumption in ancestor nodes for routing through the union of disjoint sets for different subtrees in the network. The SMDC algorithm includes four phases. Firstly the cluster trees are constructed respectively in the target area. Then the disjoint node sets for each subtrees will be found; thirdly the disjoint subtrees are connected via the closest node between two subtrees; and the last phase is to disconnect the subtrees which have been connected to a new tree branch from their previous tree structure. This paper also presents the simulation to compare the SMDC algorithm with some related works including conventional minimum spanning tree algorithm. Simulation results show that the SMDC algorithm can reduce the redundant energy consumption and the number of hops which results in the reduction of total energy consumption. Especially, it is more efficient as the number of sensor nodes in a target area increases.
