Here, the sensor network under consideration has a hybrid network architecture composed of fixed and mobile sensor nodes. From a communication perspective, mobility of nodes can be handled either by the medium access control (MAC) protocol [7] at the data link layer or by the routing protocol in the networking layer. Cross-layered approaches [8] are also proposed for mobility management. This work focuses on handling mobility in the _network layer_, which is implemented by the _routing protocol_. The design of our geocasting protocol and mobility handling mechanism are independent of the underlying MAC protocol although we use some cross-layer information provided by MAC layer in the network layer such as localization information. After construction of the _geocast structure_ (_i.e._, routing trees plus local coverage areas of sensors and sinks in the network layer), mobile nodes move, which changes the structure of the trees and local coverage areas. In such a WSN, it is crucial to support mobility of nodes by keeping the routing trees and local coverage areas up-to-date for efficient query dissemination. Since the global updating mechanism discussed in our previous work [5, 6] may be costly, there is a need for a mechanism to locally associate/re-associate mobile nodes and their child nodes to new parent nodes and update local coverage areas of sensors and sinks. In this work, we propose a mechanism, called _local updating_, which detects the changes in the neighborhood of a mobile node and updates only the parts of the geocast structure that are affected by mobility. Managing node mobility in a tree-based forwarding scheme creates an extra overhead in the network. In this paper, the reduction of the message overhead and the overall energy consumption of the WSN is the foremost goal as well as reliability of geocasting of queries. Hence, we discuss what is a better method to handle mobility in tree-based routing of queries: Periodic _global updates_ initiated by sinks or _local updates_ triggered by mobile sensors. The proposed local updating mechanism utilizes _beacon_packets sent by mobile nodes to keep track of topology changes. A _beacon_ packet is only forwarded to the one-hop neighbors of a mobile node in local updating; on the other hand, a _hello_ packet sent by a sink is flooded all over the network in global updating. The distinctive features of the proposed local updating solution are:  
1. Sending beacon packets from mobile sensor nodes instead of hello messages from every sink node,
2. The use of proactive procedures to speed up the parent-child re-association and coverage area updating phases,
3. A reduced impact of the messaging overhead to manage node mobility by resorting to local updating procedures. In the remainder of this paper, we first discuss the related works in Section 2. For completeness, in Section 3 we briefly explain our previous work, the local coverage area based geocasting of queries and how we construct and maintain local coverage areas with the global updating mechanism. Section 4 gives the details of our new method, _local updating_ mechanism. We evaluate the performance of global and local updating mechanism in Section 5. To compare global and local updating mechanism, we test their performances in terms of routing accuracy and communication overhead for different scenarios where we vary the network size to see the scalability of the methods, the mobility rate (_i.e._, number of mobile nodes) and the mobility speed to see the effects of mobility on the performance of the methods. Finally, Section 6 draws the conclusions.