p:tree ajax events are updating other components - ajax

Question

I have a problem with ajax events of the p:tree component
Here's the xhtml code:
<form id="form1">
<!-- Other components -->
<p:panel id="panel1" binding="#{panel1}"
header="..." toggleable="true" toggleSpeed="500"
collapsed="false" dynamic="true"
rendered="#{service.checkMethod(...)}">
<div class="column">
<p:tree id="treeId" value="#{tree.root}"
var="node" selectionMode="single"
rendered="#{tree != null}"
selection="#{flowScope.selectedNode}"
widgetVar="treeId"
process="tree">
<p:ajax event="select" process="#this"
update="#this :#{anotherPanel.clientId} :#{anotherPanel2.clientId}"
listener="#{service.onNodeSelect}" oncomplete="setSelectedNode()" />
<p:ajax event="expand" process="#this" listener="#{service.onNodeExpand}" />
<p:ajax event="collapse" process="#this" listener="#{service.onNodeCollapse}" />
<p:treeNode>
<h:outputLabel value="#{node.attribute}" />
</p:treeNode>
</p:tree>
<h:outputLabel
value="Empty"
rendered="#{tree.isEmpty()}" />
</div>
</p:panel>
<!-- Other components -->
</form>
The panel1 rendered attribute has a method which will create a new tree every time is updated, but somehow all the ajax events on the tree are calling that method. Even the expand and collapse update, which doesn't have the update defined, is doing that.
I already tried putting global="false", immediate="true", using different type of updates and process, on all the ajax events, or putting other panels between the tree and the panel, but it has the same effect. I searched all my files with Eclipse, to make sure that this method isn't called elsewhere, but it's only used here.
Is there a way to prevent the tree ajax events from re-rendering the above panel?