QGIS: split polygon features with different polygon layer

Question

I have two polygon layers. One containing vegetation features and one containing the borders of different monitoring areas. I want to calculate the total size of different vegetation types per monitoring area, however, the vegetation features often go over the borders of two areas (see example below, with red monitoring area border).

I want to split the vegetation features that cross borders so that they fit to the borders of the monitoring areas. How can that be done? I found the split line by line tool in QGIS but couldn´t find the same for polygon. Splitting manually is not an option as I have many thousand features.

Answer 1

You can use "Vector overlay tools > Intersection". It also will split vegetation polygons by monitoring area polygons.

You may think of using Union tool. But if a part of any monitoring area polygon doesn't overlap vegetation areas (little white area in the image below), that part is added to result area as if it is a part of vegetation areas.

In that case, 'Intersection' tool is more suitable than 'Union' tool. Otherwise, Union tool can lead to incorrect results in post-processing.