The shadow effect of nurse-plants in arid and semi-arid systems is very easy to spot in the field. However, quantifying this effect spatially in terms of extent, scale, and granularity is challenging. Ideally, high-res photographs from above would be fantastic. Step-ladders are relatively viable, but an angle effect would be introduced because you not get directly overhead the shrub species.
Solution: Drones. I have seen Oblivion and read all about the various negative implications. However, there are also many well-described positive opportunities. I propose remote control drone use to snap photos of nurse-plants in deserts, over time and widely, to document their immediate effect on other plant species. Importantly, repeated measures provide the opportunity to map shifts over time with disturbance and a changing climate. Most models such as the low-end Parrot AR Drone 2 for $299 has an inbuilt 720p HD camera and a GPS addon. Now, if only I had that much pocket change in my NSERC grant. Birthday present perhaps. The images are directly to your smartphone or ipad. Image processing post hoc could be applied to calculate canopy cover and extent of facilitation effect on the annuals. Depending on the noise and height to field of view ratio needed to maintain good visibility, this tool could also be used to track small mammal use of shrubs as refuges.