Experimental plots
We considered comparing pure and mixed stands of oak and pine a suitable
approach to identify potential differences in species-specific
preferences for occupying (via root placement) certain geologic
substrates, rock fractures or soil depths, etc., when growing either in
intra- or inter-specific neighborhoods. We established 12 circular
experimental plots of 25 m diameter (four plots per stand type) along a
3.5 km long transect running parallel to a narrow watershed, where pine
and oak trees were evenly distributed in pure and mixed stands. By
simultaneously examining root distribution, plant leaf water potentials
and intra-annual soil and rock water availability, we were able to
isolate and describe specific geoecohydrological niches.