Another fraction of the ANPP variance relates to biotic features
of ecosystems (Huxman et al., 2004; Webb et al., 1983). Functional
and structural traits of vegetation, such as canopy type, species
diversity, or root depth, determine water use efficiency and, hence,
ANPP at the regional scale. Species diversity increases the probability
of including different plant functional types and a broader
range of strategies to gain resource use efficiency (Chapin et al.,
1997). Lloret et al. (2007) showed how the impact of dramatic
water shortage on vegetation greenness depends on the presence
of species able to cope with drier conditions.