Question: Are succulents counted as a woody species when measuring vegetation heights?
Succulent plant species are considered to be woody in contrast to herbaceous because their function is more similar to woody vegetation than herbaceous vegetation in many applications of these data.
From a wildlife viewpoint:
Some succulents are low-growing (some Opuntia), and while others are taller (Cylindropuntia, other Opuntia, Yucca, some Agave), but nearly all are stout and provide ample protective cover via spines, thorns and mass for wildlife. This cover is more similar to the cover woody plants provide than herbaceous plants.
From a wind erosion viewpoint:
Many succulent species provide considerable obstruction to wind due to their mass and relative inflexibility. In fact, it may be possible for succulents to provide even more wind obstruction than some woody plants (especially deciduous species in the off-season).
From a biology/physiology viewpoint:
Although not all succulents produce true wood (monocots like Yucca and Agave do not produce secondary xylem, and thus are technically not “woody”), the dense nature of vascular bundles in dead monocot stems function similarly to standing dead woody material. This may provide as much protective cover for wildlife and soil erosion as woody material would provide, although the monocot material may not persist as long on the landscape.