Fig. 5

Hypothetic schemes of degradation (a) and restoration (b) processes for xerophilous forests. Three sub-figures are shown in each panel (a, b): at the top, there is a cup-ball scheme illustrating a threshold between alternative states (grey balls I and II); in the middle, the system is illustrated in a horizontal plane; whereas at the bottom, the system is illustrated as a vertical profile. In a, decades of livestock-forestry overuse causes a significant reduction in the plant cover of a hypothetic ecosystem (ball I), triggering soil erosion processes (e.g. soil, organic material, and water loss). Consequently, the system cross a threshold to an alternative state (ball II). In b, the addition of branch barriers would trigger ecosystem recovery (e.g. transition of ball Rt between state II to state I). Branch barriers obstruct or reduce water run-off (increasing soil infiltration), increasing the retention of sediment, organic matter (e.g. litter) and seeds, generating favourable microsites for the emergence and survival of new tree individuals (e.g. seedlings and saplings)