Do biological soil crusts determine vegetation changes in sandy deserts? Implications for managing artificial vegetation

Abstract

Abstract:Biological soil crusts (BSCs), which are widespread in arid and semiarid regions, such as sandy deserts, strongly influence terrestrial ecosystems. Once sand-binding vegetation has been established on sand dunes, BSCs are colonized and gradually develop from cyanobacteria dominated crusts to lichen and moss dominated crusts on dune surfaces. We conducted this study to determine if the occurrence and development of BSCs in the Tengger Desert could be used to determine sand-binding vegetation changes via altering soil moisture and water cycling using long-term monitoring data and field experimental observation. BSCs changed the spatiotemporal pattern of soil moisture and re-allocation by decreasing rainfall infiltration, increasing topsoil water-holding capacity and altering evaporation. Changes in the soil moisture pattern induced shifting of sand-binding vegetation from xerophytic shrub communities with higher coverage (35%) to complex communities dominated by shallow-rooted herbaceous species with low shrub coverage (9%). These results imply that BSCs can be a major factor controlling floristic and structural changes in sand-binding vegetation and suggest that the hydrological effects of BSCs must be considered when implementing large-scale revegetation projects in sandy deserts.

Review of the ecohydrological processes and feedback mechanisms controlling sand-binding vegetation systems in sandy desert regions of China

“…However, the SWC spatial distribution of windward topsoils was determined mainly by environmental features such as wind [64]. When deep-rooted shrub coverage decreased to <10%, the SWC at the deeper soil depths (1.5-3.0 m) was stable and improved compared to shallower soil depths [7,46].…”

“…The BSC and sub-soil layer depths increased as the years following revegetation increased, which led to an improvement in soil water availability in the topsoil [7]. Due to the low water-holding capacity of moving sand dunes, precipitation easily infiltrated into the deep soil layer and led to a higher SWC, which was close to field capacity below 2 m depth.…”

“…Therefore, the waterholding capacity of soils with different types of crusts was expected to increase in the following order: moss crusts > lichen crusts > algae crusts > cyanobacteria crusts [24]. The formation and development of BSCs also correlated with topography as the water holding capacity of the moss crusts that dominated the windward and hollow areas was significantly higher than that of the algae crusts, which mainly covered the leeward and crest areas [7,[21][22][23][25][26][27].…”

“…The presence of BSCs significantly increased topsoil water content when the one-off rainfall exceeded 5 mm, especially when the topsoil was covered by moss crust. However, there were no significant increases in topsoil water content with increasing rainfall [7]. Li et al [33] used the Limburg Soil Erosion Model to analyze topographic effects on BSCs in the sand-binding dunes.…”

“…Land desertification and soil erosion have also been shown to be regulated by sand-binding vegetation. Eco-hydrological processes and their feedback mechanisms were identified as the main problems affecting the restoration and reconstruction of some ecological engineering projects in arid regions [6,7]. Since the 1950s, as soon as the vegetation protective system was established along the Baotou-Lanzhou railway in the sand dune area, Chinese researchers began to study the water cycle and water balance of this sand-binding vegetation system [8] and met with considerable success [9,10].…”