Role of desert pavements in water infiltration on fluvial fan surfaces
in desert ecosystems
Abstract
Desert pavements are the common features widespread in arid region,
which are important for regulating the ecological and hydrologic
processes. However, few studies focused on the role of water movement in
maintaining ecologic function in desert pavement landscapes. This study
determined the role of desert pavements in water infiltration on fluvial
fans, which were reflected by characteristics of desert pavements and
infiltration parameters in the middle reaches of Hexi Corridor. Six
sites (i.e. one site in hill slope and other five sites in the piedmont)
were selected for surveying soil properties within a 50-cm depth soil
profile and measuring sorptivity (S), initial water infiltration (ii),
steady-state infiltration rate (is) and infiltration time (T) in crust
and scalped crust conditions under 5-cm pressure head. The results
indicated that desert pavement surfaces were covered by a thin layer of
protective crusts, which were primarily composed of fine earth (56.94%)
and fine-medium gravel (40.46%). Although characterized by a big range
of gravel coverage (19.48%- 97.63%), the crusts had small gravels
(mean size: 0.58 cm) and extremely low soil moisture content (SMC; less
than 1.30%), which two parameters did not significantly differ from
each site in fluvial fans. The crusts were effective in restricting
water infiltration capacity. When the crusts were scalped, the S, ii and
is would improve 1.6, 1.7 and 1.6-fold, respectively. These three
parameters significantly increased with gravel coverage and medium
gravels, but significantly decreased with crust thickness and fine
gravels. Desert pavements were closely with water regulation in arid
systems, reflecting the vegetation distribution. This study highlights
that desert pavements have a strong impact on water infiltration to
function as regulating water resource and supplying water for vegetation
growth.