Significant soil acidification caused by grazing exclusion across
China's grasslands
Abstract
Soil pH is strongly associated with soil biogeochemical cycles and
biodiversity in terrestrial ecosystems. GE has been widely adopted as an
effective practice to restore degraded grasslands. However, the effect
of GE on soil pH is still poorly understood and remains inconclusive. We
synthesized data from 63 sites in the literature and 43 additional field
sites and investigated the dynamics of soil pH following GE across
China’s grasslands. Mean pH decreased 0.13 units with GE (mean pH was
8.15 and 8.02 for grazed and GE groups, respectively, p <
0.001). The pH of surface soil (0–20 cm) showed greatest decrease rates
in GE grasslands, whereas that of deep soil (20–100 cm) had limited
responses to GE. In general, the largest decrease in the rates of soil
pH occurred after medium-term periods (5–15 years) of GE, whereas a
smaller rate of change was found over short- (≤5 years) and long-term
periods (≥15 years) of GE. Of the factors examined, the rate of soil pH
change was negatively correlated to MAP, but had no significant
relationship with MAT. The rate of soil pH change decreased linearly
with RCC, RNC, RAC and RBC. Sedge-dominated grassland had higher pH
decrease rates at 0–10 cm soil depth than grass-dominated grassland,
whereas grassland dominated by forbs and shrub species showed the
highest decrease in pH at 20–30 cm. Our results indicate that GE causes
significant soil acidification, especially in surface soil and humid
areas, which provides an important reference for future management of
China’s grasslands.