4.4 Uncertainty analysis
We combined 106 sites ranging from large temperature and precipitation
gradients covering the main grassland types in China, which offers
relatively accurate estimates on changes of soil pH following GE across
grassland ecosystems. However, there remain some uncertainties and
limitations. Uneven distribution of data collected in different types of
grassland, soil layers and durations of GE may have some bias on our
results. In addition, we were unable to evaluate several other
potentially important environmental factors, such as grazing intensities
before GE (heavy, moderate or light grazing), type of grazing management
(seasonal or perennial grazing) and livestock (e.g., cattle, sheep,
horse or yak), because most of these factors were not measured in field
sampling and the peer-reviewed literature. Despite these uncertainties,
the present study did reveal several interesting and informative
patterns, which can provide important references for future management
of the ecological environment in China’s grassland ecosystems.