Moderate grazing significantly increases water use efficiency in alpine
meadow on the Tibetan Plateau
Abstract
Water use efficiency is an important indicator of drought tolerance of
plants. The response was still unclear of water use efficiency to
different grazing intensity and its adaptive mechanisms in alpine
meadow. Here, we analyzed water use efficiency of plant dominant
species, coexisting species and functional group level plants to grazing
intensity by δ13C index in alpine meadow. Furthermore, this study
revealed the driven factors of water use efficiency combined available
nitrogen, soil bulk density, soil organic carbon, soil water content and
evapotranspiration. Grazing increased plants δ13C by 3.37%. Moderate
grazing significantly increased the δ13C of Gramineae by 4.84%
(P<0.05), and increased δ13C of Cyperaceae, Leguminosae, and
Forb by 3.45%, 0.81%, and 1.40% respectively. Some dominant species
and coexisting species have the highest δ13C value under moderate
grazing. This study indicated that moderate grazing significantly
improved the water use efficiency of alpine meadows. Path analysis
resulted showed that the water use efficiency was negatively correlated
with evapotranspiration (P<0.05), soil water content, soil
organic carbon, and soil bulk density. It was positively correlated with
available nitrogen. Our study provides new insights that moderate
grazing help to increase water use efficiency in alpine meadows. In
addition, evapotranspiration may be the main driving factor affecting
the water use efficiency of alpine meadow.