Divergent responses of above- and belowground ecosystem functioning to
shrub encroachment in the Tibetan semi-arid alpine steppes
Abstract
Semi-arid alpine ecosystems on the Tibetan Plateau are experiencing
rapid climate change and extensive anthropogenic activity, concomitant
with the encroachment of shrubs. Shrub encroachment leads to changes in
both the structure and functioning of semi-arid alpine steppes. Yet, the
encroaching impacts of shrubs on the above- and belowground ecosystem
functioning of the semi-arid alpine steppes remains uncertain. To
quantify shrub encroachment impacts on ecosystem functioning of the
semi-arid alpine steppes, two shrub encroached alpine steppe sites are
investigated, with one site encroached by a leguminous shrub (
Caragana spinifera) and another site encroached by a
non-leguminous shrub ( Dasiphora fruticosa). Results showed that
following both Leguminosae and Non-Leguminosae shrub encroachment, not
only do these alpine steppes greatly increase the individual ecosystem
functions but that this included significant enhancing of the ecosystem
multifunctionality (EMF). We concluded that the main impacts of shrub
encroachment were to facilitate belowground EMF (BEMF) rather than
aboveground EMF (AEMF) in alpine steppes. Our findings also highlight
that soil nutrients play critical roles in driving ecosystem functioning
responses to shrubs encroachment. These findings further our
understanding of shrub encroachment impacts on ecosystem functioning of
the Tibetan semi-arid alpine steppes.