Grassland type and seasonal effects have a bigger influence on plant
diversity than prairie dog disturbances in semi-arid grasslands
Abstract
1. Prairie dogs (Cynomys sp.) are considered keystone species and
ecosystem engineers for their grazing and burrowing activities
(summarized here as disturbances). As climate changes and its
variability increases, the mechanisms underlying organisms’ interactions
with their habitat will likely shift. Understanding the mediating role
of prairie dog disturbance on vegetation structure, and its interaction
with environmental conditions through time, will increase knowledge on
the risks and vulnerability of grasslands. 2. Here, we compared how
plant taxonomic and functional diversity metrics, along with
community-weighted trait means (CWM), respond to prairie dog disturbance
across grassland types and seasons in a conservation priority, semiarid
grassland of Northeast Mexico. 3. Our findings suggest that functional
metrics and CWM analyses responded to interactions between prairie dog
disturbance, grassland type and season, whilst species diversity and
cover measures were less sensitive to the role of prairie dog
disturbance. Contrary to previous studies, we found weak evidence that
prairie dog disturbance has a negative effect on vegetation structure,
except for minimal effects on C4 and graminoid cover, which depend
mainly on season. Grassland type and season explained most of the
effects on plant functional and taxonomic diversity as well as CWM
traits. Furthermore, we found that leaf area as well as forb and annual
cover increased during the wet season, independent of prairie dog
disturbance. 4. Our results provide evidence that prairie dog
disturbance is less important than grassland type and that environmental
effects have a stronger role than grazing and animal disturbances on
vegetation. We argue that a focus on disturbance and grazing effects is
misleading, and instead attention is needed on the relationships between
vegetation and environmental conditions which will be critical to
understand semi-arid grassland dynamics in the region. In addition,
explicit management strategies to mitigate climate change would need to
consider these relationships