Study Area
This study was conducted in the spring of 2017 at the Phillips 66 Oil
Refinery (35.0388889, -120.5894444) in San Luis Obispo County,
California (Fig. 2). The region is characterized by a Mediterranean-type
climate with cool, wet winters and hot, dry summers, while also
receiving occasional inputs of water from coastal fog (Baguskas et
al. , 2016). San Luis Obispo County receives an average precipitation of
33.1 cm annually and an average wind speed of 10.83 km/hr (November –
May) with average low and high temperatures range from
5.92°C - 18.9°C during the growing
season (Western Regional Climate Center 2020).
In our study area, Phillips 66 was required to mitigate for their oil
development by establishing protected areas where extant populations are
regularly monitored and restrict management actions that could
negatively affect L. nipomensis populations (USFWS, 2009).The protected area in which we conducted our study is a coastal back
dune ecosystem and the oldest part of a dune complex. These less
disturbed areas often have later successional plants with increased soil
stability as well as higher plant and insect diversity (Buckler, 1979;
Miller, Gornish and Buckley, 2010; Ferrier et al. , 2012). The
study site is dominated by non-native, invasive perennial veldt grass
(Ehrharta calycina ) with scattered native annual forbs and
perennial shrubs. The area is actively grazed by cattle during L.
nipomensis dormant season (June-November) to suppress the invasive
veldt grass.
The entire population of L. nipomensis is restricted to seven
colonies within the Phillips 66 protected area. Two of the colonies were
excluded due to their wide and sparse distribution, making these areas
ineffective for targeted sampling. One colony was newly rediscovered
from historic occurrence data not found until partway through the course
of the study. A fourth population was located along a roadside with
different ambient disturbance characteristics compared to other areas.
We conducted plant visitor observations and vegetation monitoring at the
remaining three colonies within the protected area in accordance to our
California Fish and Wildlife permit (Permit No. 2081(a)-16-010) (Fig.
2).