USGS Western Ecological Research Center
In 2010, a vegetation classification and mapping project was initiated on Santa Barbara Island in support of a seabird habitat restoration effort begun on the island in 2007. Prior to 2010, the most recent vegetation classification and map for the island was from 1990. Because the island is fairly small, a decision was made to census the island plant communities. This census was completed over a 2 week period in the spring of 2010. All stands were visited and data were recorded using the California Native Plant Society’ Rapid Assessment Protocol. Data were analyzed and a Cluster analysis performed using the Sorenson distance metric and the flexible beta (β= -0.25) group linkage method. The resulting dendogram was then split into 10 groups using PC-ORD. To better understand the nature of these groups, an indicator species analysis was performed, also using PC-ORD. The island vegetation aggregated into 2 main groups – shrublands and herbaceous stands. Under shrublands, there occur 7 alliances and 7 associations. For herbaceous stands, 9 alliances with 10 associations are present. Stands were mapped in ArcGis using heads-up digitizing from 2008 aerial imagery. Global Positioning System data collected using Garmin hand-held units aided in the drawing of hard to discern stand boundaries. Classification nomenclature adhered to the standard for California vegetation as presented in A Manual of CaliforniaVegetation (Sawyer et al. 2008). Comparisons with previous vegetation maps show changes in community boundaries involving both contraction and expansion of native plant communities. Sea Otter (Enhydra lutris nereis) Trophic Interactions and Community Effects in the Channel Islands of Southern CaliforniaWednesday, October 24, 2012 | 4:30 p.m. PDT | Salon IIIWERC Contributor: Tim Tinker, Brian HatfieldIn the late 1980’s, Southern sea otters (Enhydra lutris nereis) were experimentally translocated to San Nicolas Island in an effort to establish a self-sustaining population distinct from the mainland sea otterpopulation. Today this population remains fairly small, having increased from a dozen animals in the early 1990’s to approximately 45 animals at present. Counts of the population have been conducted fourtimes annually since the translocation. The sub-tidal invertebrate and macroalgal community has been monitored at six fixed sample sites around the Island, providing spatially explicit information oncommunity dynamics from prior to the translocation to the present. In 2003-2005 we conducted an observational study of radio-tagged sea otters at San Nicolas Island to measure diet composition and percapitarates of invertebrate prey consumption. Sea otter diets were dominated by red urchins (Strongylocentrotus franciscanus). Based on measured attack rates, prey densities, and variation in spatial-use patterns by sea otters, we predict that significant predator impacts on urchin abundance should be evident at the sub-tidal monitoring sites at the SW corner of the island over the last 2-5 years, but not at other sites. We used the combined data sets to parameterize a 3-trophic-level species interaction model, assuming a type-II functional response and using stochastic difference equations to incorporate other environmental drivers. We evaluate and compare the observed vs. model-predicted patterns of direct sea otter predator impacts on prey communities, and their indirect effects on kelp abundance. Our model predicts a trophic cascade exhibiting transient dynamics and equilibrium densities of sea otters, urchins and kelp over the long term.Avian Community Dynamics on San Miguel, Santa Barbara, and Anacapa Islands from 1993-2009Thursday, October 25, 2012 | 10:00 a.m. PDT | Salon IIIWERC Contributor: Rob KlingerEcological communities are subject to many exogenous processes and events that can lead to shifts in community composition and structure. We analyzed a 17-year dataset of landbird distribution andabundance on San Miguel, Santa Barbara, and Anacapa Islands to evaluate if their dynamics were characterized more by relatively gradual but directional changes or more rapid stochastic, non-directionalfluctuations. Data were derived from nine line transects (San Miguel N = 5; Santa Barbara N = 3; Anacapa N = 1) surveyed 11-16 times between 1993 and 2009. Empirical cumulative distributionfunctions indicated that species abundance patterns varied substantially among islands and over time within islands. In general, dominance was accounted for by ≤ 4 species on all three islands. Whendominance decreased it was generally from increased abundance among the less common species than decreases in the more common ones. San Miguel and Anacapa showed largely stochastic temporalabundance patterns, and when large changes occurred they did not persist for more than a year. There was little evidence that directional shifts occurred on San Miguel, but dominance decreased on Anacapa after2000. Directional changes in species abundance patterns on Santa Barbara occurred from 1996 through 2005, with dominance generally decreasing from year-to-year during that period. However, after 2005species abundance patterns on Santa Barbara were similar to those from 1993-1995. Less than 25% of the species were observed in all years of the surveys on any of the islands, which is consistent withexpectations from the core-satellite hypothesis. Shifts in community composition could be gradual or rapid but tended to be due to changes in satellite species more so than core ones. We hypothesize that thisindicates multiple simultaneously occurring metacommunity processes, particularly patch dynamics and species sorting, are the main drivers of landbird community dynamics in the northern islands.Population Patterns of Deer Mice (Peromyscus maniculatus) on the California Channel IslandsThursday, October 25, 2012 | 2:45 p.m. PDT | Salon IIIWERC Contributor: Rob Klinger The deer mouse (Peromyscus maniculatus) is the most ubiquitous mammal on the Channel Islands, and on other California and Baja California islands. On most of the Channel Islands, the deer mouse is theonly small mammal. The species occurs across virtually all habitats on the islands, and on some islands they reach extraordinary densities. Given the relatively simple plant and animal communities on theislands, the generally high numbers of these mice, and their position as both an intermediate consumer, and in turn a prey species for a variety of predators on the islands (including the endemic island fox), deermice play an important role in the island food webs. In spite of this, relatively little has been published on the ecology of the island deer mice. We present here the first analysis of deer mouse populations andpopulation biology across all of the California Channel Islands. Deer mice reach their highest population densities on the smallest of the islands (Anacapa and Santa Barbara), and peak numbers are lowest on thelargest islands (e.g. Santa Cruz).However, numbers on the small islands also show the greatest variation in numbers over time, with high peak numbers, but also very low numbers following declines. Numberson the larger islands tend to have more consistent population levels, and regular annual variations, with spring lows, and moderate fall highs (following peak breeding in spring and summer).This overall patternis affected by differences in the predator communities on the different islands (e.g. the presence or absence of island foxes), differences in vegetation conditions (e.g. due to introduced grazing animals, orthe removal of such non-natives), and effects of other non-native species, such as black rats (Rattus rattus).POSTERSCharacterizing Spatial Learning Patterns of Cloud Cover and Fog Inundation in the Northern Channel Islands Using Satellite DatasetsWERC Contributor: Kathryn McEachernCoastal forests in Mediterranean climates are frequently covered by clouds or immersed in fog. Previous studies suggest that clouds strongly modulate forest distributions as well as carbon budgets in these semi-arid environments. Both low level stratocumulus cloud cover and fog can enhance the water status of vegetation along the Californian coast and the Channel Islands by reducing solar insolation, raising relative humidity and supplying water directly to the landscape during otherwise warm and rainless summers. While summertime fog and stratus cover in California’s Channel Islands can ameliorate summer drought stress and enhance soil water budgets, they have different spatial patterns. These differing spatial patterns and the resulting shifts in relative ecological importance of fog and stratus are largely unknown. The overall objective of this project was to map spatial distributions of daytime cloud cover frequency for the California Channel Islands, and to predict probabilities of surface cloud (fog) contact and immersion for these islands. Daytime cloud cover maps were generated for the Channel Islands using data from GOES satellite imagery. Cloud frequency maps were compared and found to be in agreement with solar insolation data collected at several sites on Santa Cruz and Santa Rosa islands for the summer of 2005. These cloud frequency maps were then combined with airport cloud height data and topographic data to map estimated weekly and monthly fog inundation. The fog inundation maps were then compared to fog drip data collected at several sites on the two islands. Correlation between fog inundation and fog drip accumulation enabled spatial and temporal extrapolation to understand seasonal and inter-annual variations in cloud cover frequency and fog inundation and drip. Future studies will use these cloud and fog distributions for water balance modeling and studies of plant geography and forest distributions.Changing Landscapes of Santa Rosa IslandWERC Contributor: Kathryn McEachernSanta Rosa Island is on the cusp of rapid vegetation change as island management transitions from a working ranch to a National Park for conservation of natural flora and fauna. In fact, the island has experienced great change in the past as Pleistocene mammoths gave way to Native American habitation, and as ranching took over in the 1800s. No doubt, these historic changes were visible in the landscape, much as their traces are visible in the archaeological record. Now, we have the benefit of modern photography to document change. We searched local archives for landscape photographs that reach back into the 1920s, and photographed those same scenes in 2012. As this series of repeat images shows, change has been rapid already in some sites. The pace of change is influenced by the setting – whether the location is in a canyon bottom or on a hilltop, for instance. Change has been punctuated by drought over the decades – change appears slower during dry spells and faster during rainy years. Global climate change will undoubtedly influence the rate of vegetation change into the future regardless of new paradigms in landscape management. We expect that these photo-points will provide interesting documentation of Santa Rosa Island landscapes for many years to come.Sea Otter Surveys at San Nicholas Island, 1990 to the PresentWERC Contributor: Brian HatfieldFrom August 1987 to June 1990, 140 southern sea otters (Enhydra lutris nereis) were translocated to San Nicolas Island (SNI) in an effort to establish a separate population. Soon after being translocated, themajority of these animals had either returned to the mainland or had disappeared, but a small remnant population numbering in the mid-teens persisted through most of the 1990s without evidence of growth. Beginning in the late 1990s, the small population began to slowly increase. It was not until 2002 that surveys yielded more than 30 animals (including pups) and until 2006 that over 40 sea otters were counted. In late 2010, 51 animals were seen. A total count of 58 sea otters was obtained in early 2012. As of June 2012, a minimum of 170 sea otters had been born at San Nicolas Island since the beginning of the translocation. The majority of the animals occur off the west end, but they have been seen in most areas around the island. This translocated population has grown much slower than the one off the outer coast ofWashington State.Scorpion Rock Seabird Habitat Restoration: Native Plant Community Restoration to Enhance Nesting Habitat for Cassin's AukletsWERC Contributor: Josh AdamsIntroduced non-native plant species on California’s Channel Islands can greatly affect seabird nesting habitat quality. Scorpion Rock, located off the north-east end of Santa Cruz Island in the Channel Islands National Park, is an important seabird nesting location. The presence of invasive non-native plant species on Scorpion Rock has resulted in decreased abundance and quality of nesting habitat for burrow nesterssuch as Cassin’s Auklets (Ptychoramphus aleuticus) as well as other seabirds. The plant community structure prior to restoration efforts was comprised of approximately 90% exotic, annual species, primarily crystalline ice plant (Mesembryanthemum crystallinum), cheeseweed (Malva parviflora) and nettle-leafed goosefoot (Chenopodium murale). Removal of non-native, invasive vegetation and the restoration of a native perennial Coastal Sage Scrub community on Scorpion Rock is helping to provide better soil structure, nesting conditions, and cover for seabirds utilizing this location. The outplanting and maintenance of over 8,000 plants on Scorpion Rock from 2008 to present has resulted in the reestablishment of a native plant community and significant perennial vegetative cover. Examination and testing of control methods for the invasive species present on Scorpion Rock as well as the development of remote site restoration techniques has been helpful for other habitat restoration projects on the ChannelIslands.
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