California Ecosystems Research Articles

Coastal residents' literacy about seawater desalination and its impacts on marine ecosystems in California

This article examines coastal residents' awareness and knowledge about impacts of seawater desalination on marine ecosystems Carlsbad, California. The paper explores to what extent sociodemographics, motivational factors, and information use shape public awareness and self-assessed and factual knowledge. Data was collected using a mail survey (n=330) from a random sample of residents in Carlsbad. Both self-assessed and factual knowledge about the desalination plant and its impacts on marine ecosystem were low, with only two of 11 factual questions answered correctly by more than 50% of respondents. Gender, frequency of ocean use, and use of distinct information sources correlated positively with greater factual knowledge. Education, age, time of residency in local community, membership in an NGO, and place attachment to marine areas did not increase factual knowledge. Findings also demonstrate that knowledge shaped attitudes towards the seawater desalination plant as greater knowledge about marine impacts reduced support.

Grassland compost amendments increase plant production without changing plant communities

AbstractCompost amendment to grassland is a novel strategy proposed and demonstrated to increase ecosystem carbon (C) storage. However, the effects of compost applications on biomass production and plant diversity are not well known. We assessed impacts of a one‐time compost amendment over 4 yr on plant dynamics in two grazed grassland ecosystems in California: a coastal prairie and valley grassland. The valley grassland was dominated by exotic annual grasses and had significantly lower species diversity than the coastal prairie, which consisted of a mix of perennial and annual grasses and forbs. We observed large and persistent increases in aboveground biomass. Over the 4 study years, aboveground biomass from compost‐amended plots increased by 76% ± 21% at the valley grassland and 41% ± 21% at the coastal prairie, compared with controls. Plant N content was also greater from compost‐amended plots. There were no major shifts in species richness or abundance at either grassland site. Overall, plant communities at both grasslands were relatively resistant to the compost addition, but responses of some individual species were observed. Notably at the valley grassland, the abundance of forbs decreased slightly, while the abundance of grasses increased. The abundance of two noxious weeds did not change as a result of the compost amendment. Our results suggest that a single application of composted organic matter used to sequester C provided cobenefits to grassland plant dynamics. The compost amendments produced sustained increases in plant productivity and forage production as well as plant N content without greatly affecting the diversity of these exotic annual grasslands.

Deep RNA-Seq profile reveals biodiversity, plant-microbe interactions and a large family of NBS-LRR resistance genes in walnut (Juglans regia) tissues.

Deep RNA-Seq profiling, a revolutionary method used for quantifying transcriptional levels, often includes non-specific transcripts from other co-existing organisms in spite of stringent protocols. Using the recently published walnut genome sequence as a filter, we present a broad analysis of the RNA-Seq derived transcriptome profiles obtained from twenty different tissues to extract the biodiversity and possible plant–microbe interactions in the walnut ecosystem in California. Since the residual nature of the transcripts being analyzed does not provide sufficient information to identify the exact strain, inferences made are constrained to the genus level. The presence of the pathogenic oomycete Phytophthora was detected in the root through the presence of a glyceraldehyde-3-phosphate dehydrogenase. Cryptococcus, the causal agent of cryptococcosis, was found in the catkins and vegetative buds, corroborating previous work indicating that the plant surface supported the sexual cycle of this human pathogen. The RNA-Seq profile revealed several species of the endophytic nitrogen fixing Actinobacteria. Another bacterial species implicated in aerobic biodegradation of methyl tert-butyl ether (Methylibium petroleiphilum) is also found in the root. RNA encoding proteins from the pea aphid were found in the leaves and vegetative buds, while a serine protease from mosquito with significant homology to a female reproductive tract protease from Drosophila mojavensis in the vegetative bud suggests egg-laying activities. The comprehensive analysis of RNA-seq data present also unraveled detailed, tissue-specific information of ~400 transcripts encoded by the largest family of resistance (R) genes (NBS-LRR), which possibly rationalizes the resistance of the specific walnut plant to the pathogens detected. Thus, we elucidate the biodiversity and possible plant–microbe interactions in several walnut (Juglans regia) tissues in California using deep RNA-Seq profiling.

Geochemical and tectonic uplift controls on rock nitrogen inputs across terrestrial ecosystems

AbstractRock contains > 99% of Earth's reactive nitrogen (N), but questions remain over the direct importance of rock N weathering inputs to terrestrial biogeochemical cycling. Here we investigate the factors that regulate rock N abundance and develop a new model for quantifying rock N mobilization fluxes across desert to temperate rainforest ecosystems in California, USA. We analyzed the N content of 968 rock samples from 531 locations and compiled 178 cosmogenically derived denudation estimates from across the region to identify landscapes and ecosystems where rocks account for a significant fraction of terrestrial N inputs. Strong coherence between rock N content and geophysical factors, such as protolith, (i.e. parent rock), grain size, and thermal history, are observed. A spatial model that combines rock geochemistry with lithology and topography demonstrates that average rock N reservoirs range from 0.18 to 1.2 kg N m−3 (80 to 534 mg N kg−1) across the nine geomorphic provinces of California and estimates a rock N denudation flux of 20–92 Gg yr−1 across the entire study area (natural atmospheric inputs ~ 140 Gg yr−1). The model highlights regional differences in rock N mobilization and points to the Coast Ranges, Transverse Ranges, and the Klamath Mountains as regions where rock N could contribute meaningfully to ecosystem N cycling. Contrasting these data to global compilations suggests that our findings are broadly applicable beyond California and that the N abundance and variability in rock are well constrained across most of the Earth system.

Responses of riparian tetragnathid spiders to wildfire in forested ecosystems of the California Mediterranean climate region, USA

Mediterranean ecosystems of California are characterized by high interannual variability in precipitation and susceptibility to frequent high-severity wildfires. Variability in precipitation and fire severity are likely to become more pronounced because of climate change, but their relative effects on linked aquatic–terrestrial components of Mediterranean ecosystems have received limited attention. We investigated the effects of wildfire on riparian spiders of the family Tetragnathidae, which are common shoreline consumers that can be highly reliant on aquatic food resources in stream ecosystems. From 2011–2012, we assessed stream geomorphology; density and community composition of aquatic benthic macroinvertebrates; and density, Hg body loads, trophic position (TP), and reliance on aquatically derived energy (based on naturally abundant C and N isotopes) of tetragnathid spiders in study sections of 12 paired stream reaches in Yosemite National Park. The riparian zone of one member of each pair had experienced a high-severity wildfire, whereas the riparian zone of its counterpart had experienced a low-severity fire. After the 2013 Rim Fire, we resurveyed a subset of these variables in study sections of 4 reaches by means of a paired before-after–control-impact design. We also explored how reach- and catchment-scale variability might affect spider density and trophic dynamics. Differences in spider responses between paired sections were not statistically significant, but model-selection results suggested that variability in benthic invertebrate density, catchment-scale fire frequency, and precipitation were important drivers of spider density and TP. The consistent signal of precipitation across multiple spider responses suggests that climate variability could have greater effects on aquatic–terrestrial ecological linkages than the influence of fire alone.

Evidence for a uniformly small isotope effect of nitrogen leaching loss: results from disturbed ecosystems in seasonally dry climates.

Nitrogen (N) losses constrain rates of plant carbon dioxide (CO2) uptake and storage in many ecosystems globally. N isotope models have been used to infer that ~30% of terrestrial N losses occur via microbial denitrification; however, this approach assumes a small isotope effect associated with N leaching losses. Past work across tropical/sub-tropical forest sites has confirmed this expectation; however, the stable N isotope ratio (δ(15)N) of ecosystem leaching has yet to be systematically evaluated in seasonally dry climates or across major ecosystem disturbances. We here present new measurements of the δ(15)N of total dissolved N (TDN) in small streams, bulk deposition, and soil pools across eight watershed sites in California, including grassland, chaparral, and coastal redwood forest ecosystems, with and without fire, grazing, and forest harvesting. Regardless of the dominant vegetation type or disturbance regime, average δ(15)N of TDN in stream water differed only slightly (<~1‰) from that of bulk soil δ(15)N, revealing a uniformly small isotope effect associated with N leaching losses even under non-steady state conditions. Rather, lower input δ(15)N compared to TDN δ(15)N in streams pointed to fractionations via gaseous loss pathways as the dominant mechanism behind soil δ(15)N enrichment. We conclude that N leaching does not impart a major isotope effect across a broad range of ecosystems and conditions examined, thereby advancing the N gas-loss hypothesis as the principal explanation for variation in bulk soil δ(15)N.

Monitoring Spawning Activity in a Southern California Marine Protected Area Using Molecular Identification of Fish Eggs.

In order to protect the diverse ecosystems of coastal California, a series of marine protected areas (MPAs) have been established. The ability of these MPAs to preserve and potentially enhance marine resources can only be assessed if these habitats are monitored through time. This study establishes a baseline for monitoring the spawning activity of fish in the MPAs adjacent to Scripps Institution of Oceanography (La Jolla, CA, USA) by sampling fish eggs from the plankton. Using vertical plankton net tows, 266 collections were made from the Scripps Pier between 23 August 2012 and 28 August 2014; a total of 21,269 eggs were obtained. Eggs were identified using DNA barcoding: the COI or 16S rRNA gene was amplified from individual eggs and sequenced. All eggs that were successfully sequenced could be identified from a database of molecular barcodes of California fish species, resulting in species-level identification of 13,249 eggs. Additionally, a surface transport model of coastal circulation driven by current maps from high frequency radar was used to construct probability maps that estimate spawning locations that gave rise to the collected eggs. These maps indicated that currents usually come from the north but water parcels tend to be retained within the MPA; eggs sampled at the Scripps Pier have a high probability of having been spawned within the MPA. The surface transport model also suggests that although larvae have a high probability of being retained within the MPA, there is also significant spillover into nearby areas outside the MPA. This study provides an important baseline for addressing the extent to which spawning patterns of coastal California species may be affected by future changes in the ocean environment.

Assessment of the Immediate Impacts of the 2013–2014 Drought on Ecosystems of the California Central Coast

Abstract. A methodology was developed to assess the impacts of the historic 2013–2014 drought on ecosystems of California's Central Coast region, using a combination of satellite image analysis and in situ measurements of soil moisture in predominant vegetation types of the region. According to differences in Landsat drought indices for plant water stress and vegetation green cover (NDWI and NDVI, respectively), the geographic areas within the study region that were most severely impacted by the 2013 drought were the inland Carmel Valley in northern Monterey County and the coastal zones around San Simeon Point and Cambria in northern San Luis Obispo County. An expanded area of severe vegetation moisture stress, generally indicated by relative-differenced NDWI values of >400, was detected by May 2014 in both of these same geographic areas. For more detailed examination of drought impacts, the entire study region was separated into the 3 predominant vegetation types (grasslands, shrublands, and forests) to ...

Aboveground live carbon stock changes of California wildland ecosystems, 2001–2010

The balance between ecosystem emissions of carbon to the atmosphere and removals from the atmosphere indicates whether ecosystems are exacerbating or reducing climate change. Forest ecosystems in the State of California, USA, contain carbon that reaches the highest densities (mass per unit area) in the world, but it has been unresolved whether California ecosystems currently comprise a net sink or source of carbon. The California Global Warming Solutions Act of 2006 established greenhouse gas reduction targets for fossil fuel-burning sectors and ecosystems, underscoring the importance of tracking ecosystem carbon. Here, we conduct statewide spatial inventories of the aboveground live carbon stocks of forests and other terrestrial ecosystems of California, excluding agricultural and urban areas. We analyzed biomass data from field measurements of the Forest Inventory and Analysis program, published biomass information and remote sensing data on non-forest vegetation, and spatial distributions of vegetation types, height, and fractional cover derived by the Landfire program from Landsat remote sensing at 30m spatial resolution. We conducted Monte Carlo analyses of the uncertainty of carbon stock change estimates from errors in tree biomass estimates, remote sensing, and estimates of the carbon fraction of biomass. The carbon stock in aboveground biomass was 850±230 Tg (mean±95% confidence interval) in 2010. We found a net aboveground live carbon stock change of −69±15 Tg from 2001 to 2010, a rate of change of −0.8±0.2%y−1. Due to slow decay of some dead wood, all of the live carbon stock change does not immediately generate emissions. Wildfires on 6% of the state analysis area produced two-thirds of the live carbon stock loss. This suggests that increased tree densities from a century of fire suppression have allowed the accumulation of fuel for carbon losses in recent wildfires. Remote sensing errors in vegetation classification accounted for most of the uncertainty in the carbon stock change estimates. Improvements are also needed to track spatial patterns of growth and dead wood. Our results establish the beginning of a time series for the state greenhouse gas inventory and provide information on the role of forest conservation and management in California in mitigating global climate change.

Adapting California's Ecosystems to a Changing Climate

Significant efforts are underway to translate improved understanding of how climate change is altering ecosystems into practical actions for sustaining ecosystem functions and benefits. We explore this transition in California, where adaptation and mitigation are advancing relatively rapidly, through four case studies that span large spatial domains and encompass diverse ecological systems, institutions, ownerships, and policies. The case studies demonstrate the context specificity of societal efforts to adapt ecosystems to climate change and involve applications of diverse scientific tools (e.g., scenario analyses, downscaled climate projections, ecological and connectivity models) tailored to specific planning and management situations (alternative energy siting, wetland management, rangeland management, open space planning). They illustrate how existing institutional and policy frameworks provide numerous opportunities to advance adaptation related to ecosystems and suggest that progress is likely to be greatest when scientific knowledge is integrated into collective planning and when supportive policies and financing enable action.

Profiles in History

1899–1992 1923–2012 Hans Jenny at a site along the Ecological Staircase during the 1984 UC–Davis Soils 105 Field Course. Discussing the presence of a mollic epipedon in an ustic aridic soil moisture regime on the Perdiz Conglomerate, Presidio County, TX. From left, Drs. Susan Casby-Horton, Beatrix Haggard, Nelson Rolong, B.L. Allen (rock hammer in hand), and David Weindorf. Hans Jenny stands next to a soil monolith on a marine terrace above the Pacific Ocean in the Ecological Staircase in Northwestern California. He is explaining soil relationships to University of California–Davis students during the summer 1984 Field Studies of Soils in California Ecosystems, Soil Science 105 course. His career in soil science extended almost 70 years, and he maintained a lifelong devotion to education about soils. He was born in Switzerland in 1899 and came to the United States in 1926. He was appointed to a professor position at University of California–Berkeley in 1936. His passion for education about soils became readily apparent to the world after he authored the iconic book Factors of Soil Formation. A System of Quantitative Pedology in 1941. This book has been cited as a reference for soil science publications ever since and shows no signs of abating. He retired in 1967 but continued to pursue his passion for research and education about soil until his death in 1992. The life of Hans Jenny has had a far reaching influence not only on soil science and related disciplines, but also in universities, high schools, and elementary schools where the basic concepts of his system utilizing factors of soil formation are being taught to students. Hans Jenny and his wife Jean pursued their passion for preservation of unique and diverse soils and landscapes in the pygmy forest of Mendocino County, California, which was named the Hans Jenny Pygmy Forest Reserve. Sources: Photo and information courtesy of Kerry Arroues, retired USDA-NRCS Soil Scientist, Hanford, CA. Dr. B.L. Allen was born in Hillsboro, TX in 1923. He taught soil science courses at Texas Tech University (TTU) in Lubbock, TX for almost 50 years and was involved in pedology research at TTU until his passing in 2012 at the age of 88. He was an exceptional combination of a knowledgeable, persistently inquisitive soil scientist and a direct, dapper gentleman. Dr. Allen was most especially a field soil scientist. He was recognized worldwide for his work on arid and semiarid soils, particularly in the areas of soil genesis, soil morphology, soil micromorphology, soil mineralogy (especially pedogenic calcite, gypsum, and silica), and clay mineralogy (particularly sepiolite and palygorskite). He worked closely with range scientists to document and understand the relationships between range vegetation and soils in drier climates. Although his research was focused on the Southern High Plains and the Chihuahuan Desert, he was interested in similar environments worldwide. He was honored with several prestigious awards, including the Soil Science Education Award and Soil Science Distinguished Service Award (both conferred by the Soil Science Society of America). Dr. Allen also coached the TTU Soils Judging Team for 40 years, leading them to five National Collegiate Soil Judging Championships. Dr. Allen received his B.S. in Agronomy (Soils Option) from TTU and both his M.S. and Ph.D. from Michigan State University majoring in Soil Science (Geology Minor), receiving his doctorate degree in 1959. While completing his graduate studies, Dr. Allen also served as an Instructor and Assistant Professor of Agriculture at Eastern New Mexico University in Portales, NM. More than anything, Dr. Allen's students are his professional body of work. Dr. John Jacob, who completed his M.S. degree under Dr. Allen, commented that “he took a personal and abiding interest in each one of us. If he took you on as a student, you became a real ‘project’ for him. He saw much more in me than I saw in myself. I am forever indebted.” It is safe to say that this sentiment is echoed by all members of the loyal band of “Dr. Allen's students.” Contributed by Dr. Susan Casby-Horton, TTU Adjunct Professor, retired USDA-NRCS Soil Scientist and Dr. Nelson Rolong, Assistant State Soil Scientist, USDA-NRCS, Little Rock, AR.

Positive effects of non-native grasses on the growth of a native annual in a southern california ecosystem.

Fire disturbance is considered a major factor in the promotion of non-native plant species. Non-native grasses are adapted to fire and can alter environmental conditions and reduce resource availability in native coastal sage scrub and chaparral communities of southern California. In these communities persistence of non-native grasses following fire can inhibit establishment and growth of woody species. This may allow certain native herbaceous species to colonize and persist beneath gaps in the canopy. A field manipulative experiment with control, litter, and bare ground treatments was used to examine the impact of non-native grasses on growth and establishment of a native herbaceous species, Cryptantha muricata. C. muricata seedling survival, growth, and reproduction were greatest in the control treatment where non-native grasses were present. C. muricata plants growing in the presence of non-native grasses produced more than twice the number of flowers and more than twice the reproductive biomass of plants growing in the treatments where non-native grasses were removed. Total biomass and number of fruits were also greater in the plants growing in the presence of non-native grasses. Total biomass and reproductive biomass was also greater in late germinants than early germinants growing in the presence of non-native grasses. This study suggests a potential positive effect of non-native grasses on the performance of a particular native annual in a southern California ecosystem.

Aerosol emissions from prescribed fires in the United States: A synthesis of laboratory and aircraft measurements

Aerosol emissions from prescribed fires can affect air quality on regional scales. Accurate representation of these emissions in models requires information regarding the amount and composition of the emitted species. We measured a suite of submicron particulate matter species in young plumes emitted from prescribed fires (chaparral and montane ecosystems in California; coastal plain ecosystem in South Carolina) and from open burning of over 15 individual plant species in the laboratory. We report emission ratios and emission factors for refractory black carbon (rBC) and submicron nonrefractory aerosol and compare field and laboratory measurements to assess the representativeness of our laboratory-measured emissions. Laboratory measurements of organic aerosol (OA) emission factors for some fires were an order of magnitude higher than those derived from any of our aircraft observations; these are likely due to higher-fuel moisture contents, lower modified combustion efficiencies, and less dilution compared to field studies. Nonrefractory inorganic aerosol emissions depended more strongly on fuel type and fuel composition than on combustion conditions. Laboratory and field measurements for rBC were in good agreement when differences in modified combustion efficiency were considered; however, rBC emission factors measured both from aircraft and in the laboratory during the present study using the Single Particle Soot Photometer were generally higher than values previously reported in the literature, which have been based largely on filter measurements. Although natural variability may account for some of these differences, an increase in the BC emission factors incorporated within emission inventories may be required, pending additional field measurements for a wider variety of fires.

Futures Past

These maps, based on research by the San Francisco Estuary Institute’s Center for Resilient Landscapes, reconstruct California ecosystems as they were in the late 18th and early 19th centuries, and compare them to present-day landscapes. They are designed to provide an understanding of the complexity and diversity of California ecosystems, to help explain how landscapes worked, to track persistence and change, and to identify potential future scenarios. The changes made evident when the maps are compared remind us of the enormous power we have to shape the landscapes we inhabit, and of the wide range of potential options available—options to create diverse, functional, and beautiful landscapes, inspired by the past and grounded in local potential—as we imagine and then create the future.

Three Papers That Influenced The Direction of My Career

As a junior at San Diego State University I was impressed by a massive wildfire that generated an extraordinary spectacle from the back porch of my parent’s home in the formerly rural community of Bonita. During my senior year I came across a paper by Philip Wells (Wells 1969) on the evolution of plant life history strategies and fire. His model was rather counterintuitive in that he pointed out that nearly all woody dicotyledenous species were able to vegetatively resprout after fire (or other disturbances), and the lack of resprouting capacity was rare and found primarily in fire-prone chaparral shrubs in the genera Arctostaphylos and Ceanothus. I talked with one of my professors, Dr. Paul Zedler, about doing a masters degree on this phenomenon. To this day I recall his note of caution, given in a very serious tone (to paraphrase), “Well Jon, one does not set out in a graduate program to just study whales, you need to narrow your ideas.” My eventual project led to a life-long career that included life history evolution in response to fires, and it is still an important part of my research program (Pausas and Keeley, in review). My master’s thesis project was published (Keeley 1977, Keeley and Zedler 1978) and these papers have been widely cited (collectively nearly 600 citations) and appear to have played a role in stimulating several synthesis papers addressing the drivers behind resprouting and seeding evolution (Bellingham and Sparrow 2000, Bond and Midgley 2003) and brought home to me the excitement of linking ecology and evolution. While working on my master’s thesis I accepted an offer to participate as a field assistant on Dr. Harold Mooney’s NFS/IBP convergent evolution study, comparing the structure and function of mediterreanean climate ecosystems in California and Chile. Mooney and Dunn (1970) stressed an ecophysiological model to explain the convergence of evergreen sclerophyllous-leaved shrubs in mediterranean-climate environments of California and Chile, and further opened my eyes to the connections between ecology and evolution. For my job I traveled once a week to study sites around southern California to record phenological stages of chaparral species. My job title was “quantitative phenologist” and most people assumed it had something to do with studying human skull morphology; little did we recognize that future climate change threats would induce ecologists around the globe into becoming quantitative phenologists. In this project I developed a friendship with Sterling Carter, who was doing graduate studies in Chile, and her advisor Dr. Al Johnson felt that a good use of his funds would be to send me to Chile to collect seeds for planned cytological studies. Since I had spent the previous summer in the Arctic tundra doing research for Dr. Frank Pitelka, I could couple this with a trip to Tierra del Fuego to make some “comparisons” with southern hemisphere tundra. While I believe the money was well spent, the trip did not lead to any publications, but it did provide a first-hand look at the systems Mooney and Dunn (1970) had written on, and instilled in me the need to think broadly in terms of other mediterraneanclimate ecosystems. These early experiences enabled me to develop colleagues in all MTC regions; this circumstance is reflected in a recent multi-authored book (Keeley et al 2012). Finishing my master’s thesis, I discussed with Dr. Zedler doing a Ph.D. and I recall him saying, again in a very serious (but I now recognized as a somewhat affected tone) something to the effect, ‘Well Jon,

First Report of the NA2 Lineage of Phytophthora ramorum from an Ornamental Rhododendron in the Interior of California.

In July 2012, we collected a rhododendron var. Trilby with twig dieback symptoms in the lower canopy, consistent with the disease "ramorum blight" caused by Phytophthora ramorum. The symptomatic plant had been planted a year earlier to replace a dead rhododendron in a landscape setting in Placer County, California (Lat: 39.036216°; Long: -120.999274°), Sierra Nevada foothills at ~600 m elevation. Isolations yielded a culture with a fast growth rate and overall morphology resembling the P. ramorum NA2 lineage described by Ivors et al. (4). DNA was extracted from the culture as described previously (4) and six SSR loci: MS18, MS39, MS43, MS45, MS64, MS145, were amplified (2,4). Allelic patterns were compared with those of three testers from each of the three lineages NA1, NA2, and EU1 known to be present in ornamental plants in North America, and they unambiguously confirmed the isolate belongs to the NA2 lineage of the pathogen. Although the symptomatic plant was confined to a landscape setting, it had been planted in that location for a year, providing a possible source of inoculum for the surrounding area. This is the first report of P. ramorum from the Sierra Nevada eco-region in the interior of California. It is also the first report of a NA2 isolate from a plant outside of commercial nurseries in California. The mating type of the isolate was not determined, but NA2 isolates are normally A2, the same mating type of NA1 isolates. The only other report of a NA2 isolate found outside of a nursery is from Washington State (1). Although there is no evidence the pathogen may have infected other plants, the infected rhododendron was found at a location situated over 100 km east of the closest known infestation (www.sodmap.org). Additionally, this is the first report of the pathogen outside the coast mountain range of California. Because the three lineages are genetically and phenotypically distinct (3), the escape of NA2 or EU1 isolates, both still absent from plants in natural settings, could have significant implications for California ecosystems. This finding highlights that introductions of P. ramorum via ornamental plants are still possible, in spite of current regulations.

Microclimate influences on vegetation water availability and net primary production in coastal ecosystems of Central California

Field sampling and satellite remote sensing were used to test the hypothesis that site microclimate variability leading to divergent soil water use by vegetation types is closely associated with variability in annual net primary productivity (NPP) at the landscape scale. A simulation model based on satellite observations of seasonal phenology was used to estimate NPP of grassland, shrubland, and conifer forest vegetation types on the Central California coast near Big Sur. Daily microclimate at the soil surface was monitored over 4 years (2008–2011) for each vegetation type to infer soil moisture controls on plant production. Grassland soils were found to have lower soil organic matter content and were subjected to extreme radiation and wind events, and thereby dry-down faster with daily spring–summer warming than do shrubland or redwood forest soils. This reduced moisture microclimate affected the water stress on grassland plants to reduce NPP fluxes from April to October each year on the Central Coast far sooner than for shrubland or redwood stands. Results from this study suggested that the satellite-observed canopy greenness variations represented can be used to quantify plant production in coastal ecosystems at the landscape scale of defined microclimate variation.

Land use compounds habitat losses under projected climate change in a threatened California ecosystem.

Given the rapidly growing human population in mediterranean-climate systems, land use may pose a more immediate threat to biodiversity than climate change this century, yet few studies address the relative future impacts of both drivers. We assess spatial and temporal patterns of projected 21st century land use and climate change on California sage scrub (CSS), a plant association of considerable diversity and threatened status in the mediterranean-climate California Floristic Province. Using a species distribution modeling approach combined with spatially-explicit land use projections, we model habitat loss for 20 dominant shrub species under unlimited and no dispersal scenarios at two time intervals (early and late century) in two ecoregions in California (Central Coast and South Coast). Overall, projected climate change impacts were highly variable across CSS species and heavily dependent on dispersal assumptions. Projected anthropogenic land use drove greater relative habitat losses compared to projected climate change in many species. This pattern was only significant under assumptions of unlimited dispersal, however, where considerable climate-driven habitat gains offset some concurrent climate-driven habitat losses. Additionally, some of the habitat gained with projected climate change overlapped with projected land use. Most species showed potential northern habitat expansion and southern habitat contraction due to projected climate change, resulting in sharply contrasting patterns of impact between Central and South Coast Ecoregions. In the Central Coast, dispersal could play an important role moderating losses from both climate change and land use. In contrast, high geographic overlap in habitat losses driven by projected climate change and projected land use in the South Coast underscores the potential for compounding negative impacts of both drivers. Limiting habitat conversion may be a broadly beneficial strategy under climate change. We emphasize the importance of addressing both drivers in conservation and resource management planning.

NOVEL AQUATIC ECOSYSTEMS: THE NEW REALITY FOR STREAMS IN CALIFORNIA AND OTHER MEDITERRANEAN CLIMATE REGIONS

ABSTRACTTemporary streams in California and other Mediterranean climate areas are among the aquatic habitats most altered by human actions and by invasions by alien species. They typically support novel ecosystems, defined as ecosystems dominated by new combinations of organisms in highly altered habitats. Although these new ecosystems have many attributes of the ecosystems they replaced, such as native species, they typically contain many new interactions among species. Managers need to recognize this reality to find ways to direct change towards novel ecosystems with desirable features, including native species. The concept of reconciliation ecology is a practical approach to living with the new reality; it includes actively guiding ecosystem change, as illustrated by Putah Creek, Cosumnes River, Eel River and Six Bit Gulch in California. The first three waterways are all highly altered and managed with varying degrees of success to favour desired aquatic species, whereas Six Bit Gulch experiences such extreme conditions that the original ecosystem is still largely intact. The examples illustrate that most aquatic ecosystems in California are so highly altered that attempting to restore them to an earlier condition or stable state is largely not possible. Where more or less intact systems persist, it is usually because extreme environmental conditions restrict both alien invaders and human use in small watersheds. This pattern appears to be fairly typical of streams in Mediterranean climate areas. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Archeology, deep history, and the human transformation of island ecosystems

Island ecosystems and peoples face uncertain futures in the wake of predicted climate change, sea level rise, and habitat alteration in the decades and centuries to come. Archeological and paleoecological records provide important context for understanding modern environmental and sociopolitical developments on islands. We review and analyze human interactions with island ecosystems in Polynesia, the Caribbean, and California during the last several millennia. Our analysis demonstrates that human impacts on island ecosystems and cases of highly managed anthropogenic landscapes extend deep in the past, often beginning at initial settlement. There are important issues of scale and island physical characteristics, however, that make human ecodynamics on islands variable through space and time. These data demonstrate that current environmental problems have their roots in deeper time and suggest that the Anthropocene likely began by the onset of the Holocene, if not earlier.