Symposium Abstracts 2009

Keynote address: “Wings over borders – migration of shorebirds around the Pacific Basin” – Dr. Nils Warnock 
Nils will talk about the ecology of shorebird migration around the Pacific Basin, focusing on studies he and collaborators have done over the past 18 years.  His initial research out of graduate school focused on the migration of small shorebirds like the Western Sandpiper and the Dunlin through western North America. Radiotelemetry was used to follow birds and examine migration strategies and stopover ecology.  In recent years, Nils has been PI on a large-scale study of the migration of godwits and curlews around the Pacific Basin, ranging from New Zealand and Australia to Alaska to the Central Valley of California.  Using satellite telemetry, he and his colleagues have learned much about the migration of these fascinating birds (e.g. Gill et al. in press Proc. Royal Society B.).  Results of these studies will be discussed.
Oral & Poster Presentations (in alphabetical order):

  • Acuna, Shawn. “Dietary effects of Microcystis aeruginosa on Sacramento splittail, Pogonichthys macrolepidotus”
    In the upper San Francisco Estuary (the Delta and Suisun Bay) the presence of the toxic algal bloom Microcystis aeruginosa may endanger fish populations. Blooms of M. aeruginosa are a major concern of the Interagency Ecology Program Management Team (IEPMT 2005) as a possible cause of fish declines in the San Francisco Estuary. Most of the M. aeruginosa bloom is of the microcystin LR strain (MC-LR), a hepatotoxic protein that may have direct and indirect impact on the survival of fish. Splittail, Pogonichthys macrolepidotus is a native fish in the San Francisco Estuary and may be exposed to M. aeruginosa. Juvenile splittail were exposed to 3 treatments of M. aeruginosa in their diet at 5 (MC5), 10 (MC10) and 20 (MC20) ppm of MC-LR for 28 days. The concentration of MC-LR was determined per gram of the cyanobacteria by HPLC and used to calculate the 3 feeding treatments. The treatments will be compared to two controls of 0 MC-LR (MC0) and positiv e control with purified MC-LR at 5 ppm (MC5R). Each treatment and controls consisted of 3 tanks with 10 fish at 15±0.5 g per tank. Initial results showed increased incidents of clinical signs of stress, internal and external hemorrhaging, discoloration and fin damage, for MC5, MC5R, MC10 and MC20 when compared to MC0. Further analysis will be conducted to determine additional signs of toxicity. Histological analysis of liver, gonads, gills, kidneys and gut will be used to identify tissue damage and tumor formation. Chemical analyses of qPCR and HPLC will be used to determine the level of MC-LR within the tissues of exposed fish. Stress indicators of elevated RNA:DNA ratios and expression of PP1 and PP2 which are known to be expressed during exposure to MC-LR will be determined.
  • Beaudrot, Lydia. “Why orangutan males don’t kill infants”
          Infanticide is widespread among mammals, particularly common in primates, and has been shown to be an adaptive male strategy under certain conditions. Although no orangutan infanticides have been reported to date, several authors have suggested that infanticide has been an important selection pressure influencing orangutan behavior and the evolution of orangutan social systems. In this paper, we critically assess this suggestion. We begin by investigating whether wild orangutans have been studied for a sufficiently long period that we might reasonably expect to have detected infanticide. We consider whether orangutan females exhibit counterstrategies against infanticide typically employed by other mammalian females. We also assess the hypothesis that orangutan females form special bonds with particular “protector males” to guard against infanticide. Lastly, we discuss socioecological reasons why orangutan males may not benefit from infa nticide. We conclude that females do not clearly exhibit counterstrategies, that there is little support for the protector male hypothesis, and that aspects of orangutan paternity certainty, lactational amenorrhea and ranging behavior can explain why infanticide is not a strategy regularly employed by males. 

 

  • Boyko, Corin. “Mathematical models useful for forming hypotheses about how behavior affects primate group sizes
         Primatologists often consider behavioral factors such as infanticide as potentially important constraints on primate group size. However, many of the field studies which seek to test such hypotheses use between group comparisons of rates of these behaviors. Given the potential impact of individuals’ choices on the distribution of group sizes in a given population, this may not be appropriate. I use mathematical models of primate dispersal to consider how infanticide by immigrant males should affect primate group sizes which reveals more appropriate methods for testing hypotheses about the effects of behavior on primate group size.
  • Boyko, Ryan. “The willing cuckold: optimal paternity allocation, infanticide and male reproductive strategies in mammals” 
    Infanticide is believed to be an adaptive strategy in many mammalian taxa. A number of authors have modeled aspects of infanticide and its potential impact on social systems, but these analyses have generally considered males in isolation instead of in a social milieu filled with other males that are also optimizing their reproductive success. Considering infanticide in this manner, I show how infanticide risk may impact optimal male mating strategies. Infanticide risk coupled with imperfect infanticide protection in a population creates a fitness landscape with two adaptive peaks, one representing complete paternity certainty and the other which represents a compromise between maximizing paternity and minimizing infanticide risk. Which of these adaptive peaks represents the fitness-maximizing global optimum depends on a population’s socioecology and characteristics of the male. In many ecological contexts, males may adaptively reduce their paternity probability to reduce the risk of infanticide. Explicit consideration of this possibility may enhance our understanding of the dynamics of mammalian intrasexual and intersexual competition in a number of ways.
  • Cobb, Richard. “Survival analysis for ecologists: overview and a forest management application”
         Rate estimation is a common objective of statistical analysis in ecology. Survival analysis, a family of time dependent regression techniques is a highly flexible platform for individual level rate estimation. The technique is rarely utilized by ecologists, perhaps due to an emphasis on population level processes in ecological studies. However, population level rate estimates (such as per capita rates) lack mechanisms for the evaluation and incorporation of individual level heterogeneities. These heterogeneities may be important for synthesis of management objectives or explanation of temporal variation. I present tools for evaluation of individual level heterogeneities and use parameter estimates from survival models to simulate the dynamics of heterogeneous populations invaded by Sudden Oak Death, a destructive exotic disease in coastal California redwood forests. Data on infection and mortality by Sudden Oak Death was collected over seven years for 5800 individual trees from ten species. This dataset demonstrates the flexibility of survival analysis to accommodate censored (incomplete) and non-independent data. I use infection and mortality parameters from survival models to synthesize ideal forest conditions that minimize the impacts of Sudden Oak Death in redwood forests.
  • Dalrymple, Sarah. “An investigation of the complex interactions among fire, ants, forest floor fuels, and trees in Eastern Sierra forests”
         Fire consumes live and dead plant biomass, often significantly affecting wood and litter accumulation and vegetation structure. In addition, fire can impact animals directly or indirectly through habitat alteration. Less is known about how fire can affect interactions among plants and animals in fire-prone landscapes. My research explores such interactions among fire, ants, forest floor litter, and Jeffrey pine trees in the Eastern Sierra. After fire occurs in these forests, litter-free clearings form around trees and ants often nest in these exposed areas. In the Angora Fire that occurred near South Lake Tahoe in 2007, trees that had these ring-shaped clearings were damaged less and had higher survival than trees without them. Little is known about the causal relationship between ant presence and the formation of the clearings, but preliminary evidence suggests that ants can clear litter to reinforce cleared conditions around trees. I will further explore the potential benefits to ants and trees that result from this interaction, particularly when subsequent fires occur. In the context of the frequent low- to moderate-intensity fires that occurred before fire suppression began, this interaction could have great ecological importance to both ants and trees.
  • Decock, Charlotte. “The effect of elevated CO2 and O3 on sources of N2O emissions in a soybean agroecosystem” [poster]
    Atmospheric carbon dioxide (CO2) and ozone (O3) concentrations have risen sharply during the last decades. While elevated CO2 has been shown to stimulate plant growth, elevated O3 can cause premature leaf senescence, reduced photosynthesis and reduced root growth. These plant physiological changes may affect soil nutrient status and soil microbial communities, resulting in alterations in nitrogen cycling. Since nitrous oxide (N2O) is a greenhouse gas with a global warming potential 300 times greater than that of CO2, N2O emissions are of particular interest. The processes of nitrification and denitrification are the most important sources of N2O, but they occur under drastically different soil conditions . Therefore, we investigated the effect of elevated CO2 and O3 on total N2O emissions and on the fraction of emitted N2O derived from nitrification versus denitrification. We set up a laboratory incubation experiment using soils that were exposed to elevated CO2 and/or O3 in a free air concentration enrichment experiment in a soybean agroecosystem (SoyFACE). Ammonium nitrate, isotopically enriched in either ammonium ((15NH4)2NO3) or nitrate ((NH4)215NO3), was added to the soils and N2O emission rates as well as 15N content in N2O were determined after 0.8, 2, 5, 9 and 12 days of incubation. Elevated CO2 increased N2O emissions, while elevated O3 had no significant effect. After addition of (15NH4)2NO3, we observed the highest isotopic enrichment in N2O emissions from soils exposed to elevated O3 in the beginning of the incubation, while addition of (NH4)215NO3 gave the highest isotopic enrichment in N2O emissions from soils exposed to elevated CO2.  This suggests a decreased ratio of nitrification derived N2O to denitrification derived N2O under elevated CO2, while the opposite trend was more likely under elevated O3. Our data suggest that elevated CO2 and O3 have significant effects on sources of N2O emissions from soil in a soybean agroecosystem. Future research will use concentrations and 15N contents of inorganic nitrogen species in the soils at the respective sampling times together with modelling efforts to more precisely determine changes in N2O emissions from different sources under elevated CO2 and O3. Also the applicability of differences in the intramolecular distribution of 15N in N2O to source out pathways underlying N2O emissions will be explored.
  • Dolanc, Chris. “Shifting structure of high-elevation tree stands in the central Sierra Nevada, USA
    The California Climate Change Center predicts a reduction in subalpine and alpine land area of 55-75% over the next 100 years but models such as this still need to be thoroughly tested by field studies. The Vegetation Type Mapping (VTM) Project offers the opportunity to test whether tree distributions have already shifted in the recent past. Plots established by VTM crews were originally sampled from 1929-1934 and data from many plots are available on-line. I re-sampled 80 VTM plots in 2007 and 2008 at high elevations in the central Sierra Nevada. My results indicate that abundance has increased for the most common high-elevation conifers, in particular lodgepole pine and whitebark pine. Stem numbers for these two species are almost twice that of historic (VTM) conditions, for the smallest size class but similar for the larger size classes, indicating a recent departure from historic demography. This trend seems to run counter to the pre diction of decreasing subalpine land area and may represent a strong lag effect: competition from species moving upslope may eventually supplant these higher-elevation species but in the interim, conditions present at high elevations which were historically strongly limiting to growth, have ameliorated, allowing for improved recruitment and survival of native trees. The next step in my analysis is to determine whether red fir, which was historically limited to elevations lower than most re-sampled VTM plots, appears to be moving upslope.
  • Dybala, Kristen, Thomas Gardali, and John Eadie. “Seasonal survival rates in Song Sparrows” [poster]
         Understanding when in the annual cycle a population’s growth is most limited is critical knowledge for effective conservation and management action. Life history theory can predict whether adult survival or reproductive success contribute most to a population’s growth rate, but cannot identify which seasonal component of these rates should be targeted. For example, when in the adult life cycle is survival lowest? We conducted a mark-recapture analysis for a non-migratory population of Song Sparrows (Melospiza melodia), which has been studied year-round for over 30 years at the Palomarin field station in central coastal California by PRBO Conservation Science. We estimated annual survival rates for three age classes, and then compared models allowing survival to vary by season. Models incorporating season had much greater support, and survival rate estimates indicate that adult survival is lowest in the fall, suggesting the post-breeding/molt period is a critical bottleneck in the adult life cycle. By examining intra-annual variation in survival rates, critical stages within the annual cycle can be identified, leading to testable hypotheses about the mechanisms affecting survival during that stage.
  • Fonte, Steven and Johan Six. “Earthworms and residue inputs drive soil organic matter stabilization and fertilizer dynamics in Quesungual agroforestrysystem”
    The Quesungual agroforestry system, in the mountains of western Honduras, offers a viable alternative to traditional slash-and-burn practices, yet the mechanisms behind its success remain poorly understood.  The system relies on the mulching of residues from native trees (interspersed with crops) to increase long-term productivity and soil biological activity, particularly earthworms. In order to better understand the role of earthworms and residue additions, earthworm populations and litter quality were manipulated in field microcosms to examine the effects on soil structure, organic matter stabilization and soil fertility.  The addition of 15N labeled fertilizer allowed for determination of N movement into soil aggregate fractions and crop uptake of fertilizer.  Earthworms were found to interact with residue additions such that they improved soil structure and increased the stabilization of soil organic matter when plant litter is applied, but not when the soil is left bare.  Earthworms were also found to decrease the availability of P, but had no apparent effect on mid-season N availability.  Although earthworms decreased the recovery of 15N in soils, they increased plant uptake of fertilizer-derived N suggesting an increase in overall efficiency of applied N.  Results from this study suggest that residue additions and the earthworm populations they promote interact to improve the sustainability of the Quesungual system and that such interactions need to be considered in agroforestry systems throughout the tropics.  
  • Fonte, Steven, Edmundo Barrios, and Johan Six. “Earthworms, soil fertility, and organic matter dynamics in the Quesungual agroforestry system of western Honduras” [poster]
    The Quesungual slash-and-mulch agroforestry system of western Honduras has been put forth as a sustainable alternative to traditional slash-and-burn agriculture for the tropical dry forest zones across Central America. This system forgoes burning and utilizes native tree species interspersed with annual crops to stabilize hillsides, promote soil fertility, and conserve vital soil moisture.  The research presented here aims to better elucidate soil organic matter dynamics and earthworm communities in the Quesungual system via comparisons with slash-and-burn agriculture and secondary forest in a replicated field trial.  Quesungual and slash-and-burn treatments were further subdivided into plots receiving standard fertilizer applications (N-P-K) or no inorganic nutrient additions.  Earthworms were hand-sorted for each of the experimental plots in July of 2007 and returned to the lab for weighing and identification.  Soils were collected in 2006 and 2007 and fractionated to look at the distribution of C and N into different aggregate size classes, while available P was measured in bulk soils.  Results indicate that earthworm numbers and biomass are considerably lower under slash-and-burn agriculture than under the Quesungual system, with secondary forest having intermediate values.  P availability was highest in the Quesungual plots receiving inorganic fertilizer additions, despite equivalent additions of mineral P in the fertilized slash-and-burn treatment.  The influence of management on soil structure, as well as C and N distribution, appears to be less pronounced than for P and earthworm populations. Our findings thus indicate that Quesungual system receiving fertilizer additions seems to be the most advantageous for the management of soil fertility and fauna.
  • Harris, David. “When will invasive species homogenize or differentiate communities? An occupancy-based null model
         Invasive species’ potential to homogenize biotas contributes to their status as major threats to biodiversity, but predicting their effects remains difficult. Empirical studies have given conflicting results and landscapes’ spatial complexity has made generalization across systems difficult. It has long been known that cosmopolitan species homogenize landscapes and idiosyncratic ones differentiate them, but this relationship has been imprecise and is thus sometimes misinterpreted. We quantified this relationship with an intuitive, nonspatial approximation that shows that exotic species only begin to homogenize landscapes when they become more common than the pooled commonness of the other species in the community. We compared our predictions against county-level data from the lower 48 United States. The model explained more than 98% of the variation in several measures of homogenization by exotic species. Though our null model omits import ant biological complexity, its predictions give a baseline against which real invasions can be measured and can help indicate how similarity is likely to change as invasions proceed.
  • Kelley, Neil. “Diversity, distribution and paleoecology of Triassic marine reptiles”
         Early Triassic (Olenekian) marine reptile faunae are generally characterized by low diversity, high endemism and small body-size.  The sparse, scattered geographical occurrence of these fossils may partly reflect the distribution of “refugia” from the end Permian mass extinction.  Middle and Late Triassic faunae are more diverse and include both endemic and cosmopolitan components and taxa with a range of body sizes from small (~30 cm) to very large (>15 m).  This pattern is consistent with an evolutionary trend seen among a variety of marine clades: an extended recovery interval, followed by the appearance and radiation of new groups culminating in the so-called “Mesozoic Marine Revolution” (Vermeij 1977). Paleoenvironmental affinities (e.g. deep vs. shallow water) based on fossil occurences and pronounced morphological diversity (body-size, dentition etc.) indicate that Triassic marine reptiles occupied a range of ecological niches, equaling or exceeding (although not entirely overlapping) the range occupied by later Mesozoic marine reptiles.  An ecologically selective extinction/faunal turnover event occurred in the Late Triassic with most small-bodied, shallow water groups disappearing while several larger, open-water groups persisted into the Jurassic and beyond.
  • Kelly, Morgan. “Climate change and evolutionary potential: geographic variation in thermal tolerance in the copepod Tigriopus californicus
         The rapid pace of anthropogenic climate change represents an unprecedented threat to the planet’s biological diversity. The ability to adapt to a changing climate will depend on the magnitude of genetic variation for environmental tolerance and also on how this variation is distributed among populations within a species. We evaluate the potential for an evolutionary response to climate change in the intertidal copepod Tigriopus californicus using selection experiments to measure heritable variation in thermal tolerance within populations and across the species’ geographic range. We find that populations of this species are locally adapted to thermal conditions, and that realized heritability of thermal tolerance varies among populations.
  • Lacher, Iara. “A Distributed Graduate Seminar to Analyze the Priorities, Obstacles, and Opportunities that Exist for the Implementation of State Wildlife Action Plans
         This project is part of a distributed graduate seminar (DGS) funded by the National Council for Science and the Environment’s Wildlife Habitat Policy Research Program. The aim was to analyze State Wildlife Action Plans (SWAPs) with the following overarching question: How do conservation science, social, and institutional processes come together to set state and regional conservation priorities and the design and implementation of conservation solutions across the U.S.? Following characterization of the SWAPs in a pilot study, students from eight universities participated in the DGS and synthesized implementation of the SWAPs based on interviews with state agency plan coordinators and stakeholders. The DGS summarized challenges and opportunities in implementation of SWAPs and recommended ways to improve planning and implementation processes. Students from UCSB also analyzed SWAPs to compare states in terms of their emphasis on wildlife moveme nt corridor conservation. The SWAPs varied considerably in the level of attention given to wildlife movement corridors. Thus far the plans have had little influence on corridor conservation planning or implementation in the western U.S.
  • Mauritz, Marguerite. “The future of two California bunchgrasses Nassella pulchra and Bromus carinatus: Do competition with exotic annual grasses and altered precipitation regime affect the quality of native grass seed?” [poster]
         The native species of California grasslands are faced with threats from exotic invasion, development and climate change. Often studies investigate how to improve the successful establishment of native plants and optimize restoration efforts, but few look to the future and consider the ability of the restored plants to form a sustainable population. In California grasslands competition between native grasses and non-native annual Mediterranean grasses is usually measured in terms of established plant biomass or seedling growth. However, the success of seedlings depends primarily on seed nutrient content and focusing only on biomass may overlook important aspects of native grass establishment. Local adaptation and maternal environment are important for native grass competition with non-native grasses; non-native grasses increase water stress and interfere with native grasses at all life-stages, but particularly cause a reduction in seed production. Managing grasslands to reduce non-native grass competition may favor recruitment of native grasses and contribute toward the establishment of self-sustaining native grass populations. A ‘native island’ approach is becoming increasingly popular in grassland restoration. Instead of reseeding an entire plot of land, small islands of native species are established in the hope that they will spread. In such a situation, viable native grass seed production is crucial in creating a firm foundation for future recruitment. Knowing whether competition from non-native grasses reduces seed quality more than competition from native grasses will be useful in management decisions to determine native island size and the extent to which non-native grasses need to be controlled.
  • McConaghie, James. “The influence of land cover on nitrogen and water flux in small urban watersheds”
         Aquatic systems in urban areas may receive enhanced nutrient inputs from the surrounding landscape. Landscape structure is hypothesized to influence nitrogen flux into urban stream systems, and land cover composed of impervious surfaces and vegetation may control these inputs. Increased impervious surface cover may increases discharge to urban streams, and is correlated with increased nitrogen flux. Vegetation may slow water flow and retain nutrients on the landscape. Therefore, high proportions of catchment vegetation cover are expected to decrease discharge and nutrient flux to urban streams. To evaluate these hypotheses, we selected 12 catchments as part of the Baltimore Ecosystem Study-LTER in Baltimore, MD, that differ in relative proportions of land cover. High-resolution aerial imagery was used to calculate percentage cover of buildings, woody vegetation, herbaceous vegetation, pavement, and bare soil. Water quality data was collected from each stream for 18 months. We used correlation and multi-linear regression models to determine which land cover variables or combinations of variables best predict water quality. An understanding of the relationship between landscape structure and nutrient flux will help to elucidate mechanisms of material cycling and may inform better management of nitrogen in urban ecosystems.
  • Smith, Kelly. “Multi-Attribute Mate Choice Decisions and Uncertainty in the Decision Process: A Generalized Sequential Search Strategy
         The behavior of females in search of a mate determines the likelihood that a high quality male is encountered and adaptive search strategies rely on the effective use of available information on the quality of prospective mates. The sequential search strategy, a premier model of search behavior, was formulated, like most models of search behavior, on the assumption that females obtain perfect information on the quality of males encountered in the search process. We modify this strategy to allow for uncertainty and we determine how the magnitude of uncertainty and the potential for females to inspect multiple male attributes—to reduce uncertainty—influence mate choice decisions. In general, searchers are sensitive to search costs and higher costs lower acceptance criteria under all versions of the model. The choosiness of searchers increases with the variability of the quality of prospective mates under conditions of the original model. Under conditions of uncertainty searcher choosiness may increase or decrease with the variability of inspected male attributes. The behavioral response depends on the relationship between observed male attributes and the fitness return to searchers and, in some situations, on costs associated with the search process. Higher uncertainty often induces searchers to pay more for information on male attributes and the fitness return to searchers is never higher than under conditions of the original model. Further studies of the performance of alternative search strategies under conditions of uncertainty may consequently prove useful to identify search strategies likely to be used under natural conditions.
  • Van Dam, Alex. “Impact of Off-Road Vehicle Use on Dune Endemic Coleoptera”
         Scarab diversity in the Algodones Dunes (Imperial Co., CA) was assessed using a series of light-bucket transects to ascertain the impact of off-road vehicle (ORV) use. We compared dune endemic scarab species on the dunes south of Hwy. 78 that receive intense ORV use and the populations on the protected dunes north of Hwy. 78. We also compared the total numbers of Coleoptera collected. Our data indicate that unprotected dunes experienced a signiÞcant decline in Coleoptera populations, diversity, and species evenness. These results demonstrate that ORV use has a severe negative impact on Coleoptera that inhabit sand dunes.
  • Vaughn, Kurt. “Short-term Priority Influences Competitive Ability of Native Perennial Grasses
         Competition with exotic annuals is one of the greatest limitations to native grassland restoration in California. A previous study found native perennial grasses competed significantly better with a full year’s planting advantage (priority) over exotic annuals. Similarly, results from multiple (unreplicated) restoration sites in California grasslands indicate that a single year of weed control can result in far greater establishment success of perennials, even when annuals return to high levels as quickly as a year later. On an even shorter time scale, it has been proposed that the earlier germination and rapid early growth of annuals has lead to the successful supplantation of perennials. I designed an experiment to test whether a two week planting priority would increase the ability of native grasses to compete with annuals. Short term priority did not provide as strong of an advantage as control treatments with no annual competitors. Howeve r, at the end of the first growing season I found short term priority had highly significant effects on three distinct measurements of perennial planting success and fitness across all four species. On average I found short-term priority increased cover ten fold, the number of perennial individuals per plot 2.5 times and the number of flower spikes per individual 7.6 times. These findings suggest while the earlier germination of exotic annuals may not fully account for the competitive inhibition of native perennials, it can play an important role in these competitive interactions.
  • Wilkerson, Marit. “Indirect effects of domestic and wild herbivores on butterflies in an African savanna”
         Indirect food web interactions driven by livestock and wild herbivores are being increasingly recognized as crucial aspects of community dynamics in savannas and rangelands. Large ungulate herbivores can both directly and indirectly impact the reproductive structures of plants, which in turn can affect the pollinators of those plants. We examined how wild herbivores and cattle each indirectly affect the abundance of a dominant pollinator species, Colotis spp., at a set of long-term, large herbivore exclosure plots in a semi-arid savanna in central Kenya. We focused on two of the most common flowering species: Cadaba farinosa and Aspilia pluriseta. The study was conducted in four types of plots: cattle-only, wildlife-and-megaherbivore, all large herbivores and no large herbivores. We found that Cadaba flower numbers were positively correlated with Colotis abundances. Excluding browsing wildlife increased the abundances of both flowers and Colotis spp. However, we found that fl ower numbers and Colotis spp. abundances were greater in plots with cattle herbivory than plots that excluded all large herbivores. Our results suggest that wild browsing herbivores may indirectly suppress a floral visitor guild whereas well-managed cattle herbivory may benefit diverse taxa.
  • Wilkerson, Marit. “What to plant in Central Valley hedgerows: success of native flowering forb mixes at three densities” [poster]
         In California’s Central Valley, restorationists and agriculturists are focusing increased attention on planting hedgerows in once bare or weed-infested field margins. In conjunction with pollinator services research, this forb study examined how three native seed mixes succeeded in hedgerows. At sites owned by Yolo County farmers, three seed mixes were planted in winter 2008 at three different densities (1x, 2x and 4x) in nine 8m2 blocks. During the growing season in 2008, the seeding rate, type of mix, and site location were all significant factors for most planted species. A strict majority (five out of nine) of species had a higher germination rate and cover in mix 3, which contained all nine species, but the other four species often did best in mix 2 which contained only five species. Surprisingly, many species had just as high or higher rates of germination and cover at a seeding rate of 2x as they did at the highest seeding rate of 4x. Three species, Eschscholzia californica, Grindelia camporum, and Phacelia californica, were the most cost-effective species in terms of density and cover throughout the growing season. However, those species were not always the most prolific bloomers, an important consideration when providing pollinator services. These first-year results demonstrate the importance of seed mix and the “right” density for both restoration and ecosystem services projects. Practitioners also must consider their specific project objectives, cost-effectiveness vs. flowering rate vs. germination success, when determining which mix to plant at which rate.

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