Symposium Abstracts 2010

Oral Presentations (in alphabetical order):

  • Camp, Lauren – Phylogenetic analysis of parasitic Cephaloboidea (Nematoda)
         Phylogenetic trees demonstrate that parasitism has evolved numerous times within Nematoda, and that nematode parasites exploit diverse host groups. Nematodes are an appropriate group in which to investigate changes associated with parasitism due to the repeated evolution of parasitism from free-living progenitors in combination with the range of lifestyles and host types exploited by nematodes.  Phylogenetic analyses are key to identifying the free-living sister taxa of parasitic lineages for comparative analyses. Members of the nematode suborder Cephalobina include taxa that appear particularly useful for studying the evolution of parasitism. Specifically, although most species in this suborder are free-living microbivores, two genera of parasites of invertebrates are proposed to belong to Cephaloboidea.  Phylogenetic analyses of nuclear large- and small-subunit ribosomal DNA were used to infer trees for Cephaloboidea and to develop hypotheses for relationships of representative parasitic taxa, Daubaylia potomaca and Dicelis spp. Phylogenetic hypotheses based on maximum parsimony and maximum likelihood methods confirm that Daubaylia and Dicelis are nested within Cephalobidae with strong support. The present study is designed to test relationships within Cephalobidae.
  • Copeland, Stella – Effects of simulated nitrogen deposition and dry season precipitation on plant growth, reproduction, and soil fertility in a Neotropical savanna
         Increasing nitrogen (N) deposition and changing precipitation patterns in Neotropical savannas could alter plant growth, reproduction, and nutrient acquisition through decreasing or increasing the availability of soil macronutrients. We examined the potential for simulated dry season precipitation increase and N deposition to increase or decrease limitation of growth and reproduction of the abundant native Cerrado (Brazilian savanna) grasses – Loudetiopsis chrysothrix and Tristachya leiostachya. Tristachya was more likely to flower with water addition, whereas Loudetiopsis individuals flowering increased with both water and N. Diameter growth decreased in Tristachya with added N and was unaltered for Loudetiopsis. Dry season leaf senescence and root : shoot ratio decreased in Loudetiopsis with added water but both measures were unchanged in Tristachya. Tristachya foliar phosphorus concentration [P] increased while Loudetiopsis foliar [P] decreased with the water and nitrogen treatment. Foliar [N] was unaltered by any treatment for either species. Plant-available P increased in Loudetiopsis associated soils with N addition and increased in Tristachya associated soils with the N and water treatment. A path model based on the experimental results demonstrated that the data strongly supported a model with soil [P] as the only soil parameter. These results suggest that N deposition, precipitation change, and species characteristics could interact to determine global change effects on soil and plant traits through their effects on soil [P].
  • Dybala, Kristen – Seasonal survival rates in Song Sparrows        
         Wildlife populations face distinct seasons throughout the year with potentially very different stressors due to changes in behavior or environmental conditions. These seasonal fluctuations could lead to seasonal variation in survival rates, and identifying periods in which survival is most limited will provide important information for population management and conservation planning. I conducted a mark-recapture analysis to estimate annual and seasonal survival rates for a non-migratory population of Song Sparrows (Melospiza melodia). This population has been studied year-round for 30 years at the Palomarin field station in central coastal California by PRBO Conservation Science. Survival rates were not constant year-round and seasonal patterns in survival varied by age class. Juvenile survival was lowest in the post-fledging period, and adult survival was lowest at the end of the breeding season.
  • Garbach, Kelly – Spatial patterns and availability of multiple ecosystem services-The effects of restoration plantings in an agricultural ecosystem
        Conserving ecosystem services is a pressing concern given their critical role in supporting human well being and sustaining both managed and natural habitat and biodiversity. Land management to maximize provision of agricultural goods such as crops and livestock has resulted in the degradation of other services (e.g. carbon sequestration, climate regulation). Consequently, agricultural systems should be prioritized as hotspots for restoring degraded services. Management to provide multiple ecosystem services tests our ecological understanding of plant traits and their unique effects on desirable services and where they are provided. This study determines how live fences (restoration plantings bordering cattle pastures) affect spatial patterns and availability of: soil fertility; pasture productivity; and bird diversity. We studied patterns in these three key services as provided by un-pruned live fences (mature trees, intact canopy), pruned fences (annual removal of most canopy) and post-and-wire (control) fences. We found higher bird species richness and greater presence of forest-dwelling and migratory species in live fences with un-pruned canopies. Effects on soil fertility and pasture productivity extended beyond live fences and into surrounding pastures in both fence types, however the magnitude of differences in availability of mineralizable N and pasture grass biomass was greatest in un-pruned live fences.
  • Gravem, Sarah – Predator avoidance initiates trophic cascades in tidepool communities        
         The presence of predators in communities can have cascading effects on lower trophic levels, and these cascades are often caused by changes in prey behavior rather than actual consumption of prey (trait-mediated indirect interactions, TMII). To determine if algal communities in tidepools are indirectly affected by the predatory seastar Leptasterias hexactis via behavioral modification of the herbivorous snail Chlorostoma (Tegula) funebralis, we studied the 1) association of Leptasterias, Tegula and other invertebrate and macroalgal community members, 2) direct effect of Leptasterias addition or removal on refuge use by Tegula and 3) indirect effects of Leptasterias addition and removal on microalgae. We found a strong negative correlation between Leptasterias and Tegula density. Our manipulative experiment indicates that this relationship is causal. Tegula moved to a refuge habitat when Leptasterias was added (p = 0.024), and the snails colonized pools when Leptasterias was removed, but only when conspecifics were added first (p = 0.008). Therefore, an aggregative behavior may alter Tegula responses to Leptasterias, potentially altering the strength of any TMII. Tegula removal (p < 0.001) and Leptasterias addition (p = 0.001) resulted in increased diatom biomass, indicating a TMII between Leptasterias and microalgae.
  • Holzer, Katie – Amphibians in the City: Factors Influencing Pond-breeding Frogs and Salamanders in Portland, OR
         Urban environments are increasing in number, size, and intensity around the world. As many organisms are able to persist within these areas, it is important to determine what habitat factors benefit urban wildlife populations. I measured the abundances and densities of eggs and tadpoles of six pond-breeding amphibian species in Portland, OR in 83 ponds. In these ponds I also measured 21 physical, chemical, and location factors. I conducted statistical analyses to determine which factors were influential each species. I found no difference between the abundance and densities of amphibians in natural vs. man-made ponds. Native species were more abundant and more dense in ponds with greater amounts of aquatic vegetation and physical refugia. Ponds with high nitrate levels had lower densities of tadpoles. Two species of concern were more dense in ponds with pH<7. This is likely because these species use coniferous forest (with low pH needles) as upland habitat. This study provides information for restoration recommendations for pond-breeding in this area. Major recommendations include: constructing new ponds where possible (especially near coniferous forests), planting aquatic vegetation in ponds, introducing other forms of physical refugia to ponds (such as branches), and mitigating the amount of nitrate run-off entering ponds.
  • Mallek, Chris – Strength and uniformity of serotiny in a California cypress    
         Studies of serotinous conifers indicate that intraspecific variation in expression of serotiny (canopy seed storage) can interact with fire regime to strongly influence postfire propagule availability and population dynamics.  Hesperocyparis macnabiana (McNab cypress) is an uncommon and increasingly threatened serotinous conifer that occurs in widely disjunct populations throughout northern California, yet no descriptions of the strength or uniformity of serotiny for this species currently exist.  Here I examined the degree of serotiny (proportion of unopened cones that are older than one year) using 13 populations throughout the species’ range.  Although population-level degree of serotiny was consistently high (greater than 0.75), significant variation among populations was also observed.  Specifically, populations in the North Coast Range (NCR) generally exhibited a higher degree of serotiny than those in the northern Sierra Nevada and southern Cascade Ranges (SNCR).  This pattern of variation largely paralleled differences in stand-level age structures and adjacent vegetation types.  Compared with results from similar studies of other serotinous taxa, degree of serotiny in H. macnabiana is both relatively uniform and high indicating that H. macnabiana populations have evolved to capitalize primarily on episodic recruitment opportunities such as those created by infrequent, stand-replacing fires.
  • Marklein, Alison – N inputs accelerate P mineralizing enzymes across a wide variety of terrestrial ecosystems 
          Nutrients – especially nitrogen (N) and phosphorus (P) – constrain plant growth; however human activities are drastically changing the nature of such nutrient limitations on land.  Here we examine interactions between N and P cycles via meta-analysis of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial ecosystems and conditions. We provide strong evidence that N fertilization enhances phosphatase activity, from the tropics to extra-tropics and in both roots and soils. In contrast, P fertilizations strongly depress phosphatase production, implying that these enzymes are strongly responsive to changes in local nutrient cycling conditions, whether N or P. Overall our results suggest that plants optimize growth via N allocations to phosphatase enzymes, thus delaying the onset of P limitations as induced by human modifications to the global N cycle.
  • Morford, Scott – Bedrock Nitrogen inputs to northern California temperate forests    
         Traditional paradigms of nutrient cycling and limitation posit that nitrogen (N) enters terrestrial ecosystems soley from the atmosphere; yet, sedimentary rocks contain more reactive N than all other reservoirs. We tested the hypothesis that bedrock contributes N to temperate conifer forests of northern California developing on N-rich bedrock. Using a paired sampling design, we measured total N, natural abundance 15N/14N, and 87Sr/86Sr of bedrock, soils, and plants in two adjacent forests underlain by N-rich mica schist (MS) and N-poor diorite. MS rocks contained 350 – 950 ppm N, while the diorite contained  42 – 72 ppm N. Nitrogen in soils and foliage was substantially elevated in the MS site relative to the diorite site. Foliar 15N/14N averaged 2.4 and -3.8 per mil in the MS and diorite sites, respectively. 87Sr/86Sr ratios of plants and rocks were similar within sites but divergent between sites. Taken together, the positive 15N/14N of foliage, high N contents of soils and plants, and similarities in Sr isotopes among plants and rocks reveal that bedrock contributes significant amounts of N to forests underlain by MS. We conclude that bedrock nitrogen can be a source of N to terrestrial systems, potentially influencing productivity and CO2 uptake at ecosystem scales.
  • Myhre, Sarah – The movement of anoxic water during climate transition, Santa Barbara Basin
         The depth range of the Oxygen Minimum Zone (OMZ) on the California margin is responsive to global climate fluctuation on millennial to decadal scales. Here, we utilize a recent core from 400m water depth (MV0811-15JC) in Santa Barbara Basin compared to previously investigated sediment cores from the Santa Barbara Basin at 420m (MD02-2504) and 580m (MD02-2503) water depth. The new MV0811-15JC record spans the past 15 ka with an initial d18O decrease of 1.5‰ in the lower part of the core indicating that this record begins midway through the deglacial warming of surface waters. In contrast to deeper records, the shallow core is not laminated and does not indicate a shift to anoxic conditions during the Bolling Allerod (B-A). This finding constrains the upper limit of the vertical expansion of the OMZ during the B-A. In combination with the two existing records, these data provide a depth transect through the OMZ and an opportunity to constrain the expansion and contraction of anoxic intermediate waters during the transition into the modern Holocene period. In the context of modern climate change, the degree and rate of expansion of coastal anoxic waters is of great interest, both economically and ecologically.
  • Shields, Jamie – Forest Structure and Fuels Vary by Topography in Sierra Nevada Active-Fire Stands
         Forest reconstructions and limited historical data are often used to infer desired conditions for fuels-treated forests. These studies, however, rarely quantify small tree density or how stand structure and fuel load vary across a forested landscape. This study assessed forest structure and composition in unmanaged forests with the best available approximation (> 2 low-intensity fires within the last 60 years) of an active-fire regime under recent climate conditions. Objectives were to determine the species composition, diameter distribution, spatial pattern, regeneration dynamics, and fuel loads of active-fire forests and what topographic conditions influence these stand characteristics. In general, live stem density, basal area, snag volume and percentage fire-sensitive species decreased as topographic position became more xeric. Average fuel loading was similar among all topographic positions (57.4 Mg/ha) except ridge tops, where fuels were sparser (19.5 Mg/ha). Non-metric multidimensional scaling analysis separated ridge-top plots, which had greater shrub cover and were more dominated by shade-intolerant pine species, from middle-slope plots, which were associated with greater canopy cover, fuel load, and live tree basal area. Varying fuel reduction treatment characteristics with topography could provide greater habitat diversity for wildlife and promote ecological processes while still reducing the risk of crown fires.
  • Swisher, Margaret – California ground squirrel (Spermophilus beecheyi) antipredator alarm call behavior: persistence of alarm call in the absence of a predator
         California ground squirrels (Spermophilus beecheyi) are a model species for the study of natural behavioral systems that have been shaped to fit their context by known sources of selection acting through millennia of evolution. The natural history and biology of California ground squirrels have been well studied. This makes them an ideal species for studying the development and maintenance of antipredator behavior. The objective of this study is to investigate how predators and prey interact, how predators influence prey behavior, and what role environment plays in shaping animal behavior. This study will compare two populations of S. beecheyi differing in the intensity of selection from predation. The first population located in Winters CA, does not experience predation by American badgers (Taxidea taxus). The second population, located in Monterey CA, experiences heavy predation by badgers. Preliminary results indicate that while the Monterey population maintains an alarm response to presentation of a stuffed badger, the Winters population has lost this anti-predator response. Understanding how predators shape prey behavior, and how long that behavior persists, is significant for conservation and reintroduction of threatened species to habitats where they have been eliminated.
  • Tulloss, Elise – Nitrogen deposition hotspots and gradients in northern California oak savannas     
         Nitrogen (N) deposition is a component of global change that receives increasing attention, but is still relatively understudied in California.  Nitrogen deposition can affect biodiversity and ecosystem functions, but patterns of input vary spatially and temporally across scales.  I measured nitrate-N and ammonium-N inputs beneath solitary oak canopies and the adjacent open grassland in 6 oak savanna sites across north-central California.  Preliminary results indicate that a regional-scale deposition gradient exists with sites in closer proximity to urban and agricultural pollution sources receiving significantly higher overall rates of input and sites in rural, remote areas receiving significantly less N overall.  Additionally, sites closer to urban sources of pollution have a greater proportion of N input as nitrate compared to other sites, consistent with the presence of urban pollutant gases.  The oak canopy receives greater N inputs compared to the adjacent open area at all sites, but the ratio of open to canopy deposition appears to be non-linear across sites.  Rates of N deposition beneath solitary oak canopies vastly outstrip estimates of N deposition for the California oak savanna as a whole.  The oak canopy functions as a deposition hotspot in the landscape and may represent a unique environment for plant species interactions and overall community structure.

Poster presentations:

  • Beh, Maia – Ambrosia beetles show an increased attraction to burned, sudden oak death-infected tanoak trees in the Big Sur region      
         Sudden oak death (SOD), caused by the invasive pathogen Phytophthora ramorum, is devastating susceptible oak and tanoak trees in coastal California forests. The pathogen kills trees through the formation of stem cankers, but it has also been suggested that bark and ambrosia beetle attacks on the infected trees accelerate mortality. In the Big Sur area, where forests are among the most impacted by SOD, large areas were affected by fires during the summer of 2008. The attraction of bark beetles to burned coniferous trees is well documented, but little is known about the attraction of beetles to burned coastal, hardwood trees. A survey of the P. ramorum-associated beetle species in the Big Sur region, however, allows for the novel study of attraction to burned and SOD-infected trees.
  • Cobb, Richard – Disease driven extinction threat to forest trees: a species or ecosystem level problem?
         Generalist pathogens with asymmetric host impacts, that can survive saptrotrophicaly, and which have few barriers to dispersal are associated with extinction threat. However, few of these high-threat pathogens have been identified as the primary cause of species extinctions and endangerment. In contrast, North American forests have experienced region wide declines in dominant species due to disease outbreak suggesting that high-threat pathogens pose a greater extinction threat to unique ecosystem structure and function compared to endangerment of individual species. This pattern suggests that assessment of species extinction threat by forest disease is often focus on the wrong question. I illustrate this by reviewing species and ecosystem level impacts of major contemporary North American forest diseases and compare these to the emerging disease Sudden Oak Death (SOD). SOD disease (caused by the generalist pathogen Phytophthora ramorum) threatens a region wide decline in a major overstory species in coastal Northern California and Southeastern Oregon (tanoak – Lithocarpus densiflorus). SOD disease progress follows a pattern similar to other contemporary diseases such as chestnut blight and beech bark disease. These diseases result in selective removal of large individuals and species persistence as understory vegetative sprouting. Longevity of post-mortality sprouting, sprouting rates, and stand level pathogen inoculum levels determine the degree of endangerment to ecosystem function in the face of forest diseases.
  • Fontes, Vitor – Spill-over of Brazilian native pathogen to an exotic host: Eucalyptus 
         The first eucalyptus seedlings were planted in Brazil in 1903, but by 1966 there were large-scale plantations of this Australian tree. Diseases never before reported began to cause great losses in production. One example is eucalyptus rust caused by Puccinia psidii Winter. This fungus, first described in Brazil in 1884 on Psidium pomiferum, has a wide host range, all in the Myrtaceae family, to which Eucalyptus also belong. It attacks juvenile plants and tissues. From the moment that the potentially susceptible genus was introduced into areas where the pathogen already occurred, P. psidii was found to be highly infectious on them, causing one of the most serious threats to eucalypt plantations in Brazil. So far, genetic selection, using artificial inoculation, is considered the best control method. The most recent evaluation done by the Universidade Federal de Viçosa showed just 35% of the 20 most planted clones in Brazil were resistant to the disease. Emergence of native pathogens on exotic hosts poses a serious threat to these plants in their native ranges. The experience with eucalyptus rust in Brazil highlights the need for strict quarantine measures to prevent the entry of this fungus into countries where it does not occur.
  • Kefauver, Shawn – Remote Sensing of Bioindicators for Forest Health Assessment
         Tropospheric ozone is responsible for damage to human health, agricultural production, and natural ecosystems in most industrialized nations including both the United States and Spain.  As biodiversity hotspots also particularly susceptible to global climate change and with high density human populations, the high concentration of ozone in these regions is of considerable concern.  In order to address this issue, this project seeks to answer the following more specific questions:  1. To what extent is tropospheric ozone having negative effects on the health of Yellow Pines (Pinus ponderosa and Pinus jeffreyi) in the Sierra Nevada Mountains of California, USA and the Black Pine (Pinus uncinata) in the Pyrenees Mountains of Catalonia, Spain?   2.  Can the impacts of ozone on plant ecophysiology be distinguished from other possible sources of plant stress using field and imaging spectroscopy techniques?  Can the plant spectral responses to ozone uptake be effectively combined in a robust spectral index of ozone damage?  3.  How will these methods be most effectively combined to provide risk assessments of current and future ozone damage to forest health across environmental gradients using GIS, remote sensing, ozone uptake and ecological modeling techniques?  
  • Law, Yao Hua – Perceived density of conspecifics elicits density-dependent cannibalism in the insect Geocoris pallens
  • Steel, Zack, M. Wilkerson, P. Grof-Tisza, K. Sulzner – Species vulnerability in an uncertain future

  • Wu, Yonghua – Bi-directional introgressive hybridization between Lepus capensis and L.yarkandensis