Environmental and demographic drivers of a rapidly expanding sub-arctic moose population

Thesis (M.S.) University of Alaska Fairbanks, 2023Anthropogenic forces are dramatically altering the dynamics of many populations and ranges. A thorough understanding of drivers and mechanisms underlying population dynamics is needed to better understand reasons for range shifts and broaden our understanding of how environmental and demographic drivers affect population trajectories. In this thesis, I present two chapters that investigate the population dynamics of a rapidly colonizing moose (Alces alces) population in southwest Alaska. In the first chapter, I correlated environmental variables with demographic rates estimated using a multistate model and found that annual patterns of vegetation productivity and winter severity affected calf survival most strongly, followed by twinning rate. In the second chapter, I applied transient life table response experiments (tLTREs) to demographic rates and components of population structure estimated using an integrated population model (IPM). I found that, although calf survival did not have the highest sensitivity out of all other parameters, variation in calf survival contributed the most to variation in population growth rate. Together, these chapters suggest that variation in environmental conditions drove variation in population growth rate via effects on calf survival. Results uphold and add nuance to the demographic buffering hypothesis (DBH), which states that species evolve to buffer highest sensitivity demographic rates against variation that could otherwise decrease individual fitness and population sustainability. My research indicates that an outcome of the DBH is that lower sensitivity vital rates ultimately have a higher actual impact on population growth rate. Additionally, I found that the environmental drivers that currently limit population growth exhibit long-term trends consistent with climate change in ways that are amenable to moose, which suggests climate change facilitated moose colonization of the region. The lack of shortterm trends, lower adult survival in the most heavily hunted part of the study area, and the abrupt colonization that aligned with the irruption of a local caribou (Rangifer tarandus) herd indicate that human hunting pressure also played an important role in allowing moose to establish themselves at high density. These findings pertaining to drivers and mechanisms of population dynamics are relevant for conservation and management of large herbivores across the world that might similarly expand into new areas.Chapter 1: General introduction -- Chapter 2: Environmental and anthropogenic drivers of a rapidly expanding sub-arctic ungulate population -- Chapter 3: Demographic drivers of population growth for a colonizing sub-arctic ungulate -- Chapter 4: General Conclusions -- Appendix

Integrating local environmental observations and remote sensing to better understand the life cycle of a thermokarst lake in Arctic Alaska

On 29 June 2022, local observers reported the drainage of a 0.5 ha lake near Qikiqtaġruk (Kotzebue), Alaska, that prompted this collaborative study on the life cycle of a thermokarst lake in the Arctic. Prior to its drainage, the lake expanded from 0.13 ha in 1951 to 0.54 ha in 2021 at lateral rates that ranged from 0.25 to 0.35 m/year. During the drainage event, we estimate that 18,500 m3 of water drained from the lake into Kotzebue Sound, forming a 125-m-long thermo-erosional gully that incised 2 to 14 m in ice-rich permafrost. Between 29 June and 18 August 2022, the drainage gully expanded from 1 m to >10 m wide, mobilizing ~8,500 m3 of material through erosion and thaw. By reconstructing a pre-lake disturbance terrain model, we show that thaw subsidence occurs rapidly (0.78 m/year) upon transition from tundra to lake but that over a seventy-year period it slows to 0.12 m/year. The combination of multiple remote sensing tools and local environmental observations provided a rich data set that allowed us to assess rates of lake expansion relative to rates of sub-lake permafrost thaw subsidence as well as hypothesizing about the potential role of beavers in arctic lake drainage

PKC in platelet Ca²⁺ signalling

Rises in cytosolic Ca(2+) concentration ([Ca(2+)]cyt) are central in platelet activation, yet many aspects of the underlying mechanisms are poorly understood. Most studies examine how experimental manipulations affect agonist-evoked rises in [Ca(2+)]cyt, but these only monitor the net effect of manipulations on the processes controlling [Ca(2+)]cyt (Ca(2+) buffering, sequestration, release, entry and removal), and cannot resolve the source of the Ca(2+) or the transporters or channels affected. To investigate the effects of protein kinase C (PKC) on platelet Ca(2+) signalling, we here monitor Ca(2+) flux around the platelet by measuring net Ca(2+) fluxes to or from the extracellular space and the intracellular Ca(2+) stores, which act as the major sources and sinks for Ca(2+) influx into and efflux from the cytosol, as well as monitoring the cytosolic Na(+) concentration ([Na(+)]cyt), which influences platelet Ca(2+) fluxes via Na(+)/Ca(2+) exchange. The intracellular store Ca(2+) concentration ([Ca(2+)]st) was monitored using Fluo-5N, the extracellular Ca(2+) concentration ([Ca(2+)]ext) was monitored using Fluo-4 whilst [Ca(2+)]cyt and [Na(+)]cyt were monitored using Fura-2 and SFBI, respectively. PKC inhibition using Ro-31-8220 or bisindolylmaleimide I potentiated ADP- and thrombin-evoked rises in [Ca(2+)]cyt in the absence of extracellular Ca(2+). PKC inhibition potentiated ADP-evoked but reduced thrombin-evoked intracellular Ca(2+) release and Ca(2+) removal into the extracellular medium. SERCA inhibition using thapsigargin and 2,5-di(tert-butyl) l,4-benzohydroquinone abolished the effect of PKC inhibitors on ADP-evoked changes in [Ca(2+)]cyt but only reduced the effect on thrombin-evoked responses. Thrombin evokes substantial rises in [Na(+)]cyt which would be expected to reduce Ca(2+) removal via the Na(+)/Ca(2+) exchanger (NCX). Thrombin-evoked rises in [Na(+)]cyt were potentiated by PKC inhibition, an effect which was not due to altered changes in non-selective cation permeability of the plasma membrane as assessed by Mn(2+) quench of Fura-2 fluorescence. PKC inhibition was without effect on thrombin-evoked rises in [Ca(2+)]cyt following SERCA inhibition and either removal of extracellular Na(+) or inhibition of Na(+)/K(+)-ATPase activity by removal of extracellular K(+) or treatment with digoxin. These data suggest that PKC limits ADP-evoked rises in [Ca(2+)]cyt by acceleration of SERCA activity, whilst rises in [Ca(2+)]cyt evoked by the stronger platelet activator thrombin are limited by PKC through acceleration of both SERCA and Na(+)/K(+)-ATPase activity, with the latter limiting the effect of thrombin on rises in [Na(+)]cyt and so forward mode NCX activity. The use of selective PKC inhibitors indicated that conventional and not novel PKC isoforms are responsible for the inhibition of agonist-evoked Ca(2+) signalling.This work was funded by the British Heart Foundation (PG/07/100/23759). AGSH was supported by a Research Fellowship from St Catharine’s College, University of Cambridge. RAL was supported by a Wellcome Trust Summer Studentship and BBS by a Browning Summer Bursary from Magdalene College, Cambridge.This is the author accepted manuscript. The final version is available from Cell Calcium via http://dx.doi.org/10.1016/j.ceca.2015.09.00

Solar Power Tower Design Basis Document, Revision 0

This report contains the design basis for a generic molten-salt solar power tower. A solar power tower uses a field of tracking mirrors (heliostats) that redirect sunlight on to a centrally located receiver mounted on top a tower, which absorbs the concentrated sunlight. Molten nitrate salt, pumped from a tank at ground level, absorbs the sunlight, heating it up to 565 C. The heated salt flows back to ground level into another tank where it is stored, then pumped through a steam generator to produce steam and make electricity. This report establishes a set of criteria upon which the next generation of solar power towers will be designed. The report contains detailed criteria for each of the major systems: Collector System, Receiver System, Thermal Storage System, Steam Generator System, Master Control System, and Electric Heat Tracing System. The Electric Power Generation System and Balance of Plant discussions are limited to interface requirements. This design basis builds on the extensive experience gained from the Solar Two project and includes potential design innovations that will improve reliability and lower technical risk. This design basis document is a living document and contains several areas that require trade-studies and design analysis to fully complete the design basis. Project- and site-specific conditions and requirements will also resolve open To Be Determined issues