Laser glass fracture and cooling scalability in high average power gas-cooled laser amplifiers were studied by in-situ optical probing of laser glass during actual fracture events under realistic thermal load conditions.

Large wood (LW) affects several ecological and hydrogeomorphic processes in streams. The main source of LW is riparian trees falling inside channels. However, in confined valley floors, falling trees are more likely to be suspended above the channel. Eventually, these suspended trees will decompose and break to finally fall into the channel to better provide functions for streams. We evaluated changes in wood decay, length, diameter, and suspended status (suspended or non-suspended) 17 years post-harvest and nine years after the first sampling occurred in 2006 in 12 headwater streams of coastal British Columbia, Canada. We also evaluated whether changes differed among riparian management treatments (no-harvest buffers of 10 and 30 m in width, thinning, and unharvested reference sites), and identified the factors affecting wood changes and suspended status. Wood pieces advanced in decay, became shorter, and 34% of them (n = 108) changed status from suspended to non-suspended. Non-suspended wood pieces were more decayed and shorter than suspended wood. Suspended wood was longer, thicker, less decayed, and represented 46.5% (n = 147) of the wood sampled in 2006. Our findings revealed limited influences of riparian management on many aspects of wood changes considered in this study. Changes in wood characteristics were more likely for pieces that were smaller in diameter, longer, and suspended closer to the water. The transition from suspended to non-suspended LW can be a long-term process that can increase wood residence time and reduce LW in-stream functions particularly in confined stream valleys. The suspended stage is also an important mechanism underlying time lags in stream ecosystem responses to riparian tree fall. (c) 2020 John Wiley & Sons, Ltd.

Stand-level retention is an important component of sustainable forest management which aims to balance ecological, social and economic objectives. Long-term retention of mature forest structures at the time of harvesting (variable retention) is intended to produce future forest stands that more closely resemble conditions that develop after natural disturbances, thereby maintaining greater diversity of habitats for a variety of organisms. Structure includes features such as live and dead trees representing multiple canopy layers, undisturbed understory vegetation and coarse woody debris. Over the past two decades, variable retention has become common on forest lands in the temperate rainforests of coastal British Columbia (BC) and has been applied to a lesser extent in inland forest types. Our review of studies in BC and in similar forest types in our region indicates that both aggregated and dispersed retention can contribute to biodiversity conservation by providing short-term life-boating' habitat for some species and by enhancing the structural characteristics of future stands. For example, greater abundance of species present in the pre-harvest forest have been documented for vegetation, birds, carabid beetles, gastropods, ectomycorrhizal fungi and soil fauna in retention cutblocks compared to clearcuts. There are, however, some negative consequences for timber production such as wind damage to retained trees and reduced growth rates of tree regeneration compared to clearcuts. The authors suggest an adaptive management approach for balancing competing objectives when faced with uncertainty. This includes monitoring the implementation and effectiveness of various strategies for achieving goals. Over two decades of experience applying variable retention harvesting to industrial-scale management of forest lands in BC suggests that it is possible to balance production of wood with biodiversity conservation.

The mechanical response of a well-instrumented Norway spruce (Picea abies L.) tree under controlled winch loading was monitored. The main aims of this study were to understand the tree-root-soil response to lateral pull loads, to examine the applicability of simple engineering principles to the tree-root-soil response and to introduce a soil component into the tree stability analysis. The stem response was recorded with tilt sensors at three different heights; two sensors at each height tracked the response in transverse directions. These data were used to derive deflection and bending moment profiles of the stem for different lateral loads. A root on the windward side and one on the leeward side were instrumented using strain gauges. The tree was winched to failure and the data were collected from the strain gauges during winching. Using the data obtained from strain gauges on the roots, strain, bending moment, shear force and deflection profiles the roots with increasing load were calculated. Using the soil reaction force-deflection profiles of the roots, equivalent spring stiffness constants were determined. An estimate of the anchorage strength and moment–rotation relationship was made using a simple characteristic curve equation normalized by the failure moment and rotation that can be modified for different soil conditions.

T. B. MITFORD, EAST OF ASIA MINOR. ROME'S HIDDEN FRONTIER. Oxford: Oxford University Press, 2018. Vol. 1: pp. li + 425; vol. 2, pp. 332, illus. isbn9780198725176 (set); 9780198148756 (vol. 1); 9780198725169 (vol. 2). £225.00 (set). - Volume 109

In Boreal North America, management approaches inspired by the variability in natural disturbances are expected to produce more resilient forests. Wind storms are recurrent within Boreal Ontario. The objective of this study was to simulate wind damage for common Boreal forest types for regular as well as extreme wind speeds. The ForestGALES_BC windthrow prediction model was used for these simulations. Input tree-level data were derived from permanent sample plot (PSP) data provided by the Ontario Ministry of Natural Resources. PSPs were assigned to one of nine stand types: Balsam fir-, Jack pine-, Black spruce-, and hardwood-dominated stands, and, Jack pine-, spruce-, conifer-, hardwood-, and Red and White pine- mixed species stands. Morphological and biomechanical parameters for the major tree species were obtained from the literature. At 5 m/s, predicted windthrow ranged from 0 to 20%, with damage increasing to 2 to 90% for winds of 20 m/s and to 10 to 100% for winds of 40 m/s. Windthrow varied by forest stand type, with lower vulnerability within hardwoods. This is the first study to provide such broad simulations of windthrow vulnerability data for Boreal North America, and we believe this will benefit policy decisions regarding risk management and forest planning.

Until the end of the fourth century BCE the impact of Greek culture in Asia Minor was limited. Lykians, Karians, and Lydians offered alternatives to Hellenism and preserved their own languages until the end of the fourth century BCE. However, by 250 BCE these Anatolian languages ceased to be used in public or private documents, and polis organization became normative. After the overthrow of the Persian Empire the autonomy of Greek cities became the highest political objective. Greek civic decrees in the early Hellenistic period emphasized that democratic legitimacy depended on quorate citizen votes, the Greek language became the only medium for official public communication, and the native populations maintained their identity and independence by adopting polis organization. Between 400 and 250 BCE these populations did not merely absorb Greek cultural influence but underwent the encompassing experience of becoming Greek.

Ruler worship and provincial organisation in the Roman East and the oath of loyalty sworn to Augustus - SØREN LUND SØRENSEN, BETWEEN KINGDOM AND KOINON. NEAPOLIS/NEOKLAUDIOPOLIS AND THE PONTIC CITIES (Geographica Historica Band 33; Franz Steiner Verlag, Stuttgart 2016). Pp. 224, figs. 20. ISBN 978-3-515-11312-0. - ANNE KOLB und MARCO VITALE (edd.), KAISERKULT IN DEN PROVINZEN DES RÖMISCHEN REICHES. ORGANISATION, KOMMUNIKATION UND REPRÄSENTATION (De Gruyter, Berlin 2016). Pp. ix + 512, figs. including colour. ISBN 978-3-11-041671-8. - Volume 30

Windthrow is a recurring disturbance process in regions that are influenced by maritime climates, including boreal forests. Within the circumboreal region, forest management approaches have been adapted to emulate natural disturbance in order to promote biodiversity and ecosystem resilience. Few studies have evaluated windthrow outcomes in natural or managed old-growth boreal mixed-species stands, and these studies are primarily empirical. The objective of this study was to adapt the hybrid empirical mechanistic ForestGALES_BC model, to investigate windthrow dynamics in natural and managed boreal old-growth stands, under various wind regimes. ForestGALES_BC was updated by adding biomechanical data for balsam fir (Abies balsamea (L) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.). The model has the ability to simulate damage propagation during wind events by recalculating wind loading on a subject tree after failure of upwind trees. The number of iterations of this recalculation provides insights into the potential for propagation during longer duration storms. A simulation space made up of 500, 20 m x 20 m cells, was created using tree-lists from silviculture systems experiments in north eastern Quebec. The tree-lists for cells within the simulation space were edited to represent the plot conditions at the Quebec experimental sites, allowing simulation of a range of cell-(plot) and matrix-level (landscape) partial harvesting regimes. Above-canopy winds of various speeds were applied in order to test the initiation and propagation of damage within the simulated forest. Simulated outcomes were compared to observations of windthrow 6-7 years after partial harvesting at the field experimental site. Observed damage at the experimental site ranged from 1 to 40% of plot total basal area (mean = 14%, se = 1.96). For above-canopy wind speeds within the range expected for the experimental site, simulated windthrow levels in partial cuts ranged from 7 to 32% (mean =12%, se = 1.94). When the combined effects of wind speed and number of iterations (similar to event duration) were investigated, event duration was more important for wind speeds over 20 m/s. By enabling simulation of outcomes at the tree, plot (cell) and stand (simulation space) levels, the model allows investigation of a wide range of harvesting strategies, and sets the stage for inclusion of wind disturbance in ecosystem succession models and other stand or landscape-level decision-support tools for forests in windy climates. (C) 2016 Elsevier B.V. All rights reserved.

EDITORIAL article Front. Plant Sci., 06 October 2016Sec. Plant Physiology Volume 7 - 2016 | https://doi.org/10.3389/fpls.2016.01441

Terrestrial ecosystems of the Atlantic coastal plain have experienced considerable change over the past two centuries, largely due to agricultural activities and fire suppression and exclusion. Many areas that were once dominated by open longleaf pine (Pinus palustris) woodlands now support closed canopy stands of loblolly pine (Pinus taeda) with a dense midstory of broadleaved shrubs and trees. In recent years, efforts to restore the herbaceous plant communities typically found in fire-maintained longleaf pine woodlands have focused on the use of midstory thinning to produce savanna-like conditions and to facilitate the restoration of historical fire regimes through prescribed burning. Previous efforts to restore longleaf pine stands have focused on the potential of fire-suppressed longleaf pine woodlands, which have been met with some success. However, it is unclear what the potential is for loblolly pine stands to act as a 'surrogate' environment for the restoration of the often species-rich herbaceous layer of longleaf pine woodlands. To assess the effectiveness of longleaf pine restoration treatments in existing loblolly pine stands, we analyzed the drivers of plant community composition in loblolly pine stands with mechanical midstory removal treatments, untreated loblolly pine stands, longleaf pine stands, and pond pine dominated high-pocosin systems. We sampled 75 plots, from which more than 200 individual plant taxa were identified, with species richness (number of species per 0.1 ha) ranging from 9 in pond pine pocosins to 118 in longleaf pine woodlands. Plant species richness and composition varied in response to soil properties, with the first NMS ordination axis correlated with soil properties related to soil moisture and organic matter content (SUM), and the second NMS ordination axis correlated to the concentration of certain soil nutrients (P. Ca), the variability of which may be due, in part, to historic fertilizer applications. While stand types were largely distinct from each other in their vegetation composition, there was nevertheless some compositional overlap among some longleaf and loblolly pine stands. Areas of compositional overlap appear to have somewhat similar soil properties, whereby the soils found in overlapping loblolly pine stands were closer to those found in longleaf pine stands (i.e. low SUM content). Thus, an assessment of the soil properties of loblolly pine stands may allow for an identification of candidate sites for which longleaf pine restoration treatments may be most effective. (C) 2015 Elsevier B.V. All rights reserved.

Summary Disturbance is an important driver of plant community structure in many grasslands and woodlands, and alteration of disturbance regimes can have large consequences for species richness and composition. However, the response of vegetation to disturbance may change with environmental context. We resampled a unique, nested permanent vegetation plot data set in the longleaf pine ecosystem of the southeastern USA after 20 years to determine how environmental context and fire frequency jointly influence vegetation change across multiple spatial scales (0.01–1000 m2). The magnitude of vegetation change was quantified using two different, yet complementary metrics of beta‐diversity (beta turnover measured as the proportion of species turning over and Bray–Curtis dissimilarity) and by documenting changes in species richness. We used null model analysis to explore whether communities were more dynamic over time at small spatial scales relative to larger scales. Changes in species richness, beta turnover and Bray–Curtis dissimilarity were greatest on silty, frequently burned sites, whereas sandy, less frequently burned sites remained relatively stable. The amount of change detected was scale dependent: species richness increased at larger spatial scales over time, but decreased at the two smallest spatial scales. Null model analysis revealed that beta turnover standardized effect sizes (SES) were negative and significantly different from random expectation at all spatial scales except the smallest. Thus, the magnitude of compositional change across most scales was small, despite substantial changes in species richness across time. We attribute this initial contradiction to the turnover of infrequent, low‐abundance species amidst a matrix of dominant grasses. Synthesis. In contrast to previous longleaf pine studies, we found fire frequency to be less important than environmental site conditions in predicting vegetation change. Thus, future work in this ecosystem and in other fire‐dependent grasslands and woodlands should consider not only disturbance, but also environmental context. Since species richness and beta‐diversity patterns were scale dependent, we recommend sampling vegetation across multiple spatial scales in order to comprehensively quantify changes in community structure over time. We believe this study lays the groundwork for understanding how fire and environmental filtering jointly influence vegetation dynamics across space and time in fire‐dependent grasslands and woodlands.

Climatic change is exerting considerable influence on the hydrologic and biogeochemical cycles of snow-dominated montane forest ecosystems. Growing season drought stress is a common occurrence after snowmelt-derived soil water content (WC) and stream flow (Q) have declined, leading to an increase in atmospheric water demand (i.e., vapor pressure deficit, VPD). Here, we analyzed a 6-year record (2006-2011) of H2O and CO2 fluxes from the Tenderfoot Creek Experimental Forest, a montane forest in the northern Rocky Mountains to examine (1) how growing season evapotranspiration (ET), net ecosystem production (NEP), and water-use efficiency (WUE, NEP/ET) respond to changing WC and VPD, (2) how stream flow (Q), an integrated measure of catchment-level water availability, relates to NEP, and (3) how annual NEP is related to annual precipitation and the temperature-defined growing season length (GSL). Growing season NEP exhibited a linear relationship with WC and a log-linear relationship with Q, indicative of persistent water limitations when streamflow and soil moisture reach their annual minima late in the growing season. Nevertheless, years with long GSLs had relatively higher NEP, with a small net carbon sink maintained even at low levels of WC and Q, suggesting that trees are able to obtain water from deeper portions of the soil profile (>30 cm) during droughts. However, the warmer, drier climate projected for this region could bring this system closer to a critical threshold of GSL, WC, and VPD, introducing vegetation water stress that could alter the current relationship between GSL and annual NEP. (C) 2015 Elsevier B.V. All rights reserved.

Among the concerns raised by climatic change is the potential for the additional release of carbon dioxide as a result of biomass combustion. Most of the carbon emissions from wildfires are from the combustion of litter, duff, and small woody debris, whereas most, if not all, of the biomass stored in the boles of large trees is not combusted. Consequently, most of the carbon stored in forests remains unconsumed, even by high-severity wildfires. Thus the application of fuel reduction treatments, while sometimes effective in reducing fire severity and carbon emissions, nearly always result in a net reduction in carbon storage. Postfire carbon emissions from the decomposition of fire-killed biomass can continue for decades, but effects of forest regrowth can exceed the losses of carbon from biomass combustion and the decomposition of fire-killed biomass within 5-50 years, depending on the ecosystem.

Afforestation and reforestation (A/R) projects generate greenhouse gas (GHG) reduction credits by removing carbon dioxide from the atmosphere through biophysical processes and storing it in terrestrial carbon stocks. One feature of A/R activities is the possibility of non-permanence, in which stored carbon is lost though natural or anthropogenic disturbances. The risk of non-permanence is currently addressed in Clean Development Mechanism (CDM) A/R projects through temporary carbon credits. To evaluate other approaches to address reversals and their implications for policy and investment decisions, we assess the performance of multiple policy and accounting mechanisms using a forest ecosystem simulation model parameterized with observational data on natural disturbances (e.g., fire and wind). Our analysis finds that location, project scale, and system dynamics all affect the performance of different risk mechanisms. We also find that there is power in risk diversification. Risk management mechanisms likewise exhibit a range of features and tradeoffs among risk conservatism, economic returns, and other factors. Rather than relying on a single approach, a menu-based system could be developed to provide entities the flexibility to choose among approaches, but care must be taken to avoid issues of adverse selection.