1.        Zhu, Liangjun, Li, Zongshan,Zhang, Yuandong, & Wang, Xiaochun. (2016). A 211‐year growingseason temperature reconstruction using tree‐ring width inzhangguangcai mountains, northeast china: linkages to the pacific and atlanticoceans. International Journal of Climatology.

Northeast China is one of the mostvulnerable areas to climate change in high latitude regions of the NorthernHemisphere. The past temperature variations are critical to reveal the drivingmechanism of climate change and to reduce the uncertainty in predicting futureclimates. Pre-instrument climatic variability is poorly understood, because ofthe scarcity of centuries-long climatic data. Here, we present a 211-year(1803–2013) growing season (May–July) temperature reconstruction based ontree-ring width chronology of Korean pine (Pinus koraiensis) from ZhangguangcaiMountains in Northeast China. The reconstruction accounted for 41.3% of thetemperature variance during the calibration period from 1959 to 2013. Thetemperature reconstruction was similar to other nearby temperaturereconstructions and correlated well spatially to gridded land and ocean surfacetemperature data. We identified four major cold periods (1839–1846, 1884–1901,1906–1908 and 1941–1958) and three major warm periods (1855–1880, 1918–1932 and1998–2013) in the past 211 years. The multi-taper method spectral analysisrevealed significant cycles at 48.8, 11.5, 8.9, 3.9, 3.5 and 2–3 years, whichmight be associated with global climate oscillations and land-sea thermalcontrasts, such as the sea surface temperatures, El Niño-Southern Oscillation,Atlantic Multidecadal Oscillation and solar activity.

http://onlinelibrary.wiley.com/doi/10.1002/joc.4906/epdf

2.        Guangqi Li, Sandy P. Harrison,& I. Colin Prentice. (2016). A model analysis of climate and co 2, controlson tree growth and carbon allocation in a semi-arid woodland. EcologicalModelling, 175–185.

Many studies have failed to show anincrease in the radial growth of trees in response to increasing atmosphericCO2 concentration [CO2] despite the expected enhancement of photosyntheticrates and water-use efficiency at high [CO2]. A global light use efficiencymodel of photosynthesis, coupled with a generic carbon allocation andtree-growth model based on mass balance and tree geometry principles, was usedto simulate annual ring-width variations for the gymnosperm Callitriscolumellaris in the semi-arid Great Western Woodlands, Western Australia, overthe past 100 years. Parameter values for the tree-growth model were derivedfrom independent observations except for sapwood specific respiration rate,fine-root turnover time, fine-root specific respiration rate and the ratio offine-root mass to foliage area (ζ), which were calibrated to the ring-widthmeasurements by approximate Bayesian optimization. This procedure imposed astrong constraint on ζ. Modelled and observed ring-widths showed quantitativelysimilar, positive responses to total annual photosynthetically active radiationand soil moisture, and similar negative responses to vapour pressure deficit.The model also produced enhanced radial growth in response to increasing [CO2]during recent decades, but the data do not show this. Recalibration in moving30-year time windows produced temporal shifts in the estimated values of ζ,including an increase by ca 12% since the 1960s, and eliminated the[CO2]-induced increase in radial growth. The potential effect of CO2 onring-width was thus shown to be small compared to effects of climate variabilityeven in this semi-arid climate. It could be counteracted in the model by amodest allocation shift, as has been observed in field experiments with raised[CO2].

http://www.sciencedirect.com/science/article/pii/S0304380016305257/pdfft?md5=53710f9674f2f3c32910afea58716e41&pid=1-s2.0-S0304380016305257-main.pdf

3.        Després, Tiphaine,Asselin, Hugo, Doyon, Frédérik, Drobyshev, Igor, & Bergeron, Yves. (2016). Gap dynamics oflate‐successional sugar maple-yellow birch forests at their northernrange limit. Journal of Vegetation Science.

Questions: We investigated whether the gapdisturbance rate (percent area disturbed by canopy gaps per year) differed atthe northern range limit of sugar maple (Acer saccharum Marsh.) – yellow birch(Betula alleghaniensis Britton) forests compared to broadleaf temperatedeciduous forests located more to the south. As an ancillary question, weassessed the relationship between species composition and gap disturbance rateat the stand scale.

Location: Late-successional sugar maple –yellow birch forests at their northern range limit in western Quebec, Canada(between 46°70’ – 47°22’ N and 78°49’ – 78°89’ W).

Methods: To reconstruct past gapdisturbances, we identified growth releases using the boundary line methodapplied to tree-ring chronologies obtained from 0.25 ha plots sampled within 11late-successional forest stands. We reconstructed past canopy gaps usingrelease events, calculated historical gap disturbance rates, and used redundancyanalysis to evaluate the relationship between gap disturbance rate and speciescomposition at the stand scale.

Results: The mean gap disturbance rateacross the 11 late-successional stands was 0.96 ± 0.51% per year. Mean gap sizewas 39 ± 44 m2 and almost 85% of the gaps were smaller than 50 m2. Stands withsmaller gaps and lower gap disturbance rates had high importance values forbalsam fir (Abies balsamea (L.) Mill) and/or yellow birch.

Conclusions: The gap disturbance rate atthe northern limit of sugar maple – yellow birch forest was similar to thatreported in broadleaf temperate deciduous forests located ca. 575-1300 km tothe south. However, gaps were more numerous and smaller, which could relate tolatitudinal differences in allometric traits of the dominating tree species andclimate.

http://onlinelibrary.wiley.com/doi/10.1111/jvs.12480/epdf

4.        Yueh-Hsin Lo, Juan A. Blanco,Biing Tzuang Guan PhD. . Douglas-fir radial growth in interior british columbiacan be linked to long-term oscillations in pacific and atlantic sea surfacetemperatures. Canadian Journal of Forest Research.

We used Ensemble Empirical ModeDecomposition to detrend tree-ring records and to extract climate signalswithout removing low-frequency information. Tree cores of Pseudotsuga menziesiiwere examined in a semi-arid forest in southern interior BC. Ring width datawere decomposed into five oscillatory components (intrinsic mode functions,IMFs) of increasingly longer periodicities. IMF1 was considered white noise,IMF2 was used to create the first diameter growth index (DGI-1), IMF3 and IMF4were combined to create the second diameter growth index (DGI-2), whereas IMF5and the residual term together were considered as the trend term. The highestsignificant cross-correlations between DGI-1 and the NAOAugust, NIÑO12May, andPDOJanuary indices were found at 1-year lags. DGI-2 had positive and persistentcorrelations with NAOJune and PDOMay at 0 to 3 years lags, and with NAOMay at 2and 3 years lags. Our results indicate that periods of slow growth in the treering record matched periods of drought in the Pacific Northwest. Suchconditions are likely caused by oscillatory patterns in the Pacific Ocean seasurface temperatures that influence precipitation in the Pacific Northwest,which are likely exacerbated by changes in winter precipitation (snowpack)related to oscillations of the Atlantic Ocean sea surface temperatures.

http://www.nrcresearchpress.com/doi/pdf/10.1139/cjfr-2016-0203

5.        Cailleret, Maxime, Jansen,Steven, Robert, Elisabeth M. R., Desoto, Lucía, Aakala, Tuomas, & Antos,Joseph A., et al. (2016). A synthesis of radial growth patterns preceding treemortality. Global Change Biology.

Tree mortality is a key factor influencingforest functions and dynamics, but our understanding of the mechanisms leadingto mortality and the associated changes in tree growth rates are still limited.We compiled a new pan-continental tree-ring width database from sites whereboth dead and living trees were sampled (2,970 dead and 4,224 living trees from190 sites, including 36 species), and compared early and recent growth ratesbetween trees that died and those that survived a given mortality event.

We observed a decrease in radial growthbefore death in ca. 84% of the mortality events. The extent and duration ofthese reductions were highly variable (1-100 years in 96% of events) due to thecomplex interactions among study species and the source(s) of mortality. Strongand long-lasting declines were found for gymnosperms, shade- anddrought-tolerant species, and trees that died from competition. Angiosperms andtrees that died due to biotic attacks (especially bark-beetles) typicallyshowed relatively small and short-term growth reductions. Our analysis did nothighlight any universal trade-off between early growth and tree longevitywithin a species, although this result may also reflect high variability insampling design among sites.

The inter-site and inter-specificvariability in growth patterns before mortality provides valuable informationon the nature of the mortality process, which is consistent with ourunderstanding of the physiological mechanisms leading to mortality. Abruptchanges in growth immediately before death can be associated with generalizedhydraulic failure and/or bark beetle attack, while long-term decrease in growthmay be associated with a gradual decline in hydraulic performance coupled withdepletion in carbon reserves. Our results imply that growth-based mortalityalgorithms may be a powerful tool for predicting gymnosperm mortality inducedby chronic stress, but not necessarily so for angiosperms and in case ofintense drought or bark-beetle outbreaks.

http://onlinelibrary.wiley.com/doi/10.1111/gcb.13535/epdf

6.        Bakaj, Felicia, Mietkiewicz,Nathan, Veblen, Thomas T., & Kulakowski, Dominik. (2016). The relativeimportance of tree and stand properties in susceptibility to spruce beetleoutbreak in the mid‐20th century. Ecosphere, 7.

Tree susceptibility to potentially lethalagents is determined not only by attributes of individual trees, but also byneighborhood effects at a range of scales. For example, effects of disturbanceson individual trees are often contingent on the size, configuration, and otherproperties of neighboring trees. Wildfires can modify postfire properties ofindividual trees as well as of entire forest stands, both of which can affectsubsequent ecological processes, including subsequent disturbances. In recentyears, much has been learned about how disturbances interact, but numerousquestions concerning underlying mechanisms remain unresolved. For example, therelative importance of forest properties at different spatial scales indetermining how fires affect forest susceptibility to subsequent disturbancesis not well understood. This study explicitly compares the relative importanceof tree vs. fine-scale neighborhood effects (e.g., stand properties at <7 mradii), on susceptibility to a 1940s' spruce beetle outbreak. Attributes ofindividual trees and of stand structure were spatially reconstructed at five250-m2 sites that were partly burned in the late 19th century and then affectedby spruce beetle outbreak in the 1940s. Random Forest models and classificationtrees were used to compare the relative importance of variables forsusceptibility to spruce beetle attack. Individual tree properties (diameter atbreast height and age) were the most important predictors of susceptibility tothe outbreak across all sites combined and at each of the sites individually.In contrast, neighborhood effects were poor predictors of susceptibility. Thisstudy suggests wildfires reduce susceptibility to outbreaks primarily by reducingthe size of postfire live trees and only secondarily by modifying standstructure. One implication of this is that management strategies that aim tomodify stand structure over large areas in order to reduce susceptibility tospruce beetle outbreaks may be unnecessarily intensive.

http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1485/epdf

7.        Nicklen, E. Fleur, Roland, CarlA., Ruess, Roger W., Schmidt, Joshua H., & Lloyd, Andrea H. (2016). Localsite conditions drive climate–growth responses of picea mariana and piceaglauca in interior alaska. Ecosphere, 7.

The growth response of boreal forest treesto projected changes in climate will have wide ranging and cascading impacts ondisturbance regimes, climate feedbacks, carbon storage, and habitat ranges forflora and fauna. Recent findings in Alaska suggest the boreal biome is shiftingin response to changes in climate. It is unlikely such a shift will occur in auniform manner over a landscape variable in topography and site conditions,although there is little consensus of how local site characteristics willinteract with climate to alter tree growth patterns. Few studies of tree growthresponses to climate in the boreal forest have used randomized study designsencompassing the full range of site conditions, leaving open the question ofwhether observed patterns in tree growth at local scales are whollyrepresentative of the boreal forest. We addressed these issues using asystematic sampling design to quantify the landscape-scale patterns in annualgrowth for Picea mariana and Picea glauca, the two most abundant tree speciesin interior Alaska. We used measurements of annual tree growth based onincrement cores taken from trees distributed across a 1.28 million-ha studyarea in Denali National Park and Preserve. We found site-specific variables,namely near-surface permafrost, slope angle, and elevation, strongly modifiedthe magnitude, shape, and, in some cases, the direction of growth response toclimatic conditions for both species. With predicted warming, our resultssuggest both P. mariana and P. glauca will decrease growth in areas underlainby shallow permafrost. P. mariana growth may increase on flat terrain, butdecrease on steep slopes, while P. glauca growth will show the greatest increasesat high elevations during very warm summers. Our results suggest future shiftsin these species distributions in response to a changing climate will beconditional on variation in site factors operating at local scales.

http://onlinelibrary.wiley.com/doi/10.1002/ecs2.1507/epdf

8.        Jesse L. Morris, StuartCottrell, Christopher J. Fettig, Winslow D. Hansen, Rosemary L. Sherriff, &Vachel A. Carter, et al. (2016). Managing bark beetle impacts on ecosystems andsociety: priority questions to motivate future research.

Recent bark beetle outbreaks in NorthAmerica and Europe have impacted forested landscapes and the provisioning ofcritical ecosystem services. The scale and intensity of many recent outbreaksare widely believed to be unprecedented. The effects of bark beetle outbreakson ecosystems are often measured in terms of area affected, host tree mortalityrates, and alterations to forest structure and composition. Impacts to humansystems focus on changes in property valuation, infrastructure damage fromfalling trees, landscape aesthetics, and the quality and quantity of timber andwater resources. To advance our understanding of bark beetle impacts, weassembled a team of ecologists, land managers and social scientists toparticipate in a research prioritization workshop. Synthesis and applications.We identified 25 key questions by using an established methodology to identifypriorities for research into the impacts of bark beetles. Our efforts emphasizethe need to improve outbreak monitoring and detection, educate the public onthe ecological role of bark beetles, and develop integrated metrics thatfacilitate comparison of ecosystem services across sites.

https://www.researchgate.net/publication/309276187_Managing_bark_beetle_impacts_on_ecosystems_and_society_Priority_questions_to_motivate_future_research