The influence of depth,site exposure and season on the intensity of iceberg scouring in nearshore Antarctic waters

Ice scour disturbance has a significant effect on the physical and biological characteristics of polar benthos. A series of grids, each consisting of 25 markers, were deployed along depth transects and replicated at two contrasting study sites at Adelaide Island, West Antarctic Peninsula. Markers were surveyed and replaced every 3 months for 2 years in order to assess the frequency and intensity of iceberg impacts. Depth, site, season and year were all highly significant factors influencing ice scouring frequency. We observed a high variation in the duration of winter fast ice between sites and years, which had a marked effect on ice scouring frequency. The ecological effects of the disturbance regime are likely to include depth zonation of benthic assemblages, patchiness of communities at varying stages of recovery and the near denudation of sessile fauna in the shallow subtidal.

The biomechanics of concussion for ice hockey head impact events

The purpose of this research was to conduct reconstructions of concussive and non-concussive impacts in ice hockey to determine the biomechanics and thresholds of concussive injury in ice hockey. Videos of concussive and non-concussive impacts in an elite professional ice hockey league in North America were reconstructed using physical and finite element model methods. Eighty concussive and 45 non-concussive events were studied. Logistic regressions indicate significant thresholds for concussion for linear/rotational acceleration and CSDM_10%. Impacts in ice hockey were mostly long duration events, longer than 15?ms. These results have significant implications for helmet standards and development to prevent concussion.     

Phylogeography of a Palaearctic sedentary passerine,the willow tit (Parus montanus)

We analysed variation of the mitochondrial control region from willow tits through its Palaearctic distribution range. Although we found high amount of genetic variation (π=1.114%), there was almost no differentiation between subspecies or geographical localities. This may be because of a combination of several ecological and genetic factors, including a relatively homogenic habitat through the distribution range, lack of geographical barriers, high gene flow and a large long‐term effective population size. On the contrary, in the songar tit, which is sometimes considered to be conspecific with the willow tit, the mitochondrial lineages seem to correlate with the geographical locality and are clearly distinct from the willow tit. We concluded that the common ancestors of willow and songar tits existed some 1.5–2 Myr ago in the south‐eastern Asia. After the last Ice Ages, the willow tit expanded all through the Palaearctic, whereas the songar tit remained in eastern Asia.     

Winter in the Ouchitas—A severe winter storm signature in Pinus echinata in the Ouachita Mountains of Oklahoma and Arkansas,USA

Each year severe winter storms (≈ice storms) damage trees throughout the southern USA. Arkansas and Oklahoma have a history of severe winter storms. To extend that history back beyond the reach of written records, a distinctive tree ring pattern or signature is needed. Storm-caused breakage, branch loss and bending stress provide that signature. We found a severe storm signature in shortleaf pine (Pinus echinata). We used three published site chronologies, a set of five new site chronologies from a growth-and-yield study conducted by Oklahoma State University and the unpublished Shortleaf Canyon chronology from a master’s thesis at the University of Arkansas. Our method is based on two ring width values for the first and second growing seasons after the storm standardized to the ring widths of the seven growing seasons after the storm. Concordance between storm years predicted by tree ring patterns and actual storm years was tested using Cohen’s Kappa. Concern about confounding of ice storm signals by droughts led us to test concordance between severe storms and drought in July, August and September; results were inconclusive but stand as a warning that these two phenomena cannot be distinguished with certainty in the tree ring record. Damaging severe storms occurred in about 2.8% of all years. Two out of three storms identified as “severe” produced glaze icing.     

Ice binding,recrystallization inhibition,and cryoprotective properties of ice-active substances associated with Antarctic sea ice diatoms

Extracellular macromolecules associated with Antarctic sea ice diatoms were previously shown to have ice-binding activities. The function of these ice-active substances (IASs) has not been identified. Here we show that two of the IASs have a strong ability to inhibit the recrystallization of ice, possibly signifying a cryoprotectant function. To test this possibility, two species of marine diatom (one Antarctic and one temperate) were subjected to a single freeze-thaw cycle (approximately 20h at -4 or -5 degrees C) in the presence or absence of IAS. Viability, based on a double staining technique, was 15-29% higher in the presence of IAS. Etching of single crystal ice hemispheres grown from dilute IAS solutions indicated that the IASs bind to specific faces of ice and are incorporated into the ice lattice. Together, these results suggest that the IASs acts as a cryoprotectant, probably through some ice-binding mechanism.     

粤北山地常绿阔叶林自然干扰后冠层结构空间异质性动态

以受2008年冰灾破坏的广东始兴车八岭山地常绿阔叶林为研究对象,采用半球面影像技术、地统计学的空间异质性和空间自相关分析方法,连续3年(2008-2010年)对林冠结构空间异质性动态进行了检测研究.结果表明:(1)从2008到2010年,林冠开度的平均值、标准差、变异系数、最大值、最大值和最小值的差值以及林冠结构的空间异质性均在逐渐减小,且后两年较为接近;(2)受灾当年冠层结构由随机因素造成,其半方差拟合函数属纯块金模型,后两年冠层结构则由结构性因素引起,其半方差拟合函数属球状模型;(3)受灾当年冠层结构不存在空间自相关;随着时间推移其空间自相关越来越强.说明冰灾后常绿阔叶林冠层结构在没有人为干预的情况下会逐渐恢复到灾前水平,体现出天然的空间分布状况.     

Purification of antifreeze proteins by adsorption to ice

Antifreeze proteins (AFPs) can protect organisms from freezing injury by adsorbing to ice and inhibiting its growth. We describe here a method where ice, grown on a cold finger, is used to selectively adsorb and purify these ice-binding proteins from a crude mixture. Type III recombinant AFP was enriched approximately 50-fold after one round of partitioning into ice and purified to homogeneity by a second round. This method can also be used to purify non-ice-binding proteins by linkage to AFP domains as demonstrated by the recovery of a 50 kDa maltose-binding protein-AFP fusion from a crude lysate of Escherichia coli.     

Effects of salicylic acid and cold on freezing tolerance in winter wheat leaves

The effects of salicylic acid (SA) (0.01, 0.1 and 1 mM) and cold on freezing tolerance (freezing injury and ice nucleation activity) were investigated in winter wheat (Triticum aestivum cv. Dogu-88) grown under control (20/18 °C for 15, 30 and 45-day) and cold (15/10 °C for 15-day, 10/5 °C for 30-day and 5/3 °C for 45-day) conditions. Cold acclimatisation caused a decrease of injury to leaf segments removed from the plants and subjected to freezing conditions. Exogenous SA also decreased freezing injury in the leaves grown under cold (15/10 °C) and control (15 and 30-day) conditions. Cold conditions (10/5 and 5/3 °C) caused an increase in ice nucleation activity by apoplastic proteins, which were isolated from the leaves. For the first time, it was shown that exogenous SA caused an increase in ice nucleation activity under cold (15/10 and 10/5 °C) and control conditions. These results show that salicylic acid can increase freezing tolerance in winter wheat leaves by affecting apoplastic proteins.     

Determining the Ice-binding Planes of Antifreeze Proteins by Fluorescence-based Ice Plane Affinity

Antifreeze proteins (AFPs) are expressed in a variety of cold-hardy organisms to prevent or slow internal ice growth. AFPs bind to specific planes of ice through their ice-binding surfaces. Fluorescence-based ice plane affinity (FIPA) analysis is a modified technique used to determine the ice planes to which the AFPs bind. FIPA is based on the original ice-etching method for determining AFP-bound ice-planes. It produces clearer images in a shortened experimental time. In FIPA analysis, AFPs are fluorescently labeled with a chimeric tag or a covalent dye then slowly incorporated into a macroscopic single ice crystal, which has been preformed into a hemisphere and oriented to determine the a- and c-axes. The AFP-bound ice hemisphere is imaged under UV light to visualize AFP-bound planes using filters to block out nonspecific light. Fluorescent labeling of the AFPs allows real-time monitoring of AFP adsorption into ice. The labels have been found not to influence the planes to which AFPs bind. FIPA analysis also introduces the option to bind more than one differently tagged AFP on the same single ice crystal to help differentiate their binding planes. These applications of FIPA are helping to advance our understanding of how AFPs bind to ice to halt its growth and why many AFP-producing organisms express multiple AFP isoforms.     

Large-scale,millennial-length temperature reconstructions from tree-rings

Over the past two decades, the dendroclimate community has produced various annually resolved, warm season temperature reconstructions for the extratropical Northern Hemisphere. Here we compare these tree-ring based reconstructions back to 831 CE and present a set of basic metrics to provide guidance for non-specialists on their interpretation and use. We specifically draw attention to (i) the imbalance between (numerous) short and (few) long site chronologies incorporated into the hemispheric means, (ii) the beneficial effects of including maximum latewood density chronologies in the recently published reconstructions, (iii) a decrease in reconstruction covariance prior to 1400 CE, and (iv) the varying amplitudes and trends of reconstructed temperatures over the past 1100 years. Whereas the reconstructions agree on several important features, such as warmth during medieval times and cooler temperatures in the 17th and 19th centuries, they still exhibit substantial differences during 13th and 14th centuries. We caution users who might consider combining the reconstructions through simple averaging that all reconstructions share some of the same underlying tree-ring data, and provide four recommendations to guide future efforts to better understand past millennium temperature variability.