Chronosequence predictions are robust in a Neotropical secondary forest,but plots miss the mark

Tropical secondary forests (TSF) are a global carbon sink of 1.6 Pg C/year. However, TSF carbon uptake is estimated using chronosequence studies that assume differently aged forests can be used to predict change in aboveground biomass density (AGBD) over time. We tested this assumption using two airborne lidar datasets separated by 11.5 years over a Neotropical landscape. Using data from 1998, we predicted canopy height and AGBD within 1.1 and 10.3% of observations in 2009, with higher accuracy for forest height than AGBD and for older TSFs in comparison to younger ones. This result indicates that the space‐for‐time assumption is robust at the landscape‐scale. However, since lidar measurements of secondary tropical forest are rare, we used the 1998 lidar dataset to test how well plot‐based studies quantify the mean TSF height and biomass in a landscape. We found that the sample area required to produce estimates of height or AGBD close to the landscape mean is larger than the typical area sampled in secondary forest chronosequence studies. For example, estimating AGBD within 10% of the landscape mean requires more than thirty 0.1 ha plots per age class, and more total area for larger plots. We conclude that under‐sampling in ground‐based studies may introduce error into estimations of the TSF carbon sink, and that this error can be reduced by more extensive use of lidar measurements.     

自然资源资产负债表编制与资源环境承载力评价

探索编制自然资源资产负债表和建立资源环境承载力监测预警机制是十八届三中全会做出的重大决定。当前,自然资源资产负债表正处在探索试编阶段,资源环境承载力评价正在由分类评价走向综合计量的关键节点。"自然资源资产负债表编制与资源环境承载力评价技术集成与应用"项目(2016YFC0503500)面向国家资源环境统计核算的业务化需求,旨在发展自然资源资产负债表编制与资源环境承载力评价的方法与技术体系,提出自然资源资产负债表编制和资源环境承载力评价的技术标准/规范,研发自然资源资产负债表编制与资源环境承载力评价的数字化业务平台,实际应用于国家示范区并形成相应的配套政策及建议,为政府部门提供科技支撑和政策建议。     

冰核真菌的冰核活性及其种类鉴定*

作者从1993年起至今,从已分离和搜集到的500多株真菌中筛选出在-5℃具有冰核活性的真菌6株,它们-5℃的冻滴率高低顺序为F9502（100%）=F9501（100%）＞F9401（96％）=AS3．494（96%）＞F9801（94%）＞F9802（92%）,结冰点高低顺序为F9502（-2．7℃）＞F9501（-3．4℃）＞F9401（-4.4℃）＞AS34594（-4.5℃）＞F9801（-4．7℃）＞F9402（-4．8℃）,以F9502菌株活性强而稳定。经鉴定确定：F9401和F9402菌株为FusartumSportFichioldesSherb．;AS3．4594菌株为FavenaceumSacc．;F9501和F9502菌株为F.gramlnearumSchwabe;F9801菌株为F．monilijormeSheldon。F．Sportrlchloides和F．graminearum作为冰核真菌未见报道。本结果为揭示冰核真菌与植物冻害关系及冰核真菌开发应用研究提供了菌种资源,有重要应用价值。     

A first test of the hypothesis of biogenic magnetite-based heterogeneous ice-crystal nucleation in cryopreservation

An outstanding biophysical puzzle is focused on the apparent ability of weak, extremely low-frequency oscillating magnetic fields to enhance cryopreservation of many biological tissues. A recent theory holds that these weak magnetic fields could be inhibiting ice-crystal nucleation on the nanocrystals of biological magnetite (Fe₃O₄, an inverse cubic spinel) that are present in many plant and animal tissues by causing them to oscillate. In this theory, magnetically-induced mechanical oscillations disrupt the ability of water molecules to nucleate on the surface of the magnetite nanocrystals. However, the ability of the magnetite crystal lattice to serve as a template for heterogeneous ice crystal nucleation is as yet unknown, particularly for particles in the 10–100 nm size range. Here we report that the addition of trace-amounts of finely-dispersed magnetite into ultrapure water samples reduces strongly the incidence of supercooling, as measured in experiments conducted using a controlled freezing apparatus with multiple thermocouples. SQUID magnetometry was used to quantify nanogram levels of magnetite in the water samples. We also report a relationship between the volume change of ice, and the degree of supercooling, that may indicate lower degassing during the crystallization of supercooled water. In addition to supporting the role of ice-crystal nucleation by biogenic magnetite in many tissues, magnetite nanocrystals could provide inexpensive, non-toxic, and non-pathogenic ice nucleating agents needed in a variety of industrial processes, as well as influencing the dynamics of ice crystal nucleation in many natural environments.     

A Vegetation, Climate and Environment Reconstruction Based on Palynological Analyses of High Arctic Tundra Peat Cores (5000–6000 years BP) from Svalbard

As a reference for ongoing studies reconstructing past vegetation, climate and environment, pollen spectra in tundra peat profiles from Svalbard, were investigated. The base of tundra peat cores collected from Ny Ålesund, Stuphallet, Blomstrand and Isdammen has been ¹⁴C dated to 350–490 BP, 5710 BP, 4670 BP and 700–900 BP, respectively. The Stuphallet and Blomstrand (Brøggerhalvøya) peat profiles were composed of a peat developed in a nutrient enriched and wet tundra environment of steep birdcliffs. Pollen concentrations were low, Brassicaceae pollen dominated the whole profile. In contrast, the Ny Ålesund and Isdammen profiles contained high pollen concentrations and suggest a nutrient-poor, dry tundra environment. Pollen of the polar willow, Salix polaris, occurred commonly throughout all four peat profiles. In the relatively high resolution (10 years per peat core sample) analysis of the Ny Ålesund core, starting before or at the beginning of the Little Ice Age (LIA, 16th-mid 19th century), dominance of Saxifraga oppositifolia indicates a cold and dry climate, followed by a decline of Saxifraga oppositifolia and gradual increase of Salix polaris after the LIA, which indicates a moist and milder climate.     

Effects of different storage protocols on cat testis tissue potential for xenografting and recovery of spermatogenesis

The loss of genetic diversity due to premature death of valuable individuals is a significant problem in animal conservation programs, including endangered felids. Testis tissue xenografting has emerged as a system to obtain spermatozoa from dead immature animals, however protocols to store this tissue before xenografting are still lacking. This study focused on testis tissue cryopreservation and storage from the domestic cat (Felis catus) classified as “pre-pubertal” and “pubertal” according to spermatogenesis development. Grafts from testis tissue cryopreserved with DMSO 1.4M, recovered after 10 weeks xenografting, presented seminiferous tubules with no germ cells. On the contrary, testis tissue from pre-pubertal animals preserved in ice-cold medium for 2 to 5 days presented no loss of viability or spermatogenic potential, while the number of grafts of pubertal cat testis tissue with germ cells after 10 weeks of xenografting decreased with increasing storage time. Nevertheless, even grafts from pre-pubertal cat testis tissue presented lower anti-DDX4 and anti-BOULE staining (proteins necessary for the meiosis completion), when compared with adult cat testis. Finally, a strong correlation found between testis weight and xenograft outcome may help choose good candidates for xenografting.     

Surface Display of Domain Ⅲ of Japanese Encephalitis Virus E Protein on Salmonella Typhimurium by Using an Ice Nucleation Protein

A bacterial cell surface display technique based on an ice nucleation protein has been employed for the development of live vaccine against viral infection.Due to its ubiquitous ability to invade host cells,Salmonella typhimurium might be a good candidate for displaying viral antigens.We demonstrated the surface display of domain III of Japanese encephalitis virus E protein and the enhanced green fluorescent protein on S.typhimurium BRD509 using the ice nucleation protein.The effects of the motif in the ice nucleation protein on the effective display of integral protein were also investigated.The results showed that display motifs in the protein can target integral foreign protein on the surface of S.typhimurium BRD509.Moreover,recombinant strains with surface displayed viral proteins retained their invasiveness,suggesting that the recombinant S.typhimurium can be used as live vaccine vector for eliciting complete immunogenicity.The data may yield better understanding of the mechanism by which ice nucleation protein displays foreign proteins in the Salmonella strain.     

Carbohydrate-mediated inhibition of ice recrystallization in cryopreserved human umbilical cord blood

Cryopreservation of human umbilical cord blood (UCB) typically involves the cryoprotectant dimethylsulfoxide (DMSO), however, infusional toxicity and reductions in cell viability remain a concern. Ice recrystallization (IR) is an important source of cryopreservation-induced cellular injury and limits the stem cell dose in UCB units. Carbohydrates have wide-ranging intrinsic IR inhibition (IRI) activity related to structural properties. We investigated the impact of carbohydrate IRI on cell viability, induction of apoptosis and hematopoietic progenitor function in cryopreserved UCB. Mononuclear cells (MNCs) from UCB were cryopreserved in storage media containing specific carbohydrates (200 mM) and compared to 5% DMSO. Samples were analyzed under conditions of high IR (‘slow’ thaw) and low IR (‘fast’ thaw). Thawed samples were analyzed for viability and apoptosis by flow cytometry and hematopoietic function using colony-forming unit (CFU) assays. IRI of carbohydrate solutions was determined using the ‘splat cooling’ assay. Greater IRI capacity of carbohydrates correlated with increased yield of viable MNCs (r² = 0.92, p = 0.004) and CD34(+) cells (r² = 0.96, p = 0.019) after thawing under conditions of high IR. The correlations were less apparent under conditions of low IR. Carbohydrates with greater IRI modulate the induction of early apoptosis during thawing, especially in CD34+ cells (r² = 0.96, p = 0.0001) as compared to total mononuclear cells (p = 0.006), and preserve CFU capacity in vitro (r² = 0.92, p = <0.0001). Our results suggest that carbohydrates with potent IRI increase the yield of non-apoptotic and functional hematopoietic progenitors and provide a foundation for the development of novel synthetic carbohydrates with enhanced IRI properties to improve cryopreservation of UCB.     

Expression and localization of an ice nucleating protein from a soil bacterium, Pseudomonas borealis

An ice nucleating protein (INP) coding region with 66% sequence identity to the INP of Pseudomonas syringae was previously cloned from P. borealis, a plant beneficial soil bacterium. Ice nucleating activity (INA) in the P. borealis DL7 strain was highest after transfer of cultures to temperatures just above freezing. The corresponding INP coding sequence (inaPb or ina) was used to construct recombinant plasmids, with recombinant expression visualized using a green fluorescent protein marker (gfp encoding GFP). Although the P. borealis strain was originally isolated by ice-affinity, bacterial cultures with membrane-associated INP-GFP did not adsorb to pre-formed ice. Employment of a shuttle vector allowed expression of ina-gfp in both Escherichia coli and Pseudomonas cells. At 27 °C, diffuse fluorescence appeared throughout the cells and was associated with low INA. However, after transfer of cultures to 4 °C, the protein localized to the poles coincident with high INA. Transformants with truncated INP sequences ligated to either gfp, or an antifreeze protein-gfp fusion showed that the repetitive ice-nucleation domain was not necessary for localization. Such localization is consistent with the flanking residues of the INP associating with a temperature-dependent secretion apparatus. A polar location would facilitate INP–INP interactions resulting in the formation of larger aggregates, serving to increase INA. Expression of INPs by P. borealis could function as an efficient atmospheric dispersal mechanism for these soil bacteria, which are less likely to use these proteins for nutrient procurement, as has been suggested for P. syringae.