Water relation patterns of bare-root and container jack pine and black spruce seedlings planted on boreal cut-over sites     

Steven C. Grossnickle  Terence J. Blake 《New Forests》1987,1(2):101-116

Water relation patterns and subsequent growth were studied on bare-root and container jack pine (Pinus banksiana Lamb.) and black spruce (Picea mariana (Mill.) B.S.P.) seedlings during the first growing season on boreal cut-over sites.Containerized seedlings of both species had greater needle conductance compared to bare-root seedlings over a range of absolute humidity deficits. Needle conductance of containerized seedlings in both species remained high during periods of high absolute humidity deficits and increasing plant moisture stress. Bare-root seedlings of both species had a greater early season resistance to water-flow through the soil-plant-atmosphere continuum (SPAC) than container seedlings. Resistance to water flow through the SPAC decreased in bare-noot seedlings of both species as the growing season progressed, and was comparable to container seedlings 9 through 14 weeks after planting. Four weeks after field planting jack pine container seedlings had greater new root development compared to bare-root seedlings, while at the end of the summer both stock types had similar new root development. Black spruce bare-root seedlings had greater new root development compared with container seedlings throughout the growing season.  相似文献   

多重复干旱循环对北美短叶松和黑云杉苗木气体交换及水分利用效率的影响     

李吉跃 《中国林学(英文版)》1996,(2)

本文研究了多重复干旱循环对１年生北美短叶松（ＰｉｎｕｓｂａｎｋｓｉａｎａＬａｍｂ．）和黑云杉（Ｐｉｃｅａｍａｒｉａｎａ［Ｍｉｌ］Ｂ．Ｓ．Ｄ．）苗木的气体交换速率及水分利用效率的影响。结果表面，多重干旱循环对它们的气体交换（Ｃｓ，Ｐｎ，Ｔｒ）有显著影响（Ｐ＜０．５），而对其水分利用效率（ＷＵＥ）影响不大（Ｐ＞０．１）。尽管北美短叶松的气孔对轻度干旱胁迫不如黑云杉敏感，但是它对中度及严重干旱胁迫的敏感程度却高于黑云杉。在轻度及中度干旱胁迫下，北美短叶松的光合作用主要受非气孔因素的影响，而黑云杉则主要受气孔因素的影响。解除干旱胁迫后，黑云杉的气孔敏感性、光合能力及水分利用效率的恢复都要比北美短叶松更快．我们认为，延迟脱水是北美短叶松的主要耐旱机理，而忍耐脱水则是黑云杉重要的耐旱途径。轻度的干旱胁迫锻炼可以帮助北美短叶松在更严重的干旱胁迫下保持固有而较强的耐旱能力。然而，通过多重复干旱循环锻炼后黑云杉在改善耐旱能力的强度方面则大于北美短叶松  相似文献   

Distributions of microbial activities in deep subseafloor sediments   总被引：1，自引：0，他引：1  

D'Hondt S  Jørgensen BB  Miller DJ  Batzke A  Blake R  Cragg BA  Cypionka H  Dickens GR  Ferdelman T  Hinrichs KU  Holm NG  Mitterer R  Spivack A  Wang G  Bekins B  Engelen B  Ford K  Gettemy G  Rutherford SD  Sass H  Skilbeck CG  Aiello IW  Guèrin G  House CH  Inagaki F  Meister P  Naehr T  Niitsuma S  Parkes RJ  Schippers A  Smith DC  Teske A  Wiegel J  Padilla CN  Acosta JL 《Science (New York, N.Y.)》2004,306(5705):2216-2221

Diverse microbial communities and numerous energy-yielding activities occur in deeply buried sediments of the eastern Pacific Ocean. Distributions of metabolic activities often deviate from the standard model. Rates of activities, cell concentrations, and populations of cultured bacteria vary consistently from one subseafloor environment to another. Net rates of major activities principally rely on electron acceptors and electron donors from the photosynthetic surface world. At open-ocean sites, nitrate and oxygen are supplied to the deepest sedimentary communities through the underlying basaltic aquifer. In turn, these sedimentary communities may supply dissolved electron donors and nutrients to the underlying crustal biosphere.  相似文献   

Lactate dehydrogenase electrophoretic variant in a New Guinea Highland population   总被引：1，自引：0，他引：1  

N M Blake  R L Kirk  E Pryke  P Sinnett 《Science (New York, N.Y.)》1969,163(868):701-702

Six examples of a variation in the LDH-A subunit have been detected in 408 samples from three exogamous clans in the New Guinea Highlands. The New Guinea variant is similar to the Memphis-4 variant. Origin of the New Guinea variant could not be traced by genealogy but it seems likely to have persisted for several generations.  相似文献   

POTASSIUM IN RELATION TO THE SHAPE OF THE SWEET POTATO     

Robbins WR  Nightingale GT  Schermerhorn LG  Blake MA 《Science (New York, N.Y.)》1929,70(1823):558

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Direct measurements of the convective recycling of the upper troposphere     

Bertram TH  Perring AE  Wooldridge PJ  Crounse JD  Kwan AJ  Wennberg PO  Scheuer E  Dibb J  Avery M  Sachse G  Vay SA  Crawford JH  McNaughton CS  Clarke A  Pickering KE  Fuelberg H  Huey G  Blake DR  Singh HB  Hall SR  Shetter RE  Fried A  Heikes BG  Cohen RC 《Science (New York, N.Y.)》2007,315(5813):816-820

We present a statistical representation of the aggregate effects of deep convection on the chemistry and dynamics of the upper troposphere (UT) based on direct aircraft observations of the chemical composition of the UT over the eastern United States and Canada during summer. These measurements provide unique observational constraints on the chemistry occurring downwind of convection and the rate at which air in the UT is recycled. These results provide quantitative measures that can be used to evaluate global climate and chemistry models.  相似文献   

Orbital forcing of the marine isotope stage 9 interglacial     

Stirling CH  Esat TM  Lambeck K  McCulloch MT  Blake SG  Lee DC  Halliday AN 《Science (New York, N.Y.)》2001,291(5502):290-293

Milankovitch orbital forcing theory has been used to assign time scales to many paleoclimate records. However, the validity of this theory remains uncertain, and independent sea-level chronologies used to test its applicability have been restricted largely to the past approximately 135,000 years. Here, we report U-series ages for coral reefs formed on Henderson Island during sea-level high-stands occurring at approximately 630,000 and approximately 330,000 years ago. These data are consistent with the hypothesis that interglacial climates are forced by Northern Hemisphere summer solar insolation centered at 65 degrees N latitude, as predicted by Milankovitch theory.  相似文献   

The psychological risks of Vietnam for U.S. veterans: a revisit with new data and methods     

Dohrenwend BP  Turner JB  Turse NA  Adams BG  Koenen KC  Marshall R 《Science (New York, N.Y.)》2006,313(5789):979-982

In 1988, the National Vietnam Veterans Readjustment Study (NVVRS) of a representative sample of 1200 veterans estimated that 30.9% had developed posttraumatic stress disorder (PTSD) during their lifetimes and that 15.2% were currently suffering from PTSD. The study also found a strong dose-response relationship: As retrospective reports of combat exposure increased, PTSD occurrence increased. Skeptics have argued that these results are inflated by recall bias and other flaws. We used military records to construct a new exposure measure and to cross-check exposure reports in diagnoses of 260 NVVRS veterans. We found little evidence of falsification, an even stronger dose-response relationship, and psychological costs that were lower than previously estimated but still substantial. According to our fully adjusted PTSD rates, 18.7% of the veterans had developed war-related PTSD during their lifetimes and 9.1% were currently suffering from PTSD 11 to 12 years after the war; current PTSD was typically associated with moderate impairment.  相似文献   

Mitigating sea turtle by-catch in coastal passive net fisheries     

Eric Gilman  Jeff Gearhart  Blake Price  Scott Eckert  Henry Milliken  John Wang  Yonat Swimmer  Daisuke Shiode  Osamu Abe  S. Hoyt Peckham  Milani Chaloupka  Martin Hall  Jeff Mangel  Joanna Alfaro-Shigueto  Paul Dalzell  & Asuka Ishizaki 《Fish and Fisheries》2010,11(1):57-88

There is growing evidence that small-scale, coastal, passive net fisheries may be the largest single threat to some sea turtle populations. We review assessments of turtle interactions in these fisheries, and experiments on gear-technology approaches (modifying gear designs, materials and fishing methods) to mitigate turtle by-catch, available from a small number of studies and fisheries. Additional assessments are needed to improve the limited understanding of the relative degree of risk coastal net fisheries pose to turtle populations, to prioritize limited conservation resources and identify suitable mitigation opportunities. Whether gear technology provides effective and commercially viable solutions, alone or in combination with other approaches, is not well-understood. Fishery-specific assessments and trials are needed, as differences between fisheries, including in gear designs; turtle and target species, sizes and abundance; socioeconomic context; and practicality affect efficacy and suitability of by-catch mitigation methods. Promising gear-technology approaches for gillnets and trammel nets include: increasing gear visibility to turtles but not target species, through illumination and line materials; reducing net vertical height; increasing tiedown length or eliminating tiedowns; incorporating shark-shaped silhouettes; and modifying float characteristics, the number of floats or eliminating floats. Promising gear-technology approaches for pound nets and other trap gear include: replacing mesh with ropes in the upper portion of leaders; incorporating a turtle releasing device into traps; modifying the shape of the trap roof to direct turtles towards the location of an escapement device; using an open trap; and incorporating a device to prevent sea turtle entrance into traps.  相似文献   

A typology of fisheries management tools: using experience to catalyse greater success          下载免费PDF全文

Elizabeth R Selig  Oren Ahoobim  Freddy Arocha  Annabelle Cruz‐Trinidad  Rod Fujita  Mafaniso Hara  Laure Katz  Patrick McConney  Blake D Ratner  Lina M Saavedra‐Díaz  Anne‐Maree Schwarz  Djiga Thiao  Elin Torell  Sebastian Troëng  Sebastian Villasante 《Fish and Fisheries》2017,18(3):543-570

Fisheries provide nutrition and livelihoods for coastal populations, but many fisheries are fully or over‐exploited and we lack an approach for analysing which factors affect management tool performance. We conducted a literature review of 390 studies to assess how fisheries characteristics affected management tool performance across both small‐scale and large‐scale fisheries. We defined success as increased or maintained abundance or biomass, reductions in fishing mortality or improvements in population status. Because the literature only covered a narrow set of biological factors, we also conducted an expert elicitation to create a typology of broader fishery characteristics, enabling conditions and design considerations that affect performance. The literature suggested that the most commonly used management tool in a region was often the most successful, although the scale of success varied. Management tools were more often deemed successful when used in combination, particularly pairings of tools that controlled fishing mortality or effort with spatial management. Examples of successful combinations were the use of catch limits with quotas and limited entry, and marine protected areas with effort restrictions. The most common factors associated with inadequate biological performance were ‘structural’ issues, including poor design or implementation. The expert‐derived typologies revealed strong local leadership, high community involvement and governance capacity as common factors of success across management tool categories (i.e. input, output and technical measures), but the degree of importance varied. Our results are designed to inform selection of appropriate management tools based on empirical data and experience to increase the likelihood of successful fisheries management.  相似文献