Soil‐carbon preservation through habitat constraints and biological limitations on decomposer activity     

Klemens Ekschmitt  Ellen Kandeler  Christian Poll  Andreas Brune  Francois Buscot  Michael Friedrich  Gerd Gleixner  Anton Hartmann  Matthias Kstner  Sven Marhan  Anja Miltner  Stefan Scheu  Volkmar Wolters 《植物养料与土壤学杂志》2008,171(1):27-35

We review recent experimental results on the role of soil biota in stabilizing or destabilizing soil organic matter (SOM). Specifically, we analyze how the differential substrate utilization of the various decomposer organisms contributes to a decorrelation of chemical stability, residence time, and carbon (C) age of organic substrates. Along soil depth profiles, a mismatch of C allocation and abundance of decomposer organisms is consistently observed, revealing that a relevant proportion of soil C is not subjected to efficient decomposition. Results from recent field and laboratory experiments suggest that (1) bacterial utilization of labile carbon compounds is limited by short‐distance transport processes and, therefore, can take place deep in the soil under conditions of effective local diffusion or convection. In contrast, (2) fungal utilization of phenolic substrates, including lignin, appears to be restricted to the upper soil layer due to the requirement for oxygen of the enzymatic reaction involved. (3) Carbon of any age is utilized by soil microorganisms, and microbial C is recycled in the microbial food web. Due to stoichiometric requirements of their metabolism, (4) soil animals tend to reduce the C concentration of SOM disproportionally, until it reaches a threshold level. The reviewed investigations provide new and quantitative evidence that different soil C pools underlie divergent biological constraints of decomposition. The specialization of decomposers towards different substrates and microhabitats leads to a relatively longer persistence of virtually all kinds of organic substrates in the nonpreferred soil spaces. We therefore propose to direct future research explicitly towards such biologically nonpreferred areas where decomposition rates are slow, or where decomposition is frequently interrupted, in order to assess the potential for long‐term preservation of C in the soil.  相似文献   

Application of theoretical growth functions for Mongolian oak (Qurcus mongolica)     

Li Changsheng  Sun Jianfeng  Wu Zhenhai  Francois Houllier 《林业研究》1997,8(4):195-200

Four alternative functions are used for fitting tree height and diameter growth models for mongolian oak. (Quercus mongolica Fisch. et Turcz.). The data set includes 1250 random trees and 755 dominant trees coming from 510 temporary plots. The resultsshow that the Richards function is the best model for predicting height. diameter at breast height (DBH) and dominant height from age. The average growth curve of dominant height is used as a guide curve for the construction of a site index table which is partially validated using an independent data set. The Mitscherlich function is the best model for estimating height and dominant height from DBH. (Responsible Editor: Chai Ruihai)  相似文献   

Biochemical composition is not the main factor influencing variability in carbon isotope composition of tree rings     

Eglin T  Maunoury-Danger F  Fresneau C  Lelarge C  Pollet B  Lapierre C  Francois C  Damesin C 《Tree physiology》2008,28(11):1619-1628

From June to December, we determined the effects of variations in biochemical composition on delta(13)C of tree rings of 2-year-old oaks (Quercus petraea (Matt.) Liebl.) growing under semi-natural conditions, and the dependence of these effects of water stress during the growth season. Percent abundance, carbon concentration and delta(13)C were measured in holocellulose, lignin, extractive-free wood, starch and a water-soluble fraction. Relative concentrations of lignin and holocellulose in the extractive-free wood varied little during the season or in response to water stress, indicating that these compounds could not quantitatively explain the variations in whole-wood delta(13)C. Among all sampled tree rings, the relative concentration of each structural compound (holocellulose and lignin) accounted for less than 5% of the delta(13)C variability in whole wood. Variations in holocellulose and extractive-free wood delta(13)C between tree rings were almost identical (r > 0.95), whereas variations in lignin delta(13)C were less well correlated to these compounds. Whole-wood delta(13)C had a slightly altered isotopic signal compared with that of the structural compounds because of the presence of the extractive component. These results showed that variations in lignin delta(13)C and lignin concentration have little influence on extractive-free wood delta(13)C and whole-wood delta(13)C. Rather, holocellulose influences delta(13)C the most. Thus, we confirmed that, for climatic reconstruction from tree rings, removal of extractives by soxhlet is generally sufficient and sometimes unnecessary. Our findings also indicate that, in the case of rapid and severe water stress, the structural component did not accurately record the associated increase in delta(13)C because of dilution with previously formed organic matter and cessation of trunk growth. The effect of drought on carbon isotope ratios was more pronounced in the extractive compounds, making them good water stress indicators but only on a scale of days to months.  相似文献   

Low genetic diversity and strong geographic structure in introduced populations of the Eucalyptus foliar pathogen Teratosphaeria destructans     

Minette Havenga  Brenda D. Wingfield  Michael J. Wingfield  Léanne L. Dreyer  Francois Roets  ShuaiFei Chen  Janneke Aylward 《Plant pathology》2020,69(8):1540-1550

The aggressive Eucalyptus leaf pathogen, Teratosphaeria destructans, causes widespread damage in tropical and subtropical Eucalyptus-growing regions of Indonesia, China, Thailand, East Timor, Vietnam, Lao, and South Africa. Little is known regarding the origin, pathways of dispersal, or reproductive biology of this pathogen. The aim of this study was to investigate the genetic structure of a global collection of T. destructans isolates. This was achieved by developing and using polymorphic microsatellite markers. Low genotypic diversity and a limited number of private alleles were found in all investigated populations, with the highest maximum diversity of 10.7% in isolates from South Sumatra. This supports the hypothesis that T. destructans was introduced to these regions. High levels of clonality were common in all populations, especially in isolates sampled from the recent disease outbreak in South Africa, which were all identical. The global collection of isolates grouped into three distinct clusters, corresponding largely to their sampled regions. Low levels of genotypic diversity, high levels of clonality, and strong geographic structure suggest independent introductions into all the sampled areas from an unknown source. The results imply that strict biosecurity measures are needed to avoid introductions of additional genotypes in these areas.  相似文献   

A diluent for sperm cryopreservation of gilthead seabream, Sparus aurata     

Francois Chambeyron  Yonathan Zohar 《Aquaculture (Amsterdam, Netherlands)》1990,90(3-4):345-352

Sperm of gilthead seabream, Sparus aurata, was diluted with solutions of different osmolarities and pH. The effect of the different diluents on sperm motility (intensity and percentage of motile sperm) was studied. Motility was induced as early as 10 s after mixing the sperm with diluents having an osmotic pressure higher than 500 mOsm/l. The intensity of motility decreased when the osmotic pressure was reduced, and was zero or significantly inhibited when the osmotic pressure of the diluent (300–380 mOsm/l) was close to that of the fish's seminal plasma (364.6±3.03 mOsm/l). The pH of the diluent did not have any effect on sperm motility (in a range of 6.8 to 8.9). A diluent which prevents spermatozoa motility (osmotic pressure 375 mOsm/l and pH 7.35) was successfully used to cryopreserve S. aurata sperm at −196°C. This diluent is considered promising for the long-term preservation of gilthead seabream sperm.  相似文献   

Sensory threshold of 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) and concentrations in young Riesling and non-Riesling wines     

Sacks GL  Gates MJ  Ferry FX  Lavin EH  Kurtz AJ  Acree TE 《Journal of agricultural and food chemistry》2012,60(12):2998-3004

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is well-known to contribute "petrol" aromas to aged Riesling wines, but its prevalence and contribution to young Riesling or non-Riesling wines is not well understood. TDN concentrations were measured in 1-3-year-old varietal wines produced from Cabernet franc (n = 14 wines), Chardonnay (17), Cabernet Sauvignon (4), Gewurztraminer (4), Merlot (9), Pinot gris (6), Pinot noir (9), Riesling (28), or Sauvignon blanc (6). TDN concentrations in the Riesling wines, 6.4 ± 3.8 μg/L, were significantly higher than in all other varietals, 1.3 ± 0.8 μg/L. The odor detection thresholds for TDN were then determined in both model wine and a neutral white wine. Group sensory thresholds were found to be the same in both matrices, 2 μg/L, indicating little masking of TDN due to the odorants in the neutral white. The TDN sensory threshold was a factor of 10 below the previously reported odor threshold. On the basis of this revised threshold, 27 of 28 Riesling wines had suprathreshold TDN, whereas only 7 of 69 non-Riesling wines had suprathreshold TDN. The monoterpenes linalool and geraniol were also measured in the Riesling wines, and odor activity values (OAVs) were calculated for the monoterpenes and TDN. The OAV for TDN was higher than for the monoterpenes in 25 of 28 Riesling wines.  相似文献   

The Israeli-Palestinian Science Organization     

Wiesel T  Agre P  Arrow KJ  Atiyah M  Brézin E  Charfi FF  Cohen-Tanoudji C  Daar A  Jacob F  Kahneman D  Lee YT  Nicolaisen I  Nusseibeh S  Reuter H  Shoham Y  Sulston J  Walzer M  Yaari M 《Science (New York, N.Y.)》2007,315(5808):39

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Yield and foliar injury responses of mature plum trees to salinity     

G. J. Hoffman  P. B. Catlin  R. M. Mead  R. S. Johnson  L. E. Francois  D. Goldhamer 《Irrigation Science》1989,10(3):215-229

Summary The salt tolerance of mature Santa Rosa plum trees was assessed on 20-year-old trees grown in the San Joaquin Valley of California. The experimental design consisted of six levels of irrigation water salinity (electrical conductivities of 0.3 to 8 dS/m) replicated five times with each replication consisting of ten trees. Salinity treatments imposed in March 1984 did not influence tree yields harvested in June 1984. In 1985, the second year of treatments, yield from the highest salt treatment (electrical conductivity of irrigation water, EC _i , of 8 dS/m) was reduced by half; the number of fruit harvested was reduced 40%, and fruit size was reduced significantly. Foliar damage was so severe by the end of 1985 that nonsaline water was applied to the two highest salt treatments (EC _i = 6 and 8 dS/m) in an attempt to restore tree vigor. In 1986 salt effects had become progressively worse on the continuing saline treatments. A linear piece-wise salt tolerance curve is presented for soil salinity values, expressed as the electrical conductivity of saturated extracts (EC _e ) integrated to a soil depth of 1.2 m over a 2-year period. The salt tolerance threshold for relative yield (Y _r ) based on 3 years of data was 2.6 dS/m and yield reduction at salinity levels beyond the threshold was 31% per dS/m (Y _ir=100 – 31 [EC _e – 2.6]j). Significant foliar damage occurred when leaf chloride concentrations surpassed 200 mmol/kg of leaf dry weight (0.7%). Sodium concentrations in the leaves remained below 10 mmol/kg (0.02%) until foliar damage became severe. This suggests that chloride was the dominant ion causing foliar damage.  相似文献   

Salt tolerance of irrigated guayule     

E. V. Maas  T. J. Donovan  L. E. Francois 《Irrigation Science》1988,9(3):199-211

Summary The salt tolerance of guayule (Parthenium argentatum Gray cv. N565-II) was tested in small held plots (silty clay soil) in the Imperial Valley of California. Seedlings were transplanted in October 1981. Differential salination was begun in March 1982 and continued for 4 years by irrigating with waters salinized with NaCl and CaCl₂ (1:1 by wt.) to obtain electrical conductivities of 0.8, 1.4, 3, 6, 9, and 12 dS/m. Dry matter, rubber, and resin yields were determined from pollarded plants in February 1984 and uprooted plants in February 1985 and 1986. Rubber concentrations in the woody branches in 1984 and 1985 averaged 6.1 and 7.3%, respectively on a dry weight basis and were not significantly affected by soil salinity. Resin concentrations averaged 8.6% and 7.3% for the two years. In 1986, both rubber and resin concentrations decreased with increased salinity. Rubber and resin concentrations in the root crowns were approximately one percentage point less than those of the shoot. Dry matter and resin yields were not affected by salinity until the time- and depth-averaged electrical conductivity of the saturated-soil extracts ( ) taken from the rootzone (0–90 cm) exceeded 8.7 dS/m. Above 8.7 dS/m, both yields decreased 11.6% per dS/m increase in . Rubber yields decreased 10.8% per dS/m above a threshold of 7.8 dS/m. Plant mortality rather than growth reduction at high levels of salinity appears to be the limiting factor for rubber production from irrigated guayule.  相似文献   

气味指纹分析技术在食品质控和风味研究的应用   总被引：5，自引：0，他引：5  

朱丽敏  倪元颖  Soffy Venzal  Francois Soffys 《农产品加工．学刊》2005,30(9):72-76,80

着重以食用油、橙汁和奶制品为例,阐述了Sensory Array Fingerprint Analyzer Method(气味指纹分析法)对食品所建立的新型质量控制和风味研究方法.经针对7种储存时间不同的食用油、脂(大豆油、菜籽油、猪油、牛脂、禽类脂、白色油脂、棕榈油)的过氧化值和酸价的分析模型的建立,展示了应用气味指纹分析技术(电子鼻)对食用油品质控制及抗氧化能力比较的新方法,对不同品质的橙汁(半年和一年半的鲜榨汁,和浓缩还原汁)、不同种类的鲜奶(灭菌全脂奶、灭菌半脱脂奶、半脱脂生奶和乳粉还原奶)和真伪某品牌奶粉的区分,表明该技术对复杂介质样品的品质变化具有独特的识别能力.分析结果表明,该分析技术具有以下优点满意的分析灵敏度和重复性传感器检测平均重复性为1.32%RSD(n=10),对同一样品测量的重复性为1.4%RSD(n=10),对所有油样的过氧化值和酸价测定具有良好的线性关系,平均相关系数为0.998 4.不同品质样品之间区分指数DI的特异性明显(＞90).所有的数据通过化学计量学方法处理,并且该分析方法无需样品前处理.  相似文献