北温带干旱地区土壤-大气界面CO_2通量的变化特征

采用箱法对栗钙土、灰钙土、粗骨土和山地灰褐土4种有代表性的干旱土壤表面CO2通量进行观测和研究。结果表明:森林土壤(粗骨土和山地灰褐土)的通量显著大于草原土壤(栗钙土和灰钙土)。干旱区土壤表面CO2通量的平均值为230.05μmol/(m2·h),变化范围为-147.27～2319.55μmol/(m2·h)。不同土壤类型之间存在差异,粗骨土(351.82μmol/(m2·h))>山地灰褐土(347.33μmol/(m2·h))>栗钙土(193.36μmol/(m2·h))>灰钙土(162.37μmol/(m2·h))。土壤表面CO2通量存在季节变化,趋势呈"S"形。9月份最高(516.79μmol/(m2·h)),以土壤向大气释放为主;1月份最低(-7.09μmol/(m2·h)),以大气进入土壤为主;具有春夏秋冬交替规律,与气候变化趋势基本一致,土壤表面CO2通量稍有后滞。全天候土壤表面CO2通量呈"山峰"形变化,04:00最小(154.13μmol/(m2·h)),12:00最大(349.65μmol/(m2·h)),具有昼夜交替规律,比气候日变化稍有滞后。影响土壤表面CO2通量的环境因子有地表空气温度、土壤温度(0～10cm、10～20cm和20～30cm)、土壤含水量(0～10cm、10～20cm和20～30cm);其中,地表空气温度、土壤温度(0～10cm、10～20cm和20～30cm)和土壤含水量(0～10cm)分别与土壤表面CO2通量呈正相关关系,而10～20cm和20～30cm深度的土壤含水量与土壤表面CO2通量呈负相关关系,地表空气相对湿度与土壤表面CO2通量的关系不显著。大气与土壤之间的CO2存在双向转移机制,CO2不仅从土壤向大气转移,而且也从大气向土壤转移,热量在地球表面的差异性分布,导致温带和寒带地区的土壤具有平衡大气CO2浓度的功能,是温带、寒带地区的显著特征。     

Corrections and clarifications

In the response by E. A. Finch and S. M. Goldin (5 Aug., p. 813) to the technical comment "Calcium and inositol 1,4,5-trisphosphate-induced Ca(2+) release" by L. Combettes and P. Champeil (5 Aug., p. 813), in parts B and C of figure 1 (p. 814), the insets referring to Ca concentrations were inadvertantly interchanged. The concentration for figure 1B should have been, "300 nM Ca" and that for figure 1C should have been, "10 nM Ca."     

Erratum

In the article "String as a theory of everything" by M. Mitchell Waldrop (Research News, 20 Sept., p. 1251), the last line of the first column was inadvertantly omitted. The affected sentence should have read, "Not only were the strong interactions far more complex than predicted by field theory, but the particles that participated in the strong interactions-the hadrons, a group that includes protons, neutrons, pi mesons, and many others-seemed to be relatively large, extended objects as much as 1 Fermi across (10(-13) centimeter)." In the next-to-the-last line of the second full paragraph in column 2 on page 1252, 10(-19) should have been 10(+19). Finally, the words "quandary" (page 1251, column 1, paragraph 6, line 2) and "quark" (page 1252, column 3, last paragraph, line 18) were misspelled.     

Erratum

In the report "Cloud droplet deposition in subalpine balsam fir forests: Hydrological and chemical inputs" by G. M. Lovett et al. (24 Dec., p. 1303), two errors appeared in Table 2 on page 1304. The cloud deposition of SO(4)(2-), incorrectly reported as 275.8 kg ha(-1) year(-1), should have been 137.9 kg ha(-1) year(-1). The percentage of the sum contributed by clouds, reported as 81 for SO(4)(2-), should have been 68.     

Developmental behaviors: delayed appearance in monkeys asphyxiated at birth

In "Developmental behaviors: delayed appearance in monkeys asphyxiated at birth" by J. A. Sechzer et al. (19 Mar., p. 1173), the last two lines of column 1 and the first five lines of column 2, page 1175, should read "Deficits in learning and memory (10, 11) when compared with the establishment of these developmental behaviors (although significantly delayed) suggest that brain damage by neonatal asphyxia can result in a degree of dissociation..."     

Paramagnetic unit in spinach subchloroplast particles: estimation of size

A pulsed ruby laser (wavelength, 694.3 nanometers) was used to measure the dependence on light intensity of light-induced electron paramagnetic resonance (ERR) signal 1 for short flashes of uniform duration (400 microseconds). Approximately 10(18) photons per square centimeter per flash from the unattenuated beam were available to the sample of subchloroplast "system 1" particles from spinach. The experimental dependence of the EPR signal height plotted as a function of the total number of incident photons per flash was exponential. From measurement of the slope at a very low relative photon flux and the saturated EPR signal amplitude, the value for the cross section or "effective size" of the light-induced paramagnetic unit, sigma(EPR), was found to be 300 x 10(-17) square centimeter. This result is compared with a measured optical absorption cross section, sigma(694nm), of 2.5 x 10(-17) square centimeter, for the identical sample at the laser wavelength. The hundredfold difference in size supports the thesis that the paramagnetic state is a property of an aggregate of chlorophyll molecules of the same general size as the photosynthetic unit.     

Erratum

In the article "The new inflationary universe" by M. Mitchell Waldrop (Research News, 28 Jan., p. 375), it was stated incorrectly that, in the standard model, the expanding universe cooled below 10(27) degrees Kelvin about 10(35) seconds after the Big Bang. The correct time is 10(-35) second.     

Erratum

In Table 1 (p. 351) of the report "Structure-activity studies of interleukin-2" by F. E. Cohen et al. (17 Oct., p. 349), reference 15 was incorrectly cited for the entries for the 1-29, 30-49, and 100-133 deletion mutants. For all three entries, the reference should have been (16).     

Erratum

In the report "Iron photoreduction and oxidation in an acidic mountain stream" by D. M. McKnight et al. (29 Apr., p. 637), reference 17 [E. L. Madsen, M. D. Morgan, R. E. Good, Limnol. Oceanogr. 31, 382 (1986)] was cited ( p. 638) as indicating "that biological processes are not responsible for light-induced Fe(II) production." This possibility was not addressed by Madsen et al., nor did Madsen et al. use both poisoned and natural streamwater-sediment mixtures to distinguish between biotic and abiotic contributions to iron reduction. In table 1 of the same report, the values in columns two and three were incorrect. They should have been, for sodium, calcium and magnesium, respectively, 2.7 +/- 0.34 mg liter(-1)', 13.0 +/- 0.73 mg liter(-1), and 4.3 +/- 0.24 mg liter(-1).     

Corrections and clarifications

Reference 4 in the article "Demic expansions and human evolution" by L. L. Cavalli-Sforza et al. (29 Jan., p. 639) was incorrect. It should have read as follows: "F. Weidenreich, Evolution 1, 221 (1947); C. Coon, The Living Races of Man (Knopf, New York, 1965); M. H. Wolpoff, in (2), pp. 62-108."     

Erratum

The first two sentences of the report "Asian dust: Seasonal transport to the Hawaiian Islands" by J. R. Parrington et al. (8 Apr., p. 195) should have read as follows: "Transport of vast quantities of Sahara desert dust westward across the Atlantic Ocean to Bermuda has been known since the late 1960's (1, 2). Strong evidence now exists for transport of large quantities of Asian dust eastward across the North Pacific (3-7)."     

Erratum

In the Research News article "New test of variable gravitational constant" (23 Dec., p. 1316), in the third paragraph of column two on page 1317, a minus sign was left out of an exponent. The correct value for the drift of atomic clocks relative to gravitational clocks is (0.1 +/- 0.8) x 10(-11) per year.     

菰叶片净光合速率日变化及其与环境因子的相互关系

 【目的】通过研究菰叶片净光合速率日变化及其与环境因子的相互关系，目的为菰资源的开发和利用提供参考。【方法】利用Li-6400型光合作用测定系统，测定了菰叶片净光合速率和环境因子的日变化，通过相关性分析，考察了环境因子对净光合速率日变化的影响。【结果】菰功能叶片净光合速率为15.0～21.5 ?mol·m-2·s-1，光补偿点为45 ?mol·m-2·s-1，光饱和点为1 040 ?mol·m-2·s-1。菰叶片净光合速率、气孔导度和蒸腾速率的日变化均呈单峰曲线，净光合速率的峰值出现在上午11:00时，上午8:00～11:00时的平均净光合速率比下午13:00-16:00时的平均净光合速率高4.7 ?mol·m-2·s-1。气孔导度和蒸腾速率的峰值分别出现在13:00和14:00时。一日中上午5:00～11:00和下午15:00～19:00时净光合速率与光量子通量密度之间呈显著正相关 (r＝0.9874**、0.9321**)，11:00～15:00时两者之间呈不显著正相关(r＝0.4440)。上午5:00～11:00和下午15:00～19:00时净光合速率与空气温度之间呈显著正相关(r＝0.9617**、0.9852**)，11:00～15:00时两者之间呈显著负相关(r＝-0.8110*)。净光合速率与气孔导度之间呈正相关(r＝0.7936*)，与胞间CO2浓度呈负相关(r＝-0.8026*)。气孔导度和蒸腾速率与光量子通量密度之间呈显著的正相关(r＝0.9104**、0.7858*)。【结论】菰叶片的光补偿点较低，而光饱和点较高，对光环境的适应性较强，为典型的阳生植物。影响净光合速率日变化的主要环境因子是光量子通量密度和空气温度。     

Erratum

In the article "Electron microscope center opens at Berkeley" (Research News, 27 Mar., p. 1407), reference is made to the 1.2-MeV (million electron volts) high voltage electron microscope at the State University of New York at Albany. That instrument is owned by the state of New York and operated and supported by the New York State Department of Health, not by the National Institutes of Health.     

Infrared speckle observations of io: an eruption in the loki region

Speckle observations of Jupiter's satellite Io at a wavelength of 5 micrometers during July 1984 resolved the disk and showed emission from a hot spot in the Loki region. The hot spot contributed a flux approximately equal to 60 percent of that from the disk. Images reconstructed by means of the Knox-Thompson algorithm showed the spot moving across the disk as the satellite rotated. It was located at 301 degrees +/- 6 degrees west longitude, 10 degrees +/- 6 degrees north latitude, and had a radiance of (2.96 +/- 0.54) x 10(22) ergs sec(-1) cm(-1) sr(-1)/A where A is the area of the spot. For an assumed temperature of 400 K, the area of the source would be 11,400 square kilometers. An active "lava lake" similar to that seen by Voyager may be the source of the infrared emission.     

Erratum

In the abstract of the report "L-Isoleucine and L-leucine: Tumor promoters of bladder cancer in rats" by Y. Nishio et al. (21 Feb., p. 843), the third sentence should have read, "Results of 40- to 60-week carcinogenesis experiments in which N-butyl-N-(4- hydroxybutyl)nitrosamine was used as an initiator demonstrate that L-isoleucine and L-leucine promote bladder cancer in rats."     

Corrections and clarifications

In table 1 (p. 1124) of the article "Prehistoric extinction of Pacific island birds: Biodiversity meets zooarchaeology," by David W. Steadman (24 Feb., p. 1123), the column headings for modern and fossil record were reversed; under each island name, the letters "F M" should have appeared.     

Erratum

In the report by N. Yamamoto et al., "Transformation of human leukocytes by cocultivation with an adult T cell leukemia virus producer cell line" (20 Aug., p. 737), the column headings in Table 1, on page 738, under "Cells with markers (%)," should have read: Leu 1, Leu 2a, Leu 3a, Leu 4, and Ia (not immunoglobulin A).     

Erratum

In "Locus of short-term visual storage" by B. Sakitt (26 Dec., p. 1318), the sentence on lines 10-13 of paragraph I should have read "In the partial report condition, an auditory tone was presented with some delay after the letter presentation."     

固相萃取-气相色谱法测定沉积物中六氯环己烷、双对氯苯基三氯乙烷的残留量

通过对样品前处理方法和气相色谱条件的改进,建立一套稳定的沉积物中六氯环己烷、双对氯苯基三氯乙烷残留的气相色谱检测方法,满足实验室批量测定样品的要求。选择40 mL正己烷和丙酮混合液(V_正己烷∶V_丙酮=1∶1)作为提取液,并加入2 g铜粉去除硫化物,用Florisil SPE 小柱和CarbonGCB SPE 小柱串联净化,采用10 mL正己烷和丙酮混合液(V_正己烷∶V_丙酮=9∶1)进行洗脱,浓缩后用DB1701气相毛细管柱分离,用带电子捕获检测器的气相色谱仪（GC-ECD）检测,外标法定量。本研究选择沙质性状的沉积物作为基准进行加标回收实验,平均回收率在74.5%～92.0%,相对标准偏差在3.09%～6.67%;检出限为α-HCH:1.96×10^-4 mg/kg, β-HCH：1.45×10^-6mg/kg,γ-HCH：1.90×10^-4 mg/kg, δ-HCH：1.98×10^-4mg/kg, p,p′-DDD:2.47×10^-6 mg/kg, o,p′-DDT：1.08×10^-4mg/kg, p,p′-DDE：1.59×10^-4 mg/kg, p,p′-DDT：2.52×10^-4mg/kg。采用泥质性状的沉积物对本方法进行验证,加标回收率和相对标准偏差都符合沉积物样品的药残检测要求。