Breakthrough of the year. Global warming, hotter than ever

Climate change, a perennial runner-up for Breakthrough of the Year, broke from the pack this year--both in the pages of this section and in the public arena.     

广西气候变暖及其对农业的影响

根据广西壮族自治区1961-2005年气温资料,分析其年平均气温、平均最高、最低气温的时空变化特征,及其对广西农业的可能影响.结果表明,近45年全区年平均气温、平均最高气温、平均最低气温均呈上升趋势(变率分别为0.01204℃、0.00614℃、0.01688℃),全区的气候变暖主要来自最低气温升高的贡献;冬季增温最明显;增温幅度存在区域差畀,桂中和桂北的平均气温增幅较大.气候变暖将使热量资源增加,全区≥10℃活动积温将增加941-1 275℃ ,约平均增加14%;≥10℃的持续日数将增加5～50d,达291～365d.热量增加将改变作物品种布局,作物种植北界将向北移,种植高度将普遍提高,对桂北和山区的农业发展有利;但气候变暖使农业生产的不稳定性增加,作物产量波动加大;病虫草害加剧;干旱、洪涝等农业气象灾害发生频繁.     

产甲烷生化代谢途径研究进展

目的研究滇池沉积物产甲烷菌的空间分布特征。方法采集滇池草海和外海的4个不同面源污染区域沉积物,通过沉积物DNA提取、PCR扩增及产物纯化、质粒构建及阳性验证、标准曲线制作和荧光定量PCR方法,定量研究基于mcrA基因的产甲烷菌丰度及其分布特征。结果滇池沉积物产甲烷菌丰度范围为5.91×10⁷~7.74×10⁸ copies/g。产甲烷菌的拷贝数在各个采样区域差异显著(F=10.300 6,P=0.0012),并具有空间分布特征,即外海中>外海南>草海>外海北,且外海南部和中部的产甲烷菌丰度与草海和外海北部的产甲烷菌丰度具有显著差异(P<0.05)。结论滇池沉积物具有较高的产甲烷丰度,且产甲烷菌在滇池的分布空间异质性很大,临近农业面源污染区域的外海中部和临近磷、钾厂的外海南部比草海和外海北部水华密集区具有较高的产甲烷菌丰度。     

Ecological Society of America meeting. Global warming, insects take the stage at Snowbird

Despite the turmoil of not-so-distant forest fires and United Airlines troubles that threw off travel schedules, some 2600 ecologists made their way to this sun-soaked canyon last month for the Ecological Society of America's 85th annual meeting. Topics ranged from ancient droughts to photosynthesis beneath snow and how trees resist insects.     

Changes in tropical cyclone number, duration, and intensity in a warming environment

We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade.     

Global biodiversity,biochemical kinetics,and the energetic-equivalence rule

The latitudinal gradient of increasing biodiversity from poles to equator is one of the most prominent but least understood features of life on Earth. Here we show that species diversity can be predicted from the biochemical kinetics of metabolism. We first demonstrate that the average energy flux of populations is temperature invariant. We then derive a model that quantitatively predicts how species diversity increases with environmental temperature. Predictions are supported by data for terrestrial, freshwater, and marine taxa along latitudinal and elevational gradients. These results establish a thermodynamic basis for the regulation of species diversity and the organization of ecological communities.     

Heat flow and hydrothermal circulation in the cascade range, north-central Oregon

In north-central Oregon a large area of near-zero near-surface conductive heat flow occurs in young volcanic rocks of the Cascade Range. Recent advective heat flux measurements and a heat-budget analysis suggest that ground-water circulation sweeps sufficient heat out of areas where rocks younger than 6 Ma (million years ago) are exposed to account for the anomalously high advective and conductive heat discharge measured in older rocks at lower elevations. Earlier workers have proposed that an extensive midcrustal magmatic heat source is responsible for this anomalously high heat flow. Instead, high heat flow in the older rocks may be a relatively shallow phenomenon caused by regional ground-water flow. Any deeper anomaly may be relatively narrow, spatially variable, and essentially confined to the Quaternary (less than 2 Ma) arc. Magmatic intrusion at a rate of 9 to 33 cubic kilometers per kilometer of arc length per million years can account for the total heat flow anomaly. Deep drilling in the areas of high heat flow in the older rocks could indicate which model is more appropriate for the near-surface heat flow data.     

Changes in mean concentration, phase shifts, and dissipation in a forced oscillatory reaction

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference delta G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and delta G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).     

Trajectory shifts in the Arctic and subarctic freshwater cycle

Manifold changes in the freshwater cycle of high-latitude lands and oceans have been reported in the past few years. A synthesis of these changes in freshwater sources and in ocean freshwater storage illustrates the complementary and synoptic temporal pattern and magnitude of these changes over the past 50 years. Increasing river discharge anomalies and excess net precipitation on the ocean contributed approximately 20,000 cubic kilometers of fresh water to the Arctic and high-latitude North Atlantic oceans from lows in the 1960s to highs in the 1990s. Sea ice attrition provided another approximately 15,000 cubic kilometers, and glacial melt added approximately 2000 cubic kilometers. The sum of anomalous inputs from these freshwater sources matched the amount and rate at which fresh water accumulated in the North Atlantic during much of the period from 1965 through 1995. The changes in freshwater inputs and ocean storage occurred in conjunction with the amplifying North Atlantic Oscillation and rising air temperatures. Fresh water may now be accumulating in the Arctic Ocean and will likely be exported southward if and when the North Atlantic Oscillation enters into a new high phase.     

陕北黄土区退耕还林地生物结皮分布及其影响因子研究

为了科学评价黄土区退耕还林工程及其水土保持和生态效益,该文于2005年7—8月在陕西省延安市吴旗县进行了植被状况调查.通过对78个标准地的调查数据进行分析,结果表明:①干扰程度、坡向、坡度、地貌部位、植被结构、维管植物和微生境对生物结皮盖度具有明显影响.干扰程度弱,生物结皮盖度大,反之则小;阴坡生物结皮盖度大于阳坡;沟坡大于梁峁坡.②生物结皮盖度随着维管植物盖度和种数的增加而增加,但随着维管植物种数的进一步增加,生物结皮盖度反而下降.③植被结构不同,生物结皮盖度不同,草本植被结构大于乔灌草结构,乔灌草结构则大于灌草结构.      

Climatic warming and the decline of zooplankton in the california current

Since 1951, the biomass of macrozooplankton in waters off southern California has decreased by 80 percent. During the same period, the surface layer warmed-by more than 1.5 degrees C in some places-and the temperature difference across the thermocline increased. Increased stratification resulted in less lifting of the thermocline by wind-driven upwelling. A shallower source of upwelled waters provided less inorganic nutrient for new biological production and hence supported a smaller zooplankton population. Continued warming could lead to further decline of zooplankton.