CO2 balance of boreal, temperate, and tropical forests derived from a global database

Terrestrial ecosystems sequester 2.1 Pg of atmospheric carbon annually. A large amount of the terrestrial sink is realized by forests. However, considerable uncertainties remain regarding the fate of this carbon over both short and long timescales. Relevant data to address these uncertainties are being collected at many sites around the world, but syntheses of these data are still sparse. To facilitate future synthesis activities, we have assembled a comprehensive global database for forest ecosystems, which includes carbon budget variables (fluxes and stocks), ecosystem traits (e.g. leaf area index, age), as well as ancillary site information such as management regime, climate, and soil characteristics. This publicly available database can be used to quantify global, regional or biome‐specific carbon budgets; to re‐examine established relationships; to test emerging hypotheses about ecosystem functioning [e.g. a constant net ecosystem production (NEP) to gross primary production (GPP) ratio]; and as benchmarks for model evaluations. In this paper, we present the first analysis of this database. We discuss the climatic influences on GPP, net primary production (NPP) and NEP and present the CO₂ balances for boreal, temperate, and tropical forest biomes based on micrometeorological, ecophysiological, and biometric flux and inventory estimates. Globally, GPP of forests benefited from higher temperatures and precipitation whereas NPP saturated above either a threshold of 1500 mm precipitation or a mean annual temperature of 10 °C. The global pattern in NEP was insensitive to climate and is hypothesized to be mainly determined by nonclimatic conditions such as successional stage, management, site history, and site disturbance. In all biomes, closing the CO₂ balance required the introduction of substantial biome‐specific closure terms. Nonclosure was taken as an indication that respiratory processes, advection, and non‐CO₂ carbon fluxes are not presently being adequately accounted for.     

IL-1 MODIFIES SYSTEM A TRANSPORT ACTIVITY IN HUMAN RHEUMATOID SYNOVIAL CELLS

Given the importance of interleukin-1 in both rheumatic diseases and the modulation of cell metabolic activities, we studied the action of this cytokine on the neutral amino acid transport A system on rheumatoid synovial cells. In these cells IL-1 (1ng/ml) induced amino transport stimulation from 5min to 5h. This effect was obtained only after a starvation period. No concentration-related effect was found for IL-1-stimulated MeAIB uptake, and the IL-1-mediated MeAIB uptake stimulation is independent of protein synthesis. Neosynthesis or post-translational maturation of protein transport is a prerequisite for obtaining this effect. In conclusion, rheumatoid synovial cells exhibit a higher sensitivity for IL-1 than osteoarthritic ones, probably related to their intense metabolic activity.     

盐度对互花米草枯落物分解释放硅、碳、氮元素的影响

为了研究潮汐湿地盐度对枯落物分解过程中硅、碳、氮元素释放的影响,通过室内模拟不同盐度(0、5、15和30)对互花米草枯落物茎和叶分解释放过程中硅、碳、氮元素的动态变化进行测定。结果表明:(1)互花米草茎和叶枯落物失重率和分解速率均随盐度增加而降低。(2)互花米草茎和叶枯落物分解水体中硅含量均随着盐度升高而增加,并且盐度30处理下,枯落物分解硅释放量显著高于盐度0和5(P0.05)。而分解末期生物硅残留量则随盐度升高而降低。(3)不同盐度处理茎枯落物分解碳释放量无显著差异,但叶枯落物分解碳释放量在盐度5、15和30处理中显著高于淡水(P0.05)。(4)互花米草茎枯落物分解释放到水中的NH_4~+-N含量随着盐度的升高而减少,NO_3~--N含量与之相反。研究单因素盐度对枯落物分解及元素释放的影响,可以为预测潮汐湿地枯落物分解对盐水入侵的响应机制提供参考,为湿地生源要素生物地球化学循环过程研究提供基础依据。     

河内蔬菜基地冬季主要蔬菜上昆虫群落组成

应越南国家植物保护研究院的邀请 ,受我国科技部的委派 ,我们于 2 0 0 1年 1 1～ 1 2月赴越进行“小菜蛾化学信息素的分离鉴定及应用研究”。河内地处热带 ,光照充足 ,雨量充沛 ,气候湿润 ,郊区拥有数百平方公里的蔬菜基地 ,种植着各式各样的蔬菜 ,长势旺盛 ,所产各类蔬菜主要用于出口 ,但虫害较重。在进行小菜蛾PlutellaxylostellaL .化学信息素研究[1] 的同时 ,我们对主要蔬菜品种上的昆虫群落的组成及优势种昆虫进行了考查和分析。1　材料与方法选取 1 0多种蔬菜作为调查对象 ,每种蔬菜样地面积≥ 6 6 6× 2m2 ,以五点取样法选取 5个样…     

生态学的时空特性(英文)

 众所周知,几乎所有的生态学特征和现象都受限于一定的时间和空间。因此,相应的科学假设和相关的生态学结论也只能基于这些特定的时空尺度范围。我们利用颇为熟知的事例,引用生态学文献中的具体实例,提纲挈领地论述了时空在生态学研究中的重要性。这些实例包括我们在长白山对云、冷杉(Picea jezoensis, Abies nephrolepis)林林冠结构的模拟、在北美应用遥感和气象方法对碳通量的估算,以及测定湿地生态系统对加温的反应等。文中所涉及的所有生态学现象,对时间和空间都有强烈的依赖性。因而, 从生态学问题的提出,到科学假设的演绎,以至试验设计和综合数据分析,都必须以时、空为前提,才不至于导致荒谬结论。     

Ecologically heterogeneous populations of the invasive ant Wasmannia auropunctata within its native and introduced ranges

Abstract 1. The biology of most invasive species in their native geographical areas remains largely unknown. Such studies are, however, crucial in shedding light on the ecological and evolutionary processes underlying biological invasions. 2. The present study focuses on the little fire ant Wasmannia auropunctata, a species native to Central and South America that has been widely introduced and which has become invasive throughout the tropics. We characterise and compare several ecological traits of native populations in French Guiana with those in one of its introduced ranges, New Caledonia. 3. We found ecologically heterogeneous populations of W. auropunctata coexisting in the species’ native geographical area. First, we found populations restricted to naturally perturbed areas (particularly floodplains) within the primary forest, and absent from the surrounding forest areas. These populations were characterised by low nest and worker densities. Second, we found dominant populations in recent anthropogenic areas (e.g. secondary forest or forest edge along road) characterised by high nest and worker densities, and associated with low ant species richness. The local dominance of W. auropunctata in such areas can be due to the displacement of other species (cause) or the filling‐up of empty habitats unsuitable to other ants (effect). With respect to their demographic features and ant species richness, the populations of native anthropogenic habitats were to a large extent similar to the invasive populations introduced into remote areas. 4. The results point to the need for greater research efforts to better understand the ecological and demographic features of invasive species within their native ranges.     

Reduced genetic diversity, increased isolation and multiple introductions of invasive giant hogweed in the western Swiss Alps

The giant hogweed ( Heracleum mantegazzianum ) has successfully invaded 19 European countries as well as parts of North America. It has become a problematic species due to its ability to displace native flora and to cause public health hazards. Applying population genetics to species invasion can help reconstruct invasion history and may promote more efficient management practice. We thus analysed levels of genetic variation and population genetic structure of H. mantegazzianum in an invaded area of the western Swiss Alps as well as in its native range (the Caucasus), using eight nuclear microsatellite loci together with plastid DNA markers and sequences. On both nuclear and plastid genomes, native populations exhibited significantly higher levels of genetic diversity compared to invasive populations, confirming an important founder event during the invasion process. Invasive populations were also significantly more differentiated than native populations. Bayesian clustering analysis identified five clusters in the native range that corresponded to geographically and ecologically separated groups. In the invaded range, 10 clusters occurred. Unlike native populations, invasive clusters were characterized by a mosaic pattern in the landscape, possibly caused by anthropogenic dispersal of the species via roads and direct collection for ornamental purposes. Lastly, our analyses revealed four main divergent groups in the western Swiss Alps, likely as a consequence of multiple independent establishments of H. mantegazzianum .