Oscillating peat surface levels in a restiad peatland,New Zealand—magnitude and spatiotemporal variability

Hydrology, particularly the water table position below the surface (relative water level, RWL), is an important control on biogeochemical and ecological processes in peatlands. The surface elevation (SE) in a peatland oscillates in response to changes in effective stress on the peat matrix mainly caused by water level fluctuations. This phenomenon is called peatland surface oscillation (PSO). To investigate the spatiotemporal variability of PSO, surface elevation and the water level above sea level (AWL) were measured monthly (23 sites) over one year in a warm‐temperate restiad peatland, New Zealand. At one site peat surface elevation was measured indirectly by monitoring AWL and RWL continuously with pressure transducers. Annual PSO (the difference between maximum and minimum surface elevation) ranged from 3·2 to 28 cm (mean = 14·9 cm). Surface elevation changes were caused by AWL fluctuations. Spatially homogenous AWL fluctuations (mean 40 cm among sites) translated into RWL fluctuations reduced 27–56% by PSO except for three sites with shallow and dense peat at the peatland margin (7–17%). The SE‐AWL relationship was linear for 15 sites. However, eight sites showed significantly higher rates of surface elevation changes during the wet season and thus a non‐linear behaviour. We suggest flotation of upper peat layers during the wet season causing this non‐linear behaviour. Surprisingly, PSO was subjected to hysteresis: the positive SE‐AWL relationship reversed after rainfall when the surface slowly rose despite rapidly receding AWL. Hysteresis was more prominent during the dry season than during the wet season. Total peat thickness and bulk density together could only explain 50% of the spatial variability of PSO based on manual measurements. However, we found three broad types of SE‐AWL relationships differing in shape and slope of SE‐AWL curves. These oscillation types reflected patterns in vegetation and flooding. Copyright © 2007 John Wiley & Sons, Ltd.     

Systematic biotic responses to palaeoenvironmental change in the Late Pleistocene southern South China Sea: a preliminary study

Oxygen and carbon isotopes from the planktonic foraminifer Globigerinoides sacculifer, trace element contents, calcium carbonate, biogenic silica, grain size, and abundances of diatoms, radiolarians and foraminifera in a deep‐sea core from the southwestern South China Sea were analysed to investigate the response of various marine ecological communities to environmental changes over the last 200 ka. The synthesised results show that the quality of the palaeoecological environment for biological growth is primarily affected by nutrient supply and terrigenous disturbance. Ba and P are important nutrient elements for the growth of diatoms, radiolarians and planktonic foraminifera. Together with dissolved silica and calcium carbonate in sea water, these elements may control microbiotic development. However, variations in Fe content appear to affect diatom and radiolarian abundance. Optimal biotic growth occurs when nutrients are abundant and when there is minimal terrigenous disturbance. Biotic growth decreases when sea water is highly oligotrophic and terrigenous input is high. Maximum biological growth occurred in the mid Holocene, but deteriorated soon afterwards owing to increased terrigenous input, causing a decrease of biological abundance and productivity in the late Holocene. The results also indicate how the Toba volcanic eruption ca. 74 ka ago contributed to changing the ecological environment in the southern South China Sea. Copyright © 2008 John Wiley & Sons, Ltd.     

寒区环境中的古DNA分子

寒区埋藏环境常年处于负温条件下,土壤冻结或冰的形成过程产生封闭作用,可以隔离造成埋藏生物遗体同DNA氧化分解的氧气之间的接触.由于液态水含量极大地减少和冰胶结作用,使得主要依赖于液态水而发生的生物大分子的化学分解以及生物降解反应作用减慢,有机体没有成岩过程中降解以及水解作用,从而使古DNA分子可以得到较好的保存.目前绝大多数关于古DNA研究的重要成果所使用生物材料均来自寒区环境,最为引人注目的有关猛犸象、棕熊和企鹅化石古DNA的研究.这些研究分别从个体、种群和同一种群在不同时间尺度上描绘了它们与现代生物种之间的亲缘关系、过去发生的生物迁移和空间隔离以及特定生物分子水平上的时间演化.从目前来看,大量的生物标本很好地保存在那里,以至于单一考贝基因都可以获得,因此是获取古DNA并获得相应遗传信息的理想地区.     

草原与荒漠交界地区流沙的固定——以沙坡头铁路防护体系旱路固沙为例

在年降水量200~ 300mm左右的草原与荒漠交界地区,无灌溉条件下的流沙固定不仅是可能的,亦是非常成功的。以包兰铁路沙坡头铁路人工植被的建立为例,年平均降水量仅186.2mm,在扎设草方格辅助措施下,栽植固沙植物,成功地从根本上解决了流沙固定问题。油蒿是特别优良的固沙植物,天然更新能力强,并能形成群落,又能稳定相当长时期。理应成为该地区流沙固定的首选。     

植被时空变化的估算方法

Plant diversity is used as an indicator of the well-being of vegetation and ecological systems. Human activities and global change drive vegetation change in composition and competition of species through plant invasions and replacement of existing species on a given scale. However, species diversity indices do not consider the effects of invasions on the diversity value and on the functions of ecosystems. On the other hand, the existing methods for diversity index can not be used directly for cross-scale evaluation of vegetation data. Therefore, we proposed a 3-dimensional model derived from the logistic equation for estimating vegetation change, using native and non-native plant diversity. The two variables, based on the current and the theoretical maximum diversity of native plants on a given scale, and the result of the model are relative values without units, and are therefore scale-independent. Hence, this method developed can be used directly for cross-scale evaluations nf vegetation data, and indirectly for estimatinu ecosvstem or environmental chanue.     

生物土壤结皮对土壤种子库的影响

在自然光照条件下,对草原化荒漠地带的苔藓与藻类两种生物土壤结皮进行干、湿处理, 第26卷第6期2006年11月中国沙漠JOURNAL OF DESERT RESEARCHVol. 26No.6Nov. 2006研究其上种子库组成与数量特征,结果表明:①有9种植物的幼苗出现在含有生物土壤结皮覆盖的表土中,它们分别是独行菜（Lepidium ruderate L.）、油蒿(Artemisia ordosica Krasch)、灰绿藜(Chenopodium glaucum L.)、多根葱(Allium polyirhizum Turcz.ex Rgl.)、小画眉草(Rragrostis poaeoides Beauv)、 雾冰藜(Bassia dasyphylla （Fisch.et Mey）)、 马齿苋(Potulaca oleracea L.)、狗尾草(Setaria viridis (L.)) 、苋菜(Amaranthus.retroflexus L.),其中一年生草本植物有7种;②在不同类型的结皮上,土壤种子库的总储量以及每种植物种子的储量存在着显著的差异:对于湿润处理的两种结皮,萌发的幼苗总密度存在着极显著的差异（P<0.001）,对于干燥处理的两种结皮,萌发幼苗的总密度也存在着显著的差异（P<0.05）;③水分是限制结皮种子库植物种子萌发的主要原因,苔藓与藻结皮上萌发的种子总密度都存在极显著的差异（P<0.001）。     

Suspended solids induce increasing microbial ammonium recycling along the river-estuary continuum of the Yangtze River

Many large rivers worldwide are enriched with high levels of suspended solids (SS), which are known to be hotspots of many nitrogen (N) transformation processes (e.g., denitrification, nitrification). However, the influence of SS on microbial ammonium (NH₄⁺) recycling remains unclear. Water column NH₄⁺ regeneration rates (REGs) and potential uptake rates (U_pots) as well as community biological NH₄⁺ demand (CBAD) was measured in the river-estuary continuum of the third longest river in the world—Yangtze River, which has dramatic SS gradients. We found that REGs, U_pots, and CBAD all increased downriver, with higher REGs, U_pots, and CBAD in the estuary than in the river sections. The regeneration and uptake of NH₄⁺ were nearly balanced in the river sections, while the positive CBAD in the estuary indicated obvious NH₄⁺ demand of microbes. Concentrations of SS, which also control the content of chemical oxygen demand and particulate N, were the main factor influencing NH₄⁺ recycling rates and CBAD. SS-induced regenerated NH₄⁺ in the river-estuary continuum of Yangtze River was estimated to be 11.02 × 10⁸ kg N yr⁻¹ and accounted for about 14% of total N inputs, suggesting that regenerated NH₄⁺ is an important N source for microbes and may influence nutrient dynamics in lower coasts. To our knowledge, this is the first study to report NH₄⁺ recycling in Yangtze River with an emphasis on its influencing factors and contribution to N budgets.     

某金矿生物浮选可行性实验研究

某金矿生物选矿采用重选+浮选流程进行.生物重选试验表明,金精矿回收率从常规重选的55.9％提高到65.3％.重选尾矿生物浮选时,对常规浮选试剂丁基黄药做了补加生物试剂,或部分替换,以及全部替换试验.实验室上述试验结果证明,生物选矿对金矿是可行的,并具无污染、安全、降低成本的应用前景.     

青藏高原可可西里地区湖泊沉积物中有机质正构烷烃分布特征

湖泊沉积物中有机质正构烷烃分布特征对有机质母源、沉积环境等有较好的指示作用。本文通过对青藏高原高寒地区可可西里不同盐度的现代湖泊表层沉积物样中有机质正构烷烃的分析,表明正构烷烃分布主要受陆生植被、水生植物和水体盐度的控制。结果表明,有机质以眼子菜为主的沉水植物来源的正构烷烃有较高的C23正构烷烃峰和高丰度中等链长正构烷烃,以及高丰度C31、C29、C27正构烷烃峰;而没有C23正构烷烃峰,仅有高丰度C31、C29、C27正构烷烃峰,代表了陆生草本植物来源的特征。咸水、微咸水还原环境有明显高Ph丰度。C17的高丰度代表了藻类植物来源特征。不同的中等碳数正构烷烃、高盐度沉积物中未见偶碳数正构烷烃特征表明有机母质的差异是沉积物中正构烷烃组成和分布差异的主要原因。同时,C27、C29的存在不一定就是陆生木本植物来源有机质,水生植物也具有相似的特征。     

微波消解-电感耦合等离子体质谱法测定生物样品中微量硒的方法研究

生物样品中微量元素硒的分析检测,经典方法是湿法消解-氢化物发生原子荧光光谱法(HGAFS)。湿法消解处理生物样品需使用大量试剂,并且消解时间长,样品背景值高;HG-AFS的分辨率较低,已经不能满足微量硒的分析需求。解决生物样品的消解过程缓慢、试剂用量大的问题是提高样品中微量元素硒的检出限和分辨率的前提。本文采用湿法消解和微波消解两种消解体系处理样品,对两种方法制备的溶液分别采用HG-AFS和电感耦合等离子体质谱法(ICP-MS)进行测定,通过对比试验确定了微波消解ICP-MS方法可以实现生物样品中微量硒的准确测定。对比试验表明:采用高压密闭微波消解前处理样品技术可以大大缩短消解时间,减少试剂用量,降低了样品背景值;利用ICP-MS直接进行测定,方法检出限为0.01μg/g,精密度(RSD,n=12)小于4%,低于HG-AFS的检出限(0.03μg/g)和精密度(10%)。微波消解ICP-MS方法操作简单快捷,降低了方法检出限,提高了样品分析的准确度和精密度。