植物水分利用策略研究进展

水分是影响植物生长发育的重要因子之一。地球上大多数生态系统中的植物都会经历一个降水相对稀少的干旱季节,植物在不同的季节与不同的生态系统中究竟如何利用水分,利用哪些水分去获得生存,成为一个人们关注的问题。在过去的20年,稳定同位素技术在植物生态学中的应用得到了稳定长足的发展。因为陆地植物(少数排盐种类除外)在水分吸收过程中不发生同位素分馏,因此可以利用δD与δ18O数据进行水分获取方式的研究。对植物木质部水分以及其潜在水源的稳定同位素进行分析,并参考土壤水势、叶片水势、土壤含水量等数据,同时运用二元或三元混合模型,可以定量确定植物的水分利用来源。大量的研究表明,不同功能型、生长阶段、季节的植物以及不同物种往往具有不同的水分利用策略。     

华北石质山区油松林对降水再分配过程的影响

森林通过降水再分配过程影响着流域的水量平衡和物质循环。根据2005-2008年汛期华北石质山区主要造林树种油松林的林外降雨、穿透降雨、树干径流定位观测数据,探讨了人工油松林对降雨再分配过程的影响。结果表明,测定期间32场次降雨过程中油松林穿透雨量、树干径流量和林冠截留量平均值分别为8.67,0.11,1.07mm;透过率,树干径流率和林冠截留率分别为82.18%(57.74%-87.55%),1.07%(0.22%-2.07%),16.75%(11.01%-42.07%)。油松林冠层穿透降雨量、树干径流量和林冠截留量均与林外降雨量呈明显的线性关系(R2=0.995,R2=0.907,R2=0.855),根据回归方程,当林外降雨量大于0.3mm时,可发生穿透降雨,当林外降雨量大于3.51mm时,可发生树干径流;林冠截留率与林外降雨呈双曲线衰减趋势,回归方程为y=12.091+55.537/(x+0.426)(N=32,R2=0.685)。典型次降雨再分配过程表明,林冠不仅在量上对降雨进行再分配,还在时程上进行了再分配。     

Overwintering conditions affect cold hardiness,survival, and post-overwintering fitness of the pea leaf weevil

Overwintering conditions affect the physiological state of ectotherms, and therefore, their cold hardiness and survival. A measure of the lethal and sublethal impacts of overwintering conditions on pest populations is crucial to predict population dynamics and to manage pests the following spring. The impact of winter conditions can be most intense for invasive insects undergoing range expansion. Insect herbivores can display plastic host use behaviours that depend on their body condition following winter. The pea leaf weevil, Sitona lineatus L. (Coleoptera: Curculionidae), is an invasive pest of field peas, Pisum sativum L., and faba bean, Vicia faba L. (Fabaceae). Pea leaf weevil has expanded its range in North America to include the Prairie Provinces of Canada. This study investigated the effects of temperature and microhabitat on overwintering survival and cold hardiness of pea leaf weevil in its expanded range. Further, we investigated the sublethal effect of overwintering temperature and duration on post-overwintering survival, feeding, and oviposition of pea leaf weevil. We also investigated the role of juvenile hormone in modulating body condition of overwintering weevils. The overwintering survival of pea leaf weevil adults increased with soil temperature and varied with region and microhabitat. More weevils survived winters when positioned near tree shelterbelts compared to open alfalfa fields. The supercooling point of pea leaf weevil varied throughout its expanding range but did not differ for weevils held in the two microhabitats. The average threshold lethal temperature of pea leaf weevil at all three sites was −9.4 °C. Weevils that overwintered for a longer duration and at a higher temperature subsequently fed more on faba bean foliage and laid more eggs compared to those which overwintered for a shorter duration at a lower temperature. Our findings highlight that warm winters would increase overwintering survival and post-overwintering fitness, facilitating further pea leaf weevil invasion northward in the Prairie Provinces of Canada.     

自然和人工管理驱动下盐城海滨湿地景观格局演变特征与空间差异

将盐城国家级自然保护区核心区划分为人工管理区和自然湿地区两种模式,根据1987年、1997年、2007年3个时相的景观资料,运用RS、GIS技术和景观生态学方法,分析不同驱动力下湿地景观格局的变化差异。结果表明:(1)人工管理区,景观斑块平均面积由205.31 hm2降至55.60 hm2,景观多样性指数1.4284降低到1.2928,优势度从0.3634上升到0.7766,表明景观破碎化明显,景观多样性呈降低趋势,优势度则呈上升趋势。景观变化的结果导致景观带状特征变弱,镶嵌性特征十分明显;1987—1997年期间,景观格局空间演变表现为从陆地向海洋的单向演替;而1997—2007年,景观演替呈现多向性特征。(2)自然湿地区,景观优势度呈下降趋势,从0.4844下降到0.3164;而景观多样性呈上升趋势,其指数从0.9019上升到1.4754。景观带状格局发育更加明显,各景观带宽趋于均匀,并且景观从陆地向海洋呈单向演替特征。(3)影响海滨湿地景观格局演变的驱动因素是:自然湿地区主要受海洋潮汐作用影响,其主要自然过程如地貌过程和植物群落演替过程等呈连续性变化,从而导致景观演变呈带状连续性发展;人工管理区主要受人为管理影响,人为管理往往使生态过程的连续性发生突变,从而使景观演变呈多向性特征。     

Integrated outdoor culture of two estuarine macroalgae as biofilters for dissolved nutrients from <Emphasis Type="Italic">Sparus auratus</Emphasis> waste waters

An integrated outdoor cultivation of two macroalgal species: Ulva rotundata (Chlorophyta) and Gracilariopsis longissima (Rhodophyta) was designed. The macroalgae were cultured in effluents from an intensive marine culture (growout phase) of gilthead seabream Sparus aurata. The biomass evolution of the algal tanks followed a logistic curve, where the approach to the maximum stocking density of seaweeds was governed by thalli self-shading, as nutrient limitation in the cultivation tank was unlikely. The maximum stocking density of the system was approximately 27.8 g U. rotundata L⁻¹ (16.7 Kg m⁻²) and 11.9 g G. longissima L⁻¹ (7.12 Kg m⁻²). Yield was more than 3 times higher in U. rotundata than in G. longissima. Overall, U. rotundata removed a greater percentage of phosphate (8.9%) and total dissolved inorganic nitrogen (54%) flowing into the algal tanks than G. longissima. The latter species biofiltered approximately 3.2% of phosphate and 17% of the total dissolved inorganic nitrogen input. However, mean nutrient uptake rates on wet weight basis were usually higher in G. longissima than in U. rotundata. The production of total oxidised nitrogen in the algal tanks, considered as being the nitrification rate occurring on the algal fronds by nitrifying bacteria, was less than half of the ammonium uptake by the macroalgae, suggesting that seaweeds competed efficiently for ammonia against the nitrifyers. The biofiltration during a diel cycle showed that mean phosphate biofiltration was lower than 4.5% in the two species whereas ammonium was biofiltered efficiently (up to 67%), especially in U. rotundata. The metal and heavy metal content in the algal tissue at the end of the monitoring period suggested no metal contamination of tissues so that both macroalgal species could be used in the food industry. The study reveals the value of ecological engineering techniques in reducing the dissolved nutrient content in effluents from the fish farm, with the prospect of a better management practises, based on integrated mariculture designs, being developed by the local farmers.     

A comparison of physiological responses and rating of perceived exertion between high-impact and low-impact aerobic dance sessions

The aim of this study was to compare the exercise intensity and rating of perceived exertion (RPE) of a high-impact (HIP) and a low-impact (LIP) university aerobic dance session. Ten women [mean (SD) age 22.9 (2.6) years] took part in the study. An incremental treadmill test was performed by each subject to determine maximum oxygen consumption (V˙O_{2 max} ) and maximum heart rate (HR _max ). The measured V˙O_{2 max} [mean (SD)] was 49.0 (7.5) ml · kg⁻¹ · min⁻¹. The subjects were randomly assigned to LIP and HIP sessions (i.e. five of the subjects participated in the HIP session first, and the other five participated in the LIP session first). In a laboratory, heart rate, oxygen uptake and RPE were measured throughout each session for each subject. Expired air was collected continuously throughout the sessions using Douglas bags (ten bags over a 30-min period). The sessions consisted of 20 min of aerobic exercise (bags 1–7) followed by 5 min of local muscular endurance exercise (bags 8 and 9) and 5 min of flexibility exercises (bag 10). The mean intensity of the aerobic section of the LIP and HIP sessions was 51.6% and 64.7% V˙O_{2 max} , respectively. Ninety-five percent confidence intervals for the average difference between the HIP and LIP sessions demonstrate that the %V˙O_{2 max} was between 12% and 14% higher for the HIP session. The mean %HR _max for the LIP and HIP sessions was 71.4% and 76.7%, respectively, with the %HR _max in the HIP session being between 5.4% and 7.2% higher on average than that of the LIP session. On average, the RPE for the aerobic section of the HIP session (12.1) was consistently higher than that of the LIP session (11.1). HIP activity has the potential to maintain/improve the aerobic fitness of its participants. According to the literature, the exercise intensity elicited by LIP activity may have a limited training effect for the population utilised in this study, and for some individuals may result in detraining. Conversely, LIP activities may be an appropriate mode of exercise for overweight and unfit individuals. Accepted: 5 January 1998     

基于投入产出分析的中国生态足迹模型

基于投入产出分析技术的生态足迹（EF）核算模型是目前国际生态承载力研究的热点模型之一。在已有研究的基础上,引入土地利用差异转化系数（某类土地利用的产量因子与其均衡因子的乘积）改进模型,以保证投入产出表的行、列组分加和操作的有效性。研究以货币型投入产出表为基础核算中国1997年的EF,分析表明：（1）1997年中国为EF净出口国,人均EF贸易逆差0．050hm^2,占生产包含足迹的3．4％;（2）最终使用的人均EF为1．435hm^2（能源足迹占45．1％）,其中,2／3缘于居民消费,另1／3缘于资本形成;（3）第一、二、三产业包含的人均EF依次为0．499、0．721hm^2和0．183hm^2。其中,第一产业以直接占用生态空间为主,而第二、三产业以间接占用为主,如第二产业的隐藏性非能源足迹是其直接值的140余倍;（4）三大产业部门中,第三产业最终产品消费的EF最小,人均0．183hm^2,而其土地利用的经济效率最高,为0．898万元hm^-2。实践表明基于投入产出分析的EF模型不仅承袭了EF基本模型的优点,而且结构性能好,能同时识别社会各生产和消费部门的生态压力及其在不同部门之间的流转情况,并可有效避免足迹组分的重复计算。     

人工集鱼装置对热带金枪鱼类摄食模式的影响研究进展

热带金枪鱼类具有聚集在漂浮物体周围的行为特性,形成的集群表现稳定,可捕性较高。以此特性,金枪鱼围网渔业研制并投放了大量的人工集鱼装置(Fish Aggregation Device,FAD)用于聚集并捕捞金枪鱼。然而,大规模出现的FAD会使某些海域海面漂浮物的密度迅速增加,从而在一定程度上人为地改变了金枪鱼的表层栖息环境,对金枪鱼种群具有一系列可能的潜在负面影响,摄食模式的改变就是其中之一。归纳并综合了近年来国内外关于FAD对金枪鱼类摄食模式影响的相关研究,从摄食行为、日摄食量、饵料种类与组成以及生态位宽度4个方面对比了随附于FAD的金枪鱼和自由状态下同类的不同,发现大多情况下FAD的存在会使金枪鱼的摄食模式发生一定的改变。最后,归纳了过往实验存在的不足,对今后研究的发展方向进行了展望。     

Impacts of logging roads on tropical forests

Road networks are expanding in tropical countries, increasing human access to remote forests that act as refuges for biodiversity and provide globally important ecosystem services. Logging is one of the main drivers of road construction in tropical forests. We evaluated forest fragmentation and impacts of logging roads on forest resilience and wildlife, considering the full life cycle of logging roads. Through an extensive evidence review we found that for logging road construction, corridors between 3 and 66 m (median 20 m) width are cleared, leading to a loss of 0.6–8.0 percent (median 1.7%) of forest cover. More severe impacts are increased fire incidence, soil erosion, landslides, and sediment accumulation in streams. Once opened, logging roads potentially allow continued access to the forest interior, which can lead to biological invasions, increased hunting pressure, and proliferation of swidden agriculture. Some roads, initially built for logging, become converted to permanent, public roads with subsequent in‐migration and conversion of forest to agriculture. Most logging roads, however, are abandoned to vegetation recovery. Given the far‐reaching impacts of the roads that become conduits for human access, its control after the end of logging operations is crucial. Strategic landscape planning should design road networks that concentrate efficient forest exploitation and conserve roadless areas.