Response of ecosystem carbon exchange to warming and nitrogen addition during two hydrologically contrasting growing seasons in a temperate steppe

A large remaining source of uncertainty in global model predictions of future climate is how ecosystem carbon (C) cycle feedbacks to climate change. We conducted a field manipulative experiment of warming and nitrogen (N) addition in a temperate steppe in northern China during two contrasting hydrological growing seasons in 2006 [wet with total precipitation 11.2% above the long‐term mean (348 mm)] and 2007 (dry with total precipitation 46.7% below the long‐term mean). Irrespective of strong intra‐ and interannual variations in ecosystem C fluxes, responses of ecosystem C fluxes to warming and N addition did not change between the two growing seasons, suggesting independence of warming and N responses of net ecosystem C exchange (NEE) upon hydrological variations in the temperate steppe. Warming had no effect on NEE or its two components, gross ecosystem productivity (GEP) and ecosystem respiration (ER), whereas N addition stimulated GEP but did not affect ER, leading to positive responses of NEE. Similar responses of NEE between the two growing seasons were due to changes in both biotic and abiotic factors and their impacts on ER and GEP. In the wet growing season, NEE was positively correlated with soil moisture and forb biomass. Negative effects of warming‐induced water depletion could be ameliorated by higher forb biomass in the warmed plots. N addition increased forb biomass but did not affect soil moisture, leading to positive effect on NEE. In the dry growing season, NEE showed positive dependence on grass biomass but negative dependence on forb biomass. No changes in NEE in response to warming could result from water limitation on both GEP and ER as well as little responses of either grass or forb biomass. N addition stimulated grass biomass but reduced forb biomass, leading to the increase in NEE. Our findings highlight the importance of changes in abiotic (soil moisture, N availability) and biotic (growth of different plant functional types) in mediating the responses of NEE to climatic warming and N enrichment in the semiarid temperate steppe in northern China.     

不同季节杉木幼苗叶片养分和代谢组分对增温和减少降水的响应

研究冬季和夏季亚热带杉木幼苗在增温5 ℃和减少50%自然降水处理下叶片养分和代谢组分的变化.结果表明: 由于不同季节温度和水分差异,杉木叶片的养分和生理代谢组分在不同季节有不同的表现.冬季杉木叶片碳、氮、磷和钾含量显著高于夏季.夏季减少降水、增温处理对杉木叶片各类抗氧化酶活性均无显著影响,冬季减少降水处理分别显著降低超氧化物歧化酶活性20.7%和过氧化物酶活性17.8%.冬季增温后杉木叶片非酶促的抗坏血酸含量显著增加132.5%.冬季增温+减少降水处理降低杉木碳含量,促进渗透物质脯氨酸和氮含量的累积.夏季增温+减少降水处理显著提高杉木叶片碳含量3.3%.无论是冬季还是夏季,增温+减少降水处理对杉木叶片抗氧化系统无显著影响.植物对夏季增温的适应机制与冬季增温不同,杉木叶片的养分变化对同时增温+减少降水更加敏感.为了更好地管理种植林,以提高植物的生产力,在未来气候变化下,应提高植物对养分供需和对季节响应的关注.     

Daylength and thermal time responses of budburst during dormancy release in some northern deciduous trees

Dormancy release and thermal time to budburst as affected by duration of chilling outdoors, followed by different flushing temperatures and daylengths in a phytotron, were studied in cuttings of several northern tree species. In Betula pubescens, B. pendula and Prunus padus vegetative buds were released from dormancy already in December, in Populus tremula in January, whereas in Alnus incana and A. glutinosa dormancy was not released until February. Thermal time (day degrees >0°C) to budburst decreased non-linearily with increasing duration of chilling (i. e. duration outdoors), and the slope of this relationship differed among species. The estimated effective base temperature for accumulation of thermal time varied from + 1°C in P. tremula to −4°C in P. padus . The use of 0°C as base temperature is recommended. Long days reduced the thermal time to budburst at all flushing temperatures (9, 15 and 21°C) in all the above species and in Corylus avellana , whereas Sorbus aucuparia and Rubus idaeus showed no daylength response. Since the chilling requirement of all species was far exceeded even in a winter with January-March temperatures 6.5°C above normal, it is concluded that under Scandinavian conditions, the main effect of climatic warming would be earlier budburst and, associated with that, a longer growing season and increased risk of spring frost injury.     

Global warming and the earlier start of the Japanese-cedar (Cryptomeria japonica) pollen season in Toyama, Japan

Atmospheric pollen surveys were conducted in Toyama City, Japan over a 21-year period (1983–2003). Airborne pollen was collected by two methods, the gravimetric method and the volumetric method. The gravimetric method indicated that the start of the Cryptomeria japonica pollen season, as indicated by pollen dispersion, has advanced from day 73 (from January 1) in 1983 to day 47 in 2003. Measurements taken using the volumetric method confirmed this trend. There was a significant correlation between the start dates obtained by both methods. Meteorological data indicated that the most noticeable elevation in temperature during the experimental period occurred in February – an increase of 2.1°C. Significant correlations existed between the mean temperatures and the start dates of the pollen season. These results support the steadily increasing number of reports indicating a global warming trend. The temperature change in February in affecting the start dates of the C. japonica pollen season is particularly relevant in the context of human health. Further studies will be needed to clarify the effects of the global warming trend on the pollen season and human health in more detail.     

城市绿地热效应全年变化特征及其与背景气象因子的关系

城市绿地能够调节热气候,是城市实现高质量可持续发展的重要空间载体。以往研究着重探讨城市绿地夏季降温效应的空间特征,较少分析绿地热效应的全年变化规律与潜在影响因子。在南京城区选择7个代表性城市公园,采用热气候定点观测方法获取公园大气温度全年观测数据,并与城市中心区参照点进行对比,分析公园热效应的全年动态变化规律及背景气象因子的影响。研究发现,由于植被覆盖率、冠层郁闭度及海拔不同,不同公园热效应的季节、昼夜规律存在显著差异,主要表现为3种形式：全年降温型,全年昼升夜降型,以及夏季全天降温、春秋冬季昼升夜降型。与城市中心区相比,公园夏季最高可降低气温7.7℃,冬季最高可增温3℃。大气温度、相对湿度,风速与太阳辐射4个背景气象因子能解释23.5%-77.4%的公园热效应变异。夏冬两季日间热效应主要受太阳辐射和气温的影响,夜间热效应主要受风速影响：太阳辐射每升高100W/m²,夏季日间降温强度减少0.3℃,冬季日间增温强度增加0.2-0.5℃;气温每升高1℃,夏季日间降温强度提高0.1-0.14℃,冬季日间增温强度提高0.05-0.08℃;风速每增加1m/s,夏季夜间降温强度减少0.05-0.78℃,冬季夜间降温强度减少0.4-1.1℃。研究结果有助于深入认识城市绿地热效应的复杂形成机制,并为夏热冬冷地区城市自然空间保护与气候适应性设计提供科学参考。     

Effect of open-field experimental warming on the leaf phenology of oriental oak (Quercus variabilis) seedlings

Aims An open-field warming experiment enables us to test the effects of projected temperature increase on change in plant phenology with fewer confounding factors and to study phenological response to temperature ranges beyond natural variability. This study aims to (i) examine the effect of temperature increase on leaf unfolding and senescence of oriental oak (Quercus variabilis Blume) under experimental warming and (ii) measure temperature-related parameters used in estimating phenological response to temperature elevation.Methods Using an open-field warming system with infrared heaters, we increased the air temperature by ~3°C in the warmed plots compared with that of the control plots consistently for 2 years. Leaf unfolding and senescence dates of Q. variabilis seedlings were recorded and temperature-related phenological parameters were analysed.Important findings The timing of leaf unfolding was advanced by 3–8 days (1.1–3.0 days/°C) and the date of leaf senescence was delayed by 14–19 days (5.0–7.3 days/°C) under elevated air temperatures. However, the cumulative degree days (CDD) of leaf unfolding were not significantly changed by experimental warming, which suggest the applicability of a constant CDD value to estimate the change in spring leaf phenology under 3°C warming. Consistent ranges of advancement and temperature sensitivity in spring phenology and delayed autumn phenology and proposed temperature parameters from this study might be applied to predict future phenological change.     

极端生理耐受性导致果蝇Zaprionus indianus 在温带地区广泛分布（英文）

在过去的十年中, Zaprionus indianus这一温带适应性果蝇已经入侵印度次大陆, 并扩大了其在该地区的分布。Z. indianus能成功入侵是由于它具有很强的适应性和对极端生理条件的耐受性。对Z. indianus (温带狭域分布种类) 和黑腹果蝇Drosophila melanogaster (全球广域分布种类)在极端温度下未成熟期和成虫期发育阈值的比较研究表明, 两者的死亡率和发育起点温度存在显著差异。为了检测越冬期间未成熟期和成虫期抗逆性和存活率的变化, 以采自印度温带和热带不同地点的Z. indianus种群进行饲养实验。在温带地区的田间养虫笼中以及恒定的实验室条件下监测这些种群的卵孵化率和成虫存活率, 直至全部成虫死亡。结果表明, 由于温带地区卵孵化率和存活率高, 导致总的孵化率和存活率在不同纬度间存在显著差异。卵至成虫发育实验结果表明, 低温条件下产下的卵在温度适中时成功发育成成虫。由此可见, 这种昆虫在未成熟期具有的气候适应性以及在成虫期具有的抗逆性可为该物种提供季节性保护。考虑到气候变暖情况, 即温度增加0.6℃, 温度的少许改变都可能导致种群存活能力的显著增强和发育历期缩短。这些结果可解释Z. indianus为什么能够轻易突破障碍并适应新的环境。     

Effects of the 2003 heatwave and climatic warming on mollusc communities of the Saône: a large lowland river and of its two main tributaries (France)

The study of the dynamics of mollusc populations of the Saône and its two main tributaries, the Doubs and Ognon, over several years has provided us with the opportunity of highlighting the consequences of climatic warming and especially of the heatwave of 2003 on these organisms. From 1987 to 2003, the mean temperature of the waters of the Saône upstream of Lyon (Couzon) increased by 1.5°C. In addition, the summer of 2003 was the hottest since 1500 at least. We used correspondence analysis to identify structure change in mollusc data dating from September 1996 to December 2004. The results revealed: (1) during the period from September 1996 to July 2003, a significant progressive change in the mollusc community structure of the Saône upstream of Lyon, probably linked to the increase of temperature; (2) from July to August 2003 during the heatwave, a sudden change in the structure of mollusc communities and a significant decrease of species richness and density of gastropods and bivalves. During 2004, mollusc density and particularly that of Pisidium remained dramatically low. Similar observations were performed at four other sites along the Saône and in the lower reaches of its two main tributaries. This suggests that the resilience of the mollusc populations (i.e., the speed with which they return to a predisturbance state) to the heatwave is low. In this way, as different climatic models have predicted an increase in the frequency of summers as hot as that of 2003 during this century, more than half the mollusc species currently inhabiting the potamic area of the Saône, Doubs and Ognon, and probably other large rivers, are probably directly threatened with extinction.     

Microbial physiology and soil CO2 efflux after 9 years of soil warming in a temperate forest – no indications for thermal adaptations

Thermal adaptations of soil microorganisms could mitigate or facilitate global warming effects on soil organic matter (SOM) decomposition and soil CO₂ efflux. We incubated soil from warmed and control subplots of a forest soil warming experiment to assess whether 9 years of soil warming affected the rates and the temperature sensitivity of the soil CO₂ efflux, extracellular enzyme activities, microbial efficiency, and gross N mineralization. Mineral soil (0–10 cm depth) was incubated at temperatures ranging from 3 to 23 °C. No adaptations to long‐term warming were observed regarding the heterotrophic soil CO₂ efflux (R₁₀ warmed: 2.31 ± 0.15 μmol m^?2 s^?1, control: 2.34 ± 0.29 μmol m^?2 s^?1; Q₁₀ warmed: 2.45 ± 0.06, control: 2.45 ± 0.04). Potential enzyme activities increased with incubation temperature, but the temperature sensitivity of the enzymes did not differ between the warmed and the control soils. The ratio of C : N acquiring enzyme activities was significantly higher in the warmed soil. Microbial biomass‐specific respiration rates increased with incubation temperature, but the rates and the temperature sensitivity (Q₁₀ warmed: 2.54 ± 0.23, control 2.75 ± 0.17) did not differ between warmed and control soils. Microbial substrate use efficiency (SUE) declined with increasing incubation temperature in both, warmed and control, soils. SUE and its temperature sensitivity (Q₁₀ warmed: 0.84 ± 0.03, control: 0.88 ± 0.01) did not differ between warmed and control soils either. Gross N mineralization was invariant to incubation temperature and was not affected by long‐term soil warming. Our results indicate that thermal adaptations of the microbial decomposer community are unlikely to occur in C‐rich calcareous temperate forest soils.     

Holocene and actual degradation of the environement in the Mamora forest (Morocco)

The results of absolute datations on the beige sands in Mamora forest have shown large movement (remaniement) and an expansion (épandage) on the plateau surface between 22–26.000 years. This evolution can only be due to a climatic change towards a draught and the disparition of the vagetation. The lack of vegetation has yield an ecological desequililbrium which has resulted into desertification. But the post-period to 20.000 years rather little invistigated we have tried to find the signs that would inform us on the evolution of this forest field during the Holocene. This study relies especially on the morphological analysis of the recent formations, in the closed fields and the costal dunal formations. The holocene levels show a variety in their texutral formations, in their color and the rich levels of the organic matters like: carbon, bone remains etc... Absolute datations and palynological analysis help to determine the nature of this evolutions and the climatic changes during a Holocene. Are they a climitic or an anthropical crises? The question being raised here is:     

Life‐history traits of temperate and thermophilic barracudas (Teleostei: Sphyraenidae) in the context of sea warming in the Mediterranean Sea

This study indicated that the life‐history traits of European barracuda Sphyraena sphyraena are apparently better suited to their environmental conditions compared to the more physically restricted life‐history traits of the yellow‐mouth barracuda Sphyraena viridensis, which co‐habit the north‐western Mediterranean Sea. The latter thermophilic species has a considerably higher reproductive potential as it invests its energy reserves in larger numbers of hydrated eggs per spawning batch. This would favour its population growth rates within the study area, especially if sea warming continues, in which case it is likely that the spawning phenology of this species would give it an advantage.     

Diverting residual biomass to energy use: Quantifying the global warming potential of biogenic CO2 (GWPbCO2)

To calculate the global warming potential of biogenic carbon dioxide emissions (GWP_bCO2) associated with diverting residual biomass to bioenergy use, the decay of annual biogenic carbon pulses into the atmosphere over 100 years was compared between biomass use for energy and its business-as-usual decomposition in agricultural, forestry, or landfill sites. Bioenergy use increased atmospheric CO₂ load in all cases, resulting in a ¹⁰⁰GWP_bCO2 (units of g CO₂e/g biomass CO₂ released) of 0.003 for the fast-decomposing agricultural residues to 0.029 for the slow, 0.084–0.625 for forest residues, and 0.368–0.975 for landfill lignocellulosic biomass. In comparison, carbon emissions from fossil fuels have a ¹⁰⁰GWP of 1.0 g (CO₂e/g fossil CO₂). The fast decomposition rate and the corresponding low ¹⁰⁰GWP_bCO2 values of agricultural residues make them a more climate-friendly feedstock for bioenergy production relative to forest residues and landfill lignocellulosic biomass. This study shows that CO₂ released from the combustion of bioenergy or biofuels made from residual biomass has a greenhouse gas footprint that should be considered in assessing climate impacts.     

Correlations between the actual redox-state potential (E0') of biophase and heart activity in vivo

In CFY rats the tissue redox-state potential (E0') in heart, m. vastus medialis and in the liver, and the heart frequency and QRS amplitudes were measured parallel. It was observed that following compensatory redosis caused by konakion both the autorhythmic heart frequency and QRS amplitudes increased, while after compensatory oxidosis induced by urea occurred the opposite. Following compensatory redosis caused by konakion acetylcholine decreased, but adrenaline increased the heart frequency and QRS amplitudes more intensively than at normal E0' values. After compensatory oxidosis caused by urea, acetylcholine decreased the heart frequency and QRS amplitudes significantly less. Adrenaline decreased the heart frequency in such milieu. On the basis of these data the following conclusions are proposed; For the realization of autorhythmic activity, for negative type acetylcholine and for positive type adrenaline effects in heart, a relatively low primordial tissue E0' value is an essential back-ground element. Among the mechanisms controlling autorhythmicity and sympathetic/parasympathetic effects the actual and permanently changing tissue E0' value is also an important modifying, or through biochemical redox feed-back mechanisms even a regulatory factor of heart activity.     

Ageing and thermal performance in the sub-Antarctic wingless fly Anatalanta aptera (Diptera: Sphaeroceridae): older is better

Senescence is a progressive biological process expressed in behavioural, morphological, physiological, biochemical and cellular age-related changes. Age-associated alterations in activity are regularly found in insects when examining whole-organism senescence over the adult lifespan. In addition, overall stress resistance usually decreases with senescence. In the present study, we measured the critical thermal minimum (CT_min) and the subsequent recovery period over the lifespan of the sub-Antarctic wingless fly, Anatalanta aptera. Experiments were conducted on males and females in seven age groups: newly emerged, 1.5-, 5-, 7-, 13-, 15- and 18-month-old adults. Surprisingly, CT_min decreased significantly with ageing in A. aptera, from −3.8 ± 0.5°C just after the emergence to −5.6 ± 0.7°C in the 18-month-old flies. The subsequent recovery period remained similar between the seven groups tested. Our unexpected results contradict the previous data collected in other insects. We have demonstrated for the first time that ageing may improve rather than impair locomotor activity during unfavourable thermal conditions. It raises questions and challenges the literature dealing with ageing. These fascinating results also question the underpinning mechanisms involved in the improvement of the thermal performance with ageing in A. aptera.     

Design and performance of combined infrared canopy and belowground warming in the B4WarmED (Boreal Forest Warming at an Ecotone in Danger) experiment

Conducting manipulative climate change experiments in complex vegetation is challenging, given considerable temporal and spatial heterogeneity. One specific challenge involves warming of both plants and soils to depth. We describe the design and performance of an open‐air warming experiment called Boreal Forest Warming at an Ecotone in Danger (B4WarmED) that addresses the potential for projected climate warming to alter tree function, species composition, and ecosystem processes at the boreal‐temperate ecotone. The experiment includes two forested sites in northern Minnesota, USA, with plots in both open (recently clear‐cut) and closed canopy habitats, where seedlings of 11 tree species were planted into native ground vegetation. Treatments include three target levels of plant canopy and soil warming (ambient, +1.7 °C, +3.4 °C). Warming was achieved by independent feedback control of voltage input to aboveground infrared heaters and belowground buried resistance heating cables in each of 72‐7.0 m² plots. The treatments emulated patterns of observed diurnal, seasonal, and annual temperatures but with superimposed warming. For the 2009 to 2011 field seasons, we achieved temperature elevations near our targets with growing season overall mean differences (?T_below) of +1.84 °C and +3.66 °C at 10 cm soil depth and (?T^above) of +1.82 °C and +3.45 °C for the plant canopies. We also achieved measured soil warming to at least 1 m depth. Aboveground treatment stability and control were better during nighttime than daytime and in closed vs. open canopy sites in part due to calmer conditions. Heating efficacy in open canopy areas was reduced with increasing canopy complexity and size. Results of this study suggest the warming approach is scalable: it should work well in small‐statured vegetation such as grasslands, desert, agricultural crops, and tree saplings (<5 m tall).     

长江口强壮箭虫和肥胖箭虫的丰度变化对环境变暖的响应

根据1959年和2002年在长江口28°00′～32°00′N,122°00′～123°30′E海域4个季节8个航次海洋调查资料,分析强壮箭虫(Sagitta crassa)和肥胖箭虫(Sagitta enflata)丰度的平面分布和季节变化特征,并结合同步的温度资料分析不同生态类群的强壮箭虫和肥胖箭虫对环境变暖的响应.结果表明:长江口水域春、夏、秋3季强壮箭虫平均丰度均小于1.00 ind/m3,出现率低,无集群性.1959年冬季平均丰度达3.24 ind/m3,出现率较高,有明显的集群性,而2002年冬季平均丰度锐减为0.001 ind/m3,几无分布.肥胖箭虫夏季平均丰度、出现率和集聚强度明显高于其它季节.2002年夏季平均丰度达16.06 ind/m3,较1959年增加3.71 ind/m3,且分布区明显扩大.可见,暖温种强壮箭虫和暖水种肥胖箭虫对长江口海域变暖的响应不同,可作为长江口海洋变暖长期变化的重要指示种.     

一种濒危大疣蛛的潜在分布区域以及气候变暖的影响

本研究的目的是i)确定伊比利亚半岛一种大疣蛛(Macrothele calpeiana)分布的气候相关性以预测其潜在分布,ii)详细阐述该物种在伊比利亚半岛的分布假说,iii)通过推断模型预测确认该物种在北非和整个地中海地区的适合区域,iv)预测气候变暖对蜘蛛潜在分布区的影响。基于物种的存在、远离目前环境条件下的可能缺失以及其它的气候参数,使用广义线性模型发展了潜在分布的可预测模型。蜘蛛在伊比利亚半岛上的潜在分布远大于目前已知的分布区,延伸到尚未发现蜘蛛分布的葡萄牙广大地区。本文提出了该种大疣蛛在适合分布区域内没有分布的历史因素。北非具有适合该物种的条件但却没有该属物种的分布支持了大疣蛛(Macrothele)祖先的东方起源假说。对地中海地区蜘蛛分布的推断突出显示了阿根廷地区有合适的分布区,该地区也发现有另一种欧洲大疣蛛。气候变暖将对现存于伊比利亚的M.calpeiana种群产生负面影响,因为气候变暖将减少并破碎化蜘蛛在北非的潜在栖息地。目前,急需确认在葡萄牙广大地区是否存在蜘蛛物种,发展对该属的系统发育研究以确定大疣蛛属起源和扩散史的理论。