Starting dates and basic temperatures in phenological observations of plants

 Several methods have been used in plant phenology to find the best starting date in spring and the best threshold or basic temperature for growth and development of perennial plants. In the present paper the date giving the highest correlation coefficient for development to various phenophases, in relation to 24-hourly mean air temperatures was chosen as the best starting value in further analyses. For many woody plants this date was very often found to be 1 April based on phenological and climatological observations at about 60 sites in western Norway (at about 61°N). The early flowering species Corylus avellana and Salix caprea and the early leaf-bud breaking Prunus padus seemed to start development earlier in Spring, while the late sprouting Fraxinus excelsior showed the highest correlation coefficient using 15 April. If daytime temperatures were used in the calculations, the ”best” starting date was generally found to be later than for the 24-hour mean temperatures. This variation must be seen as resulting from the different basic temperatures for the development of various species. Estimates of basic temperatures in various species and periods may be given, for example by finding the value having the least variance in heat sums or by various regression analyses. A technique has been developed to minimise the influence of significance of correlation, using the intercept with the temperature axis by merging the two least squares rectilinear regression lines that can be found between plant development and mean air temperature (from the estimated best starting date) at r=+1 or –1. The basic temperature seemed to vary from –5.9°C for leaf-bud break of P. padus to 5.5°C for leaf-bud break of F. excelsior, with basic temperatures of several other woody plants having intermediate values. These values are compared with those found by other methods. Received: 26 May 1998 / Accepted: 7 September 1998     

A phenological study of flowering period and flower colours of aromatic plants in Greece

The flowering period and flower colour spectrum of 170 aromatic plant species are studied in 18 representative regions in Greece. The duration of the early to late flowering of the species is recorded for each region and for Greece as a whole. The basic flower colours (green, yellow, red and violet) are defined and the colour spectra for each region and for the whole country are given by converting absolute to relative values. The Sørensen similarity coefficient is applied to compare regions and the relationship among them as well as with a control region (Athos peninsula). Conclusions are drawn as to the time of maximum flowering and the decrease in the proportion of flowering species from north to south. In addition, interpretations are given for the symmetrical flowering curve of Greece as a whole, compared to the skewed curves of the islands.Nomenclature follows T. G. Tutin et al. (eds.) 1964–1980. Flora Europaea 1-5, Cambridge.     

Evaluation of several degree-day estimation methods in California climates

 Procedures for estimating degree-day accumulations are frequently employed instead of the more accurate method of calculating degree-days from hourly temperature data because on-site temperature data are commonly restricted to daily minimum and maximum temperature records. Data from seven methods of estimating degree-days at each of nine locations during 2 years in California were compared by month to degree-day values calculated by hourly summation. Methods included three sine-wave approaches, three triangulation approaches and the averaging (i.e., rectangle) method. Results of the double-sine and corrected-sine (i.e., corrected for day length) methods were nearly identical to those of the single-sine method. The double triangulation and corrected triangulation methods produced very similar results to the single triangulation method. The averaging method and sine-wave methods deviated to a greater extent from degree-day accumulations calculated from hourly temperatures from November through February than did the triangulation methods. Degree-day estimations from the late spring and summer months were more similar to one another for all estimation methods than during the cooler months of the year. Since no advantages were noted in the more complicated double and corrected methods, the single triangulation method or the sine-wave method is preferred as they are less complicated procedures. Of the various temperature threshold cut-off methods evaluated, error levels were unaffected when estimating degree-days using the sine-wave method. The employment of a horizontal cut-off with the triangulation method did not significantly increase the amount of error in the estimation of degree-days. However, an increase in error was observed when employing the intermediate cut-off and vertical threshold cut-off techniques with the triangulation method for computing degree-days. Received: 26 May 1998 / Accepted: 28 October 1998     

北京地区木本春季物候特征与生物学特性的关系

植物物候是植物生活史中的重要性状,也是指示气候与自然环境变化的重要指标,现已成为全球变化领域的研究热点之一。传统物候研究多假设物候由气候因素决定,如气温、降水、光照等,并主要从植物物候的年际变化角度探讨了气候因素对物候特征的影响。然而,不同物种的物候存在较大差异表明植物物候还与自身生物学特性（如系统发育和功能性状）有关,但植物生物学特性如何影响植物物候仍缺乏深入研究。基于北京地区44种木本植物1965-2018年的展叶始期和开花始期观测资料,以展叶始期和开花始期的3类物候特征（平均物候期、物候对温度的响应敏感度和物候期的积温需求）为例,探究植物物候特征与系统发育和功能性状的关系。首先,利用系统发育信号Blomberg’s K和进化模型检验植物物候特征是否具有系统发育保守性,并通过系统发育信号表征曲线直观表达植物物候特征的进化模式;之后,利用广义估计方程分析植物生活型、传粉型与物候特征的关系,以揭示不同植物的资源利用方式及生存策略的差异。研究发现：（1）除展叶始期的温度敏感度外,其余物候特征的进化均受随机遗传漂变和自然选择力的共同作用,可推断物候特征具有系统发育保守性,即亲缘关系越近的物种物候特征越相似。（2）开花始期的系统发育信号强度比展叶始期更大,表明繁殖物候的系统发育可能比生长物候更保守。（3）植物展叶始期及其积温需求与生活型密切相关。灌木比乔木的展叶时间早、积温需求少。植物开花始期与传粉型相关,风媒植物开花显著早于虫媒植物。研究成果有助于深入理解物候变化的生物学机制,对于丰富物候学的理论研究有重要意义,同时对植物保护也具有重要的指导价值。     

Mismatches between ecosystem services supply and demand in urban areas: A quantitative assessment in five European cities

Assessing mismatches between ecosystem service (ES) supply and demand can provide relevant insights for enhancing human well-being in urban areas. This paper provides a novel methodological approach to assess regulating ES mismatches on the basis of environmental quality standards and policy goals. Environmental quality standards (EQS) indicate the relationship between environmental quality and human well-being. Thus, they can be used as a common minimum threshold value to determine whether the difference between ES supply and demand is problematic for human well-being. The methodological approach includes three main steps: (1) selection of EQS, (2) definition and quantification of ES supply and demand indicators, and (3) identification and assessment of ES mismatches on the basis of EQS considering certain additional criteria. While ES supply indicators estimate the flow of an ES actually used or delivered, ES demand indicators express the amount of regulation needed in relation to the standard. The approach is applied to a case study consisting of five European cities: Barcelona, Berlin, Stockholm, Rotterdam and Salzburg, considering three regulating ES which are relevant in urban areas: air purification, global climate regulation and urban temperature regulation. The results show that levels of ES supply and demand are highly heterogeneous across the five studied cities and across the EQS considered. The assessment shows that ES supply contributes very moderately in relation to the compliance with the EQS in most part of the identified mismatches. Therefore, this research suggests that regulating ES supplied by urban green infrastructure are expected to play only a minor or complementary role to other urban policies intended to abate air pollution and greenhouse gas emissions at the city scale. The approach has revealed to be appropriate for the regulating ES air purification and global climate regulation, for which well-established standards or targets are available at the city level. Yet, its applicability to the ES urban temperature regulation has proved more problematic due to scale and user dependent constraints.     

Regional trends for bud burst and flowering of woody plants in Norway as related to climate change

Data series for bud burst, beginning of flowering and petal fall for 20 species of deciduous trees and conifers at four sites in different regions of southern Norway have been analysed and related to temperature series. On average, the spring phenophases occurred 7 days earlier during the period 1971-2005. The most significant linear trends were observed for the earliest phases. The trends in this period were compared with trends in other periods, the longest one starting in 1927. Those starting in cold decades and ending in 2005 were in most instances statistically significant, whereas hardly any significant trend appeared for series starting in warm decades. This fact showed that the results of trend studies are very sensitive to the choice of starting year. There were significant decadal variations in 40% of the series. The dates of occurrence of the phenophases, varying from the first days of May to the first days of June, correlated with seasonal temperature series, in most cases strongest to mean temperatures for the seasons March-May and April-May. The North Atlantic Oscillation Index (NAOI) for January and February appeared to have some predictive power for the date of occurrence of the recorded phases. The basis for this may be that the oscillations described by the index are of importance for the fulfilment of physiological chilling requirements needed to break bud dormancy. The same genotypes of the trees were grown in region West Norway and in Central Norwegian region; during the period 1965-2005 the trends towards earlier bud burst were more pronounced and steeper at the western site.     

Simulating phenological characteristics of two dominant grass species in a semi-arid steppe ecosystem

Vegetation phenology has a strong effect on terrestrial carbon cycles, local weather, and global radiation partitioning between sensible and latent heat fluxes. Based on phenological data that were collected from a typical steppe ecosystem at Xilingol Grazing and Meteorological Station from 1985 to 2003, we studied the phenological characteristics of Leymus chinensis and Stipa krylovii. We found that the dates for budburst of L. chinensis and S. krylovii were delayed with increasing temperature during winter and spring seasons; these results differed from existing research in which earlier spring events were attributed to the changes in increasing air temperature in winter and spring. The results also suggested that water availability was an important controlling factor for phenology in addition to temperature in grassland plants. The classical cumulative temperature model simulated the phenology well in wet years, but not in the beginning of growing season in all years from 1985 to 2003. The disparity between the simulation and the observation appeared to be related to soil water. Based on our research findings, a water-heat-based phenological model was developed for simulating the beginning of growing season for these two grass species. The simulated results of the new model showed a significant correlation with the observation of beginning date of the growing season, and both mean values of the absolute error were less than 6 days.     

The impact of climate change on the physical characteristics of the larger lakes in the English Lake District

1. The larger lakes of the English Lake District have been the subject of intensive scientific study for more than 60 years. Year‐to‐year variations in the weather have recently been shown to have a major effect on their physical characteristics. The area is mild but very wet and the dynamics of the lakes are strongly influenced by the movement of weather systems across the Atlantic. 2. Here, we combine the results of long‐term measurements and the projections from a Regional Climate Model (RCM) to assess the potential impact of climate change on the surface temperature and residence times of the lakes. 3. The RCM outputs used were produced by the U.K. Hadley Centre and are based on the IPCC ‘A2’ scenario for the emission of greenhouse gases. These suggest that winters in the area will be very much milder and wetter by the 2050s and that there will be a pronounced reduction in the summer rainfall. 4. An analysis of the meteorological data acquired between 1940 and 2000 shows that there have been progressive increases in the winter air temperature and in the rainfall which are correlated with the long‐term change in the North Atlantic Oscillation. The trends reported during the summer were less pronounced and were correlated with the increased frequency of anticyclonic days and a decrease in the frequency of westerly days in the British Isles. 5. A simple model of the year‐to‐year variations in surface temperatures showed that the highest winter temperatures were recorded in the deeper lakes and the highest summer temperatures in the lakes with the shallowest thermoclines. When this model was used to predict the surface temperatures of the lakes in the 2050s, the greatest winter increase (+1.08 °C) was observed in the shallowest lake and the greatest summer increase (+2.18 °C) in the lake with the shallowest thermocline. 6. The model used to estimate the seasonal variation in the residence time of the lakes showed that the most pronounced variations were recorded in lakes with a short residence time. Average winter residence times ranged from a minimum of 10 days to a maximum of 436 days and average summer values from a minimum of 23 days to a maximum of 215 days. When this model was used to predict the residence time of the lakes in the 2050s, the greatest winter decrease (−20%) was observed in the smallest lake and the greatest summer increase (+92%) in the lake with the shortest residence time. 7. The results are discussed in relation to trends reported elsewhere in Europe and the impact of changes in the atmospheric circulation on the dynamics of the lakes. The most serious limnological effects were those projected for the summer and included a general increase in the stability of the lakes and a decrease in the flushing rate of the lakes with short residence times.     

Comparison of chlorophyll fluorescence with several other techniques used to assess chilling sensitivity in plants

Chilling tolerance in eight taxa was estimated from field and controlled environment observations and compared to tolerance estimated using a variety of techniques. The controlled environment observations suggested that the eight taxa could be ranked from chilling tolerant to chilling sensitive in the order: pea ( Pisum sativum L. cv. Greenfeast), Passiflora edulis Sims., Passiflora ligularis Juss. and Passiflora quadrangularis L., pepino ( Solanum muricatum L.) cultivars Comeraya, Suma, Miski, and mungbean [ Vigna radiata (L.) R. Wilcz]; although the relationship between the passionfruit as a group and the pepinos was unclear.
The change in the variable component of chlorophyll fluorescence (F_R) with time near 0°C in darkness was the most reliable method of ranking the plants according to relative chilling tolerance. It was also sufficiently sensitive to discriminate clearly between the closely related pepino cultivars. The Passiflora species and pea were not susceptible to short term reductions in F_R, with or without a 20 min exposure to light. Exposure to light at temperatures near 0°C emphasised the reductions in F_R in the more sensitive species. Pea was the only species capable of recovering a measurable F_R after a 60 min exposure to white light.
Measurement of electrolyte leakage and ethylene evolution from leaf disks after a low temperature treatment could allow discrimination between closely related varieties, but not between genera. Catalase activity was reduced in all taxa in response to low temperature. However, both initial catalase levels and relative response to dark treatment at 20°C enabled the ranking of plants within the closely related subgroups according to susceptibility to chill injury.
No one method clearly distinguished chilling sensitivity over all taxa.     

西安和宝鸡木本植物花期物候变化及温度敏感度对比

植物物候是指示生态系统对气候变化响应的重要证据。已有研究多基于代表性站点的物候观测数据研究物候特征及其对气候变化的响应规律。同一气候区内,不同站点的物候变化及对温度变化响应的敏感度是否一致仍需深入探讨。本文选择同属于暖温带湿润区汾渭平原气候区的西安和宝鸡为研究区,利用"中国物候观测网"在两个站点21个共有物种的开花始期和开花末期数据,比较了1987—2016年两站点各植物花期物候变化特征及其对温度变化响应的敏感度差异。结果表明,西安和宝鸡各物种的开花始期和开花末期均以提前趋势为主。大部分物种开花始期在西安的提前趋势(平均趋势-0.57 d/a)明显强于在宝鸡的提前趋势(平均趋势-0.29 d/a),但开花末期趋势差异不显著。除紫薇和迎春的敏感度差异较大外,其他物种开花始期和开花末期的温度敏感度在两站点间非常接近,无显著差异。由此可见,在同一气候区的不同站点,因增温幅度不同,植物的始花期变化存在较大差异,不能用单站点的物候变化反映整个气候区的物候变化。但同一植物在单站点的温度敏感度可以较好的反映同一气候区其他站点的植物物候-气候关系。本文研究结果可为利用有限站点的物候观测数据分析区域物候...     

Photosynthetic and gas exchange characteristics of dominant woody plants on a moisture gradient in an African savanna

We determined key photosynthetic gas exchange parameters, and their temperature dependence, in dominant woody plants at four savanna sites on a moisture gradient in Botswana, southern Africa. Leaf stable carbon and nitrogen (N) isotope and morphological measures were made concurrently. Sampling of these predominantly non‐N‐fixing species took place during an exceptional rainfall season, representing near‐optimum conditions for primary production at these sites. The mean specific leaf area and leaf size were positively related to mean annual rainfall (MAR); species with larger leaves of lower density were more abundant in wetter sites. Almost all species at all sites showed high net light‐saturated photosynthetic rates (A_max?10 μmol CO₂ m^?2 s^?1) due both to high CO₂ carboxylation (V_c,max) and RubP‐regeneration capacity (J_max). These high rates were associated with high values of leaf [N]. Across all sites, the temperature response of A_max showed no clear optimum, and a gradual drop from 25°C to 35°C, without notable temperature limitation at leaf temperatures in excess of 35°C. Dark respiration rate (R_day) across all species and sites increased exponentially with increasing leaf temperature. Species sampled at selected sites revealed a negative relationship between leaf δ¹³C (stable carbon isotope ratio) and MAR, suggesting higher leaf‐level water‐use efficiency at drier sites when integrated over the life of the leaf. At wetter sites, specific leaf [N] was lower and photosynthetic nitrogen‐use efficiency increased, a pattern reflected at the ecosystem level by less ¹⁵N enrichment of leaves at these sites. Taken together, the results suggest a switch from water‐use to nitrogen‐use efficiency constraints with increasing moisture availability. These constraints impact leaf form and function significantly, and may emerge at the ecosystem level in aspects of water and N cycling.     

Effects of recent climate trends on the distribution of potential natural vegetation in Central Germany

Introducing climate quotients for the growing season (Q_gs) provides a way to quantify effects of climate trends with respect to Potential Natural Vegetation (PNV), especially beech forests (Fagus sylvatica L.) in Central Germany. What is crucial in this regard is the great influence of the dominant decrease in the amount of precipitation (up to 40% in the last 50 years) during the growing season versus the dormant season. However, precipitation during the dormant season (which is predominantly increasing: up to 40% in the last 50 years) is also important for replenishing the soil water supply. The Q_gs values of the Climatic Normal period of 1971–2000 are generally higher (up to 12% in lowland areas) compared with the Climatic Normal period of 1961–1990, the extent of the difference being in general inversely proportional to elevation above sea level. What this means for the area under investigation is that humidity conditions, which generally improve as the elevation above sea level increases, have a positive effect on the site potential. However, a comparison of the climatologically important period of 1991–2003 with the period of 1961–1990 (area-wide increase between 12% and 16%) could not identify this positive effect of elevation on precipitation for the area under investigation. With regard to the recent climate-based trends of PNV, we have shown that all natural spatial units in Central Germany are affected by progressing continentality (i.e., dryness) during the growing season and the resulting deterioration of the site potential. The area of potential beech forest at lower elevation has decreased in favour of oak forest as PNV, while less change is observed in the montane area.     

Habitat-specific responses in the flowering phenology and seed set of alpine plants to climate variation: implications for global-change impacts

The timing of the snowmelt is a crucial factor in determining the phenological schedule of alpine plants. A long-term monitoring of snowmelt regimes in a Japanese alpine area revealed that the onset of the snowmelt season has been accelerated during the last 17 years in early snowmelt sites but that such a trend has not been detected in late snowmelt sites. This indicates that the global warming effect on the snowmelt pattern may be site-specific. The flowering phenology of fellfield plants in an exposed wind-blown habitat was consistent between an unusually warm year (1998) and a normal year (2001). In contrast, the flowering occurrence of snowbed plants varied greatly between the years depending on the snowmelt time. There was a large number of flowering species in the fellfield community from mid- to late to late June and from mid- to late July. The flowering peak of an early-melt snowbed plant community was in the middle of the flowering season and that of a late-melt snowbed community was in the early flowering season. These habitat-specific phenological patterns were consistent between 1998 and 2001. The effects of the variation in flowering timing on seed-set success were evaluated for an entomophilous snowbed herb, Peucedanum multivittatum, along the snowmelt gradient during a 5-year period. When flowering occurred prior to early August, mean temperature during the flowering season positively influenced the seed set. When flowering occurred later than early August, however, the plants enjoyed high seed-set success irrespective of temperature conditions if frost damage was absent. These observations are probably explained based on the availability of pollinators, which depends not only on ambient temperature but also on seasonal progress. These results suggest that the effects of climate change on biological interaction may vary depending on the specific habitat in the alpine ecosystem in which diverse snowmelt patterns create complicated seasonality for plants within a very localized area.     

Isolation and molecular characterization of <Emphasis Type="Italic">Xylella fastidiosa</Emphasis> from coffee plants in Costa Rica

Coffee plants exhibiting a range of symptoms including mild to severe curling of leaf margins, chlorosis and deformation of leaves, stunting of plants, shortening of internodes, and dieback of branches have been reported since 1995 in several regions of Costa Rica’s Central Valley. The symptoms are referred to by coffee producers in Costa Rica as “crespera” disease and have been associated with the presence of the bacterium Xylella fastidiosa. Coffee plants determined to be infected by the bacterium by enzyme linked immunosorbent assay (ELISA), were used for both transmission electron microscopy (TEM) and for isolation of the bacterium in PW broth or agar. Petioles examined by TEM contained rod-shaped bacteria inside the xylem vessels. The bacteria measured 0.3 to 0.5 μm in width and 1.5 to 3.0 μm in length, and had rippled cell walls 10 to 40 nm in thickness, typical of X. fastidiosa. Small, circular, dome-shaped colonies were observed 7 to 26 days after plating of plant extracts on PW agar. The colonies were comprised of Gram-negative rods of variable length and a characteristic slight longitudinal bending. TEM of the isolated bacteria showed characteristic rippled cell walls, similar to those observed in plant tissue. ELISA and PCR with specific primer pairs 272-l-int/272-2-int and RST31/RST33 confirmed the identity of the isolated bacteria as X. fastidiosa. RFLP analysis of the amplification products revealed diversity within X. fastidiosa strains from Costa Rica and suggest closer genetic proximity to strains from the United States of America than to other coffee or citrus strains from Brazil.     

河北省草本植物物候特征及其对气候变暖的响应

以1981—2006年河北省8个国家农业气象观测站的草本植物物候观测资料和47个气象站的地面观测资料为基础,运用EOF和REOF等统计学方法,研究了河北省草本植物物候期的变化特征及其对气候变暖的响应。结果表明:河北省草本植物展叶始期总体呈提前趋势,其中东部沿海平原提前趋势最大,中南部平原次之,西北部山区最小;黄枯始期主要表现出推迟趋势,生长季长度以延长趋势为主;春季气温对展叶始期的影响显著,河北省春季气温上升1℃,草本植物展叶始期提前4.1d;各站点生长季倾向率与年均温倾向率呈正相关,即年均温升幅大的站点,生长季延长的幅度也较大;草本植物物候变化特征及其对气候变暖的响应与木本植物基本一致,研究结果对丰富河北省物候与气候变化关系研究具有一定意义。     

A theory for exaggerated secondary sexual traits in animal-pollinated plants

We analyze two mathematical models of adaptive investment in rewarding plant traits. In both models, the attractiveness of a particular trait value declines as the mean value in the population increases (asymmetric competition), giving relatively rewarding traits a competitive advantage. Including this competition for pollinator visits in a standard model of hermaphroditic sex allocation shifts additional allocation to pollinator rewards at the expense of allocation to pollen and seeds. In the second model, plants can invest additional resources in pollinator rewards but suffer reduced viability and rising costs due to excess pollen removal and within-plant selfing (geitonogamy). Despite these accumulating costs, increasing the magnitude of asymmetric competition exaggerates the ESS investment in rewards beyond the equilibrium in cases where attractiveness depends only on a plant’s absolute reward value. We suggest that the type of frequency dependent selection modeled here is fundamentally equivalent to sexual selection in animal populations (with some unique exceptions). Testing the main assumptions of our models may reveal whether seemingly “extravagant” floral traits are strictly analogous to the exaggerated secondary sexual traits of animals. An erratum to this article can be found at     

Comparison of the urban heat island intensity quantified by using air temperature and Landsat land surface temperature in Hangzhou,China

This study compared different measures of urban heat island (UHI) intensity, which were calculated using both air temperature (T_air) at a height of 1.5 m and Landsat land surface temperature (LST) in Hangzhou, China. Two UHI-driven indicators (range and magnitude) and two land-cover-driven indicators (urban-rural and urban-agriculture) were calculated to quantify the UHI intensity based on hourly T_air from five stations and fifteen Landsat 5 LST images. Pearson correlation testing and a moving average times series of the previous 30 days were used to investigate the relationship between UHI intensities calculated by different indicators and data. The results indicate that the land-cover-driven indicators explain UHI better than the UHI-driven indicators, while the calculated values of UHI intensity using Landsat LST and hourly T_air are not comparable. We also investigated the influence of weather conditions on UHI intensity. Generally, Landsat-LST-based UHI performs best on hot sunny days, while T_air-based UHI has a better chance during the nighttime following a dry sunny day. This study suggests that the value of UHI intensity can be influenced by the selected indicators, the data used, the acquisition time and the weather conditions. Thus, these factors should be considered when comparing UHI intensity between different cities or quantifying their influences (e.g., population size, land use and land cover change) on UHI intensity.     

Changes in phenological events in response to a global warming scenario reveal greater adaptability of winter annual compared with summer annual arabidopsis ecotypes

Background and AimsThe impact of global warming on life cycle timing is uncertain. We investigated changes in life cycle timing in a global warming scenario. We compared Arabidopsis thaliana ecotypes adapted to the warm/dry Cape Verdi Islands (Cvi), Macaronesia, and the cool/wet climate of the Burren (Bur), Ireland, Northern Europe. These are obligate winter and summer annuals, respectively.MethodsUsing a global warming scenario predicting a 4 °C temperature rise from 2011 to approx. 2080, we produced F₁ seeds at each end of a thermogradient tunnel. Each F₁ cohort (cool and warm) then produced F₂ seeds at both ends of the thermal gradient in winter and summer annual life cycles. F₂ seeds from the winter life cycle were buried at three positions along the gradient to determine the impact of temperature on seedling emergence in a simulated winter life cycle.Key ResultsIn a winter life cycle, increasing temperatures advanced flowering time by 10.1 d °C^–1 in the winter annual and 4.9 d °C^–1 in the summer annual. Plant size and seed yield responded positively to global warming in both ecotypes. In a winter life cycle, the impact of increasing temperature on seedling emergence timing was positive in the winter annual, but negative in the summer annual. Global warming reduced summer annual plant size and seed yield in a summer life cycle.ConclusionsSeedling emergence timing observed in the north European summer annual ecotype may exacerbate the negative impact of predicted increased spring and summer temperatures on their establishment and reproductive performance. In contrast, seedling establishment of the Macaronesian winter annual may benefit from higher soil temperatures that will delay emergence until autumn, but which also facilitates earlier spring flowering and consequent avoidance of high summer temperatures. Such plasticity gives winter annual arabidopsis ecotypes a distinct advantage over summer annuals in expected global warming scenarios. This highlights the importance of variation in the timing of seedling establishment in understanding plant species responses to anthropogenic climate change.     

1980—2018年中国东部主要木本植物展叶始期的温度相关时段变化

木本植物春季展叶始期的年际变化通常受其发生前一段时间的气温影响,这个时段被称作温度相关时段(temperature-relevant period, TRP)。TRP开始时间和长度的变化反映了气候增暖对植物发育过程的影响。利用中国物候网观测数据,分析了1980—2018年中国东部8个代表性站点162种木本植物展叶始期的TRP开始时间、结束时间和长度变化。结果显示:(1)亚热带站点比温带站点木本植物的平均TRP开始时间早约43 d,长度长约13 d。(2)TRP开始时间在温带地区北部(哈尔滨和牡丹江)变化不显著,在南部(北京、西安和民勤)以0.41—0.53 d/a的速度显著提前。在亚热带,除桂林外,其他站点展叶始期TRP长度延长和缩短的物种比例相近。这表明气候增暖对不同站点植物TRP的影响不仅取决于增暖的幅度,还和站点的背景气候条件相关。(3)乔木TRP平均开始时间和结束时间分别比灌木晚6.49 d和3.92 d,TRP长度略短于灌木。这与灌木采取机会主义的生存策略有关,而乔木在春季的展叶期较为保守以降低霜冻风险。(4)无论在亚热带还是温带地区,展叶越早的物种,TRP开始时间越早,长度...     

基于暴露度-恢复力-敏感度的城市适应气候变化能力评估与特征分析

城市是人口和社会经济活动最密集的地方,随着城市化进程和气候变化的发展,城市地区面临的气候风险和影响日益凸显。提升城市适应气候变化能力已成为城市应对气候变化挑战最重要的任务和途径。通过梳理和评价我国城市适应气候变化能力及其关键要素,以期为区域适应政策的制定和实施提供科学依据。基于IPCC适应能力评价框架,构建了基于暴露度-敏感度-恢复力的城市适应气候变化能力评估框架,进而筛选了19项指标,将指标划分为适应气候变化能力对应的5个等级,以熵权法赋权重;采用集对分析方法,评估我国286个地级市的适应气候变化能力水平,并分析了主要限制因素。结果显示,我国东部的适应能力整体高于西部地区,适应能力较低的区域主要集中在西北的甘肃陕西部分城市、华中的两湖和江西等城市以及西南的广西云南等城市;城市适应能力的各项限制要素主要表现为,适应能力高主要为暴露度-恢复力-敏感度的(低-高-低)的组合;适应能力低则分别包括暴露度-恢复力-敏感度(高-高-高)、(低-低-低)和(高-低-低)3种组合。提高城市适应气候变化能力,对西部西北的甘肃-陕西等城市,重点在于提升应对气候变化的恢复力,例如建立良好的灾后恢复与应急系统等;对于华中、西南等城市则以提高气候风险的防御能力为主。