广东省寒害极值变化及其对冬种生产的影响

基于广东省86个气象观测站1961—2017年冬种生产季的逐日气温资料,采用数理统计方法分析冬种寒害极值的时空分布特征,并运用广义极值分布理论估算市县级的寒害重现期,旨在为当前冬种区域寒害风险评估、预警以及实时气象防灾减灾等提供技术支撑.结果表明: 冬种主产区积寒极值总体呈下降趋势,其中,湛江、梅州自20世纪80年代中期以来显著下降,茂名、韶关和广州自21世纪以来显著下降;极端最低气温总体呈先降后升的趋势,其中,韶关自20世纪80年代后期以来显著上升,但广州近5年开始出现下降趋势.冬种生产季极端积寒极值发生的站次数由多到少的顺序为70年代>21世纪>90年代>60年代>80年代,极端最低气温极值发生站次数由多到少的顺序为60年代>90年代>21世纪>70年代>80年代.2、5、10、20、50和100年一遇的寒害理论预测值呈明显的纬向分布特征,积寒表现为北多南少,极端最低气温表现为南高北低,与寒害实际发生过程中的积寒、极端最低气温分布趋势一致.典型个例表现为南部寒害重现期长、北部短.广东冬种主产区的湛江、茂名寒害重现期长,极端寒害发生的概率小但危害重,其冬种作物面积位居前列,生产上应引起重视.研究成果可为广东各级政府和有关部门指导冬种生产和制定应对气候变化对策提供科学参考.     

闽北地区森林群落物种多样性的测定

采用8个物种多样性指数对闽北地区的8个森林群落类型物种多样性进行测定,并选用4个种一多度关系模型(对数正态分布、Weibull分布、对数级数分布、生态位优先占领模型)分析其物种-多度关系,把多样性指数与对数正态分布、Weibull分布和生态位优先占领模型的有关参数进行线性回归,以分析多度模型参数描述物种多样性的可行性。结果表明：(1)多数物种多样性指数对群落的测度是一致的,(2)对数正态分布、Weibull分布和生态位优先占领模型对8个群落的物种多度拟合效果很好;(3)对数正态分布、Weibull分布和生态位优先占领模型有关模型参数与部分物种多样性指数的线性关系达显著或极显著水平。通过闽北地区8个类型森林群落物种多样性指数测定,使生物多样性较准确地数量化,同时还说明采用改进单纯形法进行非线性分布函数的拟合是简单有效的,可推广应用。     

华南地区香蕉、荔枝寒害的气候风险区划

基于华南地区（广东、广西、福建）224个气象站点1951—2006年气候资料和香蕉、荔枝历史灾情资料,采用日最低气温≤5.0 ℃、持续日数≥3 d寒害过程的积寒和表征香蕉、荔枝年度寒害的气候致灾风险信息,构建了基于气候变化背景下的寒害综合气候风险指标,编制了香蕉、荔枝寒害等级风险概率地理分布图和气候风险区划图,并评述了香蕉、荔枝寒害气候风险的区域分异规律.结果表明：随着气候变暖,研究区香蕉、荔枝抗寒性降低,寒害致灾风险增加;香蕉、荔枝寒害各等级气候风险概率均呈纬向分布.基于综合气候风险指数的大小将香蕉、荔枝寒害划分为高、中、低3个气候风险区,这为农业结构布局的调整提供了重要依据.     

塔里木荒漠河岸林不同生境群落物种多度分布格局

为解释塔里木荒漠河岸林群落构建和物种多度分布格局形成的机理, 本文以塔里木荒漠河岸林2个不同生境(沙地、河漫滩) 4 ha固定监测样地为研究对象, 基于两样地物种调查数据, 采用统计模型(对数级数模型、对数正态模型、泊松对数正态分布模型、Weibull分布模型)、生态位模型(生态位优先占领模型、断棍模型)和中性理论模型(复合群落零和多项式模型、Volkov模型)拟合荒漠河岸林群落物种多度分布, 并用K-S检验与赤池信息准则(AIC)筛选最优拟合模型。结果表明: (1)随生境恶化(土壤水分降低), 植物物种多度分布曲线变化减小, 群落物种多样性、多度和群落盖度降低, 常见种数减少。(2)选用的3类模型均可拟合荒漠河岸林不同生境群落物种多度分布格局, 统计模型和中性理论模型拟合效果均优于生态位模型。复合群落零和多项式模型对远离河岸的干旱沙地生境拟合效果最好; 对数正态模型和泊松对数正态模型对洪水漫溢的河漫滩生境拟合效果最优; 中性理论模型与统计模型无显著差异。初步推断中性过程在荒漠河岸林群落构建中发挥着主导作用, 但模型拟合结果只能作为推断群落构建过程的必要非充分条件, 不能排除生态位过程的潜在作用。     

华南地区龙眼寒害灾损风险评估

基于华南地区64个基本气象站1961—2012年逐日气象资料,采用公认的龙眼寒害灾害指标,结合农业气象灾害风险研究的方法与模拟技术,并考虑龙眼寒害灾损减产风险在不同生育期（花芽生理期、花芽形态分化期、休眠期）之间的差别,对1961—2012年华南地区龙眼不同发育时段的寒害灾损最大风险进行定量评估与分析.结果表明： 在花芽生理期,各地区龙眼受灾最严重的是轻度寒害,其次为重度寒害,最后为中度寒害;不同寒害致灾等级对各地龙眼造成的危害程度不同,在轻度寒害威胁下,龙眼受灾轻重次序为福建、广东和海南、广西,中度寒害威胁下,龙眼受灾轻重次序为海南、广东和广西、福建,重度寒害威胁下,龙眼受灾轻重次序为海南、广东和广西、福建.在花芽形态分化期,各地区龙眼受灾最严重的是轻度寒害,其次为重度寒害,最后为中度寒害;该时段内不同寒害致灾等级对各地龙眼造成的危害程度相似,龙眼受灾轻重次序均为海南、广东和广西、福建.在休眠期,各地区龙眼寒害受灾最严重的是轻度寒害,其次为重度寒害,最后为中度寒害;该时段内不同寒害致灾等级对各地龙眼造成的危害程度不完全相同,轻度和重度寒害威胁下,各地龙眼受灾轻重次序为海南、广东和广西、福建,中度寒害威胁下,海南和广西龙眼受灾最轻,其次为广东,福建受灾最严重.同一寒害致灾等级下,不同发育时段龙眼寒害灾损减产最大风险指数差异显著：轻度寒害威胁下,各地区龙眼在花芽生理期受到危害最重,其次为花芽形态分化期,休眠期危害最轻;中度和重度寒害威胁下,各地区龙眼在花芽生理期受到危害最重,其次为休眠期,花芽形态分化期危害最轻.     

气候变化背景下广东早稻播期的适应性调整

利用广东省86个气象站1961-2009年资料以及2009年早稻地理分期播种试验数据,分析了气候变暖背景下广东早稻生长季的气候变化特点,并探索适应气候变化的广东早稻播种期调整的可行性。结果表明,自1997年以来,广东早稻生长季气候变化较为显著:(1)广东早稻生长季气候变暖明显,热量资源增加显著;光照资源略有减少;降水量略多于常年,但年际变幅加大;(2)春季低温阴雨天气结束日期提前,总日数减少;早稻幼穗分化期低温冷害结束日期提早;"龙舟水"期间降水集中期推后。在考虑气候资源与灾害变化特征的基础上,提出了广东早稻播种期调整方案为南部地区提前7-10d,中部地区提前5-7d,北部地区提前3-4d。广东早稻播期调整的研究,不仅是早稻应对气候变化的需要,而且对全年农业生产布局调整也具有重要意义。     

气候变化对广东省双季稻种植气候区划的影响

基于广东省86个气象站1961—2016年的气温资料和1∶25万数字高程模型(DEM)数据,采用线性趋势分析、累积距平和反距离权重插值等方法,分析影响双季稻种植的关键气候因子(双季稻安全生育期日数、≥10 ℃积温)时空变化特征,结合气候因子在1961—1990年、1971—2000年、1981—2010年、气候因子突变前(1961—1997年)、突变后(1998—2016年)等5个时间段的变化,研究了气候变化对广东双季稻熟性搭配分布区域及其面积的影响.结果表明: 广东省双季稻安全生育期日数、≥10 ℃积温的空间分布表现为南高北低、平原高山区低.近56年,广东双季稻安全生育期日数以1.7 d ·10 a^-1的速率显著增加,≥10 ℃积温以43 ℃·d·10 a^-1的速率显著上升,各气候因子均在1997年发生了突变.广东双季稻熟性搭配可分为早熟+早熟、早熟+晚熟和晚熟+晚熟3个气候区.早熟+早熟区主要分布在北部中亚热带地区,早熟+晚熟区主要分布在中部南亚热带地区,晚熟+晚熟区主要分布在南部北热带地区.受气候变化的影响,广东晚熟+晚熟区面积明显扩大,早熟+晚熟区面积明显减小,而早熟+早熟区的面积变化不明显.与1961—1990年相比,1971—2000年和1981—2010年广东省晚熟+晚熟区面积分别增加了1.22×10⁶和2.56×10⁶ hm²,早熟+晚熟区的面积分别减小了1.13×10⁶和2.56×10⁶ hm².与突变前(1961—1997年)相比,突变后(1998—2016年)晚熟+晚熟区的面积增大一倍多,早熟+晚熟区面积缩小近一倍.     

气候变化对广东省荔枝种植气候区划的影响

基于广东省86个气象站1961—2021年的气温、降水量资料和1:250000数字高程模型(DEM)数据,采用线性趋势分析、累积距平和反距离权重插值等方法,分析了影响荔枝种植的关键气候因子年平均气温(T_y)、年极端最低气温(T_min)、上年12—2月日平均气温≤10℃低温寒积量(∑(10-t)_12-2)、3月平均降水量(R₃)的时空变化特征,以及1961—1990年、1971—2000年、1981—2010年、1991—2020年、年平均气温突变前(1961—1997年)、突变后(1998—2021年)等6个气候时段的变化特征,研究了气候变化对广东省荔枝种植气候区划的影响。结果表明：广东省T_y、T_min的空间分布表现为南高北低、平原高山区低的格局,∑(10-t)_12-2总体呈北多南少、山地多平原少的空间分布,R₃大体表现为从西南向东北递增的特征;1961—2021年,广东省T_y、T_...     

山西霍山油松林的物种多度分布格局

物种多度格局分析对理解群落结构具有重要的意义。该文首次选用描述种-多度关系的生态位模型(生态位优先模型NPM、分割线段模型BSM、生态位重叠模型ONM)、生物统计模型(对数级数分布模型LSD、对数正态分布模型LN)以及中性理论模型NT, 对山西霍山油松(Pinus tabulaeformis)林的物种数量关系进行了拟合研究, 并采用卡方(χ²)检验、Likelihood-ratios (L-R)检验、Kolmogorov-Smirnov (K-S)检验和赤池信息量准则(AIC)选择最适合模型, 结果表明: (1)描述乔木层物种多度格局的最优生态位模型为NPM (3种检验方法均接受该模型, p > 0.05, 且该模型具有最小的 AIC值), ONM的拟合效果次之, 不服从BSM; 三种生态位模型均可较好地拟合灌木层物种多度格局; ONM是草本层最佳生态位模型, BSM、NPM拟合效果较差; LSD可以描述油松林各层物种多度结构; LN可以很好地解释灌草层物种数量关系; NT不能解释油松林任何层次的物种多度结构。(2)霍山油松林乔木层和灌木层的物种丰富度和物种多样性均明显小于草本层; 该群落物种富集种少而稀疏种多, 且群落的均匀度相对较小。(3)从该区油松林种-多度分布来看, 同一个模型可以拟合不同的物种多度数据, 相同的数据可以由不同的模型来解释。因此, 研究森林群落物种分布时, 应采用多个模型进行拟合, 同时选用多种方法筛选最优模型。     

浙江龙王山森林群落物种多度分布特征及其与海拔的关系

虽然大量研究已利用模型拟合的方法对植物群落的物种多度分布(SAD)进行了不同数学模型拟合,但对SAD形状(曲线的偏斜度)如何在环境梯度上连续变化的研究仍然不足; 尤其是森林群落,同一地区不同植被类型群落SAD的模型拟合和形状变化是否一致,仍无明确定论。该研究针对安吉小鲵国家级自然保护区中分布的主要森林植被类型,采用样方调查法,记录了28个20 m × 20 m样方中的物种组成及其个体多度。通过对数级数和对数正态模型对样方中的SAD曲线进行拟合,选择最优模型,并通过Gambin模型中的α值和Weibull模型中的η值反映SAD的形状,以及Weibull模型中λ值反映SAD的变化尺度(物种间个体多度的差异程度),分析海拔高度与SAD的形状和变化尺度之间的关系。结果表明:(1)该地区的森林群落物种多度分布主要符合对数级数模型。(2)当包含所有样方时,α值和η值与海拔高度无显著相关性,λ值与海拔呈显著正相关。(3)针对不同的植被类型,常绿与落叶阔叶混交林中α值和η值与海拔高度呈负相关,但在落叶阔叶林中λ值与海拔高度之间具有正相关关系,而α值和η值与海拔高度之间均无显著相关性。该研究结果表明,不同植被类型SAD的形状变化与海拔之间的关系存在差异,说明海拔对不同植被类型中各物种多度分布具有不同影响。因此,在关于植物群落的物种多度分布及其与影响因子关系的研究中,需要考虑区分不同的植被类型。     

Normal and Extreme Wind Conditions for Power at Coastal Locations in China

In this paper, the normal and extreme wind conditions for power at 12 coastal locations along China’s coastline were investigated. For this purpose, the daily meteorological data measured at the standard 10-m height above ground for periods of 40–62 years are statistically analyzed. The East Asian Monsoon that affects almost China’s entire coastal region is considered as the leading factor determining wind energy resources. For most stations, the mean wind speed is higher in winter and lower in summer. Meanwhile, the wind direction analysis indicates that the prevalent winds in summer are southerly, while those in winter are northerly. The air densities at different coastal locations differ significantly, resulting in the difference in wind power density. The Weibull and lognormal distributions are applied to fit the yearly wind speeds. The lognormal distribution performs better than the Weibull distribution at 8 coastal stations according to two judgement criteria, the Kolmogorov–Smirnov test and absolute error (AE). Regarding the annual maximum extreme wind speed, the generalized extreme value (GEV) distribution performs better than the commonly-used Gumbel distribution. At these southeastern coastal locations, strong winds usually occur in typhoon season. These 4 coastal provinces, that is, Guangdong, Fujian, Hainan, and Zhejiang, which have abundant wind resources, are also prone to typhoon disasters.     

Downscaling climate parameters in Fars province,using models of the fifth report and RCP scenarios

Climate change is responsible for many extreme weather events on the Earth, including sea level rising, drastic shifts in temperature and precipitation regimes, and changes in flood and drought frequency. In the present study, based on IPCC's latest report, outputs of three GCMs, the EC-EARTH, the HadGEM2-ES and the MIROC5 were downscaled by the LARS-WG model and under RCP4.5 and RCP8.5 scenarios. Also, variations in precipitation, maximum and minimum temperatures for the time series 2021–2040, 2041–2060 and 2061–2080 have been projected and the precipitation extreme values in Gumbel distribution were evaluated. For this purpose, the climate records obtained from Shiraz, Lar and Abadeh synoptic stations in Fars province were used to establish the baseline period (1985–2010). The results of all the stations show that Changes in maximum and minimum temperatures under RCP4.5 and RCP8.5 scenarios have increased. The increase in minimum temperature for the baseline period compared to the upcoming period 2021–2040 under the selected scenarios were 1.43 and 1.65C, respectively. The increase in precipitation for the baseline period compared to the upcoming period (2021–2040) under the two scenarios were up to 2.93 and 1.95, respectively. Furthermore, longer return periods are accompanied by higher amounts of probable maximum precipitation under RCP4.5 and RCP8.5, where extreme precipitation is showing higher level of rise under the latter scenario.     

An Extreme Value Analysis of Pollutant Concentrations in Surface Soils Due to Atmospheric Deposition

Risk assessments often rely on deterministic models using long-term averages or “steady-state” values of input variables. Such models do not provide the information needed to estimate acute exposures. This study uses extreme value theory to examine the frequency and magnitude of daily pollutant concentrations in surface soils predicted at six U.S. locations. Concentrations are predicted using a deposition-leaching model and 50 years of historical precipitation data. A stochastic model also is used to generate 1000 years of precipitation data as modeling inputs for each location. The annual maximum concentrations at each site are fitted to a Gumbel type I distribution to estimate occurrence probability. For soluble pollutants, the predicted concentration varied substantially with precipitation, and the maximum daily concentrations exceeded annual averages by 4 to 8 times. Observed and synthetic precipitation data produced similar results at most study locations, though the synthetic data provided a slightly better fit to the Gumbel type I distribution. The precipitation model allows the generation of representative precipitation data that extend limited historical records. The extreme value analysis facilitates the evaluation of maximum pollutant concentrations, return periods, and other statistics that are important in evaluating acute exposures.     

A global analysis of the comparability of winter chill models for fruit and nut trees

Many fruit and nut trees must fulfill a chilling requirement to break their winter dormancy and resume normal growth in spring. Several models exist for quantifying winter chill, and growers and researchers often tacitly assume that the choice of model is not important and estimates of species chilling requirements are valid across growing regions. To test this assumption, Safe Winter Chill (the amount of winter chill that is exceeded in 90% of years) was calculated for 5,078 weather stations around the world, using the Dynamic Model [in Chill Portions (CP)], the Chilling Hours (CH) Model and the Utah Model [Utah Chill Units (UCU)]. Distributions of the ratios between different winter chill metrics were mapped on a global scale. These ratios should be constant if the models were strictly proportional. Ratios between winter chill metrics varied substantially, with the CH/CP ratio ranging between 0 and 34, the UCU/CP ratio between −155 and +20 and the UCU/CH ratio between −10 and +5. The models are thus not proportional, and chilling requirements determined in a given location may not be valid elsewhere. The Utah Model produced negative winter chill totals in many Subtropical regions, where it does not seem to be useful. Mean annual temperature and daily temperature range influenced all winter chill ratios, but explained only between 12 and 27% of the variation. Data on chilling requirements should always be amended with information on the location and experimental conditions of the study in which they were determined, ideally including site-specific conversion factors between winter chill models. This would greatly facilitate the transfer of such information across growing regions, and help prepare growers for the impact of climate change.     

A general extreme value theory model for the adaptation of DNA sequences under strong selection and weak mutation

Recent theoretical studies of the adaptation of DNA sequences assume that the distribution of fitness effects among new beneficial mutations is exponential. This has been justified by using extreme value theory and, in particular, by assuming that the distribution of fitnesses belongs to the Gumbel domain of attraction. However, extreme value theory shows that two other domains of attraction are also possible: the Fréchet and Weibull domains. Distributions in the Fréchet domain have right tails that are heavier than exponential, while distributions in the Weibull domain have right tails that are truncated. To explore the consequences of relaxing the Gumbel assumption, we generalize previous adaptation theory to allow all three domains. We find that many of the previously derived Gumbel-based predictions about the first step of adaptation are fairly robust for some moderate forms of right tails in the Weibull and Fréchet domains, but significant departures are possible, especially for predictions concerning multiple steps in adaptation.     

Optimal Low Temperature and Chilling Period for Both Summer and Winter Diapause Development in Pieris melete: Based on a Similar Mechanism

The cabbage butterfly, Pieris melete hibernates and aestivates as a diapausing pupa. We present evidence that the optimum of low temperature and optimal chilling periods for both summer and winter diapause development are based on a similar mechanism. Summer or winter diapausing pupae were exposed to different low temperatures of 1, 5, 10 or 15°C for different chilling periods (ranging from 30 to 120 d) or chilling treatments started at different stages of diapause, and were then transferred to 20°C, LD12.5∶11.5 to terminate diapause. Chilling temperature and duration had a significant effect on the development of aestivating and hibernating pupae. The durations of diapause for both aestivating and hibernating pupae were significantly shorter when they were exposed to low temperatures of 1, 5 or 10°C for 50 or 60 days, suggesting that the optimum chilling temperatures for diapause development were between 1 and 10°C and the required optimal chilling period was about 50–60 days. Eighty days of chilling was efficient for the completion of both summer and winter diapause. When chilling periods were ≥90 days, the durations of summer and winter diapause were significantly lengthened; however, the adult emergence was more synchronous. The adaptive significance of a similar mechanism on summer and winter diapause development is discussed.     

Interaction between photoperiod, temperature, and chilling in dormant larvae of the tree-hole mosquito, Toxorhynchites rutilus Coq.

1. Unchilled, diapausing larvae of Toxorhynchites rutilus rely on photoperiod for the maintenance of diapause. The photoperiodic clock is temperature-compensated between 16.5 degrees and 25 degrees C, maintaining both a similar set-joint and inherent accuracy over this range. The rates of development among larvae terminating diapause are dependent upon both temperature and photoperiod. 2. Chilling of dormant Toxorhynchites rutilus can promote response to progressively shorter daylengths, thus decreasing the critical photoperiod. Chilling can also accelerate response to long days, thereby decreasing the depth of diapause and, after prolonged exposure, can eventually terminate diapause directly, leaving subsequent morphogenesis independent of photoperiod. 3. The optimal temperature for these effects of chilling is above 4 degrees C, below 16.5 degrees C, and may lie around 7 degrees C. 4. Temperatures between 5 degrees and 15 degrees C are vernal and autumnal rather than hibernal. The interaction between chilling and photoperiod may then represent an adaptive compromise between selection due to long-term climatic trends and the vagaries of spring weather.     

Stochastic simulation of daily air temperature and precipitation from monthly normals in North America north of Mexico

A simple, stochastic daily temperature and precipitation generator (TEMPGEN) was developed to generate inputs for the study of the effects of climate change on models driven by daily weather information when climate data are available as monthly summaries. The model uses as input only 11 sets of monthly normal statistics from individual weather stations. It needs no calibration, and was parameterized and validated for use in Canada and the continental United States. Monthly normals needed are: mean and standard deviation of daily minimum and maximum temperature, first and second order autoregressive terms for daily deviations of minimum and maximum temperatures from their daily means, correlation of deviations of daily minimum and maximum temperatures, total precipitation, and the interannual variance of total precipitation. The statistical properties and distributions of daily temperature and precipitation data produced by this generator compared quite favorably with observations from 708 stations throughout North America (north of Mexico). The algorithm generates realistic seasonal patterns, variability and extremes of temperature, precipitation, frost-free periods and hot spells. However, it predicts less accurately the daily probability of precipitation, extreme precipitation events and the duration of extreme droughts.