民勤荒漠区典型草本植物马蔺的物候特征及其对气候变化的响应

植物物候反映了过去一段时间气候条件的累积对植物生长和发育的综合影响.通过收集1974-2007年民勤荒漠区典型草本植物马蔺的物候观测数据以及民勤治沙综合试验站同步观测的气象资料,分析了马蔺的物候特征及其对不同时间尺度气候变化的响应过程,结果表明:(1)马蔺的平均生长季长度约为201.7 d,并呈现出逐年增加的趋势,大致表现为每10a延长0.8d,但随着年份的变化并不显著(P＞0.1).(2)除开花期的开始时间出现明显的延后外(P＜0.1),马蔺其它物候期的开始和结束时间均表现为轻微的延后趋势,且随着年份的变化不显著(P＞0.1).马蔺各个物候期的持续时间不同年份差异较大,其中萌动期、开花期和果熟期的持续时间随着年份出现减少的趋势,而展叶期和黄枯期的持续时间随着年份则出现增加的趋势,但其变化均不显著(P＞0.1).(3)马蔺整个生长季的延长可能受气温和降水的综合作用,其物候期的开始时间对物候期开始之前3周到3个月之间的积温有着显著的响应(P＜0.01),而对于长时间尺度的积温则响应不显著(P＞0.1);其部分物候期的开始时间对于中短时间尺度的累积降雨有着较显著的响应(P＜0.1),但是对于长时间尺度的累积降雨则所有物候期都响应较弱(P＞0.1).(4)马蔺的物候期特征除了受区域气候变化影响之外,可能还与其自身的水分利用机制有关,未来的气候变化可能会进一步影响到该地区典型荒漠草本植物的物候特征.     

近30年北京自然历的主要物候期、物候季节变化及归因

根据中国物候观测网资料并结合气象观测数据, 重新编制了北京颐和园地区1981-2010年的自然历。通过与原自然历比较, 揭示了北京物候季节变化特征, 分析了1963年以来物候季节变化的可能原因。研究发现: 与原自然历相比, 1981-2010年北京的春、夏季开始时间分别提前了2天和5天, 秋、冬季开始时间分别推迟了1天和4天; 夏、秋季长度分别延长了6天和3天, 春、冬季长度则分别缩短了3天和6天; 各个物候期的平均日期、最早日期、最晚日期在春、夏季以提前为主, 在秋、冬季以推迟为主; 且春、秋、冬季节内部分物候期次序也出现了不同程度的变化。春、夏、冬季开始日期前的气温变化和秋季开始日期前的日照时数变化可能是北京颐和园地区物候季节变化的主要原因; 不同物种、不同物候期对气温变化的响应程度不同, 导致了物候季节内各种物候现象出现的先后顺序发生变化。     

我国东部温带植物群落的季相及其时空变化特征

 植物群落季相阶段的划分,对于诊断地方、区域和全球尺度上生态系统对气候变化的快速响应和进行遥感植被生长季节的地面检验,具有重要 的科学意义。该文利用物候累积频率拟合法对我国东部温带地区7个站点1982～1996年的植物群落季相阶段进行划分,并分析了植物群落季相的 空间差异和年际变化及其与气候因子的关系。结果表明：1）各站点多年平均变绿期和旺盛光合期初日随纬度的升高而推迟,凋落期和休眠期初 日随纬度的升高而提前;多年平均变绿期、旺盛光合期和凋落期长度随纬度的变化不甚明显,而休眠期则随纬度的升高明显延长;2）在研究期 间内,站点平均变绿期初日以0.6 d&;#8226;a^－1的平均速率显著提前,且长度以0.7 d&;#8226;a^－1的平均速率显著延长;旺盛光合期初日呈不显著推迟,长 度呈不显著缩短;凋落期初日呈微弱提前,长度呈微弱延长;休眠期初日呈微弱提前,但长度却以0.9 d&;#8226;a^－1的平均速率显著缩短;3）站点平 均变绿期初日与当月平均气温的负相关显著,平均气温每升高1 ℃,初日提前约4.3 d;站点平均旺盛光合期初日与初日前第二个月到初日当月 平均气温的负相关显著,平均气温每升高1 ℃,初日提前约4.4 d;站点平均凋落期和休眠期初日与气温的相关均不显著。     

Responses of leaf unfolding and flowering to climate change in 12 tropical evergreen broadleaf tree species in Jianfengling,Hainan Island

为了探讨我国热带地区植物物候与气候变化的关系, 利用海南岛尖峰岭热带树木园12种热带常绿阔叶乔木植物2003-2011年物候观测资料结合同期月平均气温和降水数据, 运用积分回归分析方法, 筛选出影响海南岛12种乔木(8种本地种、4种引入种)展叶始期与开花始期的气象因素以及不同气象因素月值变化(月平均气温和月降水量)综合作用对这些树种物候期的动态影响, 最终建立积分回归-物候预测模型, 对气候变化背景下我国热带地区植物物候变化趋势进行了预测。结果表明: 海南岛12种热带常绿阔叶乔木展叶始期与开花始期均对气候变化做出较明显的响应, 几乎所有的树种展叶始期与开花始期的发生都受到气温和降水的共同影响。多数树种展叶始期受展叶前冬季及春季气温影响显著, 且在临近展叶始期的月份, 气温的影响更显著。上一年秋季月降水量对各树种开花始期的影响比其他时段显著, 这验证了降水的滞后性假说。本地种展叶始期对气候变化的响应比其开花始期对气候变化的响应更敏感, 引入种则相反。各树种展叶和开花在受气温和降水综合影响最明显的月份(假设其余11个月份月平均气温和月降水量不变), 月平均气温升高0.1 ℃、月降水量增加10 mm可使展叶始期和开花始期提前或推迟1-3天。积分回归分析方法为解释海南岛热带常绿阔叶乔木物候与气温和降水的动态关系提供了有效的途径, 基于气温和降水与物候资料建立的积分回归-物候预测模型具有对气温和降水变化影响下物候响应的解释率和预测精度高(R²≥ 0.943)的优点, 对于预测气候变化影响下的植物物候变化趋势有一定的适用性。     

海南岛尖峰岭12种热带常绿阔叶乔木展叶期与开花期对气候变化的响应

为了探讨我国热带地区植物物候与气候变化的关系, 利用海南岛尖峰岭热带树木园12种热带常绿阔叶乔木植物2003-2011年物候观测资料结合同期月平均气温和降水数据, 运用积分回归分析方法, 筛选出影响海南岛12种乔木(8种本地种、4种引入种)展叶始期与开花始期的气象因素以及不同气象因素月值变化(月平均气温和月降水量)综合作用对这些树种物候期的动态影响, 最终建立积分回归-物候预测模型, 对气候变化背景下我国热带地区植物物候变化趋势进行了预测。结果表明: 海南岛12种热带常绿阔叶乔木展叶始期与开花始期均对气候变化做出较明显的响应, 几乎所有的树种展叶始期与开花始期的发生都受到气温和降水的共同影响。多数树种展叶始期受展叶前冬季及春季气温影响显著, 且在临近展叶始期的月份, 气温的影响更显著。上一年秋季月降水量对各树种开花始期的影响比其他时段显著, 这验证了降水的滞后性假说。本地种展叶始期对气候变化的响应比其开花始期对气候变化的响应更敏感, 引入种则相反。各树种展叶和开花在受气温和降水综合影响最明显的月份(假设其余11个月份月平均气温和月降水量不变), 月平均气温升高0.1 ℃、月降水量增加10 mm可使展叶始期和开花始期提前或推迟1-3天。积分回归分析方法为解释海南岛热带常绿阔叶乔木物候与气温和降水的动态关系提供了有效的途径, 基于气温和降水与物候资料建立的积分回归-物候预测模型具有对气温和降水变化影响下物候响应的解释率和预测精度高(R²≥ 0.943)的优点, 对于预测气候变化影响下的植物物候变化趋势有一定的适用性。     

The phenology of <Emphasis Type="Italic">Rubus fruticosus</Emphasis> in Ireland: herbarium specimens provide evidence for the response of phenophases to temperature,with implications for climate warming

To date, phenological research has provided evidence that climate warming is impacting both animals and plants, evidenced by the altered timing of phenophases. Much of the evidence supporting these findings has been provided by analysis of historic records and present-day fieldwork; herbaria have been identified recently as an alternative source of phenological data. Here, we used Rubus specimens to evaluate herbaria as potential sources of phenological data for use in climate change research and to develop the methodology for using herbaria specimens in phenological studies. Data relevant to phenology (collection date) were recorded from the information cards of over 600 herbarium specimens at Ireland’s National Herbarium in Dublin. Each specimen was assigned a score (0–5) corresponding to its phenophase. Temperature data for the study period (1852 – 2007) were obtained from the University of East Anglia’s Climate Research Unit (CRU); relationships between temperature and the dates of first flower, full flower, first fruit and full fruit were assessed using weighted linear regression. Of the five species of Rubus examined in this study, specimens of only one (R. fruticosus) were sufficiently abundant to yield statistically significant relationships with temperature. The results revealed a trend towards earlier dates of first flower, full flower and first fruit phenophases with increasing temperature. Through its multi-phenophase approach, this research serves to extend the most recent work—which validated the use of herbaria through use of a single phenophase—to confirm herbarium-based research as a robust methodology for use in future phenological studies.     

民勤荒漠植被对气候变化的响应

运用民勤荒漠区1974-2009年物候观测资料和2002-2010年植被样方观测资料以及同期气象资料,分析了荒漠植被对气候变化的响应.结果表明:1961-2010年,民勤荒漠区气温升高,空气湿度增大,年均气温升高速率大于全球水平和中国近百年平均水平;植物对气温变化的响应主要表现在春季物候提前、秋季物候推迟、生长季延长;植被对降水量变化的响应主要表现为植被盖度和纯盖度随降水量减少而降低,植株密度、植物多度随降水量变化而波动;植被盖度和纯盖度与年降水量的相关性较高,然后依次为6-7月和4-5月的降水量;植株密度和植物多度与9月降水量呈正相关;植物春季物候提前的次序是芽初膨大期＞芽开放期＞开花始期＞展叶始期和展叶盛期＞花蕾序出现＞开花盛期＞开花末期＞果实成熟期;秋季物候推迟的次序是叶全变色期＞落叶始期＞叶初变色期＞落叶末期.春季气温升高对民勤荒漠区植物物候的影响大于秋季气温升高对物候的影响.     

西安木本植物物候与气候要素的关系

根据1963–2007年中国物候观测网西安观测站的物候和气温、降水资料,分析了西安站34种木本植物春季展叶始期、展叶盛期、始花期和盛花期等4个关键物候期的变化趋势、对气候变化的阶段响应特点及其与气温、降水变化的关系。结果表明,1963年以来,西安地区气温呈显著上升趋势,特别是1994年前后,气温发生明显突变,上升趋势更加明显;西安春季物候变化主要呈现提前趋势。在45年中,观测到的34种植物的展叶始期平均提前1天,展叶盛期平均提前1.4天,始花期平均提前9天,盛花期平均提前12天;以突变点为界,34个物种1995–2007年的4种物候期比1963–1994年平均提前了4.34±0.77天;春季物候期的早晚主要受春季气温的影响,特别是春季物候期发生当月和上一月的平均气温对物候期的影响最为显著。叶物候和物候发生期前一月的降水量有较为明显的相关关系,花物候期和降水的关系不明显。     

Asymmetric effects of cooler and warmer winters on beech phenology last beyond spring

In temperate trees, the timings of plant growth onset and cessation affect biogeochemical cycles, water, and energy balance. Currently, phenological studies largely focus on specific phenophases and on their responses to warming. How differently spring phenology responds to the warming and cooling, and affects the subsequent phases, has not been yet investigated in trees. Here, we exposed saplings of Fagus sylvatica L. to warmer and cooler climate during the winter 2013–2014 by conducting a reciprocal transplant experiment between two elevations (1,340 vs. 371 m a.s.l., ca. 6°C difference) in the Swiss Jura mountains. To test the legacy effects of earlier or later budburst on the budset timing, saplings were moved back to their original elevation shortly after the occurrence of budburst in spring 2014. One degree decrease in air temperature in winter/spring resulted in a delay of 10.9 days in budburst dates, whereas one degree of warming advanced the date by 8.8 days. Interestingly, we also found an asymmetric effect of the warmer winter vs. cooler winter on the budset timing in late summer. Budset of saplings that experienced a cooler winter was delayed by 31 days compared to the control, whereas it was delayed by only 10 days in saplings that experienced a warmer winter. Budburst timing in 2015 was not significantly impacted by the artificial advance or delay of the budburst timing in 2014, indicating that the legacy effects of the different phenophases might be reset during each winter. Adapting phenological models to the whole annual phenological cycle, and considering the different response to cooling and warming, would improve predictions of tree phenology under future climate warming conditions.     

The response of <Emphasis Type="Italic">Corylus avellana</Emphasis> L. phenology to rising temperature in north-eastern Slovenia

Knowledge of plant–weather relationships can improve crop management, resulting in higher quality and more stable crop yields. The annual timing of spring phenophases in mid-latitudes is largely a response to temperature, and reflects the thermal conditions of previous months. The effect of air temperature on the variability of hazelnut (Corylus avellana L.) phenophases (leafing, flowering) was investigated. Meteorological and phenological data for five cultivars were analysed over the periods 1969–1979 (P1) and 1994–2007 (P2) in Maribor, Slovenia. Phenological data series were correlated strongly to the temperature of the preceding months (R ²: 0.64–0.98) and better correlated to daily maximum and mean temperatures than to daily minimum temperatures. About 75% of phenophases displayed a tendency towards earlier appearance and a shorter flowering duration during P2, which could be explained by the significant temperature changes (+0.3°C/decade) from December to April between 1969 and 2007. An increase in air temperature of 1°C caused an acceleration in leafing by 2.5–3.9 days, with flowering showing higher sensitivity since a 1°C increase promoted male flowering by 7.0–8.8 days and female flowering by 6.3–8.9 days. The average rate of phenological change per degree of warming (days earlier per +1°C) did not differ significantly between P1 and P2. An estimation of chilling accumulation under field conditions during 1993–2009, between 1 November and 28 February, showed that all four of these months contributed approximately similar amounts of accumulated chilling units. The growing degree days (GDD) to flowering were calculated by an estimated base temperature of 2°C and 1 January as a starting date, given the most accurate calculations. In general, thermal requirements were greater in P2 than in P1, although this difference was not significant. Longer-time series data extended to other agricultural and wild plants would be helpful in tracking possible future changes in phenological responses to local climate.     

我国东部北亚热带植物群落季相的时空变化

研究我国东部亚热带植物群落物候与气候变化的关系,对于揭示东部季风区生态系统对气候变化响应的整体特征和空间分异,具有重要的科学意义。作者利用物候累积频率拟合法对盐城、武汉、合肥、屯溪1982-1996年的植物群落季相阶段进行划分,并分析了季相阶段的时空变化及其与气温的统计关系。结果表明：（1）各站多年平均变绿期、旺盛光合期和休眠期初日均有随海拔升高而推迟的倾向,而多年平均季相阶段长度的空间分异特征不明显。休眠期初日随海拔升高而推迟的事实表明,树木秋季叶变色和落叶除受到气温的影响外,还可能与光照和霜等其它环境因素有关,从而使得海拔升高对秋季物候期提早的影响有所削弱,其生态机制有待进一步研究。（2）各站变绿期初日以提前为主,长度以延长为主;旺盛光合期和凋落期初日均以提前为主,长度延长与缩短参半;休眠期初日提前与推迟参半,长度以缩短为主。（3）各站变绿期和旺盛光合期初日与前期平均气温多呈显著负相关,而凋落期和休眠期初日与前期平均气温相关不显著。利用最佳时段气温-物候回归模型重建的1982-2006年季相阶段初日的时间序列显示,盐城、武汉和屯溪的变绿期初日呈显著提前的趋势,盐城、合肥和武汉旺盛光合期初日也呈显著提前的趋势。值得注意的是,在2002-2006年期间,各站变绿期和旺盛光合期初日均表现出明显推迟的倾向,与各地该时段前期平均气温呈下降的倾向一致。（4）从北亚热带各站到温带北部的哈尔滨,平均每向北1个纬度,多年平均变绿期和旺盛光合期初日分别显著推迟2.7-4.0 d和1.8-2.8 d,而长度则多呈不显著缩短的趋势;凋落期初日提前不显著,但长度显著缩短1.8-2.6 d;休眠期初日显著提前2.9-3.3 d,且长度显著延长5.8-7.0 d。总体上看,上述观测事实符合植物物候空间变化的一般规律,即在生长季节前半段,低纬地区的植物物候早于高纬地区;在生长季节后半段,高纬地区的植物物候早于低纬地区。     

Warming delays the phenological sequences of an autumn‐flowering invader

Phenology can play an important role in driving plant invasions; however, little is known about how climate warming, nitrogen (N) deposition, and invasion stages influence the phenological sequences of autumn‐flowering invaders in a subtropical climate. Accordingly, we conducted an experiment to address the effects of experimental warming, N‐addition, and community types on the first inflorescence buds, flowering, seed‐setting, and dieback of invasive Solidago canadensis. Warming delayed the onset of first inflorescence buds, flowering, seed‐setting, and dieback; N‐addition did not influence these four phenophases; community types influenced the onset of first seed‐setting but not the other phenological phases. Seed‐setting was more sensitive to experimental manipulations than the other phenophases. The onset of first inflorescence buds, flowering, and seed‐setting was marginally or significantly correlated with ramet height but not ramet numbers. Our results suggest that future climate warming might delay the phenological sequences of autumn‐flowering invaders and some phenophases can shift with invasion stages.     

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.     

Predicting apricot phenology using meteorological data

The main objective of this study was to develop feasible, easy to apply models for early prediction of full flowering (FF) and maturing (MA) in apricot (Prunus armeniaca L.). Phenological data for 20 apricot cultivars grown in the Belgrade region were modeled against averages of daily temperature records over ten seasons for FF and eight seasons for MA. A much stronger correlation was found between the phenological timing and temperature at the very beginning than at the end of phenophases. Also, the length of developmental periods were better correlated to daily maximum than to daily minimum and mean air temperatures. Using prediction models based on daily maximum temperatures averaged over 30-, 45- and 60-day periods, starting from 1 January for FF prediction and from the date of FF for MA prediction, the onset of examined phenophases in apricot cultivars could be predicted from a few weeks to up to 2 months ahead with acceptable accuracy. The mean absolute differences between the observations and cross-validated predictions obtained by 30-, 45- and 60-day models were 8.6, 6.9 and 5.7 days for FF and 6.1, 3.6 and 2.8 days for MA, respectively. The validity of the results was confirmed using an independent data set for the year 2009.     

Is water availability really the main environmental factor controlling the phenology of woody vegetation in the central Sahel?

Rainfall distribution and the soil moisture regime have been recognized to be the key drivers of the phenological rhythms in Sahelian woody plants, although different climate triggers have been assumed to be involved in determining the date of the onset of the phenophase. However, almost no comparisons have been made of the actual relative predictive power of these environmental factors. The aim of our study was to quantify the ability of several factors to predict phenophase occurrence in the dominant woody populations of northern Mali. Canopy leafing, flowering and fruiting were monitored from May 2005 to July 2007. Multiple logistic regressions were used to test the predictive power of cumulative rainfall, soil moisture, air temperature, air humidity and day length, with time lags of up to 2 months. Artificial variables derived from time lags observed in phenophases were included as predictors to account for possible auto-correlation and cross-correlation among phenophases. Surprisingly, a decrease in temperature associated with different time lags was most often found to be the strongest predictor of both leafing and reproductive phenophases. In Sahelian shrubs, morphological and physiological adaptations strongly contribute to the relative independence of their activity from water availability, leaf phenology being a way to adjust the plant water balance to current water availability and atmospheric water content. This study provides insight towards the development of a mechanistic understanding of phenological control in the Sahel, which is becoming increasingly important in the context of expected climate changes.     

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     

The influence of air temperature on the starting dates of the pollen season of alnus and populus

In this work we have studied the influence of air temperature on the starting dates of Alnus and Populus pollination in two different climatic regions in Europe: central Italy and The Netherlands. The start of the Alnus pollen season varied between 27th January and 16th February in the Italian stations while in The Netherlands it showed an average delay of about one month. For Populus the beginning of the pollen season was delayed on an average 15 days at Dutch places compared to central Italy. In the former it varied between 14th March and 21st April while in the latter between 28th February and 24th March. Significant correlations exist between the beginning of pollination for these taxa and temperature conditions in the preceding periods. The highest correlations found were with daily mean decade temperature for three decades before the average starting dates of the pollen season. These correlations were better for The Netherlands than for central Italy perhaps because the temperature in Holland is the more prominent meteorological factor (relative to precipitation) compared with central Italy, where precipitation has much influence in winter. This study indicated correlations between the pollination and temperature also during the dormant period in the preceding season.     

唐古特白刺叶功能性状沿气候梯度的变异特征

叶功能性状与植物的生长对策及资源利用效率密切相关,研究叶功能性状沿气候梯度的变异特征能为理解植物对气候变化的响应机制提供一种简便可行的测定指标。以我国西北荒漠地区广泛分布的唐古特白刺（Nitraria tangutorum）为研究对象,对其比叶面积（SLA）、单位质量和单位面积叶氮含量（N_mass、N_area）、单位质量和单位面积叶建成成本（CC_mass、CC_area）进行测定,分析这些叶功能性状及性状相关关系沿气候梯度的变异特征。结果表明,唐古特白刺叶功能性状（CC_area除外）在气候梯度下存在显著差异,其中,温度是决定唐古特白刺SLA变化的主要因子,SLA随着温度的增加而增加;降水和温度对唐古特白刺N_mass、N_area和CC_mass均有显著影响,N_mass和N_area随着降水和温度的增加而降低,而CC_mass呈增加趋势。沿气候梯度,唐古特白刺SLA-N_mass、CC_mass-N_mass和CC_area-N_area的线性正相关关系发生平移,导致在相同SLA、CC_mass和CC_area下,降水和温度较低的地区具有更高的N_mass和N_area。这一结果表明唐古特白刺能通过调节叶功能性状之间的关系来适应气候的变化,并形成性状间的最佳功能组合。     

Area under disease progress curve and apparent infection rate of Alternaria blight disease of Indian mustard (Brassica juncea) at different plant age

Plant age has a major influence on the incidence of Alternaria blight disease in Indian mustard crops. Disease progression was monitored twice a week on the two chosen Indian mustard cultivars viz., Varuna and Rohini throughout the season. Severity of blight caused by Alternaria brassicae and Alternaria brassicicola decreased with delay in sowing. Calculation for A-value (Area under disease progress curve – AUDPC) and r-value (apparent infection rate) in crops sown on different dates could identify the speed of progress in the disease on leaves and pods, as the crop does not posses resistance to the pathogen till date. Thus, the probable dates of sowing enabling slow disease progress or the weather conditions coinciding with the different crop phenological stages demarcated the advantageous dates of sowing from the disadvantageous ones. However, cultivar Varuna is more susceptible as compared to the other cultivar Rohini, as apparent infection rate both on leaves and pods was higher in former. Highest per cent disease severity (PDS) for season highly correlated with date of sowing, i.e. delayed date of sowing increased PDS.     

Climate controls on vegetation phenological patterns in northern mid- and high latitudes inferred from MODIS data

Recent studies using both field measurements and satellite-derived-vegetation indices have demonstrated that global warming is influencing vegetation growth and phenology. To accurately predict the future response of vegetation to climate variation, a thorough understanding of vegetation phenological cycles and their relationship to temperature and precipitation is required. In this paper, vegetation phenological transition dates identified using data from the moderate-resolution imaging spectroradiometer (MODIS) in 2001 are linked with MODIS land surface temperature (LST) data from the northern hemisphere between 35°N and 70°N. The results show well-defined patterns dependent on latitude, in which vegetation greenup gradually migrates northward starting in March, and dormancy spreads southward from late September. Among natural vegetation land-cover types, the growing-season length for forests is strongly correlated with variation in mean annual LST. For urban areas, the onset of greenup is 4–9 days earlier on average, and the onset of dormancy is about 2–16 days later, relative to adjacent natural vegetation. This difference (especially for urban vs. forests) is apparently related to urban heat island effects that result in both the average spring temperature and the mean annual temperature in urban areas being about 1–3°C higher relative to rural areas. The results also indicate that urban heat island effects on vegetation phenology are stronger in North America than in Europe and Asia. Finally, the onset of forest greenup at continental scales can be effectively described using a thermal time-chilling model, which can be used to infer the delay or advance of greenup onset in relation to climatic warming at global scale.