Maize potential yields and yield gaps in the changing climate of northeast China

Northeast China (NEC) is not only one of the major agricultural production areas in China, but it is also the most susceptible to climate variability. This led us to investigate the impact of climate change on maize potential yield and yield gaps in this region, where maize accounts for about 30% of the nation's production. The APSIM‐Maize model was calibrated and validated for maize phenology and yields. The validated model was then used to estimate potential yields, rain‐fed potential yields, and yield gaps for assessing the climate impacts on maize productivity in NEC. During maize growing seasons from 1981 to 2010, the analysis indicates a warming trend all across NEC, whereas the trends in solar radiation and total precipitation tended to decrease. When the same hybrid was specified in APSIM for all years, a simulated increase of maximum temperature resulted in a negative impact on both potential yield and rain‐fed potential yield. A simulated increase in minimum temperature produced no significant changes in potential or rain‐fed potential yield. However, the increase of minimum temperature was shown to result in a positive impact on the on‐farm yield, consistent with our finding that farmers adopted longer season hybrids for which the increase in minimum temperature provided better conditions for germination, emergence, and grain filling during night time. The gap between potential and rain‐fed potential yields was shown to be larger at locations with lower seasonal precipitation (<500 mm). Our results indicate that regions with the largest yield gaps between rain‐fed potential and on‐farm yields were located in the southeast of NEC. Within NEC, on‐farm maize yields were, on average, only 51% of the potential yields, indicating a large exploitable yield gap, which provides an opportunity to significantly increase production by effective irrigation, fertilization, herbicide, and planting density in NEC.     

Effect of Four Sowing Date Environments on Growth, Development and Yield Potentials of 15 Pearl Millet Cultivars (Pennisetum americanum L Leeke) During Autumn-Winter Seasons in Marin, N.L., Mexico

A study has been undertaken on the growth, development, andyield potentials of 15 pearl millet cultivars showing a largegenetic variability in growth parameters in different sowingenvironments Sowing date had a significant effect on growthstages (GS1, GS2, GS3), thermal units accumulated in respectivegrowth stages, days to flowering, and yield components of thepearl millet cultivars Significant genotype x sowing date interactionswere also observed for the majority of the variables mentioned. A decline in both temperature and length of photopenod oversuccessive sowing dates from July to September had a drasticeffect on phenology and yield potentials of the pearl milletcultivars. Higher grain yield in the July sowing experiment, compared tothose for other sowing dates, could be related to a longer photopenod(> 13 h), higher temperatures, and a significant differencebetween day and night temperatures. Key words: Environment, growth, yield potentials, thermal units, pearl millet     

Maize growing duration was prolonged across China in the past three decades under the combined effects of temperature,agronomic management,and cultivar shift

Maize phenology observations at 112 national agro‐meteorological experiment stations across China spanning the years 1981–2009 were used to investigate the spatiotemporal changes of maize phenology, as well as the relations to temperature change and cultivar shift. The greater scope of the dataset allows us to estimate the effects of temperature change and cultivar shift on maize phenology more precisely. We found that maize sowing date advanced significantly at 26.0% of stations mainly for spring maize in northwestern, southwestern and northeastern China, although delayed significantly at 8.0% of stations mainly in northeastern China and the North China Plain (NCP). Maize maturity date delayed significantly at 36.6% of stations mainly in the northeastern China and the NCP. As a result, duration of maize whole growing period (GPw) was prolonged significantly at 41.1% of stations, although mean temperature (Tmean) during GPw increased at 72.3% of stations, significantly at 19.6% of stations, and Tmean was negatively correlated with the duration of GPw at 92.9% of stations and significantly at 42.9% of stations. Once disentangling the effects of temperature change and cultivar shift with an approach based on accumulated thermal development unit, we found that increase in temperature advanced heading date and maturity date and reduced the duration of GPw at 81.3%, 82.1% and 83.9% of stations on average by 3.2, 6.0 and 3.5 days/decade, respectively. By contrast, cultivar shift delayed heading date and maturity date and prolonged the duration of GPw at 75.0%, 94.6% and 92.9% of stations on average by 1.5, 6.5 and 6.5 days/decade, respectively. Our results suggest that maize production is adapting to ongoing climate change by shift of sowing date and adoption of cultivars with longer growing period. The spatiotemporal changes of maize phenology presented here can further guide the development of adaptation options for maize production in near future.     

气候变化背景下东北三省春玉米产量潜力的时空特征

以东北三省春玉米种植区为研究区域,利用当地地面气象观测资料、农业气象观测站春玉米多年试验资料和县级春玉米实际产量资料,使用验证后的农业生产系统模拟模型(APSIM-Maize),分析研究区域春玉米1961—2015年不同水平产量潜力及实际产量的时空分布特征,并解析气候波动对产量潜力的影响.结果表明: 1961—2015年,研究区域春玉米潜在产量平均值为12.2 t·hm^-2,且呈现明显的经向和纬向空间分布,即由南向北递减、西部高于东部.研究区域春玉米可获得产量平均值为11.3 t·hm^-2,与潜在产量呈相似的分布特征.在目前农户的栽培水平下,春玉米农户潜在产量和农户实际产量全区多年平均值分别为6.5和4.5 t·hm^-2.在品种和栽培管理措施不变的条件下,研究区潜在产量、可获得产量和农户潜在产量总体呈显著减少趋势,减幅分别为0.34、0.25和0.10 t·hm^-2·(10 a)^-1.农户实际产量呈增加趋势,增幅为1.27 t·hm^-2·(10 a)^-1.气候波动使东北三省春玉米潜在产量、可获得产量和农户潜在产量年际间波动范围分别为10.0～14.4、9.8～13.3和4.4～8.5 t·hm^-2.     

Observed changes in winter wheat phenology in the North China Plain for 1981–2009

Climate change in the last three decades could have major impacts on crop phenological development and subsequently on crop productivity. In this study, trends in winter wheat phenology are investigated in 36 agro-meteorological stations in the North China Plain (NCP) for the period 1981–2009. The study shows that the dates of sowing (BBCH 00), emergence (BBCH 10) and dormancy (start of dormancy) are delayed on the average by 1.5, 1.7 and 1.5 days/decade, respectively. On the contrary, the dates of greenup (end of dormancy), anthesis (BBCH 61) and maturity (BBCH 89) occur early on the average by 1.1, 2.7 and 1.4 days/decade, respectively. In most of the investigated stations, GP2 (dormancy to greenup), GP3 (greenup to anthesis) and GP0 (entire period from emergence to maturity) of winter wheat shortened during the period 1981–2009. Due, however, to early anthesis, grain-filling stage occurs at lower temperatures than before. This, along with shifts in cultivars, slightly prolongs GP4 (anthesis to maturity). Comparison of field-observed CERES (Crop Environment Resource Synthesis)-wheat model-simulated dates of anthesis and maturity suggests that climate warming is the main driver of the changes in winter wheat phenology in the NCP. The findings of this study further suggest that climate change impact studies should be strengthened to adequately account for the complex responses and adaptations of field crops to this global phenomenon.     

抽雄期前后大风倒伏对夏玉米生长及产量的影响

利用2013年8月1日河南省南阳地区夏玉米大风倒伏灾害的调查数据,分析抽雄期前后不同类型倒伏对夏玉米生长及产量形成的影响,研究不同品种的抗倒性差异和适播期.调查对象为5个播期的浚单20和3个播期的郑单958,倒伏类型划分为根斜、根倒、茎折和折断4种.研究表明： 各品种及播期均于抽雄前～抽雄后15 d倒伏率较高.浚单20各播期的总倒伏率为86.0%～98.5%,郑单958各播期的总倒伏率为60.0%～76.4%,且播种越早的播期总倒伏率越低.浚单20倒伏发生时,播期Ⅱ～Ⅴ的夏玉米生育时期接近抽雄,以根倒类型为主,倒伏率为53.0%～84.3%,已过抽雄期的播期Ⅰ夏玉米以茎折倒伏为主,倒伏率为37.5%.倒伏发生后干物质积累显著降低,各倒伏类型对干物质积累的影响总体表现为茎折>根倒>根斜,播种越晚的总干物质积累越少.倒伏对干物质分配比例影响表现为叶片和茎杆干物质比例增大,果穗干物质比例减少.根倒和茎折两种倒伏类型使穗长显著变短,穗粗显著变细,穗粒数显著减少,抽雄后发生倒伏也会使百粒重显著降低;而根斜倒伏类型对各性状的影响均不显著.倒伏后产量损失严重,不同倒伏类型中茎折类型减产最多,浚单20和郑单958平均减产率分别为74.2%和68.7%,尤其是茎折发生在抽雄之前难以形成产量;其次是根倒,平均减产率分别为46.3%和46.5%;根斜产量损失最小,平均分别为8.4%和13.2%.大风倒伏灾害后,浚单20产量平均为4959.9 kg·hm^-2,产量随播期的推迟而减少;郑单958平均为6026.1 kg·hm^-2,随播期变化不明显.总体上,郑单958品种抗倒性好于浚单20.     

基于统计和过程模型的河南省夏玉米最适播种期时空分布特征

播种期是影响夏玉米产量的重要因素,研究夏玉米最适播种期的时空分布特征对指导夏玉米生产有重要意义.本文应用统计模型和APSIM Maize过程模型分析了河南省夏玉米最适播种期的时空分布特征.结果表明: 河南省夏玉米的最适播种期为5月30日至6月13日,南早北晚,北部地区以6月4日至13日播种为宜,西部山区应在5月30日左右播种,南部地区应尽量保证在6月8日前播种.晚熟品种‘农大108’应比中熟品种‘丹玉13’至少提前播种2 d,气候变暖背景下若收获期可推迟1周,则最适播种期将至少推迟3 d.在生长季降水偏少年型下,夏玉米应较正常年型晚播7 d左右;而在生长季降水偏多年型下,夏玉米应早播7 d左右.1971—2010年,河南省夏玉米最适播种期变化趋势不显著,但是由于温度变化和品种改良对冬小麦成熟期的影响,导致河南省驻马店以南地区、中部的伊川、内乡、南阳,以及北部的林州和西部的三门峡地区夏玉米可播种期提前,可播种范围扩大.统计方法和APSIM模型计算的夏玉米最适播种期在76.7%的研究站点无显著差异.结合两种方法,北部地区应保证需水关键期降水充足和灌浆期温度适宜,做到“见雨即播”.南部地区在满足上述两个指标的条件下,应在播种期降水达到一定有效值时进行播种,对于南部和偏南部地区,该有效值分别为3.9和8.3 mm.     

Single rice growth period was prolonged by cultivars shifts,but yield was damaged by climate change during 1981–2009 in China,and late rice was just opposite

Based on the crop trial data during 1981–2009 at 57 agricultural experimental stations across the North Eastern China Plain (NECP) and the middle and lower reaches of Yangtze River (MLRYR), we investigated how major climate variables had changed and how the climate change had affected crop growth and yield in a setting in which agronomic management practices were taken based on actual weather. We found a significant warming trend during rice growing season, and a general decreasing trend in solar radiation (SRD) in the MLRYR during 1981–2009. Rice transplanting, heading, and maturity dates were generally advanced, but the heading and maturity dates of single rice in the MLRYR (YZ_SR) and NECP (NE_SR) were delayed. Climate warming had a negative impact on growth period lengths at about 80% of the investigated stations. Nevertheless, the actual growth period lengths of YZ_SR and NE_SR, as well as the actual length of reproductive growth period (RGP) of early rice in the MLRYR (YZ_ER), were generally prolonged due to adoption of cultivars with longer growth period to obtain higher yield. In contrast, the actual growth period length of late rice in the MLRYR (YZ_LR) was shortened by both climate warming and adoption of early mature cultivars to prevent cold damage and obtain higher yield. During 1981–2009, climate warming and decrease in SRD changed the yield of YZ_ER by ?0.59 to 2.4%; climate warming during RGP increased the yield of YZ_LR by 8.38–9.56%; climate warming and decrease in SRD jointly reduced yield of YZ_SR by 7.14–9.68%; climate warming and increase in SRD jointly increased the yield of NE_SR by 1.01–3.29%. Our study suggests that rice production in China has been affected by climate change, yet at the same time changes in varieties continue to be the major factor driving yield and growing period trends.     

The complementary effects of plant resistance and the choice of sowing and harvest times in reducing carrot fly (Psila rosae) damage to carrots

The benefits of combining a partially-resistant carrot cultivar with different sowing and lifting dates to reduce carrot fly, Psila rosae, damage were investigated at Wellesbourne in 1983 and 1984-85. The partially-resistant cv. Sytan was less damaged and supported fewer insects than the susceptible cv. Danvers on all lifting dates. The estimated reduction of carrot fly larvae on Sytan compared with Danvers ranged from 33 to 95%. Nine combinations of sowing and lifting dates provided more than 75% marketable roots of Sytan compared with only three combinations of dates for Danvers. An early June sowing of both cultivars provided roots of a marketable size with the least attack. More than 90% of Sytan roots were still marketable in December and fewer insects were produced by the end of the season on these roots than on those sown earlier. In addition, sowing in June decreased the number of pupae produced on cv. Danvers by 10 times compared with earlier sowings. Combining partial resistance with specific sowing and lifting times enabled satisfactory yields of marketable carrots to be obtained in a field infested by high populations of carrot fly.     

When to start and when to stop: Effects of climate on breeding in a multi‐brooded songbird

Climate warming has been shown to affect the timing of the onset of breeding of many bird species across the world. However, for multi‐brooded species, climate may also affect the timing of the end of the breeding season, and hence also its duration, and these effects may have consequences for fitness. We used 28 years of field data to investigate the links between climate, timing of breeding, and breeding success in a cooperatively breeding passerine, the superb fairy‐wren (Malurus cyaneus). This multi‐brooded species from southeastern Australia has a long breeding season and high variation in phenology between individuals. By applying a “sliding window” approach, we found that higher minimum temperatures in early spring resulted in an earlier start and a longer duration of breeding, whereas less rainfall and more heatwaves (days > 29°C) in late summer resulted in an earlier end and a shorter duration of breeding. Using a hurdle model analysis, we found that earlier start dates did not predict whether or not females produced any young in a season. However, for successful females who produced at least one young, earlier start dates were associated with higher numbers of young produced in a season. Earlier end dates were associated with a higher probability of producing at least one young, presumably because unsuccessful females kept trying when others had ceased. Despite larger scale trends in climate, climate variables in the windows relevant to this species’ phenology did not change across years, and there were no temporal trends in phenology during our study period. Our results illustrate a scenario in which higher temperatures advanced both start and end dates of individuals’ breeding seasons, but did not generate an overall temporal shift in breeding times. They also suggest that the complexity of selection pressures on breeding phenology in multi‐brooded species may have been underestimated.     

Phenological responses of upland rice grown along an altitudinal gradient

High altitude upland rice (Oryza sativa L.) production systems are expected to benefit from climate change induced increase in temperatures. The potential yield of rice genotypes is governed by the thermal environment experienced during crop development phases when yield components are determined. Thus, knowledge on genotypic variability in phenotypic responses to variable temperature is required for assessing the adaptability of rice production to changing climate. Although, several crop models are available for this task, genotypic thermal constants used to simulate crop phenology vary strongly among the models and are under debate. Therefore, we conducted field trials with ten contrasting upland rice (O. sativa L.) genotypes on three locations along an altitudinal gradient with five monthly staggered sowing dates for two years in Madagascar with the aim to study phenological responses at different temperature regimes. We found that, crop duration is equally influenced by genotype selection, sowing date and year in the high altitude. In contrast, in mid altitudes genotype has no effect on crop duration. At low altitudes crop duration is more affected by sowing date. Grain yield is strongly affected by low temperatures at high altitudes and severly influenced by frequent tropical cyclones at low altitudes. In high altitude, genotype explained 68% of variation in spikelet sterility, whereas in mid and low altitudes environment explained more than 70% of the variation. The phenological responses determining crop duration and yield, the basic genotypic thermal constants, and the analyses of genotypic thermal responses with regard to spikelet sterility reported here, provide valuable information for the improvement of rice phenological models urgently needed to develop new genotypes and better adapted cropping calendars.     

How do various maize crop models vary in their responses to climate change factors?

Potential consequences of climate change on crop production can be studied using mechanistic crop simulation models. While a broad variety of maize simulation models exist, it is not known whether different models diverge on grain yield responses to changes in climatic factors, or whether they agree in their general trends related to phenology, growth, and yield. With the goal of analyzing the sensitivity of simulated yields to changes in temperature and atmospheric carbon dioxide concentrations [CO₂], we present the largest maize crop model intercomparison to date, including 23 different models. These models were evaluated for four locations representing a wide range of maize production conditions in the world: Lusignan (France), Ames (USA), Rio Verde (Brazil) and Morogoro (Tanzania). While individual models differed considerably in absolute yield simulation at the four sites, an ensemble of a minimum number of models was able to simulate absolute yields accurately at the four sites even with low data for calibration, thus suggesting that using an ensemble of models has merit. Temperature increase had strong negative influence on modeled yield response of roughly ?0.5 Mg ha^?1 per °C. Doubling [CO₂] from 360 to 720 μmol mol^?1 increased grain yield by 7.5% on average across models and the sites. That would therefore make temperature the main factor altering maize yields at the end of this century. Furthermore, there was a large uncertainty in the yield response to [CO₂] among models. Model responses to temperature and [CO₂] did not differ whether models were simulated with low calibration information or, simulated with high level of calibration information.     

种植方式对夏玉米光合生产特征和光温资源利用的影响

为研究套种与直播两种种植方式对夏玉米光合生产特征和光温资源利用的影响,选取郑单958和登海661为研究对象,设置3个播期,密度为67500株·hm^-2,以地上干物质积累量和作物生长速率、叶面积指数、穗位叶的单叶光合速率来评价夏玉米的光合生产特征;以Richards模型拟合籽粒灌浆过程;结合气象数据计算夏玉米光能利用率.结果表明：直播处理比套种处理籽粒产量增加1.17%～3.33%（P<0.05）,但千粒重显著降低;生育期随播期提前而延长;直播条件下叶面积指数和单叶光合速率在灌浆前期显著高于套种,但灌浆后期下降较快;与套种相比,直播开花前和开花后具有较高的干物质积累量和较快的作物生长速率.Richards模型解析表明,直播处理达到最大灌浆速率的时间明显早于套种,起始势较套种高,但灌浆期、活跃灌浆期和灌浆速率最大时的生长量均低于套种;与套种相比,直播处理生育期间总积温和总辐射量分别减少150～350 ℃·d和200～400 MJ·m^-2,但籽粒光能利用率较套种提高10.5%～24.7%.因此,直播较套种有优势,在夏玉米大田生产条件下,重视叶片的光合生产特征,延缓叶片衰老,有利于提高夏玉米的光能利用率,进一步挖掘增产潜力.     

Similarities in butterfly emergence dates among populations suggest local adaptation to climate

Phenology shifts are the most widely cited examples of the biological impact of climate change, yet there are few assessments of potential effects on the fitness of individual organisms or the persistence of populations. Despite extensive evidence of climate‐driven advances in phenological events over recent decades, comparable patterns across species' geographic ranges have seldom been described. Even fewer studies have quantified concurrent spatial gradients and temporal trends between phenology and climate. Here we analyse a large data set (~129 000 phenology measures) over 37 years across the UK to provide the first phylogenetic comparative analysis of the relative roles of plasticity and local adaptation in generating spatial and temporal patterns in butterfly mean flight dates. Although populations of all species exhibit a plastic response to temperature, with adult emergence dates earlier in warmer years by an average of 6.4 days per °C, among‐population differences are significantly lower on average, at 4.3 days per °C. Emergence dates of most species are more synchronised over their geographic range than is predicted by their relationship between mean flight date and temperature over time, suggesting local adaptation. Biological traits of species only weakly explained the variation in differences between space‐temperature and time‐temperature phenological responses, suggesting that multiple mechanisms may operate to maintain local adaptation. As niche models assume constant relationships between occurrence and environmental conditions across a species' entire range, an important implication of the temperature‐mediated local adaptation detected here is that populations of insects are much more sensitive to future climate changes than current projections suggest.     

基于ORYZA2000模型的北京地区旱稻适宜播种期分析

确定适宜播种期是制定合理的作物栽培管理方案的关键内容之一。在作物模型ORYZA2000有效性验证的基础上,以北京地区为例,利用该模型结合长期历史气候资料,对确定旱稻适宜播种期做了初步研究。结果表明：在不考虑水分因子条件下,北京地区旱稻297安全播期的范围较广,多年平均为3月26日-6月4日;受温度升高的影响,最早播期有提前趋势,而最晚播种期有延后趋势。在同一年份内,播期不同旱稻的产量也有一定的变化,呈现为先升高而后降低的趋势。播期过早或过晚导致生育期平均温度偏低是影响穗干物质累积且造成减产的主要原因,在适宜的播期范围内才能获得高产。以90%-100%当年最高产量潜力作为适宜播期的产量指标,确定北京地区旱稻297的适宜播期变化在5月11日-5月19日之间,相应的产量变化在6689-7257 kg/hm2范围内。研究方法可为其他地区旱稻的播期研究提供借鉴。     

Modern maize hybrids in Northeast China exhibit increased yield potential and resource use efficiency despite adverse climate change

The impact of global changes on food security is of serious concern. Breeding novel crop cultivars adaptable to climate change is one potential solution, but this approach requires an understanding of complex adaptive traits for climate‐change conditions. In this study, plant growth, nitrogen (N) uptake, and yield in relation to climatic resource use efficiency of nine representative maize cultivars released between 1973 and 2000 in China were investigated in a 2‐year field experiment under three N applications. The Hybrid‐Maize model was used to simulate maize yield potential in the period from 1973 to 2011. During the past four decades, the total thermal time (growing degree days) increased whereas the total precipitation and sunshine hours decreased. This climate change led to a reduction of maize potential yield by an average of 12.9% across different hybrids. However, the potential yield of individual hybrids increased by 118.5 kg ha^?1 yr^?1 with increasing year of release. From 1973 to 2000, the use efficiency of sunshine hours, thermal time, and precipitation resources increased by 37%, 40%, and 41%, respectively. The late developed hybrids showed less reduction in yield potential in current climate conditions than old cultivars, indicating some adaptation to new conditions. Since the mid‐1990s, however, the yield impact of climate change exhibited little change, and even a slight worsening for new cultivars. Modern breeding increased ear fertility and grain‐filling rate, and delayed leaf senescence without modification in net photosynthetic rate. The trade‐off associated with delayed leaf senescence was decreased grain N concentration rather than increased plant N uptake, therefore N agronomic efficiency increased simultaneously. It is concluded that modern maize hybrids tolerate the climatic changes mainly by constitutively optimizing plant productivity. Maize breeding programs in the future should pay more attention to cope with the limiting climate factors specifically.     

Impact of climate change on plant phenology in Mediterranean ecosystems

Plant phenology is strongly controlled by climate and has consequently become one of the most reliable bioindicators of ongoing climate change. We used a dataset of more than 200 000 records for six phenological events of 29 perennial plant species monitored from 1943 to 2003 for a comprehensive assessment of plant phenological responses to climate change in the Mediterranean region. Temperature, precipitation and North Atlantic Oscillation (NAO) were studied together during a complete annual cycle before phenological events to determine their relative importance and potential seasonal carry‐over effects. Warm and dry springs under a positive phase of NAO advance flowering, leaf unfolding and fruiting dates and lengthen the growing season. Spatial variability of dates (range among sites) was also reduced during warm and dry years, especially for spring events. Climate during previous weeks to phenophases occurrence had the greatest impact on plants, although all events were also affected by climate conditions several months before. Immediate along with delayed climate effects suggest dual triggers in plant phenology. Climatic models accounted for more than 80% of variability in flowering and leaf unfolding dates, and in length of the growing season, but for lower proportions in fruiting and leaf falling. Most part of year‐to‐year changes in dates was accounted for temperature, while precipitation and NAO accounted for <10% of dates' variability. In the case of flowering, insect‐pollinated species were better modelled by climate than wind‐pollinated species. Differences in temporal responses of plant phenology to recent climate change are due to differences in the sensitivity to climate among events and species. Spring events are changing more than autumn events as they are more sensitive to climate and are also undergoing the greatest alterations of climate relative to other seasons. In conclusion, climate change has shifted plant phenology in the Mediterranean region.     

Temporal trends in phenology of the honey bee Apis mellifera (L.) and the small white Pieris rapae (L.) in the Iberian Peninsula (1952–2004)

Abstract.  1. The first adult appearance of two insect species, the honey bee Apis mellifera (L.) and the small white Pieris rapae (L.), was examined between 1952 and 2004 in Spain.
2. After factoring out the variability resulting from the broad geographical and topographical range of the 798 sampling localities, multiple regression models were used to detect temporal trends in phenology.
3. The best models were repeated, including spring temperature as the explanatory variable to examine the effects of climate on appearance phenology.
4. Both species showed similar temporal trends, delaying their appearance phenology until the mid-1970s and advancing it since that time.
5. The appearance times for both species were negatively related to mean temperature between February and April, with both species appearing earlier in years with warmer springs.
6. The strong dependence of appearance dates on temperature indicates that climatic fluctuations are primarily responsible for the inter-annual variability in spring appearance phenology of both species, and consequently account for the observed long-term trends.
7. This study demonstrates that insect phenology is an accurate and sensitive bioindicator of climate change.     

Advanced departure dates in long-distance migratory raptors

Evidences for phenological changes in response to climate change are now numerous. One of the most documented changes has been the advance of spring arrival dates in migratory birds. However, the effects of climate change on subsequent events of the annual cycle remain poorly studied and understood. Moreover, the rare studies on autumn migration have mainly concerned passerines. Here, we investigated whether raptor species have changed their autumn migratory phenology during the past 30 years at one of the most important convergent points of western European migration routes in France, the Organbidexka pass, in the Western Pyrenees. Eight out of the 14 studied raptor species showed significant phenological shifts during 1981–2008. Long-distance migrants displayed stronger phenological responses than short-distance migrants, and advanced their mean passage dates significantly. As only some short-distance migrants were found to delay their autumn migration and as their trends in breeding and migrating numbers were not significantly negative, we were not able to show any possible settling process of raptor populations. Negative trends in numbers of migrating raptors were found to be related to weaker phenological responses. Further studies using data from other migration sites are necessary to investigate eventual changes in migration routes and possible settling process.     

Effect of Sowing Date and Cultivar on Root System Development in Pea (Pisum sativum L.)

In many species, root system development depends on cultivar and sowing date, with consequences for aerial growth, and seed yield. Most of the peas (Pisum sativum L.) grown in France are sown in spring or in mid-November. We analyzed the effect of two sowing periods (November and February) and three pea cultivars (a spring cultivar, a winter cultivar, a winter recombinant inbred line) on root development in field conditions. For all treatments, rooting depth at various dates seemed to be strongly correlated with cumulative radiation since sowing. Maximum root depth varied from 0.88 to 1.06 m, with the roots penetrating to greater depths for February sowing than for November sowing in very cold winters. The earlier the crop was sown, the sooner maximum root depth was reached. No difference in root dynamics between cultivars was observed. In contrast, the winter recombinant inbred line presented the highest root density in the ploughed layer. These findings are discussed in terms of their possible implications for yield stability and environmental impact.