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| 1 | 祁连山中部近500年来降水重建序列分析显示文摘利用祁连山中部地区祁连圆柏(Juniperus przewalskii)年轮宽度资料,重建了该地区公元1480年以来上年8月至当年7月的年降水量.重建显示过去5个世纪大致可分为4次主要的干、湿期:16世纪偏湿,17世纪干旱,18~20世纪初偏湿,20世纪偏干(20~30年代极端干旱).采用经验模态分解(EMD)方法对重建序列的进一步分析显示,重建降水序列可分解为高频至低频8个尺度的分量,各分量在不同时段周期和振幅的变化过程与原序列降水的高低值时期对应较为一致,趋势项显示了过去5个世纪研究区降水量呈平缓上升的总体趋势.其中2~3和5~8年的主要分量揭示了降水量与ENSO等大气环流和海气耦合相联系的变化特征,10~13年尺度的分量显示了区域降水与太阳活动的可能联系.结合已有研究的集成分析揭示了研究区更为可靠、一致的干湿变化记录,显示了过去5个世纪以来干旱事件频繁持续的特征和19~20世纪高降雨记录增多的趋势,区域降水经历着较大变化,但其变化幅度仍不可预知.该重建提供了更多的低频降水信息,是对研究区已有树轮重建降水量信息的重要补充. | 田沁花 周秀骥 勾晓华 赵平 范泽鑫 Samuli HELAMA | 2012 | 中国科学:地球科学2012，42，4： | 8 |
| 2 | Analysis of reconstructed annual precipitation from tree-rings for the past 500 years in the middle Qilian Mountain显示文摘The ring-width chronology of a Juniperus przewalskii tree from the middle of the Qilian Mountain was constructed to estimate the annual precipitation (from previous August to current July) since AD 1480.The reconstruction showed four major alternations of drying and wetting over the past 521 years.The rainy 16th century was followed by persistent drought in the 17th century.Moreover,relatively wet conditions persisted from the 18th to the beginning of 20th century until the recurrence of a drought during the 1920s and 1930s.Based on the Empirical Mode Decomposition method,eight Intrinsic Mode Functions (IMFs) were extracted,each representing unique fluctuations of the reconstructed precipitation in the time-frequency domain.The high amplitudes of IMFs on different timescales were often consistent with the high amount of precipitation,and vice versa.The IMF of the lowest frequency indicated that the precipitation has undergone a slow increasing trend over the past 521 years.The 2-3 year and 5-8 year time-scales reflected the characteristics of inter-annual variability in precipitation relevant to regional atmospheric circulation and the El Ni?o-Southern Oscillation (ENSO),respectively.The 10-13 year scale of IMF may be associated with changing solar activity.Specifically,an amalgamation of previous and present data showed that droughts were likely to be a historically persistent feature of the Earth's climate,whereas the probability of intensified rainfall events seemed to increase during the course of the 19th and 20th centuries.These changing characteristics in precipitation indicate an unprecedented alteration of the hydrological cycle,with unknown future amplitude.Our reconstruction complements existing information on past precipitation changes in the Qilian Mountain,and provides additional low-frequency information not previously available. | TIAN QinHua ZHOU XiuJi GOU XiaoHu ZHAO Ping FAN ZeXin Samuli HELAMA | 2012 | Science China Earth Sciences2012，55，5： | 7 |
| 3 | Quantifying temporal changes in Tornionjoki river ice breakup dates and spring temperatures in Lapland since 1802显示文摘Cryophenological 记录(即观察系列结冰并且冰的决裂日期) 当在冷区域估计环境变化时,是很重要的。这里,我们在北 Fennoscandia 采用了河冰决裂日期和空气温度的非常地长的观察记录自从 1802,检验他们的相互关系。与现代数据一起,历史的观察为用 t 测试执行的这分析包括参考设置。4 月 5 月季节的温度历史为决裂 timings 被用作气候的对应物。两个记录(温度和决裂) 在他们的本地工具相对前面、随后的亚时期在哪个期间是显然不同的期间显示出七亚时期。这些亚时期的开始并且结束的年发生在时间的同意。这研究的主要调查结果如下被总结:(1 ) 在温度和河冰决裂记录之间的 synchrony 排除了变化将由于历史的系列的质量发生的可能性(即不同类问题经常连接了到历史的时间系列) ;( 2 )学习记录同意在 第19 世纪期间显示出更低的春天温度和以后的河冰决裂,与 第20 个世纪条件相比,证实在学习区域的更凉爽的春天温度的流行,与在西北欧洲的小冰川期( 15701900 )气候的概念一致;(3 ) 最近的亚时期与附随地最早的河冰决裂表明最高的春天温度,在过去的二个世纪的上下文在学习区域显示出当前的春季气候的相对温暖;(4 ) 在河环境的人为的变化的效果(例如水坝的建设和拆毁) 应该在决裂记录为非气候的变化在第 20 世纪期间被考虑;(5 ) 这研究强调重要性多一世纪(即历史) 为气候和环境历史的高度有趣的观点的 cryophenological 信息。 | Samuli HELAMA Jianmin JIANG Johanna KORHONEN Jari HOLOPAINEN Mauri TIMONEN | 2013 | Journal of Geographical Sciences2013，23，6： | 2 |
| 4 | The supralong Scots pine tree -ring record for Finnish Lapland Part 1 : Chro- nology construction and initial inferences 显示文摘 | Samuli Helama Matti Vartiainen Jari Holopainen | 2002 | The Holocene2002，，12： | 1 |
| 5 | Inter-and intra-seasonal effects of temperature variation on radial growth of alpine treeline Norway spruce显示文摘A widely accepted standpoint contends that plant growth near the cold edge of the species range,such as treelines,does not depend on the annual temperature seasonality(i.e.difference between maximum and minimum temperature values) but rather on the warmth of summer season.In contrast to this expectation,we show that the growth of treeline Norway spruce(Picea abies) is well explained by temperature seasonality as a single climatic determinant.To do so,the tree-ring data of spruce trees growing on alpine treeline in Lapland was compared with long climate records.Biennial time-series of temperature seasonality capture both the decadal and abrupt growth fluctuations with a correlation coefficient of r = 0.601.We also show that the archetypal association between summer temperature and treeline tree growth may in fact be by far a more complex relationship than previously thought.Spruce growth appears responsive to lateJune(r = 0.494) and mid-July(r = 0.310) temperatures but unresponsive to temperatures during the early July,that is,during the grand period of the tracheid formation.Climatic warming may enhance the treeline spruce growth unless the warming is concentrated on unresponsive interval in the midst of the growing season.Water relations did not play significant role as agents of P.abies growth. | Samuli HELAMA Raimo SUTINEN | 2016 | Journal of Mountain Science2016，13，1： | 0 |
| 6 | Use,calibration and verification of agroecologicalmodels for boreal environments:A review显示文摘Past assessments report negative impacts of the climate crisis in boreal areas;but milder and shorter winters and elevated atmospheric CO_(2) may provide opportunities for agricultural productivity potentially playing a significant role in future food security.Arable cropping systems are expanding in boreal areas,but the regional mainstay will likely continue to be livestock production.Agroecological models can when appropriately calibrated and evaluated,facilitate improved productivity while minimising environmental impacts by identifying system interactions,and quantifying greenhouse gas emissions,soil carbon stocks and fertiliser use.While models designed for temperate and tropical zones abound,few are developed specifically for boreal zones,and there is uncertainty around the performance of existing models in boreal areas.We reviewed model performance across boreal environments and management systems.We identified a dearth of modelling studies in boreal regions,with the publication of three or less papers per year since the year 2000,constituting a significant research gap.Models IFSM and BASGRA_N performed best in grassland production,DNDC best in predicting soil N_(2)O and NH_(3) emissions.No model outperformed all others,strengthening the case for ensemble modelling.Existing agroecological models would be worthy of further evaluation,providing model improvements designed for boreal systems. | Daniel Forster Samuli Helama Matthew T.Harrison Clarence Alan Rotz Jinfeng Chang Phillippe Ciais Elizabeth Pattey Perttu Virkajärvi Narasinha Shurpali | 2022 | Grassland Research2022，1，1： | 0 |
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