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1.
基于数字相机图像的长白山森林物候模拟 总被引：1，自引：1，他引：0
植被物候作为全球植被和陆面过程模型的重要参数,对其状态的准确描述在很大程度上决定着模型的模拟精度。温带森林作为北半球中高纬度地区主要植被类型及全球重要碳源,研究其物候期的变化将提高对区域碳通量的估算精度。本文以长白山阔叶红松林为研究对象,探讨了数字相机图像在物种尺度物候模拟及群落尺度物候模型改进方面的作用,结果如下：（1）物种尺度上,利用数字相机能获取两种植被（红松,蒙古栎）较为准确的物候期（与人工观测数据比较,绝对误差〈3d）;（2）群落尺度上,基于数字相机图像获取的冠层状态数据提高了基于气象数据的物候模型（GSI：growingseasonindex）的模拟精度（R2=0．9）,尤其是秋季物候模拟,为进一步分析群落物候的环境控制因子提供了有力手段。研究表明：数字相机不仅能够提供精确地基于物种尺度的物候数据,还可为遥感物候数据的校正提供参考,同时为生态模型中物候模块的改进及降低区域尺度碳通量模拟不确定性提供了新的思路。 相似文献
2.
基于1982—2015年GIMMS NDVI 3g V1.0数据、3小时温度、逐日降水和日太阳辐射数据集、数字高程模型、中国植被区划数据及实测物候验证数据,利用季节性植被物候提取法、Theil-Sen median趋势分析法和偏最小二乘回归分析等方法,研究中国第二、三级阶梯地形过渡带植被物候的时空变化规律,探讨植被物候对海拔、经纬度和气候变化的响应。结果表明：① 34 a间过渡带山前植被物候时空变化显著。时间上,植被物候呈返青期（Start Of Season, SOS）提前（-0.3187 d/a, p<0.01）、枯黄期（End Of Season, EOS）推迟（0.1171 d/a, p>0.1）和生长季长度（Length Of Growing Season, LOS）延长（0.4358 d/a, p<0.01）趋势;空间上,按SOS像元的86.24%提前、EOS像元的69.66%推迟和LOS像元的84.42%延长分布。② 34 a间过渡带山前植被物候地带性特征明显。垂直地带性方面,在中低纬度地区的物候始末期受以400 m等高线为界的海拔梯度影响,由平原到山地产生SOS平均提前8d,EOS提前25~36 d的分段式变化;水平地带性方面,低纬度和中高纬度地区的植被物候以35°N（秦岭-淮河一线,中国南北方的分界线）、43.5°N（暖温带落叶阔叶林区与温带草原区的分界）为转折点,由南向北SOS以-0.78 d/°、4.89 d/°和-1.56 d/°分段变化,EOS以-3.96 d/°、-1.85 d/°和0.89 d/°分段变化。③ 34 a间过渡带植被物候受气象因素驱动。对于植被返青期,气温对中纬度地区SOS的影响最大,降水的贡献随着纬度的降低而增大,太阳辐射在中纬度地区的贡献力大于低纬度地区;对于植被枯黄期,中纬度地区对EOS的多因素贡献力为太阳辐射>气温>降水（太阳辐射对草原区无贡献力）,低纬度地区贡献力排序与之相反;本研究对宏观地理带中不同植被区划的物候变化认知有学术意义,也为地理因素与气候因素共同影响的植被物候变化提供了新的认识。 相似文献
3.
ZHAO Guangshuai SHI Peili ZONG Ning HE Yongtao ZHANG Xianzhou HE Honglin ZHANG Jing 《资源与生态学报(英文版)》2017,8(1):50-56
Vegetation phenology is a sensitive indicator of global warming, especially on the Tibetan Plateau. However, whether climate warming has enhanced the advance of grassland phenology since 2000 remains debated and little is known about the warming effect on semiarid grassland phenology and interactions with early growing season precipitation. In this study, we extracted phenological changes from average NDVI in the growing season (GNDVI) to analyze the relationship between changes in NDVI, phenology and climate in the Northern Tibetan Damxung grassland from 2000 to 2014. The GNDVI of the grassland declined. Interannual variation of GNDVI was mainly affected by mean temperature from late May to July and precipitation from April to August. The length of the growing season was significantly shortened due to a delay in the beginning of the growing season and no advancement of the end of the growing season, largely caused by climate warming and enhanced by decreasing precipitation in spring. Water availability was the major determinant of grass growth in the study area. Warming increased demand for water when the growth limitation of temperature to grass was exceeded in the growing season. Decreased precipitation likely further exacerbated the effect of warming on vegetation phenology in recent decades due to increasing evapotranspiration and water limitations. The comprehensive effects of global warming and decreasing precipitation may delay the phenological responses of semiarid alpine grasslands. 相似文献
4.
1982-2013年青藏高原植被物候变化及气象因素影响 总被引：12，自引：3，他引：9
根据NDVI3g数据,本文定义了18种植被物候指标研究植被物候变化情况。根据1:100万植被区划,把青藏高原划分为8个植被区分。对物候变化比较显著的区域,采用最高温度、最低温度、平均温度、降水、太阳辐射数据,运用偏最小二乘法回归（PLS）研究物候变化的气候成因。结果表明：① 青藏高原生长季初期物候指标,转折发生在1997-2000年,转折前初期物候指标平均提前2~3 d/10a;青藏高原末期物候指标转折发生在2004-2007年左右,生长季长度物候指标突变发生在2005年左右,转折前末期物候指标平均延迟1~2 d/10a、生长季长度平均延长1~2 d/10a;转折之后生长季初期物候指标推迟趋势的显著性水平仅为0.1,生长季末期物候指标、生长季长度指标趋势不显著。② 高寒草甸与高寒灌木草甸是青藏高原物候变化最剧烈的植被分区。高寒草甸区生长季长度的延长主要是由生长季初期物候指标提前导致的。高寒灌木草甸区生长季长度的延长主要是由于初期物候指标的提前,以及末期物候指标的推迟共同作用导致的。③ 采用PLS进一步分析气象因素对高寒草甸与高寒灌木草甸物候剧烈变化的影响。表明,温度对物候的影响占主导地位,两植被分区均显示上年秋季、冬初温度对生长季初期物候具有正的影响,该时段温度一方面会导致上年末期物候指标推迟,间接推迟生长季开始时间;另一方面高温不利用冬季休眠。除夏季外,其余月份最小温度对植被物候的影响与平均温度、最高温度的影响类似。降水对植被物候的影响不同月份波动较大,上年秋冬季节降水对初期物候指标具有负的影响,春初降水对初期物候指标具有正的影响。8月份限制植被生长季的主要因素是降水,此时降水与末期物候指标模型系数为正。太阳辐射对植被物候的影响主要在夏季与秋初。PLS方法在物候变化研究中具有较好的效果,本文研究结果将会对植被物候模型改进,提供有力的科学依据。 相似文献
5.
伏牛山地森林植被物候及其对气候变化的响应 总被引：4，自引：1，他引：3
研究植被物候是理解植被与气候关系的重要途径。在植被对气候变化响应的敏感地区,开展植被物候研究有助于揭示气候变化对植被的影响机制。基于2000-2015年MODIS EVI时间序列影像数据,利用Savitzky-Golay （S-G）滤波方法和动态阈值法提取伏牛山地2000-2015年森林植被物候参数,结合气温、降水数据,运用Man-Kendall趋势检验、Sen斜率、ANUSPLIN插值和相关性分析等方法,研究伏牛山地森林植被物候对气候要素（气温、降水）变化的响应。结果表明：① 伏牛山地森林植被生长季始期主要集中在第105~120 d,生长季末期主要集中在第285~315 d,生长季长度主要集中在165~195 d。从海拔梯度看,随海拔升高,生长季始期、末期和长度整体上分别呈显著推迟、提前及缩短趋势。② 生长季始期和生长季末期整体上呈推迟趋势,推迟的像元分别占森林植被的76.57%和83.81%。生长季长度整体呈延长趋势,延长的像元占比为61.21%。生长季始期变化特征主要是由该地区的春季气温降低所导致的。③ 研究区森林植被生长季始期与3月平均气温呈显著偏相关,且呈负相关的区域最多,即3月平均气温降低,导致生长季始期推迟;生长季末期与9月降水呈显著偏相关区域最多,且两者主要呈正相关,即9月降水增加,使生长季末期推迟。植被生长季长度由整个生长期的气温和降水来共同作用,对大多数的区域而言,8月的平均气温和降水与生长季长度的关系最为密切。 相似文献
6.
基于2000—2011年MOD13Q1产品的EVI时序,借助QA-SDS数据集消除云、阴影和冰雪等的影响后,采用非对称高斯函数拟合法进行时序重构,并运用动态阈值法提取云南高原山地典型森林植被的物候特征参数(即生长期开始时间、峰值时间、结束时间和生长期长度),进而分析了不同植被类型物候期规律及其主要控制因素。结果表明:1.从寒温性森林植被到热性森林植被的EVI值呈递增趋势;2.森林植被生长期开始时间、峰值时间和结束时间分别大致发生在3月中旬至4月中下旬、6月中旬至下旬和8月中旬至10月初,生长期长度为135～195 d;3.由寒温性植被向热性植被的生长期高峰时间和生长期结束时间总体呈延迟趋势,且生长期延长,生长期开始时间则由暖性植被向寒温性植被、暖性植被向热性植被双向提前;4.高原山地热量梯度决定了森林植被物候的空间格局,水分条件则主要控制着EVI和物候期的年际波动。 相似文献
7.
东北黑土区是中国重要的粮食生产基地,也是中国气候变化最敏感的地区之一。然而,气候变化背景下东北黑土区气候及物候变化对农业生产力的综合影响并不清晰,未来农业生产风险评估的定量化程度不够,风险等级制定缺乏依据。本文借助遥感产品、气候资料和模拟数据等资料,综合运用多元线性回归、相关分析及干旱危险性指数等方法,探究东北黑土区作物物候动态及其气候响应特征,辨识气候与物候变化对农业生产的复合效应及未来可能风险。结果表明：① 2000—2017年东北黑土区29.76%的区域作物生长季开始期呈显著延后趋势,16.71%的区域作物生长季结束期呈提前态势,生长季开始期受气温的影响范围广,且滞后时间长;生长季结束期与前期气候变化关系更加密切,且带状差异性响应格局尤其明显。② 气候变化和物候期改变对作物生产的解释能力较生长季同期气候变化的解释能力增加了70.23%,解释面积扩大了85.04%。③ RCP8.5情景下东北黑土区粮食总产量呈现上升趋势,粮食生产风险表现出“南增北减”的演变特征,风险区面积不断扩大,全球温升2.0 ℃时,松嫩黑土亚区南部粮食减产量可能达到10%。研究有助于深入认识气候—物候—作物生产的关联机理及未来粮食生产风险,对制定气候变化应对策略,保障国家粮食安全具有重要意义。 相似文献
8.
Liang Liang 《自然地理学》2013,34(6):489-509
Geographic variations in plant phenology are known to be affected by climatic differences over space, but the role of adaptation variability of plant populations is less well understood. In this study, I examined the geographic variations in spring and autumn phenology of white ash (Fraxinus americana L.) in a common garden and related observations over a 2-year period (2013 and 2014) to climatic and geographic factors of their provenances. Spring leaf-out of trees with northern provenances occurred later in 2013, but slightly earlier in 2014, than those with southern provenances. This difference was potentially caused by the counterbalancing effect of chilling and forcing in response to interannual temperature fluctuations. In both years, leaf senescence of white ash occurred significantly earlier for trees with northern than southern provenances, reflecting strong adaptation to a photoperiod gradient. The growing season length for white ash, therefore, is constrained by spring and fall phenology through different environmental cues. Spring phenology exerted a greater influence on the interannual variability of growing season length. Identifying these detailed adaptive patterns facilitates a better understanding of phenological change over space and allows development of genotype-sensitive phenological models to predict the ecological impact of climate change. 相似文献
9.
《地理学报(英文版)》2019,(3)
Spatio-temporal changes in the differentiation characteristics of eight consecutive phenological periods and their corresponding lengths were quantitatively analyzed based on long-term phenological observation data from 114 agro-meteorological stations in four maize growing zones in China. Results showed that average air temperature and growing degree-days (GDD) during maize growing seasons showed an increasing trend from 1981 to 2010, while precipitation and sunshine duration showed a decreasing trend. Maize phenology has significantly changed under climate change: spring maize phenology was mainly advanced, especially in northwest and southwest maize zones, while summer and spring-summer maize phenology was delayed. The delay trend observed for summer maize in the northwest maize zone was more pronounced than in the Huang-Huai spring-summer maize zone. Variations in maize phenology changed the corresponding growth stages length: the vegetative growth period (days from sowing date to tasseling date) was generally shortened in spring, summer, and spring-summer maize, although to different degrees, while the reproductive growth period (days from tasseling date to mature date) showed an extension trend. The entire growth period(days from sowing date to mature date) of spring maize was extended, but the entire growth periods of summer and spring-summer maize were shortened. 相似文献
10.
GAO Jiangbo LIU Lulu GUO Linghui SUN Dongqi LIU Wanlu HOU Wenjuan WU Shaohong 《地理学报(英文版)》2023,33(1):37-58
The black soil region of northeast China is a vital food base and is one of the most sensitive regions to climate change in China. However, the characteristics of the crop phenological response and the integrated impact of climate and phenological changes on agricultural productivity in the region under the background of climate change are not clear. The future agricultural risk assessment has been insufficiently quantified and the existing risk level formulation lacks a sound basis. Based on remote sensing products, climate data, and model simulations, this study integrated a logistic function fitting curvature derivation, multiple linear regression, and scenario simulation to investigate crop phenology dynamics and their climate response characteristics in the black soil region. Additionally, the compound effects of climate and phenology changes on agricultural production and possible future risks were identified. The key results were as follows: (1) From 2000 to 2017, 29.76% of the black soil region of northeast China experienced a significant delay in the start of the growing season (SOS) and 16.71% of the total area displayed a trend for the end of the growing season (EOS) to arrive earlier. The time lagged effects of the SOS in terms of the crop response to climatic factors were site and climatic parameter dependent. The influence of temperature was widespread and its effect had a longer lag time in general; (2) Both climatic and phenological changes have had a significant effect on the inter-annual variability of crop production, and the predictive ability of both increased by 70.23%, while the predictive area expanded by 85.04%, as compared to that of climate change in the same period of the growing season; (3) Under the RCP8.5 scenario, there was a risk that the future crop yield would decrease in the north and increase in the south, and the risk area was constantly expanding. With a 2.0℃ rise in global temperature, the crop yield of the southern Songnen black soil sub-region would reduce by almost 10%. This finding will improve our understanding of the mechanisms underlying climate change and vegetation productivity dynamics, and is also helpful in the promotion of the risk management of agrometeorological disasters. 相似文献
11.
Sunyurp Park 《Singapore journal of tropical geography》2010,31(3):371-383
Hypertemporal MODIS time series data provide a unique opportunity to investigate a dynamic relationship between leaf phenology and the climatic pattern of diverse, cloud‐prone Hawaiian ecosystems. Harmonic analysis summarized the complex greenness signals of Hawaiian tropical ecosystems into two main phenological wave forms – a moisture‐limited and a light‐limited type. Greenness maximums occurred during the wet season in dry and mesic ecosystems, and during the dry season in wet forests. The magnitude and periodicity of greenness fluctuations were also rainfall‐dependent. The annual greenness amplitude increased with increasing mean annual precipitation (MAP) in dry and mesic ecosystems. In wetter environments where MAP was greater than 3000 mm, however, annual greenness amplitude decreased with MAP. Annual greenness periodicity was stronger in drylands than in wet forests, and it weakened as annual precipitation increased. This result shows that rainfall is less important as a limiting factor in wet forests than it is in drylands. Therefore, leaf phenology is not governed by rainfall seasonality as forest wetness increases in the region. 相似文献
12.
了解植被物候与城市化之间的关系对于认识人类活动对生态系统的影响至关重要。基于呼和浩特市近20 a MODIS的两种植被指数数据,利用动态阈值法提取了植被物候,结合城市化指标,研究了2001—2020年呼和浩特市植被物候对城市化的响应。研究表明：森林和灌木地返青期（Start of growing season,SOS）发生较早（平均值第132 d）,但其枯黄期（End of growing season,EOS）也较早（第265 d）。SOS较晚的是耕地（第168 d）,EOS较晚的是草地（第275 d）,表明研究区木本植物SOS和EOS均早于草本植物。人造地表植被物候年际变化较大,在SOS和EOS的物候变化率分别为每10 a提前4.1 d和推迟0.7 d。此外,以人造地表比率和城乡梯度信息（即从城市核心到周边农村地区的同心环）为城市化指标,探讨了呼和浩特市中心城区植被物候对城市化的响应。研究发现SOS随人造地表比率上升而提前,EOS则出现相反的趋势。从城乡梯度上看,在特定范围内,远离城市中心SOS波动上升,即距城市中心越远植被SOS越晚,而EOS逐渐下降,即距城市中心越远植被EOS越早。总之,不同的城市化指标显示了植被物候对城市化的非线性响应。 相似文献
13.
Monier M Abd El-Ghani 《Journal of Arid Environments》1997,35(4):673-683
The phenology of ten common desert plant species, representing the main life-forms in western Saudi Arabia, was studied in relation to air temperature, relative humidity, soil temperature, precipitation and soil water potential. Environmental data collected between 1989 and 1991 revealed a little year to year variation in precipitation and soil water potential. Six different patterns of phenological behaviour were detected among these species. The vegetative growth of most extended over a longer period in 1989 than in 1990, while their flowering activities were characterized by one prominent maximum. Fruiting patterns were usually parallel to flowering patterns, with maximum fruiting approximately 4–6 weeks after flowering. 相似文献
14.
基于蒙特卡洛生存分析探究东北森林物候的影响因素 总被引：1，自引：0，他引：1
植被是生态环境变化的指示器,分析植被物候的影响因素不仅有助于气候变化分析,提高区域气候模式的模拟精度,而且对于准确评估植被生长趋势、生产力以及全球碳收支均具有重要意义。基于遥感的植物物候监测已取得了长足的发展和进步,但当前利用大范围、长时间序列的遥感数据分析植被物候影响因素的研究尚不多,采用线性回归模型对非线性的植被物候影响因素进行分析可能存在偏误。因此,本文提出一种基于蒙特卡洛模拟的生存分析方法,对东北森林物候的影响因素进行量化分析。首先利用东北森林地区1982-2009年间AVHRR GIMMS NDVI数据,应用双Logistic曲线拟合方法对植被春季返青期（SOS）、秋季落叶期（EOS）及植被生长期（GSL）进行提取;然后基于蒙特卡洛模拟和生存分析构建植被物候影响因素分析模型;最后运用所构建模型探讨了东北森林区春季返青期、秋季落叶期的可能影响因素。结果发现：温度、降水和风力对中国东北森林关键物候期有一定影响,其中温度是春季返青期和秋季落叶期的最主要驱动因素,长期平均温度比短期内的温度突变对物候影响更显著,落叶期前的风速增加有可能使落叶时间提前;除了环境因素,春季返青早的年间秋季落叶倾向于更晚。研究表明,结合蒙特卡洛方法的生存分析可以较好地对物候期的影响因素进行定量分析,可为物候现象的归因分析提供一种新的方法。 相似文献
15.
气候变化背景下1981-2010年中国玉米物候变化时空分异 总被引：1，自引：0，他引：1
基于中国玉米种植区内114个农气站1981-2010年的长序列物候观测数据,量化分析了玉米8个连续物候期的时空分异特征和相应的生长阶段长度变化规律。结果表明：1981-2010年间,玉米生育期内平均温度和有效积温(GDD）呈现增加趋势,降水量和日照时数呈现减少趋势。气候变化背景下,玉米物候期发生了显著变化。春玉米物候期以提前趋势为主,包括西北内陆玉米区春玉米、西南山地丘陵玉米区春玉米;夏玉米和春夏播玉米各物候期在不同区域均呈现推迟的趋势,西北内陆玉米区夏玉米各物候期推迟的幅度大于黄淮平原夏玉米各物候期推迟的幅度。玉米物候期的变化改变了相应生长阶段的长度,中国春/夏/春夏播玉米营养生长期（播种期—抽雄期）呈现不同程度的缩短趋势,而对应的生殖生长期（抽雄期—成熟期）呈现不同程度的延长趋势;春玉米生育期（播种期—成熟期）延长,夏/春夏播玉米生育期缩短。 相似文献
16.
1982~1999 年我国东部暖温带植被 生长季节的时空变化 总被引：23，自引：1，他引：22
利用1982~1996 年5 个站点的植物群落物候观测数据和物候累积频率拟合法, 划分各站逐年的植被物候季节, 并确定各季节初日对应的当地归一化差值植被指数(NDVI) 阈值。 在此基础上, 通过对物候站各年NDVI 曲线的年型聚类分析和区内所有像元逐年NDVI 曲线的空间聚类分析, 实现植被物候季节的时空外推估计, 从而得到我国暖温带落叶阔叶林地区1982~1999 年植被物候季节初日和生长季节长度的时空格局。结果表明, 多年平均的植被物 候季节初日和生长季节长度呈现出主要随纬度和海拔高度变化的空间格局。在这18 年中, 整 个区域的物候春季初日以提前为主, 且以华北平原提前的趋势最为显著;夏季、秋季和冬季 初日以推迟为主, 也以华北平原推迟的趋势比较显著;因此, 华北平原植被生长季节呈显著 延长的趋势。本文揭示的植被物候季节初日的趋势变化与华北地区各季节气温的趋势变化基本吻合;植被生长季节的趋势变化特征与欧洲单种植物物候生长季节, 以及欧亚大陆和我国温带遥感植被生长季节的趋势变化基本一致, 但植被生长季节初、终日期和长度的趋势值明显大于后者, 表明该地区植物物候对于气候变暖的响应更加敏感。 相似文献
17.
西藏纳木错植物物候及其对气候的响应 总被引：4，自引：0，他引：4
利用纳木错流域1O种代表性植物2007年和2008年的物候观测资料,分析了植物生殖物候的基本特征及气候条件对其的影响.植物最早5月中旬进入开花期,大部分植物的盛花期在6月中旬至7月下旬,开花的最适温度范围为8.5-8.9℃,花期延续到9月下旬.从6月上旬开始,大部分植物进入果期,多数植物果期与花期重叠.纳木错具有高寒地带植物物候的普遍特征:生长期较短(5个月左右)、早花现象、晚花现象.同2007年相比,2008年雨季提前,虽然气温偏低,大部分植物花期和果期普遍缩短5 d左右,但物候期提前约20 d.植物物候的年际变化对气候变化,特别是对降水量的季节分配更敏感. 相似文献
18.
蒙古高原是中国重要的北方生态屏障。在全球气候变化的背景下,研究蒙古国植被物候变化特征对于认识蒙古国草地生态系统对气候变化的响应和促进区域畜牧业可持续发展具有重要意义。本研究利用非对称高斯拟合法对蒙古国2001—2019年MOD13Q1产品中的归一化植被指数（Normalized Differential Vegetation Index,NDVI）数据拟合,得到较为平滑的NDVI时间序列数据;基于TIMESAT平台,采用动态阈值法分析获得蒙古国连续19a植被物候数据。研究分析了蒙古国植被物候的空间分布及年际变化趋势,发现蒙古国植被返青期（Start of growing season,SOS）主要集中在110~150d,总体呈微弱推迟趋势,植被枯黄期（End of growing season,EOS）主要集中在270~310d,总体呈提前趋势,从而导致蒙古国生长季长度（Length of growing season,LOS）呈缩短趋势,且缩短时间最长可达2d以上。采用偏相关分析方法分析了植被物候对地形、降水、地表温度等地理要素的响应,表明蒙古国植被物候具有明显的空间异质性和海拔依赖性,不同植被物候对降水、地表温度（Land Surface Temperature,LST）的响应不同,SOS与日间LST呈显著正相关,EOS与夜间LST呈显著正相关,而LOS与年均降水呈显著负相关关系。 相似文献
19.
巴丹吉林沙漠腹地地温变化特征 总被引：2，自引：1，他引：1
以巴丹吉林沙漠苏木巴润吉林观测站地温与气象数据为基础,分析巴丹吉林沙漠腹地地温变化特征。结果表明：（1）巴丹吉林沙漠地温、气温日变化特征明显,最高值出现时刻为17：00左右,相对东部地区滞后3 h;不同季节地温与气温变化趋势基本保持一致,地温变化相对气温、太阳辐射明显滞后;（2）地温在11月末至2月降至0 ℃以下,深度60 cm下全年高于0 ℃,地温变化幅度随深度增加逐渐减小;（3）地温变化幅度直接由太阳辐射强度决定,但影响地温的环境因子存在季节性特征,春、秋、冬季主要影响因子为气温、太阳辐射及降水,气温和太阳辐射的影响具有连续性,降水则导致地温骤减,风速仅在夏季影响地温。 相似文献
20.
D.E. Fresnillo Fedorenko O.A. Fernández C.A. Busso O.E. Elia 《Journal of Arid Environments》1996,33(4):409-416
The phenology ofMedicago minimavar.minimaandErodium cicutariumwas studied at two different field sites in the Calden District (approx. 10 million ha), a temperate semi-arid phytogeographical region in central Argentina. One site had been protected from wild and domestic herbivores for the 6 previous years. The other adjacent site had been exposed to continuous grazing by cattle for several decades. A phenological key was made for each species in 1988, and this key was improved during the 1989 growing season when phenological observations were made every 1–3 weeks.The growth cycle ofM. minimaandE. cicutariumwas similar at the two studied sites. Initiation of the cycle occurred in autumn and appeared to be associated with soil water availability. Phenological patterns were very dynamic at the reproductive stage in both species. This stage started earlier and was faster inE. cicutariumthan inM. minima. The end of the growing season occurred during late spring, concomitant with high maximum air temperatures. Our results suggest that these species hasten their development when air temperature increases and soil water availability decreases. This could be an important strategy in these species which allows them to persist as seeds, and produce a new generation under favourable environmental conditions. 相似文献