共查询到20条相似文献，搜索用时 62 毫秒
1.
François Lebourgeois Nicolas Delpierre Eric Dufrêne Sébastien Cecchini Sébastien Macé Luc Croisé Manuel Nicolas 《European Journal of Forest Research》2018,137(3):349-365
We aimed at identifying which drivers control the spatio-temporal variability of fruit production in three major European temperate deciduous tree species: Quercus robur, Quercus petraea and Fagus sylvatica. We analysed the relations of fruit production with airborne pollen, carbon and water resources and meteorological data in 48 French forests over 14 years (1994–2007). In oak, acorn production was mainly related to temperature conditions during the pollen emission period, supporting the pollen synchrony hypothesis. In beech, a temperature signal over the two previous years eclipsed the airborne pollen load. Fruit production in Quercus and Fagus was related to climate drivers, carbon inputs and airborne pollen through strongly nonlinear, genus-specific relations. Quercus and Fagus also differed as regards the secondary growth versus fructification trade-off. While negative relationships were observed between secondary growth and fruit production in beech, more productive years benefited to both secondary growth and reproductive effort in oak. 相似文献
2.
Pollen flow from external sources is important for the conservation of tree species in fragmented forests or small populations, because it can be sufficient to prevent differentiation among them, and appears to be able to prevent the loss of their genetic diversity through genetic drift. In this study, we examined the genetic heterogeneity of pollen pools accepted by each Quercus semiserrata seed parent at the Khun Wang Royal Agriculture Research Center, Thailand, both within and among two mast fruiting years (2005 and 2007), using paternity analysis and analysis of molecular variance (AMOVA). The mating systems of the trees were also examined using the multilocus mating system model (MLTR), after determining the genotypes at eight microsatellite loci of 26 seed-trees and 435 seeds from 8 seed-trees in the 2 mast fruiting years. The average distance of effective pollen flow within the plot was estimated to be 52.4 m, and 95% of effective pollen was dispersed within 200 m, indicating that effective pollen flow is highly localized and that most effective pollen is contributed by near-neighbor trees. The proportion of effective pollen that immigrated from external sources was estimated to be 26.2%. The AMOVA analysis based on the pollen haplotypes showed that the pollen pools, both total and for each reproductive year, significantly genetically differed among the seed parents. Using a mixed mating model, the estimate of biparental inbreeding for the total population (tm − ts) was 0.013, indicating that a low proportion of mating occurred among close relatives. The effective number of pollen donors (Nep) was estimated to be 9.987 using the TwoGener model, or 10.989 using the mixed mating model. The effective number of pollen donors of seeds was higher in the mast fruiting year 2005 than in the other examined year, 2007. Consequently the allelic richness and genetic diversity of seeds produced in 2005 were higher than those produced in 2007. Overall, the results show that high outcrossing rates, high levels of gene flow from other populations and heterogeneity in the pollen received by an individual may enhance the ability of populations to maintain effective population sizes. Therefore, these processes may be sufficient to prevent loss of genetic diversity through genetic drift of Q. semiserrata at this study site. 相似文献
3.
Vinod Prasad KHANDURI 《中国林学(英文版)》2012,14(1):20-29
Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination,viz.flowering phenology,pollen production variability and pollen dispersal,for five successive years at two different locations (at the lower and higher elevations).The study reveals that elevation and the hour of the day are the main determinants of anthesis and microsporangium dehiscence,because both are related to temperature and humidity.The receptivity of ovulate cone strobili or female strobili occurred earlier at the lower elevation than at the higher elevation,with a longer receptivity period in the latter case.The phenology of male and female cones varied significantly between years and elevations.The determinations of pollen yield considered various sources of variability,i.e.,the number of pollen strobili per branch,strobili per tree,microsporangia per tree and pollen grains per tree.Each of these parameters revealed significant year-to-year and elevation effects.Year-to-year variation in the production of pollen cone and pollen grains with mass production after a three-year period revealed a three-year cycle of masting in pollen production in P.roxburghii.The pollen dispersal decreased quickly with distance from the pollen source.As a consequence,a distance of 600 m was proposed as a minimum to prevent contamination by pollen in the management of seed orchards.The results ultimately suggest that the ample production of pollen grains per tree along with flowering synchrony and long dispersal of pollen grains results in homogeneity in large populations. 相似文献
4.
Yasuharu Hoshino Hitoshi Yonenobu Koh Yasue Yoshihiro Nobori Takumi Mitsutani 《Journal of Wood Science》2008,54(3):183-188
We developed ring-width chronologies for living trees of Japanese beech at two forest sites on the northern-most part of Honshu
Island, Japan. A statistical threshold (running expressed population signal) yielded these site chronologies spanning 1853–1994
(142 years) and 1867–1994 (128 years). We examined two factors, climate and masting, that could affect the variations of radial
growth. The response function analysis revealed that the ring width correlated positively with July and August temperatures
of the previous growth year. The optimal radial growth of Japanese beech may largely depend on a warm previous summer with
above-average temperatures. The years of good masting coincided mostly with those showing abrupt growth depression, although
only the short-term records of masting were available.
Part of this work was presented at the 6th Pacific Regional Wood Anatomy Conference, Kyoto, December 2005, and the 7th International
Conference on Dendrochronology, Beijing, June 2006 相似文献
5.
以山东省泰安市徂徕山林场和重庆铁山坪林场为试验区,分别于2005年5月和2006年9月获取了低密度和高密度的LiDAR点云数据,分别进行了林分平均高的反演试验.通过两个试验区的对比,分析了不同点云密度对机载LiDAR数据反演林分参数的影响.结果表明:对于两种密度的点云数据,使用分位数法都可以很好地进行林分平均高的估计,高密度点云的反演结果略好一些,但二者结果差异不大;高密度的点云可以进行更小尺度的林分高估计和单木树高的估计,从而可以减少甚至避免对实地树高测量的依赖. 相似文献
6.
在吉林省长白山地区模拟检测了大气CO2浓度升高对土壤氮循环关键过程的影响。试验采用完全随机区组设计的开顶箱系统模拟环境CO2和高浓度CO2,起始于1999年春。选取长白山特有树种长白松(Pinus sylvestris var.sylvestri-formu),种子播种于1999年5月份,萌芽后开始CO2熏蒸处理。CO2熏蒸处理始于每年4月末止于10月末。分别在2006年6月、8月和2007年6月采集土壤样品,并检测土壤硝化酶(NEA)、反硝化酶(DEA)和固氮酶活性。结果表明,高浓度C02使土壤硝化酶(NEA)活性显著提高,提高幅度2006年6月为30.3%,2006年8月为30.9%,2007年6月为11.3%;土壤反硝化酶活性(DEA)在2006年6月份(P<0.012)和2006年8月份(P<0.005)被C02浓度升高显著抑制;在整个研究过程中没有发现C02浓度升高对固氮酶活性产生显著影响。因此,本研究认为C02浓度升高显著影响了土壤硝化酶(NEA)和反硝化酶活性(DEA)。图3表1参44。 相似文献
7.
Rui Li Ruiping Hou Kebin Zhang Yunfang Liu Zhen Bian 《Frontiers of Forestry in China》2008,3(3):342-346
Vegetation fluctuation is an important part of vegetation dynamics. The characteristics of vegetation fluctuation are quite
different between grassland and forest communities. By inferring from ecologic and statistical information, grassland vegetation
fluctuation and its fluctuation ratio were defined, and an equation for the fluctuation ratio was established for the first
time with the fluctuation coefficients specified via expert weighting method. The quantitative grassland vegetation fluctuation
and its fluctuation ratio between the years 2002 and 2006 in Yanchi County, Ningxia, northwestern China, in the northern farming-pastoral
ecotones, were studied. Results showed that the largest positive fluctuation ratio of 0.685, implying the best vegetation
growth in recent years occurred in 2003, while the most negative fluctuation ratio of −1.098, i.e., the worst vegetation growth
during this period, occurred in 2005.
__________
Translated from Journal of Beijing Forestry University, 2007, 29 (6): 129–133 [译自: 北京林业大学学报] 相似文献
8.
9.
Andreas Bolte Lutz Hilbrig Britt Grundmann Friederike Kampf Jörg Brunet Andreas Roloff 《European Journal of Forest Research》2010,129(3):261-276
It is believed that European beech (Fagus sylvatica L.) will increase its competitive ability at its northern range margin in Scandinavia due to climate change. In mixed old-growth
forests of beech and Norway spruce (Picea abies (L.) Karst.) at Siggaboda nature reserve (southern Sweden), stand structure characteristics were sequentially recorded in
the years 2004, 2005 and 2007 as well as growth in stem diameter using tree-coring analyses. Using these measurements, we
studied the effects on stand dynamics of an extreme storm event (2005 “Gudrun” hurricane), drought and heat (mid-summer 2006,
spring 2007) and subsequent bark beetle attacks on spruce (growing season 2007), overlaid with warming tendencies. The storm,
which caused disastrous damage in many stands nearby, had comparatively little impact on the structure of the spruce–beech
stand. All together, only 32 trees (19 spruces, 10 beeches, 3 other species) per hectare were thrown or broken mainly in the
leeward direction (NE) or impacted by secondary damage by uprooted neighbour trees; this represents 7% of the total tree number
and 11% of the growing stock. Diameter and height structure did not change significantly. However, the 2006 drought and the
2007 attack of biotic agents changed the stand structure and composition strongly due to the death of about 19% of the dominating
older spruce trees that accounted for 35% of total stand volume. This resulted in a considerable increase in beech’s contribution
to stem number (4% increase) and wood volume of the living stand (7% increase). A comparison of diameter growth of beech and
spruce during the periods 1894–1949 and 1950–2005 showed a distinct decrease in growth superiority of spruce during the last
50 years. These results support the idea of a northward migration of European beech as a nemoral tree species in Sweden, due
to a higher tolerance to the abiotic and biotic threats accompanying climate change and an increased competitive ability compared
to boreal tree species Norway spruce. 相似文献
10.
华北落叶松传粉生物学的研究 总被引：7，自引：1，他引：7
本文研究了华北落叶松雌雄球花在树冠上的分布和树冠周围花粉密度变化规律、传粉机制、胚珠接收花粉量及结实状况等。雌球花主要分布在树冠中上部2－4龄枝上，雄球花分布范围较广，且常与雌球花混生；树冠周围花粉密度与雄球花的分布密切相关，中部最大，依次向上下两端减少。依据雌球花形态特征的变化，可将传粉期为5个阶段，整个期间无传粉滴出现，由球被顶端大裂片的珠被毛接收花粉。最佳传粉期约为2天。胚珠平均接收4粒花粉，虽然胚珠接收的花粉数与饱满种子的产量有一定的关系，但并不是造成空粒的主要原因。此外，讨论了不同授粉方式对种子产量的重要意义。 相似文献
11.
A study was conducted to determine the effects of elevated CO2 on soil N process at Changbai Mountain in Jilin Province, northeastern China (42°24′N, 128°06′E, and 738 m elevation). A
randomized complete block design of ambient and elevated CO2 was established in an open-top chamber facility in the spring of 1999. Changpai Scotch pine (Pinus sylvestris var. sylvestriformis seeds were sowed in May, 1999 and CO2 fumigation treatments began after seeds germination. In each year, the exposure started at the end of April and stopped at
the end of October. Soil samples were collected in June and August 2006 and in June 2007, and soil nitrifying, denitrifying
and N2-fixing enzyme activities were measured. Results show that soil nitrifying enzyme activities (NEA) in the 5–10 cm soil layer
were significantly increased at elevated CO2 by 30.3% in June 2006, by 30.9% in August 2006 and by 11.3% in June 2007. Soil denitrifying enzyme activities (DEA) were
significantly decreased by elevated CO2 treatment in June 2006 (P < 0.012) and August 2006 (P < 0.005) samplings in our study; no significant difference was detected in June 2007, and no significant changes in N2-fixing enzyme activity were found. This study suggests that elevated CO2 can alter soil nitrifying enzyme and denitrifying enzyme activities.
Foundation project: This research was supported by the National Natural Science Foundation of China (No. 90411020) and Major
State Basic Research Development Program of China (973 Program) (2002CB412502). 相似文献
12.
The aim of this study is to follow each development stage of inflorescence in order to understand the biological feature of flowering and the development of male gametophyte in Anthurium andreanum ““Arizona““ and to try to find the optimum conditions for its pollination. The methods of dissection and paraffin section were adopted to examine the structural characteristics of anthurium‘s tiny floret and the development of the microspore. All the florets of the anthurium arrange on the rhachis helically subtended by a colorful bract. Each tiny floret has one gynoecium, four tepals and four stamina. The bract and the florets show different colors during the whole blooming period. The ovary is bicarpellary and has two locules, each of which has one anatropous ovule. The placenta is of a central placentation type. The stylar canal cells not only can produce the secretory mucilage but also can release their own cytoplasm caused by their self-disintegration before the pistil reaches its maturity. The wall of the anther is composed of four layers: epidermis, endothecium, middle layer and tapetum. The tapetal cells and the middle layers‘ cells degenerated completely during meiosis of microsporocytes. The pollen grains were 2-celled at the time of anther dehiscence. Early morning, when the inflorescences stay at their fiRb development stage, is the optimum opportunity for pistil to get pollen grains. The pollen-collection should be done at the end of the seventh stage. 相似文献
13.
The objective of the study was to investigate in vivo interspecific pollination success between Pinus radiata, P. maximinoi, P. oocarpa and P. tecunumanii. Pinus radiata was control pollinated with pollen lots of P. maximinoi, P. oocarpa and P. tecunumanii in a P. radiata seed orchard at Karatara (Southern Cape, South Africa). Pollination success was determined by counting the number of visible ovules, pollen grains inside and outside P. radiata ovules, as well as pollen tubes visible inside P. radiata ovules. Conelets were harvested and studied at eight time intervals, including 24 h after pollination, and weekly for 7 weeks after pollination. Histology studies with a standard fixation-dehydration-embedding sequence and paraffin wax method were used to determine the number of visible pollen grains inside versus outside the ovules and number of pollen tubes. Results indicated that pollen grains did sift through the cone scales within 24 h after pollination. However, P. radiata differed significantly (time by type of cross interaction) from the other three hybrid combinations in terms of number of visible ovules, visible pollen grains inside and outside of the ovules as well as pollen tubes, confirming limited interspecific hybridisation success. Future studies need to determine the percentage of fertile ovules in cross combination as a tool in predicting pollination success. 相似文献
14.
The Great Spotted Woodpecker Dendrocopos major （L.）, one of the natural predators of Anoplophora glabripennis （Motsch.） （Coleoptera： Cerambycidae）, is resident to Wulate Qianqi County of the Inner Mongolia and widely found in shelter plantations. In August 2005 and 2006, 174 and 153 nest-cavities of Great Spotted Woodpeckers were found respectively in Wulate Qianqi County and 22 breeding nest-cavities were investigated in 2007. The results showed that mostly willow species were selected for nesting by the Great Spotted Woodpecker, but mature poplar trees also could be chosen. Nest cavities were often found with a protuberance above the cavity entrance or with a downward sloping gradient, or both. The selection of the height of the nest-cavity height was not significant. The vertical diameter of the nest-cavity entrance （VDE） and the horizontal diameter of the nest-cavity entrance （HDE） ranged from 5.0 to 5.8 cm. The results also indicated that the compass orientation of more than 60% of nest-cavities were towards the north, northeast and east. This study suggests a convergence of some nest-cavity characteristics of the Great Spotted Woodpecker in shelter plantations and will help us to make artificial nest for conserving the woodpecker and, as well, use the bird for controlling pests. 相似文献
15.
The pollen morphology of 7 taxa of three genera of the subfamily Caesalpinioideae in Korea was investigated by light microscope
(LM) and scanning electron microscope (SEM). The pollen grains of this subfamily are monads, prolate spheroidal or subprolate,
and trizonocolporate. Sculpture pattern is reticulate or perforate. Based on sculpture pattern, colpus width and grain shape
at equatorial view, 4 major pollen types of the subfamily are discernible;Caesalpinia, Cercis, Gleditsia I, andGleditsia II.
This study was supported by Korean Academic Promotion Foundation.
During this study, Botanic Garden of Kyoto University, Japan, Anmyondo Arboretum and Dr. Byongsoo Kang at Dongkuk Univ., Korea
provided materials and informations which are greatly appreciated. 相似文献
16.
Michael A. Wulder Stephanie M. Ortlepp Joanne C. White Nicholas C. Coops Sam B. Coggins 《Forest Ecology and Management》2009,258(7):1181-1187
Since 1999, the mountain pine beetle (Dendroctonus ponderosae Hopk. [Coleoptera: Scolytidae]) has impacted over 13 million hectares of pine forests in western Canada. Successful mitigation of the beetle depends on the accurate and timely identification of currently infested trees and on sustained control activities over several successive years. We monitored the success of mitigation activities in reducing damage caused by mountain pine beetle at two sites (A and B) on the leading edge of the current beetle epidemic in western Canada. Using three years of digital high spatial resolution aerial imagery (2006–2008) and one season of field measurements (2008), we estimated retrospective ratios of trees attacked by beetle in the current year (green attack) to trees attacked in the previous year (red attack), hereafter referred to as G:R. Our results indicate that mitigation activities slowed the rate of population growth, with G:R found to be decreasing or stable over sites A and B while mitigation was ongoing in 2005 and 2006 (site A 1.06:1; site B 0.32:1). When mitigation was discontinued over site A in 2007, the G:R increased markedly (1.94:1), while continued mitigation at site B in 2007 further reduced the G:R (0.22:1). Despite the cost associated with mitigation, its efficacy is rarely assessed and even more rarely documented. The approach presented herein enables a sample-based appraisal of mitigation efforts. 相似文献
17.
油杉花粉个体发育与传粉过程 总被引：2，自引：0，他引：2
应用常规压片法和整体染色透明法对油杉小孢子的发生和雄配子体的发育过程进行观察,研究其传粉生物学特征.结果表明:油杉小孢子母细胞在1月26日-2月5日进行减数分裂,在减数分裂过程中胞质分裂为同时型,四分体排列方式多为左右对称型;小孢子经过连续4次有丝分裂后,于2月底形成5-细胞型的成熟花粉粒,成熟花粉由两个原叶细胞、一个不育细胞、一个精原细胞和一个管细胞组成,其中两个原叶细胞在花粉成熟时已退化;经TCC法检验,花粉生活力为92.6%;3月1日-8日为油杉传粉期,3日-5日为传粉高峰;在传粉期间,胚珠珠孔端无传粉滴产生,珠孔端耳状结构边缘粘附有花粉.虽然花粉母细胞发育表现出不同步现象,产生少数具3个或4个气囊的异形花粉,但从小孢子的发生及雄配子体发育的整个过程看,未见败育或其他异常现象,能形成大量正常的成熟花粉,因此,花粉个体发育不是影响油杉结籽率低的主要因素,而造成油杉球果结籽率低的主要原因可能在于其传粉过程. 相似文献
18.
19.
To investigate the roles of protein phosphatases 1 and 2A in the development of pollen tubes of Picea wilsonii Mast., pollen grains were cultured in standard medium in the presence and absence of the protein phosphatase inhibitors okadaic acid and calyculin A. At nanomolar concentrations, these compounds blocked pollen tube growth, causing abnormal morphologies of the pollen tubes. Studies with Fluo-3 revealed that the inhibitors reduced the pollen-tube tip-to-base cytoplasmic calcium (Ca(2+)) gradient and arrested extracellular Ca(2+) uptake. The transmission electron microscope observations indicated that the fusion of paramural bodies with plasma membranes occurred frequently in the tip and sub-tip regions of control pollen tubes, but fusion rarely occurred in inhibitor-treated pollen tubes. Staining with aniline blue showed that callose accumulated in the tip regions of inhibitor-treated pollen tubes. Immunolabeling of pollen tubes revealed that acidic pectin epitopes recognized by the monoclonal antibody JIM5 were present in the tip region and on the flanks of the sub-tip in normal pollen tubes. In inhibitor-treated pollen tubes, these epitopes existed only in the extreme tip region and at higher concentrations than in control pollen tubes. The esterified pectin recognized by JIM7 was located preferentially at the extreme tip region in normal pollen tubes, but at basal sites in inhibitor-treated tubes. Fourier transform infrared (FTIR) analysis further confirmed the changes in acidic and esterified pectin distributions and their relative contents. These results suggest that protein phosphatase 1 or 2A, or both, are involved in the regulation of Ca(2+) uptake across the plasma membrane, in exocytotic activity and in the biosynthesis of cell wall components, all processes that occur in the tip region of pollen tubes and that control pollen tube development. 相似文献
20.
江西庐山自然保护区爬行动物多样性调查与分析 总被引：2，自引：0，他引：2
为促进自然保护区的管理,加强生物多样性的保护,申报国家级自然保护区,于2005年8月中旬、2006年5月下旬~6月上旬、2006年7月下旬,前后3次对江西庐山自然保护区爬行动物资源进行了实地调查.结果表明:江西庐山自然保护区现已记录的爬行动物有42种,隶属3目9科,占江西省已记录80种爬行动物的52.50%,比庐山爬行动物原记录新增10种,其中32种属东洋界种类,10种属广布种、无古北界种类,42种爬行动物均属"国家保护的有益的或者有经济、科学研究价值的陆生野生动物".最后同江西省其它6个自然保护区的爬行动物进行了物种相似性系数比较和聚类分析,并提出了5条保护建议. 相似文献