秦岭中段不同坡向锐齿栎种子雨、土壤种子库与幼苗更新

以秦岭中段不同坡向(阳坡、半阳坡、半阴坡及阴坡)锐齿栎天然林为对象,对锐齿栎种子雨、种子库的数量、质量动态以及幼苗发育过程进行研究.结果表明: 锐齿栎种子雨一般从8月中旬开始,9月中下旬到10月上旬达到高峰期,11月中上旬结束;不同坡向的种子雨降落历程、发生时间和组成不同;半阳坡种子雨强度最大,为134.13粒·m^-2,其余大小依次为阳坡、半阴坡、阴坡;阳坡种子雨降落时间最早、持续时间最长,高峰期持续时间也最长,阴坡种子雨降落时间最晚、持续时间最短,高峰期持续时间也最短;种子活力及成熟种子占其种子雨的比例大小顺序为半阳坡>阳坡>半阴坡>阴坡.从种子雨降落结束到翌年8月,各坡向土壤种子库总储量大小顺序均为半阳坡>阳坡>半阴坡>阴坡;各坡向的土壤种子库中成熟、未成熟、被啃食种子数量和种子活力均随时间变化呈递减趋势,而霉烂种子数量增加;各坡向土壤种子库中的种子均主要集中在枯落物层,其次为0~2 cm土层,而在2~5 cm土层中只有极少量种子存在.4种坡向中锐齿栎幼苗的密度差异显著,半阳坡幼苗最多,其余依次是阳坡、半阴坡和阴坡.半阳坡更适合锐齿栎种子的萌发和幼苗生长.     

高寒草甸植物群落多样性及土壤因子对坡向的响应

坡向是山地的重要地形因子之一,是导致植物群落物种多样性和结构特征产生差异的间接环境因子,它通过改变光照、温度、水分和土壤养分等生态因子而对生物多样性、植物生长发育、生产力以及生态系统功能等产生重要影响.本文研究了青藏高原高寒草甸不同坡向上的植物群落物种多样性变化特点及与环境因子的关系.结果表明:阳坡-阴坡生境梯度上,土壤含水量的变化趋势为阴坡＞半阴半阳坡＞阳坡,土壤温度和光照度的变化趋势为阳坡＞半阴半阳坡＞阴坡,土壤养分含量除了全氮和有机碳为阴坡＞阳坡＞半阴半阳坡外,其他养分总体呈现阴坡＞半阴半阳坡＞阳坡.阳坡-阴坡生境梯度上植物群落物种多样性的变化趋势为:阴坡＞半阴半阳坡＞阳坡,阳坡的主要功能群是禾草类,而阴坡则是杂草类.相关分析表明,在阴阳坡微生境梯度上,光、热、水、土均影响了物种多样性的变化,而其中土壤含水量是引起这种变化的主要因素.     

甘南高寒草甸植物功能性状和土壤因子对坡向的响应

研究甘南高寒草甸不同坡向植物功能性状和土壤因子及二者的关系.结果表明:禾草是阳坡的优势功能群,杂草和灌木是阴坡的优势功能群.阴坡植物群落生物量显著大于阳坡,但叶片氮磷比显著小于阳坡.不同坡向上,除叶片氮含量变化不显著外,叶片磷含量、比叶面积和物种平均高度大小均为阴坡＞偏阴坡＞阳坡.植被的生存策略在阴阳坡发生了很大变化,这种变化可以从不同坡向植物叶性状的差异和优势功能群的改变反映出来.土壤温度大小为阳坡＞偏阴坡＞阴坡;土壤含水量大小为阴坡＞偏阴坡＞阳坡;除了全磷含量自阳坡到阴坡出现递增趋势外,土壤全氮、有机质和速效氮的大小均为阴坡＞阳坡＞偏阴坡.比叶面积、物种平均高度与土壤全磷、有机质和土壤含水量均呈显著正相关,与土壤pH呈显著负相关.土壤水分和土壤pH共同影响着高寒草甸不同坡向植物功能性状和土壤养分的分布.     

桂林岩溶石山植物群落植物功能性状对不同坡向环境因子的响应

该研究以桂林岩溶石山不同坡向的植物群落为对象,探讨植物功能性状(比叶面积、叶绿素含量、木材密度和环境因子随坡向的变化规律。结果表明:比叶面积和叶绿素含量为阴坡>半阴坡>阳坡,阴坡和半阴坡分别与阳坡差异性显著;木材密度为阴坡<半阴坡<阳坡,阴坡、半阴坡分别与阳坡差异性显著。土壤有机质含量表现为阴坡大于阳坡,且阴坡与阳坡差异性显著;土壤全磷、土壤有效磷均表现为阳坡含量最高,且阴坡与阳坡差异性显著;土壤有效钾、土壤全钾则分别为阴坡、半阴坡含量最高,土壤全钾含量在各坡向上差异均显著,而土壤有效钾则为阴坡、半阴坡与阳坡均差异性显著。回归分析表明群落水平比叶面积在阴坡和半阴坡上与土壤有机质含量呈显著负相关;群落水平叶绿素含量与土壤全磷含量和土壤有效钾含量在阴坡上呈显著正相关;在不同坡向梯度上群落水平木材密度与环境因子无相关性。群落水平上植物功能性状随坡向的变化规律,反映了岩溶石山植物群落构建过程中环境对功能性状的筛选效应。     

桂林岩溶石山灌丛植物叶功能性状和土壤因子对坡向的响应

植物功能性状反映了植物对生长环境的响应和适应,是连接植物与环境的桥梁,研究植物功能性状特征及其随坡向梯度的变化规律,对认识不同微气候生境下植物群落空间格局形成及适应机制具有重要意义。以桂林岩溶石山灌丛植物为研究对象,分析了灌木群落水平上植物叶功能性状与环境因子关系随阴坡-阳坡梯度的变化规律。结果表明:比叶面积为阴坡大于阳坡,叶干物质含量和叶片厚度为阳坡大于阴坡;土壤含水量、有机质含量、总有机碳含量和有效氮含量为阴坡大于阳坡,土壤温度和土壤全氮含量为阳坡大于阴坡;多元逐步回归分析表明,影响群落水平植物叶功能性状的主要环境因子随阴坡-阳坡梯度而发生显著的变化。在阴坡上,对比叶面积影响显著的是土壤有效氮含量,对叶干物质含量影响显著的是土壤温度和土壤总有机碳含量。而在阳坡上,对比叶面积影响显著的环境因子是土壤含水量和土壤pH值,对叶干物质含量影响显著的环境因子是土壤全氮含量,对叶片厚度影响显著的环境因子是土壤温度、土壤全氮含量和土壤全磷含量。同一叶功能性状在阴坡-阳坡梯度上受到不同环境因子的控制,同时各叶功能性状又能够对阴坡-阳坡所处特殊生境产生一定的适应性。     

火烧迹地木炭对兴安落叶松种子萌发的影响

通过对大兴安岭兴安落叶松火烧迹地木炭的野外调查和取样,分别选取不同来源（兴安落叶松,白桦,灌木,草本）的木炭,以及不同火烧时间（当年,1年,4年,5年）的木炭,研究不同种类木炭浸提液,以及相同种类不同火烧时间木炭浸提液对兴安落叶松种子萌发的影响。研究结果发现,不同来源、不同时间的木炭对兴安落叶松种子的萌发均有显著性的影响,但作用力的方向和大小也各不相同,这说明木炭对种子萌发的影响因素非常复杂。     

辽宁省长白落叶松人工林立地分类研究

利用通径分析(PA)、主成分分析(PCA)、典范分析(CA),筛选影响长白落叶松(Larisolgensis)生长的主导因子和研究地形、土壤、林木三者相互关系。结果表明,坡向、土壤质地、土壤厚度是主导因子;坡向与土壤质地、土厚、土壤有机质密切相关。利用生态学的立地分类方法,将辽宁东部长白落叶松人工林划分为3个立地类型组,14个主要立地类型。阴坡立地类型组有厚层、中层粉砂壤土类型和厚层、中层壤质土类型以及厚层粘壤土类型;半阴、半阳坡立地类型组有厚层、中层粉砂壤土类型,厚层、中层壤质土类型,中层砂质土类型和薄层土立地类型;阳坡立地类型组有厚层、中层、薄层土立地类型。     

岷江干旱河谷灌丛α多样性分析

通过对岷江干旱河谷植被及其环境因子的系统取样调查 ,研究了该地区植物群落的α多样性及其与环境因子的关系。土壤、植被、地形三者之间的典范相关分析结果表明 ,三者两两之间均存在着较高的相关性。土壤因子与地形因子之间 ,海拔和坡向起较大的作用 ,主要影响土壤中的全氮、有机质和土壤含水量 ;地形因子和植被之间 ,海拔和坡向影响灌木层的多样性和盖度 ;植被和土壤因子之间 ,土壤中的全氮量、有机质和土壤含水量影响灌木层的盖度和多样性。随着海拔的增加 ,草本和灌木群落的多样性都呈现出先增加后减小而后又增加的趋势 ,草本层的α多样性明显高于灌木层的α多样性 ,草本层和灌木层均在14 0 0～ 16 0 0 m和 2 0 0 0～ 2 2 0 0 m两个海拔段有较高的α多样性 ;华帚菊 -小黄素馨灌丛、金花小檗 -忍冬灌丛、绣线菊灌丛有着较高的多样性 ,西南野丁香灌丛、莸灌丛、小马鞍羊蹄甲 -白刺花灌丛的群落多样性较低 ;样带的多样性 ,灌木层 :样带 3>样带 1>样带 2 ,草本层 :样带 1>样带 3>样带 2 ;不同坡向的多样性 ,灌木层 :阴坡 >半阴半阳坡 >阳坡 ,草本层 :半阴半阳坡 >阴坡 >阳坡 ;不同坡形上的多样性 ,无论是灌木层还是草本层 ,多样性大小为凹坡 >平坡 >凸坡 ;灌木层和草本层在不同坡位上的多样性大小均为上     

中度火干扰对兴安落叶松林土壤呼吸的影响

通过测定中度火干扰后塔河地区兴安落叶松(Larix gmelinii)林生长季土壤呼吸(R_s),并进一步探究火干扰后影响土壤呼吸变化的主要环境因子。选择在塔河林业局火烧4年后兴安落叶松林中度火烧迹地设置样地,选择临近未过火区域设置对照样地。土壤呼吸通量用LI-8100进行测量,土壤异养呼吸(R_h)采用壕沟法进行测量。火烧迹地与未火烧对照样地生长季土壤呼吸速率平均值分别为(3.67±1.03)μmol CO_2m~(-2)s~(-1),(4.21±1.25)μmol CO_2m~(-2)s~(-1)。火烧迹地土壤呼吸速率显著降低(P0.05)。生长季土壤呼吸组分的动态变化表明,土壤呼吸速率的降低是因为土壤自养呼吸(R_a)显著降低导致的(P0.05)。温度是控制这一地区生长季土壤呼吸变化的主要环境因子。与对照样地相比,火烧迹地土壤呼吸的变化与土壤温度具有更强的相关性。塔河地区兴安落叶松林火烧迹地和未火烧对照样地Q_(10)分别为5.85±1.06,4.25±1.19,火干扰后Q_(10)显著增加(P0.05)。研究结果表明:在全球气候变化的背景下火干扰后中国塔河地区兴安落叶松林生态系统对温度的变化更为敏感。本研究结果将为研究中国塔河地区火干扰后碳循环变化提供数据支持。     

微地形对大西沟新疆野杏萌发层土壤因子的影响

野杏是新疆野果林的主要建群种和种质资源树种。野杏在种子萌发成苗期,幼苗的根系主要分布在0—15 cm土层中。为了阐明坡向、坡位、坡度和坡形等微地形因子对野杏种子萌发层土壤特征和养分分布的影响,在新疆伊犁州霍城县大西沟的封育野果林内(44°26′01.09″—44°26′17.12″N,80°46′27.49″—80°47′03.26″E)设置样地,测定0—15 cm土层的土壤砾石、酸碱值、有机质和全氮、全磷、全钾、水解性氮、有效磷和速效钾含量,分析各土壤因子和地形因子的关系。结果表明:(1)东北坡土壤养分含量较高,其土壤砾石含量、酸碱值、有机质、全磷、水解性氮和速效钾含量与东南坡、南坡皆存在显著差异(P0.05),阴坡的土壤有机质、全氮、有效磷和速效钾含量都高于阳坡,不同坡向的土壤特征和养分分布存在显著差异(P0.05);(2)不同坡位的土壤有机质、全氮、全磷和有效磷含量均表现为中坡位下坡位上坡位,土壤砾石、全钾和速效钾含量均呈现上坡位中坡位下坡位,全钾、全磷和有效磷含量在同坡位分布较均匀,不同坡位的土壤特征和土壤养分分布无显著差异(P0.05);(3)不同坡度下的土壤水解性氮和有效磷含量是缓坡中坡缓中坡陡坡,土壤砾石、酸碱值、全氮、水解性氮、有效磷和速效钾含量有显著差异(P0.05),陡坡土壤有机质、全氮、水解性氮和有效磷含量均低于其他坡度,而土壤砾石、土壤酸碱值和全钾在陡坡土层中含量最高,缓坡与缓中坡的土壤养分含量丰富,陡坡较为贫瘠,坡度对土壤特征和土壤养分分布有显著影响(P0.05);(4)不同坡形下的土壤砾石、全钾、水解性氮、有效磷和速效钾含量是凸形坡凹形坡直线坡,不同坡形下的土壤特征和土壤养分(除全钾和速效钾)均存在显著差异性(P0.05)。野果林地形因子对野杏萌发层土壤特征和土壤养分分布有显著影响,东北坡、中坡位、缓坡和凸形坡土壤养分含量较为丰富,是适宜野杏萌发的地形。研究结果可为探究影响野杏种子萌发和生长的气候与土壤水热等因子奠定良好基础。     

不同年龄香果树种子雨和种子库及其更新特征

对宝天曼自然保护区香果树种子雨、土壤种子库进行了观测,并进行不同微生境播种实验,研究其种子萌发及幼苗生长动态。结果表明:(1)不同龄级香果树种子雨持续时间及其高峰期有所不同,种子雨强度存在极显著差异。(2)20~50龄级香果树的种子饱满率、土壤种子库中种子密度均显著低于其他龄级,但其不同类型种子的水平和垂直分布规律一致;大约80%的香果树种子在其萌发前消失,剩余种子中以霉烂种子密度最高(9.81粒·m-2),饱满种子密度最低(1.94粒·m-2)。(3)野外育苗实验表明,不同龄级香果树所产饱满种子的萌发率及幼苗存活率差异不显著,其种子萌发率约为16.93%,但仅有3.86%的幼苗寿命超过5个月;不同微生境对香果树幼苗存活率产生显著影响,林窗是其最适宜微生境。研究认为,人工采集香果树种子,于次年4月份在原生境下播种;清理母树冠下和冠缘的地被物,增加林缘空地地被物覆盖度,以减少香果树种子的损失,改善香果树种子萌发和幼苗生长的光照条件,以利于幼苗根系的生长,促进香果树的自然更新。     

Influence of temperature on fractional composition of proteins and respiration of germinating seeds of Gmelin and Siberian larch

The influence of optimal and contrasting temperatures on the fractional composition of proteins and respiration of germinating seeds of Gmelin larch (Larix gmelinii (Rupr.) Rupr.) and Siberian larch (Larix sibirica Ledeb.) was revealed. The dominance of globulins (salt-soluble fraction) and insoluble proteins was noted in viable air-dry seeds of larch. Optimal and contrasting temperatures of germination of seeds caused significant changes in the content and dynamics of separate fractions of protein, the contrasting temperatures causing greater changes: increasing in the content of insoluble proteins, intense consumption of globulins at separate stages of germination. Respiration of the seeds during germination at contrasting temperatures also increased more than at an optimal temperature. Thermal regime of germination affected the character of relations between the respiration rate and contents of different protein fractions.     

Spatial variation of seedling distribution in an east Mediterranean pine woodland at the beginning of post-fire succession

Most of the area in pine woodlands is occupied by perennial seeders that regenerate from seeds in the first winter after the fire and by annuals. Control of the germination in the regenerating vegetation after wildfire is therefore a primary ecological component of the post-fire succession in this ecosystem. The aim of the study presented here was to determine the distribution of Pinus, Cistus and other plants seeds around burned Pinus halepensis trees, and to measure the conditions related to seed germination in the upper soil layers in the same locations. The study was carried out in a 50-year old planted Pinus halepensis woodland that was burned down by a wildfire in July 1995. The variation of seedbank density was determined by collecting samples under the canopies of burned trees and in a nearby open area. Pine seedbank density decreased and that of Cistus and annuals increased with increasing distance from the burned trunks. Most pine seeds were present in the ash layer while those of the other plants were in the soil. In situ germination experiments showed that seedling density decreased with distance from the burned trunks while the proportion of pines in the seedling population increased. This was a result of seedbank variation and germination inhibition by the high pH conditions caused by the ash. The establishment of sparse pine seedling under the dead tree canopies insured their rapid development without interference by other plants and played a key role in the regeneration and stability of the pine woodland community. The concomitant mass germination of the perennial seeders in the rest of the area prevented invasion by annuals.     

Comparative seed biology and co-existence of two fynbos shrub species

Abstract. Fire-prone fynbos communities include numerous species which are difficult to distinguish in terms of conventional niche axes since they are morphologically similar and share the same broad life-history traits. These species compete for space after each fire and lottery theory predicts that those with dissimilar per capita regeneration would not co-exist in the long-term. We studied seed production, soil seed bank dynamics, germination and post-fire seedling establishment and mortality of two obligate reseeding, morphologically similar shrubs which co-occur in dune fynbos throughout the southwestern Cape. Passerina paleacea produced 30 x more plump seeds and maintained soil seed banks between 1.5 x (pre-dispersal) and 2.6 x (post-dispersal) times larger than Phylica ericoides. Seeds of both species showed a high degree of dormancy although germination was stimulated by direct fire-related cues for Phylica only. Approximately 4 x more Passerina seedlings than Phylica seedlings were counted at the end of the winter germination period after a mild autumn fire. However, seedling mortality in the first five months of the dry summer was more than twice as high for Passerina than for Phylica. We suggest that the long-term co-existence of these two species does not result from similar post-fire regeneration success but rather from population instabilities arising from differential regeneration in relation to fire regime. The results predict that hot fires followed by dry summers would favour Phylica over Passerina as the former has fire-stimulated germination and greater drought tolerance; cool fires followed by moist summers would favour Passerina.     

海南霸王岭陆均松种子雨和土壤种子库特征

为了解陆均松(Dacrydium pierrei)的自然更新能力,对海南霸王岭陆均松进行为期3年的种子雨、种子库及幼苗幼树观测,并分析其与环境因子的关系。结果表明,陆均松种子雨和种子库有效种子数量太少并存在季节性差异;其结实存在大小年现象;种子雨的扩散密度随着距母树距离的增加而逐渐减少;土壤种子库种子数量在枯枝落叶层所占比例最大,但有活力种子数量极少。幼苗幼树适宜生存的海拔范围为800~1 400 m,经度、纬度、坡度与幼苗幼树分布有明显相关性。因此,选择适宜季节采摘种子,提高种源数量和质量,清除林下枯枝落叶,增加种子萌发能力等以减少陆均松更新的限制条件的人工抚育措施应适当考虑。     

Seed rain and soil seed bank of Picea asperata Mast. in subalpine coniferous forest of western Sichuan,China

Abstract

Dragon spruce (Picea asperata Mast.) is widely planted on clear-cuts from natural subalpine coniferous forests in western Sichuan. To assess the natural regeneration potential of this species in spruce plantations of different ages, field studies on the seed rain, seed bank, and seedling recruitment were conducted in 20-year, 30-year, and 60-year plantations, and in a retained natural forest ca. 150 years old for comparison. Moreover, a series of temperature and light regimes were also designed in March 2003 to test germination/dormancy responses of the P. asperata seeds to different conditions. In the plantations considered, both the densities of seed rain and soil seed bank increased with increasing stand age, whereas they were both low beneath the natural forest partially due to low adult density of P. asperata adult trees. P. asperata has a transient seed bank, and ca. 60% of seeds were found in the litter layer. Seed decay and seed predation were the two most important factors affecting soil seed bank dynamics, which caused a number of seed losses from the soil. Only a small fraction germinated and produced seedlings, and the indices of the losses from the seed bank via germination in the 30-year plantation, 60-year plantation and natural forest were 4.75, 5.10, and 2.80%, respectively. High seedling mortality was observed after seedling emergence, and most of the germinated seedlings died out within one growing season. The P. asperata seeds showed a high percent germination and no significant differences under most light and temperature regimes except for full sunlight or temperature below 5°C. In conclusion, despite a substantial number of seed produced, the high depletion of soil seed, the low seedling output, and high seedling mortality may obscure the natural regeneration potential of this tree species.     

文峪河上游华北落叶松林的种子雨、种子库与幼苗更新

华北落叶松林下更新不良,为探究其制约因素,开展了山西省文峪河上游5个华北落叶松林分的种子雨、土壤种子库和幼苗更新的研究。结果表明:(1)华北落叶松种子主要集中于9—10月散落。2011年为华北落叶松种子丰年:种子产量高,种子雨密度达(961.93±377.40)粒/m2;种子质量高,完整种子占(89.31±16.13)%。2012年为种子平年,种子产量低,种子雨密度为(252.73±115.12)粒/m2。华北落叶松种子雨主要源于毗邻树木,华北落叶松纯林和落叶松云杉林的种子雨密度显著高于其他3个针阔混交林。(2)土壤种子库主要由上年种子雨组成,2012年4月的土壤种子库密度为(695.18±297.23)粒/m2,完整种子占(59.73±9.56)%。种子自然萌发前,约(78.98±24.76)粒/m2具发芽力,基本可满足更新需要。但种子活力保持期少于2 a,只能形成短期持久土壤种子库。(3)华北落叶松更新不良,种子年后仍难以实现幼苗建成,当年生幼苗的出现频度平均为1.6%,且林下难以存活。幼苗发生与种子储量关联性不强,种源条件不是制约华北落叶松更新的主要因素。     

Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands

The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation; and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons (spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture. Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be more influential.     

植冠与土壤种子库储存种子的萌发特性及策略

为明确黄土丘陵沟壑区植物种子库如何调控种子萌发来提高个体适合度,选择研究区7种具有种子库的主要物种为研究对象,以刚成熟和室内储存种子为对照,比较植冠宿存(5个宿存期)和土壤埋藏(5a埋藏期)对植物种子萌发特性的影响,探讨植冠种子库与土壤种子库储存下的种子萌发策略。结果表明:7种植物种子经过不同种子库储存后萌发特性表现出明显的种间差异,黄刺玫(Rosa xanthina)和水栒子(Cotoneaster multiflorus)种子萌发力表现为植冠宿存不变型、土壤储存增强型,土壤储存明显提高水栒子种子萌发速率;达乌里胡枝子(Lespedeza davurica)和狼牙刺(Sophora davidii)种子萌发力表现为植冠宿存增强型、土壤储存减弱型,种子萌发历时表现为植冠宿存延长型,土壤种子库储存还可加快达乌里胡枝子萌发速率、缩短萌发历时;茭蒿(Artemisia giralaii)和铁杆蒿(Artemisia gmelinii),种子萌发率随植冠宿存时间先升高后降低,随土壤储存时间先降低后升高,土壤储存可推迟其萌发,铁杆蒿种子萌发速率在植冠与土壤储存后均加快;紫丁香(Syringa oblata)种子萌发率随植冠宿存先升高后降低,土壤储存明显加快其种子启动萌发与速率。在黄土丘陵沟壑区,植物种子经过植冠或土壤种子库储存,或增加、加快、提早萌发充分利用有利条件提高占据性,或减少、减缓、推迟萌发分摊不利条件的风险;而且该区植物植冠与土壤储存后种子萌发特性间的关系,体现各自适应环境与应对干扰的分工与协作策略,主要表现为:单一主导型和相辅相成型。     

黑龙江省大兴安岭林区火烧迹地森林更新及其影响因子

林火干扰是大兴安岭森林更新的影响因子之一,研究火烧迹地森林更新的影响因子(立地条件、火前植被、火干扰特征)对理解生态系统的结构、功能和火后演替轨迹具有重要意义。选取呼中及新林林业局55个代表性火烧样地,利用增强回归树分析法分析了火烧迹地森林更新的影响因素。结果表明:(1)立地条件是影响针、阔叶树更新苗密度的主要因素;海拔对针叶树更新苗密度的影响最大;坡度对阔叶树更新苗密度影响最大;(2)距上次火烧时间对针叶树更新苗比重影响最大,其次是林型;(3)中度林火干扰后森林更新状况好于轻度和重度火烧迹地。根据火烧迹地森林更新调查分析可知:林型影响火后演替模式,火前为针叶树或阔叶树纯林,火后易发生自我更新(火后树种更新组成与火前林型相同),而针阔混交林在火干扰影响下易于发生序列演替(火后初期以早期演替树种更新为主)。