天然次生林中水曲柳种子库的空间格局与过程

 研究土壤种子库的空间格局与过程是认识林木更新的基础。应用地统计学方法定量分析了东北林业大学帽儿山实验林场天然次生林中土壤种子库水曲柳（Fraxinus mandshurica）种子的统计特征、空间格局、尺度和格局的变化过程。结果表明,落种后水曲柳种子库的平均密度有很大变幅（5.8～105个·m-2）,平均年削减率为91.6%～92.7%,5～8月的削减率高达98%以上。变异函数分析及理论模型拟合显示,一年之内种子库的空间格局强度及尺度变化非常明显。种子雨可形成较强的异质性格局,空间自相关尺度较大,为36.     

林分光照空间异质性对水曲柳更新的影响

 光照是森林更新动态中极为关键的环境因子。本研究在东北天然次生林中选择样地,应用地统计学理论结合实验生态学方法,定量分析林分光照空间异质性特征,同时进行林下播种水曲柳（Fraxinus mandshurica）的更新实验,探测更新格局特征。通过空间关联性分析,研究探讨是否林分光照的空间变异对水曲柳更新有重要影响作用。研究结果表明： 1）生长季林分平均光照仅为全光照的4.2%～4.6%,在空间分布上呈现非常明显的异质性特征,空间自相关变异（62.5%～78.2%）主要体现在10.9～12.4 m的尺度上。2）林分光照不同的空间样点上,水曲柳更新幼苗发生数量和秋季幼苗存活数量均存在显著差异,光照相对强的微生境中,更新苗发生数量较多且存活率高,而在光照较弱的微生境中则更新较差,更新具有十分明显的空间格局。3）更新格局与林分光照空间异质性特征紧密关联。在光照空间异质性程度较高、空间变异较复杂的条件下,更新相应呈现出较复杂的空间格局,自相关的变异表现在较小尺度范围（2.12～6.97 m）。在光照空间异质性程度较低、空间变异复杂性较小的条件下,更新格局的复杂程度明显变小,空间自相关变异（>83%）表现在较大的尺度上（30 m）,对更新格局起主要的影响作用,随机变异的影响很小（<17%）。这些研究结果说明,林分光照环境在水曲柳更新中的作用十分关键,林分光照的空间异质性对更新格局起决定性作用。     

基于景观尺度过程模型的长白山净初级生产力空间分布影响因素分析

对长白山自然保护区的净初级生产力(NPP)的空间分布格局进行了模拟,对它们与环境因子和植被因子间的相互关系进行了分析．结果表明,1995年NPP的模拟值平均为0．680kgC·m^-2·年^-1,变幅为0．105-1．241kgC·m^-2·年^-1(82．1％),其中阔叶红松林的NPP最高(1．084kgC·m^-2·年^-1)．环境条件决定了长白山植被年NPP空间分布的大趋势．土壤含水量对NPP的限制最大,呈负相关关系(R=-0.65),长白山植物生长一般不存在水分不足的问题．植被的NPP与LAI高度正相关(R＝0．81),当LAI增大到4-5m^2·m^-2时,NPP出现饱和．植被的NPP与冠层蒸腾量呈显著的正相关关系(R＝0．77)．岳桦林和阔叶林对环境因子、LAI和冠层蒸腾的响应与其它植被有较大差异。     

黑河流域荒漠绿洲过渡带两种优势植物种群空间格局特征

应用地统计学的原理和方法,对降水量117．1mm、降水量和潜在蒸发量比值为0．05的荒漠绿洲过渡带斑块状植被优势植物泡泡刺、红砂种群的密度、盖度以及泡泡刺沙堆体积和高度的空间格局进行了研究．结果表明,泡泡剌和红砂种群平均盖度分别为1．56±2．34％和0．23±0．22％;密度分别为1．5±1．8丛·100m^-2和2．3±2．1株·100m^-2．泡泡刺灌丛沙堆是稳定戈壁下垫面受风沙流干扰形成的一种景观,灌丛高度和体积都比较小,平均值分别为0．18±0．15m和0．10±0．18m^3．泡泡刺种群在样地内靠近绿洲和浅山区有几条明显的分布带,而红砂分布相对均匀．用半方差函数分析表明,两种种群密度和盖度的块金值与基台值之比都比较小,介于0．08～0．12之间,说明在总空间异质性中随机因素所起的作用很小。占8％～12％．两种种群盖度和密度的变程相近,基本在34m以内,其中随机因素引起的异质性对应的尺度在10m以下,而结构性因素引起的异质性对应的尺度为10～34m．泡泡刺和红砂种群盖度和密度的空间异质性均具有各向同性和各向异性特征,其中红砂种群的各向同性的范围略大于泡泡刺种群．泡泡刺种群空间格局的塑造主要受降水量及其形成地表径流的控制．     

采伐干扰对华北落叶松细根生物量空间异质性的影响

以华北落叶松天然林为研究对象,选择采伐干扰林分(样地A)和未采伐干扰林分(样地B),利用根钻法分3层(0—10cm,10—20cm,20—30cm)获取各径级细根(≤1mm、1—2mm、2—5mm3级活细根,≤2mm死亡细根)生物量数据。采用地统计学变异函数和经典统计相结合的数据分析方法对采伐干扰造成的细根生物量空间异质性的变化进行定量研究。主要研究结果如下:采伐干扰林分样地A各经级细根生物量均值减少;同一土层相同径级细根生物量样地A与样地B相比差异显著(P<0.05);不同土层的细根生物量异质性具有显著差别(P<0.05)。0—10cm土层,未采伐干扰林分≤1mm细根生物量呈现较明显的空间自相关变异,采伐干扰林分则表现为随机性变异特征,采伐干扰导致≤1mm细根生物量空间分布特征更加复杂(分维数D=1.978);10—20cm土层,采伐干扰林分各径级细根生物量异质性程度明显降低,只有未采伐干扰林分的5.4%—88.9%。20—30cm土层,未采伐干扰林分≤1mm细根生物量在较小尺度范围(<2.9m)表现出明显的空间自相关变异(结构方差比86.1%),受采伐干扰林分各径级细根生物量异质性程度只有未采伐干扰林分的8.9%—45.9%,且呈现随机性变异。各径级细根生物量空间异质性的垂直分异均表现为随土层深度的增加异质性强度明显降低。     

采用地统计学方法对水曲柳人工纯林表层根量的估计

采用地统计学的变异函数分析方法定量研究了水曲柳纯林表层根量的空间异质性特征,利用地统计学的克里格内插法结合定积分,对水曲柳纯林表层(0～10 cm)各类型根量进行了估测。结果表明:1)水曲柳细根(<2 mm)、粗根(≥2 mm)、活根和土壤总根变异函数曲线的理论模型符合球状模型,其它植物活根符合指数模型,水曲柳及其它植物死根符合线性模型。水曲柳及其它植物死根的空间变异主要是由随机性因素引起;水曲柳细根、粗根、活根、其它植物活根和土壤总根的空间变异主要是由结构性因素引起,且空间自相关程度均属中等(空间结构比在2 5 %和75 %之间)。水曲柳粗根的空间变异尺度为13.2 m,水曲柳细根、水曲柳活根、土壤总根和其它植物活根的空间变异尺度均大于33.9m。根据理论模型的拟合参数估计,水曲柳细根、水曲柳活根和土壤总根的空间变异尺度为6 1m,其它植物活根为183m。(2 )平均值成对二样本t检验结果表明,变异函数分析结果基础上的克里格内插法适用于水曲柳样地各空间位置处各类型根量的估计。利用此估计值,拟合其与位置坐标值之间的多元回归关系均为二元十次余弦级数多项式。利用此多项式,通过定积分的方法(积分区间为整块样地的大小) ,估计出水曲柳纯林表层根量为1.5 92 6 t/ hm2 ,水曲柳细根为0 .6 86 5 t/     

华北山地典型天然次生林土壤氮素空间异质性对落叶松幼苗更新的影响

在华北山地典型天然次生林中选择研究样地,应用地统计学理论和格局分析方法,定量分析林分土壤氮素空间异质性特征,探测更新幼苗空间格局特征;依据协同变异函数理论模型参数,定量估计土壤氮素营养空间异质性与落叶松更新格局之间的空间关联性,探讨土壤氮素空间变异对落叶松幼苗更新格局的影响程度.研究结果表明:(1)无论是以华北落叶松为优势树种的寒温性针叶林,还是以白桦和山杨为优势树种的山地阔叶林,不同空间样点间土壤氮素总量及速效态氮素均存在很大差异.阔叶林中,硝态氮在整个研究样地尺度(＞70.71m)上表现出很强的空间自相关性(结构因素所占比重为81.5%).针叶林中,硝态氮则在相对小的尺度范围(47.90m)呈现更明显的空间自相关变异.且阔叶林中土壤氮含量显著地高于针叶林.(2)华北落叶松苗更新空间分布格局呈明显的集聚分布.更新的空间格局变异主要由空间自相关因素引起(针叶林为77.4%,阔叶林为85.2%),随机变异占的比例较低(分别为22.6%和14.8%).(3)阔叶林土壤氮含量相对高,更新与氮素的空间关联性不明显,与全氮的协同变异呈随机性(R2=0.078).针叶林土壤氮含量相对低,更新与氮素的空间关联性明显,与全氮的协同变异呈现明显的空间自相关性,氮素空间异质性对更新格局与过程具有更重要的影响.整个研究样地水平上,硝态氮与更新的协同变异呈现明显的空间自相关性(空间结构比为59.4%～77.7%).NO-3-N含量较高或铵、硝态氮的比例较低的土壤环境中,更新苗发生数量较多.     

深圳福田无瓣海桑-海桑林能量的研究

在研究生物量、生产力的基础上,对深圳福田无瓣海桑-海桑林中2种红树植物海桑和无瓣海桑各组分的干重热值、林分能量现存量、年能量净固定量进行了研究．结果表明,各组分样品干重热值有一定的差异,树叶干重热值最高,纫根干重热值最低;海桑各组分样品干重热值比无瓣海桑相应组分稍高．林分能量现存量(1999年10月)为84774．72kJ·m^2,其中无瓣海桑种群能量现存量为54693．26kJ·m^-2,占林分总的64．54％,海桑种群能量现存量为30051．46kJ·m^-2,占林分总量的35．46％．林分凋落物的能量归还量(1999年)为24549．54kJ·m^-2·年^-1,其中无瓣海桑种群的能量归还量为17223．99kJ·m^-2·年^-1,占总林分的70．16％,海桑种群的能量归还量为7325．55kJ·m^-2·年^-1,占总林分的29．84％．林分能量净固定量为50391．4kJ·m^-2·年^-1,其中无瓣海桑种群和海桑种群的能量净固定量为分别为31778kJ·m^-2·年^-1和18613．4kJ·m^-2·年^-1．     

科尔沁草甸草地放牧和割草条件下土壤种子库研究

研究了科尔沁沙地草甸草地在放牧、割草两种利用方式下的土壤种子库的大小、组成及其与地上植被的关系．结果表明,在自由放牧下,土壤种子库密度为6158±1647粒·m^-2,在割草利用下,土壤种子库密度为8312±2540粒·m^-2．放牧干扰下,种子库组成以矮小、短命的一年生植物为主,其中一二年生植物占81．66％,占比例最大的前4种植物分别为虎尾草(38．55％)、灰绿藜(15．42％)、毛马唐(14．95％)和狗尾草(9．83％),多年生植物种子密度仅为1129±302粒·m^-2;割草干扰下,一二年生植物占68．08％,其中狗尾草占52．7％;而割草地多年生植物种子密度为2653±811粒·m^-2．放牧地土壤种子库密度与地上植物相关不显著;割草地土壤种子库密度与地上植物多度显著相关(r=0．76,P<0．01)．放牧地种子库的Shannon—Wiener指数、丰富度指数分别为2．96和2．98,明显小于割草地的3．10和5．09,表明自由放牧更易使物种多样性下降．     

东海区底层及近底层鱼类资源的空间异质性

运用空间自相关指数和变异函数分析东海区底层及近底层鱼类资源的空间自相关性和空间变异．其空间分布平均场的Geary c和Moran Ⅰ指数分别为0．38和0．52,各向同性随机变异占总变异的59．9％。表明其空间分布具有中等自相关特性,空间变异中由随机引起的变异大于由空间相关尺度过程引起的变异;各方向变异属于几何异向性,资源密度的年际变化与C、C0和C+C0均呈正相关,说明年际平均密度的增加由空间自相关变异和随机变异共同引起,随机变异略强于空间自相关变异。     

天然次生林中水曲柳种子的扩散格局

 种子扩散是种群动态中的一个关键环节,研究其扩散格局对了解种子库及更新格局有重要意义。于1999～2000年在天然次生林中选择样地并设置样带,共设取样点1376个,观察和估计了水曲柳(Fraxinus mandshurica)的种子雨格局。结果发现,母树附近,尤其是冠幅范围内,各方向的种子雨没有显著差别。但种子雨密度随距离有明显变化,冠幅范围内平均可达462～903个·m-2。距冠缘10～20 m急剧减少,为50～190个·m-2。72.5%～96.4%的种子散落在距母株树干10 m 的范围内。饱满种子顺风     

Changes in the spatial variation of soil properties following shifting cultivation in a Mexican tropical dry forest

The role of secondary vegetation in restoring soil fertility during shifting cultivation in the tropics is well known. Yet the effect of secondary succession on the spatial patterns of soil properties has received little attention. To determine whether changes in the plant community as a result of shifting cultivation affect the scale of spatial dependence for biologically important soil nutrients, we sampled three dry tropical forest stands in Campeche, Mexico. These stands represented a gradient of cultivation history: one mature forest stand, a forest fallow that had undergone one cultivation-fallow cycle, and a forest fallow that had undergone two cultivation-fallow cycles. We used an analysis of semivariance to quantify the scale and magnitude of spatial dependence for organic matter content (OM), phosphorus (P), potassium (K), and aluminum (Al) in each stand. The scale of spatial dependence varied with cultivation history, but the degree of spatial dependence did not differ among stands. In the mature forest P and K were autocorrelated over distances >7.5 m. In the forest fallows 48–88% of the variation in soil P and K was autocorrelated over distances up to 1.1–5.1 m. In contrast, the range of autocorrelation for Al (∼2.5 m) did not differ among stands. We conclude that shifting cultivation changes the range of autocorrelation for biologically important soil nutrients at a scale that may influence plant growth. The finer scaled pattern of soil nutrients in forest fallows is likely to persist with continued shifting cultivation, since fallows are cleared every 3–15 years.     

红松老龄林主要树种的空间异质性特征与比较的定量研究

 空间异质性研究对认识不同尺度上的生态系统结构、功能和过程具有重要的理论意义。采用地统计学理论和方法,通过空间异质性特征和比较研究了我国东北红松老龄林中主要树种,即红松(Pinus koraiensis)、云杉(Picea koraiensis)、冷杉(Abies nephrolepis)、枫桦(Betula costata)和紫椴(Tilia amurensis)的空间异质性程度、空间异质性组成、尺度和格局问题。结果表明：红松老龄林中主要树种虽然生长在同一林分中,但是它们的空间异质性与格局具有明显的差异。红松的空间异质性程度最高,分数维较低,其空间异质性主要由空间自相关部分组成,在450m的尺度内,具有明显的空间格局。枫桦的空间异质性程度最低,分数维最大,空间异质性主要由随机部分组成,在大于100m的尺度上不存在明显的空间格局。云杉和冷杉由于生长的立地相似,因此具有相似的空间异质性特征和格局。紫椴是红松最重要的伴生树种,其空间异质性程度、空间异质性组成、尺度和格局等方面与红松接近。红松老龄林中主要树种空间异质性与格局在一定尺度上的差异,反映这些树种在生态系统中具有不同的生态学功能和过程。     

Variation in soil seed bank species composition of a dry coniferous forest: spatial scale and sampling considerations

In order to assess the effects of disturbance on soil seed bank spatial structure, variation in seed bank species composition was analyzed at two spatial scales in mature (undisturbed) and recently disturbed stands of Interior Douglas-fir forest in south-central British Columbia. Coarse-scale analysis among stands 10–100 km apart using Multi-Response Permutation Procedures showed that individual mature stands were mainly characterized by unique seed bank species compositions. Disturbance had an homogenizing effect on seed bank species composition at the coarse scale––there was less variability among stands following disturbance by both low and high severity fires, and by non-salvage logging. In contrast, finer scale analysis among sampling units c. 10 m apart showed that heterogeneity in seed bank species composition was greater on severely burned and logged sites, commensurate with greater levels of soil disturbance, than on lightly burned and undisturbed sites. Despite the high intensity of seed bank sampling (sixty 25 cm² soil samples from each of 16 sites), species-area curves leveled off only when infrequent species were removed from the dataset. The number of seed bank samples required to account for the common species ranged from 84 on severely burned sites, to 196 on undisturbed sites; more than the 240 samples collected per disturbance class in this study would have been required to account for the remaining infrequent species. Overall, this study highlights the importance of sampling intensively within multiple stands to capture the variation in species composition inherent to these dry coniferous forest soil seed banks.     

Long-Term Effects of Forest Regrowth and Selective Logging on the Seed Bank of Tropical Forests in NE Costa Rica1.

To investigate long-term effects of land use on the soil seed bank, we compared the abundance/density, species richness, life form distribution, and species composition of seeds stored in the soil of four 15–20 yr-old second-growth stands, two old-growth stands, and two previously selectively-logged stands in the Caribbean lowlands of Costa Rica. Surface soil (10 cm deep, 4.7 cm diameter) was collected at 10 m intervals along three 120–160 m long transects in each stand (44–48 soil cores, 22–24 combined seed bank samples per site). Seed density was highest but variable in second-growth stands (8331–14535 seeds/m²), low and homogeneous in old-growth stands (2258–2659 seeds/m²), and intermediate and highly variable in selectively-logged stands (1165–6854 seeds/m²), which also had contrasting logging intensities. Species richness was strongly dependent on seed density, but showed less variation. Life form distribution did not differ statistically among or within land-use categories. In each stand, herbs-forbs, shrubs, and vines dominated the seed bank (> 75% of the species richness and abundance), whereas trees were a minor component (< 20% of the species richness and < 5% of the abundance) and were predominandy early successional. Shrubs and vines were most abundant in second-growth stands where regrowth vegetation was repeatedly cut before abandonment, whereas grasses and sedges were most abundant in the only forest stand that was completely surrounded by pastures. In terms of species composition, old-growth stands were more similar to selectively-logged stands than to second-growth stands, but across stands, selectively-logged forests were most distinct from the other two forest types. An inventory of the standing woody vegetation in each site showed little representation of the woody taxa found in the seed bank. We discuss these results in the context of the main factors that have been postulated to influence the abundance, life form, and species composition of tropical forest seed banks, and explore the role of the latter during intermediate phases of tropical forest succession and regeneration.     

茂兰喀斯特森林中华蚊母树群落土壤种子库动态初探

 茂兰喀斯特森林中华蚊母树群落900m2样地内共有种子植物59种,其中19种主要植物已繁殖产生种子。群落每年以种子雨形式向种子库输入种子351.1粒·m-2,其中对群落更新有用的成熟有效种子150.8粒·m-2。土壤种子库中活力种子丰富,共有41种2510.5～2646.8粒·m-2。种子库中活力种子的种类和数量均随时间的变化而变化,不同时间种子库的差异主要在于现存植物活力种子的变化。土壤种子库每年输出活力种子171.9粒·m-2,其中萌发输出21.9粒·m-2,动物采食输出133.5粒·m-2,病菌危害引起的输出为3.2粒·m-2,种子自然衰老引起的输出为13.3粒·m-2。每年输出超过输入21.1粒·m-2。演替前期植物种子没有输入,只有缓慢输出,但没有萌发输出。     

A long-term study of Pinus banksiana population dynamics

Abstract. The long-term population dynamics of a pure, naturally-established stand of Pinus banksiana (jack pine) in southeastern Manitoba, Canada is described. The study was initiated at stand age 15, when all 468 trees in a plot were mapped and their trunk diameter at breast height (DBH) measured. The plot was remeasured eight times — every five years (six years in one case) — and mortality and DBH changes recorded. Total mortality over the 41-yr study period was ca. 84 %. Mortality was initially very low, increased once the stand entered the self-thinning stage from ages 25–46, and declined at ages 46–56. Mortality was restricted to the smallest size classes throughout. The stand reached the self-thinning line at ca. age 30. The self-thinning slope was significantly less steep than the theoretically expected value of ?0.5. The distribution of DBH values was initially symmetric, showed increasing positive skewness during the period of highest mortality, and became symmetric again at later stages. Size (DBH) inequality was highest just prior to the onset of density-dependent mortality, and subsequently declined. Tree DBH values were positively autocorrelated both initially and at later stages of stand development, but were spatially independent during the period of highest density-dependent mortality. The stand initially had a strongly clumped pattern at all spatial scales. Patterns of mortality were non-random during stand development, however, resulting in increased spatial regularity over time. Mortality was initially restricted to high density patches of the stand, but occurred throughout the plot once the self-thinning line was reached. Mortality during the self-thinning stage deviated from random expectation at local spatial scales (1–2m radius), suggesting that individuals were competing with their immediate neighbours. It is argued that an integrated approach, incorporating both population size and spatial structures, is essential in improving our understanding of long-term plant population dynamics.     

The effect of stand age and microhabitat on soil seed banks in Mediterranean Aleppo pine forests after fire

Soil samples from three microhabitats (gaps, beneath shrubs and beneath trees) in five stands of various post-fire ages (6–55 years) were collected in an east Mediterranean Aleppo pine Pinus halepensis forest. Total germinable seed bank densities varied between 300 and 1300 seeds per m². Herbaceous taxa were the major constituents of the germinable seed bank in gaps, regardless of stand age. Perennials were the major components beneath shrubs in all stands except the youngest stand where herbaceous species were the major components in all microhabitats. Important tree and shrub species (e.g., Pinus halepensis, Quercus calliprinos, Pistacia lentiscus, Phillyrea latifolia) of the mature pine forest were not an important component of the soil seed bank and therefore, little resemblance was observed between the above-ground plant species composition and soil seed bank composition. This is consistent with the fact that these species regenerate by resprouting rather than by germination from the seed bank. Both microhabitats and forest-stands, which were of different ages, contributed to the variation in taxa richness, germinable seed density and diversity among samples. The effect of small-scale spatial heterogeneity (among microhabitats) was much more pronounced. In contrast to other studies, species richness, species diversity, and density of seed banks did not decrease with post-fire age. Moreover, stand age was a poor predictor for these attributes of the soil seed bank in an Aleppo pine forest. The heterogeneity plays an important role in conservation and management of this ecosystem.