秦岭冷杉和巴山冷杉种群年龄结构及动态的比较分析

在秦岭林区对不同生境条件下濒危种秦岭冷杉(Abies chensiensis)和广布种巴山冷杉(Abies fargesii)种群的年龄结构、生命表、存活曲线以及时间序列预测进行了比较分析.结果表明:秦岭冷杉在各个坡向上幼龄林林木株数均明显小于巴山冷杉.在各个坡向上,秦岭冷杉均呈衰退型,而巴山冷杉均呈稳定型.坡向对秦岭冷杉种群存活曲线的影响比巴山冷杉的影响大.在未来的20、40及60a,秦岭冷杉种群Ⅱ、Ⅲ龄级的种群表现为先增后减的不稳定趋势,而Ⅳ龄级以后的种群表现为小幅度的增加趋势.巴山冷杉种群各龄级株数在未来的20、40及60a均呈明显的增加态势.最后,给出了对不同生境的秦岭冷杉应采取的具体管理措施.     

Scale-dependent determinants of heterogeneity in fire frequency in a coniferous boreal forest of eastern Canada

Despite the recognized importance of fire in North American boreal forests, the relative importance of stochastic and determinist portions of intra-regional spatial variability in fire frequency is still poorly understood. The first objective of this study is to identify sources of spatial variability in fire frequency in a landscape of eastern Quebec’s coniferous boreal forest. Broad-scale environmental factors considered included latitude, longitude, human activities and belonging to a given bioclimatic domain, whereas fine-scale factors included slope, position on the slope, aspect, elevation, surficial deposit and drainage. The average distance to waterbodies was also considered as a potential intermediate-scale source of variability in fire frequency. In order to assess these environmental factors’ potential influence, they were incorporated into a proportional hazard model, a semi-parametric form of survival analysis. We also used a digital elevation model in order to evaluate the dominant aspect within neighborhoods of varying sizes and successively incorporated these covariates into the proportional hazard model. We found that longitude significantly affects fire frequency, suggesting a maritime influence on fire frequency in this coastal landscape. We also found that position on the slope was related to fire frequency since hilltops and upperslopes were subject to a lower fire frequency. Dominant aspect was also related to fire frequency, but only when characterized within a neighborhood delimited by 4,000 to 10,000-m radii (5,027–31,416 ha). A 2–6-fold variation in fire frequency can be induced by geographic and topographic contexts, suggesting a substantial intra-regional heterogeneity in disturbance regime with potential consequences on forest dynamics and biodiversity patterns. Implications for forest management are also briefly discussed. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

巴山冷杉种群结构及空间分布格局的研究

在太白山自然保护区设置 2 0 m× 2 0 m样地 8块 ,应用相邻格子法进行每木调查 ,并对巴山冷杉(Abies fargesii)种群结构和分布格局进行了动态分析。结果表明 ,种群大小结构为进展型 ,幼苗、幼树的后备资源储备量大 ,约 95 4株 / hm2 ;种群在 ～ 发育阶段死亡率较高 ,达 82 .3% ,随后死亡率趋于稳定 ;存活曲线属于Pearl 或 Deevey C型 ;种群的空间分布格局总体为聚集分布 ,负二项分布参数 (K) 1.6 0 0 ,扩散型指数 (Iδ) 1.6 2 9,丛生指标 (I) 7.6 77,Cassie指标 (CA) 0 .6 2 5 ,扩散系数 (C) 8.6 77,聚块性指标 (m* / m) 1.6 2 5。离散拟合符合负二项分布模型 ;但随着植株年龄的增长及发育阶段的不同 ,分布格局由初期的聚集分布逐渐扩散为随机分布 ,离散拟合由负二项 (Negative Binomial)分布转变为泊松 (Poisson)分布     

冷杉根系抗拔法测强曲线的建立与应用

采用抗拔法进行了冷杉根系抗拉强度的实验研究，得出抗拉法可以用于对冷杉根系抗拉强度进行检测，通过采用多种回归模型进行分析比较，求得最佳冷杉根系侧强曲线公式，并取得了较好的应用效果。分析了影响冷杉根系侧强曲线的因素，其中冷杉根系的根径和根长为影响其侧强曲线的主要因素，根系的抗拉强度的大小是根径与根长共同作用的结果。     

林内和迹地云冷杉幼树光合和蒸腾特性的研究

横断山区云、冷杉林更新成活率低。通过野外定点观测的试验数据,展示了林内和采伐迹地上云、冷杉光合速率的日变化和年变化,光合速率与光、温度的关系及其蒸腾速率的变化状况;并从生理生态的角度分析了这些光合和蒸腾特性的变化原因及与环境因子的关系。阐述了云、冷杉天然更新不良的主要限制因素,从而为加快云、冷杉林人工更新的进程提供了科学依据。     

沙松纸浆用材林不同家系苗期生长差异比较

通过对东北地区10个种源的77个家系沙松纸浆用材林苗期的苗高、地径和当年高生长指标测定和分析,比较不同家系苗期生长差异,结果表明:不同家系沙松间苗高、地径、当年高生长量均存在显著差异;苗高生长表现良好的为东京城04、东京城05和柴河04号家系;地径生长表现良好的为露水河08、东京城04和柴河05号家系;当年高生长表现最好的为露水河14号家系。     

Do changes in spatial distribution, structure and abundance of silver fir (Abies alba Mill.) indicate its decline?

Silver fir decline was investigated based on changes in spatial distribution of fir, fir abundance in forest stands, dbh (age) structure of fir, and abundance of fir regeneration. The authors used a large-scale approach to study the dynamics of silver fir over nearly 40 years. Based on Silva-SI, a spatial information system, the majority of total forest area in Slovenia was analysed for changes in the distribution of silver fir in the period 1970-2008 using artificial neural networks (ANNs), with respect to site, stand, and forest management variables. Additionally, changes in abundance of silver fir (hereafter fir) in the same period were analysed with a general linear model, while changes in the dbh structure of fir and fir regeneration were analysed with non-parametric tests. Most selected indicators confirmed the hypothesis of fir decline in the period 1970-2008, as evidenced by a reduction in the area of forests with a share of fir in the total growing stock >25% (from 18.9% to 9.5% of total area), a reduction in the share of fir in the growing stock of forest stands (from 17.5% to 7.5%), ageing of the fir population, and a disproportionate share of fir saplings in the total saplings relative to fir's share in the growing stock of forest stands. A 1.5% increase in fir distribution area in the observed period contradicts the decline hypothesis. ANNs showed that the spatiotemporal dynamics of fir was most affected by four variables: forest type, share of fir in the potential natural vegetation, mean annual precipitation, and mean annual temperature. The latter two, together with the growing stock at the start of study period, the degree of connectivity between fir stands, and bedrock type, were significant predictors of decline of fir abundance in forest stands. Significant differences in spatiotemporal dynamics and changes in fir abundance were found between forest types representing a complex of site conditions and past forest management. A further decline of abundance of fir on a large spatial scale in the next decades is expected. Conservation of fir in forest stands will depend mainly on the successful regeneration of fir and sufficient recruitment.     

Synergistic effects of past historical logging and drought on the decline of Pyrenean silver fir forests

The causal factors and effects of forest declines are not well understood in temperate conifer forests. Most studies have focused on climatic and environmental stressors and have obviated the potential role of historical forest management as a predisposing factor of decline. Here, we assess if the recent silver fir (Abies alba) decline observed in the Spanish Pyrenees was predisposed by historical logging and incited by warming-induced drought stress. We analysed a dataset of environmental, structural, and historical variables at the tree and stand level including 32 sites with contrasting degrees of defoliation distributed over 5600 km². We followed a dendroecological approach to reconstruct historical logging and to infer the effects of warming-induced drought stress on growth. The silver fir decline was more severe and widespread in western low-elevation mixed forests dominated by trees of small size and slow growth. These sites were subject to higher water deficits than eastern sites, where late-summer rainfall as the key climatic variable controlling silver fir growth was higher. Declining sites showed more frequent growth releases induced by historical logging than non-declining sites. Historical logging and warming-induced drought acted as long-term predisposing and short-term inciting factors of silver fir decline in the Pyrenees, respectively. We suggest that biomass increases caused by past intense logging affected the vulnerability of silver fir against late-summer water deficit. Future research in declining temperate conifer forests should consider the interacting role of predisposing historical management and inducing climatic stressors such as droughts.     

色季拉山急尖长苞冷杉林及其采伐迹地土壤养分特征研究

【目的】了解西藏色季拉山优势树种急尖长苞冷杉(Abies georgei var.smithii)林地及其采伐迹地的土壤养分状况,为森林管理及采伐迹地的恢复提供理论依据。【方法】以急尖长苞冷杉林地及其采伐迹地土壤为研究对象,采用单因素方差、化学计量比(C/N、C/P、N/P)及主成分分析等方法,对照全国第二次土壤普查标准,对其0～10,10～20,20～40,40～60,60～100 cm土层的pH和8种养分(有机质、全氮、水解氮、全磷、速效磷、全钾、速效钾、缓效钾)含量、土壤肥力限制性因素及土壤综合肥力进行比较分析。【结果】(1)急尖长苞冷杉林及其采伐迹地的土壤pH为4.35～5.70,均为酸性土壤。(2)急尖长苞冷杉林及其采伐迹地的土壤有机质、全氮及水解氮含量总体上随土层的加深而递减,其他养分含量变化规律不统一;不同养分含量在各土层间的差异性略有不同;除全磷、全钾外,急尖长苞冷杉林土壤有机质、全氮和水解氮、速效磷、速效钾、缓效钾含量分别为57.19,2.17 g/kg和723.47,22.86,247.83,744.30 mg/kg,采伐迹地中分别为46.50,1.67 g/kg和557.80,10.55,87.87,188.03 mg/kg,均表现为急尖长苞冷杉林大于采伐迹地。(3)除土壤C/N外,急尖长苞冷杉林的土壤C/P(101.64)和N/P(6.15)均高于采伐迹地(55.29和3.05),且急尖长苞冷杉林及其采伐迹地的化学计量比均高于中国陆地土壤平均水平,其中急尖长苞冷杉林及其采伐迹地土壤全磷含量分别为0.45和0.50 g/kg,均处于全国第二次土壤普查分级标准中的较缺水平(0.4～0.6 g/kg)。(4)3个主成分的累计贡献率达79.334%,分别为39.534%,26.347%和13.453%,依次受有机质、全氮、水解氮和速效钾、缓效钾及全磷、速效磷的影响;急尖长苞冷杉林内0～100 cm土层土壤肥力指数均值(0.552)大于采伐迹地(0.278),各土层土壤肥力指数亦均高于采伐迹地。【结论】采伐森林会对土壤肥力造成负面影响,因此采伐过后要及时进行更新恢复,全磷是其土壤肥力的限制性因素。     

川西北岷江冷杉种群的空间格局

以四川王朗国家自然保护区岷江冷杉林1hm2样地的调查数据为基础,研究岷江冷杉的径级结构和重要值,运用Ripley’s K函数分析其空间格局和种内不同生长阶段的空间关联。结果表明：岷江冷杉在群落中占据绝对优势,中大径级林木较多。不同生长阶段的岷江冷杉主要呈聚集分布,可能与物种种子扩散方式有关;幼树和小树在所有空间尺度上均呈聚集分布,聚集强度随着尺度增大呈增大后减小的趋势,大树的空间格局随尺度增大,由随机（1~3m）趋于聚集分布（4~50m）。随着种群发育（幼树→小树→大树）,岷江冷杉的聚集强度逐渐减小。幼树与小树在中小尺度上（1~25m）呈正向关联,不同生长阶段的岷江冷杉均与枯立木呈现出正向关联,随尺度变化而变化;岷江冷杉的聚集分布和种内的正向关联关系体现出了种群的生物学特性（耐荫）、干扰机制（林窗更新）和物种内部相互有利的生态关系。根据岷江冷杉的空间属性和更新机制,可以适当的进行人为干扰,以促进岷江冷杉林的发展。¬