亚高山云冷杉混交林树木生长释放与干扰分析

对云南碧塔海亚高山云冷杉林内４个样地冠层树木的生长压制和释放的历史，用树木年轮分析方法进行了重建，然后根据生长释放频率推测林冠干扰强度（每１０年冠层树木的死亡百分率）。４个林分（１个中龄林，３个成过熟林）生长释放的平均百分率为４８％～９２％。中龄林内，平均生长释放频率为７１％／１０ａ，成过熟林则为７４％～９５％／１０ａ，在油麦吊云杉〔Ｐｉｃｅａｂｒａｃｈｙｔｙｌａｖａｒ．ｃｏｍｐｌａｎａｔａ（Ｍａｓｔ．）ＣｈｅｎｇｅｘＲｅｈｄ．〕占优势的林分和大果红杉（Ｌａｒｉｘｐｏｔａｎｉｎｉｖａｒ．ｍａｃｒｏｃａｒｐａＬａｗ）油麦吊云杉混交林分内，估测的林冠干扰强度分别为４８％／１０ａ和５９％／１０ａ。  

黑河胜山国家自然保护区红松和红皮云杉 生长释放判定及解释

在黑龙江胜山国家自然保护区实验区的阔叶红松林内随机设置3个样方,采用生长变化百分率与前一年径向生长的相互关系建立生长释放界限标准曲线,对样地内所有胸径大于10 cm的红松(Pinus koraiensis)和红皮云杉(Picea koraiensis)进行生长释放判定分析。结果表明:前一年的径向生长对释放事件的判定很重要。无论是从年轮宽度变化还是生长变化百分率曲线上看,红皮云杉在各样方的所有样本变化都具有较强的一致性,而红松可能是由于受微环境的影响,一致性相对略差一点。几乎所有红松样本都有过至少1次释放,单株平均释放个数为2.75次,且87.5%的样本有过至少1次主要释放;红皮云杉由于年轮序列比较短,释放比率相对较低,平均释放个数为0.92次,41.7%的样本有过1次以上主要释放。两树种释放事件的年份主要发生在1930-1960年和1970-1990年两个时间段内。通过对样方中幼树的更新状况、树木年轮相关系数与个体间距之间的关系及温度、降水变化分析得出:风、火等干扰产生的林窗、微环境变化、温度和降水等气候因素都可能是产生生长释放的原因。  

Development and application of boundary-line release criteria

Identifying releases from suppression represents one of the most fundamental dendroecological procedures for quantifying forest disturbance histories. In this study we evaluate boundary-line release criteria, which incorporates the effects of growth history on release response. In eastern hemlock (Tsuga canadensis L.) the maximum possible value of a pulse in percent-growth change is dependent on growth decline immediately prior to the pulse. Maximum values of percent-growth-change decline exponentially as prior growth rate increases. This negative exponential rate is quantified as a boundary line, which is used to scale each percent-growth change pulse by the maximum possible value predicted by prior growth rate. The consistency of the relationship between radial growth prior to a release and the magnitude of the release is evaluated in multiple eastern hemlock data sets. Trees from diverse sites show large releases that approach the maximum value predicted by the prior-growth rates. These sites tend to have a history of disturbance, suggesting that disturbance is the most influential variable determining the magnitude of release response. Possible exceptions are sites on the northern and western borders of eastern hemlock's range, which consistently fall short of the boundary line and may be exhibiting unique relationships between prior growth and percent-growth change. Yet overall the relationship between prior growth and percent-growth change appears to be consistent across much of eastern hemlock's range. Furthermore, we demonstrate that similar boundary lines occur in Pinus ponderosa (Laws.), Pinus echinata (Mill.), Quercus alba (L.), and Quercus macrocarpa (Michx.). This suggests that prior growth could form the basis of a more unified set of release criteria better able to standardize release responses within and among species. Standardized release criteria would allow more accurate comparisons of disturbance histories among sites, species, and even across landscapes.  

Dendroecological study of a subalpine fir (Abies fargesii) forest in the Qinling Mountains, China

Dendroecological techniques were used to investigate the stand dynamics and the disturbance history of the subalpine fir forest in the Qinling Mountains of Shaanxi Province, China. The results indicated that 68% of the fir trees experienced 1–2 release events for a total of 10–29 (an average of 15.8) years, and 1–2 suppression events for a total of 10–27 (an average of 13.4) years before they reached canopy. Large number of Abies fargesii and Betula albo-sinensis recruitment coincided temporally with larger increases in the ring-width index from the 1830s to 1880s, suggesting occurrence of a major stand-wide disturbance during this time period. Few seedlings and saplings were found in the forest, and there was a dramatic decline in recruitment after 1890, probably because of the intensive cover of understory umbrella bamboo (Fargesia spathacea). Radial growth analyses indicated frequent canopy opening resulting from small-scale disturbances in the forest. Thus, the subalpine fir forest experienced frequent small-scale disturbances and infrequent large-scale disturbances in its developmental history, and these disturbances coupled with the understory umbrella bamboo might have influenced tree growth and species recruitment.  

典型阔叶红松林干扰历史重建及干扰形成机制

该文依托于小兴安岭典型阔叶红松(Pinus koraiensis)林9 hm2森林动态监测样地,对样地内林窗边缘主要树种红松和臭冷杉(Abies nephrolepis)进行生长释放判定分析,重建了冠层树木的干扰历史。结果表明:整体上林窗木与非林窗木的生长变化百分率变化规律基本一致,而不同林窗间生长变化百分率存在明显的差异,林窗干扰及其产生的影响存在较大的变异性。在1733–1738、1748–1752、1769–1771、1798–1801、1827–1833、1841–1844、1935–1939及1968–1973年间红松生长释放较强,其中1752、1770、1800、1830、1842、1937及1970年出现了明显的干扰峰;在1889–1904、1932–1938、1947–1973和1986–2005年间臭冷杉生长释放较强,其中1894、1934、1951、1968和1990年出现了明显的干扰峰。红松干扰存在2.0 a、3.5 a、3.8 a、7.3–7.9 a和9.1–18.2 a的显著周期,臭冷杉干扰存在3.5–3.6 a、7.5–48.8 a和65–85 a的显著周期。风干扰是典型阔叶红松林干扰释放的主要因子,异常温度也影响该地区树木生长释放事件。太阳活动通过影响局地风速、温度、降水等气候因子以及其他大尺度气候模态影响林窗动态,可能是小兴安岭典型阔叶红松林的干扰机制之一。  

火烧伤害对兴安落叶松树干径向生长的影响

在大兴安岭塔河林业局瓦拉干林场22支线截取3个兴安落叶松(Larix gmelinii)火疤圆盘,预处理和交叉定年后,测定垂直年轮(径向)和沿年轮(横向)方向2次火烧间的年轮宽度变化.通过生长趋势拟合、火烧后生长面积与正常(理论)生长面积比较,分析火烧伤害对兴安落叶松树干生长的影响.结果表明:火烧后横向年轮生长呈现出窄—宽—正常的趋势,这种趋势可以用3次曲线来拟合,即y=0.01x3-0.14x2+ 0.85x+ 0.56(DF=3,F=227.7,P＜0.0001,y为平均年轮宽度,x为偏离火烧点距离).在本文分析的3个圆盘中,火烧后的横向生长释放都出现在距火烧部位1/3范围内.火烧后径向上年轮宽度变化规律也较为明显,即在火灾后的几年时间内,年轮宽度值较火灾前都呈增加趋势.火烧后3个圆盘的径向生长释放持续时间分别为14、5a和11a.通过面积计算整体来看,火烧导致圆盘1较正常情况下损失了67.2％,圆盘2比正常情况下增加了6.6％,圆盘3增加了13.7％.上述分析表明,火烧导致的径向生长损失,可以较好地由横向和径向生长释放予以补偿,但是具体补偿多少因烧伤程度不同而有差异.火烧可直接改变树干径向生长变化,同时,这种变化也受其他因素影响,例如像树龄、树种特性、火灾间隔期等因素,这些因素的差异就可能导致补偿程度的不同.