共查询到17条相似文献，搜索用时 218 毫秒
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利用黑龙江省孟家岗林场长白落叶松人工林间伐标准地定位观测数据,其于间伐林分断面积与相同年龄、相同立地、相同保留木株数的未间伐林分面积,随时间趋于一致的假设,根据未间伐人工林林分断面积生长的一般预测模型导出了间伐林分的断面积生长预测模型,同时,结合抚育间伐技术批示的确定,进行和林分的动态模拟。 相似文献
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日本落叶松人工林密度调控技术研究 总被引：1，自引：0，他引：1
以日本落叶松中幼林抚育间伐样地监测数据,利用树冠竞争因子（CCF）、林分密度指数、单位断面积生长过程等指标,分析了抚育间伐对断面积和蓄积两方面的影响,结果表明：间伐林分的断面积和蓄积有相同的生长过程,即林分在一定间伐强度范围内（强度小于50％）间伐强度越大,年均生长率越大;用树冠竞争因子描述日本落叶松人工林断面积的生长过程,未间伐林分的立木度接近稳定状态,而间伐林分降低了林分的CCF值,随着林龄的增加,CCF值不断增加,逐渐向未间伐林分靠近。总的来说间伐林分在间伐初期要小于未间伐林分,但随着林龄的增大及林木竞争的加剧,间伐林分逐渐向未间伐林分靠近。 相似文献
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以Richards和Schumacher模型为原型,利用地位级指数代替地位指数来反映林分的立地质量,通过选取不同的密度指标,分别拟合蒙古栎间伐、未间伐林分的断面积、蓄积量生长模型。结果表明:选用不同的密度指标直接影响着模型的预估效果,林分断面积生长模型选用林分密度指数作为密度指标时预估效果更好,且Schumacher模型要优于Richards模型;林分蓄积量生长模型选用林分断面积作为密度指标时预估效果更好,当认为模型中的渐近值参数只与立地质量相关、而与密度无关时,选用林分断面积作为密度指标的Richards模型要优于Schumacher模型,而在Schumacher模型渐近值参数中引入密度指标后,对林分蓄积量的预估精度又要略优于Richards模型。建议在研究蒙古栎断面积、蓄积量生长模型时,分别选用林分密度指数和林分断面积作为密度指标较好。 相似文献
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杉木林间伐强度试验20年生长效应的研究 总被引：9，自引：3，他引：9
1976年6月在江西省奉新县下林场开展间伐强度对杉木林生长效应的定位研究,供试林分10年生,1996年11月,历时20年。结果表明:强度、中度、弱度间伐林分平均树高及其定期生长量均比对照有所提高,增加约3%~8%,但定期生长量无显著差异,间伐不能有效促进树高生长。间伐林分平均胸径及其定期生长量比对照分别增加约7%~19%和6%~28%,均显著或极显著大于对照,间伐可有效促进胸径生长。间伐林分总断面积及其定期生长量比对照分别增加约4%~6%和1%~7%,但间伐强度之间无显著差异;间伐林分保留木断面积小于对照,间伐不能有效增加林分总断面积、保留木断面积及其生长量。间伐林分单株材积及其定期生长量于伐后5年和8年即有显著或极显著差异,间伐可以有效促进林分个体生长量。间伐林分单位面积材积总生长量比对照增加约2%~4%,保留木材积、活立木主伐材积及其定期生长量与对照比较增减值均在允许误差范围之内,差异不显著,间伐不能有效增加材积生长量及其总产量。按生长效果而言,杉木林实行占株数40%左右强度间伐为宜。 相似文献
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以固定样地观测和临时样地调查相结合的办法收集林分现实生长与经间伐或间伐设计后所保留群体的生长资料;以固定样地观测资料为依据,以林分平均胸径连年生长量及胸径度离散度的指标,确定不同地位指数林分间伐的起始年龄;采用Ｒｉｃｈａｒｄｓ函数模拟合理密度与生长水平下的林分平均树高及胸径生长;并采用间伐或间伐设计前,后林分生长标准的调查资料,以地位级指数,林林分平均胸径及胸径离散度为自变量建立起人工速生丰产林的 相似文献
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抚育间伐对人工红松林生长效应的影响 总被引：2，自引：0，他引：2
利用不同间伐强度后40 a的人工红松林,连续抚育3次的长期定位观测资料,分析了抚育间伐对人工红松单木胸径和材积、林分断面积和蓄积、林分枯损和总收获量的影响。研究结果表明:间伐可以增加单木平均胸径和材积的生长率,且不同间伐强度表现为相同的规律,即中度(33.2%)强度(43.4%)弱度(23.1%)对照(0.0%);间伐后林分的断面积和蓄积生长率,具有相似的自然规律,间伐样地的生长率均高于对照;林木枯损率随间伐强度的增加而降低;间伐后的林分总收获量平均增加11.6%,间伐林分之间差别不明显。在整个研究阶段,不同的抚育阶段表现不同的规律,抚育间伐可以延缓单木胸径和材积生长速度的降幅;而不同抚育阶段内,林分断面积和蓄积生长率均为增长,也就是说,在一定阶段内间伐可以有效地提高林分平均断面积和蓄积生长率;从林分枯损状况来看,应该减少间伐间隔期。 相似文献
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Diameter distribution models for even-aged Eucalyptus grandis plantations in Zimbabwe were developed using the two-parameter Weibull function. The analysis was based on data from Correlated Curve Trend (CCT) experiments replicated on four different sites. Parameters of the Weibull distribution were predicted using stand characteristics as regressors. Two sets of parameter models were estimated: a set with and one without stand basal area as a predictor. Stand variables such as dominant height, age, site index and number of stems were used in both sets. The models were further calibrated to result in a given number of stems and stand basal area simultaneously. The usability of constructed models was tested both in prediction of yield in a stand inventory situation and in simulation of growth in connection with different growth models. The results indicated that models not including stand basal area produce considerably less precise stand volume estimates compared to models including also stand basal area. Calibration improved the accuracy of diameter distribution models. In growth simulation diameter distribution models can be connected both to single tree growth models and to stand projection models. The usability of calibration in growth simulation depends on the accuracy of the prediction of stand characteristics. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):364-369
In single‐tree selection, trees removed by harvest or lost through mortality are replaced by ingrowth from the seedling/sapling bank. Because the level of ingrowth is governed not only by the recruitment rate of new seedlings, but also by mortality and growth rates within the seedling/sapling stratum, knowledge of how these processes are related to the tree stratum is important for successful application of single‐tree selection. Therefore, Norway spruce (Picea abies (L.) Karst.) regeneration (0.1 m ≤ height ≤ 2.0 m) was measured on seventy 100 m2 circular subplots at each of two sites in central and northern Sweden. Both sites had previously been selectively logged, but the time elapsed since the last harvest was at least 30 yrs. Basal area of trees of at least 2 m height within three different radii from the subplot centres was measured. Measurements on regeneration included height and leader length. Influence of local stand basal area on density and growth of regeneration was analysed by ordinary least‐squares linear regression for each of four height intervals. Regeneration was significantly aggregated at both sites, but number of Norway spruce seedlings and saplings per circular subplot was not correlated to local stand basal area. Out of 36 regressions, only eight showed a significantly (p < 0.05) negative correlation between seedling and sapling height growth and local stand basal area. In five of these cases, removal of one point (subplot) made p > 0.05. The results suggest that density and growth of Norway spruce regeneration in selectively logged uneven‐aged Norway spruce stands is affected more by ground conditions than by local stand basal area. 相似文献
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Vindhya Prasad Tewari 《林业研究》2010,21(1):13-18
对用于评价印度拉贾斯坦邦热带干旱区沙漠柚木极限林分密度的公式进行了研究。对5个不同密度的林分基面积预测模型进行测试和比较,这些模型属非线性生长函数的轨迹不变量代数差形式。这些模型可根据林分变量,如优势高／公顷、立木数／公顷,预测林分基面积,还可用于评估不同造林方案。利用所收集的22块样地的数据建立模型。使用各种可能的树龄数据结构,用定性和定量标准比较了这些替代模型。使用Akaike信息准则差异统计来分析各种模型的预测能力。结果表明：Hui和Gadow提出的模型预测效果最好,推荐在本研究区域内使用该模型来预测沙漠柚木林分基面积。但是,此模型并未使用间伐林分数据,因此,不能准确地预测林木有明显自然死亡的林分基面积。 相似文献
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David D. Reed Kurt S. Pregitzer Hal O. Liechty Andrew J. Burton Glenn D. Mroz 《Forest Ecology and Management》1994,70(1-3):319-327
Sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forests were examined at four locations along an acid deposition and climatic gradient in the Great Lakes region of the USA. The study sites were matched in terms of physiography, soils, stand history, and vegetative characteristics. Measurements of basal area and biomass growth were made for the 1988–1991 growing seasons. There were no significant differences in either basal area of biomass increment among the four sites over the 4 year period. There was a great deal of year-to-year variability with relative basal area growth rates ranging from as low as 0.2% to as high as 2.4% on a single site in successive years. Growth efficiency measures reflected this variability with as much as an 800% difference between successive years on a single site. When coupled with year-to-year variability of up to 34% in leaf area related to heavy seed years and defoliation, this indicates that growth efficiency and leaf area measures are not consistent indicators of aboveground productivity for tolerant deciduous species, especially if derived from short-term measurements or temporary plots. 相似文献