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本文根据农林复合系统中林分（以林带为主体）的特殊性，结合树木生长发育和林带结构变化规律，将农林复合系统中林分生长发育划分为幼龄期、中龄期（速生期）和防护成熟期。并采用林分径级离散度、防护成熟龄、更新龄等量化指标将３个生长发育时期定量化；对于东北地区农田林网中杂交杨、乡土杨的幼龄期为０～５、０～８，速生期６～１５、９～２４，实际防护成熟期１６～３３、２５～３６，防护成熟期１６～自然成熟龄、２５～自然成熟龄。同时给出各生长发育时期相应的经营措施。为农林复合系统中林木经营提供可靠的依据。 相似文献
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《西部林业科学》2017,(1)
以三峡库区柏木纯林和柏木青冈混交林为研究对象,研究不同林分类型柏木林土壤有机碳与土壤呼吸特征。结果表明,柏木青冈混交林土壤各土层(0~20cm,20~40cm,40~60cm)的总有机碳、微生物生物量碳、易氧化有机碳及水溶性有机碳含量均极显著高于柏木纯林;混交林土壤各土层转化酶活性总体上均显著高于柏木纯林,但2种林分之间的土壤C/N无显著性差异;柏木青冈混交林各土层土壤呼吸强度分别比柏木纯林高出22.3%、18.3%、5.3%;各林分土壤有机碳、转化酶活性、C/N均与土壤呼吸强度存在显著的相关性。可见,与柏木纯林相比,柏木青冈混交林具有更大的有机碳储量,表现出更强的土壤固碳能力。 相似文献
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<正> 用材林的主伐年龄主要依据工艺成熟龄(目的材种平均生长量达最大时)来确定。在相同条件下工业材种出材率在很大程度上与林分平均直径、林分平均年龄和立地条件有关。计算工艺成熟龄时,先根据树种和立地条 相似文献
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为研究鄂西山区日本落叶松人工林林分碳储量变化规律并确定碳储量成熟龄,利用8～41年生日本落叶松人工林87个标准地和249株样木树干生物量测定数据,以建立的单木树干生物量估算方程为基础,利用生物量扩展因子和碳系数推算出各林分单位面积碳储量,构建林分碳储量预估方程。结果表明:该区域日本落叶松人工林平均单株树干生物量为85.334 kg(2.694～395.214 kg),以胸径或树高为变量的一元和二元方程对单木树干生物量的拟合优度均在0.9以上,而二元方程拟合优度和精度更高;林分平均单位面积碳储量为77.465 t·hm-2(4.573～172.512 t·hm-2),其中单位面积碳储量为60～120 t·hm-2的样地占总样地数的64.4%;利用Richards、Korf和Compertz 3个模型对林分碳储量进行预估,林分碳储量及其平均和连年碳积累量均十分相近,其中最大连年碳积累量和最大平均碳积累量分别为6.2和3.9 t·hm-2左右,峰值林龄分别为13～15 a和23 a。Richards、Go... 相似文献
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不同密度南方型杨树人工林的主伐年龄研究 总被引：4，自引：1，他引：4
根据湖北省10个县、市31块标准地的11种主要密度类型林分的调查资料,从技术经济学的角度,以林分数量成熟与经济成熟为依据,对各密度类型林分的主伐年龄进行了研究,结果表明:①南方型杨树各种密度类型人工林的年均收益最大值出现在材积连年生长量最大值与数量成熟龄之间,一般早于数量成熟龄1～2a。②林分的主伐年龄与数量成熟龄表现出随着林分密度的减少而逐渐变大的总趋势,而主伐年龄时的最大年均净收益则随林分密度增大而增加,与林分单位面积蓄积量的变化趋势基本一致。③培育造纸、刨花板等小径材林分的轮伐期为5～6a,木芯板、火柴、家具等中径材的轮伐期为6～9a,培育胶合板等大径材的年限则需要10～12a。 相似文献
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湖南长防林一期工程碳汇量评价研究 总被引：1，自引：1，他引：0
通过对湖南长防林一期工程碳汇量的评价研究,发现:①随着林龄的增长,各林分生物量增量及碳汇量增量逐渐增大;②随着林龄的增长,各林分之间生物量及碳汇量的增长速度差异较大,增长速度最大的常绿落叶阔叶混交林是增长速度最小的经济林的11.8倍。各林分生物量及碳汇量的增长速度为:常绿落叶阔叶混交林>松木林分>针阔混交林>杉木林分>低质低效林改造>柏木林>封山育林>经济林;③1991～2002年湖南长防林一期工程总碳汇量为1012.86t。 相似文献
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不同立地条件下桤木人工幼林生物量和生产力的比较 总被引：1，自引：0，他引：1
对不同立地条件下5年生四川桤木人工林的生物量和生产力进行了研究.结果表明：花垣地区和汨罗地区桤木人工林单株生物量分别为33.42和22.77 kg/株,林分生物量分别为54.65和57.66 t/hm^2,生产力分别为10.93和11.53 t/（hm^2.a）.对汨罗地区桤木进行间伐,同时适当施肥提高林地土壤养分含量,是提高林分生产力的必要途径. 相似文献
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在全球气候变化背景下,人工林不仅具有木材生产功能,还肩负起固碳的生态功能。认知林分蓄积和生态系统碳的生长规律,对人工林的多目标经营和可持续发展具有重要意义。以湖南省杉木人工林为例,从生态系统的角度出发,应用建立的杉木蓄积和生态系统碳生长模型,探讨了林分蓄积与生态系统碳生长之间的关系。结果表明:杉木林分蓄积成熟龄为18~27 a,随立地指数的增加而提高,随林分保留密度的增加而下降;生态系统碳成熟龄为16~35 a,随立地指数和保留密度的增加而下降;立地指数对林分蓄积和生态系统碳数量成熟龄的关系具有重要影响,在立地指数较低时,生态系统碳比林分蓄积晚成熟约15 a,而立地指数较高时,恰好相反。今后,为达到人工林的多功能经营目标,应根据立地条件,综合评估各种生产和生态功能的成熟龄。 相似文献
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本文通过拟合不同立地条件下的杉木林分生长模型,研究其数量、工艺、经济成熟,并以净现值最大的经济成熟为主,认为闽南国营林场人工杉木林分在不同立地条件下的采伐年龄可确定为:Ⅰ立地条件下为30年左右;Ⅱ立地条件下为24—28年;Ⅲ立地条件下为24年。 相似文献
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This study estimates the optimal rotation period of various tree species in Kenya and applies it in the management of lumbering forests through optimal synchronization of forest plantations to achieve a steady supply to lumbering firms. The optimal rotation period of three tree species, pine, cypress, and eucalyptus, was estimated using data from Kenya Forest Service. A combined application of Chang simple production model and ? Faustmann? model? reveals the optimal biological harvest age is 25 years for pine, 25 years for cypress, and 14 years for eucalyptus. However, introducing the prices and using the Faustmann optimal rotation model at the current market interest rate of 10.5%, the Faustmann rotation age for pine stand will be maximized at 12.67 years, cypress at 23.5 years, and eucalyptus at 38.4 years. The research further indicates significant variability in land expectation value and soil rent of various species and proposes an inclusion of “species” as a variable in forest land valuation. In the conclusion, nonmarket factors affecting the optimal yield were further explained and recommendations on sustainable yield production were suggested. 相似文献
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A. Wehrli P. J. Weisberg W. Schönenberger P. Brang H. Bugmann 《European Journal of Forest Research》2007,126(1):131-145
Simulation models such as forest patch models can be used to forecast the development of forest structural attributes over
time. However, predictions of such models with respect to the impact of forest dynamics on the long-term protective effect
of mountain forests may be of limited accuracy where tree regeneration is simulated with little detail. For this reason, we
improved the establishment submodel of the ForClim forest patch model by implementing a more detailed representation of tree
regeneration. Our refined submodel included canopy shading and ungulate browsing, two important constraints to sapling growth
in mountain forests. To compare the old and the new establishment submodel of ForClim, we simulated the successional dynamics
of the Stotzigwald protection forest in the Swiss Alps over a 60-year period. This forest provides protection for an important
traffic route, but currently contains an alarmingly low density of tree regeneration. The comparison yielded a significantly
longer regeneration period for the new model version, bringing the simulations into closer agreement with the known slow stand
dynamics of mountain forests. In addition, the new model version was applied to forecast the future ability of the Stotzigwald
forest to buffer the valley below from rockfall disturbance. Two scenarios were simulated: (1) canopy shading but no browsing
impact, and (2) canopy shading and high browsing impact. The simulated stand structures were then compared to stand structure
targets for rockfall protection, in order to assess their long-term protective effects. Under both scenarios, the initial
sparse level of tree regeneration affected the long-term protective effect of the forest, which considerably declined during
the first 40 years. In the complete absence of browsing, the density of small trees increased slightly after 60 years, raising
hope for an eventual recovery of the protective effect. In the scenario that included browsing, however, the density of small
trees remained at very low levels. With our improved establishment submodel, we provide an enhanced tool for studying the
impacts of structural dynamics on the long-term protective effect of mountain forests. For certain purposes, it is important
that predictive models of forest dynamics adequately represent critical processes for tree regeneration, such as sapling responses
to low light levels and high browsing pressure. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):518-527
The study was focused on severe forest regeneration problems that are typical for highly productive peatlands. The aim of the study was to give recommendations for practical forestry on how to renew the forests. Experiments with different forest regeneration methods on highly productive peatlands were set up in nine mature Norway spruce (Picea abies (L.) Karst.) forests in northern, central and southern Sweden. The treatments in the study were natural regeneration in shelterwoods (at densities of 140 and 200 stems ha‐1), planting of bare‐root spruce seedlings after site preparation (mounding) in the shelterwoods and on clearcuts, and planting without site preparation on clearcuts. Judging from the extent of windthrow in the denser shelterwoods and the stocking of natural regeneration under remaining shelter trees 4–5 years after final cut, shelterwood regeneration is a promising method. On clearcuts, planting without site preparation resulted in poor seedling survival, large extent of damage to the seedlings and small height increment. Planting in mounds on the clearcuts was much more successful. The best survival of planted seedlings was observed in the shelterwoods. Both the denser and the sparse shelterwoods seemed to give satisfactory protection to the seedlings. Final recommendations on the most suitable forest renewal method(s) will be made in about five years after the removal of the shelter trees. 相似文献
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紫色土桤柏混交模式研究 总被引：3，自引：0，他引：3
桤柏混交林是紫色土的主要人工混交类型,在长江防护林建设中有重要作用。根据1983年营造的8种混交模式林分,研究了桤柏混交改良土壤、促进柏木生长的效果,用模糊综合评判方法,提出了不同立地类型的混交模式。 相似文献
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秦岭山地云杉林结构特征与更新动态的研究 总被引：8，自引：0，他引：8
云杉 (ＰｉｃｅａａｓｐｅｒａｔａＭａｓｔ.)林是秦岭林区高中山地带的顶极群落类型之一 ,由于其蓄积量高、材质优良 ,亦为秦岭林区开发利用最早的森林类型 (张仰渠 ,1 988)。陕西省云杉天然林面积日渐稀少 ,且资源分散 ,因此恢复云杉林在高山地带特有的防护作用 ,是秦岭林区一个重要的研究课题。本文根据对该林区天然云杉林、择伐更新林及皆伐迹地更新林的调查对比分析 ,研究了云杉林的结构特征及其更新动态 ,以期为探索该区云杉林的恢复途径及扩大这一树种资源提供科学依据。1 研究区概况及方法1 1 研究区概况 该研究在陕西省宝鸡市… 相似文献
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Age structure and regeneration dynamics of subalpine fir (Abies fargesii) forest were studied across the altitudinal range in both the north and south aspects of the Qinling Mountains, China. Ages of individual fir trees were determined based on the number of rings counted from cores and the number of years to reach coring height estimated using age–height regression. Fir age structure and regeneration dynamics were similar in both the north and south aspects. A unimodal population age structure was found at the low- and mid-elevations in both aspects, indicating that environmental factors might play an important role in shaping A. fargesii age structure and regeneration at those sites. There was a recruitment pulse during the time period 1830–1890 at each altitudinal site, but no stem recruitment occurred at the low- and mid-elevations in the last century, which might be attributed to the intensive cover of understory bamboo. Fir trees were, however, persistently recruited at the upper limits during the last 150 years, and the fir tree density at the upper limits was significantly higher than that at the lower limits in both aspects. The fir population at the upper limits showed a significant increase in recruitment and stem density relative to the fir population at the low- and mid-elevations in the last century. We propose that the differences in recruitment might promote variations in stand structure and regeneration dynamics of the subalpine fir forests along the altitudinal gradient in the Qinling Mountains, China. 相似文献
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Thomas Wohlgemuth Raphael Schwitter Peter Bebi Flurin Sutter Peter Brang 《European Journal of Forest Research》2017,136(5-6):1029-1040
The two storms Vivian (1990) and Lothar (1999) left an area of roughly 9000 ha of fully damaged protection forests in Swiss mountain regions. Given this huge dimension, questions arose on how to manage these areas to keep the protection gap, i.e. the time period with reduced overall protection against natural hazards, short. Quantifications are presented for the stability of lying logs left in place, the frequency of post-disturbance mass movements, and the tree regeneration in windthrow areas. The average height above ground of unsalvaged lying logs decreased from 2.1 m shortly after disturbance to 0.8 m 20 years later. In the period 1990–2014, the number of avalanches in windthrow areas was markedly small, and annual rates of shallow landslides and debris flows in windthrow areas did not differ from rates in comparable undamaged forested areas. Regeneration density rarely exceeded 4000 stems ha?1 20 years post-windthrow at elevations above 1200–1500 m a.s.l. Mean height of tallest trees reached 5.6 m in areas that were cleared and 6.5 m in those left unsalvaged. Trees planted post-windthrow were 1.0–2.4 m taller than naturally regenerated ones. Practitioners rated the protective effect to be acceptable 24 years post-disturbance in only 5 out from 16 observed windthrow areas (31%), with planting trees as the main cause of success. We conclude that in protection forests the regeneration speed after disturbance rarely meets practitioner’s expectations in terms of both stem density and stand structure. However, leaving woody debris from wind disturbance in place proved to replace protective effects for an astonishingly long time. An intensive management with salvage logging, planting and even technical constructions seems therefore only inevitable on windthrown areas where risks seem too high based on hazard, damage potential and possible spread of bark beetles to nearby protection forests. A management alternative applicable to many other cases of windthrown protection forests is to plant trees between lying stems. 相似文献
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我国防护林更新改造技术研究综述 总被引：4，自引：0，他引：4
防护林更新改造技术是防护林经营中的一项重要内容,国内外对其研究还不深入,很多领域有待加强。该文在有关文献的基础上对我国防护林更新改造技术体系进行了总结和评述,为以后有关研究提供依据。 相似文献
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Sandra Molina ColónAriel E. Lugo Olga M. Ramos González 《Forest Ecology and Management》2011,262(2):170-177
We report results of new research on (1) community composition of novel subtropical dry forests developing on abandoned pastures and agricultural fields in both private and protected public lands and (2) seed germination and growth rates of plantings of native tree species on degraded soils. We found that novel dry forests were dominated by introduced species, which accounted for 59 percent of the Importance Value (IV) of stands. These forests had high species dominance, with the most dominant species averaging 51 percent of the IV but reaching values as high as 92 percent. The floristic similarity between novel and mature native forests was low (5.6 percent) compared with the similarity among novel forest stands (26 percent). Collectively, the emerging novel forests had relatively high species richness (39 species/1.2 ha). After 45-60 years of growth and development, novel forests lagged mature native forests in basal area, tree density, and species richness, and lagged stands of similar age and past land use inside a protected area. Novel forest stands inside the protected Guánica Forest had higher species richness than those located outside in private lands. Most regeneration was from seed (67 percent of the new stems were single stems). The results from the germination and planting experiment show that seeds of 17 of 21 native tree species germinated in the laboratory and grew successfully in abandoned pastures when planted and watered for a period of 13 months. Our research shows that after the initial invasion and dominance of introduced species on degraded sites, the stands diversify with native species thus evolving towards new forest types with novel species combinations. 相似文献