共查询到20条相似文献，搜索用时 187 毫秒
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本文通过章古台地区引种日本落叶松，其生长性状与当地主要造林树种樟子松，与清原海洋林场，湾甸子实验林场日本落叶松进行对比分析，证明日本落叶松适应性强，生长快，可在章古台地区良好生长，将成为樟子松更新改造的理想树种。 相似文献
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二白杨伐根化学除萌技术的研究 总被引：1，自引：0，他引：1
二白杨是河西走廊的主要乡土树种。更新改造时因二白杨伐根萌蘖性强,挖伐根、割萌条既费工费时费资金,又容易破坏土壤、植被,引起沙化,破坏生态环境。我们试用化学除萌技术,筛选出杀死或抑制萌条生长的最佳药剂、剂型和剂量,为目的树种生长创造了良好条件,为今后“小老树”改造、树种更替和二白杨萌芽更新提供了科学依据。 相似文献
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京密引水渠担负着输送北京城市饮用水的重任,是连接北京市地表水源——密云、怀柔水库与市区的一条城市生命线。而现有的防护林带由于林龄老化、树种单一、病虫害严重等各种问题,已不能很好的发挥涵养水源、保护水质等防护功能,急需进行更新改造,建成内部结构稳定、抗逆性强、林龄组分布合理、 相似文献
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杉木纯林改混交林阔叶树种的选择 总被引：1，自引：0，他引：1
为了可持续利用选出多种杉木纯林改造的阔叶树种的人工复层林的经营模式 ,在杉木纯林间伐后采用多种更新改造阔叶树的随机设计试验。调查分析表明 ,树种间的造林效果达到显著、极显著的差异 ,米老排为效果最佳树种 ,其次为光皮桦、火力楠、细柄阿丁枫 ,初步认为桤木不适宜作为改造树种 相似文献
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防护林建设是一个地区森林建设的重要组成部分,多种因素影响彰武县防护林退化严重。文章概况介绍了彰武防护林的现状,分析了立地条件差异大、降水量偏低、土壤沙化严重、有害生物灾害、树种选择欠佳和人为毁坏森林等防护林退化的主要原因,并提出了树种结构调整、提高苗木质量、提高水分利用率、有害生物防治和加大违法案件打击力度等退化防护林更新改造措施,以保证防护林的林分质量,发挥防护林的功能,为其他地区的防护林更新改造提供参考。 相似文献
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在不同生境条件下开展相思类树种造林试验研究,结果表明:厚荚相思对海岸前沿不良生境适应性强,可作为更新改造的主要树种之一;厚荚相思、纹荚相思、直干大叶相思及马占相思在低郁闭度林带下套种保存率高,生长量以厚荚相思表现最佳;基干林带间隔带状皆伐方式更新厚荚相思与湿地松、厚荚相思与木麻黄无性系多行配置种间关系稳定,单行混交易引起种间矛盾和空间的激烈竞争;后沿沙地厚荚相思与马占相思生长快,干形通直,蓄积量大,出材率高,是理想的更新树种。 相似文献
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通过对定海松林及更新层的调查，发现多数松林在皆伐后演替为落叶阔叶林，少数为常绿落叶阔叶林和灌、草丛。更新树种共计34种，占优势的仅9种，且多为落叶阔叶树种。针对演替类型及更新树种存在单调贫乏的现状，结合海岛具体实际，提出封山育林、人工造林和树种选择的方向性建议，将为松村线虫病除治迹地的更新改造提供依据。 相似文献
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雨雪冰冻灾害对仙居县林木的危害情况调查 总被引：3，自引：0，他引：3
2008年3～4月,在仙居县4个乡镇2个国有林场设置了44块标准地对林木受雨雪冰冻灾害情况进行调查,结果认为：在海拔500m以上,雨雪冰冻造成林木腰折、翻蔸与海拔高程无显著相关,杉类、松类、阔叶类各树种间出现腰折、翻蔸有显著差异;腰折、翻蔸木胸高断面积损失率为松木〉阔叶树〉杉木,断梢木胸高断面积受害率为杉木〉阔叶树〉松木,折枝木胸高断面积受害率为阔叶树〉松木〉杉木,正常林木胸高断面积保存率为杉木〉松木及阔叶树．土层浅薄处林木多出现翻蔸,土层深厚处林木多出现腰折．雨雪冰冻对不同坡向、坡位的林木危害无显著差异,但由于微地形条件,不同地块的林木受害程度差异较大． 相似文献
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Competition is a well-documented contributor to tree mortality in temperate forests, with numerous studies documenting a relationship between tree death and the competitive environment. Models frequently rely on competition as the only non-random mechanism affecting tree mortality. However, for mature forests, competition may cease to be the primary driver of mortality.We use a large, long-term dataset to study the importance of competition in determining tree mortality in old-growth forests on the western slope of the Sierra Nevada of California, U.S.A. We make use of the comparative spatial configuration of dead and live trees, changes in tree spatial pattern through time, and field assessments of contributors to an individual tree's death to quantify competitive effects.Competition was apparently a significant contributor to tree mortality in these forests. Trees that died tended to be in more competitive environments than trees that survived, and suppression frequently appeared as a factor contributing to mortality. On the other hand, based on spatial pattern analyses, only three of 14 plots demonstrated compelling evidence that competition was dominating mortality. Most of the rest of the plots fell within the expectation for random mortality, and three fit neither the random nor the competition model. These results suggest that while competition is often playing a significant role in tree mortality processes in these forests it only infrequently governs those processes. In addition, the field assessments indicated a substantial presence of biotic mortality agents in trees that died.While competition is almost certainly important, demographics in these forests cannot accurately be characterized without a better grasp of other mortality processes. In particular, we likely need a better understanding of biotic agents and their interactions with one another and with competition. 相似文献
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Leszek Bujoczek Janusz Szewczyk Małgorzata Bujoczek 《European Journal of Forest Research》2018,137(4):401-418
Standing and downed deadwood at different stages of decay provides a crucial habitat for a wide range of organisms. It is particularly abundant in unmanaged forests, such as strictly protected areas of national parks and nature reserves. The present work used the available data for such sites in Poland, analyzing a total of 113 studies concerning 79 sites to determine the causes contributing to variation in deadwood volume based on the duration of conservation, changes in deadwood volume over time (for those sites which were examined multiple times), elevation above sea level, forest type, stage of forest development, input of dead trees from the years preceding deadwood measurements, live tree volume, and the proportion of downed to standing deadwood). Depending on species composition and site altitude, most tree stands fell into one of four categories: subalpine spruce forests, montane beech-fir forests, low altitude beech-fir forests, or oak-hornbeam and riparian forests. The mean deadwood volume for all forest types amounted to 172.0 m3/ha. The mean volume of deadwood in montane beech-fir forests (223.9 m3/ha) was statistically significantly greater than in the other three forest types, for which it ranged from 103.5 to 142.5 m3/ha. A direct effect of the duration of conservation on deadwood volume was not identified. Nevertheless, analysis of repeated measurements on the same sample plots at 10-year intervals showed a consistent rise in mean deadwood volume. A linear regression model for all the analyzed factors reported from montane beech-fir forests and subalpine spruce forests showed that in addition to site altitude, another statistically significant variable was the input of dead trees (R2?=?63.54%). 相似文献
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The effectiveness of retention trees and patches in preserving diversity of nine epiphytic and epixylic old-growth forest lichens was studied in north boreal spruce forests in Finland. We compared (1) 7–8-year-old retention cuts, with at least 5–10 living or dead retention trees per hectare, (2) 10–12-year-old clear-cuts, with some scattered living and dead retention trees on the sites, (3) old-growth spruce forests, and (4) 7-8-year-old retention patches (0.06–0.45?ha) representing the original tree species composition of old-growth forests. The occurrence of indicator lichens was studied on 150 deciduous trees and snags in each forest category. The species richness was significantly higher in old-growth forests than in the clear-cuts and retention cuts, but did not differ between old-growth forests and retention patches. Only three species were found in clear-cuts and two in retention cuts. Foliose cyanolichens Leptogium saturninum and Nephroma bellum thrived on solitary retention trees, whereas humidity-requiring pin lichens from the genus Chaenotheca were found only in old-growth forests and retention patches. Our results suggest that the ability of epiphytic and epixylic species to survive on retained trees depends on several factors: (1) substrate quality (tree species, tree type and diameter of a tree), (2) environmental factors (e.g. humidity, slope exposition), and (3) morphological and physiological characteristics of species. Besides of substrate trees, the retained conifers (esp. spruce) seem to be important in retention patches to provide the shading necessary to maintain humidity. 相似文献
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Reforestation is one of the most important and efficient measures of water and soil conservation. Based on field investigations
in the Shangyang Soil Conservation and Reforestation Station in Huizhou, Guangdong Province, China, we studied the variation
in vegetation development, vegetation succession processes and soil erosion. The regional vegetation consists mainly of monsoon
evergreen broad-leaved forests (MEBF). The area was deforested and became a denuded hill area with extremely high soil erosion
in the 1960s and 1970s. Then, the area was closed in order to allow recovery of the vegetation. Under natural conditions the
vegetation development and succession processes were slow during which soil erosion and strong sunshine and evaporation slowed
down the development of the vegetation. About 25 years later, the vegetation cover was still merely 35% or so. The dominant
vegetation types were heliophilous herbage and shrubs which formed a poorly developed shrub-herbage community and erosion
remained high. In contrast, reforestation with selected tree species dramatically speeded up the vegetation succession process.
About 12 years after reforestation, vegetation cover of the Acacia auriculiformis plantations in the Shangyang Station was 90% and erosion was under control. After 23 years, understory vegetation, consisting
of indigenous species, had developed in the plantations. The planted trees and naturally developing herbage, shrubs, bamboo,
local trees and liana formed a complex vegetation community in three layers. It will take 60 years for the vegetation to succeed
from bare land to a secondary growth forest under natural conditions. Reforestation may speed up the vegetation succession
process. The time may be reduced to 20 years. Reforestation is the most effective measure of vegetation restoration and erosion
control in this area.
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Translated from Acta Ecologica Sinica, 2006, 26(8): 2558–2565 [译自: 生态学报] 相似文献
17.
柞蚕场封山育林对植被恢复的影响 总被引：2，自引：0，他引：2
对柞蚕场、柞蚕场封山育林6a、9a的植被调查数据进行了分析,结果表明:柞蚕场封山育林可明显促进蒙古栎等乔木的生长和郁闭,但由于萌生,林木的水平分布多呈现聚集于母树的丛状分布;封育后由于林分郁闭,林内光照降低,灌木和草本植物的盖度有所减少;通过多样性指数测度,封育后乔木层、灌木层、草本层的多样性指数均高于柞蚕场;封育后由于森林凋落物的增加使枯落物存储量不断增加,可改善土壤肥力、提高林地涵养水分的功能. 相似文献
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在对天宝岩国家级自然保护区不同海拔天然猴头杜鹃林乔木种群全面调查基础上,对猴头杜鹃林进行立木分级,采用动态可比性林木分级法研究了猴头杜鹃林种群结构。研究结果表明：不同海拔天然猴头杜鹃林均以Ⅳ级木占绝对优势,该级林木株数远远大于其他级林木数量。此外,各海拔天然猴头杜鹃林Ⅳ级木数量呈现高〉低〉中,而其在相应海拔所占比例却与海拔呈正相关;低海拔天然猴头杜鹃种群处在A型种群的前中期,中海拔种群处在A型种群的后期,高海拔天然猴头杜鹃种群则处在A型种群的中后期。 相似文献
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Kokoro Kikuchi Takumi Akasaka Yuichi Yamaura Futoshi Nakamura 《Journal of Forest Research》2013,18(5):389-397
The conservation of cavity trees in plantations is important for maintaining biodiversity because cavity trees are one of the forest attributes most strongly affected by forestry operations. We surveyed the occurrence of cavities at the tree-level and the abundance of cavity trees and the number of uses by secondary cavity users at the stand-level in natural and conifer plantation forests in Hokkaido, Japan. We classified cavities into two types by their formation processes: excavated and non-excavated. Excavated cavities were more common in dead trees than in live trees. Non-excavated cavities showed high occurrence in dead and live broad-leaved trees. The abundance of non-excavated cavity trees was two times greater than that of excavated cavity trees in natural forests, but, in plantations, excavated cavity trees were dominant. The abundance of non-excavated cavity trees was lower in thinned plantations than in not-thinned plantations. The number of cavity uses increased with the number of cavity trees, indicating the importance of maintaining cavity trees. Conifer plantations are established by removing native broad-leaved trees, which results in a lower abundance of non-excavated cavity trees in these locations. The conservation of broad-leaved trees is important for maintaining the current and future resource of non-excavated cavity trees in plantation forests, as is the conservation of dead trees, which showed a high occurrence of excavated cavities. 相似文献
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在延安对刺槐、油松、侧柏纯林及刺槐 侧柏、刺槐 油松混交林等几种黄土高原主要人工林群落外貌结构、林下植物多样性特征进行了研究.结果表明:混交林群落外貌结构较为复杂,林下植物群落类型各不相同;林下植物的Simpson多样性指数和Shnnon-wiener多样性指数分别为0.902 57～0.674 88和2.012 88～1.479 67,刺槐 油松林最高,16年生刺槐纯林最低;32年生刺槐纯林林下植物优势度最高者是糙隐子草,16年生刺槐纯林则为牡蒿,其它林型都是铁杆蒿;本地区选择防护林类型时,应优先选择刺槐 油松或刺槐 侧柏混交,对已有的成熟或衰退刺槐纯林可采取择伐萌蘖抚育,并间植油松或刺柏,形成针阔混交林. 相似文献