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221.
222.
湖北白蜡是我国特有珍稀濒危植物,仅在湖北省中部大洪山南麓残存,其自然分布区位于京山县与钟祥市接壤一条狭长地带内,现有的湖北白蜡大多为萌芽更新混交林,主要有五个类型,即湖北白蜡-铜钱树混交林,湖北白蜡-黄连木混交林,湖北白蜡-青檀混交林,湖北白蜡-三角枫混交林,湖北白蜡-菱叶海桐混交林,其中湖北白蜡处于优势地位,群落相对稳定,但在自然演替中,由于人为破坏严重,其它树种的入侵,对湖北白蜡构成严重威胁。 相似文献
223.
间伐强度对水曲柳木材材质的影响 总被引:5,自引:0,他引:5
郭明辉 《东北林业大学学报》2001,29(6):36-37
研究了不同间伐强度对水曲柳木材材质的影响,结果表明:间伐强度对水曲柳木材的纤维长度和胞壁率无显著影响;对生长轮宽度、晚材率、生长轮密度、木材硬度有显著影响;材质综合评定表明重度间伐的林分木材材质最优,轻度间伐林分材质次之,未间伐林分材质相对较差,可采取间伐的培育措施对水曲柳林木进行定向培育。 相似文献
224.
水曲柳人工林土壤养分的空间异质性研究 总被引:7,自引:1,他引:7
采用地统计学的变异函数分析方法,定量研究了14年生水曲柳人工林表层土壤(0~10cm)养分的空间异质性特征。结果表明:(1)土壤有效磷、全钾和速效钾变异函数曲线的理论模型符合指数模型,土壤pH值符合球状模型,土壤全氮、水解氮和全磷的理论模型符合指数模型或球状模型;(2)土壤养分各项指标的空间变异主要是由结构性因素引起,且空间自相关程度均属中等以上(空间结构比均在25%以上);(3)土壤pH值的空间自相关范围最大(2.27~4.46m),土壤全磷的自相关范围(0.73~0.97m)小于全钾和全氮(分别为1.02~1.05m和0.90~1.18m),土壤有效磷的自相关范围(0.90~1.20m)小于速效钾(0.95~2.86m)和水解氮(1.41~4.25m),速效养分的自相关范围均大于或近似等于相应养分的全量养分。(4)土壤pH值、氮、磷和钾素的空间格局明显,土壤pH值、全氮、水解氮、全磷、有效磷、全钾、速效钾的分数维分别为1.789~1.862,1.217~1.952,1.838~1.927.1.878~1.935,1.899~1.944,1.936~1.965,1.907~1.963。 相似文献
225.
水曲柳的生长规律 总被引:4,自引:1,他引:4
水曲柳是我国东北林区的珍贵阔叶树种之一,由于长期的不合理采伐,这一资源已近枯竭。为了恢复和发展水曲柳资源,在长白山地区通过实验,对水曲柳的生长规律进行了研究。结果显示:水曲柳的高生长期与径生长期不同步,表现出先高生长,后径生长的现象。林隙自由生长木的高生长量和胸径生长量都远远大于林内丛生木的高生长量和胸径生长量。林隙木在后期的生长策略上表现为径生长占主导;相反,林内丛生木在后期的生长策略上表现为高生长占主导。对林分进行人工抚育,改善树木的生长条件,水曲柳的平均胸径达到24cm和32cm时的培育期可以分别比自然条件下(未抚育)的林分缩短15a和20a。 相似文献
226.
A.?Juodvalkis L.?Kairiukstis R.?VasiliauskasEmail author 《European Journal of Forest Research》2005,124(3):187-192
This paper summarises the results from 35 years-observed thinning experiments on 256 permanent sample plots in 10–60 year-old
stands of ash, aspen, birch, oak, pine and spruce in Lithuania. Thinning enhanced crown projection area increment of residual
trees. The largest effect was observed in stands of aspen and birch (growth increase by 200%), followed by ash and oak (over
100%), and spruce and pine (about 80%). Thinning also promoted dbh increment, especially in younger stands, and the increase
of dbh increment was positively correlated with the thinning intensity. The strongest reaction was exhibited by oak and aspen,
while ash, birch and conifers reacted to a lower extent. Low and moderate intensities of thinning stimulated volume production
in younger stands while the opposite was observed in older stands with increasing removals. Spruce stands exhibited relatively
strongest increase of volume increment and pine, –the weakest, while the effect on deciduous species was intermediate. The
results demonstrate that significant increase in volume increment is achievable with thinning of only young forest stands,
e.g. 10–20 year-old pine, birch and ash, or 10–30 year-old oak, aspen and spruce. 相似文献
227.
Direct herbivore damage to trees in temperate silvopastoral agroforestry systems is a major management consideration. Individual plastic tree-shelters may sometimes cause poor tree development and they have limited life span. Therefore, some alternative tree-shelter products were tested on four year old Acer pseudoplatanus and Fraxinus excelsior. Damage to the main stem was assessed by determining the area of bark removed by sheep browsing. Wobra®, a paint-on abrasive substance applied to the main stem, was effective in reducing sheep damage. However, some damage did occur due to breach of the protective barrier as a result of stem diameter increases and its removal through rubbing by animals. Anipel®, a systemic bittering agent supplied through the root system, was not effective in preventing significant damage compared to no-treatment controls, possibly because of poor uptake of the active ingredient into the tree. Within treatments, there were significant differences in damage incurred. Most notably Fraxinus suffered more damage than Acer, an effect which may be related to differences in tree size and/or relative palatability. 相似文献
228.
Variations of fine root diameter with root order in Manchurian ash and Dahurian larch plantations 总被引:1,自引:0,他引:1
Xiangrong Wang Zhengquan Wang Youzhi Han Jiacun Gu Dali Guo Li Mei 《Frontiers of Forestry in China》2007,2(1):34-39
Fine root lifespan and turnover play an important role in carbon allocation and nutrient cycling in forest ecosystems. Fine
roots are typically defined as less than 1 or 2 mm in diameter. However, when categorizing roots by this diameter size, the
position of an individual root on the complex lateral branching pattern has often been ignored, and our knowledge about relationships
between branching order and root function thus remains limited. More recently, studies on root survivals found that longevity
was remarkably different in the same branching level due to diameter variations. The objectives of this study were: (1) To
examine variations of fine root diameter from the first-to fifth-orders in Fraxinus mandshurica Rupr and Larix gmelinii Rupr roots; and (2) To reveal how the season, soil nutrient, and water availability affect root diameter in different branch
order in two species. This study was conducted at Maoershan Forest Research Station (45°21′–45°25′N, 127°30′–127°34′E) owned
by Northeast Forestry University in Harbin, northeast China. Both F. mandshurica and L. gmelinii were planted in 1986. In each plantation, fine roots of two species by sampling up to five fine root branch orders three
times during the 2003 growing season from two soil depths (i.e., 0–10 and 10–20 cm) were obtained. The results showed that
average diameters of fine roots were significantly different among the five branch orders. The first-order had the thinner
roots and the fifth order had the thickest roots, the diameter increasing regularly with the ascending branch orders in both
species. If the diameter of fine roots was defined as being smaller than 0.5 mm, the first three orders of F. mandshurica roots and the first two orders of L. gmelinii roots would be included in the fine root population. The diameter ranges of the fine roots from first-order to fifth-order
were 0.15–0.58, 0.18–0.70, 0.26–1.05, 0.36–1.43, and 0.71–2.96 mm for F. mandshurica, and 0.17–0.76, 0.23–1.02, 0.26–1.10, 0.38–1.77, and 0.84–2.80 mm for L. gmelinii. The average coefficient of variation in first-order roots was less than 10%, second-and third-order was 10–20%, and fourth-and
fifth-order was 20–30%. Thus, variation in root diameter also increased with the ascending root order. These results suggest
that “fine roots”, which are traditionally defined as an arbitrary diameter class (i.e., <2 mm in diameter) may be too large
a size class when compared with the finest roots. The finest roots have much shorter lifespan than larger diameter roots;
however, the larger roots are still considered a component of the fine root system. Differences in the lifespan between root
diameter and root order affect estimates of root turnover. Therefore, based on this study, it has been concluded that both
diameter and branch order should be considered in the estimation of root lifespan and turnover.
__________
Translated from Acta Phytoecologica Sinica, 2005, 29(6): 871–877 [译自: 植物生态学报] 相似文献
229.
冰冻条件下外源SA对水曲柳幼苗叶片内抗氧化酶的影响 总被引:8,自引:1,他引:8
分析了冰冻胁迫下外源水杨酸 (SA ,5mmol·L- 1 和 10mmol·L- 1 )对水曲柳幼苗叶片内抗氧化酶的影响。SOD活性受到SA抑制 ,且随外源SA的浓度增加而下降 ,导致超氧自由基上升。SA也能抑制CAT和APX活性 ,CAT活性随SA浓度增加而降低 ,APX活性也有这种趋势。尽管SA提高了POD活性 ,但由于CAT和APX活性受到抑制 ,H2 O2 含量上升。GR活性也受到SA抑制 ,呈现随SA浓度增加而降低的趋势。经 5mmol·L- 1 SA处理的叶片内MDA含量下降 ,平均比对照低 35 19% ,表明低浓度SA能降低冰冻引起的伤害。 相似文献
230.
Lastvears.manvrescarchaboutintcr-sPecificrclationshipofmixcdstandsforIarchandasht`crcrePeatcd,mostof\`tich,hot`cvcr,isfortheplantingtypeoflinc-bclt.Thispaperanalysisash-larchrclationshipfor26agcdartificialIarchstandmixedwithcvenagcdashinnaturalreqencration.SlTEANDMEASUREMENTMETHOl)ArtincialIarchstandmcasuredlocatcdatecologicaIcxPCrimcntstationinMaocrshanMountainForcstryFarmofNortbcastForcstryUnivcrsity'(El27'34',N45"24').LarchttasplantcdonagrcatPCaccofdescrtcdfieIdinl967t"itha… 相似文献