共查询到18条相似文献，搜索用时 640 毫秒
1.
为培育巨尾桉大径材,对造林密度为1650株·hm-2的10年生巨尾桉,开展二次间伐试验,首次间伐在造林后3 a进行,第二次问伐在第1次间伐后3 a进行,分别设置间伐株数2/3、1/2、1/3及不间伐(对照)4种间伐强度处理,采用随机区组试验设计.分析不同间伐强度对巨尾桉林分胸径、树高、单株材积、林分蓄积和经济效益的影响.结果表明:第2次间伐保留密度为645株·hm-2的林分,其平均胸径23.6 cm、立木单株材积0.552 5 m3、林分蓄积356.379 m3·hm-2、经济效益为293 385元·hm-2,分别比对照增加21.2％、54.2％、5.2％、28.4％,均优于其他不同处理.表明间伐强度以株数1/3为宜,保留密度为645株·hm-2的巨尾桉大径材林分,其胸径、单株材积、林分蓄积量和经济效益达到最大值. 相似文献
2.
尾巨桉2种留萌密度的幼林生长比较 总被引：2，自引：0，他引：2
为探讨留萌密度对尾巨桉（Eucalyptus urophlla×E.grandis）萌芽林生长量的影响,分4个生长时期（0.3年生,1.4年生,2.3年生和3.3年生）对广西东门林场尾巨桉2种留萌密度（留萌1株和留萌2株）的萌芽林的生长量进行了调查研究.结果表明：2种留萌密度下桉树萌芽林的胸径,树高及林分蓄积量均有不同程度的差异.留萌1株的萌芽林平均树高和平均胸径均显著高于留萌2株的萌芽林,而且这种差异会随林龄的增加而增加;而留萌2株的林分蓄积量表现出高于留萌1株的萌芽林的态势,但差异随着林龄的增加而减小. 相似文献
3.
通过2012—2013年顺昌县大历镇阔叶树保留木资源调查分析,结果表明:不同径阶阔叶树保留木的株数分布整体上呈"L"形,每个径阶阔叶树保留木达200株以上的主要分布于径阶为6~14cm之间,共有1 499株,占总数的73.37%;径阶16cm以上保留的株数仅占总数的26.63%。阔叶树保留木中间层中径木,共有1 978株,占总数的96.82%;上层大树仅65株,仅占总数的3.18%。不同径阶的阔叶树保留木蓄积量分布基本上呈正态分布,径阶5~14cm阔叶树保留木蓄积量为63.82m~3,占总保留木阔叶树蓄积量187.29m~3的34.08%;径阶16cm以上的阔叶树保留木蓄积量为123.47m~3,占总保留木阔叶树蓄积量的65.92%,是径阶5~14cm阔叶树保留木蓄积量1.93倍。阔叶树中间层中径木蓄积量为146.08m~3,占总蓄积量的78%;上层大树蓄积量为41.21m~3,蓄积量占总数的22%。阔叶树保留木胸径5~14.9cm共需补偿3 191元,胸径15cm以上需补偿12 347.00元,大历镇阔叶树保留木共需补偿15 538.00元。阔叶树保留株数平均值为138.6株?hm~(-2),阔叶树蓄积量保留平均值为12.75m~3?hm~(-2),阔叶树保留木不炼山造林成本从造林至郁闭前需投资27 000元?hm~(-2)。 相似文献
4.
为提高尾巨桉林分的经营效果,开展制造胶合板材用尾巨桉培育,研究以8 a为主伐年龄的3种造林初植密度即1 950株·hm~(-2)、1 650株·hm~(-2)和1 335株·hm~(-2)的生长与经济效益情况,结果表明:尾巨桉3种不同初植密度造林成活率均达96. 4%以上,林分主伐时保存率平均80. 2%,主伐时立木株数能达到1 545株·hm~(-2)左右为宜;尾巨桉胶合板材造林8周年主伐时,以初植密度1 950株·hm~(-2)处理的,单位面积林分蓄积量、产材量、产值及净利润均为最大。说明以生产胶合板材为目标的尾巨桉造林初植密度1 950株·hm~(-2)较合理,可获得较好的经济收益。 相似文献
5.
对 5 9年生尾叶桉纸浆林生长分析表明 :(1)密度与树高、胸径呈反比。 3种密度的树高、胸径大小均为密度B >C >D。两配置树高、胸径也以配置B >A。 (2 )密度对单株材积的影响与对胸径影响的规律一致。 5 9年生时单株材积生长量以密度B最高 ,达到 0 0 85 33m3·株 - 1,是最低单株材积密度D的 2 0 4倍。两配置单株材积以配置B >A。 (3) 4 7年生时单位面积蓄积量大小为密度B >C>D ,密度B达到 94 185m3·hm- 2 ,是最低D处理蓄积量的 1 15倍 ;5 9年生时蓄积量最大者为密度C ,达到 12 7 6 0m3·hm- 2 ,是最低蓄积密度D的 1 17倍。随着时间的变化 ,密度控制尤为重要。 4 7、5 9年生时单位面积蓄积均以配置B >A ,配置B分别比配置A高 2 4 82 %、2 3 5 3%。 (4)对胸径D和冠幅CW 值用方程进行回归拟合 ,结果以乘幂CW=a×Db 拟合最好。方程表达式为CW=0 4 72 4×D0 6 715。 (5 )编制的经营密度表反映出 ,随着胸径D的递增 ,基本经营密度N0 逐渐下降 ;当D≥ 18cm时 ,N0 的下降趋势渐趋平缓 相似文献
6.
西江林业局尾巨桉人工林一元材种出材率表编制 总被引：1，自引：0，他引：1
在广东省西江林业局尾巨桉无性系人工林中选择并设置70个标准地,分别进行林分因子调查,同时选择163株样木以2.0 m或2.6 m段材长分径阶进行样木伐倒造材,以实际经济材造材出材率为基础拟合并选择较优的单株木一元材积比方程,然后根据材积比方程进行理论造材并编制尾巨桉单株木一元经济材出材率表;接着利用单株木一元经济材出材率表对所调查的标准地进行理论造材,以林分理论造材出材率为基础拟合并选择较优的林分一元材积比方程,最后根据材积比方程研制尾巨桉林分一元经济材出材率表。所编制的数表均符合国家精度检验标准,可为本地区桉树生产经营提供参考。 相似文献
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8.
通过林地调查和室内分析化验,结果表明广西钦州市桉树二代萌芽林林地土壤酸性、有机质、全N、水解N、全K、速效K含量均降低;土壤磷素含量降低,全P含量为0.28～0.38g.kg-1、有效P含量为0.3～1.1mg.kg-1;Cu、B的含量也降低,且B含量偏低,仅为0.01～0.03 mg.kg-1。针对上述结果,提出了相应的测土配方施肥方案。分别以普通HA桉树肥、桉树专用肥、鸡粪+普通复合肥和钦州市林科所桉树配方复混肥4种肥料进行施肥对比试验,寻找最佳施肥方式。试验表明:尾巨桉施肥肥效明显,施用几种肥料对桉树二代萌芽林生长量均有显著促进作用,不同种类的肥料对桉树二代萌芽林前期生长量的肥效差别主要受肥料总养分含量、N、P、K百分含量及养分的合理配比影响。不同处理萌芽林分间的保留株数、树高、胸径、材积及蓄积均达极显著水平,钦州市林科所桉树配方复混肥较适合当地桉树二代萌芽林林木生长,3年生单株材积及蓄积量分别达到0.076 m3.株-1、105.396 m3.hm-2。 相似文献
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10.
为了解2种更新方式(植苗更新和萌芽更新)尾巨桉(Eucalyptus urophylla×E. grandis)人工林的碳汇功能,对广西宁明县4年生(中龄林)尾巨桉植苗林和萌芽林碳储量及其分布格局进行研究。结果表明,尾巨桉植苗林和萌芽林各器官中碳含量为456.5～485.3 g/kg,以树叶碳含量最高,其次为树干、树枝、树根,最低为树皮。植苗林和萌芽林生态系统碳储量分别为130.35和138.81 t/hm~2,其中乔木层分别占37.46%和42.30%,灌草层分别占0.93%和0.83%,现存凋落物层分别占2.05%和2.23%,土壤层分别占59.56%和54.64%。植苗林和萌芽林乔木层地上部分年净生产力分别为22.21和25.16 t·hm~(-2)·a~(-1),年净固碳量分别为10.58和11.91 t·hm~(-2)·a~(-1),年净吸收CO_2量分别为38.79和43.67 t·hm~(-2)·a~(-1)。 相似文献
11.
Coppice regeneration of eucalypt plantations is increasingly being used in Australia to reduce re-establishment costs. However, little is known about the impact of early coppice reduction regimes on harvester performance during clearfelling. The trial compared the productivity, time consumption, cost and fuel use of a single-grip harvester (Hyundai 210LC-9 base and SP 591LX harvesting head) clearfelling a 10.5-year-old, second-rotation coppiced Eucalyptus globulus stand in south-west Western Australia for chip logs. Coppice stems had been reduced to one stem or two stems per stool or left untreated. Time and piece counts were used to determine harvester productivity. Harvester cycle and elemental times and the number of logs and harvester head passes per stem were obtained from video recordings. Harvester fuel use was determined by refilling the fuel tank to the same point each day. Stem size was the major factor influencing harvester productivity (20.8 m3 per productive machine hour without delays [PMH0], 11.8 m3 PMH0?1 and 8.6 m3 PMH0?1 in the single-stem (mean stem volume [MSV] 0.21 m3), two-stem (MSV 0.09 m3) and untreated trial areas (MSV 0.06 m3), respectively. Estimated harvester cost (AU$ m–3) was considerably greater for the two-stem and untreated trial areas, which reflected the lower harvester productivity in these areas. Processing time represented over 60% of the total cycle time for all trial areas. Coppice characteristics resulted in significantly different moving/positioning times between trial areas. However, this difference had no impact on cycle times. Number of logs per stem was a significant variable in cycle and processing time regressions for all trial areas and felling time for the single-stem trial area. Number of harvester head passes was a significant variable in cycle and processing time regressions for the single-stem trial area and processing times for the two-stem trial area, although its effect was less than that of the number of logs per stem. Fuel consumption (L PMH0?1) was relatively constant between the trial areas, hence harvester energy intensity (L m?3) reflected the harvester productivity in each trial area. 相似文献
12.
The impacts of wood harvest, biomass removal and inter-rotation site management practices on productivity of Acacia mangium in South Sumatra were studied over 12 years across successive rotations. The productivity measured as MAI increased from 29.4 m3 ha?1 year?1 in the first to 48.0 m3 ha?1 year?1 in the second rotation. Whole tree harvesting (total stem, branches and leaves) caused a 21 % reduction in volume compared to harvesting merchantable wood alone in the next rotation. The rates of nutrients accumulation in trees were highest during the first year of growth, and declined from age 2 years. Significant amounts of nutrients were recycled through litter fall from 1 year after planting. Results highlight the importance of management which promotes nutrient supply on stand growth. Removal of slash and litter lowered soil pH, by about 0.1 unit. A small reduction was also found in soil organic carbon and nitrogen in the top soil during the first 3–4 years but values returned to pre-harvest levels by the end of the rotation. Extractable soil phosphorus and exchangeable cations decreased by the end of second rotation but these measures underestimate the nutrient pools available for A. mangium. These findings along with results from other studies have helped to implement operations which promote conservation of site resources for sustainable production in the region. 相似文献
13.
The structure of forest stands changes through developmental phases. This study is carried out in the unmanaged, oriental beech (Fagus orientalis Lipsky) stands in the north of Iran. The aim of this research was to quantify structural characteristics of stands in the stem exclusion phase using common structural indices, which include mingling, tree–tree distance, stem diameter, and tree height differentiation. According to our measurements from three stands, naturally regenerated stands tend to be mixed in species composition have slightly heterogeneous diameter distributions and uniform tree height. The average distance between trees was 3.3 m. Stocking volume of the stands had an average of 540 m3 ha?1 and 412 stem ha?1. Dead wood volume was 24 m3 ha?1, and as a standing volume, the most frequent species in dead wood pool was oriental beech (F. orientalis) (48 %). The common form of dead trees was snag (41 %). The mean value of mingling and tree-to-tree interval indices revealed that beech was mixed intensively with hornbeam and appears to be a more successful competitor for space and light compared with hornbeam; moreover, we found relatively high evidence of inter-species competition in this phase. A better understanding of stand characteristics in the stem exclusion phase as a critical part of the natural dynamics of forest ecosystems could facilitate predictions about the future changes within the stand. 相似文献
14.
A species introduction experiment including several tropical pines and eucalypts was established in 1966/1967 in the Tchianga research station in Angolan Highlands. Despite 27 years of political conflict (1975-2002) and lack of management, the research experiment has remained relatively well conserved. We measured the best conserved plots that were 41 years old in 2007 to obtain information on the growth of different pine species. We calculated stand characteristics including basal area, dominant height, mean diameter, and stand volume for Pinus patula Schiede ex Schiltdl. Et Cham., Pinus pseudostrobus Lindl., Pinus kesiya Royle ex Gordon, Pinus devoniana Lindl., Pinus chiapensis (Martinez) Andresen, Pinus elliottii Engelm., Pinus greggii Engelm. Ex Parl., Pinus montezumae Lamb. and Pinus oocarpa Schiede ex Schltdl. The growing stock volume at 41 years was the highest in P. pseudostrobus, 1,325 m3·ha-1, followed by P. kesiya with 1,200 m3·ha-1. The widely planted P. patula had a growing stock volume of 892 m3·ha-1. P. oocarpa and P. pseudostrobus had the highest stand basal area, over 80 m2·ha-1. Using increment core analyses we studied the temporal development of stand characteristics. Analysis of the mean annual increment (MAI) showed that rotation lengths of 20-30 years would maximize wood production. With these rotation lengths, the MAI of P. pseudostrobus would be 35 m3·ha-1. Other productive species were P. kesiya, P. oocarpa and P. chiapensis. P. patula had a maximum MAI of 20 m3·ha-1. P. greggii had the lowest mean annual volume production, only about 13 m3·ha-1. 相似文献
15.
Comparison of taper functions between two planted and coppiced eucalypt clonal hybrids, South Africa
In addition to regeneration through seed, certain eucalypts are able to regenerate via the production of coppice shoots following
felling, which can then be selectively thinned over time and managed as a coppice stand for the commercial production of timber.
Little information could be found if tree form differs between coppiced (where one or two stems had been left per stump) and
planted eucalypts, or whether different volume taper models would need to be developed. To determine if this was necessary,
rotation-end stem taper data was collected from an Eucalyptus grandis × E. urophylla and an E. grandis × E. camaldulensis trial to compare volume taper equations for planted versus coppiced commercially grown Eucalyptus clonal hybrids. For treatment comparisons, taper data were collected from the parent crop (1R), the replanted crop (2R),
as well as from coppiced stands where either a single (Cop_Sngl) or double stem (Cop_Dbl) had been left per stump. Stem taper functions used for treatment comparisons indicated differences between clones, as well as between treatment, with
the models based on single stems (1R, 2R or Cop_Sngl) being significantly different from those containing two stems (Cop_Dbl).
Despite any non-significant model differences (for example between 1R, 2R and Cop_Sngl single stem crops) the percentage magnitude
of any bias in utilizable volume differences when comparing the individual models (between a 6.31% over-prediction to a 3.8%
under-prediction) still needs to be taken into account as these differences may have importance in terms of the volume and
product prediction. 相似文献
16.
Tran Van Do Phung Dinh Trung Mamoru Yamamoto Osamu Kozan Nguyen Toan Thang Dang Van Thuyet 《Journal of Sustainable Forestry》2018,37(1):1-14
Forest ecosystems can modify the atmospheric CO2 through biomass accumulation mostly in tree stems with diameter at breast height (DBH) ≥ 10 cm. Aboveground biomass increment (ΔAGB), and changes in stand AGB, no. stems and basal area (BA) were calculated from mortality, recruitment, and growth data of tree stems in tropical evergreen broadleaved forest, Central Highland Vietnam. Data were derived from ten 1-ha permanent plots established in 2004, where all stems with DBH ≥ 10 cm were tagged, identified to species, and measured for DBH in 2004 and 2012. In an 8-year duration, the increment was 53 ± 10 stems ha–1, 7.8 ± 0.3 m2 ha–1 for BA and 86.0 ± 4.6 Mg ha–1 for AGB. The stem mortality rate was 0.9% year–1 and the stem recruitment rate was 2.2% year–1. Annual ΔAGB was 10.8 Mg ha–1 year–1, equaling to 5.4 Mg C ha–1 year–1. Of which, tree stems of 35–80 cm DBH classes accounted for 65%. The results indicated that the forest is in stage of carbon sequestration. Any disturbances causing death of 35–80 cm DBH tree stems will much reduce carbon sequestration capacity and it will take a long time for AGB to return to pre-disturbance stage. 相似文献
17.
《Scandinavian Journal of Forest Research》2012,27(1):2-12
Abstract Tree mortality, its causes, and the input of dead charred wood were studied in 11 managed 30–45-year-old Scots pine (Pinus sylvestris L.) stands 1 year after experimental low-intensity prescribed burnings in southern Finland. First, the relationship between fire-induced tree damage and several external variables, e.g. stand density, within-stand wind speed, open-air wind speed, the Finnish Forest Fire Index (FFI) and flame height, was studied. Secondly, the study examined which damage and morphological characteristics best predicted tree mortality. Tree mortality was very variable in the experimental plots, ranging from 0% to 48% on the basis of stem number and from 0% to 41% in terms of wood volume. The input of dead and charred wood decreased with stand age, being 19.4 m3 ha?1 in 30–35-year-old stands, but only 1.7 m3 ha?1 in 45-year-old stands. The input of dead wood was on average 10 m3 ha?1, representing less than 5% of the mean volume before the prescribed fire. The external variables that best explained fire-induced damage were within-stand wind speed, flame height and FFI. Tree mortality was best predicted by charred stem ratio with bark thickness, and by charred stem ratio with tree diameter. The results indicate that prescribed burning that is conducted downwind increases tree mortality and changes subsequent stand structure with increasing within-stand wind speed. 相似文献
18.
《Forest Ecology and Management》2001,141(3):165-174
The effects of long rotation periods and heavy low thinning on chestnut (Castanea sativa Mill.) coppices have been evaluated from a bio-ecological point of view. Aboveground tree biomass and its partitioning, bio-ecological indexes such as litter production, leaf area index (LAI), radiation regime, and growth efficiency have been analyzed for 4 years in thinned and unthinned permanent plots established in a coppice stand aged 11 years under normal rotation (NR) and in a coppice stand aged 35 years under long rotation (LR). A decrease in LAI, litter production and growth rate with the age was observed. LR showed high current annual increments (>16.0 m3 ha−1 per year and 8.0 Mg ha−1 per year for volume and aboveground biomass, respectively). Only slight differences in growth efficiency were observed. The adoption of heavy thinning (one third of basal area removal) affected stocking and determined significant differences in the light regime below the canopy, amount of gaps in canopy cover and LAI values, particularly in the years immediately after thinning, whereas slight differences were observed in growth efficiency. Nevertheless, chestnut showed a good aptitude, more evident in the younger stand, to re-build a homogeneous canopy cover: only a few years after thinning, canopy cover characteristics of thinned plots were similar to those of control plots and differences were not significant. Growth and increments in thinned plots were practically the same as in control plots, a consequence of consistently higher performances of released trees in the thinned plots. The results concur to a positive evaluation of a cultivation system based on long rotation periods and heavy thinnings, not only for the obtainable revenue, but especially from a bio-ecological point of view and make it a valid alternative either to abandonment or traditional over-exploitation of chestnut coppice stands. 相似文献