共查询到20条相似文献，搜索用时 313 毫秒
1.
以巨桉工业人工林为对象,采用“空间换时间法”,研究一个轮伐期巨桉林枯落物和细根碳储量,结果表明,1～6年生巨桉林枯落物碳储量为0．641～6．648t·hm^-2,不同年龄巨桉林枯落物碳储量1年为2．263±1．022t·hm^-2,2年为3．414±1．873t·hm^-2,3年为2．270±1．262t·hm^-2,4年为2．305±1．664t·hm^-2,5年为3．011±1．630t·hm^-2,6年为4．139±2．509t·hm^-2,6年生巨桉林枯落物碳储量最大。枯落物凋落量在年龄序列中表现为“高一低一高”的趋势;1～6年生巨桉林细根碳储量为0．101～0．637t·hm^-2,不同年龄巨桉细根碳储量1年为0．318±0．109t·hm^-2,2年为0．308±0．139t·hm^-2,3年为0j255±0．154t·hm^-2,4年为0．263±0．076t·hm^-2,5年为0．390±0．128t·hm^-2,6年为0．438±0．199t·hm^-2,6年生巨桉林细根碳储量最大,3、4年生较小,这与细根生物量的年龄变化趋势相一致。 相似文献
2.
对中甸山楂、西南花楸、川白桦、光核桃等4种滇西北亚高山乡土阔叶树种1年生容器苗的育苗容器规格和育苗磬质进行了研究。其相关的试验结果表明：4种树种不同育苗容器规格和育苗基质处理的150日容器苗苗木的苗离、地径、苗木主根长、侧根数、苗木的干、鲜重6项指标在不同处理间存在明显差异。依据试验结果提出中甸山楂、西南花楸一年生容器苗培育宜采用巾型规格的容器,其容器规格为11cm×15cm。白桦和光核桃一年生容器苗培育需使用中、大型规格的容器,其容器规格为11cm×15cm或15cm×18cm。中甸山楂和西南花楸一年生容器苗培育宜选用C基质生土（40％）＋山基士（40％）＋沙子（20％）和D基质生土（40％）＋火烧土（40％）＋山基土（20％）;白桦一年生容器苗培育宜选用C基质;光核桃一年生容器苗培育宜选用C基质或D基质,但推荐用D基质。 相似文献
3.
基于中国陆地生态系统通量观测研究网络（ChinaFlux）3年（2005．2007年）的观测数据,研究了千烟洲中亚热带人工林（QYF）和长自山温带混交林（CBF）的气体调节通量动态和气体调节价值累积过程。本文将气体调节服务区分为植被气体调节服务和净生态系统气体调节服务。采用碳税法、造林成本法和工业制氧法对气体调节服务价值化,研究表明气体调节通量具有显著的季节变化。千烟洲人工林和长白山混交林植被的日均CO2吸收量分别为82．00kg·hm^-2·d和59．37kg·hm^-2·d,对应的O2通量分别为59.65kg·hm^-2·d和43．19kg·hm^-2·d。千烟洲人工林和长白山混交林的植被气体调节价值累积过程曲线均为S型,年均植被气体调节服务价值分别为14342．69元·hm^-2和10384．18元·hm^-2。就净生态系统气体调节服务而言,千烟洲人工林全年各月均表现为CO2的净吸收和O2的净释放,而长白山混交林则主要在5-9月表现为CO2的净吸收。千烟洲人工林的净生态系统气体调节价值累积过程曲线为S型,而长白山混交林则为单峰型。千烟洲人工林和长白山混交林的年均净生态系统气体调节服务价值分别为8470．52元·hm^-2和5091．98元·hm^-2。植被气体调节服务和净生态系统气体调节服务主要发生为5-10月。 相似文献
4.
通过野外观察和实验室可控条件下的测定,研究了杨小舟蛾蛹的羽化日节律特征和第1 4代羽化进程差异,统计了各代次羽化率和历期,分析了其羽化影响因子。结果表明：杨小舟蛾蛹羽化表现为“驼峰型”节律特征,羽化高峰出现在4：00和17：00;其1 4代蛹在相同羽化条件下羽化进程存在差异,羽化完成总虫数80%所需时间逐渐缩短,相同世代雌雄羽化高峰间隔也逐渐缩短;杨小舟蛾蛹1 4代在相同羽化条件下的平均羽化率间存在显著差异,分别为（31.41±1.16）%、（43.67±1.84）%、（38.20±1.39）%和（27.81±2.42）%;各代羽化历期存在显著差异,分别为（10.71±0.45）、（8.56±0.17）、（6.88±0.68）、（6.43±0.66）d。羽化影响因子分析表明：不同温度和湿度处理间羽化率存在显著差异,较好的组合为光期温度（30±1）℃、暗期温度（24±1）℃,光期湿度（50±10）%、暗期湿度（70±10）%,光周期处理间差异不显著。 相似文献
5.
通过在田林县3个不同林龄的马尾松人工林分中设置标准样地并进行每木调查,以D—H曲线进行平均木选择,分径阶伐倒平均木获得生物量数据。以幂指数模型和线性函数为基础对马尾松人工林的单株生物量模型进行了模拟,得到树干、树叶、树皮、树枝、树根和总生物量的回归模型分别为：W=166．0860×（DOH）-2．0497、W=9．1446×（DOH）＋2．1403、W=10．1717×（D^2H）^0.5959、W=0．0035×D^2.9702、W=32．7589×（D^2H）^0.8546、W=258．2048×（D^2H）＋2．0278。数据分析结果表明,马尾松林分平均木生物量随林龄的增加而增大,各器官的生物量所占总生物量的百分比出现明显的变化;各器官的生物量均以树干为最高,并随着林龄的增加而升高;树枝、树叶和树根的比例随着林龄的增加而出现下降。 相似文献
6.
用互比排列设置刺槐林改造更新小区，采用多指标综合分析法探讨理想的更新方式，其结果表明：在同一降雨量、雨强、历时的条件下，林地土壤含水量三年均值，皆伐带状更新区最高，皆伐萌芽更新区次之，对照区（未改造更新）最低；单位面积逗流量三年均值，皆伐带状更新区比皆伐萌芽更新区增加２６．４％，比对照区增加９６．５％，但增加的逞流量仅为引发土壤侵蚀逞流量的４０％～６０％，没有引起新的土壤侵蚀。皆伐带状更新方式通过引进更新树种，改变了林分结构和组成，使刺槐林变成混交林，延续和强化了水保效益，是一种理想的刺槐林改造更新方式。 相似文献
7.
在撒哈拉以南的非洲地区,黄独脚金寄生杂草（Strigahermonthica）侵扰是限制小农产自给性农业生产的主要因素之一。土壤肥力低加之总体环境退化是寄生杂草侵扰产生的重要原因。引入改良的耕作制度来解决寄生杂草侵扰和土壤肥力下降的问题势在必行。本文对肯尼亚西部双峰高原地区内,用豆科植物--印度田菁改良的休耕地对玉米产量和农田寄生杂草侵扰的作用进行了研究。实验处理分阶段进行,处理包括田菁改良6和18个月的休耕地、未经耕作自然植物再生6和18个月的休耕地、连续种植玉米未施肥的耕地和连续种植玉米同时施加氮和磷肥的耕地。结果表明,与未施肥玉米地相比,田菁改良休耕地明显（p〈0.5）增加玉米产量.除草管理降低了第一季度（428000±63000株·hm-2）、第二季度（51000±1500株·hm-2）玉米地寄生杂草植株种群。实验周期内,除草管理降低玉米地土壤中寄生杂草种子种群数。短期田菁改良休耕地对玉米产量的促进作用明显好于未施肥的玉米地,但是短期杂草休耕地对玉米产量无显著影响。种植玉米和除草控制寄生杂草效果要好于休耕。 相似文献
8.
9.
窄冠速生刺槐引种栽培试验初报 总被引：2，自引：0，他引：2
窄冠速生刺槐是中国林业科学研究院经过十多年的选育和测定，已通过国家鉴定的刺槐优良无性系。窄冠速生刺槐具备以下优良性状：（1）速生。1年生苗高可达5m以上，胸径可达3cm以上；2年生平均胸径可达5．2cm以上；6年生胸径可达24cm以上；8年生树高平均生长量1．5～1．8m、胸径2．1～2．5cm，是目前生长速度最快的荒山荒地绿化造林树种。（2）干形好。在较好立地条件下生长的树木，其树干形率达到0．8，树干通直。（3）树冠窄。分枝角度≤30°，形成圆满树冠。（4）托叶刺小或无。由于窄冠速生刺槐具备上述几方面的优良性状，比过去选育的刺槐优良无性系更显特色，是营建速生丰产林的首选树种之一，而且还是城市园林绿化和营造景观林的优良树种。 相似文献
10.
为探讨桂东丘陵区森林小气候效应,选择苍梧县具代表性的几种人工林作为研究对象,对其林内外的小气候进行观测。结果表明,荷木湿地松（Schima superba×Pinus elliotti）混交林内的气温、大气相对湿度与林外的差值较大;湿地松大叶栎（Pinus elliotti×Castanopsis fissa）混交林光合有效辐射最大,达1663．8μmol／（m^2·s）,与光合有效辐射最低的竹林相差97．4％。初步认为,林分类型和结构对林分小气候及森林防火、防虫等生态效应有着重要影响。 相似文献
11.
Mohsen Javanmiri Pour Mohmmad Reza Marvie Mohadjer Vahid Etemad Mahmoud Zobeiri 《林业研究》2012,23(2):299-304
We investigated the effects of grazing on natural regeneration, quantity, and diversity of woody species and dominant herb species in Kheyroud forest in northern Iran. We sampled vegetation in 5m2 plots in custom units, which are demarcated resource areas traditionally used by local livestock producers. The authors quantified number of species, height of seedlings, and diameter of seedlings. Height classes were 0-30 cm, 30-130 cm, and >130 cm, and diameter classes were 0-2.5 cm, 2.5-5 cm and 5-7.5 cm. The density of seedlings declined with distance from corral until reaching the custom unit boundary. Most seedlings had diameters of 0-2.5 cm and heights of 0-30 cm. Predominant species, Carpinus betulus and Acer capadocicum, were in plots near the centers of custom units, Fagus orientalis, Acer velutinum, Quercus castanifolia species were dominant in plots near the custom unit boundary. Plant species such as Oplismenus undulatifolius, Euphorbia amygdaloides, Rubus fruticos and Pteridium aquilinum were dominant in plots nearer to forest corral. Healthy seedlings were more numerous in plots nearest the corral, while defective and deformed seedlings were more abundant away from the corral. We conclude that grazing had negative effects on the quantity and quality of vegetative regeneration. Continuation of overgrazing will not only endanger the sustainability of forest ecosystems, but also will increase the challenge of sustainable forest management. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(5):417-426
Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m3 shelterwood with 200 stems ha-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth. 相似文献
13.
The conversion of anthropogenic into more natural, self-regenerating forests is one of the major objectives of forestry throughout
Europe. In this study, we present investigations on permanent plots with different silvicultural treatment in NE German pine
stands. Management of old-growth pine stands on acidic and nutrient-poor sandy sites differs in fencing, thinning, and planting
of certain tree species. The investigations were carried out on the community, population, and individual level of the pine
forest ecosystems. Thus, vegetation changes, size and height of tree populations, and height increment of tree individuals
were observed over a time span of 6 years. Special attention was paid to short-lived tree species such as, e.g., Frangula alnus and Sorbus aucuparia, as well as to Fagus sylvatica as one of the most typical forest tree species of Central Europe. Vegetation changes are interpreted as a consequence of
natural regeneration of formerly degraded forest sites, involving an increase in nutrient availability. High browsing pressure
can be considered as a key factor for the inhibition of tree seedlings and growth of saplings. Some Sorbus aucuparia individuals, however, succeeded in growing out of the browsing height also in unfenced stands. Few found specimens of Fagus sylvatica proved that this species is able to establish spontaneously on these relatively dry, acidic sites under continental climate
influence. Such natural regeneration processes, also including spontaneous rejuvenation of trees, can be integrated into silviculture
as passive forest conversion management. An active management like thinning of stands, planting of trees, and fencing can
accelerate forest conversion with regard to height growth and species number of trees. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1-4):261-269
The aim of the study was to address the question of whether shelterwood cutting should be discouraged as a forest regeneration method in Norway spruce (Picea abies (L.) Karst.) forests on highly productive peatlands due to a higher risk of windthrow in such forests. The total extent of windthrow was observed during six years after shelterwood cutting in nine spruce forests on fertile peatlands in north, central and south Sweden. Shelterwoods at densities of 140 and 200 stems ha‐1 were studied. At the end of the six year study period, 43% of all trees in the sparser shelterwoods and 38% of the trees in the denser shelterwoods had blown down. With respect to results from recent studies of the development of naturally regenerated and planted seedlings under the shelter trees, the extent of windthrow was regarded acceptable. Analysis of wind data from national weather stations close to the experiments showed that the acceptable extent of windthrow could not be explained by low frequencies of high winds during the shelterwood period. On the contrary, according to the wind observations made at the weather stations selected in central and south Sweden, the annual number of days with high winds (>21 ms‐1) during the six years after the shelter‐wood cutting was larger than the average high wind frequency for the last 40 years. Observations of maximum wind speeds show that the mean annual gale force during the shelterwood period was higher than the long term average. Thus, the results from this study do not justify avoidance of shelterwood cutting in spruce peatland forests because of the risk of windthrow. Each of the shelterwoods in the experiment was located close to a large clearcut, and the shelterwood cuttings were carried out as heavy thinnings. For further reduction of windthrow, denser shelterwoods and no clearcutting in adjacent stands are suggested when using shelterwood systems in practical forestry. 相似文献
15.
Context
Recruitment is an important process in forest stand dynamics, especially in uneven-aged stands. Continuous recruitment is a prerequisite for diverse, uneven-aged silvicultural systems, but patterns may vary significantly.Aims
The main goals of the study were to examine the recruitment of the main tree species in selection and irregular shelterwood stands in silver fir?CEuropean beech?CNorway spruce forests and to determine the main predictors of the recruitment occurrence.Methods
Data from 5,486 permanent inventory plots were used to study recruitment of saplings into the tree layer (diameter at breast height ??10?cm).Results
Recruitment rate differed significantly between selection (7.6?trees?ha?1?year?1) and irregular shelterwood (26.1?trees?ha?1?year?1) stands. Shade-tolerant fir and beech recruited with higher probability in selection stands, while light-dependent sycamore recruited with higher probability in irregular stands. In addition, forest types, soil pH, stand basal area, mean diameter, and the basal area of the same tree species with respect to recruitment were found to be important predictors of recruitment occurrence.Conclusions
The application of different uneven-aged silvicultural systems and their forms makes it possible to considerably influence the future tree species composition of uneven-aged forests. 相似文献16.
Forest tree species in the eastern US such as American chestnut (Castanea dentata (Marsh.) Borkh) and oaks (Quercus spp.) have been negatively impacted by forest changes over the past century. Many mature, introduced pine (Pinus spp.) plantations exist in the Midwest US following establishment 50–60 years ago yet have little economic and ecological value. As oak and chestnut have similar site preferences to pines, these stands may be ideal sites for hardwood restoration plantings. We sought to determine optimal management strategies for converting pine plantations by manipulating their canopies. We underplanted hybrid American chestnut and northern red oak (Quercus rubra L.) seedlings into three canopy treatments (control, shelterwood, clearcut) and included an open field treatment. For each of two growing seasons, 0, 30, or 60 g 19N–6P–12K of controlled-release fertilizer (CRF) were also applied to seedlings. Soil chemical parameters and leaf nutrients were analyzed throughout the study. Chestnut and oak seedlings had significantly greater height after two growing seasons in the clearcut and shelterwood than the control and open field, and chestnut had significantly greater diameter as well. Chestnut height and RCD growth were threefold that of oak after two growing seasons. In general, fertilization increased seedling growth more in the clearcut and open field than shelterwood and control for both species. Soils had significantly higher pH, K, and S in the open field than in pine stands. Results suggest that pine plantations may serve as target sites for restoration of these hardwood species. Shelterwoods and clearcuts are both favorable conversion options for oak and chestnut, and addition of CRF may augment further growth increase, especially in open environments. 相似文献
17.
《Forest Ecology and Management》1997,90(1):29-49
Clearcutting and shelterwood cutting of mature Norway spruce peatland forests were compared regarding the effects on the forest flora. Repeated observations of the field and bottom layer vegetation were made before and until 7 or 8 years after harvesting at four sites located along a gradient from southern to northern Sweden. Clearcutting resulted in a greater change of species composition compared with shelterwood cutting. Diversity, measured as Simpson's index, and species number per subplot were lower in the clearcut than in the shelterwood after 7 or 8 years. By applying Ellenberg's indicator values, it was concluded that shelterwood regimes may preserve species preferring shaded and moist conditions, whereas those species decreased after clearcutting. Species preferring high levels of nitrogen increased in the clearcut.According to both multivariate and univariate analyses, the vegetation changed in a similar direction at all sites, although the level of response differed considerably. Despite these similarities, there was a marked site effect, which was not surprising considering the large geographic variation between sites.It is concluded that shelterwood cutting might be a better alternative than clearcutting for forests on fertile peatland sites, with respect to conservation of vascular plants and bryophytes. 相似文献
18.
Tropical montane cloud forest has been undergoing a drastic reduction because of its widespread conversion to pastures. Once these forests have been cleared exotic grasses are deliberately introduced for forage production. Exotic grass species commonly form monodominant stands and produce more biomass than native grass species, resulting in the inhibition of secondary succession and tree regeneration. The purpose of this study was to assess the effect of native vs. exotic grass species on the early establishment of two native tree seedlings (Mexican alder, Alnus acuminata and Jalapa oak, Quercus xalapensis) on an abandoned farm in central Veracruz, Mexico. Seedling survival and growth were monitored (over 46 weeks) in relation to grass cover and height, and available photosynthetic active radiation (PAR). More seedlings survived in the presence of the native grass Panicum glutinosum than those growing with the exotic grass Cynodon plectostachyus (92% vs. 48%). The causes of seedling mortality varied between species; Q. xalapensis was affected by herbivory by voles but mainly in the exotic grass-dominated stands, whereas A. acuminata seedlings died due to competition with the exotic grass. A. acuminata seedlings increased more in height in the exotic grass-dominated stands (102 ± 7.8 cm) compared to native grass-dominated stands (51 ± 4.7 cm). Grass layer height, cover and available PAR were correlated (Pearson; p < 0.05). In the exotic grass dominated plots, grass layer height was correlated with the relative height growth rates of Q. xalapensis (Pearson; p < 0.05). These results indicate that the exotic grass may be affecting tree regeneration directly (grass competition) and indirectly (higher herbivory). Passive restoration may occur once P. glutinosum dominated pastures are abandoned. However, when C. plectostachyus dominates, introduction of early and mid successional tree seedlings protected against vole damage is needed. 相似文献
19.
对四川犍为地区引种栽培的互叶白千层扦插苗进行抽样调查,采用相关性分析、“x¯±s”法和主成分分析法对其苗木质量进行评价和苗木分级研究。结果表明:评定互叶白千层苗木质量可以苗高(H)、地径(D)和全株生物量作为表型指标,结合主根数量,并辅以根系长度作为辅助参考综合评价指标。提出了以苗高和地径作为该树种苗木分级的质量指标,并得出互叶白千层扦插苗的3级分级标准,Ⅰ级苗木:苗高>17.66 cm,地径>1.98 mm;Ⅱ级苗木:苗高为11.48~17.66 cm,地径为1.36~1.98 mm;Ⅲ级苗木:苗高<11.48 cm,地径<1.36 mm。可为互叶白千层苗木分级和筛选提供一定的理论依据。 相似文献
20.
Silvicultural treatments creating large canopy openings failed to restore regeneration of balsam fir (Abies balsamea (L.) Mill.) due to browsing pressure from white-tailed deer (Odocoileus virginianus Zimmermann). Consequently, we tested two alternative silvicultural treatments aimed at improving balsam fir establishment on Anticosti Island (Québec, Canada). In 1998 and 1999, we set up shelterwood seed cutting using three harvest intensities (0, 25 and 40% of basal area) and strip clearcutting with scarification using three different strip widths (15, 30 and 45 m), both with fenced and unfenced regeneration plots, in balsam fir stands. After 8 years, shelterwood seed cutting did not allow the establishment of new balsam fir seedlings, nor the development of unbrowsed balsam fir seedlings. In the strip clearcutting, deer browsing suppressed growth of palatable species in all strip widths. This favoured the development of unpalatable species, especially white spruce (Picea glauca (Moench) Voss). Our study demonstrates that the use of silvicultural treatments alone is unlikely to restore balsam fir regeneration on Anticosti Island, as long as the deer population remains higher than 20 deer/km2. 相似文献