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1.
Although it is generally accepted that the rate of accumulation of biomass declines as forests age, little is known about the relative contributions to this decline of changes in net primary production (NPP) and tree mortality. We used 10-15 years of observations of permanent plots in three small watersheds in and near the H.J. Andrews Experimental Forest, Oregon, to examine these issues. The three watersheds are of similar elevation and potential productivity and support young (29 years at last measurement), mature (approximately 100 years) and old (approximately 400 years) forest dominated by Pseudotsuga menziesii (Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg. Accumulation of tree bole biomass was greatest in the young stand, reaching approximately 7 Mg ha-1 year-1 in the last measurement interval. Bole biomass accumulation was relatively constant (approximately 4-5 Mg ha-1 year-1) in the mature stand, and there was no net accumulation of bole biomass in the old-forest stand. The NPP of boles increased with time in the young stand, from approximately 3 to approximately 7 Mg ha-1 year-1, but was nearly constant in the mature and old-forest stands, at approximately 6 and 3-4 Mg ha-1 year-1, respectively. Mortality increased slowly in the young stand (from < 0.1 to 0.3 Mg ha-1 year-1), but fluctuated between 1-2 and 2-6 Mg ha-1 year-1 in the mature and old-forest stands, respectively. Thus, declining biomass accumulation with stand age reflects, in approximately equal amounts, both decreasing NPP and increasing mortality.  相似文献   

2.
Seasonal changes in biomass, net primary productivity and turnover of dry matter of para grass (Brachiaria mutica) under a mixed tree stand and in an adjacent open stand in northern India are presented. Both stands attained peak values of live shoot biomass in September with a higher value under mixed tree stand (665 g m–2) than in the open stand (522 g m–2). The net aboveground production was 590 and 527 g m–2 yr–1 under mixed tree stand and in the open, respectively. The belowground net primary production was also greater under mixed tree stand (100 g m–2 yr–1) than in the open (76 g m–2 yr–1). Maximum aboveground and belowground net primary productions in both stands were obtained during the rainy season. The total net primary production for para grass was about 15% higher under mixed tree stand than in the open. The turnover rates of total plant biomass were greatest in the rainy season and the least during the summer season. The system transfer functions showed that the production of para grass on both stands was aboveground-oriented, accounting for 85–87% of annual total net primary production.  相似文献   

3.
The United Nations Framework Convention on Climate Change (UNFCCC) requires reporting net carbon stock changes and anthropogenic greenhouse gas emissions, including those related to forests. This paper describes the status of carbon stocks in sub tropical forests of Pakistan. There are two major sub types in subtropical forests of Pakistan viz a viz Subtropical Chir Pine and Subtropical broad leaved forests. A network of sample plots was laid out in four selected site. Two sites were selected from sub tropical Chir Pine (Pinus roxburghii) forests and two from Subtropical broadleaved forests. Measurement and data acquisition protocols were developed specifically for the inventory carried out from 2005 to 2010. In total 261 plots (each of 1ha.) were established. Estimation of diameter, basal area, height, volume and biomass was carried out to estimate carbon stocks in each of the four carbon pools of above-and below-ground live biomass. Soil carbon stocks were also determined by doing soil sampling. In mature (~100 years old) pine forest stand at Ghoragali and Lehterar sites, a mean basal area of 30.38 and 26.11 m2·ha-1 represented mean volume of 243 and 197 m3·ha-1,respectively. The average biomass (t·ha-1) was 237 in Ghoragali site and 186 t·ha-1 in Lehterar site, which is equal to 128 and 100 t C ha-1 including soil C. However, on average basis both the forests have 114.5± 2.26 t·ha-1 of carbon stock which comprises of 92% in tree biomass and only 8% inthe top soils. In mixed broadleaved evergreen forests a mean basal area(m2·ha-1) was 3.06 at Kherimurat with stem volume of 12.86 and 2.65 at Sohawa with stem volume of 11.40 m3·ha-1. The average upper and understorey biomass (t·ha-1) was 50.93 in Kherimurat site and 40.43 t·ha-1 in Sohawa site, which is equal to 31.18 and 24.36 t C ha-1 including soil Cstocks. This study provides a protocol and valuable baseline data for monitoring biomass and carbon stocks in Pakistan’s managed and unmanaged sub-tropical forests.  相似文献   

4.
森林生物量和生产力直接关系到森林生态系统的固碳能力。该文以冰砬山3个年龄阶段的蒙古栎次生林为研究对象,采用标准木收获法建立了生物量与胸径的相对生长方程,推算了各林龄的生物量、生产力及其分配规律。结果表明：幼龄林、中龄林和近熟林的乔木层生物量分别为112.09 t.hm^-2、224.92 t.hm^-2和276.18 t.hm^-2。蒙古栎林分配到其地上生物量的比例,随着林龄的增加而增大,与此同时分配到根系生物量的比例从幼龄林的36%下降到28%。蒙古栎林乔木层的年平均净生产力在中龄林达到最大12.13 t.hm^-2.a^-1,比幼龄林和近熟林分别高3.43 t.hm^-2.a^-1和1.42 t.hm^-2.a^-1。在所有不同年龄阶段,各器官的生产力占总生产力的比例平均为叶（45%）〉树干（30%）〉根（18%）〉枝（7%）。  相似文献   

5.
We estimated the aboveground net primary production (ANPP) in five self-thinning jack pine (Pinus banksiana) stands in Wood Buffalo National Park, NWT, Canada. The stands (11 to ca.175 years old) were selected to examine the relationship between stand density and tree size and its effect on carbon dynamics. Aboveground litterfall was collected from each stand from 1997 to 2012. Stand biomass was estimated by measuring tree size every 5 years and estimating the individual mass using allometric relationships. ANPP was then estimated by summing the litterfall mass, dead stem mass increment and stand biomass increment. We determined the proportional contribution of each organ to the total litter and the seasonal pattern of needle litterfall. There was a lower turnover rate of aboveground biomass in older stands than younger stands. The ANPP increased in the youngest stand (<30 years old) showed a decreasing trend in stands >50 years old. The maximum ANPP was estimated to be ca. 500?g m?2 year?1 in dry matter, which was found in 30–50 year-old stands.  相似文献   

6.
森林生物量、碳储量是评价森林生长状况的重要指标。通过野外样地调查及室内烘干称重等方法,研究了苏木山林场不同林龄华北落叶松人工林乔木层、灌木层、草本层生物量以及乔木层净生产力、碳储量积累特点和变化趋势。结果表明:幼龄林、中龄林、近熟林平均木的生物量分别为26.41 kg、32.70 kg、107.81 kg;林分生物量分别为43.66 t·hm^-2、79.88 t·hm^-2、125.83 t·hm^-2;灌木层和草本层生物量之和分别为1.44 t·hm^-2、1.19 t·hm^-2、0.95 t·hm^-2;乔木层净第一生产力分别为2.56 t·hm^-2·a^-1、3.07 t·hm^-2·a^-1、3.40 t·hm^-2·a^-1,碳储量分别为22.20 t·hm^-2、40.55 t·hm^-2、63.80 t·hm^-2。苏木山华北落叶松人工林生物量、碳储量随林龄增加而增大,各器官碳储量从大到小依次为干>根>枝>皮>叶。  相似文献   

7.
南方型杨树人工林生物量与生产力研究   总被引：7，自引：2，他引：7  
对湖北省10个县、市31块标准地的11种主要密度类型林分的生物量与生产力进行了研究。结果表明:南方型杨树单木生物量随着林分密度的增大而减小,林分生物量随密度的增大而增加。在各组份生物量中,树干最大,树枝其次。单木和林分地上部分生物量占总生物量的比例,达91.22％～92.19％,且林分密度越高,比例越大。中等密度林分的生物量结构特征较合理,生产潜力较大,应作为全省杨树栽培的主要模式。林分密度对净生产力有显著影响,随着林分密度的降低,林分和林分各组份的净生产量也随之降低。  相似文献   

8.
The growth, aboveground biomass production and nutrient accumulation in black alder (Alnus glutinosa (L.) Gaertn.), silver birch (Betula pendula Roth.) and Scots pine (Pinus sylvestris L.) plantations during 7 years after planting were investigated on reclaimed oil shale mining areas in Northeast Estonia with the aim to assess the suitability of the studied species for the reclamation of post-mining areas. The present study revealed changes in soil properties with increasing stand age. Soil pH and P concentration decreased and soil N concentration increased with stand age. The largest height and diameter of trees, aboveground biomass and current annual production occurred in the black alder stands. In the 7-year-old stands the aboveground biomass of black alder (2100 trees ha−1) was 2563 kg ha−1, in silver birch (1017 trees ha−1) and Scots pine (3042 trees ha−1) stands respective figures were 161 and 1899 kg ha−1. The largest amounts of N, P, K accumulated in the aboveground part were in black alder stands. In the 7th year, the amount of N accumulated in the aboveground biomass of black alder stand was 36.1 kg ha−1, the amounts of P and K were 3.0 and 8.8 kg ha−1, respectively. The larger amounts of nutrients in black alder plantations are related to the larger biomass of stands. The studied species used N and P with different efficiency for the production of a unit of biomass. Black alder and silver birch needed more N and P for biomass production, and Scots pine used nutrients most efficiently. The present study showed that during 7 years after planting, the survival and productivity of black alder were high. Therefore black alder is a promising tree species for the reclamation of oil shale post-mining areas.  相似文献   

9.
SCHoNENBERGER  WALTER 《Forestry》1984,57(1):59-73
In the alpine timberline ecotone at 1350 m in the CraigieburnRange, New Zealand, four distinct mountain beech stand types(a pole, a coppice, a high forest and a shrublike stand) wereanalysed for stand biomass and leaf area by means of allomet-ricregressions based on stem diameter. Differences between stand types in terms of age, structure,biomass and leaf area are interpreted as development stagesafter stand breakdowns due to external impacts. Vegetative reproduction,mainly coppicing, plays an important part in stand regeneration. The young pole stand had 177 t ha–1, the coppice stand272 t ha–1, and the mature high forest stand 323 t ha–1aboveground dry weight. A low mountain beech shrub stand withgnarled, windshaped dwarf trees had only 135 t ha–1. Foliageaccounted for only 3–5% in all stands, the leaf area indexwas also low, at 3.0 in the shrub stand and 3.7–7.4 inthe forest stands. The low foliage proportion is consideredto be a response to the harsh environment.  相似文献   

10.
The biomass and net primary production of Mongolian scotch pine (Pinus sylvestris L. var.mongolica) plantations of west Kerqin sandy land were measured. According to average standard trees, the biomass, net primary production and their distributions of trunk, bark, branch, leaf and root of 16-year-old stand were analyzed. The regressive equation for the estimation of each organ biomass was established through dimensional analysis. Preferable equation with higher precision was selected. The study results showed that the total biomass of the forest community was 62.023 t/hm2 and net primary production was 5.045 t/(hm2·a), which indicates that the community of plantation possesses high bio-productivity. (Responsible Editor: Chai Ruihai)  相似文献   

11.
Pure stands of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) and mixed stands of Douglas-fir and naturally established red alder (Alnus rubra Bong.) were examined on two different sites for soil properties, tree growth and nutrition, and aboveground ecosystem biomass and net primary production. One site (Mt. Benson, Nanaimo, B.C.) was nitrogen (N)-deficient and had a low site index (expected Douglas-fir height of 24 m at 50 years). The other site (Skykomish, western Washington) was N-rich and had a site index of 45 m at 50 years. Soil N accretion on the red alder units was estimated at 65 (Mt. Benson) and 42 (Skykomish) kg ha?1 year?1 for 23 years to a soil depth of 50 cm. At the current stage of plantation development, presence of red alder at the infertile Mt. Benson site increased average Douglas-fir diameter but did not affect its basal area and basal area growth rate; including alder stem biomass increased total stand basal area and basal area growth 2.5 fold. Presence of red alder at the fertile Skykomish site decreased average diameter, basal area, and basal area growth of Douglas-fir; including alder biomass left total stand basal area and basal area growth unchanged. Douglas-fir foliar N concentrations on Mt. Benson increased from 0.93 without alder to 1.41% on the red alder unit but were 1.55% for both units at Skykomish. Although alder did not affect Douglas-fir aboveground biomass and net primary production on Mt. Benson, total ecosystem biomass doubled and production tripled when alder biomass was included. Conversely, at Skykomish, Douglas-fir biomass and production decreased, and total ecosystem values were essentially unchanged. Mixing red alder and Douglas-fir seems to have great potential for increasing Douglas-fir growth and ecosystem production on infertile, N-deficient sites but probably has limited value on fertile, N-rich sites.  相似文献   

12.
对福建省沙县官庄国有林场10年生杉木纯林,通过间伐人工诱导营建杉木苦竹混交林的林分生产力进行研究。结果表明:杉木苦竹混交林林分结构合理,层次明显,呈复层林分。混交林中杉木平均木树干生物量分别是高密度杉木纯林(2500株.hm-2)、低密度杉木纯林(1125株.hm-2)的122.7%、107.9%,净生产量分别是高密度杉木纯林、低密度杉木纯林的122.6%、104.0%;叶对树干的净同化率为5.75 kg.kg-1.a-1,比低密度杉木纯林提高5.7%。混交林中苦竹立竹数6000株.hm-2,现存生物量9.43 t.hm-2,年平均净生产量为1.2 t.hm-2.a-1;8 a间伐竹材和竹笋年平均产量分别达到9.608 t.hm-2和7.587 t.hm-2,取得了一定收益,达到了长短结合,以短养长的目的,是较好的经营模式。人工诱导构建杉木苦竹混交林具有较高生产力。  相似文献   

13.
根据我国不同森林类型共1 266个样地的生物量、生产力和蓄积量资料,建立中国主要森林类型生物量与蓄积量、生物量与群落生长量和年凋落量之间的函数关系,并利用1973-2003年间中国6次森林资源清查资料,研究中国森林植被净生产量及其动态变化。研究结果表明:1999-2003年间中国森林植被净生产量为1 360.64×106t/a,平均生产力为9.53 t/(hm2.a),植被净生产量构成以幼龄林和中龄林为主且存在较大的区域差异,东北和西南地区植被净生产量较高;其它地区植被净生产量相对较小。近30年中国森林植被净生产量由第一次森林资源清查时的790.13×106t/a增加到1999-2003年间的1 360.64×106t/a,20世纪70年代末期,中国森林植被净生产量较低,之后开始逐步增加;中国森林植被平均生产力的变化与净生长量的变化不同,20世纪70年代末期,中国森林植被平均生产力较高,而后开始下降,直到90年代末之后才开始恢复增长。  相似文献   

14.
ABSTRACT

Grey alder (Alnus incana) is a highly productive indigenous tree species, potential for short-rotation forestry in the Baltic and Nordic countries. The aim of the study was to investigate the development of a new forest generation, as well as the nitrogen (N) and carbon (C) storages and fluxes in a grey alder regenerating coppice (COP) after clear-cut and in an adjacent unharvested 21-year-old stand (MAT), which had reached its bulk maturity. The regeneration of COP was rapid and 5 years after clear-cut, stem mass was 6.4?t?ha?1. The nitrogen demand of the aboveground part of the 5-year-old COP trees was estimated to be roughly half of the corresponding value for MAT, depending mostly on leaf production. The annual N leaching flux in MAT was in the range of 16–29?kg?ha?1, the corresponding values for COP were roughly half of that. Net nitrogen mineralization did not differ significantly between MAT (117?kg?ha?1) and COP (129?kg?ha?1). For the soil respiration study, a 32-year-old grey alder stand growing at a similar site was included; soil respiration was significantly higher in MAT compared to COP in all study years in both studied stands.  相似文献   

15.
环洞庭湖不同类型防护林生物量研究   总被引：1，自引：0，他引：1  
罗佳  田育新  杨楠  姚敏 《湖南林业科技》2011,38(5):27-29,43
以环洞庭湖的杨树、马尾松、杉木等3种防护林为研究对象,对其生物量进行研究.结果表明:3种林分中不同树种营养器官生物量所占比例的大小顺序有所差异,各主要造林树种单株生物量均以地上部分占绝对的优势,占全株生物量的87％以上.3种林分中,杉木林分生物量最高,为232 172.5 kg/hm2;马尾松林的生物量最低,为87 4...  相似文献   

16.
Above-ground biomass distribution, leaf area, above-ground net primary productivity and foliage characteristics were determined for 90- and 350-year-oldPinus edulis-Juniperus monosperma ecosystems on the Colorado Plateau of northern Arizona. These ecosystems have low biomass, leaf area and primary productivity compared with forests in wetter environments. Biomass of the 350-year-old pinyon-juniper stand examined in this study was 54.1 mg ha−1; that of the 90-year-old stand was 23.7 mg ha−1. Above-ground net primary production averaged 2.12 mg ha−1 year−1 for the young and 2.88 mg ha−1 year−1 for the mature stand; tree production was about 80% of these values for both stands. Projected ecosystem leaf area (LAI) of the stands was 1.72 m2 m−2 and 1.85 m2 m−2, respectively. Production efficiency (dry matter production per unit leaf area) was 0.129 kg m−2 year−1 for the young, and 0.160 kg m−2 year−1 for the mature stand. Production efficiency of the study sites was below the 0.188 kg m−2 year−1 reported for xeric, pure juniper stands in the northern Great Basin. Biomass of pinyon-juniper ecosystems of northern Arizona is generally below the 60–121 mg ha−1 reported for pinyon-juniper stands of the western Great Basin in Nevada. A climatic gradient with summer precipitation decreasing between southeast Arizona and northwest Nevada occurs in the pinyon-juniper region. Great Basin pinyon-juniper ecosystems lie at the dry-summer end of this gradient while pinyon-juniper ecosystems of the Colorado Plateau lie at about the middle of this gradient. In spite of wetter summers, pinyon-juniper ecosystems of northern Arizona are less productive than those of the Great Basin.  相似文献   

17.
We estimated above- and belowground biomass and net primary production (NPP) of a 73-year-old Scots pine (Pinus sylvestris L.) forest stand in the Belgian Campine region. Total biomass for the stand was 176 Mg ha(-1), of which 74.4% was found in stems. The root system contained 12.6% of total biomass, most of it in coarse roots (> 5 mm). Fine roots (< 5 mm) comprised only about 1.7% of total biomass, and more than 50% of fine root biomass was retrieved in the litter layer and the upper 15 cm of the mineral soil. The ratio of belowground biomass to aboveground biomass was 0.14, which is lower than that of other Scots pine forests and other coniferous forests. Between 1995 and 2001, mean annual NPP was 11.2 Mg ha(-1) year(-1), of which 68.7% was allocated to aboveground compartments. Stems, needles and cones made relatively high contributions to total NPP compared with branches. However, branch NPP was possibly underestimated because litterfall of big branches was neglected. The proportion of total NPP in belowground components was 31.3%. Coarse root NPP (2% of total) was low compared with its biomass. Fine root NPP was 3.3 Mg ha(-1) year(-1), representing about 29.5% of total NPP; however, the estimate of fine root NPP is much more uncertain than NPP of aboveground compartments. The ratio NPP/GPP (gross primary production) was 0.32, which was low compared with other coniferous forests.  相似文献   

18.
lntroductionMongoIianscotchpine(PinussyvesmeL.var,mon-gohbe)isafondamentaItreespeciesincoIdtemper-atezone,mainlydistributedinHeiIongjiangProvinceandDaxing'anMOuntainforestregionoflnnerMon-goIiaAutonomousRegion.Withhighendurancetocold,droughtandpoorsoil,thistreespecieshasthecharacteristicsoff8stgroWth,shortfinaIcuttingageandgoodqualitytimber,atc-.IthasbeenproventhatMongoIianscOtchpineisoneofthemostsuccessfuIIyintroducedtreespeciesinsemi-aridregionafterbeingintroducedinto13provincesandau…  相似文献   

19.
证据显示印度喜马偕尔北部的喜马拉雅州森林生物量大量减少。政府通过局部测定核查了森林生物量减少情况。本文以树木生物量来衡量森林退化,评估了主要用地类型内森林生物量的现状,检查了森林可持续性。结果表明,保育林分树木地上部最大生物量平均为1158t·hm-2,保护林、休耕地、耕作非灌溉地、草地、果园和耕地灌溉地的平均生物量依次是728,13,11,8,5和3t·hm-2。当地农民用于烧柴、马料或其他用途的树木生物量仅占可获得的生物总量的0.31%。现在的取用水平只能在短期内维持森林可持续性,从长期来看森林再生不足。采用对数生长模型对未来30年的森林生物量进行料模拟,并通过敏感性分析对影响系统行为的输入变量的相对显著性进行了分析。拟合模型强调了未来的森林资源降低不可避免。政府部门应该积极响应,出台相应政策才能有效地保护森林资源。  相似文献   

20.
对季节性淹水的洞庭湖滩地进行开沟抬垄造杨树林试验。结果表明：滩地开沟抬垄造林降低了杨树林地的相对淹水时间和高度,提高了杨树造林保存率,促进树高和单株材积的生长,提高单位面积蓄积,提高径阶≥12cm的林木的比例和林分木材的价值;开沟抬垄造林能显著提高杨树林分生物量和生产力,开沟抬垄营造的7年生杨树单株生物量、保存林分生物量、林分平均净生产量分别为32.32kg／hm^2、32.34t／hm^和4.62t／（hm^2·年）,分别是未开沟抬垄的1.43、3.16和3.2倍;滩地开沟抬垄与未开沟抬垄营造的杨树林各器官生物量大小均遵循干〉根〉皮〉枝〉叶的规律;开沟抬垄造杨树林增加的木材效益比开沟抬垄工程总投入多,经济效益较好,第1个轮伐期年均利润为166.3元／（hm^2·年）,投入产出比是0.95。  相似文献   

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