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1.
This analysis employs a spruce budworm (Choristoneura fumiferana Clem.) decision support system to examine costs and benefits of sequestering (protecting) carbon in forests through pest management. We analyzed 24 alternative spruce budworm protection scenarios for outbreaks on Prince Albert Forest Management Area (PAFMA) in Saskatchewan and Crown License 1 in New Brunswick. Scenarios included two outbreak severities (moderate and severe), three protection frequencies (very aggressive—protecting every year of the outbreak; aggressive—protecting the peak 3 years of outbreak; and semi-aggressive—protecting every second year of outbreak), and four protection program sizes (10,000 ha, 25,000 ha, 100,000 ha, or 150,000 ha). Under a severe outbreak, the largest (150,000 ha), very aggressive protection scenario provided the highest net CO2 protected at 24.95 million metric tons (Mt) in PAFMA and 29.19 Mt in License 1. This protection scenario also provided the highest net present value at $64.23 M and $91.36 M in PAFMA and License 1, respectively. On the other hand, benefit/cost ratios were maximized under the smallest (10,000 ha) protection size at 11.90 and 15.37 using the aggressive and semi-aggressive protection frequencies in PAFMA and License 1, respectively. Finally, the discounted cost per ton of CO2 protected was minimized at $0.48 and $0.37 using the smallest aggressive and semi-aggressive protection frequencies in PAFMA and License 1, respectively. The comparable costs and benefits from the moderate outbreak scenarios were similar, but generally less than, the severe outbreak scenarios. These results provide forest managers with important information needed to justify such carbon sequestration programs on economic grounds.  相似文献   

2.
Longer forest rotation ages can potentially increase accumulation of carbon in harvested wood products due to a larger proportion of sawlogs that can be used for manufacturing durable wood products such as lumber and plywood. This study quantified amounts of carbon accumulated in wood products harvested from loblolly pine (Pinus taeda L.) stands grown in Mississippi by extending rotation ages traditionally used to manage these stands for timber. The financial viability of this approach was examined based on carbon payments received by landowners for sequestering carbon in standing trees and harvested wood products. Results indicated a potential to increase carbon accumulated in wood products by 16.11 metric tons (t) of carbon dioxide equivalent (CO2e) per hectare (ha) for a rotation increase of 5 years and 67.07 tCO2e/ha for a rotation increase of 65 years. Carbon prices of $50/tCO2e and $110/tCO2e would be required to provide a sufficient incentive to forest landowners to extend rotations by 5 and 10 years, respectively. With 2.8 million ha of loblolly pine stands in Mississippi, this translates to a possible increase in wood products carbon of 45 million tCO2e and 80 million tCO2e for harvest ages increased by 5 and 10 years, respectively. Higher carbon prices lengthened rotation ages modestly due to low present values of carbon accumulated with long rotations.  相似文献   

3.
The structure of eight Quercus gambelii (Gambel's oak) communities in the Lincoln National Forest, New Mexico, USA were examined. Belt transects were used to estimate the density and basal area of the trees and the density of juvenile woody plants. In addition, diameter size-class distributions of Q. gambelii were examined to determine community development. The communities were estimated to be 109–137 years old and mid to late-successional. Total tree density was 3586–6480 plants/ha, with Q. gambelii having a relative density of 94–100%. Total basal area was 20.1–42.0 m2/ha, with Q. gambelii relative basal area 82–100%. The density and basal area of all other species present was low. Quercus gambelii juvenile density ranged from 1760 to 9160 plants/ha. Juveniles of all other species found were zero to 847 plants/ha. Based on Weibull analyses, all of the diameter size-class distributions of Q. gambelii were unimodal. There were few or no individuals in the smallest (1–5 cm) diameter size-classes, suggesting that recruitment of small Q. gambelii plants into the adult population may be below the replacement rate for these stands. Pooled size-class distributions for the other species were non-normal with most individuals in the smallest diameter size-classes. Low light levels below the canopy, a lack of canopy gaps, or browsing by Cervus elaphus (elk = red deer) may be the primary causes of poor recruitment because there were large numbers of Q. gambelii juveniles, but these individuals are not entering the small-tree size-class in any of the communities.  相似文献   

4.
Nitrate in the soil water below the root zone is a pre-condition for nitrate leaching, and it indicates loss of nutrients from the forest ecosystem. Nitrate leaching may potentially cause eutrophication of surface water and contamination of ground water. In order to evaluate the extent of nitrate leaching in relation to land-use, a national monitoring programme has established sampling routines in a 7×7 km grid including 111 points in forests. During winters of 1986–1993, soil samples were obtained from a depth of 0–25, 25–50, 50–75 and 75–100 cm. Nitrate concentrations in soil solutions were determined by means of a 1 M KCl extraction. The influence of forest size, forest-type, soil-type, tree species and sampling time on the nitrate concentrations was analysed in a statistical model. The analysis focused on data from depth 75–100 cm, as nitrate is considered potentially lost from the ecosystem at this depth. The range of nitrate concentrations was 0–141 mg NO−3–N dm−3 and the estimated mean value was 1.51 mg NO−3–N dm−3. The concentration was influenced by (1) forest size (concentrations in forests <10 ha were higher than concentrations in forests >50 ha), (2) forest-type (afforested arable land had higher concentrations than forest-type `other woodland'), (3) soil-type (humus soils showed above average concentrations, and fine textured soils had higher concentrations than coarse textured soils), and (4) sampling time. Unlike other investigations, there was no significant effect of tree species. A few sites deviated radically from the general pattern of low concentrations. The elevated concentrations recorded there were probably caused by high levels of N deposition due to emission from local sources or temporal disruptions of the N cycle. The nitrate concentration in the soil solution below the root zone was mostly rather low, indicating that, generally, N saturation has not yet occurred in Danish forest ecosystems. However, median concentrations exceeding drinking water standards (11.3 mg NO−3–N dm−3) were found at 7% of the sites. Furthermore, 30% of the sites had median concentrations above 2 mg NO−3–N dm−3, suggested as an elevated level for Danish forest ecosystems, equalling annual N losses of more than 2–6 kg ha−1 year−1.  相似文献   

5.
The lowland rain forests of Central America are poorly known from the standpoint of management for timber production. We studied the stand dynamics of a logged Costa Rican rain forest under three different regimes of post-logging silvicultural treatment. The site was located on low hills with Ultisols in Holdridge's Tropical Wet Forest life zone. The Pentaclethra macroloba-dominated forest had been high graded before planned management began. Management of the 540 × 540 m (29.2 ha) experimental area began with a timber harvest in the whole area during 1989–1990, 4 trees ha−1 being cut overall for 10.1 m3 ha−1. The experimental plots were 180 × 180 m (3.24 ha), comprising a 100 × 100 m (1.0 ha) central permanent sample plot (PSP) with a 40-m wide buffer strip. Two types of post-harvest silvicultural treatment: liberation/refinement (in 1991) and shelterwood (in 1992) were applied under a complete randomized block design with three replicates, using logged but untreated plots as controls. PSP data reported are for the 1988–1996 period for individuals with ≥10 cm DBH. The most marked changes in forest structure were caused by silvicultural treatment, basal area under the liberation/refinement treatment being reduced to ca. 65% of its probable mature forest value. Recruitment exceeded mortality in the years following intervention under all three treatments, but forest structural recovery was slowest under the liberation/refinement treatment. Post-intervention mortality rates appeared higher under the liberation/refinement treatment than under the control or shelterwood treatments, though differences were not statistically significant. In relation to tree attributes, mortality rates increased with decreasing DBH increment, crown illumination and quality of crown form. Commercial DBH increments were higher under the liberation/refinement treatment than in control plots during the 1993–1996 period. On the basis of its response to intervention during the first seven years of management, the forest appears resilient and productive; trends over time in mortality rates under the most intense silvicultural regime require close attention however. Pentaclethra-dominated forests are important components of the productive forest resources of Costa Rica and Nicaragua and, given current deforestation rates in areas such as southern Nicaragua, it is now urgent that the existing biophysical knowledge of these forests be applied to forest conservation and management.  相似文献   

6.
The purpose of this study was to determine if spatially-explicit commercial timber inventories (CTI) could be used in conjunction with satellite imagery to improve timber assessments and forest biomass estimates in Amazonia. As part of a CTI, all commercial trees ≥45 cm DBH were measured and georeferenced in 3500 ha of a logging concession in NW Mato Grosso, Brazil. A scientific inventory was conducted of all trees and palms ≥10 cm DBH in 11.1 ha of this area. A total of >20,000 trees were sampled for both inventories. To characterize vegetation radiance and topographic features, regional LANDSAT TM and ASTER images were obtained. Using a stream network derived from the ASTER-based 30 m digital elevation model (DEM), a procedure was developed to predict areas excluded from logging based on reduced impact logging (RIL) criteria. A topographic index (TI) computed from the DEM was used to identify areas with similar hydrologic regimes and to distinguish upland and lowland areas. Some timber species were associated with convergent landscape positions (i.e., higher TI values). There were significant differences in timber density and aboveground biomass (AGB) in upland (6.0 stems ha−1, 33 Mg ha−1) versus lowland (5.4 stems ha−1, 29 Mg ha−1) areas. Upland and lowland, and timber and non-timber areas could be distinguished through single and principal component analysis of LANDSAT bands. However, radiance differences between areas with and without commercial timber on a sub-hectare scale were small, indicating LANDSAT images would have limited utility for assessing commercial timber distribution at this scale. Assuming a 50 m stream buffer, areas protected from logging ranged from 7% (third order streams and above) to 28% (first order and above) of the total area. There was a strong positive relationship between AGB based on the scientific inventory of all trees and from the commercial timber, indicating that the CTI could be used in conjunction with limited additional sampling to predict total AGB (276 Mg ha−1). The methods developed in this study could be useful for facilitating commercial inventory practices, understanding the relationship of tree species distribution to landscape features, and improving the novel use of CTIs to estimate AGB.  相似文献   

7.
More than just an environmental challenge, the problem of carbon dioxide emissions is a basic human rights issue. This paper proposes a solution to the problem based on the proposition of Green Human Right that all men are created equal and thus entitled to equal carbon dioxide emissions per person. Countries with per capita carbon dioxide emissions above that of the global average must pay for the privilege to pollute. Conversely, countries with that below the global average are entitled to compensations.To determine the excess or slack carbon dioxide emissions of individual countries, the total carbon dioxide emissions of every country are adjusted for international trade to account for carbon dioxide out-sourcing and carbon sequestration by forests and forest products to arrive at their net carbon dioxide emissions. Countries with above the global average in net per capita carbon dioxide emissions have excess emissions. Those with below the global average have slack emissions. Total excess or slack carbon dioxide emissions are determined by multiplying the per capita excess or slack per capita emissions by its population. They then pay into or get compensated from the Green Climate Fund based on their respective excess or slack carbon dioxide emissions.Based on the total excess carbon dioxide emission figures from 2009 and $10 per ton of carbon dioxide emissions, major excess emission countries and the amount of money they would pay into the Green Climate Fund are the U.S. $40.8 billion, Japan $7.8 billion, U.K. $5.1 billion, Canada $4.7 billion, Germany $4.6 billion, and Russia $4.2 billion. China, for the first time, also would become an excess emission country and would pay $446 million, thus obliterating the artificial separation between developed and developing countries and removing a major stumbling block in climate change negotiations. Major slack emission countries and the amount of money they would earn from the Green Climate Fund are India $3.7 billion, Pakistan $645 million, Bangladesh $626 million, Nigeria $433 million, Ethiopia $358 million, the Philippines $351 million and Vietnam $333 million.The incentives created by the proposed solution would propel all countries to focus on controlling or lowering their total global carbon dioxide emissions. Excess emission countries have incentives to reduce their carbon dioxide emissions to lower their payments. Slack countries also have incentives to lower or limit their emissions, if they want to keep earning money over time. When the price of carbon dioxide emissions is high enough, its impact on the global carbon dioxide emissions would be significant. Furthermore, as a dynamic system, every year the price set for carbon dioxide emissions would depend on how quickly the total global carbon dioxide emissions are being reduced through conservation efforts and technical innovations. Once the price is set, there is total transparency. Every country will know exactly how much it would either pay into or earn from the Green Climate Fund, sparing rich countries from haggling over how much each will pay and poor countries over how much each will earn.  相似文献   

8.
Reduced impact logging in an eastern Amazonian terra firme forest left more than half of the next crop trees growing at a rate corresponding to a rotation of more than a century to attain 60-cm dbh. Two years after the logging, in 20 ha of the logged forest, tree competitors around crop trees were eliminated. Competitors were defined as trees whose crowns overtopped crop trees, those within 2 m of them, and trees as tall as or taller than the crop trees closer than indicated by a basal area of 15–25 m2/ha, depending on their summed diameters. During the subsequent 5.7 years, increment of the liberated crop trees was 20% greater than that of comparable crop trees left in another 20 ha of the same logged forest without liberation. Had the competing trees been identified at the time of the logging the 5.8/ha that were merchantable could have increased the yield from 25 m3/ha to as much as 43 m3/ha. This added harvest should have more than paid the entire cost of the liberation, including the elimination of the remaining unmerchantable trees. Additionally, a prospective reduction of 25% in the wait for the next harvest, as compared with logging only, would have been created. Where the economical sustainability of tropical wood productivity and quality is a goal, the wisdom of neglect of liberation is questioned.  相似文献   

9.
Uneven-aged management using single-tree or group selection has been in practice for many decades, especially in northern hardwood forests. Use of stocking regulation tools is thought to produce and maintain specific stand structures that upon regulation, are sustainable over time. We evaluated stand structures in northern hardwoods in Upper Michigan across three ownerships that practice different approaches toward uneven-aged management. Industry land (MeadWestvaco—MWV) uses primarily diameter limit cutting combined with a sawyer-select harvest method, retaining a maximum diameter of 45.7 cm (18 in.) with a residual basal area of 16.1 m2/ha (70 ft2/ac) and a cutting cycle of 10 years. The Michigan Department of Natural Resources (DNR) uses a crop tree release technique with a residual basal area of 18.4 m2/ha (80 ft2/ac) and a cutting cycle of 20 years. Both ownerships view regeneration of new cohorts as inevitable given the intensity of disturbance and the forest type. The third ownership (the Ford Forestry Center School Forest at Michigan Technological University—FFC) employs strict stocking regulation using the BDq method (residual basal area of 16.1 m2/ha (70 ft2/ac), maximum diameter of 50.8–55.9 cm (20–22 in.), and a q-ratio of 1.3) with a cutting cycle ranging from 12 to 15 years.Stand structure on a total of 25 stands was characterized for these ownerships to assess the impact of management strategy on stand structure and species composition. Differences in species composition and lower diversity indices were found where increasing sugar maple dominance was an objective (FFC ownership). All ownerships showed reduced relative importance values of mid-tolerant species such as yellow birch in their stands as compared to values reported for old-growth or unmanaged stands. Diameter distributions were classified into one of three shape categories (negative exponential, increasing q-ratio, and rotated sigmoid) using the regression of DBH, DBH2, and DBH3 on the log10 of trees per hectare. The best model in terms of adjusted-R2 and root mean square error (RMSE) was selected for each stand. All management strategies resulted in similar occurrences of distribution shapes, despite some evidence of a trend toward a rotated sigmoid distribution. These trends suggest that several different diameter distribution shapes in uneven-aged northern hardwoods in the Lake States are possible following a variety of management approaches, with sugar maple increasing in dominance with strict adherence to certain stocking regulation guidelines.  相似文献   

10.
Biodiversity loss is a major problem in terms of loss of genetic and ecosystem services and more specifically via impacts on the livelihoods, food security and health of the poor. This study modeled forest management strategies that balance economic gains and biodiversity conservation benefits in planted tropical forests. A forest-level model was developed that maximized the net present value (NPV) from selling timber and carbon sequestration while maintaining a given level of biodiversity (as per the population density of birds). The model was applied to Eucalyptus urophylla planted forests in Yen Bai Province, Vietnam. It was found that the inclusion of biodiversity conservation in the model induces a longer optimal rotation age compared to the period that maximizes the joint value from timber and carbon sequestration (from 8 to 10.9 years). The average NPV when considering timber values plus carbon sequestration was 13 million Vietnamese Dong (VND) ha− 1 (765 USD ha− 1), and timber, carbon sequestration and biodiversity values were 11 million VND (676 USD) ha− 1. Given this differential, governments in such tropical countries may need to consider additional incentives to forest owners if they are to encourage maximizing biodiversity and its associated benefits. The results also have some implications for implementing the climate control measure of “Reducing Emissions from Deforestation and Forest Degradation-plus (REDD +)” in developing countries, i.e., payment for carbon sequestration and biodiversity benefits in planted forests.  相似文献   

11.
A financial assessment of forest investments is comprehensive if the analysis includes reliable yield estimates, land expectation value (LEV) and risk calculation. All of these aspects were considered and applied to teak plantations in Colombia, an emergent economy where high forest productivity, low opportunity cost of land, and decreased financial/economic risk have substantially contributed to promote forest investments. The von Bertalanffy non-linear mixed effect model was used to estimate forest yields using data collected from 31 permanent sample plots, measured over a 17 year period. A stochastic version of LEV along with other financial criteria was calculated by using a computer algorithm and Monte Carlo simulation. Finally, probabilities obtained from stochastic financial calculations were used in logistic models to estimate probabilities of success for a forest plantation project, a measure of risk assessment, after changing land prices. Results suggest that the potential forest productivity (i.e., the biological asymptote) ranges from 93 to 372 m3 ha− 1. The mean annual increment is 27.8 m3 ha− 1 year− 1, which is attained 6 years after the forest plantation is established. Profitability analyses for teak plantations in Colombia suggest a LEV of US$7000 ha− 1. The risk analyses indicate negligible financial risk for forestlands whose prices are lower than US$2000 ha− 1.  相似文献   

12.
The availability of coarse woody debris (CWD) and distribution of dead trees into categories of mortality (dead standing, broken and uprooted) were investigated in north-temperate forests of central Europe (Lithuania). The studied area comprised 188.7 ha and included 18 different stands 40–130 years of age with a variety of tree species (spruce (Picea abies (L.) Karst.), pine (Pinus sylvestris L.), alder (Alnus glutinosa (L.) Gaertn.), birch (Betula pendula Roth and B. pubescens Ehrh.), aspen (Populus tremula L.), oak (Quercus robur L.), forest types (caricus-sphagnum, vaccinium-myrtillus, oxalis, myrtillus-oxalis, caricus-calamagrostis) and edaphic conditions (peaty, sandy, loamy soils of different moisture). The stands were excluded from wood harvesting for at least 30 years. A total of 11 365 dead trees (over 10 cm in DBH) or 6160.7 m3 of dead wood was found (60.2 trees/ha and 32.6 m3/ha). The volume of CWD per hectare was larger in older stands (rS=0.78, P<0.01). Tree mortality during the last 2 years consisted of 482 trees and 381 m3, or 1.28 trees/ha×year and 1.01 m3/ha×year. In 25–33% of cases it was wind-related. Uprooted and broken trees were of larger DBH than dead standing. The distribution into the categories of mortality was strongly dependent on tree species (chi-square test, d.f.=10,P=0). Dead standing dominated in CWD of pine and alder. Broken trees comprised almost a half in CWD of aspen, and about one-third in birch, alder and oak. Uprooting most often occurred in spruce, aspen and birch. Edaphic conditions and stand age had a pronounced impact on distribution into mortality categories for spruce (chi-square test, d.f.=20, P<0.00001) and pine (d.f.=8, P≤0.0003). On peat soil, only a minority of trees of both pine and spruce was uprooted, and standing dead prevailed. In CWD of spruce and pine, the proportions of both dead standing and broken decreased and that of uprooted trees increased on mineral soils of higher moisture and bulk density in older stands. By contrast, uprooting in birch and alder occurred less often on more wet sites, where the proportions of standing snags were higher. A total of 41 species of wood-decomposing polypores were found in the study area. Among those, 10 (24%) were of conservation value.  相似文献   

13.
In 1984, a liming experiment with a surface application of 4 t ha−1 of dolomitic limestone was started at the acidic N-saturated Norway spruce forest “Höglwald” in southern Germany and monitored until 2004. The decay of surface humus due to the accelerated mineralisation accounted for 18.5 ± 2.7 t ha−1 C or 50% of the initial pool and 721.6 ± 115.0 kg ha−1 N or 46% for N. Due to some translocation of organic material to the mineral soil the values to 40 cm depth are slightly lower (13.5 ± 4.4 t ha−1 C or 15% of the initial pool and 631.6 ± 192.8 kg ha−1 N or 13% for N). In the control plot NO3− concentrations at 40 cm depth were above the European level of drinking water (0.8 mmolc l−1 or 50 mg NO3− l−1) for nearly the whole investigation period. Liming increased NO3− concentrations in seepage water for approximately 15 years, and accelerated leaching losses by 396.2 NO3−–N kg ha−1 from 1984 to 2003. The increase in pH of the soil matrix was more or less restricted to the humus layer and the upper 5 cm of the mineral soil during the whole time span, while the base cations Ca and Mg reached deeper horizons with seepage water. From 1984 to 2003, an amount that nearly equalled the applied Mg, was leached out of the main rooting zone, while most of the applied Ca was retained. The time series of the elemental concentrations in needles showed minor changes. Ca concentrations in needles increased with liming, while Mg remained nearly unchanged, and P decreased in older needles.  相似文献   

14.
Hispolon was the main antitumor active ingredient in Phellinus sensu lato species. In order to confirm the dual regulating estrogenic ingredient and obtain more effective natural estrogen replacement drugs, hispolon was separated from Phellinus lonicerinus (Bond.) Bond. et sing. Hispolon exhibited significant anti-proliferative effect against estrogen-sensitive ER (+) MCF-7 cells in the absence of estrogen, and exhibits antagonistic effects on 17β-estradiol (E2)-induced MCF-7 cell proliferation when E2 and the different concentrations of hispolon were treated simultaneously. Hispolon also inhibited the proliferation of estrogen-negative ER (−) MDA-MB-231 cells at the concentration of 5.00 × 10− 5 M. The yeast two-hybrid experiments showed that hispolon had strong and non-selective effects on the estrogen receptor (ER) α and ERβ at a concentration of 1.00 × 10− 6 M. The ERβ-binding ability of hispolon was larger than ERα in the concentration range of 1.00 × 10− 9 M and 1.00 × 10− 7 M. Hispolon could increase the body weight coefficient, serum E2 and progesterone contents in immature female mice at dose of 9.10 × 10− 6 mol/kg, and increase coefficient of thymus and spleen in mice. The Gscores of hispolon-ERα and hispolon-ERβ docked complexes were − 7.93 kcal/mol and − 7.79 kcal/mol in docking simulations. Hispolon presented dual regulating estrogenic activities, which showed estrogenic agonist activity at low concentration or lack of endogenous estrogen, and the estrogenic antagonistic effect was stimulated at high concentrations or too much endogenous estrogen. Hispolon could be used for treating the estrogen deficiency-related disease with the benefit of non-toxic to normal cells, good antitumor effects and estrogenic activity.  相似文献   

15.
Four new C14-polyacetylene glycosides, namely coreosides A–D (1–4), were isolated from the capitula of Coreopsis tinctoria, a Snow chrysanthemum or Snow tea that is used as a folk tea for prevention of cardiovascular disease in southern Xinjiang, China. Coreosides A–D feature a long chain structure as its aglycon with two acetylenes on C-8 and C-10 and two olefinics on C-6 and C-12 sites, which construct a large conjugate system. The structures were elucidated on the basis of spectroscopic evidences and hydrolysis. Compounds 1–4 exhibited significant inhibition against cyclooxygenase-2 at the concentration of 1 × 10− 6 mol/L, with its IC50 values of 0.22–8.8 × 10− 2 μmol/L.  相似文献   

16.
We estimated gross photosynthetic production (GPP) of the forest floor vegetation in a 40-year-old Scots pine stand in southern Finland with three different methods: measurements of CO2 exchange of single leaves of field and ground layer species, measurement campaigns of forest floor net CO2 efflux at different irradiances with a manually operated soil chamber, and continuous measurements of forest floor net CO2 efflux with an automatic transparent chamber system. We upscaled the measured light response curves from the manual soil chambers using the biomass distribution of the forest floor species, a modelled seasonal pattern of photosynthetic capacity and a model of light extinction down the canopy. Leaf gas exchange measurements as well as measurements of net CO2 efflux with the manual chamber indicated saturation of photosynthesis at relatively low (50–400 μmol m−2 s−1) light levels. Leaf and patch level measurements gave similar rates of photosynthetic CO2 fixation per unit leaf biomass suggesting that reduction in photosynthetic production due to within-patch shading was small. Upscaling of photosynthetic production to the stand level and continuous measurements with the automatic soil chambers indicated that momentary photosynthetic production by the forest floor vegetation in the summer was typically about 2 μmol m−2 (ground) s−1. Cumulative upscaled GPP over the period of no snow (from 20 April to 20 November) in year 2003 was 131 g C m−2. Continuous measurements with the automatic soil chamber system were in line with the upscaling, the cumulative GPP being 83 g C m−2 and the seasonal pattern of photosynthetic rate similar to that of the upscaled photosynthesis.  相似文献   

17.
Dammarane Sapogenins (DS), with main ingredients of protopanaxatriol (PPT, 33%) and protopanaxadiol (PPD, 16%), is an alkaline hydrolyzed product of ginsenosides and had significant activities in improving learning and memory and decreasing chemotherapy-induced myelosuppression. In the present study, the pharmacokinetics and oral bioavailabilities of PPT and PPD were investigated when a single dose of DS was administrated orally (75 mg/kg) and intravenously (i.v., 30 mg/kg) to rats. Their in vitro stabilities in the GI tract were also investigated. PPT and PPD concentrations were measured by LC–MS. The results showed that PPT was eliminated rapidly from the body with an average t1/2, λz value of 0.80 h and CL of 4.27 l/h/kg after i.v. administration, while PPD was eliminated relatively slowly with a t1/2, λz of 6.25 h and CL of 0.98 l/h/kg. After oral administration, both PPD and PPT could be absorbed into the body, but their systemic exposures were quite different. PPT was absorbed into the body quickly, with a Tmax of 0.58 h and a Cmax of 0.13 μg/ml, while PPD was absorbed relatively slowly with a Tmax of 1.82 h and a Cmax of 1.04 μg/ml. The absolute bioavailabilities of PPT and PPD were estimated as 3.69% and 48.12%, respectively. The stability test found that PPT was instable in the stomach with 40% degradation after 4 h incubation at 37 °C, both in pH 1.2 buffer and in the stomach content solution. The instability in the stomach might be one of the reasons for PPT's poor bioavailability.  相似文献   

18.
Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 × 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5–6.8 m3 ha−1 year−1 for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha−1 year−1, with an average of 14 and 21 stems ha−1 year−1 at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha−1 year−1at the northern and southern site, respectively.  相似文献   

19.
Pre-marked skid trails, directional felling and climber cutting when logging in tropical rainforests may be important ways of reducing damage to the forest, thus creating a healthier stand and improving future yields.This study, carried out in a virgin dipterocarp rainforest in the south of Sabah, Malaysia, compared two types of logging (both with and without pre-cutting climbers): conventional selective logging (CL) and supervised logging (SL). The latter is a selective logging system in which both pre-marked skid trails and directional felling were implemented. The pre-marked skid trails were aligned parallel to each other, spaced 62 m apart. A randomised complete block 2 × 2 factorial design was used in the experiment, consisting of 16 gross treatment plots, each of 5.76 ha with a 1 ha net plot in the centre.Fewer trees tended (0.050 < P ≤ 0.100) to be logged in SL plots than in CL plots (on average 9.4 and 13.0 trees ≥60 cm diameter breast height ha−1). Pre-felling of climbers resulted in four more dipterocarp trees being logged ha−1, compared with no climber cutting: a statistically significant difference (P ≤ 0.050). The basal areas lost of both large trees (≥ 60 cm dbh) and small dipterocarp trees (10–29 cm dbh) tended to differ between the logging systems, with CL leading to greater losses.There were significant differences in the residual stands left by the logging systems, with respect to the number of dipterocarps and their basal area in the diameter class 10–29 cm; ca 30% more stems being found after SL. No significant differences (or tendencies) in these variables were found in the residual stands in other diameter classes, or when trees of all species were considered.  相似文献   

20.
Reforestation and afforestation have been suggested as an important land use management in mitigating the increase in atmospheric CO2 concentration under Kyoto Protocol of UN Framework Convention on climate change. Forest inventory data (FID) are important resources for understanding the dynamics of forest biomass, net primary productivity (NPP) and carbon cycling at landscape and regional scales. In this study, more than 300 data sets of biomass, volume, NPP and stand age for five planted forest types in China (Larix, Pinus tabulaeformis, Pinus massoniana, Cunninghamia lanceolata, Pouulus) from literatures were synthesized to develop regression equations between biomass and volume, and between NPP and biomass, and stand age. Based on the fourth FID (1989–1993), biomass and NPP of five planted forest types in China were estimated. The results showed that total biomass and total NPP of the five types of forest plantations were 2.81 Pg (1 Pg = 1015 g) and 235.65 Mg ha−1 yr−1 (1 Mg = 106 g), respectively. The area-weighted mean biomass density (biomass) and NPP of different forest types varied from 44.43 (P. massoniana) to 146.05 Mg ha−1 (P. tabulaeformis) and from 4.41 (P. massoniana) to 7.33 Mg ha−1 yr−1 (Populus), respectively. The biomass and NPP of the five planted forest types were not distributed evenly across different regions in China. Larix forests have the greatest variations in biomass and NPP, ranging from 2.7 to 135.37 Mg ha−1 and 0.9 to 10.3 Mg ha−1 yr−1, respectively. However, biomass and NPP of Populus forests in different region varied less and they were approximately 50 Mg ha−1 and 7–8 Mg ha−1 yr−1, respectively. The distribution pattern of biomass and NPP of different forest types closely related with stand ages and regions. The study provided not only with an estimation biomass and NPP of major planted forests in China but also with a useful methodology for estimating forest carbon storage at regional and global levels.  相似文献   

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