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1.
The impacts of elevated temperature and CO2 on young silver birch (Betula pendula Roth) saplings after 0, 25, 50 or 75% artificial defoliation were assessed by measuring plant height and dry mass of aboveground compartments and roots and various morphological and physiological variables. Defoliation either increased or decreased plant growth depending on the severity of damage and the climatic treatment. At 21 °C and 400 mg L?1 CO2, defoliated plants were not able to compensate for the lost foliage, but growth compensation and adaptation to the changed conditions were greater; growth of young defoliated silver birch saplings increased, which led to increased height and a tendency to enhance final aboveground and root biomass and leaf nitrogen and carbon content compared to the nondefoliated controls. Nevertheless, the short-term effect of the different climatic conditions did not result in a significant overgrowth of defoliated plants. A slight increase in temperature and CO2 were the most acceptable conditions for defoliated plants; however, a 4 °C increase with correspondingly higher CO2 was more stressful as shown by less growth in height and biomass allocation to leaves, stems and roots. The findings from the pilot experiment are more applicable to young birch trees, but stress on young trees may be reflected in future tree growth.  相似文献   

2.
集成生物圈模型（IBIS）是目前最复杂的基于动态植被模型的陆面生物物理模型之一.应用该模型对国际CEOP计划半干旱区基准站之一的吉林通榆观测站（44°25＇N , 122°52＇E）草地和农田生态系统2003年全年的CO2和水、热通量变化进行模拟,并将结果与涡度相关法测定的观测值进行了对比分析,以检验IBIS模型在半干旱区的模拟能力.对比结果表明：除CO2通量模拟结果不够理想外,IBIS模型较好地模拟了通榆观测站的感热通量和潜热通量.总体上看,该模型对农田生态系统模拟的偏差小于对退化草地的模拟.  相似文献   

3.
Soil CO2 production seasonality at a number of depths was investigated in a temperate forest in Japan and in a tropical montane forest in Thailand. The CO2 production rates were evaluated by examining differences in the estimated soil CO2 flux at adjacent depths. The temperate forest had clear temperature seasonality and only slight rainfall seasonality, whereas the tropical montane forest showed clear rainfall seasonality and only slight temperature seasonality. In the temperate forest, the pattern of seasonal variation in soil respiration was similar at all depths, except the deepest (0.65 m–), and respiration was greater in summer and less in winter. The contribution of the shallowest depth (around 0.1 m) was more than 50% of total soil-surface CO2 flux all year round, and the annual mean contribution was about 75%. CO2 production mostly appeared to increase with temperature in shallower layers. In contrast, in the tropical forest, soil CO2 production seasonality appeared to differ with depth. The CO2 production rate in the shallowest layer was high during the rainy season and low during the dry season. Soil CO2 production at greater depths (0.4 and 0.5 m–) showed the opposite seasonality to that in the shallower layer (around 0.1 m). As a result, the contribution from the shallow depth was greatest in the tropical forest during the rainy season (more than 90%), whereas it decreased during the dry season (about 50%). CO2 production appeared to be controlled by soil water at all depths, and the different ranges of water saturation seemed to cause the difference in seasonality at each depth. Our results suggest the importance of considering the vertical distribution of soil processes, particularly in areas where soil water is a dominant controller of soil respiration.  相似文献   

4.
Planting hedgerows on farm field edges can help mitigate greenhouse gas (GHG) emissions from agricultural landscapes by sequestering carbon (C) in woody biomass and in soil. Sequestration rates however, must be assessed in terms of their overall global warming potential (GWP) which must also consider GHG emissions. The objectives of this study were to (1) compare carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions from two types of hedgerows and adjacent annual agricultural production fields, and 2) better understand how climate, soil properties and plant species configurations affect hedgerow GHG emissions. At eight study sites in the lower Fraser River delta of British Columbia, we measured emissions from soil in both planted (P-Hedgerow) and remnant hedgerows (R-Hedgerow), as well as in adjacent annual crop production fields over 1 year using a closed-static chamber method. CO2 emissions were 59 % higher in P-Hedgerow than R-Hedgerow, yet there were no significant differences of relative emissions of CH4 and N2O. The environmental variables that explained the variation in emissions differed for the three GHGs. CO2 emissions were significantly correlated with soil temperature. CH4 and N2O and emissions were marginally significantly correlated with soil organic carbon (SOC) and soil water-filled pore space (WFPS), respectively. Emissions were not significantly correlated with hedgerow plant species diversity. While hedgerows sequester carbon in their woody biomass, we demonstrated that it is critical to measure hedgerow emissions to accurately ascertain their overall GHG mitigation potential. Our results show that there are no CO2e emission differences between the management options that plant new diverse hedgerows or conserve existing hedgerows.  相似文献   

5.
Soil respiration and soil carbon dioxide (CO2) concentration were investigated in a tropical monsoon forest in northern Thailand, from 1998 to 2000. Soil respiration was relatively high during the rainy season and low during the dry season, although interannual fluctuations were large. Soil moisture was widely different between the dry and wet seasons, while soil temperature changed little throughout the year. As a result, the rate of soil respiration is determined predominantly by soil moisture, not by soil temperature. The roughly estimated annual soil respiration rate was 2560gCm–2year–1. The soil CO2 concentration also increased in the rainy season and decreased in the dry season, and showed clearer seasonality than soil respiration did.  相似文献   

6.
Branch CO2 efflux of Norway spruce tree [Picea abies (L.) Karst.] was measured in ten branches at five different whorls during the growing season 2004 (from June till October) in campaigns of 3–4 times per month at the Beskydy Mts., the Czech Republic. Branch CO2 efflux was measured using a portable infrared gas analyzer (LI-6250, LI-COR, Inc., USA), operating as a closed system. Branch woody-tissue temperature was measured continuously in 10-min intervals for each sample position during the whole experiment period. On the basis of relation between CO2 efflux rate and woody-tissue temperature, a value of Q10 and of normalized CO2 efflux rate (E10–CO2 efflux rate at 10°C) was calculated for each sampled position. Estimated Q10 values ranged from 2.12 to 2.89, and E10 ranged from 0.41 to 1.19 μmolCO2m−2s−1. Differences in branch CO2 efflux were found between orientations, east-side branches presented higher efflux rate than west-side branches. The highest branch CO2 efflux rate values were measured in August and the lowest in October, which corresponds with woody-tissue temperature and growth processes during these periods. Branch CO2 efflux was significantly and positively correlated with branch position within canopy and woody-tissue temperature. Branches from the upper whorls showed higher CO2 efflux activity and seasonal dynamics than branches from the lower whorls.  相似文献   

7.
Rhizosphere-induced changes of Pinus densiflora (S. and Z.) grown at elevated atmospheric temperature and carbon dioxide are presented based on experiments carried out in a two-compartment rhizobag system filled with forest soil in an environmentally controlled walk-in chamber with four treatment combinations: control (25°C, 500 μmol mol?1 CO2), T2 (30°C, 500 μmol mol?1 CO2), T3 (25°C, 800 μmol mol?1 CO2), and T4 (30°C, 800 μmol mol?1 CO2). Elevated temperature and atmospheric carbon dioxide resulted in higher concentration of sugars and dissolved organic carbon in soil solution, especially at the later period of plant growth. Soil solution pH from the rhizosphere became less acidic than the bulk soil regardless of treatment, while the electrical conductivity of soil solution from the rhizosphere was increased by elevated carbon dioxide treatment. Biolog EcoPlate? data showed that the rhizosphere had higher average well color development, Shannon–Weaver index, and richness of carbon utilization compared with bulk soil, indicating that microbial activity in the rhizosphere was higher and more diverse than in bulk soil. Subsequent principal component analysis indicated separation of soil microbial community functional structures in the rhizosphere by treatment. The principal components extracted were correlated to plant-induced changes of substrate quality and quantity in the rhizosphere as plants’ response to varying temperature and atmospheric carbon dioxide.  相似文献   

8.
This study examined the temperature distribution during rotation welding process using birch (Betula spp.) wood dowel and Chinese larch (Larix gmelinii) substrates. Wood dowels were divided into two categories including an untreated group and a group pretreated with cupric chloride. The mechanics test results indicated that the pullout resistance of the pretreated group with welded time 3 s showed the best performance. As a fitting analyses result, both the untreated group and pretreated group showed a significant nonlinear relationship among temperature, welded depth and welded time. In the untreated group case, a linear regression relationship was found between the highest temperature of the welding interface and the depth. However, two-stage fitting was used to fit the regression for the pretreated group. Compared with the untreated group, thermogravimetric (TG) analysis of the pretreated group welding interface presented two pyrolytic peaks, and it illustrated that the pretreatment promoted the depolymerization and pyrolysis of wood constituents.  相似文献   

9.
One-year-old seedlings ofPinus koraiensis, Pinus sylvestriformis, Phellodendron amurense were grown in open-top chambers (OTCs) with 700 and 500 ώmol/mol CO2 concentrations, control chamber and on open site (ambient CO2, about 350 ώmol/mol CO2) respectively at the Open Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, and the growth course responses of three species to elevated CO2 and temperature during one growing season was studied from May to Oct. 1999. The results showed that increase in CO2 concentration enhanced the growth of seedlings and the effect of 700 (ώmol/mol CO2 was more remarkable than 500 ώmol/mol CO2 on seedling growth. Under the condition of doubly elevated CO2 concentration, the biomass increased by 38% in average for coniferous seedlings and 60% for broad-leaved seedlings. With continuous treatment of high CO2 concentration, the monthly-accumulated biomass of shade-tolerantPinus koraiensis seedlings was bigger in July than in August and September, while those ofPinus sylvestriformis andPhellodendron amurense seedlings showed an increase in July and August, or did not decrese until September. During the hot August, high CO2 concentration enhanced the growth ofPinus koraiensis seedlings by increasing temperature, but it did not show dominance in other two species. Foundation Item: This paper was supported by Chinese Academy of Sciences and the Open Research Station of Changbai Mountain Forest Ecosystem.  相似文献   

10.
Betulin, which is a medicinal pentacyclic triterpene, is abundant in the bark of white birch (Betula platyphlly). The bark of birch was collected at Tayuan Forest Farm of Jiagedaqi, Heilongjiang Province in September 2000. Supercritical fluid extraction (SFE) that is a new separation technology has been used for the processing pharmaceutical and natural products. In this paper, the extraction of betulin from the bark of birch by supercritical CO2 extraction was studied. The authors investigated and analyzed a few parameters such as modifier dosage, extraction pressure and extraction temperature. The optimal extraction conditions showed that the modifier dosage used for per gram bark powder was 1.5 mL, the extraction pressure was at 20 Mpa, and the extraction temperature was at 55 ℃. The velocity of flow of liquid CO2 was at 10 kg/h. The pressure and temperature in separation vessel were at 5.5 Mpa and 50 ℃, respectively.  相似文献   

11.
At the Takayama deciduous broadleaved forest Asiaflux site in Japan, the ecosystem carbon dynamics have been studied for more than two decades. In 2005, we installed non-dispersive infrared CO2 sensors in the soil below the site’s flux tower to systematically study vertical soil–air CO2 dynamics and explain the behavior of soil surface CO2 efflux. Soil–air CO2 concentrations measured from June 2005 through May 2006 showed sinusoidal variation, with maxima in July and minima in winter, similar to the soil CO2 effluxes measured simultaneously using open-flow chambers. Soil–air CO2 concentrations increased with soil depth from 5 to 50 cm: from 2,000 to 8,000 ppm in the summer and from 2,000 to 3,000 ppm in the winter under snow. Summer soil–air CO2 concentrations were positively correlated with soil moisture on daily and weekly scales, indicating that the Oi, Oe, and A horizons, where decomposition is accelerated by high-moisture conditions, contributed substantially to CO2 emissions. This result is consistent with the short residence time (about 2 h) of CO2 in the soil and larger emissions in shallow soil layers based on our diffusion model. We revealed for the first time that soil–air CO2 concentrations in winter were correlated with both snow depth and wind speed. CO2 transfer through the snow was hundreds of times the gas diffusion rates in the soil. Our estimate of the CO2 efflux during the snow-cover season was larger than previous estimates at TKY, and confirmed the important contribution of the snow-cover season to the site’s carbon dynamics.  相似文献   

12.
随着大气CO2浓度的升高,主要由其引起的温室效应与对生物新陈代谢的影响变得越来越显著。森林生态系统在全球碳循环中扮演着重要的角色。为了评估和理解森林土壤CO2通量及其随空气和土壤温度的季节和昼夜变化规律,我们在长白山北坡典型阔叶红松林内利用静态箱技术进行了原位观测。实验在整个生长季(6月初至9月末)昼夜进行,利用气相色谱进行气体分析。结果表明: 长白山阔叶红松林土壤是大气二氧化碳源,其CO2通量具有明显的季节和昼夜变化规律。通量的变化范围是(0.30-2.42)μmol穖-2穝-1,平均值为0.98μmol穖-2穝-1。土壤CO2排放的季节规律表明,土壤CO2通量的变化与气温和土壤温度的变化有关。CO2平均通量的最大值出现在7月((1.27±23%)μmol穖-2穝-1),最小值出现在9月((0.5±28%)μmol穖-2穝-1)。土壤CO2的昼夜波动与土壤温度变化有关,而在时间上滞后于温度的变化。森林下垫面土壤CO2通量与土壤温度显著相关,与6cm深度土层温度相关系数最大。基于气温和土壤温度计算的Q10值范围为2.09-3.40。图2表3参37。  相似文献   

13.
Terrestrial ecosystems represent a major sink for atmospheric carbon (C) and temperate forests play an important role in global C cycling, contributing to lower atmospheric carbon dioxide (CO2) concentration through photosynthesis. The Intergovernmental Panel of Climate Change highlights that the forestry sector has great potential to decrease atmospheric CO2 concentration compared to other sectoral mitigation activities. The aim of this study was to evaluate CO2 sequestration (CO2S) capability of Fagus sylvatica (beech) growing in the Orfento Valley within Majella National Park (Abruzzo, Italy). We compared F. sylvatica areas subjected to thinning (one high-forest and one coppice) and no-management areas (two high-forests and two coppices). The results show a mean CO2S of 44.3 ± 2.6 Mg CO2 ha?1 a?1, corresponding to 12.1 ± 0.7 Mg C ha?1 a?1 the no-managed areas having a 28% higher value than the managed areas. The results highlight that thinning that allows seed regeneration can support traditional management practices such as civic use in some areas while no management should be carried out in the reserve in order to give priority to the objective of conservation and naturalistic improvement of the forest heritage.  相似文献   

14.
Knowledge regarding the interactive effects of elevated [CO2], warming and drought on dry mass production, allocation and water use efficiency (WUE) of tree seedlings is limited, particularly in trees exhibiting different stomatal regulation strategies. Seedlings of Callitris rhomboidea (relatively anisohydric) and Pinus radiata (relatively isohydric) were grown in two [CO2] (Ca (400 μmol mol?1) and Ce (640 μmol mol?1)) and two temperature (Ta (ambient) and Te (ambient?+?4 °C)) treatments in a sun-lit glasshouse under well-watered conditions prior to imposition of the drought. Ce increased mass production in C. rhomboidea (but not in P. radiata), while drought limited mass production in both species. Mass production was greatest in the combination of Ce, Te and well-watered conditions. Pinus radiata allocated relatively more dry mass into roots and had higher plant WUE than C. rhomboidea. Noticeably, mass allocation patterns in C. rhomboidea varied as a function of the treatments, but those of P. radiata were constant. Ce enhanced leaf WUE of both species, but to a greater degree under drought stress than well-watered conditions. Moderate drought stress increased both leaf and plant WUE compared to well-watered conditions. C. rhomboidea exhibited plasticity to variable climate conditions through morphological adjustments, while P. radiata exhibited a highly conservative strategy. Collectively, these findings indicate that the two species have different strategies in resource acquisition and utilisation under changing environmental conditions. Future studies on tree response to climate change need to fully consider the integration of species traits, including stomatal behaviour and hydraulic strategies.  相似文献   

15.
Extreme droughts can adversely affect the dynamics of soil respiration in tree plantations. We used a severe drought in southwestern China as a case study to estimate the effects of drought on temporal variations in soil respiration in a plantation of Eucalyptus globulus. We documented a clear seasonal pattern in soil respiration with the highest values (100.9 mg C–CO2 m?2 h?1) recorded in June and the lowest values (28.7 mg C–CO2 m?2 h?1) in January. The variation in soil respiration was closely associated with the dynamics of soil water driven by the drought. Soil respiration was nearly twice as great in the wet seasons as in the dry seasons. Soil water content accounted for 83–91% of variation in soil respiration, while a combined soil water and soil temperature model explained 90–99% of the variation in soil respiration. Soil water had pronounced effects on soil respiration at the moisture threshold of 6–10%. Soil water was strongly related to changes in soil parameters (i.e., bulk density, pH, soil organic carbon, and available nitrogen). These strongly influenced seasonal variation in soil respiration. We found that soil respiration was strongly suppressed by severe drought. Drought resulted in a shortage of soil water which reduced formation of soil organic carbon, impacted soil acid–base properties and soil texture, and affected soil nutrient availability.  相似文献   

16.
A participatory network was set up to study tree phenology in the Western Alps. We used data collected in 2006 and 2007 on birch, ash, hazel, spruce and larch to assess how local air temperature, altitude and other topographic variables influenced dates of budburst and leaf unfolding. Altitude was, as expected, a main predictor variable of budburst and leafing dates with delays ranging from 2.4 to 3.4 days per 100 m. Ash was the only species with strong evidence of a year difference in the altitudinal gradient with the warm year (2007) characterized by a weaker altitudinal gradient. We found a latitudinal gradient in the appearance of budburst for one coniferous species (larch) and curvature affected leafing in ash. Thermal sum (sum of Degree-Days above 0 °C) was increasing with altitude for budburst (birch, ash and larch) and leafing (birch and ash). Understanding of altitude and topography effects in addition to temperature in phenological models should improve projections of future changes in mountain regions.  相似文献   

17.
The impacts of elevated atmospheric CO2 concentrations (500 μmol·mol−1 and 700 μmol·mol−1) on total soil respiration and the contribution of root respiration ofPinus koraiensis seedlings were investigated from May to October in 2003 at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences, Jilin Province, China. After four growing seasons in top-open chambers exposed to elevated CO2, the total soil respiration and roots respiration ofPinus koraiensis seedlings were measured by a Li-6400-09 soil CO2 flux chamber. Three PVC cylinders in each chamber were inserted about 30 cm into the soil instantaneously to terminate the supply of current photosynthates from the tree canopy to roots for separating the root respiration from total soil respiration. Soil respirations both inside and outside of the cylinders were measured on June 16, August 20 and October 8, respectively. The results indicated that: there was a marked diurnal change in air temperature and soil temperature at depth of 5 cm on June 16, the maximum of soil temperature at depth of 5 cm lagged behind that of air temperature, no differences in temperature between treatments were found (P>0.05). The total soil respiration and soil respiration with roots severed showed strong diurnal and seasonal patterns. There was marked difference in total soil respiration and soil respiration with roots severed between treatments (P<0.01); Mean total soil respiration and contribution of root under different treatments were 3.26, 4.78 and 1.47 μmol·m−2·s−1, 11.5%, 43.1% and 27.9% on June 16, August 20 and October 8, respectively. Foundation item: This study was supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (KZCX1-SW-01) and the National Natural Science Foundation of China (30070158). Biography: LIU Ying (1976-), female, Ph. D. Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan  相似文献   

18.
The Dahurian larch forest in northeast China is important due to its vastness and location within a transitional zone from boreal to temperate and at the southern distribution edge of the vast Siberian larch forest. The continuous carbon fluxes were measured from May 2004 to April 2005 in the Dahurian larch forest in Northeast China using an eddy covariance method. The results showed that the ecosystem released carbon in the dormant season from mid-October 2004 to April 2005, while it assimilated CO2 from the atmosphere in the growing season from May to September 2004. The net carbon sequestration reached its peak of 112 g.m^-2.month ^-1 in June 2004 （simplified expression of g （carbon）.m^-2.month^-1） and then gradually decreased. Annually, the larch forest was a carbon sink that sequestered carbon of 146 g-m^-2.a^-1 （simplified expression of g （carbon）.m^-2.a^-1） during the measurements. The photosynthetic process of the larch forest ecosystem was largely affected by the vapor pressure deficit （VPD） and temperature. Under humid conditions （VPD 〈 1.0 kPa）, the gross ecosystem production （GEP） increased with increasing temperature. But the net ecosystem production （NEP） showed almost no change with increasing temperature because the increment of GEP was counterbalanced by that of the ecosystem respiration. Under a dry environment （VPD 〉 1.0 kPa）, the GEP decreased with the increasing VPD at a rate of 3.0 μmol.m^-2.s^-1kPa -1 and the ecosystem respiration was also enhanced simultaneously due to the increase of air temperature, which was linearly correlated with the VPD. As a result, the net ecosystem carbon sequestration rapidly decreased with the increasing VPD at a rate of 5.2 μmol.m^-2.s-1.kPa^-1. Under humid conditions （VPD 〈 1.0 kPa）, both the GEP and NEP were obviously restricted by the low air temperature but were insensitive to the high temperature because the observed high temperature value comes within the category of the optimum range.  相似文献   

19.
We examined vertical and seasonal variations in stem respiration rates in a 50-year-old plantation of Japanese cypress, Chamaecyparis obtusa (Sieb. et Zucc.) Endl., in central Japan, and discuss a practical and precise method to scale a point-measured stem CO2 efflux rate up to whole-stem respiration. For five selected trees, stem CO2 efflux rates were measured at breast height (1.3 m) and at five or six points above breast height (at approximately 2 m intervals) every 1 or 2 months over two consecutive years. Daily total stem respiration rate (surface area basis) was greater inside the crown than below the crown, especially during the growing season. By incorporating the vertical profile of the respiration rate, annual whole-stem respiration was estimated for each sample tree (R y). We then compared this estimate (R y) with another estimate of annual whole-stem respiration (R′y) obtained using a conventional method; it is assumed that the area-based respiration rate at breast height is constant throughout the stem. The ratio of these two estimates (R′y/R y) was usually less than 1, indicating that the assumptions used to calculate R′y underestimate annual whole-stem respiration. We found that R′y/R y was negatively correlated with the ratio of crown length to tree height (crown ratio). These results suggest that annual whole-stem respiration in this C. obtusa plantation is substantially affected by the relative proportion of within-crown stem with higher respiratory activity. Methodologically, our results imply that incorporating the crown ratio into the conventional method would improve the accuracy of annual whole-stem respiration estimates.  相似文献   

20.
Several studies have been conducted on the response of crops to greater concentrations of atmospheric CO2 (CO2 fertilization) as a result of climate change, but only few studies have evaluated this effect on multipurpose agroforestry tree species in tropical environments. The objectives of this study were to quantify differences in growth parameters and in leaf carbon (C) and nitrogen (N) concentrations of Cedrela odorata L. and Gliricidia sepium (Jacq.) Walp. seedlings under current ambient temperature (32°C daytime, 22°C night time) and CO2 (360 ppm) (AMB); CO2 fertilization (800 ppm, 32°C daytime, 22°C night time) (fCO2); elevated ambient temperature (360 ppm, 34°C daytime, 25°C night time) (TEMP); and a combination of elevated temperature (32°C daytime, 22°C night time) and CO2 fertilization (800 ppm) (TEMPxfCO2). Results showed significant differences (P < 0.05) in seedling growth parameters (seedling height, number of stem leaves, leaf area ratio, shoot and root biomass, and shoot/root ratio) between treatments for both tree species. The greatest increases in growth parameters occurred in the TEMP and TEMPxfCO2 treatments compared to the AMB treatment for both tree species. However, growth parameters were significantly lower (P < 0.05) in the fCO2 treatment compared to that of the AMB treatment. Leaf N concentration was 1.1 to 2.1 times lower (P < 0.05) in all treatments when compared to current ambient conditions (AMB) in both tree species, but no significant changes in leaf C concentrations were observed. Results from our study suggested that fCO2 had the greatest negative impact on tree growth parameters, and leaf N concentrations were affected negatively in all treatments compared to current ambient conditions. It is expected that such changes in growth parameters and plant N content may impact the long-term cycling of nutrients in agroforestry systems.  相似文献   

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