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1.
半干旱草原碳收支对陆地生态系统碳源汇功能变化具有重要影响。本文基于通榆草甸草原站2011~2017年和毛登典型草原站2013~2017年涡动相关法观测数据,分析了生长季碳通量日变化特征,研究了碳通量日变化过程对主要环境因子的响应。结果表明:两处草原7月碳吸收活动最强,草甸草原生长季各月总初级生产力(gross primary production, GPP)、生态系统呼吸(ecosystem respiration, Re)和净碳交换量(net ecosystem exchange, NEE)的峰值均高于典型草原。NEE的日变化以单峰型为主,但7月、8月饱和水汽压差较高时,GPP在正午前后降低,引起NEE的双峰型日变化。光合有效辐射是草甸草原NEE日变化的主导因子,而在典型草原,浅层土壤含水量(5 cm)也主导了NEE日变化。水分亏缺使草原碳交换速率显著降低,草甸草原固碳速率对水分亏缺的敏感性强于典型草原。同时,水分亏缺也改变了GPP、Re和NEE对温度和光合有效辐射的响应关系。  相似文献   

2.
A model computation on the evaporative demand in relation to precipitation indicated that, under a changing climate with elevating temperatures, evapotranspiration could exceed the concurrent precipitation during the growing period in southern Finland (61° N), but not in northern Finland (66° N). This could reduce the supply of soil water to enable tree growth on sites with soil of low water holding capacity. This in turn could reduce the productivity of Scots pine more in southern Finland than in northern Finland. In northern Finland, the reduction in growth due to a limited supply of water was partly compensated by the enhanced growth due to a rise in temperature outside dry periods.  相似文献   

3.
Impacts of extreme precipitation on tree plantation carbon cycle   总被引:2,自引:0,他引:2  
Extreme precipitation events are expected to increase in frequency and magnitude in future due to global warming, but relevant impacts on tree plantation ecosystem carbon cycle are unknown. In this study, we use an atmosphere–vegetation interaction model (AVIM2) to estimate the likely impacts of extreme precipitation events on carbon fluxes and carbon stocks of a tree plantation in south China. Our results indicate that shifting from moderate precipitation events to extreme precipitation events whilst keeping monthly precipitation unchanged could decrease the tree plantation carbon accumulation. Tree plantation net primary productivity, net ecosystem productivity, soil carbon stock and vegetation carbon stock could decrease by 4.2, 28, 4.3 and 1.4 % during the studying period of 1962–2004, respectively. Though reductions in net primary productivity and net ecosystem productivity are relatively smaller than their annual variations, our sensitivity test shows that the tree plantation carbon stock could decrease by 3.3 % if the assumed extreme precipitation regime lasts for 500 years. Observed and simulated gross primary productivity, ecosystem respiration and net ecosystem productivity have significant positive correlation with soil water content (SWC), especially the deep SWC. The mechanism for the extreme precipitation effect is that the increase in extreme precipitation events will cause SWC to decrease, consequently, reducing carbon fluxes and stocks.  相似文献   

4.
利用耦合模式比较计划第5阶段(CMIP5)中5个全球气候模式3种典型浓度路径(RCPs)预估结果,基于植被净初级生产力模型,估算安徽省21世纪近期(2018—2030年)、中期(2031—2050年)和远期(2051—2099年)植被净初级生产力及其对气候变化的响应。结果表明:对不同模式在安徽省模拟能力的评估可知,气温以多模式集合模拟效果优于单个模式,MIROC-ESM-CHEM对降水的模拟能力较好。未来安徽省将持续变暖,北部变暖幅度高于南部,其中RCP8.5情景下变暖趋势更显著;全省降水量将增加,南部增加多于北部。随着气候趋于暖湿化,植被净初级生产力总体增加;与基准年相比,21世纪近期增加不明显,中后期显著增加,空间上南部增加总体高于北部。从气候变化响应来看,安徽省植被净初级生产力与降水量和平均气温均显著相关,并且对降水量的响应程度更高。  相似文献   

5.
We hypothesized that the responses of boreal Norway spruce (Picea abies) forests to climate change would be region-specific due to regional differences in temperature and water availability. In this context, we analyzed the adaptive effects of varied thinning intensities on the gross primary production (GPP), total stem wood growth, and timber yield over a 100-year period using a process-based ecosystem model. Our simulations represented Norway spruce forests for five different bioclimatic zones spanning southern to northern Finland (61–67oN). Ten thinning regimes with thinning intensities ranging from 5 to 50 %, as well as an unthinned regime, were included in the calculations. The results showed that at the southern sites without thinning, the cumulative GPP and total stem wood growth were lower under the changing climate than in the current climate over the simulation period due to greater water depletion via evapotranspiration and reduced soil water availability. At the central and the northern sites, the climate changes increasingly enhanced the GPP and total stem wood growth due to the mitigation of low-temperature limitation and the improved soil water availability. Thinning generally mitigated the soil water deficit by reducing water evaporation and led to a reduction of the natural mortality. At the southern sites, light and moderate thinning intensities increased the GPP and total stem wood growth relative to sites with a changing climate that experienced no thinning. Moreover, moderate thinning resulted in the greatest timber yield. Heavy thinning, in which a large proportion of standing trees were removed, reduced the GPP and total stem wood growth despite allowing increased soil water availability. At the northern sites, all levels of thinning, including light thinning, decreased the GPP and stem wood growth, indicating that soil water availability was not a limiting factor for growth prior to thinning.  相似文献   

6.
Previous research has shown that various fluxes of carbon from and into ecosystems are correlated with summary climatic measures, such as actual evapotranspiration (AET). The best known of these is a regression of net primary production of terrestrial vegetation against AET published by Rosenzweig (1968). Rosenzweig intended this regression to represent steady state relationships of net primary production to climate. Nevertheless, it is tempting to use such regressions to predict transient responses of carbon flux to climate change, and several models take such an approach. Here, using a more detailed ecosystems model, we show that lags in population responses to climate change and non-linear changes in soil nitrogen availability that limit tree growth cause large departures from this regression during the transition between current climate and a 2 × CO2 climate. Simple models that do not consider population or soil dynamics may err when applied to the period of transition during a changing climate.  相似文献   

7.
This study was undertaken to assess the potential impacts of climate change on agriculture in the Sikasso region of southern Mali, as part of an effort by the U.S. Agency for International Development (USAID) to integrate climate change adaptation considerations into their development projects. The region is considered to be the breadbasket of Mali, providing a substantial amount of the country’s food supplies as well as cotton for exchange earnings. The project had two components: modeling how climate change could affect production of cereal and cash crops in southern Mali; and conducting a stakeholder-driven vulnerability and adaptation assessment to identify potential options for addressing current and projected risks to agriculture from climate change. Projected changes in crop yields were based on a previous analysis that was extended for the purposes of this study. The projections suggested that the sensitivity of maize to changing weather conditions is relatively small (generally less than 10% change) under both dry and wet scenarios in 2030 and 2060. White (Irish) potatoes, the primary cash crop, are the most sensitive to changing weather conditions, with yields decreasing under both dry and wet conditions; yields could decrease by about 25% by 2060. Stakeholder workshops, field interviews, and an expert analysis were used to assess current and future climate-related vulnerability and to identify potential adaptation options. The main focus of the assessment was farmers in a village of about 3,000 people in the Sikasso region that practiced a rice-potato rotation system typical to the region. The farmers emphasized adaptation measures that require outside financial and technical assistance, for example installation of a water gate that would retain more water in the inland valley and increase the water table to flood rice fields during the rainy season and for furrow irrigation of potatoes during the dry season. Adaptations emphasized by both the farmers and representatives of regional technical services were crop diversification and germplasm improvement; soil and water management; access to equipment (plows, carts, oxen, and improved stoves); credit stockage villageois (CSV); and fertilizer.  相似文献   

8.
The future forests of eastern North America will be shaped by at least three broad drivers: (i) vegetation change and natural disturbance patterns associated with the protracted recovery following colonial era land use, (ii) a changing climate, and (iii) a land-use regime that consists of geographically variable rates and intensities of forest harvesting, clearing for development, and land protection. We evaluated the aggregate and relative importance of these factors for the future forests of New England, USA by simulating a continuation of the recent trends in these drivers for fifty-years, nominally spanning 2010 to 2060. The models explicitly incorporate the modern distribution of tree species and the geographical variation in climate and land-use change. Using a cellular land-cover change model in combination with a physiologically-based forest landscape model, we conducted a factorial simulation experiment to assess changes in aboveground carbon (AGC) and forest composition. In the control scenario that simulates a hypothetical absence of any future land use or future climate change, the simulated landscape experienced large increases in average AGC—an increase of 53% from 2010 to 2060 (from 4.2 to 6.3 kg m−2). By 2060, climate change increased AGC stores by 8% relative to the control while the land-use regime reduced AGC by 16%. Among land uses, timber harvesting had a larger effect on AGC storage and changes in tree composition than did forest conversion to non-forest uses, with the most pronounced impacts observed on private corporate-owned land in northern New England. Our results demonstrate a large difference between the landscape’s potential to store carbon and the landscape’s current trajectory, assuming a continuation of the modern land-use regime. They also reveal aspects of the land-use regime that will have a disproportionate impact on the ability of the landscape to store carbon in the future, such as harvest regimes on corporate-owned lands. This information will help policy-makers and land managers evaluate trade-offs between commodity production and mitigating climate change through forest carbon storage.  相似文献   

9.
A coupled climate–carbon cycle model composed of a process-based terrestrial carbon cycle model, Sim-CYCLE, and the CCSR/NIES/FRCGC atmospheric general circulation model was developed. We examined the multiple temporal scale functions of terrestrial ecosystem carbon dynamics induced by human activities and natural processes and evaluated their contribution to fluctuations in the global carbon budget during the twentieth century. Global annual net primary production (NPP) and heterotrophic respiration (HR) increased gradually by 6.7 and 4.7%, respectively, from the 1900s to the 1990s. The difference between NPP and HR was the net carbon uptake by natural ecosystems, which was 0.6 Pg C year?1 in the 1980s, whereas the carbon emission induced by human land-use changes was 0.5 Pg C year?1, largely offsetting the natural terrestrial carbon sequestration. Our results indicate that monthly to interannual variation in atmospheric CO2 growth rate anomalies show 2- and 6-month time lags behind anomalies in temperature and the NiNO3 index, respectively. The simulated anomaly amplitude in monthly net carbon flux from terrestrial ecosystems to the atmosphere was much larger than in the prescribed air-to-sea carbon flux. Fluctuations in the global atmospheric CO2 time series were dominated by the activity of terrestrial vegetation. These results suggest that terrestrial ecosystems have acted as a net neutral reservoir for atmospheric CO2 concentrations during the twentieth century on an interdecadal timescale, but as the dominant driver for atmospheric CO2 fluctuations on a monthly to interannual timescale.  相似文献   

10.
Climate change is predicted to increase fire frequency and exacerbate water scarcity. The effect of these changes on the tree harvest decision in a forested catchment is investigated using stochastic dynamic programming, taking a stand of mountain ash (Eucalyptus regnans) in south–eastern Australia as a case study. We find that for a range of water and carbon sequestration values, it is optimal to cease harvesting in the absence of climate change. Whether it is optimal to do so under climate change will depend on the magnitude of the increases in fire frequency and water value. Potential increases in forest productivity also have a significant impact on the tree harvest decision.  相似文献   

11.
The interest in the national levels of the terrestrial carbon sink and its spatial and temporal variability with the climate and CO2 concentrations has been increasing. How the climate and the increasing atmospheric CO2 concentrations in the last century affect the carbon storage in continental China was investigated in this study by using the Modified Sheffield Dynamic Global Vegetation Model (M-SDGVM). The estimates of the M-SDGVM indicated that during the past 100 years a combination of increasing CO2 with historical temperature and precipitation variability in continental China have caused the total vegetation carbon storage to increase by 2.04 Pg C, with 2.07 Pg C gained in the vegetation biomass but 0.03 Pg C lost from the organic soil carbon matter. The increasing CO2 concentration in the 20th century is primarily responsible for the increase of the total potential vegetation carbon. These factorial experiments show that temperature variability alone decreases the total carbon storage by 1.36 Pg C and precipitation variability alone causes a loss of 1.99 Pg C. The effect of the increasing CO2 concentration alone increased the total carbon storage in the potential vegetation of China by 3.22 Pg C over the past 100 years. With the changing of the climate, the CO2 fertilization on China's ecosystems is the result of the enhanced net biome production (NBP), which is caused by a greater stimulation of the gross primary production (GPP) than the total soil-vegetation respiration. Our study also shows notable interannual and decadal variations in the net carbon exchange between the atmosphere and terrestrial ecosystems in China due to the historical climate variability.  相似文献   

12.
Changes in the duration of the photosynthetically active period strongly influence the changes in the carbon sequestration potential of boreal forests under climatic warming. In this paper, current theories on the effects of environmental variables such as spring air and soil temperature, photoperiod and chilling temperatures on the timing and initiation of photosynthesis in boreal deciduous and coniferous trees are discussed. Different dynamic phenological modeling approaches are reviewed, and model simulations are utilized to demonstrate model predictions under changing climatic conditions. A process-based forest ecosystem model is applied to estimate the relative importance of the duration of the photosynthetically active period on the amount of annual gross primary production and net primary production of boreal coniferous forests. All applied modeling approaches predict an increasing duration of the photosynthetically active period as a result of climatic warming. However, the magnitude of the response to increasing temperature varies between models and therefore affects the predictions of the changes in production.  相似文献   

13.
为了应对全球气候变化带来的挑战,2020年9月中国提出努力争取在2060年前实现碳中和。对此,生态系统固碳被寄予厚望;然而,生态学理论认为,成熟生态系统的碳输入输出趋于平衡,没有碳的净积累,也就没有碳汇功能,而未成熟的生态系统虽有碳的净积累并具有碳汇功能,但自然界任何未成熟生态系统从它建立的时候开始都在不断地向成熟生态系统演替,即任一生态系统演替的最终结果必然是碳输入输出达到平衡状态。由于森林生态系统碳库是陆地生态系统中最大的碳库,所以人们对其在碳中和上的贡献充满期待。本文以森林生态系统为例,分别考虑森林生态系统碳库的生物量碳库和土壤有机碳库,并基于全球最新研究成果,论证了森林生态系统土壤碳库积累过程具有长久的固碳功能,且不违背成熟生态系统碳输入输出趋于平衡的生态学理论,它能为实现碳中和目标做出贡献。  相似文献   

14.
The ocean's thermal inertia is a major contributor to irreversible ocean changes exceeding time scales that matter to human society. This fact is a challenge to societies as they prepare for the consequences of climate change, especially with respect to the ocean. Here the authors review the requirements for human actions from the ocean's perspective. In the near term (~2030), goals such as the United Nations Sustainable Development Goals (SDGs) will be critical. Over longer times (~2050–2060 and beyond), global carbon neutrality targets may be met as countries continue to work toward reducing emissions. Both adaptation and mitigation plans need to be fully implemented in the interim, and the Global Ocean Observation System should be sustained so that changes can be continuously monitored. In the longer-term (after ~2060), slow emerging changes such as deep ocean warming and sea level rise are committed to continue even in the scenario where net zero emissions are reached. Thus, climate actions have to extend to time scales of hundreds of years. At these time scales, preparation for “high impact, low probability” risks — such as an abrupt showdown of Atlantic Meridional Overturning Circulation, ecosystem change, or irreversible ice sheet loss — should be fully integrated into long-term planning.摘要在全球变化背景下, 海洋的很多变化在人类社会发展的时间尺度上 (百年至千年) 具有不可逆转性, 海洋巨大的热惯性是造成该不可逆性的主要原因. 这个特征为人类和生态系统应对海洋变化提出一系列挑战. 本文从海洋变化的角度总结了人类应对气候变化的要求, 提出需要进行多时间尺度的规划和统筹. 在近期 (到2030年) , 实现联合国可持续发展目标至关重要. 在中期 (2050–2060年前后) , 全球需要逐步减排并实现碳中和目标. 同时, 适应和减缓气候变化的行动和措施必须同步施行; 全球海洋观测系统需要得以维持并完善以持续监测海洋变化. 在远期 (在2060年之后) , 即使全球达到净零排放, 包括深海变暖和海平面上升在内的海洋变化都将持续, 因此应对全球变化的行动需持续数百年之久. 在该时间尺度, 应对“低概率, 高影响”气候风险 (即发生的可能性较低, 但一旦发生影响极大的事件带来的风险, 例如: 大西洋经圈反转环流突然减弱, 海洋生态系统跨过临界点, 无可挽回的冰盖质量损失等) 的准备应充分纳入长期规划.  相似文献   

15.
Northern Canadian Wetlands: Net Ecosystem CO2 Exchange and Climatic Change   总被引:3,自引:0,他引:3  
Northern Canadian peatlands represent a long term sink for atmospheric carbon dioxide (CO2), however there is concern they may become a net source of CO2 due to climatic change. Climatic change is expected to result in significant changes in regional hydrology in boreal and subarctic regions of Canada. A hydrologic model predicted a summer water table drop of 0.14 m in northern Canadian fens given an increase in summer temperature and rainfall of 3°C and 1 mm d-1, respectively. Moreover, surface peat temperature increased by 2.3°C. Net ecosystem exchange of CO2 was modelled using these modelled hydrologic and thermal changes with respiration:peat temperature and water table:net ecosystem production relationships developed from measurements at wetlands in northern Sweden and near Churchill, Manitoba. Model results indicate that the net atmospheric CO2 sink function of fens may be enhanced under future 2 × CO2 scenarios, while bogs may become a net source of atmospheric CO2. If the net ecosystem productivity response to the new hydrologic conditions was ignored then the model predicts a decrease in summer carbon storage for all peatland types.  相似文献   

16.
Climate change impacts on regional rice production in China   总被引:1,自引:0,他引:1  
Rice (Oryza sativa L.) production is an important contributor to China’s food security. Climate change, and its impact on rice production, presents challenges in meeting China’s future rice production requirements. In this study, we conducted a comprehensive analysis of how rice yield responds to climate change under different scenarios and assessed the associated simulation uncertainties of various regional-scale climate models. Simulation was performed based on a regional calibrated crop model (CERES-Rice) and spatially matched climatic (from 17 global climate models), soil, management, and cultivar parameters. Grain-filling periods for early rice were shortened by 2–7 days in three time slices (2030s, 2050s, and 2070s), whereas grain-filling periods for late rice were shortened by 10–19 days in three time slices. Most of the negative effects of climate change were predicted to affect single-crop rice in central China. Average yields of single-crop rice treated with CO2 fertiliser in central China were predicted to be reduced by 10, 11, and 11% during the 2030s, 2050s, and 2070s, respectively, compared to the 2000s, if planting dates remained unchanged. If planting dates were optimised, single-crop rice yields were predicted to increase by 3, 7, and 11% during the 2030s, 2050s, and 2070s, respectively. In response to climate changes, early and single-crop rice should be planted earlier, and late rice planting should be delayed. The predicted net effect would be to prolong the grain-filling period and optimise rice yield.  相似文献   

17.
Little is known about climate change and its impacts for the arid coastal and mountainous regions in northern Chile. The Elqui river basin, part of the Norte Chico of Chile between 27oS and 33oS latitude, is located south of the hyper-arid Atacama desert. Despite water scarcity, agricultural development in this region has been enhanced by agronomic practices and the marketing of valuable products. This paper characterizes the actual climate conditions and presents an overview and analyses of past climate variability, and future possible climate trends, emphasizing those relevant to agriculture. Precipitation shows an important decrease during the first decades of the past century. Runoff shows decreasing trends for the first half of the past century and increases for 1960 to 1985. Drought appears to be increasing. Statistical downscaling was accomplished using the Long Ashton Research Station Weather Generator. Both future periods of 2011 to 2030 and 2046–65 showed trends to higher minimum and maximum temperature. The number of hot days (maximum temperature greater than or equal to 30°C) has a strong increasing trend during October to April. Even though the downscaled results for precipitation do not show trends, the continuation of the present trend of low amounts is a concern. We discuss some implications of climatic changes for agriculture and we emphasize the importance of adaptation, especially to deal with water scarcity.  相似文献   

18.
The carbon cycle of terrestrial ecosystems is an important scientific issue in global climate change research.Plantation forest plays an important role in terrestrial carbon budget in China.In this study,eddy covariance flux data measured at Xiaolangdi forest ecosystem research station(XLD) in 2007 and 2008 are used to analyze the seasonal variation and meteorological control of CO2 flux in a 30-yr-old mixed plantation.The plantation forest mainly consists of Quercus variabilis,Platycladus orientalis,and Robinia pseudoacacia.The results show that the seasonal variations of net ecosystem exchange of CO2(NEE),gross primary production(GPP),and ecosystem respiration(Re) display single-peak curves.The maximum of carbon sequestration appears during May and June each year.The relative contribution of carbon release from ecosystem respiration to GPP varied slightly between 2007 and 2008.The relationship between NEE and photosynthetic active radiation(Qp) accords with the rectangular hyperbola model on diurnal scale,and shows a good linear correlation on monthly scale.The ecosystem photosynthetic parameters:the maximum photosynthetic rate(Pmax),the ecosystem photosynthetic photonyield(α),and the daytime ecosystem respiration(Rd) exhibit seasonal variations.Pmax reaches the maximum in August each year,with small interannual difference.The interannual differences of α and Rd are obvious,which is attributed to the changes of meteorological factors,such as solar radiation,vapor pressure deficit(D),precipitation,etc.Parameters Re,GPP,and NEP(net ecosystem production) have obvious exponential relations with temperature on monthly scale.There is a hysteresis in the response of GPP and NEP to temperature,i.e.,the carbon sequestration is not the maximum when the temperature reaches the peak value.The Q10 values were 1.37 and 1.45 in 2007 and 2008,respectively.On monthly scale,Re,GPP,and NEE increase as D increases,but rise slowly and even decrease when D is higher than 1.5 kPa.  相似文献   

19.
There is great international concern over the increase of atmospheric carbon dioxide and its effect on vegetation and climate, and vice versa. Many studies on this issue are based on climate model calculations or indirect satellite observations. In contrast we present a 12-year study (1994–2005) on the net ecosystem exchange of carbon dioxide (NEE) and precipitation surplus (i.e., precipitation–evaporation) of a grassland area in the centre of the Netherlands. On basis of direct flux observations and a process-based model we study and quantify the carbon uptake via assimilation and carbon release via soil and plant respiration. It appears that nearly year-round the assimilation term dominates, which indicates an accumulation of carbon dioxide. The mean net carbon uptake for the 12-year period is about 3 tonnes C per hectare, but with a strong seasonal and interannual variability depending on the weather and water budget. This variability may severely hamper the accurate quantification of carbon storage by vegetation in our present climates and its projection for future climates.  相似文献   

20.
Tropical rainforest plays an important role in the global carbon cycle, accounting for a large part of global net primary productivity and contributing to CO2 sequestration. The objective of this work is to simulate potential changes in the rainforest biome in Central America subject to anthropogenic climate change under two emissions scenarios, RCP4.5 and RCP8.5. The use of a dynamic vegetation model and climate change scenarios is an approach to investigate, assess or anticipate how biomes respond to climate change. In this work, the Inland dynamic vegetation model was driven by the Eta regional climate model simulations. These simulations accept boundary conditions from HadGEM2-ES runs in the two emissions scenarios. The possible consequences of regional climate change on vegetation properties, such as biomass, net primary production and changes in forest extent and distribution, were investigated. The Inland model projections show reductions in tropical forest cover in both scenarios. The reduction of tropical forest cover is greater in RCP8.5. The Inland model projects biomass increases where tropical forest remains due to the CO2 fertilization effect. The future distribution of predominant vegetation shows that some areas of tropical rainforest in Central America are replaced by savannah and grassland in RCP4.5. Inland projections under both RCP4.5 and RCP8.5 show a net primary productivity reduction trend due to significant tropical forest reduction, temperature increase, precipitation reduction and dry spell increments, despite the biomass increases in some areas of Costa Rica and Panama. This study may provide guidance to adaptation studies of climate change impacts on the tropical rainforests in Central America.  相似文献   

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