氮沉降对凋落物分解的影响研究进展

过去几十年的人类活动增加了陆地生态系统的氮输入量,对凋落物分解的影响有促进、抑制和没有影响3种情况。凋落物的基质质量影响凋落物的分解,其中木质素、纤维素、酚类物质、N浓度、P浓度、C/N比、C/P比、木质素/N比具有重要作用。人类活动引起的全球变化,如CO₂增加、温度上升和降水变化,影响了氮沉降的速率和凋落物分解。未来氮沉降对凋落物分解的研究热点包括加强氮沉降对热带与亚热带森林凋落物和阔叶树种凋落物分解影响的研究,氮沉降对凋落物分解影响研究的长期化,采用13C同位素研究凋落物分解,注重凋落物分解对氮沉降与大气CO₂浓度升高、气候变暖、降水变化、紫外线辐射增强、P沉降交互作用响应的研究。     

Predicting response of fuel load to future changes in climate and atmospheric composition in the Southern United States

The model projected ecosystem carbon dynamics were incorporated into the default (contemporary) fuel load map developed by FCCS (Fuel Characteristic Classification System) to estimate the dynamics of fuel load in the Southern United States in response to projected changes in climate and atmosphere (CO₂ and nitrogen deposition) from 2002 to 2050. The study results indicated that in 2002 the total fuel load of the Southern United States was about 1.15 P g (1 P = 10¹⁵), which will decrease to 1.11 P g in 2050. The declination of fuel load is mainly due to the climate change, especially the reduced precipitation in 2050, while the effects of elevated CO₂ and nitrogen deposition will increase fuel load. Interactions among all factors will result in 1% reduction in the fuel load in 2050. In response to the spatial heterogeneity in environmental changes, the dynamics of fuel load from 2002 to 2050 vary strongly among the study states. The declined precipitation in the northern inland of the study region may lead to 20% fuel load reduction in Tennessee and Kentucky by the year of 2050, while the elevated precipitation and decreased daily mean temperature in the coastal states, especially in South Carolina, North Carolina, and Virginia, may result in fuel load accumulation. The temporal–spatial variation of the fuel load may be overestimated since the adjustments of forest management regime in response to climate change were not considered in current study.     

Effect of climate change and nitrogen deposition on central-European forests: Regional-scale simulation for South Bohemia

The simulation of forest production until 2100 under different environmental scenarios and current management practices was performed using a process-based model BIOME-BGC previously parameterized for the main Central-European tree species: spruce, pine, beech and oak and adapted to include forest management practices. Climatic scenario HadCM3 used in the simulations was taken from the IPCC database created within the 3rd Assessment Report. It was combined with a scenario of CO₂ concentration development and a scenario of N deposition. The control scenario considered no changes of climatic characteristics, CO₂ concentration and N deposition. Simulation experiment was performed for the test region - South Bohemia - using a 1 km × 1 km grid. The actual data on the regional forest cover were aggregated for each grid cell in such a way that each cell represented an even-aged single-dominant species stand or non-forested area, and a standard management scenario depending on the stand age and species was applied to each cell. The effect of environmental variables was estimated as the difference of simulated carbon pools and fluxes in 2050 under environmental changes and under control scenario.The model simulation for the period to 2050 with only climate change under constant CO₂ concentration and N deposition indicated a small decrease of NPP (median values by species reached −0.9 to −1.7% for different species), NBP (−0.3 to −1.7%) and vegetation carbon (−0.3 to −0.7%), whereas soil C slightly increased. Separate increase of N deposition gave small positive effect on carbon pools (0.8-2.9% for wood C and about 0.5% for soil C) and more expressed effect on carbon fluxes (1.8-4.3% for NPP and 1.0-9.7% for NBP). Separate increase of CO₂ concentration lead to 0.6-2.4% increase of wood C pool and 0.1-0.5% increase of soil C. The positive effects of CO₂ concentration and N deposition were more pronounced for coniferous than for deciduous stands.Replacement of 0.5% of coniferous plantations every year by natural broadleaved stands evoked 10.5% of increase of wood carbon pool due to higher wood density of beech and oak compared to spruce and pine, but slightly decreased soil and litter carbon pools.     

Influence of climate change,fire and harvest on the carbon dynamics of black spruce in Central Canada

The results of EFIMOD simulations for black spruce (Picea mariana [Miller]) forests in Central Canada show that climate warming, fire, harvesting and insects significantly influence net primary productivity (NPP), soil respiration (Rs), net ecosystem production (NEP) and pools of tree biomass and soil organic matter (SOM). The effects of six climate change scenarios demonstrated similar increasing trends of NPP and stand productivity. The disturbances led to a strong decrease in NPP, stand productivity, soil organic matter (SOM) and nitrogen (N) pools with an increase in CO₂ emission to the atmosphere. However the accumulated NEP for 150 years under harvest and fire fluctuated around zero. It becames negative only at a more frequent disturbance regime with four forest fires during the period of simulation. The results from this study show that changes in climate and disturbance regimes might substantially change the NPP as well as the C and N balance, resulting in major changes in the C pools of the vegetation and soil under black spruce forests.     

Simulating the productivity of a subalpine forest at high elevations under representative concentration pathway scenarios in the Qilian Mountains of northwest China

The current work adopted the Biome-BioGeochemical Cycle model to simulate the net primary productivity (NPP) of a subalpine forest (Picea crassifolia forest) under four representative concentration pathway (RCP) scenarios in the Qilian Mountains of northwest China. This study also investigated the responses of forest’s NPP to different combinations of climatic changes and CO₂ concentration increase. Results showed that (1) under the RCP scenarios, greater increases in temperature, precipitation, and CO₂ concentration caused larger increments in forest NPP; (2) the effect of CO₂ concentration (increased NPP from 19.9% to 21.7%) was more significant than that of climate change (increased NPP from 7.5% to 17.1%); (3) the simultaneous increments in climatic change and atmospheric CO₂ concentration led to a remarkable increase in P. crassifolia forest NPP (ranging from 33.1% to 41.3%), with the combination of the two exerting strong interactive effects on forest NPP; and (4) the response of the forest’s NPP to future global change was more intense at high elevations than at low ones, with the temperature being the main factor controlling forest NPP variation at the high-elevation regions. These valuable predictions can help clarify how subalpine forest ecosystems respond to simultaneous or independent changes in climate and CO₂ concentration.     

Determining photosynthetic responses of forest species to elevated [CO2]: Alternatives to FACE

Free air CO₂ enrichment (FACE) experiments are considered the most reliable approach for quantifying our expectations of forest ecosystem responses to changing atmospheric CO₂ concentrations [CO₂]. Because very few Australian tree species have been studied in this way, or are likely to be studied in the near future because of the high installation and maintenance costs of FACE, there are no clear answers to questions such as: (1) which species will be the winners in Australia's natural forests and what are the implications for biodiversity and carbon (C) sequestration; and (2) which will be the most appropriate species or genotypes to ensure the sustainability of Australia's plantation forests.     

Carbon gains and recovery from degradation of forest biomass in European Union during 1990–2005

The net gain of carbon in European Union (EU) forest vegetation during 1990–2005 was estimated at 360–400 Tg CO₂ year⁻¹ by analysing international data. This amount is at low end of the range of recent corresponding estimates, but greater than earlier estimates published for the period 1971–1990. The sequestration took place almost exclusively in areas which were already forested in 1990. In 2005, new plantations, established after 1990, contributed only about 8% to the estimated net gain. The sequestration was estimated to be the greatest in Germany, France, Italy, Finland and Poland regardless of data source and method of estimation. On a per capita basis, the sequestration was estimated to be the greatest in Finland and Latvia. Carbon sequestration in forests is an important component of the long-term carbon balance of the EU. Carbon sequestration in forests is partly driven by a recovery of the ecosystems from human-induced degradation in the 19th century and the first half of the 20th century. Forest management has affected carbon sequestration and merits attention in climate policy presuming that new policies and measures are reconciled with those already in place for the promotion of the diverse goals of land management in Europe.     

Effects of atmospheric and climate change at the timberline of the Central European Alps

? This review considers potential effects of atmospheric change and climate warming within the timberline ecotone of the Central European Alps. After focusing on the impacts of ozone (O₃) and rising atmospheric CO₂ concentration, effects of climate warming on the carbon and water balance of timberline trees and forests will be outlined towards conclusions about changes in tree growth and treeline dynamics.

? Presently, ambient ground-level O₃ concentrations do not exert crucial stress on adult conifers at the timberline of the Central European Alps. In response to elevated atmospheric CO₂ Larix decidua showed growth increase, whereas no such response was found in Pinus uncinata. Overall climate warming appears as the factor responsible for the observed growth stimulation of timberline trees.

? Increased seedling re-establishment in the Central European Alps however, resulted from invasion into potential habitats rather than upward migration due to climate change, although seedlings will only reach tree size upon successful coupling with the atmosphere and thus loosing the beneficial microclimate of low stature vegetation.

? In conclusion, future climate extremes are more likely than the gradual temperature increase to control treeline dynamics in the Central European Alps.

     

Temperature sensitivity of soil CO2 production in a tropical hill evergreen forest in northern Thailand

Tropical forests, like boreal forests, are considered key ecosystems with regard to climate change. The temperature sensitivity of soil CO₂ production in tropical forests is unclear, especially in eastern Asia, because of a lack of data. The year-round variation in temperature is very small in tropical forests such that it is difficult to evaluate the temperature sensitivity of soil CO₂ production using field observations, unlike the conditions that occur in temperate and boreal forests. This study examined the temperature sensitivity of soil CO₂ production in the tropical hill evergreen forest that covers northern Thailand, Laos, and Myanmar; this forest has small temperature seasonality. Using an undisturbed soil sample (0.2 m diameter, 0.4 m long), CO₂ production rates were measured at three different temperatures. The CO₂ production (SR, mg CO₂ m⁻² s⁻¹) increased exponentially with temperature (T, °C); the fitted curve was SR = 0.023 e^0.077T, with Q₁₀ = 2.2. Although still limited, our result supports the possibility that even a small increase in the temperature of this region might accelerate carbon release because of the exponential sensitivity and high average temperature.     

Modelling impacts of changes in carbon dioxide concentration,climate and nitrogen deposition on carbon sequestration by European forests and forest soils

Changes in the Earth's atmosphere are expected to influence the growth, and therefore, carbon accumulation of European forests. We identify three major changes: (1) a rise in carbon dioxide concentration, (2) climate change, resulting in higher temperatures and changes in precipitation and (3) a decrease in nitrogen deposition. We adjusted and applied the hydrological model Watbal, the soil model SMART2 and the vegetation model SUMO2 to asses the effect of expected changes in the period 1990 up to 2070 on the carbon accumulation in trees and soils of 166 European forest plots. The models were parameterized using measured soil and vegetation parameters and site-specific changes in temperature, precipitation and nitrogen deposition. The carbon dioxide concentration was assumed to rise uniformly across Europe. The results were compared to a reference scenario consisting of a constant CO₂ concentration and deposition scenario. The temperature and precipitation scenario was a repetition of the period between 1960 and 1990. All scenarios were compared to the reference scenario for biomass growth and carbon sequestration for both the soil and the trees.     

CO_2和O_3浓度升高对森林生态系统影响的研究进展

系统收集和整理了国内外关于CO2和O3复合胁迫对森林影响的研究,从两者的复合胁迫对森林树木的光合作用、地上部分生长、根系生长、土壤环境、种间竞争的影响等方面进行了阐述,并对该领域有待深入研究的方向进行了展望;提出应深入开展对植物地下水平和分子水平的研究,为解决全球气候变化对森林造成的影响提供借鉴,同时为生态系统的管理提供依据。     

Use of 3-PG and 3-PGS to simulate forest growth dynamics of Australian tropical rainforests: I. Parameterisation and calibration for old-growth,regenerating and plantation forests

Accurate information concerning regional to ecosystem-scale carbon dynamics within tropical rainforests is important because of the increasing certainty that the global climate will change significantly within the next century. Tropical forests of north Queensland, Australia, are highly sensitive to climate change and substantial shifts in the distribution of these forests are likely to occur with minor variations in climate. The focus of this research was the development of a model-based system for assessing forest growth and biomass accumulation dynamics within Australia's tropical rainforest bioregion and predicting the impacts of climate change on these dynamics. This paper presents the parameterisation and calibration of (a) the 3-PG (Physiological Principles Predicting Growth) model to a selection of restored rainforest and commercial timber plantations and (b) a modified version 3-PGS which uses satellite data, enabling the spatial assessment of mature tropical rainforest growth and production throughout the wet tropics bioregion. Statistically significant relationships were observed between 3-PG and 3-PGS modelled and field measured estimates of stand structural attributes including, basal area (BA), diameter at breast height (DBH) and above-ground biomass (AGB) throughout the bioregion. 3-PG and 3-PGS modelled leaf area index (LAI) and net primary production (NPP) related well to published estimates at other similar rainforest sites. These results indicate that the simple, process-based models are effective at capturing the growth dynamics of structurally complex old-growth, restoration and plantation rainforests.     

The impact of nitrogen deposition on carbon sequestration by European forests and heathlands

In this study, we present estimated ranges in carbon (C) sequestration per kg nitrogen (N) addition in above-ground biomass and in soil organic matter for forests and heathlands, based on: (i) empirical relations between spatial patterns of carbon uptake and influencing environmental factors including nitrogen deposition (forests only), (ii) ¹⁵N field experiments, (iii) long-term low-dose N fertilizer experiments and (iv) results from ecosystem models. The results of the various studies are in close agreement and show that above-ground accumulation of carbon in forests is generally within the range 15–40 kg C/kg N. For heathlands, a range of 5–15 kg C/kg N has been observed based on low-dose N fertilizer experiments. The uncertainty in C sequestration per kg N addition in soils is larger than for above-ground biomass and varies on average between 5 and 35 kg C/kg N for both forests and heathlands. All together these data indicate a total carbon sequestration range of 5–75 kg C/kg N deposition for forest and heathlands, with a most common range of 20–40 kg C/kg N. Results cannot be extrapolated to systems with very high N inputs, nor to other ecosystems, such as peatlands, where the impact of N is much more variable, and may range from C sequestration to C losses.     

A process model for simulating net primary productivity (NPP) based on the interaction of water-heat process and nitrogen: a case study in Lantsang valley

Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity (NPP) of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen (N) cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator (BEPS) model. With the established database (leaf area index, land cover, daily meteorology data, vegetation and soil) at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g?m-2?a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model (without considering nitrogen effect), it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.     

Carbon Stock in Community Managed Hill Sal (Shorea robusta) Forests of Central Nepal

Community forests of developing countries are eligible to participate in the Reducing Emissions from Deforestation and Forest Degradation (REDD+) scheme. For this, estimation of carbon stock and the sequestration is essential. The carbon stock in the living biomass of nine community managed Shorea robusta forests of the mid hill regions of central Nepal (managed for 4–29 yr) were estimated. The carbon stock of trees and shrubs was estimated using an allometric equation while the biomass of herbaceous vegetation was estimated by the harvest method. The carbon stock in the living biomass of the studied forests ranged from 70–183 Mg ha^?1(mean: 120 Mg ha^?1) and it increased with increasing soil organic carbon. However, the carbon stock did not vary significantly with species richness and litter cover. The biomass and carbon stock in the forests managed for >20 yr were significantly higher than in the forests managed for < 20 yr. The carbon stock increased with the management duration (p < .05) with sequestration rate of 2.6 Mg C ha^?1 yr^?1. The local management has had positive effects on the carbon stock of the forests and thus the community forests have been acting as a sink of the atmospheric CO₂. Therefore, the community managed forests of Nepal are eligible to participate in the REDD+ scheme.     

Carbon sequestration in the growing stock of trees in Finland under different cutting and climate scenarios

In this work the aim was to determine how carbon sequestration in the growing stock of trees in Finland is dependent on the forest management and increased production potential due to climate change. This was analysed for the period 2003–2053 using forest inventory data and the forestry model MELA. Four combinations of two climate change and two management scenarios were studied: current (CU) and gradually warming (CC) climate and forest management strategies corresponding to different rates of utilisation of the cutting potential, namely maximum sustainable removal (Sust) or maximum net present value (NPV) of wood production (Max). In this analysis of Finland, the initial amount of carbon in the growing stock was 765 Mt (2,802 Tg CO₂). At the end of the simulation, the carbon in the growing stock of trees in Finland had increased to 894 Mt (3,275 Tg CO₂) under CUSust, 906 Mt (3,321 Tg CO₂) under CUMax, 1,060 Mt (3,885 Tg CO₂) under CCSust and 1,026 Mt (3,758 Tg CO₂) under CCMax. The results show that future development of carbon in the growing stock is not only dependent on climate change scenarios but also on forest management. For example, maximising the NPV of wood production without sustainability constraints results, over the short term, in a large amount of wood obtained in regeneration cuttings and a consequent decrease in the amount of carbon in growing stock. Over the longer term, this decrease in the carbon of growing stock in regenerated forests is compensated by the subsequent increase in fast-growing young forests. By comparison, no drastic short-term decrease in carbon stock was found in the Sust scenarios; only minor decreases were observed.     

Contribution To Climate Change Of Forest Fires In Spain: Emissions And Loss Of Sequestration

ABSTRACT

Forest fires contribute to climate change mainly due to emission of greenhouse gases by biomass burning and loss of sequestration by sink destruction. The average contribution in Spain between 1998 and 2015 was 9,494,910 Mg CO_{2 eq} per year, 23.8% from biomass burning and 76.2% from loss of carbon sequestration, the latter three times higher than the former, although the emissions from combustion are usually the only accounted. Regarding to the vegetation burned, 43.6% of emissions come from forest (17.7% conifers, 4.8% hardwoods and 21.1% Eucalyptus), 53.7% from scrublands and 2.7% from grasslands. The loss of sequestration is 6.6% in the fire year and by 93.4% in previous years. Scrubland burning produces a greater amount of emissions than forests, but forest regeneration is slower, with greater influence on the loss of sequestration. It is essential a forest management focused on increase fire resilience and adaptation to climate change, increase the effectiveness of extinction works to reduce fire damages and implement actions to recover the burnt vegetation, because the loss of sinks is a critical aspect.     

Carbon dioxide sequestration capability of an unmanaged old-growth broadleaf deciduous forest in a Strict Nature Reserve

The seasonal trend of plant carbon dioxide (CO₂) sequestration is related to the photosynthetic activity, which in turn changes in response to environmental conditions. Great interest has turned to the CO₂ sequestration (CS) potential of temperate forests which play an important role in global carbon (C) cycle contributing to the lowering of atmospheric CO₂ concentration. In such context, the CS of an unmanaged old broad-leaf deciduous forest developing inside a Strict Nature Reserve, and its variations during the year were analyzed considering the monthly variations of leaf area index (LAI) and net photosynthetic rates (N_P). Overall, the total yearly CS of the forest was 141 Mg CO₂ ha^?1 year^?1 with the highest CS value monitored in June (405 Mg CO₂ month^?1) due to the highest LAI (5.0 ± 0.8 m² m^?2) and a high N_P in all the broadleaf species. The first CS decline was observed in August due to the more stressful climatic conditions that constrained N_P rates. Overall, the total CS of the forest reflects the good ecological health of the ecosystem due to its conservative management.     

大气CO2增长和气候变化对森林的影响研究进展

本文概述了过去１０多年中，国内外大气ＣＯ２增长对林木影响及气候变化对森林影响方面的研究结果。内容包括：在大气ＣＯ２倍增的情况下，净光合作用和生物产量、气孔的水气传导率及水分利用效率的变化；ＣＯ２与温度的共同影响及与养分供应的共同影响；暗呼吸，根茎比，光合适应现象。本文还介绍了气候变化对植被带、个别森林影响的宏观研究情况，以及古气候与古植被相互关系的研究。