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About 47% of the earth’s land area is classified as dryland, wherein the farming system is characterized by an annual rainfall of approximately 300 – 500mm, with much of the rainfall in the spring and early summer. The low rainfall, which is not only insufficient but irregular, constitutes a major challenge to profitable farming in dry areas. Meeting this challenge in the years ahead will require a more sustainable product per unit area of land, conservation and rational use of natural resources, protection of the environment, improved management practices, cost-effective technologies, and favorable government policies and incentives for farmers to increase their productivity. In this review, we discuss the major ingredients essential for sustainable dryland agriculture which include: efficient use of water, seeding at rates corresponding to the soil water supply, management practices that minimize water loss and soil erosion, managing soil fertility and organic matter, selection of suitable crop species and management of pests. We conclude that an approach integrating scientific technologies with indigenous farming methods offers the best hope for sustainable agriculture in the drylands of the world. [ABSTRACT FROM AUTHOR]

Soil erosion and drought are twin problems in hills-gully area of the Loess Plateau, China, and they are main causes of desertification and poverty in the area. To combat desertification and improve rural economy in the area, a case study for reconstruction of the degenerated eco-environment in a small watershed has been conducted since 1997. The agriculture structure was changed by construction of terraces and conversion of cropping land to forest/grass land. The reconstruction results show that decreasing cropping land and rationally rearrangement of land use are key points to reduce soil and water loss in a watershed scale. The primary experiment results have shown that the reconstruction models based on the eco-environment condition are successful not only in restoration of vegetation but also in increasing farmer income. As a result, the severe soil erosion and the degradation of vegetation began to be controlled. [ABSTRACT FROM AUTHOR]

Dust aerosol in eastern Asia (yellow sand, kosa) is one of the most notable topics in atmospheric environment problems. The number of days of observational dust event was high in 2001 and 2002, and low in 2003 in downstream areas in eastern Asia, such as Japan. The aerosol is simulated by the combination of the meteorological model, RAMS, and the transport model, CMAQ, in this study. Simulated surface concentrations show good agreement with those observed by laser particle counters at some surface observation sites. We divided dust aerosol in the transport model into six different tracers according to their emission areas; Kazakhstan, Mongolia, three parts of Xinjiang, and Inner Mongolia. As for dust concentration at surface in Beijing, dust from Mongolia accounts for more than half, that from Inner Mongolia does one third, and dust from Xinjiang does the other approximately 15%. It is found that not only reduction of the amount of emission in Mongolia but also the change of transport from Mongolia toward downstream areas is main reason for less dust events in 2003. Large snow cover in 2003 cannot account for all the reduction of the emission in Mongolia compared to the other two years. [ABSTRACT FROM AUTHOR]

China is a country with severe land degradation and blown sand disasters. The arid and semi-arid regions, in which land desiccation, vegetation degeneration, wind erosion, sandification, Gobi-pebblization and salinization occur, take up one third of China’s total land area. Vegetation degradation is most serious in lower flood plains of the inland rivers and the semi-arid Agro-pastoral Ecotone due to excessive use of water resources, grassland reclamation, overgrazing and collection of firewood and herbal medicines. Wind erosion features are common around terminal dry lakes, in inland-river fluvial plains, and the semi-arid dry grasslands. Studies by the methods of aeolian sand transport, soil texture analysis, 137Cs tracing and archaeology confirmed that the rate of wind erosion is normally between 1000 to 2000 ton km−1 a−1. The gravel Gobi on Mongolian Plateau has been formed to a large degree by wind erosion. The severity of sandification has been manifested by the twelve sandy deserts and lands occupying 710, 000 km2, and the enlargement of sandy land at increasing spreading rates in the past three decades. Salinization has not received enough public attention yet, but soil salinization in Ningxia and Hetao Plains and dry lake basins is unfavorable for crop growth and natural vegetation. Salinization of surface water and ground water in the lower reaches of most inland rivers restricts utilization of insufficient water resources. The exacerbation of sand and dust storms disasters is the ultimate outcome of desertification in China. [ABSTRACT FROM AUTHOR]

In order to act against acid deposition problems in East Asian regions, the Acid Deposition Monitoring Network in East Asia (EANET) was established on the decision at the First Intergovernmental Meeting in 1998 among participating countries including China, Indonesia, Japan, Malaysia, Mongolia, Philippines, Republic of Korea, Russia, Thailand and Viet Nam. Based on the decision, the preparatory phase activities of EANET were started from 1998, and finished successfully in 2000. From January 2001, the regular phase activities were started. Major activities of EANET are, 1) to implement the national monitoring of acid deposition, 2) to develop and implement the QA/QC (quality assurance/quality control) programs, 3) to develop and implement training programs, etc. The acid deposition monitoring covers four environmental media; wet deposition, dry deposition, soil and vegetation, and inland aquatic environment. In addition to the mentioned activities, Network Center for EANET has joint research projects among participating countries of EANET. As one of them, joint project with Mongolia was performed to accumulate information on plant sensitivity to acid deposition in Ulaanbaatar, which will be reviewed briefly. [ABSTRACT FROM AUTHOR]

Critical levels of ozone (O3) and sulfur dioxide (SO2) for protecting European forests are not evaluated to apply to East Asian vegetation. Based on the results obtained from the long-term experimental studies on the effects of chronic exposure to O3 or SO2 on 30 young potted grown tree species using open-top chambers, we analyzed dose-response relationships between the whole-plant dry mass increment during the experiment and concentration of air pollutants to establish Asian critical levels. While the annual mean concentration of SO2 corresponding to a 10% reduction in the whole-plant dry mass increment for the most sensitive tree species was estimated to be 5–15 nl l−1 (ppb), it was over 30 ppb for the less sensitive tree species. The AOT40 of O3 corresponding to a 10% growth reduction for the sensitive tree species was estimated to be 8–15 ppm-h for a growing season (6 months) and over 31 ppm-h for the less sensitive species. Critical level of N load for a sensitive Japanese evergreen broad-leaved tree species was considered to be about 50 kg N ha−1 y−1. Furthermore, model estimation suggested that N load in a part of southern China have already exceeded this value. These critical values were estimated by the results obtained from limited experimental studies on the effects of air pollutants or N load on the growth of tree species native to relatively cool temperate zone. Therefore, information about sensitivity of plants grown in tropical to semiarid zones should be accumulated to cover East Asian vegetation. [ABSTRACT FROM AUTHOR]

This study assessed the future impacts of global climate change on the distribution and functioning of terrestrial ecosystems in Japan using the Bio-Geographical and GeoChemical model (BGGC model). The model enables us to simulate the carbon and nitrogen cycles within ecosystems on the basis of estimated potential natural vegetation distribution. In this study, changes in net primary productivity (NPP) and the distribution of potential natural vegetation were evaluated for assessments of climate change impacts. The GCMs experimental data used for future climate conditions were the CSIRO-Mk2 and ECHAM4/OPYC3 for each of A2 and B2 scenarios in the SRES. Comparison of the averages of simulated NPP under each scenario with the average NPP under current climate conditions showed that the average NPP could increase about 19 to 33 percent by the year 2050s and 25 to 53 percent by the year 2080s with changes in potential natural vegetation type. [ABSTRACT FROM AUTHOR]

A method for 3-D remote sensing of forest canopies using high-resolution, helicopter-borne scanning lidar is presented. The lidar device can scan almost all the ground surface with high resolution because a laser beam with a small footprint and a high scanning rate illuminates the ground surface from a slow-moving helicopter. The method permits the generation of 3-D images such as a Digital Elevation Model, Digital Terrain Model, and Digital Canopy Height Model (DCHM). The validity of the method was demonstrated in two applications. First, we estimated tree height from a DCHM of a forest on a steep slope, and found that errors were within 0.47 m for tree height (0.19 m RMSE). These results show that the estimation of tree height was greatly improved compared with estimates in previous studies. Second, we estimated carbon stocks in each tree and in the stand as a whole. From lidar-derived tree heights and allometric relationships between tree height and carbon stocks, we accurately estimated total carbon stocks of each tree in a coniferous Japanese cedar (Cryptomeria japonica) forest as well as carbon stocks at the stand scale. [ABSTRACT FROM AUTHOR]

The preliminary results of long-term CO2 flux measurements at forest sites in East Asia are explained and compared with each other. The features of seasonal variation of CO2 fluxes are different among deciduous-broadleaf, evergreen-coniferous, deciduous-coniferous and tropical forests in East Asia, and the causes of difference are discussed. The integrated yearly NEP (net ecosystem production) estimated from the CO2 flux by eddy covariance method in various forests of East Asia has a notable difference in the range of 2 to 8 tC ha−1 year−1. The main factors of this difference are the annual mean temperature and tree species. Furthermore, remaining issues are discussed, such as the quantitative estimation of the CO2 flux by the eddy covariance method and the synthetic analysis of the carbon budget under collaborations with biological survey. [ABSTRACT FROM AUTHOR]

The CO2 flux network, AmeriFlux, aims to quantify and understand the role of terrestrial ecosystems in the global carbon cycle. The network has grown to over 100 sites, with about 25 cluster sites in different disturbance classes or different vegetation types within a climate zone. This chapter summarizes the network objectives, recent findings of AmeriFlux research, and future directions necessary to meet global climate change research goals. The information gained from flux sites, multi-factor experiments on processes, and multi-observation networks can help to improve and parameterize models that are applied to quantify and understand carbon budgets across regions and continents. [ABSTRACT FROM AUTHOR]

The increase of atmospheric CO2 concentrations has stimulated research activity at natural CO2 springs, i.e. CO2-emitting vents mostly occurring at sites of former volcanic action. Besides a number of valuable benefits (long-term CO2 enrichment; CO2 gradients over space; natural conditions; free CO2; cheap experiments; possibility to introduce selected vegetation; source of plant material for controlled-condition experiments), emission from the vents may induce variability in atmospheric (composition, temperature, vertical CO2 gradients, short-term CO2 fluctuations) and soil conditions (pH, temperature, CO2 concentrations), and create an environment differing from the CO2-enrichment scenarios. Biological investigations at CO2 springs should previously record all relevant environmental factors and their co-variance. Here we review pros and cons of CO2 springs with the aim to help the selection of the best CO2 springs and control sites to investigate plant responses to CO2 enrichment in natural conditions. [ABSTRACT FROM AUTHOR]

The effects of the air velocity less than 1.3 m s−1 on net photosynthetic rates, transpiration rates and water use efficiencies of plant seedlings canopies and single leaves were assessed. Control of air movement is important to enhance gas exchange between plants and the ambient air, and would consequently be important to promote plant growth. The suppression of the transpiration rate was more considerable than that of the net photosynthetic rate at low air velocities, and the water use efficiency was higher at lower air velocities. Importance of air velocity for controlling the gas exchange of plantlets in micropropagation and plants in space farming under microgravity conditions was emphasized. Control of air movement was also important to make the environmental variables uniform inside the plant canopy. [ABSTRACT FROM AUTHOR]

It is clear from the project summaries below that the Biosphere 2 Laboratory (B2L) delivered handsomely as a controlled environment facility for experimental ecosystem and global climate change research. Ironically, the short and medium term experiments with model complex systems revealed that some of the most exciting and unexpected questions involved carbon cycling in benthic and soil metabolism, the very same processes that caused the first closed mission in the facility to fail, and eventually made the apparatus available for research. The effects of elevated [CO2] on these processes in the marine and agriforest mesocosms was to stimulate flux and to reduce Csequestration, by reduced carbonate deposition and enhanced metabolism of soil C reserves, respectively. The extent to which this and other themes that emerged from experiments were products of the initial conditions established in B2L model systems, or are general principles that prevail in natural ecosystems, remains to be seen. [ABSTRACT FROM AUTHOR]

Our laboratory studies the regulation of CO2 fixation in phototrophic micro-organisms. The expression of genes encoding enzymes responsible for assimilating CO2 is primarily regulated by a LysR-type transcriptional activator, CbbR, that functions by binding specific sites in the promoter region of both the cbbI and cbbII CO2 fixation operons under appropriate growth conditions. This straightforward model of regulation has a further level of complexity in the non-sulfur photosynthetic bacterium Rhodopseudomonas palustris. The recent genome sequencing project of this organism identified a unique two-component system interposed between the structural genes of the cbbI operon (encoding form I RubisCO) and CbbR. Two-component systems are a paradigm of gene regulation in Bacteria. In general, they consist of a sensor kinase and a response regulator, that upon stimulation, transduces an external stimulus in a His-Asp phospho-relay, ultimately modulating gene expression. The system identified in R. palustris, in addition to its peculiar modular architecture, also has multiple PAS motifs, suggesting a complex redox sensing activity coordinating a multi-step phospho-relay which regulates CO2 fixation under specific growth conditions. [ABSTRACT FROM AUTHOR]

Rubisco is an inefficient enzyme; this inefficiency is greatest when CO2 availability at the site of Rubisco is low. We hypothesise that the selection pressure for a more efficient Rubisco will be greatest in species growing under CO2 limited conditions, particularly when low light levels reduce the cost effectiveness of a carbon concentrating mechanism. We determined the specificity factor for four marine diatoms, Thalassiosira antarctica, Skeletonema costatum, Chaetoceros socialis, and Thalassiosira hyalina adapted to the arctic environment. [ABSTRACT FROM AUTHOR]

Resemblances and differences on photosynthesis of C3 plant and cyanobacterium Synechococcus PCC7942 were discussed with a simplified model of photosynthesis and photorespiration. Then the transformation of the cyanobacterium was shown with Chromatium vinosum (Cv) RuBisCO. Total RuBisCO activity and photosynthesis were compared with wild type S. 7942 and RuBisCO high expression mutant. Results were explained with RuBisCO environment of S. 7942 mutant. For excluding the influence of inorganic carbon concentrating mechanism (CCM) on the effect of RuBisCO, carboxysome less mutant was created with homologous recombination of ccm operon to be replaced with kanamycine resistant gene. And the deletion of the operon was confirmed by genomic PCR on the transformant. The confirmation was performed with three primers. Electron micrograms of S. 7942 show the existence of carboxysome in wild type and its absence in the mutant. Growth rate of CL mutant on different CO2 concentration shows that there is a possibility to increase a photosynthetic ability of a cyanobacterium with increases the RuBisCO activity. [ABSTRACT FROM AUTHOR]

We generated and analyzed transgenic tobacco plants with enhanced activities of fructose-l,6-bisphosphatase (FBPase) and/or sedoheptulose-l,7-bisphosphatase (SBPase) in the chloroplasts. The photosynthetic CO2 fixation and the final dry matter under atmospheric conditions (360 ppm CO2) in the transgenic plants were increased compared with those in the wild-type plants. Levels of the intermediate compounds in the Calvin cycle and the accumulation of carbohydrates were also higher than those in the wild-type plants. The transgenic tobacco also increased in the initial activity of Rubisco compared with that in the wild-type plants. These data suggest that both FBPase and SBPase involved in the regeneration of RuBP seem to be one of the limiting factors that participate in the regulation of the carbon flow through the Calvin cycle and the determination of the partitioning of carbon to end products. [ABSTRACT FROM AUTHOR]

Under many environmental conditions plant photosynthesis and growth are limited by the availability of CO2 at the site of ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO). We expressed ictB, a gene involved in HCO3− accumulation in Synechococcus sp. PCC7942, in higher plants. The transgenic Arabidopsis thaliana and Nicotiana tabacum plants exhibited significantly faster photosynthetic rates than the wild types under limiting, but not under saturating CO2 concentrations. Similar results were obtained in Arabidopsis plants bearing ictB from Anabaena sp. PCC7120. Growth of transgenic A. thaliana plants maintained under low humidity was considerably faster than that of the wild type. There was no difference in the amount of RubisCO or the activity of the enzyme activated in vitro in the wild types and the transgenic plants. In contrast, the in vivo RubisCO activity, without prior activation of the enzyme, in plants grown under low humidity was considerably higher in ictB-expressing plants than in their wild types. The CO2 compensation point in the transgenic plants was lower than in the wild types suggesting a higher CO2 concentration in close proximity to RubisCO. This may explain the higher activation level of RubisCO and enhanced photosynthesis and growth in the transgenic plants. These data indicated a potential use of ictB for the stimulation of crop yield. [ABSTRACT FROM AUTHOR]

Plant cells must constantly monitor and manage the levels of reactive oxygen species (ROS) accumulating within their cytosol and organelles. Extensive enzyme and metabolite-based antioxidant systems help regulate redox homeostasis, but how these systems are regulated in response to ROS challenge has remained obscure. One of the earliest responses to ROS perturbations in plants cells is the activation of specific mitogen-activated protein (MAP) kinases. Since MAPkinase cascades are involved in many aspects of eukaryotic signal transduction, these ROS-responsive kinases seem likely to form a key part of the antioxidant regulation network. Using ozone; a potent ROS generator and a phytotoxic air pollutant, we have demonstrated rapid and transient activation of MAPKs in various plant species. Genetic manipulation of the ROS-responsive MAPKs, SIPK/AtMPK6 in tobacco and Arabidopsis respectively, render the plants hypersensitive to ozone. Examination of MAPK activation profiles following ROS stress in SIPK/MPK6 transgenic plants reveals an interesting interplay between SIPK/MPK6 and another MAPK, WIPK/MPK3. Proteomic analysis of specifically suppressed transgenic lines has provided novel insights into the specific metabolic networks controlled by the ROS-responsive MAPK cascades during the cell’s response to oxidative challenges. We have also been able to extend the same findings to poplar through heterologous expression of SIPK, which provides evidence for the potential of exploiting MAPK pathways for crop improvement. [ABSTRACT FROM AUTHOR]

Synergistic effects of air pollution, extreme weather conditions and biotic agents related to global climate change have caused serious deterioration of forest condition in the Tatra National Park since early 1990s. Atmospheric deposition of sulfate (SO42−), nitrate (NO3−) and acidity (H+) are above the established critical load limits for forests. In addition, ambient ozone (O3) concentrations are also elevated mainly due to a long-range transport of polluted air masses. Ambient O3 concentrations have been monitored since 1992 with active UV monitors and passive samplers showing significant differences along the elevational gradient. High O3 values in spring indicate a potential for O3 stratospheric intrusion into troposphere. Ozone AOT40 index for protection of natural forest vegetation (10,000 ppbh) is commonly exceeded in the middle of vegetation period. Acidic impact may explain about 10–30% of a dieback observed in naturally oligotrophic Norway spruce (Picea abies) ecosystems probably due to acidification of soils leading to Al3+ mobilization limiting growth of fine roots. This may cause weakened resistance of trees to wind throws frequently observed in the foothills of the Tatra Mountains. Seventy year-long observations of meteorological conditions provide a unique opportunity for comparing current status of the Tatra forests within a context of long-term trends. Extremely high spring and summer temperatures, low precipitation and relative humidity observed during last decade are new factors disturbing ecological stability of natural and man-made forests. Warm and dry vegetation periods favor frequent bark beetle (Ips typographus) outbreaks affecting large areas of the Tatra forests. [ABSTRACT FROM AUTHOR]

To determine whether CO2 (a key contributor to climate change), and O3 (an important air pollutant), interact to affect needle N dynamics; we grew Pinus ponderosa Dougl. ex Laws. seedlings for three seasons (1998–2000) in outdoor chambers with ambient or elevated CO2 combined with low or elevated O3. Nitrogen concentration (area basis) was measured for attached and abscised needles. Nitrogen retranslocation was determined by comparing N for attached needles in July vs. October, and N resorption by comparing N for needles which abscised from July to October vs. attached needles in October. Ozone, and to a lesser extent CO2, reduced needle N depending on age class and sampling date, but there were no CO2 × O3 interactions. There was a significant CO2 × O3 interaction for N retranslocation for 1998 needles in 1999 (O3 reduced higher retranslocation with elevated CO2), but CO2 and O3 had only marginal effects on N retranslocation or resorption for other needles. Abscission of year-old needles increased with elevated CO2, but not O3. Long-term studies are needed to determine if the responses to elevated CO2 and O3 in our seedlings persist as trees mature and have multiple age-classes of needles. [ABSTRACT FROM AUTHOR]

The effects of elevated carbon dioxide concentration ([CO2]) on the structure of xylem cells in trees have not yet been clarified, in spite of the importance of woody plants as large, long-term carbon sinks. We review recent studies that have investigated how elevated [CO2] affects growth ring features. In general, elevated [CO2] enhances radial growth, especially when sufficient nutrients are supplied. The mean density of growth rings also increased but sometimes it decreased or remained unchanged, depending on the extent of cell division, cell expansion and cell wall thickening under elevated [CO2]. [ABSTRACT FROM AUTHOR]

Pre-industrial global atmospheric carbon dioxide (CO2) concentration (Ca), was ca. 280 µl l−1, is now 376 µl l−1, and may be 700 µl l−1 by 2100. Temperature is now ca. 0.6°C greater than pre-industrially, and may be ca. 4°C greater by 2100. Warming is decreasing frost, snow and ice cover. Rain may increase in some areas, particularly high latitudes, but decrease in others. Also cloud, and therefore solar radiation reaching vegetation, will change. Agriculture must adapt to such changes, which affect crop growth, yield, and pests and diseases. Stimulation of yields of cereals, sugar beet, potatoes, pastures and forests by ca. 20–30% is expected with Ca of 700 µl l−1. This results from increased photosynthesis. However, heat speeds respiration and crop development, shortening the growing season and thus limiting yield; a 4°C rise decreases dry matter by ca 20–30% in cereals and 20% in sugar beet. Quality of products (N-content, types of proteins in grain, and sugar beet storage tissue) are also affected. The biochemical and physiological mechanisms responsible for these effects are discussed, emphasising crop interaction with environment, including nutrition and water. Rates of environmental change are very rapid, however technology including plant breeding — but probably not current genetic engineering methods — may allow adjustment. Socio-economic pressures (consumer demand, world trade etc) may affect agriculture more than climate change per se. Advanced simulation modelling, linked closely to agronomic and plant research, is required to assess the consequences of putative changes on such complex systems. [ABSTRACT FROM AUTHOR]

The long-term responses of trees to elevated CO2 are especially crucial (1) to mitigating the rate of atmospheric CO2 increase, (2) to determining the character of future forested natural ecosystems and their spread across the landscape, and (3) to determining the productivity of future agricultural tree crops. Therefore, we initiated a long-term CO2-enrichment experiment on sour orange trees in 1987. Four sour orange trees (Citrus aurantium L.) have been grown from seedling stage at 300 µmol mol-1 CO2 above ambient in open-top, clear-plastic-wall chambers at Phoenix, Arizona. Four control trees have been similarly grown at ambient CO2. All trees have been given ample water and nutrients. The ratios of wood plus fruit annual biomass increments of the elevated-CO2 trees to those of the control trees reached a peak of about 3.0 two years into the experiment, declined from about year 2 to year 8, and has plateaued at about 1.75 for the past 9 years. The enhancement ratio for net photosynthesis was about 2.8 in year 2 but had declined to 1.3 by the 14th year, indicating some acclimation to the elevated CO2. Initial reductions in leaf N concentrations disappeared by year 7, while carbohydrate concentrations remained higher. Intrinsic water use efficiency determined from carbon isotope ratios was increased under elevated-CO2 by the same amount as biomass, which implies water use was unchanged. Storage proteins have been detected in the leaves of the enriched trees, which might be a mechanism that enables a six-fold increase in the rate of bud burst in the spring. [ABSTRACT FROM AUTHOR]