Kenji Omasa

Voxel-Based 3-D Modeling of Individual Trees for Estimating Leaf Area Density Using High-Resolution Portable Scanning Lidar

A method for accurate estimation of leaf area density (LAD) and the cumulative leaf area index (LAI) profiles of small trees (Camellia sasanqua and Deutzia crenata) under different conditions was demonstrated, which used precise voxel-based tree models produced by high-resolution portable scanning lidar. In this voxel-based canopy profiling (VCP) method, data for each horizontal layer of the canopy of each tree were collected from symmetrical azimuthal measurement points around the tree using optimally inclined laser beams. The data were then converted into a voxel-based three-dimensional model that reproduced the tree precisely, including within the canopy. This precise voxel model allowed the LAD and LAI of these trees, which have extremely dense and nonrandomly distributed foliage, to be computed by direct counting of the beam-contact frequency in each layer using a point-quadrat method. Corrections for leaf inclination and nonphotosynthetic tissues reduced the estimation error. A beam incident zenith angle near 57.5deg offered a good correction for leaf inclination without knowledge of the actual leaf inclination. Non-photosynthetic tissues were removed by image-processing techniques. The best LAD estimations showed errors of 17% at the minimum horizontal layer thickness and of 0.7% at the maximum thickness. The error of the best LAI estimations was also 0.7%

The Difference in Sterility due to High Temperatures during the Flowering Period among Japonica-Rice Varieties

Summary The objectives of this study are to compare the floret sterility induced by a high temperature given in the daytime during the flowering period among nine japonica rice varieties, and to clarify the mechanism of the high-temperature-induced sterility. Nine japonica rice varieties were subjected to 35.0, 37.5 or 40.0°C day- temperature conditions (1000-1600) for six consecutive days using sun-lit phytotrons, and the percentage of fertility, pollination and germinated pollen grains on the stigmas were examined. The temperature that caused 50% sterility varied with the variety, and a difference of approximately 3.0°C was observed between the most tolerant and susceptible varieties. Under the 37.5°C day-temperature condition, the percentage of florets with 10 or more germinated pollen grains was roughly coincident with the percent fertility, but under the 40° C day-temperature condition, it was higher than the percent fertility. Many of the florets with less than 10 germinated pollen grains had less than 20 total pollen grains on their stigmas under both temperature conditions. From these results, we concluded that sure pollination under high-temperature conditions is an important factor and that the high-temperature tolerance of the processes following pollen germination is also required for fertility under excessively high temperature conditions.

High Temperature at Flowering Inhibits Swelling of Pollen Grains, a Driving Force for Thecae Dehiscence in Rice(Oryza sativa L.)

Summary To clarify the mechanism of high temperature-induced floret sterility in rice (Oryza sativa L.), we studied the effects of high temperature at flowering on the ability of thecae to dehisce and on pollen-grain swelling which causes thecae dehiscence. Two japonica rice cultivars, grown in four L pots under submerged soil conditions were subjected to high (39°C) and moderate (34°C) temperatures from 10 : 00 to 16 : 00 for three consecutive days at the flowering stage. The percentage of the thecae dehisced in response to artificial opening of the florets by removing lemma and the mean diameter of the pollen grains measured during four minutes after the artificial opening were examined to determine the ability of the thecae to dehisce and that of the pollen grains to swell, respectively. The high temperature given on the day of flowering decreased both the percentage of the dehisced thecae and the diameter of the pollen grains but did not affect the relationship between them. The thecae of the plants which had been subjected to the high temperature for one or two days before flowering, however, showed a lower dehiscence percentage than those of the plant treated on the day of flowering against the same pollen-grain diameter. We concluded that high temperature given on the day of flowering decreased the ability of the pollen grains to swell resulting in poor thecae dehiscence, and that, besides this decrease, high temperature given just before the days of flowering lowered the function of thecae themselves to dehisce, causing poorer thecae dehiscence.

Plant Responses to Air Pollution and Global Change

Preface by Kenji Omasa, Isamu Nouchi and Luit J. De Kok Contributors Plant Responses to Air Pollution: Metabolism of atmospheric sulfur gases in onion.- Impact of atmospheric NH3 deposition on plant growth and functioning - a case study with Brassica oleracea L..- How sensitive are forest trees to ozone? - New research on an old issue.- Northern conditions enhance the susceptibility of birch (Betula pendula Roth) to oxidative stress caused by ozone.- Physiological responses of trees to air pollutants at high elevation sites.- Complex assessment of forest condition under air pollution impacts.- Evaluation of the ozone-related risk for Austrian forests.- Causes of differences in response of plant species to nitrogen supply and the ecological consequences.- Plant Responses to Climate Change: Long-term effects of elevated CO2 on sour orange trees.- Plant responses to climate change: impacts and adaptation.- Effects of elevated carbon dioxide concentration on wood structure and formation in trees.- Plant Responses to Combination of Air Pollution and Climate Change: Carbon dioxide and ozone affect needle nitrogen and abscission in Pinus ponderosa.- Effects of air pollution and climate change on forests of the Tatra Mountains, Central Europe.- Genetics and Molecular Biology for Functioning Improvement: MAPK signalling and plant cell survival in response to oxidative environmental stress.- Expression of cyanobacterial ictB in higher plants enhanced photosynthesis and growth.- Improvement of photosynthesis in higher plants.- Modification of CO2 fixation of photosynthetic prokaryote.- Specificity of diatom Rubisco.- Regulation of CO2 fixation in non-sulfur purple photosynthetic bacteria.- Experimental Ecosystem and Climate Change Research: Experimental ecosystem and climate change research in controlled environments:lessons from the Biosphere 2 Laboratory 1996-2003.- Importance of air movementfor promoting gas and heat exchanges between plants and atmosphere under controlled environments.- Pros and cons of CO2 springs as experimental sites.- Global Carbon Cycles in Ecosystem and Assessment of Climate Change Impacts: Carbon dynamics in response to climate and disturbance: Recent progress from multi-scale measurements and modeling in AmeriFlux.- Synthetic analysis of the CO2 fluxes at various forests in East Asia 3-D remote sensing of woody canopy height and carbon stocks by helicopter-borne scanning lidar.- Assessments of climate change impacts on the terrestrial ecosystem in Japan using the Bio-Geographical and GeoChemical (BGGC) Model.- Air Pollution and Global Change in Asia: Establishing critical levels of air pollutants for protecting East Asian vegetation - A challenge.- Major activities of acid deposition monitoring network in East Asia (EANET) and related studies.- Land degradation and blown-sand disaster in China.- Impact of meteorological fields and surface conditions on Asian dust.- A case study on combating desertification at a small watershed in the hills-gully area of loess plateau, China.- A recipe for sustainable agriculture in drylands.- Index

Climate Change and Plants in East Asia

This investigation is made of the possible climatic change scenarios due to a doubling of carbon dioxide concentration in the atmosphere. The three global climate or general circulation models(GCM) have been used to produce the climatic change scenarios for Monsoon Asia. Using these scenarios, the information was obtained on the possible distribution of annual air temperature, annual precipitation, annual global solar radiation, annual net radiation, and annual average of radiative dryness index on the Monsoon Asia. Regional averages of relative changes in climatic elements under 2xC02 induced warm climates were calculated for the four sub-areas corresponding to the ice and desert climate area(I), cool and/or warm temperate climate area (II), subtropical and/or tropical climate area(III), and humid tropical area (IV). The relative changes in annual temperature were fairly large on the sub-area I than on the other sub-areas. The grid mesh maps showing the regional distribution of climatic elements under 2xC02 conditions can be used approximately as climatic change scenarios for Monsoon Asia.

Effects of Elevated CO2 and Global Climate Change on Rice Yield in Japan

Long-term CO2 x temperature experiments on rice using Temperature Gradient Chambers (TGCs) revealed that nearly doubled CO2 concentration in the atmosphere increases crop dry matter production by 24% through the enhancement of radiation conversion efficiency to biomass, but not through the promotion of radiation interception rate. Although temperature gave a negligibly small influence on the CO2 effect on biomass production, it significantly affected the grain yield through spikelet fertility. High temperatures were most damaging rice spikelets at the moment of their flowering and made them sterile. The temperature (Tmh) at which 50% spikelets are sterile was 38.2°C for a high temperature-tolerant genotype ‘Koshihikari’, and 36.6°C for a sensitive genotype ‘Akihikari’. Those findings from TGC experiments were parametrized and incorporated into rice growth simulation model SIMRIW.

3-D modeling of tomato canopies using a high-resolution portable scanning lidar for extracting structural information.

In the present study, an attempt was made to produce a precise 3D image of a tomato canopy using a portable high-resolution scanning lidar. The tomato canopy was scanned by the lidar from three positions surrounding it. Through the scanning, the point cloud data of the canopy were obtained and they were co-registered. Then, points corresponding to leaves were extracted and converted into polygon images. From the polygon images, leaf areas were accurately estimated with a mean absolute percent error of 4.6%. Vertical profile of leaf area density (LAD) and leaf area index (LAI) could be also estimated by summing up each leaf area derived from the polygon images. Leaf inclination angle could be also estimated from the 3-D polygon image. It was shown that leaf inclination angles had different values at each part of a leaf.

Estimation and Error Analysis of Woody Canopy Leaf Area Density Profiles Using 3-D Airborne and Ground-Based Scanning Lidar Remote-Sensing Techniques

Vertical profiles of the leaf area density (LAD) of a Japanese zelkova canopy were estimated by combining airborne and portable ground-based light detection and ranging (lidar) data and using a voxel-based canopy profiling method. The profiles obtained by the two types of lidars complemented each other, eliminating blind regions and yielding more accurate LAD profiles than could be obtained by using each type of lidar alone. In the combined results, the mean absolute errors (MAEs) of LAD ranged from 0.20 to 0.42 m2 m-3, and the mean absolute percentage errors (MAPEs) of the leaf area index (LAI) ranged from 22.3% to 27.2%, for ground areas from 4 to 32 m2, respectively. A laser beam coverage index ¿ incorporating the lidars beam settings and a beam attenuation factor was proposed. This index showed general applicability to explain the LAD estimation error for LAD measurements using different types of lidars and with different beam settings. Parts of the LAD profiles that were underestimated even when data from both lidars were combined were interpolated by using a Gaussian function. The interpolation yielded improved results for ground areas of 16 and 32 m2; the respective MAEs of LAD were 0.17 and 0.11 m2 m-3, and the respective MAPEs of LAI were 8.0% and 9.4%. The proposed method improves lidar-derived LAD estimation and is adapted to broadleaved canopies. The index ¿ was tested against an actual canopy scenario and could be used to determine appropriate lidar measurement settings when data from different sources of lidar data are combined to estimate LAD profiles.

Alleviatory effects of calcium on the toxicity of sodium, potassium and magnesium chlorides to seed germination in three non-halophytes

Saline soils contain numerous salts with varying impact on seed germination. Seeds of three non-halophytic species found in Chinese sandy deserts (Artemisia ordosica, Aristida adscensionis and Bassia dasyphylla) were incubated in salt solutions (NaCl, KCl or MgCl 2 , each with or without CaCl 2 ) at 20°C in the dark. The effects of each salt on the percentage of seeds from which visibly detectable radicles emerged, and the percentage of seeds with emerging radicles surviving to a length of at least 4 mm, were examined. NaCl, KCl and MgCl 2 were toxic to emerging radicles in all three species, but before radicle emergence these salts reduced seed germinability only in A. ordosica. The toxic effects of each salt on the radicles were alleviated in all three species by the addition of low concentrations of CaCl 2 . MgCl 2 was more toxic than NaCl and KCl, and the concentration of CaCl 2 needed to alleviate the toxicity of MgCl 2 was several times higher than that required for alleviation of NaCl or KCl toxicity. These results suggest that Ca 2+ present in saline soils alleviates the toxic effects of other salt components on seed germination, and that the results of germination experiments with a single salt are not always applicable to field conditions.

Effects of sodium, magnesium and calcium salts on seed germination and radicle survival of a halophyte, Kalidium caspicum (Chenopodiaceae)

Kalidium caspicum (L.) Ung.-Sternb. is a common species of highly saline habitats of north-western China, which in previous germination research has been shown to be rather sensitive to NaCl toxicity. To investigate the effects of different salts on the seed germination and radicle survival of this halophytic shrub, seeds were incubated in various salt (NaCl, Na2SO4, MgCl2, or MgSO4 with or without CaCl2) or polyethylene glycol-6000 solutions. The germination percentage and the percentage of emerging radicles surviving to a length of at least 4 mm were examined. The survival of K. caspicum radicles depended mainly on the cation composition of the media: both Na + and Mg 2+ had toxic effects on the radicles, while Ca 2+ alleviated the toxicity of these cations. Mg 2+ was more toxic than Na + and a higher concentration of Ca 2+ was needed to alleviate its toxicity. It was suggested that the establishment of seedlings of K. caspicum in the field is facilitated by the marked alleviation of salt toxicity by Ca 2+ and that the proportion of soluble Na, Mg and Ca ions in the soil determines the distribution of K. caspicum in the field.