Deciduous Broadleaf Tree Species Research Articles

Effects of ozone exposure on growth and photosynthesis of the seedlings of Liriodendron chinense (Hemsl.) Sarg, a native tree species of subtropical China

Little is known about the response of trees to elevated ozone (O3) in the subtropical region of China, where ambient O3 concentrations are high enough to damage plants. In this study, pigment content, gas exchange and chlorophyll (Chl) a fluorescence in leaves of Liriodendron chinense (Hemsl.) Sarg seedlings, a deciduous broadleaf tree species native in subtropical regions, were investigated at 15, 40, and 58 days after O3 fumigation (DAF) at a concentration of 150 mm3 m-3 (E-O3). At the end of experiment, seedlings were harvested for biomass measurement. E-O3 caused visible injuries on the mature leaves e.g. necrotic patches and accelerated early defoliation. Relative to the charcoal-filtered air (CF) treatment, E-O3 significantly decreased shoot and root biomass, pigment content, light-saturated net photosynthesis (P Nsat), stomatal conductance (g s), maximum rate of carboxylation (Vcmax), photochemical quenching coefficient (qp) and effective quantum yield of PSII photochemistry (ΦPSII), and also caused a slight reduction in relative increase of basal diameter. Therefore, L. chinense can be assumed to be an O3-sensitive tree species, which will be threatened by increasing ambient O3 concentrations in China.

Variation in foliar δ 15N among oriental oak ( Quercus variabilis) stands over eastern China: Patterns and interactions

The patterns of variation in natural abundance of foliar and soil ( 15N) (expressed as δ 15N) related to geographical and climatic variables frequently vary over plant species or plant function groups. It is essential to identify the pattern of foliar δ 15N for specific plant species which has a widespread distribution and to explore the underlying mechanisms in the context of environmental change such as global warming and anthropogenic nitrogen deposition. Oriental oak ( Quercus variabilis Bl.), characterized by cork bark, is a widely distributing deciduous broadleaf tree species that can be found in temperate and subtropical areas of East Asia. In this study, the variations in foliar and soil 15N were investigated based on the data of leaf and soil samples collected in 22 stands over eastern China (from 24 to 41° N in latitude and 102 to 123° E in longitude), and the mechanisms were discussed. The results showed that for oriental oak stands, mean foliar and soil δ 15N were − 4.8‰ and 2.0‰, respectively, indicating an evident 15N enrichment in the soils. The average foliar δ 15N value of oriental oak in warm temperate forest was significantly lower ( p < 0.01), while a higher enrichment factor was also observed in temperate forests, than that in the subtropical areas. Over the eastern China, the foliar δ 15N increased linearly and significantly with increasing mean annual precipitation (MAP) (R 2 = 0.481 and p < 0.001) and mean annual temperature (MAT) (R 2 = 0.285 and p = 0.01) and decreasing pH value of rain water (R 2 = 0.333 and p = 0.005). With these results in eastern China, there are great implications in understanding how nitrogen dynamics of ecosystems responds to warming, drought and acid rain.

シラカンバ、ハリギリ、ミズナラ樹冠葉の光合成特性における光環境への順化

シラカンバ、ハリギリ、ミズナラ樹冠葉の光合成特性における光環境への順化

Susceptibility to photoinhibition of three deciduous broadleaf tree species with different successional traits raised under various light regimes

ABSTRACTThe susceptibility to photoinhibition of tree species from three different successional stages were examined using chlorophyll fluorescence and gas exchange techniques. The three deciduous broadleaf tree species were Betula platyphylla var. japonica, pioneer and early successional, Quercus mongolica, intermediate shade‐tolerant and mid‐successional, and Acer mono, shade‐tolerant and late successional. Tree seedlings were raised under three light regimes: full sunlight (open), 10% full sun, and 5% full sun. Susceptibility to photoinhibition was assessed on the basis of the recovery kinetics of the ratio of vaviable to maximum fluorescence (Fv/Fm) of detached leaf discs exposed to about 2000 μmol m−1 s−1 photon flux density (PFD) for 2 h under controlled conditions (25 to 28 °C, fully hydrated). Differences in susceptibility to photodamage among species were not significant in the open and 10% full sun treatments. But in 5% full sun, B. platyphylla sustained a significantly greater photodamage than other species, probably associated with having the lowest photosynthetic capacity indicated by light‐saturated photosynthetic rate (B. platyphylla, 9·87, 5·85 and 2·82; Q. mongolica, 8·05, 6·28 and 4·41; A. mono, 7·93, 6·11 and 5·08 μmol CO2 m−1 s−1for open, 10% and 5% full sun, respectively). To simulate a gap formation and assess its complex effects including high temperature and water stress in addition to strong light on the susceptibility to photoinhibition, we examined photoinhibition in the field by means of monitoring ΔF/F′m on the first day of transfer to natural daylight. Compared with ΔF/F′m in AM, the lower ΔF/F′m in PM responding to lower PFD following high PFD around noon indicated that photoinhibition occurred in plants grown in 10 and 5% full sun. The diurnal changes of ΔF/F′m showed that Q. mongolica grown in 5% full sun was less susceptible to photoinhibition than A. mono although they showed little differences both in photosynthetic capacity in intact leaves and susceptibility to photoinhibition based on leaf disc measurements. These results suggest that shade‐grown Q. mongolica had a higher tolerance for additional stresses such as high temperature and water stress in the field, possibly due to their lower plasticity in leaf anatomy to low light environment.

A power function for forest structure and regeneration pattern of pioneer and climax species in patch mosaic forests.

The DBH-class distribution in natural deciduous broad-leaved forests was elucidated with a power function. A power function (y=ax b, y: stem density, x: represents DBH class, a and b: constants) fits the distribution better than an exponential function (y = a exp bx). The parameter b in the power function is approximately −2. This means that the natural forests studied have a patch-mosaic structure and that tree cohorts regenerate from gaps. Parameter a implies the number of juveniles, and b means size-dependent mortality. The value of −2 for parameter b means that when trees in a given DBH class double their DBH, the density of the size class should decrease by one-fourth. This phenomenon results from self-thinning and is caused by horizontal space competition among trees, called the `tile model'. The parameter describing DBH-class distribution for a forest with self-thinning patches should be approximately −2. I call this the `−2 power law' for DBH-class distribution. In a typical natural forest dominated by deciduous broadleaf tree species, trees are recognized as pioneer or climax species by the parameters describing their regeneration patterns. When I applied the power functional model to the DBH-class distribution of each dominant species, in pioneer species parameter a was high and b was less than −2 (markedly less than zero), suggesting that there are many juveniles, but mortality is high. On the other hand, in climax species parameter a was low value and the value of b was larger (negative, but closer to zero), suggesting that there are not many juveniles, but mortality is low. A power-function analysis of DBH-class distribution can be used to clarify the patch mosaic structure of a forest, and to clarify the regeneration pattern of pioneer and climax species by applying the function for each species.

The Development of a New Dendrometer and Its Application to Deciduous Broadleaf Tree Species in Hokkaido, Northern Japan

A new sensitive dendrometer system was invented by using a potentiometer and datalogger and applied to the stem of some canopy trees of a stand of deciduous broad-leaf tree species native to Hokkaido, northern Japan. Different types of diameter/age growth curves were observed at the fine level for different species: (1) an ordinary type with smooth and gradual growth; and (2) a slow growth curve mixed with intermittent stair-like periods of rapid growth. Possible reasons for the presence of stair-like rapid growth were examined, including the significance of water availability condition.