Ali M. Quoreshi

Effects of deicing salt on the vitality and health of two spruce species, Picea abies Karst., and Picea glehnii Masters planted along roadsides in northern Japan.

In northern Japan, the growth of Picea abies Karst., and Picea glehnii Masters, which have been planted along the highways, is often suppressed due to several environmental stresses. To examine the adverse effects of deicing salt, the primary source of stress,we measured needle life span, photosynthetic capacity, and water potential and transpiration rate of the two spruce species at a site with damaged trees, near the roadside and a site with healthy trees, located far from the highway. Results from the analysis showed large amounts of sodium and chlorine in the soil and snow at the damaged site. These elements had accumulated in the needles of the spruce. Moreover, physiological traits of the spruce, at the damaged site were also affected. Therefore, we concluded that poor physiological traits might be attributed to an accumulation of deicing salt in the needles, resulting in the suppression of tree growth.

Root growth characteristics, biomass and nutrient dynamics of seedlings of two larch species raised under different fertilization regimes

The effects of different fertilization regimes on root growth characteristics, nutrient uptake and biomass production of Japanese larch (Larix kampferi Sarg.) and its hybrid larch (L. gmelinii × L. kampferi) seedlings were examined for one growing season. Seedlings were raised in the greenhouse under three fertilizer levels (10, 20, 40 mg N seedling−1 season−1) and two delivery schedules, conventional (C) and exponential (E) for 12 weeks. Root growth, biomass allocation and nutrient loading capacity of seedlings were measured for a 3-week interval. By the end of growing season, seedlings fertilized with low dose conventionally (10C) and exponentially (10E) developed relatively longer root and larger root surface areas than those fertilized at high dose exponential loading (40E). At final harvest, the 40E treated Japanese larch had 134% and 155% more shoot mass as compared with those raised under 20E and 10E treated seedlings, respectively. The seedlings fertilized under 10C and 10E showed a high root mass ratio, while 40E treated seedlings showed a low root mass ratio. These data indicated that different nutrient levels (10 mg, 20 mg and 40 mg) strongly affected root growth characteristics. The same seasonal dose (10 mg) applied exponentially (10E) accumulated more N in seedlings compared to the 10C treatment. Exponential fertilization enhanced an increase in N concentration of the whole plant suggesting exponential delivery schedule is an efficient fertilization technique for greater nutrient uptake of plants. In contrast, N concentration of whole plant was declined for seedlings treated with conventional fertilization due to growth dilution. Late in the growing season, seedlings raised under 40E did not significantly improved dry mass production of root, but nutrient accumulation increased without a concomitant increased in root dry mass production. The result suggests that seedlings fertilized exponentially at medium and high dose rates (20E and 40E) induced luxury nutrient consumption within the plant.

Growth characteristics of root-shoot relations of three birch seedlings raised under different water regimes

Three birch species (Betula ermanii, B. maximowicziana, B. platyphylla var. japonica) widespread in northern Japan were raised under different water regimes (ca. 23, 35, and 60%) to study root-shoot increment and gas exchange traits in relation to their habitat preferences in natural conditions. Total biomass of all birches was larger for medium, wet and dry treatment. Maximum root length of B. platyphylla raised at dry or wet condition was higher than other species. Root growth rate of three birches peaked around mid July to early September while shoot growth rate was found maximum between late June and mid August. Root growth of three birches was suppressed under dry and wet treatment, especially for B. ermanii. Allocation percentage of biomass to roots of three birches ranged from 30 to 40% but it mainly allocated to elongate the root length under dry and wet condition. Fine roots of B. ermanii and B. maximowicziana under wet condition were distributed mainly on soil surface. In the dry treatment, B. platyphylla allocated photosynthates to elongate the root length and fine root production (< 2 mm) and had highest plasticity of roots to different water conditions among the three birches. Specific leaf area (SLA) of three birches decreased with decreasing soil moisture content. Plasticity in SLA of B. platyphylla was found largest. Net photosynthetic rate (Pn) and water use efficiency (WUE) of B. platyphylla showed highest among all the treatments. Leaf nitrogen content of B. platyphylla was also relatively higher under different water conditions as compared to the other two birch species, suggesting B. platyphylla may enable to invade to various growing conditions with different water regimes.

Effect of ectomycorrhizal infection on growth and photosynthetic characteristics of Pinus densiflora seedlings grown under elevated CO2 concentrations

The effect of ectomycorrhizal Pisolithus tinctorius (Pt) infection was studied on the growth and photosynthetic characteristics of Pinus densiflora seedlings grown at ambient (360 µmol mol−1, AC) and elevated (720 µmol mol−1, EC) CO2 concentrations. After 18 weeks, Pt inoculation had led to significantly increased dry mass and stem diameter of P. densiflora at both CO2 concentrations, relative to non-inoculated seedlings. Moreover, EC significantly increased the ectomycorrhizal development. The phosphate content in needles inoculated with Pt was about three times higher than without inoculation at both CO2 concentrations. The PAR saturated net photosynthetic rates (Psat) of P. densiflora inoculated with Pt were clearly higher than for control seedlings at both CO2 concentrations, and the maximum net photosynthetic rate (PN) at saturated CO2 concentration (Pmax) was higher than in controls. Moreover, the carboxylation efficiency (CE) and RuBP regeneration rate of the PN/Ci curve for P. densiflora inoculated with Pt were significantly higher than for non-inoculated seedlings at both CO2 concentrations, especially at EC. The water use efficiency (WUE) of seedlings inoculated with Pt grown at EC was significantly raised. Allocation of photosynthates to roots was greater in Pt inoculated pine seedlings, because of the enhanced activity of ectomycorrhiza associated with seedlings at EC. Moreover, PN of non-inoculated seedlings grown for 18 weeks at EC tended to be down regulated; in contrast, Pt inoculated seedlings showed no down-regulation at EC. The activity of ectomycorrhiza may therefore be enhanced physiological function related to water and phosphate absorption in P. densiflora seedlings at EC.