Growth of Japanese and hybrid larch seedlings grown under free-air O₃ fumigation—an initial assessment of the effects of adequate and excessive nitrogen

Abstract

Ground-surface ozone (O 3 ) and nitrogen (N) deposition in forests are increasing rapidly in East Asia. The Japanese larch (JL) has been transplanted from central Japan to northern areas. Because the JL suffers from shoot blight disease and grazing by voles, the hybrid larch (F 1 ) was developed to overcome these weak points. For sustainable use of these larches, we should know the growth responses of larches to elevated O 3 (eO 3 ) and excessive N deposition in northern Japan. Two-year-old JL and F 1 seedlings were potted in well-weathered immature volcanic ash soil with basal dressing of balanced fertilizer containing 47 kgN ha -1 yr -1 , due to a lack of nutrients in the soil. To simulate eO 3 , seedlings were grown in a free-air O 3 fumigation system (60 nmol mol -1 in daytime). Also, to simulate acid rain, NH 4 NO 3 (50 kgN ha -1 yr -1 in total) was applied to the plants. Independent of the N loading, the dry mass of needle litter in both JL and F 1 was less at eO 3 than at ambient O 3 . Re-translocation of N before the needle shedding of both larches was lower under eO 3 . As a result, the aboveground biomass per needle (i.e. productive efficiency) was higher at eO 3.

Effects of nitrogen loading under low and high phosphorus conditions on above- and below-ground growth of hybrid larch F1 seedlings

“…However, high litter N concentration was observed at only N100P0 in both 2015 and 2016. Previous reports indicated that excessive N loading leads to high litter N concentration (Aber et al 1989, Uddling et al 2006, Watanabe et al 2011, Dong-Gyu et al 2015. The characteristic of N100P0 is that it is P limited and has a high needle N: P ratio.…”

Seasonal and Yearly Variation in Photosynthetic Capacity of Short- and Long-shoot Needles of the Canopy of Japanese Larch Trees as a Basis for Determining for O3 Sensitivity

“…Ozone (O3) sensitivity of larch seedlings is strongly related to the nitrogen condition of the soil (e.g. [21,24]) as well as the stomatal conductance (Gs) [6]. O3 sensitivity appears to increase with the foliar N content in many plant species, since both Psat and Gs increase (e. g. [4,6]).…”

“…Sensitivity to O3 in larch depends strongly on N conditions [20,21] as well as Gs (i.e. gas diffusion in both water and CO2, e.g.…”

Retranslocation of foliar nutrients of deciduous tree seedlings in different soil condition under free-air O3 enrichment

“…Details of the O3 exposure in field station as well as the plot design can be found in Watanabe et al (2013). O3 concentration of 80 ± 7 nmol mol -1 was applied during daylight hours (about 7 h per day) from early-August to mid-November in treatment plots, while at the same time, the control plots were subjected to ambient daytime O3 concentration of 26.5 nmol mol -1 (Kam et al 2015) Each of the free-air enrichment plot was unevenly divided into 3 parts, replaced with 3 different soil types: about 84% of the plot area was divided into 2 parts, each equally consisting of brown forest soil (B) and volcanic ash soil (V); about 16% of the area was serpentine soil (S). All of these soil types are widely distributed across northern Japan (Kim et al 2011).…”

“…Furthermore, elevation of O3 is expected to continuously increase for at least several decades in the foreseeable future (Ohara et al 2007). In addition, eO3 can accelerate foliar senescence (Hoshika et al 2012) and reduce the retranslocation rate of nitrogen (N - Kam et al 2015), resulting in nutrient deficiencies in leaves caused by the decline of N acquisition (Karnosky et al 2007).…”