“Hiwada“ is a major roofing material of wooden cultural buildings in Japan, and can be harvested from outer bark of large-diameter trees of hinoki (Chamaecyparis obtusa) at roughly 10-year intervals. Hinoki is well known for having no normal resin canals in either xylem or phloem, but tangential bands of traumatic resin canals in the bark
can be easily detected on the cross section of “hiwada” material. To clarify whether “hiwada” harvest is a stimulus to form traumatic resin canals in the phloem of hinoki, the distribution and the formation of resin canals were investigated on the occasion of the second “hiwada” harvest experiment at Kibune site in Kyoto in October 2011. The first “hiwada” harvest in 2002 did not affect xylem and phloem production in subsequent years. Tangential bands of traumatic resin canals were scattered widely in the secondary phloem of most sample trees regardless of the debarking treatment, and their occurrence was not synchronous within the trees studied. After the second harvest in 2011 microscopic investigation confirmed that the debarking treatment did not induce traumatic resin canal formation. The pathogenous stem canker fungus Cistella japonica was isolated from outer barks of some sample trees, but its presence was not related to the incidence of resin canals. The injuries due to the samplings in October and December induced the formation of traumatic resin canals, consistent with previous studies, generally in the following year in the latest 2 growth rings of the phloem. In conclusion, “hiwada” harvest dose not induce the formation of traumatic resin canals in the hinoki phloem. Although the cause is unfortunately entirely unknown, traumatic resin canal bands are common in the hinoki bark.
We applied combustion ash from a woody biomass power generator to a young hinoki cypress plantation (Chamaecyparis obtusa, 1 kg of ash per tree per year) in the southwestern part of Shikoku Island, Japan, and we monitored the annual diameter and height growth for two years. Linear mixed-effects models indicated that the ash application decreased annual increment of stem diameter and tree height, and the two-year serial ash application lowered the annual tree growth more than the single-year ash application. The results of the laboratory leaching test suggested that a high concentration of K+, SO42‒, and Cl‒ was leached from the combustion ash during the first rainfall, and the highly concentrated eluate might effect on the growth of the young hinoki cypress. The ash application to conifer plantations should be considered to determine the ash amount that influences tree growth and the use of the scattering technique.
To evaluate the impact of typhoon disturbances to productivity in old secondary Castanopsis cuspidate stands that reduce resprouting ability, we monitored fluctuations in aboveground net primary production (ANPP) in a Castanopsis cuspidata coppice stand (57 years old in 2008) in Kumamoto, Japan, on an annual scale for 18 years (1990–2008). The average ANPP was 11.96 (range 8.82–15.5) Mg/ha/yr. This value is slightly lower than that of young Castanopsis stands in the same area (13.33 Mg/ha/yr for 10–16-year-old stands). Defoliation and stem breakage caused by several typhoons resulted in large annual fluctuations in ANPP. Old coppice stands over 50 years old are more susceptible to disturbance by typhoons and may show larger fluctuations and declines in ANPP with increasing stand age. Our results imply that typhoon disturbances play a more important role in the ANPP dynamics of old Castanopsis coppice stands than in young coppice stands.
Precipitation and stream water chemistry were monitored between 2001 and 2014 in the Katsura Fudo-yatsu experimental watershed in Ibaraki prefecture, Japan. In the monitoring period, the annual fluxes of non sea-salt SO42- and inorganic N ions by precipitation tended to decrease. Annual mean concentration of stream water SO42- was almost constant in the period 2001-2011, increased after forest thinning operations conducted in 2012 and 2013. Annual mean concentration of stream water NO3- t ended to decrease before the thinning operations, and turned to increase after the operations. Similar increasing pattern after the thinning operations was observed in the concentrations of Ca2+ and K+. Stream water Si concentration exhibited very small fluctuation and tended to increase gently.