Masafumi Ueda

Diurnal changes in branch diameter as indicator of water status of Hinoki cypress Chamaecyparis obtusa

Abstract. We investigated use of strain gauges for monitoring the water status of trees by measuring changes in the diameter of the largest spreading branch of a 27-year-old Chamaecyparis obtusa tree. The change in xylem diameter in the branch is more closely related than the change in phloem diameter to the change in leaf water potential. Since the diurnal changes in diameter match the diurnal changes in water balance (sap flow velocity – transpiration), measuring the change in xylem diameter using a strain gauge is useful in evaluating the water status of C. obtusa.

Water status of Hinoki cypress (Chamaecyparis obtusa) under reduced hydraulic conductance estimated from diurnal changes in trunk diameter

Abstract. To estimate the water status of Hinoki cypress (Chamaecyparis obtusa) under reduced hydraulic conductance, we measured diurnal changes in the trunk diameter of two 20-year-old trees during a hot dry summer. One tree showed a greatly reduced water-transport area in its trunk cross-section and leaf specific hydraulic conductivity. Diurnal changes in trunk diameter were measured at the xylem surface using a strain-gauge method. At the start of the experiment, the diurnal changes in trunk diameter were similar in both trees with shrinking during the day and swelling at night. However, in the trunk of the tree with reduced hydraulic conductance, the maxima and minima decreased rapidly as days passed. These differences in trunk diameter changes might be caused by the differences in the leaf-specific hydraulic conductance.

Host selection of small cedar longicorn beetle, Callidiellum rufipenne (Coleoptera:Cerambycidae), on Japanese cedar, Cryptomeria japonica, in terms of bark water content of host trees

We caught the adults of a secondary wood-boring insect, Callidiellum rufipenne (Motschulsky), on Japanese cedar, Cryptomeria japonica D. Don., trees and logs with manipulated bark water contents to clarify the mechanism of host selection by C. rufipenne. More C. rufipenne were trapped when the bark water content range was ca. 120–200%. Fewer C. rufipenne were trapped at higher and lower bark water contents. These findings indicate that C. rufipenne adults do not simply select weakened or dying trees. Bark water content is one of important factors for C. rufipenne choosing their host for oviposition.

Water status of hinoki cypress, Chamaecyparis obtusa, attacked by secondary woodboring insects after typhoon strike

We estimated the water status of six 31-year-old hinoki cypress (Chamaecyparis obtusa) trees that were struck by a large typhoon. Measurements were made of the trunk water-conduction area of xylem, leaf water potentials, and diurnal changes in trunk diameters. The secondary woodboring insects, Callidiellum rufipenne and Ovalisia vivata, on the trees were captured by the sticky-trap banding method. In trees on which these wood borers were captured, water conduction areas were reduced, leaf water potentials were lower, and trunk diameter changes (Rε) fluctuated during the day, suggesting that the trees had been damaged by the typhoon and were under water stress. The secondary woodboring insects attacked the water-stressed trees.

Live crown tops of Japanese cedar (Cryptomeria japonica) approach one another in height at urban forest sites

Since the 1980s, we have found Japanese cedar, Cryptomeria japonica (L. f.) D. Don, trees with crown tops affected by dieback in isolated urban forests on the low altitude plain. To clarify future growth of C. japonica in these forests, we investigated their growth, decline levels and water status. The live crown-top heights from the ground (LCTHs) per diameter at breast height (dbh) were lower in forests with C. japonica top dieback than in forests with no top dieback. Furthermore, in a forest with C. japonica top dieback, the LCTHs were similar between trees although dbh and decline levels were different. Moreover, water status near the top of the live foliage was very similar although decline levels were different, suggesting that in urban forests, where C. japonica top dieback is observed, the LCTH is subject of restriction. A sudden increase in temperatures since the 1980s may be restricting the LCTHs of C. japonica in urban forests. We conclude that LCTHs of C. japonica in urban forests are becoming lower and more equal in each forest. If temperature continues to increase, height restriction will become more severe and LCTHs of C. japonica in urban forests will become even lower.