The effects of selective logging on stand structure and the regeneration of subboreal forests in Hokkaido, northern Japan

We investigated the effects of selective logging on stand structure and regeneration in selectively logged subboreal forests in Taisetsuzan National Park in Hokkaido in northern Japan. The basal area decreased and the size structure of trees altered in the stands studied due to repeated, intense selective logging, in which larger trees were cut down as a priority. Sapling density in the stands was much lower than that in primary forests. In the simple and multiple regression analyses that were used to estimate the effects of selective logging on sapling density, sapling density had a significant positive correlation with tree density and had little correlation with the density of logged stumps or the height ofSasa (dwarf bamboo) growing on the forest floor. These results suggest that the establishment sites around canopy trees influenced the establishment of saplings, rather than the gaps caused by selective logging. However, both the coefficient of determination and the standardized partial regression coefficient of multiple regression analysis were higher for the stand with a dense cover ofSasa than for the stand with a sparse cover ofSasa. Thus, the success of regenerating forests with selective logging depends on both the site of advanced regeneration and the light conditions that regulate growth.     

Distribution and physical properties of colluvium and saprolite in unchannelized valleys in Tsukuba Experimental Basin, Japan

To clarify the role of colluvium and saprolite in the hydrological processes of a forested mountain, the thickness and the physical properties of them were investigated at the Tsukuba Experimental Basin. We measured their thickness using a penetrometer, surveyed soil profiles, and analyzed undisturbed cylindrical samples for measurements of physical properties. At the zero-order basin, which is mainly covered by volcanic ash, the colluvium is mostly over 1.0 m in thickness. Along the axis of the basin, we found colluvium over 6.0 m thick. The saprolite thickness is heterogeneously distributed over the hillslopes and along the axis of the hollow, where it is rather thick. The physical properties of shallow colluvium, deep colluvium and saprolite, particularly bulk density and total porosity, are different. Thick colluvium and saprolite play an important role as a buffer against direct runoff.     

Starch Characteristics of the Rice Mutant du2‐2 Taichung 65 Highly Affected by Environmental Temperatures During Seed Development

The effects of environmental temperature (21 vs. 28°C) during rice seed development on the starch characteristics (apparent amylose content, amylopectin chain length distribution, and gelatinization properties) of nonwaxy Taichung 65 (T65), waxy Taichung (T65wx), du2‐2 mutated low‐amylose strain Taichung (76‐3/T65), and Koshihikari were studied. Amylose contents increased with decreasing environmental temperatures. Analysis of the amylopectin chain length distribution showed that the relative amounts of long chains with degree of polymerization (DP) > 25 in all starches decreased if maturation occurred at 21°C. Gelatinization onset, peak, and conclusion temperatures and enthalpies decreased with decreasing environmental temperatures. Of all starches studied, the du2‐2 mutated low‐amylose Taichung (76‐3/T65) was most affected by maturation temperatures. These results indicate that the du2‐2 mutated low‐amylose Taichung (76‐3/T65) may be a useful strain in understanding biochemical and genetic starch biosynthesis response to slight changes in temperature.     

Improving the accuracy of estimating blood calcium concentration in Holstein cows using electrocardiographic variables

We previously reported the possibility of using the electrocardiogram variable to estimate blood calcium (Ca) concentration in dairy cows based on the strong positive correlation between the blood Ca concentration and the inverse of the corrected ST peak interval (STc⁻¹). To improve the accuracy of the estimation of blood Ca concentration, we investigated the relationship between blood Ca concentration and STc⁻¹ for each postpartum day and available variables other than STc⁻¹. We measured multiple variables (milk yield, calving number, age, body temperature, etc.), including serum total Ca concentration (tCa), blood ionized Ca concentration (iCa) and STc⁻¹ in 462 Holstein cows on days 0, 1, 2, 3, 5, and 7 postpartum. A very high correlation was observed between iCa and tCa. The association between tCa and STc⁻¹ for each postpartum day had a high coefficient of determination of 0.61–0.79 postpartum 0–2 days but decreased after the third day. In the investigation using the data from postpartum days 0–2, STc⁻¹, heart rate interval, calving number, and age were highly correlated with tCa. In addition, a multiple regression equation was obtained with tCa as the objective variable and STc⁻¹ and calving number as explanatory variables. The estimation accuracy was improved as compared with the simple regression equation using only STc⁻¹ as the explanatory variable. This multiple regression equation was used for 11 cows suspected of having hypocalcemia, and it was able to correctly detect cows requiring early treatment, except for one cow.