Development of Diameter Growth Models by Thinning Intensity of Planted Quercus glauca Thunb. Stands

Background and objective: This study was conducted to develop diameter growth models for thinned Quercus glauca Thunb. (QGT) stands to inform production goals for treatment and provide the information necessary for the systematic management of this stands.Methods: This study was conducted on QGT stands, of which initial thinning was completed in 2013 to develop a treatment system. To analyze the tree growth and trait response for each thinning treatment, forestry surveys were conducted in 2014 and 2021, and a one-way analysis of variance (ANOVA) was executed. In addition, non-linear least squares regression of the PROC NLIN procedure was used to develop an optimal diameter growth model.Results: Based on growth and trait analyses, the height and height-to-diameter (H/D) ratio were not different according to treatment plot (p > .05). For the diameter of basal height (DBH), the heavy thinning (HT) treatment plot was significantly larger than the control plot (p < .05). As a result of the development of diameter growth models by treatment plot, the mean squared error (MSE) of the Gompertz polymorphic equation (control: 2.2381, light thinning: 0.8478, and heavy thinning: 0.8679) was the lowest in all treatment plots, and the Shapiro-Wilk statistic was found to follow a normal distribution (p > .95), so it was selected as an equation fit for the diameter growth model.Conclusion: The findings of this study provide basic data for the systematic management of Quercus glauca Thunb. stands. It is necessary to construct permanent sample plots (PSP) that consider stand status, location conditions, and climatic environments.

Multi-stemming strategies of Quercus glauca in an evergreen broad-leaved forest: when and where

Aims Multi-stemming supports plants’ resilience to disturbances and then contributes to soil stabilization and forest function, especially in mountain habitats. Many questions remain about (i) the ontogenetic phase at which multiple stems can occur, (ii) how habitat drivers affect multi-stemming and (iii) whether ontogenetic phase and habitat drivers interact. We asked these questions for Quercus glauca (ring-cupped oak), the dominant species and sprouter across large warm-temperate areas of Asia; its multi-stemmed trees reflect individual survival, population regeneration and forest ecosystem stability. Methods In a 5-ha permanent plot of subtropical evergreen broad-leaved forest in eastern China, we examined the temporal patterns and spatial distribution of multi-stemmed trees of Q. glauca within 99 quadrats of 20 m × 20 m. Important Findings There were three temporal modes for multi-stemming among the Q. glauca trees and most of them appeared to produce multiple stems from an early stage. Environmental disturbances related to slope convexity appear to be the main drivers of multi-stemming of Q. glauca. Moreover, the closer to the ridge, the earlier the multi-stemming occurs. Thus, also for other woody species in other forests and climate zones, ontogeny and environmental drivers promoting disturbance (not only geomorphology, but also extreme weather events, soil drought, fire), as well as soil fertility, need to be considered in combination to better understand multi-stemming and its consequences for community structure.

Dimorphic Sessile Apterae of the Aphid Neothoracaphis glaucae (Hemiptera) on the Evergreen Oak Quercus glauca

Species of the aphid genus Neothoracaphis (Hormaphidinae, Nipponaphidini) produce tiny, sessile, sclerotized apterous adults on leaves of oaks. Among Japanese species, “N. glaucae” has been known to have the largest, ovate apterae, while “N. saramaoensis” has smaller, elongated oval apterae on Quercus glauca. Through examining mitochondrial DNA sequences of Japanese Neothoracaphis species, we found that the two are the same species with a clear dimorphism. Neothoracaphis glaucae (Takahashi) was adopted as the valid name for the species. In Tokyo, Japan, apterae of the smaller type are abundantly seen throughout the year, and those of the larger type are generally few in number from summer to autumn. Alates, which are supposed to be sexuparae, appear from November to January. Nymphs developing into the alates are covered with long, semitransparent, bristle-like wax filaments. We conclude that N. querciphaga, N. elongata, and N. yanonis are distinct species and that both the genus Neothoracaphis and the three Neothoracaphis species other than N. yanonis form monophyletic groups among Japanese Nipponaphidini species we have examined.

Assessment of Broad-Leaved Forest Stand Management

There are many broad-leaved forests in Japan that were formerly managed for charcoal production, which have been abandoned for decades. Appropriate thinning can revitalize these forests if the cost balance of the management is positive. Two critical elements are the construction of spur roads to facilitate mechanized harvesting operations and management planning that considers stand properties such as the growing stock, species, and tree size distribution. We surveyed three abandoned former broad-leaved coppice stands; one coastal, one cool temperate and one warm temperate. The stock in all three stands exceeded 300 m3 ha-1, two- to three-fold the official forest registry data estimates. The dominant species in terms of tree numbers are Castanopsis sieboldii, Pieris japonica, and Quercus glauca. Medium-sized trees involve those well suited for firewood, i.e., Quercus acuta, Quercus glauca, Quercus serrata, etc. Each plot contained a few large trees that potentially have a high market value, e.g., Cinnamomum camphora, Zelkova serrata, Abies firma, etc. The average income from harvested trees was estimated to be 10200 JPY (Japanese Yen) m-3, whereas the thinning costs would be 3200 to 5400 JPY m-3, with the additional spur road construction costs. The management cost balance of a broad-leaved stand in a 60 year rotation was evaluated with both Net Present Value (NPV) (for interest rates of 1, 2, 3, and 4%) and Internal Rate of Return (IRR). This balance was compared with that of a typical plantation stand of Japanese cedar (Cryptomeria japonica) and of a fast-growing plantation stand of Chinese fir (Cunninghamia lanceolata). The estimated NPVs were largest for the fast-growing plantation stand, second largest for the typical plantation stand, and lowest for the broad-leaved stand with a NPV interest rate of 1 + %. However, the IRR of the broad-leaved stand was the highest, followed by that of the fast-growing plantation stand, while the IRR of the typical plantation stand was the lowest. This order was the same for NPVs assuming higher interest rates. 1 JPY=0.0086 € on April 29, 2019.

Stomatal frequency of Quercus glauca from three material sources shows the same inverse response to atmospheric pCO2

Background and AimsThe inverse correlation between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many plants has been widely used to estimate palaeo-CO2 levels. However, apparent discrepancies exist among the obtained estimates. This study attempts to find a potential proxy for palaeo-CO2 concentrations by analysing the stomatal frequency of Quercus glauca (section Cyclobalanopsis, Fagaceae), a dominant species in East Asian sub-tropical forests with abundant fossil relatives.MethodsStomatal frequencies of Q. glauca from three material sources were analysed: seedlings grown in four climatic chambers with elevated CO2 ranging from 400 to 1300 ppm; extant samples collected from 14 field sites at altitudes ranging from 142 to 1555 m; and 18 herbarium specimens collected between 1930 and 2011. Stomatal frequency–pCO2 correlations were determined using samples from these three sources.Key ResultsAn inverse correlation between stomatal frequency and pCO2 was found for Q. glauca through cross-validation of the three material sources. The combined calibration curves integrating data of extant altitudinal samples and historical herbarium specimens improved the reliability and accuracy of the curves. However, materials in the climatic chambers exhibited a weak response and relatively high stomatal frequency possibly due to insufficient treatment time.ConclusionsA new inverse stomatal frequency–pCO2 correlation for Q. glauca was determined using samples from three sources. These three material types show the same response, indicating that Q. glauca is sensitive to atmospheric pCO2 and is an ideal proxy for palaeo-CO2 levels. Quercus glauca is a nearest living relative (NLR) of section Cyclobalanopsis fossils, which are widely distributed in the strata of East Asia ranging from the Eocene to Pliocene, thereby providing excellent materials to reconstruct the atmospheric CO2 concentration history of the Cenozoic. Quercus glauca will add to the variety of proxies that can be widely used in addition to Ginkgo and Metasequoia.