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Ito E.,Japan Forestry and Forest Products Research Institute | Furuya N.,Japan International Research Center for Agricultural science | Tith B.,Forest Wildlife Research and Development Institute | Keth S.,Forest Wildlife Research and Development Institute | And 10 more authors.
Japan Agricultural Research Quarterly | Year: 2010

The Reducing Emissions from Deforestation and Forest Degradation in Developing Countries (REDD) initiative requires accurate estimates of carbon stock changes in forested areas. However, estimating carbon emissions from stumps of various heights left by illegal loggers is difficult. To remedy this problem, we examined two methods of estimating diameter at breast height (DBH) from a reference diameter observation measured at any stump height. The one-reference diameter (OD) observation model estimates DBH from a single diameter observation using empirical coefficients derived mainly from emergent dipterocarp trees. The two-reference diameter (TD) observation model estimates DBH from two diameter observations and assumes a logarithmic relationship between diameter and height. Prediction data to establish the models were collected in Cambodian lowland evergreen forests that are undergoing intensive illegal logging of emergent dipterocarp trees for timber. The OD model performed better than the TD model in predicting DBH and is extremely practical, as it requires only a single diameter observation. Validation data previously collected in the Southeast Asian tropical forests established the general validity of the OD model. This study may improve the reliability of the REDD scheme by providing a reliable method to assess carbon emissions from Southeast Asian tropical forests.


Ota T.,Kyushu University | Ahmed O.S.,Trent University | Franklin S.E.,Trent University | Wulder M.A.,Natural Resources Canada | And 9 more authors.
Remote Sensing | Year: 2014

In this study, we test and demonstrate the utility of disturbance and recovery information derived from annual Landsat time series to predict current forest vertical structure (as compared to the more common approaches, that consider a sample of airborne Lidar and single-date Landsat derived variables). Mean Canopy Height (MCH) was estimated separately using single date, time series, and the combination of single date and time series variables in multiple regression and random forest (RF) models. The combination of single date and time series variables, which integrate disturbance history over the entire time series, overall provided better MCH prediction than using either of the two sets of variables separately. In general, the RF models resulted in improved performance in all estimates over those using multiple regression. The lowest validation error was obtained using Landsat time series variables in a RF model (R2 = 0.75 and RMSE = 2.81 m). Combining single date and time series data was more effective when the RF model was used (opposed to multiple regression). The RMSE for RF mean canopy height prediction was reduced by 13.5% when combining the two sets of variables as compared to the 3.6% RMSE decline presented by multiple regression. This study demonstrates the value of airborne Lidar and long term Landsat observations to generate estimates of forest canopy height using the random forest algorithm. © 2014 by the authors.


Iida S.,Japan Forestry and Forest Products Research Institute | Shimizu T.,Japan Forestry and Forest Products Research Institute | Kabeya N.,Japan Forestry and Forest Products Research Institute | Nobuhiro T.,Japan Forestry and Forest Products Research Institute | And 8 more authors.
Hydrological Processes | Year: 2012

Tipping-bucket flow meter and rain gauge (TBFM/TBRG) are widely used for the measurement of gross rainfall (GR), throughfall (TF), and stemflow (SF) to evaluate the amount of interception loss (I). However, TBFM/TBRG cannot measure the inflow rate during tipping and underestimates the inflow rate. To correct this systematic bias, 33 total calibrations were conducted for five types of TBFM/TBRG in the laboratory. The tipping time increased with the bucket volume, and the underestimation during one tip was higher for TBFM/TBRG of larger capacity. With the use of the scaled actual inflow rate and the actual volume of a single tip from the measured static volume of a single tip when the inflow rate is zero, the common calibration curves were obtained as quadratic equations for each of the five types within an error range of ±3%. We measured GR and TF by using TBRG and TBFM with a resolution of 0.2mm and measured SF by TBRG with a single-tip static volume of 15.7cm3 in a Japanese temperate coniferous forest (TCF) and a Cambodian tropical deciduous forest (TDF). At both sites, the calibration curves needed to be applied to obtain GR, TF, and SF on an event scale with an underestimation degree of less than 3%. Without applying any calibrations, the higher rainfall intensities in TDF caused larger underestimations of GR, TF, and SF and larger overestimations of I compared with results for TCF. On an annual scale, the degree of overestimation of I relative to GR (ΔI/GR) was 1.2% in TCF and 3.5% in TDF, and ΔI/I was at least 10% at both sites. © 2012 John Wiley & Sons, Ltd.


Kenzo T.,Japan Forestry and Forest Products Research Institute | Yoneda R.,Japan Forestry and Forest Products Research Institute | Yoneda R.,Japan International Research Center for Agricultural science | Sano M.,Japan Forestry and Forest Products Research Institute | And 4 more authors.
Japan Agricultural Research Quarterly | Year: 2012

In this study, we demonstrate changes in leaf morphological and physiological traits with tree height from dark understory to bright canopy conditions in various tree species in the Cambodian tropical dry evergreen forest. The vegetation mainly consisted of Dipterocarpaceae and Myristicaceae and the canopy trees usually reached 30-40 m in height. We investigated 25 individuals of 18 tree species ranging from 0.8 to 33 m in height. We measured the leaf photosynthetic rate, stomatal conductance and respiration rate for 3 to 5 leaves per sampling position in the early dry season. All leaves were then divided into two parts: one for measuring dry weight, nitrogen content and δ13C; the other for observation of leaf morphology. The leaf morphological traits, such as leaf mass per area (LMA), cuticle thickness, palisade layer thickness, leaf hardness and stomatal density increased linearly with tree height. The leaf nitrogen content per unit leaf area (Narea) peaked at 10 m from the ground, though the nitrogen content per unit dry leaf mass (Nmass) decreased linearly with tree height. Higher LMA, cuticle thickness and hard leaves in canopy condition may contribute to high drought tolerance and physical strength. The leaf-area-based photosynthetic rate (Amax-area) peaked at an intermediate tree height of approximately 10 m, and then decreased toward the upper canopy. In contrast, the leafmass-based photosynthetic rate (Amax-mass) decreased linearly with tree height. Reduction of leaf nitrogen content and stomatal conductance mainly limit photosynthetic capacities with tree height. Overall, many leaf morphological traits could be summarized in a simple and significant relation with tree height, though increasing tree height, which is related to the micro-climatic gradient, leads to both nitrogen and stomatal constraints of leaf photosynthetic capacities, even when considering many different tree species.


Iida S.,Japan Forestry and Forest Products Research Institute | Ito E.,Hokkaido Research Center | Shimizu A.,Kyushu Research Center | Nobuhiro T.,Japan Forestry and Forest Products Research Institute | And 6 more authors.
Japan Agricultural Research Quarterly | Year: 2013

Although information about the hydrologic and ecological features of lowland evergreen forests in central Cambodia has been collected since the beginning of the 21st century, measurements of the transpiration process remain very limited. This paper describes the differences detected in transpiration (q) and crown-level stomatal conductance (GS) between Calophyllum inophyllum (which undergoes successive leaf exchange) and Drypetes sp. (which performs irregular leaf exchange) (hereafter referred to as Calophyllum and Drypetes, respectively), and the analysis of these differences in consideration of their contrasting leaf phenologies. We evaluated q using sap flow measurements and obtained daily GS values. Calophyllum and Drypetes had high and low periods between which q and GS differed significantly. Within high/low periods, smaller scatter in the plot of GS versus vapour pressure deficit (D) was found in Calophyllum compared to Drypetes. For a given value of D, q in high periods was 1.3 and 1.9 times larger than in low periods for Calophyllum and Drypetes, respectively. The smaller scatter for Calophyllum was the result of relatively constant physiological activity that was maintained by successive leaf fall. For both species, high periods were recorded after remarkable leaf-fall events; thus, our current dataimplied that leaf phenology is one of the most important factors affecting transpiration.


Toriyama J.,Japan Forestry and Forest Products Research Institute | Ohta S.,Kyoto University | Araki M.,Japan Forestry and Forest Products Research Institute | Kosugi K.,Kyoto University | And 6 more authors.
Hydrological Processes | Year: 2011

Both evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low Ks at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWCsm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m3 m-3, respectively. The mean coarse pore volume of the soil matrix (CPVsm) in the Ef and Df groups was 0·231 and 0·115 m3 m-3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. © 2010 John Wiley & Sons, Ltd.

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