Nobuya Mizoue

Image analysis measure of crown condition, foliage biomass and stem growth relationships of Chamaecyparis obtusa

Abstract Tree crown condition has been visually assessed under forest health monitoring programs in many countries, but the assessments suffer from observer bias and lack of information on the relationship with actual foliage biomass (FM). It is hypothesized here that the image analysis measure DSO, based on fractal analysis of tree crown images taken from the ground, is closely related to actual FM and stem growth and would help to interpret the results of visual assessments. Thirty-two Japanese cypress (Chamaecyparis obtusa Endl.) in two even-aged stands (22 and 39 years old) were felled and photographed. DSO values of crown images were calculated and FM, crown size and current stem volume increment (VI) were measured. It was found that, by pooling data from both stands, foliage biomass density (FMD) (dry weight of foliage, FM, divided by crown surface area, CSA) showed a strong linear relation to DSO (r2=0.973) and FM showed strong proportionality to the product of CSA and DSO (CSA×DSO) (r2=0.990). Stem VI also had a strong linear relationship with CSA×DSO, with the slopes of the fitted curves of the two stands being significantly different. The image analysis measure DSO could be useful in non-destructively estimating actual FMD and, when coupled with measurements of crown size and stem growth, actual FM and growth efficiency.

Importance of rubberwood in wood export of Malaysia and Thailand

AbstractsWe examined the contribution of rubberwood to the timber export markets of Malaysia and Thailand. In Malaysia, rubberwood has grown from 26% of total exported wood products in 1998 to 35% in 2007. A high proportion of furniture products (80%) is rubberwood, whereas the contribution of rubberwood to other wooden products is less than 20%. Only 10% of sawn timber and logs is rubberwood. In Thailand, rubberwood contributes to around 60% of total exported wood products, arising from a high share of not only furniture products (70%) but also other wood products (around 50%) and sawn timber and logs, which have increased in share from 40% in 1998 to 79% in 2007. We conclude that the high proportion of rubberwood products in the wood export markets of these two countries is a result of: (1) scarcity of raw wood materials because of strict controls on the logging of natural forests; and (2) governmental support to rubberwood production, including financial support to rubber planters and technical assistance to downstream timber processors.

Evaluation of data quality in Japanese National Forest Inventory

We evaluated the quality of data being collected for the Japanese National Forest Inventory (NFI). The inventory program commenced in 1999 but has not incorporated a quality assurance (QA) program; we sought to determine what effect this was having on the quality of data being collected. Forty-eight plots in four prefectures were measured by operational field teams and then remeasured by a control team that made careful and unhurried measurements. The paired data were evaluated, including diameter, total height, tree count, species richness, and topographic condition. Compared to the control team, all field teams of each prefecture tended to significantly underestimate all of the continuous variables. Most variables had larger variability in the inventory data than has been reported in the published literature. The findings of consistent bias and large variation in the field team measurements call for urgent implementation of a quality assurance program (extensive field training and regular remeasurement) in the Japanese NFI to improve data quality, and this conclusion could be applied to the inventory system of any country that does not include a QA program.

Estimating forest biomass increment based on permanent sample plots in relation to woodfuel consumption: a case study in Kampong Thom Province, Cambodia

To assess the sustainability of forest use for woodfuel, above ground biomass increment must be examined against woodfuel consumption. However, reliable data on the biomass increment of tropical forests are very limited. In this study, we estimated above ground forest biomass increment in Kampong Thom Province, Cambodia, using two consecutive measurements of 32 permanent sample plots in 1998 and 2000, and forest inventory data of 540 plots collected in 1997. The permanent sampling plot data were used to determine the relationship between initial biomass and subsequent biomass increment over a 2-year period. This relationship was applied to the inventory data to obtain a robust estimate of biomass increment across the major forest types for the entire province. The weighted average annual above ground biomass increment for the whole province was 4.77 Mg/ha, or 2.3% of biomass. Woodfuel consumption was estimated to be about 2% of biomass increment for the province, suggesting that deficiency of woodfuel may not occur in this province. However, localized variation needs to be taken into account and there is a need to examine the effects of stand age and factors such as soil type, microtopography, and species composition on biomass increment and to consider woodfuel collection rate in specific forest areas with respect to accessibility for firewood collection.

Calibrating view angle and lens distortion of the Nikon fish-eye converter FC-E8

Recently, an inexpensive digital camera that can equip with a fish-eye converter lens, FC-E8, has been available from Nikon. The converter has more than 180° view angle and lens distortion. The objectives of the present study were to develop a procedure for calibrating the view angle and lens distortion of the fish-eye converter, and to examine the effect of the calibration on light environment estimates. Based on unpublished data provided by the Electric Image Technical Center of Nikon, a 12-order poly-nomial expression for the calibration was derived. The expression enabled us to calibrate the view angle and lens distortion for all selectable resolution digital images. Using a Nikon Coolpix 990 digital camera with the fish-eye converter, 105 hemispherical photographs were taken in 15 stands, and then the canopy cover and weighted openness were measured as the light environment estimates. The calibrated estimates were significantly higher than uncalibrated ones, but the differences were comparatively small, with the average differences being 0.658% for canopy cover and 0.344% for weighted openness. A strongly positive correlation between calibrated and uncalibrated estimates was observed. Both slope and intercept of the regression lines of the calibrated estimate against the uncalibrated one were significantly different between canopy cover and weighted openness, suggesting that the calibration effect would be different among light environment estimates. In conclusion, we should pay attention to the view angle and lens distortion of the fish-eye converter in estimating light environments using the Coolpix digital camera.

Effects of residual trees on tree height of 18- and 19-year-old Cryptomeria japonica planted in group selection openings

This study examined the effects of residual trees on the height of 18- and 19-year-old Cryptomeria japonica planted in group selection openings of about 0.1 ha at Yufuin in Oita Prefecture in southern Japan. We first developed a general model expressing variation in the height for all of the planted trees within the openings from indices of both between-cohort competition (the effects of residual trees) and within-cohort competition (among the even-aged planted trees). The between-cohort competition index was calculated both with and without taking into account the direction that residual trees were positioned from subject trees. The two models suggested that residual trees located near the northern edge of the opening were not effective competitors for light for the planted trees within the opening. In addition, our results indicated that both between-cohort competition and within-cohort competition are important for explaining tree height in closed stands within group selection openings. Using the general model, we then estimated the potential loss of height growth for locally dominant trees within the openings that could be attributed only to the influence of residual trees. These results indicated that in addition to the effect of opening size, both the degree of crowding and the direction of residual trees from the planted trees are important factors affecting the height of individual trees planted in group selection openings.

Deforestation and forest degradation as measures of Popa Mountain Park (Myanmar) effectiveness

The effectiveness of protected areas (PAs) has often been measured by comparing deforestation or land cover loss before and after PA establishment or within and outside the PA. Such evaluations ignore forest degradation or the decline in quality of the ecological values of the forest. Landsat image processing and geographical information systems were used to study forest cover changes in and around Popa Mountain Park (central Myanmar). Deforestation inside the Park was lower than outside the Park, but forest degradation, namely the net area that changed from dense forest to open forest, within the Park had grown at rates exceeding those outside the Park. The effectiveness of the PA was overestimated by adopting deforestation as the only indicator of conservation effectiveness. Forest degradation studies can be used to evaluate the effectiveness of PAs.

effects of logging and recruitment on community phylogenetic structure in 32 permanent forest plots of kampong thom, cambodia

Ecological communities including tropical rainforest are rapidly changing under various disturbances caused by increasing human activities. Recently in Cambodia, illegal logging and clear-felling for agriculture have been increasing. Here, we study the effects of logging, mortality and recruitment of plot trees on phylogenetic community structure in 32 plots in Kampong Thom, Cambodia. Each plot was 0.25 ha; 28 plots were established in primary evergreen forests and four were established in secondary dry deciduous forests. Measurements were made in 1998, 2000, 2004 and 2010, and logging, recruitment and mortality of each tree were recorded. We estimated phylogeny using rbcL and matK gene sequences and quantified phylogenetic α and β diversity. Within communities, logging decreased phylogenetic diversity, and increased overall phylogenetic clustering and terminal phylogenetic evenness. Between communities, logging increased phylogenetic similarity between evergreen and deciduous plots. On the other hand, recruitment had opposite effects both within and between communities. The observed patterns can be explained by environmental homogenization under logging. Logging is biased to particular species and larger diameter at breast height, and forest patrol has been effective in decreasing logging.

Changes in determinants of deforestation and forest degradation in Popa Mountain Park, Central Myanmar.

Implementing effective conservation requires an understanding of factors affecting deforestation and forest degradation. Previous studies have investigated factors affecting deforestation, while few studies have examined the determinants of both of deforestation and forest degradation for more than one period. To address this gap, this study examined factors influencing deforestation and forest degradation during 1989–2000 and 2000–2005 in the Popa Mountain Park, Myanmar. We applied multinomial logistic regression (MNL) using land cover maps derived from Landsat images as the dependent variables as well as spatial and biophysical factors as the independent variables. The MNL models revealed influences of the determinants on deforestation and forest degradation changes over time. For example, during 1989–2000, deforestation from closed forest was positively correlated to the distance from the park boundary and was negatively correlated with distance from villages, roads, the park circular road, slope, western aspect and elevation. On the other hand, during 2000–2005, deforestation of closed forest was positively correlated with distance from villages, roads, the park circular road, slope and western aspect, and negatively correlated with distance from the park boundary and elevation. Similar scenarios were observed for the deforestation of open forest and forest degradation of closed forest. The study also found most of the determinants influenced deforestation and forest degradation differently. The changes in determinants of deforestation and forest degradation over time might be attributable to the general decrease in resource availability and to the effect of conservation measures conducted by the park.

Within country accuracy of tree crown transparency estimates using the image analysis system CROCO: a case study from Switzerland

Abstract We evaluated the accuracy of tree crown transparency estimates made with the image analysis system CROCO compared to visual estimates by field observers in Switzerland. Data from Swiss field training courses in 1998 and 1999 each comprising four sessions were used and the median values of the different observers’ scores were assumed as the true values. First, Swiss reference photographs alone were used to obtain the calibration curves needed to predict crown transparency from the image analysis measure DSO. In this case, the CROCO estimates were biased for many species. Second, data from the first three field training sessions were added to the reference photos to derive the calibration curves. In this second case, CROCO provided unbiased estimates of both years, while the estimates by some of the field teams were significantly different from the true values. The result suggests that CROCO can be used as a more reliable reference to detect observer bias within a country than control observers. We conclude that few reference photographs alone are not sufficient, so additional field data should also be used to estimate crown transparency more accurately using CROCO.