Hideo Miguchi

Impact of severe drought associated with the 1997–1998 El Niño in a tropical forest in Sarawak

The impact of the unusually severe drought associated with the 1997-1998 El Nino on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993-1997) in a core plot (1.38 ha) was 0.89 % y -1 , while that during the drought period (1997-1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y -1 , respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993-1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12-30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.

An interactive effect of simultaneous death of dwarf bamboo, canopy gap, and predatory rodents on beech regeneration

To clarify the interactive effect of the simultaneous death of dwarf bamboo (Sasa kurilensis), forest canopy gap formation, and seed predators on beech (Fagus crenata) regeneration, we analyzed beech demography from seed fall until the end of the first growing season of seedlings in an old-growth forest near Lake Towada, northern Japan. The simultaneous death of S. kurilensis took place in 1995. We established four types of sampling site differing in forest canopy conditions (closed or gap) and Sasa status (dead or alive). Beech seed survival and emergence ratio were both highest in gaps with dead Sasa (gap-dead), because rate of predation was lowest. Seedling survival during the first growing season was also highest in the gap-dead treatment, because of less predation and less damping off. As a result, even though density of seed fall was lowest in the gap-dead treatment, the living seedling density there was highest at the end of the first growing season. Predation, which caused the greatest mortality during the seed and seedling stages, was significantly lower at both sites in gaps and sites with dead Sasa. This was probably due to changes in the behavior of rodents in response to the structure of the forest canopy and undergrowth. Both the death of Sasa and canopy gap formation allowed seedlings to avoid damping off because of the high light availability. The indirect effect of the simultaneous death of Sasa and canopy gap formation in reducing predation contributed more to beech regeneration than their direct effect in increasing light for the seedlings.

Geographical variation in the early regeneration process of Siebold's Beech (Fagus crenata BLUME) in Japan

The causes and timing of seed death in early regeneration process of Siebolds beech (Fagus crenata Blume) was studied at 15 sites along a snowfall gradient in Japan, in order to clarify why the seedling density of the species has geographic difference remarkably. Seed production did not significantly differ along the snowfall gradient. Pre-dispersal seed mortality by insect damage was higher at sites with light snowfall than at sites with heavy snowfall, but this only seemed to be a minor factor influencing the population. A large proportion of the viable nuts that fall in autumn ware killed in winter before germination. Winter mortality was much higher at sites with thin snow cover than that at sites with thick snow cover, and this factor was strongly correlated with the geographic variation of seedling regeneration probability. There was little seed mortality by winter desiccation. The main factor contributing to the geographic difference seemed to be a seed predation by rodents in winter. Deep snow cover may reduce the success of rodents finding seeds in winter. Thus the observed relationship between snowpack depth and early mortality may be due to an indirect effect through the process of seed predation.p>

Short-term changes affecting regeneration of Fagus crenata after the simultaneous death of Sasa kurilensis

Abstract Question: The aim of the present study is to determine whether seed/seedling predation will increase and Fagus survival will decline with the recovery of the Sasa cover. Methods: We examined Fagus crenata regeneration for seven years in an old-growth Fagus-Sasa forest near Lake Towada, northern Japan, by examining the effects of simultaneous death of Sasa, tree canopy gap formation, mast seeding of Fagus and seed and seedling predation by rodents on the survival of Fagus seeds and current year seedlings. We established four types of sites differing in forest canopy (closed or gap) and Sasa status (dead or alive) following the simultaneous flowering and death of Sasa kurilensis (dwarf bamboo) in 1995. Results: Fallen Fagus seed was abundant in 1997 and 2000 (mast years). In sites with alive Sasa, survival from the first growing season was low due to high seed and seedling predation. In sites with dead Sasa, seed survival under the canopy was high for both mast years, but in gaps it varied between years. Seedling survival was highest in canopy gaps with dead Sasa (gap-dead) in 1998, because of higher light levels and lower predation by rodents. However, seedling survival in these plots was low in 2001, apparently because rapid Sasa recovery favoured rodent predation. In both mast years, Sasa die-back had significant positive effects on seed and seedling survival under closed canopies because the seedlings there were more successful in escaping predation. Conclusion: The change in successful sites for the early stage of regeneration of Fagus appears to reflect the combined effects of canopy gap, seed/seedling predation and revegetation of Sasa. Nomenclature: Satake et al. (1989). Abbreviations: PPFD = Photosynthetic photon flux density; RPPFD = Relative photosynthetic photon flux density.

Evaluation of Camera-Trap Designs for Photographing Chest Marks of the Free-Ranging Asiatic Black Bear, Ursus thibetanus

Estimating animal numbers in the wild is important for decisive conservation and management. However, it is difficult to perform, especially for rare or elusive species because it often requires assumption and high costs, and it is also labor intensive. The Asiatic black bear (Ursus thibetanus), distributed in southern and eastern Asia, is threatened in much of its native habitat and is designated as “vulnerable” according to the IUCN Red List (Garshelis and Steinmetz 2008). In Japan, the bear is divided into 19 local populations based on habitat continuity (Yoneda 2001). The population in Kyushu is probably extinct, and five populations located mainly in western Honshu are considered threatened (Ministry of the Environment 2002). On the other hand, conflicts with humans, such as crop damage, and injury to humans have recently increased in most local bear populations in Japan because of changes or expansion in bear distribution (Oi and Yamazaki 2006). These events have led to heavy culling to prevent nuisance behavior, but the effect of such operations on population viability is becoming a cause for concern. Therefore, accurate evaluation of the current status of each local population is essential for conservation and management. In recent years, the mark-recapture model has been applied using a DNA fingerprinting method (genetic tagging) based on genetic material obtained from collected bear hair (Woods et al. 1999; Mowat and Strobeck 2000). Development of this investigation method known as a “hair-trap” appears to be effective for estimating bear populations, which has been an almost impossible task in the past. However, it has been reported that the method may have a potential weakness associated with high genotyping error rates due to the low quantity and quality of DNA (Gagneux et al. 1997; Goossens et al. 1998). In addition, the high cost of DNA analysis limits extensive and consistent monitoring. Consequently, we paid attention to the “camera-trap” method, which is relatively simple, cost effective, and easy to perform. It also has great advantages in field studies for animal conservation and management. Recently, this method that identifies individuals based on natural markings such as coat patterns from photographs has been used frequently for estimating mainly felid populations (e.g., Foster and Harmsen 2011; O’Connell et al. 2011). The Asiatic black bear is well known to have a crescent-shaped chest mark which is considered to be unique to each bear (Higashide et al. 2012). In other words, if chest marks can be photographed by a cameratrap, this method will be applicable for estimating bear populations and for researching other ecological topics. However, the chest mark is difficult to photograph, because it is not very visible while the bear is walking, in contrast to many other animals which have natural marks over their whole body. Although Ngoprasert et al. (2010) managed to photograph some chest marks in their preliminary study, their results were unsuccessful. Consequently, it is necessary to develop a practical camera-trap technique for effectively photographing chest marks. In addition, a method must be devised for inducing a bear into a posture that enables their chest mark to be clearly photographed. We devised two types of camera-trap as part of a study to identify individual Asiatic black bears by natural markings as a prelude to estimating population size. This paper describes the design of the traps and assesses their utility. It also evaluates the photography success rate and photographic quality.