Entity

Time filter

Source Type


Oda T.,University of Tokyo | Suzuki M.,University of Tokyo | Egusa T.,University of Tokyo | Uchiyama Y.,Kanagawa Prefecture Natural Environment Conservation Center
Hydrological Processes | Year: 2013

In this paper, we examined the role of bedrock groundwater discharge and recharge on the water balance and runoff characteristics in forested headwater catchments. Using rigorous observations of catchment precipitation, discharge and streamwater chemistry, we quantified net bedrock flow rates and contributions to streamwater runoff and the water balance in three forested catchments (second-order to third-order catchments) underlain by uniform bedrock in Japan. We found that annual rainfall in 2010 was 3130mm. In the same period, annual discharge in the three catchments varied from 1800 to 3900mm/year. Annual net bedrock flow rates estimated by the chloride mass balance method at each catchment ranged from -1600 to 700mm/year. The net bedrock flow rates were substantially different in the second-order and third-order catchments. During baseflow, discharge from the three catchments was significantly different; conversely, peak flows during large storm events and direct runoff ratios were not significantly different. These results suggest that differences in baseflow discharge rates, which are affected by bedrock flow and intercatchment groundwater transfer, result in the differences in water balance among the catchments. This study also suggests that in these second-order to third-order catchments, the drainage area during baseflow varies because of differences between the bedrock drainage area and surface drainage area, but that the effective drainage area during storm flow approaches the surface drainage area. © 2012 John Wiley & Sons, Ltd. Source


Tsukada H.,Japan National Agriculture and Food Research Organization | Nakamura Y.,Japan National Agriculture and Food Research Organization | Kamio T.,Japan National Agriculture and Food Research Organization | Inokuma H.,Obihiro University of Agriculture and Veterinary Medicine | And 5 more authors.
Bulletin of Entomological Research | Year: 2014

Haemaphysalis longicornis (Acari: Ixodidae) is one of the most common and important arthropod disease vectors in Japan, carrying Japanese spotted fever and bovine theileriosis. The recent expansion of sika deer (Cervus nippon, Artiodactyla: Cervidae) populations, the most common wild host of H. longicornis, has also caused concern about increasing the risk of vector-borne diseases in Japan. We used generalized linear mixed model analysis to determine the relative contribution of deer density and other biological and abiotic factors on the abundance of H. longicornis ticks questing at each developmental stage. A total of 6223 H. longicornis adults, nymphs, and larvae were collected from 70 sites in three regions of central Japan. The abundance of questing adult and nymphal ticks was associated with deer density and other biotic and abiotic factors. However, the abundance of questing larvae showed no association with deer density but did show an association with other biotic and abiotic factors. These findings show that a high density of deer along with other biotic and abiotic factors is associated with increased risk of vector-borne diseases through amplified local abundance of questing nymphal and adult H. longicornis. Further, questing larvae abundance is likely regulated by environmental conditions and is likely correlated with survival potential or the distribution of other host species. © 2013 Cambridge University Press. Source


Tamura A.,Kanagawa Prefecture Natural Environment Conservation Center | Tamura A.,Research Division
Japanese Journal of Conservation Ecology | Year: 2010

Deer-proof fences have been used to protect and restore endangered perennial herbs in some areas of Japan where the forest floor vegetation has been diminished by browsing sika deer (Cervus nippon Temminck). However, little work has been done to evaluate the optimal timing for installing such deer-proof fences. Thus, I surveyed the occurrence, number of individuals, and number of mature individuals of 12 perennial species inside seven deer-proof fences over 5 years post-establishment, three of which were installed in 1997 (1997 fences), and the other four in 2003 (2003 fences). The occurrence of six species was equal between the 1997 fences and the 2003 fences, while that of the remaining six species was higher within the 1997 fences than the 2003 fences. Past records indicated that three of these latter six species were distributed equally between the areas of the 1997 and 2003 fences. These results suggest that the potential distribution of nine species found within the 1997 fences was equal to that of the 2003 fences. The number of individuals of four of these nine species was greater in the 1997 fences than in the 2003 fences, or showed differing relative rankings. These findings suggest that these four species have difficulty recovering, given the assumption that the fences were constructed in regions where the forest floor was subjected to the continual sika deer browsing. In contrast, the remaining five species did not show significantly different numbers of individuals between the 1997 and 2003 fences. Thus, these five species appear to be unaffected by 10 or 16 years, respectively, of sika deer browsing. These findings demonstrate that some species have difficulty recovering once the forest floor has been diminished by browsing sika deer. Thus. Source


Tamura A.,Kanagawa Prefecture Natural Environment Conservation Center
Nihon Ringakkai Shi/Journal of the Japanese Forestry Society | Year: 2013

Recovery of dwarf bamboo (Sasamorpha borealis) and regeneration of tree species were investigated inside and outside two deer-proof fences in a beech forest diminished by sika deer. One fence was installed in 1997 (1997F) and the other was installed next to it in 2002 (2002F). The time lag in installing the deer-proof fences was evaluated from the data 7 years after the installation of the fences. The height of the S. borealis protected by 1997F was equal to that protected by 2002F. Coverage of S. borealis inside 1997F grew wider with progress of time, but that inside 2002F did not increase. Floor vegetation inside 1997F consisted of S. borealis (21%), trees (18%), and shrubs (35%) in relative dominance, while that inside 2002F consisted solely of shrubs (82%). The density of regenerated trees higher than S. borealis was 1,250/ha in both 1997F and 2002F. These findings demonstrated that the early establishment of deerproof fences enables the best possible recovery of S. borealis. In contrast, our evaluation suggested that early establishment of deer-proof fences is not necessary for the regeneration of tall trees. Further monitoring is required to predict the future regeneration of trees. Source


Koike S.,Tokyo University of Agriculture and Technology | Nakashita R.,Japan Forestry and Forest Products Research Institute | Naganawa K.,Tanzawa Black Bear Research Group | Koyama M.,Karuizawa Town | Tamura A.,Kanagawa Prefecture Natural Environment Conservation Center
Journal of Mammalogy | Year: 2013

The diets of large, scarce mammals are difficult to study. We compared the food habits of Asiatic black bears (Ursus thibetanus) in the Tanzawa area, Japan, from before (1989-1993) and after (2001-2010) 2000 using both fecal contents and carbon and nitrogen stable isotope ratios in bear hairs. Bears ate the same foods before and after 2000, but some food categories differed in their frequencies of occurrence in autumn. Fruits of Prunus grayama, vine fruits, colonial insects, and Sasa vegetation declined and fruits of Swida controversa and sika deer (Cervus nippon) increased significantly as parts of the fall diet after 2000. Hair samples from 18 bears collected between 1973 and 2009 indicated that bears had higher summertime δ15N rates after 2000 than before, indicating more meat in the diet. Thus, the Tanzawa bear population's diet changed over 2 decades. Habitat conditions may have changed, causing bears to adjust their food habits. We discuss some factors, such as vegetation changes caused by overabundant deer or bears eating deer carcasses, that may be partly responsible. We argue that long-term diet studies are valuable for detecting habitat changes at scales that may not be apparent solely with habitat monitoring. © 2013 American Society of Mammalogists. Source

Discover hidden collaborations