Kanagawa Prefecture Natural Environment Conservation Center

Abstract We examined the spatial variability for the characteristics of surface soil layers in forested headwater catchments, which is important for estimating soil erodibility (K-factor). Soil samples with 30 cm in depth from surface were collected at 26 locations within two neighboring headwater catchments, located in Tanzawa Mountains in Japan. Soil bulk density, particle size and organic matter contents for calculating soil erodibility factor was analyzed 5 cm interval with depth. Soil bulk density ranged from 0.4 to 1.1 g/cm3 (mean: 0.7; SD: 0.2) with low bulk density associated with litter ground cover condition and 300 of topography. Soil organic matter contents ranged from 5 to 12% (mean: 9; SD: 2) with high values occurred at ridgeline due to litter ground cover condition. Estimated soil erodibility ranged at 5 cm depth was 0.011 to 0.018 Mg h MJ−1 mm−1, while K factor in 30 cm depth was 0.012 to 0.017 Mg h MJ−1 mm−1. Because of the calculation for the soil erodibility mainly depend on the particle size, K factor based on 30 cm soil depth was from 0.012 to 0.017 Mg h MJ−1 mm−1 with 0.014 Mg h MJ−1 mm−1 of mean value (SD: 0.002). Because of soil particle size was not spatial varied, K-factor did not significantly differ depending on the locations with suspect to slope gradient, aspects, and altitude within catchments. Thus, mean soil erodibility can be applicable for estimating soil erosion using RUSLE model. These findings support the simplification of erosion risk assessments by allowing the use of representative K-factor values in forested headwater catchments, potentially improving the efficiency and accuracy of erosion modeling in mountainous regions.

To understand the characteristics of movement and activity rangeActivity range of sika deer (Cervus nippon), we tracked 42 individuals (33 females, 9 males) in the Tanzawa MountainsThe Tanzawa Mountains by GPS collars during 2008–2020. We confirmed 4 movement patternsMovement patterns as residentialResidential (27 deer, 64.3%), seasonal migrationSeasonal migration (12, 28.6%), mixed migrationMixed migration (1), and dispersalDispersal (2), showing a high residential proportion. Migration occurred in January–February, May, and October–November mainly. Seasonal migrantsSeasonal migrants took 38 (12–190) hours and moved 6.2 (1.9–13.4) km with a 0–1200 m summer-winter elevation range. The annual core areaAnnual core area and home rangeHome range of all individuals were 1.106 and 4.117 km2, showing a size order as disperser>seasonal migrants>mixed migrants>residents. The seasonal core areaSeasonal core area and home range of residents were 0.182 and 0.705 km2, and that of adults in summer was the smallest. Core area and home range of seasonal migrants were 0.172 and 0.657 km2, and most migrants showed a summer-low-winter-high typeSummer-low-winter-high type in elevation. The winter range of migrant males was smaller than that in summer resulting from narrow forage distributionForage distribution and sever topography limiting the activity ranges. The concentrative migration from hunting to protected areas around hunting start periodHunting start period suggests that hunting pressureHunting pressure might be an important migration triggerMigration trigger. The concentrative distribution of protected areasProtected areas, high food availabilityFood availability due to snow decrease, and high overlap rate (80.8–86.2%) between activity range and protected area suggest that sika deer used summit areas as both refuge from hunting and feeding sites in winter.

This study investigated runoff to clarify the effect of bedrock groundwater dynamics on runoff generation processes in granodiorite headwater catchments (NA and NB) located in the western Tanzawa Mountains, Central Japan. The rainfall–runoff response and water balance calculated using the hydrological cycle (HYCY) model with outflow were also analyzed based on the observed precipitation, runoff, and bedrock groundwater level (at a depth of 50 m). In 2013, the annual runoff rate was 398 mm (21% of the rainfall) in NA and 1209 mm (63% of the rainfall) in NB, respectively. The bedrock groundwater level varied for approximately 3 m, and responded to 30-mm rainfall events. The significant relationship between the base flow and bedrock groundwater level indicated that the bedrock groundwater markedly influenced base flow generation. The calculated annual bedrock infiltration values of 656 mm (34% of the rainfall) in NA and 52 mm (3% of the rainfall) in NB significantly influenced the runoff rate. Our results demonstrated that significant and negligible amounts of bedrock groundwater infiltration were observed, even in neighboring catchments. Those bedrock groundwater dynamics significantly influenced the observed differences in the runoff rate and base flow generation.

The estimated number of sika deer within the Tanzawa Mountains has decreased since the Kanagawa Prefecture sika deer management plan commenced. Meanwhile, unit-specific culling has resulted in various trends in deer density across small monitoring units. Deer abundance is usually surveyed within small monitoring units; therefore, the evaluation of deer abundance changes across the entire management area comprising individual units is difficult. We examined the relationship between deer body condition indicators and densities estimated at both individual unit and entire management scales in the Tanzawa Mountains during 2004–2015. Winter fawn body mass in the study area increased at least until 2011, irrespective of the increase/decrease in deer density in each unit. Observed variations in body mass were related to the estimated number of deer within the entire management area. Winter fawn hind foot length was not related to any density estimates. Inconsistencies between deer density changes in each unit and body mass might derive from the deer movement between units and mitigation of density-dependent food limitations caused by a reduction in the number of deer within the entire management area. We suggest that winter fawn body mass can provide additional evidence of deer abundance changes within management areas.

Abstract The tryphonine parasitoids (Hymenoptera, Ichneumonidae) of a serious pest of beech trees, Fagineura crenativora Vikberg & Zinovjev, 2000 (Hymenoptera, Tenthredinidae, Nematinae), are reviewed. Three species, Cteniscus (Cteniscus) fagineurae sp. nov., Eridolius tanzawanus sp. nov. and Exyston elongatus sp. nov., are described. Key to main koinobiont parasitoids of F. crenativora is given.

Damp forests are vulnerable ecosystems and have peculiar species compositions. Deer can cause severe damage to damp forest composition and structure. However, little is known about the effect of deer on soil seed banks of damp forests and the restoration potential of soil seed banks. I surveyed the compositions of the soil seed bank and floor vegetation both inside and outside a deer exclosure in an old-growth damp forest in eastern Japan using the seedling emergence method. Floor vegetation was composed of 71 % palatable and 1 % unpalatable species inside the exclosure but 6 % palatable and 83 % unpalatable species outside the exclosure. Forty-four species and 642 seeds m−2 germinated inside the exclosure, whereas 39 species and 985 seeds m−2 germinated outside the exclosure. Seed bank composition was 29 % palatable and 43 % unpalatable species inside the exclosure and 1 % palatable and 73 % unpalatable species outside the exclosure. Percentage similarity between the soil seed bank outside and the floor vegetation inside the exclosure was very low. These results indicate that the soil seed bank outside the exclosure has little potential to aid the recovery of floor vegetation. Conservation measures, such as deer exclosures and deer control, must be introduced before the floor vegetation is retrogressed by sika deer grazing.

The pollen allergy problem of Japanese cedar has been a nation-wide problem in spring time in Japan. It is said that about 20% of people suffer Japanese cedar pollinosis in urban areas. New projects substituting Japanese cedar forest stands with low-pollen or sterile male Japanese cedar trees started from 2008. The propagation of male sterile Japanese cedar genotypes is one of the most important steps in that project. We developed a micropropagation technique using an in vitro culture of male sterile Japanese cedar genotypes. Leafy shoot segments were used for explants. There was a genotypic difference in tissue culture response. Among the cytokinin tested, zeatin and 6-benzylaminopurine (BAP) were relatively effective for bud induction. More buds were induced in the medium containing zeatin than that containing BAP with the male sterile genotype Fukushima 5. Shoots developed from buds on the medium 1/2 LP containing 5 g l−1activated charcoal. Shoots produced roots on a medium containing 23.8 μM (5 mg l−1) 4-chloroindole-3-acetic acid and 0.044 μM (0.01 mg l−1) BAP. Rooted plantlets were successfully habituated and cultured in pots outside. The in vitro cultured materials will be used for the micropropagation of male sterile Japanese cedar in order to reduce the pollen in the air.

丹沢山地におけるブナ衰退機構を検討するため，2002年から2004年にかけてマクロ，メソ，サイトの3つの空間スケールでブナ林を現地調査し，林分構造および衰弱と枯死の両方を含んだブナ衰退の現状についてGISを用いて定量的に解析した．マクロスケールの調査から，ブナ林のブナ混交率は大半が30％以下であり，樹高，平均胸高直径および立木密度を基準におおむね3つの地域に区分できることを示した．ブナの衰退は，東丹沢から丹沢中央の標高が1400 mを越える主稜線部にかけて進み，西丹沢や東丹沢の北側に位置する地区などで少なかった．衰退が進行する地区には，高標高地や平坦地のブナ林が多かった．また，平均日射指数が高いほど，もしくは土壌水分指数が低いほど，衰退が進んでいた．衰退が進行する丹沢山と檜洞丸の山頂一帯におけるメソスケールの調査からは，南から西向き斜面でブナの衰退が進む傾向が示された．また，林分調査の調査から，衰退が進む地点では，ブナ以外の樹種の樹勢低下やブナ高木の集団的な衰退を認めた．以上の衰退現況を踏まえた，丹沢山地のブナ衰退要因の空間階層的な関係を検討し，今後の研究課題を整理した．

森林における景観パッチの空間パターンは，生物の生息状況に大きな影響を与えることが明らかになっており，生物多様性の維持には景観的な視点からの解析が要求されている．近年，私有の人工林では管理放棄が広範囲に認められ，パッチの質の低下に加えて生物の生息に好適とはいえない空間パターンの形成が進み，人工林景観における生物多様性の低下が懸念されている．本研究では，人工林管理政策の違いが将来的なランドスケープ構造にどのような影響を与えるのか，生物多様性保全の観点から評価を行うことを目的とした．森林管理ランクが明らかな神奈川県丹沢山地の民有人工林を材料として，異なる3つの間伐方針をシナリオとしたシミュレーションを行った．シナリオごとに時系列的に創出されるランドスケープの変化について，手入れランクの異なる林分パッチの形状，パッチ密度，近接性，分断度を測定し，生物多様性への有効性を検討した．その結果，現行の2種類の間伐方針に沿った森林管理はいずれも生物多様性の保全に効果的だと考えられたが，どちらがより効果的かは断言できなかった．