Publications by authors named "Hiroyuki Sase"

Article Synopsis
  • The study investigates how seasonal rainfall changes and forest maturity affect the deposit of nutrients in rehabilitated forest ecosystems in Bintulu, Malaysia.
  • Using ion exchange resin to measure ion deposition, results showed significant seasonal differences in the deposition of certain ions, particularly lower levels of Ca and NH₄ during low-precipitation seasons across established forest plots.
  • Findings highlight the importance of precipitation patterns and the age of trees in influencing nutrient cycling, with younger forest stands showing variations in ion concentrations based on rainfall, adding to our understanding of forest ecosystem health.
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Elevated nitrogen (N) deposition due to intensified emissions of NH and NO is a global problem with profound consequences on living organisms and the environment. Although N emission rates are currently considered to be high in East Asia, reports on the current N deposition level and composition are still limited, especially in northeastern China, where official N deposition monitoring sites are unavailable. This limits our understanding of the spatio-temporal N deposition patterns and their influencing factors at regional to continental scales.

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To select urban greening tree species suitable for the purification of the atmosphere polluted by black carbon (BC) particles, it is necessary to clarify the determinants of the amount of BC particles deposited on the tree leaves. In the present study, we investigated the relationship between the amount of BC particles that were deposited from the atmosphere and firmly adhered to the leaf epicuticular wax, and leaf surface traits in seedlings of nine tree species grown for two years under natural conditions (Fuchu, Tokyo, Japan). There was a significant interspecific difference in the maximum amount of BC particles deposited on the leaf surface, and the order was as follows: > > > > ≒ > ≒ ≒ .

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Spatial variations in sulfur (S) and nitrogen (N) deposition have changed in East and Southeast Asia in recent decades. Nevertheless, in this region, including the tropics, regional-scale assessments of the long-term risk of acidification and eutrophication (N saturation) for terrestrial ecosystems using a critical load approach have not been updated since 2001. To evaluate future risks, maps of critical loads and exceedances were updated using recently acquired spatial datasets of soil properties, soil minerals, climate, tree plantations, and the annual S and N depositions estimated using the Community Multiscale Air Quality (CMAQ) model.

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Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future.

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As black carbon (BC) particles can be deposited on the leaf surfaces, urban greening is considered to be effective in purifying urban air. However, little information on the seasonal variations in the amount of BC particles deposited on the leaf surfaces (BC amount on the leaves) is available in Japanese urban greening tree species. Therefore, we investigated seasonal variations in the BC amount on the leaves of evergreen (, , and ) and deciduous (, , , and ) broad-leaved tree species.

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Scientific and public interest in acid deposition and its ecological impacts have increased throughout 1990s in East Asia (Northeast and Southeast Asia). After being established in 2001, the Acid Deposition Monitoring Network in East Asia (EANET) celebrates the 20th anniversary in 2021, and is now being expanded in scope reflecting the shifting social concern from acid deposition to broader air quality and climate change in recent years. This paper reviews the past 30 years of development of scientific research and policy related to acid deposition in East Asia.

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Air pollution and atmospheric deposition have adverse effects on tree and forest health. We reviewed studies on tree and forest decline in Northeast and Southeast Asia, Siberia, and the Russian Far East (hereafter referred to as East Asia). This included studies published in domestic journals and languages.

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Article Synopsis
  • - The study examined seasonal changes in throughfall (TF) and stemflow (SF) chemistry in a Japanese cedar forest, revealing distinct trends in ion fluxes influenced by seasonal winds.
  • - Canopy interactions significantly affected the fluxes of NH4+ and K+ ions, with water droplet behavior on leaves changing as they aged, impacting ion absorption and leaching.
  • - A decrease in the contact angle (CA) of water droplets on older leaves correlated with higher NH4+ fluxes, while K+ levels were negatively affected, suggesting that increased wettability may enhance nutrient uptake and leaching.
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