Changes in the anatomy, morphology and mycorrhizal infection of fine root systems of Cryptomeria japonica in relation to stand ageing.

Biomass allocation to fine roots often increases under soil nutrient deficiency, but the fine root biomass does not often increase in old stands, even under nutrient limitation. Therefore, in old stands, the morphology, anatomy, branching architecture and mycorrhization of fine roots may compensate efficiently for nutrient acquisition by the low fine root biomass. In this study, changes in the morphology, anatomy and arbuscular mycorrhizal infection at each branching position of fine root clusters were evaluated in relation to stand age.

Terrestrial-aquatic linkage in stream food webs along a forest chronosequence: multi-isotopic evidence.

Long-term monitoring of ecosystem succession provides baseline data for conservation and management, as well as for understanding the dynamics of underlying biogeochemical processes. We examined the effects of deforestation and subsequent afforestation of a riparian forest of Japanese cedar (Cryptomeria japonica) on stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) and natural abundances of radiocarbon (Δ¹⁴C) in stream biota in the Mt. Gomadan Experimental Forest and the Wakayama Forest Research Station, Kyoto University, central Japan.

Estimation of radioactive 137-cesium transportation by litterfall, stemflow and throughfall in the forests of Fukushima.

Since the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, large areas of the forests around Fukushima have become highly contaminated by radioactive nuclides. To predict the future dynamics of radioactive cesium ((137)Cs) in the forest catchment, it is important to measure each component of its movement within the forest. Two years after the accident, we estimated the annual transportation of (137)Cs from the forest canopy to the floor by litterfall, throughfall and stemflow.

Nitrate isotopic composition reveals nitrogen deposition and transformation dynamics along the canopy-soil continuum of a suburban forest in Japan.

Rationale: Heavy nitrogen (N) deposition often causes high nitrate (NO3(-)) accumulation in soils in temperate forested ecosystems. To clarify the sources and production pathways of this NO3(-), we investigated NO3(-) isotope signatures in deposition processes along the canopy-soil continuum of a suburban forest in Japan.

Methods: The stable isotopes of N and oxygen (O) were used to trace the source and transformation dynamics of nitrate (NO3(-)) in two forest stands: a plantation of Cryptomeria japonica (coniferous tree; CJ) and a natural secondary forest of Quercus acutissima (broadleaf, deciduous tree; QA).

Consequence of altered nitrogen cycles in the coupled human and ecological system under changing climate: The need for long-term and site-based research.

Anthropogenically derived nitrogen (N) has a central role in global environmental changes, including climate change, biodiversity loss, air pollution, greenhouse gas emission, water pollution, as well as food production and human health. Current understanding of the biogeochemical processes that govern the N cycle in coupled human-ecological systems around the globe is drawn largely from the long-term ecological monitoring and experimental studies. Here, we review spatial and temporal patterns and trends in reactive N emissions, and the interactions between N and other important elements that dictate their delivery from terrestrial to aquatic ecosystems, and the impacts of N on biodiversity and human society.

Differences between height- and light-dependent changes in shoot traits in five deciduous tree species.

The effects of tree height on shoot traits may in some cases differ in magnitude and direction from the effects of light. Nevertheless, general patterns of change in shoot traits in relation to variations in height and light have not so far been revealed. A comprehensive analysis of the differences between the effects of height and light on a range of leaf and shoot traits is important for the scaling of these traits to individual trees.

Nematomorph parasites indirectly alter the food web and ecosystem function of streams through behavioural manipulation of their cricket hosts.

Nematomorph parasites manipulate crickets to enter streams where the parasites reproduce. These manipulated crickets become a substantial food subsidy for stream fishes. We used a field experiment to investigate how this subsidy affects the stream community and ecosystem function.

Separate estimation of N export into baseline N leakage without disturbance and N loss due to insect defoliation in a pine forest watershed in central Japan.

Pine wilt disease (PWD) is caused by a non-native pest that has spread extensively throughout Japan. Previous research has indicated that most infected trees have died and the litter deposited has resulted in changes to stream-water chemistry, particularly increased nitrate (NO(3)(-)) concentrations. In this study, we divided stream nitrogen (N) export into N loss due to PWD and baseline N leakage without disturbance based on long-term monitoring.

Foliage nitrogen turnover: differences among nitrogen absorbed at different times by Quercus serrata saplings.

Background And Aims: Nitrogen turnover within plants has been intensively studied to better understand nitrogen use strategies. However, differences among the nitrogen absorbed at different times are not completely understood and the fate of nitrogen absorbed during winter is largely uncharacterized. In the present study, nitrogen absorbed at different times of the year (growing season, winter and previous growing season) was traced, and the within-leaf nitrogen turnover of a temperate deciduous oak Quercus serrata was investigated.

Allocation of nitrogen within the crown during leaf expansion in Quercus serrata saplings.

Early season leaf growth requires a large amount of nitrogen, and the amount of N provided for new leaf development has been well tested. Although shoot position within the crown strongly influences leaf properties, little is known about absorbed and remobilized nitrogen allocation in the tree crown. Thus, we investigated differences in the allocation of recently absorbed nitrogen in the tree crown.

Shoot development and extension of Quercus serrata saplings in response to insect damage and nutrient conditions.

Background And Aims: Plants have the ability to compensate for damage caused by herbivores. This is important to plant growth, because a plant cannot always avoid damage, even if it has developed defence mechanisms against herbivores. In previous work, we elucidated the herbivory-induced compensatory response of Quercus (at both the individual shoot and whole sapling levels) in both low- and high-nutrient conditions throughout one growing season.

Soil functional responses to excess nitrogen inputs at global scale.

There is little evidence that nitrogen (N) cycling in the highly weathered, low-phosphorus (P), acidic soils found in Southern Hemisphere continents will differ greatly from that in North America and Europe. Evidence from the 'south' shows: the similarity in forms and temporal patterns in losses of N from different land uses; that the C:N ratios of the forest floor/litter layer from different continents are strongly predictive of a range of processes on a global scale; that generalizations based on Northern Hemisphere experience of the impact of N additions to 'P-limited' ecosystems are likely to fail for southern ecosystems where anatomical and physiological adaptation of native plants to low-P soils makes questionable the concept of 'P-limitation'; that the greatest threats in the 'south' are probably changes in land use that may greatly increase N inputs and turnover; that localized increases in N inputs produce similar effects to those seen in the 'north'.

Effects of NO3- availability on NO3- use in seedlings of three woody shrub species.

We determined the effects of short-term cultivation with various amounts of available nitrate nitrogen (NO3-) on NO3- use by woody shrub species. Nitrate concentration ([NO3-]) and nitrate reductase activity (NRA) were measured in leaves and roots of seedlings of Hydrangea hirta (Thunb.) Siebold, Lindera triloba (Sieb.