Relationship between the vertical distribution of fine roots and residual soil nitrogen along a gradient of hardwood mixture in a conifer plantation.

In forest ecosystems, understanding the relationship between the vertical distribution of fine roots and residual soil nitrogen is essential for clarifying the diversity-productivity-water purification relationship. Vertical distributions of fine-root biomass (FRB) and concentrations of nitrate-nitrogen (NO -N) in soil water were investigated in a conifer plantation with three thinning intensities (Control, Weak and Intensive), in which hardwood abundance and diversity were low, moderate and high, respectively. Intensive thinning led to the lowest NO -N concentration in soil water at all depths (0-100 cm) and highest FRB at shallow depths (0-50 cm).

Assessment of the effect of thinning on the resistance of Pinus thunbergii Parlat. trees in mature coastal forests to tsunami fluid forces.

The Great East Japan Tsunami, triggered by the earthquake that occurred on March 11, 2011 in the Pacific Ocean, caused significant fatalities and socioeconomic damage. As recovery of a disaster area requires significant time, all possible mitigation measures must be prepared in advance for future events. As a tsunami countermeasure, coastal forests have been acknowledged to considerably reduce tsunami energy and decrease tsunami-related damage.

Defoliation by Gypsy Moth (Lepidoptera, Erebidae) Induces Differential Delayed Induction of Trichomes in Two Birch Species.

Outbreaks of the gypsy moth (Lymantria dispar japonica Motschulsky) cause serious defoliation in birch. A single year of defoliation has no significant impact on the trees, whereas continuous defoliation events could be fatal. How birch species avoid serious damage caused by gypsy moth outbreak is yet to be revealed.

Conspecific distance-dependent seedling performance, and replacement of conspecific seedlings by heterospecifics in five hardwood, temperate forest species.

The mechanisms driving species diversity in the context of Janzen-Connell model are best understood by evaluating not only conspecific distance-dependent (CDD) seedling performance, but also replacement of conspecific seedlings by heterospecific seedlings beneath adult trees. We evaluated CDD and replacement as a log response ratio of seedling performance (height, age) directly beneath and at a distance from adult plants in a temperate forest, and examined the log response ratio of that between conspecifics and heterospecifics beneath adults for five hardwood species with different ecological traits (e.g.

Influence of planting density and thinning on timber productivity and resistance to wind damage in Japanese larch (Larix kaempferi) forests.

In recent years, forest damage caused by typhoons has occurred frequently in Hokkaido, northern Japan. According to predictive reports, a typhoon's intensity increases and it then maintains its intensity as it moves north. The relationship between this prediction and forest damage is not clear, but the importance of dealing with forest damage is increasing.

Leaf diseases drive the Janzen-Connell mechanism regardless of light conditions: a 3-year field study.

In forests, negative density/distance-dependent seedling mortality (NDD) caused by natural enemies plays a key role in maintaining species diversity [Janzen-Connell (J-C) model]. However, the relative importance of natural enemies in mediating NDD under heterogeneous light conditions has remained unclear. We examined the relative importance of pathogens (i.

Floral sex allocation at individual and branch levels in Betula platyphylla var. japonica (Betulaceae), a tall, wind-pollinated monoecious tree species.

Floral sex allocation at the individual and first-order branch levels and the relation between these levels were examined in Betula platyphylla var. japonica, a wind-pollinated monoecious tree. Floral sex allocation at the individual level varied with resource availability in a pattern similar to that predicted by the Masaka and Takada model (Journal of Theoretical Biology 240: 114-125).

Floral sex ratio strategy in wind-pollinated monoecious species subject to wind-pollination efficiency and competitive sharing among male flowers as a game.

To explain the floral sex ratio strategy in wind-pollinated monoecious species, we developed four models with special reference to wind-pollination efficiency (WPE) and competitive sharing among male flowers (CSM). WPE is a function that follows a Poisson distribution and explains the frequency of seeds fertilized by an individual via wind-pollination, whereas CSM is defined by the sharing of female flowers among male flowers within the local breeding population. We argued the applicability of the results to the actual tendencies observed in wind-pollinated monoecious species and found that a game model with WPE and CSM was the most applicable.