Effects of understory dwarf bamboo on soil water and the growth of overstory trees in a dense secondary Betula ermanii forest, northern Japan

The original publication is available at www.springerlink.comArticleECOLOGICAL RESEARCH. 18(6):767-774(2003)journal articl

Memet Fuat, Piraye ve Nazım

Taha Toros Arşivi, Dosya Adı: Nazım Hikmetİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033

The effect of population density on shoot morphology of herbs in relation to light capture by leaves

Plants change their shapes, depending on their environment, for example, plant height increases with increasing population density. We examined the density-dependent plasticity in shoot morphology of herbs by analysing a mathematical model which identifies a number of key factors that influence shoot morphology, namely (i) solar radiation captured by leaves; (ii) shading from neighbouring plants; and (iii) utilisation efficiency of resource by leaves, stems and veins. An optimisation theory was used to obtain optimal shoot morphology in relation to maximal light capture by leaves, under trade-offs of resource partition among organs. We first evaluated the solar radiation flux per unit leaf area per day for different shoot forms. Our model predicts that the optimal internodal length of the stem that brings about the maximal light capture by leaves increases with plant population density, and this is consistent with experimental data. Moreover, our simple model can also be extended to explain the morphological plasticity in other herbs (i.e. stemless plants) that are different from our model plants with a stem. These findings illustrate how optimisation theory can be used for the analysis of plasticity in shoot morphology of plants in response to environmental changes, as well as the analysis of diversity in morphology

Nap1 regulates proper CENP-B binding to nucleosomes

CENP-B is a widely conserved centromeric satellite DNA-binding protein, which specifically binds to a 17-bp DNA sequence known as the CENP-B box. CENP-B functions positively in the de novo assembly of centromeric nucleosomes, containing the centromere-specific histone H3 variant, CENP-A. At the same time, CENP-B also prevents undesired assembly of the CENP-A nucleosome through heterochromatin formation on satellite DNA integrated into ectopic sites. Therefore, improper CENP-B binding to chromosomes could be harmful. However, no CENP-B eviction mechanism has yet been reported. In the present study, we found that human Nap1, an acidic histone chaperone, inhibited the non-specific binding of CENP-B to nucleosomes and apparently stimulated CENP-B binding to its cognate CENP-B box DNA in nucleosomes. In human cells, the CENP-B eviction activity of Nap1 was confirmed in model experiments, in which the CENP-B binding to a human artificial chromosome or an ectopic chromosome locus bearing CENP-B boxes was significantly decreased when Nap1 was tethered near the CENP-B box sequence. In contrast, another acidic histone chaperone, sNASP, did not promote CENP-B eviction in vitro and in vivo and did not stimulate specific CENP-B binding to CENP-A nucleosomes in vitro. We therefore propose a novel mechanism of CENP-B regulation by Nap1

STRUCTURE AND SUCCESSION OF ALPINE PERENNIAL COMMUNITY (POLYGONUM CUSPIDATUM) ON MT. FUJI (Twelfth Symposium on Polar Biology)

Successional process of herbaceous perennial was investigated on the alpine zone of Mt. Fuji. The study site is located at the timberline of the southeast slope where it is mainly covered by various growing types of Polygonum cuspidatum patch. The structure of these patches was studied in relation to the successional stage of the alpine timberline. Measurements of shoot height, density of shoots, biomass above the ground and soil nutrient condition were carried out in patches of various sizes. The biomass of large, medium and small patches was 3400, 970 and 120g, respectively. In the central part of the large patch, a low density and low biomass area (dead center) existed, and where other species have invaded. These various-sized patches play a significant role in the successional process on the alpine zone

Availability and temporal heterogeneity of water supply affect the vertical distribution and mortality of a belowground herbivore and consequently plant growth.

We examined how the volume and temporal heterogeneity of water supply changed the vertical distribution and mortality of a belowground herbivore, and consequently affected plant biomass. Plantago lanceolata (Plantaginaceae) seedlings were grown at one per pot under different combinations of water volume (large or small volume) and heterogeneity (homogeneous water conditions, watered every day; heterogeneous conditions, watered every 4 days) in the presence or absence of a larva of the belowground herbivorous insect, Anomala cuprea (Coleoptera: Scarabaeidae). The larva was confined in different vertical distributions to top feeding zone (top treatment), middle feeding zone (middle treatment), or bottom feeding zone (bottom treatment); alternatively no larva was introduced (control treatment) or larval movement was not confined (free treatment). Three-way interaction between water volume, heterogeneity, and the herbivore significantly affected plant biomass. With a large water volume, plant biomass was lower in free treatment than in control treatment regardless of heterogeneity. Plant biomass in free treatment was as low as in top treatment. With a small water volume and in free treatment, plant biomass was low (similar to that under top treatment) under homogeneous water conditions but high under heterogeneous ones (similar to that under middle or bottom treatment). Therefore, there was little effect of belowground herbivory on plant growth under heterogeneous water conditions. In other watering regimes, herbivores would be distributed in the shallow soil and reduced root biomass. Herbivore mortality was high with homogeneous application of a large volume or heterogeneous application of a small water volume. Under the large water volume, plant biomass was high in pots in which the herbivore had died. Thus, the combinations of water volume and heterogeneity affected plant growth via the change of a belowground herbivore

Vegetation changes between 1978, 1991 and 2003 in the Nakoudojima island that had been disturbed by feral goats

Changes in vegetation of the Nakoudojima island between 1978, 1991 and 2003 were quantified with aerial photographs. The island was divided into 9200 plots (10m×10m) on the aerial photographs and the plots were categorized into forest, grassland, bare ground or others. Percentages of the grassland increased 66.3% to 69.0% and those of the bare ground increased from 7.0% to 15.5% for 23 years. Some grasslands became bare ground between 1978 and 1991, which resulted in a decrease in the area of the grassland and an increase in the area of the bare ground during this period. On the other hand, some bare ground changed to grasslands between 1991 and 2003, which meant an increase of grasslands. These changes in vegetation would be due mainly to grazing and trampling, and their termination caused by feral goats. Percentages of the forest decreased from 16.2% to 6.0% for 23 years. Many forests changed into grasslands or bare ground even after the eradication of feral goats, which suggests that canopy trees in the forest died by natural disturbances in addition to the lack of seedlings by the grazing of feral goats.小笠原諸島媒島にて、23年間の植生の変化を航空写真を用いて定量的に評価した。1978年、1991年、2003年の航空写真から森林、草地、裸地の面積の変化を調べた。この間、媒島の植生は、野生化ヤギによる食害と踏圧およびヤギ排除によるそれらからの開放を経験した。草地が島全体に占める割合は、23年間で66.3%から69.0%に、裸地が占める割合は7.0%から15.5%に増加した。1978年から1991年にかけて、草地の一部が裸地に変化した。その結果、草地の面積は減少し、裸地の面積は増加した。1991年から2003年にかけて、裸地の一部が草地に変化した。その結果、草地の面積は増加し、裸地の面積は減少した。以上の結果は、草地と裸地の変化は、ヤギによる食害、踏圧とそれらからの開放によって引き起こされたことを示唆する。一方で、森林が占める割合は、16.2%から6.0%に23年間で減少した。これは、森林が、野生化ヤギの有無にかかわらず、草地や裸地に変化したことを意味する。以上は、森林の減少は、ヤギの食害による実生の定着の欠如に加え、種子供給源である林冠木の枯死によることを示唆する