Search

1. Diverse aquatic environments in floodplains support high biodiversity, including plankton, benthos, nekton (fish), and amphibians. Variation in aquatic communities among waterbodies should be explained not only by the spatial variation in the environment at low flow but also by the hydrological dynamics and biological responses over flood and recession periods. However, very few studies have examined the formation processes of floodplain aquatic communities over flood periods. 2. In this study, we aimed to obtain a mechanistic understanding of the assembly of aquatic communities on a temperate floodplain by conducting intensive fieldwork during and after seasonal flooding. The study was conducted in the Butokamabetsu River catchment in northern Hokkaido, where snowmelt causes annual spring floods. At peak flow, floodwater not only flow through main stream river and the extant side channels, but also flow through some palaeo-side channels, which are usually isolated from the mainstream river and harbour stagnant water. As the floods recede, palaeo-side channels become isolated from the mainstream river and their flow cease, but the timing of the flow cessation varied among palaeo-side channels. We hypothesised that this spatial asynchrony in the timing of flow cessations shapes diverse floodplain aquatic communities. Therefore, we conducted field surveys of four faunal groups (plankton, benthos, nekton [fish], and amphibian) during and after the spring flood in 2019. 3. The post-flood aquatic communities varied spatially, according to the flow at peak flood, the timing of flow cessation, and the flow at low flow. Plankton composition was influenced by the water flow at peak flood, and they were more abundant in waterbodies that were never flushed by floodwaters. Fish composition was also influenced by the water flow at peak flood; in particular, salmonids were more abundant in waterbodies that were hydrologically connected to the main stream at peak flood. The presence of amphibian eggs was influenced by the timing of flow cessation; eggs were laid in waterbodies with stagnant water during breeding season. The benthic composition was influenced by flow at low flow. After the flood had receded, these different distribution patterns of the four biological groups led to gradual variation of aquatic communities among waterbodies on a floodplain. 4. Overall, this study showed that hydrological dynamics during flood recession shapes the post-flood aquatic communities, and the spatial variability in the hydrological dynamics and the different responses of the four faunal groups support diverse aquatic communities on a floodplain. Importance of the natural geomorphological complexities, where paleo-side channels with wide range of hydrological connectivity to the river channel co-occur, as well as the natural hydrological dynamics of snowmelt recession, where the flooding discharge gradually decrease over a certain period in spring for floodplain aquatic communities are highlighted., 水の満ち引きが多様な生物の共存を実現 --自然氾濫原において多くの生物の共存を可能とする河川氾濫の役割--. 京都大学プレスリリース. 2021-12-13.

We studied movement of a native salmonid, white-spotted char (Salvelinus leucomaenis), in a 1-km tributary in northern Hokkaido, Japan, in May–July 2018. Based on physical mark–recapture of 501 unique individuals and detection by mobile PIT antenna over monthly intervals, a majority of fish (70%–80%) stayed within 60 m of previously released locations, demonstrating what appeared to be restricted movement patterns. However, fixed PIT antenna data showed that as much as 17% of marked individuals emigrated from the study area during the 2-month study period. Probability of emigration did not depend on where in the 1-km segment individuals had been released, indicating that emigration likely represented long-distance movement. Once emigrants made a decision to emigrate, they left the tributary within 1–3 median days by moving downstream in a unidirectional manner, based on detections at a total of three antenna arrays deployed throughout the tributary. Our multiscale analysis provided strong support for co-existence of short- and long-distance movement patterns, and we conclude that movement data at multiple spatial scales complement each other to characterize population-scale movement.

We report that spin polarization occurs over millimeters in polycrystalline bulk samples of chiral disilicide NbSi$_2$ and TaSi$_2$. As previously demonstrated in the experiments using single crystals of NbSi$_2$ and TaSi$_2$, electrical transport measurements allow detection of direct and inverse signals associated with the chirality-induced spin polarization even in the chiral polycrystals. The spin polarization signals also appear in nonlocal measurements, in which charge current flows only in the area millimeters away from the detection electrode. These data mean that the spin polarization phenomena occur regardless of the presence of crystalline grains in the polycrystals, indicating a robustness and resilience of the chirality-induced spin polarization. On the basis of the experimental data, we found that the sum rule holds for the spin transport signals. A distribution of handedness over the samples was determined on average in the polycrystals. While the mechanism of preserving the spin polarization over millimeters remains to be clarified, the present study may open up prospects of spin control and manipulation over macroscopic length scales using chiral materials., 6 pages, 5 figures

Trees are recognized as a carbon reservoir, and precise and convenient methods for forest biomass estimation are required for adequate carbon management. Airborne light detection and ranging (LiDAR) is considered to be one of the solutions for large-scale forest biomass evaluation. To clarify the relationship between mean canopy height determined by airborne LiDAR and forest timber volume and biomass of cool-temperate forests in northern Hokkaido, Japan, we conducted LiDAR observations covering the total area of the Teshio Experimental Forest (225 km 2 ) of Hokkaido University and compared the results with ground surveys and previous studies. Timber volume and aboveground tree carbon content of the studied forest stands ranged from 101.43 to 480.40 m 3 ha –1 and from 30.78 to 180.54 MgC ha –1 , respectively. The LiDAR mean canopy height explained the variation among stands well (volume: r 2 = 0.80, RMSE = 55.04 m 3 ha –1 ; aboveground tree carbon content: r 2 = 0.78, RMSE = 19.10 MgC ha –1 ) when one simple linear regression equation was used for all types (hardwood, coniferous, and mixed) of forest stands. The determination of a regression equation for each forest type did not improve the prediction power for hardwood (volume: r 2 = 0.84, RMSE = 62.66 m 3 ha –1 ; aboveground tree carbon content: r 2 = 0.76, RMSE = 27.05 MgC ha –1 ) or coniferous forests (volume: r 2 = 0.75, RMSE = 51.07 m 3 ha –1 ; aboveground tree carbon content: r 2 = 0.58, RMSE = 19.00 MgC ha –1 ). Thus, the combined regression equation that includes three forest types appears to be adequate for practical application to large-scale forest biomass estimation.

A mixed forest in northern Japan, which had been a weak carbon sink (net ecosystem CO2 exchange [NEE] = -0.44 +/- 0.5 Mg C ha(-1) yr(-1)), was disturbed by clear-cutting in 2003 and was replaced with a hybrid larch (Larix gmelinii x L. kaempferi) plantation in the same year. To evaluate the impact of the clear-cutting on the ecosystem's carbon budget, we used 10.5 years (2001-2011) of eddy covariance measurements of CO2 fluxes and the biomass observation for each ecosystem component. BIOME-BGC model was applied to simulate the changes in the carbon fluxes and stocks caused by the clear-cutting. After clear-cutting in 2003, the ecosystem abruptly became a large carbon source. The total CO2 emission during the first 3 years after the disturbance (2003-2005) was 12.2 +/- (0.9-1.5; possible min-max range of the error) Mg C ha(-1), yet gradually decreased to 2.5 +/- (1-2) Mg C ha(-1) during the next 4 years. By 2010, the ecosystem had regained its status as a carbon sink (NEE = -0.49 +/- 0.5 Mg C ha(-1) yr(-1)). Total gross primary production, ecosystem respiration, and NEE during the 7 years after the clear-cutting (2003-2009) were 64.5 +/- (2.6-7), 79.2 +/- (2.6-7), and 14.7 +/- (1.3-3.5) Mg C ha(-1), respectively. From 2003 to 2009, the understory Sasa biomass increased by 16.3 +/- 4.8 Mg C ha(-1), whereas the newly planted larch only gained 1.00 +/- 0.02 Mg C ha(-1). The BIOME-BGC simulated observed carbon fluxes and stocks, although further modification on the parameter set may be needed according with the tree growth and corresponding suppression of Sasa growth. Ecosystem carbon budget evaluation and the model simulation suggested that the litter including harvest residues became a large carbon emitter (similar to 31.9 Mg C ha(-1)) during the same period. Based on the cumulative NEE during the period when the forest was a net carbon source, we estimate that the ecosystem will require another 8-34 years to fully recover all of the CO2 that was emitted after the clear-cutting, if off-site carbon storage in forest products is not considered. (C) 2014 Elsevier B.V. All rights reserved.

We report long-term continuous phenological and sky images taken by time-lapse cameras through the Phenological Eyes Network ( http://www.pheno-eye.org . Accessed 29 May 2018) in various ecosystems from the Arctic to the tropics. Phenological images are useful in recording the year-to-year variability in the timing of flowering, leaf-flush, leaf-coloring, and leaf-fall and detecting the characteristics of phenological patterns and timing sensitivity among species and ecosystems. They can also help interpret variations in carbon, water, and heat cycling in terrestrial ecosystems, and be used to obtain ground-truth data for the validation of satellite-observed products. Sky images are useful in continuously recording atmospheric conditions and obtaining ground-truth data for the validation of cloud contamination and atmospheric noise present in satellite remote-sensing data. We have taken sky, forest canopy, forest floor, and shoot images of a range of tree species and landscapes, using time-lapse cameras installed on forest floors, towers, and rooftops. In total, 84 time-lapse cameras at 29 sites have taken 8 million images since 1999. Our images provide (1) long-term, continuous detailed records of plant phenology that are more quantitative than in situ visual phenological observations of index trees; (2) basic information to explain the responsiveness, vulnerability, and resilience of ecosystem canopies and their functions and services to changes in climate; and (3) ground-truthing for the validation of satellite remote-sensing observations.

Wild edible plants, ecological foodstuffs obtained from forest ecosystems, grow in natural fields, and their productivity depends on their response to harvesting by humans. Addressing exactly how wild edible plants respond to harvesting is critical because this knowledge will provide insights into how to obtain effective and sustainable ecosystem services from these plants. We focused on bamboo shoots of Sasa kurilensis, a popular wild edible plant in Japan. We examined the effects of harvesting on bamboo shoot productivity by conducting an experimental manipulation of bamboo shoot harvesting. Twenty experimental plots were prepared in the Teshio Experimental Forest of Hokkaido University and were assigned into two groups: a harvest treatment, in which newly emerged edible bamboo shoots were harvested (n = 10); and a control treatment, in which bamboo shoots were maintained without harvesting (n = 10). In the first year of harvesting (2013), bamboo shoot productivities were examined twice; i.e., the productivity one day after harvesting and the subsequent post-harvest productivity (2-46 days after harvesting), and we observed no difference in productivity between treatments. This means that there was no difference in original bamboo shoot productivity between treatments, and that harvesting did not influence productivity in the initial year. In contrast, in the following year (2014), the number of bamboo shoots in the harvested plots was 2.4-fold greater than in the control plots. These results indicate that over-compensatory growth occurred in the harvested plots in the year following harvesting. Whereas previous research has emphasized the negative impact of harvesting, this study provides the first experimental evidence that harvesting can enhance the productivity of a wild edible plant. This suggests that exploiting compensatory growth, which really amounts to less of a decline in productivity, may be s a key for the effective use of wild edible plants.

11-mercaptoundecanoic acid (MUA) monolayer and MUA–copper ion–MUA bilayer assembled using thiolate–coppcr ion–carboxylate bridges on MUA monolayer electrode were prepared, and tried to control electron transfer rate of redox ions. The soaking solution to assemble MUA on gold electrode changed from ethanolic MUA solution to 1-butanolic one, then the differential interfacial capacitance decreased from 2.5±0.1 μF cm−2 to 1.6±0.2 μF cm−2, and electron rate constant, k0 of [Co(phen)3]3+ decreased from 20×10−6 cm s−1 to 8.3×10−6 cm s−1. These results show that highly ordered MUA monolayer can be obtained only changing soaking solvent to assemble MUA, Obtained highly ordered MUA monolayer electrode was block off completely redox anion by electrostatic repulsion and MUA film thickness. Moreover using MUA–copper ion–MUA bilayer electrode, k0 of [Co(phen)3]3+ decreased under 1/400 against using MUA monolayer electrode, that value become to under 0.02×10−6 cm s−1. This study shows that the combination of electrode surface charge and length of insulating spacers is able to control electron transfer rate of various electroactive ions.