ABSTRACT
Introduction: As a renewable forest resource, bamboo plays a role in sustainable forest development. However, traditional cutting systems, selection cutting (SeC) and clear-cutting (ClC), result in an unsustainable production of bamboo forests due to labor-consuming or bamboo degradation. Recently, a strip clear-cutting (StC) was theoretically proposed to promote the sustainability of bamboo production, while little is known about its application consequence. Methods: Based on a 6-year experiment, we applied the strip clear-cutting system in a typical running bamboo (Phyllostachys glauca McClure) forest to assess its feasibility and sustainability. Using SeC and ClC as controls, we set three treatments with different strip widths (5 m, 10 m, and 20 m) for strip clear-cutting, simplified as StC-5, StC-10, and StC-20, respectively. Then, we investigated leaf physiological traits, bamboo size and productivity, population features, and economic benefits for all treatments. Results: The stands managed by StC had high eco-physiological activities, such as net photosynthetic rate (P n), photosynthetic nitrogen use efficiency (PNUE), and photosynthetic phosphorus use efficiency (PPUE), and thus grew well, achieved a large diameter at breast height (DBH), and were tall. The stand biomass of StC (8.78 t hm-2 year-1) was 1.19-fold and 1.49-fold greater than that of SeC and ClC, respectively, and StC-10 and StC-20 were significantly higher than SeC or ClC (p< 0.05). The income and profit increased with the increase in stand density and biomass, and StC-20 and StC-10 were significantly higher than SeC or ClC (p< 0.05). Using principal components analysis and subordinate function analysis, we constructed a composite index to indicate the sustainability of bamboo forests. For the sustainability assessment, StC-10 had the highest productive sustainability (0.59 ± 0.06) and the second highest economic sustainability (0.59 ± 0.11) in all cutting treatments. StC-10 had the maximum overall sustainability, with a value of 0.53 ± 0.02, which was significantly higher than that of ClC (p< 0.05). Conclusion: The results verified that StC for Phyllostachys glauca forests is feasible and sustainable as its sustainability index outweighs those of traditional cutting systems (SeC and ClC), and 10 m is the optimum distance for the strip width of StC. Our findings provide a new cutting system for managing other running bamboo forests sustainably.
ABSTRACT
Graphenes were prepared via micromechanical cleavage of natural graphite flakes and transferred onto a silicon wafers with a 285 nm SiO2 thick film on the surface. Nickel was used as the electrodes to study the magnetoresistance of graphenes devices at room temperature. We find that the magnetoresistances of graphenes shows positive sign while the magnetoresistances of pure nickel have negative sign at the same external magnetic field when a Z-direction magnetic field (0.24 T, graphenes on the X-Y plane) is applied. The magnitude of magnetoresistance of graphenes is about +0.20% and 5 times larger than that of the same thickenss pure nickel film. When the magnetic field is along the X-direction (-0.26 T, perpendicular to Y-direction current), the magnetoresistance of graphenes and nickel film both have negative sign and value of -0.04% and -0.03%, respectively. The magnetoresistance of graphenes and nickel film both have positive sign and value of +0.09% and +0.04%, when the magnetic field is along the Y-direction (-0.24 T, parallel to Y-direction current), respectively. The mechanism of these observations is attributed to the edge ferromagnetism of graphenes. Our work shows that grapheses may play an important role in spin device operated at room temperature.
