A study was conducted to determine the influences of initial planting densities, thinning intensities, exposures and slope sites on physical property （wood density） and mechanical properties such as modulus of elast...A study was conducted to determine the influences of initial planting densities, thinning intensities, exposures and slope sites on physical property （wood density） and mechanical properties such as modulus of elasticity （MOE）, bending strength, impact strength, compression strength along grain and hardness） of Pinus sylvestris var. mongolica plantation in Mao＇ershan Forest Farm, Northeast China. Results show that the different initial planting densities （1.5 m×1.0 m, 1.5 m×2.0 m and 1.5 m×2.5 m） had significant effects on wood density and MOE, and the highest mean wood density and indexes of mechanical properties occurred in the stand with an initial planting density of 1.5 m×1.0 m. The indexes of mechanical properties such as hardness of end, bending strength, MOE and compression strength along grain of wood increased after mild thinning, but decreased after violent thinning. The exposures （sunny slope and shady slope） had a significant effect on MOE, and the highest mean MOE occurred on sunny slope. The slope sites （upper site and lower site） had a significant effect on wood density and main mechanical properties, except hardness. The highest mean wood density and mechanical properties occurred at lower site.展开更多
In order to examine the causes of degradation of Pinus sylvestris var. mongolica plantations on sandy land, the foliar concentrations of N, P, K and C were analyzed and compared between the field grown P. sylvestris v...In order to examine the causes of degradation of Pinus sylvestris var. mongolica plantations on sandy land, the foliar concentrations of N, P, K and C were analyzed and compared between the field grown P. sylvestris var. mongolica trees from two provenances （natural forests and plantations）. The results indicated that natural tree needles had lower N, P and C concentrations, and higher K concentrations than those of plantation tree needles. For plantation tree needles, ratios of N： P, P. K and N： K increased with tree age before 45 years old; but they were not clear for the natural tree needles. Compared with the conclusions reported on Pinus spp., we found that the foliar N and P concentrations were in the optimal range for both natural and plantation tree needles. This result suggested that N or P might not be the absolute limit factors in plant nutrient for P sylvestris var. mongolica on sandy land. However, foliar K concentrations in both natural and plantation tree needles were much lower than those reported on Pinus spp. （〉4.80 g kg-1）.The N： P ratio of natural needles was in the adequate ranges, but N： P ratio of plantation needles was out of the adequate ranges. These results indicated that there was a better balanced nutrition status in the natural forest than in the plantations. If only considering the foliar nutrient concentrations of P sylvestris var. mongolica from different provenances, it might be concluded that the degradation phenomenon of P. sylvestris var. mongolica plantations was not induced by nutrition deficiency of absolute nutrients of N and P, but might be induced by other mineral nutrients or by the effectiveness of N and P nutrients. The unbalanced nutrition status and relatively quick decomposition of needles in the plantations might also contribute to the degradation.展开更多
基金This study was supported by National Natural Science Foundation of China (30471355) and the Key Technologies R&D Program of Heilongjiang Province (G99B5-3)
文摘A study was conducted to determine the influences of initial planting densities, thinning intensities, exposures and slope sites on physical property （wood density） and mechanical properties such as modulus of elasticity （MOE）, bending strength, impact strength, compression strength along grain and hardness） of Pinus sylvestris var. mongolica plantation in Mao＇ershan Forest Farm, Northeast China. Results show that the different initial planting densities （1.5 m×1.0 m, 1.5 m×2.0 m and 1.5 m×2.5 m） had significant effects on wood density and MOE, and the highest mean wood density and indexes of mechanical properties occurred in the stand with an initial planting density of 1.5 m×1.0 m. The indexes of mechanical properties such as hardness of end, bending strength, MOE and compression strength along grain of wood increased after mild thinning, but decreased after violent thinning. The exposures （sunny slope and shady slope） had a significant effect on MOE, and the highest mean MOE occurred on sunny slope. The slope sites （upper site and lower site） had a significant effect on wood density and main mechanical properties, except hardness. The highest mean wood density and mechanical properties occurred at lower site.
基金The research was supported by Innovation Research Project of Chinese Academy of Sciences (KZCX3-SW-418), and the 100 Young Researcher Project of Chinese Academy of Sciences.
文摘In order to examine the causes of degradation of Pinus sylvestris var. mongolica plantations on sandy land, the foliar concentrations of N, P, K and C were analyzed and compared between the field grown P. sylvestris var. mongolica trees from two provenances （natural forests and plantations）. The results indicated that natural tree needles had lower N, P and C concentrations, and higher K concentrations than those of plantation tree needles. For plantation tree needles, ratios of N： P, P. K and N： K increased with tree age before 45 years old; but they were not clear for the natural tree needles. Compared with the conclusions reported on Pinus spp., we found that the foliar N and P concentrations were in the optimal range for both natural and plantation tree needles. This result suggested that N or P might not be the absolute limit factors in plant nutrient for P sylvestris var. mongolica on sandy land. However, foliar K concentrations in both natural and plantation tree needles were much lower than those reported on Pinus spp. （〉4.80 g kg-1）.The N： P ratio of natural needles was in the adequate ranges, but N： P ratio of plantation needles was out of the adequate ranges. These results indicated that there was a better balanced nutrition status in the natural forest than in the plantations. If only considering the foliar nutrient concentrations of P sylvestris var. mongolica from different provenances, it might be concluded that the degradation phenomenon of P. sylvestris var. mongolica plantations was not induced by nutrition deficiency of absolute nutrients of N and P, but might be induced by other mineral nutrients or by the effectiveness of N and P nutrients. The unbalanced nutrition status and relatively quick decomposition of needles in the plantations might also contribute to the degradation.
