共查询到20条相似文献，搜索用时 187 毫秒
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对永春县高海拔山地9年生柳杉×木荷混交林补植火炬松、马尾松4年后的生长数据进行调查,结果表明:4年生火炬松的地径生长与13年生柳杉已无显著差异,树高已显著高于13年生柳杉,远大于木荷,与马尾松相比,同林龄火炬松的树高和地径生长均显著大于马尾松。补植造林后,林分蓄积量得到了显著提高。可见,在高海拔特殊立地条件下,火炬松可用来作为快速绿化的先锋树种,造林成效显著。 相似文献
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利用FNL再分析资料、卫星资料和自动站资料对2019年7月22~23日京津冀一次区域性暴雨过程进行了环流形势、卫星云图、动热力结构的分析。结果表明:此次暴雨发生在500hPa两槽一脊、副热带高压北抬、低空急流的大尺度环流背景下。西南方向的水汽输送和黄渤海的补充水汽为暴雨提供了良好的水汽条件,在河北中部的水汽辐合抬升则为暴雨提供了抬升条件。此次暴雨的产生受中尺度对流云团的连续生成合并影响,降水效率高。在暴雨中心整层表现为低层辐合、高层辐散,上升速度中心明显,使得高层的抽吸作用更强,更有利于上升运动的维持与发展,为降水强度增大提供了有力的动力条件,高空弱冷空气的入侵对能量锋区不稳定能量的释放起到了触发作用。 相似文献
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《Scandinavian Journal of Forest Research》2012,27(1-4):381-395
Eleven 27 to 29‐year‐old Scots pine provenance trials were studied in areas 400 m or less below timberline in northern Sweden. Functions describing geographic variation in the local provenance showed that survival as well as height and volume growth decreased with increasing latitude and elevation. Survival decreased by 7% per degree increase in latitude and 16% per 100 m increase in elevation. Beeting increased the survival by on average 2.4%, but less at high latitudes and altitudes. Tree height and volume per hectare decreased by 0.8 m and 15 m3, respectively, per degree increase in latitude and by 1.3 m and 24 m3, respectively, per 100 m increase in elevation. Transfer functions for provenances at different sites showed that the effect of latitudinal transfer on survival was reduced close to timberline. On average, a southward transfer of one latitudinal degree increased survival by about 7%, which is lower than in previous studies. No altitudinal transfer effects on survival were detected. Volume/ha was increased by southward transfer in northern parts of the area. Spacing had only a slight effect on performance and did not influence the functions presented. 相似文献
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介绍了我国高原湿地资源及其保护管理的现状,指出了高原湿地所具有的重大生态功能和面临的主要威胁及其变化,提出了加强高原湿地保护管理的对策和建议。 相似文献
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