本文提出了一种基于虚拟网格划分的拥塞控制和能量平衡路由协议(congestion control and energy balance,CCEB),该协议利用多主节点、多路径地选取和更新方法,有效地均衡了网络能耗,延长了网络生命周期.在路径选择过程中,该协议综合考...本文提出了一种基于虚拟网格划分的拥塞控制和能量平衡路由协议(congestion control and energy balance,CCEB),该协议利用多主节点、多路径地选取和更新方法,有效地均衡了网络能耗,延长了网络生命周期.在路径选择过程中,该协议综合考虑了下一跳节点的剩余能量、队列占有率以及前向度量指标,使靠近Sink节点的网格内拥有更多的转发主节点.在数据转发阶段,利用预测的方法对各节点进行拥塞检测和能量判断,避免使用发生拥塞或者剩余能量较少的节点转发数据.最后,通过NS2仿真平台实验,验证了CCEB协议在均衡能耗和缓解拥塞方面的有效性.展开更多
Alpine treeline ecotones are harsh environment for tree establishment due to low temperature. Tree establishment at treelines requires favorable climate, suitable microsites, and viable seeds. But most researches have...Alpine treeline ecotones are harsh environment for tree establishment due to low temperature. Tree establishment at treelines requires favorable climate, suitable microsites, and viable seeds. But most researches have been addressed treeline microclimate and its effects on tree regeneration, the knowledge of seed quantity and quality and its controls on seedling recruitment were limited. We measured seed rain, soil seed bank, seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var. smithii （smith fir） along altitudinal gradient, with focus on treeline ecotone in the Sygera Mountains, southeastern Tibetan Plateau. Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate. Seed quantity and seedling recruitment were better in north-facing slope than in south slope. The treeline ecotone above 42oo m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment. The emergence and overwintering rates of transplanting seeds from 3600-38oo m also went down remarkably above 4200 m at north-facing slope. It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment. Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance. This study also provides evidence to support stable treeline position in southeastern Tibetan Plateau.展开更多
文摘本文提出了一种基于虚拟网格划分的拥塞控制和能量平衡路由协议(congestion control and energy balance,CCEB),该协议利用多主节点、多路径地选取和更新方法,有效地均衡了网络能耗,延长了网络生命周期.在路径选择过程中,该协议综合考虑了下一跳节点的剩余能量、队列占有率以及前向度量指标,使靠近Sink节点的网格内拥有更多的转发主节点.在数据转发阶段,利用预测的方法对各节点进行拥塞检测和能量判断,避免使用发生拥塞或者剩余能量较少的节点转发数据.最后,通过NS2仿真平台实验,验证了CCEB协议在均衡能耗和缓解拥塞方面的有效性.
基金supported by the foundations of Special Research Program for Public-welfare Forestry(Grant No.200804001)Tibet Plateau Ecological Safety Barrier Monitor Evaluation Method and Technology Research(Grant No.KZCX2-XB3-08)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA05090311)
文摘Alpine treeline ecotones are harsh environment for tree establishment due to low temperature. Tree establishment at treelines requires favorable climate, suitable microsites, and viable seeds. But most researches have been addressed treeline microclimate and its effects on tree regeneration, the knowledge of seed quantity and quality and its controls on seedling recruitment were limited. We measured seed rain, soil seed bank, seed germination rate and seedling recruitment in natural forests in combination with seed transplanting manipulation to evaluate the controls of seed quantity and quality on seedling recruitment of Abies georgei var. smithii （smith fir） along altitudinal gradient, with focus on treeline ecotone in the Sygera Mountains, southeastern Tibetan Plateau. Both seed quantity and seed quality of smith fir decreased with increasing altitude and was thereby associated with decline in seed germination rate. Seed quantity and seedling recruitment were better in north-facing slope than in south slope. The treeline ecotone above 42oo m appeared as the threshold altitude to sharply decrease seed quality and seedling recruitment. The emergence and overwintering rates of transplanting seeds from 3600-38oo m also went down remarkably above 4200 m at north-facing slope. It also underpins the fact that treeline ecotone is the bottleneck of seedling recruitment. Our results suggest that seed quantity and quality are the principal limitation of treeline upward advance. This study also provides evidence to support stable treeline position in southeastern Tibetan Plateau.
