Alhagi sparsifolia Shap. （Fabaceae） is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the dis- t...Alhagi sparsifolia Shap. （Fabaceae） is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the dis- tribution of one-year-old A. sparsifolia seedlings to different groundwater depths in controlled plots. The eco- logical adaptability of the root systems of A. sparsifolia seedlings was examined using the artificial digging method. Results showed that： （1） A. sparsifolia seedlings adapted to an increase in groundwater depth mainly through increasing the penetration depth and growth rate of vertical roots. The vertical roots grew rapidly when soil moisture content reached 3%-9%, but slowly when soil moisture content was 13%-20%. The vertical roots stopped growing when soil moisture content reached 30% （the critical soil moisture point）. （2） The morphological plasticity of roots is an important strategy used by A. sparsifolia seedlings to obtain water and adapt to dry soil conditions. When the groundwater table was shallow, horizontal roots quickly expanded and tillering increased in order to compete for light resources, whereas when the groundwater table was deeper, vertical roots developed quickly to exploit space in the deeper soil layers. （3） The decrease in groundwater depth was probably respon- sible for the root distribution in the shallow soil layers. Root biomass and surface area both decreased with soil depth. One strategy of A. sparsifolia seedlings in dealing with the increase in groundwater depth is to increase root biomass in the deep soil layers. The relationship between the root growth/distribution of A. sparsifolia and the depth of groundwater table can be used as guidance for harvesting A. sparsifolia biomass and managing water resources for forage grasses. It is also of ecological significance as it reveals how desert plants adapt to arid environments.展开更多
轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能...轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能演变的空间分布特征和结构特征,最后使用XGBoost-SHAP机器学习模型探讨了其驱动因素以及它们之间的交互效应。研究表明:从时间维度上看,2012—2023年间站点功能信息熵总体呈现波动下降趋势。从空间维度上看,二环内变化型站点居多,二环至五环相对稳定,五环至六环站点变化明显,整体站点功能动态不稳定,变化型站点占比高达76%。从结构维度上看,站点功能构成经历了明显的变化,商服型和交通型站点增长,居住型、产业型及公共型站点减少或波动下降。从驱动因素上看,站点范围内的POI(point of interest)数量、路网密度和生产总值等是影响北京地铁站点功能混合度水平的主导因素,且各个主导因素之间存在交互效应。本文研究结果对于改善地铁站点周边土地的使用效率和增强站点的活力具有重要意义。展开更多
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-EW-316)the National Natural Science Foundation of China (31070477,30870471)the West Light Foundation of the Chinese Academy of Sciences (XBBS201105)
文摘Alhagi sparsifolia Shap. （Fabaceae） is a spiny, perennial herb. The species grows in the salinized, arid regions in North China. This study investigated the response characteristics of the root growth and the dis- tribution of one-year-old A. sparsifolia seedlings to different groundwater depths in controlled plots. The eco- logical adaptability of the root systems of A. sparsifolia seedlings was examined using the artificial digging method. Results showed that： （1） A. sparsifolia seedlings adapted to an increase in groundwater depth mainly through increasing the penetration depth and growth rate of vertical roots. The vertical roots grew rapidly when soil moisture content reached 3%-9%, but slowly when soil moisture content was 13%-20%. The vertical roots stopped growing when soil moisture content reached 30% （the critical soil moisture point）. （2） The morphological plasticity of roots is an important strategy used by A. sparsifolia seedlings to obtain water and adapt to dry soil conditions. When the groundwater table was shallow, horizontal roots quickly expanded and tillering increased in order to compete for light resources, whereas when the groundwater table was deeper, vertical roots developed quickly to exploit space in the deeper soil layers. （3） The decrease in groundwater depth was probably respon- sible for the root distribution in the shallow soil layers. Root biomass and surface area both decreased with soil depth. One strategy of A. sparsifolia seedlings in dealing with the increase in groundwater depth is to increase root biomass in the deep soil layers. The relationship between the root growth/distribution of A. sparsifolia and the depth of groundwater table can be used as guidance for harvesting A. sparsifolia biomass and managing water resources for forage grasses. It is also of ecological significance as it reveals how desert plants adapt to arid environments.
文摘轨道交通站点的功能综合反映了城市土地利用状况和城市空间活力。轨道交通站点与城市用地的和谐发展,对于优化城市交通、提升土地使用效率具有显著的正面影响。首先运用信息熵测算站点功能多样性,进一步运用优势度与均匀度探究站点功能演变的空间分布特征和结构特征,最后使用XGBoost-SHAP机器学习模型探讨了其驱动因素以及它们之间的交互效应。研究表明:从时间维度上看,2012—2023年间站点功能信息熵总体呈现波动下降趋势。从空间维度上看,二环内变化型站点居多,二环至五环相对稳定,五环至六环站点变化明显,整体站点功能动态不稳定,变化型站点占比高达76%。从结构维度上看,站点功能构成经历了明显的变化,商服型和交通型站点增长,居住型、产业型及公共型站点减少或波动下降。从驱动因素上看,站点范围内的POI(point of interest)数量、路网密度和生产总值等是影响北京地铁站点功能混合度水平的主导因素,且各个主导因素之间存在交互效应。本文研究结果对于改善地铁站点周边土地的使用效率和增强站点的活力具有重要意义。
