北洛河流域植物多样性地理格局与环境关系

通过野外调查和历史文献及标本统计分析，确定并分析北洛河流域种子植物信息数据.结果表明：该区共有种子植物123科581属1671种，占黄土高原种子植物的83.67%、67.24%、51.83%，集中分布于大型科（>50种）、较大科（21~50种）和单种属（1种）、小型属（2~5种）内.11个干流流经的地理单元植物相似性聚类分为5组，较早分离的是黄龙县，最大类因子午岭山脉连接而包含4个地理单元（富县、合水县、宜君县、黄陵县）.富县、合水县和黄龙县植物丰富度SD值最高，洛川县、华池县和甘泉县SD值最低.该区地理成分在属级水平上有15个分布区类型16个变型，以温带分布及其变型为主（287属，占49.40%），并与热带分布及其变型联系紧密（115属，占19.79%），植物丰富度SD值与温带成分显著正相关；黄陵县、洛川县、黄龙县R/T值最高，热带性质最强，华池县、定边县R/T值最低，热带性质最弱.R/T值受海拔影响，随温度和降水从东南向西北递减.该区植物起源古老，分化程度高，物种多样性丰富，地理成分复杂，是重要的植物种质资源库.植物物种多样性地带性格局过渡性明显，体现出这些类群的生态位需求.需加强保护该区原生环境和植物，合理开发利用，可选择6大优势科（菊科、禾本科、蔷薇科、豆科、唇形科和毛茛科）中适地适树适草的物种（温带性质），进行植被恢复和水土流失治理.

Relationship between geographical pattern of plant diversity and environmental factors in Beiluo River Basin

The diversity of seed plants in Beiluo River Basin was identified through field investigation and statistical analysis of historical documents. Result:There were 1671 species of seed plants belonging to 581genera and 123 families in this area, accounting for 83.67%, 67.24% and 51.83% of the total seed plants in the Loess Plateau. of all the detected 1671 species, the majority (>65%) belonged to large (>50 species) and larger family (21~50 species), and more than half (~56%) belonged to single species genus and small genus (2~5 species). According to cluster analysis of the plant similarity for the 11main streams, 5groups were obtained, with Huanglong County as the firstly separated category, and the largest category including four geographical units, i.e. Fu County, Heshui County, Yijun County and Huangling County, which were all affected by the connection of Ziwuling mountains. The SD values of floristic richness of Fu County, Heshui County and Huanglong County were highest, while those of Luochuan County, Huachi County and Ganquan County were the lowest. There were 15 areal types and 16forms of geographical elements at the genus level in this area, which were dominated by the temperate distribution and its forms (287genera, accounting for 49.40%) and closely related to the tropical distribution and its forms (115 genera, accounting for 19.79%). There was a significant positive correlation between SD value of plant richness and temperate components. Huangling County, Luochuan County and Huanglong County had the highest R/T value and the strongest tropical property, while Huachi County and Dingbian County had the lowest R/T value and the weakest tropical property. The R/T value was affected by altitude and had a similar distribution pattern with temperature and precipitation decreasing from the southeast to the northwest. It is concluded that the plants in this area are important plant germplasm resources, because they have an ancient origin, a high degree of differentiation, rich species diversity and complex geographical elements. The transition pattern of plant species diversity zone is significant, which reflects the niche demands of these groups. Species of the six dominant families (Asteraceae, Poaceae, Rosaceae, Fabaceae, Lamiaceae and Ranunculaceae) that are suitable for the land and trees and grasses (temperate in nature) can be selected for vegetation restoration and soil erosion control.