Analysis of spatial and temporal changes of regional ecological pattern in the northwest of Jingjinji as water conservation area during the past 30 years

• ZHU Zijuan, 
• ZUO Lijun, 
• ZHANG Zengxiang, 
• WANG Yafei, 
• SUN Feifei, 
• PAN Tianshi, 
• ZHAO Xiaoli, 
• WANG Xiao