Landscape Dynamics And Its’ Imp-acts On The Habitat Of Black-necke D Crane In Napa Wetland In The L-ast Two Decades

The research of landscape pattern change is the important way which could recognize the ecosystem process and understand ecosystem changing mechanism of wetland. Napa Wetlands is the most representative of seasonal plateau lake-ma rsh. Also, Napa Wetlands is one of the important wintering habitats of black-nec ked crane. So, to carry out the study of landscape pattern change and to assess black-necked crane habitat quality would be necessary. In this paper, by interpreti ng the three TM/ETM+remote sensing images in1995,2005and2014with the ENVI and ArcGIS platform supporting, the landscape status and their changes were analyzed, the driving factors were researched, and also the habitat quality o f black-necked crane was assessed. The results show that:1. According to the landscape patch area,the landscape of the research location changed significantly. The natural wetlands declined substantially, such as the open standing water and marsh-wet meadow, and the area of non-wetland landscape increased significantly, such as the mesophytic meadow, construction land and bare land. From1995to2005,the area of open standing water decreased263.82hm2and dropped24.48percent, the area of marsh-wet meadow decreased14.29hm2and dropped1.60percent. From2005to2014,the area of open standing water decreased422.22hm2and dropped52.90percent, the area of marsh-wet meadow decreased359.15hm2and dropped40.78percent. From1995to2014,the area of open standing water dropped64.60percent, the area of marsh-wet meadow dropped41.73percent.The loss area of natural wetlands from1995to2005was smaller than the size of the loss from2005to2014, and the loss of natural wetlands was significantly slower than the rate from2005to2014.2.According to the landscape pattern index, the number of patches increaesd, the mean area of patches decreased, the mean distance between the patches redu-ced, which indicated that the landscape fragmentation was increased from1995t-o2005. From2005to2014, the number of patches decreased, the mean area of patches increased, which indicated that the landscape fragmentation was decrease -d with time. The previous period the main evolution mode is the landscape frag-mentation, after the period of time landscape patches changed into each other th-at became the main evolution mode.3.The main factors of landscape pattern change of Napa wetland was human disturbance activities which included the national and local policies of wetlands reclamation and the unreasonable wetland developments of the local residents. I-n recent years, human activities that had impacted on the landscape pattern of N-apa wetland more significantly including:the highway construction, the alteration of wetland’s sinkholes and the grazing activities of local residents.Moreover, the climate of Napa wetland became more warm and more dry than before in the global warming trend. The combined effects of climate changes and human activi ties had aggravated the reverse succession process of Napa wetland.4.According to field investigation and literature,the main habitat factors of bl-ack-necked crane were human-caused disturbance,food and water conditions.The habitat quality evaluation model was built based on the three major habitat facto-rs. According to the result of the habitat assessment, the area of suitable habitat and second suitable habitat of the black-necked crane reduced on a large area,th-e area of unsuitable habitat and second unsuitable habitat increased on a large a-rea.The habitat fragmention is significant,the suitable habitat distributed continuo-usly had changed into concentrated ditributed in the north of the study area.Finally,the protection measures of Napa wetland and black-necked crane habi tat were proposed according to the analysis of landscape change and the results of habitat quality evaluation.