Based on Landsat TM images, we explored the pattern of variation of suitable waterbird habitats from 1990 to 2008 in the Dongtan area of Chongming Island at the Changjiang (Yangtze) River mouth. By applying our highly...Based on Landsat TM images, we explored the pattern of variation of suitable waterbird habitats from 1990 to 2008 in the Dongtan area of Chongming Island at the Changjiang (Yangtze) River mouth. By applying our highly accurate indicator model (R=0.999, P<0.01), we quantified the variations of fluctuation intensity for local waterbird habitats during 1990-2008, and for the main waterbird groups (Anatidae, Charadriidae, Ardeidae and Laridae) from 2006 to 2008, to evaluate the impact of habitat quantity change on the waterbird habitat status and the population dynamics of the different waterbird groups. The results show that the aquaculture ponds (AP) and the Scirpus mariqueter zone (SMZ) underwent drastic habitat changes during certain periods (AP: 1997-2000, 2000-2003, 2005-2008; SMZ: 1997-2000), and the fluctuation intensity differed among habitat types in the order AP>SMZ>TSH (total suitable habitat)>BSA (bare mud flat and shallow water area). The abandonment of tracts of aquaculture ponds in Dongtan in mid-2006 brought about an intensive population fluctuation, caused by rapidly changing habitat with the population expanding to adjacent areas. At present, Anatidae and Ardeidae are threatened in the Dongtan area with declining populations because of their very "picky" habitat requirements (i.e., high reliance on AP). The Charadriidae experienced enormous population declines in the late 1990s, however, they have since recovered to normal levels as habitat change has stabilized. Our findings suggest that the current challenges for habitat management are the protection and stabilization of AP and SMZ habitats.展开更多
We studied the population dynamics of endangered mountain nyala Tragelaphus buxtoni between 2003-2005 in the Bale Mountains National Park. Line-transect sampling and total count methods were used to gather data on dem...We studied the population dynamics of endangered mountain nyala Tragelaphus buxtoni between 2003-2005 in the Bale Mountains National Park. Line-transect sampling and total count methods were used to gather data on demographics and movement patterns. The population＇s age-group composition was 58% adults, 25% sub-adults, 9% juveniles, 5% calves and 3% unidentified with a female-male sex ratio of 2：1. Population density was found to be significantly different between the two sub-populations （Dinsho Sanctuary and Gaysay/Adelay）. A significant difference was found for age-group composition across the two sub-populations except adult females, sub-adult males and calves. The Dinsho sub-population was an isolated group. Separation and containment of the mountain nyala population could have negatively affected their ability to search for habitat requirements and mates from distant areas. The population varied between 830-908 individuals （95% CI）, a reduction of 45% from earlier reports. However, the mean population density increased due to contraction of the species＇ habitat range. We observed a population decrease of 2%-5% per year over the course of our study. Many of the assessed demographic parameters did not significantly change over the three years. This suggests that the decrease in nyala population was not due to random variations in reproduction. Anthropogenic factors such as competition with livestock for forage, habitat encroachment and poaching by the local people might have been partly responsible for the depleted population in our study areas [Current Zoology 56 （6）： 660q569, 2010].展开更多
基金Supported by the National Basic Research Program of China (973 Program) (Nos. 2010CB951204, 2008DFB90240)the National Special Research Fund for Non-Profit Sector (Marine) (No. 200805080)
文摘Based on Landsat TM images, we explored the pattern of variation of suitable waterbird habitats from 1990 to 2008 in the Dongtan area of Chongming Island at the Changjiang (Yangtze) River mouth. By applying our highly accurate indicator model (R=0.999, P<0.01), we quantified the variations of fluctuation intensity for local waterbird habitats during 1990-2008, and for the main waterbird groups (Anatidae, Charadriidae, Ardeidae and Laridae) from 2006 to 2008, to evaluate the impact of habitat quantity change on the waterbird habitat status and the population dynamics of the different waterbird groups. The results show that the aquaculture ponds (AP) and the Scirpus mariqueter zone (SMZ) underwent drastic habitat changes during certain periods (AP: 1997-2000, 2000-2003, 2005-2008; SMZ: 1997-2000), and the fluctuation intensity differed among habitat types in the order AP>SMZ>TSH (total suitable habitat)>BSA (bare mud flat and shallow water area). The abandonment of tracts of aquaculture ponds in Dongtan in mid-2006 brought about an intensive population fluctuation, caused by rapidly changing habitat with the population expanding to adjacent areas. At present, Anatidae and Ardeidae are threatened in the Dongtan area with declining populations because of their very "picky" habitat requirements (i.e., high reliance on AP). The Charadriidae experienced enormous population declines in the late 1990s, however, they have since recovered to normal levels as habitat change has stabilized. Our findings suggest that the current challenges for habitat management are the protection and stabilization of AP and SMZ habitats.
文摘We studied the population dynamics of endangered mountain nyala Tragelaphus buxtoni between 2003-2005 in the Bale Mountains National Park. Line-transect sampling and total count methods were used to gather data on demographics and movement patterns. The population＇s age-group composition was 58% adults, 25% sub-adults, 9% juveniles, 5% calves and 3% unidentified with a female-male sex ratio of 2：1. Population density was found to be significantly different between the two sub-populations （Dinsho Sanctuary and Gaysay/Adelay）. A significant difference was found for age-group composition across the two sub-populations except adult females, sub-adult males and calves. The Dinsho sub-population was an isolated group. Separation and containment of the mountain nyala population could have negatively affected their ability to search for habitat requirements and mates from distant areas. The population varied between 830-908 individuals （95% CI）, a reduction of 45% from earlier reports. However, the mean population density increased due to contraction of the species＇ habitat range. We observed a population decrease of 2%-5% per year over the course of our study. Many of the assessed demographic parameters did not significantly change over the three years. This suggests that the decrease in nyala population was not due to random variations in reproduction. Anthropogenic factors such as competition with livestock for forage, habitat encroachment and poaching by the local people might have been partly responsible for the depleted population in our study areas [Current Zoology 56 （6）： 660q569, 2010].
