Tracking desertification on the Mongolian steppe through NDVI and field-survey data     

《International Journal of Digital Earth》2013,6(1):50-64

Abstract

Changing environmental and socio-economic conditions make land degradation, a major concern in Central and East Asia. Globally satellite imagery, particularly Normalized Difference Vegetation Index (NDVI) data, has proved an effective tool for monitoring land cover change. This study examines 33 grassland water points using vegetation field studies and remote sensing techniques to track desertification on the Mongolian plateau. Findings established a significant correlation between same-year field observation (line transects) and NDVI data, enabling an historical land cover perspective to be developed from 1998 to 2006. Results show variable land cover patterns in Mongolia with a 16% decrease in plant density over the time period. Decline in cover identified by NDVI suggests degradation; however, continued annual fluctuation indicates desertification – irreversible land cover change – has not occurred. Further, in situ data documenting greater cover near water points implies livestock overgrazing is not causing degradation at water sources. In combination of the two research methods – remote sensing and field surveys – strengthen findings and provide an effective way to track desertification in dryland regions.  相似文献   

The piosphere revisited: plant species patterns close to waterpoints in small, fenced paddocks in chenopod shrublands of South Australia     

G.A. Heshmatti  J.M. Facelli  J.G. Conran   《Journal of Arid Environments》2002,51(4):547

The Waite–Nicolson rangeland management method for semi-arid chenopod shrublands predicts that smaller paddocks with medium to moderate stocking rates help to preserve the native vegetation. Vegetation cover around waterpoints in three small paddocks (<2000 ha) from Middleback Station, South Australia was studied using multivariate analysis. Data from quadrats sampled along radiating transects were tested for correlations with a number of site features and grazing history factors. Two significant associations were detected: quadrats with an abundance of Rhagodia parabolica and less palatable species such as Maireana pyramidata, and Atriplex stipitata were correlated positively with proximity to water points, paddock age and stocking rate, and negatively with paddock size. In contrast, quadrats with species such as Rhagodia ulicina and the more palatable M. sedifolia were correlated with increasing distance from the water points and paddock size, but negatively with age and stocking rates. Transect direction was not correlated with either group. Twelve of the 20 species examined, including the important forage species A. vesicaria, also were not correlated with those paddock and grazing features included here. These results suggest that the distribution of some chenopod shrub species in fenced paddocks is still possibly affected by a combination of these factors in the long term by grazing at densities of 6 ha sheep⁻¹ and that the method, although maintaining the fodder species, may not be preserving biodiversity at these grazing levels, although further study is needed.  相似文献   

Infiltration rate of soil around drinking troughs in the Kruger National Park, South Africa     

I. Thrash 《Journal of Arid Environments》1997,35(4):617-625

Soil particle size distribution and infiltration of water into the soil were measured in transects radiating from drinking troughs in the Kruger National Park. Soil particle size distribution remained relatively constant along the transects, making it unlikely that any gradients in the infiltration rate were the result of variation in the soil particle size distribution. Concentration of large herbivores around the troughs was indeed causing a negative impact on the infiltration rate of the soils, with implications for the rate of soil loss and the soil moisture regime.  相似文献