Study on spatial-temporal heterogeneities of urban ecological security of Guangzhou based on spatial statistics Temporal and spatial variability of soil available nutrients in arable Lands of Heyang County in South Loess Plateau Spatial heterogeneity of vegetation coverage and its temporal dynamics in desert steppe, Inner Mongolia Impacts of Stocking Rate on the Spatial Patterns of Species in Temperate Typic Steppe, Inner Mongolia Spatial Heterogeneity Dynamics of Canopy Structure in a Montane Evergreen Broadleaved Forest Following a Natural Disturbance in North Guangdong Study on variability of soil available nutrients in Shanxi province