Empirical verification of multiple states in drylands is scarce, impeding the design of indicators to anticipate the onset of desertification. Remote sensing-derived indicators of ecosystem states are gaining new ground due to the possibilities they bring to be applied inexpensively over large areas. Remotely sensed albedo has been often used to monitor drylands due to its close relationship with ecosystem status and climate. Here, we used a space-for-time-substitution approach to evaluate whether albedo (averaged from 2000 to 2016) can identify multiple ecosystem states in African drylands spanning from the Saharan desert to tropical Africa. By using latent class analysis, we found that albedo showed two states (low and high; the cut-off level was 0.22 at the shortwave band). Potential analysis revealed that albedo exhibited an abrupt and discontinuous increase with increased aridity (1 - [precipitation/potential evapotranspiration]). The two albedo states co-occurred along aridity values ranging from 0.72 to 0.78, during which vegetation cover exhibited a rapid, continuous decrease from similar to 90% to similar to 50%. At aridity values of 0.75, the low albedo state started to exhibit less attraction than the high albedo state. Low albedo areas beyond this aridity value were considered as vulnerable regions where abrupt shifts in albedo may occur if aridity increases, as forecasted by current climate change models. Our findings indicate that remotely sensed albedo can identify two ecosystem states in African drylands. They support the suitability of albedo indices to inform us about discontinuous responses to aridity experienced by drylands, which can be linked to the onset of land degradation.
1.Henan Univ Technol, Coll Informat Sci & Engn, 100 Lianhua Rd, Zhengzhou 450001, Henan, Peoples R China 2.Chinese Acad Sci, Inst Remote Sensing & Digital Earth, Key Lab Digital Earth Sci, Beijing 100094, Peoples R China 3.Univ Rey Juan Carlos, Dept Tecnol Quim & Energet, Tecnol Quim & Ambiental, Mostoles 28933, Spain 4.Univ Rey Juan Carlos, Tecnol Mecan, Mostoles 28933, Spain 5.Univ Autonoma Guerrero, Cuerpo Acad UAGro CA Riesgos Nat & Geotecnol 93, Chilpancingo 39070, Guerrero, Mexico 6.Univ Rey Juan Carlos, Dept Biol & Geol, Fis & Quim Inorgan, Mostoles 28933, Spain 7.Univ Alicante, Dept Ecol, Alicante 03690, Spain 8.Univ Alicante, Inst Multidisciplinar Estudio Medio Ramon Margale, Alicante 03690, Spain
Recommended Citation:
Zhao, Yanchuang,Wang, Xinyuan,Novillo, Carlos J.,et al. Remotely sensed albedo allows the identification of two ecosystem states along aridity gradients in Africa[J]. LAND DEGRADATION & DEVELOPMENT,2019-01-01,30(12):1502-1515