Remotely‐sensed slowing down in spatially patterned dryland ecosystems

Ecography, vol. 2022

Abstract

Regular vegetation patterns have been predicted to indicate a system slowing down and possibly desertification of drylands. However, these predictions have not yet been observed in dryland vegetation due to the inherent logistic difficulty to gather longer‐term in situ data. Here, we evaluate the theoretical prediction that regular vegetation patterns are associated with empirically derived temporal indicators (autocorrelation, variance, responsiveness) of critical slowing down in a dryland ecosystem in Sudan using different remote sensing products. We use recently developed methods using remote‐sensing EVI time‐series in combination with classified regular vegetation patterns along a rainfall gradient in Sudan to test the predicted slowing down. We tested our empirical findings against theoretical predictions from a stochastic version of a spatial explicit model that has been used to describe vegetation dynamics in drylands under aridity stress. Overall, three temporal indicators (responsiveness, temporal autocorrelation, variance) show slowing down as vegetation patterns change from gaps to labyrinths to spots towards more arid conditions, confirming predictions. However, this transition exhibits non‐linearities, specifically when patterns change configuration. Model simulations reveal that the transition between patterns temporarily slows down the system affecting the temporal indicators. These transient states when vegetation patterns reorganize thus affect the systems resilience indicators in a non‐linear way. Our findings suggest that spatial self‐organization of dryland vegetation is associated with critical slowing down, but this transition towards reduced resilience happens in a non‐linear way. Future work should aim to better understand transient dynamics in regular vegetation patterns in dryland ecosystems, because long transients make regular vegetation patterns of limited use for management in anticipating critical transitions.

Authors 4

1. Michiel P. Veldhuis corresponding Aachen Institute of Environmental Sciences (CML)

   Leiden University · University of Groningen · Princeton University

   Affiliation as printed

   Dept of Ecology and Evolutionary Biology, Princeton Univ. Princeton NJ USA

   Groningen Inst. for Evolutionary Life Sciences (GELIFES), Univ. of Groningen Groningen the Netherlands

   Inst. of Environmental Sciences (CML), Leiden Univ. Leiden the Netherlands

   Dept of Ecology and Evolutionary Biology, Princeton Univ., Princeton, NJ, USA

   Groningen Inst. for Evolutionary Life Sciences (GELIFES), Univ. of Groningen, Groningen, the Netherlands

   Inst. of Environmental Sciences (CML), Leiden Univ., Leiden, the Netherlands

2. Ricardo Martínez‐García

   Princeton University · ICTP South American Institute for Fundamental Research · Universidade Estadual Paulista (Unesp)

   Affiliation as printed

   Dept of Ecology and Evolutionary Biology, Princeton Univ. Princeton NJ USA

   ICTP South American Inst. for Fundamental Research&Inst. de Fisica Teorica, Univ. Estadual Paulista – UNESP Sao Paulo SP Brazil

   Dept of Ecology and Evolutionary Biology, Princeton Univ., Princeton, NJ, USA

3. Vincent Deblauwe

   University of California, Los Angeles · International Institute of Tropical Agriculture

   Affiliation as printed

   Center for Tropical Research, Inst. of the Environment and Sustainability, Univ. of California, Los Angeles Los Angeles CA USA

   International Inst. of Tropical Agriculture Yaoundé Cameroon

   Center for Tropical Research, Inst. of the Environment and Sustainability, Univ. of California, Los Angeles, Los Angeles, CA, USA

4. Vasilis Dakos

   Centre National de la Recherche Scientifique · École Pratique des Hautes Études · Université de Montpellier · Institut des Sciences de l'Evolution de Montpellier · Institut de Recherche pour le Développement

   Affiliation as printed

   Inst. des Sciences de l'Evolution Montpellier, Univ. of Montpellier/CNRS/EPHE/IRD Montpellier France

   Inst. des Sciences de l'Evolution Montpellier, Univ. of Montpellier/CNRS/EPHE/IRD, Montpellier, France