Thresholds for boreal biome transitions

摘要: Although the boreal region is warming twice as fast global average, way in which vast forests and tundras may respond poorly understood. Using satellite data, we reveal marked alternative modes frequency distributions of tree cover. At northern end at dry continental southern extremes, treeless tundra steppe, respectively, are only possible states. However, over a broad intermediate temperature range, these states coexist with forest (∼75% cover) two more open woodland (∼20% ∼45% cover). Intermediate covers (e.g., ∼10%, ∼30%, ∼60% between distinct relatively rare, suggesting that they represent unstable where system dwells transiently. Mechanisms for such instabilities remain to be unraveled, but our results have important implications anticipated response ecosystems climatic change. The data shows no gradual decline cover toward its limits. Instead, analysis suggests it becomes less resilient sense easily shift into sparse or state. Similarly, relative scarcity ∼10% abruptly abundant If inferences correct, climate change invoke massive nonlinear shifts biomes.