Abstract
Broad-scale climate control of vegetation is widely assumed. Vegetation-climate lags are generally thought to have lasted no more than a few centuries. Here our palaeoecological study challenges this concept over glacial–interglacial timescales. Through multivariate analyses of pollen assemblages from Lake El'gygytgyn, Russian Far East and other data we show that interglacial vegetation during the Plio-Pleistocene transition mainly reflects conditions of the preceding glacial instead of contemporary interglacial climate. Vegetation–climate disequilibrium may persist for several millennia, related to the combined effects of permafrost persistence, distant glacial refugia and fire. In contrast, no effects from the preceding interglacial on glacial vegetation are detected. We propose that disequilibrium was stronger during the Plio-Pleistocene transition than during the Mid-Pliocene Warm Period when, in addition to climate, herbivory was important. By analogy to the past, we suggest today's widespread larch ecosystem on permafrost is not in climate equilibrium. Vegetation-based reconstructions of interglacial climates used to assess atmospheric CO2–temperature relationships may thus yield misleading simulations of past global climate sensitivity.
Highlights
Broad-scale climate control of vegetation is widely assumed
As we focus on variability at glacial–interglacial timescales, similar principal curve analyses were performed with pollen spectra averaged for each marine isotope stage
The principal curve suggests that differences in pollen composition among glacials and among interglacials are in the same range as glacial–interglacial variability, during the Plio-Pleistocene transition (PPT)
Summary
Broad-scale climate control of vegetation is widely assumed. Vegetation-climate lags are generally thought to have lasted no more than a few centuries. Patterns of Late Pleistocene interglacial vegetation histories (marine isotope stage (MIS) 11, 9, 7 and 5) as inferred from long-term pollen records from Greece[9] and the Massif Central[10] are, in addition to their established relationship with interglacial climate, hypothesized to reflect the different locations of glacial refugia, creating unique interglacial migrational patterns. This accords with the suggestion that in addition to climate, post-glacial migration limitations might explain the current distribution of many European plant species[11]. To assess the impact of herbivory, fire and soil disturbance on vegetation, common non-pollen palynomorphs in lake sediments can be used including Sporormiella[25] (a coprophilous fungal spore), Gelasinospora[26] (a fungal spore characteristic of burned soils) and Glomus[27,28] (an endomycorrhizal fungal spore characteristic of disturbed soils), respectively
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