Climate Stability and the Origin of Agriculture

A novel approach to quantify and locate potential microrefugia using topoclimate, climate stability, and isolation from the matrix

Global Change Biology ◽

10.1111/j.1365-2486.2012.02661.x ◽

2012 ◽

Vol 18 (6) ◽

pp. 1866-1879 ◽

Cited By ~ 123

Author(s):

Michael B. Ashcroft ◽

John R. Gollan ◽

David I. Warton ◽

Daniel Ramp

Keyword(s):

Climate Stability ◽

Novel Approach ◽

The Matrix

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Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

10.26686/wgtn.17151233.v1 ◽

2021 ◽

Author(s):

◽

Maia Bellingham

Keyword(s):

Carbon Dioxide ◽

New Zealand ◽

Chemical Weathering ◽

Southern Alps ◽

Grain Sizes ◽

Denudation Rates ◽

Climate Stability ◽

Mountain Landscapes ◽

Carbon Dioxide Cycling

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood. To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering. Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments. Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

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A methylotrophic origin of methanogenesis and early divergence of anaerobic multicarbon alkane metabolism

Science Advances ◽

10.1126/sciadv.abj1453 ◽

2021 ◽

Vol 7 (27) ◽

pp. eabj1453

Author(s):

Yinzhao Wang ◽

Gunter Wegener ◽

Tom A. Williams ◽

Ruize Xie ◽

Jialin Hou ◽

...

Keyword(s):

Carbon Dioxide ◽

Energy Conservation ◽

Life Forms ◽

Short Chain ◽

Present Evidence ◽

Origin And Evolution ◽

Ancestral Form ◽

Climate Stability ◽

Long Chain

Methanogens are considered as one of the earliest life forms on Earth, and together with anaerobic methane-oxidizing archaea, they have crucial effects on climate stability. However, the origin and evolution of anaerobic alkane metabolism in the domain Archaea remain controversial. Here, we present evidence that methylotrophic methanogenesis was the ancestral form of this metabolism. Carbon dioxide–reducing methanogenesis developed later through the evolution of tetrahydromethanopterin S-methyltransferase, which linked methanogenesis to the Wood-Ljungdahl pathway for energy conservation. Anaerobic multicarbon alkane metabolisms in Archaea also originated early, with genes coding for the activation of short-chain or even long-chain alkanes likely evolving from an ethane-metabolizing ancestor. These genes were likely horizontally transferred to multiple archaeal clades including Candidatus (Ca.) Bathyarchaeia, Ca. Lokiarchaeia, Ca. Hadarchaeia, and the methanogenic Ca. Methanoliparia.

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