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Search Results for: du z
Centennial-scale reductions in nitrogen availability in temperate forests of the United States
Forests cover 30% of the terrestrial Earth surface and are a major component of the global carbon (C) cycle. Humans have doubled the amount of global reactive nitrogen (N), increasing deposition of N onto forests worldwide. However, other global changes—especially climate change and elevated atmospheric carbon dioxide concentrations—are increasing demand […]
Patterns of bryophyte succession in a 160 year chronosequence in deciduous and coniferous forests of boreal Alaska
Bryophytes are dominant components of boreal forest understories and play a large role in regulating soil microclimate and nutrient cycling. Therefore, shifts in bryophyte communities have the potential to affect boreal forests’ ecosystem processes. We investigated how bryophyte communities varied in 83 forest stands in interior Alaska that ranged in […]
Gap regeneration within mature deciduous forests of Interior Alaska: Implications for future forest change
Increased fire severity in boreal forests of Interior Alaska is shifting forest canopy composition from black spruce (Picea mariana) to deciduous species, including trembling aspen (Populus tremuloides) and Alaska paper birch (Betula neoalaskana). Because deciduous trees are less flammable than black spruce, the dominant disturbance regime in deciduous forests could […]
Reduced North American terrestrial primary productivity linked to anomalous Arctic warming
Warming temperatures in the Northern Hemisphere have enhanced terrestrial productivity. Despite the warming trend, North America has experienced more frequent and more intense cold weather events during winters and springs. These events have been linked to anomalous Arctic warming since 1990, and may affect terrestrial processes. Here we analyse multiple observation […]
Assessing oxygen depletion in the Northeastern Pacific Ocean during the last deglaciation using I/Ca ratios from multiple benthic foraminiferal species
Paleo-redox proxies are crucial for reconstructing past bottom water oxygen concentration changes brought about by ocean circulation and marine productivity shifts in response to climate forcing. Carbonate I/Ca ratios of multiple benthic foraminifera species from Ocean Drilling Program Hole 1017E—a core drilled within the Californian oxygen minimum zone (OMZ), on […]
Tundra is a consistent source of CO2 at a site with progressive permafrost thaw during six years of chamber and eddy covariance measurements
Current and future warming of high latitude ecosystems will play an important role in climate change through feedbacks to the global carbon cycle. This study compares six years of CO2 flux measurements in moist acidic tundra using autochambers and eddy covariance (Tower) approaches. We found that the tundra was an […]
Non-linear CO2 flux response to seven years of experimentally induced permafrost thaw
Permafrost, the “always-frozen” deep soil layers of the Arctic, naturally undergoes freeze-thaw cycles with the passage of the brief Arctic spring and summer, which thaws the uppermost layers and fosters a burst of tundra plant growth and pooling meltwater from thawed soil. For millennia, this cycle has re-frozen the […]
Increased greenhouse-gas intensity of rice production under future atmospheric conditions
Rising global temperatures and CO2 levels are increasing the amount of global-warming methane (the flaming red molecule depicted here) produced by rice farming: with more CO2 in the air to pull in for photosynthesis, rice plants grow faster and supply soil microbes with more sugars seeped from their roots. In […]
Carbon protection and fire risk reduction: toward a full accounting of forest carbon offsets
Management of forests for carbon uptake is an important tool in the effort to slow the increase in atmospheric CO2 and global warming. However, some current policies governing forest carbon credits actually promote avoidable CO2 release and punish actions that would increase long-term carbon storage. In fire-prone forests, management that […]