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Rate of tree carbon accumulation increases continuously with tree size
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Forests are major components of the global carbon cycle, providing
substantial feedback to atmospheric greenhouse gas concentrations1
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Our ability to understand and predict changes in the forest carbon
cycle—particularly net primary productivity and carbon storage—
increasingly relies on models that represent biological processes
across several scales of biological organization, from tree leaves to
forest stands2,3. Yet, despite advances in our understanding of productivity
at the scales of leaves and stands, no consensus exists about
the nature of productivity at the scale of the individual tree4–7, in
part because we lack a broad empirical assessment of whether rates
of absolute treemass growth (and thus carbon accumulation) decrease,
remain constant, or increase as trees increase in size and age. Here we
present a global analysis of 403 tropical and temperate tree species,
showing that for most species mass growth rate increases continuously
with tree size. Thus, large, old trees do not act simply as senescent
carbon reservoirs but actively fix large amounts of carbon
compared to smaller trees; at the extreme, a single big tree can add
the same amount of carbon to the forest within a year as is contained
in an entire mid-sized tree. The apparent paradoxes of individual
tree growth increasing with tree size despite declining leaf-level8–10
and stand-level10 productivity can be explained, respectively, by
increases in a tree’s total leaf area that outpace declines in productivity
per unit of leaf area and, among other factors, age-related
reductions in population density. Our results resolve conflicting
assumptions about the nature of tree growth,inform efforts to undertand
and model forest carbon dynamics, and have additional implications
for theories of resource allocation11 and plant senescence1
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Raulerson Life Cycle.pdf
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PEK-RIC
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Ray 1977.pdf
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PEK-RIC
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Re-evaluation of forest biomass carbon stocks and lessons from the world’s most carbon-dense forests
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From analysis of published global site biomass data (n = 136) from primary forests, we discovered (i) the world’s highest known total biomass carbon density (living plus dead) of 1,867 tonnes carbon per ha (average value from 13 sites) occurs in Australian temperate moist Eucalyptus regnans forests, and (ii) average values of the global site biomass data were higher for sampled temperate moist forests (n 44) than for sampled tropical (n 36) and boreal (n 52) forests (n is number of sites per forest biome). Spatially averaged Intergovern- mental Panel on Climate Change biome default values are lower than our average site values for temperate moist forests, because the temperate biome contains a diversity of forest ecosystem types that support a range of mature carbon stocks or have a long land-use history with reduced carbon stocks. We describe a framework for identifying forests important for carbon storage based on the factors that account for high biomass carbon densities, including (i) relatively cool temperatures and moderately high precipitation producing rates of fast growth but slow decomposition, and (ii) older forests that are often multiaged and multilayered and have experienced minimal human disturbance. Our results are relevant to negotiations under the United Nations Framework Convention on Climate Change re- garding forest conservation, management, and restoration. Conserv- ing forests with large stocks of biomass from deforestation and degradation avoids significant carbon emissions to the atmosphere, irrespective of the source country, and should be among allowable mitigation activities. Similarly, management that allows restoration of a forest’s carbon sequestration potential also should be recognized.
Eucalyptus regnans climate mitigation primary forest deforestation and degradation temperate moist forest biome
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Test Conversation 4
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Test Converstion 3
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Rebuilding Soils on Mined Land for Native Forests in Appalachia
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The eastern U.S. Appalachian region supports the world’s most extensive
temperate forests, but surface mining for coal has caused forest loss. New
reclamation methods are being employed with the intent of restoring native
forest on Appalachian mined lands. Mine soil construction is essential to
the reforestation process. Here, we review scientific literature concerning
selection of mining materials for mine soil construction where forest
ecosystem restoration is the reclamation goal. Successful establishment and
productive growth of native Appalachian trees has been documented on mine
soils with coarse fragment contents as great as 60% but with low soluble salt
levels and slightly to moderately acidic pHs, properties characteristic of the
region’s native soils. Native tree productivity on some Appalachian mined
lands where weathered rock spoils were used to reconstruct soils was found
comparable to productivity on native forest sites. Weathered rock spoils,
however, are lower in bioavailable N and P than native Appalachian soils and
they lack live seed banks which native soils contain. The body of scientific
research suggests use of salvaged native soils for mine soil construction when
forest ecosystem restoration is the reclamation goal, and that weathered rock
spoils are generally superior to unweathered rock spoils when constructing
mine soils for this purpose.
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Recent acceleration of biomass burning and carbon losses in Alaskan forests and peatlands
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Climate change has increased the area affected by forest fires each year in boreal North America1,2. Increases in burned area and fire frequency are expected to stimulate boreal carbon losses3–5. However, the impact of wildfires on carbon emissions is also affected by the severity of burning. How climate change influences the severity of biomass burning has proved difficult to assess. Here, we examined the depth of ground-layer combustion in 178 sites dominated by black spruce in Alaska, using data collected from 31 fire events between 1983 and 2005. We show that the depth of burning increased as the fire season progressed when the annual area burned was small. However, deep burning occurred throughout the fire season when the annual area burned was large. Depth of burning increased late in the fire season in upland forests, but not in peatland and permafrost sites. Simulations of wildfire-induced carbon losses from Alaskan black spruce stands over the past 60 years suggest that ground-layer combustion has accelerated regional carbon losses over the past decade, owing to increases in burn area and late-season burning. As a result, soils in these black spruce stands have become a net source of carbon to the atmosphere, with carbon emissions far exceeding decadal uptake.
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Reconciling nature conservation and traditional farming practices: a spatially explicit framework to assess the extent of High Nature Value farmlands in the European countryside
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Over past centuries, European landscapes have been shaped by human management. Traditional, low intensity agricultural practices, adapted to local climatic, geographic, and environmental conditions, led to a rich, diverse cultural and natural heritage, reflected in a wide range of rural landscapes, most of which were preserved until the advent of industrialized agriculture (Bignal & McCracken 2000; Paracchini et al. 2010; Oppermann et al. 2012). Agricultural landscapes currently account for half of Europe’s territory (Overmars et al. 2013), with ca. 50% of all species relying on agricultural habitats at least to some extent (Kristensen 2003; Moreira et al. 2005; Halada et al. 2011). Due to their acknowledged role in the maintenance of high levels of biodiversity, low-intensity farming systems have been highlighted as critical to nature conservation and protection of the rural environment (Beaufoy et al. 1994; Paracchini et al. 2010; Halada et al.2011; Egan & Mortensen 2012).
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Reconstruction of the history of anthropogenic CO2 concentrations in the ocean
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The release of fossil fuel CO2 to the atmosphere by human activity has been implicated as the predominant cause of recent global climate change1. The ocean plays a crucial role in mitigating the effects of this perturbation to the climate system, sequestering 20 to 35 per cent of anthropogenic CO2 emissions2–4. Although much progress has been made in recent years in understanding and quantifying this sink, considerable uncertainties remain as to the distribution of anthropogenic CO2 in the ocean, its rate of uptake over the industrial era, and the relative roles of the ocean and terrestrial biosphere in anthropogenic CO2 sequestration. Here we address these questions by presenting an observationally based reconstruction of the spatially resolved, time-dependent history of anthropogenic carbon in the ocean over the industrial era. Our approach is based on the recognition that the transport of tracers in the ocean can be described by a Green’s function, which we estimate from tracer data using a maximum entropy deconvo- lution technique. Our results indicate that ocean uptake of anthro- pogenic CO2 has increased sharply since the 1950s, with a small decline in the rate of increase in the last few decades. We estimate the inventory and uptake rate of anthropogenic CO2 in 2008 at 140 6 25 Pg C and 2.3 6 0.6 Pg C yr21, respectively. We find that the Southern Ocean is the primary conduit by which this CO2 enters the ocean (contributing over 40 per cent of the anthro- pogenic CO2 inventory in the ocean in 2008). Our results also suggest that the terrestrial biosphere was a source of CO2 until the 1940s, subsequently turning into a sink. Taken over the entire industrial period, and accounting for uncertainties, we estimate that the terrestrial biosphere has been anywhere from neutral to a net source of CO2, contributing up to half as much CO2 as has been taken up by the ocean over the same period.
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