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Old-growth forests as global carbon sinks. Nature

January 2008

Authors:

Sebastiaan Luyssaert

Vrije Universiteit Amsterdam

Schulze Ernst Detlef

Max Planck Institute for Biogeochemistry Jena

Alexander Knohl

Georg-August-Universität Göttingen

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LETTERS

Old-growth forests as global carbon sinks

Sebastiaan Luyssaert

1,2

, E. -Detlef Schulze

, Annett Bo

rner

, Alexander Knohl

, Dominik Hessenmo

ller

Beverly E. Law

, Philippe Ciais

& John Grace

Old-growth forests remove carbon dioxide from the atmosphere

1,2

at rates that vary with climate and nitrogen deposition

. The seques-

tered carbon dioxide is stored in live woody tissues and slowly

decomposing organic matter in litter and soil

.Old-growthforests

therefore serve as a global carbon dioxide sink, but they are not

protected by international treaties, because it is generally thought

that ageing forests cease to accumulate carbon

5,6

.Herewereporta

search of literature and databases for forest carbon-flux estimates.

We find that in forests between 15 and 800 years of age, net ecosys-

tem productivity (the net carbon balance of the forest including

soils) is usually positive. Our results demonstrate that old-growth

forests can continue to accumulate carbon, contrary to the long-

standing view that they are carbon neutral. Over 30 per cent of the

global forest area is unmanaged primary forest, and this area con-

tains the remaining old-growth forests

. Half of the primary forests

(6 3 10

hectares) are located in the boreal and temperate regions of

the Northern Hemisphere. On the basis of our analysis, these forests

alone sequester about 1.36 0.5 gigatonnes of carbon per year. Thus,

our findings suggest that 15 per cent of the global forest area, which

is currently not considered when offsetting increasing atmospheric

carbon dioxide concentrations, provides at least 10 per cent of the

global net ecosystem productivity

. Old-growth forests accumulate

carbon for centuries and contain large quantities of it. We expect,

however, that much of this carbon, even soil carbon

, will move back

to the atmosphere if these forests are disturbed.

We conducted a literature search to test the hypothesis that old-

growth forests continue to accumulate atmospheric carbon dioxide

(CO

). Site-level estimates of the annual sums of carbon-cycle com-

ponents were compiled, including those of biometry-based net prim-

ary production (NPP), eddy-covariance or biometry-based net

ecosystem production (NEP) and chamber-based heterotrophic res-

piration. The data set was completed with site information related to

stand characteristics, standing biomass and stand age. Data were com-

piled from 519 plot studies that reported one or more components of

the carbon cycle. The studies involved boreal (,30%) and temperate

(,70%) forests and represented the full range of conditions of such

forests, excluding those subjected to experimental treatments such as

fertilization and irrigation (Supplementary Information, section 1.1).

Tropical forests were excluded from the analysis because only 12 sites

were found for which NEP and age estimates are available.

The NEP is the net carbon balance of the forest as a whole, and is

the difference between CO

uptake by assimilation and losses

through plant and soil respiration. On the basis of our global data

set we find that in forests between 15 and 800 years old, the NEP is

usually positive; that is, the forests are CO

sinks (Fig. 1a). The

maximum probabilities of finding a single forest to be a source of

carbon at 60, 180 and 300 years of age are 0.20, 0.25 and 0.35,

respectively. However, the probability of finding an ensemble of

ten old-growth forests that are carbon neutral is negligible

(Supplementary Fig. 1). In the small number of case studies on the

effect of age on the carbon balance of forests, several have demon-

strated some age-related decline in NEP but very few have shown old

forests to be sources

1,2,10–13

. Our NEP estimates suggest that forests

200 years old and above sequester on average 2.4 6 0.8 tC ha

(tC, tonnes of carbon; Fig. 1a). In our model (Supplementary

Information, section 1.3), we find that old-growth forests accumulate

0.4 6 0.1 tC ha

in their stem biomass and 0.7 6

0.2 tC ha

in coarse woody debris, which implies that about

1.3 6 0.8 tC ha

of the sequestered carbon is contained in roots

and soil organic matter.

The commonly accepted and long-standing view that old-growth

forests are carbon neutral (that is, that photosynthesis is balanced by

respiration) was advanced in ref. 6 and was originally based on ten

years’ worth of data from a single site

. It is supported by the observed

decline of stand-level NPP with age in plantations

14,15

, but is not

apparent in some ecoregions

. Yet a decline in NPP is commonly

assumed in ecosystem models (Supplementary Information, section

1.4). Moreover, it has led to the view that old-growth forests are

redundant in the global carbon cycle.

If, however, the hypothesis of carbon neutrality

were correct, the

expected probabilities of observing a sink or source would be equal

and around one-half, the average sink strength for a random

ensemble of forests 200 years old and above would be zero and the

mean CO

release from heterotrophic respiration would equal the

mean CO

sequestration through NPP (thus, the ratio of hetero-

trophic respiration to NPP would be approximately one).

However, we observe this ratio to be well below one on average

(Fig. 1b) and not to increase with age. Hence, all three quantitative

tests fail to support the hypothesis of carbon neutrality. The currently

available data consistently indicate that carbon accumulation con-

tinues in forests that are centuries old.

In fact, young forests rather than old-growth forests are very often

conspicuous sources of CO

(Fig. 1a) because the creation of new

forests (whether naturally or by humans) frequently follows disturb-

ance to soil and the previous vegetation, resulting in a decomposition

rate of coarse woody debris, litter and soil organic matter (measured

as heterotrophic respiration) that exceeds the NPP of the

regrowth

2,17–22

(Fig. 1b).

The scatter in the relationship between NPP and age is consid-

erable, but given the climatic, edaphic and biological diversity of the

observations in combination with differences in disturbance histor-

ies, this is to be expected. There is some degree of age-related decline

in NPP beyond 80 years of age (Fig. 1c), and temperate and boreal

forests both show a consistent pattern of declining NPP beyond an

early maximum (Supplementary Fig. 2a) when analysed separately.

The decline in NPP could be partly attributed to the presence or

absence of management (Supplementary Fig. 2b). However, we

expect that this decline is not strictly a management effect, but a

Department of Biology, Universi ty of Antwerp, 2610 Wilrijk, Belgium.

College of Forestry, Oregon State University, Corvallis, Oregon 97331-5752 , USA.

Max-Planck Institute for

Biogeochemistry, 07701 Jena, Germany.

ETH Zu¨rich, Institute of Plant Sciences, CH-8092 Zu¨rich, Switzerland.

Laboratoire des Sciences du Climat et de l’Environnement, IPSL-LSCE,

CEA-CNRS-UVSQ, 91191 Gif sur Yvette Cedex, France.

School of GeoSciences, The University of Edinburgh, Edinburgh EH9 3JN, UK.

Vol 455

11 September 2008

doi:10.1038/nature07276

213

reflection of differences in disturbance history between managed and

unmanaged forests.

Consistent with earlier studies

, biomass continues to increase for

centuries irrespective of whether forests are boreal or temperate

(Supplementary Fig. 3). In the course of succession, plants compete

for resources and self-thinning

(or thinning by humans in the case

of managed forests) occurs (Fig. 2), so the older stands contain a

relatively small number of individuals, although of course these trees

tend to be large. Obviously biomass cannot accumulate forever. Our

data (Supplementary Fig. 3) suggest a possible upper limit some-

where between 500 and 700 tC ha

(equivalent to 1,400 to 1,800

cubic metres of wood per hectare); these high-biomass forests were

located in the Pacific Northwest USA

We speculate that when high above-ground biomass is reached,

individual trees are lost because of lightning, insects, fungal attacks of

the heartwood by wood-decomposers, or trees becoming unstable in

strong wind because the roots can no longer anchor them. If old-

growth forests reach high above-ground biomass and lose individuals

owing to competition or small-scale disturbances, there is generally

new recruitment or an abundant second canopy layer waiting in the

shade of the upper canopy to take over and maintain productivity.

Although tree mortality is a relatively rapid event (instantaneous

to several years long), decomposition of tree stems can take decades.

Therefore, the CO

release from the decomposition of dead wood

adds to the atmospheric carbon pool over decades, whereas natural

regeneration or in-growth occurs on a much shorter timescale. Thus,

old-growth forest stands with tree losses do not necessarily become

carbon sources, as has been observed in even-aged plantations (that

is, where trees are all of the same age). We recognize that self-thinning

theory was originally developed and validated for even-aged single-

species stands; however, it has been shown to hold for uneven-aged

multi-species plant communities (Supplementary Information, sec-

tion 1.3). In reasonable agreement with our observations (Fig. 1b),

self-thinning theory predicts that the ratio between heterotrophic

respiration and NPP is constant and around 0.65 6 0.02 (indicating

a carbon sink; Supplementary Fig. 4), as long as stand density is

driven by small-scale, rather than stand-replacing, disturbances.

Old stands, with sufficiently high densities (that is, through develop-

ment of a multilayer canopy structure) are thus expected to maintain

biomass accumulation for centuries. Hence, we postulate that bio-

mass accumulation and decline are largely driven by stand structure.

A stand must be spared for centuries from stand-replacing distur-

bances (such as fires, insect outbreaks, wind-throw and avalanches)

in order to accumulate sufficient aboveground biomass to become

old growth. Because the cumulative probability of disturbances is

higher in stands with high above-ground biomass, old stands are

rarer than young stands, even in unmanaged landscapes. At the land-

scape level, we expect a mosaic of forests characterized by different

times since the last stand-replacing disturbance

. Despite differences

in age and density, these forests are, however, expected to follow the

same relationship between biomass and density (Fig. 2).

−4

NEP (tC ha

–1

)

Rh:NPP

1 3 10 31 100 315 1,000

Age (years)

NPP (tC ha

–1

)

Figure 1

Changes in carbon fluxes as a function of age. a, Observed NEP

versus age; positive values indicate carbon sinks and negative values indicate

carbon sources.

b, Observed ratio of heterotrophic respiration (Rh) to NPP

versus age; Rh:NPP , 1 indicates a carbon sink.

c, Observed NPP versus age.

It appears that temperate and boreal forests both show a pattern of declining

NPP. Most probably, the late-successional increase in NPP is caused by the

combination of data from different climate regions or the combination of

disturbance regimes (Supplementary Fig. 2a, b). In each panel, the green

dots show observations of temperate forests, the orange dots show

observations of boreal forests, the thick black line shows the weighted mean

within a moving window of 15 observations, the grey area around this line

shows the 95% confidence interval of the weighted mean and the thin black

lines delineate the 95% confidence interval (where visible) of the individual

flux observations.

100 315 1,000 3,150 10,000 31,500

100

1,000

Density (trees per hectare)

Biomass (tC ha

–1

)

Figure 2

Biomass accumulation as a function of stand density. Each data

point represents a different forest, many of which have different growing

conditions and tree species. Not all growing conditions and species

compositions allow for the accumulation of the global maximum observed

biomass. Self-thinning, the process of density-dependent mortality, is shown

(solid line, of slope c) as the relationship between the logarithm of above-

ground biomass and the logarithm of stand density according to ref. 23

(c 520.51 6 0.08, r

5 0.25, P , 0.01). The green dots show observations of

temperate forests, the orange dots show observations of boreal forests and

the grey area (which is barely wider than the solid line) shows the 95%

confidence interval of the median.

LETTERS NATURE

Vol 455

11 September 2008

214

Under the Kyoto Protocol (http://unfccc.int/resource/docs/

convkp/kpeng.pdf) only anthropogenic effects on ecosystems are con-

sidered (Article 2 of the Framework Convention on Climate Change

(http://unfccc.int/resource/docs/c onvkp/conveng.pdf); Supplementary

Fig. 5) and the accounting for changes in carbon stock by afforestation,

reforestation and deforestations is mandatory (Article 3.3), operating

from a base line of 1990. Leaving forests intact was not perceived as an

anthropogenic activity. In addition, the potential consequences of

excluding old-growth forests from national carbon budgets and from

the Kyoto Protocol were downplayed in the carbon-neutrality hypo-

thesis

. However, over 30% (1.3 3 10

ha) of the global forest area is

classified

by the Food and Agriculture Organization of the United

Nations as primary forest, and this area contains the world’s remaining

old-growth forests. Half (0.6 3 10

ha) of the primary forests are located

in the boreal and temperate regions of the Northern Hemisphere. On the

basis of our analysis, we expect that these forests alone sequester at least

1.3 6 0.5 GtC yr

. Hence, 15% of the global forest surface, which is

currently not being considered for offsetting increasing atmospheric

concentrations, is responsible for at least 10% of the global NEP

Sporadic disturbances will interrupt carbon accumulation, implying

that net biome productivity

will be lower, but it will remain positive

as demonstrated by the accumulation of carbon in soils

4,26

,coarsewoody

debris and charcoal

27,28

The present paper shows that old-growth forests are usually carbon

sinks. Because old-growth forests steadily accumulate carbon for cen-

turies, they contain vast quantities of it. They will lose much of this

carbon to the atmosphere if they are disturbed, so carbon-accounting

rules for forests should give credit for leaving old-growth forest intact.

METHODS SUMMARY

We conducted a literature and database search to determine the fate of the carbon

sequestered in forests. Observation-basedestimates were compiled for carbon-cycle

components, including biometry-based NPP, eddy-covariance or biometry-based

NEP and chamber-based heterotrophic respiration

. The data set was extended

with site information related to stand characteristics, standing biomass and stand

age. In general, uncertainties in flux estimates were not reported in the literature.

Therefore, weestimated the total uncertainty for every component flux containedin

the data set using a consistent framework based on expert judgment

(Supplementary Information, section 1.2). The uncertainty framework in our data-

base was designed to account for differences in data quality between sites due to

length of time series, methodology and conceptual difficulties (that is, gap filling

and dark respiration). Also, an uncertainty of 20% was assigned to the biomass, age

and density estimates. These uncertainties were propagated through the statistical

analyses by means of random realizations based on Monte Carlo principles. Within

each of the 1,000 random realizations, normally distributed random errors, based

on the uncertainty framework of our database, were added to the observed fluxes.

Therefore, all results that are based on flux data are reported as the weighted mean

and the 95% confidence interval of the probability distribution.

Despite the climatic, edaphic and biological diversity of our observations,

above-ground biomass was observed to be related to stand density in the way

described by self-thinning theory

. Although, this theory was initially developed

for even-aged single-species plant communities, we applied it to our data

(Supplementary Information, section 1.3) to determine the components of the

flux-computed NEP, specifically the above-ground biomass, woody debris and

soil sequestration. Furthermore, self-thinning theory was used to calculate the

theoretical ratio of heterotrophic respiration to NPP and compare it with the

observed ratio in support of the hypothesis that biomass accumulation and

decline are largely driven by stand structure.

Received 18 January; accepted 7 July 2008.

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Supplementary Information is linked to the online version of the paper at

www.nature.com/nature.

Acknowledgements We thank all site investigators, their funding agencies and the

various regional flux networks (Afriflux, AmeriFlux, AsiaFlux, CarboAfrica,

CarboEuropeIP, ChinaFlux, Fluxnet-Canada, KoFlux, LBA, NECC, OzFlux,

TCOS-Siberia and USCCC), and the Fluxnet project, whose support was essential for

obtaining our measurements. S.L. was supported by CoE ECO UA-Methusalem and

the Research Foundation - Flanders (FWO-Vlaanderen) with a post-doctoral

fellowship and a research grant. A.K. was supported by the European Union with a

Marie Curie fellowship, and B.E.L. was supported by the regional North American

Carbon Program project ORCA (US Department of Energy, Terrestrial Carbon

Program, award number DE-FG02-04ER63917). E.-D.S. was supported by

DFG-Exploratories. Additional funding for this study was received from

CarboEuropeIP (project number GOCE-CT-2003-505572) and Ameriflux.

Author Contributions S.L., B.E.L., A.K. and P.C. compiled the data set. S.L., A.B. and

D.H wrote code and analysed the data. S.L., E.-D.S., A.K., B.E.L., P.C. and J.G.

designed the analyses and wrote the manuscript.

Author Information Reprints and permissions information is available at

www.nature.com/reprints. Correspond ence and requests for materials should be

addressed to S.L. (sebastiaan.luyssaert@ua.ac.be).

NATURE

Vol 455

11 September 2008 LETTERS

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Carbonate weathering is essential in regulating atmospheric CO2 and carbon cycle at the century timescale. Plant roots accelerate weathering by elevating soil CO2 via respiration. It however remains poorly understood how and how much rooting characteristics (e.g., depth and density distribution) modify flow paths and weathering. We address this knowledge gap using field data from and reactive transport numerical experiments at the Konza Prairie Biological Station (Konza), Kansas (USA), a site where woody encroachment into grasslands is surmised to deepen roots. Results indicate that deepening roots can enhance weathering in two ways. First, deepening roots can control thermodynamic limits of carbonate dissolution by regulating how much CO2 transports vertical downward to the deeper carbonate-rich zone. The base-case data and model from Konza reveal that concentrations of Ca and dissolved inorganic carbon (DIC) are regulated by soil pCO2 driven by the seasonal soil respiration. This relationship can be encapsulated in equations derived in this work describing the dependence of Ca and DIC on temperature and soil CO2. The relationship can explain spring water Ca and DIC concentrations from multiple carbonate-dominated catchments. Second, numerical experiments show that roots control weathering rates by regulating recharge (or vertical water fluxes) into the deeper carbonate zone and export reaction products at dissolution equilibrium. The numerical experiments explored the potential effects of partitioning 40 % of infiltrated water to depth in woodlands compared to 5 % in grasslands. Soil CO2 data suggest relatively similar soil CO2 distribution over depth, which in woodlands and grasslands leads only to 1 % to ∼ 12 % difference in weathering rates if flow partitioning was kept the same between the two land covers. In contrast, deepening roots can enhance weathering by ∼ 17 % to 200 % as infiltration rates increased from 3.7 × 10−2 to 3.7 m/a. Weathering rates in these cases however are more than an order of magnitude higher than a case without roots at all, underscoring the essential role of roots in general. Numerical experiments also indicate that weathering fronts in woodlands propagated > 2 times deeper compared to grasslands after 300 years at an infiltration rate of 0.37 m/a. These differences in weathering fronts are ultimately caused by the differences in the contact times of CO2-charged water with carbonate in the deep subsurface. Within the limitation of modeling exercises, these data and numerical experiments prompt the hypothesis that (1) deepening roots in woodlands can enhance carbonate weathering by promoting recharge and CO2–carbonate contact in the deep subsurface and (2) the hydrological impacts of rooting characteristics can be more influential than those of soil CO2 distribution in modulating weathering rates. We call for colocated characterizations of roots, subsurface structure, and soil CO2 levels, as well as their linkage to water and water chemistry. These measurements will be essential to illuminate feedback mechanisms of land cover changes, chemical weathering, global carbon cycle, and climate.

Carbon–nitrogen interactions in European forests and semi-natural vegetation – Part 2: Untangling climatic, edaphic, management and nitrogen deposition effects on carbon sequestration potentials

Article

Full-text available

Mar 2020
BG

The effects of atmospheric nitrogen deposition (Ndep) on carbon (C) sequestration in forests have often been assessed by relating differences in productivity to spatial variations of Ndep across a large geographic domain. These correlations generally suffer from covariation of other confounding variables related to climate and other growth-limiting factors, as well as large uncertainties in total (dry + wet) reactive nitrogen (Nr) deposition. We propose a methodology for untangling the effects of Ndep from those of meteorological variables, soil water retention capacity and stand age, using a mechanistic forest growth model in combination with eddy covariance CO2 exchange fluxes from a Europe-wide network of 22 forest flux towers. Total Nr deposition rates were estimated from local measurements as far as possible. The forest data were compared with data from natural or semi-natural, non-woody vegetation sites. The response of forest net ecosystem productivity to nitrogen deposition (dNEP ∕ dNdep) was estimated after accounting for the effects on gross primary productivity (GPP) of the co-correlates by means of a meta-modelling standardization procedure, which resulted in a reduction by a factor of about 2 of the uncorrected, apparent dGPP ∕ dNdep value. This model-enhanced analysis of the C and Ndep flux observations at the scale of the European network suggests a mean overall dNEP ∕ dNdep response of forest lifetime C sequestration to Ndep of the order of 40–50 g C per g N, which is slightly larger but not significantly different from the range of estimates published in the most recent reviews. Importantly, patterns of gross primary and net ecosystem productivity versus Ndep were non-linear, with no further growth responses at high Ndep levels (Ndep > 2.5–3 g N m−2 yr−1) but accompanied by increasingly large ecosystem N losses by leaching and gaseous emissions. The reduced increase in productivity per unit N deposited at high Ndep levels implies that the forecast increased Nr emissions and increased Ndep levels in large areas of Asia may not positively impact the continent's forest CO2 sink. The large level of unexplained variability in observed carbon sequestration efficiency (CSE) across sites further adds to the uncertainty in the dC∕dN response.

Forstlich ungenutzte Wälder in Deutschland Bedeutung für den Naturschutz und ökonomische Effekte der Umsetzung des 5 %-Ziels der Nationalen Strategie zur biologischen Vielfalt

Article

Feb 2020

Die Bundesregierung hat 2007 im Rahmen der Nationalen Strategie zur biologischen Vielfalt (NBS) u.a. das Ziel formuliert, 5% der deutschen Waldfläche einer natürlichen Entwicklung zu überlassen. Die andauernde Kritik von forst- und holzwirtschaftlichen Lobbyverbänden nimmt der vorliegende Artikel zum Anlass aufzuzeigen, dass der Beitrag, den ungenutzte Wälder zur Erhaltung der Biodiversität leisten können, nicht durch forstlich bewirtschaftete Wälder erbracht werden kann und dass durch die Umsetzung des 5%-Ziels weder eine Verknappung des Rohstoffs Holz noch eine Gefährdung der Versorgung des deutschen Clusters Forst und Holz, noch signifikant zunehmende Importströme von Holz und Holzprodukten zu befürchten sind. Durch die Fokussierung auf die vermeintlich negativen ökonomischen Effekte von Waldnaturschutzmaßnahmen droht vielmehr die Diskussion um die eigentlichen Probleme - um die mangelnde Kontrolle der hohen Holzeinfuhren nach Deutschland, um die Mitverantwortung des Wirtschaftsbereichs Forst und Holz sowie um den zu hohen Ressourcenverbrauch unseres Gesellschafts- und Wirtschaftssystems - aus dem Blick zu geraten.

The role of socialisation of the forest management system in Poland in the face of the need to mitigate climate change

Article

Full-text available

Dec 2022

Climate change will have a significant impact on forests as most of the factors determining their condition are modified by the effects of the climate change process. Some of these effects are a change in the distribution and amount of precipitation, an increase in the frequency of extreme meteorological phenomena, including hurricane winds, temperature distribution, or a change in the length of the growing season. In order to maintain the productivity of Polish forests and the range of ecosystem services they provide, the forestry sector will have to adapt to these changes. However, forestry will also have to take a part in holding back climate change. Achieving climate neutrality by mid-21st century and ensuring a 55% reduction in greenhouse gas emissions by 2030 will not be possible without using the ability of forests to absorb and permanently store carbon.

Малонарушенные лесные территории мира: концепция, методика выделения, результаты многолетнего мониторинга

Conference Paper

Full-text available

Apr 2016

Стр. 17-21 Малонарушеные лесные территории (МЛТ) – последние сохранившиеся крупные лесные массивы, не преобразованные деятельностью человека. В 2014 г. проанализировано сокращение МЛТ за 2000-2013 годы. Около 20% всех лесов мира являются малонарушенными. Площадь МЛТ в мире сократилась на 7,2%. Основной причиной деградации МЛТ является фрагментация лесных массивов, и лишь в 14% случаев - непосредственное сокращение лесного покрова.

Assessing impacts of selective logging on water, energy, and carbon budgets and ecosystem dynamics in Amazon forests using the Functionally Assembled Terrestrial Ecosystem Simulator

Article

Full-text available

Oct 2020

Tropical forest degradation from logging, fire, and fragmentation not only alters carbon stocks and carbon fluxes, but also impacts physical land surface properties such as albedo and roughness length. Such impacts are poorly quantified to date due to difficulties in accessing and maintaining observational infrastructures, as well as the lack of proper modeling tools for capturing the interactions among biophysical properties, ecosystem demography, canopy structure, and biogeochemical cycling in tropical forests. As a first step to address these limitations, we implemented a selective logging module into the Functionally Assembled Terrestrial Ecosystem Simulator (FATES) by mimicking the ecological, biophysical, and biogeochemical processes following a logging event. The model can specify the timing and aerial extent of logging events, splitting the logged forest patch into disturbed and intact patches; determine the survivorship of cohorts in the disturbed patch; and modifying the biomass and necromass (total mass of coarse woody debris and litter) pools following logging. We parameterized the logging module to reproduce a selective logging experiment at the Tapajós National Forest in Brazil and benchmarked model outputs against available field measurements. Our results suggest that the model permits the coexistence of early and late successional functional types and realistically characterizes the seasonality of water and carbon fluxes and stocks, the forest structure and composition, and the ecosystem succession following disturbance. However, the current version of FATES overestimates water stress in the dry season and therefore fails to capture seasonal variation in latent and sensible heat fluxes. Moreover, we observed a bias towards low stem density and leaf area when compared to observations, suggesting that improvements are needed in both carbon allocation and establishment of trees. The effects of logging were assessed by different logging scenarios to represent reduced impact and conventional logging practices, both with high and low logging intensities. The model simulations suggest that in comparison to old-growth forests the logged forests rapidly recover water and energy fluxes in 1 to 3 years. In contrast, the recovery times for carbon stocks, forest structure, and composition are more than 30 years depending on logging practices and intensity. This study lays the foundation to simulate land use change and forest degradation in FATES, which will be an effective tool to directly represent forest management practices and regeneration in the context of Earth system models.

Comparing Spatial Pattern in Unaltered Old-Growth and Disturbed Forest Landscapes

Article

Full-text available

May 1993

Used geographic information systems to analyze the structure of a second-growth forest landscape (9600 ha) in Michigan and Wisconsin, that contains scattered old-growth patches, and compared this landscape to a nearby, unaltered old-growth landscape on comparable landforms and soils to assess the effects of human activity on forest spatial pattern. The natural old-growth landscape is dominated by the original forest cover of eastern hemlock Tsuga canadensis, sugar maple Acer saccharum and yellow birch Betula alleghaniensis. The disturbed landscape has only scattered, remnant patches of old-growth ecosystems among a greater number of early successional hardwood and conifer forest types. The disturbed landscape has significantly more small forest patches and fewer large, matrix patches than the intact landscape. Forest patches in the fragmented landscape are significantly simpler in shape (lower fractal dimension, D) than in the intact old-growth landscape. Change in fractal dimension with patch size, a relationship that may be characteristics of differing processes of patch formation at different scales, is present within the intact landscape but has been obscured by human activity in the disturbed landscape. Important ecosystem juxtapositions of the old-growth landscape, such as hemlock with lowland conifers, have been lost in the disturbed landscape. Significant landscape heterogeneity in this glaciated region is produced by landforms alone, without natural or human disturbances. -from Authors

The human footprint in the carbon cycle of temperate and boreal forests

Article

Full-text available

Jun 2007

Temperate and boreal forests in the Northern Hemisphere cover an area of about 2 × 107 square kilometres and act as a substantial carbon sink (0.6-0.7 petagrams of carbon per year). Although forest expansion following agricultural abandonment is certainly responsible for an important fraction of this carbon sink activity, the additional effects on the carbon balance of established forests of increased atmospheric carbon dioxide, increasing temperatures, changes in management practices and nitrogen deposition are difficult to disentangle, despite an extensive network of measurement stations. The relevance of this measurement effort has also been questioned, because spot measurements fail to take into account the role of disturbances, either natural (fire, pests, windstorms) or anthropogenic (forest harvesting). Here we show that the temporal dynamics following stand-replacing disturbances do indeed account for a very large fraction of the overall variability in forest carbon sequestration. After the confounding effects of disturbance have been factored out, however, forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities. The effect is always positive over the range of nitrogen deposition covered by currently available data sets, casting doubts on the risk of widespread ecosystem nitrogen saturation under natural conditions. The results demonstrate that mankind is ultimately controlling the carbon balance of temperate and boreal forests, either directly (through forest management) or indirectly (through nitrogen deposition).

Beyond annual budgets: carbon flux at different temporal scales in fire-prone Siberian Scots pine forests

Article

Nov 2002

Primary production and turnover of organic matter in different forest ecosystems of the Western Paci

Article

Apr 1967

This review is intended to introduce an outline of the results of community metabolism studies on various forest ecosystems of the Western Pacific area made by Japanese investigators in these past ten years. In 1955,SATOO opened this line of research by publishing his first report(65)on the productivity of artificial plantations in this country. A few years later, in 1957 and 1958,four groups of ecologists and forest scientists including ourselves began almost simultaneously to follow him, and the fields of study were expanded to include various types of natural and artificial vegetation ranging from subarctic conifer forests of Hokkaido to the tropical jungle of Southeast Asia. Since that time, more than one hundred stands belonging to some forty different forest types have been investigated, of course mostly within Japan Proper, but also in the Ryukyus(40), Thailand(21,22,24,42,44-47,93,100)and Cambodia(23). Steady progress has been made in the methodology for analysing the metabolism of forest community. These studies were, therefore, not always based on one and the same method, making it difficult to compare the results obtained by different authors. Thus the contents of this review are more or less tentative ; yet we hope, this may well be a useful starting point for more advanced studies to be made under the framework of the International Biological Programme.

FAO. 2005. Global Forest Resources Assessment 2005: progress Towards Sustainable Forest Management. FAO, Rome, IT

Book

Jan 2005

Self-Thinning in Overcrowded Pure Stands Under Cultivated and Natural Conditions

Article

Jan 1963

Changes in carbon storage and fluxes in a chronosequence of ponderosa pine

Article

Apr 2003
GLOBAL CHANGE BIOL

Forest development following stand-replacing disturbance influences a variety of ecosystem processes including carbon exchange with the atmosphere. On a series of ponderosa pine (Pinius ponderosa var. Laws.) stands ranging from 9 to> 300 years in central Oregon, USA, we used biological measurements to estimate carbon storage in vegetation and soil pools, net primary productivity (NPP) and net ecosystem productivity (NEP) to examine variation with stand age. Measurements were made on plots representing four age classes with three replications: initiation (I, 9–23 years), young (Y, 56–89 years), mature (M, 95–106 years), and old (O, 190–316 years) stands typical of the forest type in the region. Net ecosystem productivity was lowest in the I stands (−124 g C m−2 yr−1), moderate in Y stands (118 g C m−2 yr−1), highest in M stands (170 g C m−2 yr−1), and low in the O stands (35 g C m−2 yr−1). Net primary productivity followed similar trends, but did not decline as much in the O stands. The ratio of fine root to foliage carbon was highest in the I stands, which is likely necessary for establishment in the semiarid environment, where forests are subject to drought during the growing season (300–800 mm precipitation per year). Carbon storage in live mass was the highest in the O stands (mean 17.6 kg C m−2). Total ecosystem carbon storage and the fraction of ecosystem carbon in aboveground wood mass increased rapidly until 150–200 years, and did not decline in older stands. Forest inventory data on 950 ponderosa pine plots in Oregon show that the greatest proportion of plots exist in stands ∼ 100 years old, indicating that a majority of stands are approaching maximum carbon storage and net carbon uptake. Our data suggests that NEP averages ∼ 70 g C m−2 year−1 for ponderosa pine forests in Oregon. About 85% of the total carbon storage in biomass on the survey plots exists in stands greater than 100 years, which has implications for managing forests for carbon sequestration. To investigate variation in carbon storage and fluxes with disturbance, simulation with process models requires a dynamic parameterization for biomass allocation that depends on stand age, and should include a representation of competition between multiple plant functional types for space, water, and nutrients.

The carbon budget of coarse woody debris in a temperate broad‐leaved secondary forest in Japan

Article

Feb 2007
TELLUS B

We evaluated the carbon budget of coarse woody debris (CWD) in a temperate broad-leaved secondary forest. On the basis of a field survey conducted in 2003, the mass of CWD was estimated at 9.30 tC ha−1, with snags amounting to 60% of the total mass. Mean annual CWD input mass was estimated to be 0.61 tC ha−1 yr−1 by monitoring tree mortality in the forest from 1999 to 2004. We evaluated the CWD decomposition rate as the CO2 evolution rate from CWD by measuring CO2 emissions from 91 CWD samples (RCWD) with a closed dynamic chamber and infrared gas analysis system. The relationships between RCWD and temperature in the chamber, water content of the CWD, and other CWD characteristics were determined. By scaling the measured RCWD to the ecosystem, we estimated that the annual RCWD in the forest in 2003 was 0.50 tC ha−1 yr−1 or 10%–16% of the total heterotrophic respiration. Therefore, 0.11 tC ha−1 yr−1 or 7% of the forest net ecosystem production was sequestered by CWD. In a young forest, in which CWD input and decomposition are not balanced, the CWD carbon budget needs to be quantified for accurate evaluation of the forest carbon cycle and NEP.

Postfire carbon pools and fluxes in semiarid ponderosa pine in Central Oregon

Article

Aug 2007
GLOBAL CHANGE BIOL

Forest fire dramatically affects the carbon storage and underlying mechanisms that control the carbon balance of recovering ecosystems. In western North America where fire extent has increased in recent years, we measured carbon pools and fluxes in moderately and severely burned forest stands 2 years after a fire to determine the controls on net ecosystem productivity (NEP) and make comparisons with unburned stands in the same region. Total ecosystem carbon in soil and live and dead pools in the burned stands was on average 66% that of unburned stands (11.0 and 16.5 kg C m−2, respectively, P<0.01). Soil carbon accounted for 56% and 43% of the carbon pools in burned and unburned stands. NEP was significantly lower in severely burned compared with unburned stands (P<0.01) with an increasing trend from −125±44 g C m−2 yr−1 (±1 SD) in severely burned stands (stand replacing fire), to −38±96 and +50±47 g C m−2 yr−1 in moderately burned and unburned stands, respectively. Fire of moderate severity killed 82% of trees <20 cm in diameter (diameter at 1.3 m height, DBH); however, this size class only contributed 22% of prefire estimates of bole wood production. Larger trees (> 20 cm DBH) suffered only 34% mortality under moderate severity fire and contributed to 91% of postfire bole wood production. Growth rates of trees that survived the fire were comparable with their prefire rates. Net primary production NPP (g C m−2 yr−1, ±1 SD) of severely burned stands was 47% of unburned stands (167±76, 346±148, respectively, P<0.05), with forb and grass aboveground NPP accounting for 74% and 4% of total aboveground NPP, respectively. Based on continuous seasonal measurements of soil respiration in a severely burned stand, in areas kept free of ground vegetation, soil heterotrophic respiration accounted for 56% of total soil CO2 efflux, comparable with the values of 54% and 49% previously reported for two of the unburned forest stands. Estimates of total ecosystem heterotrophic respiration (Rh) were not significantly different between stand types 2 years after fire. The ratio NPP/Rh averaged 0.55, 0.85 and 1.21 in the severely burned, moderately burned and unburned stands, respectively. Annual soil CO2 efflux was linearly related to aboveground net primary productivity (ANPP) with an increase in soil CO2 efflux of 1.48 g C yr−1 for every 1 g increase in ANPP (P<0.01, r2= 0.76). There was no significant difference in this relationship between the recently burned and unburned stands. Contrary to expectations that the magnitude of NEP 2 years postfire would be principally driven by the sudden increase in detrital pools and increased rates of Rh, the data suggest NPP was more important in determining postfire NEP.

Are old forests underestimated as global carbon sinks?

Article

Apr 2001
GLOBAL CHANGE BIOL

Old forests are important carbon pools, but are thought to be insignificant as current atmospheric carbon sinks. This perception is based on the assumption that changes in productivity with age in complex, multiaged, multispecies natural forests can be modelled simply as scaled-up versions of individual trees or even-aged stands. This assumption was tested by measuring the net primary productivity (NPP) of natural subalpine forests in the Northern Rocky Mountains, where NPP is from 50% to 100% higher than predicted by a model of an even-age forest composed of a single species. If process-based terrestrial carbon models underestimate NPP by 50% in just one quarter of the temperate coniferous forests throughout the world, then global NPP is being underestimated by 145 Tg of carbon annually. This is equivalent to 4.3–7.6% of the missing atmospheric carbon sink. These results emphasize the need to account for multiple-aged, species-diverse, mature forests in models of terrestrial carbon dynamics to approximate the global carbon budget.

Old-growth forests as global carbon sinks. Nature

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