Carbon Storage in a Pacific Northwest Conifer Forest Ecosystem

Carbon Storage in a Pacific Northwest Conifer Forest Ecosystem
Author: Jack E. Janisch
Publisher:
Total Pages: 340
Release: 2001
Genre: Carbon cycle (Biogeochemistry)
ISBN:

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As concern over global warming intensifies, sequestration and storage of atmospheric CO2 has become an important scientific and policy issue. Confusion persists, however, over interpretation of forest carbon (C) source-sink dynamics, in part because conclusions drawn depend on temporal and spatial scales of analysis (e.g. day-week scale vs. successional-scale), type of disturbance, and methodology (e.g. massbased vs. flux-based). There is a need to resolve this confusion given that strategies for mitigating anthropogenic CO2 emissions are based on estimates of forest C fluxes during various stages of succession, over which C fluxes and stores may change. Empirical study of changes in forest C stores can help to resolve this confusion by clarifying the C sources-sink dynamics of forests in space and time. To better understand the impacts of disturbance on C source-sink dynamics, changes in C stores of an evergreen-dominated forest on the Wind River Ranger District in Southwestern Washington, U.S.A., were investigated along a 500-year chronosequence of 36 stands. Principle objectives were to evaluate 1) decomposition rates (k) of logs, stumps, and below-ground coarse roots, 2) net primary productivity (NPP) of dominant tree species' boles at the stand level, and 3) successional changes in net ecosystem productivity (NEP) for live trees and coarse woody debris (CWD), here called NEPW. In the case of decomposition, log and stump k values did not differ significantly within the two principle species studied, indicating substitution of log k values for stump k values in models of forest C budgets may be valid when stump decomposition data is lacking. Decomposition rates between species differed, with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) decomposing more slowly (k = 0.013 yr-1) relative to western hemlock (Tsuga heterophylla (Rafi) Sarg. (k = 0.036 yr-1). This difference in k between species was observed for both above-ground stumps and logs as well as below-ground coarse roots. Given our mean k estimates and adjusting for regenerating stand age, these stands are losing C at a rate of 0.16-0.83 Mg C ha-1 yr-1 (assuming all CWD is P. menziesii) to 0.13-1.68 Mg C ha-1 yr-1 (assuming all CWD is T. heterophylla) from stumps, logs, and snags. Including coarse roots increases these losses to 0.28-1.25 Mg C ha-1 yr-1 and 0.30-2.53 Mg C ha-1 yr-1, respectively. Based on these findings, if fragmentation of these decomposing C pools is ignored, and fragmented fractions have oxidized to CO2, stands thought to be net C sinks could in reality be net C sources to the atmosphere. Net primary production in tree boles (NPPb) of regenerating stands (so called second-growth) ranged between 0.15-5.28 Mg C ha-1 yr-1. NPPb of 500-year old stands ranged between 1.3-3.9 Mg C ha-1 yr-1, similar to NPPb of boles in 20-25 year old secondgrowth. Mean radial increment widths from old-growth stands indicated that NPPb of these stands (neglecting mortality) can increase, decrease, or remain relatively constant. Based on 5-year increments for the previous fifteen years, the majority of old-growth stands sampled showed small increases in radial growth over time. Timing of the transition from negative to positive of NEPW ranged between 0 and 57 years after disturbance and depended strongly on live-tree growth rates as well as the fate of CWD and harvested wood. Estimated maximum and minimum NEPW were 3.9 Mg C ha-1 yr-1 and 14.1 Mg C ha-1 yr-1, respectively. Maximum mean C stores of 393 Mg C ha-1 were reached approximately 200 years after disturbance. At a rotation age of 80 years, regenerating stands stored approximately 50% as much C in woody biomass as a 500-year old primary forest, indicating conversion of older forests to plantations released C to the atmosphere. Given the high biomass of mature and old-growth stands relative to younger regenerating stands in the forest studied, landscape C stores in live wood would appear to be maximized in stands of older age classes.

Comparing Algorithms for Estimating Foliar Biomass of Conifers in the Pacific Northwest

Comparing Algorithms for Estimating Foliar Biomass of Conifers in the Pacific Northwest
Author: Crystal Lynn Raymond
Publisher:
Total Pages: 36
Release: 2013
Genre: Conifers
ISBN:

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Accurate estimates of foliar biomass (FB) are important for quantifying carbon storage in forest ecosystems, but FB is not always reported in regional or national inventories. Foliar biomass also drives key ecological processes in ecosystem models. Published algorithms for estimating FB in conifer species of the Pacific Northwest can yield signifi cantly different results, but have not been rigorously compared for species other than Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). We compared five algorithms for estimating FB for seven common coniferous species in the Pacific Northwest. Algorithms based on diameter at breast height (DBH), or on DBH and height, consistently yield higher estimates of FB than algorithms based on sapwood area. At the tree level, differences between algorithms increased with increasing DBH for all species, but their order and magnitude differed by species. At the stand level, differences among algorithms were muted by the mix of species and diameter classes that contributed to total FB of stands of different seral stages and species composition. Significant differences among estimates of FB from different algorithms show the need for consistent methods for estimating FB for carbon accounting, tests of the sensitivity of ecosystem models to these differences, and more field observations to compare algorithms.

Comparing algorithms for estimating foliar biomass of conifers in the Pacific Northwest

Comparing algorithms for estimating foliar biomass of conifers in the Pacific Northwest
Author: Crystal Lynn Raymond
Publisher:
Total Pages: 23
Release: 2013
Genre: Conifers
ISBN:

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Accurate estimates of foliar biomass (FB) are important for quantifying carbon storage in forest ecosystems, but FB is not always reported in regional or national inventories. Foliar biomass also drives key ecological processes in ecosystem models. Published algorithms for estimating FB in conifer species of the Pacific Northwest can yield signifi cantly different results, but have not been rigorously compared for species other than Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). We compared five algorithms for estimating FB for seven common coniferous species in the Pacific Northwest. Algorithms based on diameter at breast height (DBH), or on DBH and height, consistently yield higher estimates of FB than algorithms based on sapwood area. At the tree level, differences between algorithms increased with increasing DBH for all species, but their order and magnitude differed by species. At the stand level, differences among algorithms were muted by the mix of species and diameter classes that contributed to total FB of stands of different seral stages and species composition. Significant differences among estimates of FB from different algorithms show the need for consistent methods for estimating FB for carbon accounting, tests of the sensitivity of ecosystem models to these differences, and more field observations to compare algorithms.

Final Report on the Project Entitled "The Effects of Disturbance & Climate on Carbon Storage & the Exchanges of CO2 Water Vapor & Energy Exchange of Evergreen Coniferous Forests in the Pacific Northwest

Final Report on the Project Entitled
Author:
Publisher:
Total Pages:
Release: 2011
Genre:
ISBN:

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This is the final technical report containing a summary of all findings with regard to the following objectives of the project: (1) To quantify and understand the effects of wildfire on carbon storage and the exchanges of energy, CO2, and water vapor in a chronosequence of ponderosa pine (disturbance gradient); (2) To investigate the effects of seasonal and interannual variation in climate on carbon storage and the exchanges of energy, CO2, and water vapor in mature conifer forests in two climate zones: mesic 40-yr old Douglas-fir and semi-arid 60-yr old ponderosa pine (climate gradient); (3) To reduce uncertainty in estimates of CO2 feedbacks to the atmosphere by providing an improved model formulation for existing biosphere-atmosphere models; and (4) To provide high quality data for AmeriFlux and the NACP on micrometeorology, meteorology, and biology of these systems. Objective (1): A study integrating satellite remote sensing, AmeriFlux data, and field surveys in a simulation modeling framework estimated that the pyrogenic carbon emissions, tree mortality, and net carbon exchange associated with four large wildfires that burned ~50,000 hectares in 2002-2003 were equivalent to 2.4% of Oregon statewide anthropogenic carbon emissions over the same two-year period. Most emissions were from the combustion of the forest floor and understory vegetation, and only about 1% of live tree mass was combusted on average. Objective (2): A study of multi-year flux records across a chronosequence of ponderosa pine forests yielded that the net carbon uptake is over three times greater at a mature pine forest compared with young pine. The larger leaf area and wetter and cooler soils of the mature forest mainly caused this effect. A study analyzing seven years of carbon and water dynamics showed that interannual and seasonal variability of net carbon exchange was primarily related to variability in growing season length, which was a linear function of plant-available soil moisture in spring and early summer. A multi-year drought (2001-2003) led to a significant reduction of net ecosystem exchange due to carry-over effects in soil moisture and carbohydrate reserves in plant-tissue. In the same forest, the interannual variability in the rate carbon is lost from the soil and forest floor is considerable and related to the variability in tree growth as much as it is to variability in soil climatic conditions. Objective (3): Flux data from the mature ponderosa pine site support a physical basis for filtering nighttime data with friction velocity above the canopy. An analysis of wind fields and heat transport in the subcanopy at the mesic 40-year old Douglas site yielded that the non-linear structure and behavior of spatial temperature gradients and the flow field require enhanced sensor networks to estimate advective fluxes in the subcanopy of forest to close the surface energy balance in forests. Reliable estimates for flux uncertainties are needed to improve model validation and data assimilation in process-based carbon models, inverse modeling studies and model-data synthesis, where the uncertainties may be as important as the fluxes themselves. An analysis of the time scale dependence of the random and flux sampling error yielded that the additional flux obtained by increasing the perturbation timescale beyond about 10 minutes is dominated by random sampling error, and therefore little confidence can be placed in its value. Artificial correlation between gross ecosystem productivity (GEP) and ecosystem respiration (Re) is a consequence of flux partitioning of eddy covariance flux data when GEP is computed as the difference between NEE and computed daytime Re (e.g. using nighttime Re extrapolated into daytime using soil or air temperatures). Tower-data must be adequately spatially averaged before comparison to gridded model output as the time variability of both is inherently different. The eddy-covariance data collected at the mature pondero ...

Methods for Calculating Forest Ecosystem and Harvested Carbon with Standard Estimates for Forest Types of the United States

Methods for Calculating Forest Ecosystem and Harvested Carbon with Standard Estimates for Forest Types of the United States
Author:
Publisher:
Total Pages: 224
Release: 2006
Genre: Carbon sequestration
ISBN:

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This study presents techniques for calculating average net annual additions to carbon in forests and in forest products. Forest ecosystem carbon yield tables, representing stand-level merchantable volume and carbon pools as a function of stand age, were developed for 51 forest types within 10 regions of the United States. Separate tables were developed for afforestation and reforestation. Because carbon continues to be sequestered in harvested wood, approaches to calculate carbon sequestered in harvested forest products are included. Although these calculations are simple and inexpensive to use, the uncertainty of results obtained by using representative average values may be high relative to other techniques that use site- or project-specific data. The estimates and methods in this report are consistent with guidelines being updated for the U.S. Voluntary Reporting of Greenhouse Gases Program and with guidelines developed by the Intergovernmental Panel on Climate Change. The CD-ROM included with this publication contains a complete set of tables in spreadsheet format.

Carbon and Nitrogen in Forest Ecosystems—Series I

Carbon and Nitrogen in Forest Ecosystems—Series I
Author: Yowhan Son
Publisher: MDPI
Total Pages: 180
Release: 2021-01-20
Genre: Science
ISBN: 3039367447

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Understanding the differences in carbon and nitrogen distribution and cycling both spatially and temporally using various approaches is essential in forest ecosystems. In addition, the influence of biotic and abiotic factors as well as natural and artificial disturbances on carbon and nitrogen cycling need to first be understood before drawing their implications to forest management practices. This Special Issue aims to understand carbon and nitrogen distribution and cycling in forest ecosystems for ecosystem-based forest management under different natural and artificial disturbances.

Climate Change, Carbon, and Forestry in Northwestern North America

Climate Change, Carbon, and Forestry in Northwestern North America
Author: David Lawrence Peterson
Publisher:
Total Pages: 128
Release: 2004
Genre: Carbon sequestration
ISBN:

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Interactions between forests, climatic change and the Earths carbon cycle are complex and represent a challenge for forest managers they are integral to the sustainable management of forests. In this volume, a number of papers are presented that describe some of the complex relationships between climate, the global carbon cycle and forests. Research has demonstrated that these are closely connected, such that changes in one have an influence not only on the other two, but also on their linkages. Climatic change represents a considerable threat to forest management in the current static paradigm. However, carbon sequestration issues offer opportunities for new techniques and strategies, and those able to adapt their management to this changing situation are likely to benefit. Such changes are already underway in countries such as Australia and Costa Rica, but it will probably take much longer for the forestry sector in the Pacific Northwest region of North America (encompassing Oregon, Washington, Montana, Idaho, British Columbia and Alaska) to change their current practices.