Biodiversity, carbon storage and dynamics of old northern ... - BPAN.fi

More documents

Recommendations

Info

ing age. A few eddy covariance studies of old (>200 yrs) temperate forests in North America indicate ecosystem carbon accumulation rates of about 150–500 g C m -2 yr -1 . Repeated sampling of soil carbon in a temperate beech forest (250 yrs) and a boreal spruce forest (90 yrs), both unmanaged, indicates soil carbon accumulation rates of 60–160 g C m -2 yr -1 . Indirect evidence from several chronosequence studies indicates ecosystem carbon accumulation rates of about 4.5–170 g C m -2 yr -1 for forests 120 to >200 years old, with the lowest values for the oldest forests. Comparisons of forest stands of different ages also indicate that older forests have higher carbon stocks than younger forests. Although changes in soil or total ecosystem carbon stocks are difficult to monitor, and the various methods have their problems, the consistent direction of the results of the various studies provide convincing evidence that old forests function as carbon sinks for a long time. The carbon stocks in biomass of old forests continue to increase with age, possibly for several hundred years, although the rate of biomass accumulation and thus the carbon sink will decrease with increasing age. Also, carbon stocks of forest soil and dead organic matter (especially coarse woody debris) appear to increase with stand age. Changes in forest biomass carbon stocks in boreal and northern temperate forests are largely determined by tree species and age of forest stands, site productivity and disturbance history. Forest soil carbon stocks are driven by site productivity and soil type (primarily driving litter production but also influencing decomposition), litter quality, and local topography and disturbance history. The relationships between external drivers and soil carbon stocks are complex, and it is therefore difficult to describe clear patterns in the response of soil carbon stocks to such drivers. Generally, variation in soil carbon stocks with environmental drivers is most pronounced for the organic layer, less so for the mineral soil and total soil carbon stocks. Effects of harvesting on carbon stocks Modern forest management incorporates various management measures which influence carbon stocks and fluxes. The most fundamental effect comes with the removal of biomass from the forest, directly reducing the biomass carbon stocks. Harvesting produces considerable amounts of logging residue of various sizes. Most of it will be of small dimensions and decompose rather quickly over a decade or so, but stumps represent coarse woody debris with a slow decay rate (lasting up to a century). The carbon from logging debris and natural litter production will partly be incorporated into the soil organic matter, and partly be released to the atmosphere as CO 2. It is less clear how soil carbon stocks respond to the harvesting event as such. After the first rush of logging residues, little additional litter will be produced in a clear-cut stand for some decades. During the first few decades, decomposition of litter and soil organic matter will exceed production of biomass and the overall carbon stock will decline. Some studies indicate that the amount Biodiversity, carbon storage and dynamics old northern forests 11
of soil carbon may be reduced after harvesting for several decades. Such effects of harvesting on soil carbon stocks are affected by reduced production and input of litter and coarse woody debris rather than by increased decomposition rates. Total carbon stocks in managed forests will increase with longer rotation period, less thinning and harvesting of logging debris and stumps, and management of regeneration sites to ensure rapid restocking of forest stands, such as site preparation, planting of productive species or provenances, and fertilization. Knowledge gaps Many studies on forest carbon and its role in the global carbon cycle have been published over the last 10–15 years, but there are still important gaps in our knowledge. Although the dynamics of tree growth and biomass carbon stocks are reasonably well understood for forests a bit older than harvestable age, such dynamics in old forest, with trees approaching their natural life span, are poorly known. In particular we have inadequate knowledge of old forest tree mortality under natural dynamics and whether gap-filling dynamics will compensate biomass loss by natural mortality agents. Another important area requiring better knowledge is the variation in soil carbon stocks with stand age, site productivity, and other environmental factors, as well as the responses of soil carbon to disturbances like biomass harvesting. A key issue to resolve is whether soil carbon stocks will accumulate indefinitely or reach some steady state in a matter of decades or centuries, depending on the forest type and climatic conditions. We also need to improve our understanding of the linkages between biodiversity structure and ecosystem functions, particularly how these interact with the carbon and nitrogen cycles and the relationships between these biogeochemical cycles. A challenging issue beyond the natural sciences is whether and how the various goods of biodiversity, carbon sequestration, timber production, recreation and other amenity values of forests may be handled and arbitrated within a common framework of ecosystem services. Policy implications Although the climate effects of forest management are challenging to assess realistically due to complex interactions of changes in the carbon cycle and the biophysical climate forcing of forests, as well as poorly understood substitution effects of harvested forest biomass, we can still make some recommendations for forest management in a climate perspective. As forest ecosystems continue to accumulate carbon for a long time, protection of forest carbon stocks by increasing the amount of old forest is a credible policy option that will also benefit biodiversity conservation. In managed forests, prolonged harvesting cycles will also increase forest carbon stocks. Thinning of production forest and harvesting of logging residues and stumps will decrease forest carbon stocks, whereas intensive management to ensure rapid establishment of well- 12 Biodiversity, carbon storage and dynamics old northern forests
Page 1: Biodiversity, carbon storage and dy
Page 7 and 8: Biodiversity, carbon storage and dy
Page 9 and 10: 6 Biodiversity, carbon storage and
Page 13: Natural forest dynamics and biodive
Page 19 and 20: Forests in the Nordic countries als
Page 21 and 22: The role of old forests in the carb
Page 25 and 26: ests (Box 2). As truly pristine or
Page 27 and 28: From previous page UN Framework Con
Page 29 and 30: From previous page Previous conside
Page 31 and 32: floods, insect attacks) operating a
Page 33 and 34: Danish Draved forest (Bradshaw et a
Page 35 and 36: In wet and cool forests the process
Page 37 and 38: into conifer plantations gradually
Page 39 and 40: Most of the largest and presumably
Page 41 and 42: years, large trees and amounts and
Page 43 and 44: factors are also reflected in the E
Page 45 and 46: from the forest inventories, mainly
Page 49 and 50: contain if our aim is to maintain t
Page 51 and 52: The development time and duration o
Page 53 and 54: qualities of dead wood, both overal
Page 55 and 56: Figure 4.1. Number of Swedish wood-
Page 57 and 58: different spatial scales. Most of t
Page 59 and 60: Table 4.4. Habitat elements for red
Page 61 and 62: GPP is the production of organic co
Page 63 and 64: 2006). Because forest inventories c
Page 65 and 66:
stock is presented by Nord-Larsen e
Page 67 and 68:
An extensive dataset of successiona
Page 69 and 70:
The ratio of soil organic matter st
Page 71 and 72:
Callesen et al. (2003) analysed 234
Page 73 and 74:
Managed pine-dominated stand, south
Page 75 and 76:
cutting has also been questioned. Y
Page 77 and 78:
Stand vs selective management Uneve
Page 79 and 80:
Table 5.2. Qualitative effects of f
Page 81 and 82:
5.7 Old forests - carbon sources or
Page 83 and 84:
of mortality dynamics in forest mod
Page 85 and 86:
Table 5.3. Summary of eddy covarian
Page 87 and 88:
(Vaccinium myrtillus) domination of
Page 89 and 90:
Table 5.5. Indirect evidence from c
Page 91 and 92:
Woody debris can be a large carbon
Page 93 and 94:
Old forests: Data syntheses The glo
Page 95 and 96:
litter (coarse woody debris, leaves
Page 97 and 98:
Generally, variation in soil carbon
Page 99 and 100:
Species composition or growing stoc
Page 101 and 102:
(calcareous) coniferous and tempera
Page 103 and 104:
More realistic assessments of all c
Page 105 and 106:
6.5 Implications for forest policy
Page 107 and 108:
Overall, it is clearly documented t
Page 109 and 110:
Berglund, B.E. (ed.) (1991): The cu
Page 111 and 112:
Ge, Z.-M., Kellomäki, S., Peltola,
Page 113 and 114:
Klemedtsson, L., Klemedtsson, Å.K.
Page 115 and 116:
Mielikäinen, K. (1980): Manty-koiv
Page 117 and 118:
Rantakari, M., Lehtonen, A., Linkos
Page 119 and 120:
Swann, A., Fung, I.Y., Levis, S., B
Page 121 and 122:
118 Biodiversity, carbon storage an
Page 123 and 124:
Naturskogens dynamikk og biologisk
Page 125 and 126:
kan bli redusert etter høsting i f
Page 127 and 128:
124 Biodiversity, carbon storage an
Page 129 and 130:
sellä ja näiden resurssien vaihte
Page 131 and 132:
korvaako aukkoihin syntyneiden puid
Page 133 and 134:
Other tree species mention in the t
show all

Biodiversity, carbon storage and dynamics of old northern ... - BPAN.fi

Create successful ePaper yourself

Delete template?

Save as template?