Annett Börner

Old-growth forests as global carbon sinks

Old-growth forests remove carbon dioxide from the atmosphere at rates that vary with climate and nitrogen deposition. The sequestered carbon dioxide is stored in live woody tissues and slowly decomposing organic matter in litter and soil. Old-growth forests 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. Here we report a search of literature and databases for forest carbon-flux estimates. We find that in forests between 15 and 800 years of age, net ecosystem 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 contains the remaining old-growth forests. Half of the primary forests (6 × 108 hectares) are located in the boreal and temperate regions of the Northern Hemisphere. On the basis of our analysis, these forests alone sequester about 1.3 ± 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.

Atlas of Stem Anatomy in Herbs, Shrubs and Trees

1. Introduction to Volume 2 2. Monographic Descriptions Actinidiaceae Adoxaceae Apiaceae Aquifoliaceae Araliaceae Asteraceae - Mutisieae - Cardueae - Lactuceae - Inuleae - Gnaphalieae - Calenduleae - Astereae - Anthemideae - Senecioneae - Heleniae - Heliantheae - Eupatorieae - Tageteae - Summary Balsaminaceae Boraginaceae Callitrichaceae Campanulaceae Caprifoliaceae Clethraceae Convolvulaceae Cornaceae Diapensiaceae Diervillaceae Dipsacaceae Ebenaceae Frankeniaceae Garryaceae Hippuridaceae Hydrangeaceae Lamiaceae Lentibulariaceae Linnaeaceae Myrsinaceae Oleaceae Orobanchaceae Plantaginaceae Polemoniaceae Rafflesiaceae Roridulaceae Sapotaceae Sarraceniaceae Scrophulariaceae Solanaceae Styracaceae Valerianaceae Verbenaceae 3. Ecological, Morphological, Taxonomical and Functional Significance of Stem Features Within the Dicotyledons 4. Anatomical Adaptations to Environmental Conditions 5. Ontogeny of the Xylem 6. Secondary Woodiness and Paedomorphosis 7. Conclusions References Alphabetic List of Species

Temperature sensitivity of the turnover times of soil organic matter in forests

Soils represent the largest carbon pool in the terrestrial biosphere, and climate change might affect the main carbon fluxes associated with this pool. These fluxes are the production of aboveground litter and root litter, and decomposition of the soil organic matter (SOM) pool by soil microorganisms. Knowledge about the temperature sensitivity of the decomposition of different SOM fractions is crucial in order to understand how climate change might affect carbon storage in soils. In this study, the temperature sensitivity of the turnover times of three different SOM fractions (labile, intermediate, and stabilized) was investigated for 11 forest sites along a temperature gradient. Carbon-14 isotope analyses of the SOM fractions combined with a model provided estimates of their turnover times. The turnover times of the labile SOM fraction were not correlated with mean annual soil temperature. Therefore it was not possible to estimate temperature sensitivity for the labile SOM fraction. Given considerable evidence elsewhere for significant temperature sensitivities of labile SOM, lack of temperature sensitivity here most likely indicates limitations of the applied methodology for the labile SOM fraction. The turnover times of the intermediate and the stabilized SOM fractions were both correlated with mean annual soil temperatures. The temperature sensitivity of the stabilized SOM fraction was at least equal to that of the intermediate SOM fraction and possibly more than twice as high. A correction for confounding effects of soil acidity and clay content on the temperature sensitivities of the intermediate and stabilized SOM fractions was included in the analysis. The results as observed here for the three SOM fractions may have been influenced by (1) modeling assumptions for the estimation of SOM turnover times of leaf and needle longevities, constant annual carbon inputs, and steady-state SOM pools, (2) the occurrence of summer drought at some sites, (3) differences between sites in quality of the SOM fractions, or (4) the relatively small temperature range. Our results suggested that a 1 degree C increase in temperature could lead to decreases in turnover times of 4-11% and 8-16%, for the intermediate and stabilized SOM fractions, respectively.

Anatomical Adaptations to Environmental Conditions

In this chapter we compare anatomical structures of various species within plant communities. Combinations of similar environmental factors cause similar growth conditions, and therefore form plant communities with similar characteristics (such as plant size, life form and growth form, leaf properties and physiological behavior). This principle is expressed in large-scale vegetation zones as well as in small-scale plant communities. The similarity in species composition was the basis for phytosociology (Braun-Blanquet 1951, Reinalter 2007). In the following we explore if this similarity is also evident with respect to wood anatomy.

Evolution of stems

Writing a comprehensive story about stem evaluation is difficult because evidence of only few early plants has been preserved over millions of years. Samples exist of plants which were fossilized under anaerobic conditions, enclosed in resin (amber) or carbonized. The majority of plants from sites with aerobic soil conditions are not preserved.

Anatomical adaptations to temporarily changed environmental conditions

Two principal capacities characterize seed plants. Primarily, cell formation pathways determine the basic structure of plant bodies, and the formation of different cell types.

Technically altered wood products

This chapter gives an extremely brief overview over a few frequently used products made from technically altered wood— plywood, particleboards, granulated cork stoppers, hardboards, pencils and paper.

Stem anatomical structures of major taxonomic units

This chapter describes the anatomy of major stem-forming taxa within the taxonomic hierarchic system.

Coexistence of algae, fungi and vascular plants

The symbiotic relationship between fungi and the roots of vascular plants is called mycorrhiza.

Structure of the cell wall and cell contents

The cell wall of seed plants principally consists of several layers: the middle lamella, the primary, secondary and tertiary wall, a concept presented by Evert 2006. Secondary walls consist of macro-fibrils.