Carbon dynamics of young experimental afforestations in Thuringia [Elektronische Ressource] / vorgelegt von Axel Don

Sujets

• Biologie

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2007
• Nombre de lectures: 7
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Carbon dynamics
of young experimental afforestations
in Thuringia
Dissertation
zur Erlangung des Grades eines Doktors der Naturwissenschaften
der Geowissenschaftlichen Fakultät
der Eberhard Karls Universität Tübingen
vorgelegt von
Dipl. Geoökologe Axel Don
aus Kassel
2007Tag der mündlichen Prüfung: 19. 11. 2007
Dekan: Prof. Dr. Peter Grathwohl
1. Berichterstatter: Prof. Dr. Thomas Scholten (Geographisches Institut, Eberhard
Karls Universität Tübingen)
2. Berichterstatter: Prof. Dr. Ernst-Detlef Schulze (Max-Planck Institut für
Biogeochemie, Jena)
3. Berichterstatter: Prof. Dr. Nina Buchmann (Institut für Pflanzenwissenschaften,
ETH Zürich, Schweiz)
2Contents
Plates I - III ...................................................................................................................................................4
1. Introduction and hypotheses.................................................................................................................7
2. Overview on the six manuscripts .......................................................................................................11
2.1 Background: Afforestations and the Kyoto protocol......................................................11
2.2 The biodiversity experiment BIOTREE (manuscript 1) .................................................12
2.3 Factors influencing tree survival and establishment (manuscript 2) ..............................14
2.4 Land use changes and soil C (manuscript 3)......................................................................15
2.5 Effect of afforestations on net biome productivity (NBP) compared to
non-afforested grassland (manuscript 4) ...........................................................................18
2.6 The detectability of the C flux balances with soil C inventories (manuscript 5) ..........21
2.7 The impact of earthworms on soil carbon turnover rates (manuscript 6) ...................22
3. Conclusions.............................................................................................................................................25
4. Outlook....................................................................................................................................................27
4.1 Projected C sequestration depending on tree species and diversity................................27
4.2 Changes in soil fauna along with forest development ......................................................28
4.3 Soil C sequestration mechanism in the subsoil ..................................................................28
References for chapter 1 - 4......................................................................................................................30
Summary ......................................................................................................................................................35
Zusammenfassung......................................................................................................................................37
Manuscript 1: Exploring the functional significance of forest diversity: A new long-term
experiment with temperate tree species (BIOTREE)................................................39
Manuscript 2: Establishment success of 19 different tree species on afforestations –
Results of a biodiversity experiment (in German)......................................................71
Manuscript 3: Conversion of cropland into grassland – implications for soil organic carbon
stocks in two soils with different texture.....................................................................91
Manuscript 4: Impact of afforestation of an extensively managed grassland on C fluxes...........113
Manuscript 5: Spatial and vertical variation of soil carbon at two grassland sites –
implications for measuring soil carbon stocks..........................................................141
Manuscript 6: Organic carbon sequestration in earthworm burrows.............................................165
Acknowledgments ....................................................................................................................................193
3A
B C
Plate I: Aerial view from NO on the BIOTREE site Mehrstedt, container with the measurement equipment of the
eddy covariance tower in front (A); eddy covariance tower and meteorological station on the afforestation site
Mehrstedt (B); eddy covariance tower on the grassland site at Mehrstedt.
4C D
Plate II: Representative soil profiles of the Mehrstedt site with a Stagnic Vertisol (A) and the Kaltenborn site with
a Ortoeutric Arenosol (B); fresh sample core (8.7 cm diameter) taken with the machine driven Cobra corer at the
Mehrstedt site (C); Earthworm burrow with casts deposited on the walls in about 35 cm soil depth at the
Mehrstedt site (D).
5A B
100 m
C
Plate III: Historical (1953, A) and recent (2004, B) aerial picture (500x900 m) of the south-western part
of the BIOTREE site Mehrstedt including some experimental plot, non afforested grassland (NW) and
a forest patch (“Steingraben”) planted in 1930-33 with spruce and pine (by courtesy of the Thüringer
Landesamt für Vermessung und Geoinformation); site preparation on the former grassland of the
Mehrstedt site with deep ploughing of the planting rows (2m distance)(C).
61. Introduction and hypotheses
1. Introduction and hypotheses
Land use is a key factor controlling the carbon (C) dynamics of the biosphere (Cannell et
al., 1999; Guo and Gifford, 2002; IPCC, 2000). On the one hand, land use affects the net
primary productivity NPP (C input) of an ecosystem by fertilisation, melioration, harvest
and disturbance frequency and intensity. On the other hand, C loss by harvest and
C-leaching with seepage water and C exchange with the atmosphere as CO and other trace 2
gases is directly linked to the land use. The CO exchange between land surface and the 2
atmosphere has become a major concern in relation to the observed and predicted climate
change (IPCC, 2000). 15 times more C is turned over by the terrestrial biosphere than C is
emitted by human activities (IPCC, 2007; Schimel, 1995).
About 50-70% of total C in European forests and more than 95% in grasslands is stored
as soil organic carbon (Dixon et al., 1994; Mund and Schulze, 2006; Nöllert, 2003). If land
use change, such as the conversion of grassland into forest only slightly affects soil C stocks,
it can have significant effects on the total C balance of the system and its CO emissions. 2
-1 -1C accumulation in soils is a rather slow process rarely exceeding 1 t C ha a in the long
term whereas soil disturbances (e.g. ploughing, wind throw, fire) can cause a rapid soil C loss
(Guo and Gifford, 2002; Jandl et al., 2007; Soussana et al., 2004). This asymmetrical dynamic
was summarized as the “slow in - fast out” feature of ecosystems (Körner, 2003), pointing to
the fact that soil C pools are sensible and could possibly release large amounts of CO into 2
the atmosphere without having an mechanism to re-capture this CO at similar rates.2
Most studies on afforestations found decreasing mineral soil C stocks during the first
years to decades after forest establishment (Guo and Gifford, 2002; Paul et al., 2002; Post
and Kwon, 2000; Thuille and Schulze, 2006). A literature review on the effect of
-1afforestations on soil C reported decreasing soil C stocks with 0.63% a for <30 cm soil
depth during the first 5 years since conversion into forest (Paul et al., 2002). Afforestations
-1on grasslands showed especially high soil C losses of 0.28 % a or 10% decreased soil
C stocks after a non-defined time period (Guo and Gifford, 2002; Paul et al., 2002). The
mechanisms behind this decline are still unclear. Decreased C-input of fine roots when
herbaceous vegetation is suppressed by tree shading or damaged by site preparation may be
one mechanism of how afforestations lead to declining soil C stocks (Thuille and Schulze,
2006). Other studies relate C losses of young afforestations to enhanced mineralisation due
to the disturbance during site preparation (Harkness and Harrison, 1989).
7M
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1. Introduction and hypotheses
This thesis is part of the long-term research experiment “Biodiversity and ecosystem
functioning in experimental tree stands” (BIOTREE) which was set up to investigate the
influence of tree diversity on processes in ecosystems. On three sites in Thuringia a total of
70 ha were planted with more than 200 000 tree seedlings, providing the possibility to study
the C dynamics of young afforestations. This thesis serves as a baseline for further studies in
this unique experiment which has an expected running time of 100 years. The design and the
characteristics of the three sites are presented in manuscript 1 (in press, PPEES) (Fig. 1).
The establishment of experimental plots with certain mixtures out of 19 different tree
species was a critical endeavour. Different factors such as summer drought and damages by
voles and rabbits put a risk on the establishment success of the trees (manuscript 2, AFJZ
2007).
BIOTREE method (manuscript 1)
Climate, soil, geology, experimental d