scispace - formally typeset
Search or ask a question

Showing papers by "Ernst Detlef Schulze published in 2004"


Journal ArticleDOI
TL;DR: The experimental design explicitly addresses criticisms provoked by previous biodiversity experiments, in particular, the choice of functional groups, the statistical separation of sampling versus complementarity effects, and testing for the effects of particular functional groups differ from previous experiments.

526 citations


Journal ArticleDOI
TL;DR: To facilitate future carbon and nutrient inventories, mixed-effect linear models were used to develop new generic biomass functions for Norway spruce in Central Europe and the Akaike Information Criterion was used for model selection.
Abstract: To facilitate future carbon and nutrient inventories, we used mixed-effect linear models to develop new generic biomass functions for Norway spruce (Picea abies (L.) Karst.) in Central Europe. We present both the functions and their respective variance-covariance matrices and illustrate their application for biomass prediction and uncertainty estimation for Norway spruce trees ranging widely in size, age, competitive status and site. We collected biomass data for 688 trees sampled in 102 stands by 19 authors. The total number of trees in the "base" model data sets containing the predictor variables diameter at breast height (D), height (H), age (A), site index (SI) and site elevation (HSL) varied according to compartment (roots: n = 114, stem: n = 235, dry branches: n = 207, live branches: n = 429 and needles: n = 551). "Core" data sets with about 40% fewer trees could be extracted containing the additional predictor variables crown length and social class. A set of 43 candidate models representing combinations of lnD, lnH, lnA, SI and HSL, including second-order polynomials and interactions, was established. The categorical variable "author" subsuming mainly methodological differences was included as a random effect in a mixed linear model. The Akaike Information Criterion was used for model selection. The best models for stem, root and branch biomass contained only combinations of D, H and A as predictors. More complex models that included site-related variables resulted for needle biomass. Adding crown length as a predictor for needles, branches and roots reduced both the bias and the confidence interval of predictions substantially. Applying the best models to a test data set of 17 stands ranging in age from 16 to 172 years produced realistic allocation patterns at the tree and stand levels. The 95% confidence intervals (% of mean prediction) were highest for crown compartments (approximately +/- 12%) and lowest for stem biomass (approximately +/- 5%), and within each compartment, they were highest for the youngest and oldest stands, respectively.

279 citations


Journal ArticleDOI
TL;DR: In this article, estimates of the carbon balance of forests, grasslands, arable lands and peatlands were used to obtain country-specific estimates of terrestrial carbon balance during the 1990s, showing that forests and grasslands were a net sink for carbon, whereas croplands were carbon sources in all European countries.
Abstract: . We summed estimates of the carbon balance of forests, grasslands, arable lands and peatlands to obtain country-specific estimates of the terrestrial carbon balance during the 1990s. Forests and grasslands were a net sink for carbon, whereas croplands were carbon sources in all European countries. Hence, countries dominated by arable lands tended to be losing carbon from their terrestrial ecosystems, whereas forest-dominated countries tended to be sequestering carbon. In some countries, draining and extraction of peatlands caused substantial reductions in the net carbon balance. Net terrestrial carbon balances were typically an order of magnitude smaller than the fossil fuel-related carbon emissions. Exceptions to this overall picture were countries where population density and industrialization are small. It is, however, of utmost importance to acknowledge that the typically small net carbon balance represents the small difference between two large but opposing fluxes: uptake by forests and grasslands and losses from arable lands and peatlands. This suggests that relatively small changes in either or both of these large component fluxes could induce large effects on the net total, indicating that mitigation schemes should not be discarded a priori. In the absence of carbon-oriented land management, the current net carbon uptake is bound to decline soon. Protecting it will require actions at three levels; a) maintaining the current sink activity of forests, b) altered agricultural management practices to reduce the emissions from arable soils or turn into carbon sinks and c) protecting current large reservoirs (wetlands and old forests), since carbon is lost more rapidly than sequestered.

241 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the net CO2 exchange (NEE) over ecosystems differing in land use (forest and agriculture) in Thuringia, Germany, and found that large contrasts were found in NEE rates between the land uses of the ecosystems.
Abstract: Eddy covariance was used to measure the net CO2 exchange (NEE) over ecosystems differing in land use (forest and agriculture) in Thuringia, Germany. Measurements were carried out at a managed, even-aged European beech stand (Fagus sylvatica, 70–150 years old), an unmanaged, uneven-aged mixed beech stand in a late stage of development (F. sylvatica, Fraxinus excelsior, Acer pseudoplantanus, and other hardwood trees, 0–250 years old), a managed young Norway spruce stand (Picea abies, 50 years old), and an agricultural field growing winter wheat in 2001, and potato in 2002. Large contrasts were found in NEE rates between the land uses of the ecosystems. The managed and unmanaged beech sites had very similar net CO2 uptake rates (�� 480 to � 500 g C m � 2 yr � 1 ). Main differences in seasonal NEE patterns between the beech sites were because of a later leaf emergence and higher maximum leaf area index at the unmanaged beech site, probably as a result of the species mix at the site. In contrast, the spruce stand had a higher CO2 uptake in spring but substantially lower net CO2 uptake in summer than the beech stands. This resulted in a near neutral annual NEE (� 4gCm � 2 yr � 1 ), mainly attributable to an ecosystem respiration rate almost twice as high as that of the beech stands, despite slightly lower temperatures, because of the higher elevation. Crops in the agricultural field had high CO2 uptake rates, but growing season length was short compared with the forest ecosystems. Therefore, the agricultural land had low-to-moderate annual net CO2 uptake (� 34 to � 193 g C m � 2 ), but with annual harvest taken into account it will be a source of CO2 ( 1 97 to 1 386 g C m � 2 ). The

190 citations


Journal ArticleDOI
TL;DR: In this paper, the Roth-C model was used to assess the ecosystem carbon balance of an agricultural ecosystem in Thuringia, Germany, growing winter wheat in 2001, which indicated an annual net ecosystem exchange (NEE) uptake in the range from −185 to −245 g C m −2 per year.

181 citations


01 Jan 2004
TL;DR: Friedlingstein et al. as mentioned in this paper explored the network of feedbacks between the physical climate system and the carbon cycle and found that human actions can also lead to feedbacks on climate.
Abstract: In most scenario calculations to date, emissions from fossil-fuel burning are prescribed, and a carbon cycle model computes the time evolution of atmospheric CO2 as the residual between emissions and uptake by land and ocean, typically without considering feedbacks of climate on the carbon cycle (see, e.g., Schimel et al. 1996). The global carbon cycle is, however, intimately embedded in the physical climate system and tightly interconnected with human activities. As a consequence, climate, the carbon cycle, and humans are linked in a network of feedbacks, of which only those between the physical climate system and the carbon cycle have been explored so far (Friedlingstein, Chapter 10, this volume). One example of a carbon-climate feedback begins with the modification of climate through increasing atmospheric CO2 concentration. This modification affects ocean circulation and consequently ocean CO2 uptake (e.g., Sarmiento et al. 1998; Joos et al. 1999; Matear and Hirst 1999). Similar feedbacks occur on land. For example, rising temperatures lead to higher soil respiration rates, which lead to greater releases of carbon to the atmosphere (e.g., Cox et al. 2000; Friedlingstein et al. 2003). Human actions can also lead to feedbacks on climate. If climate change intensifies pressure to convert forests into pastures and cropland, then the climate change may be amplified by the human response (Raupach et al., Chapter 6, this volume). These positive feedbacks increase the fraction of the emitted CO2 that stays in the atmosphere, increasing the growth rate of atmospheric CO2 and accelerating climate change. Negative feedbacks are also possible. For example, a northward extension of forest or

159 citations



Journal ArticleDOI
TL;DR: The LA-C-GC-IRMS method will be useful in elucidating short-term climate effects on the delta13C signal in tree rings, indicating a signal related to the forest stand's climate history.
Abstract: We present a new, rapid method for high-resolution online determination of delta13C in tree rings, combining laser ablation (LA), combustion (C), gas chromatography (GC) and isotope ratio mass spectrometry (IRMS) (LA-C-GC-IRMS). Sample material was extracted every 6 min with a UV-laser from a tree core, leaving 40-microm-wide holes. Ablated wood dust was combusted to CO2 at 700 degrees C, separated from other gases on a GC column and injected into an isotope ratio mass spectrometer after removal of water vapor. The measurements were calibrated against an internal and an external standard. The tree core remained intact and could be used for subsequent dendrochronological and dendrochemical analyses. Cores from two Scots pine trees (Pinus sylvestris spp. sibirica Lebed.) from central Siberia were sampled. Inter- and intra-annual patterns of delta13C in whole-wood and lignin-extracted cores were indistinguishable apart from a constant offset, suggesting that lignin extraction is unnecessary for our method. Comparison with the conventional method (microtome slicing, elemental analysis and IRMS) indicated high accuracy of the LA-C-GC-IRMS measurements. Patterns of delta13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was +/- 0.24 per thousand. Isotopic patterns of the two Scots pine trees were broadly similar, indicating a signal related to the forest stand's climate history. The maximum variation in delta13C over 22 years was about 5 per thousand, ranging from -27 to -22.3 per thousand. The most obvious pattern was a sharp decline in delta13C during latewood formation and a rapid increase with spring early growth. We conclude that the LA-C-GC-IRMS method will be useful in elucidating short-term climate effects on the delta13C signal in tree rings.

85 citations



Book ChapterDOI
01 Jan 2004
TL;DR: The Weidenbrunnen site in the Lehstenbach catchment was selected as a EURO-FLUX site (Valentini et al. 2000) and was also used in the following CARBOEUROFLUX program for systematic investigations with respect to the data quality of turbulent fluxes.
Abstract: The investigation of carbon fluxes is of immense interest in ecosystem and climate research. Forest ecosystems may be a sink for anthropogenic carbon, if the assimilation is larger than the respiration. Alternatively, increasing temperatures due to climate change (IPCC 2001) may be a reason for increasing respiratory fluxes. While low-altitude spruce sites in Germany are significant carbon sinks (e.g. Bernhofer et al. 2003), sites above 600 m a.s.l. are only small sinks or may change their character by climate change. Therefore the Weidenbrunnen site in the Lehstenbach catchment was selected as a EUROFLUX site (Valentini et al. 2000) and was also used in the following CARBOEUROFLUX program for systematic investigations with respect to the data quality of turbulent fluxes. Overviews of the European carbon program and of the worldwide FLUXNET program are respectively given by Valentini (2003) and Baldocchi et al. (2001). All relevant references are also provided herein. Furthermore, the site was used for process studies to separate assimilation and respiration fluxes, and to study the exchange conditions between the forest and the atmosphere (Wichura et al., this Vol.). All of these studies were part of the ecosystem research of the Lehstenbach catchment, the main research area of the Bayreuth Institute of Terrestrial Ecosystem Research (BITOK). The main results for the carbon dioxide flux measurements since 1997 are discussed in this chapter.

23 citations