Showing papers by "Ernst Detlef Schulze published in 2002"
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TL;DR: It is demonstrated that the consequences of species loss on the nitrogen budget of plant communities may be more severe if legume species are lost, and there is indication that P availability in the soil facilitates the legume effect on biomass production and biomass nitrogen accumulation.
Abstract: To investigate how plant diversity loss affects nitrogen accumulation in above-ground plant biomass and how consistent patterns are across sites of different climatic and soil conditions, we varied the number of plant species and functional groups (grasses, herbs and legumes) in experimental grassland communities across seven European experimental sites (Switzerland, Germany, Ireland, United Kingdom (Silwood Park), Portugal, Sweden and Greece). Nitrogen pools were significantly affected by both plant diversity and community composition. Two years after sowing, nitrogen pools in Germany and Switzerland strongly increased in the presence of legumes. Legume effects on nitrogen pools were less pronounced at the Swedish, Irish and Portuguese site. In Greece and UK there were no legume effects. Nitrogen concentration in total above-ground biomass was quite invariable at 1.66 ± 0.03% across all sites and diversity treatments. Thus, the presence of legumes had a positive effect on nitrogen pools by significantly increasing above-ground biomass, i.e. by increases in vegetation quantity rather than quality. At the German site with the strongest legume effect on nitrogen pools and biomass, nitrogen that was fixed symbiotically by legumes was transferred to the other plant functional groups (grasses and herbs) but varied depending on the particular legume species fixing N and the non-legume species taking it up. Nitrogen-fixation by legumes therefore appeared to be one of the major functional traits of species that influenced nitrogen accumulation and biomass production, although effects varied among sites and legume species. This study demonstrates that the consequences of species loss on the nitrogen budget of plant communities may be more severe if legume species are lost. However, our data indicate that legume species differ in their N 2 fixation. Therefore, loss of an efficient N 2 -fixer (Trifolium in our study) may have a greater influence on the ecosystem function than loss of a less efficient species (Lotus in our study). Furthermore, there is indication that P availability in the soil facilitates the legume effect on biomass production and biomass nitrogen accumulation.
357 citations
01 Dec 2002
TL;DR: In this article, the authors performed continuous eddy covariance measurements of carbon dioxide over an unmanaged beech forest in the Hainich National Park in Central Germany as part of the EU project CARBOEUROFLUX.
Abstract: Unmanaged forests at a late stage of successional development are considered to be insignificant as carbon sinks, since in theory, assimilation is thought to be balanced by respiration. However, little experimental evidence for this hypothesis exists so far for forests at the ecosystem level. Therefore, we performed continuous eddy covariance measurements of carbon dioxide over an unmanaged beech forest in the Hainich National Park in Central Germany as part of the EU project CARBOEUROFLUX. This forest shows typical characteristics of an ‘advanced’ forest with large dead wood pools, a diverse stand structure and a wide tree age class distribution, up to 250 years. This forest was a large carbon sink over 2 years, with 494 g C m −2 per year in 2000 and 49 0gCm −2 per year in 2001. Daytime summer fluxes were strongly controlled by photosynthetic photon flux density ( R 2 = 0.7–0.9), with minor effects of the ratio of diffuse to total downward radiation or the vapor pressure deficit. Nighttime CO 2 fluxes were mainly controlled by soil temperature ( R 2 = 0.8) and soil moisture. In addition, high nighttime CO2 fluxes (4–6 mol m −2 s −1 ) were found directly before and during bud break in spring as well as just after leaf fall of both years (2000 and 2001), reflecting stand physiology corresponding to phenological changes, independent of soil temperature. Additional wind profile measurements at five heights within the canopy revealed a decoupling of above and below canopy air flow under conditions of low friction velocity ( u ∗ < 0. 4ms −1 ), probably indicating down slope drainage. In conclusion, unmanaged forests at a comparatively late stage of successional development can still act as significant carbon sinks with large implications for forest management practice and negotiations about biological sinks within the Kyoto Protocol. © 2003 Elsevier Science B.V. All rights reserved.
334 citations
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TL;DR: In this article, the authors characterized charring of a softwood and hardwood and found that the wood was dominated by (di)- O -alkyl structures, and the chars by alkyl and aromatic structures.
270 citations
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TL;DR: In this paper, the authors reconstruct the history of tree growth and quantify the standing biomass along a chronosequence of six Norway spruce stands (Picea abies [L] Karst; 16-142 years old) on acid soils in a mountainous region with high nitrogen deposition.
155 citations
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TL;DR: In this article, the authors present scientific concerns regarding verification, which lead to scientific doubts that the practices encouraged by the Agreement can actually increase carbon sequestration under a full carbon accounting scheme.
Abstract: The Sixth and Seventh Conference of the Parties (COP 6 and 7) at The Hague, Bonn and Marrakesh came to a final Agreement on the Kyoto Protocol, which is thus ready for ratification by the individual nations. The Agreement was only achieved by allowing countries to offset their fossil fuel emission targets (on average 95% of the 1990 emissions) by increasing biological carbon sequestration, and by trading carbon credits. Activities that would count as increasing biological carbon sequestration include afforestation and reforestation, and changes in management of agriculture and forestry. According to the Agreement reached in Marrakesh, biological carbon sequestration may reach an offset of up to 80% of the required reduction in fossil fuel emissions (4% of the 5% reduction commitment). We explain why the allowable offset rose as high during the course of the negotiations. It is highlighted that major unintended consequences may be a result of the policy as it stands in the Marrakesh Accord. Major losses of biodiversity and primary forest are expected. We present scientific concerns regarding verification, which lead to scientific doubts that the practices encouraged by the Agreement can actually increase sequestration under a full carbon accounting scheme. We explain that there is a ‘win-win’ option that would protect high carbon pools and biodiversity in an economically efficient way. But, this is not supported by the Agreement. Despite the very positive signal that most nations of the United Nations will devote major efforts towards climate protection, there remains a most urgent need to develop additional rules to avoid unintended outcomes, and to promote the ‘win-win’ options that we explain.
150 citations
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TL;DR: In this article, the effects of fire and site type on carbon (C) and nitrogen (N) balances were determined by following the change of total and component C and N pools along four chronosequences of fire-prone Siberian Scots pine ecosystems.
Abstract: Effects of fire and site type on carbon (C) and nitrogen (N) balances were determined by following the change of total and component C and N pools along four chronosequences of fire-prone Siberian Scots pine ecosystems. These differed in the mean return interval of surface fires (unburned – moderately burned, 40 years – heavily burned, 25 years) and site quality (lichen versus Vaccinium site type). Of the Vaccinium site type (higher site quality) only a moderately burned chronosequence was studied. A total of 22 even-aged stands were investigated with stand ages ranging from 2 to 383 years. The C balance was dominated by the opposing dynamics of coarse woody debris (CWD) and biomass and could be divided into three phases: (1) Young stands (up to 40 years)acted as a net source for C of 6-10 mol C m-2 year-1 because the previous generation CWD pool originating from stand-replacing crown fires decayed much faster than biomass increased. During this period the C pool in the unburned lichen type chronosequence decreased from 807 to 480 mol C m-2. (2) Middle aged stands (40-100 years) being in a stage of maximum biomass accumulation were a net sink of 8-10 mol C m-2 year-1. (3)Maturestands (100 to > 350 years) continued to sequester C at a lower rate (0.8-2.5mol C m-2 year-1). Differences in the rates of C sequestration during the two later phases could be explained by the complex interaction between surface fire regime and site type. Recurrent surface fires resulted in enhanced mortality and regularly redistributed C from the living to the CWD pool thereby lowering the rate of C sequestration. Site quality determined the potential to recover from disturbance by fire events. Differences in site type did not correlate with soil and total ecosystem N pool size. However, the N status of needles as well as the N pool of physiologically active tissue was highest in the stands of the Vaccinium type. The “woody” C pool (biomass + CWD) was sensitive to differences in surface fire regime and site type. It was lowest in the heavily burned lichen type chronosequence (297 ± 108 mol C m-2), intermediate in the unburned and moderately burned lichen type chronosequence (571 ± 179 mol C m-2) and highest in the moderately burned Vaccinium type chronosequence (810 ± 334 mol C m-2). In contrast, the total soil C pool (organic plus mineral layer down to a depth of 25 cm) was independent of stand age, surface fire regimeand site type and fluctuated around a value of 250 mol C m-2. The organic layer C pool oscillated in response to recurring surface fires and its C pool was dependent on time since fire increasing at a rate of about 1.5 mol C m-2 year-during the first 40 years and then reaching a plateau of 170 mol C m-2. The total ecosystem N pool was 7.4 ± 1.5 mol N m-2 on average of which only 25 % were stored in biomass or coarse woody debris. Total ecosystem N was independent of stand age, surface fire regime and site type. No correlation was found between total ecosystem C and N pools. Average total ecosystem C:N ratio was 114 ± 35 mol C mol N-1. A conceptual model illustrating how changes in the regime of stand-replacing crown fires and recurrent surface fires and changes in site quality interact in determining the long-term C balance in Siberian Scots pine forests is presented.
110 citations
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100 citations
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TL;DR: Energy and latent heat fluxes were measured over ombrotrophic bogs in European Russia (Fyodorovskoye) and in central Siberia (Zotino) using the eddy covariance technique, as part of the EuroSiberian Carbonflux Project as mentioned in this paper.
Abstract: Energy and latent heat fluxes λ E were measured over ombrotrophic bogs in European Russia (Fyodorovskoye) and in central Siberia (Zotino) using the eddy covariance technique, as part of the EuroSiberian Carbonflux Project. The study covered most of the snowfree periods in 1998, 1999 and 2000; in addition some data were also collected under snow in early spring and late autumn 1999 and 2000. The snowfree period in Europian Russia exceeds the snowfree period in central Siberia by nearly 10 weeks. Marked seasonal and interannual differences in temperatures and precipitation, and hence energy partitioning, were observed at both sites. At both bogs latent heat fluxes (λ E ) exceeded sensible heat fluxes ( H ) during most of the snowfree period: maximum λ E were between 10 and 12 MJ m −2 d −1 while maximum H were between 3 and 5 MJ m −2 d −1 . There was a tendency towards higher Bowen ratios at Fyodorovskoye. Net radiation was the most influential variable that regulated daily evaporation rates, with no obvious effects due to surface dryness during years with exceptionally dry summers. Total snowfree evaporation at Fyodorovskoye (320 mm) exceeded totals at Zotino (280 mm) by 15%. At the former site, evaporation was equal to or less than precipitation, contrasting the Zotino observations, where summer evaporation was distinctly higher than precipitation. During the entire observation period evaporation rates were less than 50% of their potential rate. These data suggest a strong ‘mulching’ effect of a rapidly drying peat surface on total evaporation, despite the substantial area of free water surfaces during parts of the year. This effect of surface dryness was also observed as close atmospheric coupling. DOI: 10.1034/j.1600-0889.2002.01354.x
76 citations
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TL;DR: A three-year trace gas climatology of CO 2 and its stable isotopic ratios, as well as CH 4, N 2 O and SF 6, derived from regular vertical aircraft sampling over the Eurasian continent is presented in this article.
Abstract: A three-year trace gas climatology of CO 2 and its stable isotopic ratios, as well as CH 4 ,N 2 O and SF 6 , derived from regular vertical aircraft sampling over the Eurasian continent is presented. The four sampling sites range from about 1° Et o 89°E in the latitude belt from 48° Nt o 62°N. The most prominent features of the CO 2 observations are an increase of the seasonal cycle amplitudes of CO 2 and d13C‐CO 2 in the free troposphere (at 3000 m a.s.l.) by more than 60% from Western Europe to Western and Central Siberia. d18O‐CO 2 shows an even larger increase of the seasonal cycle amplitude by a factor of two from Western Europe towards the Ural mountains, which decreases again towards the most eastern site, Zotino. These data reflect a strong influence of carbon exchange fluxes with the continental biosphere. In particular, during . . . . . . — —
73 citations
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TL;DR: In this paper, the authors used light aircraft and at intervals of approximately 14 days, vertical profiles of temperature, humidity, CO 2 concentration and 13 C/ 12 C and 18 O/ 16 O ratio, as well as concentrations of CH 4, CO, H 2 and N 2 O, from about 80 to 3000 m above ground level have been determined for the atmosphere above a flux measurement tower located near the village of Zotino in central Siberia (60°45′N, 89°23′E).
Abstract: Using light aircraft and at intervals of approximately 14 days, vertical profiles of temperature, humidity, CO 2 concentration and 13 C/ 12 C and 18 O/ 16 O ratio, as well as concentrations of CH 4 , CO, H 2 and N 2 O, from about 80 to 3000 m above ground level have been determined for the atmosphere above a flux measurement tower located near the village of Zotino in central Siberia (60°45′N, 89°23′E). As well as being determined from flask measurements (typically at heights of 100, 500, 1000, 1500, 2000, 2500 and 3000 m) continuous CO 2 concentration profiles at 1 Hz have also been obtained using an infrared gas analyser. This measurement program is ongoing and has been in existence since July 1998. Data to November 2000 are presented and show a seasonal cycle for CO 2 concentration of about 25 μmol mol −1 within the atmospheric boundary layer (ABL) and about 15 μmol mol −1 in the free troposphere. Marked seasonal cycles in the isotopic compositions of CO 2 are also observed, with that of oxygen-18 in CO 2 being unusual: always being depleted in the ABL with respect to the free troposphere above. This is irrespective of whether the CO 2 concentration is higher or lower in the free troposphere. We interpret this as indicating a net negative discrimination being associated with the net terrestrial carbon exchange, irrespective of whether photosynthesis or respiration dominates the net carbon flux in this region. During winter flights, large fluctuations in CO 2 concentration with height are often observed both within and above the stable ABL. Usually (but not always) these variations in CO 2 concentrations are associated with more or less stoichiometrically constant variations in CO and CH 4 concentrations. We interpret this as reflecting the frequent transport of polluted air from Europe with very little vertical mixing having occurred, despite the large horizontal distances traversed. This notion is supported by back-trajectory analyses. Vertical profiles of CO 2 concentration with supplementary flask measurements allow more information on the structure and composition of an air mass to be obtained than is the case for flask measurements or for ground-based measurements only. In particular, our data question the notion that there is usually anything like “well mixed background air” in the mid-to-high northern latitudes during the winter months. DOI: 10.1034/j.1600-0889.2002.01335.x
59 citations
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TL;DR: In this paper, an introduction is given to the geography of Russian forests and specific conditions of the study sites located along the 60° latitude east of Moscow (Fyedorovskoe) near the Ural Mountains (Syktivkar) and in Central Siberia near the Yennisei river (Zotino).
Abstract: An introduction is given to the geography of Russian forests and to the specific conditions of the study sites located along the 60° latitude east of Moscow (Fyedorovskoe) near the Ural Mountains (Syktivkar) and in Central Siberia near the Yennisei river (Zotino). The climatic conditions were similar at all three sites. The main ecological parameter that changes between European Russia and Siberia is the length of the growing season (230 d above 0 °C NE Moscow to 170 d above 0 °C in Central Siberia) and to a lesser extent precipitation (580 mm NE Moscow to 530 mm in Central Siberia). The experimental sites were generally similar to the regional conditions, although the Tver region has less forest and more grassland than the central forest reserve, and the Komi region has slightly less wetland than the study area. The Krasnoyarsk region reaches from the arctic ocean to arid central Asia and contains a significant proportion of non-forest land. The boreal forest of west and east Yennisei differs mainly with respect to wetlands, which cover almost half of the land area on the west bank. All sites are prone to disturbance. Heavy winds and drought or surplus water are the main disturbance factors in European Russia (a 15–20 yr cycle), and fire is the dominating disturbance factor in Siberia (220–375 yr for stand replacing fires). DOI: 10.1034/j.1600-0889.2002.01342.x
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TL;DR: In this article, long-term eddy covariance measurements of energy and water fluxes and associated climatic parameters were carried out above a Scots pine (Pinus sylvestris) forest in the middle taiga zone of Central Siberia.
Abstract: Long-term eddy covariance measurements of energy and water fluxes and associated climatic parameters were carried out above a Scots pine (Pinus sylvestris) forest in the middle taiga zone of Central Siberia. Data from June 1998 through October 2000 are presented. With the exception of winter 1998/1999, data collection over this period were more or less continuous. A distinct seasonality in surface energy exchange characteristics was observed in all years. In early spring in the absence of physiological activity by the vegetation, about 80% of the net radiation was partitioned for sensible heat, resulting in Bowen ratios, b, as high as 8. In the 1‐2 wk period associated with onset of photosynthesis in spring, evaporation rates increased rapidly and b rapidly dropped. However, even during summer months, sensible heat fluxes typically exceeded latent heat fluxes and b remained above 2.0. Observed daily evaporation rates varied between 0.5‐1.0 mm d−1 in spring and autumn and 1.5‐2 mm d−1 in midsummer. The overall average for the three growing seasons examined was 1.25 mm d−1. Precipitation was on average 230 mm for the growing period, with evaporation over the same time being about 190 mm for both 1999 and 2000. This represented only about 35% of the equilibrium evaporation rate. There was typically a positive hydrological balance of 40 mm for the growing season as a whole. However, in all three years examined, evaporation exceeded precipitation totals by 20‐40 mm in at least one calendar month during summer. During the growing season, daily averaged surface conductances varied between 0.15 and 0.20 mol m−2 s−1 (3‐4.5 mm s−1) in dry or cool months and 0.30‐0.35 mol m−2 s−1 (6.5‐8 mm s−1) in moist and warm months. Despite a negative hydrological balance during midsummer, there was little evidence for reduced canopy conductances in response to soil water deficits. This may have been the consequence of roots accessing water from within or just above a perched water table, located at about 2 m depth.
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TL;DR: In lichen-type forests, it was found that ANPP at the landscape level declined sharply when the interval between stand-replacing fires was less than 120 years, illustrating that fire strongly influences ANPP of boreal Scots pine forests.
Abstract: Temporal patterns of stem and needle production and total aboveground net primary production (ANPP) were studied at the tree and stand level along four chronosequences of Siberian Scots pine (Pinus sylvestris L.) forests differing in site quality (poor lichen type or the more fertile Vaccinium type) and in frequency of surface fires (unburned, moderately burned (fire return interval of approximately 40 years), or heavily burned (fire return interval of approximately 25 years)). The maximum range of variability in aboveground production was quantified for: (1) possible long-term changes in site quality; (2) stand age; (3) non-stand-replacing, recurring surface fires; and (4) interannual climate variability. For (1) and (2), total ANPP was low in the lichen-type chronosequence, reached a maximum of 170 g C m(-2) year(-1) after 100 years and decreased to 100 g C m(-2) year(-1) in older stands. Maximum ANPP in the Vaccinium-type chronosequence was 340 g C m(-2) year(-1) and occurred earlier in the 53-year-old stand than in the other stands. Along the lichen-type chronosequences, peak ANPP was paralleled by maximum carbon allocation to stem growth. (3) In mature trees, damage by recurrent surface fires decreased stem growth by 17 +/- 19% over a 10-year period relative to pre-fire values. At longer timescales, ANPP was hardly affected by fire-related differences in mortality. (4) Needle- plus stem-NPP, reconstructed for a 3-year period, varied within a range of 15 g C m(-2) year(-1) in the lichen-type stands and 35 g C m(-2) year(-1) in the Vaccinium-type stands. For the same period, the coefficient of variance was higher for needle-NPP (20 +/- 10%) than for stem-NPP (12 +/- 7%). Needle- and stem-NPP did not covary in time. Most 30-year time series of stem-NPP at the tree level exhibited strong autocorrelation. In older trees, stem-NPP was positively correlated with growing season precipitation. Thus, the factors driving variability in ANPP ranked according to their maximum influence as: stand age (controlled by the frequency of stand-replacing fires) > site quality > growth depression because of surface fire damage approximately equal age-related reduction in ANPP > interannual variability approximately equal long-term effects of fire (stand density reduction). In lichen-type forests, we found that ANPP at the landscape level declined sharply when the interval between stand-replacing fires was less than 120 years, illustrating that fire strongly influences ANPP of boreal Scots pine forests.
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TL;DR: The demography of Picea abies trees was studied over a period of about 30 years on permanent plots in six forest types of an unmanaged forest located in a forest reserve of the Southern Taiga, NW of Moscow.
Abstract: The demography of Picea abies trees was studied over a period of about 30 yr on permanent plots in six forest types of an unmanaged forest located in a forest reserve of the Southern Taiga, NW of Moscow. This study encompassed a broad range of conditions that are typical for old growth spruce forests in the boreal region, including sites with a high water table and well drained sites, podzolic soils, acidic soils and organic soils. At all sites stand density, tree height, breast height diameter and age has been periodically recorded since 1968. Tree density ranged between 178 and 1035 trees ha −1 for spruce and between 232 and 1168 trees ha −1 for the whole stand, including mainly Betula and Populus . Biomass ranged between 5.4 and 170 t dw ha −1 for spruce and between 33 to 198 t dw ha −1 for the whole stand. Averaged over a long period of time, biomass did not change with stand density according to the self-thinning rule. In fact, on most sites biomass remained almost constant in the long term, while stand density decreased. The study demonstrates that the loss of living trees was not regulated by competitive interactions between trees, but by disturbances caused by climatic events. Dry years caused losses of minor and younger trees without affecting biomass. In contrast, periodic storms resulted in a loss of biomass without affecting density, except for extreme events, where the whole stand may fall. Dry years followed by wet years enhance the effect on stand density. Since mainly younger trees were lost, the apparent average age of the stand increased more than real time (20% for Picea ). Average mortality was 2.8 ± 0.5% yr −1 for spruce. Thus, the forest is turned over once every 160–180 yr by disturbances. The demography of dead trees shows that the rate of decay depends on the way the tree died. Storm causes uprooting and stem breakage, where living trees fall to the forest floor and decay with a mean residence time ( t 1/2 ) of about16 yr (decomposition rate constant k d = 0.042 yr −1 ). This contrasts with trees that die by drought or insect damage, and which remain as standing dead trees with a mean residence time of 3–13 yr until they are brought to ground, mainly by wind. These standing dead trees require an additional mean residence time of about 22 yr for decay on the ground ( k d = 0.031) . In conclusion, we demonstrate that, rather than competitive interactions, it is climate extremes, namely drought, rapid changes of dry years followed by wet years, and storm that determine stand structure, biomass and density, which then affect the net exchange with the atmosphere. The climatic effects are difficult to predict, because the sensitivity of a stand to climate extremes depends on the past history. This may range from no effect, if the stand was recovering from an earlier drought and exhibited a relatively low density, to a total collapse of canopies, if drought reduces stand density to an extent that other climatic extremes (especially wind) may cause further damage. DOI: 10.1034/j.1600-0889.2002.01344.x
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TL;DR: In this article, the authors present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (excluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia.
Abstract: We present soil organic carbon (SOC) inventories and carbon isotope compositions from over 900 samples collected in areas of minimally disturbed mature vegetation on freely drained soils (excluding peatlands) on a 1000 km transect along the Yennisey River, central Siberia. Carbon inventories over 0–30 cm depth range widely from 1.71 to 7.05 kg m −2 . While an effect of changing climate or vegetation along the transect cannot be ruled out, the observed differences in SOC inventories are largely the result of variations in mineral soil texture, with inventories in fine-textured soils being approximately double those in coarse-textured soils. The δ 13 C values of SOC in the 0–5 cm interval ranged from −26.3 to −28.0‰ , with δ 13 C values for the 5–30 cm interval being 0.9 ± 0.8‰ (1σ) enriched in 13 C relative to the 0–5 cm samples. The average δ 13 C value for the 0–5 cm interval for all samples was −27.1 ± 0.6‰ (1σ) and for the full 0–30 cm interval the average was −26.5 ± 0.5‰ (1σ) . In general, δ 13 C values were higher in coarse-textured soils and lower in fine-textured soils. The results of detailed sampling of soils in Pinus sylvestris forest growing on sand near the Zotino flux tower suggest an SOC inventory in these soils of 2.22 ± 0.35 kg m −2 over 30 cm and an average δ 13 C value of −26.3 ±0.2‰ over the 0–5 cm depth interval and −25.9 ± 0.3‰ over 0–30 cm. Recent burning had no effect on SOC inventories, but clearing has led to an average 25% decrease on SOC inventories from 0–30 cm over 12 yr. Neither burning nor clearing had a discernible effect on the δ 13 C value of SOC. DOI: 10.1034/j.1600-0889.2002.01334.x
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TL;DR: In this article, the authors used a linear regression analysis applied to flask measurements of CO, CH4 and δ 13 C versus CO2 in the free troposphere, which indicated that industrial emissions over Europe are a dominant source of synoptic variability in wintertime in air masses reaching Fyodorovskoye.
Abstract: As part of the EUROSIBERIAN CARBONFLUX project, regular measurements have been performed in the lower troposphere over a southern taiga forest area in Fyodorovskoye, Western Russia (56 ◦ 28 � N, 32 ◦ 56 � E). Up to 70 flights have been made between May 1998 and December 2000, plus additional intensive campaigns to study the diurnal variability of atmospheric trace gases within the boundary layer. We sampled flasks between 100 and 3000 m for analysis of CO2, δ 13 C and δ 18 Oi n CO 2 ,C H 4 and CO. In addition, in-situ CO2, relative humidity, pressure and temperature were performed for a better description of the vertical variability and accurate determination of the boundary layer height. The peak-to-peak amplitude of the seasonal cycle of atmospheric CO2 within the boundary layer of 26.5 ppm is about twice the one observed in the free troposphere (14.6 ppm). The spring draw down of CO2 also occurs one month earlier than in the free troposphere aloft. There is also an increase by factor of two in the vertical variability of CO2 within the free troposphere between summer and winter, which may be related to the variability of advection and mixing. Linear regression analysis applied to flask measurements of CO, CH4 and δ 13 C versus CO2 in the free troposphere indicates that industrial emissions over Europe are a dominant source of synoptic variability in wintertime in air masses reaching Fyodorovskoye. On the other hand, the variability of trace gases in the boundary layer observed during intensive campaigns is consistent with the patterns of proximate sources over the underlying southern taiga landscape at Fyodorovskoye.
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TL;DR: In this paper, the authors used peat accumulation above the hypocotyl of pine trees and the eddy covariance flux methodology to measure the net ecosystem productivity in a bog located in the middle taiga of Siberia.
Abstract: Net ecosystem productivity (NEP) was studied in a bog located in the middle taiga of Siberia using two approaches, the accumulation of peat above the hypocotyl of pine trees, and the eddy covariance flux methodology. NEP was 0.84 tC ha −1 yr −1 using the peat accumulation method; it was 0.43–0.62 tC ha −1 yr −1 using eddy covariance over three growing seasons. These data were compared with NEP of the surrounding forest, which was 0.6 tC±1.1 ha −1 yr −1 . The trees growing on the bog reached a total height of about 3 m and an age of 80–120 yr when peat accumulation reached 0.5–0.6 m. At that stage the growth rate of the oldest trees declined. This indicates that there is a maximum age that can be reached by trees growing on hummocks (<150 yr), depending on conditions. The data show that the determination of NEP in bogs by using the peat accumulation above the hypocotyl is a useful method which can be applied on a wide range of bog types, but it may systematically overestimate NEP. The total sink capacity for carbon assimilation of bogs is comparable to that of forest, although methane emissions and losses of dissolved organic carbon must be taken into account when assessing the regional carbon cycle. DOI: 10.1034/j.1600-0889.2002.01386.x
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TL;DR: It is concluded that almond trees did not adapt physiologically to a limited water supply, but maximized their carbon gain for a given amount of water available by phenological processes such as high growth rate during periods of low evaporative demand of the atmosphere.
Abstract: Water use, both at the level of a single leaf and the whole plant, was studied for 1- to 4-year-old almond trees (Prunus dulcis) under arid conditions in the Negev Desert (Israel). By planting the trees into lysimeters of different volumes (7, 14 and 21 m3), the amount of water available to the plants was experimentally controlled. Each year, at the beginning of the growing season, the lysimeters, which had been filled with local homogenized loess, were watered to field capacity. The trees received different relative amounts of water in relation to their leaf area on the one hand and lysimeter volume on the other, which caused different rates of soil drying throughout the season. The following hypotheses were tested. (1) The amount of CO2 assimilated per transpiration and (2) biomass production per unit of water used increases with (a) decreasing amount of soil water applied and (b) increasing leaf area, which should enhance growth in spring during periods of low evaporative demand. At the leaf level, the ratio of daily CO2 assimilation (A) to daily transpiration (E) was independent of lysimeter size, leaf area and pre-dawn water potential, but decreased with increasing leaf-to-air vapour pressure difference (D
l). Consequently, during the course of the season, A/E decreased from spring to summer in accordance with rising D
l. However, when measured at a constant D
l, the seasonal course in A/E disappeared. At the whole plant level, the ratio of total lifetime biomass production (B) to the amount of water transpired (W) increased with leaf area (i.e. demand for water), the increase being stronger with increasing water supply. We conclude that almond trees did not adapt physiologically to a limited water supply, but maximized their carbon gain for a given amount of water available by phenological processes such as high growth rate during periods of low evaporative demand of the atmosphere.
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TL;DR: In this article, eddy covariance measurements of CO2 and water vapour were carried out in a natural regenerating forest after a fire event and the results were compared with previous studies on coniferous forests where biospheric exchanges of energy were dominated by sensible heat fluxes and small carbon uptake rates.
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TL;DR: In this article, the authors give an overview about the biological control of net carbon fluxes, ranging from gross primary productivity, GPP (photosynthesis), and net primary productivity (plant growth), to net ecosystem productivity, NEP (CO2 assimilation minus heterotrophic respiration), including non-respiratory losses, such as harvest and fire.
Abstract: The Kyoto protocol and the agreement reached at Bonn requires an assessment of the net carbon balance at different scales, ranging from projects and nations to continents. In the following we give an overview about the biological control of net carbon fluxes. Depending on the processes under consideration, these range from gross primary productivity, GPP (photosynthesis), and net primary productivity, NPP (plant growth), to net ecosystem productivity, NEP (CO2 assimilation minus heterotrophic respiration), and net biome productivity, NBP, including non-respiratory losses, such as by harvest and fire. We give an overview about the quantification of these processes based on Europe and Siberia. The Kyoto commitment is focused on the woody component of NPP, which is in the order of 1 to 2 t C ha-1 year-1. But, if all respiratory and non-respiratory losses are considered, the NBP decreases to less than 0.5 t C ha-1 year-1. Given the uncertainty of the assessments, and the difference between NPP and NBP it appears questionable to include biological sinks into the carbon accounting of fossil fuel emissions.
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TL;DR: Based on the IGBP-transect initiative, a north south transect was estab- lished across Europe ranging from north Sweden to central Italy in order to study effects of global change as discussed by the authors.
Abstract: Europe is characterized not only by large geo- morphological variability but also by a long history of land use. This resulted in a highly variegated landscape. Based on the IGBP-transect initiative, a north south transect was estab- lished across Europe ranging from north Sweden to central Italy in order to study effects of global change. Mainly process oriented studies were established on plots along the transect, and these were used to establish functional relationships as basis for landscape integration. However, it became apparent that the transect approach was not sufficient to mirror the European environment. From early on, the assessment of land cover was not constrained to this transect but complemented with measurements focused on Europe at a continental scale. Also, continental networks of flux measurements and ecosys- tem experiments were established, because these were able to encompass a larger inherent variability of climate, geology and land use. Resulting from the Kyoto protocol emphasis moved stronger from observations along transects towards a continental scale quantification of fluxes given the reporting needs. In this process the transect and the networks merged into research clusters, which provided a scaling and verifica- tion mechanism. Thus, the European situation may serve as an example of how the initial idea of transects has further evolved and broadened to continental scale studies in a region where anthropogenic land use dominates over climate change.
16 Jan 2002
01 Jan 2002