1,435 research outputs found
The ecology of Central European tree species: Trait spectra, functional trade-offs, and ecological classification of adult trees
No full textLeaf Size and Leaf Area Index in Fagus sylvatica Forests: Competing Effects of Precipitation, Temperature, and Nitrogen Availability
No full textPlants across diverse biomes tend to produce smaller leaves and a reduced total leaf area when exposed to drought. For mature trees of a single species, however, the leaf area-water supply relationship is not well understood. We tested the paradigm of leaf area reduction upon drought by a transect study with 14 mature Fagus sylvatica forests along a steep precipitation gradient (970-520 mm y(-1)) by applying two independent methods of leaf size determination. Contrary to expectation, average leaf size in dry stands (520-550 mm y(-1)) was about 40% larger and SLA was higher than in moist stands (910-970 mm y(-1)). As a result of increased leaf sizes, leaf area index significantly increased from the high- to the low-precipitation stands. Multiple regression analyses suggested that average leaf size was primarily controlled by temperature, whereas the influence of soil moisture and soil C/N ratio was low. Summer rainfall of the preceding year was the most significant predictor of total leaf number. We assume that leaf expansion of beech was independent of water supply, because it takes place in May with ample soil water reserves along the entire transect. In contrast, bud formation, which determines total leaf number, occurs in mid-summer, when droughts are severest. We conclude that leaf expansion and stand leaf area of beech along this precipitation gradient are not a simple function of water availability, but are controlled by several abiotic factors including spring temperature and possibly also nitrogen supply, which both tend to increase toward drier sites, thus overlaying any negative effect of water shortage on leaf development.Deutsche Bundesstiftung Umwel
Nutrient dynamics along a precipitation gradient in European beech forests
No full textPrecipitation as a key determinant of forest productivity influences forest ecosystems also indirectly through alteration of the nutrient status of the soil, but this interaction is not well understood. Along a steep precipitation gradient (from 970 to 520 mm yr-1 over 150 km distance), we studied the consequences of reduced precipitation for the soil and biomass nutrient pools and dynamics in 14 mature European beech (Fagus sylvatica L.) forests on uniform geological substrate. We tested the hypotheses that lowered summer precipitation (1) is associated with less acid soils and a reduced accumulation of organic matter on the forest floor, and (2) reduces nutrient supply from the soil and leads to decreasing foliar and root nutrient concentrations. Soil acidity, the amount of forest floor organic matter, and the associated organic matter N and P pools decreased to about a half from wet to dry sites; the C/P and N/P ratios, but not the C/N ratio, of forest floor organic matter decreased. Net N mineralization (and nitrification) rate and the available P and K pools in the mineral soil did not change with decreasing precipitation. Foliar P and K concentrations (beech sun leaves) increased while N remained constant, resulting in decreasing foliar N/P and N/K ratios. N resorption efficiency increased toward the dry sites. We conclude that a reduction in summer rainfall significantly reduces the soil C, N and P pools but does not result in decreasing foliar N and P contents in beech. However, more effective tree-internal N cycling and the decreasing foliar N/P ratio towards the dry stands indicate that tree growth may increasingly be limited by N and not by P with decreasing precipitation.Open-Access-Publikationsfonds 201
Belowground drought response of European beech: fine root biomass and carbon partitioning in 14 mature stands across a precipitation gradient
No full textHow tree root systems will respond to increased drought stress, as predicted for parts of Central Europe, is not well understood. According to the optimal partitioning theory, plants should enhance root growth relative to aboveground growth in order to reduce water limitations. We tested this prediction in a transect study with 14 mature forest stands of European beech (Fagus sylvatica L.) by analysing the response of the fine root system to a large decrease in annual precipitation (970-520 mm yr(-1)). In 3 years with contrasting precipitation regimes, we investigated leaf area and leaf biomass, fine root biomass and necromass (organic layer and mineral soil to 40 cm) and fine root productivity (ingrowth core approach), and analysed the dependence on precipitation, temperature, soil nutrient availability and stand structure. In contrast to the optimal partitioning theory, fine root biomass decreased by about a third from stands with > 950 mm yr(-1) to those with < 550 mm yr(-1), while leaf biomass remained constant, resulting in a significant decrease, and not an increase, in the fine root/leaf biomass ratio towards drier sites. Average fine root diameter decreased towards the drier stands, thereby partly compensating for the loss in root biomass and surface area. Both delta C-13-signature of fine root mass and the ingrowth core data indicated a higher fine root turnover in the drier stands. Principal components analyses (PCA) and regression analyses revealed a positive influence of precipitation on the profile total of fine root biomass in the 14 stands and a negative one of temperature and plant-available soil phosphorus. We hypothesize that summer droughts lead to increased fine root mortality, thereby reducing root biomass, but they also stimulate compensatory fine root production in the drier stands. We conclude that the optimal partitioning theory fails to explain the observed decrease in the fine root/leaf biomass ratio, but is supported by the data if carbon allocation to roots is considered, which would account for enhanced root turnover in drier environments
Nutrient dynamics along a precipitation gradient in European beech forests
No full textPrecipitation as a key determinant of forest productivity influences forest ecosystems also indirectly through alteration of the nutrient status of the soil, but this interaction is not well understood. Along a steep precipitation gradient, we studied the consequences of reduced precipitation for the soil and biomass nutrient pools and dynamics in 14 mature European beech (Fagus sylvatica L.) forests on Triassic sandstone. We tested the hypotheses that lowered summer precipitation (1) is associated with less acid soils and (2) a reduced accumulation of organic matter on the forest floor, and (3) reduces nutrient supply from the soil and leads to decreasing foliar and root nutrient concentrations. Soil acidity, the amount of forest floor organic matter, and the associated organic matter N and P pools decreased to about a half from wet to dry sites; the C/P and N/P ratios, but not the C/N ratio, of forest floor organic matter were reduced as well. Net N mineralization and P and K pools in the mineral soil did not change with decreasing precipitation. Foliar P and K concentrations (beech sun leaves) increased while N remained constant, resulting in decreasing foliar N/P and N/K ratios. Estimated N resorption efficiency increased toward the dry sites. We conclude that a reduction in summer rainfall significantly reduces the soil C, N and P pools but does not result in decreasing foliar N and P contents in beech. However, the decreasing foliar N/P ratios towards the dry stands indicate that the importance of P limitation for tree growth declines with decreasing precipitation
Variation of soil and biomass carbon pools in beech forests across a precipitation gradient
No full textTemperate forests have recently been identified as being continuing sinks for carbon even in their mature and senescent stages. However, modeling exercises indicate that a warmer and drier climate as predicted for parts of Central Europe may substantially alter the source/sink function of these economically important ecosystems. In a transect study with 14 mature European beech (Fagus sylvatica L.) forests growing on uniform geological substrate, we analyzed the influence of a large reduction of annual precipitation (970-520 mm yr-1) on the carbon stocks in fast and slow pools, independent of the well-known aging effect. We investigated the C storage in the organic L, F, H layers, the mineral soil to 100 cm, and in the biomass (stem, leaves, fine roots), and analyzed the dependence of these pools on precipitation. Soil organic carbon decreased by about 25% from stands with > 900 mm yr-1 to those with < 600 mm yr-1; while the carbon storage in beech stems slightly increased. Reduced precipitation affected the biomass C pool in particular in the fine root fraction but much less in the leaf biomass and stem fractions. Fine root turnover increased with a precipitation reduction, even though stand fine root biomass and SOC in the organic L, F, and H layers decreased. According to regression analyses, the C storage in the organic layers was mainly controlled by the size of the fine root C pool suggesting an important role of fine root turnover for the C transfer from tree biomass to the SOC pool. We conclude that the long-term consequence of a substantial precipitation decrease would be a reduction of the mineral soil and organic layer SOC pools, mainly due to higher decomposition rates. This could turn temperate beech forests into significant carbon sources instead of sinks under global warming
Genotypic variation and phenotypic plasticity in the drought response of fine roots of European beech
No full textHow temperate trees respond to drier summers, as predicted by climate change models for parts of Europe and eastern North America, will depend on the drought susceptibility of the root systems. We investigated the importance of the genetic constitution for the belowground drought response of European beech (Fagus sylvatica L.), in four populations from regions differing in precipitation (520-970 mm year(-1)). Saplings were grown at ample (10 vol.%; well-watered) or reduced (5 vol.%; drought treatment) soil water content in the Gottingen Rhizolab Facility for two consecutive summers, and the responses of fine root biomass, root morphology, root depth distribution, and fine root production and turnover were investigated by a combined mini-rhizotron and harvest technique approach. In the drought treatment, total root mass per plant was reduced by 30-40% as a result of: (1) a reduction in median fine root lifespan by roughly 50% and hence an increase in fine root turnover; and (2) a 10-fold reduction in relative fine root growth rate (productivity per standing root biomass). The root: shoot ratio did not increase with drought. Although beech plants originating from drier climates tended to reduce their root biomass in response to drought less than those from wetter climates, analyses of variance revealed no significant influence of genotype on root mass, morphology, growth rate or turnover. However, most fine root traits showed marked differences between the well-watered and drought treatments. We conclude that beech saplings respond to summer drought primarily by shortening root lifespan, whereas root system structure and root: shoot carbon partitioning pattern are unaltered. Beech fine root growth and turnover exhibited high phenotypic plasticity, but genotypic variation was of minor importance. In contrast, genotype had a strong influence on leaf and shoot morphogenesis and growth
On the niche breadth of Fagus sylvatica: soil nutrient status in 50 Central European beech stands on a broad range of bedrock types
No full textThe soil nutrient status of 50 Central European stands
of Fagus sylvatica on 13 acidic to basic bedrock types was investigated with the aim (i) to
define the extremes of important soil chemical and nutrient status
parameters tolerated by beech forests, (ii) to investigate the dependency of
these parameters on bedrock type and soil acidity, and (iii) to analyse the
importance of the organic layer for the nutrient status of beech forests.
Based on the parameters exchangeable cation pool (Ca + Mg + K, N/P ratio
of the organic layer and C/N ratio of the mineral soil, three nutrient
supply classes were identified: (1) limestone and claystone soils (C/N 15–18 mol mol, N/P 20–26 mol mol, (Ca + Mg + K) 5–38 mol m
per 10 cm soil), (2) silicate-rich sandstone, tertiary sand, loamy loess and
moraine soils (C/N 20–26 mol mol, N/P 24–45 mol mol,
(Ca + Mg + K) 2–3 mol m 10 cm, and (3) soils derived from
silicate-poor sandy deposits (C/N 28–34 mol mol, N/P 47–59 mol mol, (Ca + Mg + K) 1–3 mol m 10 cm. Soil chemical
extremes tolerated by beech were 3–99% base saturation, 3.2–7.3 of
pH (HO), and minima of resin-exchangeable P of 11 mol m, and of
(Ca + Mg + K) of 0.4 mol m in the topsoil (0–10 cm). A highly
variable amount of exchangeable Al in the mineral soil was identified as the
key factor controlling the accumulation of C in the organic layer (OL, OF,
OH). Increasing organic layer N/P ratios (19 to 59 mol mol from
basic to acidic soils point at a growing importance of P limitation over N
limitation with increasing acidity in beech forest soils.Sur la niche écologique du hêtre Fagus
sylvatica : statut nutritif des sols de 50 peuplements de
hêtre d'Europe centrale. Le statut nutritif des sols de 50 peuplements de Hêtre (Fagus sylvatica) croissant
sur 13 types de roches mère a été étudié dans le but de
(i) définir les conditions d'alimentation édaphiques extrêmes
tolérées par le hêtre, (ii) étudier les relations roche
mère-conditions édaphiques, et (iii) analyser l'importance de couche
organique pour le statut nutritif des forêts de hêtre. En se basant
sur la réserve de cations échangeables, le rapport N/P de la couche
organique et le rapport C/P du sol minéral, trois classes d'alimentation
minérale ont été identifiées : (1) sols calcaire et argileux
(C/N 15–18 mol mol, N/P 20–26 mol mol, (Ca + Mg + K) 5–38 mol m par 10 cm de sol), (2) grès siliceux, sables tertiaires,
loess limoneux et sols de moraine (C/N 20–26 mol mol, N/P 24–45 mol mol, (Ca + Mg + K) 2–3 mol m 10 cm, et (3) sols
dérivés de dépôts siliceux pauvres en bases (C/N 28–34 mol mol, N/P 47–59 mol mol, (Ca + Mg + K) 1–3 mol m 10 cm. Le hêtre tolère les valeurs chimiques extrêmes
suivantes: saturation en base de 3 à 99 %, pH (HO) de 3.2 à
7.3, valeur minimale de P échangeable de 11 mol m, et de
(Ca + Mg + K) de 0.4 mol m dans l'horizon supérieur (0–10 cm).
La quantité très variable d'Al échangeable dans le sol
minéral a été identifiée comme le facteur clé
contrôlant l'accumulation de C dans la couche organique (OL, OF, OH).
L'augmentation du rapport N/P des humus des sols basiques aux sols acides
indique dans les sols de hêtraie une limitation croissante par le P par
rapport au N lorsque l'acidité augmente
Temperature effects on root exudation in mature beech (Fagus sylvatica L.) forests along an elevational gradient
No full textAbstract
Aims
Root exudation may have a large impact on soil biological activity and nutrient cycling. Recent advances in in situ-measurement techniques have enabled deeper insights into the impact of tree root exudation on rhizosphere processes, but the abiotic and biotic controls of exudation rate remain poorly understood. We explored the temperature dependence of root exudation in mature beech (Fagus sylvatica L.) trees.
Methods
We measured fine root exudation in seven beech forests along an elevational gradient (310–800 m a.s.l.) and related carbon (C)-flux rates to mean daily temperature, actual precipitation, mean summer temperature (MST) and precipitation (MAP), soil moisture (SWC), and stand structure.
Results
Average mass-specific exudation (averaged over all sampling dates) ranged from 12.2 µg C g−1 h−1 to 21.6 µg C g−1 h−1 with lowest rates measured at highest elevations and peak rates at mid-elevation (490 m). Regression analyses showed a highly significant positive effect of site-specific daily air and soil temperature on exudation rates (p < 0.01) with an average increase by 2 µg C g−1 h−1 per 1 °C-temperature increase, while the relation to mean summer or annual temperature and mean temperature of the measuring year was less tight. Exudation decreased with increases in mean annual precipitation and soil moisture, but increased with increasing stem density.
Conclusions
The root exudation rate of beech trees roughly triples between 10 °C and 20 °C mean daily temperature, evidencing a large temperature influence on root-borne C flux to the soil.
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Root Branching Is a Leading Root Trait of the Plant Economics Spectrum in Temperate Trees
No full textGlobal vegetation models use conceived relationships between functional traits to simulate ecosystem responses to environmental change. In this context, the concept of the leaf economics spectrum (LES) suggests coordinated leaf trait variation, and separates species which invest resources into short-lived leaves with a high expected energy return rate from species with longer-lived leaves and slower energy return. While it has been assumed that being fast (acquisitive) or slow (conservative) is a general feature for all organ systems, the translation of the LES into a root economics spectrum (RES) for tree species has been hitherto inconclusive. This may be partly due to the assumption that the bulk of tree fine roots have similar uptake functions as leaves, despite the heterogeneity of their environments and resources. In this study we investigated well-established functional leaf and stature traits as well as a high number of fine root traits (14 traits split by different root orders) of 13 dominant or subdominant temperate tree species of Central Europe, representing two phylogenetic groups (gymnosperms and angiosperms) and two mycorrhizal associations (arbuscular and ectomycorrhizal). We found reflected variation in leaf and lower-order root traits in some (surface areas and C:N) but not all (N content and longevity) traits central to the LES. Accordingly, the LES was not mirrored belowground. We identified significant phylogenetic signal in morphological lower-order root traits, i.e., in root tissue density, root diameter, and specific root length. By contrast, root architecture (root branching) was influenced by the mycorrhizal association type which developed independent from phylogeny of the host tree. In structural equation models we show that root branching significantly influences both belowground (direct influence on root C:N) and aboveground (indirect influences on specific leaf area and leaf longevity) traits which relate to resource investment and lifespan. We conclude that branching of lower order roots can be considered a leading root trait of the plant economics spectrum of temperate trees, since it relates to the mycorrhizal association type and belowground resource exploitation; while the dominance of the phylogenetic signal over environmental filtering makes morphological root traits less central for tree economics spectra across different environments.Open-Access-Publikationsfonds 202
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