Browsing by Author "Rose, Laura"

Due to the expected increases of number and intensity of summer droughts in Central Europe the identification of drought tolerant ecotypes becomes more important in future forestry. A common garden experiment with seedlings of Fagus sylvatica provenances from the center (Germany) and eastern margin (Poland) of the species' distribution range was conducted. Responses of morphological, physiological, chemical and growth parameters to three drought treatments were analyzed. Relative growth rates of the marginal provenance were lower as compared to the central provenance. The marginal seedlings showed a tendency to higher total biomasses because of higher seed masses. In both provenances drought decreased biomass production and root/shoot ratio which was lower in the central provenance. A lower specific root area of the marginal provenance indicated a better adaptation to low xylem water potentials. Under moderate drought, lower leaf delta(13)C signatures may indicate lower stomatal limitation (or a reduced rate of CO(2) assimilation) in the marginal provenance. We conclude that marginal beech provenances may exhibit a better drought adaptation.

In large areas of Central Europe, grassland management has shifted from extensive grazing and mowing to highly intensive systems during the past 50 years. Although effects on biodiversity have intensively been studied, little is known about the response of important ecosystem functions, in particular, water and nutrient cycling, to management intensification. We conducted a two‐factorial grassland management experiment (GRASSMAN) with two cutting frequencies (one/three cuttings per year) and two fertilization levels (non‐fertilized/N‐fertilized) in a moderately species‐rich temperate grassland to analyse the effects of management regimes on evapotranspiration (ET) and infiltration (I). Both were measured in the growing season 2009 with small, weighable lysimeters that contained undisturbed soil monoliths and vegetation. Aboveground biomass production (ANPP), belowground biomass, root length density, plant diversity, water use efficiency (WUE), and climatic factors were also measured. Fertilization with 180 kg N ha−1yr−1 increased aboveground biomass production by 50–70% and stand ET by 10–15% (or 20–40 mm), whereas I and ground water recharge decreased by about 50%. Consequently, fertilization increased the WUE of the grassland plants by 20–30%. However, increasing the mowing frequency from 1 to 3 had no significant effect. We found close relations between ANPP, ET and I and conclude that grassland management intensification influences the water balance primarily through fertilization effects on productivity. In areas of Central Europe with abundant grassland, ground water recharge must have significantly decreased with management intensification in the past 50 years.

Livestock grazing can be a means to maintain biodiversity in grasslands, but the outcome for vegetation structure and species composition depends on livestock type and grazing regime. This study aims at disentangling the effects of plant functional‐group abundance and livestock type on the above‐ and below‐ground biomass and N allocation in temperate pastures.We investigated the effects of cattle, sheep and mixed stocking on above‐ground biomass (AGB) and belowground biomass (BGB) and plant N pools in a replicated grazing experiment in two pasture community types with different plant functional‐group abundance (diverse vs. grass‐dominated swards).In the six treatments, AGB was reduced up to 80% compared with an ungrazed control. Cattle reduced AGB to a larger extent than sheep in diverse pastures (80 vs 44% reduction) while sheep grazing tended to do so in grass‐dominated pastures (57 vs 46% reduction); mixed stocking led to intermediate values. Grazing reduced AGB more than the N pool in AGB, thus lowering the biomass C/N ratio relative to the ungrazed control. Neither BGB nor the N pool in BGB differed between the grazing treatments and the control plots.We conclude that livestock type and functional‐group abundance are interacting factors that influence plant biomass and N pools in swards of managed temperate pastures. The contrasting biomass removal rates of cattle and sheep could be used to increase the structural heterogeneity and total plant species pool of pastures by keeping different livestock species in neighbouring patches.

Question Plant functional traits have the potential to characterize species ecological strategies and predict ecosystem responses to environmental changes. (1) Do trait responses to land‐use intensification alter trait‐based species rankings, and (2) does land‐use intensification alter relationships among interrelated leaf traits? Location Solling Mountains, Central Germany (Grassland management experiment, GrassMan). Methods Over the course of 2 yr with differing weather conditions, we analysed the specific leaf area (SLA) of eight grassland species and related it to leaf nitrogen per mass (Nmass) or area (Narea) in an old‐growth grassland with two fertilization levels (none vs NPK fertilization, 180‐30‐100 kg·ha−1·yr−1) and two cutting frequencies (one vs three cuts per season). Results NPK fertilization led to an expected increase in SLA, Nmass and Narea, while the effect of altered cutting frequency on leaf traits was more species‐specific. Species‐specific responses to management significantly altered trait‐based species rankings. A significant SLA–Nmass relationship occurred in unfertilized plots, whereas the SLA–Narea relationship was stronger in fertilized plots. This was mostly caused by a decrease in the among‐species variation in Nmass upon fertilization. Conclusions Although our results reflect only short‐term community responses, they indicate that trait‐based species ranking and the relationships between plant functional traits are not always consistent across different management regimes. Hence, trait values used to characterize species and communities should never be discussed without consideration of the set of environmental conditions under which they were measured.

Background and aims Plant traits may characterize functional ecosystem properties and help to predict community responses to environmental change. Since most traits used relate to aboveground plant organs we aim to explore the indicative value of root traits. Methods We examined the response of root traits (specific root length [SRL], specific root surface area [SRA], root diameter [RD], root tissue mass density [TMD], root N concentration) in six grassland species (3 grasses, 3 herbs) to four management regimes (low vs. high mowing frequency; no fertilization vs. high NPK fertilization). The replicated experiment in temperate grassland with long continuity simulated the increase in grassland management intensity in the past 50 years in Central Europe. Results Increasing mowing frequency (one vs. three cuts per year) led to no significant root trait changes. NPK fertilization resulted in considerable trait shifts with all species responding in the same direction (higher SRL, SRA and N concentration, lower TMD) but at different magnitude. Fertilization-driven increases in SRA were mainly caused by lowered tissue density while root diameter reduction was the main driver of SRL increases. Conclusion We conclude that root morphological traits may be used as valuable indicators of environmental change and increasing fertilization in grasslands.

Background: Agricultural intensification has transformed most grasslands of Central Europe from non-intensive to highly intensive management during the last 50 years, resulting in large reductions of species diversity. This impoverishment has raised concern with regard to ecosystem functions. Positive diversity effects on productivity have been found in experiments with synthetic grasslands but were rarely confirmed in semi-natural grasslands in the field. Aims: Our objective was to investigate the diversityproductivity relationship independently from management effects in mature grassland. Methods: We conducted a three-factorial experiment (fertilisation, mowing frequency, diversity; n?=?6) in a permanent grassland to disentangle effects of management intensity and diversity on above-ground biomass (AGB), fine root biomass and root distribution patterns. Herbicides were applied to increase the diversity gradient across the plots. Results: While fertilisation had a strong positive effect on AGB and the cutting frequency a minor one, AGB was negatively related to species richness. Root biomass and distribution gave no indication of below-ground complementary resource use. Conclusions: The N-driven productivity increase since the 1950s is by far more influential on above-ground productivity than any diversity effect. Field manipulation studies in mature communities are needed to understand the productivitydiversity relationship in grasslands under changing land use.