Crop productivity and plant physiology are affected by rising temperatures and altered precipitation patterns due to climate change. We studied the impacts of an increase in soil temperature of 2.5 °C, a decrease in summer precipitation amount of 25%, a reduction in summer precipitation frequency of 50%, and their interactions on photosynthesis, biomass production, and yield of spring barley (Hordeum vulgare L. cv. RGT Planet) in a temperate agricultural ecosystem near Stuttgart (Germany). Leaf gas exchange of barley appeared to be affected mainly by drought in the form of reduced precipitation frequency or by a combination of changes in soil temperature and precipitation patterns. In contrast, biomass production and yield parameters were more affected under soil warming alone. In addition, biomass of roots increased under soil warming at stem elongation. Stable grain yield was observed under reduced precipitation amount and also under increased evaporation through soil warming. These findings provide additional evidence that barley is relatively drought tolerant, which should be taken into consideration in the context of appropriate crop selection under climate change.

Background and aimsGiven that environmental factors like atmospheric CO2, temperature, and water availability will likely change simultaneously, it is difficult to make accurate predictions about future crop production. Effects of elevated CO2 or drought on aboveground plant growth are relatively well studied, while effects on the rhizosphere are rarely dealt with. The present work investigates the root exudation pattern of different osmotic protectants such as ions and sugars of two cultivars of barley grown under different water and CO2 levels.MethodsBarley (Hordeum vulgare L.) plants were grown in plant containers in climate chambers with an optimal and reduced water supply and two CO2 concentrations (380 and 550ppm) and harvested at the stem elongation growth stage and when the inflorescences emerged.ResultsThe responses of root exudation to CO2 enrichment, watering level, and cultivar and their interactions varied with the developmental stage. While K+/Na+ ratio in root exudates remained stable at the stem elongation stage (DC30), it was higher at the booting stage (DC49) in the cv. Bambina than in cv. Golden Promise. At DC30, in general the exudation of sugars, dissolved organic carbon (DOC) and their ratio (SUG/DOC) were lower at e[CO2] compared to ambient CO2 at normal watering conditions. Under reduced watering conditions, plants exuded on average 55% more sucrose than under well-watered conditions. The modern cv. BA exuded on average 53% more fructose than the older cv.GP. In contrast, at DC49, sucrose, DOC and SUG/DOC exudation were not affected by any factor. At e[CO2] plants exuded on average 39% less fructose than under ambient CO2. A water and CO2 interaction on glucose exudation was found at this stage. Under reduced water conditions, plants growing at ambient CO2 exuded less glucose but at e[CO2] exuded similar (GP) or even higher (BA) glucose levels than under normal water supply. Although drought and cultivar factors affected the root exudation of barley, the strongest effects in the exudation pattern were caused by CO2.ConclusionsThis study presents a non-destructive percolation method for the collection of root exudates which can be used to give an insight into the complex interaction between global warming-associated environmental factors that cause yield losses and changes in crop quality and components of the belowground plant metabolism.

Atmospheric CO2 enrichment affects C3 crops both directly via increased carbon gain and improved water use efficiency and indirectly via higher temperatures and more frequent climatic extremes. Here we investigated the response of spring wheat (Triticum aestivum L. cv. Triso) to CO2 enrichment (550 vs. 380 mu mol/mol) and heat, applied as a constant +4 degrees C increase or a typical heat wave either before or after anthesis, or as two typical heat waves before and after anthesis. We applied a climate chamber approach closely mimicking ambient conditions. CO2 enrichment increased above-ground biomass and yield by c. 7 and 10%, but was not able to compensate for adverse heat stress effects, neither before nor after anthesis, with few exceptions only. Yield depression due to heat stress was most severe when two heat waves were applied (-19%). This adverse effect was, however, compensated by CO2 enrichment. Applying heat stress before or after anthesis did not exert different effects on yield for both +4 degrees C warming and heat wave application. However, +4 degrees C depressed yield more than a heat wave at ambient CO2, but not so at elevated CO2. Thus, the interactive effects were complex and prediction of future wheat yield under CO2 enrichment and climate extremes deserves more attention.

Elevated CO2 promotes leaf photosynthesis and improves crop grain yield. However, as a major anthropogenic greenhouse gas, CO2 contributes to more frequent and severe heat stress, which threatens crop productivity. The combined effects of elevated CO2 and heat stress are complex, and the underlying mechanisms are poorly understood. In the present study, the effects of elevated CO2 and high‐temperature on foliar physiological traits and the proteome of spring wheat grown under two CO2 concentrations (380 and 550 µmol mol−1) and two temperature conditions (ambient and post‐anthesis heat stress) are examined. Elevated CO2 increases leaf photosynthetic traits, biomass, and grain yield, while heat stress depresses photosynthesis and yield. Temperature‐induced impacts on chlorophyll content and grain yield are not significantly different under the two CO2 concentrations. Analysis of the leaf proteome reveals that proteins involved in photosynthesis as well as antioxidant and protein synthesis pathways are significantly downregulated due to the combination of elevated CO2 and heat stress. Correspondingly, plants treated with elevated CO2 and heat stress exhibit decreased green leaf area, photosynthetic rate, antioxidant enzyme activities, and 1000‐kernel weight. The present study demonstrates that future post‐anthesis heat episodes will diminish the positive effects of elevated CO2 and negatively impact wheat production.

Rising CO2 concentrations associated with drought stress is likely to influence not only aboveground growth, but also belowground plant processes. Little is known about root exudation being influenced by elements of climate change. Therefore, this study wanted to clarify whether barley root exudation responds to drought and CO2 enrichment and whether this reaction differs between an old and a recently released malting barley cultivar. Barley plants were grown in pots filled with sand in controlled climate chambers at ambient (380 ppm) or elevated (550 ppm) atmospheric [CO2] and a normal or reduced water supply. Root exudation patterns were examined at the stem elongation growth stage and when the inflorescences emerged. At both dates, root exudates were analyzed for different compounds such as total free amino acids, proline, potassium, and some phytohormones. Elevated [CO2] decreased the concentrations in root exudates of some compounds such as total free amino acids, proline, and abscisic acid. Moreover, reduced water supply increased proline, potassium, electric conductivity, and hormone concentrations. In general, the modern cultivar showed higher concentrations of proline and abscisic acid than the old one, but the cultivars responded differentially under elevated CO2. Plant developmental stage had also an impact on the root exudation patterns of barley. Generally, we observed significant effects of CO2 enrichment, watering levels, and, to a lesser extent, cultivar on root exudation. However, we did not find any mitigation of the adverse effects of drought by elevated CO2. Understanding the multitude of relationships within the rhizosphere is an important aspect that has to be taken into consideration in the context of crop performance and carbon balance under conditions of climate change.

In even-aged, 120-year-old Norway spruce stands with underplanted beech (in 1995) four permanent research plots were established, each 100 × 100 m in size. Twelve subplots were selected on each plot along a light gradient from complete canopy closure to open light conditions. On each plot, photon flux density (PFD) was measured continuously, and during same time interval (August 2008, 2009), color digital hemispherical photographs were taken. Cumulative PFD values for measuring points were compared with potential PFD radiation obtained from hemispherical photograph analysis for different angle of hemisphere and different parameters from hemispherical image analysis (gap fraction, total openness and direct, indirect and total amount of radiation). Cumulative and average daily values for the plots were compared; 120° hemispherical photograph angle, gap fraction and total openness were the variables that explained the largest proportion of variance in light transmittance. Determination coefficients between direct and total light component were highest for the total potential radiation and lowest for the diffuse light component. Comparison between potential and instantaneous light measurements for radial, height increment and SLA of young beech showed that instantaneous radiation measurements explained height increment best; 120° of hemisphere proved to be the best explaining angle.

Fine root dynamics in mono-specific stands of mature Fagus sylvatica L. and Picea abies Karst. was studied from December 2003 to December 2004 in a stand in Southern Germany. Minirhizotrons were used to draw between species comparisons concerning fine root (≤1 mm) longevity and temporal patterns of fine root dynamics (growth and mortality) as related to seasonal changes in soil water content and soil temperature. In F. sylvatica, median fine root longevity from early seasonal to late-seasonal cohorts was low (77 days). Fine root dynamics scaled positively with seasonal changes in soil water and temperature indicating accelerated fine root turnover during favourable soil conditions. In contrast, fine root longevity in P. abies (273 days) was significantly higher when compared to F. sylvatica and increased from early seasonal to late-seasonal cohorts. Fine root dynamics in P. abies did not correlate with soil environmental conditions. Rather a large proportion of new fine roots occurred during the dry season in superficial soil layers. The data suggest species inherent patterns of fine root longevity and temporal patterns of fine root dynamics.

A substantial number of experiments have shown root proliferation and concentration in nutrient-rich patches. This article focuses on root clustering observed on tree roots in forest stands and water uptake within these zones. Root clustering is seen as a rule in natural soils for optimized exploitation of aggregated resources. In summary, root distribution in nature is caused by two factors: (1) vertical gradients in soil organic mater and infiltration of precipitation, and (2) clusters of available nutrients accompanied by preferential uptake of the seepage water.

A previous study by Schmid and Kazda (I. Schmid and M. Kazda. 2001. Can. J. For. Res. 31: 539–548) evaluated the vertical distribution and radial growth of coarse roots greater than 2 mm diameter in pure and mixed stands of Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.). The vertical distribution of roots of Norway spruce was fitted by an exponential function, while the root distribution of European beech was approximated by a gamma distribution. Now, in the present paper, planar point process models have been applied to investigate the spatial (two-dimensional) distribution of data for roots between 2 and 5 mm diameter. After a homogenization with respect to the vertical axis, the pair correlation function and the L function were estimated to fit Matérn-cluster point process models to the given root data. The models were finally vertically retransformed to provide information on the inhomogeneous spatial patterns of small roots as well as on the original shape and size of the root clusters. All models based on vertically transformed data confirmed that the root distribution patterns are not completely random, as they indicated root clustering for both species, with different degrees of exploitation intensity (clustering) between the two species. According to the Matérn-cluster models, Norway spruce had stronger clustering in smaller cluster regions, while roots of European beech formed weaker clusters in larger cluster regions. Furthermore, beech root clusters seemed to avoid overlapping. Together with previous studies on the root system of both species, the present study indicates more intensive belowground intraspecific competition for spruce than for beech. On the other hand, the clustering characteristics described indicate that European beech has a more sophisticated rooting system than Norway spruce. The spatial distribution of the inhomogeneous raw data is characterized by the clustering properties analysed in the present paper and by the vertical distribution previously studied.

Distribution of small roots (diameter between 2 mm and 5 mm) was studied in 19 pits with a total of 72 m(2) trench profile walls in pure stands of Fagus sylvatica and Picea abies. Root positions within the walls were marked and transformed into x-coordinates and y-coordinates. In a GIS-based evaluation, zones of potential influence around each root were calculated. The total potential influence produced isoline maps of relative root influence zones, thus indicating small root clustering. The questions studied were (1) whether there were marked clusters of small roots in the soil and (2) whether trees surrounding the pit (defined as tree density) correlate with the root abundance and distribution on the trench profile walls. Small roots of both species showed maximum abundance in the top 20 cm of the soil, where pronounced root clusters occurred next to areas with only low root accumulation. The area of root clusters did not differ significantly between the two stands. Weighted clumping, WC, calculated as a product of root class, and its area was used as an index of root clustering, which again did not differ between beech and spruce stands. However, evaluations on a single root level showed that beech achieved the same degree of clustering with lower number of roots. Regardless of soil properties related to root clusters, a significantly higher clustering acquired per root for beech than for spruce suggests beech to be more efficient in belowground acquisition of space. Because none of the parameters describing root clustering were correlated with tree density around the investigated soil profiles, clusters of small roots are inherently present within the tree stands.

Light conditions were measured along six transects from 35 m inside of a mixed Norway spruce/Scots pine forest to an adjoining clear-cut in NW-Austria. Photosynthetic photon flux density (PFD) was recorded every minute of the day from 5:00 a.m. to 8:00 p.m. for three weeks in July. PFD decreases exponentially from the clear-cut to the interior of the forest following the gap fraction. Low light intensity classes (< 50 µmol photons m2/s) decrease from the stand towards the open, whereas the clear-cut receives light of higher intensities (> 200 µmol photons m2/s) for most of the day. PFD values assessed during the day were compared with photosynthetic light response curves measured on advanced planting of broadleaf species in the same stand. The high light compensation point of Quercus petraea enables carbon gain in deep shade for about 60% of the day. The other shade tolerant species Fagus sylvatica and Acer pseudoplatanus can perform net photosynthesis at 80% and 90% of the time, respectively. This reduces the possibility of advanced planting of light demanding species to the first few meters of the inner part of the forest edge.

Only very limited information exists on the plasticity in size and structure of fine root systems, and fine root morphology of mature trees as a function of environmental variation. Six northwest German old-growth beech forests (Fagus sylvatica L.) differing in precipitation (520 – 1030 mm year−1) and soil acidity/fertility (acidic infertile to basic fertile) were studied by soil coring for stand totals of fine root biomass (0–40 cm plus organic horizons), vertical and horizontal root distribution patterns, the fine root necromass/biomass ratio, and fine root morphology (root specific surface area, root tip frequency, and degree of mycorrhizal infection). Stand total of fine root biomass, and vertical and horizontal fine root distribution patterns were similar in beech stands on acidic infertile and basic fertile soils. In five of six stands, stand fine root biomass ranged between 320 and 470 g m−2; fine root density showed an exponential decrease with soil depth in all profiles irrespective of soil type. An exceptionally small stand fine root biomass (<150 g m−2) was found in the driest stand with 520 mm year−1 of rainfall. In all stands, fine root morphological parameters changed markedly from the topsoil to the lower profile; differences in fine root morphology among the six stands, however, were remarkably small. Two parameters, the necromass/biomass ratio and fine root tip density (tips per soil volume), however, were both much higher in acidic than basic soils. We conclude that variation in soil acidity and fertility only weakly influences fine root system size and morphology of F. sylvatica, but affects root system structure and, probably, fine root mortality. It is hypothesized that high root tip densities in acidic infertile soils compensate for low nutrient supply rates, and large necromasses are a consequence of adverse soil chemical conditions. Data from a literature survey support the view that rainfall is another major environmental factor that influences the stand fine root biomass of F. sylvatica.

The aim of this study was to combine data on photosynthetic performance, growth and mineral nutrition of Quercus petraea, Fagus sylvatica and Acer pseudoplatanus growing six years under a Norway spruce canopy. Three years old saplings were planted on several adjoining plots from the forest edge up to 35 m inside the spruce forest on nutrient poor dystric cambisols. Growth parameters, photosynthetic capacity and leaf nutrition were repeatedly measured on 11 to 13 selected plants for each species every year from 1996 to 2001. The general performance of the plants growing along the light gradient from forest edge into the closed canopy decreased in the order F. sylvatica, Q. petraea and A. pseudoplatanus. The photosynthetic performance of Acer declined from the second year onwards as consequence of low nutrient supply. The plants had in most cases higher leaf nitrogen concentration in shade. This increase going along with declining light input was the best in Quercus and was found in Acer leaves only in the second year after the planting. The growth parameters of all investigated plants were not correlated to the light environment within the range of canopy gap fraction between 0.05 and 0.62. However, the total leaf area as well as nutrient amounts in the foliage were good predictors for total plant height and plant diameter at root collar of Fagus and Quercus, but failed in most cases for Acer. These results emphasise the important role of nutrient acquisition for young broadleaves introduced in Norway spruce stands and underline the different requirements for nutrient supply at the species level.

Methods: In order to assess intermediate-term speech outcome after pharyngeal flap surgery for velopharyngeal dysfunction in children with cleft palate between 1980 and 1998, their pre- and postoperative speech performance was analyzed in a blinded fashion by speech pathologists and adult lay people. Speech was evaluated on the basis of tape recordings with regard to resonance, intelligibility, articulation, voice and secondary speech disorders. Results: Twenty-three patients could be evaluated. Both lay assessors and speech pathologists noted a significant improvement in speech performance after pharyngeal flap surgery. The percentage of children who improved was 83% (19/23, 95% confidence interval: 0.68–0.98, p = 0.002) when rated by lay people, and 87% (20/23, CI 0.73–1.01, p < 0.0001) when rated by professionals. Rated on a 5-point scale, the mean improvement per speech characteristic was 0.52 ± 0.32 scale points when judged by lay people, and 0.75 ± 0.8 points when judged by experts. Experts considered none of the children to have normal speech after surgery. Agreement with regard to outcome between lay people and speech pathologists occurred in 87% of the patients. Conclusion: The cranially based pharyngeal flap can improve speech performance in cleft palate children with chronic velopharyngeal insufficiency. However, it cannot be expected that this type of surgery will result in normal speech.

Recent knowledge about root systems of trees mostly originates from studies in pure stands. But the root systems may change if more than one species is present. The fine root system (d < 2mm) of spruce was characterized for pure stands and for comparable mixed spruce/beech stands to a soil depth of 80 cm. This made it possible to estimate the effects of interspecific competition on stagnic cambisol and on dystric cambisol, respectively. An additional pure beech stand was studied on stagnic cambisol to evaluate the mixture effect also on the root system of beech. The total fine root biomass was greater in each mixed stand compared to the neighbouring pure stand. Fine roots of beech were over-represented in the rooting zone of the mixed stand, which indicates a competitive displacement of fine roots of spruce. In addition, spruce developed a more superficially distributed root system in the mixed compared to the pure stands. The low abundance of spruce roots in mixed stand and the limitation of spruce roots to the uppermost soil layers underlines the high competitive ability of beech in the rooting zone of the investigated mixed stands.

Vertical root distribution was studied in pure Norway spruce (Picea abies (L.) Karst.) stands and in adjacent mixed stands of spruce and European beech (Fagus sylvatica L.) with comparable site conditions. The investigation was carried out in two regions of Austria with different bedrock material. One site was located on nutrient rich, poor-aerated stagnic cambisol, the other on nutrient poor, well-aerated podsolic cambisol. A modified trench profile wall technique was used to study the coarse root distribution on altogether 160 m(2) of profile walls. The fine root biomass was estimated using soil core cylinders.Coarse roots were more abundant on nutrient poor than on nutrient rich site. showing the greatest cross-section (CS-)area in the humus and upper mineral soil layer in all of the four investigated stands. No significant difference in total root CS-area was found between pure and mixed stand in both regions. Coarse roots of Norway spruce were markedly stronger limited to the upper soil layers in mixture with beech than in pure spruce stands. This limitation to the upper soil was especially pronounced for the mixed stand on stagnic cambisol. The fine root biomass was greater in spruce stand on nutrient poor, well-aerated soil than on stagnic soil, whereas the mixed stands did not differ. The fine root system of spruce was markedly shallower in stagnic than in podsolic cambisol in pure stands and, compared to the basal area, spruce fine roots were under-represented in the mixed stands on both soil types. Like the coarse roots, fine roots of spruce showed a clear shift towards the upper soil layers in mixture with beech.This shift towards a more superficially distributed root system of spruce in mixture with beech together with the under-represented fine root biomass of spruce in these stands indicates a higher belowground competitive ability of beech compared to spruce on both nutrient rich and nutrient poor sites. (C) 2002 Elsevier Science B.V. All rights reserved.