Factors controlling soil water-recharge in a mixed European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)–Norway spruce [<Emphasis Type="Italic">Picea abies</Emphasis> (L.) Karst.] stand

The spatial dynamics of soil water-recharge in a forest stand is the product of a number of interacting processes. This study focuses on the role of tree species and antecedent soil water content upon horizontal and vertical patterns of soil water recharge in heavy clay soils of a mixed European beech–Norway spruce stand and of a pure Norway spruce stand after rewetting periods with different rain quantities and intensities. Volumetric water content (VWC) was measured at 194 locations across 0.5-ha plots in each stand using time-domain reflectometry (TDR) with fixed 30- and 60-cm vertical waveguides. This was repeated 28 times (as close as possible) before and after rewetting periods during the vegetation seasons in 2000 and 2001. In addition, the locations of all trees within the plots were recorded. Geostatistics was used to describe the spatial correlation between VWC measurements and to interpolate soil water recharge in space. Spatial patterns of soil water recharge were then evaluated according to antecedent soil water-content and tree species distribution. Open-field precipitation of 30 mm (maximum intensity 10 mm h^–1) on extremely dry initial soil conditions resulted in higher subsoil (30–60 cm soil depth) recharge and erratic recharge patterns. This was presumably due to preferential flow in opening shrinkage cracks of the heavy clay soil. A comparable quantity and intensity of rainfall under moderately dry antecedent soil water conditions resulted in almost exclusively topsoil (0–30 cm soil depth) water recharge and patterns of recharge that were clearly related to tree species distribution. The higher recharge around beech trees can be attributed to the lower interception rates there. Spatial patterns of soil water recharge reflect patterns of antecedent soil water conditions.     

Intra-annual growth response of adult Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> [L.] KARST.) and European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) to an experimentally enhanced,free-air ozone regime

Several findings indicate an impact of ozone on stem diameter growth leaving the question unanswered, if and how the intra-annual growth pattern is changed. In this study the hypotheses are tested, that (1) ozone will alter the absolute growth and (2) alter and shift the period of growth activity within a year. Our data originates from the free air ozone fumigation experiment ‘Kranzberger Forst’ in a mixed stand of Norway spruce and common beech near Freising/Germany. Annual and intra-annual growth reactions of a sample of five adult beech and five spruce trees, exposed to double ambient ozone were examined and compared to the same number of untreated reference trees. Diameter increments were measured with plastic diameter girth bands and high-resolution, automatically logging micro-dendrometers, mounted at breast height (1.3 m). We used the increment data from the growth periods 2000 to 2005. The high-resolution micro-dendrometer data were examined by fitting a Weibull function to the standardized annual growth profiles to obtain curve parameters for statistical tests. We estimated the parameters ‘T’ which represents the point of time, when 63% of the annual diameter increment is performed and the parameter ‘m’, the Weibull module, which was used as an indicator for the span of time needed to complete the annual growth. The statistical significance of these curve parameters, together with the absolute diameter increment, was tested by use of mixed regression models. The analysis of the growth curve parameters revealed a significantly altered intra-annual growth pattern of both species induced by ozone. Spruce under ozone showed reduced absolute annual diameter increment and a preponed growth activity compared to untreated trees. Beech’s absolute diameter increment was not affected under ozone, but its growth activity was delayed. For both species, ozone fumigation did not alter the individual length of the annual growing season. These results are discussed with respect to drought, tree ring anatomy and tree allometry. The study shows that ozone is able to change growth behaviour of trees even if increment losses are not obvious. This article belongs to the special issue "Growth and defence of Norway spruce and European beech in pure and mixed stands".     

Are marginal beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) provenances a source for drought tolerant ecotypes?

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 δ¹³C signatures may indicate lower stomatal limitation (or a reduced rate of CO₂ assimilation) in the marginal provenance. We conclude that marginal beech provenances may exhibit a better drought adaptation.     

Quantitative genetics of cold hardiness and growth in <Emphasis Type="Italic">Eucalyptus</Emphasis> as estimated from <Emphasis Type="Italic">E.</Emphasis><Emphasis Type="Italic">urophylla</Emphasis> × <Emphasis Type="Italic">E. tereticornis</Emphasis> hybrids

Interspecific hybrids of Eucalyptus urophylla S. T. Blake × E. tereticornis Smith were used for quantitative genetic analysis of cold hardiness (CH) and growth traits height (H), diameter at breast height (D) and volume (V) at 0.5, 1.5, 2.5 and 4 years of age. The effect of E. tereticornis male variance was significant (P < 0.05) for CH as well as 2.5- and 4-year-old growth except for H ₄, and E. urophylla female × E. tereticornis male interaction was significant for 0.5- and 1.5-year-old growth and CH except for CH _0.5, whereas E. urophylla female effect was not significant for the majority of traits analyzed. Both additive and dominance gene action were present in the genetics of all the traits measured at most ages, indicating that those traits may be improved by hybrid breeding. The σ _D ²/σ _A ² ratios tended to decline after 1.5 years of age in CH and growth traits, implying that breeding value predictions derived from older performance might be more reliable. Estimates of narrow-sense heritability (h ² ) for CH and growth ranged from 0.03 ± 0.05 to 0.28 ± 0.13, depending on trait and age. Additive genetic correlations between CH and V were 0.28 ± 0.48 and 0.69 ± 0.30 at ages 1.5 and 2.5, respectively, suggesting that selection for growth would cause a favorable increase in cold hardiness in E. urophylla × E. tereticornis hybrids.     

AFLP fingerprinting of <Emphasis Type="Italic">Populus deltoides</Emphasis> and <Emphasis Type="Italic">Populus </Emphasis>×<Emphasis Type="Italic"> canadensis</Emphasis> elite accessions

Amplified fragment length polymorphism (AFLP) was used in genetic fingerprinting of 22 elite Chinese Populus deltoides and Populus × canadensis accessions. The results indicated that each of the nine AFLP primer pairs selected generated fingerprint profiles that were unique to each of the accessions. Therefore, each accession was definitively identified by any of the nine primer pairs. Furthermore, the inter-accession genetic relationships inferred based on 461 polymorphic fragments from the nine AFLP primer pairs were largely consistent with phylogenetic relationships based on morphologic traits. Bootstrap analysis showed that three AFLP primer pairs were required to obtain genetic similarity values with a maximum CV of 10% while 10 AFLP primer pairs could give a maximum CV of 5%. Thus, AFLP can readily be applied for a rapid and accurate evaluation of the degree of similarity between poplar cultivars. In this study, the number of AFLP fragments used was sufficient to establish a reliable estimate of genetic similarity among accessions, with a maximum CV of 5.12%. Therefore, the information on the genetic relationships among the poplar accessions generated in this study in connection with knowledge on agronomic traits may have an impact on poplar breeding and planting in China.     

Does tree-ring formation follow leaf phenology in Pedunculate oak (<Emphasis Type="Italic">Quercus robur</Emphasis> L.)?

We monitored leaf phenology and xylogenesis of 12 Pedunculate oaks in northern Poland in 2014. We hypothesized that the individual trees, which differed in size, age and habitat (tree stand or gap), also diverged in terms of the seasonal patterns of leaf phenology and xylogenesis. The samples used for wood formation observations were collected most frequently during the early leaf phenophases (from March to end of June). The transverse sections of the cambial region were cut with a sledge microtome. We counted the number of cambial cells, measured the width of xylem increment and assessed the timing of xylogenesis and earlywood-vessel formation. We found significant differences in leaf phenology and timing of xylogenesis among individual trees. The smallest differences in wood formation among the trees were observed at the beginning of the vegetation season when the first earlywood vessels were detected (9 days). The dates of completion of the first tangential row of earlywood vessels varied by up to 30 days, while for the completion of the entire earlywood dates varied by up to 32 days. The highest productivity of cambial cells (13 cell layers) was observed around the time of bud swelling at mid-April. In the last days of April, the number of cambial cell layers decreased and subsequently increased again when the leaves were nearly fully expanded at the end of May. To summarize, we observed a high seasonal variability in the number of cambial cell layers. Differences in the time of cessation of cambial activity and xylogenesis amounted to 1 month. We conclude that: (1) oak tree-ring widths and earlywood-vessel sizes and numbers may not be sensitive indicators for early spring temperature and spring defoliation; (2) the missing association between leaf phenophases and xylogenesis as well as the phenological variability may be the reasons for the lack of a clear climatic effect on the above-mentioned parameters.     

Can drought tolerance of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> (L.) <Emphasis Type="Italic">Karst</Emphasis>.) be increased through thinning?

To investigate whether drought tolerance of individual trees can be increased through the provision of more growing space, trees from a thinning experiment were analysed for reductions in radial growth during drought years and their subsequent recovery. Tree-ring widths were quantified on increment cores as well as stem discs of 32 trees from stands of a thinning trial established in 1974 in 27-year-old spruce stands in the Alpine Foreland of Southwest Germany. Three different thinning regimes of the trial were selected for this study: unthinned control (8 trees), moderate (13 trees) and heavy thinning (11 trees) intensities. All trees sampled were of a co-dominant to dominant canopy status. The standardisation of growth data was carried out using the software program ARSTAN (University of Arizona). For the year 1976—a widespread and severe drought year in Germany—we found year ring widths were not reduced compared to those of the pre-drought years for all treatments. However, we observed the formation of false year rings and resin ducts for this year in all trees investigated. The drought events in 1992 and 2003 led to severe growth depressions in the year of the drought event in all trees, regardless of previous thinning regimes. However, the resilience—the recovery of basal area growth in subsequent years—was significantly more rapid in trees from heavily thinned stands, even if the drought event occurred more than 10 years after the last thinning intervention. This indicates a shorter stress period for trees with more growing space, which may reduce the susceptibility to secondary pathogens or pest species such as bark beetles.     

Soil microorganisms alleviate the allelopathic effect of <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> × <Emphasis Type="Italic">E</Emphasis>. <Emphasis Type="Italic">urophylla</Emphasis> leachates on <Emphasis Type="Italic">Brassica chinensis</Emphasis>

Soil microbes may be critical players in determining the allelopathic potential of some plants. Low levels of plant community biodiversity in Eucalyptus plantations have been attributed to the allelopathic potential of these tree species. The role of soil microbes in the allelopathic effect of leaf leachates of the hybrid tree Eucalyptus grandis × E. urophylla, was tested in Petri dish assays with Brassica chinensis as a receiver plant. Soils were collected from either a local garden (soil A) or a Eucalyptus plantation (soil B) and half of each soil was sterilized to remove microbes. These soils were then treated with E. grandis × E. urophylla leachates for 0–72 h. Seed germination of B. chinensis was significantly inhibited in soils treated with leaf leachates relative to untreated soils. The inhibitory effect of the leaf leachates was more pronounced in sterilized soils. Total phenolic content was obvious lower in nonsterile leachate-treated soils than in sterile soils. Biomass of B. chinensis was negatively correlated with the total phenolic content in soils. Our findings suggest that soil microbes can alleviate the allelopathic potential of Eucalyptus and thereby its negative impact on plant growth.     

Amelioration of planting stress by soil amendment with a hydrogel–mycorrhiza mixture for early establishment of beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) seedlings

Introduction   

The mortality of nursery-grown beech (Fagus sylvatica L.) seedlings after out planting into the field is usually high.     

5<Emphasis Type="Italic">Α</Emphasis>-Reductase inhibitory tannin-related compounds isolated from <Emphasis Type="Italic">Shorea laeviforia</Emphasis>

Five tannin-related compounds – gallic acid, flavogallonic acid dilactone, valoneic acid dilactone, gallagyldilactone, ellagic acid – were isolated from the heartwood of Shorea laeviforia, and the inhibitory activity of each against rat liver 5-reductase was evaluated. Valoneic acid dilactone and gallagyldilactone exhibited positive inhibitory activity, but gallic acid and ellagic acid did not. Flavogallonic acid dilactone stimulated 5-reductase activity, even though this compound is structurally similar to valoneic acid dilactone. The kinetic study of valoneic acid dilactone and gallagyldilactone indicated that the inhibitory behavior of 5-reductase were not competitive against the substrate (testosterone) and were partially competitive against the cofactor (NADPH). Additionally, double inhibition analysis of valoneic acid dilactone and NADP⁺ showed synergetic inhibition. These results suggested that neither valoneic acid dilactone nor gallagyldilactone can affect the binding of testosterone but that either compound could interact with an enzyme–NADP⁺ complex to inhibit 5-reductase.     

Fitness consequences of seed size in the valley oak <Emphasis Type="Italic">Quercus lobata</Emphasis> Née (Fagaceae)

Introduction   

We examined the functional relationship between seed size and seedling performance in the valley oak (Quercus lobata Née) by means of a 13-year common garden experiment.     

Activities of some defense proteins associated with age or plant family in larch needles of <Emphasis Type="Italic">Larix olgensis</Emphasis> and <Emphasis Type="Italic">L. kaempferi</Emphasis> × <Emphasis Type="Italic">L. gmelinii</Emphasis>

Defence proteins are a kind of chemical defence compounds. They play a key role in plant restraining biotic and abiotic harm. To illuminate activities of some defense proteins associated with age or plant family of larch, the larch needles were collected from two different families of Korean larch, Larix olgensis and a hybrid larch, L. kaempferi × L. gmelinii, respectively, and then the activities of defence proteins in those were tested using a UV spectrophotometry. The results showed that the activities of protective enzymes at the16-/17- and 19-year-age groups were higher than those at the other age groups in the both larch species. While the activities of polyphenol oxidase (PPO) at the 16-/17-year-age group and phenylalanine ammonia-lyase (PAL) and protease inhibitors at the 19-year-age group were the highest among all age groups. Then, compared with L. olgensis, the hybrid larch had significant effects on the activities of protective enzymes. The effects of plant family on the activities of PAL and chymotrypsin inhibitor were significantly different, and then those on the activities of PPO were not significantly different. The effects of the two families in L. olgensis on the activities of trypsin inhibitor (TI) were significantly different, while those in the hybrid larch on the activities of TI were contrary. To conclusions showed that the different age and plant family significantly affected the activities of defence proteins in the needles of two larch species, and then enhanced the larch resistance to pests. These could play a key function in forestry tree genetic improvement and management in future.     

Differences in leaf functional traits between red and green leaves of two evergreen shrubs <Emphasis Type="Italic">Photinia</Emphasis> × <Emphasis Type="Italic">fraseri</Emphasis> and <Emphasis Type="Italic">Osmanthus fragrans</Emphasis>

Leaf functional traits are adaptations that enable plants to live under different environmental conditions. This study aims to evaluate the differences in leaf functional traits between red and green leaves of two evergreen shrubs Photinia × fraseri and Osmanthus fragrans. Specific areas of red leaves are higher than that of green leaves in both species. Thus, the material investment per unit area and per lamina of red leaves is significantly lower than that of green leaves, implying an utmost effort of red leaves to increase light capture and use efficiency because of their low leaf-chlorophyll concentration. The higher petiole length of green leaves compared with that of red leaves indicates that adult green leaves may have large fractional biomass allocation to support the lamina structures in capturing light with maximum efficiency and obtaining a high growth rate. The high range of the phenotypic plasticity of leaf size, leaf thickness, single-leaf wet and dry weights, and leaf moisture of green leaves may be beneficial in achieving efficient control of water loss and nutrient deprivation. The high range of phenotypic plasticity of leaf chlorophyll concentration of red leaves may be advantageous in increasing resource (especially light) capture and use efficiency because this leaf type is juvenile in the growth stage and has low leaf-chlorophyll concentration.     

Low pre-death growth rates of oak (<Emphasis Type="Italic">Quercus robur</Emphasis> L.)—Is oak death a long-term process induced by dry years?

• Background and purpose   

A complex interplay between biotic and abiotic factors is believed to be responsible for several oak declines in pedunculate oak (Quercus robur L.). This study aims to clarify the temporal process of oak declines, as well as identifying individual tree and environmental variables that affects growth rate and that may increase the risk of mortality. The study was performed in southern Sweden at three sites.     

Is leaf area of Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> L. Karst.) and European larch (<Emphasis Type="Italic">Larix decidua</Emphasis> Mill.) affected by mixture proportion and stand density?

Key message

Trees with otherwise equal dimensions have different leaf areas if they are located in different stand types. While leaf area of European larch is affected by mixture proportion, leaf area of Norway spruce is affected by stand density.

Context

Leaf area is a key parameter for evaluating growth efficiency of trees, and therefore needs to be measured as consistently and accurately as possible. This is even more important when comparing monospecific and mixed stands.

Aims

The aim of the study is to find combinations of parameters and allometric relationships that can be used to estimate accurately the leaf area of individual trees.

Methods

Allometries of the measured leaf area of 194 trees in 12 stands were analysed in order to find variables affecting leaf area. Existing functions from the literature were validated. Finally, models were fitted to find the most appropriate method for estimating leaf area of mixed and monospecific stands of Norway spruce and European larch.

Results

Allometric relationships of leaf area to other measurable characteristics of trees vary in different stand types. Besides individual tree dimensions such as diameter and crown surface area, leaf area of Norway spruce is related to stand density, whereas the leaf area of European larch is dependent on the admixture of Norway spruce in the stand.

Conclusion

In contrast to models for estimating individual tree leaf area of Norway spruce, models for leaf area of European larch have to consider mixture proportions in order to correctly interpret the growth efficiency of mixed stands.

     

Comparative microsporogenesis and flower development in <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis> × <Emphasis Type="Italic">E. grandis</Emphasis>

Microsporogenesis and flower development in Eucalyptus urophylla × E. grandis were examined using chromosome tableting to provide a method to predict the meiotic stages in this species. Although microsporogenesis was normal, cytokinesis during meiosis of pollen mother cells occurred simultaneously, with strong asynchronism observed in the two different lengths of stamens in a flower bud. In a single flower, the developmental period of microsporogenesis in anthers on the longer stamens was always ahead of those on the shorter stamens. Flower development was also asynchronous at different locations on a branch. Flower buds on the upper side of the branch were larger in diameter than those on the lower side. In addition, a correlation was observed between microsporogenesis development and flower bud diameter growth. The pachytene stage was first observed when the diameter of the flower buds increased to 3.0 mm, and the majority of the meiotic stages were observed when bud diameters ranged from 3.5 to 5.0 mm. This study showed that the developmental stages of microsporogenesis in Eucalyptus urophylla × E. grandis could be distinguished readily, which may be applicable to future breeding studies.     

Ethanol production with <Emphasis Type="Italic">β</Emphasis>-xylosidase,xylose isomerase,and <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> from the hydrolysate of Japanese beech after hot-compressed water treatment

Ethanol was produced from the hydrolysate collected as the water-soluble (WS) portion after hot-compressed water (HCW) treatment of Japanese beech. The process involved saccharification with β-xylosidase followed by isomerization with xylose isomerase and fermentation with Saccharomyces cerevisiae. Several process schemes were compared to investigate the effect of process integration of saccharification, isomerization, and fermentation. Higher ethanol yields were obtained for the processes that integrated isomerization and fermentation or saccharification and isomerization. Integration of isomerization and fermentation was effective in converting xylose into ethanol. Similarly, integration of saccharification and isomerization was effective in converting xylooligosaccharides into xylulose. It is presumed that the saccharification reaction toward xylose and the isomerization reaction toward xylulose were linked and therefore each reaction was enhanced.     

Fitness of heat and desiccation tolerant hybrid strains of <Emphasis Type="Italic">Heterorhabditis</Emphasis> <Emphasis Type="Italic">bacteriophora</Emphasis> (Rhabditidomorpha: Heterorhabditidae)

Entomopathogenic nematodes of the genus Heterorhabditis are a suitable alternative to chemical insecticides because of their high control effect against insects in cryptic environments and their environmental safety. The availability of H. bacteriophora hybrid strains with increased tolerance to environmental extremes could be a driving force for a more widespread use of nematode-based plant protection products. However, increase in heat and desiccation tolerance of hybrid strains could compromise their fitness regarding virulence, host penetration and reproductive capacity. The fitness of heat and desiccation tolerant hybrid strains was compared to the commercial strain EN 01. Only the heat tolerant strains were superior or similar in fitness to strain EN 01. The strains with increased desiccation tolerance were usually less fit, a possible result of a trade-off effect of selection for desiccation tolerance. Hybrid strains selected for enhanced tolerance after an adaptation to stress were generally better in fitness ranking compared to those for which adaptation prior to stress exposure was excluded. This might be a result of pleitropy. Host penetration and virulence was not correlated. The commercial strain had the highest reproduction per mean number of nematodes penetrating the host insect, which is a result of automatic selection of inbred lines with high reproduction potential during the commercial production process in liquid culture.     

Sprouting characteristics of <Emphasis Type="Italic">Quercus pubescens</Emphasis> Willd. and <Emphasis Type="Italic">Quercus frainetto</Emphasis> Ten. trees after a wildfire: To cut or not to cut the burned trees?

The aims of this study were to analyze the sprouting characteristics of Quercus pubescens and Q. frainetto trees after a wildfire and to recommend the appropriate silvicultural treatments in order to achieve dense sprout origin regeneration. This study was carried out in the area that was burned in a wildfire in northeastern Greece. Three years later, 140 Q. pubescens trees and 140 Q. frainetto trees were selected. Seventy trees for each species were individuals that were cut after the fire and were in the form of stumps, while 70 trees were intact top-killed trees, as a result of fire. In each stump and intact tree that was selected, various parameters were measured or counted: the diameter at the level of ground, the number of the developed sprouts (if any) and the height as well as the basal diameter of the tallest sprout, etc. Both species have similar sprouting behavior after a wildfire. Mother tree dimensions positively influenced the number of sprouts and the growth of the tallest sprout per individual. The mean height of the tallest sprout per stump, after three growing seasons from the forest fire, is high in both species (2.08 m for Q. pupescens and 2.29 m for Q. frainetto). Cut stumps had more sprouts than intact trees in both species. Forest practice, in order to maximize the sprouting of Q. pubescens and Q. frainetto trees after a forest fire, should cut the burned trees before the next growing season.