Temperate Broad-leaved Forest Research Articles

Vegetation and fire history with their implication for climatic change and fire events since the last deglacial in the Aso Valley, central Kyushu, southwestern Japan: new pollen and charcoal data

To better understand the response of forest vegetation to climate and fire regimes with reference to human activities over the last deglacial period in the Aso Caldera, central Kyushu, southwestern Japan, a 33.9 m long sediment core was examined in order to reconstruct the vegetational and fire history using pollen and charcoal analyses. The results show that a cool temperate broad-leaved deciduous forest, dominated by Quercus (deciduous oaks) with Carpinus and Fagus, prevailed in the Aso Valley from ca. 14.6 ka cal. b.p., indicating warming since the last glacial period. The landscape was presumably covered by a mosaic of deciduous Quercus forests and terrestrial Artemisia communities. Around 12.8–11.7 ka cal. b.p., Quercus dominated the forest and fires occurred frequently. Co-expansion of distinctive Ulmus–Zelkova and Celtis–Aphananthe forests coupled with a progressive retreat of Quercus in the early Holocene could reflect a strengthening of the East Asian summer monsoon under mild and humid climate conditions. Around 8 ka cal. b.p., significant increases in Cyclobalanopsis (evergreen oaks), Castanopsis/Castanea and Podocarpus indicate a further warming, in particular an increased winter temperature. Warm temperate lucidophyllous forests, dominated by Cyclobalanopsis, flourished after 7.3 ka cal. b.p., probably corresponding to the “Holocene Climatic Optimum” interval. Progressive expansion of Quercus at the expense of Cyclobalanopsis began around 6.4 ka cal. b.p. and paralleled an increase in charcoal until ca. 4.8 ka cal. b.p.; this could be evidence of fire disturbance induced by the early-middle Jomon people. The disturbed evergreen forest experienced a temporary recovery but then opened again from 3.6 ka cal. b.p. due to extensive fire deforestation, as suggested by the high charcoal levels during this time. Human exploitation and buckwheat (Fagopyrum) agriculture may have contributed to the opening of the forest, which allowed secondary forests (primarily Pinus and Quercus) and herbaceous communities (mainly Poaceae) to spread. These results are discussed in comparison with other high-resolution pollen data from western Japan to better elucidate the vegetation and fire history over the last deglacial in the Aso Caldera.

Impact of Altitude on Population Structure and Regeneration Status of Two Rhododendron Species in a Temperate Broad Leaved Forest of Arunachal Pradesh, India

An attempt had been made to study the impact of altitude on population structure and regeneration status of two Rhododendron species as well as its associated species in a temperate forest of Arunachal Pradesh. Population structure was worked out based on the density of seedlings, saplings and adults while, the regeneration status was determined from the population size of seedlings, saplings and adults. The mid altitude site (Hanuman Camp) has highest density (2692 indi- viduals ha -1 ) comprising of seedlings, saplings and adults of all species followed by lower altitude (Shagong) site (2379 individuals ha -1 ) and lowest at (Yarlung) higher altitude site (2180 individuals ha -1 ). However, the relative proportion of seedlings of all woody species was recorded highest in low altitude site, while it was lowest in higher altitude. Conversely, the relative proportion of saplings and adults were highest in higher altitude. The selected Rhododendron species shows reverse J shaped population structure and fair regeneration status in all study stands having higher number of seedlings compared to saplings. However, the number of saplings is less than the adults. It was observed that the seedling populations dominate the overall population of the selected Rhododendron species. Moreover, it was found that although altitude does not affect re- generation status, but affects the population structure of the selected Rhododendrons. The fluctuation in population density of seedlings, saplings and adults along the altitudinal gradient may be linked with the prevailing environmental factors.

Survival and Growth of Seedlings of Two Rhododendron Tree Species along an Altitudinal Gradient in a Temperate Broad Leaved Forest of Arunachal Pradesh, India

Seedling survival and growth of two Rhododendron species viz., Rhododendron kenderickii and Rhododen- dron grandewere studied along an altitudinal gradient in a temperate forest. Differences in survivality and relative growth responses of the two selected rhododendrons in terms of height, collar diameter and leaf number were monitored seasonally. High seedling mortality was recorded highest in winter season as well as in the higher altitude. Both the species attain maximum growth in terms of height, collar diameter and mean leaf number during rainy season while, minimum in winter season. Moreover, both the Rhododendron species exhibit variation in growth response with altitude and higher total growth was recorded in lower altitude. The result of the present study showed that the survival and growth of seedlings of both the selected Rhododendron species were greatly influenced by altitude as well as season. This variability may be due to the variation in light, temperature, moisture and edaphic factors in various seasons as well as at different altitudes, which results into development of an array of microclimatic conditions for differential growth behavior of different species.

Functional–structural water flow model reveals differences between diffuse- and ring-porous tree species

A functional–structural (FS) model of tree water flow is applied for single trees in an old-growth temperate broad-leaved forest stand. Roots, stems and branches are represented by connected porous cylinder elements that are divided into the inner heartwood cylinders surrounded by xylem and phloem. Xylem water flow is simulated by applying a non-linear Darcy water flow in porous media driven by the water potential gradient according to the cohesion–tension theory. The flow model is based on physiological input parameters such as the hydraulic conductivity, stomatal response to leaf water potential and root water uptake capability and, thus, can reflect the different properties of the two diffuse-porous tree species Fagus sylvatica and Tilia cordata and the ring-porous species Fraxinus excelsior. The structure of the canopy is obtained by applying an automatic tree skeleton extraction algorithm from point clouds obtained by terrestrial laser scans allowing an explicit representation of the water flow path in the stem and branches.Supported by measurements of stem sap flow, the model reveals differences of the simulated stomatal closure due to low branch xylem water contents between the tree species. The diffuse-porous species reduced the transpiration by the stomatal closure only at hot days with a high potential transpiration. For the ring-porous ash the simulated reduction is much higher with a mean value of all trees over the observation period of 0.72. The model gives insights to the mechanism that lead to the stomatal closure and can spot the axial xylem hydraulic conductance along the flow pathway as the limiting factor of leaf water supply at days with moist soil water conditions.

Impacts of elevated CO2 and temperature on soil respiration in warm temperate evergreen Quercus glauca stands: an open-top chamber experiment

We conducted an open-top chamber experiment for 3 years to examine the effect of elevated CO2 and temperature on soil respiration in experimental stands of Quercus glauca, an evergreen tree species common in the warm temperate zone of Japan. Seedlings of Q. glauca were planted in open-top chambers and treated with factorial combinations of ambient and elevated (ambient × 1.4, ambient × 1.8) CO2 concentrations and ambient and elevated (+3°C) air temperatures. Elevated CO2 significantly increased the total soil respiration rate (P < 0.001) and the soil respiration rate at 15°C (R 15) (P < 0.05) but had no significant effect on the temperature coefficient Q 10. Although temperature significantly affected total soil respiration rate (P < 0.05), neither the R 15 nor the Q 10 of total soil respiration was affected significantly by the air temperature increase. Annual soil respiration rate, estimated from R 15, Q 10, and soil temperature data, tended to increase with elevated CO2 concentration. These results suggest that soil respiration rate in Japanese warm temperate broad-leaved forests dominated by Q. glauca is sensitive to elevated CO2 and is likely to increase under future climatic conditions.

The inhibiting effect of nitrate fertilisation on methane uptake of a temperate forest soil is influenced by labile carbon

Upland soils are the most important terrestrial sink for the greenhouse gas CH4. The oxidation of CH4 is highly influenced by reactive N which is increasingly added to many ecosystems by atmospheric deposition and thereby also alters the labile C pool in the soils. The interacting effects of soil N availability and the labile C pool on CH4 oxidation are not well understood. We conducted a laboratory experiment with soil columns consisting of homogenised topsoil material from a temperate broad-leaved forest to study the net CH4 flux under the combined or isolated addition of NO 3 − and glucose as a labile C source. Addition of NO 3 − and glucose reduced the net CH4 uptake of the soil by 86% and 83%, respectively. The combined addition of both agents led to a nearly complete inhibition of CH4 uptake (reduction by 99.4%). Our study demonstrates a close link between the availability of C and N and the rate of CH4 oxidation in temperate forest soils. Continued deposition of NO 3 − has the potential to reduce the sink strength of temperate forest soils for CH4.

Stemflow and dissolved organic carbon cycling: temporal variability in concentration, flux, and UV-Vis spectral metrics in a temperate broadleaved deciduous forest in the eastern United States

No known research has examined the concentration and flux of dissolved organic carbon (DOC) for stemflow across temporal scales from within single storm events to seasonal and annual scales or employed UV-Vis spectral metrics to examine the chemical character of dissolved organic matter (DOM) of stemflow drainage. Thus, our study examined stemflow DOC concentration and flux and DOM character from American beech ( Fagus grandifolia Ehrh.) and yellow poplar ( Liriodendron tulipifera L.) to address this data gap. Intrastorm stemflow DOC concentrations and fluxes diminished by an order of magnitude over time for American beech but remained relatively constant for yellow poplar. Stemflow DOM aromaticity, however, generally increased and E2:E3 ratios generally decreased as events progressed, suggesting transport of different compounds at different moments. Although less enriched in DOC than yellow poplar, American beech stemflow DOC fluxes were double per annum. Differential interspecific stemflow DOM characteristics are ascribed to (i) significant differences in SUVA254 values (aromaticity) for the leafless season and annually and (ii) significantly higher E2:E3 and SR ratios for yellow poplar stemflow than for American beech annually and across leafed and leafless seasons. Our results suggest that stemflow significantly affects the amount and chemical character of carbon flux to the forest floor that may engender hot spots around tree boles.

Shrubs protect oak seedlings against ungulate browsing in temperate broadleaved forests of conservation interest: A field experiment

In many oak-rich temperate broadleaved forests of conservation value, high ungulate browsing pressure restricts oak regeneration. We examined the protection of oak ( Quercus sp.) seedlings from browsing provided by naturally occurring shrubs in 10 forests across southern Sweden over 3 years. We planted oak seedlings in four plots in each forest; two with naturally regenerated shrubs and two with no shrubs. Ungulate browsers were excluded from two plots at each site, one with and one without shrubs. Fencing provided the best protection against ungulate browsers for the seedlings. The probability of a seedling being browsed (browsing frequency) was approximately 20% units lower for individuals growing among shrubs than for individuals growing in the absence of shrubs. When browsing did occur, the intensity (measured as a reduction in height growth) was significantly lower for seedlings in shrubs. Regression analyses showed that browsing frequency increased on seedlings in tall shrubs, and decreased on seedlings that had been browsed previously. Browsing intensity decreased if the seedling grew in tall and dense shrubs. Browsing frequency and intensity increased on oak seedlings that over topped the shrub canopy. Increased abundance of the prickled Rubus idaeus and Rubus fruticosus coll. in plots with shrubs did not affect browsing frequency and intensity. Two and a half years after planting, oak seedling mortality increased by the presence of shrubs. Although shrubs restricted oak seedling growth, we conclude that shrubs initially facilitated oak regeneration by concealment, and subsequently by numeric dilution. Shrubs may be used to reduce browsing damages if long-term evaluation indicates a net positive outcome for oak survival and growth.

Analyzing forest canopies with ground-based laser scanning: A comparison with hemispherical photography

We tested ground-based high resolution laser scanning as a tool for analyzing the complex canopy structure of temperate broad-leaved forests. The canopies of 35 groups of trees were analyzed by laser scans from various positions inside a mixed stand to generate three-dimensional (3D) point clouds of the axes and leaves. The scan data was used to produce hemispheric views of the canopy at various locations that were compared to synchronously taken hemispherical photographs of the same part of the canopy. We conclude that terrestrial laser scanning (TLS) in mature forests can overcome several of the methodological problems inherent to conventional canopy analysis with optical methods and thus may soon offer a promising tool for functional research in complex forest canopies. Certain limitations of the TLS approach, mostly caused by hardware limitations that will probably soon be overcome, are encountered.

Understory succession in post-agricultural oak forests: Habitat fragmentation affects forest specialists and generalists differently

The herbaceous understory forms the richest stratum in temperate broadleaved forests in terms of plant diversity. Understanding the process of understory succession is thus of critical importance for the development of management guidelines for biodiversity restoration in post-agricultural plantation forests. We studied effects of stand age, forest fragmentation, and soil and canopy conditions on species richness and abundance of four species groups in the understory of post-arable oak plantations in southern Sweden: herbaceous forest specialists, habitat generalists and open-land species, and woody species. The group of forest specialists may approach the richness of continuously forested sites after 60–80 years in non-fragmented plantations, but many forest species were sensitive to habitat fragmentation. Open-land species richness decreased during succession, while the richness of woody species and of generalists remained stable, and was not affected by fragmentation. Abundance of generalists gradually decreased in non-fragmented plantations, probably due to competition from colonizing forest specialists. Soil pH in post-arable stands remained consistently higher than in continuously forested stands, which maintained differences in species composition. The development of a shrub layer seemed to imply a competitive advantage for forest specialists compared to generalist species. For successful recovery of a rich understory, we suggest that post-arable plantations should be established on loamy soils of intermediate to high pH proximate to older forest with source populations, and that a continuous overstory canopy cover of 70–80% is maintained by regular light thinnings and promotion of a shrub layer.

Carbon dioxide fluxes over an ancient broadleaved deciduous woodland in southern England

Abstract. We present results from a study of canopy-atmosphere fluxes of carbon dioxide from 2007 to 2009 above a site in Wytham Woods, an ancient temperate broadleaved deciduous forest in southern England. Gap-filled net ecosystem exchange (NEE) data were partitioned into gross primary productivity (GPP) and ecosystem respiration (Re) and analysed on daily, monthly and annual timescales. Over the continuous 24 month study period annual GPP was estimated to be 21.1 Mg C ha−1 yr−1 and Re to be 19.8 Mg C ha−1 yr−1; net ecosystem productivity (NEP) was 1.2 Mg C ha−1 yr−1. These estimates were compared with independent bottom-up estimates derived from net primary productivity (NPP) and flux chamber measurements recorded at a plot within the flux footprint in 2008 (GPP = 26.5 ± 6.8 Mg C ha−1 yr−1, Re = 24.8 ± 6.8 Mg C ha−1 yr−1, biomass increment = ~1.7 Mg C ha−1 yr−1). Over the two years the difference in seasonal NEP was predominantly caused by changes in ecosystem respiration, whereas GPP remained similar for equivalent months in different years. Although solar radiation was the largest influence on daily values of CO2 fluxes (R2 = 0.53 for the summer months for a linear regression), variation in Re appeared to be driven by temperature. Our findings suggest that this ancient woodland site is currently a substantial sink for carbon, resulting from continued growth that is probably a legacy of past management practices abandoned over 40 years ago. Our GPP and Re values are generally higher than other broadleaved temperate deciduous woodlands and may represent the influence of the UK's maritime climate, or the particular species composition of this site. The carbon sink value of Wytham Woods supports the protection and management of temperate deciduous woodlands (including those managed for conservation rather than silvicultural objectives) as a strategy to mitigate atmospheric carbon dioxide increases.

Trophic niche differentiation in millipede communities of forests of the temperate and tropical belts

The degree of trophic differentiation of millipedes in taxocenes of temperate and tropical forests was estimated by isotopic analysis. The isotope ratio variation among species was notably wider in a tropical forest (23 millipede species, δ15N ranges within 10‰) than in a temperate broad-leaved forest (9 species, δ15N range less than 3‰). It is suggested that partitioning of food resources among species contributes significantly to the maintenance of high diversity of soil saprotrophic animals in tropical ecosystems.

Habitat associations of saplings and adults in an old-growth temperate forest in the Changbai mountains, northeastern China

Species-habitat association analysis is useful to detect spatial arrangement of individual plants, to discover rules about the distribution of species and to generate hypotheses about the possible underlying process controlling observed structures. Quantifying methods were used to classify habitats in terms of topographical variables in a mixed temperate broad-leaved Korean pine forest of the Changbai mountains in northeastern China. All of the 625 20 m × 20 m quadrats of the plot could be unambiguously assigned to one of three habitat categories (low-plateau, high-plateau and slope). Torus-translation tests were used to estimate species-habitat associations. Many species are clearly distributed in a biased fashion with respect to habitats. Fifteen (55.6%) out of 27 species showed strong positive or negative association with specific habitats. We compared species-habitat associations at the sapling and adult stages. Adjusted density values indicated few species exhibit extremely strong habitat associations. Only 9 out of 26 species had adjusted densities > 3 in the habitat for which they had strong positive affinity. Few species show the same associations at the small tree and large tree stages. Only 3 out of 22 occurring associations with a specific habitat appeared to have a consistent habitat association at the two stages. These results suggest that species-habitat associations exist in the 25-ha plot of the temperate forest of the Changbai mountains. Owing to limitations in our statistical methodology, we partly underestimated associations by ignoring rare species. Regeneration niches can contribute to co-existence, but regeneration niches due to habitat associations play a limited role in species co-existence, since most species show a similar trend in habitat associations at the sapling and adult stages. We should pay more attention to shifts in habitat associations, i.e. niche shifts at different stages of existence.

Regionalization and distribution pattern of vegetation of Northeast China

Aims Our objectives were to consider a new scheme for vegetation regionalization of Northeast China, espe- cially for vegetation in the Songliao Plain, and to illustrate the distribution pattern of vegetation as determined by altitude. Methods We clustered the sites from Inner Mongolia steppe, east forest and central Songliao Plain with temper- ature, precipitation, soil types and underground water depth using principle component analysis (PCA). We also analyzed the physiognomy, topography of Northeastern China using GIS, vegetation types and soil types of Songnen Plain. Important findings The dominant vegetation of Songliao Plain is meadow, an unzonal vegetation type. The Sti- pa communities, an indicator of the zonal vegetation type, mainly distributed on the second mesa in Songnen Plain, are a sandland vegetation type that is distributed discontinuously among meadow vegetation. Therefore, the vegetation of Songliao Plain should be regionalized as an area of temperate broad-leaved deciduous forest, and the east boundary of temperate steppe region should be moved toward to the west of the Da Hinggan Mountains. The

Stand structure, phenology and fruit yield of Illicium griffithii in western Arunachal Pradesh, North-East India

Illicium griffthii is an important medicinal tree species of the temperate broad-leaved forests of Northeast India. The species has high demands for its fruits. In view of scanty information on the species in natural stands, this investigation explores three forest stands under different management regimes in Western Arunachal Pradesh with particular reference to study stand structure, fruit production and phonological behaviour of I. griffthii. The study revealed that I. griffthii was an important species in the middle storey and it grew frequently with other top canopy species. The tree species richness, stand density and total basal cover of three stands varied between 27 to 40 species, 482 to 568 tree ha-1, and 18.08 to 59.28 m2 ha-1, respectively. The data showed that high biotic pressure resulted decline in tree species richness, stand density and total basal area while moderate level of pressure was beneficial. The contribution of I. griffthii to total stand density and basal cover was high at all three forests. It was interesting to note that these forests supported 72-81% tree species used for fuel, fodder, timber, edible fruits and other useful products, thus provided diverse opportunities to communities to visit these stands. The dominance-diversity curve showed that the resource allocation were homogenous to shared by a few species at different stands. Tree girth class structure showed that all forest stands are still evolving. The phenological progression of I. griffithii showed no marked leaf fall event, the flowering phase prevailed between February to April and mature fruits in October. The fruit yield for I. griffithii varied from 0.015 kg to 23.28 kg per tree for 11 to 180 cm girth class individuals. The study concluded that in view of high demand of fruits of I. griffithii, these forests may face higher pressure in near future, therefore information on stand structure, phenology and fruit productivity would help the management planners. It is suggested that if local communities could be educated about the potential of I. griffithii and promoted in agroforestry systems, the income of local farmers could be increased substantially, at the same time the species could be conserved in natural stands.

Modeling stand water budgets of mixed temperate broad-leaved forest stands by considering variations in species specific drought response

This modeling study used recent observations at a temperate broad-leaved forest in Central Germany to calculate water balances of a Fagus sylvatica monoculture and mixed stands of F. sylvatica, Tilia spp., Acer spp., Carpinus betulus, Fraxinus excelsior and Quercus robur. To simulate soil water flow the modeling framework Expert-N was applied which combines models that describe the physiological and hydrological processes of the plant-soil system including models of evapotranspiration (Penman–Monteith equation), interception (revised Gash model) and soil water flow (Richards equation). Measurements of rainfall partitioning, volumetric soil water content, evapotranspiration and tree transpiration provided reliable data for the parameterization and the calibration of the model for three stands of different diversity levels. They allowed to include species specific physiological (transpiration rates, response to dry soil water conditions) and structural (leaf area dynamics) characteristics. During the 3-year long observation period 2005–2007 the mean yearly precipitation was 652 mm, the simulated mean yearly interception loss of the three observed forest stands was between 219 and 272 mm, the transpiration accounted for 197–225 mm, the forest floor evaporation for 96–104 mm, the drainage for 16–60 mm and the runoff for 13–50 mm. The calculations of the water balance were sensitive to the species composition of the forest and showed differences of rainfall interception and root water uptake between the stands. The applied stand-level model was able to simulate the water dynamics of the monospecific and mixed forest stands. It was shown that differences in drought tolerance of tree species can have a strong impact on the simulated soil water extraction during periods when available soil water is low.

Food habits of Japanese deer in an evergreen forest: Litter-feeding deer

We observed the feeding behaviors of wild Japanese sika deer ( Cervus nippon yakushimae) in a warm temperate broad-leaved evergreen forest of the island of Yakushima using the focal animal sampling method from April 2002 to June 2006. Sika deer fed on species of at least 73 woody plants, 13 vines, 8 herbaceous plants, 8 ferns, 1 moss, and 3 fungi. We investigated time spent feeding on each food category in each season (spring: April–June; summer: July–September; autumn: October–December; winter: January–March). During each season, 45.6–59.8% of the deer diet consisted of fallen woody leaves. Half of the fallen leaves were those tinged with red and yellow colors. Fallen reproductive parts of plants constituted 8.7–23.7% of the seasonal deer diet. In contrast, living woody parts of plants and herbaceous plants, including ferns and moss, constituted 4.4–22.5% and 0.8–9.2% of the seasonal diet, respectively. Deer also fed on animal matters as minor food items, such as the feces of monkeys and raccoon dogs, bones of deer and monkeys, and bird carcasses. Animal matters constituted 0.3–1.6% of the seasonal diet. Sympatric monkeys supplied food to deer as a result of their daily activities. Monkey-supplied foods comprised 1.7–10.9% of the seasonal diet of sika deer. Monkeys tended to supply many fruits and seeds. Overall, 75.0% of the annual deer diet consisted of forest litter, even though deer had access to abundant living edible leaves in the study area. Therefore, sika deer in this forest ecosystem function ecologically as decomposers rather than primary consumers.

Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

Abstract. Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE) in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS), based on the flux data obtained during June–August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR) differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max) at CBS under cloudy skies during mid-growing season (from June to August) increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (kt) ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when kt exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD) and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP) and greater increase in ecosystem respiration (Re) at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in cloudiness is an important factor that should be included in evaluating regional carbon budgets under climate change conditions.

Productivity of temperate broad-leaved forest stands differing in tree species diversity

• Understanding the effects of tree species diversity on biomass and production of forests is fundamental for carbon sequestration strategies, particularly in the perspective of the current climate change. However, the diversity-productivity relationship in old-growth forests is not well understood. • We quantified biomass and above-ground production in nine forest stands with increasing tree species diversity from monocultures of beech to stands consisting of up to five deciduous tree species (Fagus sylvatica, Fraxinus excelsior, Tilia spp., Carpinus betulus, Acer spp.) to examine (a) if mixed stands are more productive than monospecific stands, (b) how tree species differ in the productivity of stem wood, leaves and fruits, and (c) if beech productivity increases with tree diversity due to lower intraspecific competition and complementary resource use. • Total above-ground biomass and wood production decreased with increasing tree species diversity. In Fagus and Fraxinus, the basal area-related wood productivity exceeded those of the co-occurring tree species, while Tilia had the highest leaf productivity. Fagus trees showed no elevated production per basal area in the mixed stands. • We found no evidence of complementary resource use associated with biomass production. We conclude that above-ground productivity of old-growth temperate deciduous forests depend more on tree species-specific traits than on tree diversity itself.

Does root competition asymmetry increase with water availability?

Background: Below-ground competition as a major structuring force in plant communities can be either symmetric or asymmetric with important consequences for the coexistence of plants. It is a matter of controversy whether asymmetry in competition increases with resource availability or not. Aims: This study tested the hypotheses that root competition between mature Fagus sylvatica and Quercus petraea trees is asymmetric and that asymmetry is more pronounced in non-water-limited environments. Methods : Initially equal-sized tree fine roots were grown for 365–390 days in root growth chambers in situ and exposed to competition by either a conspecific or an allospecific root. Relative root growth rate was used to determine asymmetry in root competition. Different soil moisture regimes were considered by conducting a throughfall reduction experiment and by including data from earlier experiments with contrasting moisture regimes. Results: The competitive interaction between Fagus and Quercus fine roots is asymmetric; root morphology appears to depend on the presence of a competitor; and asymmetry in root competition increases with increasing soil moisture availability. Conclusions: Below-ground competition in temperate broad-leaved mixed forests can be as asymmetric as competition for light, with asymmetry decreasing with increasing water shortage.