Fine root biomass and morphology of <Emphasis Type="Italic">Pinus densiflora</Emphasis> under competitive stress by <Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis>

The fine root (diameter ≤2.0 mm) biomass and morphology of Japanese red pines (Pinus densiflora) grown under different aboveground conditions (i.e., high and low competitive environments) were examined in a pine–cypress mixed forest. All P. densiflora subject trees were about 40 years old, and the aboveground condition (i.e., size) of red pines appeared to be influenced by the surrounding Japanese cypress (Chamaecyparis obtusa). Smaller P. densiflora exhibited lower fine root biomasses, shorter root lengths, and lower root tip densities, but longer specific root lengths and higher specific root tip densities relative to larger pines. These results suggest that P. densiflora may adjust the morphological traits of fine roots to the different conditions in biomass allocation to fine roots of individuals with different aboveground growth.     

Foraging ability and growth performance of four subtropical tree species in response to heterogeneous nutrient environments

Considering the ubiquitous heterogeneity in spatial distribution of soil nutrients, we conducted a pot experiment to investigate the foraging traits and growth performance of four important subtropical tree species in a heterogeneous nutrient environment. The tested species exhibited large differences in foraging traits as well as growth benefits obtained from root foraging. Pinus massoniana, Schima superba and Liriodendron chinese all showed a higher degree of root morphological plasticity (expressed as relative fine root mass difference; RFRMD) than Cunninghami lanceolata (P < 0.05). P. massoniana exhibited the largest degree of morphological plasticity, followed by L. chinese and S. superba, whereas there were no significant differences in RFRMD among the three species. S. superba was the only species that exhibiting both morphological plasticity and physiological plasticity. Both P. massoniana and S. superba exhibited greater whole-seedling biomass and high sensitivity in response to nutrient heterogeneity, resulting from both types of plasticity. In contrast, both types of root plasticity were poor for C. lanceolata, resulting in poor growth benefit in heterogeneous environments. As for L. chinese, the root proliferation in nutrient-rich patches occurred at the expense of depressed root growth in other parts of the root system, leading to the lack of increment in total root biomass and nutrient absorption in heterogeneous environments. Our results provide insight and practical advice for silviculture and forest management.     

Dry matter production and allocation in Eucalyptus cloeziana and Eucalyptus argophloia seedlings in response to soil water deficits

Effects of soil water availability on seedling growth, dry matter production and allocation were determined for Gympie (humid coastal) and Hungry Hills (dry inland) provenances of Eucalyptus cloeziana F. Muell. and for E. argophloia Blakely (dry inland) species. Seven-month-old seedlings were subjected to well-watered (100% field capacity, FC), moderate (70% FC) and severe (50% FC) soil water regimes in a glasshouse environment for 14 wk. There were significant differences in seedling growth, biomass production and allocation patterns between species. E. argophloia produced twice as much biomass at 100% FC, and more than three times as much at 70% and 50% FC than did either E. cloeziana provenance. Although the humid provenance of E. cloeziana had a greater leaf area at 100% FC conditions than did the dry provenance, total biomass production did not differ significantly. Both E. cloeziana provenances were highly sensitive to water deficits. E. argophloia allocated 10% more biomass to roots than did E. cloeziana. Allometric analyses indicated that relative biomass allocation patterns were significantly affected by genotype but not by soil water availability. These results have implications for taxon selection for cultivation in humid and subhumid regions.     

Intraspecific variation in growth and allocation patterns in seedlings of Pinus pinaster Ait. submitted to contrasting watering regimes: can water availability explain regional variation?

? Interpopulation variation in key functional traits of Pinus pinaster Ait. is well recognized. However, the relative importance of drought tolerance to explain this regional variation in the species remains elusive.

? Here, we raise the question whether water availability constitutes a likely driver of regional variation in biomass allocation, growth and morphological traits of ten populations that cover the distribution range of P. pinaster. We carried out an experiment where seedlings of five families per population were submitted to two contrasting watering treatments.

? The effects of water availability and population were significant for relative diameter and height growth rate, biomass allocation and number of lateral stems and dwarf shoots. Total dry mass significantly differed between watering treatments but it did not among populations. Populations could be clustered into four main groups. Root mass fraction explained most of the variation and significantly correlated to altitude but not to aridity.

? The geographical pattern of genetic variation found in morphology and biomass allocation did not translate into population differences in drought tolerance or phenotypic plasticity to water availability, indicating that water availability is not a likely driver of the regional variation observed in the studied traits of P. pinaster at the seedling stage.

     

淹水对河竹鞭根系统生物量分配及异速生长模式的影响

为了揭示长期淹水对河竹鞭根系统生物量分配及异速生长模式的影响,调查测定了人工喷灌供水(CK)和淹水处理(TR)3、6个月的河竹1年生竹鞭及其根系的生物量,分析了河竹鞭、根生物量分配对淹水环境的适应和响应策略。结果表明: 淹水条件下河竹根系生长受到抑制,生物量分配比例鞭>根。与CK相比,淹水条件下河竹根系生物量及根系生物量/总生物量显著降低,鞭生物量/总生物量升高。随着淹水时间的延长,河竹鞭、根大量生长,生物量显著升高,但根生物量/总生物量、鞭生物量/总生物量和水中鞭生物量/总生物量变化并不明显。河竹鞭、根生物量间的关系在TR和CK处理下均符合幂函数增长关系,但淹水条件下的异速生长指数b要高于CK。研究表明河竹在鞭根系统生长和物质分配上具有较大的生态可塑性和可调节性,可以通过鞭根系统的生物量合理分配和异速生长调节以逐步适应淹水环境。研究结果可为河竹在水湿地和江河湖库消落带植被恢复中的应用提供参考。     

紫茎泽兰(Eupatorium adenophorum)对光强的生态适应性

紫茎泽兰(Eupatorium adenophorum)是我国主要外来入侵植物之一,在我国西南地区迅速传播,引起了巨大的经济损失。本文比较研究了不同光强下生长14个月的(透光率RI分别为10%、20%、30%、55%、100%)紫茎泽兰幼苗的生物量分配、叶片形态和生长反应特性。结果表明:紫茎泽兰在不同的光强条件下显示出极强的叶生态适应性。植株总生物量随光强升高而增加(RI从10%到55%),但在全光照下总生物量反而有所下降。株高也随光强增大(RI从10%到30%)而增大,但到达一定程度(RI30%)后,株高反而下降。在弱光照条件下,从比叶面积(SLA),叶面积比(LAR)和比茎长(SSL)等指标表明,植物通过叶片变薄、变大增加单位生物量的叶面积来捕获光能。随着光强的升高,平均相对生长速率增加,在本试验尺度下,RI在55%左右达到平均相对生长速率最大值。植株在RI为30%–55%下生长状况好于全光照条件下的幼苗。在高遮荫条件下能阻止其它生物的生存和生长,这可能是紫茎泽兰强入侵性的一种生态适应策略。结论:紫荆泽兰对光照强度拥有极强的生态适应性,可能是紫荆泽兰入侵性比较强的重要原因之一。图3参26。     

Leaf nitrogen productivity is the major factor behind the growth reduction induced by long-term salt stress

Plant growth response to salinity on a scale of years has not been studied in terms of growth analysis. To gain insights into this topic, 2-year-old Mediterranean Fan Palm (Chamaerops humilis L.) and Mexican Fan Palm (Washingtonia robusta H. Wendl) seedlings, each with its own distinct plant morphology, were grown for 2 years in a peat soil and irrigated with water of 2 dS m(-1) (control) or 8 dS m(-1) (saline). Plants were harvested on seven occasions and the time trends in relative growth rate (RGR, the rate of increase of biomass per unit of biomass already existing) and its components were analysed. In the long term, salinity produced a slight reduction in the mean RGR, values in both species. In the short term, salinity caused a reduction in RGR. However, during the second year, plants irrigated with 8 dS m(-1) grew somewhat more quickly than the control plants, probably as a result of delay in the growth kinetics due to salinity. Regarding RGR components, leaf nitrogen productivity (the rate of biomass gain per unit leaf N and time) was the major factor causing the differences in RGR resulting from salinity. Washingtonia robusta showed a relatively high plasticity in plant morphology by increasing root and decreasing stem biomass allocation in the presence of salinity. However, the long-term response of W. robusta to salinity, based to a great extent, on this morphological plasticity, was less effective than that of C. humilis, which is based mainly on the contribution of leaf N to RGR values.     

Loblolly and slash pine height and diameter are related to soil drainage in winter on poorly drained silt loams

Soil drainage characteristics in winter and the heights and diameters of 10-year-old loblolly and slash pines (Pinus taeda L. and P. elliottii Engelm. var. elliottii) were measured on three poorly-drained silt loam sites that had been bedded, furrowed, or disked before planting. Quadratic response functions were used to determine the relationship between depth to water table or volume of drained soil in winter and mean tree height or diameter. These quadratic response functions (species × height or diameter: drainage characteristics) showed that diameter and height were significantly related to soil drainage in winter on these silt loams soils. Slash pines grew better than loblolly pines under more poorly drained conditions while loblolly pines grew better under the better drained conditions. On unbedded silt loams, the soil drainage in winter needed to maximize tree height was 42 cm for loblolly and 49 cm for slash pine. Pines planted on beds did not generally grow better than those on flat-disked plots because where bedding would be most benefical the practice did not form enough additional drainage to significantly influence pine development.     

The influence of damage level in Pinus sylvestris foliage on the performance of diprionid sawflies

I tested the presence of rapid and delayed induced resistance in Pinus sylvestris L. by biotests, rearing three species of diprionid sawflies on defoliated and undefoliated trees. I damaged the pines artificially by cutting mature needles with scissors at the beginning of the growing season. Four levels of defoliation were created on the basis of levels of removed needle biomass. Sawfly larval and cocoon weights were retarded and relative growth rates delayed as a result of an increase in damage level. The larval periods were prolonged at most 2–6 days. The response to the damage was partly species‐specific. The needle water content decreased in the following growing season in connection with low and moderate damage and increased at high damage levels. The nutrient contents of the foliage in the damaged and undamaged trees did not differ significantly. The Scots pine showed damage‐induced changes in food quality after extensive defoliation, which affected, via plant, species using the same host.     

Physiological, morphological and allocational plasticity in understory deciduous trees: importance of plant size and light availability

In a 4-year study, we investigated changes in leaf physiology, crown morphology and whole-tree biomass allocation in seedlings and saplings of shade-tolerant sugar maple (Acer saccharum Marsh.) and intermediate shade-tolerant yellow birch (Betula alleghaniensis Britt.) growing in natural understory light (0.5 to 35% of full sunlight) or in understory light reduced by 50% with shade nets to simulate the effect of gap closure. Leaf physiological parameters were mainly influenced by the light gradient, whereas crown morphological and whole-tree allocational parameters were mainly influenced by tree size. No single physiological, morphological or allocational trait was identified that could explain the difference in shade tolerance between the species. Yellow birch had higher growth rates, biomass allocation to branches and leaf physiological plasticity and lower crown morphological plasticity in unmodified understory light than sugar maple. Sugar maple did not display significant physiological plasticity, but showed variation with tree size in both crown morphology and whole-tree biomass allocation. When sugar maple was small, a greater proportion of whole-tree biomass was allocated to roots. However, physiological differences between the species decreased with decreasing light and most morphological and allocational differences tended to disappear with increasing tree size, suggesting that many species differences in shade-tolerance are expressed mainly during the seedling stage. Understory trees of both species survived for 4 years under shade nets, possibly because of higher plasticity when small and the use of stored reserves when taller.     

Relative importance of photosynthetic physiology and biomass allocation for tree seedling growth across a broad light gradient

Studies of tree seedling physiology and growth under field conditions provide information on the mechanisms underlying inter- and intraspecific differences in growth and survival at a critical period during forest regeneration. I compared photosynthetic physiology, growth and biomass allocation in seedlings of three shade-tolerant tree species, Virola koschynii Warb., Dipteryx panamensis (Pittier) Record & Mell and Brosimum alicastrum Swartz., growing across a light gradient created by a forest-pasture edge (0.5 to 67% diffuse transmittance (%T)). Most growth and physiological traits showed nonlinear responses to light availability, with the greatest changes occurring between 0.5 and 20 %T. Specific leaf area (SLA) and nitrogen per unit leaf mass (N mass) decreased, maximum assimilation per unit leaf area (A area) and area-based leaf N concentration (N area) increased, and maximum assimilation per unit leaf mass (A mass) did not change with increasing irradiance. Plastic responses in SLA were important determinants of leaf N and A area across the gradient. Species differed in magnitude and plasticity of growth; B. alicastrum had the lowest relative growth rates (RGR) and low plasticity. Its final biomass varied only 10-fold across the light gradient. In contrast, the final biomass of D. panamensis and V. koschynii varied by 100- and 50-fold, respectively, and both had higher RGR than B. alicastrum. As light availability increased, all species decreased biomass allocation to leaf tissue (mass and area) and showed a trade-off between allocation to leaf area at a given plant mass (LAR) and net gain in mass per unit leaf area (net assimilation rate, NAR). This trade-off largely reflected declines in SLA with increasing light. Finally, A area was correlated with NAR and both were major determinants of intraspecific variation in RGR. These data indicate the importance of plasticity in photosynthetic physiology and allocation for variation in tree seedling growth among habitats that vary in light availability.     

Stand density and fertilization effects on aboveground allocation patterns and stem form of Pinus sylvestris in young stands

The increasing demand for forest biomass for energy generation could be partially met by growing denser stands and use of fertilizer. Before this is done at large scale, more knowledge of the effects of stand density and fertilization on aboveground allocation patterns and stem form is needed. Therefore, effects of pre-commercial thinning (PCT) to 3000 stems ha^?1, an unthinned dense control (C), and PCT combined with two levels of fertilization (100 kg ha^?1 of nitrogen applied either during the establishment of the field experiment (F1) or annually (F2)) were examined in 23- to 26-year-old Scots pine (Pinus sylvestris L.) stands six years after the establishment of the field experiment. In total, 114 sample trees were harvested using destructive biomass sampling. The growth allocation and stem form of trees with diameter at breast height (DBH; 1.3 m height) >5.0 cm were not affected by either the PCT or fertilization. Small trees (DBH < 5 cm) in denser, unthinned control plots had more slender stems (lower DBH/height ratios) and allocated less growth to branches and foliage than trees in PCT plots. Fertilization had little effect on the stem form and growth allocation of the smallest trees. Therefore, effects of stem density and fertilization on stem form and growth allocation to foliage were only found for small suppressed trees, and the treatments had very little influence on dominant and codominant trees.     

S and P intersterility groups in Heterobasidion annosum; Infection frequencies through bark of Picea abies and Pinus sylvestris seedlings and in vitro growth rates at different oxygen levels

Seedlings of Norway Spruce and Scots Pine were inoculated with S and P strains of the root rot fungus Heterobasidion annosum. Infection frequencies through the living bark layers were not related to subgroup affiliation in neither spruces nor pines. Growth rates in vitro were not related to growth rates in vivo. Oxygen concentration had a stronger effect on the growth rates of P than on S strains.     

Modelling above and below ground carbon dynamics in a mixed beech and spruce stand influenced by climate

Tree growth and carbon dynamics are important issues especially in the context of climate change. However, we essentially lack knowledge about the effects on carbon dynamics especially in mixed stands. Thus, the objective of this study was to test the effects of climatic changes on the above and below ground carbon dynamics of a mixed stand of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) by means of scenario simulations. To account for the typical tree interactions in a mixed-species stand a spatial explicit tree growth model based on eco-physiological processes was applied. Three different climate scenarios considering altered precipitation, temperature, and radiation were calculated for an unthinned and a thinned stand. The results showed significant changes of above and belowground biomass over time, especially when temperature and radiation were increased additionally to decreased precipitation. The reduction in biomass increments of Norway spruce were more attenuated above than below ground. In contrast, the results for beech were the opposite: The belowground increments were reduced more. These results suggest a shift in the species contribution to above and belowground biomass under dryer and warmer conditions. Distinct effects were also found when thinned and unthinned stands were compared. A reduced stand density changed the proportions of above and below ground carbon allocation. As a main reason for the changed growth reactions the water balance of trees was identified which lead to changed biomass allocation pattern. This article belongs to the special issue “Growth and defence of Norway spruce and European beech in pure and mixed stands”.     

Genetic variation in nutrient utilization and growth traits in picea abies seedlings

Genetic variation in nitrogen (N) and phosphorus (P) utilization (amount of total biomass produced per unit nutrient in the needles) and growth traits in seedlings from 30 open‐pollinated families of Picea abies (L.) Karst. was estimated. Seedlings were grown under two nutrient regimens: free access to nutrients and restricted access. There was a strong treatment effect on most growth traits. With free access, families allocated relatively more biomass to the stem and less to the roots than they did with restricted access. Heritabilities for growth traits were higher with free access treatment (0.33–0.81) than with restricted access treatment (0.20–0.45). Family variance components for N and P utilization were significant (p < 0.05) with restricted access but not with free access. Genetic correlation between nutrient utilization and height traits with restricted access ranged from none to moderate ( — 0.31 to 0.56). Genetic correlations between the same trait assessed in the two treatments were strong for height and moderate for biomass.     

Plasticity of reproductive allocation of a woody species (Ulex europaeus) in response to variation in resource availability

Context

While many woody perennials grow and reproduce in varying environments, their ability to modify their reproductive allocation under varying resource availability is unclear.

Aims

This study aimed to demonstrate the occurrence of plasticity of reproductive allocation in a pioneer woody species (Ulex europaeus).

Methods

We studied seed production in 144 plants under different irradiance and population densities. We measured their basal area, their whole shoot biomass and photosynthetic biomass, and their reproductive output (number of fruits per individual and number of seeds per fruit).

Results

We found that newly produced photosynthetic biomass was influenced by environmental variation, which in turn determined its reproductive output. In addition, in low light conditions investment in reproduction was more reduced than investment in growth indicating plasticity of reproductive allocation.

Conclusion

These results provide the first evidence for plasticity of reproductive allocation of a woody plant. It may lead to the ability of this pioneer species to survive and to continue to reproduce even at low rates in non-optimal shady habitats and to maintain a non-empty seed bank in forest systems with long unfavourable periods between two disturbances.     

Influence of the fertilisation method in controlled ectomycorrhizal inoculation of two Mediterranean pines

The influence of the fertilisation method: soluble (SF) vs. slow-release fertiliser (SRF) and of inoculation with Laccaria laccata (Scop.) Fr., Pisolithus tinctorius (Pers.) Coker & Couch and Melanogaster ambiguus (Vittad.) Tul & C. Tul. on ectomycorrhizal colonization and growth of Pinus pinea L. and Pinus pinaster Ait. was evaluated. For both pines, mycorrhization with L. laccata was not affected by the fertilisation method. Percentages of ectomycorrhizas (ECM) formed by P. tinctorius were dependent on the fertilisation method, the inoculum type (vegetative or spores) and the pine species involved. ECM formed by M. ambiguus were increased with fertilisation in both pines. Inoculation significantly improved P. pinea biomass when seedlings were fertilised with SRF whereas no effect was found in non-fertilised ones. For non-fertilised P. pinaster, inoculation with L. laccata and both inocula of P. tinctorius increased seedling biomass whereas fertilisation neutralised the fungal effect. Fertilisation increased P. pinea and P. pinaster biomass, independently of the inoculation treatment.     

Functional relationships between crown morphology and within-crown characteristics of understory saplings of three codominant conifers in a subalpine forest in central Japan

Light-related plasticity of crown morphology and within-crown characteristics were investigated in understory sun and shade saplings of three codominant subalpine conifers, Abies mariesii M.T. Mast., Abies veitchii Lindl. and Picea jezoensis var. hondoensis (Mayr) Rehd. Compared with those of sun saplings, current-year shoots of shade saplings allocated less biomass to needles, resulting in less dense needle packing and hence less mutual needle shading. The proportion of lateral branch biomass in foliage was either similar in sun and shade saplings or greater in shade saplings, depending on the species, suggesting that, over the lifetime of a branch, greater needle longevity in shade compensates for reduced biomass investment in needles of current-year shoots of shade saplings. Saplings with slower-growing branches tended to have greater needle life spans, suggesting that plasticity of branch growth rate and plasticity of needle life span are interdependent. Both Abies species showed greater light-related plasticity of needle life span and branch growth than P. jezoensis. The greater shade tolerance of the Abies species derives from their broad flattened crowns with slow-growing branches. This type of crown development incurs substantial support costs, but the long needle life span of shade saplings of the Abies species compensates, at least in part, for their low annual investment in foliage, especially in the case of A. mariesii, which has a longer needle life span and slower-growing and stouter branches than A. veitchii. Compared with the Abies species, P. jezoensis had a less plastic crown morphology, and less variability of needle life span and branch growth in response to light, resulting in lower shade tolerance. However, compared with the flattened crown of Abies shade saplings, the conical crown of P. jezoensis saplings imposes a smaller support cost, making this species better adapted to rapid height growth than to survival in shade.     

Seedling biomass allocation and vital rates of cloud forest tree species: Responses to light in shade house conditions

Patterns of above- and below-ground biomass allocation in seedlings of nine common cloud forest (CF) tree species of western Mexico were examined under varying controlled light conditions using artificial shade houses. We analysed the relationships between vital rates (growth and survival) and four morphological traits (SLA, biomass allocation to stems, leaves and roots). We hypothesised that these traits represent differentiation axes in the way seedlings face the heterogeneous light regime typical of the CF understorey. For all species, traits between the different light levels, i.e. allocation to leaves, roots and stems differed among light levels. Five species had the largest SLA in the lowest light levels at the end of the experiment (Citharexylum, Dendropanax, Fraxinus, Quercus and Magnolia). Juglans was the only species with a large SLA at the highest light level (377.47 cm² g⁻¹). In contrast, light levels did not cause any significant variation in SLA of Persea and Simplococarpon at the end of the experiment. The relative height growth rates (RHGR) of the seedlings of five species were significantly different between light levels (P < 0.05). Overall, all species grew better in the highest light levels. The RHGR of three species were correlated positively with SLA. In turn, allocation to stem, leaves and root biomass were strongly correlated with the RHGR of five species (e.g. Citharexylum, Dendropanax and Fraxinus). Survival did not vary significantly between treatments in any species, only in the case of Simplococarpon (P < 0.05) and was correlated with all morphological variables. For this species, Peto and Peto's test showed a significantly larger survival of seedlings in the highest light level. The mean responses of these species based on all traits to the controlled light variation did not differed significantly. Our results show that these species display a wide range of resource allocation patterns when exposed to the varying light conditions that may be found in the forest understorey and highlight the role of morphological traits in this variation.     

Biomass allocation and nitrogen limitation in a Cryptomeria japonica plantation chronosequence

We investigated soil net nitrogen mineralization rate, above- and belowground biomass allocation, and nitrogen use in a Cryptomeria japonica plantation chronosequence. Total biomass accumulation showed an asymptotic accretion pattern, and the peak total biomass accumulation rate occurred approximately 30 years after afforestation. Soil net nitrogen mineralization rate was lowest 30 years after afforestation. Between years 30 and 88, net nitrogen mineralization increased again. These results indicate that an imbalance in soil nitrogen supply and plant nitrogen demand occurred approximately 30 years after afforestation. Furthermore, leaf nitrogen concentration, which was used as an index of plant nitrogen status, was lower in mature forest than in young forest, suggesting that mature stands did not take up nitrogen as successfully. If soil resources such as nitrogen limit plant growth, plants may increase biomass allocation to fine root structure; however, fine root biomass was not higher in 30- and 88-year-old stands than in younger stands, suggesting that changes in biomass allocation may not be effective against nitrogen deficiency in a C. japonica plantation chronosequence.