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1.
? 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. 相似文献
2.
? Among the traits of breeding interest for the common walnut tree Juglans regia L., characteristics such as timing of budbreak and leaf fall, water-use efficiency and growth performance are regarded as being of utmost relevance in Mediterranean conditions. ? The authors evaluated intraspecific variation in δ13C (carbon isotope composition, surrogate of intrinsic water-use efficiency, WUEi) for 22 J. regia families grown in a progeny test under supplementary irrigation, and investigated whether such variation correlated with climatic indicators of native habitats. The genetic relationships between δ13C, growth and phenology were also assessed during two consecutive years. ? Overall, the most water-use-efficient families (i.e. with higher δ13C), which originated mainly from drought-prone provenance regions which have a high vapour pressure deficit and low rainfall, exhibited less height growth and smaller DBH. Using a stepwise regression procedure, δ13C was included as the main explanatory variable of genotypic variation in growth traits, together with growing season duration (for DBH in both years) and flushing (for height in 2007). ? It was concluded that WUEi is largely unconnected to phenology effects in the explanation of growth performance for J. regia, therefore suggesting the opportunity of simultaneously selecting for low WUEi and extended growing period to maximise productivity in non-water-limited environments. 相似文献
3.
? Mycorrhizal fungi and hydrogels (water-absorbing polymers) can improve water availability for trees. The combination of both factors for plant performance under water limitation has not yet been studied. ? To investigate the influence of the ectomycorrhizal fungus Paxillus involutus, hydrogel and the combination of both factors, a drought-sensitive poplar, Populus euphratica, was examined in this study. ? After 16 weeks of inoculation, no ectomycorrhizas were found. Nevertheless, P. involutus-inoculated poplars displayed increased concentrations of soluble sugars and osmolality, leading to an improved water status. Growth was diminished compared with non-inoculated P. euphratica. The presence of hydrogels in the rooting medium resulted in increased biomass and higher plant water content and decreased the osmolality of plant tissues. Drought markedly decreased water contents in rooting medium and plants, and leaf chlorophyll fluorescence, and stimulated the root growth, concentrations of soluble sugars and osmolality in plants. Under drought conditions, P. euphratica exhibited osmoregulation by accumulation of low-molecular-weight carbohydrates. ? These data indicate that adding hydrogels to soils may improve the plant performance. The reasons for improved osmoregulation by fungi and hydrogels were probably related to their stimulating influence on the formation of soluble carbohydrates under drought conditions. 相似文献
4.
? Variation in the ability of western redcedar (Thuja plicata Donn ex D. Don) populations to withstand water stress may exist because this species is found in coastal and interior biogeoclimatic subzones representing the full range of precipitation regimes in British Columbia, Canada. ? Seven western redcedar populations from locations in British Columbia, representing a wide range of habitat types, were assessed for their gas exchange and water relations response to controlled drought. ? Before drought, population variation occurred in stomatal conductance, net CO2 assimilation rate and intrinsic water use efficiency and the relative water content at turgor loss point. During drought, populations had different responses of net CO2 assimilation to decreasing predawn shoot water potential. After drought, populations differed in stomatal conductance and intrinsic water use efficiency, plus osmotic potential at turgor loss point, osmotic potential at saturation and apparent cuticular transpiration. Western redcedar populations from drier-inland habitats had a lower osmotic potential at turgor loss point, lower relative water content at turgor loss point and lower apparent cuticular transpiration in response to drought than populations from coastal origin with temperate maritime habitat. ? Reduction of cuticular water loss and adjustments of cellular water relations in response to drought was found to occur among seven western redcedar populations originating along a precipitation gradient while; there were minimal population differences in the gas exchange response to drought. 相似文献
5.
? The effect of two weeds (grasses and broom, Cytisus scoparius) competition on the growth and functional traits of European beech saplings (Fagus sylvatica) was investigated in an experimental plantation in the French Massif central. ? We hypothesized that grasses would have a much more harmful effect than broom on beech growth through strong competition for soil water and nitrogen. ? A randomized block design was used with three separate blocks, each possessing three types of vegetation; grasses (mainly Agrostis capillaris, Holcus mollis and H. lanatus), broom, and bare soil as a control. ? Two years after plantation beech sapling growth was significantly greater in bare soil than with competition from grasses, and was intermediate on broom. Growth was positively correlated with beech leaf nitrogen content (Nm) and xylem water potential (Ψx). N and Ψx were dependent, with nitrogen uptake probably decreasing with increasing drought. There was no clear correlation between growth and light transmitted 10 cm below the apex of the saplings. ? Beech leaf mass on an area basis (LMA) was correlated with the three resource variables (water, nitrogen and light) and with growth, confirming that LMA is a sensitive functional trait integrating the degree of stress experienced by the saplings. ? The results suggest that broom is less competitive than grasses and, if properly managed on a sufficiently well-watered site, can generate satisfactory conditions for beech establishment and growth. 相似文献
6.
? The aim of this study is to assess the impact of drought on insect-tree relationships. Survival and feeding performances of leaf-beetles, Chrysomela populi put in cages with leaves of host-plants submitted to different levels of water stress were compared. ? Ninety 1-year-old poplar (Populus × euramericana) cuttings were grown in a greenhouse, and distributed into 3 groups submitted to different water treatments during six weeks. Adult C. populi were then encaged for four days with these cuttings, together with the five terminal leaves of a twig. Beetle survival and consumed leaf areas were then determined. ? Predawn leaf water potential values indicated that the drought treatments induced different levels of plant water stress. Plant height growth and total leaf numbers were reduced by plant stress. Beetle survival and leaf areas eaten were also reduced proportionally to plant water deficit. ? In conclusion, this experiment suggests that drought has a negative impact on C. populi survival and feeding. 相似文献
7.
? The short-term effect of organic residue management on the growth and nutrition of Pinus pinaster Ait. seedlings, and on nutrient leaching and chemical properties of an acid soil was assessed through a lysimeter experiment. Treatments included absence, placement on the soil surface, and incorporation into the soil (with and without legume cover cropping) of organic residues (forest floor litter or forest floor litter plus harvest residues). ? Residues placed on the soil surface enhanced seedling growth. Organic residues reduced nutrient losses (NO 3 ? , Ca and Mg) and resulted in nutrient accumulation in the soil. Harvest residues positively affected K seedling nutrition status and enhanced K soil accumulation. ? Legume cover cropping reduced soil nutrient losses (N, Ca, Mg and K) during the early stage of seedling growth; it also improved seedling nutrition status (N and P), but without any effect on growth. ? Harvest residues plus forest floor litter placed on the soil surface was the most appropriate management to both reduce nutrient losses through leaching and increase height of seedlings at the end of the experimental period (two years). 相似文献
8.
? Quercus ilex L., the dominant species in Mediterranean forests and one with a great capacity for resprouting after disturbances, is threatened by the expected increase in fire frequency and drought associated with climate change. ? The aim of this study was to determine the contribution of photosynthesis limitants, especially mesophyll conductance (g mes) during this species’ resprouting and under summer drought. ? Resprouts showed 5.3-fold increased g mes and 3.8-fold increased stomatal conductance (g s) at mid-day with respect to leaves of undisturbed individuals. With increased drought, structural changes (decreased density and increased thickness) in resprouts contributed to the observed higher photosynthesis and increased g mes. However, g mes only partially depended on leaf structure, and was also under physiological control. Resprouts also showed lower non-stomatal limitations (around 50% higher carboxylation velocity (V c,max) and capacity for ribulose-1,5-bisphosphate regeneration (J max)). A significant contribution of g mes to leaf carbon isotope discrimination values was observed. ? g mes exhibits a dominant role in photosynthesis limitation in Q. ilex and is regulated by factors other than morphology. During resprouting after disturbances, greater capacity to withstand drought, as evidenced by higher g mes, g s and lower non-stomatal limitants, enables increased photosynthesis and rapid growth. 相似文献
9.
? Cork oak mortality is a recurrent problem in southwestern Portugal. Despite the perception of increasingly visible damage in oak woodlands on drought-prone sites, the role of the various environmental factors in their decline is not clear. ? To describe the spatial patterns of cork oak (Quercus suber L.) mortality, a cork oak mortality index (MI) was determined for each landscape feature (agroforestry system, soil type, slope and aspect) using a GIS approach. To achieve this goal, a logistic regression model was formulated analyzing interactions between landscape attributes and allowing a prediction of cork oak mortality. ? Maximum values of MI were found in (i) shrublands and open woodlands with shrub encroachment (MI 6 and 3, respectively), where competition for soil water between tree and understory increases; and (ii) on lower slopes in the rounded hilltops and smooth hillsides or shallow soils where access to groundwater resources during summer drought is difficult. ? The model highlighted the importance of the agroforestry systems on cork oak mortality and may be used to identify sensitive areas where mitigation actions should be employed in a scenario of increasing drought severity in these Mediterranean ecosystems. 相似文献
10.
? 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. 相似文献
11.
? Studies dealing with the estimation of biomass, site productivity and the contribution of forests to the global carbon balance require the use of allometric equations. There have been a great number of equations developed to estimate biomass components of trees and shrubs in various ecosystems. However, there are less literature compilations that address the calculations of biomass components. ? I report a total of 229 sets of allometric equations to estimate biomass components for 102 species in 72 different forest communities of arid, semi-arid, subtropical, tropical and temperate Latin-American ecosystems. ? The selection of the appropriate allometric model is a key element in the accurate estimation of biomass, stand productivity, carbon stocks and fluxes, and as a consequence, it is important to apply special effort to the selection and estimation of biomass equations. ? I also discuss statistical methods of parameter estimation and recommend the dissection of two conventional allometric equations when biomass studies are conducted on a wide range of diameters. In order to use nondestructive procedures of biomass estimation such as the fractal theory, the null hypothesis that the mean slope b value is equal to 2.67 was rejected for Latin American biomass species. ? This information is critical for the establishment of environmental projects that aim to estimate conventional parameters (i.e., productivity, habitat quality and fuel wood) as well as environmental features (i.e., stocks and fluxes of carbon and nitrogen). 相似文献
12.
? Transplant shock, implicated by depressed seedling physiological status associated with moisture stress immediately following planting, limits early plantation establishment. Large root volume (Rv) has potential to alleviate transplant shock because of higher root growth potential and greater access to soil water. ? We investigated impacts of drought and transplant Rv on photosynthetic assimilation (A), transpiration (E), stomatal conductance (g s ), predawn leaf xylem water potential (ΨL), and growth of northern red oak (Quercus rubra L.) seedlings to explain mechanisms associated with susceptibility to transplant shock. One year-old barerooot seedlings were graded into four Rv categories and either well watered or subjected to drought consisting of low, medium, or high moisture stress by discontinuing irrigation at 22-day intervals for 3 months. Thereafter, all treatments were re-watered to examine recovery. ? Transplant shock was signified by reduced A, E, g s, and ΨL, which generally increased with increasing moisture stress and Rv. Physiological status improved during recovery, though stress was still evident in seedlings exposed to medium or high moisture stress and in larger Rv seedlings. Growth declined with increasing moisture stress but was generally similar among Rv treatments, likely reflecting greater A at the whole plant level and/or reliance upon stored reserves in large Rv seedlings. ? The most effective drought avoidance mechanisms were root growth, stomatal regulation, reduced leaf area, and higher growth allocation to roots relative to shoots. Our results suggest that large initial Rv does not enhance drought avoidance during the first season after transplant in northern red oak seedlings. 相似文献
13.
? We investigated the effects of flooding for three weeks on physiological responses and uptake of NH 4 + and NO 3 ? by black spruce (Picea mariana (Mill.) BSP.) and tamarack (Larix laricina (Du Roi) K. Koch) seedlings fertilized with labeled (15NH4)2SO4 or K15NO3 in a growth chamber experiment. ? Flooding reduced photosynthesis (A), transpiration (E), water use efficiency (WUE), and current uptake of NH 4 + and NO 3 ? in both species. ? Under flooding, there were no significant differences between the two species in uptake of either NH 4 + or NO 3 ? at the whole-plant level but black spruce had higher translocation of NH 4 + to the shoots than did tamarack. ? Under non-flooded conditions, black spruce seedlings exhibited higher uptake of both NH 4 + and NO 3 ? than did tamarack and demonstrated preferential uptake of NH 4 + (19. 7 mg g?1dw) over NO 3 ? (12.3 mg g?1dw after three weeks). In contrast, non-flooded tamarack seedlings had equal uptake of NH 4 + (4.96 mg g?1dw) and NO 3 ? (4.97 mg g?1dw). ? We hypothesize that the ability of tamarack to equally exploit both 15NH 4 + and 15NO 3 ? would confer an advantage over black spruce, when faced with limitations in the availability of different forms of soil nitrogen. 相似文献
14.
? Managed laurel forests in the Canary Islands have undergone clear-cutting with rotation periods of less than 30 y. Forest owners have recently requested a drastic reduction in the cutting interval. The effects of this new harvesting cycle on organisms like epiphytic bryophytes are not well known. ? This study investigates how time since last clear-cut, host species and characteristics of tree zones influence the biomass, cover and richness of epiphyte bryophytes in managed laurel forests in La Palma, Canary Islands. Four forest ages (8, 15, 25 and 60 y) and three host tree species (Erica arborea, Laurus novocanariensis and Myricafaya) were studied. ? Biomass, cover and richness of bryophytes increased through the chronosequence, both at the level of each plot and overall for L. novocanariensis. Most of the biomass (53%) and richness (81%) was concentrated in one of the tree species (L. novocanariensis), in plots for which 60 y had elapsed since the last clear-cutting. Trunks supported greater bryophyte biomass and richness than canopies, even in the oldest plots. ? Our results suggest that the current rotation periods used to manage laurel forests are insufficiently long to allow for complete reestablishment of epiphytic bryophyte assemblages. 相似文献
15.
? Several techniques were used to investigate the threshold minimum temperature inducing severe frost damage during winter in Scots pine (Pinus sylvestris L.) needles and stems from southern provenances in the Iberian Peninsula. ? Chlorophyll (Chl) fluorescence, electrolyte leakage (EL), visual scoring (VS), and the normalized difference vegetation index (NDVI) were compared. ? Chl fluorescence, and in particular the maximum potential photosystem II (PSII) efficiency — estimated through the dark-acclimated FV/FM ratio-, was found to be a simple, non-destructive indicator of freezing tolerance in needles, as expected. ? Moreover, the existence of a Chl-containing tissue, the cortical bark chlorenchyma, allowed us the use of Chl fluorescence as a new non-destructive indicator of frost damage in live tissues of Pinus sylvestris L. stems. ? Freezing tolerance values of southern provenances are compared with those found by other authors in the northern distribution limit of the species. 相似文献
16.
? Seven RAPD markers were used to assess the genetic diversity and structure of ten Tunisian natural Ceratonia siliqua L. populations from different geographic and bioclimatic zones. ? The species maintain a high diversity within population as estimated by the percentage of polymorphic loci and Shannon’s index (P% = 76.31, $\bar H'_{pop} = 0.569$ ). The range of variation between populations was large. Populations from the upper semi-arid bioclimates, with more continuous distribution area showed the highest level of variation. ? A high genetic differentiation among populations (ΦST = 0.250 and $\bar G_{ST} = 0.347$ ), as a result of population isolation was revealed. Nevertheless, the genetic structure is in accordance with bioclimate indicating that ecological factors also should influence differentiation. Populations from the sub-humid, upper semi-arid and mean semi-arid zones clustered together and were distinct from those of the lower semi-arid ones. ? Conservation strategy should be made according to the level of polymorphism within population and bioclimate. 相似文献
17.
? Five temperate broad-leaved tree species were compared with respect to their water consumption strategies under ample and restricted water supply. We measured synchronously leaf conductance (g L) in the sun canopy, xylem sap flux (J s) and leaf water potential (predawn, ψpd and noon, ψnoon) in adult trees in a mixed stand and related them to the fluctuations in vapor pressure deficit (D) and soil moisture. ? Maximum g L was particularly high in F. excelsior, C. betulus and T. cordata and revealed a higher D sensitivity. ψpd remained constantly high in A. pseudoplatanus, C. betulus and F. excelsior, but decreased in T. cordata and F. sylvatica with decreasing soil moisture. ? J sddecreased linearly with decreasing soil matrix potential in all species except for F. excelsior. Apparent hydraulic conductance in the soil-to-leaf flow path (L c) was higher in A. pseudoplatanus than in the other species. ? F. sylvatica maintained a low maximum g L and reduced J sd markedly upon drought, but faced severe decreases in ψpd and ψnoon. F. excelsior represents an opposite strategy with high maximum g L and stable ψpd. ? The species drought sensitivity increases in the sequence F. excelsior < C. betulus < T. cordata < A. pseudoplatanus < F. sylvatica. 相似文献
18.
? Artificial defoliation is often used to simulate defoliation by herbivory and is usually considered a good indication of a plant’s response to a given type of damage. However, the findings of studies directly comparing the two defoliation types are inconsistent. ? Here, the short term effects of artificial and insect defoliation by larvae of Paropsisterna agricola on growth, biomass allocation and photosynthetic capacity of Eucalyptus globulus seedlings were compared in a glasshouse experiment. The artificial defoliation was carried out to closely resemble the spatial patterns observed for insect defoliation. ? Height and diameter increments were reduced as a result of insect defoliation, whereas artificial defoliation had no significant effect on height. Increased photosynthetic capacity was observed in response to both treatments, but the magnitude of this increase was larger in insect-than in artificially-defoliated seedlings. Significant reductions in foliar carbohydrate content and total biomass were noticeable in artificially-defoliated seedlings. Although the foliar carbohydrate levels also decreased across the crown zones following insect defoliation treatment, seedlings allocated a large amount of their biomass in the branches of the damaged zone. ? Despite our best endeavours to simulate insect defoliation in the artificial treatment, the latter may not reflect accurately the full strength of the effects. However, artificial and insect defoliation were similar in their direction of the responses they caused in E. globulus seedlings. 相似文献
19.
? Water and carbon fluxes, as measured by eddy covariance, climate, soil water content, leaf area index, tree biomass, biomass increment (BI), litter fall and mortality were monitored for 10 successive years in a young beech stand in Hesse forest (north-eastern France) under contrasting climatic and management conditions. ? Large year-to-year variability of net carbon fluxes (NEE) and to a lesser extent, of tree growth was observed. The variability in NEE (coefficient of variation, CV = 44%) was related to both gross primary production (GPP) and to variations in total ecosystem respiration (TER), each term showing similar and lower interannual variability (CV = 14%) than NEE. Variation in the annual GPP was related to: (i) the water deficit duration and intensity cumulated over the growing season, and (ii) the growing season length, i.e. the period of carbon uptake by the stand. Two thinnings occurring during the observation period did not provoke a reduction in either GPP, water fluxes, or in tree growth. Interannual variation of TER could not be explained by any annual climatic variables, or LAI, and only water deficit duration showed a poor correlation. Annual biomass increment was well correlated to water shortage duration and was significantly influenced by drought in the previous year. ? The relationship between annual NEE and biomass increment (BI) was poor: in some years, the annual carbon uptake was much higher and in others much lower than tree growth. However this relationship was much stronger and linear (r 2 = 0.93) on a weekly to monthly time-scale from budburst to the date of radial growth cessation, indicating a strong link between net carbon uptake and tree growth, while carbon losses by respiration occurring after this date upset this relationship. ? Despite the lack of correlation between annual data, the NEE and BI cumulated over the 10 years of observations were very close. ? On the annual time-scale, net primary productivity calculated from eddy fluxes and from biological measurements showed a good correlation. 相似文献
20.
?The study aimed at clarifying basic life traits (fecundity, mortality and development) of Monochamus galloprovincialis, the vector of Bursaphelenchus xylophilus, the causative agent of the Pine Wilt Disease, in Portugal. ? Mating and oviposition experiments were conducted on P. sylvestris logs under laboratory conditions during two years. Larval development was followed outdoors. ? Fecundity was high, with 138.2 eggs per female. ? For the first time, the number of larval instars (4) in M. galloprovincialis was recognized and instars were described. ? Informations are provided on the shape and size of the larval galleries. Boring of galleries in sapwood and heartwood started at the third instar. All instars could overwinter but adults emerged simultaneously resulting in a univoltine life cycle for the majority of the individuals. ? An obligatory diapause in the forth instar was assumed. However, 8.1% of the insects had a two year development. ? Important differences in mortality were noted between the two experimental years, which could be explained by differences on the size of the breeding logs. ? There is a high biological proximity between M. galloprovincialis populations in France and those in Portugal and Northern Europe. However, a higher fecundity and longevity was observed in France, as well as a higher percentage of insects with a two year development, compared with portuguese populations. 相似文献
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