Trees最新文献

Key Message

Atlantic Forest tree seedlings with contrasting ecological characteristics present specific growth and physiological responses to nitrogen and phosphorus addition in the soil.

Abstract

Nitrogen (N) and phosphorus (P) are commonly the most limiting nutrients for plant growth in tropical forests. Many of these ecosystems are exposed to increasing rates of anthropogenic nutrient deposition. This study aims to assess how five Atlantic Forest tree species respond to N and P addition to the soil. Five species with different levels of shade tolerance were subjected to nine weekly soil applications of (NH₄)₂SO₄ (84 kg N ha⁻¹ treatment N), NaH₂PO₄ (45 kg P ha⁻¹ treatment P), both nutrients (treatment N + P), or water. Soil, foliar nutrient concentrations, and biometric and gas exchange analyses were performed. No changes in the soil pH or total N and P availability were observed in the soil after N addition, whereas P accumulated in the soil and leaves of three species after P addition. The pioneer species H. popayanensis presented increased total biomass with P and N+P treatments, while C. floribundus increased with P treatment and C. pachystachya increased with N + P treatment. N and P treatments reduced the photosynthesis of C. pachystachya and the stomatal conductance of C. pachystachya and C. floribundus. The growth rate and total biomass of C. estrellensis reduced with N and P treatments and increased with N+P treatment. Aspidosperma polyneuron presented reduced photosynthesis with N treatment, but increased total biomass with all treatments, especially N + P. The diversity of growth and physiological responses to N and P addition suggests that each species has specific nutrient requirements and uses strategies related to the niche occupied by each one.

Key message

The response of herbivore abundance to birch genotypic diversity varies depending on the host specificity of the herbivores. Specialist, but not generalist, herbivores were affected by birch genotypic diversity.

Abstract

Biological control is an important ecosystem service mediated through plant diversity. Responses of herbivore abundance to plant genotypic diversity may depend on host specificity, especially the host-feeding type. We conducted a common-garden experiment by manipulating plot-level genotypic diversity (number of source populations per plot) of Erman’s birch (Betula ermanii) to understand how birch genotypic diversity affected the abundance of three herbivore feeding types (chewers, galls, and suckers). Specifically, we investigated whether the effects of plant genotypic diversity on herbivore abundance were additive or non-additive. Furthermore, we examined this mechanism as a possible change in plant phenotype (plant productivity and/or leaf traits) and/or herbivore foraging behavior (associational resistance with neighboring plant individuals). We found that genotypic diversity had a significant positive effect on condensed tannin concentration; however, it did not affect plant growth. There was no effect of increasing birch genotypic diversity on the density of chewers (generalists) and chewing herbivory, whereas the density of galls and suckers (specialists) decreased significantly. A negative non-additive effect was observed with regard to gall density and a negative additive effect on sucker density was observed. Gall density was not related to the increase in condensed tannins affected by birch genotypic diversity. This implies that associational resistance is more likely to explain the negative non-additive effects on gall density. Our study shows that the loss of birch genotypic diversity due to shrinking population sizes will strongly affect specialist herbivores in the boreal forests of Hokkaido.

Key message

Dendroclimatic sensitivity varies by axial position for Sequoiadendron giganteum: negative correlations with June temperature strengthen with height, while positive correlations with snow water are strongest in the lower trunk.

Increment cores collected along trunks of mature Sequoiadendron giganteum provide new and updated ring-width chronologies ideal for assessing how height above ground affects sensitivity of radial growth to climatic variation. Chronologies from 61 living trees at nine locations across the geographic distribution span 1973 yr. Analyses of subsets of 18–44 trees reveal that correlations between radial increments and climate (temperature, water availability) vary with axial position. Negative correlations with maximum and minimum June temperature intensify with height and are strongest at the highest position analyzed (60 m above ground). Sensitivity to the hydroclimate variable of April-1 snow water equivalent is stronger at lower trunk positions (10 m) compared to breast height or the upper trunk, and a similar relationship is identified for the standardized precipitation evapotranspiration index using a 12-month window ending in September. Drought-induced low-growth years computed as radial increment relative to the mean of 10 yr before and after are more weakly expressed at breast height compared to higher on the trunk (10–60 m). Analysis of regional upper (maximum core height = 87 m) versus lower trunk (above buttress) chronologies corroborate differing inter-annual correlations with climate depending on height above ground. Accounting for axial variation in dendroclimatic sensitivity can maximize the quality of environmental reconstructions using tree rings and improve biophysical understanding of Sequoiadendron, especially in the context of an increasingly arid climate.

Key message

This work belongs to the Tunisian conservation strategies of local fruit tree resources. Results highlighted the important genetic richness of Tunisian peach as an unexplored source for peach future breeding.

Abstract

Tunisia is characterized by a rich genetic heritage of fruit trees. Nevertheless, local Tunisian accessions of different fruit crops face several threats that are causing a dramatic loss of some of these valuable landraces. This study was conducted to evaluate the genetic diversity and population structure of 23 Tunisian peach accessions using 27 microsatellite (SSR) loci. These Tunisian accessions were compared with accessions from America, mainland Spain and the island of La Palma (Canary Islands, Spain). A considerable genetic diversity was observed in Tunisian genotypes with allelic richness value of 0.47. The genetic richness was 0.37 in La Palma genotypes, 0.3 in mainland Spain and 0.38 in the American genotypes. Eight private alleles were obtained in the Tunisian genotypes, while six were observed in the mainland Spanish pool, five in the American pool and six in the La Palma pool. Structure analyses and similarity dendrogram based on SSRs were clearly consistent with a geographic structuring and highlighted the different introduction pathways of Prunus persica into Tunisia.

Key message

Variation in lateral organ morphology identifies the timing of annual transitions between bud scale and needle identity in conifer buds.

Abstract

Vegetative tissue is generated from the shoot apical meristem (SAM) at branch tips. Temperate and boreal conifers have determinate growth, in which a year’s complement of needles all begin to form in the summer of Year 1 (Y1), overwinter in a protective bud, then emerge and mature in spring and summer of Year 2 (Y2). Buds are protected by bud scales (bss), which are initiated in spring Y1 prior to needle initiation. Through the annual cycle of needle and bud formation, the SAM alternately produces needle or bs lateral organs. Detailed classification of vegetative lateral organ morphologies in Picea abies (Norway spruce) showed that while the majority of lateral organs are clearly either of needle or bs type, a number of organs in any given bud are intermediate, having both needle and bs characteristics. These transitional organs form the basal outer protective layers of the bud. This work documents the variety of bs morphologies involved in forming the overall bud. Needle and bs counts show a clear distinction in initiation times for each type. bs initiation coincides with spring bud elongation, while needle initiation lags this by 2–3 months. This suggests distinct, temporally separated signals for bs and needle tissue differentiation. The transitional forms suggest some primordia form at times when they are susceptible to both needle and bs differentiation signals. Measurements of shoot apex dimensions show that, in addition to an increasing number of needle primordia on the shoot apex over the summer, the needle primordia themselves undergo an expansion in the fall prior to dormancy.

Ubiquitin-specific proteases (UBPs), the largest group of deubiquitinating enzymes (DUBs), play pivotal roles in various aspects of plant physiology including growth, development, and stress response by maintaining the ubiquitin molecule pool or removing ubiquitin from targeted proteins. While numerous studies exist on UBPs across various plant species, studies focusing on the Fagaceae family remain scarce. In this study, 20 UBP genes were identified in Quercus robur and phylogenetically classified into 12 groups, supported by domain organization and conserved motif composition. The gene structures and chromosomal localizations of these genes were elucidated. To understand the evolution of the QrUBP gene family, synteny analysis was conducted among Q. robur and five other plant species. Notably, four QrUBP genes (QrUBP3, QrUBP12A, QrUBP16, and QrUBP23) were found to have at least four isogenous gene pairs, implying important roles in the phylogenetic process of the UBP gene family. Moreover, cis-acting elements analysis reveals that the QrUBP promoters contain a large number of hormone-response elements and stress-response elements. The RT-qPCR analysis of roots, stems, and leaves indicates that some of the QrUBP genes were expressed ubiquitously, while others were organ-specific. For example, QrUBP15* was primarily expressed in roots, while QrUBP8 showed tissue-specific expression in stems. Additionally, comprehensive physicochemical and subcellular localization analyses were conducted. Collectively, this comprehensive study provides insights into the UBP gene family in Q. robur, laying a solid foundation for future investigations elucidating the functional roles of QrUBP genes in plant growth and stress responses.

Micropropagated clones from thirteen hybrid aspen (Populus tremula L. x P. tremuloides Michx.), two P. tremula clones, and seedlings of three open pollinated P. tremula families were field-tested up to the age of 17 years on three sites in northwestern Germany. Twelve of these clones have earlier been approved under the category “Tested Material” in the multiclonal variety ‘Grosshansdorf’. Growth and development of the tissue culture derived clones and the seedlings were monitored in a long-term field trial. Survival, growth potential, and trunk as well branching habit were studied. The field evaluations have shown no negative effects of micropropagation on the growth potential, or tree morphology of hybrid aspen clones. On more favorable sites the hybrid aspen clones demonstrated their distinct superiority as compared to P. tremula trees. Our data indicates that miropropagated hybrid aspen clones offer new opportunities as a choice material for their better performance, especially on more favorable sites.

The increasing number of climate-associated disasters in the Himalayan region causing a huge impact on human life and the ecosystem are the bellwethers of climate change. Weather records from the high Himalayas, though sparse and limited to the past few decades, show its sensitivity to global climate change. However, short observational records preclude our understanding of long-term climate variation over the topographically controlled Himalaya. In view of this, tree-ring data of Himalayan birch trees from the cold-arid Lahaul-Spiti, Himachal Pradesh, western Himalaya is analyzed in the present study. The response function analysis of Himalayan birch chronologies with climate variables revealed a significant impact of February–March minimum temperature in radial growth of Himalayan birch. Taking this relationship as a guide, we developed the first record of winter/spring (February–March) minimum temperature for this region. The reconstructed minimum temperature record reveals annual to decadal scale variability associated with several prolonged cold and warm periods. A strong association of warm/cold phases of February–March temperature with low/high snow water equivalent of western Himalaya, as well as seasonal snow and glacial derived streamflow of the upper Indus River basin was identified. The observed hydrological linkages were further tested using river flow records of the Satluj and Indus Rivers of the western Himalaya. The observed opposite relationship between winter–spring minimum temperature and the summer hydro-climatic records can be of immense use to policymakers, agriculture stockholders, and hydropower project officials to take precautionary measures in advance.

Key message

The yield of epicuticular waxes of Bulnesia retama was increased mainly by water stress, and marginally by UV-B. Natural populations from the most stressful ecoregions showed higher productivity and plasticity.

Abstract

Bulnesia retama is a tree/shrub endemic to the arid and semi-arid zones of South America. This species produces outer stem waxes that can be used in industry, and has been exploited in the past degrading natural populations. Considering the need to diversify marginal dryland economies by making sustainable use of local resources, we aimed to study the productivity of outer stem waxes of natural populations of B. retama from three eco-regions with different environmental stress (rainfall and altitude). We studied the wax productivity of the three populations in response to water stress and UV-B. We conducted two pot experiments with seedlings propagated from seeds of the different environmental backgrounds. We regulated water availability by differential irrigation and manipulated UV-B using selective absorbance filters. We collected stem waxes by the traditional method of brushing dry stems. We found that water stress was the main promoter of stem wax production in this species, while the effect of UV-B was marginal, and was only detected in combination with water stress. Seedlings from the most stressful eco-regions showed the highest stem wax productivity and were the most plastic to variations in environmental conditions. Environmental stress, particularly water stress, was the determining factor in the outer stem wax yield of this species, and in the productive potential of different natural populations, which could be related to ecotypes with different wax yield potential. This knowledge can be used for exploiting this resource sustainably, to select ecotypes for cultivation, and to develop productive varieties through classical breeding.

Key message

There were significant differences in the anatomical characteristics of Nothofagus alpina between the site with silvicultural condition similar to a regrowth forest, and with the sites with plantation regime.

Abstract

Nothofagus alpina has been a species of interest due to the high quality of its wood. To evaluate the early use of this wood in plantation regimes, wood from intermediate cuts has to be studied. Therefore, the variations in some anatomical characteristics of juvenile wood obtained from thinning of N. alpina trees growing under three different silvicultural conditions were evaluated. Using the decreasing granulometry sanding technique, wood samples were prepared to capture images from the transverse plane using reflectance microscopy. The anatomical characteristics considered in this work vary, from pith to bark, with statistically significant differences being found in the position closest to the bark. On the other hand, there were some similarities between the specimens that came from sites with a plantation regime and differences with the sites similar to a regrowth forest. Therefore, the possible impact of silvicultural conditions on the anatomical characteristics of N. alpina wood was pointed out, mainly the diameter of the vessels and wall thickness.