Effects of different planting configurations and clones on biomass and carbon storage of a 12-year-old poplar ecosystem in southern China

The main objective of this study was to compare the effects of two densities (278 stems·ha−1 with two spacings of 6 m × 6 m or 4.5 m × 8 m, 400 stems·ha−1 with two spacings of 5 m × 5 m or 3 m × 8 m) and three poplar clones (NL95, NL895, and NL797) on productivity and carbon (C) sequestration of poplar ecosystems. The results showed that planting density significantly affected the biomass of a single tree. The mean tree biomass of clone NL95 was higher in all spacings than that of the other clones, with a significant difference for the 6 m × 6 m spacing. The biomass of poplar trees ranged from 78.9 to 110.3 Mg·ha−1, with the highest tree biomass observed in the square configuration. Soil C concentration (0–100 cm) increased after 12 years of management. Soil C storage ranged from 138.1 to 164.3 Mg C·ha−1, and the highest soil C storage was in the NL797 poplar plantation with 6 m × 6 m spacing. Our results suggested that clones NL95 and NL797 should be chosen for planting, with a planting density of 278 stems·ha−1 and spacing of 6 m × 6 m.

Assessment of the condition of Balsam poplar trees (Populus balsamifera L.) in a residental area of Bratsk

In this study, we investigated the health status of balsam poplar (Populus balsamifera L.) trees in a residential area of the city of Bratsk (Irkutsk Oblast, Russia). Visual and instrumental assessment of the health status of pruned and unpruned trees was performed. The identified internal defects in the tree were analyzed with a Resistograph device, which enabled the extent of decayed wood to be determined. Visual analysis revealed various types of damage: dried branches, brittle crowns, frost cracks, mechanical damage, curvature of trunks, decay and inclusions of foreign bodies. We compared trees with and without canopy pruning. We found that pruned trees were significantly more damaged than non-pruned trees. Decomposing wood at different stages of development was found in all the trees studied. A tree passport combining the visual and instrumental assessment data was compiled for each tree. The results of the research were used to formulate conclusions and recommendations for improving the management of urban trees in order to restore their ecological and aesthetic functions.

First report of an invasive pest, Phyllonorycter populifoliella (Lepidoptera: Gracillariidae) from Ladakh

<p><em>Phyllonorycter populifoliella</em> (Treitschke 1883), is an invasive pest and is first reported on poplar trees, from the eastern region of Ladakh, India. The details of the taxonomic identification based on genital morphology are presented. Besides, host range, feeding habits and level of infestation in different hamlets of Ladakh are also presented. This study is important for further understanding the pest biology, its diversity and management by adopting control strategies. It is also important to restrict its dispersal to other states of the Indian union and to devise pest management strategies for this pest.</p><p> </p>

Characterization of bronze leaf disease in western Canadian aspen and poplar trees

Aspen and poplar trees are important horticultural plants grown in Canada for aesthetic, commercial woodlot and windbreak applications. Bronze leaf is a destructive disease in <i>Populus </i>spp. and is caused by the fungal pathogen <i>Apioplagiostoma populi </i>Barr. This pathogen is often difficult to isolate and confirm from infected plant tissues and has been mainly identified by disease symptoms and morphological characteristics of <i>A. populi</i> when fruiting bodies form on infected leaves or branches. Affected leaves and branches typically become necrotic and bronze in colour. Air-borne spores and nursery shipments containing infected plants play an important role in the efficient movement of the pathogen. In this study, bronze leaf disease samples from symptomatic trees in Canada were examined microscopically for <i>A. populi</i> perithecia and asci. Pathogen-specific genomic sequences were identified for the development of sensitive stringent diagnostics that indicated branches and petioles were the most effective tissues for detecting <i>A. populi</i>. Leaf samples from symptomatic trees were collected in Canada and examined for perithecia to microscopically characterize <i>A. populi</i> asci and ascospores. Disease associated DNA sequences of the internal transcribed spacer (ITS) 5.8S region of the nuclear ribosomal were isolated from perithecia and symptomatic tree samples. Morphological and molecular biological data from this study characterized the relationship and epidemiology of <i>A. populi</i> and enabled the development of rapid diagnostic methods that restrict the extent of further losses in amenity and commercial plantings of aspen and poplar.

Overexpression of SHORT-ROOT2 transcription factor enhanced the outgrowth of mature axillary buds in poplar trees

Plant branching is usually prevented by an actively proliferating apex. In poplars, one GRAS family member, SHORT-ROOT2 (PtSHR2), was preferentially expressed in axillary buds (AXBs) and was inducible during bud maturation and activation. Overexpression of PtSHR2 (PtSHR2OE) in hybrid poplar impaired the apical dominance and simultaneously promoted the outgrowth of axillary branches below the maturation point (BMP), accompanied by regulated expression of genes critical for axillary meristem initiation and bud formation. Following a detained phenotypic characterization, we compared the IAA and trans-zeatin levels in apical shoots and AXBs of wild-type and PtSHR2OE trees, together with gene expression analyses and defoliation, decapitation, and hormone reapplication assays. PtSHR2OE AXBs contained a significantly lower ratio of auxin to cytokinin than wild-type AXBs, particularly in those below the BMP. Decapitation induced a faster bud burst in PtSHR2OE trees than in wild-type plants, and it could be strongly inhibited by exogenously applied auxin and cytokinin biosynthesis inhibitor, but only partially inhibited by N-1-naphthylphthalamic acid (NPA). An impaired basipetal auxin transport, rather than an insufficient auxin biosynthesis or auxin insensitivity, disturbed the local hormonal homeostasis in PtSHR2OE AXBs, which in turn enhanced the axillary bud initiation and promoted the bud release.

Trunks of multi-stem black poplars may have different genotypes – evidence from the Oder valley in Poland

The black poplar (Populus nigra L.) is an ecologically and economically important tree species, characteristic for floodplain forests in Europe. It is now considered to be endangered in many European countries due to the loss of its natural habitat caused by the development of river engineering and intensive land use management of riverside areas. Multi-stem specimens can be found occasionally in natural black poplar populations. The percentage of such individuals is low, although in some stands it may be over a dozen percent. The origin of multi-stem trees may be different. As a consequence, trunks being part of such a tree can have the same or different genotypes. The study aimed to find out whether all trunks of multi-stem black poplars are ramets of the same genet or if their genotypes are different, in which case they increase the gene pool of the population. We used 13 microsatellite nuclear markers to analyze the genotypes of 83 trunks belonging to 34 multi-stem black poplar trees from five natural populations from the Oder river valley in Poland. We also performed the sibship analysis of all trunks. The results showed that the trunks being part of the particular individual had distinct genotypes in five trees (14.7%). This indicates that they were formed as a result of the fusion of two genetically different individuals. The sibship analysis revealed that one multi-stem tree was represented by full-sibs. In the remaining four trees the fused trunks were not related. Nevertheless, we found three pairs of half-sibs between different trees that were distant from each other. The majority of the multi-stem trees we examined developed most probably due to the damage to the apical meristem of the main shoot of a single-stem tree. Nevertheless, some of them were indeed formed from two distinct individuals. Therefore, if a particular population consists of a small number of individuals, we recommend to study the genotypic homogeneity of each multi-stem tree.

Volatile emission and biosynthesis in endophytic fungi colonizing black poplar leaves

Plant volatiles play a major role in plant–insect interactions as defense compounds or attractants for insect herbivores. Recent studies have shown that endophytic fungi are also able to produce volatiles and this raises the question of whether these fungal volatiles influence plant–insect interactions. Here, we qualitatively investigated the volatiles released from 13 endophytic fungal species isolated from leaves of mature black poplar (Populus nigra) trees. The volatile blends of these endophytes grown on agar medium consist of typical fungal compounds, including aliphatic alcohols, ketones and esters, the aromatic alcohol 2-phenylethanol and various sesquiterpenes. Some of the compounds were previously reported as constituents of the poplar volatile blend. For one endophyte, a species of Cladosporium, we isolated and characterized two sesquiterpene synthases that can produce a number of mono- and sesquiterpenes like (E)-β-ocimene and (E)-β-caryophyllene, compounds that are dominant components of the herbivore-induced volatile bouquet of black poplar trees. As several of the fungus-derived volatiles like 2-phenylethanol, 3-methyl-1-butanol and the sesquiterpene (E)-β-caryophyllene, are known to play a role in direct and indirect plant defense, the emission of volatiles from endophytic microbial species should be considered in future studies investigating tree-insect interactions.