Christmas Tree Plantations Research Articles

Survey of Phytophthora Diversity Reveals P. abietivora as a Potential Phytophthora Root Rot Pathogen in Québec Christmas Tree Plantations.

Christmas trees are an economically and culturally important ornamental plant in North America. Many microorganisms are pathogens of firs cultivated as Christmas trees. Among those, Phytophthora causes millions of dollars in damage to plantations annually. In Canada, it is unknown which species are responsible for Phytophthora root rot (PRR) of cultivated Abies species. Between 2019 and 2021, soil and root samples were collected from 40 Christmas tree plantations in Québec province. We used soil baiting and direct isolation from unidentified root fragments to assess the diversity of culturable Phytophthora spp. The obtained isolates were identified using a multilocus sequencing and phylogenetic approach. A total of 44 isolates were identified, including eight P. chlamydospora, eight P. abietivora, seven P. gonapodyides, three P. gregata, six P. megasperma, and two P. kelmanii isolates, plus 10 isolates belonging to a previously unknown taxon that is phylogenetically close to P. chlamydospora and P. gonapodyides. Among the known species, P. abietivora was the most prevalent isolated species associated with trees showing aboveground PRR-like symptoms. Pathogenicity trials confirmed the pathogenicity potential of P. abietivora on both Fraser fir and balsam fir seedlings. Our study provides a first snapshot of the Phytophthora diversity in Québec's Christmas tree productions and describes multiple potential first associations between Phytophthora species and Abies balsamea and A. fraseri.[Formula: see text] Copyright © 2024 His Majesty the King in Right of Canada, as represented by the Minister of Natural Resources Canada. This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Managing Cone Formation and Leader Growth in Fraser Fir Christmas Tree Plantations with Plant Growth Regulators

Early cone formation is a consistent issue in Fraser fir Christmas tree plantations in the eastern United States. Growers must remove cones by hand, resulting in significant labor costs, as cones degrade the aesthetic value of Christmas trees. In this study, we conducted two series of experiments in collaboration with several Christmas tree farms to determine the effectiveness of applying plant growth regulators (PGRs), specifically GA-inhibitors, in reducing cone formation and shoot growth in Fraser fir. In the first experiments we investigated the effectiveness of paclobutrazol, applied as a soil injection or as a foliar spray in reducing cone formation. The highest rate of soil application (300 mL of paclobutrazol per tree) reduced cumulative coning by approximately 38%. Leader growth control of soil applied paclobutrazol increased with application rate. In the second set of experiments, we compared four GA-inhibitors (paclobutrazol, chlormequat chloride, uniconazole-p, daminozide) applied as foliar sprays on coning and leader growth. Overall, paclobutrazol was the most effective compound for reducing coning and shoot growth. The results confirm earlier findings that application of GA-inhibitors can reduce, but not eliminate, coning. Likewise, PGR application can reduce shoot growth and possibly increase tree density but will not eliminate the need for shearing.

Asiatic dayflower (Commelina communis) control in Douglas fir

AbstractAsiatic dayflower (Commelina communis L.) is becoming increasingly invasive in Christmas tree plantations in the U.S. Northeast. Response of C. communis to preemergence or postemergence herbicides was evaluated in separate field and greenhouse experiments. The preemergence herbicides consisted of two application rates of flumioxazin (215 and 429 g ai ha−1), hexazinone plus sulfometuron-methyl (316 and 527 g ai ha−1), indaziflam (41 and 82 g ai ha−1), and S-metolachlor (2,136 and 4,272 g ai ha−1). The postemergence herbicides were: bentazon at 1,121 g ai ha−1, clopyralid at 280 g ae ha−1, mesotrione at 526 g ai ha−1, topramezone at 294 g ai ha−1, and triclopyr at 842 g ae ha−1. At 16 wk after treatment, higher rates of flumioxazin (429 g ha−1), hexazinone plus sulfometuron-methyl (527 g ha−1), indaziflam (82 g ha−1), and S-metolachlor (4,272 ha−1) provided 80% to 92% control and reduced C. communis plant density by 84% to 93% compared with the nontreated control. The lower rates of flumioxazin (215 g ha−1), hexazinone plus sulfometuron-methyl (316 g ha−1), and S-metolachlor (2,136 ha−1) gave 65% to 72% control and reduced C. communis plant density by 27% to 75% compared with the nontreated control. The postemergence application of mesotrione at 526 g ha−1, topramezone at 294 g ha−1, and triclopyr at 842 g ha−1 resulted in 76% to 90% control and reduction in dry biomass of 10- to 12-leaf C. communis at 28 d after treatment. Bentazon at 1,121 g ha−1 and clopyralid at 280 g ha−1 applied postemergence were ineffective with <10% control and reduction in C. communis dry biomass. This study showed that C. communis can be managed effectively with currently registered preemergence and postemergence herbicides in Christmas trees.

Untangling the role of a novel agroecosystem as a habitat for declining farmland birds

AbstractAs a result of agricultural industrialisation, traditionally managed habitats have dramatically declined throughout Europe. As a result, farmland specialists across several taxa have become increasingly threatened. Concurrently, altered farming practices have also contributed to the emergence of novel agricultural habitats, such as Christmas tree plantations, but knowledge of their impact on biodiversity is still scarce. In the following study, we analysed the drivers behind the territory selection of four declining farmland birds—Common linnet (Linaria cannabina), Tree pipit (Anthus trivialis), Woodlark (Lullula arborea) and Yellowhammer (Emberiza citrinella)—in a landscape dominated by Christmas tree plantations. Our study suggests that Christmas tree plantations provide well‐suited breeding conditions for the species and thus may represent important refuges in human‐modified landscapes. We found that all four species favoured young Christmas tree plantations (<6 years) for territory establishment. In particular, the territories of Tree pipit and Woodlark were characterised by a high proportion of young plantations, which provide open habitat structures rich in bare ground. However, older plantations (>6 years) were also of high importance for some of the model organisms, especially for Common linnet and Yellowhammer. The territory establishment of Yellowhammer was additionally favoured by brushwood plantations, clear‐cut/fringe vegetation and low‐growing shrubland. We attribute the high value of Christmas tree plantations mainly to the coexistence of open habitat structures rich in bare ground and less intensively managed stands, which both represent important foraging sites for the model organisms. At least in intensively used agricultural areas, Christmas tree plantations may represent important refuges for declining farmland birds. Therefore, further measures aiming to promote habitat quality while reducing the use of herbicides in the plantations should be addressed.

Biochar restructures plant–soil–microbe relationships in a woody cropping system

AbstractBiochars are porous charcoal‐like materials that can enhance soil health and plant growth, but their use has not been adequately evaluated in woody cropping systems. To fill this knowledge gap, we investigated the effects of two slow pyrolysis pine biochars on plant performance, soil physicochemical properties, extracellular enzyme activities, and root‐associated fungal community composition in an experimental Christmas tree plantation over 3 yr. Both biochars stimulated the activities of five extracellular enzyme activities between 67 and 446%, but appeared to reduce N availability. Structural equation modelling identified increased soil moisture as a potential mechanism of biochar's effects on all measured enzyme activities, whereas increased dissolved organic C was a possible mechanism of biochar's effect on N and P targeting enzymes. This finding suggests that biochar‐induced increases to dissolved organic C have a specific effect on nutrient targeting enzymes. Biochar was found to negatively impact tree growth and survival, but impacts varied between tree species and biochar type. High‐throughput sequencing showed that biochar decreased the diversity of root‐associated fungal communities, with the ectendomycorrhizal species Wilcoxina mikolae becoming hyper‐dominant on balsam fir in response to one of the biochars. Changes to root‐associated fungal communities may have been partially responsible for negative effects on conifer performance. Although our study identified negative effects of biochar on plant performance and fungal diversity, we also found widespread changes to soil chemistry and microbial function that might be leveraged in systems with more acidic soils or different crops to increase plant performance.

On the structural complexity of central European agroforestry systems: a quantitative assessment using terrestrial laser scanning in single-scan mode

Agroforestry systems provide important ecosystem functions and services. They have the potential to enrich agricultural monocultures in central Europe with structural elements otherwise absent, which is expected to be accompanied by a surplus of ecosystem functions. Here we used quantitative measures derived from terrestrial laser scanning in single-scan mode to describe the structural complexity, the canopy openness, the foliage height diversity and the understory complexity of four common agroforest systems in central Europe. We accessed silvopasture systems with grazing ponies and cattle as well as fellow deer, short rotation forests with agricultural use between the tree rows, tree orchards with grazing sheep and Christmas tree plantations on which chickens forage. As a reference, we used data for 65 forest sites across Germany, representing different forest types, various dominant tree species, stand ages and management systems. We found that overall stand structural complexity is ranked as follows: forest > silvopasture systems > short rotation forest > tree orchard > Christmas tree plantation. Consequently, if overall structural complexity of an agricultural landscape shall be enriched, there is now strong evidence on how this may be achieved using agroforests. However, if the focus lies on selected structures that serve specific functions, e.g. dense understory to provide animal shelter, specific types of agroforests may be chosen and the ranking in overall structural complexity may be less important.

Phytodiversity in Christmas‐tree plantations under different management regimes

AbstractChristmas trees are increasingly being cultivated throughout Europe. Christmas‐tree plantations (CTP) are characterised by intensive vegetation management, which is essential for ensuring tree quality. Within conventional CTP, herbicides are applied extensively, whereas in organic plantations, alternative methods for vegetation management, such as grazing, are implemented. A further characteristic of organic CTP is the application of organic fertiliser. We compared soil conditions, habitat structure and phytodiversity of differently managed CTP for deriving management recommendations for promoting plant species diversity in CTP. We focused on four different plantation types, representing a gradient of land‐use intensity: conventional CTP in open landscapes (CTP‐OPEN) and on former windthrows (CTP‐WIND), organic CTP (CTP‐ORG) and fir‐greenery plantations (FIR) as a baseline for lowest land‐use intensity. Our study discovered clear differences in soil characteristics, habitat structure and phytodiversity among the different plantation types. However, former land use had only little impact, as the differences between the two conventional CTP (CTP‐OPEN/‐WIND) were small. Soil conditions were similar among the three types of CTP compared to FIR. In contrast, habitat structure and phytodiversity differed between the two conventional CTP and the less intensively managed CTP‐ORG and FIR. Conventional CTP were characterised by open vegetation with relatively low plant species richness and a low number of stress‐tolerant species, but some neophytes. In contrast, CTP‐ORG and FIR had a high cover of grasses, the highest overall species richness and the highest number of stress‐tolerant species. For promoting plant species diversity in CTP, we recommend a reduction in management intensity, especially herbicide application.

Flexible habitat use in a migratory songbird expanding across a human-modified landscape: is it adaptive?

Behavioural plasticity during habitat selection plays a key role in determining whether organisms may thrive under human-induced rapid environmental changes. As organisms rely on environmental cues to make decisions, these behavioural responses may be maladaptive. We studied the European stonechat Saxicola torquatus as a model open-habitat bird species breeding in three structurally different land-use types generated by agriculture and forestry activities. In this mosaic landscape, we compared the relative attractiveness and the breeding habitat quality of intensive grassland, Christmas tree plantations and clear-cut patches in plantation forests to test whether habitat selection was adaptive. We examined the settlement pattern of territorial males to evaluate habitat preference. We recorded key parameters reflecting reproductive performances, adult and first-year survival to estimate the individual fitness of the birds and assess the quality of the different land-use types for breeding. Stonechats preferentially settled in clear-cut patches, but their fitness was not found to be markedly different in comparison with the other occupied habitats. Although they produced slightly lower-quality offspring in clear-cut patches, we did not find a negative consequence on first-year survival probabilities or any among-habitat differences in adult survival. With our analysis integrating multiple components of individual fitness, we show that all occupied land-use types are similarly rewarding for the breeding stonechats. Our study shows that some species can benefit from novel land-use types emerging in the landscape as a result of human activities. Flexible habitat selection in the stonechat has most probably contributed to its recent population increase in Western Europe.

Ad hoc breeding of a genetically depauperate landrace of noble fir (Abies procera Rehder) using SNP genotyping via high-throughput targeted sequencing

Pedigree reconstruction via DNA markers and subsequent quantitative genetic analyses in production stands of trees is an alternative to traditional forest tree breeding. The method requires variable DNA markers; preferably cost-efficient to genotype. We tested the approach in breeding for Christmas tree traits in a Danish landrace of Abies procera. Initial analysis with simple sequence repeats (SSRs) revealed a substantial reduction in genetic diversity of Danish A. procera compared with direct imports from the USA, indicating a genetic bottleneck. Due to the reduced genetic variation, the SSRs were not variable enough for pedigree reconstruction, and 145 single nucleotide polymorphisms (SNPs) were therefore identified and genotyped via high-throughput targeted sequencing. In the field, we phenotypically selected 674 superior trees, based on criteria for good Christmas trees, among 21,000 trees in three Christmas tree plantations originating from an A. procera clonal seed orchard. By SNP-genotyping and parentage analysis, pedigree was reconstructed for the selected individuals, and genetic predictions for the Christmas tree traits were estimated. A final selection of 45 trees out of the 674 genotyped, based on an index of predicted values for different traits, foresees a gain in the Christmas tree score and branch angle score of 16% and 10%, respectively. The study clearly demonstrated the benefits of pedigree reconstruction, even though mass selection seemed to give similar gain. Primarily, the possibilities to control the level of inbreeding, and to check whether the production stands, from where we select trees, actually originate from the declared and desired parent pool.

Field establishment of Abies stocktypes in Christmas tree plantations

ABSTRACT Identification of stocktype attributes that speed up field establishment has potential to reduce rotation time of Christmas tree productions. Such morphological and physiological attributes can be targeted in the nursery production. This study tested the effects of container type and nursery seedling density on stocktype attributes at planting and the effects of these on field performance over two years in Abies lasiocarpa and A. nordmanniana Christmas tree stock. Nursery conditions had a considerable impact on seedling attributes at planting. Although sets of these correlated stocktype attributes contributed to forecast field performance, the predictive power was low. No simple relationships were found between plant biomass, stem diameter or height at planting and biomass at final harvest in either of the two species under the range of stocktype variation and field conditions tested. Contrary, stem diameter and stem height at planting explained some of the responses in stem diameter and height after two years in the field. Thus, any target seedling approach would have to be based on a combined set of stocktype attributes exploring more productive stocktypes. The differences observed between stocktypes were largely due to size differences and ontogenetic drift, and stocktypes converged towards a similar field phenotype over time.

A Review of Non-Chemical Weed Control Practices in Christmas Tree Production

Weeds interfere with Christmas tree growth at any time and at any stage of production. Growers mostly rely on mechanical mowing and applications of herbicides for weed control in their fields. However, herbicides can be phytotoxic to non-target plants, can cause environment-related issues, and their repeated application can even cause herbicide-resistant weeds. The main objective of this manuscript is to provide a review of non-chemical weed control strategies in Christmas tree production and identify areas where current practices could potentially be improved or in which further research is required. Preventing the introduction of weed seeds requires controlling weeds along farm roads, maintaining clean equipment, and eliminating new weeds before they start seeding. Mowing helps to reduce the number of seeds produced by the weeds and can significantly reduce competition with trees. Shropshire sheep are well suited for grazing Christmas tree plantations as they prefer grazing on grasses and weeds rather than on coniferous trees. Weeds can also be controlled around Christmas trees by mulching. Organic mulch can improve soil moisture, maintain soil temperatures, enhance root establishment and transplant survival, and improve plant establishment and overall growth. Incorporating cover crops into Christmas tree plantations may improve tree growth, quality, and soil fertility and can supplement conventional nitrogen fertilizers. However, if cover crops are not properly managed, they can be highly competitive with the trees. Flaming can cause suppression of many annual weed species but is less effective on larger weeds and needs to be applied with caution. Several insects have been used as biological agents to control selective weed species. However, further research is required to focus on several potential biological agents, different types and depths of mulches, on cover crops types and their competition with different species of Christmas trees and their effects on seedling survival and growth.

Effects of Christmas-tree plantations on phytodiversity: implications for conservation

Perennial crops such as Christmas trees have increasingly been cultivated throughout Europe. However, knowledge on the influence of Christmas-tree plantations (CTP) on biodiversity is still scarce. We examined phytodiversity and soil and habitat-structure characteristics within young (CTP-YOUNG, tree age ≤ 6 years) and old (CTP-OLD, tree age > 6 years) conventionally managed CTP in comparison with the three most dominant habitat types within the study area: (1) intensively managed grasslands (GRASS), (2) windthrows (WIND) and (3) non-native spruce forests (FOREST) (nper sample type = 18). Our study revealed clear differences in soil characteristics, habitat structure and plant-species richness between the five sample types. These differences were most pronounced between three groups of habitats: (1) CTP, (2) GRASS and (3) WIND/FOREST. CTP were characterized by a typical habitat structure composed of a distinct shrub layer, an intermediate herb layer and a low litter cover. In contrast to the other sample types CTP had a comparably high cover of bare ground and stones/gravel. Due to the practiced management CTP were characterized by a unique plant species community composed of a high number of ruderal species and some neophytes. The differences between CTP-YOUNG and CTP-OLD were generally small. Next to management, phytodiversity in CTP was influenced by the size of CTP. Small-scale CTP generally had a higher phytodiversity. For the cultivation of Christmas trees, we recommend the reduction of herbicide use as far as possible. New plantations should be implemented preferentially within homogeneous landscapes composed of habitats with low importance for biodiversity.

Organic fertilization of Christmas tree (Abies balsamea(L.) Mill.) plantations with poultry manure in northwestern New Brunswick, Canada

At the instigation of local growers, an experiment was conducted on balsam fir (Abies balsamea (L.) Mill.) Christmas tree plantations in northwestern New Brunswick, Canada. The objective was to com...

Beetle biodiversity in anthropogenic landscapes with a focus on spruce plantations, Christmas tree plantations and maize fields

In Europe, anthropogenic habitats that are optimised for agriculture and forestry purposes have widely replaced natural habitats. To assess their value for biodiversity, we compared beetle communities among three anthropogenic land use types, namely spruce plantations, Christmas tree plantations and maize fields. These three land use types are all characterised by high phytobiomass and vertical plant structure and represent a gradient of anthropogenic impact linked to fertilisation, pesticide use, frequent operation of machinery and rotation period length. We found that all components of beetle diversity, i.e. abundance, number of species and Simpson diversity as well as the number of threatened beetle species decreased with increasing anthropogenic impact from spruce plantations to Christmas tree plantations to maize fields. However, beetle biomass was relatively high in maize fields, due to the abundant species in this land use type having a high body mass. Community composition changed with anthropogenic impact. Beetle communities in maize fields were characterised by a higher frequency of zoophagous beetles and a lower frequency of saprophagous/mycetophagous and xylophagous beetles than those in Christmas tree plantations and spruce plantations. The low value of maize fields for beetle biodiversity is concerning because the area covered by maize increased over the last decade by 26.7% and now constitutes 13.5% of arable land globally.

Incidence of Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) in Nova Scotia, Canada Christmas tree (Pinaceae) plantations

AbstractThe occurrence of Bursaphelenchus xylophilus (Steiner and Buhrer) (Nematoda: Aphelenchida: Parasitaphelenchidae) (pinewood nematode) in Canada prevents export of wood products, including Christmas trees (Pinaceae), to Europe. A nationwide survey in 1992 extracted B. xylophilus from mature, dead, or dying balsam fir (Abies balsamea (Linnaeus) Miller; Pinaceae), but not young, healthy Christmas trees. Three species known to harbour B. xylophilus are found in Nova Scotia, but incidence of B. xylophilus within these species is unknown. Monochamus Dejean (Coleoptera: Cerambycidae) species were collected from nine and 20 sites, in 2014 and 2015, respectively, using panel traps baited with a Monochamus lure and evaluated for the presence of pinewood nematode using molecular methods after DNA isolation. Beetles were processed for DNA isolation individually in 2014 and in batches (same species and sex from same collection site and date) in 2015. Bursaphelenchus xylophilus was recovered from all three Monochamus species (M. marmorator Kirby, M. notatus (Drury), and M. scutellatus (Say)) captured in Nova Scotia Christmas tree plantations. Percentage of beetles harbouring B. xylophilus varied with species and sex. Fourteen beetle samples were selected and sent for polymerase chain reaction sequencing. Sequencing results indicated that Bursaphelenchus xylophilus found in Nova Scotia are most similar to isolates from Canada (New Brunswick and Québec), the United States of America, and China.

Detection of Delphinella shoot blight in plantations of balsam fir (Abies balsamea) Christmas trees in Quebec, Canada

Christmas trees produced in Quebec, Canada, mostly include balsam fir (Abies balsamea), which is a species susceptible to Delphinella shoot blight. Over the past decade, the Canadian forests and Christmas tree industry have encountered an increase in Delphinella shoot blight, and only a few studies have assessed and quantified the damage caused by this disease. The different developmental stages of the disease were studied and the presumed causal pathogenic agent was isolated from infected needles in this work. Delphinella balsameae was isolated less frequently than its phylogenetically closely related pathogen Sydowia polyspora. Furthermore, species-specific PCR protocols to detect both D. balsameae and S. polyspora were developed and the occurrence of these species in infected and symptomless needles sampled in Christmas tree plantations was evaluated. While D. balsameae was detected only in diseased needles, S. polyspora was frequently found in both asymptomatic needles and in needles displaying shoot blight. Experiments showed that D. balsameae is the more prevalent agent associated with fir tree shoot blight in Quebec.

Presence of Phytophthora species in Swedish Christmas tree plantations

Phytophthora cryptogea, P. gonapodyides, P. lacustris, P. megasperma, P. plurivora, P. taxon paludosa and an unknown Phytophthora species were isolated from waterways and soil samples in Christmas tree fields in southern Sweden. In addition, P. megasperma was isolated from a diseased Norway spruce (Picea abies) plant from one of the fields in Svalov. Inoculation tests were sequentially carried out with one isolate from each of the three species P. cryptogea, P. megasperma, and P. plurivora, all known pathogens on conifers. The same three isolates were used to study a few morphological features to confirm the identification, and temperature-growth relationships were carried out to see how well the organisms fit into Swedish climatic conditions. Seedlings of Norway spruce and Nordmann fir (Abies nordmanniana) were inoculated in the roots and the stems. None of the isolates caused extensive root rot under the experimental conditions, but all three species could be re-isolated from both Norway spruce and Nordmann fir. Phytophthora root rot is currently of minor concern for Christmas tree growers in Sweden. However, the Phytophthora isolations from soil and water indicate the presence of this damaging agent, which may lead to future problems.

Experiences in Transplanting Wood Ants into Plantations for Integrated Pest Management

Ants can function efficiently as biocontrol agents in open field horticulture. Temperate wood ants can control forest pests, including species damaging forest regeneration plots and fruit plantations. Thus, they possess potential as biocontrol agents in open field horticulture, if they can persist in these systems. Here we present observationson activity and survival of wood ants transplanted from forests into different types of plantations. Mound fragments were transplanted into a conifer seedling plot, an organic and a conventional Christmas tree plantation, and into an organic apple plantation. Colonies survived at least one year in all types of plantations. In some cases, however, ants moved to new locations or migrated between mound fragments, leaving some inactive. Our compiled experiences suggest that this can be prevented by providing a minimum mound size, keeping a minimum spacing between mounds and incorporation of sand and scent marked wood pieces from donor colonies to imitate naturally occurring nests. We also observed that the ants preyed upon and significantly reduced the number of winter moth larvae (Operophtera brumata – a pest in apple and other fruit orchards) in two of four apple varieties. In conclusion, wood ants were tolerant to highly diferente habitat settings and will likely persist in most types of perennial horticultural systems, if managed properly. As they prey on winter moths and multiple other pest species, they are a potential new biocontrol agent for open agricultural systems.

Bionomics of the pine needle scale (Hemiptera: Diaspididae), an emerging pest in Christmas tree (Pinaceae) plantations in southern Québec, Canada – ERRATUM

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Bionomics of the pine needle scale (Hemiptera: Diaspididae), an emerging pest in Christmas tree (Pinaceae) plantations in southern Québec, Canada

AbstractThe pine needle scale, Chionaspis pinifoliae (Fitch) (Hemiptera: Diaspididae), has the status of an emerging pest in Christmas tree (Pinaceae) plantations in Québec, Canada. The scale is not known to cause any significant damage yet and is not generally monitored by growers. However, it can be an obstacle for exportation to Christmas tree markets where scale insects are strictly regulated. In this study, we describe its life cycle in Christmas tree plantations in southern Québec. We confirm the presence of both parthenogenetic and sexual forms of the scale on Fraser fir Abies fraseri (Pursh) Poiret (Pinaceae) grown as Christmas trees, and of parasitoid and Coccinellidae (Coleoptera) specialists that could contribute to its control.