Target and non-target effects of genetically modified trees

Uncertainties of realized benefits and the potential for environmental effects of genetically modified (GM) trees may comprise an obstacle for an environmentally safe deployment and social acceptance of such products. Through a series of studies I explored target and non-target effects of GM trees in an objective to increase our knowledge of both benefits and environmental effects of these products. In these studies I used two Populus hybrid lines, modified for altered lignin synthesis and Bacillus thuringiensis mediated insect resistance against Coleopteran insects. The studies range from bioassays and controlled microcosm studies in the greenhouse to studies using potted plants in the field and studies designed to address environmental effects of leaf litter from GM trees on aquatic ecosystems. Results show a strong support of realized benefits in terms of resistance effectiveness of the insect resistant trees. Damage levels of relevant herbivorous insects were reduced both in the greenhouse and in the field. However, it is also indicated that benefits in term of growth may be conditionally determined and depend on environmental context, herbivore loads and interactions with non-target herbivores. In this respect, unexpected changes in innate resistance as shown here may be of importance for realized benefits. It is further shown how leaf litter from GM trees may cause effects that cross ecosystem boundaries. For example, lignin modification affected leaf litter quality and the decomposition of litter from one lignin modified line was significantly decreased. Further, leaf litter from insect resistant trees did not affect litter quality but did cause significant changes in the community composition of insects colonizing the litter. Given the signs of environmental control over realized benefits I believe that the field performance of these products needs further confirmation. Studies designed to target different aspects of environmental variability that may occur throughout the lifetime of a trees may be needed for a proper judgment of realized benefits. In such assessments effects on non-target organisms and environments need to be considered and the cause of environmental effects explained. Eventually assessments of GM trees need to relate costs and risks of these products to the costs associated with alternative management measures

Elevational clines predict genetically determined variation in tropical forest seedling performance in Borneo: implications for seed sourcing to support reforestation

While much research has focused on genetic variation in plants in relation to abiotic clines in temperate and boreal forests, few studies have examined similar relationships in tropical forests. Genetic variation in desirable performance traits of trees, such as drought tolerance, fast-growth, and carbon sequestration rates, is widely used to improve reforestation efforts in nontropical systems. However, evolutionary processes such as local adaptation are poorly understood in tropical forests making it difficult to locate desired phenotypes. To test for genetic variation in growth rate in relationship to climatic clines, we conducted a common garden study over 18 months in a nursery using four dipterocarp tree species, represented by 9-12 half-sib families, sourced across an elevational gradient ranging from lowland to hill forests (circa 130-470 m above sea-level) in Malaysian Borneo. We found genetic variation in growth for all four species with fast-growing half-sib families growing 42-88% faster than poorly performing half-sib families. Furthermore, in three species we found that elevation of seedling origin predicted seedling performance; in Shorea fallax and S. johorensis, half-sib families originating from low elevations performed the best. In S. argentifolia half-sib families' seedlings from low elevations grew slowly. Because elevation is a good proxy for climate, the finding of elevational clines predicting genetic variation in growth provides evidence of evolution affecting the function of tropical tree species. Our research highlights opportunities to better understand evolutionary processes in tropical forests and to use such information to improve seed source selection in reforestation

Symphony for the native wood(s): Global reforestation as an opportunity to develop a culture of conservation

1. The stewardship of forests across multiple human generations has potential to lead to cultural innovations fostering sustainable uses. Nevertheless, positive culture-nature interactions are often disrupted due to colonial exploitation and a lack of intrinsic value ascribed to nature in capitalist economies. There is global recognition that restoring degraded ecosystems is critical to promote the welfare of people and nature by reducing the negative impacts of global climate change and diminishing biodiversity. However, with a focus on technical remedies, restoration and reforestation efforts generally fail to address the root causes of ecosystem degradation.2. In this perspective paper, we call for explicit incorporation of cultural values into global reforestation efforts. We focus on music as a cultural ecosystem service as music has been a prominent part of human history with clear sociological and psychological attributes that may invite mass interest and participation. We illustrate the value of musical linkages via three case studies from Europe, Africa and Hawaii focusing on native tree species, their wood, musical ecology and their interaction with culture.3. We show that multi-generational stewardship of native ecosystems in Europe has allowed the refinement of the violin to its current form, one that is culturally significant for millions of people and has created a multi-million dollar industry. This development stems from a 500-year tradition of craftsmanship handed down across generations and illustrates that ecocultural interactions can be a strong dynamo for development of unique commodities.4. In contrast, in regions where extirpation of native plant species was used as a deliberate colonization strategy, many ecocultural linkages face risk of extinction. Our case studies from Africa and Hawaii illustrate how native tree species of particular value for musical expression were nearly lost and along with loss of music, important cultural connections to nature.5. In the context of restoration, there is also evidence that music-based linkages can revitalize nature-culture interactions and promote restoration of native ecosystems. Incorporating native trees in global reforestation efforts is critical for ensuring that reforestation efforts capture the synergies needed for developing new ideologies that promote the well-being of co-dependent humans and all life

Using intraspecific molecular and phenotypic variation to promote multi-functionality of reforestation during climate change – A review of tropical forest case studies in South-east Asia

The study of intraspecific genetic variation in plant traits for use in tropical forest restoration has broad potential for increasing our ability to achieve multi-functional objectives during this era of climate change. Developing seed-sourcing guidelines that optimize phenotypic characteristics best suited to a particular planting site as well as to future conditions imposed by environmental change could be useful for effective reforestation. Because evolution operates differently across tree species, this is an especially cumbersome task in tropical forests that contain thousands of species. Partially due to this high plant diversity, research and application of intraspecific variation in genetics, plant traits, and plant function in tropical forests wane far behind less diverse forest biomes. To examine the potential for improving reforestation efforts in tropical forests by considering intraspecific variation in plant traits and functions, we review the state of knowledge on intraspecific variation in South-east Asia as a case study. We focus on the dipterocarp family (Dipterocarpaceae), a highly diverse family of 16 genera with approximately 695 known species that often dominate lowland tropical rainforests of South-east Asia with many of these forests in a degraded state and in need of restoration. We found that there is research accumulating to understand genetic variation in approximately 10% of these 695 species. Intraspecific molecular variation exists at different spatial scales among species with 74% of species having moderate to high population differentiation (Fst > 0.10) and 92% of species with evidence of fine-scale genetic structure. Although this suggests a high potential for trait variation, few studies associated molecular with phenotypic variation. Seventeen tree species across 11 studies revealed intraspecific variation in traits or functions. Research indicates that intraspecific variation in growth may vary two-fold and drought tolerance four-fold among genotypes highlighting the possibility to pre-adapt trees to climate change during reforestation and to use intraspecific variation to promote the use of native species in commercial forestry. Our review presents opportunities and ideas for developing seed-sourcing guidelines to take advantage of intraspecific variation in traits and function by identifying how to locate this variation, which species would benefit, and how to test for trait variation. We also highlight an emerging area of research on local adaptation, common garden studies, and adaptive drought conditioning to improve reforestation during climate change

Popular Cultural Keystone Species are also understudied — the case of the camphor tree (Dryobalanops aromatica)

Along with landscape degradation and loss of biodiversity there is also a co-occurring loss of cultural and linguistic diversity. When species become rare, there is a corresponding loss of cultural practices and linguistic elements associated with that species. Although cultural assessments of tree species can help in identifying Cultural Keystone Species (CKS) and be used to enhance the cultural relevance of conservation actions, such information is typically lacking for endangered species were the cultural connections may have been lost. Here, we review historic written accounts to assess the cultural status of the critically endangered camphor tree, Dryobalanops aromatica, native to Southeast Asia which is recognized for its camphor and crystals forming in the wood. We found that despite centuries of use, the importance of the tree for specific cultures has not been fully understood. Published literature indicate that it could be a CKS to multiple communities. The tree was once culturally significant for many cultures in its native range and beyond, but contemporary data is lacking, especially with respect to persistence and memory of use in relation to cultural change. By virtue of being a culturally recognized tree species, as well as having a distinct ecological role within its natural distribution, we propose D. aromatica as a flagship species for conservation and restoration of the habitat it defines. Our review highlights the usability of historic accounts as starting points for identifying CKS and effective conservation of biocultural diversity, especially concerning endangered species. We propose that future research should pay attention to inter and intra-community dynamics of local knowledge on the species, and causes and consequences of varying cultural importance across temporal and spatial scale

Seedling and tree growth after Chequered-Gap-Shelterwood-Cutting and in conventional clear-cutting system

To achieve sustainability both ecological and production aspects need to be considered in forest management. Chequered gap shelter wood system (CGSS), consist of small clear-felled gaps with alternating areas of trees, giving the forest a chessboard appearance which potentially could combine the advantages from both the clear-cut system and continuous cover forestry. This approach will introduce more edges which might influence the effect of wind, temperature and solar radiation on seedlings and trees. In this study we evaluate 1) the influence of the forest edge and 2) the north- and south facing part in the gaps on the growth of seedlings and trees (Pinus sylvestris and Picea abies) in gaps and shelter forests, respectively, and compare the growth with that in a conventional clearcutting system. Overall, edges effected seedling growth negatively and tree growth positively. Seedlings also grew better at the northern sun exposed parts compared to the southern shaded parts of the gaps. As a consequence of these edge effects seedlings had a lower, and shelter trees a higher, growth in the CGS-system compared to the reference areas. Seedlings in the central part of the gaps grew better than seedlings in the reference area. Norwegian spruce seems to be the most suited tree species for this silvicultural approach. Given the contrasting effect of edges on seedlings and trees the production over the whole rotation need to be evaluated in future studies

Short-term effects of continuous cover forestry on forest biomass production and biodiversity: Applying single-tree selection in forests dominated by Picea abies

The rotation forestry system provides high biomass production, but could also have a negative impact on species sensitive to disturbance. Continuous cover forestry (CCF) could contribute to solving these conflicting goals, but its feasibility in nutrient limited boreal forests is yet unresolved. In a unique experiment, we simultaneously assessed the short-term effect of single-tree selection on both biomass production and biodiversity (vascular plants, bryophytes, wood-inhabiting fungi), and tested fertilization as a way to mediate growth-biodiversity trade-offs. We found that unharvested stands and stands subjected to single-tree selection had a similar species assemblage of vascular plants, bryophytes, and wood-inhabiting fungi. Fertilization increased growth by 37% and induced shifts in two understory species (favoring the grass Avenella flexuosa and disfavoring the bryophyte Hylocomium splendens). We conclude that single-tree selection may become a useful tool to enhance biodiversity in managed forests

Progeny selection for enhanced forest growth alters soil communities and processes

Genetic enhancement of tree species is integral to global forest management practices with mass propagation of enhanced plant material being used to reforest whole landscapes. It is unclear, however, how genetic enhancement of basic traits such as tree growth may influence the function of life supporting soil ecosystems. We studied the potential cascading effects of genetic increases in growth of Norway spruce (Picea abies) on a range of soil chemical and biological properties. Because this species is a prime candidate for the genetic enhancement of boreal forest landscapes and it has been introduced around the world, its impacts on soil microbiomes are likely of importance both locally and globally. In a 40-year common garden, we assessed how genetic increases in growth generated through controlled crossing of high-quality "plus" trees from across the central boreal zone of Sweden influenced a range of soil properties beneath the canopies. Properties included pH, carbon, nitrogen, nitrate, ammonium, phosphate, respiration rate, and the composition of microbial communities assessed via phospholipid fatty acids (PLFAs). We found that Norway spruce family significantly affected each of the seven chemical properties assessed, with differences of up to 140% among families, and that three of the seven were significantly correlated with mean family growth rate. We also found that fungal PLFAs varied significantly across Norway spruce families, but these differences were not strongly related to mean family growth rate. This study, representing just one cycle of selective breeding, suggests that genetic increases in tree growth rates may also be inadvertently altering soil communities and ecosystem services. Such alterations across forest landscapes may have unexpected implications for the function of forest ecosystems (i.e., nutrient cycling) as well as processes of global significance (i.e., carbon sequestration)

Long-term yield and biodiversity in stands managed with the selection system and the rotation forestry system: A qualitative review

There is an increasing interest in implementing Continuous Cover Forestry (CCF) as a tool to mitigate negative effects of the traditional rotation forestry system on biodiversity. However, the effects of CCF on forest growth and yield and on biodiversity is still poorly known. In this qualitative review, we compare biodiversity and longterm yield between the selection system, which is a type of CCF practiced in full-storied forests, and the traditional rotation forestry system. We specifically focus on forests dominated by Picea abies, which is a tree species of high economic relevance. Our literature search resulted in 17 publications on stand growth and yield and 21 publications on biodiversity. A majority of simulation studies found a higher long-term yield in the rotation forestry system, but it is challenging to conclude which system is the most productive. The magnitude of the difference in yield between systems, and how it varies across different environmental conditions, remains to be determined. For biodiversity, comparisons of species assemblage and individual species were only made to certain phases of the rotation cycle (recent clearcuts and middle-aged stands). Nevertheless, two aspects can be highlighted: i) the species assemblage in clearcuts differ substantially from stands managed with the selection system. Some of these effects may however be short lasting as examplified by studies on beetle assamblages showing that middle-aged rotation forestry stands become more similar to stands managed with the selection system, ii) the selection system maintains a similar species assemblage as the uncut control during the first years after cutting. In conclusion, management with the selection system may come with a loss in long-term stand yield, but much of the species assemblage is maintained after logging. We recommend future studies to specifically focus on long-term effects on biodiversity - in particular on species of conservation concern. There is also a need to establish a long-term research infrastructure to further develop the field