•BC3F3 hybrids had lower resistance than Chinese chestnut under severe blight pressure.•Differences among BC3F3 families were significant under severe blight pressure.•BC3F3 chestnut had higher ...pathogen resistance than American chestnut across sites.•Interactions between location and breeding generation were significant.•Disease incidence in chestnut was positively related to tree basal diameter.
The loss of American chestnut (Castanea dentata) in eastern North America to chestnut blight, a disease caused by the fungal pathogen (Cryphonectria parasitica), has devastated ecological and utilitarian processes and functions. A backcross breeding approach has been developed to confer disease resistance to hybrid seedlings, and forest reintroduction trials will provide important information on performance and durability of resistance in real-world forest conditions. Three plantings were established in 2009 in mesic, even-aged regeneration harvests (site index averaged 23 m for Quercus rubra) and were examined for eight-year blight resistance. These plantings are the first forest field trials to test blight resistance of the most advanced breeding generation currently available, the third generation of the third backcross (BC3F3), against less advanced breeding generations (BC1F3, BC2F3), disease-resistant Chinese chestnut (C. mollissima), and disease-susceptible American chestnut. We also examined if C. parasitica infection was related to tree size and growth. The pathogen infected 36 percent of trees across locations by year 8, but 31 percent of trees died prior to detection of infection. Non-pathogen related mortality was probably due to factors that are typical of hardwood plantings, including repeated deer browsing and native and non-native pest damage. The BC3F3 generation exhibited resistance more similar to the Chinese chestnut than the American chestnut, but exhibited significantly lower resistance than Chinese chestnut at the location with the highest blight incidence; genetic family differences among BC3F3 progeny were significant at this location. Interactions between planting location and breeding generation affected resistance rankings, suggesting additional or longer-term testing is needed to determine resistance of a particular breeding line across a variety of sites. Probability of disease incidence was positively related to ground-line diameter (GLD), but this relationship depended on location and breeding type. At two locations, American chestnut had 50 percent probability of C. parasitica infection when GLD was approximately 70 mm, and the BC3F3 had 50 percent probability when GLD was between 93 and 126 mm. The Chinese chestnut maintained low probability of disease incidence (<35 percent) across all GLD sizes, regardless of location. While a relatively high level of disease resistance was associated with the most advanced breeding generation, BC3F3, the plantings are too young to determine durable blight resistance.
•Survival of bareroot pin oak seedlings increased with initial basal diameter.•Understory release had no benefit to planted pin oak seedlings.•Oak seedlings dominated small natural regeneration but ...did not recruit.•Shelterwood harvest increased growth of planted pin oaks but released competitors.•Selection harvest also increased growth of pin oaks with less competitor release.
Developing competitive oak advance reproduction prior to canopy disturbance is understood to be important for oak regeneration success. In the early 2000s, a study was installed in southeastern Missouri to examine the effects of midstory and understory release on natural and artificial sources of pin oak (Quercus palustris Muenchh.) advance reproduction. The findings obtained three years after midstory and understory release indicated photosynthetically active radiation increased from 3 to 15 % and a corresponding increase in density of pin oak reproduction as well as the survival and growth of both natural and artificial pin oak reproduction compared to control. In 2010, eight years after the midstory and understory was removed, three different overstory harvests were applied to release the established pin oak advance reproduction. Here, we investigated the effects of the midstory and understory removal and the subsequent overstory harvests on underplanted and naturally regenerated oak advance reproduction. We also tested effects of a later midstory release on the density of natural pin oak advance reproduction. Results indicate that the survival of bareroot pin oak seedlings increased with increasing initial basal diameter. The survival of Root Production Method (RPM®) container pin oak seedlings, however, was not dependent on the size at the time of planting. The early understory removal with triclopyr herbicide was ineffective in ensuring survival of planted pin oak seedlings. Shelterwood increased the growth of oak advance reproduction but did not eliminate competition from other species. A late release also failed to increase the growth of oak advance reproduction. Given shelterwood also favored oak competitors in our study, multiple applications of midstory and understory competition control treatments following the shelterwood treatment will be imperative for successful oak regeneration.
► Eucalyptus and other planted forests are expanding rapidly in Brazil and world-wide. ► By the year 2100, planted forests may represent 20% of the global forest area. ► This raises demands for their ...contribution to forest biodiversity conservation. ► Planted forest establishment in Brazil provides forest restoration opportunities. ► More consideration needs to be given to biodiversity-related ecosystem services.
Forests provide important habitat for much of the world’s biodiversity, and the continuing global deforestation is one of our greatest environmental concerns. Planted forests represent an increasing proportion of the global forest area and partly compensate for the loss of natural forest in terms of forest area, habitat for biodiversity and ecological function. At current rates, over 30% of the remaining natural forest area will be lost by the end of the century and planted forests would then represent over 20% of the total forest area. This places a greater demand on planted forests to contribute to the conservation of biodiversity and their provision of biodiversity-dependent ecosystem services. We reviewed recent trends of deforestation, afforestation and reforestation to evaluate the effects on forest biodiversity and the provision of ecosystem services. We placed particular emphasis on eucalypt plantations which continue to expand in numerous countries, especially in Brazil where rapid plantation expansion is creating the largest area of cultivated eucalypt forest worldwide. While government policies to associate plantation establishment with the protection and restoration of natural forests appear to be effective in the highly fragmented Atlantic forest, deforestation continues in Amazonia, mainly due to forest conversion associated with agricultural expansion. We conclude by reviewing methods for conserving biodiversity in planted forests at the stand- and landscape scales and with a view to enhancing the provision of biodiversity-related ecosystem services.
•First multi-site experiment on native forest restoration from conifer plantations in South America.•Partial canopy removal facilitated higher establishment success of native seedlings.•Seedlings ...experienced lower water stress under partial canopy cover.•Strip-cutting offers ecological advantages over clearcutting for native forest restoration.
Extensive areas of native vegetation have been cleared to establish commercial exotic tree plantations in south-central Chile, a region known as a world biodiversity hotspot. Despite increasing societal demands to restore native forests in parts of the landscape, documented experiences for this form of restoration are lacking. We conducted a landscape-replicated experiment to test the influence of different harvesting treatments (clearcut, strip-cutting and unharvested control) on the early establishment of native tree species in 20-year-old Pinus radiata plantations. Group plantings of shade-intolerant (Nothofagus dombeyi; Nothofagus obliqua), semi-tolerant (Nothofagus alpina; Laurelia sempervirens) and shade–tolerant species (Aextoxicon punctatum; Cryptocarya alba) were established across the treatments, and seedling performance and water status were monitored during the first two growing seasons. Mean survival was significantly higher in the strip-cuttings (77%) and control (70%) than in the clearcuts (38%), while mean height and root collar diameter growth were significantly higher in the strip-cuttings (16 cm year−1; 0.2 cm year−1) and clearcuts (16 cm year−1; 0.2 cm year−1) than in the control (5 cm year−1; 0.1 cm year−1). Shade-intolerant and semi-tolerant species showed the highest growth responses to openings. Leaf water potential was significantly higher in seedlings in the strip-cuttings than those in the control and clearcuts, and stomatal conductance was significantly higher in the strip-cuttings and clearcuts than in the control. Higher seedling performances and lower water stress in the strip-cutting treatment suggest that partial canopy removal is a suitable method for artificial regeneration of native tree species with different shade tolerances for native forest restoration from P. radiata plantations.
•Converting larch plantations to mixed stands is feasible by enrichment planting.•Growth of Manchurian walnut is inhibited in gaps below the lower gap size limit.•Growth of Korean spruce increases ...along canopy openness gradients.•Biomass allocations are not affected by low-intensity canopy treatments.•A gap of 160 m2 can provide appropriate environments for seedling establishment.
Larch (Larix spp.) plantations are important for timber production in Northeast China, but this monoculture practice has led to problems such as decreased soil fertility and water-holding capacity. To examine the possibility of gradually converting pure larch plantations to mixed stands by small-scale canopy regulation, we planted seedlings of two species with contrasting shade tolerance, light-demanding Manchurian walnut (Juglans mandshurica Maxim.) and shade-tolerant Korean spruce (Picea koraiensis Nakai), in larch plantations with four different canopy retention intensities (larger gap, 160 m2; smaller gap, 45 m2; thinning, 25% intensity based on basal area; and control, forest understory). After two growing seasons, we found that both species had higher survival rates and growth rates in larger gaps than in forest understories, but the detailed responses to treatments differed between species. Manchurian walnut responded strongly to larger gaps but insensitively to other treatments, especially with respect to biomass accumulation. In contrast, Korean spruce responded gradually with increasing canopy openness. However, canopy treatments had almost no effect on non-structural carbohydrate (NSC) concentration, biomass allocation, and NSC pool allocation, which only differed between species. Our findings indicated that the two species of contrasting shade-tolerance were able to survive and grow in larch plantations, and a small-scale canopy treatment, especially creating gaps of ∼160 m2 in size, could significantly improve seedling survival and growth during the first two years. Therefore, enrichment planting in conjunction with a low-intensity canopy regulation may play an effective role in converting larch plantations to mixed stands while maintaining continuous stand functions during the conversion process.
Successful European beech (Fagus sylvatica L.) regeneration is both of great ecological and economical importance in European forest ecosystems and severely threatened by climate change impacts. To ...increase our knowledge of beech regeneration dynamics under climate change and the potential for controlling it through forest management, we studied interactive effects of solar radiation (PHAR), water and nutrient availability on the height growth of artificially (AR) and naturally regenerated (NR) beech seedlings. The study was conducted in the framework of experimental canopy gaps, under the influence of the 2018/19 drought and heatwaves. We measured PHAR by means of hemispherical photography, approximated water availability based on the inverse of modeled fine root density distributions of overstorey beech (BGRB) and oak (BGRO) and approximated nutrient availability based on soil fertility (SF), derived from forest site mapping. Results indicate that seedling resource availability and resulting growth responses increase with canopy gap size and vary among locations within the gap. Multiplicative non-linear mixed models suggest that AR and NR relative height growth (RI) was best explained by interactive effects of PHAR, BGRB, BGRO and SF, which reflect complementary resource use patterns of beech seedlings. At optimal resource availability, AR reached a potential RI of 174%, which is about 20% higher compared to NR. While the low light growth responses of AR and NR both reflect saturation at 5 to 15% PHAR, depending on individual size and the availability of the remaining resources, NR showed a higher RI than AR at intermediate and high PHAR levels in cases of limited BGR and SF. In contrast to AR, NR growth was affected to a lesser extent by SF and BGRB and not significantly affected by BGRO. These results suggest that overstorey oaks have a lower effect on water availability of beech seedlings than overstorey beeches. Additionally, NR showed higher tolerance to water and nutrient limitation than AR, probably due to better root system development. In conclusion, site-specific potential for mitigating the effects of climate change on beech regeneration through forest management lies in the adaptation of silvicultural systems, i.e., the creation of canopy gaps larger than 200 m2, thus significantly exceeding the average gap size of the natural disturbance regime, and the choice of the regeneration method.
•Beech seedling height growth depends on multiple, interactive resources.•Seedling performance increased over light, water and nutrient availability in gaps.•Natural regeneration showed higher growth rates than artificial regeneration.•Overstorey trees caused species specific water limitation for seedlings (beech>oak).•Larger gaps (>200 m2) may help mitigate climate change threats to beech regeneration.
► This paper assesses the vulnerability of eucalypt plantations to climate change. ► Eucalypt plantations are widely grown, so have significant exposure to change. ► Eucalypt plantations have medium ...vulnerability to climate change. ► Identifying genotypes at potentially marginal sites would minimise vulnerability. ► A database and mapping system is proposed to protect this valuable resource.
Eucalypts are grown in plantations in more than 90 countries, so it is important to assess their vulnerability to climate change. Global mean annual temperature over land has already increased by about 0.9°C in the last century and many countries have agreed that urgent action should be taken to limit the increase in global mean temperature below 2°C. Unfortunately, as emissions are currently tracking at higher levels than the worst case scenario envisaged by the Intergovernmental Panel on Climate Change it appears increasingly unlikely that temperature increase can be limited to 2°C. This paper assesses the vulnerability of eucalypt plantations to climate change. Vulnerability is a function of potential impact, which is related to exposure and sensitivity, and adaptive capacity. Eucalypt plantations total more than 20million hectares and are grown in many countries around the world, so have significant exposure to climate change. About 41% of more than 800 eucalypt taxa grow naturally in Australia within narrow climatic ranges of less than 2°C, so are potentially sensitive to climatic change. Fortunately, the small number of commercially important species tend to have much wider climatic tolerances, but genetic selection to improve growth may well be reducing their climatic adaptability. Efforts have been made to simulate eucalypt growth under changing climatic and atmospheric conditions. If photosynthesis and water use efficiency are increased by increasing atmospheric carbon dioxide levels then some plantations may enjoy significant yield increases. However, recent results from eucalypts growing under elevated CO2 conditions in whole tree chambers suggest there is little if any ‘fertilisation effect’ on photosynthesis, though water use efficiency is increased. Consequently, productivity may increase in some plantations and decrease in others. Fortunately, the adaptive capacity of eucalypt plantations is high. Many eucalypts are grown on short rotations of less than ten years, so changing silvicultural practices and planting different genotypes to match changing climatic conditions is relatively easy. While the vulnerability of eucalypt plantations is only at a medium level it is concluded that sharing information about where particular eucalypt genotypes are grown, identifying potentially marginal climatic areas and recommending genotypes suitable for changing conditions would help to further reduce potential vulnerability. The development of a eucalypt database and mapping system is proposed as a major collaborative project to help to protect one of global forestry’s most valuable resources.
► Most eucalypt plantations are managed in regions with high environmental stresses. ► Clonal plantations with interspecific hybrids strongly contributed to improve site-genotype adaptations. ► ...Continuous gains in productivity of eucalypt plantations have been obtained in Brazil. ► There are a number of risks associated with intensive, high yielding plantations. ► Integration of breeding and silviculture are imperative to sustain productivity.
Organized forestry in Brazil began in the late 1960s, stimulated by a government policy which subsidized afforestation programs from 1967 to 1989 to develop an internationally-competitive wood-based industry, managed by the private sector. Currently, planted forests in Brazil total about 6.9million ha, from which 4.9million ha is planted with eucalypt (around 25% of world plantation), 1.6million ha with pine, and 0.42Mha with other species. Roundwood consumption of forest plantations totaled 170.1millionm3 in 2011, eucalypt plantation accounted for 80.6% of this total.
Most eucalypt plantations are managed in short rotations (6–8years) and are established in regions with water, nutritional and frost stresses of low to high degrees. The mean annual increment is 40m3ha−1year−1 roundwood, ranging from 25 to 60m3ha−1year−1 depending on the level of environmental stress. Improving natural resources use efficiency by breeding and matching genotypes to sites and using appropriate site management practices is a key challenge to sustain or increase productivity.
The wide range of eucalypt species and hybrids with different climatic and edaphic suitability associated with the easy propagation by seeds and cloning allow the adaptation of plantations to various tropical and subtropical regions in Brazil. The possibility of using eucalypt wood in a range of purposes has led large and small enterprises to establish eucalypt forests for multiple uses. The desirable characteristics in association with the accumulated knowledge on eucalypt silviculture encourage the use of this genus in most plantations. The most important factors in the selective process for a genotype are wood characteristics, productivity level, susceptibility to pests and diseases, drought tolerance, especially in tropical regions (frost free), and frost tolerance in subtropical regions (mostly without water deficit). In regions with pronounced seasonality and moderate to long drought periods, the planting of hybrid genotypes predominates, propagated by cloning. Under subtropical conditions, the planting of single species predominates, propagated by seed. Clonal plantations with interspecific hybrids have been fundamental for eucalypt adaptation in regions under water and nutritional stresses. Given the rapid advances in eucalypt breeding, regarding adaptation to water stress and resistance to diseases and pests, and the adoption of clonal propagation techniques, genotypes are rapidly becoming obsolete and are replaced by more productive ones after harvesting. Thus, the replanting of crops has become a common procedure after the second half of the 1990s in Brazil.
This paper describes the basic requirements for integrating genetic and silvicultural strategies to minimize abiotic and biotic constraints in eucalypt plantations.
•No significant net negative interactions occurred in multi-cropped plantings.•Large-diameter oak seedlings had greater survival than standard seedlings.•Large-diameter oak seedlings produced greater ...growth than standard seedlings.•White oak height growth was most similar to eastern white and shortleaf pine.•Eastern U.S. oaks and pines exhibit substantial compatibility when multi-cropped.
Loblolly pine (Pinus taeda L.), shortleaf pine (Pinus echinata Mill.), and eastern white pine (Pinus strobus L.) seedlings were multi-cropped with standard and large-diameter white oak (Quercus alba L.) seedlings to test for neutral or positive effects of multi-cropping. The study was established in 2014 in three complete blocks within recent clearcuts in eastern Tennessee, USA. Each block consisted of six multi-cropped treatments and four monocultures randomly assigned to ten 14.63 × 21.95 m plots. Within each block, monocultures of white oak and each pine species were planted in four control plots. Multi-cropped treatments included loblolly pine planted with white oak at a 0.31 m spacing, loblolly pine planted with white oak in alternating rows at a 1.74 m spacing, shortleaf pine planted with white oak at a 0.31 m spacing, shortleaf pine planted with white oak at a 1.74 m spacing, eastern white pine planted with white oak at a 0.31 m spacing, and eastern white pine planted with white oak at a 1.74 m spacing. Each plot with white oak received 20 standard (~0.127 cm in basal diameter) and 20 large-diameter (~0.632 cm in basal diameter) white oak seedlings that were randomly assigned to planting locations. Initial height, basal diameter, and early survival were recorded for each seedling just after planting. Height growth, basal diameter growth, survival, herbivory, and insect damage were recorded in early December 2014, 2015, 2016, 2017, 2018, and 2019. In 2019, percent survival among treatments did not differ significantly for white oak (p = 0.152), loblolly pine (p = 0.396), shortleaf pine (p = 0.246), or eastern white pine (p = 0.065). In addition, mean height growth and mean basal diameter growth did not differ significantly among treatments for white oak (p = 0.698 and 0.437, respectively), loblolly pine (p = 0.630 and 0.762, respectively), shortleaf pine (p = 0.324 and 0.251, respectively), or eastern white pine (p = 0.623 and 0.823, respectively). Survival was greater for large-diameter white oak seedlings than standard seedlings (p < 0.001). Mean height and mean basal diameter growth in large-diameter white oak seedlings were significantly greater than in standard seedlings ((p < 0.001) and (p < 0.001), respectively). Although these plantings are in the early stages of development, the lack of significant differences in seedling performance among treatments suggests species compatibility and no net negative impact of multi-cropping white oak with the three pine species.
