Showing papers in "New Forests in 2021"

An overview of forest loss and restoration in the Brazilian Amazon

Abstract: Forest restoration is a strategy to reverse forest loss and degradation. We overviewed deforestation in the period 1975–2018 in the Brazilian Amazon and the projects, techniques, and scientific publications conducted to recover forest in the area by 2019. We used GIS to assess forest loss and a systematic data collection gathered from 12 universities, five major environmental agencies, and an ad-hoc bibliographic survey that rendered information from 405 restoration projects and 152 published studies. The Brazilian Amazon has undergone an accelerated deforestation in the last 43 years, resulting in 20% (788,353 km2) of its territory deforested by 2018. Deforestation rate was 27,033 km2 yr−1 between 1975 and 1987 and 14,542 km2 yr−1 between 1988 and 2018 (1.97% yr−1 of forest loss between 1975 and 2018). In 2018, 41 Amazonian municipalities were classified as priority areas for monitoring and control deforestation and 21 additional municipalities were deemed as areas with controlled deforestation. Our survey identified 405 projects of forest restoration in 191 municipalities between 1950 and 2017. The majority (229) of these projects used seedling planting as the main forest restoration technique. Forest restoration projects based upon agroforestry systems (144), assisted natural regeneration (27), and natural regeneration (5) were also identified. Despite a considerable number of projects and publications, the region still lacks scientific studies that reinforce the choice of best practices for forest restoration, and the information currently available is not enough to quantify what has already been recovered or the potential area to be restored.

Complexities underlying the breeding and deployment of Dutch elm disease resistant elms

Abstract: Dutch elm disease (DED) is a vascular wilt disease caused by the pathogens Ophiostoma ulmi and Ophiostoma novo-ulmi with multiple ecological phases including pathogenic (xylem), saprotrophic (bark) and vector (beetle flight and beetle feeding wound) phases. Due to the two DED pandemics during the twentieth century the use of elms in landscape and forest restoration has declined significantly. However new initiatives for elm breeding and restoration are now underway in Europe and North America. Here we discuss complexities in the DED ‘system’ that can lead to unintended consequences during elm breeding and some of the wider options for obtaining durability or ‘field resistance’ in released material, including (1) the phenotypic plasticity of disease levels in resistant cultivars infected by O. novo-ulmi; (2) shortcomings in test methods when selecting for resistance; (3) the implications of rapid evolutionary changes in current O. novo-ulmi populations for the choice of pathogen inoculum when screening; (4) the possibility of using active resistance to the pathogen in the beetle feeding wound, and low attractiveness of elm cultivars to feeding beetles, in addition to resistance in the xylem; (5) the risk that genes from susceptible and exotic elms be introgressed into resistant cultivars; (6) risks posed by unintentional changes in the host microbiome; and (7) the biosecurity risks posed by resistant elm deployment. In addition, attention needs to be paid to the disease pressures within which resistant elms will be released. In the future, biotechnology may further enhance our understanding of the various resistance processes in elms and our potential to deploy trees with highly durable resistance in elm restoration. Hopefully the different elm resistance processes will prove to be largely under durable, additive, multigenic control. Elm breeding programmes cannot afford to get into the host–pathogen arms races that characterise some agricultural host–pathogen systems.

Projecting global and regional outlooks for planted forests under the shared socio-economic pathways

Abstract: There is rising global interest in growing more trees in order to meet growing population, climate change, and wood energy needs. Using recently published data on planted forests by country, we estimated relationships between per capita income and planted forest area that are useful for understanding prospective planted forest area futures through 2100 under various United Nations Intergovernmental Panel on Climate Change-inspired Shared Socio-economic Pathways (SSPs). Under all SSPs, projections indicate increasing global planted forest area trends for the next three to four decades and declining trends thereafter, commensurate with the quadratic functions employed. Our projections indicate somewhat less total future planted forest area than prior linear forecasts. Compared to 293 million ha (Mha) of planted forests globally in 2015, SSP5 (a vision of a wealthier world) projects the largest increase (to 334 Mha, a 14% gain) by 2055, followed by SSP2 (a continuation of historical socio-economic trends, to 327 Mha, or an 11% gain), and SSP3 (a vision of a poorer world, to 319 Mha, a 9% gain). The projected trends for major world regions differ from global trends, consistent with differing socio-economic development trajectories in those regions. Our projections based on empirical FAO data for the past 25 years, as well as those by other researchers, suggest that achieving the much more ambitious global planted forest targets proposed recently will require exceptional forest land and investment supply shifts.

Genotype by environment interaction analysis of growth of Picea koraiensis families at different sites using BLUP-GGE

Abstract: This study investigated the growth (height, diameter at breast height and volume) of Picea koraiensis families at two sites and explored the genotype × environment interaction (GEI) of growth traits to provide a theoretical basis for the improvement of P. koraiensis families. Genetic variation analysis and genetic parameter estimation of growth traits were carried out using 52 families of three provenances, Muling (M), Jinshantun (J), Wuyiling (W), of P. koraiensis at Jiangshanjiao (JSJ) and Qingshan (QS) forest farms in Heilongjiang Province, China. The variance analysis of the multisite test and the type B correlation coefficient of growth traits between the two sites were less than 0.2, indicating that the growth traits of the family had extremely significant GEI, and the growth of families of provenances J and W (experienced colder conditions) at JSJ and QS was significantly better than that of provenance M (grew in relatively warm areas). The main drivers of GEI might be the annual average temperature and frost-free period. The families from provenances J and W that experienced colder conditions might have higher environmental adaptability and superior growth compared with families from provenance M. The family with the highest but unstable volume yield at JSJ and QS was M410 and W010, respectively. While, the top five families with high and stable yields were J085, J097, W037, W045 and J068 by stability analysis (BLUP-GGE) of joint-site. This study enhanced our understanding of the GEI of P. koraiensis families and benefits the selection of optimal families.

Assessing tree height and density of a young forest using a consumer unmanned aerial vehicle (UAV)

Abstract: Accurate, cost-effective monitoring and management of young forests is important for future stand quality. There is a critical need for a rapid assessment tool for forest monitoring and management. This study uses a low-cost unmanned aerial vehicle (UAV) to complete a tree height and tree density assessment in a newly forested Chinese fir (Cunninghamia lanceolata (Lamb) Hook) planting (15 sample plots), Shunchang County, Fujian, China (1.12 ha). Images obtained from a Phantom4-Multispectral UAV were used to generate a digital surface model (DSM) with DJI Terra software (0.02 m spatial resolution). Based on the DSM, the individual trees were identified and the height of each corresponding tree was determined. The impacts of factors related to individual tree detection (ITD) and tree height accuracy were also analyzed. For the tree-level, the highest accuracy of ITD for Chinese fir was 98.93% (F-score = 98.93%). Remotely sensed individual tree heights produced an R2 value of 0.89, RMSE value of 0.22 m when compared to a field survey. At the stand-level, tree height assessment yielded R2 = 0.95, RMSE = 0.12 m, and tree density assessment yielded R2 = 0.99, RMSE = 48 tree ha−1. The results highlight that UAVs can successfully monitor forest parameters and hold great potential as a supplement or substitute tool in field inventory.

Effects of environmental factors on plant functional traits across different plant life forms in a temperate forest ecosystem

Abstract: Plant functional traits have been shown to vary with environmental conditions. However, we lack empirical data on how plant functional traits of different plant life forms respond to environmental factors. We studied the influence of environmental conditions on the distribution of plant functional traits in a Quercus wutaishanica forest with the aim of exploring the patterns of functional traits across different life forms and determining the driving factors of functional trait variation at fine spatial scales. We collected data on environmental factors (soil nutrients and soil moisture, canopy variables, topography) of 70 20 m × 20 m plots. Leaves were harvested from 26 species (4 tree species, 7 shrub species and 15 herbaceous species), and community-weighted mean (CWM) trait values for leaf area (LA), leaf mass per unit area (LMA), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC) were calculated. We also measured the height (H) of plants. The importance of biotic and abiotic factors in controlling plant functional traits was quantitatively assessed using redundancy analysis (RCA). Regression was used to determine relationships between CWM trait values and environment variables. We found that plant functional traits varied with life forms of plants. LA, LMA and LCC of trees were greater than those of the understory, whereas LNC, LPC and LKC of herbaceous were greater than those of trees. Responses of plant functional traits to environmental factors varied with different life forms. The combined effect of canopy, topography and soil factors had a greater impact on plant functional traits in understory layer than tree layer. General linear models showed that openness is the main factor affecting various functional traits of undergrowth plants, and the relationship between the element content in leaves of herbaceous plants and environmental factors is greater than that of shrub plants. The strong correlation of plant functional traits and environmental factors at fine spatial scales indicates that Q. wutaishanica forests have high spatial variability. Considering the variation of traits in different life form of plants and their interactions with biotic factors, it provides further insights into ecological mechanisms of shaping plant communities and driving plant community dynamics.

Biomass allocation and nutrient use efficiency in response to water stress: insight from experimental manipulation of balsam fir, concolor fir and white pine transplants

Abstract: Plants under water stress alter their normal morphological and physiological processes. However, biomass allocation and nutrient use efficiency remain largely unknown under the interactive effect of irrigation and fertilization for many economically important conifer species. In this study, we compared biomass allocation and resources use efficiency of two-year-old (plug+1) containerized balsam fir [Abies balsamea (L) Mill.] ‘Cooks’ and concolor fir [Abies concolor (Gord. & Glend.) Lindl. Ex Hildebr.] ‘Cibola’, and one-year-old bare-root white pine [Pinus strobus L.] transplants grown under variable watering and fertilization conditions. In a controlled greenhouse setting, transplants were submitted to three irrigation levels and two fertilization rates in a factorial experimental design. Fir species, mainly concolor fir, had a greater capacity to utilize water resulting in decreased stem water potential than white pine, leading to increased aboveground growth and shoot-to-root (S/R) ratio. White pine transplants had a higher assimilatory nutrient efficiency, nutrient use efficiency (NUE), root weight ratio, and a lower nitrogen availability index than the two fir species, suggesting a better ability to tolerate water stress. The high rates of fertilization increased nutrient concentration more than growth, suggesting luxury consumption. These results indicate that white pine responds to drought stress by closing their stomata and decreasing their S/R ratio to limit physiological activities, while the two fir species exhibit increased water uptake via expanded fine root networks, increasing the NUE and S/R ratio. However, there was no clear trend for the irrigation and fertilization interaction for NUE for three species, making it difficult to generalize responses.

Monitoring drought response and chlorophyll content in Quercus by consumer-grade, near-infrared (NIR) camera: a comparison with reflectance spectroscopy

Abstract: A user-friendly and affordable broad-band digital Near Infrared (NIR) camera (Canon PowerShot S110 NIR) was compared with a narrow-band reflectance spectrometer (USB2000, Ocean Optics) at leaf scale for monitoring changes in response to drought of three ecologically contrasting Quercus species (Q. robur, Q. pubescens, and Q. ilex). We aimed to (a) compare vegetation indices (VIs; that is: NDVI, Normalized Difference Vegetation Index; GNDVI, Green NDVI and NIRv, near-infrared reflectance of vegetation) retrieved by NIR-camera and spectrometer in order to test the reliability of a simple, low-cost, and rapid setup for widespread field applications; (b) to assess if NIR-camera VIs might be used to quantify water stress in oak seedlings; and (c) to track changes in leaf chlorophyll content. The study was carried out during a water stress test on 1-year-old seedlings in a greenhouse. The camera detected plant status in response to drought with results highly comparable to the visible/NIR (VIS/NIR) spectrometer (by calibration and standard geometry). Consistency between VIs and morpho-physiological traits was higher in Q. robur, the most drought-sensitive among the three species. Chlorophyll content was estimated with a high goodness-of-fit by VIs or reflectance bands in the visible range. Overall, NDVI performed better than GNDVI and NIRv, and VIs performed better than single bands. Looking forward, NIR-camera VIs are adequate for the early monitoring of drought stress in oak seedlings (or small trees) in the post-planting phase or in nursery settings, thus offering a new, reliable alternative for when costs are crucial, such as in the context of restoration programs.

Effect of climate change on potential distribution of Cedrus libani A. Rich in the twenty-first century: an Ecological Niche Modeling assessment

Abstract: The present study is focused on the potential distribution of the Lebanese cedar (Cedrus libani) in the present and in the future throughout the twenty-first century The location of this work encompasses Lebanon, Syria and Turkey Twenty-four environmental variables are used and two Representative Concentration Pathways (RCP) scenarios for two different time periods are studied: RCP 45 2050, RCP 45 2070, RCP 85 2050 and RCP 85 2070 The most interesting novelty is the use of 13 General Circulation Models and 6 algorithms (Climate Space Model, Envelope Score, Environmental Distance, Genetic Algorithm for Rule-set Production, Maximum Entropy and Support Vector Machines) were considered for modelling Area Under the Curve is used as goodness of fit and building the final consensus map The global habitat suitability area would enlarge in the forecasted scenarios with respect to the present, although it would be more restricted in 2070 due to the altitudinal shift This study also suggests an interesting approach to manage C libani stands by means of afforestation programs aiming to face global warming in the late twenty-first century

Achievements and prospects of genetic engineering in poplar: a review

Abstract: Poplars play important role in global forestry. Besides being cultivated as an agro-forestry crop, they provide mankind with fuel wood, timber wood, plywood, sports goods, raw material for paper industry and recently, they are being used as a potential biofuel source. However, a number of biotic and abiotic stresses reduce poplar yield and productivity. Further, there is a strong felt need of paper and pulp industries to have reduced lignin content or modified lignin composition of poplar wood, which will assist in manufacturing better quality paper using less environmentally hazardous chemicals. Because of the non-availability of resistance donor sources and long generation period, conventional breeding could achieve success in genetic improvement of poplars. To circumvent these bottlenecks, genetic engineering interventions have been applied for poplar crop improvement. With the availability of Populus trichocarpa genome sequence in public domain, now numerous genes and transcription factors governing various metabolic pathways got identified, which can be targeted for genetic engineering for poplar improvement. Genome editing technology has really expedited the pace of poplar improvement programmes. This review provides an insight into various research efforts focused on poplar genetic engineering for improvement of silviculturally important traits.

Early indications of success rehabilitating an underperforming teak (Tectona grandis) plantation in Panama through enrichment planting

Abstract: Enrichment planting can be an effective strategy for increasing the ecological and economic value of timber plantations, but success depends on appropriate matching of under- and overstory species and site conditions This case study in the Panama Canal Watershed explores the viability of enrichment planting for rehabilitating underperforming teak (Tectonia grandis) plantations, which are common in the area Two high-value timber species native to the neotropics, Dalbergia retusa and Terminalia amazonia, were underplanted in an established teak plantation at the Agua Salud research site in the province of Colon, Panama Seedling survival, basal diameter, height, total biomass and relative growth rate were assessed for the two years following planting In contrast with the widespread belief that teak is a poor nurse tree, both species achieved promising early growth with low mortality in plantation understory conditions Neither understory light availability nor combined above- and below-ground effects of crowding pressure from teak strongly predicted growth of either species D retusa, thought to be more shade-tolerant, performed equally across a range of intermediate light levels whereas T amazonia, thought to be more heliotropic, performed best at the highest light levels, though light relationships explained little variation in seedling growth These early findings support the suitability of either species for use in enrichment plantings in established, underperforming teak plantations in the Panama Canal Watershed Longer-term research is needed to evaluate the potential of enrichment planting to increase profitability and ecosystem services such as carbon sequestration and water resource management in these plantations

The development of soil organic carbon under young black locust ( Robinia pseudoacacia L.) trees at a post-mining landscape in eastern Germany

Abstract: The aim of this study was to evaluate the potential of short rotation alley cropping systems (SRACS) to improve the soil fertility of marginal post-mining sites in Brandenburg, Germany. Therefore, we annually investigated the crop alleys (AC) and black locust hedgerows (ABL) of a SRACS field trail under initial soil conditions to identify the short-term effects of tree planting on the storage of soil organic carbon (SOC) and its degree of stabilization by density fractionation. We detected a significant increase in SOC and hot-water-extractable organic C (HWEOC) at ABL, which was mainly restricted to the uppermost soil layer (0–10 cm). After 6 years, the SOC and HWEOC accumulation rates at ABL were 0.6 Mg and 46 kg ha−1 year−1, which were higher than those in the AC. In addition, comparatively high stocks of approximately 4.6 Mg OC and 182 kg HWEOC ha−1 were stored in the ABL litter layer. Density fractionation of the 0–3 cm soil layer at ABL revealed that the majority of the total SOC (47%) was stored in the free particulate organic matter fraction, which was more than twice that of the AC. At the same time, a higher and steadily increasing amount of SOC was stored in the occluded particulate organic matter fraction at ABL, which indicated a high efficiency for SOC stabilization. Overall, our findings support the suitability of black locust trees for increasing the soil fertility of the reclaimed mining substrate and, consequently, the high potential for SRACS to serve as an effective recultivation measure at marginal sites.

Tree diversity and timber productivity in planted forests: Pinus patula versus mixed cloud forest species

Abstract: Planted forests contribute to maximizing timber production but their role as valuable habitat for diversity is of increasing concern, particularly in tropical montane cloud forest (TMCF) landscapes, which present extremely high diversity and endemism. We compared tree diversity, potential timber productivity and estimated net revenues in planted forests of Pinus patula and mixed TMCF species in southern Mexico. These planted forests were 21 years-old and established under similar environmental conditions in abandoned pastures previously occupied by TMCF. Adult tree height and density were similar between planted forests, but sapling and seedling density were reduced in P. patula in comparison to the mixed forest (0.05 and 0.28 sapling m−2 and 0.08 and 0.56 seedling m−2, respectively). The diversity of adults was similar, but that of saplings and seedlings was lower in P. patula than in the mixed forest (saplings: 3.39 and 9.14 effective species; seedlings: 2.85 and 9.59, respectively). Timber volume was similar between planted forests; however, due to higher establishment costs and lower market price, the net present value (NPV) of the mixed forest was considerably lower than that of P. patula. The mixed forest only achieved a positive NPV with subsidies and an interest rate < 5% under a 30% harvesting intensity. To ameliorate biobiodiversity loss, TMCF landscapes require alternative measures; e.g., a supply of a diverse mix of native seedlings, stimulation of the market for native species, compensatory mechanisms for mixed plantations of native species and landscape approaches that combine economically profitable and ecologically desirable species.

Ecosystem restoration after bauxite mining: favorable indicators for Technosols construction and soil management using liming and subsoiling

Abstract: Although its economic importance, bauxite mining causes the loss of natural ecosystems. In this sense, the Technosols building from materials made or modified by man, such as mine tailings, is necessary for recovering degraded areas. Additionally, the Technosols management, such as subsoiling and liming, increases chances of plants establishment and growth. In this study, a degraded area by bauxite mining with constructed Technosol in the Eastern Amazon, Brazil, was tested under three different soil management treatments: Technosol-1 (Tech-1), Liming only; Technosol-2 (Tech-2), Subsoiling + 200 g of NPK in the pit; Technosol-3 (Tech-3), Scarification + liming + all Tech-2 procedures. In every treatment and in a reference forest (R-forest), 8 years after the initial seedling planting, three types of indicators were assessed: structural (horizontal vegetation structure, density of natural regeneration, and soil cover), compositional (species diversity, ecological groups, and dispersal syndromes), and functional (chemical properties of Technosols and dry matter and nutrients from the litter stock). The most representative species in all treatments were Croton matourensis and Vismia guianensis, both coming from the natural regeneration and common in early successional stages. Coverage rates in all treatments showed less than 5% of exposed Technosol and the diversity, ecological group, and dispersal syndrome indexes followed a successful trajectory along 8 years. Tech-2 and Tech-3 presented the best chemical attributes and nutrients in the litter stock, but they would probably last several decades to reach the R-forest attributes. Thus, subsoiling alone or with liming provided the best chemical results for soil, litter, and vegetation performance, being recommended to speed up restoration of degrades areas by bauxite mining in the Amazon.

Influence of heterozygosity and competition on morphological tree characteristics of Quercus rubra L.: a new single-tree based approach

Abstract: In Europe, the non-native Northern red oak (Quercus rubra L.) is widely recommended for future cultivation. However, outside its natural range, Northern red oak has to date been insufficiently studied both in terms of silviculture and genetics. To clarify this, we studied the architecture of 92 (pre-) dominant Northern red oak trees in five German federal states using the non-destructive terrestrial laser scanning method (TLS). In addition, individual-based heterozygosity was calculated based on microsatellite data obtained by analyzing twelve potentially adaptive genic (EST derived markers) and eight putatively selectively neutral nuclear microsatellite markers. With these data the individual heterozygosity of the sample trees was calculated. Mean or median branch angles as well as branch angle ranges of first order branches decreased with individual heterozygosity calculated group-wise for all markers (HoAll) and for EST-derived markers (HoEST). Most other tree characteristics, including the number of bark anomalies and mean stem non-circularity and crown characteristics such as crown volume, crown surface area, or mean branch length of first order branches responded exclusively to competition. We conclude that competition, not genetics, is the main driver of Northern red oak stem and crown characteristics. Thus, stem quality and crown dimension can primarily be controlled by silvicultural interventions. The significant relationship between Northern red oak branch angle traits and individual tree heterozygosity was unexpected, and at this time we do not have any validated explanation for this. This issue needs to be further investigated.

Can habitat prediction models contribute to the restoration and conservation of the threatened tree Abies pinsapo Boiss. in Southern Spain

Abstract: We examined the association between habitat variables and the relative impacts of topographic microclimates as a valuable tool for restoration and conservation of Abies pinsapo in southern Spain. We used presence–absence data from A. pinsapo and 79 environmental variables and biomod species distribution models to describe the current and future species habitat across the Sierra de las Nieves Natural Park (southern Spain). A. pinsapo habitat was most strongly associated with microtopographic (solar incidence) and temperature variables, indicating climate-driven changes in microhabitat use. Most of the temperature variation among the study site was attributable to topographic microclimates rather than regional temperature differences, such that differences in microhabitat associations occurred principally between north- and south-facing slopes within the same region. The current potential distribution suggests that around 8.7% (56.44 km2) of the study area is highly suitable for A. pinsapo, with 9.7% (62.84 km2) being moderately suitable. Under different global circulation models and climate change scenarios, the net decrease in suitable habitat is predicted to be 93% of the current distribution by 2040, disappearing altogether by 2099. Our findings also show a sharp reduction of potential restoration areas (1.8% of the current areas). Microclimatic variation generated by the topography offers the microclimate-driven locations of habitat suitability which could shape species’ distribution restoration actions and their responses to environmental change. The approach presented here can provide a rapid assessment of the future conservation status of other important forest tree species in Spain, improving our understanding of the vulnerability of endangered species under climate change, and can be an effective tool for biodiversity conservation, restoration, and management.

The current situation and future perspectives of Quercus ilex and Pinus halepensis afforestation on agricultural land in Spain under climate change scenarios

Abstract: Between 1994 and 2017, 137,455 ha of agricultural land were afforested in Andalusia (Spain), using a great diversity of tree species, under the Common Agricultural Policy scheme. Quercus ilex and Pinus halepensis were the most used species. In view of the need to know the spatial distribution of survival according to the potential species habitat, the current survival was assessed under current and foreseeable future climate change scenarios, using ensemble species distribution models (SDMs). Predicted potential distributions together with 2009 survival data were used to predict the distribution of the survival rate of the two species. The set modelling approach gave very accurate results for the current potential distribution of Q. ilex (AUCtrain = 0.908, TSS = 0.647, Kappa = 0.647) and P. halepensis (AUCtrain = 0.983, TSS = 0869, Kappa = 0.868) and moderately accurate estimates of the distribution of the survival rate of Q. ilex and P. halepensis (RMSE = 0.23). It was found that 25–38% of the Q. ilex and P. halepensis plantations planted between 1993 and 2000 were established in the optimal area of occurrence (probability of occurrence > 70%), but only 12.3% (Q. ilex) and 22.9% (P. halepensis) presented simultaneously an acceptable survival rate (> 50%). In addition, the volume of the environmental space defined by Q. ilex decreased, while that defined by P. halepensis remained constant in future projections under climate change. The potential of SDMs to predict the survival rate distribution of Q. ilex and P. halepensis and to assess the future stability for each of these species has been confirmed. In the worst case, ~ 5% of Q. ilex and ~ 33% of P. halepensis of planted surface would withstand climate change.

Seasonal timing and recurrence of methyl jasmonate treatment influence pine weevil damage to Norway spruce seedlings

Abstract: Defense can be induced in conifer seedlings to reduce pine weevil (Hylobius abietis) damage, by treatment with the plant hormone methyl jasmonate (MJ). Few studies have addressed important practical issues regarding the use of MJ such as treatment incidence and timing, seedling age and its compatibility with plant nursery practices. We examined if levels of pine weevil damage depend on seasonal timing and recurrence of MJ treatment, and if the observed effects depend on plant age. Norway spruce (Picea abies) seedlings from two age cohorts (1 year and 1.5 years old) received four MJ treatments: MJ application before winter storage in the previous year, after winter storage but before spring/summer planting, repeated MJ application (both before winter storage, and before planting) or no MJ application at all. Pine weevil damage was evaluated in a lab and field experiment. We found that the timing and recurrence of MJ treatment affected the amount of damage inflicted by pine weevils in different ways, but these effects were consistent among age cohorts. MJ application before winter storage provided the most effective protection, and this reduction in damage was comparable to that provided by a currently used physical protection method against pine weevil feeding. Our results indicated that MJ can be applied in line with nursery practices (before winter storage) and provides adequate protection for two growing seasons.

Vegetation restoration is associated with increasing forest width

Abstract: Monitoring and assessment reveal important information about restoration areas and can also be useful for understanding ecological processes such as succession and species-area relationships. Herein, we investigated whether the time after restoration determines the similarity between restoration forests and reference ecosystems, and whether the age and width of the forest as well as the surrounding forest cover have an influence on forest restoration. The tree stratum, seed rain, and regenerating stratum were monitored in a reference ecosystem and four 10-year and 20-year-old restoration forests of different widths in southeastern Brazil. We verified that both 10- and 20-year-old restoration forests were like the reference ecosystem in the species richness, diversity, number of individuals, and functional groups of the tree stratum and seed rain. However, the floristic composition of the three strata evaluated plus the number of regenerating plants were lower in the restoration forests than in the reference ecosystem, which may be due to the agricultural matrix where the restoration forests were inserted. We also found that most of the ecological indicators were associated with increasing forest width meaning that wider strips can recover more vegetation attributes. The study indicates that various indicators can be recovered within a decade of active restoration (seedling planting) in the tropics. The regenerating stratum however may require more than two decades to recover. As the restoration was associated with increasing forest width, restoration practitioners should restore wider areas so that more biological groups can be recovered.

The long-term effects of thinning and mixing on species and structural diversity of Chinese fir plantations

Abstract: Plantations are playing an increasingly important role in providing forest products and improving the ecological environment, but they also face many challenges, such as low biodiversity, severe pest and disease problems, reduced productivity, and diminished soil fertility. Reasonable management strategies are vital for their sustainability. In this study, we took a Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantation as an example to demonstrate the effects of thinning and mixing on the species diversity and structural diversity of plantations at the stand level over a rotation period (1993–2018). An intermediate thinning (26% of plant abundance) was conducted in a Chinese fir pure plantation in mid-age (2008), and a mixed forest stand of Chinese fir and Michelia macclurei Dandy was established directly. Thinning and mixing greatly increased the species diversity at the stand level, enhanced the mixture, transformed the pattern from regular to random distribution, and made the size differentiation of trees random. Thinning and mixing also greatly improved the mixture and dominance of Chinese fir. M. macclurei had an obvious advantage in tree size and maintained a high mixture proportion. Moreover, the diameter classes of the stands were bimodal. Chinese fir and M. macclurei showed a unimodal distribution of diameter, but other later-coming species with a larger number of individuals displayed a typical reverse J-shaped distribution. Our results suggest that both thinning and mixed planting may promote species diversity and structure over a long timescale, but thinning achieves these characteristics earlier because thinning directly manipulates structure in a way that accelerates stand development.

New allometric equations for quantifying tree biomass and carbon sequestration in seasonally dry secondary forest in northern Thailand

Abstract: As tropical deforestation and forest degradation accelerate, carbon-credit trading could provide a financial incentive to preserve and regenerate forests. Since carbon trading relies on the accurate quantification of carbon stocks, allometric equations are urgently needed to derive above-ground dry biomass (AGB) from easily measured variables. Few allometric equations have been published for regenerating secondary forests in Southeast Asia. This study established new allometric equations, to determine AGB and carbon in regenerating secondary forests on shifting cultivation fallows in northern Thailand. To develop the equations, data were collected from 78 trees (136 felled individual stems, including coppices) ranging in size from 1 to 32.9 cm diameter at breast height (D). The dependent variable was AGB. The independent variables were D, tree height (H) and wood density (WD). Wood density varied significantly among species (p < 0.05). Consequently, including WD in the function D2H × WD predicted AGB most accurately, compared with other functions that excluded it. Mean carbon concentration in stems, branches, and leaves was 44.84% ± 1.63 of dry mass, but it varied significantly among tree species (p < 0.05). The new allometric equation revealed that tree ABG was highest in secondary forest, followed by the 7-year-fallow and the 4-year-fallow: 105.3, 38.3 and 10.3 Mg ha−1, respectively, while above-ground carbon was 47.7, 17.4, and 4.6 Mg C ha−1, respectively. Natural regeneration accumulated carbon slower than reported for active restoration, suggesting that managed restoration is preferable to passive regeneration on fallows in northern Thailand. The allometric equations, derived from this study, can be used to accurately determine tree ABG and carbon storage in regenerating secondary forest, with higher precision than has hitherto been possible, thus satisfying the monitoring requirements of REDD+ and other carbon-trading schemes.

Large-scale historical afforestation failure with Pinus cembra in the Swiss Prealps

Abstract: Between the nineteenth and early twentieth centuries, large-scale afforestation projects were undertaken in the Swiss Prealps. The Swiss stone pine (Pinus cembra L.), an emblematic alpine tree with important economic potential, conservation value and ecological relevance, was one of the species used in these afforestation efforts. We investigated the distribution and site characteristics of all known natural populations and planted stands in the canton of Fribourg (Switzerland). Between 1885 and 1952, artificial afforestation was carried out in the mountainous regions of the canton of Fribourg. Nearly 450,000 seedlings of P. cembra were planted. One century later, only approximately 650 trees survived (0.15% of all planted trees). Moreover, no natural regeneration can be observed in the afforested stands. Since no known harvest activities were undertaken in these planted stands, the whole afforestation campaign of P. cembra in the canton of Fribourg can be described as a failure. Possible causes are investigated and discussed. In this region, P. cembra occurs naturally only in particular microrefugia with markedly rough topography. We argue that the lack of knowledge or consideration of the ecology of the species at a local scale can be an important factor leading to this failure. In the actual context of large-scale afforestation projects anticipating and mitigating the negative effects of global warming, our study highlights the importance of a precise understanding of species ecology and regional conditions.

Recycled alkaline paper waste influenced growth and structure of Pinus taeda L. forest

Abstract: Alkaline residues of recycled paper production (ARRP) can be an alternative for correcting soil acidity and adding bases to Pinus taeda L. systems. Our aim was to investigate the effect of increasing doses of ARRP on tree, forest floor (litter and root), and soil composition in a 3-year-old Brazilian pine forest plantation. In 2007, ARRP treatments of 0, 10, 20, 30 and 40 T ha−1 were imposed. Tree growth and needle elemental composition were evaluated in 2008 and 2018; elemental composition of the trunk was evaluated in 2018. In 2017, accumulation and composition of litter layers were assessed: new litter, old litter, first and second sublayers of fragmented litter (Fr and Fm), and the humified layer (H); roots present in F and H layers were quantified (amount and elemental composition). In addition, soil chemical properties at different depths were evaluated in 2008, 2012, and 2017. The application of ARRP improved growth by ~ 16% up to 20 T ha−1 after 10 years. Also, ARRP increased Ca concentration in needles, trunks, roots, and all litter fractions since Ca was a major component of ARRP. There was no change in total litter accumulation with ARRP application, but an increase in the humidified fraction was observed. Root growth was enhanced by ARRP, leading to great changes in root composition in Fr and H fractions. Changes in soil pH, Ca2+, and Al3+ were observed in the 0–10 cm soil layer. Findings suggest that application of ARRP to established pine forests has the potential for improving productivity.

Intraspecific variability in cold tolerance in Pinus brutia sampled from two contrasting provenance trials

Abstract: Turkish red pine (Pinus brutia Ten.), is the most important tree species for afforestation in the Mediterranean basin due to its drought tolerance and fast growth rate. Cold damage to trees caused by harsh winter conditions is common on many sites in Turkey. Adaptation to climate change has been investigated primarily through the movement of species from warmer and drier climates, such as the Mediterranean P. brutia, to higher latitudes and cooler sites in central-north Turkey. In order to better guide species and provenances movement to new (and often harsh) environments for afforestation, the limits of tolerance to cold and drought should be better known. Thus, we designed an experiment to quantify the cold hardiness of nine P. brutia provenances originating from two different provenance trials in Turkey (Ankara, cold inner site; Antalya, warm Mediterranean site). Branches sampled at the end of January were exposed to cold temperatures between − 5 and − 40 °C. Visual damage observation, relative electric leakage and chlorophyll fluorometry (CF) screening methods were used to assess variation in cold hardiness among populations. Overall, P. brutia can tolerate winter temperatures up to − 16 °C. Even though there were significant differences on cold hardiness among populations, the operational application is limited due to the reduced magnitude of those differences. Measuring CF was the fastest and most easily replicated method to estimate cold hardiness and was as reliable as REL. We recommend that P. brutia should not be planted in cold areas where minimum annual temperatures are under − 16 °C. We also conclude that even though phenotypic plasticity exists for cold hardiness among the tested populations of P. brutia, the observed differences resulted from acclimation to the conditions of the provenance trial sites rather than from adaptation through natural selection.

From facilitation to competition: the effect of black locust (Robinia pseudoacacia L.) on the growth performance of four poplar-hybrids (Populus spp.) in mixed short rotation coppice

Abstract: Short rotation coppices play an important role in providing biomass for energetic use. Mixing fast-growing tree species in short rotation coppices may show complementarity effects and increased yield. The aim of this study was to analyze the effect of species interaction in mixed short rotation coppices with fast-growing Populus spp.-hybrids and the N-fixing Robinia pseudoacacia. Four different Populus-hybrids (AF2, Fritzi Pauley, Hybride 275 and Max 1), planted alternately in pure and mixed stands with R. pseudoacacia were used for the analysis. Height and root collar diameter were measured once a year, over a period of four years (2014–2017). Additionally, in the third year, aboveground competition was surveyed with a terrestrial laser scanner and root biomass was analyzed to assess belowground competition. Soil nitrogen was also determined in order to verify enrichment properties of mixtures compared to pure stands. Populus-hybrids’ stem volume showed no significant differences between stand types in the first year after planting. In the second and third year, however, two Populus-hybrids (AF2 and Max 1) had a higher stem volume increment of up to 3.8 times than stem volume increment in pure stands. This may be related to the fact that soil nitrogen was 39% higher in the mixtures than in pure stands. However, in the 4th year after stand establishment, R. pseudoacacia’s crowns were so massive and broad, that this species was far more competitive than the Populus-hybrids. With the exception of P. ‘Fritzi Pauley’, which showed no significant differences between stand types, growth rates reversed for the other three Populus-hybrids. AF2, Max 1 and Hybride 275 showed up to 75% lower stem volume increment in mixtures compared to pure stands. We assume that, in spite of the initially observed facilitation between the species, the competition exerted by R. pseudoacacia started dominating after 4 years and began to surpass the benefits of facilitation.

Nitrogen loading of Eucalyptus globulus seedlings: nutritional dynamics and influence on morphology and root growth potential

Abstract: Achieving successful outplanting of trees on increasingly harsher sites is a global concern. In Chile, for example, new Eucalyptus globulus plantations are being targeted to poorer, low fertility sites where additional stresses often negatively affect seedling performance during the first field season. Nitrogen-loading during the later stages of nursery production can, however, significantly improve seedling physiological performance on harsher sites by increasing plant growth and nutrient storage reserves for subsequent root growth after outplanting. Maximizing these benefits, and applying the concept of loading throughout the entire crop cycle, requires a better understanding of nitrogen (N) dynamics. Thus, for container E. globulus, considered one of the most important plantation species worldwide, we evaluated the effects of increasing N supply (50 to 600 mg N L−1) on seedling morphological traits, biomass production, root growth potential, and foliar N. After 15 weeks of N application, seedlings showed an increase in all growth variables evaluated up to 300 mg N L−1, whereas higher rates allowed luxury consumption. Modeling growth responses revealed, however, an apparent ammonium antagonism with other macronutrient cations suggests that high rates of this N-form may negate the potential benefits of N-loading, or that other modifications to the fertilizer solution may promote additional growth at higher N rates. Foliar N concentration, which was easily and accurately measured with a leaf chlorophyll meter, showed a gradient from basal to apical leaves suggesting a strong translocation of N in E. globulus seedlings. Our results suggest nursery management that supplies 300 mg L−1 of N through the entire growing season could improve seedling nutritional status, morphological attributes, and growth of new roots, attributes that may improve establishment on low fertility sites.

Pinus pseudostrobus assisted migration trial with rain exclusion: maintaining Monarch Butterfly Biosphere Reserve forest cover in an environment affected by climate change

Abstract: In the Trans-Mexican Volcanic Belt in central-western Mexico, drought stress causes the decline of two of the most ecologically and economically important conifers: Abies religiosa and Pinus pseudostrobus. Since P. pseudostrobus is distributed immediately below the lower elevation limit of A. religiosa, it would be a logical choice of species to fill gaps that may be created by the decline of A. religiosa. We assessed the feasibility of upward assisted migration and explored the effect of rain reduction using four P. pseudostrobus provenances in a rain exclusion field test at the border of the Monarch Butterfly Biosphere Reserve (MBBR) in Mexico. Our results show that, although populations were transferred between − 1.4 and − 3.3 °C mean annual temperature, and 30% of the precipitation (− 200 mm) was excluded, no statistically significant differences were found among treatments or populations for height increment (overall average 1.52 m) or survival (overall average 87%). These findings suggest that it is feasible to migrate P. pseudostrobus upward, towards the MBBR border, which also coincides with the sites where A. religiosa is in decline. This may present the additional benefit of discouraging change in land use from forestry to potato production by maintaining a healthy barrier of trees. If assisted migration is not included in management and reforestation programs, climate change could induce significant mortality in the present A. religiosa forest, facilitating expansion of the agricultural frontier toward the MBBR.

Instrinsic relationship among needle morphology, anatomy, gas exchanges and tree growth across 17 Picea species

Abstract: The genus Picea has wide geographical range and includes species with great economic and ecological value in the northern hemisphere. Growth traits, gas exchange parameters and needle morphology and anatomy vary greatly among Picea species, but the instrinsic relationship among these traits has not been well studied for the genus Picea. We thus conducted a common garden experiment to study the relationship for these traits in 13 native and 4 exotic Picea species growing at an experimental site in Tianshui, Gansu, China. Nearly all of these traits were significantly different among the 17 species and most traits were under relatively strong genetic control. The four species introduced from abroad (P. abies, P. pungens, P. glauca and P. mariana) exhibited good growth performance in the experimental site. We found that the growth traits showed significantly positive correlation with branching characteristics. Moreover, the species with good growth performance had a relatively high photosynthetic rate. The correlation analysis based on needle morphological and anatomical traits revealed that needle traits were interrelated and needle anatomical traits might be impacted by needle size due to the increase of mesophyll area and central cylinder area with needle length. Furthermore, the relationship between needle structures and gas exchange parameters may indicate that a higher photosynthetic rate can be attributed to variations in needle structures. In addition, both the cluster analysis and principal component analysis based on needle morphology, anatomy, gas exchanges and growth traits might partially reflect the evolutionary history of the 17 Picea species. Our study represents a comprehensive survey of variation within the genus Picea to date and opens new avenues for exploring the instrinsic relationship among growth traits, needle gas exchange and needle morphology and anatomy.

Drought resistance and gum yield performances in a Senegalia senegal (L.) Britton progeny trial in Senegal

Abstract: With continued global change as a result of land use changes, invasive species and changing climatic patterns, it is becoming increasingly important to understand the adaptability of Senegalia senegal provenances to maximize resilience in managed and natural populations of this species. The objective of this study is to investigate Senegalia senegal genotypic differences in water use efficiency (WUE) measured by stable 13C isotope composition in foliage according to their ploidy levels. Secondary objectives are to discuss inherent adaptive variation related to soil pH, survival, growth indexes, gum arabic yield and WUE within provenance in the climate change context. A Senegalia senegal progeny trial, in Dahra, Senegal was used in this study: 443 adult trees consisting of 60 families nested within 4 provenances were assessed in this study. Results showed significant differences in gum yield among provenances (P = 0.0002) and families (P < 0.0001). Diamenar and Ngane provenances showed overall similar annual gum yield despite a lower tree survival rate of Ngane than Diamenar. Growth traits, especially stem volume index and crown area index were larger on Ngane provenance, which also displayed significantly higher foliar WUE and lower leaf area index (LAI) than the other provenances. WUE was positively correlated with gum yield (P = 0.0302), but the coefficient of determination was only 2%. Foliar δ13C varied significantly (P < 0.0001) between diploids (− 27.91‰) and polyploids (− 27.12‰). However, within each provenance no significant difference was found. Only 15% of isotope compositions could be explained by ploidy level variation. Differences found in growth and gum yield may be attributed to genotype-specific variation. However, a significant correlation between soil pH and tree survival rate was found (P = 0.0051; r = 0.60). This study confirmed a possible improvement of the gum arabic sector through genotype based selection. Ngane and Diamenar seem to be more profitable to grow in Dahra than the other tested provenances. Future research should investigate the effect of soil pH, other soil physical and chemical properties, and management activities to improve site quality on tree survival and gum yields among provenances. Further, more research is needed to clarify inherent traits underlying drought tolerance in the field and gum yield performance.

Prediction of the suitable distribution of Eucalyptus grandis in China and its responses to climate change

Abstract: Assessment of potentially suitable geographic areas in China and their response to climate change can provide a reference for sustainable development of Eucalyptus grandis plantations Under current and future conditions, the potentially suitable areas for this species were predicted using MaxEnt modelling from known successful plantings of E grandis in China The dominant environmental factors affecting the distribution of E grandis and ecological similarities between the species’ natural distribution in Australia and the suitable areas in China were analysed Results show that the majority of the highly suitable areas identified for E grandis in China are concentrated in the Sichuan Basin and southeastern hilly regions Under future climate scenarios, the most suitable area for E grandis is expected to increase through to the 2070s The distribution of suitable areas in the Sichuan Basin are predicted to expand eastward to lower elevations, and suitable areas in China’s southeastern hilly regions would move to areas experiencing high solar radiation and lower seasonal temperature variances The dominant ecological factors affecting the distribution of E grandis were found to be: solar radiation, altitude, seasonal temperature and precipitation variance, maximum temperature of the warmest month, annual mean temperature, slope, isothermality, soil available water content, precipitation in the driest quarter and mean diurnal temperature range Collectively, these factors account for over 851% of the variation in suitable areas Compared with the species’ natural distribution in Australia, suitable areas in China feature higher precipitations during the driest quarters; a condition favourable to rapid growth of E grandis