Silvicultural Systems for Restoration of Mahogany in Degraded Landscapes in Africa: Influence of Mixed Rainforest Plantation on Growth and Pest Damage

African mahogany, one of the world’s most valuable timber species is threatened by over-exploitation in natural forests and failure of plantations due to attacks by the shoot borer Hypsipyla robusta. Mixed-species plantations has been reported to be an effective component of integrated pest management of major pest in other crops;but there is very limited empirical data on its use for managing Hypsipyla in mahogany mixed stands in West Africa. The aim of this study was to assess the effect of mixed-species stands as management intervention, on the growth of Khaya grandifoliola and Khaya ivorensis in relation to Hypsipyla robusta attack in a 10 ha experimental plantation in the wet evergreen forest type in Ghana. Khaya grandifoliola recorded faster growth than Khaya ivorensis in this forest type though the later naturally grow in this forest type while the former is introduced from the dry forest. Two years after planting, diameter and height growth were greater in the mixed-species stand than the pure stands for K. grandifoliola and K. ivorensis. Hypsipyla damage was less in the mixed stands of both K. grandifoliola and K. ivorensis compared to the pure stands, with the 20% and 10% Khaya mixed stand recording the lowest attack in both species. It can be recommended that mixed stands of the two Khaya species at 20% or lower Khaya density might be ideal for reducing the levels of Hypsipyla attack in this type of forest.

Evaluation of deriving fire cycle of forested landscape based on time-since-fire distribution

Estimation of fire cycle has been conducted by using the negative exponential function as an approximation of time-since-fire distribution of a landscape assumed to be homogeneous with respect to fire spread processes. The authors imposed predefined fire cycles on a virtual landscape of 100 cell ×100 cell, and obtained a mosaic composing of patches with different stand ages (i.e. time since fire). Graphical and statistical methods (Van Wagner 1978; Reed et al. 1998) were employed to derive fire cycle from the virtual landscape. By comparing the predefined and the derived fire cycles, the two methods and tested the effects of sample size and hazard of burning (i.e., stand’s susceptibility to fire in relation to its stand age) were evaluated on fire cycle deviation. The simulation results indicated a minimum sample size of 10 times of the annual burnt area would be required for partitioning time-since-fire distribution into homogeneous epochs indicating temporal change in fire cycle. Statistically, there was significant difference among the imposed and the derived fire cycle, regardless of sample sizes with or without consideration of hazard of burning. Both methods underestimated the more recent fire cycle without significant difference between them. The results imply that deviation of fire cycle based on time-since-fire distribution warrants cautious interpretation, especially when a landscape is spatially partitioned into small units and temporal changes in fire cycle are involved.

High-quality de novo assembly of the Eucommia ulmoides haploid genome provides new insights into evolution and rubber biosynthesis

We report the acquisition of a high-quality haploid chromosome-scale genome assembly for the first time in a tree species,Eucommia ulmoides,which is known for its rubber biosynthesis and medicinal applications.The assembly was obtained by applying PacBio and Hi–C technologies to a haploid that we specifically generated.Compared to the initial genome release,this one has significantly improved assembly quality.The scaffold N50(53.15 MB)increased 28-fold,and the repetitive sequence content(520 Mb)increased by 158.24 Mb,whereas the number of gaps decreased from 104,772 to 128.A total of 92.87%of the 26,001 predicted protein-coding genes identified with multiple strategies were anchored to the 17 chromosomes.A new whole-genome duplication event was superimposed on the earlierγpaleohexaploidization event,and the expansion of long terminal repeats contributed greatly to the evolution of the genome.The more primitive rubber biosynthesis of this species,as opposed to that in Hevea brasiliensis,relies on the methylerythritol-phosphate pathway rather than the mevalonate pathway to synthesize isoprenyl diphosphate,as the MEP pathway operates predominantly in trans-polyisoprene-containing leaves and central peels.Chlorogenic acid biosynthesis pathway enzymes were preferentially expressed in leaves rather than in bark.This assembly with higher sequence contiguity can foster not only studies on genome structure and evolution,gene mapping,epigenetic analysis and functional genomics but also efforts to improve E.ulmoides for industrial and medical uses through genetic engineering.

The Relationship of the Sapstreak Fungus, <i>Ceratocystis virescens</i>, to Sugar Maple Dieback and Decay in Northern Michigan

Unusually high levels of dieback have recently been reported in sugar maple, Acer saccharum Marsh., in Upper Michigan, and a network of plots was established to determine the extent and factors associated with the dieback. A possible contributor to this dieback is sapstreak disease caused by Ceratocystis virescens (Davidson) Moreau. Unhealthy trees with considerable crown dieback were evaluated across the western Upper Peninsula, MI to determine the prevalence of the sapstreak fungus using a minimally destructive sampling technique. Approximately 8% of 90 trees sampled were sapstreak positive and approximately 10% of trees were positive at one site that had recently been harvested. While the high levels of maple dieback present in these forests appear not to be directly caused by widespread sapstreak disease, the occurrence of sapstreak may be significantly impacting trees at some locations. However, even when present on a low number of trees, the biointeraction of sapstreak and decay rates from other fungi could be important for future tree mortality and value to the forest industry. Therefore, the effect of two sapstreak fungal isolates on the amount of decay caused by two common maple white rot fungi, Trametes versicolor (L.:Fr.) Pilat. And Irpex lacteus (Fr.:Fr.) Fr. was tested in the laboratory. Sugar maple wood blocks were precolonized by two native isolates of C. virescens followed by inoculation and incubation with decay fungi. Mean percent weight loss of blocks by white rot decay fungi ranged from 39% to 55%, but decay rates were not significantly affected by the presence of the sapstreak fungus.

Assessing the Efficacy of Two Indirect Methods for Quantifying Canopy Variables Associated with the Interception Loss of Rainfall in Temperate Hardwood Forests

Forest canopy water storage (S), direct throughfall fraction (p) and mean evaporation rate to mean rainfall intensity ratio (E/R) vary between storms and seasonally. Typically, researchers only quantify the mean growing and dormant season values of S, p and E/R for deciduous forests, thereby ignoring seasonal changes S, p and E/R .Past researchers adapted the mean method, which is usually used to estimate S, p and E/R on an annual or seasonal basis, to estimate the same canopy variables on a per storm basis (individual storm (IS) method). The disadvantage of the IS method is that it requires more expensive equipment and the calculation of the canopy variables is more labor intensive relative to the mean method. The goal of this study was to explore the use of the IS method for northern hardwood forests and to determine whether estimates of S, p and E/R derived by the IS method produce more accurate estimates of rainfall interception loss (In) using the Gash model relative to estimates derived by the mean method. The IS method estimated that S increased from approximately 0.11 mm in the early spring to 1.2 mm in the summer and then declined to 0.24 mm after fall senescence. Direct throughfall decreased from 0.4 in the early spring to 0.11 in the summer, and then increased to 0.4 after leaf senescence. When measurement period estimates of p, S and E/R derived by the IS and mean methods were applied to the Gash model, the modeled estimates of In differed from the measured values by 14.0 mm and 1.3 mm, respectively. Therefore, because the mean method provided more accurate estimates of In, the extra effort and expense required by the IS method is not advantageous for studies in northern hardwood forests that only need to model annual or seasonal estimates of In.

Estimated Carbon Sequestration in a Temperate Forest in Idaho of USA

Assessing carbon (C) sequestration in forest ecosystems is fundamental to supply information to monitoring, reporting and verification (MRV) for reducing deforestation and forest degradation (REDD). The spatially-explicit version of Forest-DNDC (FDNDC) was evaluated using plot-based observations from Nez Perce-Clearwater National Forest (NPCNF) in Idaho of United States and used to assess C stocks in?about 16,000 km2. The model evaluation indicated that the FDNDC can be used to assess C stocks with disturbances in this temperate forest with a proper model performance efficiency and small error between observations and simulations. Aboveground biomass in this forest was 85.1 Mg C ha-1 in 2010. The mean aboveground biomass in the forest increased by about 0.6 Mg C ha-1 yr-1 in the last 20 years from 1990 to 2010 with spatial mean stand age about 98 years old in 2010. Spatial differences in distributions of biomass, net primary production and net ecosystem product are substantial. The spatial divergence in C sequestration is mainly associated with the spatial disparities in stand age due to disturbances, secondly with ecological drivers and species. Climate variability and change can substantially impact C stocks in the forest based on the climatic variability of spatial climate data for a 33-year period from 1981 to 2013. Temperature rise can produce more biomass in NPCNF, but biomass cannot increase with an increase in precipitation in this forest. The simulation with disturbances using observations and estimates for the time period from 1991 to 2011?showed the effects of disturbances on C stocks in forests. The impacts of fires and insects on C stocks in this forest are highly dependent on the severity, the higher, the more C loss to atmosphere due to?fires, and the more dead woods produced by fires and insects. The rates of biomass increase with an increase in stand age are different among the species. The changes in forest C stocks?in the forest are almost species specific, non-linear and complex. The increase in aboveground biomass with an increase in stand age can be described by a high-order polynomial.

Transferability and application of microsatellites(SSRs)from Juniperus communis L.to Juniperus procera Hochst.Ex endl.

Transferability of five nuclear microsatellite markers (Jc-16, Jc-31, Jc-32, Jc-35 and Jc-37) that were originally developed for J. communis was tested to J. procera. Jc-31 & Jc-37 showed successful amplifications and polymorphism in J. procera. Jc-35 which had been reported as polymorphic in J. communis was monomorphic in J. procera while the primer pair for Jc-32 failed to record any amplification. The remaining one primer pair (Jc-16) showed double loci ampli-fication in both J. procera and the control J. communis suggesting further examination of the primer pair and its binding sites. Genetic variation of six Ethiopian J. procera populations: Chilimo, Goba, Menagesha-Suba, Wef-Washa, Yabelo and Ziquala was assessed based on the two polymorphic loci (Jc-31 & Jc-37) in 20 - 24 individuals of each population. From these two loci, a total of 41 alleles could be retrieved. Two populations that are located south east of the Great Rift Valley together harboured 75% of private alleles signifying their deviant geo-ecological zones and suggesting special consideration for conservation. Chilimo, which is at the western margin of Juniper habitat in Ethiopian central highlands scored the highest fixation (FIS = 0.584) entailing lower immigrant genes and hence higher inbreeding. The AMOVA revealed that 97% of the variation resided within the?population while still among population variation was significant

Linking tree growth rate, damage repair, and susceptibility to a genus-specific pest infestation

Pest preference and subsequent susceptibility of a host individual is likely related to previous growth patterns in that host.Emerald ash borer(Agrilus planipennis Fairmaire)is a pestiferous beetle introduced to North America from Asia.While all species of ash are susceptible to attack,some individual trees appear to survive infestation.We selected ash trees in southeastern Michigan,collected cores and categorized trees as high tolerance to emerald ash borer attack(high overall health,low crown dieback),low tolerance(low overall health,high crown dieback)and intermediate tolerance(in-between the other categories).We artificially wounded trees and measured wound closure after 3 years.Ring width indices were not correlated between high and low tolerance trees.Regression slopes comparing growth and years were significantly different between the three tolerance categories,with high tolerance trees having the steepest slope.Wound closure was greatest in high tolerance trees.High tolerance trees demonstrating more rapid(steeper regression slope),consistent(lower variance),and effective(greater wound closure)growth.Those vigorously growing trees likely had more capacity to repair damage caused by emerald ash borer,leading to healthier trees in our categorization.Linking previous host growth patterns to health may have implications related to identifying individual trees potentially tolerant to attack.

Forest Management Plans in Los Planes de La Palma, El Salvador

Fourteen farmers with small woodlots were interviewed about the forest management plans promoted by the government of El Salvador. As expected, farmers managed for many utilitarian products such as firewood and timber, but the farmers also expressed a strong set of environmental concerns revolved around the ecological value of their woodlots. Farmers generally approved of forest management plans as they saw how plans contributed to sustainable forestry on their woodlots. Farmers had concerns about specific silvicultural practices and about transportation of harvested timber.

Herbaceous-Layer Community Dynamics along a Harvest-Intensity Gradient after 50 Years of Consistent Management

In 1958, a demonstrational cutting trial totaling 22.2 ha was established in a northern hardwood forest in Alberta, MI. Eight different treatments were installed, including four diameter-limit treatments (56 cm, 41 cm, 30 cm, and 13 cm), three single-tree selection treatments with residual basal areas of 21 m2·ha–1, 16 m2·ha–1, and 11 m2·ha–1, and an uncut control. Within each treatment, a 0.4-ha permanent plot was established and subdivided into 0.04-ha square subplots. Harvests have been implemented every ten years with the most recent harvest occurring during the winter of 2008 - 2009. We quantified ground layer vegetation response before and after the most recent harvest. Nonmetric multidimensional scaling (NMS) ordination showed a very distinct separation between the most intensive management treatment (13-cm diameter-limit treatment) and the uncut control. Compositionally, the diameter-limit treatments moved with greater directionality and magnitude towards the 13-cm diameter-limit treatment following harvest, while compositional change in the residual basal area treatments was less pronounced and lacked strong directionality. Herbaceous species percent cover generally decreased with increasing residual overstory basal area across treatments. Weedy and early successional species were most abundant under lower residual basal area and diameter-limit treatments. Results based on 50 years of continuous management suggest that diameter-limit harvests likely have a greater impact on the herbaceous community than single-tree selection or no management.

Soil moisture, field-scale toposequential position, and slope effects on yields in irrigated rice (<i>Oryza sativa</i>L.) fields in Honduras

Rice (Oryza sativa L.) is an important cash crop in Honduras. The availability of inexpensive irrigation in the study area (Flores, La Villa de San Antonio, Comayagua) encourages rice farmers to neglect prescribed methods of soil and water conservation, such land leveling, puddling, and soil bunds. This study looked at the effect of failure to mitigate water loss on sloping fields. Soil moisture (Volumetric Water Content) was measured using a soil moisture probe after the termination of the first irrigation within the tillering/vegetative, panicle emergence/flowering, post-flowering/pre-maturation and maturation stages. Yield data were obtained by harvesting on 1 m2 plots in each soil moisture testing site. Data analyses looked at the relationship between yield and slope, soil moisture, farmers, and toposequential position along transects. Toposequential position influenced yields more than slope and soil moisture was not a significant predictor of yields. Irrigation politics, high water inputs, and land tenure were proposed as the major reasons for this result.

Small-Scale Spatial Patterns of <i>Copernicia alba</i>Morong near Bahia Negra, Paraguay

We assessed the spatial distribution of Copernicia alba Morong. In the study area, a lowland palm savanna floodplain, C. alba is the only overstory species. We hypothesized C. alba would be randomly distributed within natural stands. Palms were tallied in six randomly located 0.25 haplots and analyzed using a first-order, Ripley’s K function to assess the distribution of juvenile, adult, and total palm populations. While the total population had either aggregated or random distributions, when analyzing juvenile and adult population separately, we found juveniles were consistently more aggregated than the adults.

Improved Heat FT Induction Leads to Earlier and More Prolific Flowering in Poplar

Trees have a long juvenile phase before reproductive onset.This makes their breeding and studying floral development difficult.Precocious flowering using FT technology has shown promise.However,transgenic FT overexpression has significant negative pleiotropic effects.Hence,there has been interest in inducible FT expression for flower induction.Previously reported heat inducible expression of FT in poplar successfully induced flowering.However,flowering was sporadic and took up to 6 weeks.Here we report improvements in the protocol,which led to faster and more prolific flowering.Specifically,we increased the once to three times daily heat treatment.The repeated heat inductive treatments led to nearly five times higher FT expression,compared to the single daily treatment.The highly increased FT expression led to significant acceleration and abundance of flowering.

The Local Migration of Plant-Based Medicines from Rural Communities to Gral. E. Aquino, Paraguay

Rural Paraguay presents interesting opportunities for investigating the subtle differences in the use of medicinal plants across seasons and the urban versus rural dichotomy in a local setting. This study investigates three aspects of plant-based medicinal use in rural Paraguay: 1) seasonal differences and 2) differences between urban and rural residents and 3) the source of medicinal plants used to treat thirteen common ailments. Interviews performed in January through March 2015 and repeated in June through August 2015 revealed small differences between seasons and between places of residence but a larger homogeneity in the two populations, a homogeneity that stems from the recent migration of urban residents from nearby rural communities. We also found that the important cultural and preventive medicinal use of plant-based additions to yerba mate contributes to the similarities between the urban and rural populations. The findings suggest the continued strength of medicinal plant use going into the near future.

A Resource for Inactivation of MicroRNAs Using Short Tandem Target Mimic Technology in Model and Crop Plants

microRNAs (miRNAs)are endogenous small non-coding RNAs that bind to mRNAs and target them for cleavage and/or translational repression,leading to gene silencing.We previously developed short tandem target mimic (STTM)technology to deactivate endogenous miRNAs in Arabidopsis.Here,we created hundreds of STTMs that target both conserved and species-specific miRNAs in Arabidopsis,tomato,rice,and maize,providing a resource for the functional interrogation of miRNAs.We not only revealed the functions of several miRNAs in plant development,but also demonstrated that tissue-specific inactivation of a few miRNAs in rice leads to an increase in grain size without adversely affecting overall plant growth and development.RNA-seq and small RNAseq analyses of STTM156/157 and STTM165/166 transgenic plants revealed the roles of these miRNAs in plant hormone biosynthesis and activation,secondary metabolism,and ion-channel activity-associated electrophysiology,demonstrating that STTM technology is an effective approach for studying miRNA functions.To facilitate the study and application of STTM transgenic plants and to provide a useful platform for storing and sharing of information about miRNA-regulated gene networks,we have established an online Genome Browser (https://blossom.ffr.mtu.edu/designindex2.php) to display the transcriptomic and miRNAomic changes in STTMinduced miRNA knockdown plants.

Adjustment of Forest Ecosystem Root Respiration as Temperature Warms

Adjustment of ecosystem root respiration to warmer climatic conditions can alter the autotrophic portion of soil respiration and influence the amount of carbon available for biomass production. We examined 44 published values of annual forest root respiration and found an increase in ecosystem root respiration with increasing mean annual temperature （MAT）, but the rate of this cross-ecosystem increase （Q10 = 1.6） is less than published values for short-term responses of root respiration to temperature within ecosystems （Q10 = 2-3）. When specific root respiration rates and root biomass values were examined, there was a clear trend for decreasing root metabolic capacity （respiration rate at a standard temperature） with increasing MAT. There also were tradeoffs between root metabolic capacity and root system biomass, such that there were no instances of high growing season respiration rates and high root biomass occurring together. We also examined specific root respiration rates at three soil warming experiments at Harvard Forest, USA, and found decreases in metabolic capacity for roots from the heated plots. This decline could be due to either physiological acclimation or to the effects of co-occurring drier soils on the measurement date. Regardless of the cause, these findings clearly suggest that modeling efforts that allow root respiration to increase exponentially with temperature, with Q10 values of 2 or more, may over-predict root contributions to ecosystem CO2 efflux for future climates and underestimate the amount of C available for other uses, including net primary productivity.

Enhancement of Superoxide Dismutase and Catalase Activities and Salt Tolerance of Euhalophyte Suaeda salsa L. by Mycorrhizal Fungus Glomus mosseae

Arbuscular mycorrhizal (AM)-mediated plant physiological activities could contribute to plant salt tolerance. However, the biochemical mechanism by which AM fungi enhance salt tolerance of halophytic plants is unclear. A pot experiment was conducted to determine whether salt tolerance of the C 3 halophyte Suaeda salsa was enhanced by the AM fungus Glomus mosseae. When 60-day-old S. salsa seedlings were subjected to 400 mmol L-1 NaCl stress for 35 days, plant height, number of leaves and branches, shoot and root biomass, and root length of G. mosseae-colonized seedlings were significantly greater than those of the nonmycorrizal seedlings. Leaf superoxide dismutase (SOD) activity at all sampling times (weekly for 35 days after salt stress was initiated) and leaf catalase (CAT) activity at 2 and 3 weeks after salt stress was initiated were also significantly enhanced in G. mosseae-colonized S. salsa seedlings, while the content of leaf malondialdehyde (MDA), a product of membrane lipid peroxidation, was significantly reduced, indicating an alleviation of oxidative damage. The corresponding leaf isoenzymes of SOD (Fe-SOD, Cu/Zn-SOD1, and Cu/Zn-SOD2) and CAT (CAT1 and CAT2) were also significantly increased in the mycorrhizal seedlings after 14 days of 400 mmol L-1 NaCl stress. Our results suggested that G. mosseae increased salt tolerance by increasing SOD and CAT activities and forming SOD and CAT isoforms in S. salsa seedlings.

Climate-driven acceleration of glacier mass loss on global and regional scales during 1961–2016

During the past decades, glacier mass loss is becoming increasingly significant worldwide but knowledge about the acceleration is still limited despite its potentially profound impacts on sea level rise, water resources availability and glacial hazards. In this study, we analyzed the acceleration of glacier mass loss based on in-situ measurements and on the latest compilation dataset of direct and geodetic observations for the period 1961–2016. The results showed that the rate of glacier mass loss has increased worldwide during the past decades. At the global scale, the rate of glacier mass loss has been accelerating at 5.76±1.35 Gt a-2 as well as 0.0074±0.0016 m w.e.a-2 on mass balance(refer to the area-averaged mass change value) during the whole period. At regional scales, for mass change rate, the heavily glacierized regions excluding Antarctic and Subantarctic exhibited a larger acceleration compared to other regions. The highest acceleration of mass change was found in Alaska glaciers(1.33±0.47 Gt a-2) over the full period. As for mass balance, high acceleration occurred on the regions with small glaciers as well as on the heavily glacierized regions. Central Europe exhibited the highest acceleration(0.024±0.0088 m w.e.a-2) during 1961–2016. High level of consistency between the acceleration and temperature implies that climate warming had a significant effect on the accelerating of glacier mass loss. Moreover, acceleration of the contribution from the Greenland ice sheet(0.028 to0.070 mm a-2) and Antarctic ice sheet(0.023 to 0.058 mm a-2) to sea level rise exceeds acceleration of the contribution from global glaciers(0.019±0.013 mm a-2). These results will improve our understanding of the glacier retreat in response to climate change and provide critical information for improving mitigation strategies for impacts that may be caused by glacier melting.

Effective enrichment of Zn from smelting wastewater via an integrated Fe coagulation and hematite precipitation method

Coagulation is commonly applied to treat Zn-bearing wastewater from smelting industries(smelting wastewater),and thus the Zn-bearing sludge was considerably produced,which should be solidified before safety disposal.Herein,we demonstrated a novel approach to recycle Zn effectively from smelting wastewater via an integrated Fe coagulation and hematite precipitation method.First,smelting wastewater was coagulated by adding ferric chloride to generate Fe/Zn-bearing sludge(sludge for short).Secondly,the sludge was dissolved to generate an acid solution containing 2.2 g/L of Zn and 39.2 g/L of Fe.Thirdly,the Fe/Zn-bearing solution was hydrothermally treated,and 89%of Fe was eliminated to highly purified hematite block,whereas the percentage of Zn lost was below 1.1%.Finally,the hematite precipitates were collected,and the supernatant was hydrothermally treated again with the addition of glucose.When the molar ratio of glucose to Fe in the supernatant was 1.5,over 99.5%of Fe was precipitated in hematite nanoparticles with a diameter of 10-100 nm,and the residual Fe was 21.5 mg/L.The loss of Zn was below 0.4%,and the residual Zn in the solution was 2169 mg/L,290 times of that in the smelting wastewater.The major mechanism for Fe removal was the hydrolysis of ferric nitrate into hematite,which was promoted by nitrate consumption in glucose oxidation.This paper is the first report of an environment-friendly method for enriching Zn without generating any waste.

Virus-Induced Gene Silencing Offers a Functional Genomics Platform for Studying Plant Cell Wall Formation

Virus-induced gene silencing （VIGS） is a powerful genetic tool for rapid assessment of plant gene functions in the post-genomic era. Here, we successfully implemented a Tobacco Rattle Virus （TRV）-based VlGS system to study functions of genes involved in either primary or secondary cell wall formation in Nicotiana benthamiana plants. A 3-week post- VIGS time frame is sufficient to observe phenotypic alterations in the anatomical structure of stems and chemical composition of the primary and secondary cell walls. We used cell wall glycan-directed monoclonal antibodies to demonstrate that alteration of cell wall polymer synthesis during the secondary growth phase of VIGS plants has profound effects on the extractability of components from woody stem cell walls. Therefore, TRV-based VlGS together with cell wall component profiling methods provide a high-throughput gene discovery platform for studying plant cell wall formation from a bioenergy perspective.