Shelford's law of tolerance is illustrated by a bell-shaped curve depicting the relationship between environmental factor/factors’ intensity and its favorability for species or populations. It is a fundamental basis of ecology when considering the regularities of environment impacts on living systems, and applies in plant biology, agriculture and forestry to manage resistance to environmental limiting factors and to enhance productivity. In recent years, the concept of hormesis has been increasingly used to study the dose–response relationships in living organisms of different complexities, including plants. This requires the need for an analysis of the relationships between the hormetic dose–response model and the classical understanding of plant reactions to environments in terms of Shelford's law of tolerance. This paper analyses various dimensions of the relationships between the hormetic model and Shelford’s tolerance law curve under the influence of natural environmental factors on plants, which are limiting for plants both in deficiency and excess. The analysis has shown that Shelford’s curve and hormetic model do not contradict but instead complement each other. The hormetic response of plants is localized in the stress zone of the Shelford’s curve when adaptive mechanisms are disabled within the ecological optimum. At the same time, in a species range, the ecological optimum is the most favorable combination of all or at least the most important environmental factors, each of which usually deviates slightly from its optimal value. Adaptive mechanisms cannot be completely disabled in the optimum, and hormesis covers optimum and stress zones. Hormesis can modify the plant tolerance range to environmental factors by preconditioning and makes limits of plant tolerance to environmental factors flexible to a certain extent. In turn, as a result of tolerance range evolution, quantitative characteristics of hormesis (width and magnitude of hormetic zone) as well as the range of stimulating doses, may significantly differ in various plant species and even populations and intra-population groups, including plants at different development stages. Using hormetic preconditioning for managing plant resistance to environmental limiting factors provides an important perspective for increasing the productivity of woody plants in forestry.
Forests produce several types of benefits to both forest landowners and society. The social benefit of private forestry is equal to private benefit plus positive externalities minus negative externalities. This study developed alternative metrics for the evaluation of the social benefit of forest management. Forest management was assessed in terms of five criteria: economic, socio-cultural, environmental and ecological performance and the resilience of the forest ecosystem. Each criterion was described with three numerical indicators. Alternative performance indices were calculated from the indicator values using methods developed for multi-criteria decision making. It was concluded that indices based on the multiplicative Cobb–Douglas utility function might be the most recommendable when forestry should produce a balanced combination of different ecosystem services. When the indices were used to compare alternative silvicultural systems in terms of their social performance, continuous cover management was ranked better than even-aged management. The performance of even-aged management improved when it aimed at increasing the share of mixed stands and broadleaf species. Maximizing net present value (NPV) with a 1% discount rate led to better social performance than maximizing NPV with a 4% discount rate.
The challenges of a changing climate have directed greater attention to afforestation, but the effects of afforestation on soil fertility and soil biota have not been fully clarified. To explore changes in the soil conditions in two 20-year-old forest plantations established in formerly intensively fertilized plots of agricultural land, we focused on the current developmental state of the sites that received the most fertilizer and evaluated soil properties and Collembola (springtails) communities. Sessile oak (Quercus petraea) and black locust (Robinia pseudoacacia) that had been planted in the afforestation sites were assessed for differences between plantations of native and invasive species. Five adjacent reference associations, including forests and open habitats, were also analyzed and compared. Results showed that the soils in the two afforested sites were similar in their properties and Collembola communities to those of the control cultivated forests, but differed from each other in pH, calcium, phosphorus, and ammonium content. The available potassium and phosphorus contents in the soil of the sessile oak plantation were still high, while the soil organic matter content was adequate (SOM > 2.0%) in both plantations. Species richness of Collembola ranged from 18 in the cultivated arable land to 43 in the relict forest. Only a few species typical for forests (e.g., Neanura muscorum, Isotomiella minor, Entomobrya muscorum) were detected in the young plantations, while species characteristic of open habitats (e.g., Protaphorura campata, Lepidocyrtus cyaneus) occurred as well. Although more individuals and species of Collembola were present in the soil of young plantations than in arable fields, their community diversities were significantly lower compared to the control forest stands. Collembola community diversity differed significantly also between the two plantation types (with native and non-native tree species). Mean abundance in the afforested sites was about 2.5 times higher than in the cultivated arable land, yet far lower than the mean abundance in the control forests.
Toward improving reforestation of Brazilian pine (Araucaria angustifolia), two contrasting sapling sizes in either full sun or in the shade of a mixed plantation and the effect of opening the canopy were evaluated for survival, growth, gas exchange, photosynthetic pigments, and leaf anatomy 18 months after being planted. At 23 months after planting, a partial opening was made in the canopy in the mixed plantation, then the saplings were evaluated again after 2 months for the same morphophysiological traits. After 18 months, saplings planted in the full sun had higher survival, growth, pigments, and photosynthesis compared to the shaded saplings. Large saplings had higher survival and growth compared to the small ones. Shaded leaves were thinner and little differentiation of palisade parenchyma and hypodermis. After opening of the canopy, photosynthetically active radiation was 10 times higher, and the saplings quickly grew in height due to increased photosynthesis. Thus, although the species can tolerate shade, growth in the shade is limited. We recommend that for reforestation purposes of Brazilian pine, large saplings should be selected and planted in the open for better development.
The positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance. This study evaluates the composition, diversity, regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed, intermittently disturbed, and disturbed forest sites. Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories. Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north, south, east, and west transects within individual gaps. Data on natural regeneration < 350 cm height were gathered. The results show that the intensity of disturbance was disproportional to gap size. Species diversity differed significantly between undisturbed and disturbed sites and, also between intermittently disturbed and disturbed sites for Simpson’s (1-D), Equitability (J), and Berger–Parker (B–P) indices. However, there was no significant difference among forest sites for Shannon diversity (H) and Margalef richness (MI) indices. Tree species composition on the sites differed. Regeneration density on the disturbed site was significantly higher than on the two other sites. Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers. Pioneer species giving way to shade tolerant species is a natural process, thus make them worst variant in gap regeneration.
In tropical montane forests, compositional and structural changes are commonly driven by broad-scale altitudinal variation. Here, given the lack of knowledge on small-scale vegetation changes and temporal dynamics, we address the effects of small-scale variations in soil and altitude on tree community structure, temporal dynamics and phylogenetic diversity in a semi-deciduous tropical forest of the Atlantic Forest Domain, southeastern Brazil. In 2010 and 2015 we sampled thirty plots of 400 m2, set up along an altitudinal gradient between 1000 and 1500 m a.s.l.. In each plot, we collected soil samples for chemical and textural analyses. We fitted linear models to test the effects of altitude and soil on community dynamics and phylogenetic parameters. Altitude and soil explained the spatial variation in number of individuals and phylogenetic diversity metrics. From lower to higher altitudes, we found decreasing fertility, increasing tree density and decreasing phylogenetic diversity. Altitude significantly influenced the increases in total biomass (from 240.9 to 255.4 t ha−1) and individual biomass (from 0.15 to 0.17 t) recorded in the interval. And while community temporal dynamics had rates of 1.96% for mortality, 1.02% for recruitment, 1.61% for biomass loss and 2.81% for biomass gain, none of them were explained by altitude or soil. Temporal species substitution averaged 0.1 in the interval. Altogether, these results suggest that the small-scale variations in altitude and soil likely determine the conditions and resources that drive community assembly and structure, which are expressed by spatial variations along the altitudinal gradient. At the same time, temporal patterns were not influenced by altitude-related environmental variation, resulting in a similar dynamic behaviour across the gradient, suggesting that broad-scale factors may play a more important role than local ones.
Miombo woodlands near human settlements are under significant pressures from human activities, with negative consequences on their structure and composition. As studies are limited, we assessed the structure and species composition of a portion of miombo woodland along an increasing disturbance gradient from a national park, through a buffer zone to communal lands in northeast Zimbabwe. Five concentric plots of 2 and 11 m radii were established in each area to record woody species composition, diameter, height, basal area, density and volume as well as evidence of disturbance. Effects of site, growth stage and their interaction on vegetation diversity and structural parameters were tested using a general linear model (GLM). Principal component analysis (PCA) tested the association between species and site and ANOVA the differences in the level of disturbance across strata. Species diversity did not differ between sites except for evenness, which increased with disturbance. Evenness and richness were greater in seedlings and saplings than mature trees across sites, respectively. Sapling and mature tree diameters differed significantly between sites. Volume and density of mature trees declined with increasing disturbance while seedling densities peaked at intermediate disturbance levels (buffer zone). Tree harvesting, was more evident in the buffer zone and in the communal area relative to the national park. In contrast, fire frequency was greater in the national park and in the buffer zone relative to the communal area. The results of this study identify a true miombo woodland dominated by Brachystegia boehmii with a stable population, as illustrated by an inverse-J shape in diameter class distribution on all sites, and that these woodlands are generally resilient to disturbances, maintaining similar species composition and structure at various levels of disturbance. However, continued monitoring of disturbance levels and miombo woodland response is recommended to ensure sustainable utilisation of these resources.
The diversity of tree species and the complexity of land use in cities create challenging issues for tree species classification. The combination of deep learning methods and RGB optical images obtained by unmanned aerial vehicles (UAVs) provides a new research direction for urban tree species classification. We proposed an RGB optical image dataset with 10 urban tree species, termed TCC10, which is a benchmark for tree canopy classification (TCC). TCC10 dataset contains two types of data: tree canopy images with simple backgrounds and those with complex backgrounds. The objective was to examine the possibility of using deep learning methods (AlexNet, VGG-16, and ResNet-50) for individual tree species classification. The results of convolutional neural networks (CNNs) were compared with those of K-nearest neighbor (KNN) and BP neural network. Our results demonstrated: (1) ResNet-50 achieved an overall accuracy (OA) of 92.6% and a kappa coefficient of 0.91 for tree species classification on TCC10 and outperformed AlexNet and VGG-16. (2) The classification accuracy of KNN and BP neural network was less than 70%, while the accuracy of CNNs was relatively higher. (3) The classification accuracy of tree canopy images with complex backgrounds was lower than that for images with simple backgrounds. For the deciduous tree species in TCC10, the classification accuracy of ResNet-50 was higher in summer than that in autumn. Therefore, the deep learning is effective for urban tree species classification using RGB optical images.
Information on species composition of an urban forest is essential for its management. However, to obtain this information becomes increasingly difficult due to limited taxonomic expertise. In this study, we tested the possibility of using plant identification applications running on mobile platforms to fill this vacuum. Five plant identification apps were compared for their potential in identifying urban tree species in China. An online survey was conducted to determine the features of apps that contributed to users’ satisfaction. The results show that identification accuracy varied significantly among the apps. The best performer achieved an accuracy of 74.6% at the species level, which is comparable to the accuracy by professionals in field surveys. Among the features of apps, accuracy of identification was the most important factor that contributed to users’ satisfaction. However, plant identification apps did not perform well when used on rare species or outside of the regions where they have been developed. Results indicate that plant identification apps have great potential in urban forest studies and management, but users need to be cautious when deciding which one to use.
Different forest fires causing different degrees of effects occur in fire-sensitive forests due to various reasons such as climate change. Useful as well as harmful aspects of forest fires are a multi-disciplinary research topic. Geographical information systems (GIS) and remote sensing (RS) methods offer a number of benefits for researchers and operators in the field of forest fire research. The present study analyses timber pricing based on forest contractor demands of post-salvage logging processes. The effect of timber obtained from compartment units on producers’ pricing policy was modelled. Sapadere forest fire area (2500 ha) located in Antalya in Turkey was selected as the main study area. Topography parameters (aspect, slope and slope position), stand types (diameter class and crown closure), and burn severity were analyzed together using GIS and R software packages. A multi-linear regression model (R2 = 0.752) demonstrated that factors that had the most impact on pricing were slope position, aspect, stand age, crown closure and burn severity. This model can be used to estimate salvage logging prices in Calabrian pine (Pinus brutia Ten.) stands with similar parameters. Forest administrators and contractors may readily address the unit price of timber by estimating approximate costs in a given forest area for which they are going to bid. This will help reduce operational planning times of harvesting procedures in burned stands.
Simulation of fire impact on forest floor renewal in pine forests was based on predictions for 2100 by the Canadian Climate Centre for increase in temperatures of by 4.5 °C and total precipitation by 14% in the West Siberian pre-forest-steppes and empirical regression relationships between them and the degree of burnt forest floor, as well as amount of Pinus sylvestris L. regeneration. It was predicted that by 2100, pine regeneration on fire prone sites under the canopy of the dominant forest type will increase by 29–54% compared to the 1980s but on adjacent open sites, regeneration will decrease twice as much. This means that the regeneration potential and pine population stability in pre-forest-steppes will become as poor as it is today.
Traditional fire smoke detection methods mostly rely on manual algorithm extraction and sensor detection; however, these methods are slow and expensive to achieve discrimination. We proposed an improved convolutional neural network (CNN) to achieve fast analysis. The improved CNN can be used to liberate manpower. The network does not require complicated manual feature extraction to identify forest fire smoke. First, to alleviate the computational pressure and speed up the discrimination efficiency, kernel principal component analysis was performed on the experimental data set. To improve the robustness of the CNN and to avoid overfitting, optimization strategies were applied in multi-convolution kernels and batch normalization to improve loss functions. The experimental analysis shows that the CNN proposed in this study can learn the feature information automatically for smoke images in the early stages of fire automatically with a high recognition rate. As a result, the improved CNN enriches the theory of smoke discrimination in the early stages of a forest fire.
Dry afromontane forests are among the most poorly managed and endangered ecosystems. Therefore, we assessed the composition, diversity, and conservation status of woody plant species of the Debre Libanos church forests and surrounding forest lands in Oromiya Regional National State, central Ethiopia in 62 nested circular sample plots spaced 200 m apart along two transect lines. Large circular plots 314 m2 were used to sample trees with DBH of at least 10 cm, and subplots of 28.26 m2 were laid in each main plot were used to assess saplings and shrubs; a small subplot of 3.14 m2 was used to assess seedlings. In total, 70 woody plant species belonging to 62 genera and 43 families were recorded. Of these, 59, 28 and 32 were in the church, government and private forest types, respectively. The most dominant families were Fabaceae and Verbenaceae, each represented by five species. In the forests considered, trees accounted for 61%, and shrubs with diameter at breast height (DBH) of 1–10 cm accounted for ca. 33%. Among growth forms of woody species, shrubs and seedlings, followed by trees constituted much of the density of woody species in all the three ownership types of forests. The church forest had the most species (59) and highest Shannon (3.12) and Simpson (0.92) species diversity indices, and the government and private forests had a nearly similar total number of species and Shannon and Simpson species diversity indices. Most of the species with higher importance value indices (IVI) were indigenous in origin within the church forest (Juniperus procera = 82), government forest (J. procera = 66) and private forest (Acacia abyssinica = 84). The composition, diversity, and population structure of woody species in the church forest were significantly higher than in the other forest lands. However, interventions of the government and private sectors to conserve forest systems in the areas, particularly the government-owned forest and specific species such as Olea europaea need active enrichment plantings due to their limited natural regeneration. Without improved management interventions, livelihood income diversification and ecosystem services obtained from the forest will not be sustainable.
It is important to quantify and analyze forest spatial patterns for studying biological characteristics, population interaction and the relationship between the population and environment. In this study, the forest spatial structure unit was generated based on the Delaunay triangulation model (DTM), and the weights were generated using the comprehensive values of the tree diameter at breast height, total height and crown width. The distance between neighbors determined by the DTM was weighted to transform the original coordinates of trees into logical coordinates. Then, a weighted spatial pattern (WSP) was developed. After weighting, the neighboring trees were replaced, the replacement ratio was 38.3%, and there was 57.4% of the central tree. Correlation analysis showed that the uniform angle index of the WSP was significantly correlated with the tree size standard deviation under uniformity (r = 0.932) and randomness (r = 0.711). The DTM method not only considers the spatial distance between trees, but also considers the non-spatial attributes of trees. By changing the spatial topological relation between trees, this method further improves the spatial structure measurement of forest.
In Ethiopia, among many restoration efforts to reverse deforestation and land degradation, area exclosure is one of the most common practices to restore secondary forests with assisted natural regeneration. The present study in the Sekota district, northeastern Amhara region, Ethiopia evaluated the influence of areas exclosures on woody species diversity, population structure and regeneration status. A total of 36 and 27 quadrats, each 20 m × 20 m, were used to collect data in exclosures and non-exclosures, respectively. Within quadrats, four 5 m × 5 m and 2 m × 2 m quadrats at the corners were used to sample saplings and seedlings, respectively. In exclosures, 35 woody species representing 21 families and 29 genera were recorded; 19 woody species representing 13 families and 13 genera were recorded in the non-exclosure. Acacia etbaica was the most dominant species in the two land-uses. The Shannon diversity index was 1.77 ± 0.46 in exclosures and 1.39 ± 0.46 in non-exclosures. Shannon and Simpson diversity indices showed a significant difference between the two land-uses (p < 0.01). The regeneration status of all wood species in exclosures was good, only fair in non-exclosures. Area exclosures have thus played a great role in the restoration of degraded lands by improving vegetation diversity and regeneration status. The least dominant woody species should be maintained through active restoration. Continuous follow-up, maintenance of soil water conservation structure to improve soil fertility will further help enhance the woody species diversity and abundance.
Vegetation is sparsely distributed in the arid regions of northwestern China, and accurately measuring and partitioning of evapotranspiration is of importance for ecosystems in such areas. In this study, we measured and analyzed diurnal and phenological variations in evapotranspiration using the eddy–covariance method based on the Penman–Monteith, Priestley–Taylor, Shuttleworth–Wallace models, a newly proposed improved dual source model and a clumped model in a forest reserve in the Ejin oasis of Populus euphratica in 2015 and 2016 growing seasons. A sensitivity analysis was performed for the models with higher accuracies and we examined the biotic and abiotic controls on evapotranspiration. The results show that the total amounts of evapotranspiration during the two growing seasons in 2015 and 2016 were 622 and 612 mm, respectively. Phenological variations in evapotranspiration produced single-peak curves, while diurnal variations reflected the influence of high temperatures on some afternoons. The Priestley–Taylor and the improved dual source models gave the most accurate evapotranspiration values at the daily scale and appeared to be most suitable for the estimation of evapotranspiration for the species in arid regions. In addition, both models were the most sensitive to net radiation (R n).
Cinnamomum camphora (L.) J. Presl. (Laurales: Lauraceae) is widely cultivated as an important landscape tree species in many urban areas in South China, especially in Shanghai City. Pagiophloeus tsushimanus Morimoto has become a destructive insect pest of C. camphora plantations in Shanghai, but the biological and ecological traits of this pest remain largely unknown. In this study, we investigated the damage and life history and determined the larval instar of P. tsushimanus. The results indicated that P. tsushimanus is a monophagous weevil pest, and C. camphora is the unique host tree species. C. camphora plantations in all administrative districts of Shanghai have been seriously damaged by P. tsushimanus. Adults often aggregate for feeding on the tender bark of twigs and occasionally on newly emerged buds. After experiencing damage, the twigs shrink and crack and the buds will shrink. Adults tend to repeatedly mate and oviposit, and all females lay single eggs at a time. Eggs will be covered with a mixture of secretions and wood chips by female adults. Larvae (1st–2nd instar) feed on the phloem, while 3rd–5th instar can bore into the phloem and the cambium. Massive tunnels, including three shapes (inverted “L”, inverted “T”, and inverted “Z”), were observed in the trunk of each tree, and resulted in swelling of the outer bark. P. tsushimanus has one life cycle per year in Shanghai. Both adults and larvae (3rd–5th instar) overwinter from early November to early April. Adults overwinter in grooves on the underside of branches or at branch nodes, and larvae overwinter in tunnels. Five larval instars of P. tsushimanus were determined according to Dyar's and Crosby's rules. The biological traits and life history of P. tsushimanus have been identified and can provide guidance in terms of pest control and plantation management.
Models of above-ground tree biomass have been widely used to estimate forest biomass using national forest inventory data. However, many sources of uncertainty affect above-ground biomass estimation and are challenging to assess. In this study, the uncertainties associated with the measurement error in independent variables (diameter at breast height, tree height), residual variability, variances of the parameter estimates, and the sampling variability of national inventory data are estimated for five above-ground biomass models. The results show sampling variability is the most significant source of uncertainty. The measurement error and residual variability have negligible effects on forests above-ground biomass estimations. Thus, a reduction in the uncertainty of the sampling variability has the greatest potential to decrease the overall uncertainty. The power model containing only the diameter at breast height has the smallest uncertainty. The findings of this study provide suggestions to achieve a trade-off between accuracy and cost for above-ground biomass estimation using field work.
The community species abundance and diversity declined with bamboo invasion had been widely reported worldwide. However, the physiological strategies used during root competition between native species and invasive bamboo are poorly understood. To clarify the mechanisms underlying such strategies, the stoichiometric dynamics and homeostasis of nitrogen, phosphorus, organic carbon in root orders of Phyllostachys edulis (I du [=I-Pe, years 1 and 2]; II du [=II-Pe, years 3 and 4]), Cunninghamia lanceolata in transition and pure forests were analyzed. With increasing intensity of bamboo invasion, N, P, and C content of C. lanceolata root orders declined, N and P content in P. edulis rhizome orders declined, while C increased, the stoichiometric ratios in mixed forest interface mainly increased, and the stoichiometric differences within native and invasive species root orders narrowed. Meanwhile, the stoichiometric homeostasis index (H) of elements in the same root order and even the same elements in different root orders were not consistent. H of most root orders (except some H P) was greater than 4, the H ranked order was I-Pe > Cl > II-Pe in mixed interfaces, and the N:P ratio of most species root orders was greater than 16, despite being affected by invasion. Our research concluded that the bamboo invasion narrows stoichiometric differences within root orders, and the juvenile bamboo rhizome has a stronger capacity for homeostatic regulation than in adult bamboo and C. lanceolata, which is a key determinant of bamboo invasion success.
In some urban parks in Tokyo, semi-natural habitat patches are maintained as nature reserves for birds, called bird sanctuaries. Bird censuses and vegetation surveys were conducted in eight urban parks in Tokyo from December 2015 to July 2016 to determine the effectiveness of bird sanctuaries on avian species composition. The relationship between avian species composition and environmental conditions was analyzed by partial redundancy analysis (partial RDA) using vegetation variables, number of visitors, presence or absence of reserves within the same park, area of wooded parts, and normalized difference vegetation index (NDVI) in the surrounding area. The results of the partial RDA are as follows: (1) Area, lower vegetation cover, higher vegetation cover, tree species composition obtained from detrended correspondence analysis (DCA) on vegetation survey data, and NDVI in the surrounding area were considered as covariates and explained 17.4–33.6% of the total variation in bird species composition, (2) The presence or absence of sanctuary significantly explained bird species compositional variation regardless of season, indicating that the sanctuaries were beneficial for urban avoider species not only in the sanctuaries but also in the surrounding wooded area, and (3) Tree coverage within a 100 m range and leaf litter coverage also influenced avian species composition. We concluded that bird sanctuaries and other nature reserves can be beneficial to bird conservation, even within Tokyo. The positive effect of sanctuaries could be due to the limited influence of human presence and the developed vegetation within them. These reserves may play the role of core habitats within the studied urban parks.
Preventing and suppressing forest fires is one of the main tasks of forestry agencies to reduce resource loss and requires a thorough understanding of the importance of factors affecting their occurrence. This study was carried out in forest plantations on Maoer Mountain in order to develop models for predicting the moisture content of dead fine fuel using meteorological and soil variables. Models by Nelson (Can J For Res 14:597–600, 1984) and Van Wagner and Pickett (Can For Service 33, 1985) describing the equilibrium moisture content as a function of relative humidity and temperature were evaluated. A random forest and generalized additive models were built to select the most important meteorological variables affecting fuel moisture content. Nelson's (Can J For Res 14:597–600, 1984) model was accurate for Pinus koraiensis, Pinus sylvestris, Larix gmelinii and mixed Larix gmelinii—Ulmus propinqua fuels. The random forest model showed that temperature and relative humidity were the most important factors affecting fuel moisture content. The generalized additive regression model showed that temperature, relative humidity and rain were the main drivers affecting fuel moisture content. In addition to the combined effects of temperature, rainfall and relative humidity, solar radiation or wind speed were also significant on some sites. In P. koraiensis and P. sylvestris plantations, where soil parameters were measured, rain, soil moisture and temperature were the main factors of fuel moisture content. The accuracies of the random forest model and generalized additive model were similar, however, the random forest model was more accurate but underestimated the effect of rain on fuel moisture.
In addition to bacteria, the contribution of fungi to nitrous oxide (N2O) production has been recognized but the responses of these two broad and unrelated groups of microorganisms to global environmental changes, atmospheric nitrogen (N) deposition, and precipitation in terms of N2O production are unclear. We studied how these two microbial-mediated N2O production pathways responded to soil moisture conditions and to N addition in an N-limited temperate forest. Soils from a long-term N addition experiment in Changbai Mountain, northeastern China were incubated. Varied concentrations of cycloheximide and streptomycin, both inhibitors of fungal and bacterial activity, were used to determine the contributions of both to N2O production in 66%, 98% and 130% water-filled pore spaces (WFPS). The results showed that N2O production decreased significantly with increasing cycloheximide concentration whereas streptomycin was only inhibiting N2O emissions at 98% and 130% WFPS. The bacterial pathway of N2O production in N-addition (Nadd) soil was significantly more dominant than that in untreated (Namb) soil. The difference in the fungal pathway of N2O production between the soil with nitrogen addition and the untreated soil was not significant. Net N2O emissions increased with increasing soil moisture, especially at 130% WFPS, a completely flooded condition. Bacteria dominated carbon dioxide (CO2) and N2O emissions in Nadd soil and at 130% WFPS regardless of N status, while fungi dominated CO2 and N2O emissions in soil without N addition at 66% and 98% WFPS. The results suggest that flooded soil is an important source of N2O emissions and that bacteria might be better adapted to compete in fertile soils under anoxic conditions.
Japanese larch (Larix kaempferi (Lamb.) Carr.) and its hybrid are economically important coniferous trees widely grown in the Northern Hemisphere. Ground-level ozone (O3) concentrations have increased since the pre-industrial era, and research projects showed that Japanese larch is susceptible to elevated O3 exposures. Therefore, methodologies are needed to (1) protect Japanese larch against O3 damage and (2) conduct biomonitoring of O3 in Japanese larch forests and, thus, monitor O3 risks to Japanese larch. For the first time, this study evaluates whether the synthetic chemical ethylenediurea (EDU) can protect Japanese larch against O3 damage, in two independent experiments. In the first experiment, seedling communities, simulating natural regeneration, were treated with EDU (0, 100, 200, and 400 mg L−1) and exposed to either ambient or elevated O3 in a growing season. In the second experiment, individually-grown saplings were treated with EDU (0, 200 and 400 mg L−1) and exposed to ambient O3 in two growing seasons and to elevated O3 in the succeeding two growing seasons. The two experiments revealed that EDU concentrations of 200–400 mg L−1 could protect Japanese larch seedling communities and individual saplings against O3-induced inhibition of growth and productivity. However, EDU concentrations ≤ 200 mg L−1 did offer only partial protection when seedling communities were coping with higher level of O3-induced stress, and only 400 mg EDU L−1 fully protected communities under higher stress. Therefore, we conclude that among the concentrations tested the concentration offering maximum protection to Japanese larch plants under high competition and O3-induced stress is that of 400 mg EDU L−1. The results of this study can provide a valuable resource of information for applied forestry in an O3-polluted world.
In this study, nitrogen fluxes or flows in litterfall, nitrogen stocks and available nitrogen in soils of two plots representing evergreen broadleaf and Bulgarian fir forests were assessed. Both plots are in good quality sites and for this reason, the litterfall quantities and nitrogen fluxes were relatively high. The woody litterfall flux of nitrogen was significantly higher in the fir forest than in the evergreen broadleaf one. The total nitrogen stock was higher in the soil under the fir forest. However, the percentage of the available nitrogen (ammonium + nitrates) was significantly higher in the upper 20 cm soil layer of the evergreen broadleaf forest in spite of the higher average C/N ratios in the foliar litterfall of the broadleaf forest and insignificant difference of the C/N ratios in all soil layers of the two ecosystems. The microclimatic conditions (higher soil temperatures in the evergreen broadleaf forest) is probable possible cause for this difference. The available nitrogen in the soils and its retranslocation from senescing leaves cover the nitrogen requirements of trees. It is hypothesized that trees may also take up nitrogen from deeper soil layers.
Minquartia guianensis Aubl. is a slow-growing species with several uses. In the juvenile state, it is well-adapted to low light conditions of the forest understory. However, it is still unknown how climate variability affects transpiration of this species, particularly under drought stress. In this study, we aimed to assess the effect of climatic variability on sap flow rates (SFR). SFR and radial growth were measured in six trees (14‒50 cm diameter) in 2015 and 2016. Climate (precipitation, irradiance, relative humidity and temperature) and soil water content (SWC) data were also collected. SFR tended to increase in the dry season, with a negative relationship between SFR and SWC and precipitation (p < 0.001), while there was a positive association between radial growth and monthly precipitation (p = 0.004). Irradiance and temperature were the environmental factors more closely correlated with SFR during daytime (p < 0.001), whereas relative humidity and vapor pressure deficit were the most important factors at night (p < 0.001). Although negative SFR were sometimes recorded at night, the mean nocturnal sap flow was positive and across trees the nighttime sap flow accounted for 12.5% of the total daily sap flow. Increased transpiration during the dry season suggests that the root system of Minquartia was able to extract water from deep soil layers. These results widen our understanding of the ecophysiology of Amazonian trees under drought and provide further insight into the potential effect of the forecasted decline in precipitation in the Amazon region.
Chinese fir (Cunninghamia lanceolata (Lamb.) Hook), a fast-growing and economically important timber tree species in China, is widely used in construction, furniture, and paper manufacture but has a long breeding cycle. Chemical mutagens, such as ethyl methane sulfonate (EMS) and sodium azide (SA), are widely used in crops such as rice, wheat, cotton, soybean and sugarcane but their utility for tree breeding is unknown. In this study we examined the effects of EMS and SA on Chinese fir seed germination and growth. Chinese fir seeds were treated with the two chemical mutagens; were planted in Jiangle County, Fujian Province, China; and their heights were measured from 2011 to 2017. The concentrations and durations of treatment with the two chemical mutagens were significantly associated with the Chinese fir seedling and mortality rates, as well as with the heights of trees from the seedling stage to 3 years old. We also generated 127 mutants with abnormal branches and reproductive growth. We report here the effects of two chemical mutagens on Chinese fir breeding; our data will contribute to knowledge of the utility of EMS and SA in forestry.
Previous research has shown that competition between plants can have differential effects on leaf stoichiometry and non-structural carbohydrate (NSC) in different environments. However, little attention has been given to understanding these effects on non-photosynthetic organs, particularly of deciduous tree species. Here we assess the impact of competition on below and aboveground biomass, stoichiometry, nutrient composition and NSC in pure and mixed forests of two Larch species, Larix kaempferi and L. olgensis under nitrogen (N) addition. Nitrogen enrichment did not result in stronger intraspecific competition for both species and L. olgensis benefited from the presence of L. kaempferi under different N levels. Stems kept relatively stable C/N compared to roots and branches in response to competition, while N addition imposed stronger impacts on N/P of different organs rather than competition. In contrast to stable C concentrations, starch and soluble sugar concentrations were more easily impacted by competition and the addition of nitrogen. Competition forced L. kaempferi and L. olgensis to allocate more carbon into storage by increasing their starch concentration and starch/soluble sugar of stems under competition. However, no significant differences in stoichiometry and NSC concentration between intra- and interspecific competition were found. NSC and nutrient pools of L. kaempferi stems, branches and coarse roots consistently declined due to competition regardless of N addition. Coarse and fine roots of L. kaempferi accumulated more N when in competition with L. olgensis than with a conspecific neighbor under N addition. Our results show that NSC was more sensitive to competition relative to stoichiometric traits (N and P) of non-photosynthetic organs.
Water availability is a limiting factor for the establishment and development of forest species. To understand the appropriate conditions for the initial post-transplanting phase, it is necessary to understand the specific morphophysiological characteristics of the species, such as the leaf water potential and the efficiency of photosystem II. We aimed to identify the influence of different water regimes on the morphophysiological aspects of young plants of two forest species (Cedrela fissilis Vellozo and Eucalyptus saligna Sm.). Two greenhouse experiments were conducted for 28 days; one for each species. The design was completely randomized, and the treatments consisted of six different water regimes. Leaf water potential (Ψw) and chlorophyll a fluorescence were evaluated every 7 days. At the end of the experiment, morphological attributes (height, collection diameter, root volume, and dry matter) were measured and histological blades were made. The water demand of E. saligna was higher than that of C. fissilis and required greater replacement within a shorter period. The rehydration from Ψw = − 2 Mpa allowed for a fast recovery of the young C. fissilis plants (Ψw = − 1.5, Fv/Fm = 0.796), which indicated good physiological plasticity of this species when submitted to water stress at a level that is not severe. The total dry matter allocation was different among species. Seedlings of E. saligna presented the best responses when submitted to a continuous water supply regime, while C. fissilis seedlings presented the best response under intermittent irrigation conditions.
The effects of different climatic conditions on growth and chemical composition of Betula pendula in geographically different European regions, Lithuania and Romania, were compared. Birch species in the entire area have a wide natural distribution, but B. pendula is commercially more important in Lithuania than in Romania. Here we evaluated tree ring width, wood density and foliar chemical composition of mature birch trees in two European regions. Trees at the Lithuanian sites had greater radial growth and wood density with no clear changes in foliar chemistry than those at the Romanian sites. Mean wood density was 600–700 kg m−3 at Lithuanian and 350–450 kg m−3 at Romanian sites. Mean width of wood ring, earlywood and latewood for Lithuanian birch trees were several times higher than the means for Romanian birch trees. We hypothesized that the main differences in birch radial growth and wood density were due to the different climatic conditions in the studied regions. Ca, K and Mg concentrations were significantly higher and Fe and Mn were lower in the birch foliage at the Lithuanian sites compared those at the Romanian sites. Overall assessment of growth showed that silver birch cultivation is more appropriate for colder climate regions and that birch growth may change in the context of a warming climate.
Intercropping of mulberry (Morus alba L.) and alfalfa (Medicago sativa L.) is a new forestry-grass compound model in China, which can provide high forage yields with high protein. Nitrogen application is one of the important factors determining the production and quality of this system. To elucidate the advantages of intercropping and nitrogen application, we analyzed the changes of physicochemical properties, enzyme activities, and microbial communities in the rhizosphere soil. We used principal components analysis (PCA) and redundancy discriminators analysis to clarify the relationships among treatments and between treatments and environmental factors, respectively. The results showed that nitrogen application significantly increased pH value, available nitrogen content, soil water content (SWC), and urea (URE) activity in rhizosphere soil of monoculture mulberry. In contrast, intercropping and intercropping + N significantly decreased pH and SWC in mulberry treatments. Nitrogen, intercropping and intercropping + N sharply reduced soil organic matter content and SWC in alfalfa treatments. Nitrogen, intercropping, and intercropping + N increased the values of McIntosh diversity (U), Simpson diversity (D), and Shannon–Weaver diversity (H′) in mulberry treatments. However, PCA scatter plots showed clustering of monoculture mulberry with nitrogen (MNE) and intercropping mulberry without nitrogen (M0). Intercropping reduced both H′ and D but nitrogen application showed no effect on diversity of microbial communities in alfalfa. There were obvious differences in using the six types of carbon sources between mulberry and alfalfa treatments. Nitrogen and intercropping increased the numbers of sole carbon substrate in mulberry treatments where the relative use rate exceeded 4%. While the numbers declined in alfalfa with nitrogen and intercropping. RDA indicated that URE was positive when intercropping mulberry was treated with nitrogen, but was negative in monoculture alfalfa treated with nitrogen. Soil pH and SWC were positive with mulberry treatments but were negative with alfalfa treatments. Intercropping with alfalfa benefited mulberry in the absence of nitrogen application. Intercropping with alfalfa and nitrogen application could improve the microbial community function and diversity in rhizosphere soil of mulberry. The microbial community in rhizosphere soil of mulberry and alfalfa is strategically complementary in terms of using carbon sources.
Confocal Raman microspectroscopy (CRM) is an important tool for analyzing the compositional distribution of cell walls in situ. In this study, we improved the sample preparation method using paraffin-embedded sections combined with hexane dewaxing to obtain high resolution Raman images. We determined that the cell wall components of fiber cells were different from those of ray cells and vessel cells in the xylem of Populus tomentosa. Acetyl bromide and CRM methods produced similar trends when the difference in lignin intensity in the xylem region was compared between transgenic PtrLac4 and wild-type P. tomentosa. However, CRM proved more useful to analyze the lignin distribution in each cell type and distinguished the detailed difference in lignin intensity at the cellular level. Thus, CRM proved to be a useful in situ method to rapidly analyze the spatial variation of lignin content in the xylem of woody plants.
Rhizosphere soil samples of three Pinus chiapensis sites were analyzed for their physicochemical properties, soil bacteria isolated and screened in vitro for growth-promoting abilities. Nine isolates that showed promise were identified to five genera Dyella, Luteimonas, Enterobacter, Paraburkholderia and Bacillus based on the sequences of 16S rRNA gene. All the strains were isolated from non-disturbed stands. These bacteria significantly decreased germination time and increased sprout sizes. Indole acetic acid and gibberellin production and phosphate solubilisation were detected. Results indicate that these biochemicals could be essential for P. chiapensis distribution and suggest the possibility that PGPR inoculation on P. chiapensis seeds prior to planting could improve germination and possibly seedling development.
Plant species produce different types of allelopathic chemicals in nature; however, little is known about the differential regulation of plant allelopathy. Because allelopathy caused by p-hydroxybenzoic acid (pHBA) is one of the main obstacles to continuous cropping of Populus × euramericana ‘Neva’, we examined gene expression dynamics in Neva leaves induced by pHBA. The expression of genes related to photosynthesis and respiration changed, while mRNA involved in regulating gene expression during allelopathy was degraded. Some miRNAs that are involved in plant allelopathy target crucial genes for regulating reactive oxygen species. Moreover, coexpression regulatory networks were constructed based on profiles of the identified miRNA-target interactions and the differentially expressed miRNA–target pairs. These findings provide a mechanistic framework for understanding allelopathy in plants.
Mexican beech [Fagus grandifolia subsp. mexicana (Martinez) A.E.Murray] is a subspecies endemic to the Sierra Madre Oriental Mountains and considered endangered due to the low density of its populations and high degree of habitat fragmentation and environmental specificity. Because its morphological and genetic variation is associated with its ability to adapt to changes in environmental conditions, the objective of this study was to determine whether phenotypic and genotypic variation exist, and it relationships with population reduction events. In four beech populations in the states of Hidalgo and Veracruz, we analyzed 11 morphological variables for leaves and 6 microsatellite markers. The morphological variables that to discriminate between populations were related to the size of the leaf, but a robust differentiation pattern was not found, given that independent groups of leaves were identified. The populations located closest to each other, had greater genetic variation and less genetic distance; populations in the extreme north and south had the lowest genetic variation. Genetic differentiation among populations was associated with reduction in population size. In the 3 localities in Hidalgo, recent bottlenecks were identified, and in Veracruz, an old bottleneck was found. Variation in leaf morphology and genetic structure of Mexican beech populations could be the result of a combination of various geographical, climate and ecological factors.
Growth traits and genetic diversity of 23 provenances of Quercus rubra introduced from North America were analyzed in a provenance trial established with a randomized block design in Hwaseong, Gyeonggi, South Korea in 1993. Growth variables and survival at age 25 were compared with results from early stages. Height, DBH, volume and stem straightness of Q. rubra was better than those of the domestic oak (Quercus accutissima). Growth of the Dunham Island provenance from New York was the best among the 23 provenances that of the Eagle River provenance from Wisconsin was poorest. Survival rate at age 25 was on average 52%. The longitude of seed origin and growth of provenance were consistently significantly negatively correlated at all ages. Growth of coastal provenances was superior to that of the inland provenances, which were separated by the Appalachian Mountains. Genetic diversity and genetic distance among the provenances were evaluated using microsatellite markers. The allelic frequencies showed high polymorphism in 10 microsatellite loci, and 292 alleles were found. Of 10 loci, two were commonly found in the 23 provenances. The mean allelic diversity and heterozygosity observed among the provenances were similar to those from the native populations of Q. rubra in North America. Nei′s genetic distance among the 23 was estimated and showed that a clear trend between geographic and genetic distances, indicating that some provenances have high genetic diversity with superior growth performance.
Patterns of gene flow and gene introgression can be used to assess the risk of genetic pollution of wild forest trees from widespread cultivated trees. A comprehensive understanding of the genetic relationships and levels of gene flow among wild and cultivated common walnut (Juglans regia) has become an urgent issue. Using twelve microsatellite markers, we investigated the genetic diversity and gene flow between cultivated and wild trees of J. regia in the Qinling Mountains, China. A high level of genetic variation was detected in both cultivated and wild trees. The mean number of alleles per locus was 17.5. Observed heterozygosity (HO) and expected heterozygosity (HE) were 0.777 and 0.800, respectively. Pollination of mother trees was not by nearest neighbors, and a paternity of 60.7% of offspring evaluated could not be assigned to a local, sampled tree. Pollen flow from cultivated trees to wild trees was infrequent (5.4%), and selfing rates ranged from zero to 25.0%. Male parents were located from 0 to 1005 m from their female partners, with an average pollination distance of 285.1 m. These results are discussed in light of the cultivated species' diversity, outlining the frequent spontaneous genetic contributions from the wild to the cultivated compartment. In addition, the pollen flow parameters provide useful information about the dynamics of pollen movement within J. regia populations.
Quercus L. has significant societal, ecological and economic benefits in the Northern Hemisphere. However, species identification among oaks is notoriously difficult. China harbours highly diverse oaks, of which the diversity of white oaks is the most extensive; however, to date, the evolution of chloroplast (cp) genomes in white oaks in China has not been comprehensively studied. Thus, we sequenced the complete cp genomes (161,254 bp, 161,229 bp and 161,254 bp in size) of three white oak species (Quercus serrata Thunb. var. brevipetiolata A. DC. Nakai, Quercus wutaishansea Mary and Quercus mongolica Fischer ex Ledebour, respectively). Six white oak species (Quercus aliena Blume, Quercus dentata Thunb., Quercus aliena Blume var. acutiserrata Maximowicz ex Wenzig, Q. serrata var. brevipetiolata, Q. wutaishanica and Q. mongolica) and five other Fagaceae species (Quercus rubra L., Quercus variabilis Bl., Quercus aquifolioides Rehd. et Wils., Fagus engleriana Seem. and Castanea henryi Skan Rehd. et Wils.) were retrieved for comparative analyses. We detected 11 highly divergent regions (psbA, matK/rps16, rps16, trnS-GCU/trnG-GCC, trnR-UCU/atpA, trnT-GGU/psbD, ndhJ, ndhJ/ndhK, accD, ndhF and ycfI) through comparative analyses and these regions might be used as molecular markers. The ω ratio of the rps12, rpoC2 and ycf1 genes was greater than 1 in several comparison groups between white oaks and the petA gene was subjected to significant positive selection between the comparison of six white oaks and Q. variabilis. Phylogenetic analyses revealed that six white oaks were grouped with Q. rubra, forming a single clade.
Five Larix species (L. griffithii, L. speciose, L. himalaica, L. kongboensis, and L. potaninii var. australis), have survived on the Qinghai-Tibet Plateau (QTP) under specific climate conditions for decades. The lack of genomic information seriously hinders research on the evolution, conservation and ecology of these Larix resources. In this study, complete chloroplast (cp) genomes of the 5 species were assembled and compared based on next generation sequencing technology combined with polymerase chain reaction validation. The results show that the 5 cp genomes are relatively conservative in size, gene content and arrangement, and border variation. Phylogenetic analysis showed that the species are closely related as well as to seven other species of the same genus. In addition, the 5 cp genomes contained few simple sequence repeats and relatively low nucleotide variability; thus, 12 candidate polymorphic cp DNA markers will be helpful for further research on relevant population genetics. These results will provide valuable genetic information for the conservation, evolution and ecology of these species and their relatives.
The effects of genetic and environmental factors on Pinus koraiensis growth were studied based on a 35 year-old progeny trial composed of open-pollinated offspring of twenty-one plus trees. Height, DBH and volume of the offspring was analyzed using restricted maximum likelihood/best linear unbiased prediction in mixed model analysis. Significant site and family effects on the three traits were observed. The distinct growth of offspring by site with disparate climates corroborated the importance of planting species in suitable conditions. Growth differences by family was significant, emphasizing the importance of identifying families with either superior or inferior performance. The parental ranking was assigned in the sites, inferring the breeding value of each plus tree. The estimates of individual heritability ( ) of height, DBH and volume growth were 0.169–0.645, 0.108–0.331 and 0.129–0.343 respectively, with higher of the height than DBH on each site. Coefficient of variance of genetic effect was higher with DBH in some cases, indicating the scope for selection is larger for this trait despite the lower heritability compared to height. For the variation between families in terms of the performance stability across sites, consideration of the genotype by environment interaction is required in selecting materials to be used in reforestation with Korean pine. A few families with either superior or inferior performance retained their parental ranking for at least a decade. Other families with increased growth on a particular site were identified, indicating their high breeding value and low stability. Differences in the genetic performance of the families by site requires delineation of the breeding region of the species.
The aim of this study is to determine the genetic variability and differentiation among populations of pedunculate oak (Quercus robur) at the eastern margin of the species distribution range. We applied new set of 95 geographically informative nuclear SNP (single nucleotide polymorphism) loci developed using Double Digest Restriction Site Associated DNA (ddRAD), a new generation DNA sequencing technology. The study area is located in the basins of the Volga River and its two main tributaries, Kama and Belaya. Despite the strong reduction and fragmentation of pedunculate oak forests over the last several centuries and comparatively small sizes of present stands, a relatively similar genetic diversity of seven populations was observed (on average, allelic diversity υа = 1.472–1.603, observed heterozygosity HO = 0.305–0.358, expected heterozygosity HE = 0.272–0.343). The genetic distances between populations vary between 0.102 and 0.170 (on average, d0 = 0.128). We have identified the absence of a spatial genetic structure and the existence of genetically peculiar populations in the territory studied. The genetic distances of Gregorius between populations vary between 0.102 and 0.170 (on average, d0 = 0.128). Genetic differentiation among populations was statistically significant with a mean of the fixation index FST of 0.075. Populations from the Privolzhye Upplands and from northern parts of the study area make the most contribution to overall inter-population differentiation (d0 = 0.137). No significant differences exist among the samples at lowlands along the Volga river (d0 = 0.110). It was concluded that the multiplicity and different ages of local populations and the complexity of migration routes of the pedunculate oak from Pleistocene refugia and secondary Holocene shelters can cause this phenomenon.
The article “Integrating cross-sensor high spatial resolution satellite images to detect subtle forest vegetation change.
The article “Dynamic analysis of gene expression and determination of chemicals in agarwood in Aquilaria sinensis”, written by Zeqing Wu, Wanzhen Liu, Jing Li, Liangwen Yu and Li Lin was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 10th May 2019 without open access.