P values based on standard hypothesis testing are commonly reported in articles published by the Journal of Forestry Research (JFR). However, effect sizes are barely used and reported, even if they are of direct relevance to the primary questions of many of the published studies. The incorporation of effect sizes in studies published by JFR should be encouraged and promoted. Inclusion of effect sizes as a requirement in the journal guidelines will facilitate a major change in the way data are tested and interpreted, with the ultimate goal to exempt researchers from the custom of drawing conclusions merely based upon a dichotomous statistical result (P value). Such a policy can also lead to more informed decisions of whether identified effects are of practical relevance to the forestry.
In South-Eastern forests of France, risks linked to the effects of tropospheric ozone (O3) are real; its annual impact has been observed specifically near the coastline and in high altitude mountains during the period 2017 − 2019. In this study, the risk assessment of O3 pollutant was carried out using two approaches based on forest response indicators such as O3 specific foliar visible injury and by stomatal O3 flux. Phytotoxic O3 dose values (POD0) were obtained by the DO3SE model. The model requires hourly O3 concentration for POD0 calculation. A modified approach that uses measurements from passive samplers (monthly average O3 concentration) was tested for the calculation of POD0 and test results showed good agreement with the POD0 calculated using hourly O3 data. In the model input file, the average O3 concentration is used for POD0, and this could be useful for POD0 calculation when the active monitor is limited. In this study, a flux-based assessment provided better correlation with O3 specific leaf injury, which is also species-specific. Foliar visible injury in response to O3 indicates that Pinus cembra and Pinus halepensis are more affected and therefore more sensitive than Pinus sylvestris. The POD0 and stomatal conductance (G sto) seem to be induced by environmental factors, primarily rainfall and the soil water potential (ƒSWP). The correlation between the O3 flux metric and environmental variables with forest response indicators by Spearman rank test confirms P. cembra as one of the most sensitive species to O3.
Spatiotemporal dynamic vegetation changes affect global climate change, energy balances and the hydrological cycle. Predicting these dynamics over a long time series is important for the study and analysis of global environmental change. Based on leaf area index (LAI), climate, and radiation flux data of past and future scenarios, this study looked at historical dynamic changes in global vegetation LAI, and proposed a coupled multiple linear regression and improved gray model (CMLRIGM) to predict future global LAI. The results show that CMLRIGM predictions are more accurate than results predicted by the multiple linear regression (MLR) model or the improved gray model (IGM) alone. This coupled model can effectively resolve the problem posed by the underestimation of annual average of global vegetation LAI predicted by MLR and the overestimate predicted by IGM. From 1981 to 2018, the annual average of LAI in most areas covered by global vegetation (71.4%) showed an increase with a growth rate of 0.0028 a–1; of this area, significant increases occurred in 34.42% of the total area. From 2016 to 2060, the CMLRIGM model has predicted that the annual average global vegetation LAI will increase, accounting for approximately 68.5% of the global vegetation coverage, with a growth rate of 0.004 a−1. The growth rate will increase in the future scenario, and it may be related to the driving factors of the high emission scenario used in this study. This research may provide a basis for simulating spatiotemporal dynamic changes in global vegetation conditions over a long time series.
The influences of trait diversity (i.e., the niche complementarity effect) and functional composition (i.e., the mass ratio effect) on aboveground biomass (AGB) is a highly debated topic in forest ecology. Therefore, further studies are needed to explore these mechanisms in unstudied forest ecosystems to enhance our understanding, and to provide guidelines for specific forest management. Here, we hypothesized that functional composition would drive AGB better than trait diversity and stem size inequality in the (sub-) tropical forests of Nepal. Using data from 101 forest plots, we tested 25 structural equation models (SEMs) to link elevation, stem DBH inequality, trait diversity (i.e., trait richness, evenness, dispersion and divergence), functional composition [i.e., community-weighted of maximum height mean (CWM of Hmax), specific leaf area (CWM of SLA), leaf dry matter content (CWM of LDMC), and wood density (CWM of WD)] and AGB. The best-fitted SEMs indicated that CWM of Hmax promoted AGB while overruling the impacts of trait diversity indices on AGB. However, low trait diversity indices were linked with higher AGB while overruling the effects of CWM of SLA, LDMC and WD on AGB. In addition, AGB decreased with increasing elevation, whereas stem size inequality did not influence AGB. Our results suggest that divergent species’ functional strategies could shape AGB along an altitudinal gradient in tropical forests. We argue that forest management practices should include plant functional traits in the management plan for the co-benefits of biodiversity conservation and carbon sequestration that underpins human wellbeing.
Forest fires are frequent under a Mediterranean climate and have shaped the landscape of the region but are currently altered by human action and climate change. Fires have historically conditioned the presence of pine forests, depending on severity and forest regeneration. Regeneration of Mediterranean pine forests is not always successful, and a transition to shrublands or stands of resprouting species can occur, even after reforestation. This study analyses vegetation changes in two Mediterranean pine forests after severe fires and both reforested. The pines had difficulty to regenerate, even despite post-fire reforestation. The problem is the difficulty of young seedlings to survive, possibly due to increased summer drought. Problems are greater in pine species at the limit of their ecological tolerance: Pinus pinea had a much better recovery success while P. sylvestris and P. nigra virtually disappeared. Pinus pinaster had intermediate results but recovery was generally poor. A transition has taken place in many burnt areas to scrubland or to thickets of the resprouting Quercus rotundifolia, although it is not possible to know whether they will evolve into forests or remain in a sub climatic state. Resprouting species may increase fire severity but facilitates post-fire colonisation. Post-fire recovery difficulties are closely linked to issues of natural regeneration. Fire could initiate the disappearance of pine forests, but even in the absence of fire they may disappear in the long-term due to the lack of regeneration. Action is needed to increase the resilience of these forests, ensuring natural regeneration, and incorporating resprouting species in the understorey.
Turkey has a high potential for wildfires along its Mediterranean coast because of its dense forest cover and mild climate. An average of 250 wildfires occurs every year with more than 10,000 hectares destroyed due to natural and human-related causes. The study area is sensitive to fires caused by lightning, stubble burning, discarded cigarette butts, electric arcing from power lines, deliberate fire setting, and traffic accidents. However, 52% of causes could not be identified due to intense wildfires occurring at the same time and insufficient equipment and personnel. Since wildfires destroy forest cover, ecosystems, biodiversity, and habitats, they should be spatially evaluated by separating them according to their causes, considering environmental, climatic, topographic and forest structure variables that trigger wildfires. In this study, wildfires caused by lightning, the burning of agriculture stubble, discarded cigarette butts and power lines were investigated in the provinces of Aydın, Muğla and Antalya, where 22% of Turkey’s wildfires occurred. The MaxEnt method was used to determine the spatial distribution of wildfires to identify risk zones for each cause. Wildfires were used as the species distribution and the probability of their occurrence estimated. Additionally, since the causes of many wildfires are unknown, determining the causes is important for fire prediction and prevention. The highest wildfire occurrence risks were 9.7% for stubble burning, 30.2% for lightning, 4.5% for power lines and 16.9% by discarded cigarette butts. In total, 1,266 of the 1,714 unknown wildfire causes were identified by the analysis of the cause-based risk zones and these were updated by including cause-assigned unknown wildfire locations for verification. As a result, the Area under the ROC Curve (AUC) values were increased for susceptibility maps.
Effective landscape-scale fuel management strategies are essential for reducing wildfire risk in Mediterranean fire-prone areas. In this study, the minimum travel time (MTT) fire-spread algorithm as implemented in FlamMap was applied to assess the potential of alternative fuel treatments for lowering wildfire losses in a 5,740-ha study area in eastern Sardinia, Italy. Twenty-seven wildfires at 10-m resolution were simulated considering three wind speeds (15, 18, and 21 km h−1) to compare fuel treatments: no treatment (NT), irrigated agroforestry areas with shrub clearing (T1), prescribed fire in eucalyptus stands (T2), and irrigated grasslands (T3). The simulations replicated a recent large wildfire that occurred in the study area (Orrì wildfire, 2019) and considered the weather and fuel moisture conditions associated with this event. The average wildfire exposure outputs (burned area, probability of burning, conditional flame length, potential crown fire occurrence, and surfaces withflame lengths above 2.5 m) decreased after fuel treatments, compared to no treatment. T1 was the most effective strategy in mitigating wildfire hazards and provided the most significant performance for several wildfire exposure indicators. Treating only 0.5% of the study area (~ 30 ha) resulted in a decrease in all wildfire exposure metrics to ~ 10% within the study area. In addition, the total surface characterized by high flame length (average > 2.5 m) was the lowest in the T1 treatment. This study can help land and fire managers optimize fuel treatment opportunities and wildfire risk mitigation strategies in Mediterranean areas.
Due to considerable deforestation in North Korea, there is a need to plan forest restoration programs based on scientific forest management. In this study, a methodology was developed for estimating the site index values of six major tree species and the forest productivity potential. The site index values of these tree species were derived in South Korea using the Chapman-Richards equation. These values were used with data from the 6th National Forest Inventory, which included 20 types of edaphic, topographic, and climatic factors, and random forest analysis—a widely used machine learning technique for spatial prediction—to develop a new model for estimating the site index values of these species across South Korea. The prediction accuracy of this model was evaluated using the root mean square error. The results show that the prediction accuracy was high, with a root mean square error of ~ 1 m. Moreover, the importance of the variables related to climate and geography was generally high. The proposed site index estimation model for six tree species was applied across North Korea, and its effectiveness tested by comparing the estimated values with those reported in literature from North Korea. The differences between the model outputs and recorded data in the northern alpine regions were presumably due to the lack of data for high-altitude regions in South Korea. This model is based on the determination of the suitability of tree species in restoration efforts. Therefore, it can contribute to the evaluation of forest productivity in North Korea and may help plan efficient forest restoration programs.
The growth and wood properties of 240 individual Populus × euramericana cv. ‘74/76’ (hereafter poplar 107) trees planted in Hebei Plain, China was evaluated. Mean annual increments in height, breast height diameter and volume, as well as cellulose, hemicellulose and lignin contents, shrinkage, density, bending strength and modulus of elasticity in the heartwood and sapwood. Environmental factors influencing growth and wood properties were analyzed using correlation and stepwise regression. The results show that the coefficients of variation (CVs) of growth traits ranged from 10.6 to 22.4%. The CVs of the chemical properties of heartwood ranged from 4.3 to 30.2%, and for sapwood from 3.2 to 27.5%. The CVs of the physical and mechanical properties of heartwood ranged from 8.6 to 31.7%, and for sapwood from 6.4 to 29.9%. The results of one-way ANOVA showed that there were significant differences in growth traits and wood properties among sites. Soil pH, total and available phosphorus, total potassium, and soil organic matter were key soil factors affecting growth and wood properties of poplar 107, whereas mean annual ground temperatures and precipitation were the main climatic factors. To better cultivate poplar 107, area with less annual rainfall, slightly higher temperature and soil pH value close to neutral should be selected.
Managing mature Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] stands to emulate the structural complexity of natural old-growth forest requires identifying structural targets at the sub-stand level at which neighborhood dynamics and patchy disturbance shape structure. We therefore sought to describe the archetypal shapes of predominant sub-stand diameter distribution types (DDTs) observed in natural tree neighborhoods in stands comprising a chronosequence (ca. 120–450+ yrs) encompassing mature, vertical diversification, and horizontal diversification development stages. The ten 1.0 ha stands are located in the southcentral Oregon Cascades, USA. Building on the known spatial position of each tree, natural tree neighborhoods were identified using the floating neighborhood approach based on spatial tessellation connecting neighboring trees at the first- (mean 61 m2) through fifth- (mean 2058 m2) order scales. Cluster analysis was then used to objectively identify the most predominant DDTs among the relative tree size distributions observed in the trans-scale neighborhoods within each stand. Repeated measures regression was used to classify each DDT to one of six observed archetypal shapes: negative exponential, unimodal, rotated sigmoid, bimodal, concave, or multi-modal. Only three of the 81 observed DDTs deviated by < 10% from the stand average, while every stand had at least one DDT that deviated by > 50% (maximum 83%). Within each stand, five to ten predominant DDTs were observed, which deviated from the stand average by 30–48% and were characterized by two to five different archetypal shapes. Consequently, in some stands the majority of tree neighborhoods were best characterized by a different shape from that assigned at the stand level. Deviation from the stand average increased from the youngest stand in the mature development stage through the middle stands in the vertical diversification stage to the oldest stands in the horizontal diversification stage. The complexity of DDT shapes tended to increase along the chronosequence (from negative exponential and uniform toward concave and multi-modal), with shape richness highest mid-sequence and evenness peaking in the oldest stands. The high diversity of sub-stand structural complexity reduces the utility of stand-level diameter distributions as old-growth restoration targets. However, the presence in early-sequence stands of sub-stand diameter distributions common to later-sequence stands may facilitate active management at the neighborhood level to promote future old-growth condition. Restoration of sub-stand diameter structures would likely require combining spatial perspectives, such as by augmenting tree-level crop-tree management with diameter distribution targets for the resulting tree neighborhoods.
Nitraria sibirica Pall. is an important shrub with a strong salt-alkali tolerance, but the mechanism underlying this tolerance remains obscure. In this study, N. sibirica, with salt-sensitive Vigna radiata (Linn.) Wilczek as the control, was subjected to transient salt stress (100 mM NaCl), alkali stress (50 mM Na2CO3), and osmotic stress (175 mM mannitol). The ionic fluxes of Na+ and K+ in the root apical region were measured. Results show that, under salt and alkali stress, N. sibirica roots exhibited higher capacities to limit Na+ influx and reduce K+ efflux, thereby resulting in lower Na+/K+ ratios compared with V. radiata roots. Alkali stress induced stronger Na+ influx and K+ efflux in the root salt stress treatment; Na+ influx was mainly observed in the root cap, while K+ efflux was mainly observed in the elongation zone. While under osmotic stress, N. sibirica roots showed stronger Na+ efflux and weaker K+ efflux than V. radiata roots. Na+ efflux was mainly observed in the root elongation zone, while K+ efflux was in the root cap. These results reveal the ionic strategy of N. sibirica in response to transient salt, alkali, and osmotic stresses through the regulation of Na+/K+ flux homeostasis.
Red osier dogwood (Cornus sericea L.), widely distributed throughout North America, is essential for wildlife, thus biodiversity. It is recommended for reclamation or revegetation of sites disturbed by oil and gas extraction because it tolerates a wide range of soil types and high pH levels. Since germination of this species is extremely difficult with long stratification requirements and poor germination, cuttings facilitate propagation. In this study, to develop techniques to propagate the species from stem cuttings, four concentrations of indole-3-butyric acid (IBA) and two cutting ages previous year’s growth (PYG) and current year’s growth (CYG) were investigated for survival and growth. After 4 months, survival rate, height growth, and shoot biomass from PYG cuttings were enhanced with IBA. In contrast, IBA did not affect these parameters in CYG cuttings. Root morphology was significantly affected by IBA concentration and cutting age. IBA, at higher concentrations, increased root surface and length. Total root surface area and length of PYG cuttings were increased, which may facilitate the absorption of essential resources and consequently increase growth. The results indicate that increasing the concentration of IBA may be an effective way to have better plant survival and growth of previous year’s cuttings in red osier dogwood.
To test the patterns of the root morphology and architecture indexes of Tamarix chinensis in response to water and salt changes in the two media of the groundwater and soil, three-year-old T. chinensis seedlings were chosen as the research object. Groundwater with four salinity levels was created, and three groundwater level (GL) were applied for each salinity treatment to measure the root growth and architecture indexes. In the fresh water and brackish water treatments, the topological index (TI) of the T. chinensis roots was close to 0.5, and the root architecture was close to a dichotomous branching pattern. In the saline water and saltwater treatments, the TI of the T. chinensis roots was large and close to 1.0, and the root architecture was close to a herringbone-like branching pattern. Under different GLs and salinities, the total root length was significantly greater than the internal link length, the external link length was greater than the internal link length, and the root system showed an outward expansion strategy. The treatment with fresh water and a GL of 1.5 m was the most suitable for T. chinensis root growth, while the root growth of T. chinensis was the worst in the treatment with saline water and a GL of 0.3 m. T. chinensis can adapt to the changes in soil water and salt by regulating the growth and morphological characteristics of the root system. T. chinensis can adapt to high-salt environments by reducing its root branching and to water deficiencies by expanding the distribution and absorption area of the root system.
This study was performed to observe the effects of water on photosynthesis and water-related physiology in dominant shrubs in shell sand habitats. Four-year-old Periploca sepium seedlings were used as model species. A gradient of 12 water levels was established by artificially supplying the shell sand with water up to saturation and then allowing natural evapotranspiration to occur. The photosynthetic, chlorophyll fluorescence and stem sap flow parameters of P. sepium were measured under a range of water conditions. The different soil water conditions were classified according to the responses of these parameters. (1) With the increase in the relative water content (RWC) of the shell sand, the parameters of leaf photosynthesis, chlorophyll fluorescence and water-related physiology in P. sepium showed significant critical responses. The net photosynthetic rate (P n), transpiration rate (T r), instantaneous water use efficiency (WUE), potential water use efficiency (WUE i), maximum photochemical efficiency (F v/F m), actual photochemical efficiency (Φ PSII) and daily accumulation of stem sap flow all increased first and then decreased with increasing RWC, but the corresponding water conditions associated with their maximum values were not the same. An RWC of 69.40% was determined to be the optimal water condition for photosynthesis and water-related physiological activity in P. sepium. At an RWC of 36.61%, the mechanism of photosynthetic inhibition in P. sepium changed from stomatal limitation to nonstomatal limitation; this was also the minimum water requirement for maintaining normal photosynthetic processes. An RWC of 50.27% resulted in the highest WUE in P. sepium, indicating that moderate drought stress increased WUE. (2) Based on the quantitative relationship between the photosynthetic parameters of P. sepium and the shell sand water gradient, the soil water availability was classified into 6 water grades. The RWC range for maintaining strong photosynthesis and high WUE in P. sepium was 63.22–69.98%. (3) Gas exchange in P. sepium was inhibited under drought and waterlogging stresses. Under these conditions, the photosynthetic electron transport chain was blocked, and the dissipation of light energy as heat increased, which ultimately led to a decline in photosynthetic productivity; moreover, transpiration and dissipation were aggravated, and water transmission and utilization processes in P. sepium were hindered. A significant negative feedback regulation mechanism in the photosynthetic and water-related physiological processes of P. sepium was observed; this mechanism allowed P. sepium growing in shell sand to be highly adaptable to water stress.
To evaluate the relationships among clones and open pollinated families from the same plus trees and to select elite breeding materials, growth, and wood characteristics of 33-year-old Pinus koraiensis clones and families were measured and analyzed. The results show that growth and wood characters varied significantly. The variation due to clonal effects was higher than that of family effects. The ratio of genetic to phenotypic coefficient of variation of clones in growth and wood traits was above 90%, and the repeatability of these characteristics was more than 0.8, whereas the ratio of genetic to phenotypic coefficient of variation of families was above 90%. The broad-sense heritability of all characteristics exceeded 0.4, and the narrow-sense family heritability of growth traits was less than 0.3. Growth characteristics were positively correlated with each other, but most wood properties were weakly correlated in both clones and families. Fiber length and width were positively correlated between clones and families. Using the membership function method, eleven clones and four families were selected as superior material for improved diameter growth and wood production, and two families from clonal and open-pollinated trees showed consistently better performance. Generally, selection of the best clones is an effective alternative to deployment of families as the repeatability estimates from clonal trees were higher than narrow-sense heritability estimates from open pollinated families. The results provide valuable insight for improving P. koraiensis breeding programs and subsequent genetic improvement.
Acyl-CoA-binding proteins (ACBPs) are important for the transport of acyl groups for macromolecular biosynthesis involved in plant growth, development, and diverse stress (e.g., cold, drought, salinity, and heavy metals) responses. Here, we report the phylogeny and characteristics of the ACBP family in the woody plant Populus trichocarpa. Eight genes encoding ACBP proteins were identified, and they are distributed on eight chromosomes in P. trichocarpa. These PtACBP genes were divided into four subgroups according to gene structure, conserved motifs and phylogenetic relationship. Promoter analysis revealed that cis-elements were related to stress response, phytohormone response, and physical and reproductive growth regulation. Expression levels of PtACBP genes varied among different organs, with the highest expression in leaves and the lowest in stems. Quantitative real-time PCR (qRT-PCR) analysis showed that under salinity-alkali stresses (i.e., 200 mM NaCl, 75 mM Na2CO3, and 100 mM NaHCO3), four (PtACBP1, PtACBP3, PtACBP4 and PtACBP8) of eight PtACBP genes were significantly induced in roots and leaves. These data provide a comprehensive analysis of the ACBPs family in P. trichocarpa, which could be useful for gene function analyses.
Lectins are natural proteins in animals, plants, and microorganisms and can be divided into 12 families. These lectins play important roles in various environmental stresses. Some polyploid plants show tolerance to environmental stresses and to insect pests. However, the mechanism of stress tolerance is unclear. Tetraploid Robinia pseudoacacia (4×) under salt stress showed higher tolerance than diploid R. pseudoacacia (2×). As lectin can improve stress tolerance, it was questioned whether the stress resistance of polyploid plants was related to the lectin protein. In this study, salt resistance of lectin gene TRpL1 was verified by its over-expression in plants. In addition, salt resistance of lectin protein by E. coli strains was detected. The data revealed that the over-expression transgenic plants of TRpL1 showed better salt tolerance than control plants under salt stress, and the TRpL1-expressing strain also grew better in the medium with added NaCl. Therefore, tetraploid plants can resist salt stress through TRpL1 protein regulation.
To study the effects of geoclimatic variables of provenances on growth phenotypes and selected plus provenances, over 3000 trees of 22-year-old Larix kaempferi were evaluated from trials established in two climate zones for provenance selection and to explore the influence of climate variables on provenance performance. The material was replicated plantings of 84 open pollinated families from six provenances distributed in the mountains of central Japan. Provenance variation was observed in most age groups and the heritability of growth traits showed large differences. The phenotypic maximum value of height and diameter were significantly positive with altitude, and mean annual precipitation being important factors. Diameter at breast height growth was significantly negative with altitude and spring rainfall. The Ina provenance of relatively high altitudes, was well adapted to a variety of climates. Altitude might be the driving force for phenotypic and genetic variations and local adaptation.
Fraxinus mandshurica Rupr. is one of the main afforestation species in northeast China, and there is great demand for improved F. mandshurica varieties. The results of an investigation into and analysis of the growth traits of F. mandshurica provenances and families showed that there were significant differences in different periods. However, variations in growth traits decreased year by year. There was a significant negative correlation between tree heights of the provenances and sunshine hours in their areas of origin. The provenances of Xinglong, Hailin and Wuchang were selected based on the volume of 18-year-old trees. The average genetic gain from the selection of fast-growing provenances was 19.4%. Ten superior fast-growing families were selected. The average volume of the selected families was 22.6%, higher than that of all families. The correlation coefficient between heights at 6-year-old and at 18a was 0.838 for provenances, and between heights at 4-year-old and at 18-year-old was 0.303 for families. These results indicate that early selection for height in provenances or families could be performed at 6 years or 4 years, respectively. Early selection for DBH and volume in families could start at 8 years.
This research assessed the relationship between wood physical-anatomical variables and charcoal physical–mechanical properties. Nine trees were harvested and mechanically processed into standard pieces for laboratory analysis. The following variables were determined: wood density, fiber length and width, fiber lumen diameter and wall thickness, fiber wall fraction, and vessel frequency. The charcoal was produced in a laboratory and gravimetric yield, relative density, and mechanical properties established. Pearson’s correlation coefficients, multivariate statistical analysis of canonical correlation, and principal component analysis were used to evaluate the relationship between wood and charcoal properties. Fiber width was not significantly correlated with charcoal properties. Charcoal bulk density, hardness, and strength were positively correlated with wood density, fiber length, wall thickness, and wall fraction. Charcoal properties were negatively correlated with fiber lumen diameter and vessel frequency. These results will help identify the best wood with adequate physical–mechanical properties for industrial charcoal processing.
Urbanization provides both challenges and opportunities for biodiversity conservation, but patterns of urban plant diversity across land uses, especially in Asian countries, remains unclear. To determine these patterns of diversity, woody plants in 174 sample quadrats across various land use types in Kyoto City were investigated. Richness, abundance, and evenness were evaluated at city, land use, and quadrat scales, and biodiversity of different land use types was compared. At the city level, 223 species in 77 families were recorded. At the land use level, residential areas had the highest total biological richness, with moderate to low evenness, while commercial areas exhibited low richness. At the quadrat level, the low-rise residential area had higher species richness than the other land uses. Species abundance and evenness in quadrats were significantly different across land use types for the canopy layer but not for the understory. The results provide insights into urban biodiversity design and management by identifying prior land uses for biodiversity improvement and by highlighting the contribution of residential private yards. Urban heterogeneity, scale, and multidimensionality should be considered when measuring urban biodiversity.
For this study of long-term spatial patterns and trends of active fires in southern hemispheric Africa and on Madagascar from 2001 to 2020, active fire data from the MODIS FIRMS global fire data products were analyzed. The annual center of fire concentration tended to migrate toward the preserved rainforests and nature conservation areas in the Congo Basin and the mountain forests on the northeastern coast of Madagascar. Fire frequency varied seasonally at both study areas. We used geostatistical analysis techniques, such as measures of dispersion and emerging hot spot analysis, to reveal long-term trends in spatial patterns of fire events. In southern hemispheric Africa, the observed active fires tended to drift northward toward the Zambia-DRC border in the Congo basin. This northward migration progressed toward humid rainforests, which were better suited to sustaining repeated fire events. On Madagascar, the observed active fires tended to migrate toward the east coast in protected mountain forests. The spatial patterns of long-term trends showed a concentration of fires in the tropical regions of southern hemispheric Africa. Moreover, smaller clusters of new hot spots were located over eastern South Africa, overlapping with undifferentiated woodlands. On Madagascar, both hot and cold spots were identified and were separated by the highland region in the center of the island. Most of the eastern island was characterized by cold spots that received less precipitation than did the rest of the island. The presence of increasing hots spots in the densely vegetated areas highlights the urgent need for fire prevention and management in this region.
Recent reports warned that planting leguminous trees under monocultures elevates nitrous oxide (N2O) emissions through N-rich litter inputs. We hypothesized that planting trees on sandy soil can avoid the legume-derived boost of N2O emissions through limiting water availability for N2O production. Effects of planting legumes on methane (CH4) uptakes were also examined. N2O emissions and CH4 uptakes were compared among five tropical tree plantation stands including three leguminous stands (Acacia auriculiformis, Acacia mangium, and Xylia xylocarpa) and two non-leguminous stands (Eucalyptus camaldulensis, and Hopea odorata). Due to lower water contents of the soil, the N2O fluxes in our study site were at the lower end of the tropical rain forests. As we hypothesized, no clear differences in N2O emissions were observed between leguminous and non-leguminous stands. CH4 uptake rates in the present study were lower than those of other tropical forests. CH4 uptakes in leguminous stands did not differ from those in non-leguminous stands. Overall, we demonstrated that planting leguminous trees on sandy soils has a potential to enable us to manage leguminous monoculture tree plantations without boosting N2O emissions or reducing CH4 uptakes.
