Forest ecosystems are critical to ecological stability,yet their functionality is increasingly threatened by the growing frequency of drought,particularly in arid and semi-arid regions.While afforestation enhances for...Forest ecosystems are critical to ecological stability,yet their functionality is increasingly threatened by the growing frequency of drought,particularly in arid and semi-arid regions.While afforestation enhances forest cover in these areas,the capacity of planted forests to adapt to climate change is poorly understood.This study examines the drought resistance and adaptive capacity of planted and naturally growing Schrenk spruce(Picea schrenkiana Fisch.&C.A.Mey.)in the Ili River Basin,Xinjiang,China using tree-ring analysis.The results indicate that natural stands have a stronger correlation with meteorological factors than plantations.Over the past 50 years,significant growth declines occurred during 1995-1997,2007-2009,and 2012-2014,with natural forests showing a greater frequency and severity of declines compared to plantations.Planted stands demonstrated greater resistance to drought,whereas natural forests had higher resilience and recovery.Over time,natural forests have shown declining resistance to drought but increased resilience and recovery.Conversely,plantations showed declines in resistance and recovery but an increased capacity for recovery.Older natural forests are more prone to growth decline,while structurally simpler planted forests show stronger drought resistance.However,following periods of drought,natural forests demonstrated a stronger capacity for recovery.These findings provide valuable insights into the response of P.schrenkiana to climate change and offer support for the sustainable management and conservation of forest ecosystems in the Xinjiang region of China.展开更多
Conservation and enhancement of old-growth forests are key in forest planning and policies.In order to do so,more knowledge is needed on how the attributes traditionally associated with old-growth forests are distribu...Conservation and enhancement of old-growth forests are key in forest planning and policies.In order to do so,more knowledge is needed on how the attributes traditionally associated with old-growth forests are distributed in space,what differences exist across distinct forest types and what natural or anthropic conditions are affecting the distribution of these old-growthness attributes.Using data from the Third Spanish National Forest Inventory(1997–2007),we calculated six indicators commonly associated with forest old-growthness for the plots in the territory of Peninsular Spain and Balearic Islands,and then combined them into an aggregated index.We then assessed their spatial distribution and the differences across five forest functional types,as well as the effects of ten climate,topographic,landscape,and anthropic variables in their distribution.Relevant geographical patterns were apparent,with climate factors,namely temperature and precipitation,playing a crucial role in the distribution of these attributes.The distribution of the indicators also varied across different forest types,while the effects of recent anthropic impacts were weaker but still relevant.Aridity seemed to be one of the main impediments for the development of old-growthness attributes,coupled with a negative impact of recent human pressure.However,these effects seemed to be mediated by other factors,specially the legacies imposed by the complex history of forest management practices,land use changes and natural disturbances that have shaped the forests of Spain.The results of this exploratory analysis highlight on one hand the importance of climate in the dynamic of forests towards old-growthness,which is relevant in a context of Climate Change,and on the other hand,the need for more insights on the history of our forests in order to understand their present and future.展开更多
Increasing human activity is altering the struc-ture of forests,which affects the composition of communi-ties,including birds.However,little is known about the key forest structure variables that determine the richnes...Increasing human activity is altering the struc-ture of forests,which affects the composition of communi-ties,including birds.However,little is known about the key forest structure variables that determine the richness of bird communities in European temperate oak forests.We,there-fore,aimed to identify key variables in these habitats that could contribute to the design of management strategies for forest conservation by surveying 11 oak-dominated forest sites throughout the mid-mountain range of Hungary at 86 survey points to reveal the role of different compositional and structural variables for forest stands that influence the breeding bird assemblages in the forests at the functional group and individual species levels.Based on decision tree modelling,our results showed that the density of trees larger than 30 cm DBH was an overall important variable,indi-cating that large-diameter trees were essential to provide diverse bird communities.The total abundance of birds,the foliage-gleaners,primary and secondary cavity nest-ers,residents,and five specific bird species were related to the density of high trunk diameter trees.The abundance of shrub nesters was negatively influenced by a high density of trees over 10 cm DBH.The density of the shrub layer positively affected total bird abundance and the abundance of foliage gleaners,secondary cavity nesters and residents.Analysis of the co-dominant tree species showed that the presence of linden,beech,and hornbeam was important in influencing the abundance of various bird species,e.g.,Eur-asian Treecreeper(Certhia familiaris),Marsh Tit(Poecile palustris)and Wood Warbler(Phylloscopus sibilatrix).Our results indicated that large trees,high tree diversity,and dense shrub layer were essential for forest bird communities and are critical targets for protection to maintain diverse and abundant bird communities in oak-dominated forest habitats.展开更多
Temperate forest ecosystems are important habitats for many bat species. However, these habitats are increasingly affected by anthropogenic disturbances, particularly urban development, leading to landscapes with vary...Temperate forest ecosystems are important habitats for many bat species. However, these habitats are increasingly affected by anthropogenic disturbances, particularly urban development, leading to landscapes with varying land cover composition and configuration. Limited research has examined how forest and urban landscape composition and configuration influence bat activity and diversity. Using a multi-year statewide bat acoustic monitoring dataset from North Carolina, USA, we investigated the effects of forest and urban composition and configuration at multiple spatial scales on bat activity and diversity. First, we constructed single-variable landscape index regression models and found that both the composition and configuration of forests and urban developments influenced bat activity and diversity in a species-specific manner. Next, we applied a hierarchical partitioning approach to compare the relative contributions of composition and configuration indices in explaining variance in bat activity. For big brown bats and hoary bats, evergreen forest and urban development composition indices contributed the most to explaining activity variance. In contrast, for eastern red bats, evening bats, and tricolored bats, deciduous forest fragmentation indices describing landscape configuration were the most influential factors. Silver-haired bat activity variance was primarily explained by an evergreen forest fragmentation index. Lastly, urban development configuration indices were the strongest predictors of Mexican free-tailed bat activity and total bat activity. These results suggest that forest and urban landscape configuration should be considered in conservation and management planning for North American temperate forest ecosystems, particularly in regions that have not experienced drastic deforestation in recent decades.展开更多
Old-growth forests are of major importance for biodiversity conservation and climate change mitigation,as well as being a benchmark for the implementation of sustainable forest management.Although dedicated studies ha...Old-growth forests are of major importance for biodiversity conservation and climate change mitigation,as well as being a benchmark for the implementation of sustainable forest management.Although dedicated studies have significantly increased in the last decades,there is still limited knowledge of Mediterranean forests,especially those dominated by Quercus pubescens and related taxa.To fill this knowledge gap,we primarily studied in the field two downy oak forests possessing old-growth traits,localized in Sicily(Mediterranean,Italy).Second,we used a structural heterogeneity index(SHI)to assess their old-growthness level,in comparison with the downy oak stands surveyed in the Regional Forest Inventory(RFI)of Sicily.Third,we tested the effect of different sets of structural parameters on SHI scores,thus assessing whether their choice could affect the final score and the stand assessment.SHI was well proven to discriminate these two stands from the others,both showing,on average,a SHI score just higher than 80,whilst SHI in RFI plots was just under 50,a significantly lower value.The methodological approach used in our study highlights the need to standardize the parameters used to characterize the old-growthness level of Mediterranean forests in order to allow more reliable comparisons.Most of the structural parameters were higher in the two selected stands,except for the attributes related to standing deadwood,suggesting a still limited contribution of standing dead trees and snags in the potential old-growth stands under investigation.The application of a structural index has proven effective for the purpose it was tested for,demonstrating its usefulness in discriminating between two potential old-growth stands from ordinary stands of the same forest type.We believe that both forests deserve primary attention and tailored management measures,as well as inclusion in the recently established Italian Network of old-growth forests.展开更多
The study determined the carbon stocks and litter nutrient concentration in tropical forests along the ecological gradient in Kenya.This could help understand the potential of mitigating climate change using tropical ...The study determined the carbon stocks and litter nutrient concentration in tropical forests along the ecological gradient in Kenya.This could help understand the potential of mitigating climate change using tropical forest ecosystems in different ecological zones,which are being affected by climate change to a level that they are becoming carbon sources instead of sinks.Stratified sampling technique was used to categorize tropical forests into rain,moist deciduous and dry zone forests depending on the average annual rainfall received.Simple random sampling technique was used to select three tropical forests in each category.Modified consistent sampling technique was used to develop 10 main 20 m×100 m plots in each forest,with 202 m×50 m sub-plots in each plot.Systematic random sampling technique was used in selecting 10 sub-plots from each main plot for inventory study.Non-destructive approach based on allometric equations using trees’diameter at breast height(DBH),total height and species’wood specific gravity were used in estimating tree carbon stock in each forest.Soil organic carbon(SOC)and litter nutrient concentration(total phosphorus and nitrogen)were determined in each forest based on standard laboratory procedures.The results indicated that,whilst trees in rain forests recorded a significantly higher(p<0.001)DBH(20.36 cm)and total tree height(12.1 m),trees in dry zone forests recorded a significantly higher(p<0.001)specific gravity(0.67 kg m^(−3)).Dry zone tropical forests stored a significantly lower amount of total tree carbon of 73 Mg ha^(−1),compared to tropical rain forests(439.5 Mg ha^(−1))and moist deciduous tropical forests(449 Mg ha^(−1)).The SOC content was significantly higher in tropical rainforests(3.9%),compared to soils from moist deciduous(2.9%)and dry zone forests(1.8%).While litter from tropical rain forests recorded a significantly higher amount of total nitrogen(3.4%),litter from dry zone forests recorded a significantly higher concentration of total phosphorus(0.27%).In conclusion,ecological gradient that is dictated by the prevailing temperatures and precipitation affects the tropical forests carbon stock potential and litter nutrient concentration.This implies that,the changing climate is having a serious implication on the ecosystem services such as carbon stock and nutrients cycling in tropical forests.展开更多
Evergreen broad-leaved forests(EBLFs) are widely distributed in East Asia and play a vital role in ecosystem stability. The occurrence of these forests in East Asia has been a subject of debate across various discipli...Evergreen broad-leaved forests(EBLFs) are widely distributed in East Asia and play a vital role in ecosystem stability. The occurrence of these forests in East Asia has been a subject of debate across various disciplines. In this study, we explored the occurrence of East Asian EBLFs from a paleobotanical perspective. By collecting plant fossils from four regions in East Asia, we have established the evolutionary history of EBLFs. Through floral similarity analysis and paleoclimatic reconstruction, we have revealed a diverse spatio-temporal pattern for the occurrence of EBLFs in East Asia. The earliest occurrence of EBLFs in southern China can be traced back to the middle Eocene, followed by southwestern China during the late Eocene-early Oligocene. Subsequently, EBLFs emerged in Japan during the early Oligocene and eventually appeared in central-eastern China around the Miocene. Paleoclimate simulation results suggest that the precipitation of wettest quarter(PWet Q, mm) exceeding 600 mm is crucial for the occurrence of EBLFs. Furthermore, the heterogeneous occurrence of EBLFs in East Asia is closely associated with the evolution of the Asian Monsoon. This study provides new insights into the occurrence of EBLFs in East Asia.展开更多
This paper explores the synergistic effect of a model combining Elastic Net and Random Forest in online fraud detection.The study selects a public network dataset containing 1781 data records,divides the dataset by 70...This paper explores the synergistic effect of a model combining Elastic Net and Random Forest in online fraud detection.The study selects a public network dataset containing 1781 data records,divides the dataset by 70%for training and 30%for validation,and analyses the correlation between features using a correlation matrix.The experimental results show that the Elastic Net feature selection method generally outperforms PCA in all models,especially when combined with the Random Forest and XGBoost models,and the ElasticNet+Random Forest model achieves the highest accuracy of 0.968 and AUC value of 0.983,while the Kappa and MCC also reached 0.839 and 0.844 respectively,showing extremely high consistency and correlation.This indicates that combining Elastic Net feature selection and Random Forest model has significant performance advantages in online fraud detection.展开更多
Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon...Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.展开更多
The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors tha...The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors that drive forest soil Q_(10) have focused mostly on abiotic factors,such as climate and soil,while the role of biotic factors has been less examined.Here,we compiled a global dataset of 766 soil Q_(10) values and 17 matched biotic and abiotic factors to explore the factors that drive the variability of global forest soil Q_(10) using a random forest(RF)model.Our findings showed that soil Q_(10) increased with microbial biomass carbon(MBC),which was the most important predictor.Additionally,soil Q_(10) was positively correlated with leaf phosphorus content(LPC)but was negatively correlated with leaf N:P,indicating that plant ecological stoichiometry might be a factor that explained soil Q_(10) variability.All abiotic factors,including climate,soil properties,and elevation,had great predictive power and were significantly related to soil Q_(10).By comparing the soil Q_(10) in multispecies forests and monocultures,we found that Q_(10) in the mixed needle-leaved and broad-leaved forests(NF&BF)was lower than in monocultures.Our study revealed that,in addition to abiotic factors,biotic factors were also strong predictors of forest soil Q_(10),which can deepen our understanding of soil respiration in response to global warming and provide insights for improving carbon cycle models.展开更多
The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variatio...The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variations is well-documented,spatial variations(from local to regional scales)remain inadequately understood.To evaluate the scale-dependent effects of productivity,predictions from the Biome-BGC model were compared with moderate-resolution imaging spectroradiometer(MODIS)and biometric NPP data in a large temperate forest region at both local and regional levels.Linear mixed-effect models and variance partitioning analysis were used to quantify the effects of environmental heterogeneity and trait variation on simulated NPP at varying spatial scales.Results show that NPP had considerable predictability at the local scale,with a coefficient of determination(R^(2))of 0.37,but this predictability declined significantly to 0.02 at the regional scale.Environmental heterogeneity and photosynthetic traits collectively explained 94.8%of the local variation in NPP,which decreased to 86.7%regionally due to the reduced common effects among these variables.Locally,the leaf area index(LAI)predominated(34.6%),while at regional scales,the stomatal conductance and maximum carboxylation rate were more influential(41.1%).Our study suggests that environmental heterogeneity drives the photosynthetic processes that mediate NPP variations across spatial scales.Incorporating heterogeneous local conditions and trait variations into analyses could enhance future research on the relationship between climate and carbon cycles at larger scales.展开更多
Understanding competition between trees is essential for sustainable forest management as interactions between trees in uneven-aged mixed forests play a key role in growth dynamics. This study investigated nine compet...Understanding competition between trees is essential for sustainable forest management as interactions between trees in uneven-aged mixed forests play a key role in growth dynamics. This study investigated nine competition indices(CIs) for their suitability to model the effects of neighboring trees on silver fir(Abies alba) growth in Dinaric silver fir-European beech(Fagus sylvatica) forests. Although numerous competition indices have been developed, there is still limited consensus on their applicability in different forest types, especially in mature, structurally complex forest stands. The indices were evaluated using the adjusted coefficient of determination in a linear model wherein the volume growth of the last five years for 60 dominant silver fir trees was modeled as a function of tree volume and competition index. The results demonstrated that distance-dependent indices(e.g., the Hegyi height-distance competition and Rouvinen-Kuuluvainen diameter-distance competition indices), which consider the distance to competitors and their size, perform better than distance-independent indices. Using the optimization procedure in calculating the competition indices, only neighboring trees at a distance of up to 26-fold the diameter at breast height(DBH) of the selected tree(optimal search radius) and with a DBH of at least 20% of that of the target tree(optimal DBH) were considered competitors. Therefore, competition significantly influences the growth of dominant silver firs even in older age classes. The model based solely on tree volume explained 32.5% of the variability in volume growth, while the model that accounted for competition explained 64%. Optimizing the optimal search radius had a greater impact on model performance than optimizing the DBH threshold. This emphasizes the importance of balancing stand density and competition in silvicultural practice.展开更多
Warm-wet climatic conditions are widely regarded as conducive to remarkable tree growth,alleviating climatic pressures.However,the notable decline in tree growth observed in the southern edge of boreal forests has hei...Warm-wet climatic conditions are widely regarded as conducive to remarkable tree growth,alleviating climatic pressures.However,the notable decline in tree growth observed in the southern edge of boreal forests has heightened concerns over the spatial-temporal dynamics of forest decline.Currently,attaining a comprehensive grasp of the underlying patterns and their propelling factors remains a formidable challenge.We collected tree ring samples from a network of 50 sites across the Greater Xing'an Mountains.These samples were subsequently grouped into two distinct clusters,designated as Groups A and B.The percentage change of growth(GC,%)and the proportion of declining sites were utilized to assess forest decline.The decline in tree growth within Larix gmelinii forests exhibits significant regional variation,accompanied by temporal fluctuations even within a given region.Group A exhibited a pronounced increase in frequency(59.26%)of occurrences and encountered more severe declines(21.65%)in tree growth subsequent to the 1990s,contrasting sharply with Group B,which observed lower frequencies(20.00%)and relatively less severe declines(21.02%)prior to the 1980s.The primary impetus underlying the opposite radial growth increments observed in Larix gmelinii trees from the interplay between their differential response to temperatures and wetter climatic conditions,which is significantly influenced by varying stand densities.In cold-dry conditions,low-density forests may experience soil water freezing,exacerbating drought conditions and thereby inhibiting tree growth,in Group B.Trees growth in high-density stands is restrained by warm-wet conditions,in Group A.These results provide new insights into the variability at the southern edge of the boreal forest biome with different responses to density and climate.展开更多
Gabon,located on the west coast of Central Africa,is one of the most forested countries.This small but richly biodiverse country is covered by rainforests,which make up approximately 85%of its land area.These forests ...Gabon,located on the west coast of Central Africa,is one of the most forested countries.This small but richly biodiverse country is covered by rainforests,which make up approximately 85%of its land area.These forests are home to a wide variety of wildlife,including elephants and numerous bird species,making Gabon a crucial area for conservation efforts.展开更多
A better understanding of the structure and dynamics of disturbed forests is key for forecasting their future successional trajectories.Despite vulnerability of subalpine forests to warming climate,little is known as ...A better understanding of the structure and dynamics of disturbed forests is key for forecasting their future successional trajectories.Despite vulnerability of subalpine forests to warming climate,little is known as to how their community composition has responded to disturbances and climate warming over decades.Before the 1970s,subalpine forests on the southeastern Qinghai-Tibet Plateau mainly experienced logging and fire,but afterwards they were more impacted by climate warming.Thus,they provide an excellent setting to test whether disturbances and climate warming led to changes in forest structure.Based on the analysis of 3145 forest inventory plots at 4-to 5-year resolution,we found that spruce-fir forests shifted to pine and broadleaved forests since the early 1970s.Such a turnover in species composition mainly occurred in the 1994e1998 period.By strongly altering site conditions,disturbances in concert with climate warming reshuffle community composition to warm-adapted broadleaf-pine species.Thus,moderate disturbances shifted forest composition through a gradual loss of resilience of spruce-fir forests.Shifts in these foundation species will have profound impacts on ecosystem functions and services.In the future,broadleaved forests could expand more rapidly than evergreen needle-leaved forests under moderate warming scenarios.In addition to climate,the effects of anthropogenic disturbances on subalpine forests should be considered in adaptive forest management and in projections of future forest changes.展开更多
With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threat...With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threats to ecosystem stability.Understanding the current status of forest degradation and assessing potential carbon stocks in China are of strategic importance for making forest restoration efforts and enhancing carbon sequestration capacity.In this study,we used the national forest inventory data from 2009 to 2018 to develop a set of standard measures for assessing degraded forests across China,based on five key indicators:forest accumulation growth rate(FAGR),forest recruitment rate(FRR),tree species reduction rate(TSRR),forest canopy cover reduction rate(FCCRR),and forest disaster level(FDL).Additionally,we estimated standing carbon stock,potential carbon stock,and theoretical space to grow by developing a stand growth model,which accounts for stand density across different site classes,to evaluate the restoration potential of degraded forests.The results indicate that degraded forest area in China is 36.15 million hectares,accounting for 20.10% of a total forest area.Standing carbon stock and potential carbon stock of degraded forests in China are 23.93 million tons and 61.90 million tons,respectively.Overall,degraded forest varies significantly across different regions.The results highlight the important trade-offs among environmental factors,policy decisions,and forest conditions,providing a robust foundation for developing measures to enhance forest quality.展开更多
Over the past decades,the expansion of natu-ral secondary forests has played a crucial role in offsetting the loss of primary forests and combating climate change.Despite this,there is a gap in our understanding of ho...Over the past decades,the expansion of natu-ral secondary forests has played a crucial role in offsetting the loss of primary forests and combating climate change.Despite this,there is a gap in our understanding of how tree species’growth and mortality patterns vary with eleva-tion in these secondary forests.In this study,we analyzed data from two censuses(spanning a five-year interval)conducted in both evergreen broadleaved forests(EBF)and temperate coniferous forests(TCF),which have been recovering for half a century,across elevation gradients in a subtropical mountain region,Mount Wuyi,China.The results indicated that the relative growth rate(RGR)of EBF(0.028±0.001 cm·cm^(-1)·a^(-1))and the mortality rate(MR)(20.03%±1.70%)were 27.3%and 16.4%higher,respec-tively,than those of TCF.Interestingly,the trade-off between RGR and MR in EBF weakened as elevation increased,a trend not observed in TCF.Conversely,TCF consistently showed a stronger trade-off between RGR and MR compared to EBF.Generalized linear mixed models revealed that ele-vation influences RGR both directly and indirectly through its interactions with slope,crown competition index(CCI),and tree canopy height(CH).However,tree mortality did not show a significant correlation with elevation.Additionally,DBH significantly influenced both tree growth and mortal-ity,whereas and CH and CCI had opposite effects on tree growth between EBF and TCF.Our study underscores the importance of elevation in shaping the population dynamics and the biomass carbon sink balance of mountain forests.These insights enhance our understanding of tree species’life strategies,enabling more accurate predictions of forest dynamics and their response to environmental changes.展开更多
In this paper,we show that an ideal generated by matching Rota-Baxter equations is a bideal of a Hopf algebra on decorated rooted forests.We then get a bialgebraic structure on the space of decorated rooted forests mo...In this paper,we show that an ideal generated by matching Rota-Baxter equations is a bideal of a Hopf algebra on decorated rooted forests.We then get a bialgebraic structure on the space of decorated rooted forests modulo this biideal.As an application,a connected graded bialgebra and so a graded Hopf algebra on matching Rota-Baxter algebras are constructed,which simplifies the Hopf algebraic structure proposed by[Pacific J.Math.,2022,317(2):441-475].展开更多
The study area lies in the Dadu River drainage area in upstream Yangtze River.The spatial distribution of subalpine coniferous forests in 1989 and 2009 was extracted by means of a combined method of object orientation...The study area lies in the Dadu River drainage area in upstream Yangtze River.The spatial distribution of subalpine coniferous forests in 1989 and 2009 was extracted by means of a combined method of object orientation and visual interpretation,and then the overlaying analysis of these data was conducted.The type and spatial location of succession were discovered and served as the sample of dependant variable.Meanwhile,supported by GIS technology and based on DEM and thematic data,the eight variables including altitude,slope,sin and cosin of aspect,curvity of land surface,and distance to residential area,cultivated land and road were extracted served as the sample of spatial succession of subalpine coniferous forests to fit Logistic Regression,and then the contribution of each independent variable as well as the spatial property of the occurrence probability of succession was calculated.The results suggested that,during the succession of subalpine coniferous forests to meadow,the closer to the residential area and cultivated land,the greater the contribution to succession is.In particular,when the distance to the residential area decreases by one unit,the probability for its conversion to meadow will be increased by 1.15 times.During the succession of subalpine coniferous forests to deciduous-broadleaved shrubs,the sin of aspect and distance to residential area contribute more,and the probability of succession increases with increasing degree of northwardness,i.e.when the degree of northwardness increases by one unit,the probability will be increased by 1.2 times.The quantitative analysis of spatial succession property of subalpine coniferous forests will supply scientific basis to the protection and restoration of subalpine coniferous forests.展开更多
基金supported by the Tianshan Talent Program of Xinjiang(2022TSYCCX0003,2024TSYCCX0041)the National Natural Science Foundation of China(42375054)+1 种基金the Desert Meteorological Science Research Foundation of China(Sqj2021018)the Young Meteorological Talent Program of China Meteorological Administration and Youth Innovation Team of China Meteorological Administration(CMA2023QN08)。
文摘Forest ecosystems are critical to ecological stability,yet their functionality is increasingly threatened by the growing frequency of drought,particularly in arid and semi-arid regions.While afforestation enhances forest cover in these areas,the capacity of planted forests to adapt to climate change is poorly understood.This study examines the drought resistance and adaptive capacity of planted and naturally growing Schrenk spruce(Picea schrenkiana Fisch.&C.A.Mey.)in the Ili River Basin,Xinjiang,China using tree-ring analysis.The results indicate that natural stands have a stronger correlation with meteorological factors than plantations.Over the past 50 years,significant growth declines occurred during 1995-1997,2007-2009,and 2012-2014,with natural forests showing a greater frequency and severity of declines compared to plantations.Planted stands demonstrated greater resistance to drought,whereas natural forests had higher resilience and recovery.Over time,natural forests have shown declining resistance to drought but increased resilience and recovery.Conversely,plantations showed declines in resistance and recovery but an increased capacity for recovery.Older natural forests are more prone to growth decline,while structurally simpler planted forests show stronger drought resistance.However,following periods of drought,natural forests demonstrated a stronger capacity for recovery.These findings provide valuable insights into the response of P.schrenkiana to climate change and offer support for the sustainable management and conservation of forest ecosystems in the Xinjiang region of China.
基金supported by the Spanish Ministry of Science and Innovation project GREEN-RISK(Evaluation of past changes in ecosystem services and biodiversity in forests and restoration priorities under global change impacts-PID2020-119933RB-C21)A.C.received a pre-doctoral fellowship funded by the Spanish Ministry of Science and Innovation(PRE2021-099642).
文摘Conservation and enhancement of old-growth forests are key in forest planning and policies.In order to do so,more knowledge is needed on how the attributes traditionally associated with old-growth forests are distributed in space,what differences exist across distinct forest types and what natural or anthropic conditions are affecting the distribution of these old-growthness attributes.Using data from the Third Spanish National Forest Inventory(1997–2007),we calculated six indicators commonly associated with forest old-growthness for the plots in the territory of Peninsular Spain and Balearic Islands,and then combined them into an aggregated index.We then assessed their spatial distribution and the differences across five forest functional types,as well as the effects of ten climate,topographic,landscape,and anthropic variables in their distribution.Relevant geographical patterns were apparent,with climate factors,namely temperature and precipitation,playing a crucial role in the distribution of these attributes.The distribution of the indicators also varied across different forest types,while the effects of recent anthropic impacts were weaker but still relevant.Aridity seemed to be one of the main impediments for the development of old-growthness attributes,coupled with a negative impact of recent human pressure.However,these effects seemed to be mediated by other factors,specially the legacies imposed by the complex history of forest management practices,land use changes and natural disturbances that have shaped the forests of Spain.The results of this exploratory analysis highlight on one hand the importance of climate in the dynamic of forests towards old-growthness,which is relevant in a context of Climate Change,and on the other hand,the need for more insights on the history of our forests in order to understand their present and future.
基金supported part ia l l y by LIFE4Oak Forests Project LIFE16NAT/IT/000245)the RRF 2.3.121202200008 projectthe MERLiN project funded under the European Commission H2020 Programme(101036337 MERLiN H2020 LC GD 2020)。
文摘Increasing human activity is altering the struc-ture of forests,which affects the composition of communi-ties,including birds.However,little is known about the key forest structure variables that determine the richness of bird communities in European temperate oak forests.We,there-fore,aimed to identify key variables in these habitats that could contribute to the design of management strategies for forest conservation by surveying 11 oak-dominated forest sites throughout the mid-mountain range of Hungary at 86 survey points to reveal the role of different compositional and structural variables for forest stands that influence the breeding bird assemblages in the forests at the functional group and individual species levels.Based on decision tree modelling,our results showed that the density of trees larger than 30 cm DBH was an overall important variable,indi-cating that large-diameter trees were essential to provide diverse bird communities.The total abundance of birds,the foliage-gleaners,primary and secondary cavity nest-ers,residents,and five specific bird species were related to the density of high trunk diameter trees.The abundance of shrub nesters was negatively influenced by a high density of trees over 10 cm DBH.The density of the shrub layer positively affected total bird abundance and the abundance of foliage gleaners,secondary cavity nesters and residents.Analysis of the co-dominant tree species showed that the presence of linden,beech,and hornbeam was important in influencing the abundance of various bird species,e.g.,Eur-asian Treecreeper(Certhia familiaris),Marsh Tit(Poecile palustris)and Wood Warbler(Phylloscopus sibilatrix).Our results indicated that large trees,high tree diversity,and dense shrub layer were essential for forest bird communities and are critical targets for protection to maintain diverse and abundant bird communities in oak-dominated forest habitats.
基金funding support from the United States Fish and Wildlife Service,the North Carolina Wildlife Resources Commission,and the University of North Carolina at Greensboro,as part of a collective effort for the North American Bat Monitoring Program(NABat).
文摘Temperate forest ecosystems are important habitats for many bat species. However, these habitats are increasingly affected by anthropogenic disturbances, particularly urban development, leading to landscapes with varying land cover composition and configuration. Limited research has examined how forest and urban landscape composition and configuration influence bat activity and diversity. Using a multi-year statewide bat acoustic monitoring dataset from North Carolina, USA, we investigated the effects of forest and urban composition and configuration at multiple spatial scales on bat activity and diversity. First, we constructed single-variable landscape index regression models and found that both the composition and configuration of forests and urban developments influenced bat activity and diversity in a species-specific manner. Next, we applied a hierarchical partitioning approach to compare the relative contributions of composition and configuration indices in explaining variance in bat activity. For big brown bats and hoary bats, evergreen forest and urban development composition indices contributed the most to explaining activity variance. In contrast, for eastern red bats, evening bats, and tricolored bats, deciduous forest fragmentation indices describing landscape configuration were the most influential factors. Silver-haired bat activity variance was primarily explained by an evergreen forest fragmentation index. Lastly, urban development configuration indices were the strongest predictors of Mexican free-tailed bat activity and total bat activity. These results suggest that forest and urban landscape configuration should be considered in conservation and management planning for North American temperate forest ecosystems, particularly in regions that have not experienced drastic deforestation in recent decades.
基金Field surveys were carried out within the forest monitoring activities of Action A1.3 of the Project LIFE4OAKFORESTS(LIFE16NAT/IT/000245),in collaboration with“Ente di Gestione per i Parchi e la Biodiversità-Romagna”.
文摘Old-growth forests are of major importance for biodiversity conservation and climate change mitigation,as well as being a benchmark for the implementation of sustainable forest management.Although dedicated studies have significantly increased in the last decades,there is still limited knowledge of Mediterranean forests,especially those dominated by Quercus pubescens and related taxa.To fill this knowledge gap,we primarily studied in the field two downy oak forests possessing old-growth traits,localized in Sicily(Mediterranean,Italy).Second,we used a structural heterogeneity index(SHI)to assess their old-growthness level,in comparison with the downy oak stands surveyed in the Regional Forest Inventory(RFI)of Sicily.Third,we tested the effect of different sets of structural parameters on SHI scores,thus assessing whether their choice could affect the final score and the stand assessment.SHI was well proven to discriminate these two stands from the others,both showing,on average,a SHI score just higher than 80,whilst SHI in RFI plots was just under 50,a significantly lower value.The methodological approach used in our study highlights the need to standardize the parameters used to characterize the old-growthness level of Mediterranean forests in order to allow more reliable comparisons.Most of the structural parameters were higher in the two selected stands,except for the attributes related to standing deadwood,suggesting a still limited contribution of standing dead trees and snags in the potential old-growth stands under investigation.The application of a structural index has proven effective for the purpose it was tested for,demonstrating its usefulness in discriminating between two potential old-growth stands from ordinary stands of the same forest type.We believe that both forests deserve primary attention and tailored management measures,as well as inclusion in the recently established Italian Network of old-growth forests.
基金funded by the Kenya National Research Fund(NRF-Kenya,2018).
文摘The study determined the carbon stocks and litter nutrient concentration in tropical forests along the ecological gradient in Kenya.This could help understand the potential of mitigating climate change using tropical forest ecosystems in different ecological zones,which are being affected by climate change to a level that they are becoming carbon sources instead of sinks.Stratified sampling technique was used to categorize tropical forests into rain,moist deciduous and dry zone forests depending on the average annual rainfall received.Simple random sampling technique was used to select three tropical forests in each category.Modified consistent sampling technique was used to develop 10 main 20 m×100 m plots in each forest,with 202 m×50 m sub-plots in each plot.Systematic random sampling technique was used in selecting 10 sub-plots from each main plot for inventory study.Non-destructive approach based on allometric equations using trees’diameter at breast height(DBH),total height and species’wood specific gravity were used in estimating tree carbon stock in each forest.Soil organic carbon(SOC)and litter nutrient concentration(total phosphorus and nitrogen)were determined in each forest based on standard laboratory procedures.The results indicated that,whilst trees in rain forests recorded a significantly higher(p<0.001)DBH(20.36 cm)and total tree height(12.1 m),trees in dry zone forests recorded a significantly higher(p<0.001)specific gravity(0.67 kg m^(−3)).Dry zone tropical forests stored a significantly lower amount of total tree carbon of 73 Mg ha^(−1),compared to tropical rain forests(439.5 Mg ha^(−1))and moist deciduous tropical forests(449 Mg ha^(−1)).The SOC content was significantly higher in tropical rainforests(3.9%),compared to soils from moist deciduous(2.9%)and dry zone forests(1.8%).While litter from tropical rain forests recorded a significantly higher amount of total nitrogen(3.4%),litter from dry zone forests recorded a significantly higher concentration of total phosphorus(0.27%).In conclusion,ecological gradient that is dictated by the prevailing temperatures and precipitation affects the tropical forests carbon stock potential and litter nutrient concentration.This implies that,the changing climate is having a serious implication on the ecosystem services such as carbon stock and nutrients cycling in tropical forests.
基金supported by National Key R&D Program of China(No.2022YFF0800800)National Science Fund for Distinguished Young Scholars(No.32225005)+3 种基金National Natural Science Foundation of China(NSFC)(Nos.42072024,42320104005,42372033)the Young and Middle-aged Academic and Technical Leaders of Yunnan(No.202305AC160051)Basic Research Project of Yunnan Province(No.202401AT070222)the 14th Five-Year Plan of the Xishuangbanna Tropical Botanical Garden,Chinese Academy of Sciences(Nos.XTBG-1450101,E3ZKFF7B).
文摘Evergreen broad-leaved forests(EBLFs) are widely distributed in East Asia and play a vital role in ecosystem stability. The occurrence of these forests in East Asia has been a subject of debate across various disciplines. In this study, we explored the occurrence of East Asian EBLFs from a paleobotanical perspective. By collecting plant fossils from four regions in East Asia, we have established the evolutionary history of EBLFs. Through floral similarity analysis and paleoclimatic reconstruction, we have revealed a diverse spatio-temporal pattern for the occurrence of EBLFs in East Asia. The earliest occurrence of EBLFs in southern China can be traced back to the middle Eocene, followed by southwestern China during the late Eocene-early Oligocene. Subsequently, EBLFs emerged in Japan during the early Oligocene and eventually appeared in central-eastern China around the Miocene. Paleoclimate simulation results suggest that the precipitation of wettest quarter(PWet Q, mm) exceeding 600 mm is crucial for the occurrence of EBLFs. Furthermore, the heterogeneous occurrence of EBLFs in East Asia is closely associated with the evolution of the Asian Monsoon. This study provides new insights into the occurrence of EBLFs in East Asia.
基金Guangdong Innovation and Entrepreneurship Training Programme for Undergraduates“Automatic Classification and Identification of Fraudulent Websites Based on Machine Learning”(Project No.:DC2023125)。
文摘This paper explores the synergistic effect of a model combining Elastic Net and Random Forest in online fraud detection.The study selects a public network dataset containing 1781 data records,divides the dataset by 70%for training and 30%for validation,and analyses the correlation between features using a correlation matrix.The experimental results show that the Elastic Net feature selection method generally outperforms PCA in all models,especially when combined with the Random Forest and XGBoost models,and the ElasticNet+Random Forest model achieves the highest accuracy of 0.968 and AUC value of 0.983,while the Kappa and MCC also reached 0.839 and 0.844 respectively,showing extremely high consistency and correlation.This indicates that combining Elastic Net feature selection and Random Forest model has significant performance advantages in online fraud detection.
文摘Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.
基金supported by the National Natural Science Foundation of China(No.31988102)the Key Research Program of Frontier Sciences,CAS(No.QYZDY-SSW-SMC011).
文摘The sensitivity of soil respiration(R_(s))to temperature(Q_(10))is a key parameter for benchmarking the carbon(C)cycle and climate feedbacks in the context of global warming.However,previous studies on the factors that drive forest soil Q_(10) have focused mostly on abiotic factors,such as climate and soil,while the role of biotic factors has been less examined.Here,we compiled a global dataset of 766 soil Q_(10) values and 17 matched biotic and abiotic factors to explore the factors that drive the variability of global forest soil Q_(10) using a random forest(RF)model.Our findings showed that soil Q_(10) increased with microbial biomass carbon(MBC),which was the most important predictor.Additionally,soil Q_(10) was positively correlated with leaf phosphorus content(LPC)but was negatively correlated with leaf N:P,indicating that plant ecological stoichiometry might be a factor that explained soil Q_(10) variability.All abiotic factors,including climate,soil properties,and elevation,had great predictive power and were significantly related to soil Q_(10).By comparing the soil Q_(10) in multispecies forests and monocultures,we found that Q_(10) in the mixed needle-leaved and broad-leaved forests(NF&BF)was lower than in monocultures.Our study revealed that,in addition to abiotic factors,biotic factors were also strong predictors of forest soil Q_(10),which can deepen our understanding of soil respiration in response to global warming and provide insights for improving carbon cycle models.
基金supported by the National Key R&D Program of China(No.2023YFF1304001-01)the Science and Technology Project of the Department of Transportation of Heilongjiang Province(No.HJK2023B024-3)the Program of National Natural Science Foundation of China(No.32371870).
文摘The net primary productivity(NPP)of forest ecosystems plays a crucial role in regulating the terrestrial carbon cycle under global climate change.While the temporal effect driven by ecosystem processes on NPP variations is well-documented,spatial variations(from local to regional scales)remain inadequately understood.To evaluate the scale-dependent effects of productivity,predictions from the Biome-BGC model were compared with moderate-resolution imaging spectroradiometer(MODIS)and biometric NPP data in a large temperate forest region at both local and regional levels.Linear mixed-effect models and variance partitioning analysis were used to quantify the effects of environmental heterogeneity and trait variation on simulated NPP at varying spatial scales.Results show that NPP had considerable predictability at the local scale,with a coefficient of determination(R^(2))of 0.37,but this predictability declined significantly to 0.02 at the regional scale.Environmental heterogeneity and photosynthetic traits collectively explained 94.8%of the local variation in NPP,which decreased to 86.7%regionally due to the reduced common effects among these variables.Locally,the leaf area index(LAI)predominated(34.6%),while at regional scales,the stomatal conductance and maximum carboxylation rate were more influential(41.1%).Our study suggests that environmental heterogeneity drives the photosynthetic processes that mediate NPP variations across spatial scales.Incorporating heterogeneous local conditions and trait variations into analyses could enhance future research on the relationship between climate and carbon cycles at larger scales.
基金funded by the Slovenian Research and Innovation Agency(https://www.aris-rs.si/sl/)ProgramResearch Core Fund-ing No.P4-0107(TL)and No.P4-0059(MK)+1 种基金Young Researcher Program Grant(MK)funded by the Slovenian Forestry Institute(P4-0107).
文摘Understanding competition between trees is essential for sustainable forest management as interactions between trees in uneven-aged mixed forests play a key role in growth dynamics. This study investigated nine competition indices(CIs) for their suitability to model the effects of neighboring trees on silver fir(Abies alba) growth in Dinaric silver fir-European beech(Fagus sylvatica) forests. Although numerous competition indices have been developed, there is still limited consensus on their applicability in different forest types, especially in mature, structurally complex forest stands. The indices were evaluated using the adjusted coefficient of determination in a linear model wherein the volume growth of the last five years for 60 dominant silver fir trees was modeled as a function of tree volume and competition index. The results demonstrated that distance-dependent indices(e.g., the Hegyi height-distance competition and Rouvinen-Kuuluvainen diameter-distance competition indices), which consider the distance to competitors and their size, perform better than distance-independent indices. Using the optimization procedure in calculating the competition indices, only neighboring trees at a distance of up to 26-fold the diameter at breast height(DBH) of the selected tree(optimal search radius) and with a DBH of at least 20% of that of the target tree(optimal DBH) were considered competitors. Therefore, competition significantly influences the growth of dominant silver firs even in older age classes. The model based solely on tree volume explained 32.5% of the variability in volume growth, while the model that accounted for competition explained 64%. Optimizing the optimal search radius had a greater impact on model performance than optimizing the DBH threshold. This emphasizes the importance of balancing stand density and competition in silvicultural practice.
基金National Nature Science Foundation of China(No.32371871)。
文摘Warm-wet climatic conditions are widely regarded as conducive to remarkable tree growth,alleviating climatic pressures.However,the notable decline in tree growth observed in the southern edge of boreal forests has heightened concerns over the spatial-temporal dynamics of forest decline.Currently,attaining a comprehensive grasp of the underlying patterns and their propelling factors remains a formidable challenge.We collected tree ring samples from a network of 50 sites across the Greater Xing'an Mountains.These samples were subsequently grouped into two distinct clusters,designated as Groups A and B.The percentage change of growth(GC,%)and the proportion of declining sites were utilized to assess forest decline.The decline in tree growth within Larix gmelinii forests exhibits significant regional variation,accompanied by temporal fluctuations even within a given region.Group A exhibited a pronounced increase in frequency(59.26%)of occurrences and encountered more severe declines(21.65%)in tree growth subsequent to the 1990s,contrasting sharply with Group B,which observed lower frequencies(20.00%)and relatively less severe declines(21.02%)prior to the 1980s.The primary impetus underlying the opposite radial growth increments observed in Larix gmelinii trees from the interplay between their differential response to temperatures and wetter climatic conditions,which is significantly influenced by varying stand densities.In cold-dry conditions,low-density forests may experience soil water freezing,exacerbating drought conditions and thereby inhibiting tree growth,in Group B.Trees growth in high-density stands is restrained by warm-wet conditions,in Group A.These results provide new insights into the variability at the southern edge of the boreal forest biome with different responses to density and climate.
文摘Gabon,located on the west coast of Central Africa,is one of the most forested countries.This small but richly biodiverse country is covered by rainforests,which make up approximately 85%of its land area.These forests are home to a wide variety of wildlife,including elephants and numerous bird species,making Gabon a crucial area for conservation efforts.
基金supported by the National Natural Science Foundation of China(42030508)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0301)the Key technology research and development projects in Xizang Autonomous Regions(XZ202101ZY0005G).
文摘A better understanding of the structure and dynamics of disturbed forests is key for forecasting their future successional trajectories.Despite vulnerability of subalpine forests to warming climate,little is known as to how their community composition has responded to disturbances and climate warming over decades.Before the 1970s,subalpine forests on the southeastern Qinghai-Tibet Plateau mainly experienced logging and fire,but afterwards they were more impacted by climate warming.Thus,they provide an excellent setting to test whether disturbances and climate warming led to changes in forest structure.Based on the analysis of 3145 forest inventory plots at 4-to 5-year resolution,we found that spruce-fir forests shifted to pine and broadleaved forests since the early 1970s.Such a turnover in species composition mainly occurred in the 1994e1998 period.By strongly altering site conditions,disturbances in concert with climate warming reshuffle community composition to warm-adapted broadleaf-pine species.Thus,moderate disturbances shifted forest composition through a gradual loss of resilience of spruce-fir forests.Shifts in these foundation species will have profound impacts on ecosystem functions and services.In the future,broadleaved forests could expand more rapidly than evergreen needle-leaved forests under moderate warming scenarios.In addition to climate,the effects of anthropogenic disturbances on subalpine forests should be considered in adaptive forest management and in projections of future forest changes.
基金supported by National Key Research and Development Program of China(No.2021YFD2200405(S.R.L.))Natural Science Foundation of China(Grant No.31971653).
文摘With the rapid economic development and continuous expansion of human activities,forest degradation—characterized by reduced forest stock within the forest including declining carbon storage—poses significant threats to ecosystem stability.Understanding the current status of forest degradation and assessing potential carbon stocks in China are of strategic importance for making forest restoration efforts and enhancing carbon sequestration capacity.In this study,we used the national forest inventory data from 2009 to 2018 to develop a set of standard measures for assessing degraded forests across China,based on five key indicators:forest accumulation growth rate(FAGR),forest recruitment rate(FRR),tree species reduction rate(TSRR),forest canopy cover reduction rate(FCCRR),and forest disaster level(FDL).Additionally,we estimated standing carbon stock,potential carbon stock,and theoretical space to grow by developing a stand growth model,which accounts for stand density across different site classes,to evaluate the restoration potential of degraded forests.The results indicate that degraded forest area in China is 36.15 million hectares,accounting for 20.10% of a total forest area.Standing carbon stock and potential carbon stock of degraded forests in China are 23.93 million tons and 61.90 million tons,respectively.Overall,degraded forest varies significantly across different regions.The results highlight the important trade-offs among environmental factors,policy decisions,and forest conditions,providing a robust foundation for developing measures to enhance forest quality.
基金funded by the National Natural Science Foundation of China(Grant No.32271872).
文摘Over the past decades,the expansion of natu-ral secondary forests has played a crucial role in offsetting the loss of primary forests and combating climate change.Despite this,there is a gap in our understanding of how tree species’growth and mortality patterns vary with eleva-tion in these secondary forests.In this study,we analyzed data from two censuses(spanning a five-year interval)conducted in both evergreen broadleaved forests(EBF)and temperate coniferous forests(TCF),which have been recovering for half a century,across elevation gradients in a subtropical mountain region,Mount Wuyi,China.The results indicated that the relative growth rate(RGR)of EBF(0.028±0.001 cm·cm^(-1)·a^(-1))and the mortality rate(MR)(20.03%±1.70%)were 27.3%and 16.4%higher,respec-tively,than those of TCF.Interestingly,the trade-off between RGR and MR in EBF weakened as elevation increased,a trend not observed in TCF.Conversely,TCF consistently showed a stronger trade-off between RGR and MR compared to EBF.Generalized linear mixed models revealed that ele-vation influences RGR both directly and indirectly through its interactions with slope,crown competition index(CCI),and tree canopy height(CH).However,tree mortality did not show a significant correlation with elevation.Additionally,DBH significantly influenced both tree growth and mortal-ity,whereas and CH and CCI had opposite effects on tree growth between EBF and TCF.Our study underscores the importance of elevation in shaping the population dynamics and the biomass carbon sink balance of mountain forests.These insights enhance our understanding of tree species’life strategies,enabling more accurate predictions of forest dynamics and their response to environmental changes.
基金Supported by NSFC(No.12101316)Belt and Road Innovative Talents Exchange Foreign Experts project(No.DL2023014002L)。
文摘In this paper,we show that an ideal generated by matching Rota-Baxter equations is a bideal of a Hopf algebra on decorated rooted forests.We then get a bialgebraic structure on the space of decorated rooted forests modulo this biideal.As an application,a connected graded bialgebra and so a graded Hopf algebra on matching Rota-Baxter algebras are constructed,which simplifies the Hopf algebraic structure proposed by[Pacific J.Math.,2022,317(2):441-475].
基金Supported by National Natural Science Foundation of China(40901057)Key Project of Chinese National Programs for Fundamental Research and Development(2010CB951704)~~
文摘The study area lies in the Dadu River drainage area in upstream Yangtze River.The spatial distribution of subalpine coniferous forests in 1989 and 2009 was extracted by means of a combined method of object orientation and visual interpretation,and then the overlaying analysis of these data was conducted.The type and spatial location of succession were discovered and served as the sample of dependant variable.Meanwhile,supported by GIS technology and based on DEM and thematic data,the eight variables including altitude,slope,sin and cosin of aspect,curvity of land surface,and distance to residential area,cultivated land and road were extracted served as the sample of spatial succession of subalpine coniferous forests to fit Logistic Regression,and then the contribution of each independent variable as well as the spatial property of the occurrence probability of succession was calculated.The results suggested that,during the succession of subalpine coniferous forests to meadow,the closer to the residential area and cultivated land,the greater the contribution to succession is.In particular,when the distance to the residential area decreases by one unit,the probability for its conversion to meadow will be increased by 1.15 times.During the succession of subalpine coniferous forests to deciduous-broadleaved shrubs,the sin of aspect and distance to residential area contribute more,and the probability of succession increases with increasing degree of northwardness,i.e.when the degree of northwardness increases by one unit,the probability will be increased by 1.2 times.The quantitative analysis of spatial succession property of subalpine coniferous forests will supply scientific basis to the protection and restoration of subalpine coniferous forests.
