The Sixth National Survey on Desertification and Sandification was based on the results of the Third National Land Survey,using 2019 as the benchmark year.The results showed a comprehensive status of desertification and sandification in China.This paper presented a brief overview of this survey,the status and dynamic changes of desertification and sandification in China,conducted a comprehensive analysis of the current situation,and proposed some suggestions for combating desertification and sandification.The survey results showed that,until 2019,the desertification land area in China was 257.371 3 million hm2 and the sandification land area was 168.782 3 million hm2.Compared with 2014,the desertification area of China decreased by 3.788 0 million hm2 with an average annual decrease of 757.6 thousand hm2.The sandification area of China decreased by 3.335 2 million hm2 with an average annual net reduction of 667 thousand hm2.
In this paper,the situation and problems of village greening in major national strategic areas of China were investigated and analyzed,based on the satellite remote sensing image data in 2020.The results showed that:1)the village greening coverage in the Yangtze River Economic Belt was the highest,followed by the Yellow River Basin ecological protection and high-quality development area and the Yangtze River Delta integrated development area,the Beijing-Tianjin-Hebei coordinated development area was the lowest;2)The greening situation inside and outside the village was unbalanced,and the outside village greening coverage was higher;3)The greening coverage of mountain village was higher than that of plain village,and that of plain village was higher than that of pasturing village;4)Besides the upper reaches of the Yellow River where shrub and grass were the main types of village greening vegetation,and trees were main types in the other areas.Problems such as unbalanced and inadequate development of village greening,limited village greening land space and so on existed in all major national strategic areas.In view of these problems,countermeasures and suggestions were put forward from the aspects of supplementing the short board of village greening in different areas,rationally planning the village greening land space,tapping the potential of village greening,highlighting the key tasks of different types of village greening,and reasonably allocating vegetation types of village greening.
Along with continuous and rapid development of economic construction in China,the rigid demand of timber is increasing continuously,and the issue of timber safety is extensively concerned.Based on the results of previous national forest inventories of China,the basic situation of timber resources,such as ownership,origin,age group and tree species,and distribution characteristics and development trends of timber resources in China were firstly described.Then,the timber production in the past 70 years,current timber demand and timber safety were analyzed.Finally,some suggestions were put forward on ensuring timber safety from following five aspects:building national reserve forest base,cultivating precious-species and large-diameter timber forests,strengthening scientific forest management,advocating timber saving and substitution,and guiding and regulating timber import.
Under the background of China's active promotion of green development and the harmonious co-existence of man and nature,it is of great significance to discuss the integration and optimization of natural protected areas.On the basis of summarizing the existing methods,this paper proposed a procedure of the integration and optimization of protected areas according to the results of human disturbance evaluation,ecological background evaluation and human disturbance spatial early warning assessment,and including the main steps of integration and merging,zone division and boundary optimization,in order to provide a reference for the further advancement of the integration and optimization of natural protected areas in China.
The stand structure and plant diversity of Liuxihe National Forest Park were discussed,so as to provide theoretical basis for forest management and plant diversity protection of its natural secondary broad-leaved mixed forest.The results showed that:1) Liuxihe National Forest Park had higher plant diversity and stronger natural regeneration ability.Single-species family composition of tree species and understory plants were 50% or more.There were quite more species and quantity of seedlings,and the natural regeneration ability of stands was strong,but young trees were relatively few.2) There were big differences in stand canopy density,stem density and DBH,and the spatial layout of trees needed to be adjusted.In sample-plots,the canopy density was 0.64~0.90,and the stem density was 675~1 975 plants per hectare,and the DBH was between 5.0~44.5 centimeter.The spatial distribution of stands was mainly in the form of clusters,and the forest competition was medium.3) The plant diversity of arbor layer was rich,and that of shrub layer was affected by stand factors.In different forest layers,the four indexes of arbor layer were relatively high.The shrub layer was affected by stand factors such as canopy density and mean DBH,and the herb layer was basically unaffected,and the sapling and seedling layer were affected by canopy density.Therefore,forest tending and thinning should be carried out,and stand density and spatial distribution of trees should be appropriately adjusted.The quantity and quality of saplings and seedlings should be improved,and understory shrub species should be enriched.The diversity and stability of plant community should be improved in Liuxihe National Forest Park,to ensure the sustainable and stable development of forests.
Shrub and semi-shrub plants are important vegetation type for maintaining ecosystem stability in arid and semiarid zones.In this study,we collected organ samples of stems,branches,and leaves of 15 species of shrubs and semi-shrubs from the desert zone on the north slope of eastern Tianshan Mountain and determined their calorific values,ash contents and carbon contents to explore the effects of shrub species,organs,AC,and CC on the CV of shrubs and their correlations.The related research can provide a theoretical basis for gaining a through understanding of the study of material and energy cycles in typical desert environments in the arid region.The results showed:1)The whole plant CV (above-ground) of the 15 plants ranged from 14.21 KJ/g (Anabasis brevifolia) to 19.87 KJ/g (Berberidaceae),with an average of 18.38 KJ/g,which was higher than of the global average calorific value of terrestrial plants;2) Differences in calorific values and carbon contents existed between families of shrub species.We found that Leguminosae and Compositae had higher calorific values and carbon contents compared to Chenopodiaceae and Polygonaceae species;3)The calorific values,ash contents,carbon contents of the stem,branches,and leaves of the 15 plants differed.The order of the average calorific value of each organ was stem>branch>leaf,the order of the average ash content was leaf>branch>stem,and the order of the average carbon content was branch>stem>leaf;4)Calorific value was negatively correlated with ash content (P<0.01) and was positively correlated with carbon content (P<0.01).
In order to clarify the adaptability of woody ferns to drought stress,3-year-old Alsophila spinulosa seedlings were selected for drought stress and rehydration treatment through potted water control.The changes of water potential and photosynthesis in the leaves of Alsophila spinulosa were studied after 3,6,9,12 days of drought and after 3,6,and 9 days of rehydration.The results showed that with the prolongation of drought time,the water potential of Alsophila spinulosa leaves showed an overall upward trend,the net photosynthetic rate (Pn) showed a downward trend,the inter-CO2 concentration (Ci) first decreased and then increased,and the stomatal conductance (Gs) and transpiration rate (Tr) showed a trend of decreasing-increasing-decreasing.In the early stage of drought (6 days ago),the change trend of Pn,Gs and Ci was basically the same,and the decrease of Pn was mainly caused by stomatal limitation.In the later period of drought (after 6 days),the change trend of Pn was inconsistent with that of Gs and Ci,and the decrease of Pn was mainly caused by non-stomatal limitation.After rehydration,Pn and Tr of Alsophila spinulosa leaves recovered to the level of adequate water supply,while the water potential,Gs and Ci recovered to the level above that of adequate water supply.At the same time,the water use efficiency (WUE) of Alsophila spinulosa leaves increased first and then decreased with the prolongation of drought time,and showed a downward trend after 6 days of drought.And after rehydration,the WUE basically recovered to the level of adequate water supply.Taken together,Alsophila spinulosa has relatively poor drought tolerance and relatively strong rehydration recovery ability.Through the analysis of the photosynthetic physiological characteristics of drought stress and rehydration process,it is preliminarily considered that Alsophila spinulosa is a drought-avoiding plant.
In this research,the population distribution of Magnolia sinostellata was studied in Fengyuan Township,Liandu District,Lishui City,southern Zhejiang Province.Soil samples were collected to determine physicochemical properties,and the effects of soil properties on the distribution of Magnolia sinostellata were studied by grey correlation analysis.The results showed that Magnolia sinostellata was mainly distributed in public welfare forests,the germination ability was very strong,but most of the plants had a small number of sprouts per cluster.The mean habitat soil pH value was 4.96,the moisture content was very low,the organic matter was rich,and the available phosphorus was significantly insufficient.The upper vegetation wasn’t the only factor affecting soil property differences among populations.Correlation analysis showed that the distribution of Magnolia sinostellata was closely related to soil pH value,available phosphorus and rapidly available potassium.Among them,pH value had the highest correlation.The content of available phosphorus in the middle soil layer was the most correlated with the number of plants (clusters) of Magnolia sinostellata,and the pH value in the topsoil layer was the most correlated with the average number of sprouts per cluster.
In order to elucidate the effects of stand age on soil nutrients and C:N:P stoichiometry characteristics in Pinus armandii plantations,an age sequence of Pinus armandii stands (10 years old,16 years old,22 years old and 47 years old) were selected in Wumeng Mountain,Bijie City,Guizhou Province.Three representative 20 m×20 m plots were set in each forest stand.The soil pH,total carbon (TC),total nitrogen (TN),total phosphorus (TP),total potassium (TP),total calcium (TCa),soil organic carbon (SOC),available nitrogen (AN),available phosphorus (AP),and available potassium (AK) at soil depth of 0-20 cm were measured,and the stoichiometric ratio of soil C:N:P was calculated.Their changes with stand age and their relationship between the C:N:P stoichiometric ratio and the factors were explored.The results showed that the concentrations of SOC and TN among different ages ranged 23.624~65.093 g/kg and 1.533~5.157 g/kg,respectively,which were much higher than the national average level.The concentrations of TP ranged 0.327~1.097 g/kg,which was comparable to the national average soil level.These indicated that the concentrations of SOC and TN were high in the study area.The stand age had significant effects on soil nutrients and C:N:P stoichiometric ratio.With the increase of stand age,the soil TC,SOC,C:N and C:P showed a trend of first decreasing and then increasing,whereas soil pH,TK and TCa showed a trend of first decreasing and then increasing.The TN,TP,AN,AP and AK increased gradually with the increasing of stand age,whereas the soil N:P showed a wavy trend.Pearson correlation analysis showed that the correlations of soil C:N and C:P with TK and TCa were greater than those with TN and TP,indicating that the soil C:N ratio and C:P ratio of Pinus armandii plantations were mainly affected by the contents of potassium and calcium.Therefore,it is particularly important to scientifically regulate the contents of potassium and calcium in the soil during the management of Pinus armandii plantations.Results from this study can provide theoretical basis for sustainable and scientific management of Pinus armandii plantations.
The effects of drainage and afforestation on the physical and chemical properties of soil in subtropical Sphagnum mire were explored to provide a theoretical basis for scientific protection and restoration of this type of wetland.Natural Sphagnum mire in Niangniang Mountain wetland,Guizhou was selected as the control site,and Cryptomeria fortunei forest formed by drainage for afforestation in the sphagnum mire with similar site conditions for 20 years was selected as the treatment site,and the differences in the physical and chemical properties of the surface (0~10cm) soil between the two kinds of sites were compared.Main results:1) The total soil carbon content,total nitrogen content,pH,mass ratio of carbon to phosphorus (C:P),mass ratio of nitrogen to phosphorus (N:P),available potassium content,nitrate nitrogen content,ammonium nitrogen content and soil mass water content of the Sphagnum mire were significantly higher than the corresponding index values of the Cryptomeria fortunei forest (P<0.05).The soil bulk density of Sphagnum mire was significantly lower than that of the Cryptomeria fortunei forest.2) PCA showed that the overall physical and chemical properties of the soil had changed significantly after the long-term afforestation of Cryphieria fortunea forest.3) Total soil carbon content was significantly positively correlated with total nitrogen content(P<0.01),and both of them were significantly positively correlated with C:P,N:P,available potassium content,nitrate nitrogen content,mass water content,respectively (P<0.01),and significantly negatively correlated with bulk density(P<0.01).C:P,N:P,ammonium nitrogen content,nitrate nitrogen content and available potassium content were very significantly or significantly positively correlated with each other.Mass water content was negatively correlated with bulk density(P<0.01).In conclusion,after a long-term afforestation of Cryptomeria fortuneana forest in Sphagnum mire,a large amount of organic matter in the surface soil oxidized and decomposed,soil water content decreased significantly,bulk density increased significantly,soil phosphorus limitation was relieved,and the soil physical and chemical properties were significantly different overall,and the peat soil was transformed into mineral soil.
Eucalyptus is an important fast-growing tree species in southern China,which plays a significant role in ensuring national timber safety and enhancing forest carbon sequestration capacity.However,there are still no reliable tree biomass models for Eucalyptus.In this study,based on the data of above-ground biomass (including the components of stem wood,stem bark,branches and forages) from 183 sample trees and underground biomass from 124 sample trees of Eucalyptus spp.in Guangxi which was the key distribution region of Eucalyptus plantations in China,one- and two-variable biomass model systems with compatibility and additivity were developed using the new combined estimation technique integrating dummy variable modeling approach and error-in-variable simultaneous equations approach.The results showed that the determination coefficients (R2) of above- and underground biomass models were all more than 0.95,and the mean prediction errors (MPEs) were less than 3% and 6%,respectively.From the comparison of estimates resulted from 3 sets of above- and underground biomass models for Eucalyptus published before,it was found that only one set of the models could met the precision needs of relevant technical regulation,and other two sets of the models resulted in significant biased estimates,where the highest estimate error of underground biomass model had even more than 100% of relative error.The compatible and additive tree biomass models systems for Eucalyptus developed in this study would provide a basis for accurately estimating the biomass and carbon storage in Guangxi,even in the whole country.
The effects of different fertilization measures on the growth characteristics of Catalpa bignonioides seedlings were studied to provide theoretical basis for fertilizer supply of Catalpa bignonioides seedlings.Three month old Catalpa bignonioides seedlings with good and even growth were used as materials,part of "3414" scheme was used to design test:three kinds of inorganic fertilizers,including N,P and K,were combined with biochar organic fertilizer,with a total of 8 treatments and 3 fertilization measures:indifferent levels of N,P and K,deficiency of different N,P and K fertilizers and biochar addition,the changes of growth indexes and chlorophyll content(SPAD value) of Catalpa bignonioides seedlings were analyzed.The results showed that:compared with P and k elements,Catalpa bignonioides needed more nitrogen regulation.Reasonable fertilization could promote the growth and development of Catalpa bignonioides seedlings.The fertilization ratio of N,P and K is 8g/plant,4g/plant and 6g/plant,can be used as a nutrient supply plan for the cultivation of Catalpa bignonioides seedlings.
Wild Begonias in Guangxi are rich in resources,which have great prospects for development and application.Through the investigation and cultivation experiments of wild Begonia in Guangxi,and by using the Analytic Hierarchy Process(AHP) and the Entropy Weight Method(EWM),this paper comprehensively evaluated 60 species of wild Begonia in Guangxi to provide scientific basis for the introduction,domestication and gardening applications of Begonia.The evaluation system consisted of ornamental characteristics,biological characteristics,development potential and 16 evaluation factors.This study found that:1) 8 species were Class I,such as Begonia umbraculifolia,which had high ornamental value,strong resistance,wide range of suitability,and various applications.2) 14 species were Class II,such as Begonia ferox,which had high ornamental value,strong adaptability,and simple maintenance,with good development potential,but slightly inferior ornamental value.3) 18 species were Class III,such as Begonia austroguangxiensis,which had simple maintenance,strong growth potential,general development and application value.4) 13 species were Class IV,such as Begonia daxinensis,which had low adaptability.They did not have advantages in garden promotion and application,but could show their value in specific areas.5) 7 species were Class V,such as Begonia chongzuoensis,which had low garden application value and poor adaptability.They could be preserved in the gene pool as germplasm resources.The comprehensive evaluation system of wild Begonia resources established in this study has important theoretical and practical significance for the development and utilization of wild Begonia resources in Guangxi and even in China.
The characteristics of the forest land with a canopy density of more than 60% include complex tree species,a narrow interspecific character gap,and modest interspecific distances.Traditional convolutional neural networks (CNN) are superior to other classification approaches in terms of accuracy and automation,but they also have a low learning efficiency,a tough time enhancing recognition accuracy,and poor interpretability.Additionally,the typical approach of creating maps of tree species through regular segmentation overlooks changes in tree species and boundary characteristics of remote sensing objects,making it simple to create the salt and pepper phenomenon in forest areas with dense canopies.Therefore,a Grad-Swin transformer (G-ST) based on class activation mapping and Swin transformer (ST) classification model was suggested as the solution to the aforementioned issues.It incorporates transfer learning,the ST classification model,and gradient descent class activation mapping,and by integratinglong-distance features,data enhancement,feature knowledge from other fields,and prediction training attention,it increases the G-ST classification accuracy as well as the model's generalization and interpretability abilities.Thematic maps of tree species are created by using a straightforward linear iterative clustering algorithm.The results demonstrated that the accuracy of the tree species map produced by this method was greater than that of the conventional CNN combined with regular segmentation,and the boundary between trees and remote sensing objects was closer to the vectorization result.This method can therefore serve as a useful reference for tree species image segmentation,mapping,and distribution statistics.
Remote sensing classification technology has always been the hotspot and difficulty in forest and grassland monitoring.Since 2021,the annual comprehensive ecological monitoring of forest and grassland has been widely applied remote sensing classification technology in the interpretation of patch types and changes of forest land,grassland and wetland.GFDM Satellite is the first civil optical remote sensing satellite with the resolution better than 0.5 meters in our country.In this paper,we used the GFDM satellite data to identify forest land types and tree species in Taoyuan County and Jishou City of Hunan Province.The results showed that the random forest method performed well in the identification of forest land types.The overall classification accuracy of forest land,wetland and other forest land was 89.56%,and the Kappa coefficient was 0.733.The K-nearest neighbor method was used to identify Chinese fir,Masson pine,shrub group and citrus.The overall recognition accuracy of the four main tree species was 77.58%,and the Kappa coefficient was 0.697.In general,GFDM satellite has good ability in remote sensing classification and target recognition,and has great application potential in forest and grassland monitoring.
This paper took the larch forest land of Saihanba Forest Farm in Hebei Province as the research object.Through setting cement piles and reflective sheets in the selected sampling sites,aiming at the low precision of forest single tree extraction,this paper conducted the research on the method of extracting the location of forest single tree based on laser point cloud data,which provided a reference for the location and quantity statistics of single tree in forest resource survey.Through the registration of the collected forest ground point cloud data with the cloud data of each survey site using the reflector model,an improved voxel space neighborhood and RANSAC cylinder fitting method was proposed to extract the single tree position from three different size sample plots.The results showed that the single tree position extraction effect of this method was good,and the extraction accuracy was more than 93%.
The use of remote sensing technology to extract the composition and distribution of wetland vegetation communities is of great significance to the construction of wetlands.Taking Qinghai Ulandulan Lake National Wetland Park as the research area,using the number of Jilin No.1 remote sensing images,KNN and RF classification models were selected through image segmentation and feature optimization,the vegetation community of Dulan Lake wetland was divided,and the classification accuracy was verified.The results showed that according to the segmentation scale provided by ESP 2 tool,the optimal segmentation scale for object-oriented classification of vegetation communities was 18,and the segmentation scales of vegetation and non-vegetation areas were 32 and 85,respectively.For character type division,only using the threshold of image band information and related index could not accurately extract the feature category,it was necessary to combine the image geometric features and texture features to improve the classification accuracy,use the feature space optimization tool to optimize 61 image features,and finally screen out 40 image features,and use them for classification.According to the confusion matrix classification accuracy evaluation results,the classification results of KNN algorithm were better than RF,among which the overall classification accuracy of KNN was 81.80%,the Kappa coefficient was 0.79,the overall classification accuracy of RF was 72.59%,and the Kappa coefficient was 0.68.According to the classification results,the vegetation coverage rate of Dulan Lake wetland was 44.41%,and the composition and distribution characteristics of vegetation communities in the results could provide a basis for wetland ecological construction and management.
Aiming at the problem that the traditional second-class survey method of forest resources is time-consuming and laborious,it is difficult to meet the needs of forest resource dynamic monitoring under the new situation.Three forest farms in Liuhe District,Nanjing city were selected as the study area in this paper.Sparse airborne laser radar was used to extract feature parameters,combined with the data of Forest Management Inventory.Two algorithms,stepwise regression and Boruta,were used for factor screening.Three modeling methods including Stepwise Multiple Linear Regression (SMLR),Support Vector Machine (SVM) and Random Forest (RF) were compared to estimate the forest stock.The results showed that:1) Height factor was the main characteristic parameter affecting forest stock volume;2) SVM and RF algorithms performed better in model fitting and verification accuracy,SVM algorithms performed slightly inferior to RF algorithms in mixed forests,and stepwise regression methods performed poorly.In general,the modeling results of lidar extraction factor and forest stock were good,and Sparse airborne laser radar had good applicability to forest resource survey,which provided a new idea for forest resource survey in the future.
The road green spaces before and after the landscape optimization of national roads,county roads and township roads in Liquan County in 2021 were taken as the research objects.UAV aerial survey,field survey and GIS were used to obtain road green space information,and the DOM,DEM and DSM files generated from UAV aerial survey were combined to extract landscape features,propose transformation patterns and carry out landscape optimization.The species diversity of the optimized road green spaces was sampled and analyzed,and the diversity characteristics were analyzed by calculating the Margalef richness index,Shannon-Wiener diversity index,Simpson dominance index and Pielou evenness index,and recommendations were made for the development of road green space systems in Liquan County.The results of the study show that:1) UAV aerial surveys are suitable for collecting information on road green spaces with different landscape characteristics,and are universal in terms of data collection.Road green spaces are affected by road class and width,and show obvious differences in landscape configuration.The best landscape base of national roads and the worst landscape base of rural roads are found in Liquan County.There are shortcomings such as single plant species,lack of regional characteristics,poor community structure,low ecological benefits,etc.;2) Based on the characteristics of the site,it is proposed to improve the type and transformation of landscape transformation mode.The improvement is divided into two types,namely local modification and overall enrichment.Local modification is based on the design point of "breaking grey and increasing green,landscape articulation";overall enrichment is based on the design point of "adding layers,colors and numbers";the transformation type is based on "background trees+ornamental shrubs+ground cover ";3) The diversity of species on each grade of road is enhanced after landscape optimization,and the overall landscape effect is remarkable,which has certain significance for the construction of forest cities.
Data quality evaluation is the basis of land cover product selection and the premise of application.Taking Pu 'er City of Yunnan Province as the research area,weadopted the correlation coefficient of area,confusion analysisof classification type,consistency analysis for spatial pattern,and confusion matrix as the indicators for evaluation.Based on the classification results using high spatial resolution airborne images and the sub-meter visual interpretation results,we analyzed the classification accuracy and spatial consistency of 4 land cover products with 10m spatial resolution (Pu'er LC,Esri_Land_Cover_2020_10m,ESA World Cover,Dynamic World) in Pu'er City,Yunnan Province.Ourresults showed that:1) Land types and distribution patterns of 4 land cover products were basically consistent,mainly including woodland,followed by shrub,grassland and cultivated land.The area correlations were relatively high,all the correlation coefficients were greater than 0.8.2) The high spatial consistency area accounted for 64.87% of the Pu 'er city,mostly was woodland;In the low spatial consistency regions,shrub and grassland,woodland,cultivated land,construction land and other land cover types were staggered.3) The absolute accuracy evaluation showed that the overall accuracy of Pu'd LC data was the highest (88.52%),and rest of the three products had the classification accuracy for about 75%.This paper provided a good reference for the quality evaluation and the selection for land cover products.