vegetation

摘要： Landscape heterogeneity in biodiversity conservation areas can be represented by the size of the geographic range of vegetation cover types and their species composition;and is reflected in historical and contemporary LULC(Land Use/Cover).This study assesses LULC changes in a predominantly vegetated Incalaue river basin in NSR(Niassa Special Reserve)for the years 2001,2009 and 2019 to recommend conservation targets.LULC was mapped using the best available Landsat imagery of the area which were L7 EMT+(Landsat 7 Enhanced Thematic Mapper),L5 TM(Landsat 5 Thematic Mapper)and L8 OLI(Landsat 8 Operational Land Imagery).Image classification and remote sensing analysis were done using images of 30-meter resolution using the maximum likelihood supervised classification on ArcGIS ArcMap 10.4.1.Results showed that there were gains in area coverfor taller vegetation classes with the major ones being MDW(Medium Density Woodland)which increased by 51.07%;MFS(Mountain Forests)by 36.41%;and HDW(High-Density Woodland)by 17.95%over the studied period.NDVI(Normalized Difference Vegetation Index)maps show 2019 with wetter vegetation than 2001;and both wetter than 2009.The spatially dominant vegetation-class was MDW(Medium Density Woodland)covering 27.29%of the basin area largely in the elevation band 410-430 m a.s.l.Vegetation classes do not necessarily follow landform with rocky upstream section(440-510 m a.s.l)having MFS which also existed in lower altitude areas(370-430 m a.s.l);and woodland being randomly distributed across the basin while there was also WET(Wetland)in both upstream and downstream.There are multiple vegetation species localized in distribution in the landscape which makes these to be hotspot areas for conservation.Local people in the human settlement areas of Ntimbo 1 and Lizongole recognize vulnerability of ecosystems,environmental change as well as human land use/cover and climate change as the main threats.There was a large increase in human settlement area(104.17%)over the study period and this shows a need for mitigating community-wildlife conflict especially along the green vegetation riverine areas during the dry seasons.The study showed need for a plan for human LULC away from wildlife vegetation hotspot areas;identification and consideration of area-demanding threatened species that require landscape scale conservation;and prevention of degradation and loss of water source hotspots for wildlife as well as conservation of sensitive and localized vegetation species.The Mozambican land law allows individual ownership of land by citizens even in conservation areas which creates a danger of human-wildlife interactions;risks land encroachment deeper into the reserve;and potentially causing environmentaldegradingof this sensitive ecosystem hosting humans and wildlife so there is need for consistent and conservation targetedenvironmental research to inform policy and LULC decisions.

摘要： The climate in Southwest China are predominantly under the influences of three contrasting climate systems, namely the East Asian monsoon, the South Asian monsoon, and the westerlies. However, it is unclear if the diversified climate systems, in combination with the complex terrain and varying vegetation types, would result in contrasting patterns of changes in climate across the region. Based on the CRU TS data for the period 1901−2017, we examined the spatiotemporal characteristics of the regional climate, and identified types of climate change patterns and drivers. Overall, the region experienced significant increases in annual mean temperature during 1901−2017, with occurrence of a significant turning point in 1954 for a more pronounced warming (0.16 °C/10 a). The annual precipitation fluctuated greatly over the study period without apparent trend, albeit the occurrence of a significant turning point in 1928 for a slight increase in the later period (1.19 mm/10 a). Spatially the multi-year averages of selective climate variables during 1901–2017 displayed a trend of decreases from southeast to northwest, but with increasing variability. We identified five major climate change types across the study region, including warmer (T^(+)), drier (P^(−)), warmer-drier (T^(+)P^(−)), warmer-wetter (T^(+)P^(+)), and no significant changes (NSC). The type T^(+)P^(+) mainly occurred in the western parts over the plateau sub-frigid semiarid ecozone (77.0%) and the plateau sub-frigid semihumid ecozone (19.9%). The central parts of the region are characterized by the type T^(+), corresponding to six ecozones, including the mid-subtropical humid ecozone (33.1%), the plateau temperate humid-semihumid ecozone (28.8%), the plateau sub-rigid semihumid ecozone (9.5%), the southern subtropical humid ecozone (8.1%), the plateau sub-frigid arid ecozone (7.3%), and the plateau temperate semiarid ecozone (6.6%). No significant change in climate was detected for the eastern parts over the mid-subtropical humid ecozone (67.3%), the plateau temperate humid and semihumid ecozone (19.5%) and the plateau sub-frigid semihumid ecozone (8.8%). The types P^(−) and T^(+)P^(−) together accounted for less than 5% of the entire study region, which predominantly occurred in central Yunnan-Guizhou Plateau and south of the southeastern Xizang, corresponding predominantly to the mid-subtropical humid ecozone. Across the region and within the zonal climate change types, vegetation and topography both played a significant role in determining the climate variability and magnitude of changes. Our results suggest that the southwestern China experienced intensified influences of the southeasterly monsoon and the southerly monsoon in the regional climate, while the westerly alpine influences subsided;topography and vegetation affected the magnitudes of the directional changes in climate at a local scale.

摘要： Vegetation uprooting is a complex process which depends on many interrelated factors.In this paper,attention is focused on the flow-induced uprooting in river bends,where the flow characteristics vary as effected by the channel's curvature and its continuous changing in the downstream direction.Results are presented by an experimental work done in a high-amplitude meandering flume with mature herbaceous vegetation on the bed.In the first part of the paper,the variation along the bend of the geometrical(length,thickness,and radical architecture)and the mechanical(resistance force)characteristics of the roots are analyzed.In the second part of the paper,the transition from the condition of vegetation distributed on the bed to the condition of vegetation uprooted by the flow is experimentally examined.The results show that the flow-induced uprooting varies along the bend depending on the roots'geometrical and mechanical characteristics which are,in turn,influenced by the variation of the water surface elevation along the bend itself.It has been found that lower values of the resistance force occur at the apex section where the roots are characterized by higher values of length and lower values of thickness and have radical apparatuses characterized by limited encumbrance,a high number of roots,and low bushyness.The flow-induced uprooting especially develops close to the outer bank along the channel reach between the bend entrance and the apex section,where the root resistance force and the water surface slope tend to decrease in value.

摘要： Due to global climate change,Dendrolimus pests and diseases seriously threaten the protec-tion of forestry plants and the safety of crops all over the world.This paper aims to discuss the research results and frontier progress of Dendrolimus disasters based on remote sensing monitoring,trying to find the occurrence characteristics of pests.In this paper,bibliometric methods and CiteSpace knowledge graphs were used to analyze the publication trend,highly cited documents,key research institutions,and high-frequency keywords of the extracted documents in the Web of Science(WOS)database.The following conclusions are drawn:(1)The amount of research in WOS is on the rise,but it has declined in recent years.The countries with strong influence in national cooperation are mainly the United States and China.(2)The United States Department of Agriculture-Agricultural Research Service(USDA ARS)and the Chinese Academy of Sciences have published a lot.This paper reviewed the research progress of high-frequency institutions.(3)The key research topics focus on remote sensing,agriculture,and environmental sciences.Besides,the research hotspots include remote sensing monitoring,climate change,spectral reflectance,vegetation index,and precision agriculture.Finally,we put forward the current challenges and development trends of remote sensing pest monitoring.This paper can provide a reference for the research on remote sensing monitoring of Dendrolimus disasters in the future.

摘要： Both climate and land-use changes,including the introduction and spread of allochthonous species,are forecast to affect forest ecosystems.Accordingly,forests will be affected in terms of species composition as well as their soil chemical and biological characteristics.The possible changes in both tree cover and soil system might impact the amount of carbon that is stored in living plants and dead biomass and within the soil itself.Additionally,such alterations can have a strong impact on the detrital food web that is linked to litter decomposition.Although there are studies on the infuence of plant diversity on soil physical and chemical characteristics,the effects on soil biological activity and carbon storage processes remain largely unknown.The aim of this study was to investigate and compare chemical and biological variables in covariation with plant communities in an autochthonous beech forest(Fagus sylvatica L.)and a black pine plantation(Pinus nigra J.F.Arnold subsp.nigra).Our results confirmed that the two communities were considerably different,with the old-growth beech community having a lower number of plant species and the pine community was in development as a consequence of anthropogenic activities.These aspects of the two communities were also refected in the soil,with the beech soil having higher nitrogen levels and a more specialized microbial community compared to the pine soil,with most extracellular enzymes(such as peroxidase and chitinase)showing lower activity in the pine soil.

摘要： BACKGROUND Haemophilus parainfluenzae(HPI)belongs to the HACEK(Haemophilus spp.,Aggregatibacter spp.,Cardiobacterium spp.,Eikenella spp.,and Kingella spp.)group of organisms.The HACEK group of organisms are a part of the oropharyngeal flora and can cause invasive opportunistic infection such infective endocarditis(IE)in hosts with compromised immunological barriers.AIM To perform a 20-year systematic review of the literature characterizing the clinical presentation,epidemiology and prognosis of HPI IE.METHODS We performed a systematic review of Medline,Pubmed,Scopus and Embase from 2000 to 2022 to identify all cases of HPI IE.RESULTS Thirty-nine adult cases were identified.HPI IE was found to affect males slightly more than females and is common in patients with predisposing risk factors such as underlying valvular abnormalities.It mostly affected the mitral valve and had an indolent course;significantly sized vegetations(>1 cm)developed in most cases.Central nervous system septic embolization was common.It had a favorable prognosis compared to staphylococcal and streptococcal IE.CONCLUSION Clinicians should be attentive to the indolent course of HPI IE and the presence of predisposing risk factors in order to allow for timely management.

摘要： BACKGROUND Infective endocarditis(IE) is a rare disease with a high mortality rate.Leclercia adecarboxylata(L.adecarboxylata) is a movable Gram-negative bacillus of enterobacteriaceae,and it can rarely be a pathogen which often affects immunodeficient patients.There are about three cases of immunocompetent patients with monomicrobial L.adecarboxylata infection.There are only three reported cases of IE caused by L.adecarboxylata in the world.The mitral valve is often affected in IE,and the prognosis for IE with mitral valve lesions is often poor.CASE SUMMARY A 51-year-old man was found to have moderate to severe mitral stenosis on echocardiography.He came to our Cardiothoracic Surgery Department for surgical management.A diastolic murmur was heard on auscultation of the heart in the mitral region.On the second day of hospitalisation,he presented with slurred speech,reduced muscle strength in the left limb,and acute cerebral infarction on cranial computed tomography.Surgical treatment was decided to postpone.On the ninth day of admission,the patient developed a sudden high fever and shock and was transferred to the Cardiac Intensive Care Unit,where echocardiogram revealed an anterior mitral valve leaflet vegetation.After empirical anti-infective treatment with vancomycin(1g q12h),an emergency valve replacement was performed.Bacterial culture identified L.adecarboxylata.Antiinfective treatment with piperacillin-tazobactam(4.5g q8h) was added for 4 wk.Follow-up echocardiography showed normal bioprosthetic valve function after mitral valve replacement.CONCLUSION We report the first case of L.adecarboxylata IE in China,and clinicians should pay attention to this pathogen.

摘要： [Objectives]To explore the effects of spatial density of farmland shelterbelts on NDVI on the northern slope of Tianshan Mountains.[Methods]Taking the economic belt of the northern slope of the Tianshan Mountains as the research area and using the grid method,the spatial density distribution of farmland shelterbelts can be known.Combining the grid method with NDVI data,the average value of normalized difference vegetation index(NDVI)during the growing period of crops can be obtained.In addition,the protection benefits of the shelterbelts on crops were analyzed through comparing the growth of crops within the protection zone with and without protection.[Results]The grids with shelterbelt distribution were better than the grids without shelterbelt distribution,and the shelterbelt played a great role in promoting crop growth.In the middle stage of crop growth,the protection benefit of shelterbelt was significant.The spatial density of shelterbelts was unevenly distributed in the range of 0.6 to 0.8,and the protection benefits were poor.[Conclusions]It is expected to explore the effects of shelterbelts on crop growth at a larger regional scale,so as to provide a basis for the management and design of shelterbelts in the future,and to provide a theoretical basis for studying the protective effect of farmland shelterbelts on crops.

摘要： [Objectives]To explore the relationship between vegetation index and forest surface fuel load.[Methods]UAV multispectral remote sensing was used to obtain large-scale forest images and obtain structural data of forest surface fuel load.This experimental area was located in Gaoming District,Foshan City,Guangdong Province.The average surface fuel load of the experimental area was as high as 39.33 t/ha,and the forest surface fuel load of Pinus elliottii was the highest.[Results]The normalized difference vegetation index(NDVI)and enhanced vegetation index(EVI)had a moderately strong correlation with the forest surface fuel load.The regression model of NDVI(X)and forest surface fuel load(Y)was established:Y=-5.9354X+8.4663,and the regression model of EVI(X)and forest surface fuel load(Y)was established:Y=-5.8485X+6.7271.The study also found that the linear relationship between NDVI and surface fuel load was more significant.[Conclusions]Both NDVI and EVI have moderately strong correlations with forest surface fuel load.NDVI is moderately or strongly correlated with the surface fuel load of Pinus massoniana forest,shrub grassland,broad-leaf forest and bamboo forest,while EVI is only strongly correlated with surface fuel load of broad-leaf forest and bamboo forest.It is expected that the relationship between other vegetation indices and forest surface fuel load can be obtained by the method in this study,so as to find a more universal vegetation index for calculating surface fuel load.

摘要： Herbaceous marsh is the most widely distributed type of marsh wetland ecosystem,and has important ecological functions such as water conservation,climate regulation,carbon storage and fixation,and sheltering rare species.The carbon sequestration function of herbaceous marsh plays a key role in slowing climate warming and maintaining regional environmental stability.Vegetation biomass is an important index reflecting the carbon sequestration capacity of wetlands.Investigating the biomass of marsh vegetation can provide a scientific basis for estimating the carbon storage and carbon sequestration capacity of marshes.Based on field survey data of aboveground biomass of herbaceous marsh vegetation and the distribution data set of marsh in China,we analyzed the aboveground biomass and its spatial distribution pattern of herbaceous marsh on a national scale for the first time.The results showed that in China the total area of herbaceous marsh was 9.7×10^(4) km^(2),the average density of aboveground biomass of herbaceous marsh vegetation was 227.5±23.0 g C m-2(95%confidence interval,the same below),and the total aboveground biomass was 22.2±2.2 Tg C(1 Tg=1012 g).The aboveground biomass density of herbaceous marsh vegetation is generally low in Northeast China and the Tibetan Plateau,and high in central North China and coastal regions in China.In different marsh distribution regions of China,the average biomass density of herbaceous marsh vegetation from small to large was as follows:temperate humid and semi-humid marsh region(182.3±49.3 g C m^(-2))vegetation in different marsh distribution regions was the largest in the temperate humid and semi-humid marsh region(9.6±2.6 Tg C), and was the smallest in the coastal marsh region(1.1±0.1 Tg C). The spatial distribution of aboveground biomass of herbaceous marsh vegetation in China has obvious non-zonality characteristics, but also presents certain zonality in some regions. The aboveground biomass of herbaceous marsh vegetation in the Tibetan Plateau decreased with the increase of altitude. With the aggravation of drought, the aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions and temperate arid and semi-arid regions decreased first and then did not obviously change. The aboveground biomass of herbaceous marsh vegetation in temperate humid and semi-humid regions was relatively larger in the regions with higher average annual temperature. The results can provide scientific basis for accurately evaluating the adjustment action of wetland ecosystems on climate, and provide decision support for adaptive management of wetland ecosystems.