Surface sediment diatoms from the western Pacific marginal seas and their correlation to environmental variables

Diatom data of 192 surface sediment samples from the marginal seas in the western Pacific together with modern summer and winter sea surface temperature and salinity data were analyzed.The results of canonical correspondence analysis show that summer sea-surface salinity(SSS) is highly positively correlated with winter SSS and so is summer sea-surface temperature(SST) with winter SST.The correlations between SSSs and SSTs are less positively correlated,which may be due to interactions of regional current pattern and monsoon climate.The correlations between diatom species,sample sites and environmental variables concur with known diatom ecology and regional oceanographic characters.The results of forward selection of the environmental variables and associated Monte Carlo permutation tests of the statistical significance of each variable suggest that summer SSS and winter SST are the main environmental factors affecting the diatom distribution in the area and therefore preserved diatom data from down core could be used for reconstructions of summer SSS and winter SST in the region.

Monthly Variation in Crustacean Assemblage(Decapod and Stomatopod) and Its Relationships with Environmental Variables in Laizhou Bay,China

In this study,we investigated the community structure of crustaceans(decapod and stomatopod) inhabiting the sandy mud bottoms of Laizhou Bay(northeastern China) monthly from May 2011 to April 2012.Investigation was stopped from December 2011 to February 2012 because of the extreme weather and sea ice.A total of 205,057 specimens belonging to 31 species(shrimp,15;crab,15;and stomatopod,1) were collected in 148 hauls.From 2011 to 2012,Oratosquilla oratoria was the dominant biomass species(47.80%),followed by Charybdis japonica(15.49%),Alpheus japonicas(12.61%),Portunus trituberculatus(6.46%),and Crangon spp.(4.19%).Crangon spp.was the most dominant species by individual(32.55%).O.oratoria was the most-frequently encountered species(81.76%),followed by Palaemon gravieri(70.95%),C.japonica(65.54%),A.japonicas(62.16%),and P.trituberculatus(54.73%).The biomass density increased from August to September 2011 and decreased from March 2012 to April 2012.The dynamics of the ecological indices evolve in a similar manner,with high values of diversity and evenness and rich species from May to June 2011 and low values from September to October 2011.O.oratoria,C.japonica,and P.trituberculatus differed by biomass data between groups I(samples obtained from September to October 2011) and II(samples in other months).These species contributed more than 70% to the similarity of the crustacean community structure.Furthermore,the subsets of environmental variables that best matched the crustacean-assemblage structure were as follows:water depth(WD) in summer(June to August);sea surface temperature(SST),dissolved oxygen(DO),and WD in autumn(September to November);and DO,salinity,and WD in spring(March to May).The calculated correlation coefficients and significance level were higher in the period of July to August 2011 than in other months.Comparing 2011 to 2012 with 1982 to 1983,the species composition remained stable.However,the dominant species changed significantly.High value and large species,such as F.chinensis,P.trituberculatus,and T.curvirostris,have been replaced by low value and small species(i.e.,Crangon spp.,P.gravieri,and C.japonica).

Effect of flow rate on environmental variables and phytoplankton dynamics:results from field enclosures

To investigate the effects of flow rate on phytoplankton dynamics and related environment variables,a set of enclosure experiments with different fl ow rates were conducted in an artificial lake. We monitored nutrients,temperature,dissolved oxygen,p H,conductivity,turbidity,chlorophyll-a and phytoplankton levels. The lower biomass in all flowing enclosures showed that flow rate significantly inhibited the growth of phytoplankton. A critical flow rate occurred near 0.06 m/s,which was the lowest relative inhibitory rate. Changes in flow conditions affected algal competition for light,resulting in a dramatic shift in phytoplankton composition,from blue-green algae in still waters to green algae in flowing conditions. These findings indicate that critical flow rate can be useful in developing methods to reduce algal bloom occurrence. However,flow rate significantly enhanced the inter-relationships among environmental variables,in particular by inducing higher water turbidity and vegetative reproduction of periphyton( Spirogyra). These changes were accompanied by a decrease in underwater light intensity,which consequently inhibited the photosynthetic intensity of phytoplankton. These results warn that a universal critical flow rate might not exist,because the effect of flow rate on phytoplankton is interlinked with many other environmental variables.

Relationships between daily growth of different groups of swordtip squid(Uroteuthis edulis)and environmental variables in the East China Sea

Swordtip squid(Uroteuthis edulis)is one of the important economical fishing target species in the East China Sea.Uroteuthis edulis is characterized by rapid growth,extensive migration,and long spawning period and sensitive to surrounding environment.In order to assess its stock status,it is necessary to explore its spawning season,growth patterns of different populations and their relationship with the environment in advance.In this paper,based on the samples of U.edulis collected in the East China Sea from September 2017 to March 2018,we explored the relationships between daily growth of statolith microstructure and environmental variables by gradient forest method and generalized additive model.The spawning season of U.edulis was found to be nearly one year,and two dominant season groups were found:the spring group with the peak period of April and the summer group with the peak period of August.Water temperature in the depth of 25 m(Temp_25),sea surface temperature(SST)and zonal velocity were the key environmental variables for the daily growth of April-spawning group.The most suitable environmental conditions for the growth of April-spawning group were water temperature(24-27℃)and velocity(0.1-0.3 m/s).SST,Temp_25 and mixed layer depth were the key environment variables for the daily growth of August-spawning group.The most suitable environmental conditions for the growth of Augustspawning group were water temperature(21-28℃)and water depth(0-50 m).Key environmental variables of different groups suggested that early growth was significantly affected by seasonal changes of water temperature,current velocity and prey abundance.This study explored the relationships between early growth and environmental variables and provided the scientific guidance for the management and conservation of U.edulis.

DEM Production/Updating Based on Environmental Variables Modeling and Conflation of Data Sources

Availability of digital elevation models （DEMs） of a high quality is becoming more and more important in spatial studies. Standard methods for DEM creation use only intentionally acquired data sources. Two approaches which employ various types of data sets for DEM production are proposed： （1） Method of weighted sum of different data sources with morphological enhancement that conflates any additional data sources to principal DEM, and （2） DEM updating methods of modeling absolute and relative temporal changes, considering landslides, earthquakes, quarries, watererosion, building and highway constructions, etc. Spatial modeling of environmental variables concerning both approaches for （a） quality control of data sources, considering regions, （b） pre-processing of data sources, and （c） processing of the final DEM, have been applied. The variables are called rate of karst, morphologic roughness （modeled from slope, profile curvature and elevation）, characteristic features, rate of forestation, hydrological network, and rate of urbanization. Only the variables evidenced as significant were used in spatial modeling to generate homogeneous regions in spatial modeling a-c. The production process uses different regions to define high quality conflation of data sources to the final DEM. The methodology had been confirmed by case studies. The result is an overall high quality DEM with various well-known parameters.

Effects of phytoplankton community and interaction between environmental variables on nitrogen uptake and transformations in an urban river

Phytoplankton are not only the main bearer of the nitrogen cycle,but also a key link driving nitrogen cycle.However,most phytoplankton cannot directly use N_(2),and they must uptake nitrogenous nutrients(ammonium,nitrate,and urea)to meet their photosynthesis needs.We examined the uptake characteristics of several nitrogenous substrates using stable isotope technique and identifi ed the potential nitrogen transformations in the Fenhe River.Results revealed that spring phytoplankton community composed of mainly Fragilaria,Ulothrix,Microcystis,and Synedra.Urea can meet the spring partial nitrogen requirement of phytoplankton.The large uptake rate of urea depended on urease,chlorophyll a,and nitrate concentrations as shown in random forest models.Cyanobacteria explained more than 42.8%of the total abundance at all sites in summer.Upstream was dominated by Actinastrum,and Chlorella was relevant in the downstream section.The uptake rates of ammonium were higher than those of nitrate and urea.In addition,the random forest model demonstrated that ammonium,urease,and dissolved oxygen(DO)were the major contributors to the ammonium uptake rates.Ammonium was taken up preferentially in autumn and phytoplankton(Cyclotella,Chlorella,and Pseudanabaena)appeared to be able to respond to changes in nitrogen forms by adjusting their community composition.Structural equation models demonstrated that temperature-induced changes in DO directly affected the transformations of different forms of nitrogen.At the same time,dissolved organic carbon can directly act on nutrients and then indirectly affect enzyme activity.There were great diff erences in the positive and negative effects of different paths in the process of nitrate reduction to nitrite and then reduction to ammonium in time and space.These findings provide a better understanding of the underlying mechanism of nitrogen uptake and the influences of interaction between environmental variables on nitrogen transformations in urban river ecosystems.

Population structure,age and growth rates of conifer species and their relation to environmental variables at Malam Jabba,Swat District,Pakistan

This study focuses on age,growth rate and diameter distribution of pine forests in the Malam Jabba area,Swat District,Pakistan.Wood core samples were taken from twenty stands.Picea smithiana was the oldest at 234 years with a 112-cm diameter.Abies pindrow was 125 years with an 80-cm diameter while the oldest Pinus wallichiana was 122 years with 75-cm diameter.The fastest overall growth rate of 1.5±0.1 year/cm was for P.wallichiana on a west-facing aspect,while the slowest 5.8±2.6 year/cm growth was P.smithiana on an eastfacing exposure.P.wallichiana and A.pindrow exhibited marked differences in growth rates over a 5-year period.The highest growth was by P.wallichiana from 1966 to 2006.A.pindrow showed less growth over the same years,such pattern simultaneously reverse from 1911 to 1965.The relationship between diameter and age,diameter and growth rate and age and growth rate were correlated.P.wallichiana and A.pindrow ages were correlated with diameter and growth rates.P.smithiana age was positive correlated with diameter.Generally,topographic and edaphic factors did not show significant correlations with growth rates,although some appreciable correlations were recorded.The growth of P.wallichiana was correlated with elevation while A.pindrow was correlated with maximum water retaining capacity.Diameter and age produced uneven size classes and many size gaps,which could be the result of anthropogenic disturbances.

Diatom distribution in surface sediments from Chinese inshore waters and the relationship to modern environmental variables

Diatoms are widely used to study past and present changes in the marine environment. Unimodal models are appropriate for exploring the relationship between environmental properties in Chinese inshore waters and fossil diatom species derived from modem surface sediments. The best-fit relationships between two multivariate datasets （diatom species and environmental variables） were identified using canonical correspondence analysis （CCA）, which is a constrained ordination technique. The absolute abundance of diatoms in the Chinese inshore waters ranged from 500 to 48 000 valves/g, and the average absolute abundance of all the 29 sites was l l 300 valves/g. 153 species and varieties of diatoms belonging to 42 genera in all were identified in the Chinese inshore waters. There were 28 dominant diatom species in all. According to the absolute abundance of the dominant species and the spatial distribution of the currents from the Chinese inshore waters, 12 diatom assemblages were distinguished from north to south, which reflected the different oceanographic conditions at the regional scale. Of the eight environmental variables considered, the most important environmental variable is winter sea surface salinity （WSS）, which was also the only environmental variable with statistical significance. Therefore, it may be used to establish a transfer functions for the Chinese inshore waters in future paleoclimate studies.

Diatoms as indicators of environmental change in coastal areas:a case study in Lianjiang coast of East China Sea

Owing to the significant differences in environmental characteristics and explanatory factors among estuarine and coastal regions,research on diatom transfer functions and database establishment remains incomplete.This study analysed diatoms in surface sediment samples and a sediment core from the Lianjiang coast of the East China Sea,together with environmental variables.Principal component analysis of the environmental variables showed that sea surface salinity(SSS)and sea surface temperature were the most important factors controlling hydrological conditions in the Lianjiang coastal area,whereas canonical correspondence analysis indicated that SSS and pH were the main environmental factors affecting diatom distribution.Based on the modern diatom species–environmental variable database,we developed a diatom-based SSS transfer function to quantitatively reconstruct the variability in SSS between 1984 and 2021 for sediment core HK3 from the Lianjiang coastal area.The agreement between the reconstructed SSS and instrument SSS data from 1984 to 2021 suggests that diatombased SSS reconstruction is reliable for studying past SSS variability in the Lianjiang coastal area.Three low SSS events in AD 2019,2013,and 1999,together with an increased relative concentration of freshwater diatom species and coarser sediment grain sizes,corresponded to two super-typhoon events and a catastrophic flooding event in Lianjiang County.Thus,a diatom-based SSS transfer function for reconstructing past SSS variability in the estuarine and coastal areas of the East China Sea can be further used to reflect the paleoenvironmental events in this region.

Responses of Grassland Net Primary Productivity to Environmental Variables in Northern China

Various environmental factors affect net primary productivity （NPP） of grassland ecosystem. Extensive reports on the effects of environmental variables on NPP can be found in literature. However, the agreement on the relative importance of various factors in shaping the spatial pattern of grassland NPP has not yet been reached. Here a grassland in situ NPP database comprising 602 samples in northern China for 1980-1999 was developed based on a literature review of published biomass and forage yield field measurements. Correlation analyses and dominance analysis were used to quantify the separate and combined effects of environmental variables （climate topography and soil） on spatial variation in NPP separately. Grassland NPP ranged from 4.76 g C m-2a-1 to 975.94gCm-2a-1, showing significant variations in space. NPP increased with annual precipitation and declined with annual mean temperature significantly. Specifically, precipitation had the greatest impact on deserts, followed by steppes and meadows. Grassland NPP decreased with increasing altitude because of water limitation, and positively correlated with slope, but weakly correlated with aspect. Soil quality showed positive effects on NPP. Annual precipitation was the dominant factor affecting the spatial variability of net primary productivity, followed by elevation.

Environmental variables vis-a-vis distribution of herbaceous tracheophytes on northern sub-slopes in Western Himalayan ecotone

Background:In the northern hemisphere,the north face of the mountains has a high diversity of species which is attributed to the moist and shady conditions at the north face.Other environmental variables may also influence the species diversity on the northern faces of the mountain and therefore needs to be studied in detail.The northern slopes represent three different sub-slopes—north,north east,and north west.During the current investigation of Pir-Panjal and Dauladhar ranges in Bhadarwah valley,fine-scale studies on the relationship between vegetation and four variables(soil pH,moisture content,electrical conductivity,and steepness)were conducted.The study determined the role of these variables on the vegetation of three different sub-slopes.The sampling was done at the confluence of two communities(forest and grassland)at three sites on the northern sub-slopes of the lesser stratum in western Himalayan.Results:The result revealed that rich herbaceous diversity prevails on the lesser Himalayan stratum(Bhadarwah valley).As many as 65.8%species differ from site to site,whereas species commonality among the sites is minimum.The role of environmental variables on the species composition at different sub-slopes of the north mountain face is deduced through canonical correspondence analysis(CCA).Conclusions:The availability of solar light increases air and soil temperature on the north east–facing slope.All the environmental variables(soil pH,moisture,electrical conductivity,and mountain steepness)are insignificant at pure north face for the species composition.Therefore,it can be concluded that some other environmental variables may influence the species composition which are needed to be further investigated.

Influence of edaphic factors on distribution and condition of Himalayan silver birch(Betula utilis D.Don)communities in the northwestern Indian Himalayas

The basic concept of phytosociology is crucial for the assessment of species composition and dynamic ecological succession of forests supporting ecological services,functions,disturbance,and resilience that lead to the development of integrated areas such as ecological niche modeling and contribute to identifying the valuable bio-indicators which can be used in framing conservation and management planning.B.utilis is one of the most dominant tree species of treeline ecotone in the Himalayan Region.The species is also considered as indicator species for monitoring the past and recent climate change impact.The current study was carried out in the natural populations of B.utilis from the sub-alpine zone of North-western Indian Himalaya.The birch dominated forest harbors a total of 305 plant species comprising Angiosperms(51 families,160 genera and 277 species),Gymnosperms(03 families,05 genera and 07 species)and Pteridophytes(07 families,11 genera and 21 species)with Asteraceae,Ranunculaceae and Rosaceae as dominant family.Birch forests are found dominant in shady moist habitat and North West aspect.Geographical characteristics,anthropogenic and developmental activities affect the population structure of B.utilis and associated species.However,the species has fair regeneration status in the study area.The acidic nature of soil pH and spatial variation in edaphic characteristics may be due to geographical differences,rooting patterns and litter accumulation of below and above-ground vegetation.Biomass estimation of a representative population of B.utilis from each site showed that TAGBD,TCD and TBD were found maximum in ST3(Hamta Pass II site).The CCA analysis determined that environmental variables such as altitude,organic matter,available phosphorous,organic carbon,available nitrogen,and electrical conductivity played a significant role in determining tree species composition and distribution in B.utilis dominated forests.

Relationship between environmental factors and plankton in the Bayuquan Port, Liaodong Bay,China：a five-year study

To understand the relationship between the plankton community and environmental factor and water quality in the Bayuquan Port of Liaodong Bay, China, and investigations were carried ou during six dif ferent periods(April 2009, April 2010, October 2011, April 2012, October 2012, and Apri 2013). This area was characterized by high levels of nutrient and suspended solids(SPS) during surve periods, and eutrophication led to the occurrence of red tides in April and October 2012 and April 2013 Our analyses revealed that the plankton communities of Bayuquan Port lacked stability and were af fecte seriously by external disturbance(e.g., oceanographic engineering and river runof f). Our data indicate tha oil, dissolved inorganic nitrogen(DIN), SPS, and chlorophyll a(Chl- a) were key factors that regulated th phytoplankton and zooplankton communities. The partial redundancy analysis(partial RDA) suggested tha oil and SPS were the most important environmental variables af fecting the phytoplankton community i April 2010 and 2012, whereas DIN concentration played a governing role in zooplankton dynamics. Oi and Chl-a concentrations af fected signifi cantly the zooplankton community in October 2012. Therefore, th plankton communities could refl ect both dynamic changes in coastal environmental factors and the ongoin eutrophication process caused by anthropogenic activities in this area.

Response of rotifer community to environmental changes in five shallow lakes in the middle reach of Changjiang River, China

We evaluated the response of a rotifer community to environmental changes in five shallow lakes in the middle reach of the Changjiang （Yangtze） River in summer and autumn 2010. These five lakes differed in trophic status and rotifer community structure. Twenty-nine rotifer species were collected, of which Keratella cochlearis, Polyarthra dolichoptera, and Trichocerca elongate were dominant. The mean density, Shannon-Wiener diversity, and equitability among the five lakes differed significantly （P〈0.05）. The mean rotifer density was positively correlated with trophic state. The diversity was higher in lakes with high macrophyte coverage. The composition of rotifer species was closely associated with the trophic gradient. Five environmental variables, Secchi depth, conductivity, TN, NHa-N, and TP, significantly affected the composition of rotifer species. Keratella quadrata, Brachionus calyciflorus, and B. forficula were more common in eutrophic conditions. Our results suggest that eutrophication has a significant influence on the rotifer community structure and highlight the potential for using rotifer community structure as an indicator of trophic status in subtropical lakes.

Spring Voices in Korean Rice Fields:The Effect of Abiotic Variables and Syntopic Calls on the Calling Activity of the Treefrog Dryophytes suweonensis

The calling activity of anurans is influenced by environmental variables and calls produced by syntopic amphibians,among other variables.Some variables have a strong influence,such as temperature and predation dilution,while others may have a periodical influence such as the moon cycle.Here,we hypothesised that the calling activity of the Suweon treefrog,Dryophytes suweonensis,is restricted by specific environmental variables but reinforced by the calling activity of specific syntopic anurans.Within the criteria set by the experimental design,D.suweonensis calling activity was significantly influenced by moon phase,temperature,date,time to sunset and the calling activity of Pelophylax nigromaculatus and D.japonicus.These variables are expected to be related to chorus size,predation,breeding phenology and competition,suggesting a broad plasticity in the calling activity of the species.

Selection of Environmental Conditions for Nearshore Structure Design

Different from the traditional one dimensional extreme value statistical method, practical design criteria for nearshore structure design are presented based on joint probability theory in this paper. The proposed procedure considers the combined effect of tide level, huge waves and wind affecting coastal structures. The Importance Sampling Procedure (ISP) is utilized to solve the joint distribution of non Gaussian correlated multivariate distributions. The calculation results show that the ISP is a simulating technique with the advantages of efficiency and high convergency. Finally the environmental conditions are given using this technique for near shore structure design in the Qingdao area.

Intraspecific variations in fine root N and P and factors affecting their concentrations in Masson pine plantations across subtropical China

Fine roots(<2 mm)play vital roles in water and nutrient uptake.However,intraspecific variations in their chemical traits and their controlling mechanisms remain poorly understood at a regional scale.This study examined these intraspecific variations in fine roots in Masson pine(Pinus massoniana Lamb.)plantations across subtropical China and their responses to environmental factors.Root nitrogen(N)and phosphorus(P)concentrations and their mass ratios(N:P)ranged from 3.5 to 11.7 g kg^(-1),0.2 to0.9 g kg^(-1),and 7.8 to 51.6 g kg^(-1),respectively.These three chemical traits were significantly different between sites and in longitudinal patterns across subtropical China.Mean annual temperature was positively related to root N concentration but negatively related to root P concentration.There were significant,negative relationships between clay content and root P concentration and between pH and root N concentration.Available N had no significant relationship with root N concentration,while available P was a significantly positive relationship with root P concentration.The combined effects of altitude,climate(temperature and precipitation)and soil properties(pH,clay content,available N and P)explained 26%and 36%of the root N and P concentrations variations,respectively.These environmental variables had direct and indirect effects and exhibited disproportionate levels of total effects on root N and P concentrations.Root N and P concentrations explained 35%and 65%variations in their mass ratios,respectively.The results highlight different spatial patterns of chemical traits and various environmental controls on root N and P concentrations in these ecosystems.More cause-effect relationships of root chemical traits with abiotic and biotic factors are needed to understand nutrient uptake strategies and the mechanisms controlling intraspecific variations in plant traits.

Predicting Ecological Distribution of the Toxic Dinoflagellate Alexandrium minutum in China Sea Using Ecological Niche Modeling

Alexandrium minutum from the China Sea produces a range of toxins and causes damage to the local ecosystems and aquaculture.This is essential to understand environmental factors affecting potential distribution.Potential distributions of A.minutum in the China Sea were predicted based on maximum entropy modeling,and dominant environmental variables were studied through analyses of variable contributions and response curves.The results showed that highly suitable areas were mainly located in the southwest of the Yellow Sea,the Laizhou Bay,and north of Haizhou Bay.The coast of the South China Sea was predicted as a low-suitability area,and the coast of the East China Sea as an unsuitable area.Mean temperature of the coldest month(T_min)had the largest drop in permutation importance but a low percent contribution.The probability of presence of A.minutum increased with increasing concentration of nitrate(NO3−)and annual mean temperature(T_ann)over a wide range of them.The response curves decreased with increasing concentration of phosphate(PO43−)and ratio of NO_(3)^(−)to PO_(4)^(3−)(N_P_ratio)when PO_(4)^(3)−is above 0.049μmolL^(-1) and N_P_ratio above 4,indicating that low values of PO_(4)^(3−) concentration and N_P_ratio favour the occurrence of A.minutum.As a predictor,the variance of annual temperature(T_Var)had the highest percent contribution and gains.PO_(4)^(3−) was predicted to have much more information than the other variables,and exhibited the second largest drop in permutation importance and percent contribution.The T_Var and PO_(4)^(3−) are the most important dominant predictor variables.

Characterization of the microbial community response to replant diseases in peach orchards

This study attempted to monitor the development of microbial communities and reveal the correlation between the soil microbial community and soil nutrient factors over different years following the replanting of peach trees.The replanted soil(RS)and nonreplanted soil(NRS)were collected from peach orchards with different growth years(1,3,5,7,9,11,and 13 years)in the same region.The soil bacterial and fungal community diversities were analyzed by high-throughput sequencing technology.Redundancy analysis(RDA)was used to show the correlation between the soil microbial community and environmental variables.The alpha diversities of the bacterial and fungal communities indicated that RS contained a higher abundance of bacterial and fungal operational taxonomic units(OTUs)than NRS.NMDS and ANOSIM analyses showed that the soil bacterial and fungal communities were significantly(P<0.01)affected by planting years,and that the main changes occurred in the first and ninth planting years.The presence of the bacterial orders Sphingobacteriales,Burkholderiales and Actinomycetales changed significantly after replanting.Some bacteria associated with bioremediation,such as Burkholderiales and Intrasporangiaceae,and some harmful pathogens,such as Penicillium and Ophiostomatales,significantly increased after replanting(LDA score>3.0).In addition,the soil nutrient contents were lower in RS than in NRS in the early stage(1–5 years),and the RDA showed that bacterial and fungal phyla are closely associated with environmental variables,including the potential of hydrogen(pH),ammonium nitrogen(AN),available phosphorus(AP)and available potassium(AK).These results lead to a deeper understanding of the microbial responses to replanting in peach orchards.

Plant community and ecological analysis of woodland vegetation in Metema Area,Amhara National Regional State,Northwestern Ethiopia

We studied woodland vegetation in broad-leaved deciduous woodlands of Metema in northwestern Amhara regional state, Ethiopia to determine plant community types and species distribution patterns and their relationships with environmental variables, including altitude, pH, cation exchange capacity, electrical conductivity （EC）, and moisture. We used a selective approach with a systematic sampling design. A total of 74 quadrats, each 25m × 25m at intervals of 150-200 m were sampled along the established transect lines. For herbaceous vegetation and soil data collection, five subquadrats each lm x lm were established at the four corners and the center of each quadrat. Three community types were identified using TWINSPAN analysis. All three community types showed high diversity （Shannon-Weiner index）, the highest in community type II at 3.55. The highest similarity coefficient was 0.49 （49%） between community types II and III, reflecting 0.51 （51%） dissimilarity in their species richness. The canonical correspondence ordination diagram revealed that the distribution pattern of community type I was explained by moisture while that of community types III and II was explained by EC and altitude and moisture, respectively. Altitude was the most statistically significant environmental variable, followed by moisture and EC in determining the total variation in species composition and distribution patterns while pH and cation exchange capacity were non significant. In conclusion, we recommend that any intervention should take into account these three discrete community types and their environmental settings to make the intervention more successful.