Distribution Characteristics Of Vegetation Research Articles

Evolvement of Spatio-Temporal Pattern and Driving Forces Analysis of Ancient Trees Based on the Geographically Weighted Regression Model in Guangzhou and Foshan, China

Ancient trees play an important ecosystem service role in high-density cities, revealing the zonal distribution characteristics of vegetation under climate influence. The ancient trees in Guangzhou and Foshan in 2018 and 2023 were taken as study objects to explore the evolution of their spatio-temporal patterns and to analyze the spatial differentiation characteristics of their driving factors using the geographical weighted regression (GWR) model. The results showed the following: (1) The ancient trees in Guangzhou and Foshan were composed of typical subtropical evergreen broad-leaved forest communities, mainly represented by broad-leaved species of evergreen dicotyledonous plants. The dominant species mainly included Litchi chinensis, Ficus microcarpa, Canarium pimela, Ficus virens, and Dimocarpus longan. However, there was a significant difference between Guangzhou and Foshan. (2) The number of ancient trees in Guangzhou showed negative growth, while Foshan saw a significant increase. However, species diversity in both areas increased, with the highest diversity in the northeast, higher diversity in the south-central part, and lower diversity in the western and northwestern parts. (3) The maximum kernel density of ancient trees in Guangzhou and Foshan differed 22-fold, indicating a spatial distribution pattern of multiple clusters. (4) The GWR model effectively explained the driving factors of the heterogeneity of the spatial distribution of ancient trees. The results showed that artificial disturbance was the most important factor affecting the spatial distribution of ancient trees in high-density urban agglomerations in the same vegetation zone. The study clarified the characteristics of the spatial distribution and species diversity of ancient trees in the region, revealed the driving factors for the evolution of the spatial pattern of ancient trees in highly urbanized areas, and provided guidelines for policies and measures for enhancing biodiversity and conserving germplasm resources in the region.

Impact of drought on vegetation over inner Mongolia autonomous region

Abstract In recent years, remote sensing technology has become an important tool for monitoring vegetation changes in semi-arid regions. By using data collected by satellites to calculate vegetation indices, researchers can track changes in vegetation density and productivity over time. This can help identify areas of potential desertification or degraded land degradation and develop management strategies to restore degraded ecosystems. The objectives of this paper are to use multi-temporal MODIS data to extract vegetation distribution characteristics and dynamics in Inner Mongolia Autonomous Region. This study summarized the rainfall data of Inner Mongolia Autonomous Region from 2000 to 2019, and found the driest year 2001 and the wettest year 2012. The NDVI data of 4 districts of Xingan League in 2001 and 2012 were selected for analysis, and the average NDVI value and standard deviation of the 4 districts were obtained. NDVI data was combined with elevation data and vegetation data for analysis. The relationship between precipitation and NDVI is helpful to understand the impact of drought on vegetation in Inner Mongolia and provide reference for regional environmental management.

Flow Structures in Open Channels with Emergent Rigid Vegetation: A Review

On the edges of rivers where the flow velocity is low, aquatic plants flourish, with emergent rigid herbs being the most common. Since the flow structures of vegetated flow are strongly influenced by vegetation distribution patterns, homogeneous and heterogeneous canopies are defined based on the characteristics of vegetation distribution. A review summarizing recent advances in flow structures under the influence of different types of canopy arrangements, including ribbon-like homogeneous canopies, ribbon-like heterogeneous canopies, and patched heterogeneous canopies, is needed. Their flow development process, shear layer properties, coherent structure features, and momentum exchange characteristics are summarized, and a future research agenda for an in-depth understanding of the interactions between vegetation and flow is also highlighted.

The Distribution Characteristics of Vegetation in the Subrange of the Altai Mountains, Xinjiang.

The Altai Mountains are an important center of biodiversity and are a major habitat for threatened and endemic species in Asia. Moreover, the Altai Mountains are a valuable site for the study of the evolution of central Asian vegetation. The Xinjiang Altai subrange represents the largest part of the southern Altai Mountains and has many unique plant communities. After conducting a thorough literature review and field investigation, we utilized the Chinese vegetation categorization system to identify the dominant plant communities in the Xinjiang Altai subrange and report their composition and distribution characteristics. Our results show that (1) the natural plant communities present in the Xinjiang Altai subrange can be divided into eight vegetation types, eighteen vegetation subtypes, and 50 communities. Among these, two communities-Form. Calligonum rubicundum and Form. Seriphidium borotalense-Festuca valesiaca-are present only in the Xinjiang Altai subrange. (2) The Xinjiang Altai subrange is located at the junction of three major biomes containing unique vegetation types (coniferous forest, temperate broadleaf forest, and desert). Thus, the Xinjiang Altai subrange is distinct in its staggered transition from mountainous boreal taiga to temperate desert. This research provides textual data to contextualize the cultural heritage of the Xinjiang Altai subrange and also provides a scientific basis for the protection and sustainable management of natural resources found in the Xinjiang Altai.

Total and component forest aboveground biomass inversion via LiDAR-derived features and machine learning algorithms

Forest aboveground biomass (AGB) and its biomass components are key indicators for assessing forest ecosystem health, productivity, and carbon stocks. Light Detection and Ranging (LiDAR) technology has great advantages in acquiring the vertical structure of forests and the spatial distribution characteristics of vegetation. In this study, the 56 features extracted from airborne LiDAR point cloud data were used to estimate forest total and component AGB. Variable importance–in–projection values calculated through a partial least squares regression algorithm were utilized for LiDAR-derived feature ranking and optimization. Both leave-one-out cross-validation (LOOCV) and cross-validation methods were applied for validation of the estimated results. The results showed that four cumulative height percentiles (AIH30,AIH40, AIH20, and AIH25), two height percentiles (H8 and H6), and four height-related variables (Hmean, Hsqrt, Hmad, and Hcurt) are ranked more frequently in the top 10 sensitive features for total and component forest AGB retrievals. Best performance was acquired by random forest (RF) algorithm, with R2 = 0.75, root mean square error (RMSE) = 22.93 Mg/ha, relative RMSE (rRMSE) = 25.30%, and mean absolute error (MAE) = 19.26 Mg/ha validated by the LOOCV method. For cross-validation results, R2 is 0.67, RMSE is 24.56 Mg/ha, and rRMSE is 25.67%. The performance of support vector regression (SVR) for total AGB estimation is R2 = 0.66, RMSE = 26.75 Mg/ha, rRMSE = 28.62%, and MAE = 22.00 Mg/ha using LOOCV validation and R2 = 0.56, RMSE = 30.88 Mg/ha, and rRMSE = 31.41% by cross-validation. For the component AGB estimation, the accuracy from both RF and SVR algorithms was arranged as stem > bark > branch > leaf. The results confirmed the sensitivity of LiDAR-derived features to forest total and component AGBs. They also demonstrated the worse performance of these features for retrieval of leaf component AGB. RF outperformed SVR for both total and component AGB estimation, the validation difference from LOOCV and cross-validation is less than 5% for both total and component AGB estimated results.

Vertical Characteristics of Vegetation Distribution in Wuyishan National Park Based on Multi-Source High-Resolution Remotely Sensed Data

Identifying vertical characteristics of mountainous vegetation distribution is necessary for studying the ecological environment quality and biodiversity and for evaluating its responses to climate change. However, producing fine vegetation distribution in a complex mountainous area remains a huge challenge. This study developed a framework based on multi-source high-resolution satellite images to strengthen the understanding of vertical features of vegetation distribution. We fused GaoFen-6 and Sentinel-2 data to produce 2 m multispectral data, combined with ALOS PALSAR digital elevation model (DEM) data, and used an object-based method to extract variables for establishing a classification model. The spatial distribution of vegetation types in Wuyishan National Park (WNP) was then obtained using a hierarchical random forest classifier. The characteristics of different vegetation types along the elevation gradient and their distribution patterns under different human protection levels were finally examined. The results show that (1) An overall accuracy of 87.11% and a Kappa coefficient of 0.85 for vegetation classification was achieved. (2) WNP exhibits obviously vertical differentiation of vegetation types, showing four compound dominant zone groups and five dominant belts. (3) The composition of vegetation types in the scenic area differs significantly from other regions. The proportions of Masson pine and Chinese fir exhibit a noticeably decreasing trend as the distance increases away from roads, while the changes in broadleaf forest and bamboo forest are less pronounced.

Distribution characteristics of vegetation on the drift lines at small beaches in the coastal area of the Seto Inland Sea

Distribution characteristics of vegetation on the drift lines at small beaches in the coastal area of the Seto Inland Sea

Distribution characteristics of radionuclides (137Cs, 239+240Pu, 237Np, and 241Am) in vertical vegetation zone in Changbai Mountain, China

Changbai Mountain has vegetation distribution characteristics, which is an important location in northeast China to study the variation characteristics of radionuclides with vegetation distribution. Soils from three vegetation zones of mixed broadleaf and coniferous forest (MBCF), coniferous forest (CF), and alpine birch forest (ABF) in Changbai Mountain were collected to measure the artificial radionuclides of 239+240Pu, 237Np, and 241Am by SF-ICP-MS, as well as 137Cs by anti-Compton HPGe. The mean values of 240Pu/239Pu and 237Np/239Pu atomic ratios, 241Am/239+240Pu and 137Cs/239+240Pu activity ratios were 0.19 ± 0.02, 0.37 ± 0.23, 0.56 ± 0.31, 22 ± 17, respectively, indicating that the global fallout was the main source of 239+240Pu, 237Np, 137Cs and 241Am in these regions. 137Cs, 239+240Pu, 237Np, and 241Am activities in the samples are 1.1–218, 0.065–9.1, (0.018–2.9) × 10-3, and 0.039–2.0 Bq/kg, respectively. The activities of 137Cs, 239+240Pu, and 237Np in the surface soil have a similar distribution characteristic, i.e. CF > MBCF > ABF, and 241Am is CF > ABF > MBCF. The simulation results of the CDE model suggest that the migration of these radionuclides is dominant in Changbai Mountain forest soil. The inventories of 137Cs, 239+240Pu, 237Np, and 241Am in the soil cores are 1263–20843, 110–1425, 0.017–0.38, and 91–493 Bq/m2, respectively. The inventories distribution of these nuclides in the vegetation zone were as follows: 137Cs and 239+240Pu had similar distribution characteristics as ABF > CF > MBCF; 237Np as CF > MBCF > ABF; 241Am as ABF > MBCF > CF. These results showed that the content, accumulated inventory, and vertical distribution characteristics of these radionuclides were influenced by the vegetation zone distribution in the Changbai Mountain.

祁连山国家公园植被时空变化及其对人类活动的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 祁连山国家公园植被时空变化及其对人类活动的响应 DOI: 10.5846/stxb202107221990 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 甘肃省创新群体项目（20JR10RA038）；中国科学院"西部之光"交叉团队项目-重点实验室合作研究专项；国家重点研发计划项目（2019YFC0507401） Spatial and temporal changes in vegetation cover and response to human activities in Qilian Mountain National Park Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:祁连山国家公园地处青藏、蒙新、黄土三大高原交汇地带的祁连山北麓，作为国家公园体制试点之一，是我国重要的生态功能区、水源涵养地和生物多样性保护优先区域，其生态功能不可忽视。以祁连山国家公园2000-2019年归一化植被指数（NDVI）和净初级生产力（NPP）数据为基础，结合气温、降水、土地利用、矿产开采和旅游发展数据，利用泰尔-森趋势分析（Theil-Sen趋势分析）、曼-肯德尔检验（Mann-Kendall显著性检验）、土地转移概率矩阵和多元残差分析方法，分析该区域的植被时空分布特征、变化趋势特征及其对气候变化和人类活动的响应。结果表明：（1）2000-2019年祁连山国家公园内NDVI和NPP在空间上呈现出东南高西北低，由东南向西北递减的格局。时间上呈现上升趋势，上升速率分别为0.0053/a和0.0014/a；（2）祁连山国家公园内NPP提高、降低和稳定区域分别占总面积的87.29%、0.40%和12.30%。降低区域零星分布于整个国家公园，其中在走廊南山和冷龙岭交汇处，靠近甘青两省交界边缘分布最为集中。提高区域分布广泛，尤其以国家公园东部最为明显；（3）祁连山国家公园NDVI与气温呈现显著正相关区域约占40.18%，与降水呈现正相关区域约占25.70%，气温上升、降水增多促进了国家公园植被生长，适宜的水热组合对植被生长更有利；（4）人类活动对植被变化的影响具有两面性：约有28.91%矿业、旅游和水电站在整改、规范之后植被生长状况仍较差，生态环境没有明显恢复；退耕还林还草工程、生态林建设工程成效显著，近3年林地、草地面积增多。（5）祁连山国家公园大部分植被覆盖变化是由气候变化和人类活动共同导致。 Abstract:Qilian Mountain National Park is located in the north piedmont of Qilian Mountains at the intersection of Qinghai-Tibet, Mongolian-Xinjiang and Loess. As one of the national park system pilots, Qilian Mountain National park is an important ecological function area, a water retention area and a priority area for biodiversity conservation in China, and its ecological functions cannot be ignored. Based on the Normalized Difference Vegetation Index (NDVI) and Net Primary Productivity (NPP) of Qilian Mountain National Park from 2000-2019, combined with temperature, precipitation, land use, mineral extraction and tourism development data, we used the Theil-Sen slope estimation, Mann-Kendall test, land transfer matrix and multivariate residual analysis methods to analyze the spatial and temporal distribution characteristics of vegetation, change trend characteristics and its response to climate change and human activities. The results showed that (1) NDVI and NPP in Qilian Mountain National Park from 2000 to 2019 showed a spatial pattern of high in the southeast and low in the northwest, decreasing from southeast to northwest. Temporally, they showed an increasing trend, with an increase rate of 0.0053/a and 0.0014/a, respectively. (2) The improved, decreased and stable areas of NPP in Qilian Mountain National Park accounted for 87.29%, 0.40% and 12.30% of the total area, respectively. Decreased areas are scattered throughout the national park, with the most concentrated distribution at the intersection of Zoulang South Mountains and Lenglongling, near the border edge of Gansu and Qinghai provinces. The improved areas are widely distributed, especially the most obvious in the eastern part of the national park. (3) The NDVI of Qilian Mountain National Park shows a significant positive correlation with temperature in about 40.18% of the area, and a positive correlation with precipitation in about 25.70% of the area, the increase in temperature and precipitation promotes the growth of vegetation in the national park, and a suitable combination of hydrothermal conditions is more favorable to the growth of vegetation.(4) The impact of human activities on vegetation changes was two-sided:Approximately 28.91% of mining, tourism and hydroelectric power stations in the national park still had poor vegetation growth after rectification and regulation, and the ecological environment has not recovered significantly; The cropland to forest and grassland conversion projects and ecological forest projects have been effective, the area of forest and grassland has increased, in the past three years.(5) Most of the vegetation cover changes in Qilian Mountain National Park were caused by a combination of climate change and human activity. 参考文献 相似文献 引证文献

Changes in Vegetation Coverage and Migration Characteristics of Center of Gravity in the Arid Desert Region of Northwest China in 30 Recent Years

Vegetation coverage is important in global landscape change patterns, but research on temporal and spatial dynamic changes and analysis of vegetation landscape pattern is relatively lacking. The present study aimed to investigate the dynamic changes of vegetation coverage in the arid desert region of Northwest China and analyze the characteristics of its center of gravity migration. The normalized difference vegetation index (NDVI) and pixel binary model were used to calculate the vegetation coverage to analyze the vegetation distribution characteristics and vegetation migration in the arid desert area in Northwest China in 1990, 1995, 2000, 2005, 2015 and 2020. The results showed that from 1990 to 2020, the proportion of light and severe vegetation coverage in the arid desert region of Northwest China increased, while the proportion of medium vegetation coverage decreased. The distribution types of medium- and high-grade vegetation generally migrate to the southeast and south, which may be mainly due to the humid climate conditions and higher population density in this direction. The vegetation center of gravity migration is mainly concentrated in the southeast-south direction. Vegetation degradation occurs in the northwest region, and vegetation improvement is the main trend in the southeast and south region. The direction of vegetation migration may be affected by precipitation and soil humidity. This study provides a theoretical basis and has certain guiding significance for desertification control, ecological sustainable management, ecological restoration, and protection in the arid desert region of Northwest China.

국립공원 아고산대 독립훼손지 복원식생 분포특성 및 관리방안

This study was conducted to provide basic data for mid-to long-term monitoring and establishment of management plans by analyzing the existing vegetation and identifying the vegetation distribution characteristics for the restored vegetation in Nogodan and Seseokpyeongjeon in Jirisan National Park located in the subalpine zone among the independent damaged areas. Actual vegetation survey range was established in consideration of the distribution of the watershed around the damaged area. The surveyed area of Seseokpyeongjeon was 55,037㎡, and the surveyed area of Nogodan was 166,599㎡. In Seseokpyeongjeon, the vegetation coverage by the herbaceous layer was almost 90% or more, there was no bare exposure, and the coverage of the shrub layer was stabilized at 60% or more. The main emerging tree species were planted species such as Abies koreana, Betula ermanii, Fraxinus sieboldiana, Rhododendron schlippenbachii, Rhododendron mucronulatum var. ciliatum, and Weigela florida as well as natively migrated native species. In Nogodan, the shrub vegetation dominated by Quercus mongolica, Salix caprea, Rhododendron schlippenbachii, Rhododendron mucronulatum var. ciliatum, and Tripterygium regelii was the most widely distributed with 52% of the area, and the overall diet was good. The native vegetation of Nogodan was presumed to be a cypress colony. Naturalized plants were distributed in the military base demolition site, so active management was required. The study site was predicted to develop into a vegetation landscape in harmony with the surrounding natural vegetation in the long term. In the future, the restoration model for damaged areas should be set in consideration of the native vegetation of the nearby area, but the goal to achieve restoration should be set at a feasible level.

Soil physical and chemical properties and vegetation characteristics of different types of grassland in Qilian Mountains, China

Grasslands in Qilian Mountains plays an important role in maintaining the ecological security of western China. To understand soil physical and chemical properties and the distribution characteristics of vegetation, as well as their correlation in different types of grasslands in Qilian Mountains, we measured soil moisture, nutrient content, bulk density, particle composition, and vegetation characteristics in seven types of grassland in Qilian Mountains. The fractal dimension of soil particles, soil organic carbon, total nitrogen and total phosphorus storages in 0-40 cm soil layer, and plant diversity index were calculated. The results showed that there were significant differences in soil physical and chemical properties and vegetation characteristics among different grassland types. Compared with other types of grassland, alpine meadow had higher soil water, nutrient and clay content, but lower bulk density and sand content. Soil organic carbon, total nitrogen and total phosphorus storages in 0-40 cm layer ranged from 3084 to 45247, 164 to 2358 and 100 to 319 g·m-2, respectively, with high contents of organic carbon and total nitrogen and low content of total phosphorus. There was a significant positive correlation between soil total phosphorus storage and plant diversity index, indicating that soil total phosphorus content was the key factor affec-ting grassland plant diversity in Qilian Mountains. Compared with other grassland types, alpine meadow in Qilian Mountains had better vegetation status, soil moisture, and nutrient conditions.

Spatiotemporal Variation of Drought and Its Correlation With Plant Species of Yunnan Province, China

Drought is the main natural disaster in Yunnan Province, China. In the present paper monthly precipitation observation data from Yunnan Province durign the period of 1966 - 2015 were used. From the data, the selected percentage of precipitation anomalies was used as drought index. By applying the ArcGIS inverse distance interpolation method and Mann Kendall non parametric trend test method the spatiotemporal variation characteristics of drought in Yunnan province were analyzed. Results show that the drought in Yunnan Province has a slightly upward trend. In spring and winter, there is a tendency to become wet but in summer and autumn, the tendency is shown by dry condition. It was observed that the studied area is prone to a severe drought in winter, and there will be more droughts in the east part, the northwest part, and the southwest part of Yunnan province when it is autumn. In other periods, severe doughts usually attack the middle part of Yunnan province, which can be proved by the characteristics of vegetation distribution. Bangladesh J. Bot. 50(4): 1133-1142, 2021 (December)

Estimation of Evapotranspiration in Sparse Vegetation Areas by Applying an Optimized Two-Source Model

Evapotranspiration (ET) is an important part of the water, carbon, and energy cycles in ecosystems, especially in the drylands. However, due to the particularity of sparse vegetation, the estimation accuracy of ET has been relatively low in the drylands. Therefore, based on the dry climate and sparse vegetation distribution characteristics of the drylands, this study optimized the core algorithms (canopy boundary resistance, aerodynamic resistance, and sparse vegetation coverage) and explored an ET estimation method in the Shuttleworth–Wallace two-layer model (SW model). Then, the Beijing–Tianjin sandstorm source region (BTSSR) was used as the study area to evaluate the applicability of the improved model in the drylands. Results show that: (1) The R2 value of the improved model results was increased by 1.4 and the RMSE was reduced by 1.9 mm, especially in extreme value regions of ET (maximum or minimum). (2) Regardless of the spatial distribution and seasonal changes of the ET (63–790 mm), the improved ET estimation model could accurately capture the differences. Furtherly, the different vegetation regions could stand for the different climate regions to a certain extent. The accuracy of the optimized model was higher in the semi-arid region (R2 = 0.92 and 0.93), while the improved model had the best improvement effect in the arid region, with R2 increasing by 0.12. (3) Precipitation was the decisive factor affecting vegetation transpiration and ET, with R2 value for both exceeding 0.9. The effect of vegetation coverage (VC) was less. This method is expected to provide a more accurate and adaptable model for the estimation of ET in the drylands.

Interactions of diffusion and nonlocal delay give rise to vegetation patterns in semi-arid environments

Vegetation pattern is caused by local instability in phase space, which can reflect the distribution characteristics of vegetation in the studied space. In semi-arid environment, the vegetation roots will not only absorb the water resources near themselves, but also absorb the water resources in the whole study area, that is to say, the absorption of water resources by vegetation roots is a nonlocal process. Meanwhile, the feedback mechanism of soil-water diffusion plays an important role in the process of water absorption by vegetation roots. However, it is not clear that how the feedback mechanism of nonlocal water absorption by vegetation roots and soil-water diffusion affects vegetation pattern. In this paper, we construct a positive feedback vegetation-water model with nonlocal delay. The instability of Turing pattern is analyzed by analytical method, and the conditions of stable pattern occurrence are obtained. At the same time, we use multi-scale analysis method to obtain the amplitude equation of vegetation-water system. We found that the non-local water absorption intensity of vegetation roots and the feedback of soil-water diffusion can cause the phase change of vegetation pattern. The change of nonlocal water absorption intensity will produce mixed vegetation pattern structure. The enhancement of soil-water diffusion feedback intensity will change the vegetation pattern structure: low density cold spot patterns → mixed patterns → high density hot spot patterns. The isolation between vegetation patches will be increased as that nonlocal water absorption intensity is enhanced or the feedback intensity of soil-water diffusion is increased. We also revealed that increasing the feedback intensity of soil water diffusion or nonlocal strength within a certain range is helpful to increase the vegetation density, while excessive feedback intensity or nonlocal strength will induce land desertification.

Vegetation Change and Its Response to Climate Change in Yunnan Province, China

The impact of global climate change on vegetation has become increasingly prominent over the past several decades. Understanding vegetation change and its response to climate can provide fundamental information for environmental resource management. In recent years, the arid climate and fragile ecosystem have led to great changes in vegetation in Yunnan Province, so it is very important to further study the relationship between vegetation and climate. In this study, we explored the temporal changes of normalized difference vegetation index (NDVI) in different seasons based on MOD13Q1 NDVI by the maximum value composite and then analyzed spatial distribution characteristics of vegetation using Sen’s tendency estimation, Mann–Kendall significance test, and coefficient of variation model (CV) combined with terrain factors. Finally, the concurrent and lagged effects of NDVI on climate factors in different seasons and months were discussed using the Pearson correlation coefficient. The results indicate that (1) the temporal variation of the NDVI showed that the NDVI values of different vegetation types increased at different rates, especially in growing season, spring, and autumn; (2) for spatial patterns, the NDVI, CV, and NDVI trends had strong spatial heterogeneity owning to the influence of altitudes, slopes, and aspects; and (3) the concurrent effect of vegetation on climate change indicates that the positive effect of temperature on NDVI was mainly in growing season and autumn, whereas spring NDVI was mainly influenced by precipitation. In addition, the lag effect analysis results revealed that spring precipitation has a definite inhibition effect on summer and autumn vegetation, but spring and summer temperature can promote the growth of vegetation. Meanwhile, the precipitation in the late growing season has a lag effect of 1-2 months on vegetation growth, and air temperature has a lag effect of 1 month in the middle of the growing season. Based on the above results, this study provided valuable information for ecosystem degradation and ecological environment protection in the Yunnan Province.

三峡水库坝下江心洲植物群落及其性状对不同水淹强度的响应

三峡水库的运行，改变了其坝下游的水沙情势，使坝下游沙洲生境呈现出明显的水淹强度梯度变化。阐明这一梯度变化下沙洲植被组成、分布和性状结构特征，是理解植被与沙洲稳定关系的基础，更是阐明三峡工程对长江中下游地区生态环境影响的核心内容之一。选取上荆江河段第一个江心洲-太平口心滩作为研究样地，通过植被组成和分布特征的调查，对不同水淹强度下群落物种组成、多样性和功能特征进行了深入分析。结果表明：太平口心滩植被组成以草本植物为主，稀布小型灌木川三蕊柳。调查共记录物种21科33属39种，以禾本科和菊科植物为主要优势种。轻微（20-40 d）和极强水淹强度（100+d）条件下的生境物种组成同其他水淹强度生境具有显著性差异，轻微水淹强度下牛鞭草和节节草为主要优势种，极强水淹强度下虉草为主要优势种。不同水淹强度下物种多样性指数差异显著，功能多样性指数和生物多样性指数趋势基本一致。随着水淹时间的延长，植被更倾向于表现出花果期位于出露期、植株高度更加低矮、须根系、进行营养繁殖的功能性状。江心洲植被的群落结构和功能性状特征都在水淹梯度下呈现出明显的梯度变化特征。这些研究结果表明水淹强度的梯度变化是沙洲植物群落变化的重要驱动因子，为进一步研究沙洲植物群落动态变化以及沙洲植被协同演替机制，明晰大坝影响下的生态环境变化提供重要依据。;The composition and distribution characteristics of vegetation play a vital role in the development and stability of the sandbars. Operation of the Three Gorges Reservoir has changed the hydrological and sediment transport regimes in the downstream of the dam, causing a significant gradient on the sandbar habitats along the flooding durations. To clarify the composition, distribution, and structural characteristics of vegetation in the sandbar is fundamental for understanding the roles of vegetation in stabilizing the sandbar. In addition, they provide key information to clarify the relationship between the Three Gorges Project and the ecological and environmental problems in the middle and lower reaches. In this study, we selected the first sandbar, the Taipingkou Middle bar in the upper Jingjiang river section, and used the equidistant systematic sampling plots to investigate the vegetation composition and distribution characteristics. Based on the elevation information of plots and the water level data over the years, we set the plots at 5 flooding gradients levels by the flooding days in a flooding cycle:20-40 d, 40-60 d, 60-80 d, 80-100 d, and over 100 d. Statistical methods, such as importance value, species diversity index, functional diversity index and functional traits analysis, were used to analyze the species composition, diversity and functional traits of communities under different flooding duration days. The results showed that the vegetation composition was dominated by herbaceous plants, and the small shrubs Salix triandroides were sparsely distributed. A total of 39 species, belonging to 21 families and 39 genera, were recorded and the main dominant families were Poaceae and Compositae. The species composition of habitats under intermediate level (20-40 d) and maximum flooding intensity (100+ d) condition is significantly different with that found in other flooded gradients. Under the intermediate flooding intensity, Hemarthria sibirica and Equisetum ramosissimum are the main dominant species, and Phalaris arundinacea is the main dominant species under the maximum flooding intensity. Along the flooding gradient, species diversity is significantly varied. Species richness is low in both intermediate and maximum flooding intensity habitats, but the highest species diversity in the intermediate flooding condition habitats and the lowest in the maximum strong flooding intensity habitats. Basically, the trend of functional diversity index keeps same with biodiversity index, while the functional diversity index under maximum flooding conditions is not representative. As increasing of intensity of flooding stress, the vegetation tends to show the functional traits with flowering and fruit stage under the outcrop stage, while plant height reduction, fibrous root system and vegetative reproduction also show difference. The community structure and the functional traits of the sandbar plants showed obvious gradient change with the flooding gradient. The results show that the gradient change of flooding duration is an important driver shaping sandbar plant community, and provides an important basis for further research on the dynamic succession of sandbar plant community and vegetation succession mechanism of sandbar, and clarifying the ecological environment changes under the influence of dams.

Analysis of vegetation spatial distribution characteristics in Northwest China’s arid desert area

It is of great significance to study the characteristics of vegetation distribution in desert area for restoring vegetation, stabilizing ecosystem and ecological restoration in mining area. Taking the small watershed in Northwest China’s arid desert area where the typical open-pit coal mine is located as the study area, using GF-2 (Gaofen-2 satellite) images, calculating the NDVI (Normalized Difference Vegetation Index) results of the study area, extracting NDVI>0 as the vegetation cover area and combing with DEM (Digital Elevation Model), we analyse the relationship between vegetation distribution and slope aspect and water flow path. We conclude that in the natural state, the proportion of vegetation distribution on semi-sunny slope and shady slope in the study area is 74.8%, the proportion of sunny slope in the total area of the study area is 33.1%, and the proportion of vegetation distribution on this slope is only 11.9%, indicating that semi-sunny slope and shady slope are more suitable for growth in the study area. In the upper reaches of the basin, which is less affected by human activities, natural vegetation is distributed in strips along the flow path; In the mining area, which is obviously affected by human activities, the vegetation distribution characteristics change significantly with vegetation mainly distributed in the office area and being artificial greening.

Discussion on position of China’s north-south transitional zone by comparative analysis of mountain altitudinal belts

The Qinling Mountains has always been regarded as an essential dividing line between the warm temperate zone and the subtropical zone in eastern China and plays a vital role in the geoecological pattern of China. However, there is controversy about the specific location of this geographical boundary in the academic community. As a product of the combined effects of zonal and non-zonal factors, the mountain altitudinal belts (MABs) can reflect both the horizontal zonality and the vertical zonality of vegetation distribution. Using the MAB information, we can not only profoundly understand the complex mountain system of Qinling-Daba Mountains but can also judge its nature as a geographical boundary more scientifically. Therefore, based on the comparative analysis of basal belt, dominant belt characteristics and belt structure characteristics of the MABs in Qinling-Daba Mountains, subtropical and temperate mountains, this paper analyzed the MAB differences and similarities among Qinling-Daba Mountains, subtropical and temperate typical mountains, to reveal the vegetation distribution characteristics in the north-south transitional zone. The results show that: (1) The MABs of the southern part of Qinling-Daba Mountains (southern slope of the Daba Mountains) are the same or similar to those of the Subtropical Mountains, and the MABs of the northern part of Qinling-Daba Mountains (northern slope of the Qinling Mountains) are similar to those of the temperate mountains. While it shows obvious transitional characteristics in the vast area between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains: the basal belts gradually transit from the evergreen broad-leaved forest belt (basal belt in subtropical mountains) to the evergreen and deciduous broad-leaved mixed forest belt, and the dominant belts also transit from the evergreen broad-leaved forest belt to the evergreen and deciduous broad-leaved mixed forest belt or the deciduous broad-leaved forest belt. (2) The transitional zone between the subtropical zone and the warm temperate zone is located between the northern slope of the Daba Mountains and the southern slope of the Qinling Mountains. The southern boundary of the transitional zone is along the northern slope of Shennongjia Mountain-the northern slope of Micang Mountain-Baishuijiang Nature Reserve, and the northern boundary is along the southern slope of Funiu Mountain-the southern slope of Taibai Mountain-Lianhua Mountain. Additionally, in the transitional zone, the average temperature in January is between -5°C and 1°C, the annual average temperature is between 10°C and 13°C except Hanzhong Basin and Hanshui Valley, and the accumulated temperature above 10°C ranges from 2000°C to 4000°C, the annual rainfall is about 800–1000 mm. The results provide a scientific basis for revealing the characteristics of China’s north-south transitional zone and scientific division of the boundary between the subtropical zone and warm temperate zone in China.

Temporal and Spatial Variation Patterns of the Environmental Elements in the Sediments of the Liaohe Estuary and the Related Influencing Factors

Remote sensing images, field survey data, and historical monitoring data are collected to analyze the historical change trend and spatial variation rules of sediment quality of the Liaohe Estuary and further investigate the effects of sea-area utilization type and vegetation succession stage on the variation patterns of environmental elements in the sediments. The results showed that the quality of the sediments in the Liaohe Estuary is overall favorable, and the average contents of various elements all satisfy the quality standards of first-grade sediments. The nutritive elements in the sediments exhibit obvious zonal distribution patterns, while heavy metals are randomly distributed and exhibit no obvious patterns. The effect of sea-area utilization type on the enrichment of pollutants in the sediments exhibits certain significant differences, suggesting that the distributions of heavy metals and pollutants are subject to human activities and exhibit certain randomness. The main control factors are significantly different at different vegetation succession stages. Specifically, the vegetation distribution in the initial succession stage is mainly affected by salinity; with the transition from halophytic vegetation to terrestrial vegetation, the inherent correlation between vegetation distribution characteristics and the contents of total organic carbon, total nitrogen, and total phosphorus increase gradually. Meanwhile, the content of heavy-metal pollutants exhibits no significantly inherent correlation between the distributions of the plant community.