Vegetation Community Types Research Articles

Leaf Functional Traits and Their Influencing Factors in Six Typical Vegetation Communities.

Leaf functional traits (LFTs) have become a popular topic in ecological research in recent years. Here, we measured eight LFTs, namely leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), leaf phosphorus content (LPC), and leaf potassium content (LKC), in six typical vegetation communities (sclerophyllous evergreen broad-leaved forests, temperate evergreen coniferous forests, cold-temperate evergreen coniferous forests, alpine deciduous broad-leaved shrubs, alpine meadows, and alpine scree sparse vegetation) in the Chayu River Basin, southeastern Qinghai-Tibet Plateau. Our aim was to explore their relationships with evolutionary history and environmental factors by combining the RLQ and the fourth-corner method, and the method of testing phylogenetic signal. The results showed that (i) there were significant differences in the eight LFTs among the six vegetation communities; (ii) the K values of the eight LFTs were less than 1; and (iii) except for LCC, all other LFTs were more sensitive to environmental changes. Among these traits, LA was the most affected by the environmental factors, followed by LNC. It showed that the LFTs in the study were minimally influenced by phylogenetic development but significantly by environmental changes. This study further verified the ecological adaptability of plants to changes in environmental factors and provides a scientific basis for predicting the distribution and diffusion direction of plants under global change conditions.

Habitat context and functional growth traits explain alien plant invader impacts on native vegetation communities

Examining context-dependency of ecological impacts of alien plant invasions is critical to further understand the mechanisms driving impacts. We examined how different regional and local habitat contexts influence the abundance-impact associations of an invasive ground-creeper, Tradescantia fluminensis, in native forests across eastern New South Wales (NSW), Australia. Invader impacts were assessed using surveys of resident vegetation at 97 monitoring plots (5 m × 2 m) located at 14 sites, representing a gradient of T. fluminensis abundance. We modelled the association of T. fluminensis invasion with native species richness (number per plot) and foliage cover across two different habitat types (remnant vs replanted forests), two vegetation community types (wet sclerophyll vs river oak forests), and two regions (northern vs. southern NSW). We also modelled variation in native species responses amongst different functional growth forms. The negative associations of T. fluminensis and native species communities was more strongly explained by local site variables (i.e., habitat type, community type, plant growth form) than regional scales. Native richness reduced with invasion in river oak but not wet sclerophyll forest. Native richness also declined in remnant forest, although no effect of invasion was observed in replanted forest. Surprisingly, native species growth forms most like T. fluminensis (ground layer herbs, ferns) were more resistant to reductions in native richness compared to divergent forms (shrub, tree and woody vine recruits). This study highlights the need to explicitly consider local community and habitat context and functional representation of resident species when considering invader impacts and site-level management plans.

Differential response patterns of soil fungal and bacterial communities to typical vegetation types in the Yellow River floodplain ecosystem

Soil microorganisms are one of the primary driving factors of biogeochemical cycles in floodplain ecosystems. Vegetation type has an impact on the activities of soil microorganisms. However, it is currently unclear whether the composition and structure of soil bacterial and fungal communities in floodplain ecosystems have a consistent response pattern to vegetation communities. In this research, Illumina Mi-Seq sequencing technology was employed to study the soil fungal and bacterial communities covered by three typical vegetation communities in the Yellow River floodplain ecosystem. Our results showed that the underground biomass, total carbon (TC) and nitrogen (TN) were significantly different between the three vegetation communities. In the surface soil of summer, the Shannon index of fungi community was the highest in Tamarix chinensis (T. chinensis) and the lowest in Phragmites australis (P.australis). In autumn, the Shannon and Simpson indices of bacterial communities in surface soil were the highest in the P.australis and the lowest in the Sonchus arvensis (S.arvensis), but there was no significant difference in the β-diversity of bacterial community among the three vegetation communities. In autumn, the Chao1 index of fungal community in subsoil was the highest in P.australis and the lowest in S.arvensis, while there was no significant difference in the α-diversity of bacterial community among the three vegetation communities. In addition, there were considerable disparities in the fungal and bacteria community structure in various vegetation soils. Redundancy analysis (RDA analysis) showed that TN, TC, AP, pH, NO3 -, NH4 + and moisture content were key factors driving bacterial community structure, while TP, NH4 +, pH and moisture content were essential factors driving fungal community composition. These outcomes help to improve our understanding of the ecological model of soil fungal and bacterial community in floodplain ecosystems and give assistance in improving the role of an ecological barrier and floodplain service possibilities.

Retrieval of chlorophyll content for vegetation communities under different inundation frequencies using UAV images and field measurements

Karst wetlands are an important type of wetland among the global karst areas that suffer from serious ecosystem degradation. Chlorophyll content, an important parameter of vegetation functional traits, can indicate the photosynthetic activity, mutation and stress level, and nutritional state of vegetation. However, quantitative estimation of canopy chlorophyll content (CCC) of calcium-loving and alkali-resistant vegetation in karst wetlands using remote sensing technology for clarifying the relationship between canopy spectral reflectance and the CCC of vegetation communities remains a challenge. In this study, we propose a retrieval approach for estimating the CCC of seven typical vegetation communities in the largest karst wetland in China, using a combination of parameter/non– parameter estimation model, and unmanned aerial vehicle (UAV) multispectral images. We further evaluated the sensitivity of various spectral indices to the CCC of the vegetation communities and explored the influence of image feature distribution on CCC estimation accuracy. We revealed the variation patterns of leaf chlorophyll content (LCC) and CCC under different inundation frequencies in the karst wetland. We confirmed that the UAV-based inversion method proposed in this study achieved the CCC estimation of seven vegetation communities (R2 = 0.57 ∼ 0.93, RMSE = 8.80 SPAD ∼ 60.68 SPAD), and obtained high estimation accuracy (R2 = 0.77, RMSE = 22.04 SPAD) of Cladium chinense Nees (CCN, endemic vegetation in karst wetland). We found that the optimal reflectance ranges for estimating the CCC of the seven vegetation communities were 714 nm ∼ 746 nm and 814 nm ∼ 866 nm, and that the ChIrededge and MSR indices negatively influenced the CCC estimation of CCN and Carex baccans Nees (CBN), respectively. We demonstrated that vegetation communities with well-defined canopy structure (Triadica sebifera (Linnaeus) Small) achieved higher estimation accuracy with moderate uncertainty (ε = 10.80 % ∼ 15.49 %) than the herbaceous vegetation communities (CCN, CBN, and Cynodon dactylon (L.) Pers.). The bias of the CCC estimation based on linear regression and partial least squares regression models in different vegetation communities ranged from 1.61 % to 49.41 %. We confirmed that the magnitude of variations in LCC and CCC for these vegetation communities presented a decreasing pattern from that in high-frequency inundation communities to that in the low-frequency ones.

Quantitative Characteristics and Environmental Interpretation of Vegetation Restoration in Burned Areas of the Dry Valleys of Southwest China

Fire is a common natural disturbance in forest ecosystems and plays an important role in subsequent vegetation patterns. Based on the spatial sequence method, adopted as an alternative to the time successional sequence method, we selected burned areas in different locations in the Anning River Basin, which encompasses typical dry valleys. Quadrat surveys and quantitative classification were used to identify and classify the vegetation and distribution pattern and to carry out environmental interpretation during the natural restoration process after a forest fire. The results showed the following: (1) in the early stage of natural recovery after a forest fire disturbance, the vegetation community could be divided into seven community types, and Quercus guyavaefolia H. Leveille (Qg) was the dominant species in the community; (2) the vegetation samples could be divided into five ecological types, and the classification and distribution pattern of community types in this region changed most notably with altitude; and (3) a detrended correspondence analysis could be used to accurately classify vegetation community types, while a detrended canonical correspondence analysis could reveal the relationships between species and environmental factors. This study provides a scientific basis for guiding the restoration of ecosystem structural stability and biodiversity in burned areas.

How do acid or alkaline soil environments affect soil organic carbon stocks in a post-abandonment secondary succession process in Mediterranean mountain areas?

Farmland abandonment has become one of the most important land use and land cover (LULC) changes threatening mountain areas in the Mediterranean. The concomitant natural revegetation process brings with it a series of ecosystem services and disservices for these marginal areas. Secondary succession can improve soil environment properties; however, its effects can be influenced by the specific characteristics of the site (topography, climate, vegetation, etc.). Thus, the main objective of this research was to study how soil quality and carbon sequestration are affected by post-abandonment secondary succession depending on the environment (delimited from the bedrock and the typical vegetation communities of the area. Soil sampling was carried out in a representative area of the Mediterranean mid-mountains (Leza Valley, Spain) for two soil environments (acid and alkaline), at different depths (0–40 cm) and in 5 stages of the abandonment process: cropland (CRL); shrubland (SH); bushland (BS); young forest (YF); and old forest (OF). Soil physico-chemical parameters were analysed and data analysis carried out with the following results: (i) significant differences were detected between environments for most LULCs; (ii) LULC, depth and soil environment significantly affected most of the soil variables studied; (iii) alkaline soil environments showed a progressive increase of soil organic carbon (SOC) and total nitrogen (N) stocks as the revegetation process and age of abandonment advanced (from 101.16 Mg ha−1 SOC (CRL) to 181.68 Mg ha−1 SOC (OF); (iv) in acid soil environments, the highest stocks were observed in the YF (161.56 Mg ha−1 SOC) with an irregular evolution pattern.Our study showed that secondary succession can improve soil quality and SOC sequestration. However, factors such as soil environment may be of great importance in selecting the best post-abandonment management strategy in a bid to gain recovery of ecosystem services and mitigate the effects of Global Change.

Simulation of suitable habitats for typical vegetation in the Yellow River Estuary based on complex hydrodynamic processes

Estuarine ecosystems are influenced by the combination of freshwater runoff and ocean tides, and the natural environment is intricate and complex, with special natural environmental conditions and biological habitat characteristics. The Yellow River is characterized by high sediment-bearing water flow, and the estuary forms a unique clear and turbid confluence. The Water and Sand Regulation (WSRS) from the Xiaolangdi Reservoir to the estuary and nearshore has had significant impacts on the environmental conditions of water, sediment and nutrients, further affecting the growth and development of vegetation in the nearshore zone. In recent years, more studies have focused on the effects of climate change and ocean tides on vegetation in the Yellow River Estuary; however, few studies have been conducted on the effects of the WSRS on klysmoeionion. In this study, we investigated the influence of water flow, sediment and nutrients on klysmoeionion based on long-term field monitoring and indoor control experiments; constructed a three-dimensional hydrodynamic water quality model to simulate the hydrodynamic characteristics, sediment transport patterns and nutrient salt distribution in the Yellow River Estuary under the combined influence of tides and riverine water and sediment; and further combined the growth competition model of typical vegetation (including the native species Zostera japonica and invasive species Spartina alterniflora) to construct a suitable habitat simulation model for typical vegetation communities in the Yellow River Estuary. Habitat and biomass changes in Z. japonica and S. alterniflora in the Yellow River Estuary were simulated under the influence of the WSRS and climate change. The results showed that the distribution of suitable habitats for Z. japonica and S. alterniflora in the Yellow River Estuary and offshore was characterized by a zonal distribution along both sides of the estuary, with an increasing trend of suitable habitat area from the estuary to both sides of the estuary; due to environmental conditions and inter- and intra-species competition, the biomass of Z. japonica and S. alterniflora was mainly distributed in the estuary and near the northern and southern shores, with the southern shore have the most distribution. In contrast, S. alterniflora was mainly distributed in the northern shore away from the estuary and in Laizhou Bay. During the WSRS period, the suitable habitat area of Z. japonica decreased by 25%, and the biomass decreased by 50%, while the suitable habitat and biomass of S. alterniflora were not significantly affected. The growth of Z. japonica was severely affected by the dual effects of global warming and the WSRS, while the biomass of S. alterniflora showed an increasing trend. The WSRS can further consider the growth pattern of vegetation to protect the resources of Z. japonica and to curb the expansion of the invasive S. alterniflora.

Field-Scale Floating Treatment Wetlands: Quantifying Ecosystem Service Provision from Monoculture vs. Polyculture Macrophyte Communities

Global water security is critical for human health, well-being, and economic stability. However, freshwater environments are under increasing anthropogenic pressure and now, more than ever, there is an urgent need for integrated approaches that couple issues of water security and the remediation of degraded aquatic environments. One such strategy is the use of floating treatment wetlands (FTW), which are artificial floating mats that sustain and support the growth of macrophytes capable of removing nutrients from over-enriched waterbodies. In this study, we quantify a range of indicators associated with FTWs, planted with different vegetation community types (i.e., monocultures and polycultures) over the course of a three-year field-scale study. The composition of the two different types of FTWs changed significantly with a convergence in diversity and community composition between the two types of FTWs. Phytoremediation potential of the two FTW communities, in terms of nutrient standing stocks, were also similar but did compare favourably to comparable wild-growing plant communities. There were few substantial differences in invertebrate habitat provision under the FTWs, although the high incidence of predators demonstrated that FTWs can support diverse macroinvertebrate communities. This field-scale study provides important practical insights for environmental managers and demonstrates the potential for enhanced ecosystem service provision from employing nature-based solutions, such as FTWs, in freshwater restoration projects.

Plant Species Composition and Conservation Values at Dilla University Botanical and Ecotourism Garden, Dilla, Ethiopia

Ethiopia has a diverse topography with higher plant species composition and estimated to the higher proportion of endemic plant species. Currently, several factors drive natural forest destruction in the country, extensive agricultural land expansion triggered by increasing human population is probably the dominant force. The Dilla University Botanical and Ecotourism Garden was established targeting to rescue threatened flora from extinction, contribute towards conservation, and research on biodiversity and sustainable education as well as ecotourism development. The study was aimed to generate basic scientific information by identifying and documenting the formerly available plant species in to the garden and provide information for farther plant collection planning and research. Systematic sampling method was used to collect the vegetation data from 52 plots of 20 m × 20 m (400 m2) quadrats. To collect data for herbaceous plants, five 1 m × 1 m subplots were laid in each of the main plot, where four were at the corners and one at the centre. Vegetation classification was performed using R-programme version 3.6.1 software packages. Shannon–Wiener Diversity Index was used to calculate species diversity, richness, and evenness. A total of 408 plant species, including trees (30%), shrubs (25%), herb (30%), grass (6%), and 9% of other species, were collected. The identified species belong to 287 genera and 105 families. Out of this, 27 species of plants are endemic to Ethiopia and 72 plant species were screened as a medicinal plant used for the treatment of human diseases. Based on IUCN Red Data List, among the endemic plant species nineteen species were least concern; two were near threatened; two were endangered while four were vulnerable. Three vegetation community types were identified from the hierarchical clustering analysis. The result designates that Dilla University Botanical and Ecotourism Garden has high plant species composition and diversity with a good distribution. The higher composition of this ecologically, economically, and socially important plant species at its early stage makes the garden a unique garden in the country and realize to be a centre for research, education, and tourist destination.

Nitrous oxide emission from a flooded tropical wetland across a vegetation and land use gradient

Abstract This study investigated, using the closed chamber method, the impact of (1) vegetation community type (Typha latifolia, Cyperus papyrus and Phragmites mauritianus) in a natural tropical freshwater marsh wetland (marsh) and (2) conversion of a natural tropical freshwater marsh into a rice paddy wetland (rice paddy), on nitrous oxide (N2O) emission. Both the marsh and the rice paddy were continuously flooded, while the rice paddy was unfertilized. Average N2O emission from the marsh did not vary significantly (p > 0.05) among the vegetation communities, ranging from 0.5 to 0.6 μg m−2 h−1. Similarly, these N2O emission rates were not significantly different (p > 0.05) from those recorded in the rice paddy (0.7 ± 2.8 [SE] μg m−2 h−1). There was no significant correlation (p > 0.05) between environmental parameters and N2O emission. We concluded that vegetation community type does not affect N2O emission from natural tropical freshwater marshes under continuous flooding. Further, converting natural tropical freshwater marshes into continuously flooded and unfertilized rice paddies does not affect N2O emission but instead enhances carbon emission, as was depicted by the significantly lower (p > 0.05) soil organic carbon content in the rice paddy. In view of climate change mitigation, therefore, wetland management should give priority to the conservation/protection of natural wetlands.

Particle-size fractal dimensions and pore structure characteristics of soils of typical vegetation communities in the Kubuqi Desert

The goal of this study was to investigate the soil particle-size distribution (PSD) and pore structure characteristics in the Kubuqi Desert in order to provide basic data for gaining insights into the soil-modifying properties of the local vegetation. Based on laser diffraction analysis, we measured the soil PSD and calculated the single and multi-fractal dimensions of the soils under typical artificial forest and natural grassland vegetation. The diameters, volumes and surface areas of the soil pores were determined via nitrogen adsorption experiments. The relationships between the fractal characteristics and pore structure parameters of the soil were investigated via redundancy analysis and stepwise regression. The clay content was less than 2.0%, and the sand content was greater than 75.0%. There was variability in the PSD and fractal dimension, which was mainly observed for the 0–20 cm, 20–80 cm, and 80–100 cm soil layers. In the 0–80 cm, the fine particle content, single fractal dimension (D), entropy dimension (D1), ratio of D1 to the capacity dimension (D1/D0), and correlation dimension (D2) were smaller for the forest soils than for the grassland soils. The fine particle (clay and silt) content of the 80–100 cm soil layer was approximately 37.8% higher for the Salix psammophila-8a than for the Salix psammophila-3a, and it was approximately 161.4% higher for the Populus popular-35a than for the Pinus sylvestris var. mongolica-8a. The silt content, D1, D1/D0, and D2 were significantly positively correlated with the specific surface area (SSA), total pore volume (TPV), and average pore diameter (APD) of the nanopores (p < 0.05, 0.01, or 0.001), and they were significantly negatively correlated with the percentage of the micropore volume (PMV) (p < 0.05 or 0.01). In the Kubuqi Desert, the fine particle content and fractal dimensions of the soil layer below the root zone of shrub and arbor vegetation increased with increasing stand age, but the trend was reversed in the shallower soil layers. The variability of the soil PSD characteristics was strongly correlated with the variability of the nanopore parameters on the microscopic scale, suggesting that the total pore volume, average pore diameter, and percentage of the micropore volume may be potential indicators of the soil structure and quality.

中国南海北部不同岛屿植被与土壤的耦合协调发展度

PDF HTML阅读 XML下载 导出引用 引用提醒 中国南海北部不同岛屿植被与土壤的耦合协调发展度 DOI: 10.5846/stxb202103020565 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中国科学院战略性先导科技专项(XDA13010302); 国家自然科学基金项目(31770495,31870712,31971487) Coupling coordinative degree of vegetation and soil in different islands in the north of South Sea, China 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:植被和土壤是陆地生态系统两个重要的组成部分,二者相互影响相互促进,探明两者的耦合协调关系是生态恢复与重建的顺利实施的关键。基于中国南海北部大庙墩岛、涠洲岛、大汉三墩岛、甘蔗岛和蜈支洲岛等个海岛的典型植被群落植被土壤的全面调查和取样分析,建立10个植被因子和14个土壤因子的2级层次指标体系,采用层析分析法确定各因子的权重,构建5个海岛植被土壤耦合度和耦合协调度模型。结果表明,不同岛屿的植被土壤耦合度和耦合协调度模型并不完全对应,植被与土壤的综合指数在不同岛屿中也不完全一致,甘蔗岛的植被效应和大汉三墩岛的土壤效应最佳。中国南海北部5个岛屿的植被土壤耦合协调状况较好,均处于初、中级协调发展状态,且除甘蔗岛外处于植被土壤同步型。总的来说,由于岛屿远离内陆,人类干扰相对较小,在植被土壤长期的演替过程中,中国南海北部岛屿植被土壤耦合协调较好,在其恢复与生态重建时要注重提高植物多样性、抚育水平和土壤管理水平。 Abstract:Vegetation and soil are two important components of the terrestrial ecosystems. There is to some extent an interaction between vegetation and soil systems and they influence each other. Therefore, exploring the coupling coordinative relationship between vegetation and soil could be the key to successful implementation of ecological restoration and reconstruction in the terrestrial ecosystems. The islands of the South Sea in China are located on the edge of the world's largest tropical-subtropical shelf, which are an inalienable part of China's territory. Due to clear boundaries and isolation from the land, islands are faced with problems such as strong habitat heterogeneity, lack of plant germplasm resources and fresh water, large evaporation, and so on. They are special and independent ecosystems which are more vulnerable to extreme climates or natural disasters such as typhoons, and become easily degraded but difficultly to be restored. This paper is based on the comprehensive investigation and systematic determination between vegetation and soil systems in the typical vegetation communities on five islands in the northern South Sea, China, i.e., Damiaodun Island, Weizhou Island, Dahan Sandun Island, Ganzhe Island, and Wuzhizhou Island. The two-level index system combined with 10 vegetation factors and 14 vegetation factors were established to determine the weight of each factor by the analytic hierarchy process, and then to build coupling models and coupling coordination models of vegetation and soil systems in the five islands. The results showed that the vegetation-soil coupling models and coupling coordination models in different islands were not completely corresponding. In addition, the comprehensive indexes of vegetation and soil were not completely consistent in each island. The vegetation effect of Ganzhe Island and the soil effect of Dahansandun Island were the best, respectively. The coupling coordinative status of vegetation and soil was good in the five islands in the northern of South Sea, China, which were in a state of primary or intermediate coordinated development. All the islands were in the synchronization type of vegetation and soil except Ganzhe Island. In general, due to islands far from land with relative small human interference, during the long-term succession of vegetation and soil, the coupling coordination between vegetation and soil systems in the northern islands of the South Sea of China was in a good status. Therefore, special attention should be paid to improve plant diversity, tending level, and soil management level during the process of vegetation restoration and ecological reconstruction in the northern islands of the South Sea of China. 参考文献 相似文献 引证文献

Analysis of the Cooling and Humidification Effect of Multi-Layered Vegetation Communities in Urban Parks and Its Impact

As urbanization continues to accelerate, the urban heat island effects have become one of the most important issues affecting the urban environment and people’s living experience. Numerous studies have shown that urban parks and green spaces can effectively alleviate the problem of the urban heat island effect and provide cooling and humidifying effects. Vegetation communities are a fundamental part of urban parklands, and multi-layered vegetation communities are considered to have better cooling and humidifying effects. Previous studies have focused on comparative analyses between different cover types of vegetation communities but have not explored the differences in the cooling and humidifying effects of multi-layered vegetation communities of the same cover type. Therefore, the Olympic Forest Park in Beijing was selected as the subject of this study, and multi-layered vegetation-covered (tree-shrub-grass) with different degrees of densities and uncovered squares were selected for the control and comparison. The cooling and humidifying effects of multi-layered vegetation communities with different canopy densities at different times of the day through field measurements were studied, and the influencing factors for this were analyzed. The results show that the tree cover is the core factor affecting temperature; the degree of the canopy density of multi-layered vegetation communities is significantly and positively correlated with the intensity of cooling and humidification, and the cooling and humidifying effect of multi-layered vegetation communities increases as the degree of canopy density increases. The results of this study can provide some references for the planning and design of urban parks and green spaces.

Soil Infiltration Properties Are Affected by Typical Plant Communities in a Semi-Arid Desert Grassland in China

A process of infiltration from the soil surface to form soil water is known as soil infiltration; this is the only way for plants to absorb and use soil water. This process is closely related to nutrient migration, surface runoff, and soil erosion. The objectives of this study were to quantify the effect of typical plant communities on soil infiltration performance, reveal the interaction between soil infiltration rate and soil characteristics and plant roots, and determine the primary influencing elements on the Xilamuren grassland. The ring knife method was used to determine the soil infiltration rate at the 0–30 cm soil layer of six typical vegetation communities. The results indicated that the infiltration rate of the Koeleria macrantha community was highest at the soil depth of 0–5 cm, while that of the Convolvulus ammannii community was lowest, reaching 4.25 mm·min−1 and 0.53 mm·min−1, respectively. The soil infiltration rate of different plant communities gradually declined with the increment of soil depth. The strongest correlations were found between bulk density, total porosity, organic matter, root characteristics, and soil infiltration rate. The bulk density, initial water content, capillary porosity, and clay content were the primary influencing factors acting on soil infiltration in the region. Other factors indirectly impacted the infiltration rate by modifying bulk density, which was a crucial limiting factor determining the infiltration rate in the research region. The study’s findings will give theoretical and practical assistance for the prevention and management of soil deterioration and grassland restoration in this area.

Gamma diversity: derived from and a determinant of alpha diversity and beta diversity. An analysis of three tropical landscapes

Using three taxonomic groups of beetles we examine how alpha and beta diversity influence the species richness of a landscape (gamma diversity), and vice versa. That is, how the species richness of a landscape – which is a historical and biogeographical phenomenon – contributes to the values of alpha diversity (1) at a given site, (2) in a community, (3) in terms of cumulative species richness by community, and also contributes to (4) the intensity of species exchange between communities. To explore this question, we used two subfamilies of Scarabaeoidea: Scarabaeinae and Geotrupinae, and the family Silphidae. In all analyses these three taxonomic groups are considered as a single indicator group: the copronecrophagous beetles. Information is also included on the subfamily Aphodiinae (Scarabaeoidea), coprophagous beetles not included in the indicator group. Several types of vegetation located in three landscapes (tropical, transition and mountain) were studied, and these are located along an altitudinal gradient in the central part of the state of Veracruz, Mexico. We base this study on the following concepts. The alpha diversity of an indicator group reflects the number of species that use a given environment or resource in a given place or community. Spacial beta diversityis related to the response of organisms to spatial heterogeneity. Gamma diversity depends primarily on the historical and geographic processes that operate on the mesoscale level and is also affected by alpha and beta diversity. It is on this scale of landscape that human actions, such as the modification and fragmentation of vegetation, have their most important effects. These are, however, often beyond the scope of ecological analyses carried out on a local scale. In the three landscapes, sampling was carried out regularly at 67 sites, with complementary sampling at another 69 sites. Twenty-six types of vegetation communities were studied. A total of 16,152 specimens representing 60 species were captured (52 species of Scarabaeinae, 4 Geotrupinae and 4 Silphidae). In the tropical landscape the community richest in species was low deciduous forest. In the transition landscape, cloud forest was the richest. Each of these communities is the most representative of their respective altitudinal bands. In contrast, the greatest species richness in the mountain landscape occurred in the mountain grasslands and pastures; types of community favoured by or even created by human intervention. This is explained by the expansion of heliophilous species from the Mexican High Plateau into these areas. In the tropical landscape the species richness of the pastures is similar to that of its forests, but with a partially different composition which is characterized by the dominance of heliophilous and coprophagous species; the latter, in addition to the more ubiquitous species that are shared with the tropical forest. In the transition landscape the cloud forest and the coffee plantations with polyspecific shade are important in the context of conserving the fauna. This type of community offers arboreal cover and occupies the majority of this landscape, allowing the groups of insects studied to move between remnant fragments of cloud forest. On the landscape scale but not locally, the fragmentation of natural communities does not appear to have reduced the number of species for the beetles of the indicator group. In each landscape disturbance by human activity appears to have been overcome for distinct reasons. In the tropical landscape we find the heliophilous beetle fauna characteristic of pastures, and this has increased by two species of recent invaders. In the transition landscape, the coffee plantations with polyspecific shade create a communication matrix, while in the mountain landscape the expansion of the mountain pastures has made conditions more favourable for heliophilous species. These results are not necessarily expected for other groups of organisms.

Patterns of vegetation change in Yukon: recent findings and future research in dynamic subarctic ecosystems

In Yukon, Canada, average air temperature has increased by 2 °C over the past 50 years and, by the end of the century up to 6.9 °C of further warming is predicted, along with increased climate variability. As a result of these and other changes, vegetation communities are predicted to shift in space and composition. Changes to the vegetation assemblages across multiple ecological units or bioclimate zones will impact carbon and nutrient cycling, animal habitat, biodiversity levels, and other ecosystem processes. Yukon has a wide variety of vegetation communities, and paleoecological evidence indicates that significant vegetation changes have occurred throughout the territory in the past. No documented synthesis of changes to vegetation assemblages exists, restricting predictions of their future likelihood, abundance, and influence. Here, we review the literature of documented examples of vegetation change throughout Yukon that have occurred ( i) in different vegetation communities due to the persistent press of climate change and ( ii) after natural disturbances. Future research into all vegetation responses under ongoing climate change is warranted. We identify critical research gaps for each vegetation community and disturbance type that should be addressed to produce a more encompassing understanding of the response of Yukon bioclimate zones and vegetation communities to future warming and disturbances.

Classifying vegetation communities karst wetland synergistic use of image fusion and object-based machine learning algorithm with Jilin-1 and UAV multispectral images

Fine classification of wetland vegetation communities using machine learning algorithm and high spatial resolution images have attracted increased attention. However, there exist several challenges in image fusion, data dimension reduction and algorithm tuning. To resolve these issues, this paper attempts to fuse Unmanned Aerial Vehicle (UAV) images with spaceborne Jilin-1 (JL101K) multispectral images for classifying vegetation communities of karst wetland using the optimized Random Forest (RF), Extreme gradient boosting (XGBoost) and Light Gradient Boosting (LightGBM) algorithms. This study also quantitatively evaluates image fusion quality from spatial detail and spectral fidelity, and explores the effects of different image feature combinations and classifiers on mapping vegetation communities by variable selection and dimensionality reduction. Finally, this paper further evaluates and quantifies the importance and contribution rate of feature variables for typical vegetation communities using Recursive feature elimination (RFE) algorithm. The results showed that: (1) the Gram-Schmidt (GS)algorithm produced the high-quality fusion image of JL101K and UAV, and the fusion image achieved higher overall accuracy (82.8%) than the original JL101K multispectral image; (2) UAV multispectral image and its derivatives (scheme 3) achieved the highest overall accuracy (87.8%) in all classification schemes; (3) The optimized object-based LightGBM algorithm outperformed XGBoost and RF algorithm, which provided an improvement of 0.6%∼3.5% in overall accuracy (OA). McNemar's test indicated that there existed significant differences in vegetation communities’ classification between the three algorithms. (4) The average accuracy (AA) of vegetation communities in karst wetlands was mainly ranged from 60% to 90%. The water hyacinth and herbaceous vegetation were sensitive to the Mean Digital Surface Model (DSM) and Standard RedEdge band.

Effects of Salinity and Oil Contamination on the Soil Seed Banks of Three Dominant Vegetation Communities in the Coastal Wetland of the Yellow River Delta

In view of the important role of vegetation in the integrity of structures and functions of coastal wetland ecosystems, the restoration of degraded coastal wetland vegetation has attracted increased attention. In this paper, the newborn coastal wetland in the Yellow River Delta (YRD) of China was selected to research the effect of salinity and oil exploitation on the germination of soil seed banks of three dominant vegetation communities. The germination experiment with three concentration gradients of NaCl and three concentration gradients of diesel treatments showed that there were 14 species present in the soil seed bank of the multi-species community: three species in the Phragmites australis community, and five species in the P. australis—Suaeda glauca community. The species in the seed bank of the three communities were much richer than the above-ground vegetation in this study. Soil salinity had a significant inhibitory effect on the seedling numbers of germinated species, the seedling density, and the species diversity of the soil seed banks, while the inhibitory effect of diesel was indistinctive under the designed concentrations. There existed significant interactions between the vegetation community type and soil salinity on the number of germinated species, the seedling density, and the Margalef index. Soil salinity is considered an important factor for wetland vegetation restoration in the YRD, but its effect had species-specific differences. Soil seed banks of the present three communities could be used to promote the restoration of degraded wetlands within certain soil salinity and oil concentration ranges.

Mapping tundra ecosystem plant functional type cover, height and aboveground biomass in Alaska and northwest Canada using unmanned aerial vehicles

Arctic vegetation communities are rapidly changing with climate warming, which impacts wildlife, carbon cycling and climate feedbacks. Accurately monitoring vegetation change is thus crucial, but scale mismatches between field and satellite-based monitoring cause challenges. Remote sensing from unmanned aerial vehicles (UAVs) has emerged as a bridge between field data and satellite-based mapping. We assess the viability of using high resolution UAV imagery and UAV-derived Structure from Motion (SfM) to predict cover, height and aboveground biomass (henceforth biomass) of Arctic plant functional types (PFTs) across a range of vegetation community types. We classified imagery by PFT, estimated cover and height, and modeled biomass from UAV-derived volume estimates. Predicted values were compared to field estimates to assess results. Cover was estimated with root-mean-square error (RMSE) 6.29-14.2% and height was estimated with RMSE 3.29-10.5 cm, depending on the PFT. Total aboveground biomass was predicted with RMSE 220.5 g m<sup>-2</sup>, and per-PFT RMSE ranged from 17.14-164.3 g m<sup>-2</sup>. Deciduous and evergreen shrub biomass was predicted most accurately, followed by lichen, graminoid, and forb biomass. Our results demonstrate the effectiveness of using UAVs to map PFT biomass, which provides a link towards improved mapping of PFTs across large areas using earth observation satellite imagery.

Effects of forest growth in different vegetation communities on forest catchment water balance

Forest ecosystems are critical for adjusting the dynamic balance of the hydrological cycle. This balance is affected by vegetation community types, phenology, and forest density. Previous long-term catchment-scale model studies have focused on changes in forest areas while ignoring the above factors. Since the 1980s, climate change caused by increases in atmospheric CO2 levels has enhanced forest growth. Moreover, amendments to forest management policies, including intermediate cuttings caused by economic factors, have yielded unprecedented changes in forest ecosystems. In this study, we designed a methodology and created a credible model using the Soil and Water Assessment Tool (SWAT) that can precisely reflect water balance variations caused by different ecosystem situations during long-term changes in forest density. We focused on the Yamato River catchment in Western Japan, which includes three planted forests and one primeval forest, each markedly different with respect to vegetation community composition and management policy. In the process, we examined the ratio of coniferous vegetation and broad-leaved vegetation in different forest areas, used remote sensing methods to quantify the maximum and minimum leaf area index (LAI) of each forest region over 40 years, and calibrated the model by comparing the LAI growth curve, evapotranspiration, and streamflow with observed data. Moreover, we separated the decadal canopy evaporation, transpiration, and soil evaporation from the SWAT output results. We found that (1) forest evapotranspiration has increased in recent decades because of the above reasons; (2) in young or well-managed forests, the forest water balance may have changed significantly with forest growth. For long-term studies, it is necessary to distinguish the growth characteristics of different forests during different periods, and a detailed definition of a mixed forest is required. The forest parameters and growth characteristics are critical for understanding forest ecosystems and cannot be ignored at catchment-scale.