Vegetation as an indicator of environmental changes

Composition of the vegetation and the properties of its environment are related, as was shown by research. In these, mostly statistical-correlative studies, both the vegetation and some growth factors, such as plant nutrients and moisture supply were analyzed and studied on interdependence. At present the environmental conditions can be estimated in the field from the floristic composition with regard to differences both in the combination of plant species and in their relative biomass production. With a vegetation survey the spatial pattern of the different environmental conditions can be indicated. For instance, the places where moisture supply gradients occur can be detected, also a better understanding is obtained of the environmental equalization and the decreasing number of plant species and spatial diversity. Conclusions can be drawn about changes in the vegetation to be expected, from the combined occurrence of, a terrestrial vegetation indicating an eutrofied environment and a water vegetation indicating a relatively oligotrophic environment. By comparing vegetation recordings of the past and present, environmental changes that have occurred in the same place can be indicated. By vegetations situated in different places in relation with soil profile properties the consequences of environmental changes can be predicted. For instance, lowering of the ground water table and intensifying the agricultural use. On the other hand, measures can be suggested to increase the biological value of land and water, for instance, indication of seepage areas and floristically rich areas in the field.     

Assessing the effects of land use changes on soil sensitivity to erosion in a highland ecosystem of semi-arid Turkey

There has been increasing concern in highlands of semiarid Turkey that conversion of these systems results in excessive soil erosion, ecosystem degradation, and loss of sustainable resources. An increasing rate of land use/cover changes especially in semiarid mountainous areas has resulted in important effects on physical and ecological processes, causing many regions to undergo accelerated environmental degradation in terms of soil erosion, mass movement and reservoir sedimentation. This paper, therefore, explores the impact of land use changes on land degradation in a linkage to the soil erodibility, RUSLE-K, in Cankiri–Indagi Mountain Pass, Turkey. The characterization of soil erodibility in this ecosystem is important from the standpoint of conserving fragile ecosystems and planning management practices. Five adjacent land uses (cropland, grassland, woodland, plantation, and recreational land) were selected for this research. Analysis of variance showed that soil properties and RUSLE-K statistically changed with land use changes and soils of the recreational land and cropland were more sensitive to water erosion than those of the woodland, grassland, and plantation. This was mainly due to the significant decreases in soil organic matter (SOM) and hydraulic conductivity (HC) in those lands. Additionally, soil samples randomly collected from the depths of 0–10 cm (D ₁) and 10–20 cm (D ₂) with irregular intervals in an area of 1,200 by 4,200 m sufficiently characterized not only the spatial distribution of soil organic matter (SOM), hydraulic conductivity (HC), clay (C), silt (Si), sand (S) and silt plus very fine sand (Si + VFS) but also the spatial distribution of RUSLE-K as an algebraically estimate of these parameters together with field assessment of soil structure to assess the dynamic relationships between soil properties and land use types. In this study, in order to perform the spatial analyses, the mean sampling intervals were 43, 50, 64, 78, 85 m for woodland, plantation, grassland, recreation, and cropland with the sample numbers of 56, 79, 72, 13, and 69, respectively, resulting in an average interval of 64 m for whole study area. Although nugget effect and nugget effect–sill ratio gave an idea about the sampling design adequacy, the better results are undoubtedly likely by both equi-probable spatial sampling and random sampling representative of all land uses.     

The changes of densities and patterns of roads and rural buildings: a case study on Dongzhi Yuan of the Loess Plateau, China

Roads and buildings are considered as primary causes of rural landscape changes. In this study, linear regression models were used to analyze the dynamic influences of environmental factors and variables on roads and rural buildings from 1979 to 2005 in Dongzhi Yuan (tableland) of the Loess Plateau, China. The relationship between roads and rural buildings and their effects on Dongzhi Yuan are discussed also. The results showed that three environmental factors (topography, land cover, and development level) explained roads better than rural buildings referring densities and patterns. The environmental variables significantly related to roads have decreased, whereas those related to rural buildings have increased over time. Among these significant variables, percent of farmland mostly determined the densities and patterns of both roads and rural buildings. There was significant correlation between roads and rural buildings in terms of density and pattern. In addition, roads and rural buildings have increased greatly in gully areas of this region. Therefore, more attention should be paid to planning of roads and rural buildings in Dongzhi Yuan.     

Effects of land use on phosphorus loss in the hilly area of the Loess Plateau, China

The hilly area of Loess Plateau has some of the highest soil erosion rates in the world, and serious soil erosion causes great losses of plant nutrients. As the most common land use in Loess Plateau, slope farmland contributed most of the erosion soils. This study was designed to examine the effects of land use and slope angle of farmland on phosphorus (P) loss in the hilly area of loess plateau. Farmland (FR), barrenland (BR), and four forest treantment (seabuckthorn+ poplar (SP), immature seabuckthorn (IS), mature seabuckthorn (MS), immature Chinese pine (ICP)) were the types of land use; 10, 15, 20, 25, 30 degrees were the slope angles of FR that were compared. The results showed a larger proportion of P loss occurred in erosion soil fraction of FR, ICP, ICP, and the five slope treatments of FR; in SP, IS, and MS, P loss was primarily through runoff. FR produced more P loss than SP, IS, ICP, BR, and MS. 20∼30 degrees may be the slope ranges for P loss of FR; FR in this ranges would loss more P with soil erosion. SP, IS, and MS were reasonable land uses for their less runoff, soil loss, and P loss. Farmlands over 15 degrees should be abandoned or reforested for it would produce more runoff, soil loss, and P loss.     

Vegetation dynamics during different abandoned year spans in the land of the Loess Plateau of China

In this semi-arid area, many studies focused on the two-phase vegetation pattern were carried out to explore a changing vegetation trajectory on degraded land. However, this study conducted an analysis of a two-phase vegetation pattern and explored the successional vegetation trajectories in a positive succession without disturbance. In this work, 60 randomly distributed plots (1?×?1 m) were invested on four abandoned land areas (4-, 12-, 22-, and 50-year abandoned land) to determine attributes of vegetation, and soil physical and nutritional properties. It was found that vegetation distribution development went from homogeneous on 4-year abandoned land to heterogeneous on 50-year abandoned land, with a positive succession. Meanwhile, there was a significant difference in soil physical and nutritional properties for the inside and outside of vegetation patches. Vegetation patches can supply better soil physical and nutritional properties for vegetation than bare patches along the abandoned time. Vegetation diversity changes without a regular trend which may be due to the effect of environment and interspecies competition. This work picked up the slack for vegetation patterns succession research and provided a quantitative analysis approach.     

Effect of land use land cover change on soil erosion potential in an agricultural watershed

Universal soil loss equation (USLE) was used in conjunction with a geographic information system to determine the influence of land use and land cover change (LUCC) on soil erosion potential of a reservoir catchment during the period 1989 to 2004. Results showed that the mean soil erosion potential of the watershed was increased slightly from 12.11 t ha^???1 year^???1 in the year 1989 to 13.21 t ha^???1 year^???1 in the year 2004. Spatial analysis revealed that the disappearance of forest patches from relatively flat areas, increased in wasteland in steep slope, and intensification of cultivation practice in relatively more erosion-prone soil were the main factors contributing toward the increased soil erosion potential of the watershed during the study period. Results indicated that transition of other land use land cover (LUC) categories to cropland was the most detrimental to watershed in terms of soil loss while forest acted as the most effective barrier to soil loss. A p value of 0.5503 obtained for two-tailed paired t test between the mean erosion potential of microwatersheds in 1989 and 2004 also indicated towards a moderate change in soil erosion potential of the watershed over the studied period. This study revealed that the spatial location of LUC parcels with respect to terrain and associated soil properties should be an important consideration in soil erosion assessment process.     

Pollution characteristics and ecological risk assessment of heavy metals in three land-use types on the southern Loess Plateau,China

The accumulation of heavy metals in agricultural soils has been the subject of great concern because these metals have the potential to be transferred to soil solutions and subsequently accumulate in the food chain. To study the persistence of trace metals in crop and orchard soils, representative surface soil samples were collected from terrace farmland that had been cultivated for various numbers of years (3, 8, 12, 15, and >20 years), terrace orchard land that had been cultivated for various numbers of years (4, 7, 10, 12, 15, 18, 25, and >30 years), and slope farmland with various gradients (3°, 5°, 8°, 12°, 15°, and 25°) and analyzed for heavy metals (As, Cr, Cu, Hg, Ni, and Zn). These samples were collected from Nihegou catchment of Chunhua county in the southern Loess Plateau of China. The six heavy metals demonstrated different trends with time or gradient in the three land-use types. The Cu and Zn contents of the soil were higher than the referee background values of the loessal soil, and the contents of Cr and Ni, and especially those of As and Hg, were lower. Cu was the only heavy metal that just met the Grade III Environmental Quality Standard for Soils of China, while the others reached grade I. Cu and Hg were considered contaminant factors and Hg was a moderate potential ecological risk factor in the catchment. Of the sites investigated, 89.5% fell into the category with a low degree of contamination (C _d ) and rest were moderate, while all three land-use types had low potential ecological risk (RI). Changes of C _d and RI were consistent with the cultivated time in the terrace farmland and terrace orchard land. Values of RI increased while C _d decreased with the increasing of slope gradient in the slope farmland. Evaluating the ecological risk posed by heavy metals using more soil samples in a larger study area is necessary on the Loess Plateau of China.     

Toxicological effects of major environmental pollutants: an overview

The last quarter of the twentieth century had witnessed a global surge in awakening against the unabated menace of environmental pollution. Among the various types of environmental pollution, water pollution is an age-old problem but it has gained an alarming dimension lately because of the problems of population increase, sewage disposal, industrial waste, radioactive waste, etc. Present scenario of water pollution calls for immediate attention towards the remediation and detoxification of these hazardous agents in order to have a healthy living environment. The present communication will deal with the toxicological effects of major environmental pollutants, viz. heavy metals, pesticides, and phenols.     

Longitudinal distribution of heavy metals in sediments of a canyon reservoir in Southwest China due to dam construction

In this study, the longitudinal distribution of heavy metals (including As, Cd, Cr, Cu, Ni, Pb, and Zn) from sediment of a 70-km long canyon reservoir in Yunnan Province was investigated and their potential ecological risks were assessed. The results indicated that the concentration of all the detected metals in the sediments that was sampled near the dam was much higher than that sampled from upstream far from the dam. The geoaccumulation index (I _geo) and contamination factors (CF) suggested that Cd was the most important contamination factor, followed by As and Zn, while the concentration of Cr, Cu, Ni, and Pb was at uncontaminated levels. Cd posed a high potential ecological risk in the sediment. Furthermore, potential ecological risk is significantly correlated with the distance from the dam.     

Disposal of dredged sediments in tropical soils: ecotoxicological effects on earthworms

The upper limit concentrations of metals established by international legislations for dredged sediment disposal and soil quality do not take into consideration the properties of tropical soils (generally submitted to more intense weathering processes) on metal availability and ecotoxicity. Aiming to perform an evaluation on the suitability of these threshold values in tropical regions, the ecotoxicity of metal-contaminated dredged sediment from the Guanabara Bay (Rio de Janeiro, Brazil) was investigated. Acute and avoidance tests with Eisenia andrei were performed with mixtures of dredged sediment with a ferralsol (0.00, 6.66, 13.12, 19.98, and 33.30 %) and a chernosol (0.00, 6.58, 13.16, 19.74, and 32.90 %). Mercury, lead, nickel, chromium, copper, and zinc concentrations were measured in test mixtures and in tissues of surviving earthworms from the acute tests. While ferralsol test mixtures provoked significant earthworm avoidance response at concentrations ≥13.31 %, the chernosol mixtures showed significant avoidance behavior only at the 19.74 % concentration. The acute tests showed higher toxicity in ferralsol mixtures (LC50?=?9.9 %) compared to chernosol mixtures (LC50?=?16.5 %), and biomass increased at the lowest sediment doses in treatments of both test soils. Most probably, the expansive clay minerals present in chernosol contributed to reduce metal availability in chernosol mixtures, and consequently, the ecotoxicity of these treatments. The bioconcentration factors (BCF) for zinc and copper were lower with increasing concentrations of the dredged sediment, indicating the existence of internal regulating processes. Although the BCF for mercury also decreased with the increasing test concentrations, the known no biological function of this metal in the earthworms metabolism lead to suppose that Hg measured was not present in bioaccumulable forms. BCFs estimated for the other metals were generally higher in the highest dredged sediment doses.     

Wind tunnel experimental study on the effect of PAM on soil wind erosion control

In recent years, high-molecular-weight anionic polyacrylamide (PAM) have been widely tested on a variety of soils, primarily in water erosion control. However, little information is available regarding the effectiveness of PAM on preventing soil loss from wind erosion. The research adopted room wind tunnel experiment, two kinds of soils were used which were from the agro-pastoral area of Inner Mongolia, the northwest of China, the clay content of soils were 22.0 and 13.7%, respectively. For these tests, all the treatments were performed under the condition of wind velocity of 14 m s(-1) and a blown angle of 8.75%, according to the actual situation of experimented area. The study results indicated that using PAM on the soil surface could enhance the capability of avoiding the wind erosion, at the same time, the effect of controlling wind soil erosion with 4 g m(-2) PAM was better than 2 g m(-2) PAM's. Economically, the 2 g m(-2) PAM used in soil surface can control wind erosion effectively in this region. The prophase PAM accumulated in soil could not improve the capability of avoiding the wind erosion, owing to the degradation of PAM in the soil and the continual tillage year after year. The texture of soil is a main factor influencing the capability of soil avoiding wind erosion. Soil with higher clay content has the higher capability of preventing soil from wind erosion than one with the opposite one under the together action of PAM and water.     

Changes in valued “Capacities” of soils and sediments as indicators of nonlinear and time-delayed environmental effects

This paper discusses the buffering, oxygen-donating, and sorption capacities of soils and sediments as an inter-connected system for regulating the retention and release of chemical pollutants. In this context, the author discusses the chemical conditions under which sediments may serve as a source or a sink for toxic materials, and conditions under which soils may retain or release them. It is demonstrated that nonlinear, time-delayed ecological transformations in soils and sediments often can be understood in terms of the interlinked system. The author discusses some possible future long-term environmental problems that might beset Europe, and some implications for a monitoring strategy for foresseing such problems.Because the release of adsorbed toxic chemicals from heavily polluted sediments and soils can occur suddenly owing to changes in oxygen status (i.e., redox potential) or acidity, strategies for preventing the long-term release of such materials should not only consider current conditions of pH and redox potential, but also, how those conditions might change in the future.     

Assessing the soil quality of alpine grasslands in the Qinghai-Tibetan Plateau using a modified soil quality index

Soil degradation has caused various problems on the planet. Human disturbance and land use changes always negatively affect soil quality. In this study, we used a modified soil quality index (SQI) to assess soil quality under differing degrees of human disturbance and land use. The alpine grasslands were studied at different levels of degradation [i.e., severely degraded grassland, heavily degraded grassland, moderately degraded grassland, and non-degraded grassland (NDG)] in a case study conducted in Qinghai-Tibetan Plateau (QTP) to test the feasibility of using the SQI. Fifteen chemical, physical, and biological soil parameters were measured in each type of grassland. Significant variations in SQI were found across the different types of grasslands according to severity of human disturbance and changes in land use. Urease, the ratio of microbial biomass nitrogen to total nitrogen, proteinase, and soil organic carbon were found to be the most important indicators for assessing soil quality. NDG had a higher SQI than the other three types of grasslands. It was concluded that SQI is effective for assessing the soil quality of alpine grasslands in the QTP. The intensity of human disturbance had a negative effect on soil quality in the QTP.     

Sediments deposition due to soil erosion in the watershed region of Mangla Dam

Soil erosion is the most important reason of sedimentation load of water reservoirs in the world. In Pakistan, Mangla dam is one of the most important water reservoirs used for the production of electricity and for the supply of water for irrigation purposes. However, the capacity of Mangla dam reservoir has reduced by more than 20% since its construction. This study highlights the impact of rainfall on soil erosion and consequently on sedimentation deposition in Mangla dam reservoir. Sedimentation, annual rainfall, and normal rainfall data of 39 years were used in this study. Shuttle Radar Topographic Mission data were used to calculate the total drainage area of the Mangla watershed region. The sedimentation data of Mangla reservoir from 1967 to 2005 were retrieved from Water and Power Development Authority in Pakistan. The meteorological observatories in the Mangla watershed region are identified. Annual rainfall data from 1967 to 2005 for the meteorological observatories in the Mangla watershed regions were retrieved from Pakistan Meteorological Department (PMD). In addition, normal rainfall data for the years 1949 to 1978 and for the years 1979 to 2008 were also retrieved from PMD. The impact of annual rainfall is observed on sedimentation load in Mangla dam. The correlation coefficient between annual rainfall and sedimentation load is 0.94. This study shows that with an increase in rainfall, the soil erosion of the area increases which subsequently is responsible for the increase in the rate of sedimentation load in Mangla dam. This study further demonstrates that better soil management can reduce the sedimentation load in the Mangla reservoir.     

Adapting the RUSLE and GIS to model soil erosion risk in a mountains karst watershed, Guizhou Province, China

Soil erosion is a serious environmental problem in Guizhou Province, which is located in the centre of the karst areas of southwestern China. Unfortunately, Guizhou Province suffers from a lack of financial resources to research, monitor and model soil erosion at large watershed. In order to assess the soil erosion risk, soil erosion modeling at the watershed scale are urgently needed to be undertaken. This study integrated the Revised Universal Soil Loss Equation (RUSLE) with a Geographic Information System (GIS) to estimate soil loss and identify the risk erosion areas in the Maotiao River watershed, which is a typical rural watershed in Guizhou Province. All factors used in the RUSLE were calculated for the watershed using local data. It was classified into five categories ranging from minimal risk to extreme erosion risk depending on the calculated soil erosion amount. The soil erosion map was linked to land use, elevation and slope maps to explore the relationship between soil erosion and environmental factors and identify the areas of soil erosion risk. The results can be used to advice the local government in prioritizing the areas of immediate erosion mitigation. The integrated approach allows for relatively easy, fast, and cost-effective estimation of spatially distributed soil erosion. It thus indicates that RUSLE-GIS model is a useful and efficient tool for evaluating and mapping soil erosion risk at a large watershed scale in Guizhou Province.     

C/N ratio and fossil pigments in sediments ofsome Estonian lakes: an evidence of human impact andHolocene environmental change

The content of carbon (C), nitrogen(N), fossil carotenoids (TC) and chlorophyllderivatives (CD) in the sediments of five Estonianlakes was analysed. Historical records of man-inducedchanges on catchments were used for the interpretationof the obtained data. On the basis of the C/N ratiosit was estimated that the planktonic matter formed ca.25% (C/N ratio 24) to 90% (C/N ratio 8) of theorganic pool matter of lake sediments. In eutrophicLake Ruusmäe the fraction of the phytoplanktonproduced in lakes was highest, amounting toapproximately 80–95% of the deposited organic matter.Remarkable C/N changes were noted in the sedimentsfrom lakes Matsimäe and Viitna, where the contentof planktonic matter has increased during lastdecades, reflecting an increase in recreationalactivity around these lakes. The variations in pigmentconcentrations in the sediments of lakes Matsimäeand Ruusmäe could be explained by changes in theland-use that have altered the intensity of primaryproduction and conditions of TC and CD degradationbefore the final burial.     

Spatio-temporal analysis of land use/land cover change and its effects on soil erosion (Case study in the Oplenac wine-producing area,Serbia)

In this paper, various spatial modelling techniques were applied to analyse changes in soil cover and their impact on soil erosion in the Oplenac wine-producing area in Serbia in the past (1985 and 2013) and in the future (with predictions for 2041). The Integrated Valuation of Ecosystem Services and Trade-offs Sediment Delivery Ratio (InVEST SDR) model and the Modules for Land Use Change Evaluation (MOLUSCE) model, integrated with methods of remote sensing, were successfully applied and were shown to be valid tools for predicting the impact of Land Use Land Cover (LULC) changes when estimating soil loss. The results revealed that the greatest impact of land use changes between 1985 and 2013 was on a reduction in areas under vineyards and an extension of meadow and pasturelands as an individual and social response to economic conditions during the research period. The forecast for 2041 reflected the trends observed in the previous period, with the greatest changes witnessing an increase in urban areas and a decrease in areas of arable land. It was also found that the effect of LULC changes on spatio-temporal patterns in the Oplenac wine-producing area did not have a major impact on soil loss, meaning this area, with its good agro-climatic characteristics, is suitable for the intensification of agricultural production.     

The role of forest stand density in controlling soil erosion: implications to sediment-related disasters in Japan

The role of forest stand density in controlling soil erosion was investigated in Ehime Prefecture, Japan. The main objective was to compare soil erosion under different forest conditions including forest type, species composition, and stand density as influenced by thinning operations. Relative yield index (Ry) was used as an indicator of stand density to reflect the degree of management operations in the watershed. Eleven treatments were established based on the above forest conditions. Soil loss was collected in each of the 11 treatments after each rainfall event for a period of 1 year. The paper presents summary data on soil loss as affected by forest conditions and rainfall patterns. Findings showed that an appropriate forest management operation, which can be insured by stand density control, is needed to reduce soil loss. The present study plays an important role in clarifying technical processes related to soil erosion, while it helps linking these elements to current Japanese forestry issues and bringing new inputs to reducing sediment-related disasters in Japan.     

Using ecological memory as an indicator to monitor the ecological restoration of four forest plantations in subtropical China

A large area of plantations has been established worldwide and especially in China. Evaluating the restoration status of these plantations is essential for their long-term management. Based on our previous work, we used an ecological memory (EM) approach to evaluate four 26-year-old plantations that represent four common kinds of plantations in subtropical China, i.e., mixed broad-leaved plantation (MBP), mixed coniferous plantation (MCP), eucalyptus plantation (EP), and mixed legume plantation (MLP). Comparing them with the regional climax community, i.e., monsoon evergreen broad-leaved forest (BF), all four plantations accumulated nearly the same pattern of EM during succession. EM was >50 % for soil minerals, light conditions, soil age, soil animals, and soil microbes. EM was about 25 % for soil pollen and 10 % for birds, soil seed bank, and plant species. The total EM value of the four plantations ranged from 50.96 to 52.54, which indicated that all four plantations were in the regional, natural trajectory of succession and between the early and medium successional stages. The results indicated that natural succession processes are unlikely to be accelerated by planting late-stage tree species without sufficient EM. The results also demonstrated that all four plantations were in positive successional trajectories, and the positive succession dynamics were greater in the MLP and MCP. We suggest that the entire natural succession trajectory be used to evaluate the restoration of a site and that the ultimate restoration target be divided into several milestones along the reference trajectory to monitor progress. Forest restoration may be accelerated by starting with a minimum dynamic unit supporting sufficient EM.