Winter Soil Respiration from Different Vegetation Patches in the Yellow River Delta, China

Vegetation type and density exhibited a considerable patchy distribution at very local scales in the Yellow River Delta, due to the spatial variation of soil salinity and water scarcity. We proposed that soil respiration is affected by the spatial variations in vegetation type and soil chemical properties and tested this hypothesis in three different vegetation patches (Phragmites australis, Suaeda heteroptera and bare soil) in winter (from November 2010 to April 2011). At diurnal scale, soil respiration all displayed single-peak curves and asymmetric patterns in the three vegetation patches; At seasonal scale, soil respiration all declined steadily until February, and then increased to a peak in next April. But, the magnitude of soil respiration showed significant differences among the three sites. Mean soil respiration rates in winter were 0.60, 0.45 and 0.17 μmol CO(2) m(-2) s(-1) for the Phragmites australis, Suaeda heteroptera and bare soil, respectively. The combined effect of soil temperature and soil moisture accounted for 58-68 % of the seasonal variation of winter soil respiration. The mean soil respiration revealed positive and linear correlations with total N, total N and SOC storages at 0-20 cm depth, and plant biomass among the three sites. We conclude that the patchy distribution of plant biomass and soil chemical properties (total C, total N and SOC) may affect decomposition rate of soil organic matter in winter, thereby leading to spatial variations in soil respiration.     

Woody Vegetation Composition and Structure in Peri-urban Chongming Island, China

Chongming, the world’s largest alluvial island, is located within the municipality of Shanghai, China. Recent projects have now linked peri-urban Chongming to Shanghai’s urban core and as a result will soon undergo substantial changes from urbanization. We quantitatively analyzed the structure and composition of woody vegetation across subtropical, peri-urban Chongming as a basis for sustainable management of these rapidly urbanizing subtropical ecosystems elsewhere. We used 178 permanent, random plots to statistically and spatially analyze woody plant composition and tree structure across the 1,041 km² of Chongming. A total of 2,251 woody plants were measured comprising 42 species in 37 genera. We statistically and geospatially analyzed field data according to land uses and modeled air pollution removal by trees. Average tree diameter at breast height, total height, and crown widths on transportation land uses were greater than other land uses. These same values were lowest on forest land use and greater tree cover was associated with areas of increased anthropogenic activity. Less than 20 % of the woody vegetation was exotic and a species richness index was significantly different between land uses due to legacy effects. Composition of agriculture and forest land uses were similar to residential and transportation. Tree cover across Chongming was also estimated to annually remove 1,400 tons of air pollutants. We propose that this integrated and quantitative method can be used in other subtropical, peri-urban areas in developing countries to establish baseline trends for future sustainability objectives and to monitor the effects of urbanization and climate change.     

Effect of Prescribed Fire on Soil Properties and N Transformation in Two Vegetation Types in South China

Prescribed fire is a common site preparation practice in forest management in southern China. However, the effect of fire on soil properties and N transformations is still poorly understood in this region. In this study, soil properties and N transformations in burned and unburned site of two vegetation types (Eucalyptus plantation and shrubland) were compared in rainy and dry seasons after 2 years’ prescribed fire. Soil pH and soil NH₄-N were all higher in the burned site compared to the unburned control. Furthermore, burned sites had 30–40 % lower of soil total phosphorus than conspecific unburned sites. There was no difference in soil organic matter, total N, soil exchangeable cations, available P or NO₃-N. Nitrogen mineralization rate of 0–5 cm soil in the unburned site ranged from 8.24 to 11.6 mg N kg^?1 soil month^?1 in the rainy season, compared to a lower level of 4.82–5.25 mg N kg^?1 soil month^?1 in the burned sites. In contrast, 0–5 cm layer nitrification rate was overall 2.47 mg N kg^?1 soil month^?1 in the rainy season, and was not significantly affected by burning. The reduced understory vegetation coverage after burning may be responsible for the higher soil NH₄-N in the burned site. This study highlights that a better understanding the effect of prescribed burning on soil nutrients cycling would provide a critical foundation for management decision and be beneficial to afforestation in southern China.     

Plant Communities,Soil Carbon,and Soil Nitrogen Properties in a Successional Gradient of Sub-Alpine Meadows on the Eastern Tibetan Plateau of China

To assess the recovery trajectory and self-maintenance of restored ecosystems, a successional gradient (1, 3, 5, 15, and 30 years after abandonment) was established in a sub-alpine meadow of the eastern Tibetan Plateau in China. Plant communities and soil carbon and nitrogen properties were investigated and analyzed. Regression analyses were used to assess the models (linear or quadratic) relating measures of species richness, soil carbon and nitrogen properties to fallow time. We found that species richness (S) increased over the first 20 years but decreased thereafter, and aboveground biomass showed a linear increase along the fallow time gradient. The richness of different functional groups (forb, grass and legume) changed little along the fallow time gradient, but their corresponding above ground biomass showed the U-shaped, humped or linear pattern. Soil microbial carbon (MBC) and nitrogen (MBN) in the upper 20 cm showed a U-shaped pattern along the fallow time gradient. However, soil organic carbon (C_org) and total nitrogen (TN) in the soil at depth greater than 20 cm showed significant patterns of linear decline along the fallow time gradient. The threshold models of species richness reflected best the recovery over the 15 year fallow period. These results indicated that fallow time had a greater influence on development of the plant community than soil processes in abandoned fields in sub-alpine meadow ecosystem. These results also suggested that although the succession process did not significantly increase soil C, an increase in microbial biomass at the latter stage of succession could promote the decomposability of plant litter. Therefore, abandoned fields in sub-alpine meadow ecosystem may have a high resilience and strong rehabilitating capability under natural recovery condition.     

Spatiotemporal Variation of Karst Ecosystem Service Values and Its Correlation with Environmental Factors in Northwest Guangxi,China

In this investigation we analyzed the spatiotemporal variation of ecosystem service values (ESVs) and its correlation with numerous environmental factors (EFs) for the karst region of Northwest Guangxi, China, from 1985 to 2005 using remote sensing, geographic information systems (GIS) and statistical techniques. The results indicate that historically ESVs for this karst region decreased from 1985 (109.652 billion Yuan) to 1990 (88.789 billion Yuan) and then increased at the turn of the twenty-first century. However, the ESVs in both 2000 (103.384 billion Yuan) and 2005 (106.257 billion Yuan) never achieved the level recorded in 1985. The total of nutrient cycling, organic production and gas regulation combined were 72.69, 64.57, 70.18 and 72.10% of ESVs in 1985, 1990, 2000 and 2005, respectively. In contrast, the ESVs of water conservation, soil reservation, recreation and culture were determined to be relatively low contributing only 17.44, 23.82, 19.26 and 24.76% of total ESVs, respectively, during these four years. With regards to the spatial distribution of ESVs, larger values were recorded in the west and smaller ones recorded in the east. The most significant factors that were deemed to influence ESVs are annual rainfall, per capita cropland, slope and vegetation coverage. Annual rainfall and slope exert a negative force, whereas per capita cropland and vegetation coverage exert a positive force on ESVs. The results of the study would suggest that ecosystem conditions of this important karst region have been improved as the result of the implementation of rocky desertification control policies.     

宁夏灌区不同类型农田土壤氮素累积与迁移特征

在宁夏灌区选择设施菜田（n=4）和水旱轮作大田（n=4）,通过田间多点取样观测和室内分析的方法,研究了2种类型农田土壤氮素累积与分布特点,以及其迁移对浅层地下水的影响。结果表明,设施菜田0~150 cm土壤剖面溶解性总氮（TSN）、硝态氮（NO3--N）和溶解性有机氮（SON）含量都显著高于大田,前者分别是后者的1.5~5.6、1.5~3.4倍和1.6~9.8倍。设施菜田土壤氮素主要累积在0~5 cm和5~20 cm土层,而大田主要在40~100 cm土体。设施菜田和大田土壤溶解性总氮占全氮比例分别在5.4%~11.5%和2.2%~4.9%之间,前者的淋失风险较高。设施菜田各形态氮素累积量表现为SON＆gt;NO3--N＆gt;NH4＋-N,大田为NO3--N＆gt;SON＆gt;NH4＋-N。设施菜田浅层地下水中TSN、NO3--N和SON含量也都显著高于大田,前者平均含量分别是后者的9.5、13.8倍和7.0倍。因此,硝态氮和溶解性有机氮都是2种类型农田氮素累积的主要形态,也是浅层地下水污染的重要来源。     

Comparison of the Vegetation and Seed Bank on Hedge Banks of Different Ages in Brittany,France

The composition of the herbaceous cover and the seed bank of old and recent hedge banks in Brittany were studied and compared. Concentration method was used for seed bank samples. Grimes plant strategies were used to explain observed patterns. The analysis of the seed bank of these hedge banks showed that the species richness and diversity differed in relation to the date of construction of the hedge banks. The seed banks of recent hedge banks were richer and more diversified than those of old hedge banks. Differences in the floristic composition of the established plant cover between the recent and old hedge banks were determined by multivariate analyses. The species exclusively found in the seed bank and in the herb cover of recent hedge banks were mainly grassland species, whereas the species that only occurred on old hedge banks tended to be woodland species. The floristic composition of the two compartments (established vegetation and seed bank) was very different. A multivariate analysis revealed that the difference between the composition of the seed banks of recent and old hedge banks was less than that between the composition of the established vegetation and seed bank of hedge banks of the same age. Both seed bank and vegetation of recent hedge banks were dominated by ruderal species, whereas old hedge vegetation was dominated by stress-tolerant woodland species, indicating that mechanically constructed hedge banks may impose limitations on colonization by late woodland species.     

Georelational Analysis of Soil Type, Soil Salt Content, Landform, and Land Use in the Yellow River Delta, China

The Yellow River Delta, one of China’s three major river deltas, is becoming a major region for the development of agriculture and fisheries. Protecting the delicate ecology of newly formed aquatic systems as well as the evolution of soils, natural vegetation, and fauna on older upland environments in the delta is a priority in planning for the wise use of the delta’s resources for future agricultural development. In this article, we use a Geographic Information System (GIS) to analyze relationships between land-use/land-cover characteristics in the Dongying municipality, one of the most intensely developed areas of the delta, and spatial variations in soil salinity and landforms. This analysis reveals that soil salt content decreases from regionally high values in isolated depressions to relatively moderate values in embanked former back swamps, with the lowest values occurring in abandoned river courses. Comparing the present land use on this soil salinity–landform pattern shows that it is basically at odds with general concepts of land suitability for agricultural utilization of saline soils. Crop-based agriculture in the region is probably overdeveloped, whereas more appropriate agricultural development, like cattle and forest production, is underrepresented. Future development should focus on converting farmland in embanked former back swamps and abandoned river courses into grasslands and forests. Crop-based agriculture (up to 151,000 ha) could be planned at the low-salinity terrace uplands and flood plains. The article provides guidelines for decision-makers regarding agricultural land use and wetland protection in the Yellow River Delta.     

The Ecological and Environmental Characteristics and Conservation of the Wetlands in the Changjiang Estuary, China

The natural wetlands in the Changjiang Estuary, China are important ecologically. The total area of the wetlands in the Changjiang Estuary amounts to 215000 ha. The wetlands consist of littoral and sandy estuarine island areas, and are rich in biological resources. There are 136 species of vascular plant, 150 species of bird, and 68 species of benthic macro-invertebrate in the wetlands. However, the wetland in the Changjiang Estuary is a vulnerable ecosystem. Development of the wetland is mainly influenced by intensive human reclamation, pollution, movement of sediments in the Changjiang River, and the effects of tides and waves. Investigations have shown that maintaining biodiversity, providing resources for the living organisms, purifying environments and resisting natural hazards could be regarded as important functions for the protection of the wetlands. It is proposed that sustainable principles should be supported in developing the wetlands in the future.     

Effects of Tourism and Topography on Vegetation Diversity in the Subalpine Meadows of the Dongling Mountains of Beijing,China

Subalpine meadows in the Dongling Mountains (located at E115o26′-115o40′, N40o00′-40o05′) of Beijing, China are important for tourism and the provision of ecosystem services. However, because of poor management serious degradation has occurred on these subalpine meadows. The aim of this paper is to present a quantitative analysis of effects of tourism disturbance and topography on the status and diversity of montane meadow communities and to provide direction for improved management. Sixty quadrats of 2 × 2 m² along 10 transects were set up to collect data on site characteristics and vegetation status. The relationships between community composition and structure, species diversity, and tourism disturbance and topographic variables were analyzed by multivariate methods (TWINSPAN and CCA). The results showed that eight meadow communities were identified by TWINSPAN. Most of them were seriously degraded. The first CCA axis identified an elevation and tourism disturbance intensity gradient, which illustrated that tourism disturbance and elevation were most important factors influencing meadow types, composition and structure. Some resistant species and response species to tourism disturbance were identified and can be used as indicator species of tourism disturbance. Species richness, heterogeneity and evenness were closely related to tourism disturbance and elevation. It is concluded that tourism disturbance must be controlled to enable grassland rehabilitation to occur in the meadows. Measures of effective management of the meadows were discussed.     

Effects of Grazing Exclusion on Soil Properties and on Ecosystem Carbon and Nitrogen Storage in a Sandy Rangeland of Inner Mongolia, Northern China

The Horqin sandy rangeland of northern China is a seriously desertified region with a fragile ecology. The sandy alluvial and aeolian sediments have a coarse texture and loose structure and are therefore vulnerable to damage caused by grazing animals and wind erosion. We investigated whether grazing exclusion could enhance ecosystem carbon (C) and nitrogen (N) storage and thereby improve overall soil quality. We compared soil properties, C and N storage in biomass (aboveground and below-ground), and the total and light fraction soil organic matter between adjacent areas with continuous grazing and a 12-year grazing exclosure. The soil silt?+?clay content, organic C, total Kjeldahl N, available N and K, and cation-exchange capacity were significantly (P?相似文献   

Changes in Soil Properties After Establishment of Artemisia halodendron and Caragana microphylla on Shifting Sand Dunes in Semiarid Horqin Sandy Land, Northern China

In the semiarid Horqin sandy land of northern China, establishment of artificial sand-fixing shrubs on desertified sandy lands is an effective measure to control desertification and improve the regional environment. Caragana microphylla Lam. and Artemisia halodendron Turcz. ex Bess. are two of the dominant native shrub species, which are adapted well to windy and sandy environments, and thus, are widely used in revegetation programs to control desertification in Horqin region. To assess the effects of artificially planting these two shrub species on restoration of desertified sandy land, soil properties and plant colonization were measured 6 years after planting shrubs on shifting sand dunes. Soil samples were taken from two depths (0–5 cm and 5–20 cm) under the shrub canopy, in the mid-row location (alley) between shrub belts, and from nonvegetated shifting sand dune (as a control). Soil fine fractions, soil water holding capacity, soil organic C and total N have significantly increased, and pH and bulk density have declined at the 0–5-cm topsoil in both C. microphylla and A. halodendron. At the 5–20 cm subsurface soil, changes in soil properties are not significant, with exception of bulk density and organic C concentration under the canopy of A. halodendron and total N concentration under the canopy of C. microphylla. Soil amelioration processes are initiated under the shrub canopies, as higher C and N concentrations were found under the canopies compared with alleys. At the same time, the establishment of shrubs facilitates the colonization and development of herbaceous species. A. halodendron proved to have better effects in fixing the sand surface, improving soil properties, and restoring plant species in comparison to C. microphylla.     

Wetland Degradation: Its Driving Forces and Environmental Impacts in the Sanjiang Plain,China

This study investigated human-induced long-term wetland degradation that occurred in the Sanjiang Plain. Results from analyzing land-use/land-cover data sets derived from remotely sensed Landsat Multispectral Scanner/Thematic Mapper imagery for four time points showed that wetlands in the Sanjiang Plain have been severely transformed, and the area of wetlands decreased by 38 % from 1976 to 1986, by 16 % from 1986 to 1995, and by 31 % from 1995 to 2005. This study showed that transition to agricultural cultivation accounted for 91 % of wetland losses, whereas transition to grassland and forest accounted for 7 % of the wetlands losses. Institutional strategies and market policies probably exerted great impacts on agricultural practice that directly or indirectly influenced the decrease in wetlands. This study also indicated that an increased population likely led to wetland conversion to cropland by showing a high correlation between population and cropland (R ² = 0.92, P < 0.001). Wetland loss occurred during later time intervals at a low rate. This study suggests that the existing wetland-protection measures in the Sanjiang Plain should be reinforced further because of possible environmental consequences of wetland loss, such as enhanced soil carbon emission, changed hydrological cycling, and regional temperature increase.     

论我国环境教育体系构建的思路、原则与对策

随着可持续发展日益成为人类社会发展的大势所趋,实施以环境保护与可持续发展为主要内容的全民终身环境教育已日趋必要与紧迫。本文运用环境保护理论及教育学的基本原理,从世界与我国环境教育的形成与历史演变着手,论述了我国环境教育体系构建的目标、思路、原则及其主要内容,最后提出了建议与对策。     

Environmental Implications of the Erosion of Cultural Taboo Practices in Awka-South Local Government Area of Anambra State, Nigeria: 1. Forests, Trees, and Water Resource Preservation

Cultural taboos and their sanctionshave helped to check abuse of the environmentat least among the local people. The disregardfor these traditional checks and balancesespecially among Christians has adverselyaffected their enforcement at this time. Theenvironment and culture preservation inAwka-South were investigated. The faithfulobservance of the traditional laws in the studyarea was attributed to the fact that Awka-Southarea had remained occupied by the same peoplefor centuries. The study showed that thepreserved forests and their shrines in Nibotown have largely remained intact. In Nisetown, however, with nine shrines still inexistence, the rules have relaxed a little,mainly because they embraced modernization. Inthis town, the fringes of the forests may beused for farming but no felling of trees wouldbe allowed. The ``god' of the shrine in Obunaguvillage was much revered until the advent ofChristianity. This religion has had an erodingeffect on the taboos, which were put in placeto protect their forests and streams. Theabandonment of traditional cultural practicesis doing harm that goes beyond the abrogationof traditional cultural practices to seriousthreat to natural environmental structures. Thecultures of the different tribes in Nigerianeed to be revisited for evaluation and studiesto enable their integration into modernpractices that will make the environment moresustainable. This will be more productive thanthe unilateral introduction of programs,execution, and maintenance methods that arecompletely new, or in many cases run contraryto the cultural practices of the local peopleand tribes of Nigeria.     

Quantifying the Effects of Conservation Practices on Soil,Water, and Nutrients in the Loess Mesa Ravine Region of the Loess Plateau,China

A large number of soil and water conservation programs have been implemented on the Loess Plateau of China since the 1950s. To comprehensively assess the merits and demerits of the conservation practices is of great importance in further supervising the conservation strategy for the Loess Plateau. This study calculates the impact factors of conservation practices on soil, water, and nutrients during the period 1954–2004 in the Nanxiaohegou Catchment, a representative catchment in the Loess Mesa Ravine Region of the Loess Plateau, China. Brief conclusions could be drawn as follows: (1) Soil erosion and nutrient loss had been greatly mitigated through various conservation practices. About half of the total transported water and 94.8 % of the total transported soil and nutrients, had been locally retained in the selected catchment. The soil retained from small watersheds do not only form large-scale fertile farmland but also safeguard the Yellow River against overflow. (2) Check dam was the most appropriate conservation practice on the Loess Plateau. In the selected catchment, more than 90 % of the retained soil and water were accomplished by the dam farmland, although the dam farmland occupied only 2.3 % of the total area of all conservation measures. Retention abilities of the characteristic conservation practices were in the following order: dam farmland > terrace farmland > forest land and grassland. (3) The conservation practices were more powerful in retaining sediment than in reducing runoff from the Loess Plateau, and the negative effects of the conservation practices on reducing water to the Yellow River were relatively slight.     

Differential Effects of Legume Species on the Recovery of Soil Microbial Communities, and Carbon and Nitrogen Contents, in Abandoned Fields of the Loess Plateau, China

Plant–soil interactions are known to influence a wide range of ecosystem-level functions. Moreover, the recovery of these functions is of importance for the successful restoration of soils that have been degraded through intensive and/or inappropriate land use. Here, we assessed the effect of planting treatments commonly used to accelerate rates of grassland restoration, namely introduction of different legume species Medicago sativa, Astragalus adsurgens, Melilotus suaveolens, on the recovery of soil microbial communities and carbon and nitrogen contents in abandoned fields of the Loess Plateau, China. The results showed effects were species-specific, and either positive, neutral or negative depending on the measure and time-scale. All legumes increased basal respiration and metabolic quotient and had a positive effect on activity and functional diversity of the soil microbial community, measured using Biolog EcoPlate. However, soil under Astragalus adsurgens had the highest activity and functional diversity relative to the other treatments. Soil carbon and nitrogen content and microbial biomass were effectively restored in 3–5?years by introducing Medicago sativa and Astragalus adsurgens into early abandoned fields. Soil carbon and nitrogen content were retarded in 3–5?years and microbial biomass was retarded in the fifth year by introducing Melilotus suaveolens. Overall, the restoration practices of planting legumes can significantly affect soil carbon and nitrogen contents, and the biomass, activity, and functional diversity of soil microbial community. Therefore, we propose certain legume species could be used to accelerate ecological restoration of degraded soils, hence assist in the protection and preservation of the environment.     

Changes in Soil Aggregate,Carbon, and Nitrogen Storages Following the Conversion of Cropland to Alfalfa Forage Land in the Marginal Oasis of Northwest China

Maintenance of soil organic carbon (SOC) is important for sustainable use of soil resources due to the multiple effects of SOC on soil nutrient status and soil structural stability. The objective of this study was to identify the changes in soil aggregate distribution and stability, SOC, and nitrogen (N) concentrations after cropland was converted to perennial alfalfa (Medicago sativa L. Algonguin) grassland for 6 years in the marginal oasis of the middle of Hexi Corridor region, northwest China. Significant changes in the size distribution of dry-sieving aggregates and water-stable aggregates, SOC, and N concentrations occurred after the conversion from crop to alfalfa. SOC and N stocks increased by 20.2% and 18.5%, respectively, and the estimated C and N sequestration rates were 0.4 Mg C ha⁻¹ year⁻¹ and 0.04 Mg N ha⁻¹ year⁻¹ following the conversion. The large aggregate (>5 mm) was the most abundant dry aggregate size fraction in both crop and alfalfa soils, and significant difference in the distribution of dry aggregates between the two land use types occurred only in the >5 mm aggregate fraction. The percentage of water-stable macroaggregates (>2, 2–0.25 mm) and aggregate stability (mean weight diameter of water-stable aggregates, WMWD) were significantly higher in alfalfa soils than in crop soils. There was a significant linear relationship between total SOC concentration and aggregate parameters (mean weight diameter) for alfalfa soils, indicating that aggregate stability was closely associated with increased SOC concentration following the conversion of crops to alfalfa. The SOC and N concentrations and the C/N ratio were greatest in the >2 mm water-stable aggregates and the smallest in the 0.25–0.05 mm aggregates in crop and alfalfa soils. For the same aggregate, SOC and N concentrations in aggregate fractions increased with increasing total SOC and N concentrations. The result showed that the conversion of annual crops to alfalfa in the marginal land with coarse-texture soils can significantly increase SOC and N stocks, and improve soil structure.