Analysis of Land Use Change and Associated Implications on Soil Ecosystem Functions in South Eastern Nigeria

Land use change affects soil functions and its capacity to provide ecosystem services. Though much of the tropics are experiencing accelerated increases in land use change, associated impacts of such changes are poorly understood and studied. This study assessed the extent to which land use changes affect the soil ecosystem functions in a rainforest zone of south eastern Nigeria. Soil samples were collected from 24 sample locations in selected natural forest, cashew and palm plantations. Samples were analyzed in triplicate in the laboratory for geochemical analysis, after which the result was subjected to statistical analysis—ANOVA, correlation and regression. Forest carbon had higher % mean carbon content;though there was no significant difference (F (2, 21) = .246, p = .784) in carbon level across land uses. R value of .301 showed low correlation between % carbon, organic matter and % loss in ignition. Furthermore, R2 value of 9.1% total variation in the dependent variable could only be explained by the independent variables. CEC, Nitrogen, Potassium and Phosphorus content of the land uses did not differ significantly: CEC (F (2, 21) = .844, p (.44);Nitrogen (.243), p (.79), Potassium (.140), p (.87), Phosphorus (.783), p (.47). This showed that there was no significant variation in soil fertility of the land uses, although natural forest had higher concentrations for these variables. Across the land uses, soil texture equally had no significant variations: % sand (F (2, 21) = .320, p (.729) % clay (.430), p (.656), % silt (.043), p (.958). Soil carbon was seen to be more enhanced in natural forest ecosystems than other land uses. Though plantations had reduced capacities to provide ecosystem functions, establishing such in modified landscapes is still advocated as they can coexist with such and yet ensure ecosystem functions.

Preliminary Study on Biological Characteristics of Degraded Soil Ecosystems in Dry Hot Valley of the Jinsha River

Distribution characteristics of soil animals, microorganisms and enzymatic activity were studied in the dry red soil and Vertisol ecosystems with different degradation degrees in the Yuanmou dry hot valley of the Jinsha River, China. Results showed that Hymenoptera, Araneae and Collembola were the dominant groups of soil animals in the plots studied. The numbers of groups and individuals and density of soil animals in the dry red soil series were higher than those in the Vertisol series, and the numbers of individuals and density of soil animals decreased with the degree of soil degradation. Bacteria dominated microbiocoenosis not only in the dry red soils but also in the Vertisols. Microbial numbers of the dry red soil series were higher than those of Vertisol series, and decreased with the degree of soil degradation. The activities of catalase, invertase, urease and alkaline phosphatase declined with the degradation degree and showed a significant decline with depth in the profiles of both the dry red soils and the Vertisols, but activities of polyphenol oxidase and acid and neutral phosphatase showed the same tendencies only in the Vertisols. It was concluded that the characteristics of soil animals, microorganisms and enzymatic activity could be used as the bio-indicators to show the degradation degree of the dry red soils and Vertisols. Correlation among these soil bio-indicators was highly significant.

Differentiation of Soil Fauna Populations in Conventional Tillage and No-Tillage Red Soil Ecosystems

In a field experiment, the populations of major soil fauna groups including earthworms, enchytraeids,arthropods and nematodes were examined in conventional tillage (CT) and no-tillage (NT) red soil ecosystems to evaluate their responses to tillage disturbance. Earthworms, macrry and micro-arthropods were stimulated under NT with earthworms showing the highest population increase by four times, while enchytraeids and nematodes favored CT system, predicting certain adaptability of these animals to plow-disturbed soil environment. On the basis of relative response index it was found that soil fauna was more sensitive to tillage than soil resource base (C and N pools) and microflora. The population structure of soil fauna was also affected by tillage treatments. Analysis on nematode trophic groups showed that bacteria-feeding and plant parasitic nematodes were more abundant in CT soil whereas the proportions of fungivores and omnivorepredators increased in NT soil. Possible reasons for the differentiation in both size and structure of the fauna population were discussed and the ecological significance involved in these changes was emphasized.

Soil Ecosystem Degradation of Karst Regions in Southwestern China

Deeply influenced by karst geological environment, the structure of the soil ecosystem in the southwest karst area of China is characterized by strong vertical variation and space variation, structural feature of nonrenewable soil, and functional feature of poor circulation of nutrient elements and limited vegetation growth. On the basis of analyzing vulnerability in structure and function of soil ecosystem in China's southwestern karst regions, we discussed the degradation process and mechanism of soil structure, nutrient, water and microorganism in the course of soil erosion from the perspective of material and energy cycle. Finally, we put forward some recommendations for recovery of degraded soil, transformation and rational utilization of soil.

Contribution of Herbaceous Plants and Their Status and Role in Soil and Water Ecosystem

In this paper,the contemporary understanding process of herbaceous plants and their contributions are elaborated.The systematic idea of"mountain,river,forest,field,lake,and grass are a community of life"has led the grass to enter a new era of development.Broadly speaking,vegetation includes grassland,forest,crop,garden,etc.,while herbaceous vegetation is the most widely distributed on earth.From the macro and micro perspectives of soil and water ecology,this paper discusses the position and role of herbaceous vegetation in the earth's soil and water ecosystem,especially the fundamental position in mountain,river,forest,field,lake,grass and sand.Starting from the concept of soil and water ecology,the integrated protection and systematic management of mountain,river,forest,field,lake,grassland,and sand is proposed.Essentially,it is the protection and management of soil and water ecology,which summarizes various ecological systems on earth.The successful application of herbaceous plants in ecological restoration projects of mine has further enriched and developed the theory of soil and water ecology.

Assessment of the Variations in Soil Physicochemical Parameters of the Natural Forest and Plantations in Orumba North Local Government Area, Anambra State, Nigeria

Soil physicochemical parameters are the physical and chemical characteristics of soil such as pH, bulk density, organic carbon, nitrogen content, and nutrient levels at different soil depths. These parameters vary from one vegetation to the other and from one soil to the other. The study assessed the variations in soil physicochemical parameters of the natural forest and plantations in Agu Eke (Eke bush) in Etti village, Nanka and Umunnebo village, Ufuma both located in Orumba North Local Government Area, Anambra State. The experimental research design and stratified random sampling methods were used for the study and a total of 12 soil samples were collected at 30 cm depth from the selected locations of natural forest, cashew and palm plantations. The samples were analyzed using laboratory Varian AA240 Atomic Absorption Spectrophotometer, after which the result was subjected to statistical analysis—Analysis of Variance (ANOVA). The study found that there was no significant difference (variation) between the moisture contents of natural forests and the plantations;that is, the moisture contents were the same. It was also found that there was no significant variation between the bulk densities of the natural forest, oil plantation, and cashew plantation, meaning that the bulk densities were significantly the same. However, there were significant variations in nitrogen, potassium and phosphates, with p-values: sig = .000 < .05, sig = .010 < .05 and sig = .000 < .05, respectively. That is, the nitrogen and phosphate contents of the natural forest significantly vary more than those of the oil palm and cashew plantations, which probably means that by reducing natural forest to plantation, the nitrogen and phosphate contents of the natural forest reduced from what it used to be when the lands were mere forests. This shows that plantations do not have the same function of maintaining or improving soil quality as natural forests. The study recommended adopting a sustainable plantation agricultural system, such as using diverse nutrient sources (manure and compost), in order to maintain the desired soil quality.

Changes in Ecosystem Service of Soil Conservation Between 2000 and 2010 and Its Driving Factors in Southwestern China

Human activities significantly alter ecosystems and their services; however, quantifying the impact of human activities on ecosystems has been a great challenge in ecosystem management. We used the Universal Soil Loss Equation and county-level socioeconomic data to assess the changes in the ecosystem service of soil conservation between 2000 and 2010, and to analyze its spatial characteristics and driving factors in the southwestern China. The results showed that cropland in the southwestern China decreased by 3.74%, while urban land, forest, and grassland areas increased by 46.78%, 0.86%, and 1.12%, respectively. The soil conservation increased by 1.88 × 10^(11) kg, with deterioration only in some local areas. The improved and the degraded areas accounted for 6.41% and 2.44% of the total land area, respectively. Implementation of the Sloping Land Conversion Program and urbanization explained 57.80% and 23.90% of the variation in the soil conservation change, respectively, and were found to be the main factors enhancing soil conservation. The 2008 Wenchuan earthquake was one of the factors that led to the degradation of soil conservation. Furthermore, industrial adjustment, by increasing shares of Industry and Service and reducing those of Agriculture, has also promoted soil conservation. Our results quantitatively showed and emphasized the contributions to soil conservation improvement made by implementing ecological restoration programs and promoting urbanization. Consequently, these results provide basic information to improve our understanding of the effects of ecological restoration programs, and help guide future sustainable urban development and regional industrial restructuring.

Arbuscular mycorrhizal symbiosis and ecosystem processes: Prospects for future research in tropical soils

Arbuscular mycorrhizal fungi (AMF) are more widely distributed and can associate with a wide range of plant species. AMF are keystone organisms that form an interface between soils and plant roots. They are also sensitive to environmental changes. AMF are important microbial symbioses for plants under conditions of P-limitation. The AMF are crucial for the functioning of terrestrial ecosystems as they form symbiotic interactions with plants. Mycorrhizal fungi are known to influence plant diversity patterns in a variety of ecosystems globally. AMF hyphae form an extensive network in the soil. The length is a common parameter used to quantifying fungal hyphae. The mycelial network of AM fungi extends into the soil volume and greatly increases the surface area for the uptake of immobile nutrients. Also, AM symbioses improve plants tolerance to drought and enhance plants’ tolerance of or resistance to root pathogens. Also, the networks of AM hyphae play a crucial role in the formation of stable soil aggregates and in the building up of a macroporous structure of soil that allows penetration of water and air and thereby prevents erosion. The functioning of AMF symbiosis is mediated by direct and indirect effects of biotic and abiotic factors of the surrounding rhizosphere, the community, and the ecosystem. AMF have great potential in the restoration of disturbed land and low fertility soil. However, despite the importance of AMF to terrestrial ecosystems, little is known about the effects of environmental changes on AMF abundance, activity and the impact of these changes on the ecosystem services. Therefore, it is important to gain a clearer understanding of the effects of environmental changes on the AM fungal species to guide conservation and restoration efforts.

Application of fractal theory in assessing soil aggregates in Indian tropical ecosystems

Soil aggregation varies according to climatic and manage- ment factors, and is difficult to measure because of irregular shapes and sizes of soil aggregates. We applied fractal theory to assess soil aggrega- tion as affected by （1） land use change from forest to savanna, （2） nutri- ent additions in forest, ecotone, and savanna ecosystems, and （3） tillage practice and residue treatments in an agro-ecosystem. We used fractal dimensions nonlinear （D,o,-lin） and linear （Dlin） based on number of ag- gregates （N） and mass of aggregates （M） （the range of values were 2.6-2.89 and 2.694.41, respectively） to capture the variations in the sizes of soil aggregates due to land use and treatments/management in these ecosystems. The variation in the values of non-linear fractal dimension based on mass （DMnon-lin） was smaller in forest and savanna ecosystems with and without nutrient additions, while the variation was wider in agro-ecosystems with different management practices. Linear fractal dimensions based on number （Dr^i,） and mass （DMlin） of aggregates var- ied marginally in these ecosystems and did not capture the variations in soil aggregates well. The variations in non-linear fractal dimension indi- cate that continued nitrogen loading in forest accelerates the formation of macro-aggregates, whereas in savanna the situation was reversed. The values of non-linear fractal dimensions did not show significant change after 6 years of nutrient additions in the ecotone; reflecting a buffering mechanism of this system in soil aggregate formation. On the basis of non-linear fractal dimension values, we conclude that residue retention and minimum tillage are appropriate for proper maintenance of soil ag- gregate stability for sustained crop production in the Indian dry land agro-ecosystems

Spatial Variations of Soil Respiration in Arid Ecosystems

Soil respiration releases a major carbon flux back to atmosphere and thus plays an important role in global carbon cycling. Soil respiration is well known for its significant spatial variation in terrestrial ecosystems, especially in fragile ecosystems of arid land, where vegetation is distributed sparsely and the climate changes dramatically. In this study, soil respiration in three typical arid ecosystems: desert ecosystem (DE), desert-farmland transition ecosystem (TE) and farmland ecosystem (FE) in an arid area of northwestern China were studied for their spatial variations in 2012 and 2013. Along with soil respiration (SR), soil surface temperature (ST), soil moisture (SM) and soil electrical conductivity (ECb) were also recorded to investigate the spatial variations and the correlations among them. The results revealed that averaged soil respiration rate was much lower in DE than those in TE and FE. No single factor could adequately explain the variation of soil respiration, except a negative relationship between soil temperature and soil respiration in FE (P < 0.05). Geostatistical analysis showed that the spatial heterogeneity of soil respiration in DE was insignificant but notably in both TE and FE, especially in FE, which was mainly attributed to the different vegetation or soil moisture characteristics in the three ecosystems. The results obtained in this study will help to provide a better understanding on spatial variations of soil respiration and soil properties in arid ecosystems and also on macroscale carbon cycling evaluations.

Impacts of Overgrazing and Reclamation on Soil Resources in Rangeland Ecosystems in Huailai Basin, Hebei, China

The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undisturbed communities respectively were quantified and examined in study area in Huailai Basin, Hebei Province, China. There have been significantly greater constituent of C, N, P in the soils of shrubland site. Corg, Ntotal, Navail and Pavail were between 1.18 and 3.90 times more concentrated in the soils of shrubland site in comparison with the other two sites. Although the Ptotal concentration was lower in shrubland soils than in overgrazed rangeland soils, the Pavail concentration, however, was significantly greater in the soils of shrubland site, and increased by 59.1% and even 289.6% in the soils of shrubland site comparing to those in the soils of range-land and millet field sites. Among the three sites, CV exceeding 40% were found for SO4, Cl, and F ion. The CV of organic carbon also exceeded 40% but only in the soils of millet field site. The highest CV were found for F, SO4 ion in the soils of shrubland and overgrazed rangeland sites, while for Cl and SO4 ion in those of millet field site. The results also showed that the introductions of shrubs are of vital importance for the accumulation of soil nutrients and maintenance of soil fertilities, and also for the restoration and reconstruction of desertified ecosystems.

Rangeland Degradation Impacts on Vegetation Cover, Soil Properties and Ecosystem Functioning in an Arid and Semi-Arid Climate, South Africa

The negative effect of soil erosion and soil compaction is well documented for the purpose of optimum rangeland functioning, while the impact of rangeland degradation on effective soil depth is seldom quantified. The aim of this study was to quantify the response of vegetation cover and soil properties, particularly effective soil depth and soil texture to rangeland degradation. Forty-one farms were sampled in the arid and semi-arid climate of South Africa. Within these farms, data was collected over a vegetation degradation gradient. Results showed a significant decline in relative basal cover (94% ± 15% to 39% ± 17%) and soil depth (90% ± 14% to 73% ± 24%) as rangeland degraded. Soil texture changes over the degradation gradients vary for different homogeneous vegetation types. Indications regarding the loss of a functioning rangeland ecosystem were also demonstrated, using objective long-term relations between rangeland conditions and grazing capacity. The study highlights the importance of sustainable rangeland management practices to reduce the loss in effective soil depth and to ensure the sustainable utilization of the rangeland ecosystem. These results can probably extrapolate to other arid and semi-arid rangelands worldwide.

祁连山南坡微地形下典型生态系统土壤蓄水能力差异

[目的]探讨祁连山地区微地形形态下典型生态系统土壤蓄水能力差异性,为该区进一步提高水源涵养能力提供参考。[方法]以微地形不同坡向青海云杉和高山草地为研究对象,采取野外采样和室内试验分析相结合的方法,研究不同坡向对典型生态系统土壤蓄水能力的影响。[结果](1)微地形高山草地所在阳坡区域,土壤水分贮存量随坡位上升逐渐呈减少趋势,坡中上(PZS)为土壤水分贮存量最低的坡位;坡位对土壤饱和蓄水量影响较小。(2)坡位显著影响着阴坡青海云杉土壤水分贮存量,土壤贮水量沿坡位上升呈增加趋势,坡顶处(PSD)土壤水分贮存量最高;坡位对青海云杉土壤潜在蓄水能力影响显著,坡中和坡中上土壤潜在蓄水能力最强。(3)两类典型生态系统土壤蓄水能力存在显著差异,高山草地(阳坡)土壤实际蓄水能力在不同坡位均高于青海云杉,青海云杉(阴坡)土壤潜在蓄水能力在坡位和土层尺度均显著大于高山草地(阳坡)。[结论]研究区微地形坡中上至坡顶段是该区保水增蓄的重点区域,坡中上以下区域是两类生态系统土壤蓄水能力核心区域,应继续保护。

Simulation of soil erosion dynamics in grassland ecosystem of semi-arid China using the CENTURY model

Soil erosion can cause considerable effect on global natural resources and eco-environment. In the paper, the CENTURY model has been used to simulate soil erosion in Xilin Gol Grassland of Inner Mongolia. The results showed before the 1960s, the soil erosion amount was over 2 kg /m2.a in grassland ecosystem in the study area because no trees had been planted. But after the 1960s the mean annual accumulator C lost from soil organic matter due to soil erosion was only 0.3 kg /m2.a in forest ecosystem. So afforestation has exerted notable effect on decreasing soil erosion amount in Xilin Gol Grassland.

Regulating Ecosystem Service (Filtering/ Immobilization of Inorganic Pollutants) Supplied by Soil in Model Regions of Slovakia

The immobilization of soil contaminants (as one of the regulating ecosystem services) plays very important role in environment. This regulatory service prevents groundwater contamination and the entry of contaminants into the food chain. The evaluation as well as the spatial distribution of this regulatory service is important for optimal land management in a specific region. Mapping system combining input layers—slope topography, soil texture, climate region and land use (arable land, grassland)—were created for the analysis and the evaluation of potential of agroecosystem services. Filtering potential was calculated as accumulative function of soil sorption potential and potential of total content of inorganic pollutants evaluated according to The Slovak Soil Law. Calculated potential was categorised into five categories: very low, low, medium, high and very high. Four model areas were selected for the analysis of pollutant filtration, as one of the regulatory agroecosystem services, which are located in different climatic areas and different soil-ecological conditions of Slovakia. The greatest differences among model regions can be found in relation to climatic conditions, land use and diversity of soil types. The warm, dry, and lowland region has a higher potential for pollutant filtration than the moderately warm or cold region. These results are consistent with the location of the soil, its properties, processes and functions within the concept of agro-ecosystem services. Based on the results, we can state that the high risk of inorganic contaminants is inherent in soils with low content and quality of organic substances, low pH value and high concentration of contaminants.

川中丘陵区农田生态系统太阳辐射及土壤热通量数据集(2005-2021年)

太阳辐射是地表生态系统的主要能量来源,是生态系统维持本身正常运转和发展的原始动力;地表层土壤热通量是地表能量平衡的重要参数之一。四川盐亭农田生态系统国家野外科学观测研究站(简称盐亭站)是国家布局在亚热带四川盆地农业生态区的唯一农田生态系统监测野外站。该区域具有优越的光、热、水资源,非地带性土壤紫色土广泛分布,形成亚热带湿润季风气候与非地带性紫色土的最佳农业组合,农耕活跃,是四川盆地农业的主体区域。本研究基于盐亭站综合气象观测场Vaisala(芬兰)自动气象观测系统,经过数据采集、处理、数据质量控制与评估,集成2005-2021年紫色土典型农田生态系统太阳辐射和土壤热通量数据集,太阳辐射监测包括总辐射、反射辐射、紫外辐射、净辐射和光合有效辐射。数据集包含5个EXCEL文件,有各类辐射的时值、日值和月值观测及统计数据,数据量32.7 MB。本数据集可为生态系统生产能力评估、应对气候变化等方面的研究提供数据支持。

面向水土生态系统服务协同的土地利用模拟

针对水土生态系统服务功能的相关成果难以应用到实际土地利用规划中的问题。本研究以黄土高原为研究区,使用K-means聚类算法在小流域尺度上划分土地利用结构,结合InVEST模型探究土地利用结构对水土生态系统服务功能的影响。以阳泉市为典型区,设置多情景,结合多目标优化算法和PLUS模型进行未来土地利用模拟。结果表明:在小流域尺度上,黄土高原的土地利用结构可以划分为6类。农地结构、林地结构、农地-草地结构、草地结构、农地-林地-草地结构、裸地结构,最优土地利用占比分别是0.6—0.7,0.5,0.45/0.4(农地/草地),0.75—0.85,0.15/0.4/0.25—0.35(农地/林地/草地)。各土地利用结构中生态系统服务之间的约束曲线基本上是驼峰型、凹波、半凹波和凸波。从未来的土地利用数量上看,3种情景下水域和灌木面积均处于较低水平。其中,对照情景中城建用地面积最大,基准情景次之,协同情景最小。3种情景下,阳泉市均以城市建设为中心,向外依次为耕地、草地和林地的层次分布特征。土地利用的发展过程中各种土地类型之间存在替代规律,即城市建设倾向于取代耕地和草地,草地则可能取代林地和耕地,而林地则可能与草地发生替代关系。研究成果对黄土高原土地利用规划有重要参考价值。

西南高山峡谷区水土流失综合防治技术与示范

西南高山峡谷区覆盖大横断“七脉六江”地区,是国家“三区四带”重要生态安全屏障,对保障国家生态安全和区域高质量发展具有重要作用。针对西南高山峡谷区存在的水土流失分异演变地带性规律及其关键驱动机制,水土流失对农业耕作、高陡地形、岩溶地质及冻融作用等复杂驱动条件的响应及其防控机制,民族聚集区生态系统服务功能整体提升及生态生产协同的理论与对策等问题,选取兰坪、云龙、永胜、康定以及波密县为典型示范区,开展国家重点研发计划活动,以西南高山峡谷不同类型区水土流失分异规律和综合防治为主线,按照三个层次开展水土流失综合防治与示范研究,攻克高精度土壤侵蚀预报模型与监测技术瓶颈,形成生态系统服务整体提升的“水土流失防治-生态系统服务-民族经济发展”的多目标水土流失综合防治技术体系,最终为西南高山峡谷区生态系统恢复提供科学依据与技术支撑。

2005-2020年中国西北干旱区典型生态系统土壤有机碳密度数据集

土壤有机碳库是陆地生态系统碳库中最大、最为活跃的部分,在全球碳循环过程和全球气候变化中起着重要的作用。中国西北旱区位于欧亚大陆的腹地,生态系统极其脆弱,对气候变化的响应也极为敏感,是近年来众多学者关注的热点地区,土壤有机碳储量估算以及空间分布特征日益成为该区域的研究焦点之一,但是数据共享不足与实测数据相对缺乏是造成研究结果不确定性的重要因素。在收集中国生态系统研究网络(CERN)位于中国西北六省区的农田、荒漠、草地生态系统野外科学观测研究站土壤长期观测数据的基础上,通过筛选、质量控制后,采用有机碳估算模型计算生成了中国西北干旱区典型生态系统土壤有机碳密度数据集。本数据集涵盖了11个站点2005-2020年各类长期观测样地的表层(0-20 cm)和剖面分层土壤有机碳密度数据,以期为中国西北干旱区土壤碳储量估算和碳循环过程研究提供有价值的实测数据。