Functional Diversity and Size of Soil Microbial Communities Induced by Different Land Management Systems

Abstract

Soil microorganisms drive nutrients cycling to a great extent, and they play an essential role in maintaining a stable soil ecosystem and ensuring sustainable forestry development. Land management has been proven to be a real factor in influencing soil quality. The purpose of this study was to investigate the effects of different land management techniques on soil microbial communities. There were four types of land management systems selected for this study: natural masson pine, Phyllostachy pubescens, Phyllostachys praecox, and vegetable. Soils were sampled from these four systems and assayed for soil microbial biomass carbon (MBC), community level substrate utilization pattern, functional diversity, and principle component analysis. Values of MBC were significantly different (P<0.05) from one another in the order of masson pine>Phyllostachy pubescens>Phyllostachys Praecox>vegetable. Analysis of community level substrate utilization pattern indicated that carbon source utilization and total activity by soil microorganisms were greater under the masson pine system than the other three systems (P<0.01). The functional diversities of soil microbial communities characterized as Shannon and McIntosh indexes were much richer in soil under masson pine system; Shannon index was 4.483, 4.241, 4.224, and 3.938 and McIntosh index was 13.51, 7.332, 6.272, and 6.261 for natural masson pine, Phyllostachy pubescens. Phyllostachys praecox, and vegetable systems, respectively. The results from the principle components analysis (PCA), based on the data of optical density (OD) at 120 h of incubation, showed that the value of the first principal component (PC1) of soil for natural masson pine was greater (P<0.05) than those for the other three systems. The difference in scores of the second principal component (PC2) between Phyllostachy pubescens, Phyllostachys praecox, and vegetable were not statistically different. The size and activity of soil microbial communities generally decreased with soil depth, with significant differences in soil MBC, community level substrate utilization pattern, and functional diversity indexes found between A and C horizons (P<0.01). It was concluded that land management systems had a great influence on soil microbial biomass, activity, and functional diversity.     

Changes in Soil Properties and Microbial Indices across Various Management Sites in the Mountain Environments of Azad Jammu and Kashmir

The mountainous region of the Himalayas is covered with forest, grassland, and arable land, but the variation in ecosystem functions has not been fully explored because of the lack of available data. This study appraises the changes in soil properties over the course of a year (spring, summer, autumn, winter) for forest, grassland, and arable soils in a typical hilly and mountainous region of Azad Jammu and Kashmir, Pakistan. Soil samples were collected from major land-cover types in the mountain region: natural forest, grassland, and cultivated land (arable). The natural forest served as a control against which changes in soil properties resulting from removal of natural vegetation and cultivation of soil were assessed. Soil samples were collected from depths of 0–15 and 15–30 cm six times during the year and examined for changes in temperature, moisture, electrical conductivity (EC), micronutrients [iron, manganese, copper, and zinc (Fe, Mn, Cu, Zn, respectively)], and microbial population. Significant differences were found in soil temperature, soil moisture, Fe, Mn, Cu, Zn, and number of bacteria, actinomycetes, and fungi among the three land-cover types. Soil under cultivation had 4–5 °C higher temperature and 3–6% lower moisture than the adjacent soils under grassland and forest. Electrical conductivity (EC) values of forest, grassland, and arable soil were 0.36, 0.30, and 0.31 dS m^?1, indicating that soil collected from the forest had 18–20% more EC than the adjacent arable and grassland soils. On average, amounts of Fe, Mn, Cu, and Zn in the soil collected from the arable site were 6.6, 5.7, 1.7, and 0.8 mg kg^?1, compared with 24.0, 12.1, 3.5, and 1.2 mg kg^?1 soil in the forest soil, showing that arable had two to four times less micronutrients than grassland and forest. Populations of bacteria, actinomycetes, and fungi in the forest were 22.3 (10⁵), 8.2 (10⁵), and 2.5 (10³), respectively, while arable land exhibited 8.2 (10⁵), 3.2 (10⁵), and 0.87 (10³). Season (temperature) and depth showed significant effects on microbial activity and nutrient concentration, and both decreased significantly in winter and in the subsurface layer of 15?30 cm. Different contents of the parameters among arable, grassland, and forest soils indicated an extractive effect of cultivation and agricultural practices on soil. Natural vegetation appeared to be a main contributor to soil quality as it maintained the moisture content and increased the nutrient status and microbial growth of soil. Therefore, it is important to sustain high-altitude ecosystems and reinstate the degraded lands in the mountain region.     

Causes and Effects of Gully Erosion on Agricultural Lands and the Environment

This study was aimed at assessing the causes of the gully erosion and its effects on the agricultural lands in the arid region of southeastern Iran. In this study, we have used geologic maps in scales of 1:50,000 and 1:250,000, aerial photographs on a scale of 1:20,000, field observation, and GPS (global positioning system). Three soil samples were taken from 25, 50, and 75% of the gully length at each location and analyzed for pH, electrical conductivity (EC), exchangeable sodium percentage (ESP), sodium absorption ratio (SAR), cation exchange capacity (CEC), calcium (Ca), and soil texture. The causes of gully erosion, its effects on agricultural lands, characteristics of the gullies, soil depth, and vegetation of each area were evaluated. The results show that several parameters, including poor rangeland vegetation cover, overgrazing, human activities, intensive and short-period rainfall, improper land use, improper irrigation design, improper discharge of water in the channels, and soil characteristics influence the gully erosion. Gully erosion causes severe damage to agricultural lands, including soil loss, increase in surface runoff, lower soil water-holding capacity, lower quality and quantity of water, lower groundwater table, and lower agricultural production. It increased migration from villages to cities and increased socioeconomic problems and poverty. It also caused substantial damages to construction sites such as bridges, roads, and settlements as well as rivers and reservoirs and increased sediment concentration in rivers.     

Improving Soybean Performance in the Northern Great Plains through the Use of Cover Crops

Cover crops are capable of providing multiple benefits for improving soil quality and enhancing annual crop growth. Maintaining continuous plant cover on agricultural fields with cover crop is of great interest to improve nutrient cycling, prevent soil degradation, and promote further adoption of no-till farming systems. A field study was conducted in eastern South Dakota, USA, in 2007, 2008, and 2009 to evaluate four cover crop combinations [(1) no cover; (2) buckwheat (BUCK) (Fagopyrum esculentum Moench) + slender wheatgrass (Agropyron caninum L.) (SLD WHT); (3) oilseed radish (Raphanus sativus L.) (RAD) + SLD WHT; and (4) purple top turnips (Brassica rapa L.) (TURN + SLD WHT)] sown after oat (Avena sativa L.) on soybean [Glycine max (L.) Merr.] performance. The impacts of no tillage (NT) and conventional tillage (CT) were evaluated at two different planting populations. Soybean plant biomass, seed harvest index, yield, total nitrogen (N), oil concentration, and test weight were measured. Cover crops preceding soybean did not negatively impact most measured plant parameters. Seed yield was increased by the RAD + SLD WHT and TURN + SLD WHT in 2008, whereas in 2007 and 2009 no yield increase or slight yield decrease was shown by the cover crops. Soil tillage practice and planting population had a strong influence on seed yield and seed quality in all three study years.     

土地开发对农田土壤养分和盐分变异特征的影响

利用地统计学方法研究了新疆库尔勒市包头湖农场土地开发后土壤空间变异特征。结果表明:土地开发后种植区的土壤有机质和盐分降低,有效磷含量增加,碱解氮含量变化不大;尤其是土地开发后撂荒地土壤有机质含量下降明显。土壤盐分与有机质、碱解氮及速效钾的含量均呈显著正相关,与有效磷呈显著负相关。因此,土地开发后需增施有机肥,补充钾肥,并尽可能不撂荒。     

基于AHP和GIS的省级耕地质量评价研究——以吉林省为例

传统的耕地质量评价方法有评价范围小、周期长、时效性差、耗费大量的人力物力等特点。本文以吉林省为例,探讨基于GIS空间分析技术、层次分析法(AHP)和遥感数据的省级耕地质量评价理论框架体系,通过提取各项评价指标信息,进行空间权重叠加,获得最小评价单元,最后将耕地质量划分为5个等级,其中一二三级分别占18.87%,28.67%和33.15%。其研究结果表明,吉林省耕地质量空间分布有一定的规律性,中部耕地质量等级高于东西部,西部整体上好于东部。各县市的分布特点与其耕地质量分布具有较强的一致性,其结果验证了使用遥感数据评价耕地质量的适用性。该方法克服了传统耕地质量评价的局限性,基于层次分析和GIS空间分析的方法简单快速,时效性强,适用于省级耕地质量评价。     

宜兴地区不同利用方式下土壤氮、磷含量分布特性研究

采用地理信息系统(GIS)和地统计学方法,研究了太湖流域宜兴地区不同土地利用方式下土壤氮、磷的空间变异特性。结果表明,研究区土壤全氮、速效磷含量均处于I级水平,不同利用方式的土壤全氮变异系数在30%左右,速效磷处于25%~65%间,空间分布不均匀。与1982年监测结果相比,土壤全氮、速效磷含量均得到提高,其中速效磷含量提高226%,增幅十分显著。水稻田的全氮含量、菜园土的速效磷含量均显著高于其他土壤,达到极显著水平。菜园土全氮和速效磷半方差函数模型的块基比分别为44.87%和58.82%,空间相关性最弱,而人工管理措施最少的果园土其空间相关性最强,块基比分别为26.45%和21.88%。宜兴地区土壤氮磷含量分布不均,与种植制度、肥料施用量等农业管理措施有关。土壤全氮、速效磷含量分布特性与其利用方式关系密切,不同利用方式下土壤的空间相关性有明显差异。宜兴境内太湖沿岸区域土壤氮磷含量过高,需要控制肥料的施加量,提高利用率,减少农业面源污染。     

基于土地利用和人口密度的中国粮食产量空间化

将统计信息运用到地理-生态过程相关研究中,是人类活动与地理-生态过程相结合的重要体现。农业生产统计数据空间化的过程,即是恢复或重构其空间分布特征的一种手段,可以为地理-生态过程研究提供数据支持。该文以人口密度为因变量,以土地利用数据为辅助因子,将省区级粮食产量分布到空间网格上,得到了中国2000年粮食产量1km×1km网格图。通过在省级、地市州级和县级尺度上的检验,表明利用该方法进行粮食产量空间化能够正确地表达粮食产量的空间分布规律,尤其对于主要粮食产区,具有很高的数据重现精度,可以作为农业区相关研究的数据源。但其数据重现的准确性随着尺度的下降而下降。表明在粒度更细的情况下应该考虑更多的影响粮食产量的因子。在今后的研究中,有必要结合更多的因子进行粮食产量的空间化,以提高其数据重构精度。     

降雨特性和覆盖方式对麦田土壤水分的影响

为探明不同降雨特性和覆盖方式对冬小麦土壤水分的影响,利用人工模拟降雨器,模拟40和60mm/h2种降雨强度,在大田设置地膜覆盖(PM)、秸秆覆盖(覆盖量分别为1500、4500、7500和10500kg/hm2,即SM15、SM45、SM75和SM105),同时设置无覆盖处理作为对照(CK),研究不同降雨强度和覆盖方式对雨后冬小麦0～60cm土层土壤水分分布和降雨土壤蓄积量的影响。结果表明:模拟降雨前各覆盖处理土壤含水率均比CK高,其中0～20cm土层土壤含水率差异显著(P<0.05),而20cm以下各处理土壤水分相差较小,除SM105与CK差异显著外(P<0.05),其他处理与CK差异不显著;同一覆盖处理,60mm/h降雨强度条件下降雨入渗深度和入渗量明显高于40mm/h。在相同雨强条件下,不同覆盖处理可以不同程度的增加耕层土壤含水率,其中秸秆覆盖量越大,效果越明显,而PM效果最差;2种雨强条件下各处理0～60cm土层降雨土壤蓄积量规律表现一致,即SM105>SM75>SM45>SM15>CK>PM,其中SM105和SM75均显著高于CK(P<0.05),PM则显著低于CK(P<0.05);受植株冠层降雨截留的影响,同等降雨条件下,同一覆盖处理拔节前降雨土壤蓄积量大于拔节后的;相比60mm/h降雨强度,40mm/h降雨强度下各处理拔节前、后降雨土壤蓄积量变化幅度较大。     

不同地表覆被下南四湖表层底泥营养元素分布特征

对南四湖水生植被区、农田居民地、养殖区、自然水面的29个采样点表层底泥TN、TP和TOC的含量进行分析,揭示了不同地表覆被下表层底泥中营养元素的分布特征,通过对底泥和上层覆水所含营养元素进行相关分析,探讨了营养元素的可能来源。利用有机指数,对底泥有机污染进行了分析。结果表明:南四湖养殖区和农田居民地已经出现富营养化现象,水生植被区和自然水面还尚未受到富营养化威胁。表层底泥的TN主要来自内源有机氮,TP主要来自外源无机磷。