Soil fauna and soil function in the fabric of the food web

Over the last four decades, spanning David Coleman's career, and in no small measure thanks to him, soil ecologists have made tremendous progress in describing and understanding the overwhelming complexity of biological, biophysical and biochemical interactions in soil. These interactions shape the soil as a habitat for the soil food web and the vegetation and, thereby, regulate the two main life-supporting processes on Planet Earth: production and decomposition. Changes in decomposition and production processes are governed by (human-induced) changes in vegetation composition/cover, the amounts and quality of organic residues and (in)organic fertilizers entering the soil. Such modifications alter the physical environment and the soil biota. Hence, decomposition and production processes cannot be understood and/or manipulated without explicitly addressing the composition and activity of the soil food web. Using a conceptual model, we argue that quantitative understanding of biophysical interactions, in particular those between soil fauna and soil structure, are paramount to understanding biological and biochemical processes in soil and the availability of water and nutrients to plants. The need to increase the efficiency of crop production worldwide, to reverse soil degradation and to increase soil resilience will set the agenda for soil ecologists in the near future.     

庐山山地垂直自然带土壤腐殖质与土壤动物分布特征

沿庐山垂直自然带谱对常绿阔叶林(低海拔,L)、落叶常绿混交林(中海拔,M)和落叶阔叶林(高海拔,H)地面腐殖质及大中型土壤动物分布情况进行调查分析,使用调查数据探究了该垂直自然带土壤腐殖质与土壤动物分布特征。调查分析的腐殖质指标有剖面各发生层厚度、O-A过渡层厚度以及A层土壤团粒大小和有机质、总碳量、全磷、全氮、全碳含量和pH值等,土壤动物指标有类群数、个体密度和多样性指数。结果表明,L、M、H自然带地面腐殖质分别以细腐殖质(Mull)、半腐殖质(Moder)和粗腐殖质(Mor)为主;调查共获得隶属于3门8纲24目的大中型土壤动物2636头,其平均密度为2245.23 ind m^-2,优势类群前气门亚目、甲螨亚目、弹尾目动物个体数分别占总个体数的38.87%、25.36%和13.37%。皮尔逊相关性分析和典范对应分析(CCA)结果表明,土壤动物个体密度与A层土壤养分含量、类群数与O层厚度关系密切,而多样性指数既与A层土壤pH值、也与A层土壤养分含量及O-A过渡层厚度密切相关。土壤动物分布总体特点是优势类群在不同腐殖质组型土层广泛分布,而常见类群和稀有类群则分别与腐...     

Effects of climate change and local environmental factors on long-term tree water-use efficiency and growth of Pseudolarix amabilis and Cryptomeria japonica in subtropical China

Journal of Soils and Sediments - It has been well reported in many studies globally that the increased atmospheric carbon dioxide (CO2) concentration has positively influenced plant growth in the...     

调节茶园土壤pH对其土著微生物区系及生理群的影响

茶园酸性土壤按其重量1.4%的比例施用石灰,能使土壤pH值从4.1提高到6.88;土壤中细菌和放线菌数量能提高近百倍,适于酸性环境的真菌数量略低于不施用石灰的对照组;酸性土壤经pH调节后,土壤pH值在前45天呈缓慢下降趋势,随后有所升高;细菌各类生理群数量在pH调节后前期呈快速上升变化,经过20～30天稳定期后,开始下降;调节茶园酸性土壤的pH是提高茶园土壤土著微生物数量和活性的最好方法。     

阔叶林改种毛竹(Phyllostachys pubescens)后土壤固氮细菌 nifH 基因多样性的变化

【目的】毛竹是喜氮植物,土壤氮素水平对毛竹生长至关重要。生物固氮是土壤氮素的重要来源,因此,探索阔叶林改种毛竹后土壤固氮细菌和土壤氮素的变化具有重要意义。【方法】选择立地条件相近的毛竹林(100多年前由阔叶林改种而来)和阔叶林,每种林地在东北坡向位置随机选择4个10 m×10 m标准样地,每个标准样地选取5个采样点,分层采集0—20 cm(表层)和20—40 cm(次表层)土壤样品,分析了土壤pH、有机碳、碱解氮、有效磷、速效钾和含水量等常规理化性质; 采用引物对AQER和PolF,以土壤总DNA为模板扩增了固氮细菌功能基因(nifH )片段,应用变性梯度凝胶电泳(DGGE)和实时荧光定量PCR(Real-time PCR),分析了固氮细菌群落结构、多样性以及丰度(nifH 基因拷贝数)变化; 通过基因克隆测序对土壤固氮细菌进行初步鉴定。【结果】阔叶林改种毛竹后土壤pH显著(P0.05)提高; 毛竹林土壤的含水量、碱解氮以及表层土壤的速效钾显著高于(P0.05)同层的阔叶林土壤,而有效磷则显著(P0.05)低于同层的阔叶林土壤。总体来说,阔叶林改种毛竹后土壤养分含量明显提高; 阔叶林土壤固氮细菌DGGE条带数以及多样性指数(Shannon-Wiener index)都高于毛竹林; 基于DGGE条带信息的聚类分析和主成分分析(PCA)结果表明,阔叶林和毛竹林区分为2个类群,而同一林分的不同土层之间差异较小; 实时荧光定量PCR结果显示,毛竹林土壤的固氮细菌 nifH 基因丰度显著(P0.05)高于阔叶林土壤; 通过克隆测序,14个阳性克隆分别属于2个不同的菌属,其中13个均为Bradyrhizobium,1个为Azohydromonas lata,条带序列与已知序列的相似度为93%~98%。【结论】阔叶林改种毛竹后土壤固氮细菌的种类减少,而功能基因丰度却明显增加; 土壤氮素水平明显提高,这可能是土壤固氮能力增强的结果。     

Effects of single and mixed species forest ecosystems on diversity and function of soil microbial community in subtropical China

Purpose  

The objective of the present study was to evaluate soil microbial community function and diversity among eight single and mixed species forest ecosystems (18-year-old restoration) in subtropical China.     

The community structure of soil Sarcodina in Baiyun Mountain,Guangzhou, China

Community structures of soil Sarcodina in 7 different habitats within Baiyun Mountain in Guangzhou, China were investigated with qualitative and quantitative analyses. The abundance, dominance, species diversity and community similarity index of soil sarcodina with different physicochemical parameters were comparatively analyzed. A total 67 species of sarcodina belonging to 4 Super-groups, 6 First ranks and 14 Second ranks were identified. The first dominant group was Tubulinea, followed by Flabellinea, with dominance of 59.7% and 13.4%, respectively. The highest abundance of sarcodina appeared in autumn of Site 5, reaching 1.20 × 10⁵ ind g^?1; the lowest in spring of Site 2 with 1.73 × 10³ ind g^?1. Margalef's biodiversity index ranged from 1.26 (winter of Site 6) to 2.51 (summer of Site 1). Statistical analyses showed the sarcodina abundance was positively correlated with organic matter, soil moisture, soil pH, ammonia nitrogen and total nitrogen, but the correlation coefficient of total potassium was negative. Total phosphorus, nitrate nitrogen and sulphate showed no significant effect on sarcodina abundance in the present study.     

季节性放牧和全年放牧对亚高山草地生态系统中土壤动物和微生物的影响

Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems.A field soil survey was conducted to compare microbial biomass carbon (Cmin) and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province,China:perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing.A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices,including treatments of no mowing,perennial grazing (NM + G),mowing followed by seasonal grazing (M + G),mowing and no grazing (M + NG),and no mowing or grazing (NM + NG).The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site.The experiment results showed that in comparison to non-grazing treatments (M + NG and NM + NG),grazing (NM + G and M + G) reduced total fauna density (by 150 individuals m-2) and the number of taxonomic groups present (by 0.32 taxa m-2).Mowing decreased Cmin (by 0.31 mg g-1).Furthermore,the NM + G treatment (perennial grazing) had the lowest density of Collembola (16.24 individuals m-2),one of the two most common taxonomic groups,although other taxonomic groups responded differently to the treatments.Treatment effects on soil fauna were consistent with those on above-ground grasses,in which C:N ratios were greatly reduced by grazing,with this effect being the greatest for the NM + G treatment.In contrast,different grazing treatments had little effect on C:N ratio of soil.Furthermore,the traditional grazing method (mowing followed by seasonal grazing) may have less severe effects on some taxonomic groups than perennial grazing.Therefore,an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.     

亚热带典型人工林土壤酸化特征及其生物学机理初步分析

对亚热带典型人工林土壤pH和酸化生物学机理的研究表明:荒草地种植马尾松和木荷20年以后土壤的pH发生了变化,在0 ～ 60 cm处降低了0.12～0.47个单位;垂直方向上在距离树干10 cm处马尾松0～20cm土层pH低于木荷,20～60 cm土层pH大于木荷;水平方向上随着与树干距离的增加土壤pH受树木影响的程度逐渐降低,距离树干20 cm处土壤pH受树木的影响最大.树干茎流雨可能是树干基部附近土壤加速酸化的重要因素,根系的分布及其对盐基阳离子的吸收是造成马尾松和木荷土壤剖面出现酸化差异的主导因素.     

浙江天台山七子花林土壤动物群落结构特征与动态变化

2000年4月至2001年4月逐月对浙江天台山七子花林土壤动物群落特征进行调查研究,初步分析凋落物、季节、海拔等因素对土壤动物群落结构的影响。结果表明:(1)蜱螨目(57.06%)和弹尾目(21.21%)为七子花林的优势类群,膜翅目(4.72%)、双翅目(3.65%)、综合纲(2.74%)、寡毛纲(2.68%)和鞘翅目(2.57%)为常见类群。(2)七子花林各样地土壤动物的个体数量在5月份和11月份都表现为峰值,在7月份至8月份的干热期个体数量明显下降。(3)处于中海拔地区(780m)呈共优群落的七子花林样地土壤动物的密度最大、类群数最多、多样性指数最高。(4)各样地土壤动物在土层中的垂直分布表现出明显表聚性特点,然而,在7月份至8月份的干热期,出现底层土壤动物个体数量多于表层的逆分布现象。     

Effects of weed control and fertilization on soil carbon and nutrient pools in an exotic pine plantation of subtropical Australia

Purpose  

Soil carbon (C) and nutrient pools under different plantation weed control and fertilizer management treatments were assessed in a 7-year-old, F₁ hybrid (Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis) plantation in southeast Queensland, Australia. This research aimed to investigate how early establishment silvicultural treatments would affect weed biomass, soil C, nitrogen (N) and other nutrient pools; and soil C (δ¹³C) and N isotope composition (δ¹⁵N) to help explain the key soil processes regulating the soil C and nutrient pools and dynamics.     

Soil microbial biomass, activity and community composition in adjacent native and plantation forests of subtropical Australia

Purpose

Soil nitrogen (N) availability is a critical determinant of plantation productivity in subtropical Australia and is influenced by the soil microbial community. The size, structure and function of the soil microbial community can be impacted by land-use change and residue management. The objectives of this study were to examine the impact of land-use change from (1) native forest (NF) to first rotation (1R) hoop pine plantation and (2) 1R hoop pine plantation to second rotation (2R) hoop pine plantation on the soil microbial community. The impact of residue management on the soil microbial community was also investigated in the 2R forest, where soil microbial parameters were measured in tree rows (2R-T) and windrows (2R-W). In addition, relationships between soil microbial parameters and soil N parameters were investigated.

Materials and methods

Each of the four treatments (NF, 1R, 2R-T and 2R-W) had five 24-m² replicate plots from which 15 soil cores were collected and bulked at three depths (0–10, 10–20, 20–30 cm). Microbial biomass carbon (MBC) and N (MBN) and soil respiration were measured on field moist soils. In addition, carbon (C) source utilisation patterns were assessed using the whole soil MicroResp? technique (Campbell et al. 2003).

Results and discussion

Results indicate that the land-use change from NF to 1R hoop pine plantation significantly reduced MBC, respiration rate, soil total C and total N. Furthermore, the land-use change appeared to have a significant impact on the soil microbial community composition measured using MicroResp? profiles. Land-use change from 1R to 2R hoop pine plantation resulted in a decline in total C and MBN and a shift in microbial community composition. When compared to the 2R-T soils, the 2R-W soils tended to have a greater microbial biomass and respiration rate. Residue management also influenced the microbial community composition measured in the MicroResp? profiles.

Conclusions

Results indicate that land-use change had a significant impact on the soil microbial community, which was likely to be related to shifts in the quality and quantity of organic inputs associated with the change in land use. This may have significant implications for the long-term productivity of the soil resource. Further studies are required to confirm a difference in microbial community composition associated with residue management. In addition, long-term experiments in subtropical Australia are necessary to verify the results of this snapshot study and to improve our understanding of the impact of single-species plantation forestry and residue management on the soil microbial community, soil N dynamics and ultimately the long-term sustainability of the soil resource.     

Interplay of omnivory, energy channels and C availability in a microbial-based soil food web

 To study the effects of omnivory on the structure and function of soil food webs and on the control of trophic-level biomasses in soil, two food webs were established in microcosms. The first one contained fungi, bacteria, a fungivorous nematode (Aphelenchoides saprophilus) and a bacterivorous nematode (Caenorhabditis elegans), and the second one fungi, bacteria, the fungivore and an omnivorous nematode (Mesodiplogaster sp.) feeding on both bacteria and the fungivore. Half of the replicates of each food web received additional glucose. The microcosms were sampled destructively at 5, 9, 13 and 19 weeks to estimate the biomass of microbes and nematodes and the soil NH₄ ⁺-N concentration. The evolution of CO₂ was measured to assess microbial respiration. Microbial respiration was increased and soil NH₄ ⁺-N concentration decreased by the addition of glucose, whereas neither was affected by the food-web structure. Supplementary energy increased the biomass of fungi and the fungivore, but decreased the biomass of bacteria, the bacterivore and the omnivore. The omnivore achieved greater biomass than the bacterivore and reduced the bacterial biomass less than the bacterivore. The biomass of the fungivore was smaller in the presence of the omnivore than in the presence of the bacterivore at three sampling occasions. Fungal biomass was not affected by food-web structure. The results show that the effects of the omnivore were restricted to its resources, whereas more remote organisms and soil processes were not substantially influenced. The results also indicate that the presence of an omnivore does not necessarily alter the control of populations as compared with a food web containing distinct trophic levels, and that the fungal and bacterial channels may respond differently to changes in energy supply. Received: 15 December 1997     

Soil fauna community in the black soil of Northeast China under different tillage systems

Soil fauna is an important component in soil ecosystems. This study tested whether conservation tillage or conventional tillage of a black soil (Udic Mollisol) field in Northeast China could affect its soil fauna communities. Two different conservation tillage systems, no-tillage (NT) and reduced tillage (RT), as well as a conventional rotary tillage system (CT), were chosen for this study. There were 4562 individuals isolated from this study, which included two orders and 35 families. Acariformes was the most abundant family and represented 91.56% of the total faunal abundance. The abundance and the number of faunal families were higher in conservation tillage systems than in the CT. The RT system had the highest individual number of soil fauna among three tillage methods. The faunal accumulation in the soil surface also was significantly higher in the two conservation tillage systems than in the CT. Our results indicate that the conservation tillage systems could protect the soil fauna in the soil ecosystem better than the CT.     

广西猫儿山毛竹林不同层次土壤含水量的降雨响应

以漓江上游猫儿山典型森林植被毛竹林(Phyllostachys pubescens)为研究对象,对其0—20,20—50,50—80cm共3个层次的土壤体积含水量进行了定位监测,分析了各层次土壤含水量的降雨响应。结果表明:(1)3个层次土壤含水量差异显著(p0.01),年均值分别为39.49%,41.17%,44.15%,表层0—20cm土壤含水量最少,20—50cm增加,50—80cm最高。降雨与3个层次土壤含水量都呈极显著相关性。(2)从小雨到暴雨,土壤含水量对降雨的响应都可以分为平台期、上升期、峰值期和退水期;各层次土壤含水量对降雨的响应是比较复杂的。(3)在上升期,表层0—20cm土壤含水量增加最快;退水期,50—80cm土壤最快,这与前期土壤含水量及降雨强度有关系。该研究为揭示漓江上游森林植被对降水径流的调节作用,客观评估漓江上游水资源潜力,加强流域水资源管理和森林经营提供科学依据。     

Effects of water erosion on soil organic carbon stability in the subtropical China

Journal of Soils and Sediments - How the stability of soil organic carbon (SOC) is affected by soil erosion is still not clear. The main purpose of this study was to characterize how SOC stability...     

Effects of irrigation and plowing on soil carbon dioxide efflux in a poplar plantation chronosequence in northwest China

Soil respiration in forest plantations can be greatly affected by management practices. Irrigation is necessary for high productivity of poplar plantations in semi-arid northwest China. Moreover, plowing is essential for improving soil quality and reducing evaporation. In the present study, the influences of irrigation and plowing on soil carbon dioxide (CO₂) efflux were investigated in poplar plantations in 2007 and 2008. The experiments included three stand age classes receiving three treatments: control, irrigation, and plowing. Mean soil respiration in irrigation treatment stands was 5.47, 4.86, and 4.43?µmol?m^?2?s^?1 in 3-, 8-, and 15-year-old stands, respectively, during the growing season. In contrast, mean soil respiration in control stands was 3.71, 3.83, and 3.98?µmol?m^?2?s^?1 in 3-, 8-, and 15-year-old stands, respectively. During the entire observation period, mean soil respiration in plowing treatment stands increased by 36.2% compared with that in the control stands. Mean soil respiration in irrigation treatment stands was significantly higher than that in the control stands; this was mainly because fine root growth and decomposer activities were greatly depressed by soil drought, since natural precipitation could not meet their water demands. The results also suggest that plowing management can greatly increase soil CO₂ emission by modifying soil structure. After plowing, soil bulk density decreased and soil aeration was greatly improved, leading to greater rates of oxidation and mineralization.     

Effects of organic amendments on soil carbon sequestration in paddy fields of subtropical China

Purpose  

Although organic amendments have been recommended as one of the practices for crop production and soil carbon sequestration, little has been done to evaluate soil organic carbon (SOC) dynamics following long-term application of organic amendments. The objective of this research were to (1) assess the effect of long-term organic amendments on SOC dynamics in rice-based systems; (2) evaluate the relationship between soil carbon sequestration and carbon input based on various mineral and organic fertilization treatments.