Soils are natural resources of utmost. Importance for a number of ecosystem and biosphere processes such as plant production, cycling of organic matter and nutrients, storage of C and water, and release of nitrous oxides, CO2 and methane. Soil degradation, through various processes, is a matter of great concern, since their integrity is absolutely critical to increasing food production (FAO, 1995), and regulating atmospheric fluxes of greenhouse gases (Jenkinson, 199 1 ; Wallace, 1994).
Soil Health definition and relationship to soil biology
Characteristics of healthy soil
Assessment of soil health
Framework for evaluating soil health
Indicators
Types of indicators
Biological indicators
Role of biological indicators
Soil Health definition and relationship to soil biology
Characteristics of healthy soil
Assessment of soil health
Framework for evaluating soil health
Indicators
Types of indicators
Biological indicators
Role of biological indicators
Study of ligninolytic bacteria isolation and characterization from dhamdha ag...eSAT Journals
Abstract
Lignin is a complex, three-dimensional aromatic polymer consisting of dimethoxylated, monomethoxylated and non-methoxylated phenylpropanoid subunits. It is the most abundant renewable carbon source on Earth. The majority of plant biomass, including stems and leaves, is composed of lignocellulose. In present study isolation, identification and characterization of ligninolytic bacterial flora were done from the agro-field, using a lignin residue. 2 types of soil samples black and mixed soil were selected from agro fields of Dhamdha of Bhilai-Durg for isolation of ligninolyitc bacterial colony. Microbes from both mixed and black soil samples were grown in solid media by Hungate method and result shown that three types of bacterial colonies (1-MS, 2-BS), were isolated from Dhandha agro field and used to check the activity of lignolytic capability. Out of 3 types colonies only 1types of colony (j-MS), was shown potential of lignin degradation. The Morphological, gram’s reaction and endospores staining reaction, biochemical characteristics of the isolate obtained from this agro-field soil samples identified with reference to Bergey’s Manual of Determinative Bacteriology. These identified isolate (j) - Bacillus species was shown presence of Laccase, Manganese peroxidase (MnP) and Lignin peroxidase (LiP), etc. lignin degrading enzymes. This results concluded that Bacillus sps. strain was able to degrade lignin substrate which was second abundant and waste material in the world. It is also concluded that to expand on the range of products which can be obtained from lignocellulosic biomass. In this study, soil bacteria was isolated by enrichment on Kraft lignin and evaluated for their ligninolytic potential as a source of novel enzymes use to generate 2nd generation biofuel from waste streams of pulping.
Keywords: Lignocellulosic, 2nd generation biofuel, Laccase, Manganese peroxidase (MnP), and Lignin peroxidase (LiP), Bacillus species
Basic techniques in Isolation of Soil BacteriaMohammed Tayyab
Here simple techniques alongwith basic qulaitative tests of Plant Growth Promoting Bacteria (PGPRs) are discussed.
All work done in Soil Biology & Biochemistry Setion, National Agriculture Research Center Islamabad,Pakisatn
This project investigated soil recovery processes on the reclaimed territories of Kavtiskhevi and Gardabani quarries by means of soil inhabiting invertebrates.
Oribatid mites, in the Acarine suborder Oribatida, are associated with organic matter in most terrestrial ecosystems (Behan-Pelletier and Eamer, 2007; Maraun et al., 2007; Norton and Behan-Pelletier, 2009; Schneider, 2005). Their ability for dispersal is low and those that do disperse as adults (Norton, 1994). As a result, oribatid mites cannot easily escape from stress conditions. Population of oribatid mites decline rapidly when their habitat is damaged, that allows detection of environmental degradation. So, they can be considered as «early warning» indicators of stress.
Springtails (Collembola) are major components of terrestrial ecosystems, constituting a substantial proportion of the soil animal biomass and diversity and are thus frequently and easily found (Coleman et al., 2004). Like oribatids, they play an important role in plant litter decomposition and in soil formation processes. They are known as one of the pioneers of early stages of soil recovery processes and rapid colonizers of reclaimed waste sites (Hutson, 1980).
Project actions:
1. Inventory of soil arthropods ( oribatid mites, springtails);
2. Study biotic complexity of reclaimed and control sites using invertebrate animals as bioindicators;
3. Identify pioneer colonists species and species adapted to the anthropogenic pressure;
4. Reveal the effectiveness of provided reclamation activities;
5. Publish informative booklet and on line placement of the project activities and project results.
The project won the 1st Prize in National Quarry Life Award in 2014 in Georgia.
Read more: http://www.quarrylifeaward.com/project/soil-arthropod-diversity-and-quarry-rehabilitation
Abstract ─ The soil-litter system is the natural habitat for a wide variety of organisms, microorganisms and invertebrates, with differences in size and metabolism, which are responsible for numerous functions. The soil mesofauna is composed of animals of body diameter between 100 μm and 2 mm, consisting of the groups Araneida, Acari, Collembola, Hymenoptera, Diptera, Protura, Diplura, Symphyla, Enchytraeidae (Oligochaeta), Isoptera, Chilopoda, Diplopoda and Mollusca. These animals, extremely dependent on humidity, move in the pores of the soil and at the interface between the litter and the soil. The edaphic fauna, besides having a great functional diversity, presents a rich diversity of species. As a result, these organisms affect the physical, chemical and, consequently, the biological factors of the soil. Therefore, the edaphic fauna and its activities are of extreme importance so that the soil is fertile and can vigorously support the vegetation found there, being spontaneous or cultivated. The composition, distribution and density of the edaphic acarofauna varies according to the soil depth, mites size, location and the season of the year. Edaphic mites are generally found in greater quantities in the organic matter layer than in the soil mineral. The subclass Acari is divided in seven orders being the Mesostigmata, Trombidiformes, Endeostigmata and Sarcoptiformes those that frequently occur in the soil. In the order Sarcoptiformes the suborder Oribatida (formerly Cryptostigmata) is one of the more numerous groups of soil arthropods, both in number of species and specimens. Considering the above facts, it was the objective of this work to know the acarofauna of the soil in a coffee plantation and rank the taxa in a decreasing way, by the use of faunistic analysis. The soil samples were taken in coffee plantation in the Experimental Station of EPAMIG, in São Sebastião do Paraíso, MG, Brazil, in two periods, end of dry and end of rainy season of the year 2013, and the extraction of edaphic mites of the soil mesofauna was done at the Laboratory of Acarology of EPAMIG Sul/EcoCentro, in Lavras, as well as other activities related to the study. The result show that edaphic mites of the cohort Astigmatina and suborder Oribatid are dominant in both periods studied, and can be worked to be an indicative of soil quality.
FOOD WEBS 31
INTRODUCTION
“The classic marine food chain –algae, zooplank-
ton, fish– can now be considered as a variable phe-
nomenon in a sea of microbes (Karl 1999).”
The food web is one of the earliest and most fun-
damental concepts in ecology. Darwin (1845) recog-
nized the existence of a pelagic food chain. Elton is
credited with first appreciating the importance of food
chain and food web concepts (Lawton 1989), but
major antecedents include Petersen’s (1918) quantita-
tive conceptual model of the food web that is support-
ed by eel grass, and Hardy’s (1924) conceptual model
of the herring food web. Elton, and later Hutchinson
and his students, developed both population and mate-
rials-flux approaches to food webs (Hagen 1992), but
the two approaches quickly diverged. Paine (1980)
showed that population interactions do not equate with
energy flux, and asserted that energy flux was unim-
portant and “has generated few insights into ecologi-
cal processes.” This put studies of population biology
and energy-flux on separate paths that only recently
have shown signs of beginning to merge into a unified
paradigm (e. g. McQueen, et al., 1986; Hunter and
Price 1992; Polis and Winemiller 1996). Ecologists
recognize that energy input matters, although they
agree less on when and how it matters. What clearly
matters is formulating tractable hypotheses about
ecosystem structure and function. Repeated attempts
to simplify the inherent complexity of food webs have
led to Sisyphus-like progress in which investigators
have made generalizations and then have been forced
to qualify them.
SCI. MAR., 65 (Suppl. 2): 31-40 SCIENTIA MARINA 2001
A MARINE SCIENCE ODYSSEY INTO THE 21st CENTURY. J.M. GILI, J.L. PRETUS and T.T. PACKARD (eds.)
Caught in the food web: complexity made simple?*
LAWRENCE R. POMEROY
Institute of Ecology, University of Georgia, Athens GA 30602-2202, USA. E-mail: [email protected]
SUMMARY: Several historically separate lines of food-web research are merging into a unified approach. Connections
between microbial and metazoan food webs are significant. Interactions of control by predators, defenses against predation,
and availability of organic and inorganic nutrition, not any one of these, shape food webs. The same principles of popula-
tion ecology apply to metazoans and microorganisms, but microorganisms dominate the flux of energy in both marine and
terrestrial systems. Microbial biomass often is a major fraction of total biomass, and very small organisms have a very large
ratio of production and respiration to biomass. Assimilation efficiency of bacteria in natural systems is often not as high as
in experimental systems, so more primary production is lost to microbial respiration than had been thought. Simulation has
been a highly useful adjunct to experiments in both population theory and in studies of biogeochemical mass balance, but it
does not fully encompass the complexity of real systems. A major challenge for the futu.
Trends in Macrophyte Diversity in Anthropogenic Perturbed Lentic Ecosystems w...Premier Publishers
Aquatic macrophytes hold several niches within the ecosystem, including inter alia water purification, carbon sequestration and serve as microhabitats for aquatic insects. These dynamic roles make macrophytes good indicators of current environmental conditions. Hence assessing their abundance in line with wetland ecosystem dynamics and function is essential. Frequency of occurrence and density values were estimated, using twenty (20) 2 m x 2 m quadrats for each macrophyte encountered. The results of the study revealed twenty-one (21) macrophytes belonging to 16 families. These ponds varied markedly in terms of species composition and in numerical strength such that Polygonum lanigerum (1143+175st/ha), Setaria verticillata (337.5+ 32.8st/ha), Azolla pinnata (337.7+ 16.4 st/ha) recorded high density values while Lagenaria breviflora (18.7±2.19), Sida acuta (18.75±5.30), Ludwigia erecta (18.7±0.15) and Milletia aboensis (18.7±0.03) were the least abundant species. Pond A and D with 11 taxa each had the higher Shannon-Wiener (2.192, 2.214) and Simpson (0.8699, 0.8787) diversity indices respectively when compared to the other ponds. On the contrary, pond C with four taxa had the least Shannon-Wiener and Simpson diversity indices (1.253, 0.6782) respectively. Equitability and evenness ranged between 0.914 - 0. 952 and 0.814 - 0.900 respectively. Bray and Curtis cluster analysis showed that pond B was the most dissimilar compared to other ponds in terms of the taxa composition.
The Role of Soil Organisms and Functions in different Coconut based Multiple ...Agriculture Journal IJOEAR
Abstract—Sampling was done in wet and intermediate zones represented by the Walpita and Makandura research centers, respectively. Eleven land use systems were considered for the study; coconut mono culture (CM), bare land (BL) and coconut multiple cropping. Under coconut multiple cropping, nine different intercrops were selected separately for each zones. The treatments were arranged in a randomized complete block design (RCBD) with three replicates (n = 3). The experiment was conducted under mature baring coconut (>20 years) plantation. Soil Macrofauna was sampled using one transect with three replicates at each land use type using quadrate size (30×30cm) from 0-30 cm depth and visible organisms were handpicked and preserved in 75% alcohol. Dilute plate technique and Spread plate technique was used to determine the soil micro organisms’ density. Those techniques were used to cultivate the fungi and bacteria under 〖10〗^(-2) and 〖10〗^(-5) dilution level respectively.
Research identified 12 classes (Crusteacea, Oligochaeta, Hirudinea, Gastropoda, Acarina, Araneida, Scopionida, Chilapoda, Diplopoda, Amphibia, Reptelia) and 14 orders (Hemiptera, Diptera, Coleoptera, Thysanura, Hymenoptera, Lepidotera, Orthoptera, Blattaria, Mantodea, Phasmida, Dermaptera, Isoptera, Siphonaptera, Thysanoptera) of soil organisms. Class insecta shows the high diversity with 14 orders. Colony forming unit (CFU) value of bacteria was higher than that of the fungi value. Findings of intermediate and wet zones’ studies suggested that coconut multiple cropping systems may have high diversity, abundance and functional role of soil organisms. Both zones studies suggested that coconut multiple cropping systems may increase soil moisture factor, respiration rate, biomass carbon content, organic carbon percentage, total nitrogen content, organic matter content and C:N ratio in 0-30cm depth other than the coconut monoculture systems. Overall data of two different zones indicated a significant positive correlation of soil organism diversity, abundance and their functional role with cropping systems. Those data can be used as a reliable basic bio indicator for payments for ecosystem services (PES). It supports to valorize the economic value of the ecological services returned by soil organisms.
The present study aims to investigate the biodiversity of woody vegetation along a gradient of human impacting region in the three constituent parts of Ferlo Biosphere Reserve (FBR): the core area, the buffer zone and the transition area. We conducted an inventory of 110 plots of 900 m² each. Total species richness was 49 species distributed in 32 genera within 16 botanical families. The analysis of contesimal frequency showed that Guiera senegalensis is the most common species with a presence of 75% of such records. Examination of species abundance spectrum showed that four most abundant species such as Guiera senegalensis (29.5%), Combretum glutinosum (15.9%), Pterocarpus lucens (11.6%) and Boscia senegalensis (10 , 5%). These four species represent 68% of the total individuals of the RBF and are also the four most common species. The spectrum of abundance of families showed that Combretaceae is the best represented family with almost half of the number of species (49.7%). The representativeness of biological types and geographical affinity of the species has been established for the woody vegetation in the study area. The study of diversity indices revealed that the buffer zone and the transition area are subjected to multiple uses and experiencing human action. It has a greater diversity and a level of organization with higher timber stand than the central area which is an integral conservation zone.
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Safalta Digital marketing institute in Noida, provide complete applications that encompass a huge range of virtual advertising and marketing additives, which includes search engine optimization, virtual communication advertising, pay-per-click on marketing, content material advertising, internet analytics, and greater. These university courses are designed for students who possess a comprehensive understanding of virtual marketing strategies and attributes.Safalta Digital Marketing Institute in Noida is a first choice for young individuals or students who are looking to start their careers in the field of digital advertising. The institute gives specialized courses designed and certification.
for beginners, providing thorough training in areas such as SEO, digital communication marketing, and PPC training in Noida. After finishing the program, students receive the certifications recognised by top different universitie, setting a strong foundation for a successful career in digital marketing.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
1. B
Siobgy Intemational No33 (July 1996)
Diversity of Soil Fauna and
Ecosystem Function
By P.Lavelle
&q (Laboratoire dEcologie des Sois Tropicaux, Universite Pans VVORSTOM,
32 Avenue Henri Varagnat, 93143 BoMy Cedex, France
Introduction
Soils are natural resources of utmost. importance for a number of ecosystem and
biosphere processes such as plant production, cycling of organic matter and nutrients,
storage of C and water, and release of nitrous oxides, CO2 and methane. Soil
degradation, through various processes, is a matter of great concern, since their
integrity is absolutely critical to increasing food production (FAO, 1995), and
regulating atmospheric fluxes of greenhouse gases (Jenkinson, 1991 Wallace, 1994).
;
In this context, the present concern for the loss of biodiversity in soils is more closely
linked to the possible rote of species in the protection of the productive potential rather
than to ethical, aesthetic, or economic considerations (Solbrig; 1991; Freckman, 1994).
Except for a few spectacular species like the 3m-long giant "gippsland" earthworm
Megascolides australis of Southern Australia, soil fauna species do not appear on lists
of endangered species that require protection. The limited knowledge (among the local
farmers) of this fauna is mainly due to (Ortiz et al., 1994) the small size and the
difficulty in extracting and observing most species. (André et al., 1994) easily explain
this situation. For several decades, research mainly concentrated on a few pests,
looking at efficient chemical treatments that would eliminate them. More recently
however, there has been considerable development in research on the role of the whole
invertebrate conimunity in soil function. These studies consider soil fauna as a resource
with potential for soil biodiversity management (Lavelle and Barois, 1988; Swift and
Woomer, 1994). Attempts are being made to either biological control some of the more
serious pests, or use their communities as indicators of the quality of the soil system, as
most are highly sensitive to perturbations and disturbances (Bongers, 1990 for
nematodes; LavelIe, 1988 and Decaens et al, 1995for macroinvertebrates).
In a single square meter of soil of a European beech forest, as many as lo00 species of
invertebrates may be collected (Schaefer and Schauermann, 1990). Richness differs
greatly between taxa. Microarthropod communities may comprise hundreds of species
with a diversity of up to 400 to 500 species of Acari and 60 to 80 species of Collembola
. Under comparable conditions, nematodes may comprise up to 90 species, Protozoa,
60; Enchytraeidae, 22 ; earthworms, 15-17 ; Diplopoda, 15. In African savannas,
termite communities may comprise up to 60 species. Villalobos and Lavelle (1990)
collected 113 species of soil Coleoptera. Similar richness occurs in a large range of
ecosystems, and H large proportion of these species have not yet been described. It is
assumed for example, that the 3UX) earthworm species already described only represent
half o the total nuniber of existing species. In smaller groups with high specific
f
richness, the situation is much more critical (Hawksworth and Mound, 1991). André et
al. (1994) explain that the selectivity of extraction methods and sampling sites, and the
lack of interest for some groups of small species, has probably led to an
1
Fonds Docurnerrtar's URS4'Ufih
3 Cote: f 3 + ~ & 2 6 Ex: .il_
2. n
Biology InternationalNo3 (July 1996)
3 q-
underestimation of microarthropod species richness of 1-2 orders of magnitude. In
general, much less species have been identified in tropical than in temperate areas.
During the last 10 years, great efforts have been made to understand the role of
invertebrates in soil processes, and their interactions with the abiotic factors of soil
function (Lavelle et a. 1993, 1994; Beare et al., 1995; Wardle and Lavelle, in press).
l,
Dramatic effects have been observed in the regulation of microbial activity, soil
aggregation and hydraulic properties, dynamics of decomposition and soil organic
matter, plant growth and pedogenesis. Although effects have often been quantified in
experiments performed at the organisms scale, and less often at those which are relevant
to agronomic or pedologic issues, there is clear evidence that these processes may
actually operate at the ecosystem level. In addition, it was found that the functional
importance of invertebrate activities is often disproportionate to their actual abundance
(Anderson; 1988).
Soil invertebrate communities are deeply affected by human activities; in most
agroecosystems, they tend to disappear. Little if any mention is made of possible links
between the elimination of such important regulators of soil processes and the lack of
sustainability of most agricultural systems (Lavelle et al., 1994). On the other hand,
cases exist where the replacement of a diverse native fauna by a few opportunist exotic
species adapted to highly disturbed areas result in the disappearance of key functional
groups. Severe degradation of the soil (by endogeic earthworms, Rose and Wood,
1980) or damages to plant crops (by termites, rhizophagous Coleoptera larvae, or
parasitic nematodes) may also occur. For example, there is evidence that at least part of
the degradation process that affects pastures in Central Amazonia is due to a pullulation
of the earthworm species Pontoscolex corethrurus, at the expense of the loss of all
earthworm species and the majority of arthropods from the native forest. P. corethrurus
produces high amounts of compact casts at the soil surface and severe soil compaction
and subsequent depressed water infiltration rapidly occur, as those species that would
have normally decompacted the soil have been largely eliminated (Chauvel, Grimaldi,
Desjardins, Matos, Blanchart, De Oliveira Barros and Lavelle, unpublished data).
It is therefore urgent to describe the diversity of soil invertebrate communities and
evaluate their functions in order to identify management options that eventually optimise
their activities. Diversity should be addressed at the population level (genetic diversity
in key species), community (specific richness) and ecosystem (functional groups)
levels. The need to incorporate management of soil faunal communities as part of
farming systems, land remediation and other types of landuse clearly set priority on the
ecosystem level. According to Elliott and Lynch (1994), a goal for soil biodiversity
management should not only mean maximizing the number of species in an ecosystem.
More likely it means the ability to retain the current macro-(fauna) and microflora and to
emphasize certain species and processes to accomplish specific objectives. Obviously,
the broad main objective is to manage biodiversity for maximum soil resilience.
This paper attempts to synthesise the existing knowledge on the perception and function
of biodiversity of invertebrates in soils. New research areas and hypotheses are
proposed td improve our understanding and promote the idea that fauna is a resource
that needs careful management, in the same right as currently accepted physical,
chemical and microbiological components of soil fertility. P r of the ideas and
at
hypotheses presented below have been discussed at a recent TSBFNNEP workshop
held at Hyderabad (India)(Giller et al., in press andSwift, in press).
4
3. 4
Biology International No3 (July 1996)
3
First described are the functions of invertebrates in soils, followed by the current
perception of soil biodiversity, and some hypotheses on the role of this diversity.
Challenges that lay behind these scientific questions are also presented.
Invertebrates and the Soil System
Soil function is the result of complex interactions among physical, chemical and
'biological factors. A general hierarchical model has been proposed to describe the
potential importance of these factors as determinants of soil processes. Inside this
model, soil organisms are separated into four broad functional groups, again presented
. na hierarchical order, depending on their function and on the nature of the interaction
i
they develop with other organisms.
1. The hierarchical. model
A hierarchical model has been proposed in which soil processes are determined by a
suite of factors whose potential effect is determined by the scales of time and space at
which they operate (Lavelle et al., 1993). This hierarchy is a "control hierarchy" as
defined by Solbrig (1991), in which factors that operate at large scales of time and
space may constrain factors that operate at smaller scales. It is not, however, a rigid
hierarchy since factors may affect a wide range of processes that are operating at
different scales (Solbrig, 1991). The intensity of the constraint may be low, whereby
factors operating at lower levels of the hierarchy then become predominant.
At the lowest level of determination, this suite of factors includes 'Biological
Regulatory Systems' which comprise all soil organisms, divided into micro- and
macroorganisms. According to this model, any soil process is likely to be firstly
influenced by climate, then by edaphic factors (mainly clay abundance and nutrient
status), followed by the quality of material produced by the plant community and
brought as energy and nutrient sources, and finally biological systems of regulation,
i.e., a broad mutualist association of macroorganisms (roots and invertebrates) with
microorganisms (Fig. 1). Evidently, human activities deeply influence the system and
can be potentially one of the strongest determinants. This is, however, a potential
hierarchy in which all levels interact, and in some situations when higher level factors
are not particularly constraining, such as the quality of organic inputs, or the presence
and activity of key invertebrate groups may be major determinants of processes. For
example, this is the case for the role of tennites and earthworms in tropical cropping
systems, where neither the climate (in its macro- and microscales) nor soil (with little
active clay minerals) or litter quality (almost homogeneous throughout the system) may
significantly regulate such processes as decomposition of litter or soil physical
structure.
A natural corollary to the rules which is also implicit in this model is that, depending on
the intensity and relative importance of constraints operating at the upper levels of the
hierarchy, the role of soil invertebrates as measured by their effect on rates of a specific
ecosystem process may, or may not, be significant. In the former case, discussing their
function is a relevant issue; in the latter, invertebrates may simply be used as indicators
ofecosystem function since their impact is not significant to soil functioning.
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Biology International No3 (July 1996)
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Figure 1 An hierarchical model of soil function (after Lavelle et al., 1993)
:
CLIMATE
I
SOIL
L
1
PLANTCOMMUNITY
-1 HUMAN
ACTIVITIES
~~
ECOSYSTEM ENGINEERS
LITTERTRANSF'ORMERS PUNT
PRODUCTION
MICROPREDATOR FOODWEB
A
MICRO FLORA
SOIL PROCESSES
2. Major Functional Groups in Soils
All invertebrates in soils (and also roots) have developed interactions with
microorganisms. The kind of relationship (predation or mutualism) and the nature of the
microsites where developed (i.e., gut content or external structures like faecal pellets)
a l w the outline for a broad functional classification of soil organisms.
lo
Microorganisms :The Sleeping Beauty Paradox
Unlike most invertebrates, microorganisms as a whole have the capacity to digest any
substrate in the soil. However, their relative inability to move (which is more critical in
bacteria than fungi) and the discontinuous distribution of organic resources at the scale
at which they operate, cause them to be inactive for most of the time, i.e., in resting
stages that can last from months to years. Microbial communities appear as a huge
largely donnant population, with an enormus richness o species and an ability to
f
survive hard times (Jenkinson and Ladd, 1981). Turnover times of microbial biomass
are in the range of 6-18 months in nature, that is 1,OOO to 10,OOO times more than in
optimal laboratory conditions. Activation of resting microbiota and redistribution of
microorganisms and organic substrates is performed by invertebrates and mots that mix
the soil, add water and readily assimilable substrates to the soil. This function of
invertebrates and roots in the activation of dormant microflora has been referred to as
6
5. Biology Intemational No3 (July 7996)
3
the "Sleeping Beauty Paradox" (Lavelle et al., 1995). The nature of the association
between micro- and macroorganisms, however, varies greatly and mainly depends on
the size of the invertebrates involved. The presence and nature of structures produced
by the invertebrates that serve as incubators for microbial activities provide the division
of invertebrates into three major functional groups: micropredators, litter transformers
and ecosystem engineers.
Micropredat ors
The smallest invertebrates, Protozoa and Nematodes of the microfauna (average size
g."
02) do not build any structure. Predation is the only means they have to take
advantage of microbial activity. They participate in microfood webs that may include
several levels, with microbial grazers and one or two levels of predators (Hendrix et
al., 1986; Hunt et al., 1987); Moore and De Ruiter, 1991. The impact of such systems
is an overall stimulation of mineralisation of organic matter (Darbyshire, 1972; Ingham
et al., 1985). In microcosm studies, there is evidence that increased complexity of this
foodweb accelerates mineralisation (Setälä et al., 1 9 ; Couteaux et al., 1991).
91
Litter Transformers
At the next level, litter transformers include the small Oligochaeta Enchytraeidae and
arthropods of the mesofauna (Qmm) and macrofauna (>2mm). These invertebrates
build holorganic structures (their faecal pellets) that serve as incubators for microbial
activities; some time after deposition, they reingest these pellets to assimilate metabolites
that have been released by the microflora. Cases of reingestion of pellets of a given
individual or population by other individuals or populations are most likely frequent
(Vannier, 1985; Lussenhop, 1992). In these pellets, mineralisation may be enhanced in
short periods, but in the longer term, a relatively compact structure that limits aeration
and water storage as well as the accumulation of resistant humidified molecules may
result in a significant decrease of mineralisation, lasting as long as the structure's
integrity is maintained (Manlon and Anderson, 1980; Toutain et al., 1982). In types of
humus where H horizons are made of accumulated pellets of Enchytraeidae and
Microarthropods, these structures may last for several decades and significantly affect
the soil's function through the organisation of humus types (Jabiol et a. 1992). At an
l,
even larger scale of t m and space, leaching of organic acids released in these
ie
structures is known to alter clay minerals and thus participate in the formation of highly
weathered soils (Berthelin et al., 1979).
Ecosystem Engineers
A few large invertebrates (mainly earthwonns) and social insects (ants and termites) are
able to efficiently dig the soil and produce organo-mineral structures (casts and organo-
mineral pellets that are resistant macroaggregates, mounds and nests) and a large variety
of pores (galleries, chambers and voids resulting from an uncomplete backfilling of
galleries). The size of these organisms allows the development of anisosymbiotic
relationships with microflora in their proper gut, which is likely to be much more
efficient than the external relationships in faecal pellets. Mineralisation linked to the
dig stive process may be high, especially in grass eating termites that may assimilate up
o 8
t 396 o the ingested material (Wood, 1978). Endogeic earthworms may assimilate
f
between 5to 19% of the ingested organic matter depending on species and soil types, in
the course of a gut transit that may last no more than 20' to 4 hours (Lavelle, 1988).
7
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Biology lntemational No3 (July 1996)
3
This represents a several hundred-fold increase when compared to standard in-situ field
measurements.
The role of structures created by these organisms may be highly Significant in the
ecosystem function since they often are privileged sites for al basic soil processes (i.e.,
l
C and N mineralisation, denitrification or N-fixation, water and air infiltration), and
one single structure, or group of structures, may affect processes that operate at very
different scales of time and space. Some processes may be finely regulated within the
functional domain of ecosystem's engineers when complementary, or opposite effects
are observed at different scales of time and space. A simple example is represented by
termites that accelerate tremendously the mineralisation of litter through their internal
and extemal (fungus gardens) digestive processes, but then accumulate the remaining
carbon and nutrients by aggregating their pellets into the highly compact structure of the
tennitaria where virtually no mineralisation occurs until the colony dies.
3. The Main Biological Systems of Regulation (BSR)
The functioning of biological systems of regulation largely depends on the nature and
biological characteristics of all three major components i.e., characteristics of the energy
source, microbial communities and invertebrates . It is therefore possible to separately
consider (i) the litter systems, which comprise leaf litter as a food supply, surface lateral
roots, epigeic invertebrates (mainly arthropods) and microbial communities dominated
by fungi; (ii) the drilospheres, which include earthworms, soil organic matter as a food
source, and free-living soil microflora dominated by bacteria; and (iii) the
temitospheres, i.e., the whole volume of soil and organic resources that termites affect
through their activities, in association with obligate or optional mutualist
microorganisms. The rhizospheres, i.e., living subterranean roots and the soil and
microflora that they influence are another important biological system of regulation that
has an analogous functioning to that of the above mentioned systems.
4. Processes Affected by Invertebrate Activities
Invertebrate activities have significant effects on soil organic matter dynamics, the
organisation and structure of soil, and plant growth .One comrnon characteristic is that
a single process like ingesting and digesting a mixture of soil and litter may have effects
on a large range of processes, at different scales of time and space, i.e., short-term
enhancement of mineralisation during gut transit, and delayed effects in fresh and
ageing structures produced by these organisms (Fig. 2). The selective ingestion of
organic and mineral particles, mixing of soil and organic matter, and excavation of
galleries and chambers accumulated over time may have dramatic impact on the
morphology and function of soil (Fig.3). An important attribute of soils such as
aggregation, i.e., the organisation of particles in micro- to centimetre aggregates is
largely dependent on the activities of invertebrates that produce aggregates (as
organomineral faecal pellets), or other species that split them into smaller units when
they excavate , or feed on these large structures. Thisis the consequence of huge
ingestion rates by earthworms and termites thatrange from several hundred to more
than one thousand t ha-1 dry soil in soils with intense macrofauna activities.
8
7. Biology International N o33 (July 1996)
Figure 2: Consequences of the activities of an Ecosystem Engineer (an earthworm in that
example) on soil processes operating at different scales (Lavelle et al., in press)
PEDOGENESIS
The Function of Biodiversity in Soils
Soil zoologists have long asked themselves why so many species inhabited soils
(Ghilarov, 1977; Anderson, 1977; Vannier, 1985). A currently admitted reason is the
large diversity of resources andmicrohabitats that soils offer, a mixture of highly
microdivided aerial andaquatic phases. It has also been argued that the extended
Occurence of mutualistic relationships between macro- and microorganisms increase the
niche space and hence the possibility of having increased numbers of species (Lavelle,
1986; Lavelle e a. 1995).
t l,
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Siology Intemational No3 (July 1996)
3 '
Figure 3: Relationship among structures created by major functional groups of invertebrates
and roots, the structures they produce in soil, biodiversity of smaller organisms affected by
these structures and major soil processes
STRUCTURES EFFECTS ON EFFECTS ON
BIODIVERSITY FUNCTION
UIICRO- none - selection of - enhanced
'REDATORS microflora? mineralisation
,ITTER -t nhanced
rRANSFORMER 4
3o - selection of mineralisation
3 o -4 microflora +
Organic fecal - microhabitatsfor -sequestrationof
pellets smaller organic matter
invertebrates (depending on time
- food for other scale)
invertebrates
ECOSYSTEM B - Bioturbation'
ZNGINEERS 00
... .1.. .,..
.).. :.
.. .
. -selectionon litter
- Dissemination of
spores
(mycorhizae, fungi)
.
:
.
y
00 ,: :
>>
.. transformers
Large.'iompact
- Regulation of
structural porosity
structures -associated - Water storage
8 microfauna capacity
o&) - Infiltration rates
o* 0 - Aeration
smaller aggregates - selection on - SOM dynamics at
B microflora differentscales of
$me
- Nutrient cycling
- effects on root (s nchrony)
galleries, burrows,
chambers
development H
- urface structures
(runoff, infiltration..)
ROOTS
- production of - Aggregation
poIysaccharides
- selection on - Plant production
microflora
- associated food- - Overalt
webs biodiversity
Rhizosphere - root + root litter (through energy
structures feeders supply and diersity
of primary food
resources)
Classifications of soilinvertebrates based on the consequences that their activities have
3n soil processes (also referred to as their "function") are required. Such classifications
also imply a better knowledge of the interactions existing among organisms to focus on
species, or groups of species, that determine the diversity of other ones, and establish
the bases of a classification based on the functions that are actually performed.
10
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Biology Intemational No3 (July 1996)
3
1- Species Redundancy and Functional Groups
The idea that many species are redundant (di Castri and Youni%, 1990) in soil has been
long implicitly accepted by those scientists who proposed diverse functional
classifications for most zoological groups (Gisin, 1943 for Collembola; Grass& 1984
for termites; Lee, 1958 and Bouché, 1977 for earthworms). However, there is almost
immediate feedback between the effect an organism has on its environment and the
consequences for its future conditions of life. Therefore, if we can admit in a fnst
instance Andren's (1995) remark that organisms have evolved through selection to
maximize their contribution to future generations ....not to serve functions in the
ecosystem, we have to add that the effect of a dominant species on soil processes is
likely to affect theirresource base in the future. Selection may have operated on the long
term consequences of function of a species on its life condition.
On the other hand, the idea that a few keystone species (Paine, 1966) or functional
groups, that possibly comprise related taxa or mixedphyla, may determine the
abundance and diversity of smaller species, is receiving growing acceptance (Wardle
and Lavelle, 1996). The model presented in Fig.1 clearly points out the importance of
ecosystem engineers as possible regulators and determinants of communities of smaller
invertebrates. As a result, there is a need for functional classifications that 1)group
redundant species; 2) are based on well identified functions in soils, 3) give prominent
status to species or groups with key functions, but 4) recognise that some groups that
do not significantly affect the rates of any ecosystem process may serve as indicators of
on-going processes.
2- The Present Status of Functlonal Classifications
Zoologists have attempted to reduce the huge species richness of many si invertebrate
ol
groups into a smaller number of functional groups; these would implicitly group
redundant species regarding their function in soils, be easy to recognise on the basis of
morphological features, and have homogeneous impacts on soil processes. Several
classifications have been proposed since, sometimes more than one for asame
taxonomic group. Classifications grouping several large taxonomic groups with similar
ecological niches have rarely been proposed (Table 1).
These classifications are clearly centered on biological and ecological features that
describe some aspects of adaptive strategies. They have proved to be useful t describe
o
foodwebs comprised of microorganisms, micro- and mesofama (Hunt et al., 1987;
Ingham et al., 1986; De Ruiter et al., 1993).They are certainly insufficient in the case
of larger invertebrates whose function exceeds simple trophic processes by far.
Improvemen$s are still required, and should radicate in a clear view of the roles that
invertebrates play in soils, at the scale of the whole soil system, and in their respective
functional domains also called biological systems of regulation. Research is needed to
provide a clear framework for the definition of such groups.
3-The Structure and Functional Significance of Biodiversity in
Soils: Research Hypotheses
Biological systems of regulation characterise large functional domains that have general
features i common that clifferenciate h e p from other large domains. An example is the
n
drilosphere, viz. earthworms, the sum of structures (macropores, galleries, aggregates)
that they have built and the smaller organisms (microflora, fauna) that-inhaWthese
11
10. 4
m g lntemational No3 (July 1996)
by 3
structures. Inside these entities, different species will have differing impacts and
therefore different functions in the soil. To properly assess the role of biodiversity in
soils, and the conditions for its maintenance, it is essential to 1) clearly identify the links
existing among species, especially in the functional domain of a given BSR, to test to
which extent the presence of a given organism may influence the Occurence of other
ones, as the hierarchical structure proposed in Fig 1would suggest; 2) try to group key
species (ecosystem engineers, or litter transformers) that may have similar impacts in
the environment, on the basis of their real effect irrespective of their taxonomic
affinities, and morphology, when these criteria will prove to be irrelevant ; and 3)
consider biodiversity in the context of energy fluxes, a very important issue in managed
systems in which the drastic reduction in carbon fluxesmay indirectly affect
biodiversity. Research hypotheses that address these topics may be formulated as
follows:
Table 1: Functional classifications proposed for a few major groups of soil
invertebrates
Taxonomic Group Author Main criterla Categories
Proposed
Nematodes Feeding regime saprophages
Bacterial feeders
Fungivorous
Omnivorous
'Collembola. Size & morphology hyperedaphIc
as related to Epiedaphic
location in the soil Hemiedaphic
profile Euryedaphic
karthworms -Lee, 1958 Feeding regime,. kpigeic
Bouché, 1977 Habitat, Characters Anecic
Lavelle, 1981 of burrows, Size, Oligo-,meso-,or
Morphology, poly-huniic
pigmentation, endogeic
Demographic profil,
anatomy, diapause
Termites Grasse, 1984 ?-eedingregime, xylophagous
associatedmicro- Fungus growers
organisms Harvesters
Humivorous
Hypothesis 1 Nested biodiversities
.
Diversity in plant communities determines below-ground diversity in the following
order :plant diversity --> ecosystems engineers --> litter tríínsformers --> microfauna --
> microflora.
This hypothesis is a soil analogous of Hypothesis B1 developped by Solbrig (Ed.,
1991) stating that 'keystone' species are essentialfor maintaining species richness in
communifieJ....( Terborgh, 1989; Gautier-Hion and Michaloud, 1989). This hypothesis
first considers the existing links between diversity of plant and below-ground
invertebrate communi ties, and the effect of "ecosystem engineers" (sennt Stork and
Eggletoq, 1902; Lovelle, 1994) on community structure of smaller invertebrates and
microorganisms. It, is hypothesised that structures created by these organisms
considerdbly modify the habitat aiid trophic resource base of organisnis that are smaller
and less mobile. To test this hypothesis, communities of macro- and microarthropods,
12
11. 1
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T Biology International No33 (July 1996)
enchytraeidae, nematodes, and microorganisms will be sampled at three different spatial
scales:
by comparing diversity and abundance of small organisms in sites with contrasting
abundances and diversities of ecosystem engineers;
at a smaller intra-site scale, communities may also be compared in patches with high
densities of the key species considered, andpatches where they are not found
(when populations of plants and ecosystem engineers have aggregated
distributions);
at a microsite level, investigations will compare communities found in structures
produced (e.g., termite or ant mounds and nests, earthworm casts) to 'bulk soil' that was
not recently modeled by faunal activities.
Hypothesis 2. The role of structures as intermediates between
diversity and function
Diversity of soil invertebrates results in the production of structures whose abundance
and diversity are critical to the conservation and dynamics of soil organic matter,
nutrient release and maintenance of physical properties that are essentw bra sustained
primary production (Fig. 2).
This hypothesis, rather specific to the soil environment, points at the importance of
metabiotic processes in soils: structures created by keystone species influence the
location and evolution of organic resources that are commonly used by large part of the
soil community. Special emphasis is set on the role of the characters of structures, their
composition, shape, location, abundance etc., as specific microsites for the activities of
microorganisms, and hence determinants of soil organic matter and nutrient dynamics;
as specific components of the overall soil structure (macropores, aggregates, mounds,
ant cemeteries) biological structures also influence hydraulic properties of soils and their
resistance to erosion. Testing this hypothesis is another way of identifying invertebrate
functions in terms of their impact on soil properties, and the activity of smaller organisms,
irrespective of the taxonomic unit they belong to.
Hypothesis 3. The energetic bottle neck
In a soil with depleted organic resources, foodwebs tend to have a reduced number of
trophic levels, and less components at each level. This hypothesis is a simple,
application of the well known productivity hypothesis to explain species richness
(Giller, 1984) concerning soils. It can be casts of a given species of earthworm or
organo-ineral faecal pellets of large Diplopoda that could serve as a food resource to a
diverse microflora and fauna of populations of micro- and mesofauna. When the
invertebrates feed on an impoverished soil, the energetic value of casts is lower and
they will not sustain invertebrate and microbial populations that would normally have
developped in these structures. These structures with lower organic contents are also
likely to have a lower structural stability (Blanchart et al., 1993).
At t e scale of an e c ~ ~ p t c = ~ ~ be important to determine thresholds of organic
h it may ,
resources of a given quality beyond which critical levels of key faunal activities are
observed. In the African savannas of Lamto (Côte d'Ivoire) for example, the annual
cost of having an active earthworm community has been evaluated at 1.2t ha-lyr-1
organic matter from relatively young pools, irrespective of particle-size (Lavelle, 1978;
M r i et a. 1991). Similar data for other groups and situations are stll very scarce. If
a t n l,
maintenance of soil invertebrate communities at a significant level were to be
13
12. A/
Biology Intemational No33 (July 1996)
considered as part of sustainable management practices, this kind of information would
be extremely useful.
Perspectives for the Management of Soil Biodiversity
At present, there is a critical need to: (1) clearly understand the roles that invertebrates
play in soils, especially representatives of key functional groups; and (2) assess the
value of diversity to design management practices that optimize the conservation of
species, in accordance with well identified objectives. In some cases, the objective may
be conservation, in other situations, a sustainable use of soils. In the first case, the
objective will probably be to maintain a minimum diversity of plants that provide the
diversity and abundance of resources necessary to sustain a complex community. In the
case o agroecosystems and soils submitted to rehabilitation techniques, the objective is
f
to maintain key functional groups. It is essential to know if key species really exist and
what they are, and how many are necessary tosustain soil processes and plant
production at given rates. Other species that do not have the status of 'key species' may
be useful indicators of the state of the system to monitor changes occuring in the
€unction. They may be species that reflect specific structural or trophic characteristics of
the soil.
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