A census of the biomass on Earth is key for understanding the structure and dynamics of the biosphere. However, a global, quantitative view of how the biomass of different taxa compare with one another is still lacking. Here, we assemble the overall biomass composition of the biosphere, establishing a census of the ≈550 gigatons of carbon (Gt C) of biomass distributed among all of the kingdoms of life. We find that the kingdoms of life concentrate at different locations on the planet; plants (≈450 Gt C, the dominant kingdom) are primarily terrestrial, whereas animals (≈2 Gt C) are mainly marine, and bacteria (≈70 Gt C) and archaea (≈7 Gt C) are predominantly located in deep subsurface environments. We show that terrestrial biomass is about two orders of magnitude higher than marine biomass and estimate a total of ≈6 Gt C of marine biota, doubling the previous estimated quantity. Our analysis reveals that the global marine biomass pyramid contains more consumers than producers, thus increasing the scope of previous observations on inverse food pyramids. Finally, we highlight that the mass of humans is an order of magnitude higher than that of all wild mammals combined and report the historical impact of humanity on the global biomass of prominent taxa, including mammals, fish, and plants.

https://www.pnas.org/content/pnas/115/25/6506.full.pdf

The biomass distribution on Earth

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_51-52/010015216.pdf

Soil function in a changing world: the role of invertebrate ecosystem engineers

Tillage systems affect the soil physical and chemical environment in which soil organisms live, thereby affecting soil organisms. Tillage practices change soil water content, temperature, aeration, and the degree of mixing of crop residues within the soil matrix. These changes in the physical environment and the food supply of the organisms affect different groups of organisms in different ways. One of the challenges of research in soil ecology is to understand the impacts of management on the complex interactions of all organisms at the soil community level. In addition to the response of organisms to soil manipulations, agriculturalists are interested in the actions of soil organisms on the physical and chemical environment in the soil. Soil organisms perform important functions in soil, including structure improvement, nutrient cycling, and organic matter decomposition. This paper discusses the effects of tillage practices on soil organism populations, functions, and interactions. Although there is a wide range of responses among different species, most organism groups have greater abundance or biomass in no-till than in conventional tillage systems. Larger organisms in general appear to be more sensitive to tillage operations than smaller organisms, due to the physical disruption of the soil, burial of crop residue, and the change in soil water and temperature resulting from residue incorporation. Variations in responses found in different studies reflect different magnitudes of tillage disruption and residue burial, timing of the tillage operations, timing of the measurements, and different soil, crop, and climate combinations. The paper concludes with a discussion of challenges for tillage researchers.

Tillage systems and soil ecology

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers12-05/010052508.pdf

Influence of termites on ecosystem functioning. Ecosystem services provided by termites

Effects of earthworms on plant growth: patterns and perspectives

A worldwide survey of earthworms in the humid tropics revealed that 51 exotics and 151 native species are commonly found in tropical agroecosystems. On the basis of frequency records and climatic and edaphic ranges, 21 exotics and 27 native species have been selected as possible candidates for manipulation. A multivariate analysis separated these species into four groups: (i) native species with wide edaphic and medium climatic tolerances; (ii) exotic species with wide climatic and edaphic tolerances; (iii) native and exotic species with narrow edaphic tolerances but more resistant to climatic variations; and (iv) native species with limited tolerance for climatic and edaphic variations. Regarding management, species of group (ii) seem to be the most adaptable. both at regional and locallevels (multipurpose species); group (i) can be managed for specific climatic conditions whereas group (iii) should be managed in specific soil environments. Species of group (iv) may only be managed at a very local scale.

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers16-03/010021554.pdf

A survey of tropical earthworms : taxonomy, biogeography and environmental plasticity

The structure and seasonal changes of earthworm communities were evaluated in a natural savanna and in a improved grass-legume pasture in a Colombian oxisol over a period of 18 months. One plot of 90×90 m was isolated in each of the systems and each month five samples of 1 m2×0.5 m and ten of 20×20×20 cm were randomly selected from a stratified block design. Species richness was similar in the two evaluated plots (seven species), whereas diversity measured by the index, H (Shannon and Weaver 1949) was clearly different, i.e. H=2.89 in natural savanna and H=1.29 in pasture. This is explained by differences in earthworm community structure. The average annual density in the savanna was 49.8, ranging from 10.8 to 135.8 individuals (ind) m–2, and biomass was 3.3 g m–2 (hand-sorting method), ranging from 0.9 to 11.5 g m–2. In the man-made pasture, density was 80.1 ind m–2 on average, ranging from 24 to 215.8 ind m–2 and biomass was more than tenfold higher, ranging from 29.2 to 110.4 g m–2. This was especially due to the presence of a large glossoscolecid anecic species, Martiodrilus carimaguensis Jimenez and Moreno, which has been greatly favoured by conversion of savanna to pasture. Endogeic species were dominant in the natural savanna whereas the anecic species accounted for 88% of total earthworm biomass in the pasture. Total earthworm density and biomass were significantly different in the two systems studied (t-test). The results indicate a clearly positive response of earthworm communities to improved pastures, a type of land use that is being increasingly adopted in moist neotropical savannas.

/pdf/earthworm-communities-in-native-savannas-and-man-made-1qgv18sbdu.pdf

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

The soil macrofauna, i.e., invertebrates visible with the naked eye that live in the soil or on its immediato surface (eg., in the litter) and/or spend an important part of their life cycle on or in the soil, play an important part in modifying soil properties and its functioning. These invertebrates inelude: earthworms, termitas, ants, millipedes, centlpedes, sptders, beetles, grubs, crickets, cicadas, snails, scorpions, hemiptera and fiy and lepidoptera larvae that may surpass 1000 species in an ecosystem and aiso reach densities over one million individuais per hectare and a biomass over one ton in the same area. Furthermore, these organisms pertorm multiple functions in the ecosystem and may be divided in various classcs using different functional classifications. For example, some may act solely as pests while others are temporary or facultative pests and still others play mostiy beneficial roles. In Mexico, 1 27 macrofauna communities have been sampled in 37 localities, pnmarily in the State of Veracruz and in the E or SE of the country, using a standardizad methodology (TSBFl which, despite its limitations, is easy to employ and permits the taking of many samples in different ecosystems with reasonable time and efforts. Nine mam ecosystems were sampled, representing mostiy pastures, forests, annual crop land, citrus and coffee plantations. The results reve al the do mi nance of earthworms in terms of biomass in most ecosystems and of ants in terms of density. Maize fields and the coconut plantation had the lowest biomass (< 1 5 g m2), while the forests had more than 25 g m 2 and remaining ecosystems more than 35 g m2 Undor sugar cane, densities reached almost 3000 individuais m‘ while the remaming Systems had less than 1600 individuais mT As a case study, the "Los Tuxtlas" region is analyzed (Veracruz) where deforestation had a negativo effect on the epigeic arthropod population, dependent on the presence of litter for its survival, while the establishment of pastures greatly increased the earthworm biomass, which surpassed that found under nativo vegetation. Natural habitat destruction in Mexico roprosents a serious danger for the disappearance of numerous soil macrofauna species, which may attam diversity lovols much higher than those of the above-ground organisms, Furthermore, thore ts a great lack of Mexican taxonomists trained to classity at the species level many of the groups of the soil macrofauna. Therefore it is necessary to study, dassify, quantify and determine (in different Mexican ecosystems) the different organisms representing the soil macrofauna in order to determine their diversity and means of conservation and sustainable use. Due to the importance of these organisms in agroecosystems and the high monetary impact (both positivo and negative) of their activities on crops, their communities must be studied to determine: i) presence of possible ecological equilibrium or disequilibna, ii) its ongin (natural or anthropic), and mi its possible effeets (positive and/or negative) on edaphic processes and plant productivity.

/pdf/diversidad-y-rol-funcional-de-la-macrofauna-edafica-en-los-1tkty81qjq.pdf

Ana G. Moreno

Papers

A survey of tropical earthworms : taxonomy, biogeography and environmental plasticity

Earthworm communities in native savannas and man-made pastures of the Eastern Plains of Colombia

Diversidad y rol funcional de la macrofauna edáfica en los ecosistemas tropicales mexicanos

Soil macrofauna in SE Mexican pastures and the effect of conversion from native to introduced pastures

Earthworms as a resource in tropical agroecosystems