viernes, 16 de agosto de 2019

Les semences libres de Nicolas Supiot, le paysan boulanger

jueves, 15 de agosto de 2019

"And so I go to the woods. As I go in under the trees, dependably, almost at once, and by nothing I do, things fall into place. I enter an order that does not exist outside, in the human spaces
Wendell Berry

miércoles, 14 de agosto de 2019

Vascular bundles of papyrus (Cyperus papyrus)
200x(objective lens magnification)
Photo: David Maitland

lunes, 12 de agosto de 2019

sábado, 10 de agosto de 2019

Some theoretical notes on agrobiodiversity

Some theoretical notes on agrobiodiversity: spatial heterogeneity and population interactions 
Diego Griffon & Maria-Josefina Hernandez

Ecological interactions are fundamental in ecological pest management, and these interactions form networks. The properties of these networks, where interactions of all possible nature (positive, neutral, negative) coexist, are key for management, but little is known about them. The main reasons for this lack of knowledge are the difficulties in obtaining empirical evidence. These problems may be partially bypassed using a theoretical approach. Here, by means of mathematical models that represent networks of ecological interactions in agroecosystems, we characterize some architectural features that promote the self-regulation of population densities in these networks. The results show that the key features are: spatial heterogeneity and a high proportion of positive interactions.

Species survivals. Initial richness, for six different initial conditions (defined in Fig 3). Blue: survival percentage in one community (no spatial heterogeneity). Grey: survival percentage of one community in a metacommunitarian background. The curves are averages of 40 simulations for each initial condition.

Uniform perturbation (example). A persistent network obtained under the 20:10:10:60 initial condition is perturbed by a little increase in the densities of each population. Left: dynamics after the perturbation. Two populations reach very low (but non zero) densities. Right: network before and after the perturbation. Notice that both networks are the same.

The more relevant results of the models evaluated and discussed in this article can be summarized as follows: (i) The conditions under which persistent networks are obtained after the iterative process are very restricted. However, when persistent  networks are obtained, they are fundamentally resilient to perturbations. (ii) Mutualistic (and positive in general) interactions have an important and extensive effect under certain (very specific) conditions. (iii) Spatial heterogeneity increases the possibility of persistence in hypothetical communities. (iv) Ecological interactions that somehow have been neglected in the past (commensalism and amensalism, the forgotten sisters), may be: 1- More frequent than generally thought, and 2- Important for the persistence of communities.


viernes, 9 de agosto de 2019

Direct and indirect effects of urban gardening on aboveground and belowground diversity influencing soil multifunctionality      
Tresch et al., 2019

Urban gardens are popular green spaces that have the potential to provide essential ecosystem services, support human well-being, and at the same time foster biodiversity in cities. We investigated the impact of gardening activities on five soil functions and the relationship between plant (600 spp.) and soil fauna (earthworms: 18 spp., springtails: 39 spp.) in 85 urban gardens (170 sites) across the city of Zurich (Switzerland). Our results suggest that high plant diversity in gardens had a positive effect on soil fauna and soil multifunctionality, and that garden management intensity decreased plant diversity. Indices of biological activity in soil, such as organic and microbial carbon and bacterial abundance, showed a direct positive effect on soil multifunctionality. Soil moisture and disturbance, driven by watering and tilling, were the driving forces structuring plant and soil fauna communities. Plant indicator values proved useful to assess soil fauna community structure, even in anthropogenic plant assemblages. We conclude that to enhance soil functions, gardeners should increase plant diversity, and lower management intensity. Soil protective management practices, such as applying compost, mulch or avoiding soil tilling, should be included in urban green space planning to improve urban biodiversity and nature’s contribution to people.

 Expected positive relationships are given in black and negative ones in red, grey arrows represent both positive and negative effects. We expected that annual vegetables (arrows 1a) will negatively influence plant and soil fauna as well as soil multifunctionality compared to perennial grass sites, while perennial flowers (arrows 1b) will show positive effects. Management intensity (arrows 2) is expected to negatively affect plant diversity and soil fauna as well as soil multifunctionality. Higher plant diversity (arrows 3) is hypothesised to have a positive effect on soil fauna and soil multifunctionality. Soil fauna diversity and biomass (arrows 4a & 4b) are also expected to have a positive effect on soil multifunctionality. Urbanisation (arrows 5) might have a positive or negative effect on soil fauna and soil multifunctionality.

miércoles, 7 de agosto de 2019

lunes, 5 de agosto de 2019

"Todo el que disfruta cree que lo que importa del árbol es el fruto, cuando en realidad es la semilla.
He aquí la diferencia entre los que piensan y los que solo disfrutan."

Friedrich Nietzsche.


domingo, 4 de agosto de 2019

Plant domestication disrupts biodiversity effects across major crop types
Chacón‐Labella et al., 2019.

Plant diversity fosters productivity in natural ecosystems. Biodiversity effects might increase agricultural yields at no cost in additional inputs. However, the effects of diversity on crop assemblages are inconsistent, probably because crops and wild plants differ in a range of traits relevant to plant–plant interactions. We tested whether domestication has changed the potential of crop mixtures to over‐yield by comparing the performance and traits of major crop species and those of their wild progenitors under varying levels of diversity. We found stronger biodiversity effects in mixtures of wild progenitors, due to larger selection effects. Variation in selection effects was partly explained by within‐mixture differences in leaf size. Our results indicate that domestication might disrupt the ability of crops to benefit from diverse neighbourhoods via reduced trait variance. These results highlight potential limitations of current crop mixtures to over‐yield and the potential of breeding to re‐establish variance and increase mixture performance. 

viernes, 2 de agosto de 2019

Changes in diet following the rise of farming in Europe and Asia during the Neolithic period resulted in humans retaining overbites into adulthood, which led in turn to language diversification.