Feedbacks between vegetation pattern and resource loss dramatically decrease ecosystem resilience and restoration potential in a simple dryland model

Conceptual frameworks of dryland degradation commonly include ecohydrological feedbacks between landscape spatial organization and resource loss, so that decreasing cover and size of vegetation patches result in higher water and soil losses, which lead to further vegetation loss. However, the impacts of these feedbacks on dryland dynamics in response to external stress have barely been tested. Using a spatially-explicit model, we represented feedbacks between vegetation pattern and landscape resource loss by establishing a negative dependence of plant establishment on the connectivity of runoff-source areas (e.g., bare soils). We assessed the impact of various feedback strengths on the response of dryland ecosystems to changing external conditions. In general, for a given external pressure, these connectivity-mediated feedbacks decrease vegetation cover at equilibrium, which indicates a decrease in ecosystem resistance. Along a gradient of gradual increase of environmental pressure (e.g., aridity), the connectivity-mediated feedbacks decrease the amount of pressure required to cause a critical shift to a degraded state (ecosystem resilience). If environmental conditions improve, these feedbacks increase the pressure release needed to achieve the ecosystem recovery (restoration potential). The impact of these feedbacks on dryland response to external stress is markedly non-linear, which relies on the non-linear negative relationship between bare-soil connectivity and vegetation cover. Modelling studies on dryland vegetation dynamics not accounting for the connectivity-mediated feedbacks studied here may overestimate the resistance, resilience and restoration potential of drylands in response to environmental and human pressures. Our results also suggest that changes in vegetation pattern and associated hydrological connectivity may be more informative early-warning indicators of dryland degradation than changes in vegetation cover.

Saint Mathew Law and Bonini Paradox in Textual Theory of Complex Models

The mathematical models of the complex reality are texts belonging to a certain literature that is written in a semi-formal language, denominated L(MT) by the authors whose laws linguistic mathematics have been previously defined. This text possesses linguistic entropy that is the reflection of the physical entropy of the processes of real world that said text describes. Through the temperature of information defined by Mandelbrot, the authors begin a text-reality thermodynamic theory that drives to the existence of information attractors, or highly structured point, settling down a heterogeneity of the space text, the same one that of ontologic space, completing the well-known law of Saint Mathew, of the General Theory of Systems and formulated by Margalef saying: “To the one that has more he will be given, and to the one that doesn't have he will even be removed it little that it possesses.

Chebanov law and Vakar formula in mathematical models of complex systems

Ecological models written in a mathematical language L(M) or model language, with a given style or methodology can be considered as a text. It is possible to apply statistical linguistic laws and the experimental results demonstrate that the behaviour of a mathematical model is the same of any literary text of any natural language. A text has the following characteristics: (a) the variables, its transformed functions and parameters are the lexic units or LUN of ecological models; (b) the syllables are constituted by a LUN, or a chain of them, separated by operating or ordering LUNs; (c) the flow equations are words; and (d) the distribution of words (LUM and CLUN) according to their lengths is based on a Poisson distribution, the Chebanov's law. It is founded on Vakar's formula, that is calculated likewise the linguistic entropy for L(M). We will apply these ideas over practical examples using MARIOLA model. In this paper it will be studied the problem of the lengths of the simple lexic units composed lexic units and words of text models, expressing these lengths in number of the primitive symbols, and syllables. The use of these linguistic laws renders it possible to indicate the degree of information given by an ecological model.

The conversation on political issues on Twitter: an analysis of the participation and frames in the debate on the 'Wert law' and evictions in Spain

The aim of this study is to determine which social agents are involved in the political debate on Twitter and whether the interpretive hegemony of actors that have traditionally been the most prominent is tempered by the challenge of framing shared with audiences. The relationship between the interpretations expressed and the profiles of participants is analyzed in comparison with the frames used by mainstream media. The chosen methodology combines content analysis and discourse analysis techniques on a sample of 1,504 relevant tweets posted on two political issues –the approval of the education law LOMCE and the evictions caused by the crisis, which have also been studied in the front pages of four leading newspapers in Spain. The results show a correlation between political issue singularities, frames and the type of discussion depending on the participants.

Effects of landscape spatial heterogeneity on dryland restoration success. The combined role of site conditions and reforestation techniques in southeastern Spain

In occidental Europe, Spain is one of countries the most severely affected by desertification (Arnalds & Arsher 2000). Particularly, South-eastern Spain is considered as one of the most threatened areas by desertification in Mediterranean Europe (Vallejo 1997). In 2003, the Valencia Regional Forest Service implemented a restoration demonstration project in this area. The project site is a small catchment (25 ha) located in the Albatera municipality. The catchment is highly heterogeneous, with terraced slopes, south-facing slopes and north-facing slopes. The restoration strategy was based on planting evergreen trees and shrubs which can grow quickly after disturbances, and on field treatments aimed at maximizing water collection (micro-catchments, planting furrows), organic amendment (compost), and conservation (tree shelters, mulching). On south landscape unit, the whole category of restoration treatments was applied: water micro-catchment + Tubex tree shelters + mulching & compost, while on north landscape unit: netting tree shelters + mulching & compost only were applied, while in terrace landscape unit: furrows + netting tree shelters + mulching & compost were applied. Survival and growth of the planted seedlings were used as metrics of restoration success. To assess the effects of the treatments applied for soil conservation, soil loss rates (from 2005 to 2009) were evaluated using the erosion pin method. We conclude that, despite the limiting conditions prevailing on the south unit, this landscape unit showed the highest survival and growth plant rates in the area. The best seedling performances on the south landscape unit were probably due to the highest technical efforts applied, consisting in the water micro-catchment installation and the Tubex plant shelters addition. In addition, soil loss rates followed decreasing trends throughout the assessment period. Soil loss rates were highest on south landscape unit in comparison with the other landscape units, due to the more accentuated relief. North landscape unit and terrace unit showed a net soil mass gain, probably reflecting the trapping of sediments produced by plantation works.