Local ecosystem feedbacks and critical transitions in the climate

Global and regional climate models, such as those used in IPCC assessments, are the best tools available for climate predictions. Such models typically account for large-scale land-atmosphere feedbacks. However, these models omit local vegetationenvironment 5 feedbacks that are crucial for critical transitions in ecosystems. Here, we reveal the hypothesis that, if the balance of feedbacks is positive at all scales, local vegetation-environment feedbacks may trigger a cascade of amplifying effects, propagating from local to large scale, possibly leading to critical transitions in the largescale climate. We call for linking local ecosystem feedbacks with large-scale land10 atmosphere feedbacks in global and regional climate models in order to yield climate predictions that we are more confident about

Endolithic and hypolithic soil-like systems: structure and composition from the macroto submicro-levels

The paper presents a detailed study on structure and composition of endolithic and hypolithic systems. The following issues are discussed: morphology at macro to submicro levels, biochemical weathering, formation of carbonates and oxalates in situ, migration of Fe compounds, and spatial patterns of endolithic systems. Endolithic and hypolithic systems have major features attributed to soils: (a) rock layer exposed to external abiogenic factors, (b) lithomatrix inhabited by living organisms which are synthesizing and decomposing organic matter, (c) as a result initial parent rock (lithomatrix) is transformed in situ by biogenic and abiogenic factors, the products of transformation are retained and/or removed, the vertical heterogenity is established in a form of microhorizons composing microprofile. Examined profiles of endolithic systems in granitoids of East Antarctica with high quartz content had clear eluvial-illuvial differentiation patterns. Similar patterns have been discovered in different landscapes from the Plateau Ozark in Missouri to the Table Mountain in South Africa

Об управляемости, наблюдаемости и оптимизации дискретных нестационарных линейных систем Вольтерра

   Исследуются дискретные нестационарные линейные системы уравнений типа Вольтерра, существенной особенностью которых является зависимость каждого последующего состояния от всей предыстории процесса. Получено представление решений таких систем в форме Коши с учетом управляющих воздействий. Установлены необходимые и достаточные условия точечной управляемости, точечной управляемости по выходу и наблюдаемости, а также исследована линейно-квадратичная задача оптимизации рассматриваемых систем уравнений Вольтерра.   In this article, we study discrete nonstationary linear dynamic systems of Volterra type. An essential feature of such kind of systems is that their current states depend on the previous states of this system. The formula Cauchy, which gives us the solution of linear Volterra systems with the control inputs, is obtained. The necessary and sufficient conditions of the pointwise controllability, pointwise output controllability, and observability are proven. Also the linear-quadratic optimization problem for the nonstationary Volterra control systems is studied.   Исследуются дискретные нестационарные линейные системы уравнений типа Вольтерра, существенной особенностью которых является зависимость каждого последующего состояния от всей предыстории процесса. Получено представление решений таких систем в форме Коши с учетом управляющих воздействий. Установлены необходимые и достаточные условия точечной управляемости, точечной управляемости по выходу и наблюдаемости, а также исследована линейно-квадратичная задача оптимизации рассматриваемых систем уравнений Вольтерра

Dynamics of carbon pools in post-agrogenic sandy soils of southern taiga of Russia

<p>Abstract</p> <p>Background</p> <p>Until recently, a lot of arable lands were abandoned in many countries of the world and, especially, in Russia, where about half a million square kilometers of arable lands were abandoned in 1961-2007. The soils at these fallows undergo a process of natural restoration (or self-restoration) that changes the balance of soil organic matter (SOM) supply and mineralization.</p> <p>Results</p> <p>A soil chronosequence study, covering the ecosystems of 3, 20, 55, 100, and 170 years of self-restoration in southern taiga zone, shows that soil organic content of mineral horizons remains relatively stable during the self-restoration. This does not imply, however, that SOM pools remain steady. The C/N ratio of active SOM reached steady state after 55 years, and increased doubly (from 12.5 - 15.6 to 32.2-33.8). As to the C/N ratio of passive SOM, it has been continuously increasing (from 11.8-12.7 to 19.0-22.8) over the 170 years, and did not reach a steady condition.</p> <p>Conclusion</p> <p>The results of the study imply that soil recovery at the abandoned arable sandy lands of taiga is incredibly slow process. Not only soil morphological features of a former ploughing remained detectable but also the balance of soil organic matter input and mineralization remained unsteady after 170 years of self-restoration.</p