O banco de sementes do solo: uma ferramenta para a avaliação do estado de conservação dos charcos temporários mediterrânicos

Os Charcos temporários mediterrânicos (3170*) são habitats prioritários devido à enorme biodiversidade que albergam e ao grau de ameaça sob o qual que se encontram. A singularidade deste habitat resulta da coexistência de diferentes comunidades de plantas no mesmo espaço mas em períodos de tempo diferentes, o que é viabilizado pela existência de bancos de sementes abundantes e diversificados. A avaliação da composição específica e abundância do banco de sementes do solo permitiu determinar a distribuição espacial das sementes e o potencial de recuperação dos charcos. Com esta avaliação concluiu-se que existe uma maior riqueza específica nas cinturas externa e média dos charcos do que na cintura interna. Concluiu-se também que o conhecimento do banco de sementes dos charcos pode contribuir para a definição de estratégias de gestão/recuperação dos charcos, nomeadamente daqueles que possuem grau de conservação intermédio, funcionando como um valioso instrumento de gestão; The soil seed bank - a tool for assessing the conservation status of Mediterranean temporary ponds Abstract: Mediterranean temporary ponds (3170*) are priority habitats due to the huge biodiversity they shelter and because they are menaced. The uniqueness of this habitat results from the coexistence of different plant communities in the same space at different time periods, what is allowed by the existence of abundant and diversified soil seed banks. The assessment of the specific composition and abundance of soil seed bank, made possible to ascertain the spatial distribution of seeds within ponds and their recovery potential. This assessment showed that there is more specific richness in intermediate and outer belts of ponds than in the inner belt. It also showed how valuable can this information be regarding the design of management or recovery strategies for ponds, particularly for those with intermediate degree of conservation.

Existence of Homoclinic Solutions for Nonlinear Second-Order Problems

In this work, we consider the second-order discontinuous equation in the real line, u′′(t)−ku(t)=f(t,u(t),u′(t)),a.e.t∈R, with k>0 and f:R3→R an L1 -Carathéodory function. The existence of homoclinic solutions in presence of not necessarily ordered lower and upper solutions is proved, without periodicity assumptions or asymptotic conditions. Some applications to Duffing-like equations are presented in last section.

Sufficient conditions for the existence of heteroclinic solutions for Phi-Laplacian differential equations

In this paper we consider the second order discontinuous equation in the real line, (a(t)φ(u′(t)))′ = f(t,u(t),u′(t)), a.e.t∈R, u(-∞) = ν⁻, u(+∞)=ν⁺, with φ an increasing homeomorphism such that φ(0)=0 and φ(R)=R, a∈C(R,R\{0})∩C¹(R,R) with a(t)>0, or a(t)<0, for t∈R, f:R³→R a L¹-Carathéodory function and ν⁻,ν⁺∈R such that ν⁻<ν⁺. We point out that the existence of heteroclinic solutions is obtained without asymptotic or growth assumptions on the nonlinearities φ and f. Moreover, as far as we know, this result is even new when φ(y)=y, that is, for equation (a(t)u′(t))′=f(t,u(t),u′(t)), a.e.t∈R.

Systems of coupled clamped beams equations with full nonlinear terms: Existence and location results

This work gives sufficient conditions for the solvability of the fourth order coupled system┊ u⁽⁴⁾(t)=f(t,u(t),u′(t),u′′(t),u′′′(t),v(t),v′(t),v′′(t),v′′′(t)) v⁽⁴⁾(t)=h(t,u(t),u′(t),u′′(t),u′′′(t),v(t),v′(t),v′′(t),v′′′(t)) with f,h: [0,1]×ℝ⁸→ℝ some L¹- Carathéodory functions, and the boundary conditions {┊ u(0)=u′(0)=u′′(0)=u′′(1)=0 v(0)=v′(0)=v′′(0)=v′′(1)=0. To the best of our knowledge, it is the first time in the literature where two beam equations are considered with full nonlinearities, that is, with dependence on all derivatives of u and v. An application to the study of the bending of two elastic coupled campled beams is considered.