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Sufficient noise and turbulence can induce phytoplankton patchiness

Natural Science 2010年第4期2卷 320-328页

作者： Hiroshi Serizawa Takashi Amemiya Kiminori Itoh 不详

Phytoplankton patchiness ubiquitously obser- ved in marine ecosystems is a simple phy- sical phenomenon. Only two factors are required for its formation: one is persistent variations of inhomogeneous distributions in the phytopl- ankton population and the other is turbulent stirring by eddies. It is not necessary to assume continuous oscillations such as limit cycles for realization of the first factor. Instead, a certain amount of noise is enough. Random fluctua-tions by environmental noise and turbulent ad-vection by eddies seem to be common in open oceans. Based on these hypotheses, we pro-pose seemingly the simplest method to simulate patchiness formation that can create realistic images. Sufficient noise and turbulence can induce patchiness formation even though the system lies on the stable equilibrium conditions. We tentatively adopt the two-component model with nutrients and phytoplankton, however, the choice of the mathematical model is not essen-tial. The simulation method proposed in this study can be applied to whatever model with stable equilibrium states including one-com-ponent ones.

关键词： Eddy Fluctuation Noise patchiness Reaction-Advection-Diffusion Model Turbulence

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Spatio-Temporal Effect on Soil Respiration in Fine-Scale Patches in a Desert Ecosystem

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Pedosphere 2006年第1期16卷 1-9页

作者： S. PEN-MOURATOV M. RAKHIMBAEV Y. STEINBERGER Faculty of Life Sciences Bar-Ilan University Ramat-Gan 52900 (Israel) Faculty of Life Sciences Bar-Ilan University Ramat-Gan 52900 (Israel) Institute of Botany Tashkent (Uzbekistan)

Soil organisms in terrestrial systems are unevenly distributed in time and space, and often aggregated. Spatiotemporal patchiness in the soil environment is thought to be crucial for the maintenance of soil biodiversity, providing diverse microhabitats tightly interweaving with resource partitioning. Determination of a ＂scale unit＂ to help understand ecological processes has become one of the important and most debatable problems in recent years. A fieldwork was carried out in the northern Negev Desert highland, Israel to determine the influence of fine-scale landscape patch moisture heterogeneity on biogeochemical variables and microbial activity linkage in a desert ecosystem. The results showed that the spatio-temporal patchiness of soil moisture to which we attribute influential properties, was found to become more heterogenic with the decrease in soil moisture availability （from 8.2 to 0.4 g kg^-1） toward the hot, dry seasons, with coefficient of variation （CV） change amounting to 66.9%. Spatio-temporal distribution of organic matter （OM） and total soluble nitrogen （TSN） was found to be relatively uniformly distributed throughout the wet seasons （winter and spring）, with increase of relatively high heterogeneity toward the dry seasons （from 0.25% to 2.17% for OM, and from 0 to 10.2 mg kg^-1 for TSN） with CV of 47.4% and 99.7% for OM and TSN, respectively. Different spatio-temporal landscape patterns were obtained for Ca （CV = 44.6%）, K （CV = 34.4%）, and Na （CV = 92%） ions throughout the study period. CO2 evolution （CV = 48.6%） was found to be of lower heterogeneity （varying between 2 and 39 g CO2-C g^-1 dry soil h^-1） in the moist seasons, e.g., winter and spring, with lower values of respiration coupled with high heterogeneity of Na^＋ and low levels of TSN and organic matter content, and with more homogeneity in the dry seasons （varying between 1 and 50 g CO2-C g^-1 dry soil h^-1）. Our results elucidate the heterogeneity and complexity of desert system habitats

关键词： desert microbial respiration patchiness small-scale habitat soil

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Mind the gap among patches in arid plant communities:rapid root proliferation in response to N addition

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Journal of Plant Ecology 2019年第1期12卷 89-95页

作者： Maria Fernanda Reyes Martín RAguiar Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura(IFEVA)and Consejo Nacional de Investigaciones Científicas y Técnicas(CONICET) Universidad de Buenos AiresAv.San Martín 4453Buenos Aires C1417DSEArgentina

Aims In arid communities,it has been proposed that individual plants can extend their roots beyond their canopy exploring neighbour-ing bare ground *** becomes relevant in systems where the vegetation is distributed in patches surrounded by bare ***,whether roots of different species may be overlapping under bare ground areas is still *** factors control-ling root responses when no plants appear to be directly influ-encing the gap among patches are still *** aim of our study was to detect perennial grasses responses to an N enrich-ment *** In a semi-arid steppe(Patagonia,Argentina),we buried root traps filled with sieved soil with and without N addition,under bare soil *** were harvested after 4 and 6 *** neighbour-hoods(30 cm in diameter)included at least three of the dominant tussock *** harvests,we identified species in the traps by root traits and quantified diversity,biomass and specific relative growth *** Findings Bare ground areas show simultaneous root growth of different *** of perennial grass roots was higher with N addition than without it in the first harvest(4 months),but this difference disappeared in the second harvest(6 months).Root biomass was maximal after 6 months in N addition *** preferred by herbivores(Bromus pictus and Poa ligularis)showed rapid growth and responses to N *** between harvests may be an indicative that N pulses interact with rising temperatures and soil water content as growing season progress.

关键词： belowground community ecology grass species roots Patagonian steppe patchiness root growth rates zone of influence

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