University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Long-term effects of organic and conventional farming on soil erosion

Abstract: Conventional, intensive tillage farming systems have greatly increased crop production and labour efficiency But, serious questions are being raised about the energy-intensive nature of these systems and their adverse effects on soil productivity and environmental quality1,2 This concern has led to an increasing interest in organic farming systems because they may reduce some of the negative effects of conventional agriculture on the environment3,4 We compare the long-term effects (since 1948) of organic and conventional farming on selected properties of the same soil The organically-farmed soil had significantly higher organic matter content, thicker topsoil depth, higher polysaccharide content, lower modulus of rupture and less soil erosion than the conventionally-farmed soil This study indicates that, in the long term, the organic farming system was more effective than the conventional farming system in reducing soil erosion and, therefore, in maintaining soil productivity

Eco-evolutionary conservation biology: contemporary evolution and the dynamics of persistence

Abstract: Summary 1 Natural and human mediated perturbations present challenges to the fate of populations but fuel contemporary evolution (evolution over humanly observable time-scales). Here we ask if such evolution is sufficient to make the difference between population extinction and persistence. 2 To answer this question requires a shift from the usual focus on trait evolution to the emergent ‘eco-evolutionary’ dynamics that arise through interactions of evolution, its fitness consequences and population abundance. 3 By combining theory, models and insights from empirical studies of contemporary evolution, we provide an assessment of three contexts: persistence of populations in situ, persistence of colonising populations, and persistence under gene flow and in metapopulations. 4 Contemporary evolution can likely rescue some, but not all, populations facing environmental change. Populations may fail partly because of the demographic cost of selection. 5 Contemporary evolution that initiates positive population growth, such as selective founding processes, may create a ‘persistence vortex’ that overcomes the problems of small populations. 6 Complex, even shifting, relationships between gene flow and adaptation may aid the persistence of subpopulations as well as the persistence and expansion of metapopulations. 7 An eco-evolutionary perspective suggests that we expand our focus beyond the acute problems of threatened populations and growing invasions, to consider how contemporary evolutionary mechanics contribute to such problems in the first place or affect their resolution.

Habitat architecture and the abundance and body-size-dependent habitat selection of a phytal amphipod'

Abstract: Field and laboratory experiments were conducted on the effect of habitat architecture (the number, size, shape, and arrangement of habitable spaces and structures) created by benthic algae on the habitat selection of an abundant mobile amphipod, Gam- marellus angulosus, on the central coast of Maine. Amphipod population density and body size were determined in algae of different morphologies that provided amphipods with different habitat architectures. The two primary components of habitat architecture in this system were spatial (the number and size of spaces between fronds) and structural (the number, length, and width of fronds). These were measured for algae of specific mor- phologies and for artificial plants that mimicked these morphologies. Field experiments using algae and algal mimic counterparts showed that there were significantly higher den- sities of amphipods in algae with branched and filamentous morphologies than in those algae with foliose and leathery macrophyte morphologies. There was also a significant correspondence between the body size of amphipods and both components of habitat architecture. Laboratory experiments using algae and algal mimics excluded food value, predation, competition, and physical disruption in experimental treatments. When these processes were excluded, patterns of abundance and body-size scaling to habitat dimensions were the same as those in the field. It appears, through the use of algal mimics, that the spatial component (space between fronds) is an important factor in determining amphipod demographic patterns in algae. Algal mimics of different surface rugosity and color indicate that tenacity and crypsis are also important components in habitat selection of amphipods.

Circumpolar distribution and carbon storage of thermokarst landscapes

Abstract: Thermokarst is the process whereby the thawing of ice-rich permafrost ground causes land subsidence, resulting in development of distinctive landforms. Accelerated thermokarst due to climate change will damage infrastructure, but also impact hydrology, ecology and biogeochemistry. Here, we present a circumpolar assessment of the distribution of thermokarst landscapes, defined as landscapes comprised of current thermokarst landforms and areas susceptible to future thermokarst development. At 3.6 × 106 km2, thermokarst landscapes are estimated to cover ∼20% of the northern permafrost region, with approximately equal contributions from three landscape types where characteristic wetland, lake and hillslope thermokarst landforms occur. We estimate that approximately half of the below-ground organic carbon within the study region is stored in thermokarst landscapes. Our results highlight the importance of explicitly considering thermokarst when assessing impacts of climate change, including future landscape greenhouse gas emissions, and provide a means for assessing such impacts at the circumpolar scale.

Newtonian drop impact with a solid surface

Abstract: The spreading of Newtonian liquid drops after impact with a solid surface is reproted for a range of liquid and surface proeprties, drop diameters, and impact velocities. Results for liquid viscosities up to 300 mPa.s are given. For a given drop diameter and velocity, a range of liquid viscosities result in splashing even for smooth surfaces. The maximum spread radius, made dimensionless with the drop radius, is correlated as Rmax* = 0.61(Re2Oh)0.166, where Re and Oh are the Reynolds and Ohnesorge numbers. respectively. A model is proposed to account for inertial, viscous, and surface tension forces on the maximum spread radius. Good agreement is found between the model and experimental data from several sources.