Distribution of the radiative index of dryness and forest site quality in a mountainous watershed

1984 ◽  
Vol 14 (5) ◽  
pp. 717-721 ◽  
Author(s):  
S. J. Tajchman

The radiative aridity index, β (i.e., the ratio of yearly sums of net radiation to those of the latent heat of precipitation), and forest biomass were obtained for 245 terrain segments [Formula: see text] in an Appalachian watershed. A hypothesis was tested that β can be used as a site quality indicator in complex terrain. Regression analysis yielded the following relationship between the average forest biomass of the watershed (Mo = 15.94 kg m−2), the biomass (Mi), the radiative aridity index (βi), and the azimuth (Ai) of terrain segments: Mi/M0 = 2βi[l−Ai/2π + (Ai/2π)4] ± 0.27. The value of the expression in the bracket reaches its maximum for Ai = 0 (north facing slopes), and a minimum for Ai = 227° (southwest facing slopes). A possible interpretation of the obtained relationship is that p represents long term (e.g., daily and seasonal) effects of water and energy exchanges of terrain segments on growth, and the expression in the bracket represents the aspect-related effects of daily fluctuations of microclimate of terrain segments on growth.

2016 ◽  
Vol 38 ◽  
pp. 169
Author(s):  
Nara Luisa Reis de Andrade ◽  
Luciana Sanches ◽  
Renata Gonçalves Aguiar ◽  
João Gilberto de Souza Ribeiro ◽  
Osvaldo Borges Pinto Junior

The Amazon is a recognized global ecosystem, due to its high biodiversity and the magnitude of the mass and energy exchanges performed. In this study it sought to analyze the seasonal and interannual variations of microclimate in a site of tropical forest in southwestern Amazon. For this purpose, net radiation data were used, air temperature, relative humidity and wind speed collected in a micrometeorological tower belonging to the LBA, located in Jaru Biological Reserve, from 2004 to 2010. The results showed that existence of well-defined seasonal patterns was verified, with variations between wet, wet-dry, dry, dry-humid periods for all variables in question. Yet, through analysis of the interannual variations were observed warming of the increment signs and decreased moisture in the locality. This observation, although patchy, deserves special attention, since changes in the microclimate in the Amazon region may have yet unknown consequences.


2020 ◽  
Author(s):  
Laura Herrera ◽  
Carlos Hoyos ◽  
Julián Urán

<p>The heterogeneity of the urban features, in addition to the inherent challenges added by highly complex terrain, has not allowed the scientific community to reach a complete understanding of the Atmospheric Boundary Layer (ABL) dynamics regarding the land-atmosphere interactions. The intricacies are higher when trying to simulate the observed interactions and their implications for air quality in a numerical modeling framework.</p><p> </p><p>Over the last two decades, the ABL research community has dedicated several research efforts to study turbulent exchanges and ABL processes over complex terrain, and the implications of the particular features of these sites have on turbulence characteristics. A better knowledge of the ABL structure and dynamics is fundamental to understand processes such as air pollutant dispersion and disposal in the atmosphere, development and evolution of deep convection, and urban effects on meteorology. One of the aspects hindering our understanding is the lack of pertinent information from urbanized mountainous regions representative of the entire globe, useful to assess the different hypotheses and conceptual models of the Mountain Boundary Layer (MBL) dynamics. Most of the short- and long-term ABL field experiments in mountainous terrains have taken place over the high-latitude regions such as the Alps and the Rockies, and few over in the tropical Andes, where the Cordillera plays an essential role in controlling orographic rainfall intensification and the ventilation in inter-Andean valleys, resulting in knowledge gap regarding momentum, and latent and sensible heat flux exchanges over low-latitude, urban, complex terrain regions. In addition to a top-down approach, it is essential to follow a bottom-up strategy to study in detail the turbulent heat, mass, and momentum transfer in the Andean region.</p><p>The COMPLEX Experiment (COmplex terrain Measurement and modeling Project of Land-atmosphere Energy eXchanges) is a new effort focused on the long-term energy balance measurement campaign settled in the Aburrá Valley, a narrow highly complex mountainous-urban terrain located in the Colombian Andes. The primary purpose of this campaign is to identify the more relevant phenomenological features and processes responsible for ABL spatio-temporal variability, and land-atmosphere interactions in inter-Andean valleys. The long-term observational set-up includes eight sites equipped with turbulent flux sensors and net radiometers, in a cross-section of the valley, a microwave radiometer, a boundary layer radar, a scintillometer, and radiosonde intense observation periods (IOPs). We present the status of the COMPLEX experiment equipment deployment and preliminary results on the relationship of the transition between the stable boundary layer and the convective boundary layer and air quality in the region, and an exploration of the diurnal cycle of the different turbulent terms of the energy budget as a function of time and hill location.</p>


2006 ◽  
Vol 34 (1) ◽  
pp. 151-154 ◽  
Author(s):  
Katalin Debreczeni ◽  
Sándor Hoffmann ◽  
Katalin Berecz

1994 ◽  
Vol 25 (5) ◽  
pp. 331-344 ◽  
Author(s):  
Peter M. Lafleur

Evapotranspiration (ET) and precipitation were measured during five summers (1989-1993 inclusive) at a subarctic forest site near Churchill, Manitoba, Canada. Mean daily ET varied from 2.14-3.18 mm d−1 during the five summers, while mean daily precipitation (P) ranged from 1.46-3.15 mm d−1. Yearly variability in summer ET was most influenced by availability of surface moisture, then by atmospheric conditions (i.e. temperature), and least of all by net radiation. In four of the five years total summer ET exceeded P resulting in significant soil water deficits and in the other year summer ET and P were similar in magnitude. The use of equilibrium evaporation (EE) as a predictor of ET was explored. Separate relationships between ET and EE were computed for all five years. Three statistically dissimilar groups of equations were found: 1989/1990, 1991/ 1992, and 1993. A single regression equation describing all years is presented.


1997 ◽  
Vol 78 (6) ◽  
pp. 3460-3464 ◽  
Author(s):  
Terry Crow ◽  
Vilma Siddiqi

Crow, Terry and Vilma Siddiqi. Time-dependent changes in excitability after one-trial conditioning of Hermissenda. J. Neurophysiol. 78: 3460–3464, 1997. The visual system of Hermissenda has been studied extensively as a site of cellular plasticity produced by classical conditioning. A one-trial conditioning procedure consisting of light paired with the application of serotonin (5-HT) to the exposed, but otherwise intact, nervous system produces suppression of phototactic behavior tested 24 h after conditioning. Short- and long-term enhancement (STE and LTE) of excitability in identified type B photoreceptors is a cellular correlate of one-trial conditioning. LTE can be expressed in the absence of STE suggesting that STE and LTE may be parallel processes. To examine the development of enhancement, we studied its time-dependent alterations after one-trial conditioning. Intracellular recordings from identified type B photoreceptors of independent groups collected at different times after conditioning revealed that enhanced excitability follows a biphasic pattern in its development. The analysis of spikes elicited by 2 and 30 s extrinsic current pulses at different levels of depolarization showed that enhancement reached a peak 3 h after conditioning. From its peak, excitability decreased toward baseline control levels 5–6 h after conditioning followed by an increase to a stable plateau at 16 to 24 h postconditioning. Excitability changes measured in cells from unpaired control groups showed maximal changes 1 h posttreatment that rapidly decremented within 2 h. The conditioned stimulus (CS) elicited significantly more spikes 24 h postconditioning for the conditioned group as compared with the unpaired control group. The analysis of the time-dependent development of enhancement may reveal the processes underlying different stages of memory for this associative experience.


2020 ◽  
Vol 29 (1) ◽  
pp. 63-79
Author(s):  
Frida Hastrup

Dating back to medieval times, fruit cultivation in Hardanger in western Norway is rooted in what is portrayed as a perfect microclimate naturally yielding the best apples in the world. However, the viability of the comparatively minute Norwegian fruit trade is continuously threatened by competition from outside, spurring all kinds of initiatives and policies to make it sustainable. The Norwegian fruit landscape, in other words, is both the natural and perfect home of world-class fruit and a site for continuous, often state-driven interventions to make it so; indeed, the perfection of the place accentuates the need to do what it takes to make it thrive. The necessary means to accomplish such viability, however, make up a complex terrain, as the resourcefulness of the Norwegian fruit landscape is ‘measured’ according to very different units.


2012 ◽  
Vol 88 (05) ◽  
pp. 547-552
Author(s):  
Ling Li ◽  
Sergios Karatzos ◽  
Jack Saddler

Increasing concerns of oil security, greenhouse gas emissions, and sustainability have encouraged nations to consider the contribution that agriculture/forestry for bioenergy (and biofuels in particular) could make as alternatives to current fossil-based energy and transportation fuels. Despite China's large population and geographical size, it has only relatively recently developed into a highly industrialized and energy-dependent economy. Coal is, and will remain, China's dominant energy source. However, over the last few years with China's growing middle class, increasing growth in production and sale of cars/trucks and a growing chemical based sector, oil and its derivatives are predicted to experience the fastest fossil fuel growth. China's ability to produce so-called “first-generation” or conventional biofuels from sugar, starch or vegetable oil based plants is very restricted because of “food vs. fuel” issues. Thus, biomass-based and forest-based biofuels, in particular, can form a medium-to-long-term solution that could contribute to China's national biofuels targets. Oilseed trees have been suggested as an initial forest-based biodiesel strategy with about 13 million ha of marginal land identified for possible plantation. It is also estimated that 17 million tonnes of cellulosic ethanol per annum could be derived from forest biomass that is currently available in China.


2005 ◽  
Vol 55 (4) ◽  
pp. 1667-1674 ◽  
Author(s):  
Kelly P. Nevin ◽  
Dawn E. Holmes ◽  
Trevor L. Woodard ◽  
Erich S. Hinlein ◽  
David W. Ostendorf ◽  
...  

Fe(III)-reducing isolates were recovered from two aquifers in which Fe(III) reduction is known to be important. Strain BemT was enriched from subsurface sediments collected in Bemidji, MN, USA, near a site where Fe(III) reduction is important in aromatic hydrocarbon degradation. Strains P11, P35T and P39 were isolated from the groundwater of an aquifer in Plymouth, MA, USA, in which Fe(III) reduction is important because of long-term inputs of acetate as a highway de-icing agent to the subsurface. All four isolates were Gram-negative, slightly curved rods that grew best in freshwater media. Strains P11, P35T and P39 exhibited motility via means of monotrichous flagella. Analysis of the 16S rRNA and nifD genes indicated that all four strains are δ-proteobacteria and members of the Geobacter cluster of the Geobacteraceae. Differences in phenotypic and phylogenetic characteristics indicated that the four isolates represent two novel species within the genus Geobacter. All of the isolates coupled the oxidation of acetate to the reduction of Fe(III) [iron(III) citrate, amorphous iron(III) oxide, iron(III) pyrophosphate and iron(III) nitrilotriacetate]. All four strains utilized ethanol, lactate, malate, pyruvate and succinate as electron donors and malate and fumarate as electron acceptors. Strain BemT grew fastest at 30 °C, whereas strains P11, P35T and P39 grew equally well at 17, 22 and 30 °C. In addition, strains P11, P35T and P39 were capable of growth at 4 °C. The names Geobacter bemidjiensis sp. nov. (type strain BemT=ATCC BAA-1014T=DSM 16622T=JCM 12645T) and Geobacter psychrophilus sp. nov. (strains P11, P35T and P39; type strain P35T=ATCC BAA-1013T=DSM 16674T=JCM 12644T) are proposed.


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