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61.
Climate change will further increase the risk of desertification, which is already affecting large areas of the world. Many countries are making investments for the implementation of mitigation and adaptation strategies to combat desertification. The long term effectiveness of these strategies necessarily require a socioeconomic return for its sustainability. The main goal of our paper is to assess the relation between the mitigation and adaptation investments and the socio-economy of the rural population. The area of study is located in north-central Chile. The northern regions are mostly composed by arid land, which can be considered as a marginal area for agriculture. The area formed by the southern regions is optimal for the agricultural activity which is characterized by an industrialized agriculture with and increased use of technology. The indicators we have used for our study are the following: the Investments provided by the Chilean Agriculture Livestock and Forestry (ALF) promotion agencies, the ALF Gross Domestic Product (GDP) and the Population Employed in ALF. The results show that the relationship between the investments and the socioeconomy varies among the regions analyzed. Investments are positively correlated (P?≤?0.05) with the ALF GDP and the labor in ALF in the northern regions, but do not seem to be directly related to labor in ALF in the southern regions (P?≥?0.05). Therefore, our conclusion is that the Investments are significantly relevant for the agricultural activity in the arid northern regions, while in the southern regions they have no direct impact on the labor in ALF.  相似文献   
62.
The jumping spider Evarcha culicivora (Salticidae) has unusual links to Lantana camara, a plant species to which it is attracted. Three phytochemicals from the headspace of L. camara (1,8 cineole and especially β-caryophyllene and α-humulene) attract adult E. culicivora. These spiders, especially early-instar juveniles, feed on nectar, but adults may use L. camara as mating sites. The hypothesis we consider here is that, for E. culicivora juveniles, although not for adults, responding to plant odor is relevant in the specific context of acquiring nectar meals. We show that juveniles resemble adults by responding to β-caryophyllene and α-humulene, but we found no significant attraction of juveniles to 1,8 cineole. We also show that, compared to sated E. culicivora juveniles, juveniles subjected to a 5-day pre-trial fast responded more strongly to living L. camara plants and to β-caryophyllene and α-humulene, but we found no significant effect of hunger level on response by adults to living plants. These results suggest that attraction to L. camara may have different functions for E. culicivora depending on the stage of its life history.  相似文献   
63.
Modelling the local density of tropical saplings can provide insights into the ecological processes that drive species regeneration and thereby help predict population recovery after disturbance. Yet, few studies have addressed the challenging issues in autocorrelation and zero-inflation of local density. This paper presents Hierarchical Bayesian Modelling (HBM) of sapling density that includes these two features. Special attention is devoted to variable selection, model estimation and comparison.  相似文献   
64.
Good water quality of the Rio San Juan is critical for economic development of northeastern Mexico. However, water quality of the river has rapidly degraded during the last few decades. Societal concerns include indications of contamination problems and increased water diversions for agriculture, residential, and industrial water supplies. Eight sampling sites were selected along the river where water samples were collected monthly for 10 mo (October 1995-July 1996). The concentration of heavy metals and chemical constituents and measurements of bacteriological and physical parameters were determined on water samples. In addition, river discharge was recorded. Constituent concentrations in 18.7% of all samples exceeded at least one water quality standard. In particular, concentrations of fecal and total coliform bacteria, sulfate, detergent, dissolved solids, Al, Ba, Cr, Fe, and Cd, exceeded several water quality standards. Pollution showed spatial and temporal variations and trends. These variations were statistically explained by spatial and temporal changes of constituent inputs and discharge. Samples collected from the site upstream of El Cuchillo reservoir had large constituent concentrations when discharge was small; this reservoir supplies domestic and industrial water to the city of Monterrey.  相似文献   
65.
This paper considers the principal elements that underpin policy frameworks for supporting food security in protracted crisis contexts. It argues that maintaining the food entitlements of crisis-affected populations must extend beyond interventions to ensure immediate human survival. A 'policy gap' exists in that capacities for formulating policy responses to tackle the different dimensions of food insecurity in complex, fluid crisis situations tend to be weak. As a result, standardised, short-term intervention designs are created that fall short of meeting the priority needs of affected populations in the short and long term and only partially exploit the range of policy options available. The paper discusses key attributes of agency frameworks that could support more effective policy processes to address longer term as well as immediate food security needs. Additionally, it points to some main challenges likely to be encountered in developing such frameworks and, with the participation of beneficiaries, translating them into effective action.  相似文献   
66.
Coalescence is a well documented event in many red algal orders. However, it is as yet unknown if genetic compatibility and phylogenetic relationships could be factors limiting coalescence. Using controlled laboratory experiments complemented with cytological and ultrastructural analysis, in this study we test whether or not coalescence may occur between different seaweed species and between karyological phases of the same species. We also evaluate the effects of one species or karyological phase on the germination rates, germling survival and differentiation of erect axes of sporelings of a second species or phase and whether the uni- or polycystocarpic origin of the coalesced germling may affect the germination and growth or the morphology of the resulting sporeling. Results indicated that the process of coalescence is restricted to intraspecific partners only. A thick interphase with crushed cells and remains of cell walls developed in all the interspecific contacts studied. Results also indicated that coalescence may be expected between individuals of different karyological phases, as in the two cases tested (Mazzaella laminarioides and Sarcothalia crispata) the filaments of both phases grow intertwined in the new tissue of the coalesced crust. Germination rates, sporeling survival and differentiation of erect axes were all affected by the different types of experimental cultures tested. However, results suggest that allorecognition among seaweeds seems to play a minor role in coalescence. The process appears as less sensitive to genetic recognition than the cell fusion processes described for other red algal species or than the colonial fusion described for colonial invertebrates and fungi.  相似文献   
67.
The current taxonomic status of Sotalia species is uncertain. The genus once comprised five species, but in the twentieth century they were grouped into two (riverine Sotalia fluviatilis and marine Sotalia guianensis) that later were further lumped into a single species (S. fluviatilis), with marine and riverine ecotypes. This uncertainty hampers the assessment of potential impacts on populations and the design of effective conservation measures. We used mitochondrial DNA control region and cytochrome b sequence data to investigate the specific status of S. fluviatilis ecotypes and their population structure along the Brazilian coast. Nested-clade (NCA), phylogenetic analyses and analysis of molecular variance of control region sequences showed that marine and riverine ecotypes form very divergent monophyletic groups (2.5% sequence divergence; 75% of total molecular variance found between them), which have been evolving independently since an old allopatric fragmentation event. This result is also corroborated by cytochrome b sequence data, for which marine and riverine specimens are fixed for haplotypes that differ by 28 (out of 1,140) nucleotides. According to various species definition methods, we conclude that marine and riverine Sotalia are different species. Based on priority criteria, we recommend the revalidation of Sotalia guianensis (Van Bénéden 1864) for the marine animals, while riverine dolphins should retain the species name Sotalia fluviatilis (Gervais 1853), thus becoming the first exclusively riverine delphinid. The populations of S. guianensis show a strong subdivision (ΦST=0.628) along the Brazilian coast, with at least three evolutionarily significant units: north, northeastern and south/southeastern.  相似文献   
68.
ABSTRACT: The Woodlands, a totally planned community north of Houston, Texas, was studied in detail in an effort to develop a master drainage plan which minimizes adverse impact on the 100-year floodplain. A total of 40 HEC-1 and HEC-2 computer runs were made to evaluate various development, channelization, and reservoir storage options.  相似文献   
69.
The starfish Cosmasterias lurida was sampled from the pier piles of Almirante Storni in the Golfo Nuevo, northern Patagonia, from November 2001 to November 2003. In this anthropogenically modified site there is an unusually abundant food supply of mussels and large aggregations of starfishes. The reproductive cycle was studied by organ indices and histological examination of gonads. The highest gonad index (GI) values were found in the summer (February–March), followed by a drop in GI values, indicating spawning. Histological analyses indicated that gametogenesis takes place from June to January, sexual maturity occurred during the summer and spawning occurred in April. The GI and pyloric caeca index (PCI) tended to have an inverse relationship, but this was only statistically significant in males. However, biochemical analyses of the starfish indicated no transfer of nutrients between pyloric caeca and gonads in either sex. In fact, simultaneous accumulation of carbohydrates was found in the pyloric caeca and gonads of both sexes.  相似文献   
70.
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