Soil carbon dynamics in primary and secondary tropical forests in Colombia

Soils play a central role in the dynamics of biospheric carbon and in climate change. They contain the largest carbon stock of terrestrial ecosystems and return to the atmosphere a significant proportion of carbon fixed by photosynthesis. Soils of tropical forests are tremendously important in the carbon cycle because they receive the largest organic matter inputs, they have the largest respiration rates, and they are among the largest carbon reservoirs among world soils. This research assesses the main components of the soil carbon dynamics in primary (PF) and secondary (SF) tropical forests in Colombia. I evaluated the production, stocks, and decomposition rates of aboveground detritus as well as the stocks, growth, mortality, and decomposition of fine roots in these two forest types. Soil carbon outputs were evaluated as total soil, heterotrophic, and root respiration. The stocks of soil organic carbon down to 4 m deep in these two cover types and in degraded pastures (PAS) were also evaluated. ^ Soil inputs of organic carbon from above and belowground sources were lower in SF than in PF. Litterfall in SF was 58% and production of fine root detritus was 60% of that in PF. When production of woody detritus and palm fronds was considered, the difference between these forest types was even larger. However, outputs of mineral carbon through heterotrophic soil respiration were similar; in SF they equaled 97% of those in PF. As a result, soil carbon balance was positive in PF and negative in SF. Despite that soil carbon balances suggest that soils of SF are losing carbon, soil carbon stocks of SF were higher than of degraded pastures, suggesting that they have already started to recover soil carbon stocks lost under degraded pastures. This discrepancy can be partially explained by the effect of drier conditions on heterotrophic soil respiration as a consequence of a moderate El Niño event during the period of soil respiration measurements. The positive carbon balance in soils of PF despite the El Niño event, suggests that soils of PF accumulated about 664 Kg C ha−1 yr−1. Therefore, soil carbon dynamics mainly depended on successional status of vegetation and on climatic conditions. ^

The relationship between educational placement, instructional practices, and achievement gains of Black students with specific learning disabilities in secondary urban school settings

Black students, in general, are underserved academically (Darling-Hammond, 2000; Townsend, 2002) and overrepresented in special education (Donovan & Cross, 2002). Black students with disabilities are further overrepresented in more restrictive educational environments (Skiba, Poloni-Staudinger, Gallini, Simmons & Feggins-Azziz, 2006). Although the National Longitudinal Transition Study 2 (NLTS2) revealed that the academic performance of students with learning disabilities is positively related to the percentage of courses taken in the general education setting (Newman, 2006), the research specifically on placement of Black students with disabilities, particularly at the secondary level, as it relates to academic achievement is lacking. While previous studies have sought to determine which placement is better for students with disabilities, no study was found that specifically examined the impact of placement specific to Black students with specific learning disabilities (SLD) in urban settings (Fore, III, Hagan-Burke, Burke, Boon & Smith, 2008; Rea, McLaughlin & Walther-Thomas, 2002). This study examined educational placement, instructional best practices, and achievement gains of Black students with SLD in urban secondary settings using an ex post facto research design. Achievement, placement, and demographic data were collected and analyzed on approximately 314 Black eighth grade students with SLD. The Teacher Instructional Practices Survey was developed and used to collect and analyze data from the teachers of 78 of these students as it relates to instructional best practices. Results indicate no significant difference in reading but a significant difference in math gains of students served in inclusive settings as compared to resource settings with a small effect size. Also, no significant relationship was found between achievement gains and the reported use of instructional best practices. However, there was a relationship between educational placement and the use of instructional best practices. The results implied that there is a need for training with both general and special education teachers on instructional best practices for SWD and that there should be certain IEP team considerations when making placement decisions for this population of students with disabilities. It is recommended that future research in this area include classroom observations and factors other than test scores to measure growth in achievement.

International tourism : can it contribute to Nigeria's economic growth as other industrial sectors?

The growth of international tourism and the attendant economic benefits to the world nations, has been phenominal since the end of the second world war. It is considered that the industry's upsurge will continue even in the phase of various constraints exemplified in high fuel cost, constant increase in fares and the threatening world-wide recessions. Developed as well as developing countries have gained substantially from the industry. A recent development shows increasing tourist traffic towards developing countries, while developed countries still hold their fort in stable growth of tourist receipts. The strategic beneficial effects of international tourist industry are often quantified in terms of foreign exchange earnings, employments offered, and the Real Estate super-structures; but in general,the industry has innumerable direct and indirect benefits to any nation engaging in the trade. The objective of this thesis is to demonstrate by comparative analysis and proven parameters that the international tourist industry which is given low priority in development in Nigeria, can equally contribute to the nation's economic growth as other industrial sectors which receive high priority and patronage in development. The data for this paper are gathered from primary sources which are i) responses by the Federal and State Governments' tourism-related offices; ii) government publications e.a. the Third National Development Plan of Federal Republic of Nigeria; and iii) Books and collections. The secondary sources include reports,periodicals and hospitality industry publications. To formally establish the international tourist industry in Nigeria, all the governments (Federal, State and Local) and the private sector in the country, should commence the development of the industry with research and feasibility studies, to be followed by proper planning at all levels and based on the result of the research and feasibility studies.