Remote Sensing for Analyzing Forested Landscape Structure and Land-Use Histories in Guyana’s Bauxite Mining Landscapes

Monitoring secondary forest regrowth is a priority in forest restoration strategies. A site history helps in understanding the present status of natural regeneration in the three landscapes impacted by bauxite mining. Nonetheless, high rainfall in bauxite residue storage areas can facilitate natural regeneration of forest. This research analyzed the natural regeneration of forest after thirty years of different land use histories at three bauxite mining areas of the Upper Demerara—Berbice region of Guyana. There are no man made forest plantations in the three landscapes being reviewed. The methodology included: 1) the selection of three sampling landscapes with different land use histories 2) the generation Land Use/Land Cover maps using KMeans unsupervised classification of satellite images in each landscape and 3) the assessment of landscape structure of the land cover classes for year 2020 at class and landscape level using landscape metrics. The assessment of landscape structure of the land cover classes was carried-out with landscape metrics for the comparisons at class and landscape level. Principal component analysis enables the identification of main patterns among landscape-level metrics and land cover classes. Discriminant classification of the landscape classes was analyzed with the different metrics. The results suggest that Normalized Difference Vegetation Index and KMeans unsupervised classification can be used to evaluate the difference in natural forest regeneration among landscapes with differing land use histories. The landscape metrics revealed secondary stages of forest succession. The Landscape Shape Index and Edge Density were the most significant for landscape differentiation. The result of the various land uses reveals a mosaic of early, intermediate, and late successional sequences.

Restoration of Forested Lands under Bauxite Mining with Emphasis on Guyana during the First Two Decades of the XXI Century: A Review

Mining poses a major environmental threat to tropical forest ecosystems, given its role in long-term forest degradation. Like Suriname, Guyana presents one of the less disturbed forested lands in South America. The local economy is improving, thanks to the development of mining which is primarily focused on gold, diamond, and bauxite. This, however, has resulted in long-term degradation of important forest ecosystems and the pollution of water bodies, and these have given rise to increasing concentrations of sediments. Taking into consideration the afore-mentioned, this review synthesizes, for the first time, literature which describes knowledge-based restoration practices in forested fragmented landscapes at different bauxite mining areas. The principal objective of this endeavor is to learn from case studies that have been carried out in the Neotropics especially in South America, with a view to applying best practices to the Guyana context. It has been found that mining presents a serious challenge for physical, chemical, and biological restoration. Comprehensive knowledge of the ecology of the landscape—structure and configuration, soil type, physical, chemical and biological properties, dispersal mode, and the identification and quantification/inventory of plant communities is critically important pinpointed for planning restoration programmes. The process of recovering some of the ecological functions of the pristine forest, through natural regeneration, is vital to supporting biodiversity in overburden dumps and to mitigating environmental impacts. One of these many functions, functional connectivity, can be enhanced to optimize the restoration of forest cover leading to an increase in local biodiversity. Bearing in mind the afore-stated, this review synthesizes passive and active restoration through reforestation with local and exotic species, ecological management of colonization, nucleation practices, and the use of Landscape Ecology models. These have been identified as the most appropriate to follow, given that a spatially driven design can provide much needed knowledge of the restoration/reclamation plan for Bauxite Mine Lands. Ecologically sound designs are a catalyst for devising mechanisms which can (help to) reduce environmental impacts. These designs can also help to boost the velocity at which ecological processes operate, in order to increase the resilience of ecosystems and the connectivity between forest patches and continuous pristine forests.

Nutrient Release from Immersed Foliar Biomass during Caruachi Dam Reservoir Filling: Caroni River, Venezuela

Background: Decomposition process controls the release and the availability of essential nutrients, which affects the structure and the functioning of plant communities. Freshwater reservoirs are largely known to have impacts on the water quality, especially during the first phases of filling. The aim of the study was to conduct a nutrient release experiment where decomposition of fresh leaves and litter from vegetation of a low dry tropical forest was flooded. Selected species were Leguminosae species Albizia glabripetala (H. S. Irwin) G. P. Lewis & P. E. Owen (AG), Bauhinia aculeata L. (BA), Centrolobium paraense Tul. (CP) and Piptadenia leucoxyllon Barneby & J. W. Grimes (PL). Freshwater decomposition experiments were carried out at 50 cm depth inside nine floating containers in a protected area of the reservoir: litter (HJ), leaves of AG and BA (E2), and CP and PL (E3) were used. It was over 20 weeks period. Every week for two months and at week 20, a bag of each sample was extracted for analysis of Carbon, Ca, Mg, Na, K, P and S. Results: Results indicate that residual dry mass decreased by 71% for HJ, 81.4% for E2, and more than 86.8% for E3 after twenty weeks. The higher content of carbon (%) at the beginning of the experiment was E2 > E3 > HJ. After 20 weeks, the percentage of carbon loss was 2.09% for HJ, 3.02% for E2, and 1.69% for E3. S decreased between 50% - 60% during the first week;at 20 weeks, the remaining amount of S was 13% for HJ and E3 and 7% for E2. P showed a different pattern, where the second week was more important for the release. HJ and E3 followed the pattern of nutrient release: K > Mg > Na > Ca while E2 was K > Ca > Mg > Na. Conclusions: P and S release depends on the time of submergence and the species. Fresh leaves decay faster than necromass. Nutrient loss is higher than 50% for the three first weeks and seems constant between week 8 - 20. C and S concentrations incorporated in the reservoir can result in a high release of gases CH4 and S2 to the atmosphere. This study is the first publication in relation to nutrient release from the submergence of species in dry tropical forests.