The squares are a strategic place to invest in the afforestation of a city, as they are less confronted with buildings and energy transmission networks, but mainly because they are a place of social ...interaction and recreational activities. Therefore, knowing its spatial configuration and its access by the surrounding population will allow for better planning by public agencies regarding the implementation, maintenance and floristic composition of the squares. Therefore, the main objective of the study was to analyze the design of squares within the urban frame of the city of Manaus - Amazonas, Brazil. Twenty-four squares were studied through mapping and visual analysis of satellite images from the Google Earth software. Subsequently, the classification according to the type of square proposed by De Angelis and De Angelis Neto (2000) was used. A total inventory of tree specimens (DBH > 10 cm) was carried out, being registered 513 trees distributed in 13 families, 31 genus and 35 species. Of the cataloged species, 51.4% (n=18 species) are classified as exotic to Brazil and 48.6% (n=17 species) are native to Brazil. However, of the 17 native species, 15 are native to the Amazon. The insertion of Manauaras squares in its urban frame is not standardized, so it was necessary to create four subtypes of squares to meet the specific reality of Manaus. It was found that the dominant type of classification of square, regarding insertion in the urban frame, is type 3 (54.2%), followed by type 2 (29.2%) and type 4 (16.6%).
Intensively urbanized Hong Kong has a degraded countryside envelope with 170 years of afforestation history. This study assessed seedling quantity, species composition, native-exotic relativity, and ...native ecological traits in 30 years. Data were analysed by cluster analysis, two-way indicator species analysis (TWINSPAN), and principal component analysis (PCA). The plantations received 16.54 million seedlings from 209 species. Seedling profile skewed towards 142 native species (67.9%) and 9.49 million exotic seedlings (57.4%). The dominant species group had three exotic species each with >1 million seedlings. The abundant group of 27 species had contained 19 natives associated with main primary forest components. The 179 species in frequent and rare groups denoted changing and diverse species selection. Analysis of start and truncation times found 50% of natives with ascending trend and 33% of exotics with descending trend. Aggregate ecological value of natives increased progressively. TWINSPAN classified native species into two groups with signature characteristics. PCA revealed scattered distribution of natives by adoption trend, start time, truncation time, and ecological value. Ecological restoration of synergistic-mutualistic associations between native plants and wildlife has gained importance. Potential pioneer and enrichment-planting arboreal species were identified to sustain the afforestation programme. Hong Kong has a rich vascular flora with about 390 native tree species, implying that around 250 native tree species had never been used in afforestation. Large-scale planting trials should be conducted to further refine species choice in future afforestation. The findings could inform afforestation and conservation efforts in Hong Kong and other degraded tropical lands.
Afforestation is a mitigation option to reduce the increased atmospheric carbon dioxide levels as well as the predicted high possibility of climate change. In this paper, vegetation survey data, ...statistical database, National Forest Resource Inventory database, and allometric equations were used to estimate carbon density (carbon mass per hectare) and carbon storage, and identify the size and spatial distribution of forest carbon sinks in plantation ecosystems in sand source areas of north Beijing, China. From 2001 to the end of 2010, the forest areas increased more than 2.3 million ha, and total carbon storage in forest ecosystems was 173.02 Tg C, of which 82.80 percent was contained in soil in the top 0-100 cm layer. Younger forests have a large potential for enhancing carbon sequestration in terrestrial ecosystems than older ones. Regarding future afforestation efforts, it will be more effective to increase forest area and vegetation carbon density through selection of appropriate tree species and stand structure according to local climate and soil conditions, and application of proper forest management including land-shaping, artificial tending and fencing plantations. It would be also important to protect the organic carbon in surface soils during forest management.
An understanding of the processes governing natural afforestation over large spatial scales is vital for enhancing forest carbon sequestration. Models of tree species occurrence probability in ...non-forest vegetation could potentially identify the primary variables determining natural afforestation. However, inferring processes governing afforestation using tree species occurrence is potentially problematic, since it is impossible to know whether observed occurrences are due to recruitment or persistence of existing trees following disturbance. Plant functional traits have the potential to reveal the processes by which key environmental and land cover variables influence afforestation. We used 10,061 survey plots to identify the primary environmental and land cover variables influencing tree occurrence probability in non-forest vegetation in New Zealand. We also examined how these variables influenced diversity of functional traits linked to plant ecological strategy and dispersal ability. Mean annual temperature was the most important environmental predictor of tree occurrence. Local woody cover and distance to forest were the most important land cover variables. Relationships between these variables and ecological strategy traits revealed a trade-off between ability to compete for light and colonize sites that were marginal for tree occurrence. Biotically dispersed species occurred less frequently with declining temperature and local woody cover, suggesting that abiotic stress limited their establishment and that biotic dispersal did not increase ability to colonize non-woody vegetation. Functional diversity for ecological strategy traits declined with declining temperature and woody cover and increasing distance to forest. Functional diversity for dispersal traits showed the opposite trend. This suggests that low temperatures and woody cover and high distance to forest may limit tree species establishment through filtering on ecological strategy traits, but not on dispersal traits. This study shows that 'snapshot' survey plot data, combined with functional trait data, may reveal the processes driving tree species establishment in non-forest vegetation over large spatial scales.
Soils are the largest terrestrial carbon store and soil respiration is the second-largest flux in ecosystem carbon cycling. Across China's temperate region, climatic changes and human activities have ...frequently caused the transformation of grasslands to woodlands. However, the effect of this transition on soil respiration and soil organic carbon (SOC) dynamics remains uncertain in this area. In this study, we measured in situ soil respiration and SOC storage over a two-year period (Jan. 2007-Dec. 2008) from five characteristic vegetation types in a forest-steppe ecotone of temperate China, including grassland (GR), shrubland (SH), as well as in evergreen coniferous (EC), deciduous coniferous (DC) and deciduous broadleaved forest (DB), to evaluate the changes of soil respiration and SOC storage with grassland conversions to diverse types of woodlands. Annual soil respiration increased by 3%, 6%, 14%, and 22% after the conversion from GR to EC, SH, DC, and DB, respectively. The variation in soil respiration among different vegetation types could be well explained by SOC and soil total nitrogen content. Despite higher soil respiration in woodlands, SOC storage and residence time increased in the upper 20 cm of soil. Our results suggest that the differences in soil environmental conditions, especially soil substrate availability, influenced the level of annual soil respiration produced by different vegetation types. Moreover, shifts from grassland to woody plant dominance resulted in increased SOC storage. Given the widespread increase in woody plant abundance caused by climate change and large-scale afforestation programs, the soils are expected to accumulate and store increased amounts of organic carbon in temperate areas of China.
Trees hold a powerful place in American constructions of what is good in nature and the environment. As we attempt to cope with environmental crises, trees are increasingly enlisted with great fervor ...as agents of our stewardship over nature. In this innovative and impassioned book, Shaul E. Cohen exposes the way that environmental stewardship is undermined through the manipulation of trees and the people who plant them by a partnership of big business, the government, and tree-planting groups. He reveals how positive associations and symbols that have been invested in trees are exploited by an interlocking network of government agencies, private timber companies, and nongovernmental organizations to subvert the power of people who think that they are building a better world.
Background and aims Afforestation and thinning management are effective ways to mitigate global warming. Soil carbon reconstruction mechanisms can be effectively explored by linking soil aggregates ...and isotopic .sup.13C. Methods Soil samples were collected from agricultural land (AL) and larch plantations (established in 1965 and thinned in1995, UT: 2500 treeâ§ha.sup.-1, MT: 1867 treeâ§ha.sup.-1, and ST: 1283 treeâ§ha.sup.-1). The soil was separated into three aggregate sizes (LMAC: > 2 mm, SMAC: 2-0.25 mm, MIC: 0.25-0.053), minerals associated with organic matter (MAOM: < 0.053 mm), and carbon fractions within macroaggregates. Results We found that afforestation on agricultural land significantly increased the mean weight diameter (MWD). However, intensifying thinning decreased MWD by increasing SMAC. Moreover, after afforestation, the carbon concentration in soil aggregates and MAOM significantly decreased, and the carbon stability of macroaggregates weakened but could be strengthened after thinning. Thinning decreased the C/N in the soil aggregates and MAOM when no change in carbon concentration. The effect of thinning intensity on C/N was obvious with decreasing of particle size. The delta.sup.13C, mainly controlled by soil aggregates, significantly decreased in each soil aggregate after afforestation but increased after thinning. Additionally, the carbon concentrations, C/N and delta.sup.13C of small-size particles (< 0.25 mm) and the distribution of SMAC are important for SOC, C/N, CO.sub.2 fluxes and delta.sup.13C in bulk soil. Conclusion We conclude that soil aggregate distribution is conducive to soil carbon renewal, suggesting that increasing thinning intensity is beneficial for accumulating older carbon and acquiring nitrogen in more stable fractions.
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