Showing papers by "Chi Yung Jim published in 1998"

Physical and chemical properties of a Hong Kong roadside soil in relation to urban tree growth

Abstract: Tree planting in urban areas faces many limitations that suppress performance and increase management burdens. Soil problems are increasingly recognized as an important cause of establishment failures and declines. Recent citygreening programs in Hong Kong necessitate a better understanding of soil difficulties, but relevant information is lacking. A detailed study of physical and chemical properties of a representative roadside soil provides baseline data on edaphic restrictions and hints for correction and amelioration. The soil depth is inadequate for normal root expansion of trees, is excessively stony and sandy, and is beset by poor structure and heavy compaction. Root growth is likely to be restricted by the low levels of porosity and high shear strength. The densely packed surface layer reduces aeration and water movement into the lower layers. The nutrient stock is meager, and the ability to hold available moisture and nutrients is very limited. Soil reaction comparing with local natural soil is uncharacteristically alkaline with pH reaching 8.5 which may induce iron and manganese deficiency. Heavy metals register elevated concentrations especially for lead and zinc, but do not attain phytotoxic levels. The common multiple substrate problems need to be addressed properly before trees are planted. Evaluation of selected soil attributes is advocated for all planting sites.

Soil Characteristics and Management in an Urban Park in Hong Kong

Abstract: threshold. With diminished porosity, transmission of air and water, storage of plant-available moisture, and root growth suffer. Chemically, the samples have an unnatural alkaline pH; inadequate organic matter, nitrogen, phosphorus, exchangeable cations; and limited cation exchange capacity. The results can help park-soil management, including the need to evaluate soil in planned park sites, salvage high-grade soil parcels, prevent construction damage, ameliorate structure by mechanical operations and suitable amendments, and replace site soil of very poor quality. Edaphic problems can be forestalled or solved by treating soil as an integral component of park planning and management based on scientific principles and methods.

Impacts of intensive urbanization on trees in Hong Kong

Abstract: Trees in cities face a severe limitation of plantable space and an exceptionally stressful growing environment. In Hong Kong, shortage of developable land has relegated trees to a lower priority and intensified urban impacts on them, relative to other cities. The vicissitudes of urban growth and trees since the founding of Hong Kong are reviewed, and eleven specific conflicts between urbanization and trees in Hong Kong are described. Redevelopment of existing buildings has raised site coverage by impervious surface and taken away ground-level planting space within and around affected lots. Infilling of relatively low-density areas mainly for government and insti

Pressure on urban trees in hong kong: pervasive problem and possible amelioration

Abstract: Summary Urban development in Hong Kong has left a tightly-packed town plan with little intervening space for trees. Limitation of available land in relation to a large population underscores the fundamental constraint. The planting tradition adopted since the founding of the city some 150 years ago was implemented when the urban matrix was still relatively porous. Recent intensification of development has imposed increasing pressure on the meagre tree stock. Pervasive shortage of plantable space is aggravated by its poor quality which deteriorates with land-use changes. Setting back building lots for amenity planting, if applied on a large scale, should bring permeation of greenery. Existing roadside and offroad habitats, including areas containing high-calibre specimen trees and woodland plots, are often lost to vehicular-traffic infrastructure and other community needs. Proliferation of underground utilities restricts chances for roadside trees. Frequent trenching to repair buried services and recently ...

Assessing and modeling hill fire impact in country parks with SPOT HRV images and GIS

Abstract: Remote sensing and geographic information systems (GIS) techniques provide efficient tools for resource management. In this paper, these techniques are applied for resource management of country parks in Hong Kong. A spatial database is developed integrating SPOT HRV multispectral data, topographic data, hillfire recordand thematic maps. Vegetation resources are mapped based on multidate SPOT and DEM data with an overall accuracy of 74.3%. Integrated with hillfire record, the impact of hillfire on vegetation resources is assessed. Grass is the major vegetation type subject to fire. Bi‐variate relationships between hillfire, its frequency of occurrence and various terrain (elevation, slope, aspect and distance to streams) and human activities (accessibility and point sources of fire) variables are examined. A logistic regression model is used to identify hill fire prone sites with a 75.4% of correct prediction of fire vs. non‐fire sites. Elevation, vegetation and accessibility are found to be more...