Plant Site Conditions Research Articles

Species-specific holistic assessment of tree structure and defects in urban Hong Kong

Sustainable urban forests require healthy trees with stable structures to improve provision of ecosystem services including air purification and climate mitigation to urban areas. Trees in compact residential areas are particularly prone to development of defects and unstable tree structures. We assessed in detail tree species, key structural and physiological defects, tree dimensions, growing habitats and planting site conditions of 38,156 trees in 102 sampled public housing estates (PHEs) in Hong Kong. The open spaces in PHEs allowed trees to grow in representative urban habitats. PHE attributes including estate age, number of trees, species richness and tree diversity were assessed. The associations among estates, species, tree structure and defects were investigated using Canonical Correspondence Analysis (CCA) and Redundancy Analysis (RDA). The species-specific approach enlisted tree community, age, DBH and other biomass-structural traits in the data analysis and interpretation. The results showed diverse planting of 202 species from 56 families, with most species beset by multiple defects. The health and structure of two dominant tree species, Acacia confusa and Ficus microcarpa, were respectively influenced by inadequacies and stresses in planting environments, such as inclined surface of disturbed slopes, small pits and planters with poor soil quality, and soil not shielded by groundcover vegetation. Some tree defects of twigs, branches and trunks were associated with tree dimensions, especially tree height and its unnaturally high ratio to crown width and DBH. The findings verified the importance of a species-specific analysis to optimize urban-tree management and maximize benefits to the society.

Planting time, stocktype and additive effects on the development of spruce and pine plantations in Western Carpathian Mts.

Planting of seedlings is the most reliable and speedy way of forest restoration. Routine spring planting of bareroot seedlings is frequently unsuccessful in central Europe. In this study, the effects of planting time and a spring-pre-planting application of ectomycorrhiza-hydrogel additive Ectovit and hydrogel Stockosorb on the development of bareroot and container Norway spruce and Scots pine seedlings on windthrow area in Western Carpathians, northwest Slovakia were estimated. Survival and aboveground growth parameters during three consecutive years and root dry weight, short root frequency, soil and needle nutrients concentration and ectomycorrhizal fungi root colonization and identification 2 years after planting were assessed. Regardless of planting time and additive, the best developed bareroot spruce (2 + 2) survived significantly better than container spruce (2 + 0), container pine (2 + 0) and especially small-size bareroot pine (1 + 0); bareroot pine was found unsuitable for planting in conditions of planting site. Both additives improved survival of spring-planted container spruce in the summer-drought second year after planting. Container spruce survived and grew significantly better following fall compared to spring planting time. Higher number of short roots was observed in spring than in fall planted bareroot spruce. Neither planting time nor additives affected root dry weight and abundance of ectomycorrhizae. No significant effects of the treatments on pine development were found. Except of K deficiency in container spruce, sufficient or overabundant foliar macro-nutrients concentration was detected. Visual morphotyping of short roots and identification of ectomycorrhizae by DNA analysis indicated inefficient ectomycorrhizal inoculation of seedlings with Ectovit.

Simulation Model of Al-Dura Electro-station Plant of 160 MW with Genetic Algorithm Method

In the present paper, a thermodynamic analysis of Al-Dura, Baghdad station type (K– 160–13.34–0.0068), power plant has been carried out. The power plant system was simulated and a detailed parametric study undertaken. This study can be helpful to identify the plant site conditions that cause losses of useful energy taken place and also helpful to resolve some problems encountered in steam turbine, capacity unit. Developing nonlinear mathematical models based on system identification approaches during normal operation without any external excitation or disruption is always a hard effort, assuming that parametric models are available. This study included on using soft computing methods that would be helpful in order to adjust model parameters over full range of input–output operational data. In this case, the model parameters are adjusted by applying genetic algorithms as optimization methods. Comparison between the responses of the turbine – generator model with the responses of real system validates the accuracy of the proposed model in steady state and transient conditions. Simulation results shows that the efficiencies and feasibility of the developed model in term of more accurate and less deviation with the responses of read system in the steady and transient conditions, and the error of proposed function is less than 0.37%. This study presents the usage of the Cycle – tempo and Matlab/Simulink package to implement the model of the power plant. Finally, many recommendations have been suggested for improved plant performance.

Biogeochemical consequences of winter flooding in brook valleys

Climatic change has great impacts on stream catchments and their ecology. Expectations are that more extreme climate events will result in undesired flooding in stream catchments. In the Netherlands, former floodplains with a history of agricultural use are put into use again as flooding areas for the purpose of water retention. This study focuses on the effects of winter flooding on various plant site conditions in the soil, such as redox, nutrient, pH, and base status. We compared the effects on groundwater- and rainwater-dominated floodplains. Water chemistry (pH, EC, HCO3, SO4, Cl, Ca, Mg, Na, K, $$ {\text{p}}_{{{\text{CO}}_{{\text{2}}} }} $$ , NO3, NH4, and PO4) and soil nutrients (Total N and P, and bio-available P) were monitored for one year, including a 3–4 month period with winter flooding. In both floodplains no direct effect of the flood-water chemistry was detected in the pore water, because the soil pores had become saturated with groundwater or rainwater, respectively, just before flooding, flood-water did not penetrate the soil. We found that the increase in pH and ammonium concentration in the rainwater floodplain were due to changes in redox status, resulting from the completely water-filled state of the soil pores during the flooding event. Furthermore, we noticed an increase in soil nutrient contents and a shift in plant species composition in the rainwater floodplain: the vegetation included more plant species characteristic for N-richness. Finally, we conclude that winter flooding has more drastic effects on biogeochemical conditions and vegetation composition in the atmotrophic conditions characteristic for low-order subcatchments than in lithotrophic conditions in the larger, higher-order subcatchments of the stream basin.

Effects of site preparation treatments on early growth and survival of planted longleaf pine ( Pinus palustris Mill.) seedlings in North Carolina

We tested the effects of eight site preparation treatments on early growth and survival of container-grown longleaf pine ( Pinus palustris Mill.) seedlings. Treatments included an untreated check, six combinations of two initial vegetation control treatments (chopping or herbicide) with three planting site conditions (flat [no additional treatment], mounding, or bedding), and a more intense treatment consisting of chopping, herbicide, and bedding. All plots were prescribed burned after site preparation and before planting. Seedling survival was not significantly different among treatments at either 12 ( p = 0.768) or 20 ( p = 0.881) months after planting. Both bedding and mounding increased root collar diameter after 20 months when compared to flat treatments ( p ≤ 0.002). Between the vegetation control treatments, herbicides increased root collar diameter growth over chopping ( p = 0.002) while chopping did not significantly differ from the check. The most root collar growth occurred on the chopping/herbicide/bedding and herbicide/bedding treatments, with the least on the flat (check) and chopping/flat treatments. The percentage of seedlings in height growth 20 months after planting was higher on bedding and mounding treatments when compared to flat treatments ( p ≤ 0.003). Herbicide was also significantly better than chopping with respect to the percentage of seedlings in height growth ( p = 0.016). The treatments with the most seedlings in height growth were chopping/herbicide/bedding followed by herbicide/bedding and herbicide/mounding.

PRESSURE ON URBAN TREES IN HONG KONG: PERVASIVE PROBLEM AND POSSIBLE AMELIORATION

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 to install a territory-wide cable-television and communication network brings havoc to roots, and premature decline. Soils at planting sites, especially at roadsides, are beset by problems such as: shallowness, too many boulders and stones, excessively coarse texture, compaction, nutrient deficiency, alkaline reaction and pollution. Outmoded nursery practice, ineffective quality control, and lack of research on suitable cultivars have allowed widespread use of substandard planting materials. Whereas trained arboriculturists are employed by the government to look after public trees, the shortage of expertise and professionalism in the private sector degrades the quality of tree work. The poor match between species selection and planting-site conditions, and a large backlog of surgery work need to be addressed. Preservation efforts are not commensurate with the scarcity of outstanding trees, with worthwhile ones continually lost due mainly to construction activities. Transplanting, the protection of champion trees and those dwelling on old stone walls should be more earnestly adopted measures. The community needs to modify its rather apathetic attitude towards urban trees and furnish effective statutory measures to plan, plant and preserve trees to effect long-term improvement.

Physiological processes in plantation establishment and the development of specifications for forest planting stock

Both the morphological and physiological characteristics of forest planting stock vary widely with nursery culture and environment. Through the control of environmentally determined variation in phenotype, stock can be adapted to both the stress of transplanting from nursery to forest site and the particular environmental conditions of the forest site. Evidence is discussed that indicates that the stress of transplanting is primarily water stress, resulting from (i) the confinement of roots to the planting hole, (ii) poor root–soil contact, and (iii) low root permeability. These deficiencies are overcome by root growth, which is thus a central process in plantation establishment. Root growth depends largely on current photosynthesis. Photosynthesis depends on the assimilation of carbon dioxide at the expense of lost water in transpiration. Transpiration is limited by water uptake and hence depends on root growth. Root growth and photosynthesis in newly planted trees are thus mutually dependent. Because of this relationship, plant water status immediately after planting, or as soon as conditions favorable to root growth occur, is a crucial factor in determining plantation establishment success. High plant tissue water status immediately after planting, or as soon as environmental conditions permit root growth, allows the onset of a positive cycle of root growth supported by photosynthesis and photosynthesis supported by root growth; whereas low tissue water potential immediately after planting can lead to the inhibition or root growth by a lack of photosynthesis and the inhibition of photosynthesis by a lack of root growth. Stock characteristics that enhance plant water status immediately after planting are reviewed and the scope for their control considered. Stock characteristics affecting adaptation to particular planting site conditions, or capable of affecting postestablishment plantation performance, are also discussed.

Frost Heaving and Damage to Black Locust Seedlings

In the spring of 1936 a study was initiated to determine the extent of frost heaving of black locust (Robinia pseudacacia Linn.) which had been planted during the preceding winter. The areas studied were in the Tennessee River valley of northern Alabama, in Lawrence, Limestone, and Madison counties. Altogether 10 plantations were studied, and counts were made of nearly 4,000 seedlings. The winter of 1935-1936 stands out as one of the coldest the South had experienced in many years. In northern Alabama the winter was more severe than any of the present century except the winter of 1917-1918, according to the United States Weather Bureau substation at Madison, Madison County, Alabama. During the winter of 1935-1936 there were seventy-one days when the minimum temperature was 32 degrees Fahrenheit or lower, with a season's low of 5 degrees below zero. By subtracting those days in which the temperature did not go below 32 degrees, and by omitting also those in which the temperature did not rise above the freezing point, there still remained fifty days in which the temperature fluctuated close to the freezing point. It is probable that in most of these fifty instances sufficient frost action occurred to cause some lifting of newly planted seedlings. The study of frost heaving of black locust seedlings was made on the basis of three variable factors, namely: planting site conditions, size of seedlings, and time of planting. In studying the effect which planting site conditions had on frost heaving the site conditions were divided into five separate categories. These five classifications, combining both ground cover and erosion conditions, were as f allows: 1. Sodded areas, where the plant cover was sufficient to prevent any erosion. The sod of broom sedge or other plant growth was thick enough to make it necessary to scalp a spot for planting each seedling. 2. Sheet eroded areas, where plant growth existed, such as wire or crab grass, but where it was too thin or too scattered to prevent sheet erosion. 3. Gullied areas, where the land was devoid of any plant growth, and where erosion was very active. Most of these gullies were from 5 to 10 feet deep, and the sides sloped at approximately a 45 degree angle. 4. Matted areas; those gully banks which were sloped according to engineering specifications, and which were mulched with hardwood or cedar brush. 5. Poorly matted areas, which received the same treatment as under No. 4, but in which the mulch was not properly replaced around the seedlings after they had been planted. When the seedling was in the middle of a square foot of unmulched soil it was considered to be improperly protected. In selecting the areas to be studied only those plantings which furnished two or more of the above mentioned classifications were chosen. This assured comparable results, and was the only check possible. The effect which size of planting stock had on heaving was separated according to the three sizes of seedlings which were used during the season; that is, small, medium, and large seedlings as represented by plants 6-12 inches, 12-18 inches, and 18-24 inches tall, respectively. Correlation of frost heaving with time of planting was made for those plantations established in early winter and in the spring. Figure 1 depicts the percentages of