جستجوی مقالات مرتبط با کلیدواژه "جنگلکاری" در نشریات گروه "محیط زیست"

Acacia albida Delile naturally grows on the outskirts of Razm Abad village, Dashti city, Bushehr province. This species is a hardy drought-resistant tree with abundant ecological and economic potential. The forest is under threat of degradation because of its close distance to the village. This research has been carried out to identify the habitat, the causes of degradation, the possibility of seed production for future propagation, and the necessity to protect it. The forest of this species can be categorized into three forms including dense, semi-dense, and scattered form. The reproduction of this species through seeds was scarce, but coppice seedlings were found in this area. In terms of phenology, A. albida lost its leaves in July, reproduced leaves in November, and produced flowers in March. Due to the late cold in March, flowers were destroyed and fruits were not formed during this work. Deforestation of Acacia habitat for agricultural and horticultural, livestock grazing, consecutive droughts, cutting down and uprooting trees, digging agricultural wells in the vicinity of the habitat, and herbal pests are essential and serious factors of threat and destruction of this habitat. Lowering the underground water level and water out of the reach of trees and reduction of flood-water in the Sana seasonal river are other important threats of forest degradation. Protecting, forestry, using floodwater of the Sana seasonal river, and continuous monitoring and enriching the forest can help sustain and rehabilitate this valuable natural forest. It is, also, recommended to do more research on the reasons for the lack of this species in other parts of southern Iran. To study the process of forest sequence, seed and seedling production and afforestation is suggested.

Increasing concentration of atmospheric CO2 is one of the most important reasons for climate changes and global warming. one of the most appropriate solutions offered to solve this problem is its reduction by carbon sequestration in soil by plants. Concentration of atmospheric CO2 will increase to the range of 415 to 421 ppm in 21st century. Only with optimistic assumptions and low growth rates, increase of carbon-dioxide-induced temperature will be held below 2°C over the next century. Conservation, flexible energy choices and control options could lessen the potential effects of carbon dioxide otherwise it will cause global warming crisis. Besides the economic and social disadvantages, it will lead natural ecosystems to loss their stability. Thus, effort to reduce greenhouse gas concentrations through suitable management is important and ultimately will lead to sustainable development. Methods such as filtering to reduce the concentration of carbon dioxide in the atmosphere will be high costly. So at the macro levels it will not operational. The world needs to reduce the concentration of Co2 can be satisfied by less expensive methods such as the carbon sequestration by plants.

In order to survey on probably variety of temperature in a planted area compare to none planted area selected 50 Ha of planted land of near the Dez dam in shahyon of Dezful. For data comparing selected area 10 Ha as well as buffer zone in out of planted land. Then based on Random-systematic method, 3 thermometer maximum-minimum in the stable line altitude 520 meter up the sea level in planted land & 3 thermometer in none planted land in same line were installed too. Harvested data duration one month after assemblage and analysis showed that temperature difference in two areas was very salient and it was proximate to 3 c. Temperature vibration in plated land lower than none planted land meaningful.

Woody species diversity in Kelardasht region, North of Iran was studied in a mixed Picea abies and pinus nigra plantation and a mixed broad-leaved coppice stand. For this purpose by using systematic- random sampling method with circular plots of 100m² in 20×50 grid lines were inventoried. Species and number of woody plants (tree and shrub) were recorded in plots. Plant diversity, richness and evenness were determined using the Simpson, Menhinic and Peat Indices respectively. The result shows that the most frequent native trees were found in broad-leaved coppice stand. Broad-leaved coppice stand had higher diversity than coniferous stand but lower richness and evenness.

The objective of this study was to determine plant species diversity in the understory of loblolly pine plantations in different stages of growth. To conduct this study, random-systematic sampling method was used, and plot area was obtained using Whittaker’s nested plots and species / area curve. Within each plot, woody and herbaceous species were identified, and percentage cover was estimated according to abundance-dominance criterion of Braun-Blanquet. In order to data analysis, Shanonn-Wiener’s diversity index and Smith and Wilson evenness and Jacquard similarity indices were used. Results indicated that the number of plant species (richness) were 25, 38, 48, 42 and 32 in seedling, small sapling, large sapling, bole tree of growth stages and natural forest, respectively. The highest and lowest of plant species diversity were found in the large sapling (non-thinned forest) and seedling growth stages, respectively. Also, plant species diversity was higher in large sapling than bole tree (thinned forest) plantations, but there was no significant difference between them (P> 0.05). The jacquard similarity index in the large sapling and bole tree plantations were higher than seedling and natural forest.

Pure plantations reduce soil fertility so sustainable production cant be accessible. Because poplar plantations can be means for reducing harvest from forest so it is essential to have special plans for them before developing there plantations. In these study nutrients of live and senescent leaves of plantations of Populus deltoides Marsh. and Alnus subcordata C.A.Mey. have studied in pure and mixed plantations in a completely randomized block near Chamestan in north of Iran. Nitrogen content of live and senescent leaves of A. subcordata was greater than P. deltoides but Ca was greater in live and senescent leaves of P. deltoids and Mg was greater in senescent leaves of P. deltoides and P and K dont show any significant differences. Live and senescent leaves of P. deltoides in mixed treatments with A. subcordata showed more N than pure ones. There havent seen any important differences about other nutrients. Finally we can conclude that mixing A. subcordata in plantations of P. deltoides in this location and with these conditions is profitable.