جستجوی مقالات مرتبط با کلیدواژه « deforestation » در نشریات گروه « آب و خاک »

Forests have important role for ecosystem maintenance, and deforestation is one of the factors in degradation of soil quality.  In this study, using multivariate analysis, soil quality index was evaluated in three land uses including forest, grassland, and cropland at two depths of 0-10 and 10-20 cm in Sidasht of Guilan Province, Iran. The weighted additive soil quality was calculated using two methods (1) Minimum data set (MDS1) and (2) Revised minimum data set (MDS2). Also, each feature’s variance and communality and two scoring methods, namely, linear and non-linear, were compared and evaluated. In MDS2, the effects of land use on soil quality index (SQI) indicated that the mean values calculated by the non-linear scoring method was significantly more precise than the linear one. Soil quality indices in forest and grassland had the maximum values when compared to cropland. SQIW2-MDS2-NLS had the highest sensitivity index (SI= 3.14). In MDS2, the soil properties including silt, Mean Weight Diameter, pH, CaCO3 and available phosphorus were selected. Efficiency ratio of MDS2 was 80% and in soil quality assessment, MDS2 had higher efficiency than MDS1. Soil condition and change of soil management practices were reflected in MDS2 more clearly than in MDS1. Accordingly, SQIW2-MDS2-NLS method was the best means for evaluating the effects of deforestation on soil quality in the studied area.

In this study, the effects of land use change (conversion of natural forest to paddy fields) and regeneration of deforested land on some qualitative and enzymatic properties of the soil were investigated. For this study, Populus Research Station in Guilan province, Astana Ashrafieh city was selected. Soil samples were collected from 5 land uses (natural forest, populus, Alnus and Taxodium and paddy forests) and two depths (0-20 and 20-40 cm). The data were analyzed as a factorial experiment in a completely randomized design with three replications. The factors included land use type at five levels and soil depth at two levels that were studied in three replications. Therefore, the number of treatments were 5 * 2 = 10, totally 30 units accounting replications. In total, there were 30 samples of disturbed soil and 30 samples of undisturbed soil that constituted the statistical data of the experiment. Some physical, chemical and biological properties of the samples were measured. The results showed that the mean weight diameter (75%), saturated hydraulic conductivity (95%), water repellency (53%), organic carbon (52%), total nitrogen (52%) and microbial biomass carbon (53%) in the natural forest were higher than the ones in the paddy field. Also, the activity of urease and arylsulfatase in the paddy soil was significantly lower than the one in the natural forest soil. However, the activity of dehydrogenase in the paddy soil was higher than the one in natural forest soil, indicating oxygen availability and moisture affect the activity of dehydrogenase and its activity increases as the soil moisture increases. Reclamation of some deforested lands by hand planted forest showed that Populus vegetation was more effective than the other vegetation covers in increasing aggregate stability, hydraulic conductivity, and microbial biomass carbon. While Taxodium cover increased the activities of urease, arylsulfatase and acid phosphatase more than the ones in other vegetation covers. The specific activity of enzymes (enzyme activity per unit of organic carbon), in dehydrogenase was significantly higher in the paddy soil than in the soil under natural forest. This indicates that the activity of this enzyme is independent of soil organic carbon changes and is dependent on soil moisture. Overall, it can be concluded that, in comparison with the qualitative and enzymatic activity, Taxodium coating improved these properties better than populus and Alnus coating.

The soil quality is defined as the ability of soil to function as an essential part of the human habitat. In this study, the effects of land use change (conversion of forest lands into agricultural lands) on the soil physical quality were studied in the Gilan-e-Gharb region. For this study, soil samples were collected from surface and subsurface layers of both land uses, and the peak and shoulder slope positions, in Miandar and Vidjanan catchments. Soil physical properties such as soil texture and particle size distribution, soil hydraulic conductivity, bulk density, mean weight diameter of aggregates, water holding capacity, and the soil organic carbon content were measured. The results showed that land use change of the forest to agricultural lands resulted in a sharp decline in the soil organic matter (52%) and an increase in silt and sand percentage and soil bulk density. Also, deforestation decreased the mean weight diameter of aggregates (from 0.39 to 0.14 mm in Miandar) and clay percent. It caused a reduction in the total porosity followed by a decrease of soil water holding capacity, and a decrease in the saturated hydraulic conductivity (from 10.34 to 1.86 cm/h), as well. In general, the results proved that the land use change from forest to agriculture severely decreased soil physical quality and its productivity.

Land use changes such as conversion of forest to cultivated land significantly influence soil properties and modify soil forming processes. In order to study the effects of different land use on soil physical، chemical and biological properties، five sites of mountain landforms consisting of Bijarbagh (granite parent rock)، Zemeidan (basaltic andesite parent rock)، Alisorod (phyllite parent rock)، Khorma (basaltic andesite parent rock)، and Leil (andesitic basalt parent rock)، located in part of Lahijan and Langaroud regions were selected. Each site had forest cover and tea garden next to it. A representative profile in each land use was dug and three locations around the profile were selected for soil sampling (0-30 cm). This study was conducted in a factorial arrangement and completely randomized block design (CRBD). Results indicated that land use changes and parent material had significant effect on soil physical، chemical، and biological properties. Land use changes (forest to tea garden) significantly increased clay، silt، bulk density، and free iron oxides (Fed) with mean values of 12%،10. 5%،17%، and 5. 5 percent، respectively، but significantly decreased sand، pH، organic carbon (OC)، exchangeable Ca+Mg، exchangeable K، CEC، amorphous iron oxides (Feo)، biomass respiration contents and bacterial population with mean values of 3. 7%، 11%، 17. 7%، 29. 9%، 32. 6%، 18. 3%، 24%، 34%، and 22 percent، respectively.

In order to study land degradation from the soil genesis and micromorphological perspective، ten soil profiles were dug and described on five slope positions in both forest and deforested cultivated land. The soil samples were taken from all horizons for physico-chemical analysis and micromorphological studies. Forest soils had a well developed argillic and calcic horizons and also mollic epipedon. These soils were classified as Alfisols and Mollisols. Carbonate leaching into the depth of soil profile and translocation of clays to lower layers and formation of developed soils are by no means related closely with the dense forest cover and its subsequent landscape stability and favorable leaching conditions. Dominant soil orders in this area were Inceptisols and Mollisols. In cultivated landuse، no argillic horizon was observed except in toeslope position. Absence of argillic horizon or its elimination following deforestation is one of the most important and obvious pedogenetic evidences of land degradation after land use change. Outcropping of high carbonatic layers (calcic horizon)، disappearance of mollic and formation of ochric epipedon، presence of redoximorphic features attributed to runoff in lowland، decrease of solum thickness، and change of soil color were the other pedogenic indicators for land degradation in the study area. Microscopic observations showed that granular and crumb microstructures with high porosity were converted to massive and compact ones with low porosity in the deforested area. Disappearance of clay coatings besides absence of excremental pedofeatures were the other important micromorphological evidences of erosion and land degradation.

An important part of carbon cycling is carried out in the soil making land use changes, including changes in forestlands, affect SOC storage and consequently CO2 flux into the atmosphere.The aims followed in this investigation were to study the impacts of conversion of deciduous forests to coniferous ones and deforested land to rangelands, on some of the soil physicochemical properties, organic carbon (OC) storage, and soil respiration in two sites 1 and 2 (two different sets of properties), in south of Kelardasht area. Soil pH and EC are not substantially affected by land use change, but bulk densities have been on the increase through deforestation and have decreased at reforestation. By reforestation, SOC storage increased about 17.6 and 49.5 %(P<0.05) in sites 1 and 2. However, deforestation has caused SOC storage to diminish about 14.5 (P<0.05) and 4.7 %(P>0.05). CO2 emission indicated significant and positive correlation with the mean air temperature in all sources of land use. In General, the coniferous forests proved to be more efficient in organic carbon storage, and therefore could be benefited from in the reduction of soil CO2 emission.

Deforestation has been recognized as one of the biggest environmental problems in the world. It is also one of the main elements of land productivity changes and one of the biggest factors which threaten world's environmental diversity. In this study, based on environmental Kuznets theory, factors which may affect deforestation have been investigated. Results obtained from 71 studied countries show that environmental Kuznets curve was not true for them. Population growth helps the speed of deforestation while higher rate of GDP growth decreases its rate. Institutions which help with the improvement of democracy, individual assets, civil right and political liberty can decrease the pressure on natural recourses and deforestation.

To investigate the degree of forest degradation and the effect of land use change on selected soil quality attributes in loess-derived landforms, samples were taken from different land uses including forest, rangeland, degradated rangeland and farmland in Pasang watershed located in the Galikesh area of Golestan province (37°16'N, 55°30'E). The annual average temperature and mean precipitation of study area were 15°C and 730 mm respectively. Organic matter, pH, EC, CaCO3 and nutrients (N, P, K) as chemical indicators, hydraulic conductivity, bulk density and porosity as physical indicators and soil respiration as biological indicator were measured. The results showed that the amount of organic matter decreased three percent when it was turned from forest to farmland, and increased two percent from farmland to rangeland. The amount of CaCO3 in surface layer of deforested area was more than in the forest soils. The amount of soil N in forest and soil P and K in rangeland were higher than in other land uses. Bulk density and porosity in forest and MWD in rangeland were higher than in other land uses because of the decrease in organic matter due to farming activities. Soil respiration in forest was highest as compared to in other land uses. Difference of enzymes activities (L-asparaginase and Dehydrogenase) compared to microbial respiration indicates that enzymes activity is related to specific biological processes while soil microbial respiration basically depends on the general activity of soil microbial population. It could be concluded that amount of organic matter, soil N, bulk density, porosity, MWD, soil respiration and enzymes activities are suitable indicators for soil quality evaluation in this area.