Mustafa Tufekcioglu

Stocking Rate and Riparian Vegetation Effects on Physical Characteristics of Riparian Zones of Midwestern Pastures

Abstract Grazing at high stocking rates may increase sediment and nutrient loading of pasture streams through transport in precipitation runoff and bank erosion. A 3-yr (2007–2009) grazing study was conducted on 13 cool-season grass pastures to quantify effects of stocking rate and botanical composition on forage sward height, proportions of bare and manure-covered ground, and bank erosion adjacent to streams. Pastures ranged from 2 ha to 107 ha with stream reaches of 306 m to 1 778 m that drained watersheds of 253 ha to 5 660 ha. Bare and manure-covered ground were measured at a 15.2-m distance perpendicular to the stream at 30.5-m intervals at up to 30 locations on each side of the stream by the line transect method in May, July, September, and November of each year. At the midpoint of the 15.2-m line, forage sward height was measured with a falling plate meter (4.8 kg · m−2) and plant species identified. In November 2006, fiberglass pins (1.6 × 76.2 cm) were driven 73.7 cm into the stream bank at 1-m intervals from the streambed to the top of the bank along 10 equidistant transect locations on each side of the stream to measure bank erosion during spring, summer, and fall of each year. Increasing pasture stocking rates increased manure-covered ground and decreased sward height, but did not affect proportions of bare ground. The greatest, intermediate, and least net soil erosion rates occurred during the winter/early spring, late spring/early summer, and late summer/fall seasons. Stocking rates between measurements, expressed as cow-days · m−1 stream, were not related to bank erosion. Increasing stocking rates per unit of stream length will increase manure cover and decrease forage sward height, but not affect proportions of bare ground or bank erosion rates adjacent to pasture streams. Therefore, managing stocking rates may reduce nutrient loading of pasture streams.

Stream Bank Erosion as a Source of Sediment and Phosphorus in Grazed Gastures of the Rathbun Lake Watershed in Southern Iowa, United States

Livestock grazing of riparian areas can have a major impact on stream banks and stream integrity if improperly managed. The goals of this study were to determine the sediment and phosphorus (P) losses from stream bank soils under varying cattle stocking rates and to identify additional factors that impact stream bank erosion in the southern Iowa Drift Plain. The research was conducted on 13 cooperating beef cow-calf farms within the Rathbun Lake Watershed in south central Iowa. Over three years, stream bank erosion rates were estimated by using an erosion pin method. Eroded stream bank lengths and area, soil bulk density, and total P (TP) content in stream bank soil were measured to calculate soil and TP losses via stream bank erosion. The length of severely eroded stream banks and soil compaction of the riparian areas of the pastures were positively related to stocking rates. There was no direct relationship between bank erosion and stocking rate. These results suggest that use of riparian areas as pasture can negatively impact the integrity of the major source areas and that the impact could be reduced through management of livestock stocking densities within these riparian areas.

Kuraklık ve orman ekosistem dinamikleri etkileşimi

Drought is one of the important problems influencing forest ecosystems. This problem has been getting more attention recently due to impacts of global warming. Drought could decrease aboveground growth of plants by 30-70% and restrict their natural distribution boundary and biodiversity. Growth of trees is controlled by the availability of water up to 80-90%. In Turkey, drought triggered forest tree mortalities have been observed in leeward sides of Black Sea Region, Central Anatolian Region and Aegean Region. Dead trees of Scots pine and oriental spruce found in Black Sea Region, of black pine, scots pine and fir in Central Anatolian Region and of brutian pine in Aegean Region. In addition, drought triggered bark beetle infestation that caused dying of thousands of spruce trees in Eastern Black Sea Region. Main reasons of increasing drought effect are global warming, overgrazing, conversion of grassland and forest areas into croplands and increased erosion in Turkey. Grassland area in Turkey was 38.9 million ha in 1949 and this area had been decreased to 28.3 million ha till 1969 and today is 21.8 million ha. While agricultural land area was 8.5 million ha in 1935, it increased to 25 million ha in 1970 and today it is 28 million ha. Meanwhile forested land area had been decreased up to 2.6 million ha from 1950 to 1997. In Turkey, drought tolerant ecotypes of important timber species need to be selected in order to reduce the potential effects of global warming on tree mortalities. Additionally, drought risk maps of forest areas should be prepared to determine drought risk assessment and take necessary measures. Drought can further accelerate the effects and extent of erosion. Therefore, it is also important to account the effects of erosion on the productivity of agricultural and forest goods. Finally, effects of global warming need to be incorporated into afforestation strategies of Turkey.