Abstract
Pasture degradation caused by overgrazing and inappropriate fertiliser management is a major production and environmental threat in Qinghai-Tibet Plateau. Previous research has focused on the effects of mixed nitrogen (N) and phosphorus (P) fertiliser and reduced grazing pressure on the plant community of the grassland; however, the role of P and how it interacts with various defoliation (the process of the complete or partial removal of the above-ground parts of plants by grazing or cutting) intensities on the plant and soil of the grassland ecosystem have not been quantified. A field experiment was conducted to quantify how P application in combination of defoliation pressure could impact the dynamic change of the plant and soil in a native alpine grassland ecosystem of the Qinghai-Tibet Plateau, China, from May 2012 to September 2014. A split-plot design with 4 replicates and repeated measures was used to determine the growth and composition of plant community and soil physical and chemical properties under various levels of P fertiliser and defoliation intensity. The results showed that applying 20 kg P/ha increased the herbage yield of Melissitus ruthenica by 68% and total pasture yield by 25%. Close defoliation favoured the growth and plant frequency of the shorter species, whereas lax defoliation favoured that of the taller plant species. Medium P rate and cutting to 3 cm above ground gave an overall best outcome in pasture yield, quality and frequency and soil moisture and nutrient concentration. Application of P fertiliser with a moderate defoliation pressure to promote legume growth and N fixation has the potential to achieve multiple benefits in increasing pasture and livestock production and improving environmental sustainability in the alpine pasture of Qinghai-Tibet Plateau, a fragile and P-deficient ecosystem zone in China and its western neighbouring countries.
Highlights
The Qinghai-Tibet Plateau is the youngest, highest and largest plateau on the earth with an area of about 2.57 million (m) km2, representing over 26% of the total land area in China [1]
In Gannan Tibetan Prefecture of Gansu Province, for instance, the groundcover by pastures has decreased by 35% and pasture yield decreased by 15% since the 1980s [5]
The objectives of the study were 1) to investigate the impact of defoliation intensity, P fertiliser and their interactions on the herbage production, botanical composition and frequency of major pasture species/categories of an alpine meadow in Qinghai-Tibet Plateau; 2) to examine how these factors could affect the soil moisture and nutrients, and nutrients of the pasture through the above- and below-ground plant growth and competition; and 3) to develop defoliation and fertiliser management strategies/recommendations that could be incorporated in guidelines and regulations to improve the productivity and sustainability of alpine meadow for the local producers, and the local and central governments
Summary
The Qinghai-Tibet Plateau is the youngest, highest and largest plateau on the earth with an area of about 2.57 million (m) km, representing over 26% of the total land area in China [1]. The annual precipitation of the plateau is low; the water resource is rich with many rivers, lakes, glaciers and wetlands distributed throughout the region, accounting for about 20% of the total water resource in China [2]. The area of pastures in Qinghai-Tibet Plateau is approximately 150 m ha, 62.4% of the national total of China. The degraded pasture area was estimated to be over 30% of the total grassland area available for grazing in the plateau, which has led to extensive soil erosion, dust storms and water pollution to rivers and waterways [4]. In Gannan Tibetan Prefecture of Gansu Province, for instance, the groundcover by pastures has decreased by 35% and pasture yield decreased by 15% since the 1980s [5]
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