Effects of nitrogen addition on the population characteristics of Bothriochloa ischaemum and soil properties
LI Panpan, WANG Bing, LIU Guobin, LI Binbin
1. College of Forestry, Northwest A&F University, 712100, Yangling, Shaanxi, China; 2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Science and Ministry of Water Resource, 712100, Yangling, Shaanxi, China
Abstract：[Background] Grassland ecosystem plays a great role in improving regional environment condition and maintaining soil and water. With the nitrogen deposition increasing, vegetation characteristics and soil properties of grassland ecosystem would be changed, which in turn influence their effects on reducing soil erosion. Bothriochloa ischaemum community is considered as typical vegetation on the Loess Plateau. Besides, the nitrogen content of soil in this region is relatively low. Hence, researching nitrogen addition effect on the characteristics of B. ischaemum community has a great significance in vegetation construction and soil and water conservation. [Methods] B. ischaemum was seeded in the soil bin (2 m in length and 1m in width; soil bulk density was 1.2 g/cm3) with 20 cm row spacing for each plant. Totally, 50 plants of B. ischaemum were seeded for each soil bin. Watered regularly during the first year and added nitrogen in the next year. Ammonium nitrate was used as nitrogen source with four nitrogen levels (0, 2.5, 5 and 10 g N/(m2·a)), which was added to the soil once every two weeks from June to August (six times in total). Moreover, the bare loess soil was selected as control. For each treatment, there were three repetitions and 15 soil bins totally. Inflorescence number and plant height of B. ischaemum were measured before each nitrogen addition, also the soil was sampled (0-5, 5-10, 10-20, and 20-30 cm) at the same time to determine the soil organic matter, total nitrogen and phosphorus, available nitrogen and phosphorus, pH and particle size distribution. At the end of growth stage, vegetation coverage, biomass of aboveground and roots (65 ℃, 48 h) were measured. In addition to this, root characteristics such as total surface area were measured with WinRHIZO software. The differences of vegetation characteristics and soil properties between all treatments were analyzed by multiple comparison method. [Results] 1) The height and inflorescence number of B. ischaemum reached the maximum at the nitrogen addition level of 2.5 g N/(m2·a), then decreased with the enhancement of nitrogen addition. 2) The aboveground biomass increased significantly with the growing nitrogen addition level (P<0.05) and the root biomass density of B. ischaemum got its maximum at 5 g N/(m2·a) nitrogen addition level. However, with nitrogen addition increased, root biomass density showed a decreasing trend. 3) With the nitrogen addition up, the soil organic matter and nitrate nitrogen content increased, while available phosphorus content decreased, whereas, there was no significant relationship between nitrogen levels and total nitrogen or ammonium nitrogen.[Conclusions] This study indicated that nitrogen deposition had a significant effect on grassland ecosystem. The B. ischaemum grew well with the certain nitrogen addition level, while lower or higher nitrogen addition level may limit its growth. This study may make a better understanding of potential impact of nitrogen deposition on the characteristics of vegetation and soil properties, and would provide fundamental scientific basis for regional vegetation construction under the background of global atmospheric nitrogen deposition.
李盼盼1, 王兵1,2, 刘国彬1,2, 李彬彬1. 氮添加对白羊草种群及土壤特征的影响[J]. 中国水土保持科学, 2017, 15(2): 35-42.
LI Panpan, WANG Bing, LIU Guobin, LI Binbin. Effects of nitrogen addition on the population characteristics of Bothriochloa ischaemum and soil properties. SSWC, 2017, 15(2): 35-42.
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2017, Vol. 15 
