The Effect of Nitrogen Deposition on Soil Enzyme Activity in the Forest Grassland Landscape Boundary of Tibet

The simulated nitrogen deposition [control check(CK), 0 kg·hm^2/a; low nitrogen(LN),25 kg·hm^2/a; medium nitrogen(MN), 50 kg·hm^2/a; high nitrogen(HN), 150 kg·hm^2/a] was performed from July 2014 to August 2015 in the forest-grassland boundary in Zhuqudeng Village, Bujiu Township,Linzhi City, Tibet Autonomous Region to analyze the activity of enzymes(invertase, catalase, urease,amylase, cellulase, polyphenol oxidase, and β-glucosidase) in soil layers of 0-20 cm and 20-40 cm and explore the effect of different levels of nitrogen deposition on enzyme activity different layers of soil.The results showed that: ① different levels of simulated nitrogen deposition had remarkable effects on sucrase, amylase, cellulase, polyphenol oxidase and β-glucosidase in the soil layer of 0-20 cm(p < 0.05) and unremarkable effects on catalase and urease(p > 0.05); in the soil layer of 20-40 cm, the response made by sucrase, catalase, urease, amylase, cellulase, polyphenol oxidase and β-glucosidase to nitrogen deposition reached a significant level(p < 0.05). ② In the soil layer of 0-20 cm, the activity of urease and poyphenol oxidase reduced under LN treatment and enhanced under HN treatment, and the activity of invertase,catalase, amylase, cellulose, and β-glucosidase was inhibited by nitrogen deposition. ③ In the soil layer of20-40 cm, the activity of polyphenol oxidase and β-glucosidase reduced under under LN treatment and enhanced under HN treatment, and the activity of invertase, catalase, urease, amylase, and cellulase was inhibited by nitrogen deposition. ④ With the deepening of the boundary soil layer(from 0-20 cm to20-40 cm), urease and β-glucosidase made different responses to the different levels of nitrogen deposition,while invertase, catalase, amylase, cellulose, and polyphenol oxidase showed the same response to nitrogen deposition.

The Effect of Nitrogen Deposition on Soil Microorganisms in the Woodland-Grassland Border of Tibet

Nitrogen deposition was simulated from July 2014 to August 2015 in the grassland, woodland, and woodland-grassland border in Zhuqudeng Village, Bujiu Township, Linzhi County,(CK, 0 kg·hm^2·a^(-1); LN, 25 kg·hm^2·a^(-1), MN, 50 kg·hm^2·a^(-1); HN, 150 kg·hm^2·a^(-1)). NH_4NO_3 was used as nitrogen source to analyze the number of microorganisms in soil layers of 0–20 cm and 20–40 cm and explore the effect of different degrees of nitrogen deposition on soil microorganisms in grassland, woodland, and woodlandgrassland border. The results showed that: the number of bacteria in the grassland increased significantly under the treatment of LN, and the number of bacteria in the woodland-grassland border and woodland had a rising response under the influence of nitrogen deposition; the number of actinomycetes in the grassland increased in MN and HN treatment, and significantly increased in the border and woodland under LN treatment; the number of molds decreased sharply in the grassland, woodland, and woodland-grassland border.

基于正交试验不同处理对藏川杨生根质量的影响

本研究试图寻求科学培育藏川杨苗木的方法,以解决苗木供不应求的现状,为西藏造林绿化,生态系统稳定,生态环境的保护和可持续发展作出一份贡献。选用1 a生萌蘖条为材料,采用3因素3水平的L9(34)正交设验设计方案,研究插穗类型、ABT浓度和浸泡时间对藏川杨无性扦插繁殖生根质量的影响。结果表明,各试验因子对藏川杨生根率和生根质量有极显著(P<0.01)影响,且上述不同实验因子间存在正相关关系;ABT浓度、插穗类型和处理时间3个因素中,插穗在ABT溶液中浸泡时间对藏川杨扦插生根质量影响最大,其次是ABT浓度和插穗类型。基于总根系生物量,藏川杨扦插生根质量的最优组合为A_(3)B_(2)C_(1)(插穗部位基部,ABT浓度200 mg/L,浸泡时间2 h),其生根质量指数为50.19,远高于其他8种试验组合。结果表明,以1 a生萌蘖条的基部作为插穗,用200 mg/L的ABT溶液中浸泡2 h可以大大提高藏川杨硬枝扦插生根质量。

不同种源藏川杨1年生插条苗生长规律研究

本研究旨在为培育优质藏川杨苗木和选择优良种源提供参考依据。本文选用拉萨、山南、林芝和日喀则4个种源的藏川杨1a生插条苗为研究对象,定期观测其生长指标,研究了苗高和地径的生长规律。结果表明:藏川杨不同种源1a生插条苗苗高、地径生长总体呈“慢-快-慢”型生长规律,其生长高峰期在6月中旬至8月中旬,占整个生育期生长总量的60.9%;4个种源的藏川杨1a生插条苗在苗高和地径上存在显著差异,苗高生长以日喀则种源最优,而地径生长以林芝种源最优;藏川杨苗高的变异普遍比地径丰富,苗高的变异系数是地径的变异系数的1.8倍以上;但在4个种源中拉萨种源的插条苗苗高、地径变异最大,分别为29.63%、14.47%,是均值的1倍以上。结果说明培育无性藏川杨优质苗木应以日喀则和林芝种源最佳。

Short-term Effects of Nitrogen Deposition on Soil Enzyme Activities in Tibet Grasslands

[Objective] The paper was to study the effects of nitrogen deposition on enzyme activity in different layers of soil. [Method] With grass-land located in Zhuqudeng Village, Bujiu Township, Linzhi City, the Tibet Autonomous Region, as the object, nitrogen deposition was simulated from July 2014 to August 2015. Four N addition treatments were established： control （0 kg·hm^2/a）, low N （LN, 25kg·hm^2/a）, medium N （MN, 50 kg·hm^2/a） and High N （HN, 150 kg·hm^2/a）, aiming at measuring enzyme activity （invertase, catalase, urease, amylase, cellulase, polyphenol oxidase and β-glucosi- dase） in different layers of grassland soil （0 -20 cm and 20-40 cm）. [Result] （1） Different levels of simulated nitrogen deposition had significant impact on invertase and β-glucosidase at the soil depth of 0-20 cm （P〈0.05）, but no significant impact on catalase, urease, amylase, cellulase and polyphenol oxidase（P〉0.05）; invertase, polyphenol oxidase and β-glucosidase had significant response to nitrogen deposition at the soil depth of 20- 40 cm （P〈0.05）, while catalase, urease, amylase and cellulose had no significant response （P〉0.05）. （2） The activities of invertase and polyphenol oxidase were enhanced at the soil depth of 0-20 cm, and that of β-glucosidase was inhibited. （3） With the deepening of nitrogen deposition, the ac- tivities of invertase and cellulose were enhanced at the soil depth of 20-40 cm; the activity of polyphenol oxidase was reduced in LN treatment, but increased in HN treatment; the activity of β-glucosidase was increased in LN treatment, but decreased in MN treatment. （4） With the deepening of soil layers, invertase and polyphenol oxidase responded similarly to simulated nitrogen deposition. [Conclusion] The results provide certain scientific basis and fundamental data for better understanding and evaluating the effects of nitrogen deposition on enzyme activity in grassland soil.

Effects of Different Afforestation Techniques on Soil Nutrients in Populus alba Woodland

[Objective] The research aimed to study the influence of different afforestation technology measures on soil nutrients of P. alba wood-land in arid valley region of Rikaze, Tibet. It aimed to improve afforestation technology measure in arid valley region of Rikaze, Tibet, and provide theoretic basis for restoring the degraded ecosystem at upper reaches of the Yarlung Zangbo River. [ Method] In arid valley region of Duojiao Vil-lage, Nanmulin County, Rikaze City, the planted land using rooting powder, egg shell, leaves, mud and water retention agent was taken as re-search object, while the land without any afforestation measures was taken as the control, to determine soil nutrients under different afforestation measures. [Result] Under different afforestation measures, the contents of various soil nutrients were all obviously higher than control, in which available potassium, available phosphorus, alkali hydrolysable nitrogen and organic matter in soil obviously increased than control, but there was no similar rule among different measures. [Conclusion] Vegetation restoration in dry valley belt of Rikaze by different afforestation measures is favorable for improving physical-chemical properties of soil and increasing soil fertility.