CHAPARRAL CONTROL IN MOSAIC PATTERN INCREASED STREAMFLOW AND MITIGATED NITRATE LOSS IN ARIZONA1

ABSTRACT: In a 16-year paired watershed study in Arizona, a 303-acre chaparral watershed was treated by helicopter in a mosaic pattern (55 percent of watershed) with tebuthiuron herbicide pellets to control the moderately dense, heavy water-using chaparral. The objective was to determine if annual stream discharge could be increased without degrading other resource values. An adjacent untreated chaparral watershed served as the control on which to base the water quantity and quality treatment effects. Annual streamflow was increased by 1.5 to 5 inches over a seven-year evaluation period. The streamflow increase was accompanied by a small but statistically significant increase in nitrate concentration. The relatively small nitrate response was attributed to the mosaic treatment. Nitrate released from the converted areas was diluted by streamflow from untreated areas, thereby reducing nitrate concentrations in streamflow at the watershed outlet.     

Regional assessment of climate change impacts on maize productivity and associated production risk in Switzerland

A simple model of yield was used along with climate scenarios to assess the impact of climate change on grain maize productivity and associated economic risk in Switzerland. In a first application, changes in the precipitation regime alone were shown to affect the distribution of yield considerably, with shifts not only in the mean but also in the standard deviation and the skewness. Production risk was found to respond more markedly to changes in the long-term mean than in the inter-annual variability of seasonal precipitation amounts. In a further application, yield projections were generated with respect to a full climate scenario, with the emission pathway as specified in the IPCC A2 scenario. Anticipation of the sowing date was found to reduce the negative impact of climate change on yield stability, but was not sufficient to ensure average productivity levels comparable to those observed at present. We argued that this was caused by the reduction in the duration of the growing season, which had a stronger impact than suggested by previous studies. Assuming no change in price relations, the results also revealed a strong increase in production risk with climate change, with more than a doubling in the probability of yield falling short of a critical threshold as compared to today’s situation.     

污泥臭氧化减量技术的影响因子

采用臭氧作为剩余污泥的细胞裂解剂,并与生物接触氧化工艺相结合进行污泥减量的实验研究,臭氧化后的污泥上清液回流入曝气池与污水合并处理。结果表明:在臭氧投量为0.05kgO3/kgMLSS,臭氧化污泥量为进水量的5%条件下,生物接触氧化系统对SCOD和NH4-N的平均去除率分别为87.06%和84.80%,出水水质同对比实验相当;同时获得了0.054(gMLSS/去除1gSCOD)的剩余污泥产率,与对比实验相比降低了78.4%。     

猪粪堆肥与化肥配施对水稻产量和氮效率的影响

采用大田试验方法研究猪粪堆肥与化肥配施对水稻产量和氮效率的影响.结果表明:在本试验条件下,猪眄粪堆肥与化肥配施能显著提高水稻籽粒产量,增加水稻每穗实粒数.尤其是1 500 kg·hm-2猪粪堆肥 化肥配施处理,稻谷产量达8 595 kg·hm-2,比未施氮处理和化肥处理分别增产57.8%和13.6%,差异达显著水平.猪粪堆肥与化肥配施处理水稻氮素养分效率均高于化肥处理.猪粪堆肥与化肥配施的氮肥回收率为35.3%～38.6%,而化肥处理仅为27.6%.     

高应变率环境下材料的失效机理研究

采用双层约束爆炸方法对高应变率环境下材料的失效模式及其影响因素进行了研究。结果表明：材料存在拉伸断裂和绝热剪切断裂两种模式。碳含量越高,材料对绝热剪切越敏感;同种材料的淬、回火类组织比正火类组织绝热剪切敏感性高。材料的屈导比哕决定了材料的失效模式,哕越大,材料越倾向于以绝热剪切模式失效。     

水中无机氮形态变化对酮洛芬光降解的影响

研究了模拟太阳光照射下水环境中不同形态氮(NO₃^-、NO₂^-和NH₄⁺)对酮洛芬(KET)光解的影响.结果表明,KET在平均波长(200~450nm)下量子产率Φ_o为0.14. NO₃^-浓度从0.01mmol/L^-增至1.0mmol/L时, KET光解速率常数从0.0109降至0.0085; NO₂^-浓度从0.01mmol/L增至1.0mmol/L时, KET光解速率常数从0.0095降至0.0069, NH₄⁺对KET的光解基本无影响. NO₃^-的光掩蔽现象对KET光解的影响起主要作用; NO₂^-则通过光掩蔽现象和羟基自由基猝灭来抑制KET的光解.同时研究了当水环境中pE值发生变化而引起水中无机氮形态转化时,不同形态氮共存对KET光解的复合影响,随着pE值的增大,KET的光解速率先减小后增大;当NO₂^-和NH₄⁺共存时,两者对KET光解的影响存在拮抗作用,这一拮抗作用也存在于NO₂^-和NO₃^-之间.     

风蚀对窟野河流域产沙贡献的时间尺度特征

风蚀在黄土高原风水蚀复合区的侵蚀产沙中扮演着重要的角色。利用窟野河流域神木水文站水沙资料及有关气象资料,分析了风蚀对窟野河神木水文站以上流域产沙贡献的时间尺度特征。结果表明,风力的侵蚀搬运对窟野河流域产沙起着重要的作用。月时间尺度上,风沙入河量存在"存储-释放"的过程;风蚀产沙贡献在3月和11-12月出现高峰值,4-9月风蚀贡献率逐渐降低;冬春季节淤积的泥沙,在夏季逐渐被冲走,到了9月,把淤积的泥沙最大限度冲走而开始新的淤积过程;月时间尺度上风蚀贡献率与风蚀气候因子分布趋势一致;7、8两月的风沙贡献量占年风蚀贡献总量的80.5%,风沙贡献量的峰值出现在7月,约7.75×10⁶ t。季尺度上,夏季风蚀贡献率最低,仅7.8%。秋、冬季逐渐升高,春季达到最高,风蚀贡献率为28.6%。年尺度上,风力作用对神木水文站以上流域的产沙贡献为17.2%,风蚀贡献量为12.7×10⁶ t/a。     

太湖流域稻麦轮作系统实际施氮量及其多重效应——基于农户调研的实证分析

研究运用分层随机抽样法,在常州市武进区开展农户问卷调查,并利用统计软件对问卷信息进行整理和分析,得到主要结论如下:①太湖流域稻麦轮作系统稻季平均施氮量为310.91 kg·hm^-2,麦季平均施氮量为202.18 kg·hm^-2,一年两季作物平均施氮量为513.09 kg·hm^-2,氮肥过量施用现象主要存在于稻季;②施氮肥对水稻和冬小麦都具有较好的增产作用,但是当施氮量达到一定值后,水稻和冬小麦的产量、氮素累积量、氮肥农学利用率和氮肥吸收利用率都出现下降的趋势;③太湖流域稻麦轮作系统土地氮剩余量和面源氮排放量随着施氮量的增加而持续增加,在目前的氮肥施入水平下一年两季作物的氮素流失量约为41.26 kg·hm^-2。     

规模化牛场废水灌溉对土壤水分和冬小麦产量品质的影响

通过田间小区试验,设置不同的牛场废水灌溉次数,研究了冬小麦牛场废水灌溉过程中土壤水分和冬小麦产量品质的变化特征,结果表明,灌溉牛场废水土壤水分迁移和土壤贮水量与灌溉清水无显著差别,水质对土壤水分变化影响很小;冬小麦生育期内分别灌溉牛场废水2、3和4次与正常施肥灌溉施肥相比,冬小麦产量和灌溉水生产效率提高,分别提高了4.61%、6.48%、6.63%,4次牛场废水灌溉冬小麦产量略有下降,这说明灌溉牛场废水次数过多会对冬小麦造成一定的负面影响;牛场废水灌溉次数越多冬小麦籽粒中蛋白质质量分数越高,分别提高了2.50%、5.83%、8.03%,而全磷质量分数则有降低趋势。综合考虑,冬小麦生育期内牛场废水灌溉次数不应高于3次。