Long-term changes in forest floor processes in southern Appalachian forests

Soil nutrient concentrations decreased in an aggrading southern Appalachian forest over a 20-year period. Construction of nutrient budgets showed significant nutrient sequestration aboveground including increased forest floor mass. We hypothesized that the changes in forest floor mass resulted from decreased litter decomposition rates because of decreased litter quality. In 1992 and 1993, we repeated a litter decomposition experiment conducted in 1969 and 1970 to test this hypothesis. In addition, we examined microarthropod populations and functional groups as litter decomposed. For four of the five species tested, first-year decomposition rates were about the same in both experiments. Initial litter nutrient concentrations of P were lower in all tree species in the most recent sampling. N, Ca, and Mg concentrations also declined in some species. These declines often resulted in decreased nutrient release rates during decomposition. Microarthropod populations differed significantly among litter species, as well as between years (probably resulting from differences in growing-season rainfall). For some litter species we found significant relationships between microarthropod populations and nutrient concentration (primarily C and N); however, most r²-values were low. Data suggest that changes in forest floor mass probably resulted from decreased litter quality and that those changes may have an effect on microarthropod populations.     

防旱减灾经济效益计算方法初探

利用大量的统计资料，研究了防旱减灾经济效益的计算方法，其中重点提出了临时抗旱措施的经济效益计算方法，可供今后计算抗旱效益时应用和参考。     

自压喷灌系统管道减压的研究

本文对自压喷灌系统的合理减压方式和布置形式进行了分析。用递推法导出确定减压池级数及位置的计算公式。根据减压池的工况分析,探讨了减压池调节容积的计算方法。本文为自压喷灌系统的减压设计提供了方法和依据。     

膜孔灌玉米农田尿素转化和分布特性研究

为了研究膜孔灌玉米农田尿素转化和分布特性,在测坑中进行了膜孔灌和畦灌施尿素试验,分析测定了施尿素后不同时间的土壤铵态氮和硝态氮含量。研究表明：膜孔灌尿素转化完全后,土壤中氮素的主要形态为硝态氮,可作为膜孔灌农田氮素水平评价的指标;基施尿素下,土壤中的硝态氮含量逐渐增大,分布范围以施肥点为中心呈大致成半圆形;灌水方式对尿...     

缓释尿素在辽宁中部水稻上应用效果报告

2010年在辽宁省中部地区水稻上开展一次性底施缓释尿素田间试验。结果表明：在辽宁中部地区水稻上一次性施用缓释尿素比施用普通尿素,增产效果非常明显,开原和大石桥试验点增产31.1～57.0kg/667m2,增产率为5.9%～10.9%;辽中试验点增产34.7～88.9kg/667m2,增产率为10.1%～21.3%。     

柴油机燃用复合乳化燃料放热率的计算模型

提出了适用于柴油、甲醇、水三元复合乳化燃料和柴油的热力学放热率计算模型，并利用此模型对直接喷射式2135G型柴油机进行了放热率计算研究，计算结果令人满意。同时分析研究了压力传感通道效率、计算步长；乳化燃料中水的化潜热及示功图光顺程度等因素对复合乳化燃料放热率计算精度的影响。     

pH对吉林西部低平原湖泊底泥氟释放影响的实验研究

针对吉林西部低平原底泥中氟含量较高的花敖泡、道字泡、大布苏泡进行实验,通过底泥中氟长期释放实验(28 d)和不同pH对底泥氟释放影响的研究,得出高氟湖库底泥氟的释放量为37.31～223.03 mg/kg;碱性环境下底泥氟向水中迁移的速率在1.88～22.53 mg/(kg·d);酸性环境中释放的速率0.71～5.41...     

兰州-西宁-银川城市带城市流强度分析及优化建议

基于城市流理论,依据城市流强度分析方法,对兰州-西宁-银川城市带各城市的区位熵、外向功能量、城市流强度及其结构进行了测算与分析。结果表明：兰州的城市流强度远高于其他城市,是该城市带的集聚辐射中心;城市总体经济实力与城市流倾向度的相对比例关系不够协调,除兰州外,均表现出城市流倾向度高于城市总体经济实力的特点;城市总体经济...     

Nursery‐Box Total Fertilization Technology (NBTF) Application for Increasing Nitrogen Use Efficiency in Chinese Irrigated Riceland: N–Soil Interactions

High N fertilizer and flooding irrigation applied to rice in anthropogenic‐alluvial soil often result in N leaching and low use efficiency of applied fertilizer N from the rice field in Ningxia irrigation region in the upper reaches of the Yellow River. Sound N management practices need to be established to improve N use efficiency while sustaining high grain yield levels and minimize fertilizer N loss to the environment. We investigated the effects of Nursery Box Total Fertilization technology (NBTF) on N leaching at different rice growing stages, N use efficiency and rice yield in 2010 and 2011. The four fertilizer N treatments were 300 kg N ha⁻¹ (CU, Conventional treatment of urea at 300 kg N ha⁻¹), 120 kg N ha⁻¹ (NBTF120, NBTF treatment of controlled‐release N fertilizer at 120 kg N ha⁻¹), 80 kgN ha⁻¹ (NBTF80, NBTF treatment of controlled‐release N fertilizer at 80 kg N ha⁻¹) and no N fertilizer application treatment (CK). The results showed that the NBTF120 treatment increased N use efficiency, maintained crop yields and substantially reduced N losses to the environment. Under the CU treatment, the rice yield was 9634 and 7098 kg ha⁻¹, the N use efficiency was 31·6% and 34·8% and the leaching losses of TN were 44·51 and 39·89 kg ha⁻¹; NH₄⁺‐N was 5·26 and 5·49 kg ha⁻¹, and NO₃⁻‐N was 27·94 and 26·22 kg ha⁻¹ during the rice whole growing period in 2010 and 2011, respectively. Compared with CU, NBTF120 significantly increased the N use efficiency and decreased the N losses from the paddy field. Under NBTF120, the N use efficiency was 56·3% and 51·4%, which was 24·7% and 16·6% higher than that of CU, and the conventional fertilizer application rate could be reduced by 60% without lowering the rice yield while decreasing the leaching losses of TN by 16·27 and 14·36 kg ha⁻¹, NH₄⁺‐N by 0·90 and 1·84 kg ha⁻¹, NO₃⁻‐N by 110·6 and 10·14 kg ha⁻¹ in 2010 and 2011, respectively. Our results indicate that the CU treatment resulted in relatively high N leaching losses, and that alternative practice of NBTF which synchronized fertilizer application with crop demand substantially reduced these losses. We therefore suggest the NBTF120 be a fertilizer application alternative which leads to high food production but low environmental impact. Copyright © 2014 John Wiley & Sons, Ltd.     

Changes in Cd,Cu, Ni,Pb and Zn Fractionation and Liberation Due to Mussel Shell Amendment on a Mine Soil

Mining activities are related to relevant environmental pollution issues that should be controlled. We used sequential extractions to fractionate Cd, Cu, Ni, Pb and Zn retained on unamended or mussel shell‐amended mine soil samples, all of them treated with a mixture of the five heavy metals (total metal concentration of 1·57 mmol L⁻¹), after 1, 7 and 30 days of incubation. In addition, we used the stirred flow chamber technique to study the release of each of the five heavy metals from these different unamended and shell‐amended soil samples. The results indicate that the shell amendment caused a decrease in the most soluble fraction, while increasing the most recalcitrant (least mobile) fraction. With equivalent implications, the stirred flow chamber experiments showed that mussel shell amendment was associated to a decrease in heavy metal release and increased retention. The highest mussel shell dose and incubation time caused the most relevant changes in pH values and thus in metal retention, also indicating the importance of pH modifications in the mechanism of retention acting in the amended samples. In view of these results, the use of mussel shell amendment can be encouraged to increase heavy metal retention in acid mine soils, in order to minimise risks of environmental pollution. Copyright © 2016 John Wiley & Sons, Ltd.