柳杉人工林采伐后不同土地利用类型初期土壤有机碳变化

运用空间代替时间的方法研究了25年生柳杉人工林(对照)采伐后形成的柳杉人工幼龄林、经济林、苗圃地、皆伐迹地、农耕地5种土地利用类型初期土壤有机碳含量和碳储量变化。结果表明,5种土地利用类型和对照的土壤有机碳含量和碳储量均随土层的加深而降低;除经济林外,苗圃地、柳杉人工幼龄林、农耕地和皆伐迹地的土壤平均有机碳含量分别比对照降低了10.8%,28.1%,37.8%,40.1%;5种不同土地利用类型土壤碳储量排序为:皆伐迹地(214.2±17.0 t C/hm2)>经济林(191.3±13.4 t C/hm2)>柳杉人工幼龄林(173.5±15.1t C/hm2)>苗圃地(171.9±9.2 t C/hm2)>农耕地(132.7±12.1 t C/hm2),分别比对照(272.9±21.8 t C/hm2)减少了21.5%,29.9%,36.4%,37.0%,51.4%。人工林采伐后形成的不同土地利用类型,土壤有机碳含量和碳储量减小的程度与采伐后紧接着采取的人为措施有关。     

汞污染紫色土中微生物区系及生理类群

以重庆市中性紫色土为材料,通过室内模拟试验及污染现场调查,探索了汞对土壤中微生物区系和各主要生理类群繁育的影响。结果表明,汞对土壤中细菌、放线菌和真菌的增殖总体上具有抑制作用;氨化细菌受汞的抑制强烈,当HgCl2浓度为10mg·kg-1时,氨化细菌数量仅为对照的10%;硝化细菌在汞浓度较低时(<50mg·kg-1)生长受抑制,在高浓度汞作用下表现出受刺激;好气性自生固氮菌和纤维素降解菌在汞浓度较低时生长被刺激,而高浓度汞则抑制其增长;以敏感微生物种群数量变化>50%得出供试中性紫色土上汞发生毒害的临界值为5～10mg·kg-1。长期受汞污染的土壤微生物调查显示,细菌和放线菌变化方向与模拟试验结果一致,真菌在重污染区土壤上则产生抗性,而固氮菌能够指示程度较轻的土壤汞污染。     

提高种植土 pH 值、电导率方法

南方雨水多导致土壤偏酸和电导率低,原生土一般不可直接用作园林种植土。如何提高土壤的 pH 值与电导率,成为南方园林绿化工作者的重要课题。广州市生态景观林带项目——广河高速凤凰山隧道绿化工程采用增施无机肥的方法来改良种植土,是改良南方酸性种植土电导率低的有益尝试。     

不同固沙植被下沙丘土壤水分动态比较

以毛乌素沙地覆盖度>90%的油蒿、50%～60%的沙柳、35%～40%的樟子松固定沙丘为研究对象,流动沙丘为对照,采用自动监测系统实时监测降雨、0～200 cm土壤含水量及200 cm以下渗漏量,分析5—11月不同固沙植被下沙丘土壤水分动态差异,以期为固沙植被稳定性评价提供参考。结果表明:较低覆盖度樟子松与高盖度油蒿、沙柳相比更具固沙优势。3种固沙植被表层0～30 cm土壤水分受降雨影响大,对>20 mm降雨均产生响应;60～200 cm土壤水分时间变化特征存在差异,樟子松与对照变化趋势一致,油蒿和沙柳仅对40 mm降雨产生响应;0～200 cm土壤水分垂直变化没有相同规律,变异性较大,樟子松变幅最大,为(5.03±3.09)%;深层渗漏特征基本一致,均有极少量水分渗漏到200 cm以下。     

小麦秸秆截段覆盖对设施蔬菜产量和土壤性质的影响

以豆瓣菜和小麦秸秆为试材,低温季节按500 kg·(667m^2)^-1将小麦秸秆截成10 cm后覆盖并浅水种植豆瓣菜,高温季节按1 000 kg·(667m^2)^-1覆盖并浅水种植水蕹菜,研究了不同季节设施水生蔬菜田土表覆盖截段小麦秸秆的腐解规律以及对水生蔬菜产量品质和土壤性质的影响,以期为设施菜田土壤改良和小麦秸秆利用新途径提供参考依据。结果表明:经低温季节140 d和高温季节163 d的腐解,小麦秸秆腐解率分别为66.67%和85.00%;土表水层电导率前期迅速上升后缓慢下降,低温季节第3天达最大值1 180μS·cm^-1,高温季节第12天达最大值1 806μS·cm^-1;氧化还原电位表现为前期迅速下降,低温季节第3天降至-80 mV,高温季节第5天降至-180 mV,后期处理与对照变化趋势基本一致。与对照组相比,小麦秸秆还田可提高蔬菜的产量和品质,可有效增加设施土壤有机质、全氮、全磷、全钾以及速效磷、钾的含量,提高土壤脲酶活性,降低土壤硝态氮含量。     

抗旱性复混肥对土壤物理性状、持水量和马铃薯经济效益的影响

采用田间试验方法,研究抗旱性复混肥配方及其对土壤物理性质、持水量和马铃薯经济效益的影响,以期筛选出抗旱性复合肥最佳配方和施用量。结果表明:影响马铃薯产量的因素由大到小依次为:马铃薯专用肥>废弃物组合肥>保水剂,抗旱性复合肥最佳配方组合为废弃物组合肥3 000 kg/hm^2、保水剂37.50kg/hm^2、马铃薯专用肥2 230 kg/hm^2。随着抗旱性复混肥施用量的增加,土壤总孔隙度、持水量、马铃薯块茎质量和产量在增加,土壤容重在降低。经回归统计分析,抗旱性复混肥与马铃薯产量间的回归方程为:y=28.87+1.771 3x-0.035 4x2,最佳施肥量为5.28 t/hm^2,计算结果与田间施用抗旱性复混肥5.28 t/hm^2相吻合。     

The use of iron (III) ferrocyanide soil amendment for removing salt from the soil surface

Accelerated soil salinization is a worldwide concern. Our study was carried out to determine the effects of different rates (0, 5, 10, and 15?mmol kg^?1) of iron (III) ferrocyanide application to remove salts from the soil. Within two weeks of its application, iron (III) ferrocyanide at 5, 10, and 15?mmol?kg^?1 removed 12.2%, 26.5%, and 42.9% of the total salts from the soil, respectively. Results suggested that iron (III) ferrocyanide application at 15?mmol?kg^?1 is one of the most rapid and effective ways to remove substantial amounts of salts from undrained soil (land) where fresh water is scarce.     

Variation in glomalin in soil profiles and its association with climatic conditions,shelterbelt characteristics,and soil properties in poplar shelterbelts of Northeast China

Glomalin-related soil protein(GRSP)sequesters large amounts of carbon and plays important roles in maintaining terrestrial soil ecosystem functions and ecological restoration;however,little is known about GRSP variation in 1-m soil profiles and its association with stand characteristics,soil properties,and climatic conditions,hindering GRSP-related degraded soil improvement and GRSP evaluation.In this study,we sampled soils from 1-m profiles from poplar(Populus spp.)shelterbelts in Northeast China.GRSP contents were 1.8–2.0 times higher in the upper 40 cm soil layers than at 40–100 cm.GRSP-related soil organic carbon(SOC)sequestration in deeper soil layers was*1.2 times higher than in surface layers.The amounts of GRSP-related nutrients were similar throughout the soil profile.A redundancy analysis showed that in both surface and deeper layers,soil properties(pH,electrical conductivity,water,SOC,and soil nutrients)explained the majority of the GRSP variation(59.5–84.2%);the second-most-important factor in GRSP regulation was climatic conditions(temperature,precipitation,and altitude),while specific shelterbelt characteristics had negligible effects(<5%).Soil depth and climate indirectly affected GRSP features via soil properties,as manifested by structural equation model analysis.Our findings demonstrate that GRSP is important for carbon storage in deep soils,regardless of shelterbelt characteristics.Future glomalin assessments should consider these vertical patterns and possible regulating mechanisms that are related to soil properties and climatic changes.     

中国水土流失问题的初探

长期以来,水土流失直接威胁着人们赖以生存的环境,在所有的生态破坏中,水土流失称之为“环境破坏第一杀手”。针对我国山地丘陵面积大、地质条件复杂、人为破坏加速、水土流失严重的实际情况,通过丰富的历史资料和整治经验及野外工作所积累的大量数据分析,以生态恢复学为指导,总结了水土流失的基本特点,研究了水土流失治理与经济可持续发展的关系,探讨了水土流失给生态安全造成的巨大危害,展望了水土保持的预期目标,根据中国的实际情况,提出了综合治理的基本思路。