[Objective] the aims were to explore the spatial variation characteristics of soil pH value in the study area,and to provide a basis for local regional agricultural acid-base regulation. [Method] Soil samples（0-20 cm, 150-200cm） were collected and analyzed, and variance and regression analysis were used to quantify the influence degree of different factors on the spatial difference of pH value. [Results] The top soil in the study area was mainly acidic, with an average pH of 5.66. The deep soil was mainly neutral, with an average pH of 7.07. Semi-variance analysis showed that spherical model was the best fitting model for soil pH value in the study area, and structural factors were the dominant factors affecting the distribution of pH value in the study area. In terms of spatial distribution, the low pH value area was mainly located in the northeast of the study area, which highly overlapped with the traditional agricultural distribution area, while the high pH value area was located in the southern mountainous area, which showed a pattern of high pH value in the south and low pH value in the north. Regression analysis showed that soil parent material was the main controlling factor of the spatial variation of surface soil pH value in the study area, and could explain 24.8% of the spatial variation alone. Secondly, land use type and soil type had the independent ability to explain 9.2% and 8.8% of the spatial variation of soil pH value, respectively. The explanatory power of geomorphic types was low（5.6%）. [Conclusion] Soil parent material and other structural factors have the greatest influence on the spatial distribution of surface soil pH value in the study area, which is similar to the results of semi-variance analysis.However, human factors also affect the spatial distribution of pH value in the region, and long-term unreasonable fertilization may be the main reason.
近年来,全球大气氮沉降日益加剧,对土壤碳循环产生了不可忽视的影响.关于氮沉降对土壤碳循环的影响已开展了一系列的研究,然而对其响应机制和影响程度方面的认识还存在巨大分歧.运用CiteSpace文献可视化软件,对1991～2021年Web of Science核心数据库收录的2414篇关于氮沉降对土壤碳循环方面的文献进行数据挖掘,从国家、机构、作者、关键词、突现词等方面进行可视化,以阐明该领域的研究热点与前沿.结果表明:大气氮沉降对土壤碳循环影响的研究美国仍具有较高影响力,但我国在该领域的研究正持续发力,其中以中国科学院大学在该领域的发文数量最多,同时文献涉及方向广,内容丰富.当前,对于氮沉降对土壤碳循环影响的研究热点主要围绕"氮沉降对土壤碳、氮库的影响""氮沉降对土壤碳、氮耦合循环的影响""土壤生态环境对氮沉降的响应"这三个主题,氮沉降对土壤碳循环影响的研究前沿更加注重响应机制、氮利用效率和磷限制等方面.
[目的]为深入理解陕北黄土高原土壤水分时间动态特征及空间模式时间稳定性,探索代表点位预测土壤储水量和干层平均状况的可靠性.[方法]在神木六道沟流域选择一典型地形破碎区,自2014年10月至2017年7月开展土壤水分长期跟踪监测.[结果]①观测期内,夹心式干层厚度和夹心式干层内土壤含水量分别变化于20～760 cm和6.43％～10.73％之间,表现出夹心式干层随时间发育的复杂性.②土壤储水量、干层厚度和干层内土壤含水量斯皮尔曼等级相关系数均值分别为0.94、0.95和0.90,表明研究区土壤储水量及干层空间模式具有强烈的时间稳定性.③通过土壤储水量及干层时间稳定性特征分析判定,点位A5、C1和C2分别可作为预测研究区土壤储水量(R2=0.88)、干层厚度(R2=0.74)和干层内土壤含水量(R2=0.56)平均状况的代表点位.相比而言,利用土壤储水量和干层厚度代表点位预测结果精确度更高.[结论]在黄土高原地形破碎区利用代表点位预测土壤水分时空分布的方法是可行的,科学调控土壤水库可在一定程度上缓解土壤干层的形成与发展,为区域土壤干层的恢复提供了可能性.
微藻是单细胞光合生物,具有光合作用效率高、环境适应能力强、生长周期短等特点.微藻多糖是广泛存在于微藻中的一种天然大分子物质,不仅能够促进作物生长,提高作物抗逆性,还可以改善土壤理化性质,调节土壤微生物群落,是植物生物刺激剂的潜在来源.然而,微藻多糖在农业领域并未得到广泛的应用和开发.本文就微藻多糖的合成途径、生化组成、促生和抗逆作用机理及其对土壤改善作用等方面内容进行了综述,以期为微藻多糖的规模化制备及农业应用提供一定的科学理论依据.
从第三次土壤普查外业采样质量监督检查角度入手,以华北区为主,结合资料检查与现场检查案例,分析试点县外业样品采集工作的共性问题.包括点位布设、调查采样、选项设置、土壤分类、剖面描述、填报信息、内部自检、关联信息八个方面.建议注重外业采样培训的土壤发生分类理论与应用性、加强布点的时效性与代表性、提高土壤理化生性状的调查联动性、保证环节的衔接性与覆盖性、提升终端的便利性与交流性、保障剖面采样人员的专业性与资格性等,以期更好地总结试点经验,为明年全面铺开的土壤普查外业采样工作提出参考依据,避免出现同类问题.
