Promoting late-fall establishment of tall fescue with artificial soil covers to minimise soil erosion

Frequently, turfgrass seedings have been sown in the late fall, which usually results in a poor vegetative stand and the possibility of soil erosion the following spring. This study evaluates the effects of a spun-bonded polyester soil cover placed over a late-fall seeding on subsequent seedling growth and overwintering. Clemfine, Mustang, Rebel, and Rebel II cultivars of tall fescue (Festuca arundinacea Schreb.) were sown on a silt loam soil in late fall (on 17 October in 1989 and 19 October in 1990) and allowed to grow with and without a soil cover until June. In the spring the temperature under the soil cover was greater than 2°C warmer than the uncovered soil from mid-April through May. Over the winter, leaf and root weights showed no detrimental effects from being under the cover. Individual cultivars grown under the cover produced 2 to 11 times greater leaf yields and 38 to 270% better stand establishment than those sown on the exposed soil. However, plant winter injury was observed under the soil cover in small soil depressions which accumulated water originating from thawing. All cultivars had similar amounts of growth under the cover. However, leaf yields for Rebel were 30-55% less than the other cultivars when grown under the cover and this was probably related to a low seed germination rate. The covers also promoted weed growth, which comprised from 34–65% of total leaf weights and was found to be negatively correlated (r = –0.66) to the yields of the sown grass. The soil cover was found to be beneficial to improving the success of seedling establishment of late seedings of tall fescue in cold areas.     

西南喀斯特山地的土壤侵蚀研究探讨

西南喀斯特山区具有独特的喀斯特土壤特征与土壤侵蚀的环境效应,普遍面临着因土壤侵蚀导致的"石漠化"问题.已有研究认为,在气候、地质地貌、植被和人为活动等环境因素的影响下,喀斯特山区土壤侵蚀以混合侵蚀方式进行.但由于对喀斯特山区土壤侵蚀过程的认识不同,致使研究者得出土壤侵蚀强度差异较大的研究结果.有关喀斯特土壤侵蚀系统研究重点应该在土壤侵蚀机制、土壤侵蚀分级强度与土壤合理流失量等方面开展研究.     

Removal of high concentrations of polycyclic aromatic hydrocarbons from contaminated soil by biodiesel

Solubilizing experiments were carried out to evaluate the ability of biodiesel to remove polycyclic aromatic hydrocarbons (PAHs) from highly contaminated manufactured gas plant (MGP) and PAHs spiked soils with hydroxypropyl-β-cyclodextrin (HPCD) and tween 80 as comparisons. Biodiesel displayed the highest solubilities of phenanthrene (420.7 mg·L^-1), pyrene (541.0 mg·L^-1), and benzo(a)pyrene (436.3 mg·L^-1). These corresponded to several fold increases relative to 10% HPCD and tween 80. Biodiesel showed a good efficiency for PAH removal from the spiked and MGP soils for both low molecular weight and high molecular weight PAHs at high concentrations. Biodiesel was the best agent for PAH removal from the spiked soils as compared with HPCD and tween 80; as over 77.9% of individual PAH were removed by biodiesel. Tween 80 also showed comparable capability with biodiesel for PAH solubilization at a concentration of 10% for the spiked soils. Biodiesel solubilized a wider range of PAHs as compared to HPCD and tween 80 for the MPG soils. At PAH concentrations of 229.6 and 996.9 mg·kg^-1, biodiesel showed obvious advantage over the 10% HPCD and tween 80, because it removed higher than 80% of total PAH. In this study, a significant difference between PAH removals from the spiked and field MGP soils was observed; PAH removals from the MGP soil by HPCD and tween 80 were much lower than those from the spiked soil. These results demonstrate that the potential for utilizing biodiesel for remediation of highly PAH-contaminated soil has been established.     

大同市土地退化现状与动态变化研究

通过对大同市水土流失现状与动态变化、土地盐渍化和耕地数量与质量情况动态变化、土地沙漠化现状与动态变化的现状调查来分析大同市土地退化的主要成因以及采取的环境保护对策与建议.     

塔里木河上游典型绿洲土壤酶活性与环境因子相关分析

土壤酶能反映土壤生物化学过程的强度与方向,深入解析土壤酶活性与环境因子的相关性,有助于探索土壤生态过程,为开展土壤系统的科学调控提供科学依据.以塔里木河上游阿拉尔垦区为研究区,选择新开棉田、10 a棉田、30 a棉田、果园、人工林、天然林、荒草地、盐碱地及沙地等不同土地利用类型为研究对象,运用经典统计学分析绿洲土壤酶活性及环境因子的分异规律,并结合冗余分析技术研究土壤酶活性与环境因子相关关系.经典统计学分析显示,土壤过氧化氢酶、脲酶、转化酶、碱性磷酸酶活性均值分别为4.27 m L·g-1、0.34 mg·g-1、2.08 m L·g-1、0.08 mg·g-1.冗余分析结果表明:全氮、有机质、有效磷、土壤含水量、全盐与土壤酶活性呈极显著相关性(P0.01);土壤容重与土壤酶活性表现为显著相关性;其他环境因子与土壤酶活性的相关性均不显著(P0.05).环境因子与土壤酶活性相关性大小排序为全氮有机质有效磷土壤含水量全盐容重速效钾p H.     

生物炭墙对紫色土坡耕地中氟苯尼考迁移影响

采用实验室批量平衡实验,研究紫色土坡耕地土壤中氟苯尼考吸附-解吸特征及生物炭施用的影响,此外,开展野外坡底生物炭（重量占比5%）可渗透反应墙的构建试验,观测自然降雨条件下该反应墙对坡耕地小区中氟苯尼考随地表径流与下渗水迁移的影响.结果表明,氟苯尼考在紫色土中的等温吸附行为符合Freundlich方程,在低浓度范围内（<2mg/L）,生物炭的施用一方面提高了其在紫色土中的吸附量,吸附过程可能以内扩散为主,另一方面,显著降低其解吸量;紫色土坡耕地中的淋溶作用是氟苯尼考的主要迁移方式;坡底生物炭（5%）渗透墙的构建有效地减控了其在紫色土中的淋溶迁移以及深层侧向迁移.     

塔里木盆地北缘绿洲不同连作年限棉田土壤有机碳、无机碳含量与环境因子的相关性

农田土壤碳库是土壤碳库的重要组成部分,易受人类活动调节且固碳减排潜力巨大,研究土壤有机碳、无机碳含量特征及其与环境因子的关系有助于深入理解土壤生态过程,为全球碳收支平衡研究提供理论支持.本文以塔里木盆地北缘绿洲为靶区,分析土壤碳库特征,结合冗余分析、通径分析,探究土壤有机碳、无机碳含量及其与环境因子的相关关系.结果表明:(1)同一土层不同连作年限棉田土壤有机碳、无机碳含量存在显著差异(P0.05),随连作年限增加,有机碳含量呈先增加后减少趋势,而无机碳含量呈先减少后增加趋势;同一连作年限棉田不同土层土壤有机碳、无机碳含量存在显著差异(P0.05),有机碳含量均在0~20 cm层达到最大值,而无机碳含量均在20~50 cm层达到最大值.(2)通过冗余分析得出环境因子对土壤碳库特征影响的重要性排序为:磷酸酶活性p H值蔗糖酶活性过氧化氢酶活性全氮速效磷速效钾土壤含水量脲酶活性电导率;磷酸酶活性、p H值、蔗糖酶活性、过氧化氢酶活性、全氮、速效磷、速效钾与土壤有机碳、无机碳含量呈极显著相关关系(P0.01);土壤含水量、脲酶活性与土壤有机碳、无机碳含量表现为显著相关(P0.05).(3)通径分析表明,速效钾对有机碳含量直接作用显著,是影响有机碳含量的主要因素,而脲酶活性对无机碳含量直接作用显著,是影响无机碳含量的主要因素.干旱半干旱区土壤有机碳、无机碳含量研究是评价农田生态系统土壤碳的"源/汇"效应的基础数据,对研究全球碳收支平衡和陆地碳循环机制具有重要意义.     

基于稳定碳同位素技术的干旱区绿洲土壤有机碳向无机碳的转移

应用稳定碳同位素技术测定土壤无机碳稳定碳同位素组成(soil inorganic carbonδ13C,SICδ13C),并对干旱区绿洲土壤无机碳进行区分,结合土壤有机碳(soil organic carbon,SOC)与SIC含量关系进一步探讨SOC向SIC转移的碳量.结果表明,4种类型土壤SICδ13C值差异性极显著(P0.01),风沙土SICδ13C值最高且为正,均值为(0.32±0.04)‰,随土层深度增加而增加,说明风沙土原生性碳酸盐占绝对优势;灌漠土、棕漠土和盐碱土SIC的δ13C均值分别(-0.30±0.24)‰、(-1.96±0.66)‰和(-1.24±0.49)‰,随土层变化均呈先降低后逐渐增大的趋势,说明灌漠土原生性碳酸盐占优势,棕漠土和盐碱土发生性碳酸盐相对前者占优势.风沙土、灌漠土、棕漠土和盐碱土的发生性碳酸盐占SIC比例均值分别为1.33%、4.72%、15.01%、35.71%,均小于50%,说明干旱区绿洲土壤发生性碳酸盐比例总体水平较低.风沙土、灌漠土、棕漠土和盐碱土在土壤发生性碳酸盐形成或重结晶过程中固定土壤CO2的量分别为0.30、2.44、4.96、12.40 g·kg~(-1),其中固定来自大气CO2量平均为0.18、0.79、1.45、8.67 g·kg~(-1),来自SOC氧化分解转化为CO2的量分别为0.06、0.83、1.62、1.86g·kg~(-1),说明盐碱土、棕漠土SOC的贡献相对较高,灌漠土、风沙土较低;对土壤固定CO2量的来源比较发现,风沙土、盐碱土固定土壤CO2的量来自大气CO2量较高,SOC的贡献较低,而灌漠土、棕漠土固定来自SOC氧化分解CO2的量较高,大气贡献较低.研究区整体SOC向SIC的碳转移量介于0.03~2.38 g·kg~(-1)之间,平均每千克土壤固定1.09 g的CO2,说明干旱区绿洲土壤发生性碳酸盐所占比例较低,SOC的贡献较少.     

黄土高原草地土壤水分和物种多样性沿降水梯度的分布格局

研究土壤水分、生物多样性的空间变异性是认识陆地生态系统对降水变化的响应特征及适应机制的有效途径。论文利用黄土高原自东南向西北的天然降水梯度,采用样带研究方法对47个草地0~3 m土壤水分和物种多样性进行测定,系统分析了草地土壤水分和植物物种多样性在降水梯度上（250~550 mm）的空间分异及二者之间的权衡关系。结果表明：降水自东南向西北递减是控制黄土高原草地0~3 m土壤水分和物种多样性空间异质性的关键因素。随降雨减少,土壤水分呈线性递减趋势,其中浅层土壤水分（0~1 m）与年降水量相关系数最大。物种丰富度指数和物种多样性指数随降水减少呈显著的线性递减趋势,物种均匀度指数在降水梯度上没有明显变化。370 mm年均降水量是物种多样性和土壤水分权衡关系的转折点,转折点以上二者存在协同关系,即土壤水分和物种多样性沿降水梯度以相同速率变化。370 mm年均降水量以下,物种多样性和土壤水分的权衡增大,意味着维持物种多样性以消耗土壤水分为代价。     

西辽河流域沙土的氨氮解吸行为研究

采用小型回填式土柱淋溶实验方法研究了西辽河流域沙土的氨氮解吸行为。结果表明,西辽河流域沙土的氨氮解吸行为符合Langmuir和Freundlich解吸等温式;沙土氨氮解吸比率Dr在0.44～0.99之间,平均为0.75,解吸迟滞性指数TⅡ在0.05～0.65之间,平均为0.29,沙土对氨氮的解吸迟滞性较强,解吸可逆性较弱。被吸附的氨氮解吸淋失的环境风险较小;沙土氨氮解吸比率Dr与土壤有机质含量、粘粒含量和粗粘粒含量呈极显著负相关,影响程度顺序为:有机质含量>粗粘粒含量>粘粒含量;解吸分配系数k和解吸迟滞性指数与土壤有机质含量分别呈极显著和显著正相关,与粘粒含量和粗粘粒含量没有相关性;草地、农田和林地结构由于土壤有机质和团聚体含量较高,氨氮解吸迟滞性较强,氨氮流失的环境风险较小,沙荒地结构氨氮流失的环境风险较大。