Air-drying changes the distribution of Hedley phosphorus pools in forest soils

Hedley labile phosphorus(P)pools in soil tend to be several times larger than annual forest requirements,even in highly weathered soils characterized by P limitation.The discrepancy between plant and soil P status could be partly attributable to the frequently adopted air-drying pretreatment that tends to increase soil P solubility.In this study,the effects of air-drying on the distribution of Hedley P fractions were examined using soils collected under 4 forest types at Gongga Mountain,southwestern China.The results showed that the microbial biomass P(Pmic)in the organic horizon decreased markedly after air-drying.The concentrations of Hedley labile P in the air-dried samples were 31%–73%more than those in the field-moist samples.Consequently,the air-drying-induced increments of Hedley labile P pools in the surface soil horizons were 0.8–3.8 times the annual plant P requirements.The organic horizon was more susceptible to the air-drying-induced increases in Hedley labile P than the mineral horizon,probably because of the stronger release of Pmicand disruption of soil organic matter.The quality of P,indexed by the ratio of Hedley labile P to slowly cycling P,shifted in favor of the Hedley labile fractions after air-drying,further revealing that air-drying changed the distribution of Hedley P pools in forest soils.These indicated that the effects of air-drying could not be ignored when interpreting the discrepancy between the P status of plants and the Hedley labile P pools in forest soils.To more efficiently evaluate the P status in forest soils via the Hedley fractionation procedure,the use of field-moist soils is recommended.     

Response of soil respiration to nitrogen addition in two subtropical forest types

Anthropogenic activities have increased nitrogen (N) deposition in terrestrial ecosystems, which directly and indirectly affects soil biogeochemical processes, including soil respiration. However, the effects of the increases in N availability on soil respiration are not fully understood. In this study, soil respiration was measured using an infrared gas analyzer system with soil chambers under four N treatments (0, 5, 15, and 30 g N m^-2 year^-1 as control, low N (LN), moderate N (MN), and high N (HN), respectively) in camphor tree and slash pine forests in subtropical China. Results showed that soil respiration rates decreased by 37% in the camphor tree forest and 27% in the slash pine forest on average on an annual base, respectively, in the N-fertilized treatments when compared with the control. No significant differences were found in the soil respiration rate among the LN, MN, and HN treatments in both forest types as these fertilized plots reached an adequate N content zone. In addition, soil microbial biomass carbon (C) content and fine root biomass declined in N-treated plots compared to the control. Our results indicated that elevated N deposition might alter the tree growth pattern, C partitioning, and microbial activity, which further affect soil C sequestration by reducing soil respiration in subtropical forests of China.     

基于有效积温的中国水稻生长模型的构建

有效积温是指作物生长至某一生育阶段所需要积累的有效温度,是反映气象条件对作物生长影响的主要指标,研究有效积温对作物生长过程的影响对提高农业生产效率具有重要意义。该文以有效积温作为气象因子,收集中国气象数据网中的气象数据和已发表的学术论文中的水稻生长数据,建立了描述水稻生长过程的叶面积指数和干物质积累量的普适Logistic模型,并研究了水稻最大叶面积指数与最大干物质积累量、收获指数(作物经济产量与生物产量的比值)及降水量之间的关系。结果表明:有效积温为1000℃左右时,水稻叶面积指数最大,且此时干物质增长速率最大;水稻最大叶面积指数与最大干物质积累量之间表现为线性关系;最大叶面积指数和收获指数、降水量之间为二次抛物线关系,当降水量为670.5 mm时,最大叶面积指数为7.93,对应的水稻收获指数达到最大值0.50。该研究对于构建其他作物的生长模型具有一定的参考意义。     

CeO2添加比例对Fe基催化剂催化纤维素气化制氢的影响

为研究CeO2添加对生物质催化气化制氢特性的影响，该研究采用分级气化系统分析了不同CeO2/Fe2O3比例（Ce∶Fe摩尔比为0∶1、3∶7、5∶5、7∶3、1∶0）双金属催化剂对纤维素水蒸气催化重整制氢气体产物产量、组成以及催化剂的结构演变特性的影响。结果表明，CeO2/Fe2O3催化剂在制氢反应中的催化性能明显优于纯CeO2或Fe2O3催化剂，当Ce∶Fe摩尔比为3∶7时，在800℃下氢气的最大产率为21.63 mmol/g（以纤维素计，下同）；当温度大于等于800℃时，催化剂氧化还原反应后可生成CeFeO3，且CeFeO3的存在对纤维素水蒸气气化过程有促进作用。CeO2的引入提高了催化剂的氧化性能和稳定性，提高了使用寿命。该研究对生物质气化机制的深入理解具有一定的指导意义。     

小麦-玉米轮作体系不同旋耕和深耕管理对潮土微生物量碳氮与酶活性的影响

【目的】通过研究黄淮平原潮土区两年不同轮耕模式下土壤微生物量碳氮、酶活性的差异和变化特征,为该地区选择适宜的耕作制度提供理论依据。【方法】2016-2018年采用裂区设计进行田间小麦–玉米轮作系统下的轮耕试验。主处理为小麦季旋耕(RT)和深耕(DT),3个副处理为玉米季免耕(NT)、行间深松(SBR)、行内深松(SIR),共6个处理。2017、2018年玉米收获后,每10 cm一个层次,测定了0-50 cm土层土壤有机质、全氮、速效养分、微生物量碳(SMBC)、微生物量氮(SMBN)和脲酶、蔗糖酶、中性磷酸酶活性。【结果】各处理土壤有机质、全氮、速效养分、SMBC、SMBN及酶活性均随土层深度的增加而降低,40-50cm土层不受耕作方式的影响。小麦季深耕和玉米季深松对表层土壤有机质和全氮影响不明显,但显著提高了深层土壤有机质和全氮含量。小麦季旋耕显著增加了玉米季0-10 cm土层中速效养分含量,而小麦季深耕条件下的DT-SBR和DT-SIR处理则显著增加了20-40 cm土层中的速效养分含量。在0-20 cm土层,小麦季旋耕条件下的RT-NT、RT-SBR和RT-SIR处理的SMBC明显高于小麦季深耕条件下的DT-NT、DT-SBR和DT-SIR处理,但在20-40 cm土层,SMBC和SMBN均表现为小麦季深耕处理显著高于旋耕处理,且以DT-SIR处理SMBC (67.99 mg/kg)和SMBN (45.96 mg/kg)最高。小麦季深耕处理提高了深层(30-40 cm)土壤微生物量氮/全氮值,但降低了表层(0-20 cm)土壤中的微生物熵。玉米季深松处理(RT-SBR、RT-SIR、DT-SBR和DT-SIR)较免耕处理(RT-NT和DT-NT)均提高了土壤酶活性,其中,在0-20 cm土层,RT-SBR和RT-SIR处理土壤脲酶活、蔗糖酶和中性磷酸酶活性较高;而DT-SBR和DT-SIR处理则提高了深层(20-40 cm)土壤中这三种酶的活性。【结论】在本试验期内,小麦季旋耕–玉米季深松处理(RT-SBR和RT-SIR)能明显提高0-10 cm土壤速效养分含量、0-20 cm土壤微生物量碳含量,而小麦季深耕–玉米季深松处理(DT-SBR和DT-SIR)则提升了20-40 cm土层土壤有机质、全氮、速效养分、微生物量碳和氮含量;小麦季深耕处理提高了深层(30-40 cm)微生物量氮/全氮比,但降低了表层(0-20 cm)土壤微生物熵。     

不同林龄杉木林下套种阔叶树对土壤磷组分的影响

套种是杉木人工林经营的重要措施,磷是南方森林生态系统中主要限制性养分元素之一,但套种模式对土壤磷素的影响尚不明确。以亚热带杉木人工林表层(0-10 cm)土壤为对象,研究套种林(杉阔套种幼林、杉阔套种成熟林)和杉木幼林土壤理化性质和土壤各形态磷含量差异,分析套种对杉木人工林土壤磷含量的影响。结果表明:(1)不同套种林显著改变土壤总磷、土壤总无机磷、土壤总有机磷、土壤微生物生物量磷(MBP)和土壤酸性磷酸酶活性(APA),大小顺序均为杉阔套种成熟林>杉阔套种幼林>杉木幼林。(2)土壤各磷组分中活性磷含量较低,其中NaHCO3-Po在活性组分中占主导;土壤NaOH-Po是中等活性磷的主要组分,杉阔套种成熟林尤为显著;闭蓄态磷(Residual-P)在总磷含量中最高。(3)与杉木幼林相比,杉阔套种成熟林显著增加了树脂提取态磷(Resin-Pi)、碳酸氢钠提取态有机和无机磷(NaHCO3-Pi、NaHCO3-Po)、氢氧化钠提取态有机和无机磷(NaOH-Pi、NaOH-Po)、氢氧化钠残留提取态有机磷(NaOHu.s-Po)、盐酸提取态磷(HCl-Pi)和闭蓄态磷(Residual-P)含量;土壤总无机磷、NaHCO3-Po、HCl-Pi、NaHCO3-Pi、NaOHu.s-Pi和Residual-P对杉阔套种幼林的响应不敏感。(4)除含水率外不同林龄下杉阔套种林土壤磷形态与土壤理化性质(土壤总碳氮、土壤可溶性有机氮、土壤微生物生物量磷、酸性磷酸酶)呈正相关性(P<0.05)。冗余分析表明,土壤磷组分的变化主要受MBP调控,且MBP与有机磷组分(NaOHu.s-Po、NaOH-Po)和HCI-Pi呈显著正相关。总之,套种林的土壤磷素有效性高于杉木幼林,土壤养分状况更佳。     

保水剂和微生物菌肥配施对旱作燕麦土壤微生物生物量碳、氮含量及酶活性的影响

为探讨保水剂和微生物菌肥配施后旱作燕麦土壤微生物生物量碳、氮含量及酶活性的影响,在内蒙古黄土高原旱作农田设置不施用保水剂和微生物菌肥(CK)、保水剂和微生物菌肥配施(A)、单施微生物菌肥(B)和单施保水剂(C)4个处理,分析燕麦全生育期内0—10,10—20,20—40 cm土壤微生物生物量碳、氮含量及酶活性时空动态变化和产量变化。结果表明:(1)全生育期,土壤微生物量碳含量呈"双峰"曲线变化,峰值均出现在孕穗期和灌浆期;氮含量呈先降低后升高再降低趋势,苗期含量最高;过氧化氢酶、蔗糖酶、脲酶活性均呈"单峰"曲线变化,过氧化氢酶、土壤蔗糖酶峰值在孕穗期,土壤脲酶则在抽穗期。(2)除CK外,土壤微生物量碳、氮含量及过氧化氢酶、蔗糖酶和脲酶活性表现为0—10 cm10—20 cm20—40 cm,其中配施(A)对0—10,10—20 cm影响均显著(p0.05),单施(B、C)仅对10—20 cm土层影响显著(p0.05)。(3)10—20 cm土层,配施(A)与其他3个处理间差异均显著(p0.05),提高微生物量碳含量4.82%～40.28%、微生物生物量氮含量8.44%～68.66%、过氧化氢酶活性13.32%～60.16%、蔗糖酶活性10.45%～39.14%、脲酶活性12.40%～55.62%。(4)配施(A)能同时显著(p0.05)提高燕麦籽粒产量和生物产量,提高幅度分别为8.40%～20.12%和10.80%～25.09%。因此,保水剂和微生物菌肥配施在黄土高原旱作区具有较好改善土壤微生物活性效果,提高旱作燕麦产量。     

Effects of selective cutting and timing of herbicide application on growth and development of Cirsium arvense in spring barley

Recently, a new implement for controlling weeds in cereals (CombCut) has been developed. It cuts weeds in growing cereals without damaging them by using the physical differences (in height, stem thickness, straw stiffness and branching pattern) between crops and weeds. To evaluate and compare the effects of selective cutting with different timings of herbicide application on Cirsium arvense in spring barley, a randomised block experiment was conducted in Sweden in 2015–2017, in a field with a naturally occurring C. arvense population. Treatments consisted of control (C), herbicide application at 4–5‐leaf stage of C. arvense (H1), herbicide application at 8–10‐leaf stage (H2) and selective cutting at 10‐leaf stage (S). The treatments were performed in 2015 and repeated in 2016 in the same plots, and a final evaluation was performed in 2017. Compared to the control, S, H1 and H2 were equally efficient in reducing above‐ground biomass production of C. arvense and increasing spring barley grain yield per unit area. The number of C. arvense shoots per area was, however, higher in S compared to H1 and H2. No differences in control effects on shoot number were observed between H1 and H2. Our study indicates that (i) selective cutting (S) reduces C. arvense equally efficient as herbicide application and (ii) early herbicide spraying is as efficient as spraying later in the season.     

高寒区施肥和混播对燕麦人工草地土壤碳氮储量及垂直分布特征的影响

了解高寒地区燕麦人工草地在燕麦品种、施肥措施和混播水平下土壤碳氮储量潜力及垂直分布动态，为高寒地区燕麦人工草地建植提供理论依据。采用4个燕麦品种（A1：青燕1号，Avena sativa cv. Qingyan No.1；A2：林纳，A. sativa cv. Lena；A3：青海444，A. sativa cv. Qinghai 444；A4：青海甜燕麦，A. sativa cv. Qinghai）、4个施肥水平（B1：不施任何肥料，CK0；B2：尿素75kg/hm2+磷酸二铵150kg/hm2，IM；B3：有机肥1500 kg/hm2，OM；B4：尿素37.5 kg/hm2+磷酸二铵75 kg/hm2+有机肥750 kg/hm2，IM+OM）和4个箭筈豌豆混播水平（C1：0 kg/hm2；C2：45 kg/hm2；C3：60 kg/hm2；C4：75 kg/hm2）的三因素四水平正交试验设计[L16(45)]，在燕麦拔节期、抽穗期、开花期、乳熟期和收获后期研究了3个因素对高寒区燕麦人工草地土壤C、N储量的影响极其垂直分布特征，为高寒区燕麦人工草地土壤固C、固N潜力评估提供理论依据。品种、施肥和混播均显著影响了燕麦人工草地土壤C、N储量。3个因素在作物生长期对土壤C储量的积累的影响大小表现为施肥＞混播＞品种，收获后期表现为混播＞施肥＞品种；各时期对土壤N储量的影响大小均表现为施肥＞混播＞品种。采用尿素37.5 kg/hm2+磷酸二铵75 kg/hm2+有机肥750 kg/hm2的施肥处理，混播75 kg/hm2箭筈豌豆建植的燕麦人工草地土壤C、N储量最高。施肥措施造成燕麦人工草地各时期不同土层间土壤C、N储量的差异。在3种措施影响下燕麦人工草地0~50cm土层土壤C、N储量潜力分别为176.78 t/hm2和11.78 t/hm2。土壤C、N随着土层的加深而逐渐下降，0~20cm土层土壤C、N储量显著高于其它土层。     

基于无人机高光谱影像的玉米地上生物量反演

【目的】研究以玉米地上干生物量为研究对象,探讨基于无人机高光谱数据利用人工神经网络法反演生物量的可行性。【方法】在吉林省蔡家镇开展玉米氮肥梯度试验,并进行无人机高光谱数据和地上干生物量获取,共获数据30组。随机选22组数据用于建模,剩下8组用于模型的外部验证。分别基于光谱指数法和BP神经网络算法构建反演模型,比较分析各种方法反演玉米生物量的优劣。【结果】结果表明：和基于光谱指数构建的生物量反演模型相比,BP神经网络模型取得了更好的反演结果。其建模时决定系数为0.99均方根误差为0.08 t/ha,相对均方根误差为3.39%；外部验证时,决定系数为0.99,均方根误差为0.15 t/ha,相对均方根误差为8.56%。【结论】BP神经网络模型可有效提高无人机高光谱遥感反演玉米地上生物量的精度。