土壤易氧化有机碳与溶解性有机碳对荒漠草地沙漠化过程中土壤碳库变异的表征

以干旱、半干旱地区荒漠草地不同沙漠化阶段土壤为研究对象,研究不同沙漠化阶段土壤易氧化有机碳与溶解性有机碳含量和分配比例变异规律,分析不同沙漠化阶段土壤碳库指数变化,探讨荒漠草地沙漠化过程中土壤易氧化有机碳与溶解性有机碳对土壤碳库的表征作用。结果表明,随着荒漠草地沙漠化程度的加剧,易氧化有机碳含量表现出一定的波动性,但整体呈下降趋势,溶解性有机碳含量呈线性下降。易氧化有机碳和溶解性有机碳分配比例均在荒漠草地达到最大值,在半固定沙地达到最小值。利用易氧化有机碳含量计算的土壤碳库管理指数随荒漠草地沙漠化程度增加表现出先下降后上升趋势,利用溶解性有机碳含量计算的土壤碳库管理指数呈线性下降趋势。易氧化有机碳、溶解性有机碳含量与土壤有机碳均显著正相关,但溶解性有机碳的相关系数略高于易氧化有机碳。通过比较活度敏感指数和碳库管理指数敏感指数发现,荒漠草地逆向演替至固定沙地过程中,易氧化有机碳的各项敏感指数均高于溶解性有机碳。固定沙地演替至流动沙地过程中,溶解性有机碳的各项敏感指数均高于易氧化有机碳,表明易氧化有机碳能够较好地表征荒漠草地沙漠化前期土壤碳库变化,而荒漠草地沙漠化中期和后期利用溶解性有机碳表征效果更好。     

Plantago ovata in broiler chicken nutrition: Performance,carcass criteria,intestinal morphology,immunity, and intestinal bacterial population

In this experiment, the effect of dietary Plantago ovata (PO) on performance, carcass criteria, intestinal morphology, immunity, and intestinal bacterial population of broiler chickens was evaluated. A total of 250 one‐day‐old male broiler chicks (Ross 308) were randomly assigned to five treatments containing 0, 5, 10, 15, or 20 g/kg of PO with five replicate pens and 10 birds in each replicate. Dietary PO increased body weight gain and decreased feed conversion ratio in the finisher period, improving the performance index (p < .05). Dietary treatments had no effects on carcass criteria, but breast meat percentage showed an increasing trend with incremental levels of PO in the diet (p = .069). The length of small intestine, especially jejunum section, as well as the villus height, villus width, villus area, and goblet cell numbers were significantly increased with supplemental PO (p < .05). Humoral and cellular immunity parameters, and oxidation stability of meat were improved due to use of dietary PO (p < .05). Dietary PO decreased the CFU of Escherichia coli, whereas the Lactobacilli population was increased (p = .001). Broken‐line regression revealed that dietary PO at the rate of 10 g/kg may results in the best performance in broiler chickens. This study showed that PO at the level of 10 g/kg could be considered as a beneficial feed additive in broiler diet.     

Response of labile organic C and N pools to plastic film removal from semiarid farmland soil

To examine the effects of plastic film removal on grain yield and soil organic matter (SOM), a spring maize (Zea may L.) field experiment was conducted for 5 yr at Changwu Agricultural and Ecological Experimental Station of Northwest China. Compared with traditional plastic film mulching during entire growing stages (FM), plastic film removal at the silking stage (RM) resulted in a 6.3% higher average maize yield. Under the RM treatment, soil organic carbon and total nitrogen significantly increased after the 5‐yr cultivation in the 0‐ to 20‐cm layer. Significant increases in extractable organic C (EOC), KMnO₄‐oxidizable C (KMnO₄‐C) and C management index (CMI) in the 0‐ to 20‐cm layer, and light fraction organic C and EOC in the 20‐ to 40‐cm layer were observed in response to plastic film removal after the 1‐yr treatment; the responses were more significant after 5 yr. Under the RM treatment, significant increases in microbial biomass C, light fraction organic N, extractable organic N, KMnO₄‐C and CMI were also observed after five years in the 20‐ to 40‐cm layer. Moreover, KMnO₄‐C and EOC were much more sensitive than other labile SOM fractions to the application of RM, even after only 1 yr of cultivation. Therefore, compared with mulching for the whole growing season, plastic film removal at the maize silking stage is an effective option for increasing yields and enhancing SOM concentration and soil sustainability in the regions with semiarid monsoon climates that have sufficient rainfall during maize reproductive stages.     

径向谐和激励下圆形隧道衬砌的动力稳定性

对径向谐和激励下圆形隧道的动力稳定性进行了研究，从动荷载下衬砌结构的振动方程出发，得到了隧道衬砌动力失稳临界频率计算公式，对可能影响隧道衬砌动力稳定性的因素进行了参数分析，探讨了系统参数，如地基土的性质、衬砌径厚比、外激励的性质以及系统的阻尼对衬砌动力稳定性的影响，计算结果表明：隧道周围土体的性质以及系统阻尼对衬砌的动力稳定性影响不大；相反，衬砌的厚度和外激励特性对衬砌的动力不稳定区域影响较大     

不同生态因子对荚果蕨生长和光合特性的影响

为研究荚果蕨抗逆性生理机制并且为荚果蕨栽培提供理论依据和参考,以荚果蕨为实验作物,利用盆栽法、光合作用测定仪、土壤农化分析方法研究了荚果蕨生长及光合特性对土壤质量含水量、有机肥料、光照强度等生态因子的响应机制。研究结果表明:荚果蕨幼苗对于水分胁迫具有一定的抗逆性,土壤质量含水量为田间持水量的70%~75%时荚果蕨叶片长度最大,净光合速率(Pn)与蒸腾速率(Tr)表现为随着土壤含水量的增加先上升后下降,水分利用效率(Ew)变化趋势与之相反;不同有机肥料间比较腐熟猪粪肥培肥效果较好,且在1500 kg/hm2施用量时效果达到峰值;各遮阳措施均有利于荚果蕨生长,实验处理为使用透光率为30%的遮阳网时荚果蕨叶片长度最佳。荚果蕨最适宜生长条件为:土壤质量含水量为田间持水量的70%~75%;施用腐熟猪粪肥1500 kg/hm2;遮阳措施透光率为30%。     

不同供磷水平对柱花草和黑籽雀稗根际生理活性的影响

以热带柱花草和黑籽雀稗为材料，通过盆栽试验，研究不同磷水平对其根际酸性磷酸酶、微生物数量及根系活力的影响。结果表明：2种牧草根际酸性磷酸酶(ACP)活性随着磷浓度的增加而降低，在低磷(P0)处理时达最高，柱花草的ACP活性为603.24 mg/(kg·h)，黑籽雀稗为367.21 mg/(kg·h)。当高磷浓度处理时，柱花草根际ACP活性较黑籽雀稗低。各处理中，柱花草的根际微生物总量较黑籽雀稗高，柱花草根际真菌的数量随磷浓度的增加而减少，处理间差异达极显著水平，低磷处理时土壤真菌数量较多，这有利于根瘤菌的形成。2种牧草的根系活力随着施磷浓度的增加而递减。黑籽雀稗根系活力P0处理极显著高于P3和P4处理,显著高于P2处理。黑籽雀稗根系活力受供磷水平的影响大于柱花草。     

The Situation for Quinoa and Its Production in Southern Bolivia: From Economic Success to Environmental Disaster

In Bolivia, one of the world’s most important centres of plant domestication, there is growing awareness of the value of native Andean crops, both for domestic consumption and for market sale – notably the virtually boom‐like consumer demand for quinoa around the world. The southern altiplano of Bolivia, south of Oruro, relies almost purely on the production of quinoa and breeding of llamas, which have also been selected as the two commodities of priority to the government to increase the income of the country. Presently, however, quinoa is facing increasing problems in production, owing to its increasing export market and price. The flat areas around the salt desert of the southern altiplano, previously characterized by natural vegetation fed by the llamas, are being increasingly sown with quinoa, hence transformed into deserts, because intensive cultivation methods make the soil loose its fertility. Possible solutions to these problems will require extensive efforts in the south, in addition to various strategies, which also include other parts of the Bolivian altiplano and a strengthened focus on other Andean crops.     

磷硫配施对冬小麦硒吸收及转运的影响

为了探讨磷硫配施对冬小麦产量、硒的吸收及转运的影响，为生产富硒小麦或合理调控小麦硒含量提供理论依据，采用盆栽试验，设置不同磷、硫水平，在小麦成熟期测定产量及植株各部位硒含量。结果表明：硫磷的配合施用能显著提高冬小麦产量，S0.1P0.4处理下冬小麦产量最高。除颖壳外，冬小麦各部位硒含量最高值都出现在S0P0处理。不论施硫与否，施磷均能显著降低冬小麦各部位硒含量，提高小麦植株硒累积量，促进冬小麦茎叶向颖壳的硒迁移，降低根向茎叶、颖壳向籽粒的硒迁移系数，还会减小籽粒的硒分配。单独施硫会降低植株的硒累积量，促进冬小麦根向茎叶、茎叶向颖壳的硒迁移，降低颖壳向籽粒的硒迁移系数，低硫处理能增加小麦籽粒的硒分配，高硫处理则降低了籽粒的硒分配。S0P0.2处理能显著提高籽粒硒累积量，而高浓度的磷硫配施会降低籽粒硒累积量；S0.1P0和S0.1P0.2处理籽粒硒分配较大,分别是45.3%和44.8%。因此，硫磷的合理配施能显著提高小麦产量，低硫（S0.1）高磷（P0.4）处理增产最显著。低硫（S0.1）低磷（P0.2）处理能更有效地增加植株硒累积量，增强硒在籽粒中的累积。     

不同钙磷配比及浓度对多花黑麦草生长特性的影响

为揭示多花黑麦草（Lolium multiflorum Lamk）对不同钙磷环境的适应机制，设置3个不同钙磷比（1∶1、2∶1、5∶1），每个钙磷比下设置两种钙磷浓度，以不添加钙和磷的营养液处理为对照，探讨不同钙磷水平下多花黑麦草形态和生理指标的变化；并利用隶属函数综合评价法来筛选适宜多花黑麦草生长的钙磷配比及浓度。结果表明：①Ca/P比为1∶1时，随Ca2+、P浓度的增加，株高、叶宽、光合色素和脯氨酸（proline, Pro）含量均呈下降趋势，丙二醛（malondialdehyde, MDA）和超氧化物歧化酶（superoxide dismutase, SOD）活性呈升高趋势；②Ca/P比为2∶1时，随Ca2+、P的增加，株高、叶宽存在一定的下降，叶绿素含量、MDA含量和SOD活性差异不显著，类胡萝卜素和Pro含量升高；③Ca/P比为5∶1时，随Ca2+、P浓度的增加，株高、叶宽、光合色素含量升高，MDA含量下降，Pro含量和SOD活性变化不明显；④P浓度相同时，随着Ca2+浓度的增加，叶绿素、类胡萝卜素含量和SOD活性呈降低趋势；⑤通过隶属函数综合评价，多花黑麦草适宜生长的Ca、P浓度分别为50和10 mg·kg-1。以上结果为多花黑麦草的栽培种植和钙磷响应机理研究提供理论依据。     

外施苹果酸对紫色小白菜生长、生理与品质的影响

【目的】探究外施苹果酸对紫色小白菜生长、生理与品质的影响,筛选最适的外施苹果酸质量浓度,为紫色小白菜的优质培育以及高产栽培奠定理论基础。【方法】以‘京研'紫色小白菜为试验材料,采用水培技术,设置外施苹果酸0 mg/L(对照,CK)、0.5 mg/L(T1)、1.5 mg/L(T2)、3.0 mg/L(T3)、5.0 mg/L(T4)、10.0 mg/L(T5)共6个处理,研究不同质量浓度外施苹果酸对紫色小白菜叶片和根系形态学指标、根系显微结构及相关品质指标的影响。【结果】(1)随苹果酸质量浓度的增大,紫色小白菜叶片和根系形态指标均呈现先上升后下降的趋势,其中T1、T2处理显著优于对照,叶片表面积、体积较大,且可促进植株根系增长、面积增大、侧根增粗,而T5处理因苹果酸质量浓度过高阻碍了根系伸展。(2)根系显微结构观察发现,T1、T2、T3处理紫色小白菜新生侧根根尖1 cm处直径均显著高于对照,维管束和木质部区域直径增大,有助于运输更多的营养物质和水分。T5处理根系皮层细胞层数较少,细胞体积较大且排列疏松。(3)紫色小白菜叶片可溶性蛋白和维生素C含量随处理时间延长逐渐增高,随苹果酸质量浓度的增大呈先上升后下降的趋势,以T2处理最优。紫色小白菜叶片可溶性糖和总有机酸含量9 d时整体下降,且随苹果酸质量浓度的增大呈先上升后下降趋势,T1、T2处理显著高于对照。(4)苹果酸、丙二酸、琥珀酸和酒石酸含量随苹果酸质量浓度的增加呈先上升后下降的趋势,而柠檬酸含量呈先下降后上升的趋势。T1、T2、T3处理苹果酸、丙二酸、琥珀酸含量较高,对照、T4、T5处理柠檬酸含量较高。【结论】外施苹果酸能够影响紫色小白菜的生长及生理状况,施用适宜质量浓度(1.5 mg/L)的苹果酸可有效促进紫色小白菜地上部和根系生长,提高苹果酸、丙二酸、琥珀酸含量,提升植株营养品质。