贺兰山西坡不同海拔梯度草地土壤氮特征

以阿拉善左旗境内贺兰山中段(西坡)及山前地带不同海拔下的草地为研究对象,分析不同海拔梯度下草地土壤全氮的分布特征及其与气候因子、植被特征和土壤特性的关系.结果表明,土壤全氮含量随海拔的降低而逐渐降低,在典型草原中沿土壤垂直剖面依次降低,在高寒草甸、荒漠化草原和草原化荒漠0～20与20～40 cm土层中差异不显著,但高于40～60 cm土层.在海拔1 360～1 380 m草原化荒漠的5个样地上,由于放牧利用程度和植被类型的不同,0～20 cm土层土壤氮的含量变幅在0.022 8%～0.034 7%.0～20,20～40和40～60 cm土层土壤全氮含量与年降水量、植被盖度、草地生产力、土壤含水量、有机碳含量和<0.05 mm颗粒含量呈极显著正相关,与年均温、土壤pH值呈极显著负相关(P<0.001).偏相关分析显示,影响0～20 cm土层全氮(TN)含量最主要的因素是植被盖度(C)和年降水量(AP),相关方程是TN%=0.002 040 C 0.000 585 AP-0.076 800;而影响20～40 cm土层全氮含量的最主要因素是草地生产力(B),与土壤全氮回归方程为TN%=0.001 6 B 0.024 7.而各环境因素中影响土壤全氮含量最主要的因素,0～20 cm土层为土壤有机碳和年降水量,20～40 cm土层主要受土壤有机碳的影响.     

几种牧草对河西走廊盐渍化土壤改土培肥的效应研究

在河西走廊盐渍化土地上种植老芒麦、扁穗冰草、碱茅和紫花苜蓿4种优质牧草,对盐渍化程度均有一定的改良效果.其中碱茅对盐渍化土壤的改土培肥效果最好,建植3年后的碱茅,与对照比较,0～20 cm土层中自然含水量增加125.99 g/kg,总孔度增加16.14%,容重降低0.27 g/cm3,pH值由8.43降到8.10,全盐含量降低52.90 g/kg,脱盐率达到76.12%,有机质增加3.67 g/kg,碱解氮含量增加18.63 mg/kg,速效磷和钾亦随之增加.     

三江源区土壤侵蚀变化及驱动因素分析

采用修正通用土壤流失方程(revised universal soil loss equation, RUSLE)对三江源区1997-2012年的土壤侵蚀模数和土壤侵蚀量进行定量模拟,并对其生态工程实施前、后时空变化特征进行对比分析,采用空间叠加法分析降雨侵蚀力及植被覆盖度对土壤侵蚀状况的影响,利用模型参数控制法对气候变化和生态工程对土壤侵蚀变化的贡献率进行分析。结果表明:1)生态工程实施后,三江源区土壤侵蚀增加的趋势尚未得到遏制,多年平均年土壤侵蚀模数和侵蚀量较工程实施前增加6.5%,但局部地区土壤侵蚀状况有所好转,约占总面积的45%;2)长江流域在工程实施后的土壤侵蚀量与工程实施前基本持衡;黄河流域土壤侵蚀量增加明显,增幅超过45%;澜沧江流域土壤侵蚀量有所下降,降幅为9.8%;3)降水增强导致土壤侵蚀加剧的贡献率达到180%,植被恢复对土壤侵蚀变化的贡献率为-80%。全面遏制三江源区土壤侵蚀增加趋势,仍需持续努力。     

不同轮作序列对旱地胡麻土壤有机碳稳定性的影响

为了探索陇中黄土高原半干旱丘陵沟壑区胡麻轮作序列对土壤碳库的影响,2012-2016年通过4年定位试验,以连作为对照,研究了不同胡麻频率下的轮作序列(F:休闲;PWFW:25%Flax、马铃薯-小麦-胡麻-小麦;WFWP:25%Flax、小麦-胡麻-小麦-马铃薯;FWPF:50%Flax、胡麻-小麦-马铃薯-胡麻;WPFF:50%Flax、小麦-马铃薯-胡麻-胡麻;FFFF:100%Flax、胡麻-胡麻-胡麻-胡麻)对土壤团聚体、总有机碳(TOC)、土壤颗粒有机碳(POC)、土壤微生物碳(MBC)和氮(MBN)的影响。结果表明,休闲、不同轮作序列和低胡麻频率显著增加了030 cm土层<0.25 mm粒级的土壤团聚体含量、TOC和POC含量,而随胡麻频率的增加三者的含量呈下降趋势。其中,25%Flax处理下土壤团聚体含量较播前和休闲处理分别显著增加了2.02%4.04%和9.56%11.73%;土壤有机碳(SOC)较连作显著增加5.95%7.48%。50%Flax处理下胡麻位置对土壤SOC影响显著,且轮作(FWPF)显著高于连作(WPFF)。060 cm土层土壤SOC含量表现为休闲>播前≈25%Flax>50%Flax>100%Flax。与连作相比,轮作显著提高了010 cm土层土壤TOC和POC含量,呈现表层富集现象。土壤POC含量表现为25%Flax≈休闲>50%Flax>100%Flax。此外,轮作换茬显著增加了土壤MBC含量,且随着胡麻频率的增加,030 cm土层土壤MBC含量逐渐降低。与播前、休闲、轮作相比,连作显著降低土壤微生物碳氮比,50%Flax(WPFF)轮作序列和土层深度对土壤有机碳和微生物量的互作效应显著。综合来看,休闲可以显著改善土壤理化性状,25%胡麻频率的轮作序列利于保持土壤团聚体稳定性,增加土壤TOC、SOC和POC含量,而50%Flax轮作序列(WPFF)能够提高土壤微生物量和微生物碳氮比。表明25%胡麻频率的轮作序列均可维持土壤有机碳的稳定性,是旱地胡麻比较理想的轮作序列。     

高寒区轮作模式对当归田土壤特性及药材产量的影响

连作重茬造成当归产量逐年下降。采用药用植物秦艽(QJ)、羌活(QH)轮作当归(DG),以当归连作为对照,通过测定土壤和药材产量指标,利用主成分分析确定各指标权重,并结合隶属综合因子分析和聚类分析,旨在揭示不同药用作物轮作当归对土壤环境与药材产量的影响,为筛选适宜当归栽培的轮作模式提供科学依据。结果表明,不同作物轮作对当归田土壤特性和药材产量均具有显著影响,秦艽轮作当归可有效改善土壤特性,使当归成药期土壤磷和钾含量处于较低水平,而有机质维持在较高水平,对土壤水分的季节调控作用更为显著,与当归连作相比较,当归成药率提高94.10%,药材单根鲜重和药材鲜产量分别提高53.46%和125.56%,而羌活轮作当归土壤pH最高,有机质含量最低,当归连作土壤有机质含量虽高,但土壤富集磷和钾,对土壤水分季节性调控作用最小,当归成药率和药材产量均低。不同轮作模式当归成药率和药材产量依次为秦艽-当归>当归-当归>羌活-当归,综合指数大小依次为秦艽-当归(0.8132)>羌活-当归(0.3315)>当归连作(0.2051)。聚类分析将3种轮作模式分为三大类,重复小区亚类间距离均小,说明不同作物轮作对土壤的调控作用不同,高寒产区秦艽轮作当归是优化调控土壤环境,提高当归产出性能的有效轮作模式。     

Evaluation of three popular diets fed to pet sugar gliders (Petaurus breviceps): Intake,digestion and nutrient balance

Three diets fed to 12 pair‐housed sugar gliders, Petaurus breviceps, were evaluated through 5‐day intake and digestion trials following 10‐day transitions. Diets 1 and 2 comprised liquid formula mixes with added vegetables and fruit, and Diet 3 comprised extruded pellets and a liquid formula. Diets eaten contained 16 —19% crude protein, 3%–15% crude fat, 10%–11% neutral detergent fibre, 4%–20% starch and 8%–49% sugar (dry basis). Calculated individual dry matter intakes (DMI) ranged from 3.9 to 5.1 g/day, representing 58.2–78.4 kJ/day. DMI was greater for Diet 2 (7.2% BW) vs. Diet 1 (5.6; p = .006) and Diet 3 (4.2% BW; p = .003). Although these differences were no longer detectable on a MBW basis, animals were shown to have gained BW (+14.2 g; p = .03) on Diet 2. In addition to nutrient composition differing widely among diets, DM digestibility (DMD) was higher in Diet 1 (91.2%) compared to Diet 2 (87.3%; p = .03), but DMD for Diet 3 (88.9%) did not differ from other diets. Gliders demonstrated ability to digest a variety of energy substrates, including simple sugars (96%–99%), fats (81%–96%) and starches (79%–98%), as well as substantial insoluble dietary fibre (58%–75%), with significant difference among diets demonstrated for some nutrients. Animals displayed selective feeding behaviours, rejecting insoluble fibre in produce and preferring the lipid‐coated exterior of pellets. The diets used appeared to be balanced with respect to energy, protein and macromineral content, but may predispose to iron excess, other mineral imbalances (especially Ca deficiency) and obesity—clinical health issues described for pet gliders. Future focus on concentrations, types and utilization of dietary fibre in natural and captive diets, vitamin D metabolism and trace mineral interactions in sugar gliders would assist diet optimization for this highly gummivorous species.     

Effect of sweet potato vines on performance parameters and some carcass characteristics of rabbits

Conventional feedstuffs in Brazil are expensive, which has led to the search for less conventional cheaper and locally available feedstuffs. Thus, this study was carried out to determine the dietary effect of dry sweet potato vines (SPV) on the performance and some carcass characteristics of rabbits. A total of twenty‐seven weaned White New Zealand rabbits (14 male and 13 female) 35 days old with an average initial weight of 755 g were allocated into three treatments. Nine rabbits were assigned to each treatment in a completely randomized design. Three diets were formulated to similar protein and energy levels: 0SPV – diet without inclusion of dry sweet potato vines; 10SPV – diet with 10% alfalfa hay replaced by dry sweet potato vines; and 15SPV – diet with 15% of alfalfa hay replaced by dry sweet potato vines. The experiment lasted for 49 days during which data for feed intake and body weight were recorded. The daily feed intake ranged from 73.17 to 78.02 g; daily weight gain from 22.32 to 23.17 g; feed conversion ratio (FCR) from 3.16 to 3.49 and final live weight ranged from 1839.44 to 1880.55 g. None of the evaluated performance parameters as well as carcass weight, heart weight and percentages of fat and protein in meat were significantly affected by any of the tested dietary treatments. However, the liver weight was statistically lower in animals fed the diets containing 10% of SPV, mainly due to lower glucose content. Glycogen within the tissue, did not differ significantly among treatments. It was therefore concluded that up to 15% of SPV can successfully be included in the diet of rabbits as a cheaper replacement for alfalfa hay without adversely affecting performance.     

In ovo feeding of nutrients and its impact on post‐hatching water and feed deprivation up to 48 hr,energy status and jejunal morphology of chicks using response surface models

A Box–Behnken design (BBD) in a response surface methodology (RSM) was used to investigate the response of broiler chicks to in ovo feeding (IOF) of beta‐hydroxy beta‐methylbutyrate (HMB), dextrin and the timing of the first water and feed deprivation. On day 18th of incubation, 1,500 eggs were randomly assigned to 15 experimental runs of BBD, each with 4 replicates, as 3 levels IOF of HMB (0%, 0.5% and 1%) and dextrin (0%, 20% and 40%), and 3 levels of the first water and feed deprivation (6, 27 and 48 hr). Day‐old chicks from each replicate were then used to assess the effect of IOF and time first water and feed access on chick's responses. The IOF of dextrin leads to respectively 9.7%–15.5% lower hatchability for 20% and 40% inclusion (p < .05), whereas HMB inclusion appeared with no effect on hatchability (p > .05). Administration of dextrin or HMB into the amnion of embryos elevated length, width and surface area of villus, and increased glycogen content of liver and breast (p < .05). In all parameter models, the linear terms showed highest contribution (R² = 0.81–0.97) to explain existing variation in chick's responses. The first water and feed deprivation had largest effect on BW2 and glycogen content of liver and breast. It is concluded that if possible, place chicks before 7 hr of hatch to preserve BW loss and have maximum response from IOF. If not possible, use IOF with 40% dextrin + 0.5% HMB to preserve gut integrity and energy status up to 48 hr. This should give advantage to chicks to recover fast after feeding, but that would have to be confirmed by trials growing birds to slaughter age.     

Effect of feed intake level and dietary protein content on the body temperature of pigs housed under thermo neutral conditions

Feed intake and diet composition appear to affect the body temperature of pigs. Two trials were conducted to analyse the effect of feed intake level and dietary protein content on the intestinal temperature (IT) of pigs housed under thermo neutral conditions. Ten pigs (64.1 ± 1.3 kg initial body weight) fitted with an ileal cannula were used. A thermometer set to register the IT at 5‐min intervals was implanted into the ileum through the cannula. In both trials, the ambient temperature ranged from 19.1 to 21.6°C and the pigs were fed at 07:00 and 19:00 hr (same amount each time). In trial 1, the pigs were fed daily 1.2 or 1.8 kg of a wheat–soybean meal diet. The IT followed a similar pattern along a 24‐hr period regardless the feed intake level. The IT rapidly increased up to 0.61 and 0.74°C after the morning meal and up to 0.53 and 0.47°C after the evening meal in pigs fed 1.2 and 1.8 kg/d respectively. The postprandial IT was higher in pigs fed 1.8 kg after each meal (p < .05). In trial 2, pigs were fed daily 1.8 kg of a low (11%) or a high (22%) crude protein diet. The IT followed a similar pattern along the 24‐hr period regardless the dietary protein level. The postprandial IT did not differ between pigs fed the low protein or the high protein (p > .10). The IT rapidly increased up to 0.66 and 0.62°C after the morning meal in pigs fed the high‐ and low‐protein diet (p < .05), but there was no change after the evening meal (p > .10). In conclusion, the feed intake level affected the IT of pigs housed under TN conditions, but the dietary protein content had no effect.