三江源区高寒草原土壤湿度变化特征及与气候因子的关系

利用青海省三江源区兴海县牧业气象站1999-2016年高寒草原土壤湿度、牧草生育期资料,分析了高寒草原土壤湿度的年、季变化特征以及牧草生长季不同生育期土壤湿度的变化特征及与气候因子的关系。结果表明:高寒草原0-10、10-20、20-30、30-40和40-50 cm土壤湿度均随年际延长呈增加趋势,春季除40-50 cm土层外,其他各层土壤湿度均随年际延长呈显著增加趋势(P<0.05)。高寒草原牧草生长季的土壤相对湿度随年际延长呈显著上升趋势(P<0.05),且与生长季降水量之间呈极显著正相关关系(P<0.01)。随着气候变化,牧草抽穗、开花、成熟和枯黄期的土壤相对湿度随年际延长呈显著增加趋势(P<0.05)。牧草抽穗期、枯黄和全生育期的土壤湿度与气温呈显著负相关关系(P<0.05)。高寒草原牧草生长季土壤湿度的增加有利于草地植被生长。     

基于冗余分析的高寒草原土壤与草地退化关系

在高寒草原退化草地设置研究样地,观测植物群落特征、采集土壤样品、分析土壤物理化学性质,依据数量生态学基本原理,探讨高寒草原退化草地与土壤因子间关系。结果表明:不同退化程度样地沿冗余分析排序图第一排序轴分布,第一排序轴反映草地退化程度的变化;草地植物群落中与第一排序轴负相关且按相关程度大小排序的指标为盖度>地上生物量>地下生物量;第一、第二排序轴能够解释97.1%的土壤因子与草地退化关系;土壤沙砾、p H与第一排序轴正相关,土壤有机碳、土壤含水量、容重、全氮、有效氮与第一排序轴负相关;第一排序轴及所有排序轴所反映的土壤因子均与草地退化之间呈极显著相关关系(P<0.01);不同土壤因子与草地退化之间相关程度不同,土壤有机碳(r=-0.890)、土壤含水量(r=-0.864)、容重(r=-0.847)、全氮(r=-0.836)、有效氮(r=-0.821)等与高寒草原退化相关程度更高且相关关系极显著(P<0.01)。利用退化草地群落特征和土壤因子数据矩阵进行冗余分析能够较好地综合反映土壤因子与草地退化之间的关系及相关程度,土壤有机碳、土壤含水量、容重、全氮、有效氮是反映高寒草原退化的重要土壤指标。     

药剂浸泡种茎对布朗山区木薯地下害虫的防效评价

为了有效防控云南布朗山区木薯重要地下害虫的发生与危害，本试验针对性地开展种茎无害化药剂处理的防效评价研究。结果表明：选用环保型杀虫剂48%乐斯本乳油1 000倍液和1.8%阿维菌素乳油2 000倍液的1∶1混合液浸泡木薯种茎5和10 min后种植效果最好，平均出苗率分别由无任何处理对照的62.5%及清水对照的75.0%和75.6%显著提高到96.5%和97.0%，平均虫害率分别由无任何处理对照的56.8%及清水对照的45.0%和44.8%显著下降到6.3%和5.5%，平均产量分别由无任何处理对照的1 11     

More evidence that anaerobic oxidation of methane is prevalent in soils: Is it time to upgrade our biogeochemical models?

Estimating future fluxes of CH₄ between land and atmosphere requires well-conceived process-based biogeochemical models. Current models do not represent the anaerobic oxidation of methane (AOM) in land surface soils, in spite of increasing evidence that this process is widespread. Our objective was to determine whether AOM, or potential AOM, commonly occurs in 20 hydromorphic soils spanning a wide range of chemical properties. Bulk soil samples were collected under shallow water near the shoreline of 15 recently drained fish ponds in southern Bohemia (Czech Republic), as well as from below the water table at 3 peatland locations in northeast Scotland and 2 acid sulfate soils on the southern coast of Finland. Each soil slurry was incubated under both oxic and anoxic conditions, with or without the addition of alternative electron acceptors (SO₄²⁻ and NO₃⁻) or H₂PO₄⁻. Here, “oxic” and “anoxic” conditions refer to anoxic soil respectively incubated in a headspace containing air or argon. Using the isotope dilution method, we determined the gross production and oxidation rates of CH₄ after 2 days incubation under oxic headspace conditions, and after 2, 21 and 60 days incubation under anoxic conditions. Large differences in net CH₄ fluxes were observed between soil types and between incubation conditions. AOM was detected in each of the 20 bulk soil samples, which spanned >6 pH units and 2 orders of magnitude in organic C content. Significant positive relationships were found between AOM and gross CH₄ production rates under anoxic conditions, resulting in AOM rates that were sometimes higher than CH₄ oxidation rates under oxic headspace conditions. There was no relationship between net and gross CH₄ production rates, such that 2 soil types could display similar low net rates, yet conceal very large differences in gross rates. The effects of alternative electron acceptors on AOM were idiosyncratic and resulted in no net trend. We did find, however, a negative effect of SO₄²⁻ and H₂PO₄⁻ on gross CH₄ production rates under anoxic and oxic conditions respectively. Under oxic headspace conditions, CH₄ oxidation was related to soil organic C content. Taken collectively, our results suggest that AOM, or potential AOM, is prevalent over a wide range of soil types, that AOM may contribute substantially to CH₄ oxidation in soils, and that AOM in soils should be integrated to current process-based CH₄ cycling models.     

Determination and Analysis of Heavy Metal Content in the Soil from Beef Cattle Farms in Three Regions of Xinjiang

In order to study and evaluate the feeding environment of the beef cattle farms in Xinjiang, the contents of heavy mentals in the soil from 8 beef cattle farms in Xinjiang Aksu, Yili and Tacheng regions were tested according to the Field of Livestock and Poultry Environment Quality Standard (NY/T 388—1999).The atomic absorption spectroscopic method was used to determine the contents of As, Hg, Pb, Cd, and Cr.The mean contents of As, Hg, Pb, Cd, and Cr in 8 beef cattle farms soil were 0.389, 0.568, 22.708, 0.573 and 149.449 mg/kg, respectively, and they were all below the upper limit of NY/T 388—1999.The comprehensive heavy metal pollution index of 8 beef cattle farms were 0.577 to 0.994, and the index were 0.7 to 1 of two observation points in Yili and one observation point in Tacheng.The soil environment quality of these 3 farms were at the level of slight cleaning.The comprehensive heavy metal pollution index of other five observation points were ≤0.7, the soil environment was in a clean level.The soil environment of beef cattle farms in these three regions conformed to the standards of livestock for environment quality and safe products.     

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.     

Proton accumulation accelerated by heavy chemical nitrogen fertilization and its long-term impact on acidifying rate in a typical arable soil in the Huang-Huai-Hai Plain

Cropland productivity has been signiifcantly impacted by soil acidiifcation resulted from nitrogen (N) fertilization, especialy as a result of excess ammoniacal N input. With decades’ intensive agricul...     

Water circulation induced by mechanical aerators in a rectangular vessel for shrimp aquaculture

A water streamer was designed for the purpose of enhancing cost-efficient circulation between the water surface and bottom of shrimp aquaculture ponds. We took direct measurements of the water current field induced by the designed aerator in a large rectangular reservoir of dimensions (L)50 × (W)19 × (D)1.3 m³ and compared the results with those of a standard Taiwanese paddle-wheel aerator. Vertical circulation between the surface and the bottom induced by the paddle wheel aerator was less than that by the designed aerator. Furthermore, the paddle-wheel aerator consumed more electric power than the designed aerator. The structures of water current induced by the two aerators are elucidated, and the advantages and disadvantages of the aerators are discussed.Auxiliary employment of the designed aerators may contribute to delivery of high DO water throughout the pond, which is more efficient than a paddle wheel aerator.     

7株根瘤菌菌株与热研2号柱花草共生最适磷浓度研究

采用水培的方法,设3个磷水平,7个菌株,通过对株高、茎叶鲜重、茎叶干重、固氮酶活性、茎叶氮含量、茎叶磷含量的测定及综合分析,确定使热研2号柱花草接种不同根瘤菌菌株达到最佳促生性能的磷浓度。结果表明:7个菌株在中磷时鲜重和含氮量最大,低磷不利于鲜重和含氮量的增加;经主因子综合分析,菌株YM11-1、RJS9-2、PN13-3在高磷时对热研2号柱花草有最好的固氮促生效果,菌株LZ3-2、BS1-1、PN13-3在中等磷条件下有最好的固氮促生效果,菌株FS3-1-1在高磷和中磷都有最好的固氮促生效果。     

Can soil moisture deficit be used to forecast when soils are at high risk of damage owing to grazing animals?

A potentially significant cause of damage to grassland soils is compaction of unsaturated soil and poaching of saturated or nearly saturated soil by animal hooves. Damage is caused when an applied stress is in excess of the bearing strength of the soil and results in a loss of soil structure, macroporosity and air or water conductivity. Severely damaged soils can cause reduced grassland productivity and make grazing management very difficult for the farmer. The actual amount of soil damage that can occur during grazing is dependent on the grass cover which acts as a protecting layer, the soil water content and the characteristics of the grazing animal (weight and hoof size). Assuming that the farmer is knowledgeable about the characteristics of the grazing animal and grass cover, it would be very useful for short‐term operational farm planning to be able to predict when soil water contents were likely to be in a critical range with respect to potential hoof damage. In this study soil moisture deficits (SMDs) which can be derived from meteorological forecasts are evaluated for predicting when soil water conditions are likely to lead to hoof damage. Two contrasting Irish grassland soils were analysed using a Hounsfield servo‐mechanical vertical testing machine to simulate static (285.4 N) and dynamic (571 N) hoof loads on the soil over a range of estimated SMDs (0, 5, 10 and 20 mm). The deficits were analysed with respect to the soil volumetric water content, compression (displacement) and change in dry bulk density. The SMDs imposed in the laboratory were similar to those under field conditions and thus the methods used in this study are applicable elsewhere. The change in dry bulk density following loading (0.2–0.7 g/cm³) was linearly related to SMD (R² ranged from 0.90 to 0.99), leading to the conclusion that a forecast of SMD can be used to predict when grassland soils are likely to be at risk of damage from grazing.