民勤10种典型荒漠植物冠层光谱与含水率的特征分析

植物体内水分是影响植物光合作用、呼吸作用、生物量及其他生理生化指标的主要因素之一,植物含水率的调查是植被研究的重要内容,利用高光谱进行典型荒漠植物含水率与冠层光谱的关系研究对荒漠区植被遥感监测具有重要意义。本研究借助ASD便携地物光谱仪实地测定了10种典型荒漠植物的冠层光谱曲线,并采用相关系数法和植被指数法,分析了不同荒漠植物光谱特征及其与冠层含水率的关系,结果显示:1)荒漠植物反射光谱曲线具有绿色植物在可见光-近红外波段的普遍特征,有明显的"绿峰"特征和"红边效应"。2)在954-973,1 184-1 198和1 440-1462 nm三个波段,荒漠植物存在明显的水分吸收谷。其中,1 440-1 462 nm波段的光谱反射率与含水率相关系数大于0.8,二者具有很强的线性相关性。3)WBI(Water Band Index)、NDWI(Normalized Difference Water Index)、NDII(Normalized Difference Infrared Infrared Index)、MSI(Moisture Stress Index)与植物含水率显著相关(P<0.05),冠层水分含量指数与植被水分实测值具有较高的一致性,可以反映荒漠植被含水率变化。     

种植密度和施磷肥对黄花草木樨种子产量的影响

适宜的种子生产技术是保证优良品种成功推广的重要基础。2014-2016年,在甘肃河西走廊地区研究了不同株距(30、45、60 cm)以及不同施磷肥量(0、40、80、120 kg·hm^-2 P₂O₅)对黄花草木樨两个品种‘天水’和‘Norgold’种子产量及产量构成因素的影响。结果表明,密度和施肥量以及二者的互作极显著影响黄花草木樨的实际种子产量(P<0.01)。 ‘天水’在60 cm株距和80 kg·hm^-2施磷肥条件下,两年的平均种子产量最高,为1234 kg·hm^-2;而对于‘Norgold’,2015和2016年皆为45 cm株距、80 kg·hm^-2施磷肥条件下的种子产量最高,分别为1613和1428 kg·hm^-2。通径分析表明,对种子产量影响最大的种子产量构成因素为生殖枝数。     

基于PSY的仔猪繁育环节经济损失系数的估算

目前中国母猪年生产力（PSY）水平与同期发达国家相比偏低,主要表现为仔猪断奶前死亡率高,对养猪业造成较大损失。为了解中国仔猪在繁育环节的经济损失情况,基于1980~2016年中国PSY数据,总结中国近37年PSY的波动趋势及原因,对仔猪繁育环节死亡仔猪带来的乳汁及教槽料损失进行估算。估算结果为：中国仔猪繁育环节乳汁的损失系数为3.47%~3.50%,2015年损失乳汁56.17万~77.71万t;教槽料损失系数为1.63%,2015年损失教槽料4.80万t。中国仔猪繁育环节的损失系数远高于发达国家,其中乳汁与教槽料损失系数均是PSY最高的丹麦的1.59倍,均是损失系数最低的爱尔兰的2倍多。仔猪繁育环节的损失系数与仔猪断奶前死亡率有关,教槽料的损失系数由于不同生猪养殖场饲养方式不同存在较大差异,所以,要提高养殖场管理水平,尤其要加强断奶前仔猪的保育,减少死亡率。     

Pros and cons of eliminating veld burning

Fire has been a factor of the environment in Africa since time immemorial and it is often caused by natural agencies such as lightning. It is maintained that there is much prejudice against veld burning, often ill‐founded. Fire has caused and maintained most of the world's grassland. When fire has been prevented plant succession has resulted in bush encroachment in the savanna and surrounding areas or in fynbos encroachment in others. Fire results in much old grass being wasted but, if this is not removed in some manner, the grazing deteriorates. Old grass can be removed by fire, mowing or grazing, using high protein supplements. The consequences of the different methods of removal, other than mowing, may be equally deleterious.     

Determination of the potential evapotranspiration and crop coefficient for saffron using a water-balance lysimeter

Agriculture is the major consumer of water and it is possible to decrease water consumption in this sector by proper irrigation scheduling. Irrigation scheduling is based on crop water requirements. Saffron is an important crop in Iran. The main purpose of this study was to determine the potential evapotranspiration and crop coefficient for saffron using single and dual crop coefficients, in Badjgah region, College of Agriculture, Shiraz University, Shiraz, Iran. Three water-balance lysimeters were used for this experiment in a two-year study. Total saffron potential evapotranspiration values were 523 and 640 mm in the first and second growing seasons, respectively. The maximum evapotranspiration rates for saffron were 4.5 and 6.1 mm d^?1 in the first and second growing seasons, respectively. Based on the results of this study, different saffron growing stages for evapotranspiration were 30, 40, 70 and 60 days. Crop coefficient (K _c) values for the initial, mid- and late-season growth stages were 0.41–0.45, 0.93–1.05 and 0.29–0.31 in both years, respectively. Basal crop coefficient (K _cb) values for the initial, mid- and late-season growth stages were 0.15–0.16, 0.41–0.65 and 0.15–0.17 in both years, respectively.     

USE OF CVS FOR REFINING MID-SEASON FERTILIZATION NITROGEN-RATES IN WINTER WHEAT

The GreenSeeker? optical sensor is used as a management decision aid in many crops across the world. This sensor measures the normalized difference vegetative index (NDVI). It has been observed that when the by-plot coefficients of variation (CV) from the GreenSeeker? sensor NDVI readings in winter wheat (Triticum aestivum L.) was incorporated into the midseason calculation of the response index (RI), RI at harvest was better predicted than with NDVI alone. This study further evaluated the use of CV's collected from both small 1.48 m² and large 17.0 m² areas. Trials consisted of 3 seeding rates by 4 nitrogen rates. Results from this study showed that CV from NDVI readings and plant population were negatively correlated. Improved prediction of RI by utilizing CV was not found. It was however observed that when CV's were less than 5.0 and NDVI values were greater than 0.80 the RI was less than 1.2.     

城市热环境对城市生态系统服务功能时空变化的响应——以成都市为例

文章以成都市为例,通过协同分析法利用皮尔逊相关性指数及双变量局部空间莫兰指数分析城市热环境对生态系统服务功能时空变化的响应情况。结果表明:成都城市热环境的递增趋势显著,整体市域温度在2000—2015年的研究期限内上升1.0℃~2.0℃;成都市热环境对7项生态系统服务功能具有明显的负响应情况,其响应机制分为3类,即直接影响、间接影响以及连带影响;成都城市热环境对生态系统服务响应显著性空间呈"东-中-西"区域化分布。在此基础上,文章提出了成都市热环境优化规划途径。     

冬小麦籽粒中的戊聚糖含量及其相关分析

戊聚糖是小麦制粉和食品加工品质中重要的影响因子之一。研究测定了我国北方地区32个冬小麦品种(系)籽粒中的戊聚糖和蛋白质、千粒重等性状,结果表明,不同品种(系)戊聚糖含量的变幅为3.92%~7.11%,戊聚糖与蛋白质含量的相关系数为0.681,达到极显著水平,蛋白质含量还与粒宽、千粒重呈显著正相关。     

不同生境下大叶梅(Parmotrema tinctorum)个体性状变化模式分析

采用冗余分析(RDA)等方法,对12个大叶梅个体环境因子与生物性状间关系进行了探讨,对性状在不同环境下的变化模式进行了描述。结果表明:地衣性状在个体内表现了一定程度的稳定性、在总体上表现出较大程度的变异性;无论是个体内还是总体中,菌丝直径都表现了最大的稳定性。冗余分析表明,湿度与环境因子光照呈显著负相关,与菌丝直径呈最大正相关,与生物变量髓层厚度呈最大负相关;海拔与假根密度呈最大正相关,与下皮层厚度呈最大负相关。藻孢层能较好地反映环境的综合变化,黑茶渍素含量能对环境光照条件作出较好地响应。不同生境下大叶梅在各功能部分的投资比例值得深入研究,在揭示地衣对环境变化响应模式方面具有更大意义。     

Biohydrogel induced soil–water interactions: how to untangle the gel effect? A review

Biohydrogels such as microbial exudates and root‐derived mucilage are soil‐born cross‐linked polymers, able to form porous three‐dimensional networks during water uptake. The gel effect is the variation of soil properties, such as soil hydrology and soil structural stability, resulting from biohydrogel swelling in soil. Conventionally, soil–water–hydrogel interactions are investigated by measuring soil bulk properties such as water retention curves and porosity, without further analyzing the effect of biohydrogel phases in soil on a quantitative basis. Therefore, the evaluation of advanced and novel methods for the characterization of biohydrogel phases in soil and soil–water–hydrogel interactions is necessary. This review evaluates currently available methods for their potential to analyze processes associated to the gel effect. A promising approach to investigate the spatio‐temporal distribution of biohydrogel phases in porous media is based on Nuclear Magnetic Resonance (NMR) such as ¹H‐NMR relaxometry, as well as on imaging techniques such as Environmental Scanning Electron Microscopy (ESEM). Especially NMR techniques enable the identification of different water populations based on their differences in the relaxation, and thus the mobility of water molecules in biohydrogels and non‐gel water in soil pores. Rheology measures the flow behavior of biohydrogels, providing information on the structural behavior of the hydrogel network and its gelling mechanism. Soil rheology further quantifies the effect of the biohydrogel phases on the interactions between soil particles, and thus the impact on soil microstructural stability. However, rheology does not elucidate the spatio‐temporal distribution and structural state of biohydrogel phases in soil. All in all, a systematic combination of rheology, NMR and suitable imaging methods seems promising and necessary in order to elucidate the still widely unknown gel effect in soil.