白蜡木、黑胡桃木、橄榄木的干缩湿胀特性研究

实木制品的干缩湿胀性直接影响其尺寸稳定性,对白蜡木、黑胡桃木和橄榄木的干缩湿胀特性研究结果表明：三种木材全干状态下的体积干缩率分别为13.88%、10.85%、9.89%,气干状态下的体积干缩率分别为4.89%、4.71%、4.14%,气干至饱水状态下的体积湿胀率分别为18.28%、12.82%、11.54%,全干至气干状态下的体积湿胀率分别为5.94%、4.20%、3.96%。三种木材中白蜡木的干缩湿胀性最强,黑胡桃木次之,橄榄木最小。研究结果对实木制品用材含水率的控制具有一定的指导意义。     

虫害诱导家榆挥发物的日释放节律分析

以家榆为试验对象,分析挥发物的组分与日释放节律,结果表明:家榆的挥发物共有24种化合物,包含有醇类、烷类、酯类和萜烯类等。挥发物的释放存在昼高夜低的现象,在上午时释放量会迅速增加,到中午达到最大,然后在下午、晚上逐渐减少;在由明转暗时,挥发物的释放有一个短暂的爆发。挥发物的日夜释放节律与害虫天敌的活动规律相符,可能是植物发挥主动防御的结果。     

基于BIOCLIM模型的元江干热河谷稀树灌木草丛空间分布研究

根据影响干热河谷稀树灌木草丛分布的温度、数字高程模型（DEM ）以及归一化植被指数（NDVI）三个因子,使用BIOCLIM模型模拟元江县干热河谷稀疏灌木草丛空间分布,实现了元江县干热河谷空间分布的可视化表达。结果表明：干热河谷分布主要集中于除元江县城外的河谷两侧,其中东部分布较为集中,而在南部地区分布较为分散。加之近年来人为活动的加剧,对元江河谷生态环境的变化也有一定影响,该模型很好地预测了未来元江县干热面积的分布情况,以期对生物多样性保护和植被恢复提供决策支持。     

Soil organic carbon fractions and humic substances are affected by land uses of Caatinga forest in Brazil

Caatinga is a Brazilian dry ecosystem that occupies around 1 million km² and is one of the largest tropical dry forests of the world. About 46% of the area that was originally covered has been deforested. Land use can cause pronounced reduction in soil carbon stocks that play a major role in the global carbon cycle. The objective of this study was to improve our understanding of the effect of land use on oxidizable carbon fractions, total carbon stocks and humic substances in different layers of soil in a Brazilian semi-arid region. We analyzed soils from tropical dry forest (TDF), forest succession with Anadenanthera falcata (ANA), with Tabebuia alba (TAB), secondary scrubby regeneration (SCR), and non-irrigated maize (MS). Forests showed larger fractions of more labile carbon, except for TDF. The most recalcitrant fraction of carbon stock, humin fraction stock, with the different land use decreased by 38–53% compared to TDF. Oxidizable carbon fractions, carbon stocks, and humic fraction stocks were able to differentiate the successional land uses and agricultural cover from TDF, mainly in the 0–5?cm layer. Our results show that changes in land use, especially with ANA forest succession, showed a larger labile carbon fraction, indicating easy decomposition and loss. Our results provide an alternative tool for the management of deforested areas in tropical dry caatinga ecosystems. This would contribute to the conservation of dry forest systems and could serve as guideline for sustainable management of agriculturally impacted caatinga areas.     

Responses in gross primary production of Stipa krylovii and Allium polyrhizum to a temporal rainfall in a temperate grassland of Inner Mongolia,China

In the arid and semi-arid areas of China, rainfall and drought affect the growth and photosynthetic activities of plants. Gross primary productivity (GPP) is one of the most important indices that measure the photosynthetic ability of plants. This paper focused on the GPP of two representative grassland species (Stipa krylovii Roshev. and Allium polyrhizum Turcz. ex Regel) to demonstrate the effect of a temporal rainfall on the two species. Our research was conducted in a temperate grassland in New Barag Right Banner, Hulun Buir City, Inner Mongolia Autonomous Region of China, in a dry year 2015. We measured net ecosystem productivity (NEP) and ecosystem respiration flux (ER) using a transparent chamber system and monitored the photosynthetically active radiation (PAR), air and soil temperature and humidity simultaneously. Based on the measured values of NEP and ER, we calculated the GPP of the two species before and after the rainfall. The saturated GPP per aboveground biomass (GPP_AGB) of A. polyrhizum remarkably increased from 0.033 (±0.018) to 0.185 (±0.055) μmol CO₂/(gdw?s) by 5.6-fold and that of S. krylovii decreased from 0.068 (±0.021) to 0.034 (±0.011) μmol CO₂/(gdw?s) by 0.5-fold on the 1^st and 2^nd d after a 9.1 mm rainfall event compared to the values before the rainfall at low temperatures below 35°C. However, on the 1^st and 2^nd d after the rainfall, both of the saturated GPP_AGB values of S. krylovii and A. polyrhizum were significantly lower at high temperatures above 35°C (0.018 (±0.007) and 0.110 (±0.061) μmol CO₂/(gdw?s), respectively) than at low temperatures below 35°C (0.034 (±0.011) and 0.185 (±0.055) μmol CO₂/(gdw?s), respectively). The results showed that the GPP responses to the temporal rainfall differed between S. krylovii and A. polyrhizum and strongly negative influenced by temperature. The temporal rainfall seems to be more effective on the GPP of A. polyrhizum than S. krylovii. These differences might be related to the different physiological and structural features, the coexistence of the species and their species-specific survival strategies.     

Selective inhibition of endothelin receptor A improves white matter lesions in hypertensive rats

AIM:To observe whether selective inhibition of endothelin receptor A (ETRA) improves white matter lesions (WMLs), and explore the mechanism. METHODS:Sprague-Dawley rats (n=33) were randomly divided into sham operation group (n=9), treatment group[stroke-prone renovascular hypertensive rats-modified 2 vessel occlusion (RHRSP-modified 2VO) + ambrisentan (n=12)] and placebo group[RHRSP-modified 2VO + vehicle (n=12)]. Drug and vehicle administration was performed from 17th to 20th week and monitoring of systolic arterial pressure was performed weekly. Morris water maze test was conducted to evaluate the function of cognition. The protein levels of endothelin-1 (ET-1) in the cortex, corpus callosum and caudate putamen were quantitatively analyzed respectively. The severity of WMLs and the relationship between ET-1 and vessels were observed by the method of histopathology. RESULTS:The difference of systolic arterial pressure between treatment group and placebo group was not significant. The animals in treatment group exhibited shorter escape latency (P<0.05), more times of crossing platform (P<0.05), lower level of ET-1 in corpus callosum and caudate putamen (P<0.05), respectively, improved WMLs severity (P<0.05) and lower binding level of ET-1 to vessels compared with the placebo group. CONCLUSION:Selective inhibition of endothelin receptor A improves the severity of WMLs and ameliorates the cognitive function.     

不同氮素水平下有机物料添加对陇中黄土高原旱作农田N2O排放特征的影响

为了探究不同用量氮肥配施生物质炭或小麦秸秆对旱作农田N₂O排放通量的影响，在陇中黄土高原半干旱区连续进行4年不同氮素水平配施不同有机物料的田间定位试验，试验以3种施氮用量（不施氮肥、50 kg（N）·hm^-2氮肥、100 kg（N）·hm^-2氮肥）配施2种有机物料（小麦秸秆S、生物质炭B）及无有机物料 (C)共组成9个处理，于2016年11月—2017年10月，采用静态箱-气相色谱法，对N₂O通量进行全年内连续观测。研究结果表明：观测期内，各处理N₂O年平均通量大小排序SN100>CN100>SN50>CN50>BN100>SNO>BN50>CN0>BN0，各处理N₂O排放通量变化趋势一致；相较N0处理（CN0、SN0、BN0）的年平均排放通量，N50（CN50、SN50、BN50）和N100（CN100、SN100、BN100）处理分别增加了6.92%和10.03%。相较CN0、CN50和CN100，与其相同氮素水平配施生物质炭后，N₂O年平均排放通量分别降低了0.49%、3.15%和4.67%；配施秸秆后，N₂O年平均排放通量分别增加了6.37%、3.44%和2.73%。单施氮肥或小麦秸秆配施氮肥均增加了N₂O排放的增温潜势，生物质炭配施氮肥减少了N₂O排放的增温潜势。主效应分析表明，氮素、秸秆均对提升N₂O排放通量发挥显著效应，而生物质炭具有降低效应。相关分析表明，土壤温度与N₂O通量表现为显著正相关关系，土壤含水量与N₂O通量表现为显著负相关关系（P<5%）。通径分析表明，土壤温度对N₂O通量的增大作用远大于土壤含水量对N₂O通量的减小作用。秸秆或生物质炭与氮素无交互效应，N₂O排放通量随氮素水平的增加而增大，秸秆还田促进了N₂O排放而生物质炭抑制了N₂O排放。因此，添加生物质炭对旱作农田固氮减排具有较大的潜力。     

适雨灌溉下不同施肥模式对机插稻稻田水环境及产量的影响

【目的】探讨江汉平原地区适雨灌溉条件下不同施肥模式对机插稻稻田水环境及水稻生长的影响,为当地机插稻水肥管理措施的改善提供理论和数据支撑。【方法】采用田间小区试验,研究了适雨灌溉条件下,农民习惯施肥(FFP)、70%控释掺混肥+30%尿素(70%CRF+30%N)和有机无机复混肥(OIF)对稻田降雨利用率、田面水氮磷质量浓度的动态变化与径流流失量、干物质积累及水稻产量的影响。【结果】适雨灌溉下,返青期、分蘖期、拔节孕穗期和灌浆成熟期的降雨利用率分别为17.5%、100%、100%和84.2%;基肥和分蘖肥施用过后,FFP、70%CRF+30%N和OIF处理田面水TN、NH4+-N和TP质量浓度迅速提高,在第1天达到峰值,水稻移栽后30 d内70%CRF+30%N处理田面水TN、NH4+-N和TP的平均质量浓度较FFP处理分别降低40.4%、47.4%和0.5%;稻田氮磷径流流失量的90%左右在返青期,10%左右在灌浆成熟期,70%CRF+30%N处理TN、NH4+-N和TP径流损失量较FFP处理分别降低31.4%、30.9%、1.9%;70%CRF+30%N处理在返青期干物质积累量显著低于FFP和OIF处理,移栽-返青期阶段干物质积累量占总积累量比例表现为FFP处理>OIF处理>70%CRF+30%N处理,成熟期OIF处理干物质积累量显著高于70%CRF+30%N和FFP处理,实际产量表现为OIF处理>70%CRF+30%N处理>FFP处理。【结论】适雨灌溉条件下,70%CRF+30%N处理有助于减少稻田氮素流失,OIF处理有助于机插稻干物质积累与产量的增加。