宽幅带播对冬小麦冠层微环境及水分利用效率的影响

以大面积推广的多穗型品种矮抗58为供试材料,在大田条件下研究宽幅带播（幅宽8 cm）种植模式下不同带间距7 cm(KF7)、12 cm(KF12)和17 cm(KF17)对冬小麦冠层光截获、冠层温度、湿度、水分利用效率以及产量的影响。结果表明,与常规条播相比,宽幅带播群体光截获量、相对湿度和水分利用效率较高,而冠层温度较低,水分利用效率提高2.69%～13.72%,穗数增加13.82%～17.33%,产量提高3.12%～15.39%。宽幅带播下带间距增大,冠层光截获量以及湿度降低,而冠层温度则升高;宽幅带播随带间距增加,成穗数减少。在本试验条件下,KF12处理的小麦冠层结构合理,光能截获充分,冠层微环境适宜,水分利用效率最高,产量因素最为协调。     

Effect of abiotic factors on understory community structures in moist deciduous forests of northern India

Understory vegetation controls, in a significant way, the regeneration of overstory trees, carbon sequestration and nutrient retention in tropical forests. Development and organization of understory vegetation depend 3n climate, edaphic and biotic factors which are not well correlated with plant community structures. This study aimed to ~xplore the relationships between understory vegetation and abiotic factors in natural and planted forest ecosystems. A non-metric multidimensional scaling （NMS） ordination technique was applied to represent forest understory vegetation among five forest communities, i.e., a dry miscellaneous forest （DMF）, a sal mixed forest （SMF）, a teak plantation （TP）, a low-land miscellaneous forest （LMF） and a savanna area （SAV） of the Katerniaghat Wildlife Sanctuary, located in northern India. Microclimatic variables, such as photosynthetically active radiation （PAR）, air temperature （AT）, soil Lemperature （ST）, ambient atmospheric CO2 concentration, absolute air humidity （AH）, physical and chemical soil ~roperties as well as biological properties were measured. Understory species were assessed via 100 random quadrats （5 m x 5 m） in each of the five forests in which a total of 75 species were recorded encompassing 67 genera from 37 families, consisting of 32 shrubs and 43 plant saplings. DMF was the most dense forest with 34,068 understory individuals per ha of different species, whereas the lowest understory population （13,900 per ha） was observed in the savanna. Ordination and correlation revealed that microclimate factors are most important in their effect compared to ~daphic factors, on the development of understory vegetation in the various forest communities in the north of India.     

桉树人工林不同林冠高度小气候特征研究

对比分析了桉树人工林内不同高度位置的大气温度、空气湿度、水汽压、风速的变化特征,结果表明:林冠层以下日平均气温存在随高度增加而增加的辐射逆温现象;与林冠上方相比,空气相对湿度日均值雨季前(2—4月)较小,雨季(5月)以后较大,但变化幅度均较小;林冠层以下水汽压日均值较林冠上方大但变动幅度相对较小;林冠下风速明显小于林冠层以上风速,且林冠下风速层差异微小,风速相对林冠层以上较稳定,对风力有显著的削弱作用。     

种植密度与施氮量对烟田小气候及烟株光合特性的影响

探讨了烤烟种植密度(19 500、18 000、16 500株/hm~2)与施氮水平(105.0、127.5 kg/hm~2)对烟田小气候以及烟株光合作用的影响。结果表明:烟株叶面温度较田间垄间温度平均高2.50℃,二者呈正相关关系(r=0.800),受种植密度影响较大;施氮量为127.5kg/hm~2时,种植密度每增加1500株/hm~2,烟株下、中、上部垄间温度分别降低1.35、1.65和1.95℃,叶面温度分别下降1.80、1.55和1.40℃;种植密度与施氮量对垄间相对湿度的影响存在负的显著交互效应,效应值为–0.538;种植密度影响烟株中下部有效光合辐射,高种植密度下增施氮肥,导致中下部叶片有效光合辐射分别减少39.46%和56.98%;种植密度与施氮量显著影响烟株光合速率、胞间CO_2浓度,并存在交互效应,但不影响叶片气孔导度与烟株蒸腾速率,减小种植密度,增施氮肥,可提高烟株光合速率,种植密度16 500株/hm~2、施氮127.5 kg/hm~2处理各部位烟叶平均光合速率较种植密度19 500株/hm~2、施氮105.0kg/hm~2高23.09%;施氮量是影响胞间CO_2浓度的主要因素,且存在部位差异。回归分析表明,叶片气孔导度、胞间CO_2浓度和叶片蒸腾速率显著影响烟叶光合速率,有效光合辐射与垄间温度、叶面温度、田间相对湿度呈显著正相关,叶面温度与烟叶的蒸腾速率呈显著正相关,垄间相对湿度与叶片胞间CO_2浓度呈显著负相关。种植密度与氮肥施用,通过影响烟田垄间温度、叶面温度、田间相对湿度等烟田小气候,改变了烟株蒸腾速率,进而影响叶片胞间CO_2浓度,最终影响其光合速率。     

几种行道树对惠州市城市道路微气候的影响

行道树是城市道路绿化的骨干树种,对道路景观有着统领的作用,对改善环境生态有积极作用。为了弄清岭南城市主要行道树对城市道路的微气候影响,以惠州市为例,对惠州主要道路的9个常见行道树种进行了遮荫效果调查。结果表明:所有行道树都具有一定的遮光率和降温率,遮光效果较好的树种是白兰,其遮光率达95.81%,较差的是王棕和长芒杜英,遮光率为61%~63%,其它树种介于两者之间。降温率最高的树种是榕树,其降温率达9.83%,温度可下降3.5℃,降温较差的是长芒杜英,其降温率为1.5%,温度仅下降0.5℃。综合荫质与遮荫效果,遮荫效果较好的树种是榕树,较差的是王棕与长芒杜英,而白兰、海南红豆、非洲楝、高山榕、黄葛树亦具有较好的遮荫效果。今后选择岭南城市的行道树在注重遮荫功能时可优先选择榕树、白兰、海南红豆、非洲楝、高山榕、黄葛树,注重景观特色而对遮荫要求不高时可选王棕与长芒杜英。     

基于切换字典的林区小气候监测数据压缩感知方法

为降低林区小气候监测站的数据传输功耗,提出了一种切换字典的数据压缩感知方法,在对样本数据进行特征表征与分类的基础上,合理切换使用离散傅里叶变换基（Discrete Fourier transform,DFT）固定字典或K-SVD（K-singular value decomposition）学习字典,对样本数据进行稀疏表达。采用高斯函数对样本数据进行拟合,以拟合决定系数R2和拟合均方根误差（RMSE）为切换因子,定义了字典的切换策略。选用空气温度、空气湿度、土壤温度、土壤湿度作为测试对象,实验验证切换策略的可行性。实验表明,在林区小气候监测站中,当稀疏度和压缩率均相同时,结合DFT和K-SVD两种字典的优势,基于切换字典的数据压缩感知算法比单一字典具有更小的重构误差。经功耗测试实验,当稀疏度K=16时,采用切换字典的数据压缩感知算法,使监测站的平均每日电能消耗降低了16.35%,保证了林区小气候监测站的低功耗运行和数据可靠传输。     

水层对稻田小气候影响及水稻高温防御

高温热害是影响水稻产量与品质的主要气象灾害,科学防御高温对保障水稻安全生产具有重要意义。对稻田、湖泊水体小气候水温、气温进行试验观测,并与临近的气象台站观测数据同步对比分析。结果表明：三叶期、分蘖期稻田日最高水温较稻田气温高2~3℃,抽穗期则相反。稻田日最高气温与大气日最高气温之差、稻田日平均温度与大气日平均温度之差与日照时数均呈显著的负相关关系;纯水面日最高气温与大气日最高气温之差、日平均温度与大气日平均温度之差与日照时数呈显著的正相关;稻田和水面的日最低气温与大气的日最低气温差均与日照呈正相关;显示稻田通过叶片对太阳反射以及增加蒸散发有一定的自我缓解高温、调节小气候的能力。高温期间,稻田浅水灌溉即可,无需昼灌夜排。     

Canopy level fog occurrence in a tropical lowland forest of French Guiana as a prerequisite for high epiphyte diversity

Fog frequency and the meteorological processes leading to fog formation have never been studied in depth in tropical lowland forest areas. This study provides detailed evidence of frequent fog occurrence in lowland valleys of central French Guiana. Fog frequency showed a clear diurnal course, with a maximum before sunrise; average fog duration was 4.6 h. The diurnal course of visibility was positively correlated with the diurnal course of humidity in the above-canopy air. Fog persistence correlated significantly with atmospheric parameters during the dry season, but not during the rainy season. The main trigger of fog development in the lowland forest seemed to be precipitation, leading to higher soil moisture, greater evapotranspiration and, thus, higher water content of air. An increasing temperature difference between valley and hill sites after sunset, together with more frequent down-slope winds during nights with long fog periods, points at some influence of katabatic flows. The frequent occurrence of fog in the valleys correlated with significantly higher epiphyte diversities in valley forests as compared to hill forests, and supported the occurrence of the hitherto undescribed, epiphyte-rich “tropical lowland cloud forest” (LCF) in the valleys. The higher epiphyte diversity in LCF coincided with significantly higher relative air humidity in LCF than in hill forest. The ecological benefits of fog for the epiphytes in LCF are surplus of moisture and delayed onset of the stress period, particularly in the dry season.     

风沙沿线新灌区农田防护林体系小气候效益观测分析

通过对景电灌区农田林网内、灌区边缘农田与沙地交接过渡带和灌区外围沙地小气候的定点观测,结果表明,农田防护林体系能有效地防风阻沙,春季增温,夏季降温,增加空气湿度,明显地改善灌区小气候,创造有利于农作物生长的环境,确保景电灌区农业稳产和社会经济的可持续发展。     

河南安阳蜡梅园蜡梅开花状况调查及建议

对安阳蜡梅园中的蜡梅进行了为期3年的开花状况的观察与记录,总结了安阳蜡梅园小气候条件下的蜡梅开花状况,并在此基础上针对安阳蜡梅园中蜡梅栽培过程中出现的问题,提出了建议,以期更好地指导安阳蜡梅园的生产与经营。