Differential Aerosolization of Algal and Cyanobacterial Particles in the Atmosphere

Aeroalgal sampling at short height (2.5 m) over natural aquatic and terrestrial algal sources revealed that despite of being similar in size (<1 mm), algal groups vary in their atmospheric abundance. Cyanobacteria were the most abundant, while chlorophytes and bacillariophytes though present, but rare. Statistical analysis (Akaike Information Criterion) showed that climatic factors (temperature, relative humidity, rainfall, wind velocity and sunshine hours) acted in concert, and mainly affected the release and subsequent vertical movement (aerosolization) of algae from natural sources. Variation in aerosolization may affect the atmospheric abundance of algae. These findings have important implication as dispersal limitation may influence the biogeography and biodiversity of microbial algae.     

Effects of weather on avian migration at proposed ridgeline wind energy sites

With the popularity of wind energy increasing globally, concerns surfaced in the 1980s as to the potential adverse effects of wind turbines on migrating birds. Understanding how weather conditions influence passage rates can help determine the potential for increased avian–turbine collisions. Using vertical and horizontal mounted marine radars, raptor stand watch observations, and portable handheld weather stations, we studied how temperature, cloud cover, barometric pressure, wind direction, and wind speed affected avian passage rates and height of migrants over 3 ridges (Wartenbe, North Dokie, and South Dokie) being developed for wind energy in northern British Columbia. Using an Akaike's Information Criterion (AIC), we determined that a reduced model combining wind speed, barometric pressure, and cloud cover was best at explaining and predicting higher passage rates (expressed as no. birds/hr) in the fall migration for both diurnal and nocturnal migrants. Wind speed proved the most important predictor of passage rates for spring nocturnal migrants and a combination of cloud cover, temperature, and wind direction for diurnal spring migrants. Wind speed also predicted decreases in flight altitude among nocturnal migrants but increased altitude in diurnal migrants. This information coupled with migration timing and topographical areas of higher migrant activity can be useful to wind energy proponents who wish to mitigate collision risk with migrating birds. © 2011 The Wildlife Society.     

毛竹液流特征及其与环境因子的关系

运用Dynamax液流测量系统监测浙江庙山坞自然保护区毛竹液流的日变化,采用型号为EQ-15的土壤水势仪监测0～100cm土层的土壤水势,利用自动气象站同步监测太阳总辐射、空气温度、空气相对湿度、风速等气象因子。结果表明:晴朗天气条件下毛竹液流的日变化过程呈现单峰曲线,具有显著的昼夜变化规律,且变幅大;阴雨天气时液流日变化过程呈双峰或多峰曲线,而且日均液流速率和日液流量均低于晴朗天气,变化较平缓;不同径阶毛竹液流速率波动规律相同,但径级较大毛竹的日均液流速率和液流量较大一些。当0～100cm土层土壤水势在-13～-10kPa时,毛竹液流速率与土壤水势相关性不显著,但当土壤水势低于-200kPa左右时,液流速率和土壤水势呈正相关,土壤水分含量成为限制液流速率的主要因子之一;相关性分析表明,边材液流速率与空气温度、空气相对湿度、光合有效辐射、总辐射、水蒸气压亏缺呈极显著正相关,与空气相对湿度呈极显著负相关。太阳辐射、气温、空气湿度、风速等环境因子作自变量,以液流速率作因变量,经过逐步回归,建立了液流速率与环境因子的多元线性模型。     

黑河地区绿洲生态条件下麦田生物气象若干特征

观测分析了ＨＥＩＦＥ地区绿洲中麦田的微气候特征,结果表明ＳＰＡＣ中水５势随高度呈显著梯度分布,在土壤－植物以及植物－大气界面,水势值存在两个大的跳跃;水势廓线存在明显的日变化;ＳＰＡＣ各部分水势变化的起伏顺序是大气〉植物〉土壤,说明水势变化受植物水分代谢进程直到气象因子的强烈影响和控制。冠层上方近地面风温湿的时间剖而显示出白天与夜晚相比,大气混合得较好。日出前则大气较为稳定。在典型晴天条件下,麦田     

霍山石斛的光合特性研究

本文研究了霍山3种石斛的光合特性、气孔日变化与生态因子的相关性,研究结果表明,石斛光合作用的净光合速率、光饱和点、光补偿点均低,要求低光强和散射光.相对湿度是影响光合作用和气孔开闭的主要因子.相对湿度降低,净光合速率也降低.白天气温在20℃以下,相对湿度在80%以上时,气孔开闭随光强变化呈单峰曲线;气温在20℃以上,相对湿度达90%以上时,气孔开张度与光强呈强正相关,相对湿度降低到80%以下,气孔开张度与光强无相关性.气孔日变化出现双峰曲线.叶绿素b含量略高,在短波光430nm处吸收峰较高,表现了阴性植物的光合特性.     

西双版纳片断化望天树林气候边缘效应比较研究

对西双版纳片断望天林树（Shorea chinensis)林林缘小气候的季节、水平变化进行了观测研究,对比分析了4个个不小雨林斑块（30hm^2,25hm^2,20hm^2,3hm^2)的小气候边缘效应。结果表明：各雨林斑块林缘均存在明显的小气候边缘效应,其中在干季晴天最为明显,且在上较小斑块林缘出现最高气温及气日较差高于林外的现象;干季,部分林缘小气候要素（最高气温、总辐射、净辐射、最小相对湿度）林缘与林内的差值均是高于或大于雨季的相应值,而地表最高温林缘与林内的差值则是雨季强于干季,各斑块相比,小气候边缘效应波及林内的深度在最大斑块达至最浅（25m),而在最小斑块达到最深（35m)呈现出小气候边缘效应及其影响深度随片继雨林斑块面积减小而增强及向林内进一步延伸的趋势。     

Arabian sandflies (Diptera: Psychodidae) prefer the hottest nights?

Abstract. A vehicle-mounted net was used to collect hourly samples of sandflies on 15 nights during June in northern Oman. Every half hour, the temperature, relative humidity, wind velocity and light intensity were measured (there was no cloud or rainfall during this period).
The sandflies caught were mainly Phlebotomus alexandri and Sergentomyia clydei. Their circadian activity increased rapidly after sunset (18.50 hours). The high level of activity was fairly constant during 9 h of darkness until dawn, when it decreased rapidly. A few flies were still active at 07.00 hours, 1.5 h after sunrise.
A multiple regression showed that the main factor affecting sandfly activity was light intensity. When this factor was removed, by considering only the 135 catches collected during the 9 h of darkness, the second most important factor was low relative humidity, followed by low wind velocity. Temperature was not a significant factor in the analysis, because of its strong negative correlation with humidity. However, when the effect of humidity was removed from the regression, high temperature became significant, but less important than wind.
The regressions showed that, for flight activity, the optimum humidity was around 10%; the probable maximum wind velocity was 3.5 ms^-1 and 11^oC was the probable minimum temperature. Thus, when the 4 nights with highest catches (200–260 flies/night) were compared with the 4 nights with lowest catches (50–120 flies/night), the best nights had a low humidity (10–25%) and low wind speed (<0.3ms-¹) in combination with highest temperatures (31–43^oC).     

镇江内江湿地不同演替阶段植物群落小气候日动态

2005年5月,选择镇江内江湿地具有代表性的裸地、虉草群落和芦苇群落,分别代表植被群落的不同演替阶段,测定不同群落、不同层次的光照强度、气温、土温和空气相对湿度,研究其植物群落小气候的日动态.结果表明,随演替由裸地到虉草群落到芦苇群落进行,群落内光照强度、气温和土壤温度均明显降低,日变幅减小.其中,日均光照强度由1 204.7 μmol·m^-2·s^-1降至141.28 μmol·m^-2·s^-1,日均变幅由1 126μmol·m^-2·s^-1降至265 μmol·m^-2·s^-1;日均气温由32.2 ℃降至24.9 ℃,日均变幅由12.75 ℃降至4.8 ℃;日均土温由21.83 ℃降至19.47 ℃,日均变幅由4.5 ℃降至2.1 ℃.群落内空气相对湿度明显升高(由58.95%增至87.3%）,变幅减小(由29.75%降至5.15%）.生境具有早期的开放性和后期的封闭性,小气候环境朝着更为阴、凉、湿的环境变化,且波动性减弱,稳定性增强.各群落内的光强、气温、湿度及土温之间均存在一定相关,但不同演替阶段各因子间相关程度各异.     

青海高原小麦叶片净光合速率日变化的中午降低现象对环境中生态因素的响应

以土培盆栽和大田栽培小麦（Ｔｒｉｔｉｃｕｍａｅｓｔｉｖｕｍ）为研究材料,探讨了青海高原小麦在正常生长的自然条件下,出现的土壤水分含量（ＳＷＣ）的变化所引起的植物叶片相对含水量（ＲＷＣ）和叶水势（ｗｌ）的变化以及自然强光（ＰＦＤ;Ｑ）导致的高温（Ｔａ）所产生较低的空气相对温度（ＲＨ）对小麦叶片净光合速率（Ｐｎ）日变化的中午降低现象的影响。结果表明,在大田小麦正常生长的自然条件下,当ＳＷＣ等于或低干３０％时,小麦叶片的ＲＷＣ和ｗｌ下降,气孔导度（Ｇｓ）变小,气孔阻力增大,ＣＯ＿２的供给受到了限制,从而也引起了小麦叶肉细胞进行光合作用的能力下降,Ｐｎ日变化就出现了明显的中午降低现象。当ＳＷＣ在８０％左右时,小麦叶片的ＲＷＣ和ｗｌ升高,Ｇｓ增大,气孔阻力变小,ＣＯ＿２供应充分,小麦叶肉细胞进行光合作用的能力增强,Ｐｎ日变化就没有出现中午降低现象（图１）,而青海高原偶然出现的自然强光（ＰＦＤ）导致较高的Ｔａ所产生较低的ＲＨ％和较低的ＳＷＣ一样也是晴天中午,小麦叶片Ｐｎ日变化产生中午降低现象的直接原因。所以说,晴天中午,青海高原大田ＳＷＣ的高低和ＲＨ％的大小是引起小麦叶片Ｐｎ日变化出现中午降低现象轻重与否的主要生态因素     

干旱胁迫下胡杨茎流日变化分析——以塔里木河下游英苏断面为例

用PHYTALK植物生理生态监测系统对塔里木河下游英苏断面胡杨的茎流和相关环境因子的日变化进行了监测.结果表明:在极端干旱区塔里木河下游的胡杨茎流日变化表现多峰值,且夜晚仍保持一定流速;主枝与侧枝茎流日变化趋势相似,主枝流速高于侧枝;侧枝对环境变化响应更加灵敏,波动强烈,主枝相对侧枝,茎流变化响应迟钝且有明显滞后效应;茎流变化受太阳辐射、风速和大气温度影响明显,而其它环境因子如空气湿度、土壤湿度等影响则不大,气温与叶温表现出极佳相关性,气温与空气湿度呈显著负相关;同时,日变化中,不同时段起主导作用的因子不尽相同.     

美国黑核桃实生苗生态生理过程对环境因素响应的数值模拟(Ⅱ):气象要素日变化进程的数理模型

在建立植物生态生理模型（如光合作用、蒸腾作用数理模型）的过程中,气温、太阳辐射、相对湿度等气象要素的日变化及瞬时资料是必不可少的．本文根据常规台站的日常观测资料,建立了气温、太阳辐射、风速、相对湿度等气象要素日变化的数理模型．并应用实测资料对所建模型进行了验证．实践表明：（1）描述气温日变化的正弦一指数模型通常其模拟结果不甚理想,但通过引用最高温度的时间延迟参数及惯性系数,可增加模拟结果的准确性．（2）根据测量的太阳辐射日总量值以及太阳高度的日变化值等,可准确地模拟太阳辐射的日变化;（3）根据实际水汽压的日均值和气温常规资料可准确模拟相对湿度的日变化．如果区域参数已知或被正确估计。上述方法可得到较为理想的气象要素日变化的模拟结果．     

西双版纳望天树林林窗小气候特征研究

 对西双版纳望天树林林窗小气候要素的季节变化、水平差异进行了观测研究,并对比分析了两个大小不同林窗内温度垂直分布状况、相对湿度差别。结果表明：大林窗内温度、湿度、光照的日变化均比林内大;大林窗中央光照强度为林内的10倍以上,太阳总辐射量、净辐射量为林内的5倍以上,大林窗中央的蒸发耗热量大于林内,且均占各自净辐射的较大比例(70％～80％),干季大林窗内温度、湿度日变化比雨季剧烈,大林窗内具有两个加热层(幼苗冠层、地表),小林窗仅有一个加热层(幼树冠层),且前者的加热强度大于后者,相对湿度日变化则是大林窗内较剧烈。     

Correlations between weather conditions and airborne pollen concentration and diversity in a Mediterranean high-altitude site disclose unexpected temporal patterns

Relationships between meteorological factors and airborne pollen concentrations at high altitudes are virtually unknown. We used cross-correlation analyses to test the relationships between daily variation in meteorological factors (i.e. temperature, humidity and wind speed) and airborne pollen concentration, diversity (number of families and Shannon and Simpson diversity indices) and evenness (Pielou index) in an Apennine high-altitude site (Gran Sasso Massif, 2117 m elevation). In contrast to patterns observed at low altitudes, the temperature had a negative correlation with pollen abundance and diversity, whereas humidity had a positive correlation. The unexpected negative correlations with temperature can be explained with the particular position of our sampling site. Wind speed was positively correlated with pollen diversity and abundance in the short term, which can be explained by the fact that higher wind speed promotes both primary emission of pollen from the anthers and subsequent re-suspension. Evenness and wind speed were negatively correlated in the short term because of the different response of different species to meteorological conditions. In the longer term, the average concentrations of the various taxa tend to reach similar values, leading to increased values of diversity. Our finding of a decrease in pollen emission with increasing temperature has important implications for the study of the impacts of global change on high-altitude plant communities. We also detected a high abundance of Cupressaceae/Taxaceae pollen, a reflection of the expansion of thermophilic species, such as Juniperus, due to climate change.     

A Meta-analysis of Climatic and Chemical Controls on Leaf Litter Decay Rates in Tropical Forests

Although tropical forests occupy a small fraction of the earth’s total land area, they play a disproportionately large role in regulating the global carbon cycle. Yet controls on both primary productivity and decomposition in tropical forests are not well-studied in comparison with temperate forests and grasslands, despite their extreme biogeochemical heterogeneity. To evaluate the relative importance of climate and foliar chemical variables in driving decomposition in tropical forests, I performed a meta-analysis of reported leaf litter decay rates throughout tropical forest ecosystems. Using a model selection procedure based on Akaike’s Information Criterion, I found that temperature and precipitation played little direct role in regulating decomposition rates, except in montane forests where cool temperatures slowed decay. Foliar concentrations of calcium, magnesium, nitrogen, phosphorus, and potassium were important predictors of mass loss rates, although each of these factors explained a very small amount of variance when considered in isolation. The large amount of unexplained variation in decomposition rates observed both within and across tropical forest sites may be due to other factors not explored here, such as soil biota or complex plant secondary chemistry. Carbon cycling in tropical forests seems to be modulated by the availability of multiple nutrients, underscoring the need for additional manipulative experiments to explore patterns of belowground nutrient limitation across the biome. Because models of decomposition developed in temperate ecosystems do not appear to be generalizable to wet tropical forests, new biogeochemical paradigms should be developed to accommodate their unique combination of climatic, edaphic, and biotic factors.     

Effect of weather conditions on the flight activity of Nigerian blackflies (Diptera: Simuliidae)

Abstract. A vehicle-mounted net was used to make hourly catches of blackflies at 700–1000 m altitude in the River Assob valley, central Nigeria, on 20 days during the dry season. Pearson Correlation Matrix analysis of the collection data and meteorology showed that the main factors affecting flight activity of each of the four most abundant blackfly species were primarily light intensity and secondly wind velocity, whereas relative humidity was the least important factor. Right activity showed a negative linear regression against wind, with some activity occurring in wind speeds up to 15 km/h. Distance-weighted least-squares (DWLS) regressions showed little correlation of temperature with activity for Simulium hargreavesi and S.adersi , but S.squamosum and S.vorax had small peaks at 28C and 31C, respectively. DWLS regression against light intensity showed an activity peak at 6000 lux, except in Simulium adersi.     

不同灌溉量对塔克拉玛干沙漠腹地梭梭水分生理特性的影响

利用热平衡式茎流计和压力室,对不同灌溉量下塔克拉玛干沙漠腹地防护林植物梭梭的水分生理特性进行了测定.结果表明：梭梭茎干液流的日变化曲线随着灌溉量的不同而有所差异,灌溉量为每次每株35和24.5 kg条件下,茎干液流日变化曲线呈单峰型,且变幅较大,灌溉量为每次每株14 kg条件下,其日变化曲线为双峰型,变化较平缓;随着灌溉量的减少,梭梭日平均液流速率逐渐降低,其日单株耗水量也随之降低;随着灌溉量的减少,梭梭的清晨水势和午后水势逐渐降低, 且茎干液流速率与总辐射、空气温度、相对湿度和风速的相关性均增强,但不同灌溉量下,其与总辐射的相关性都最强.     

土地利用方式对喀斯特地区环境小气候日动态的影响

2007年6月,通过典型样地观测,研究了广西凌云县典型喀斯特地区5种不同土地利用方式下光照强度、气温、空气相对湿度、土壤温度、表层（0～5 cm土层）土壤含水量的日动态.结果表明：不同土地利用方式改变了地上植被的组成、覆盖度和高度,进而改变了环境小气候,研究区不同土地利用方式的小气候质量依次为林地＞灌林＞草地＞农耕地＞石漠化裸地; 石漠化裸地光照强度较强、气温和土壤温度较高、空气相对湿度和土壤含水量较低,且各因子的变幅均较大,样地环境趋于干热化;与石漠化裸地相比,林地、灌林地、草地和农耕地内的光照强度分别下降96.4%、52.0%、17.0%和44.2%,气温分别下降30.1%、20.2%、12.7%和17.8%,空气相对湿度分别提高129.2%、57.2%、18.0%和41.2%,土壤温度分别下降11.5%、8%、2.5%和5.5%,表层土壤含水量分别提高42.6%、33.2%、15.7%和14.0%,林地与灌林地各因子的变幅相对趋缓,样地环境趋于凉湿化.各样地光照强度、气温和土壤温度之间呈正相关,三者均与空气相对湿度、土壤含水量呈负相关,空气相对湿度与表层土壤含水量呈正相关.     

油松人工林SPAC水势梯度时空变化规律及其对边材液流传输的影响

 利用热扩散式边材液流茎流探针（TDP）和微型自动气象站组成的测定系统于2001年4月在北京林业大学妙峰山教学实验林场（39°54′N,116°28′E）对低山油松（Pinus tabulaeformis）人工林土壤-植物-大气体（SPAC）界面水势梯度及油松木质部边材液流传输速率的时空变化规律及其相关因子进行了连续测定。土壤水势随深度下降逐渐升高,日周期波动幅度减小,灌水后上层土壤水势迅速提高,但随着水分扩散和林地持续蒸散,土壤湿度迅速下降并逐渐与对照趋同;叶片水势连日逐渐降低,灌水后水势较对照有一定程度提高;林冠不同层次叶片水势在日周期内不同时间差异显著,但同一层次之间差异不明显;油松人工林土壤、叶片、大气水势梯度比约为1∶5∶30,灌水后SPAC相临界面水势差增大,水势梯度提高至1∶15∶90。大气水分饱和亏缺与土壤水势和叶片水势、以及土壤水势与叶片水势之间均有极显著相关性。干旱春季灌溉对油松木质部边材液流时空波动产生很大影响,灌水后连日树干上位边材液流峰值出现时间推迟1 h,连日平均液流速率提高48.59%,连日平均最大液流速率提高25.12%。木质部边材液流速率日变化和连日变化与SPAC水势和气象因子如空气相对湿度、空气温度、太阳辐射强度密切相关。与对照相比,灌水后边材液流速率与SPAC各介质水势和界面水势差的相关性下降。     

红松阔叶混交林不同大小林隙小气候特征

利用HOBO自动气象站对小兴安岭红松阔叶混交林不同大小林隙、郁闭林分和空旷地的小气候因子进行了为期一个生长季的测定.结果表明：红松阔叶混交林林隙与对照样地的光照、地面温度和气温的日变化及其在生长季的变化趋势均呈单峰型曲线.林隙和对照样地空气相对湿度的日变化均为早晨和傍晚较高,正午较低,呈高-低-高的变化趋势;生长季内呈单峰型曲线,其中郁闭林分相对湿度最大,其次为小、中、大3个林隙,空旷地最小.林隙和对照样地降水量及降雨次数随林冠层郁闭程度的增加呈递减趋势,大林隙降雨量约为小林隙的1.4倍.在生长季内,空旷地、大、中和小林隙以及郁闭林分最大风速分别为3.34、2.97、2.87、2.41和1.84 m·s^-1.     

Wind as an abiotic factor of Colorado potato beetle (Coleoptera: Chrysomelidae) flight take-off activity under field conditions

The flight take-off activity of Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), was significantly higher at a landscape-protected than at semiexposed and exposed sites in a 2-yr field study. In both years, mean daylight temperature, solar radiation, and relative humidity were generally similar at all sites, but wind speed was lower at the protected site than at the exposed sites. Results suggest that wind was the limiting abiotic factor for flight take-off at the exposed site. Caged beetles exposed to constant wind speeds of 3.4, 4.7, and 7.0 m/s showed a significant corresponding decrease in number of flight take-off. There was no cumulative effect of wind exposure on the readiness of the beetles to fly, suggesting that wind acts as a physical barrier to flight take-off. It should be possible to reduce Colorado potato beetle flight dispersal by selecting fields most exposed to wind over landscape-protected fields when rotating potato, Solanum tuberosum L., crops.