北京秋季不同树种吸附PM_(2.5)研究

在南海子公园、北京植物园、西山森林公园和松山自然保护区四个园林绿化区内以油松、白皮松、国槐、柳树和杨树等常见典型绿化树种为研究对象,于秋季采集各树种叶片,应用气溶胶再发生器获得不同树种叶片表面PM_(2.5)吸附量,并用电镜扫描叶表面特征。结果表明:南海子公园和松山自然保护区中均是桧柏和白皮松的吸附量最大,分别为0.26±0.003 8、0.18±0.022 7μg/cm~2和0.252±0.228 1、0.162±0.016 7μg/cm~2,北京植物园中则是以油松(0.33±0.122μg/cm~2)和雪松(0.43±0.099μg/cm~2)最为突出,而西山森林公园中油松吸附量明显高于其它树种同一树种,其吸附量为1.078±0393 4μg/cm~2,是最小值(五角枫)的9.6倍,说明不同树种在相同地点对PM_(2.5)的吸附量基本表现为针叶树种高于阔叶树,且针叶树种间吸附量差异较阔叶树种间差异显著;不同地点PM_(2.5)的吸附量,基本表现为西山森林公园北京植物园南海子公园松山自然保护区,树种吸附量与大气颗粒物浓度均呈正相关性,其中柳树、杨树(P0.05)和油松(P0.01)叶表面PM_(2.5)吸附量与大气颗粒物浓度成呈显著正相关,即在一定范围内,树种叶片PM_(2.5)吸附量随空气污染的加重而增加。     

重庆市主城区常见乔木树种叶片滞纳空气颗粒物功能研究

为了探求重庆市常见乔木树种滞纳空气颗粒物功能,利用空气气溶胶再发生器测定了11种乔木树种单位面积叶片对TSP、PM10和PM2.5的滞纳量。结果表明:11种乔木树种叶片滞纳TSP和PM10的能力都存在显著差异,二球悬铃木、红叶李对TSP和PM10的滞纳能力排在一二名,11种乔木对PM2.5滞纳水平较低,滞纳能力大小不明显;同一树种滞纳TSP量和PM10量在不同地区的大小排序都与环境空气质量呈正相关关系,而PM2.5无此规律;叶片细颗粒物附着量占比很低。     

保定市常见城市绿化树种对PM2.5滞纳能力的研究

为了探究绿化树种对改善城市污染的影响,选取保定市11种常见城市绿化树种,对其滞纳PM2.5能力进行了探讨。利用冠层分析仪(LAI-2000)、叶面积扫描仪和气溶胶再发生器(QRJZFSQ—I)测定各树种的叶面积指数、单位叶面积PM2.5滞纳量,并计算单位绿地面积PM2.5滞纳量,结果表明:叶面积指数、单位叶面积PM2.5滞纳量、单位绿地面积PM2.5滞纳量3个指标,都是针叶树大于阔叶树,说明针叶树对PM2.5的滞纳能力高于阔叶树;针叶树、阔叶树叶面积指数范围分别为2.172 1~3.026 3、0.873 8~2.120 5,单位叶面积PM2.5滞纳量范围分别为0.53~1.39mg/m~2、0.11~0.34mg/m~2,单位绿地面积PM2.5滞纳量范围分别为1.151 2~4.206 6mg/m~2、0.108 8~0.622 8mg/m~2。     

北京主要绿化树种叶表面微形态与PM2.5吸滞能力

以北京大兴21个绿化树种为研究对象,应用气溶胶再发生器对植物叶片在自然状态和饱和状态下PM2.5吸滞量进行定量分析,并应用原子力显微镜(AFM)对其中8个最常见的树种叶表面微形态特征进行观察,测定叶表面粗糙度等参数,阐释植物叶片吸附PM2.5机制。结果表明:21个树种自然状态下单位面积PM2.5吸滞量不尽相同,整体表现为针叶树种显著高于阔叶乔木和灌木树种,其中桧柏、白皮松较大,黄栌、紫薇吸滞量较小;饱和状态下,PM2.5吸滞量显著增加,但其吸滞能力排序与自然状态下基本保持一致。植物叶表面存在褶皱、沟槽,粗糙度相对较高的树种,PM2.5吸滞能力强;叶表面相对光滑,突起部位轮廓较平缓,粗糙度小的树种,其吸滞PM2.5能力相对较弱;不同树种粗糙度大小与其吸滞PM2.5能力排序基本一致,呈显著指数正相关(R2=0.707)。本研究为合理选择滞尘能力强的绿化树种提供理论依据,从而提高城市植被净化空气环境的效率。     

植物叶片表面特征对吸附PM_(2.5)能力的影响研究

以南京市6种常见绿化植物为对象,通过测定叶片对PM_(2.5)吸附量和观测叶表面超微结构,探讨了叶片表面特征对吸附PM_(2.5)功能的影响。结果表明:6种植物中,雪松叶片单位面积吸附PM_(2.5)的量最大,为10.21μg/cm~2,其次为龙柏、悬铃木、广玉兰和桂花,海桐吸附值最小,为1.79μg/cm~2。超微电镜观测结果显示,雪松的气孔最大,海桐的气孔最小,法桐表面粗糙有绒毛,广玉兰的表面光滑。由此可见,叶表面气孔大小、是否有蜡质层是影响叶片吸附PM_(2.5)的重要因素。     

贵阳市主要绿化树种叶面吸滞颗粒物特征及其时空变化

【目的】分析贵阳市不同树种的单位叶面积颗粒物吸滞量差异及其时空变化,以期为合理选择高效滞尘绿化树种提供依据。【方法】以14个常见园林树种为研究对象,以贵阳市城市广场、城市公园、城郊绿地和城郊森林4个不同污染背景地点为采样点。在每个采样点各个树种分别选择3株样树(除部分树种在某个采样点无分布外),定期在4个样点同步采集叶样。采用基于风蚀原理的气溶胶再悬浮方法,测定单位叶面积的颗粒物吸滞量(M)。采集叶片,电子扫描显微镜拍摄叶面显微结构影像,利用图像分析软件量化分析叶面气孔、表皮毛、叶面粗糙程度、蜡质覆盖程度等形态结构特征因子。利用通径分析方法分析叶面形态结构特征因子对叶面颗粒物吸滞量的影响程度。【结果】所测乔木和灌木2种生活型间的吸滞量无明显差异;树种间的叶面悬浮总颗粒物(TSP)吸滞量(MTSP)差异显著,各树种M_(TSP)为1.56～11.14μg·cm~(-2),红花檵木最高,雪松较高,桂花、杜鹃、琴丝竹、女贞和白玉兰居中,香樟、红叶石楠、迎春花、樱花、杨梅、栾树和银杏较弱;通径分析表明,叶面粗糙度、表皮毛密度和长度对叶面TSP吸滞量的影响大于其他叶面微形态因子,具有较多和较长表皮毛且相对粗糙的叶面具有较大吸滞量;叶面吸滞的大颗粒(PM_(10～100))和粗颗粒(PM_(2.5～10))质量百分比(97.36%)高于背景空气(80.29%),这说明叶面趋向吸滞较大粒径颗粒物(PM_(10～100)和PM_(2.5～10)),而对细颗粒(PM_(1.0～2.5))和超细颗粒(PM1)吸滞能力较弱;多数树种冬、春季M值大于夏、秋季;同一树种M值表现为市区采样点高于郊区采样点;同在市区时,树木聚集生长的城市公园采样点高于树木散生的城市广场采样点,呈现出"集聚效应"。【结论】树种间的叶面TSP吸滞量差异显著;影响叶面TSP吸滞量的最主要形态结构因子是叶面粗糙度和表皮毛密度;叶面对大颗粒和粗颗粒的吸滞量高于细颗粒和超细颗粒,高污染地点的单位叶面积吸滞量大于低污染地点。以树木叶面形态结构因子为评价指标,可筛选滞尘能力强的树种。14种参试树种中红花檵木、雪松和桂花的叶面颗粒物吸滞量远大于其余树种,可用于缓解大气颗粒物污染。     

柏木叶片滞尘量及叶面微形态解释初步研究

以柏木叶片为研究对象,定量测量叶片单位叶表面滞尘能力,采用扫描电镜分析叶表面微观结构。结果表明:(1)同一生境下的柏木叶片单位叶面积的TSP、PM_(10)、PM_(2.5)的累积滞尘量均以春季最高,秋季最低;叶片单位叶面积的TSP、PM_(10)、PM_(2.5)的滞尘速率均以春季最高,秋季最低;整体表现为春夏季高于秋冬季。(2)同一季节不同生境的叶片TSP、PM_(10)累计滞尘量表现为春季、夏季、冬季林中木孤立木,而在秋季则表现为孤立木林中木;而叶片PM_(2.5)累计滞尘量则表现为春季、秋季、冬季均林中木孤立木,而在夏季则表现为孤立木与林中木大小相等。为此,初步认为通过群植、丛植营造的森林环境,其优势树种植物叶片对大气的滞尘效应更为明显;(3)以冬季孤立木为例,随着雨后间隔时间增加,叶片的TSP、PM_(10)累计滞尘量逐渐增加,滞尘速率则表现出先减小后增大趋势;而叶片PM_(2.5)累计滞尘量、滞尘速率则均表现出逐渐增大趋势。     

城市森林三维绿量对空气微生物、颗粒物浓度的影响

通过对北京市14个研究区的单位占地面积树木绿量、空气颗粒物以及空气微生物浓度的测定,初步得出某一区域单位面积绿量与TSP、PM10、空气微生物浓度呈现显著负相关关系,单位面积绿量越高,TSP、PM10以及空气微生物浓度越低。TSP、PM10作为北京市空气质量的重要制约因子,使其不超标的最小单位面积绿量应达到每平方米3.87m3。鉴于以上结论,北京市应该在有限的绿化用地上尽量种植具有空间竞争力的,能够在将来形成巨大绿量的高大乔木树种,这样才能有效改善北京市的空气质量。     

城市绿化树种叶表面PM2.5滞纳量及其影响因素研究进展

细颗粒物(PM2.5)严重影响人类健康状况,森林植被可以通过叶表面吸附PM2.5等颗粒物,从而降低PM2.5浓度,充分起到净化环境的作用。文章从植被滞纳PM2.5过程、测定方法、影响因素和负离子以及降雨关系等方面进行系统总结。目前有关植被调控PM2.5的机制研究还比较缺乏,今后应加强空气负离子与空气颗粒物关系的研究,研究不同污染程度下植物对PM2.5影响的关键因素和降雨天气下植物叶面吸附PM2.5动态和影响因素,找出不同树种受降雨的消减量和差异的影响因素,从而为减轻城市大气PM2.5提供理论依据。     

聊城市徒骇河风景区常绿植物对大气颗粒物削减作用

文章以聊城市徒骇河风景区10种常绿植物群落为研究对象,测定植物群落内的大气颗粒物浓度和叶面积指数、叶表特征等指标,结果表明,10种群落对3种粒径大气颗粒物的吸附作用存在较大差异。刚竹、圆柏对PM2.5和PM10的吸附作用较强,而白皮松、红叶石楠对PM2.5和PM10的吸附作用则较弱;圆柏、广玉兰对TSP吸附作用较强,大叶女贞、红叶石楠对TSP的吸附作用则较弱;叶面积指数和叶表特征对植物群落吸附不同粒径大气颗粒物具有一定的影响。通过观测冬季不同常绿植物群落对不同粒径大气颗粒物的削减作用,以及叶表面特征和群落冠层对其影响,为大气颗粒物污染的治理在植物选择上提供参考。     

城市森林净化大气颗粒物污染作用研究进展

粉尘颗粒物污染,尤其是PM2.5污染,是我国大气污染的主要问题.城市森林和绿地是城市生态系统中具有自净功能的重要组成部分,利用城市森林和绿地治理大气颗粒物污染受到越来越多的关注,并具有良好的应用前景.文章概述我国粉尘颗粒物污染状况,并总结了植物净化大气污染研究概况,从4个角度总结目前城市森林与PM2.5的关系研究,包括森林对颗粒物吸附机制、PM2.5对植物的危害影响、不同尺度下植被移除PM2.5的效果比较以及影响吸附过程的其他因素,提出了今后研究的可能发展方向,包括扩大研究树种的范围、针对研究不同树种特异性吸附偏好及加强各尺度研究的结合等,以更有效地应用城市森林进行大气污染修复.     

Interactive effects of nitrogen and water availabilities on gas exchange and whole-plant carbon allocation in poplar

Cuttings of balsam spire hybrid poplar (Populus trichocarpa var. Hastata Henry x Populus balsamifera var. Michauxii (Dode) Farwell) were grown in sand culture and irrigated every 2 (W) or 10 (w) days with a solution containing either 3.0 (N) or 0.5 (n) mol nitrogen m(-3) for 90 days. Trees in the WN (control) and wn treatments had stable leaf nitrogen concentrations averaging 19.4 and 8.4 mg g(-1), respectively, over the course of the experiment. Trees in the Wn and wN treatments had a similar leaf nitrogen concentration, which increased from 12.0 to 15.8 mg g(-1) during the experiment. By the final harvest, mean stomatal conductances of trees in the wN and wn treatments were less than those of trees in the Wn and WN treatments (1.8 versus 4.6 mm s(-1)). Compared to the WN treatment, biomass at the final harvest was reduced by 61, 72 and 75% in the Wn, wN and wn treatments, respectively. At the final harvest, WN trees had a mean total leaf area of 4750 +/- 380 cm(2) tree(-1) and carried 164 +/- 8 leaves tree(-1) with a specific leaf area of 181 +/- 16 cm(2) g(-1), whereas Wn trees had a smaller mean total leaf area (1310 +/- 30 cm(2) tree(-1)), because of the production of fewer leaves (41 +/- 6) with a smaller specific leaf area (154 +/- 2 cm(2) g(-1)). A greater proportion of biomass was allocated to roots in Wn trees than in WN trees, but component nitrogen concentrations adjusted such that there was no Wn treatment effect on nitrogen allocation. Compared with WN trees, rates of photosynthesis and respiration per unit weight of tissue of Wn trees decreased by 28 and 31%, respectively, but the rate of photosynthesis per unit leaf nitrogen remained unaltered. The wN and Wn trees had similar leaf nitrogen concentrations; however, compared with the Wn treatment, the wN treatment decreased mean total leaf area (750 +/- 50 cm(2) tree(-1)), number of leaves per tree (29 +/- 2) and specific leaf area (140 +/- 6 cm(2) g(-1)), but increased the allocation of biomass and nitrogen to roots. Net photosynthetic rate per unit leaf nitrogen was 45% lower in the wN treatment than in the other treatments. Rates of net photosynthesis and respiration per unit weight of tissue were 48 and 33% less, respectively, in wN trees than in Wn trees.     

植物叶面吸附与吸收PM2.5等颗粒物中重金属研究进展

大气中的重金属主要以PM_2.5等颗粒物为载体在大气中悬浮和扩散，植物叶表面复杂的微观形态结构可以吸附PM_2.5等颗粒物，对消减近地表的大气重金属发挥着重要作用。文中对植物叶片吸附与吸收PM_2.5等颗粒物中重金属的能力和影响因素等进行综述，并针对目前研究的不足提出展望:1）深入探讨大气颗粒物中重金属的化学形态与其在大气—植物系统中的化学行为关系，进一步阐述植物叶面吸附和吸收重金属的相关机理；2）大气颗粒物粒径越小，附着的重金属含量越高，但关于亚微米级颗粒物（PM₁）的研究十分有限，进一步探究植物叶面对亚微米级颗粒物中重金属的吸附和吸收有助于筛选更高效的城市绿化树种；3）需要从角质层厚度、结构组成等角度深入探讨角质层吸附和吸收大气重金属的差异，为实现大气重金属污染治理的精准化和专业化提供科学依据。     

Canopy dynamics and aboveground production of five tree species with different leaf longevities

Canopy dynamics and aboveground net primary production (ANPP) were studied in replicated monospecific and dual-species plantations comprised of species with different leaf longevities. In the monospecific plantations, leaf longevity averaged 5, 6, 36, 46 and 66 months for Quercus rubra L., Larix decidua Miller, Pinus strobus L., Pinus resinosa Ait. and Picea abies (L.) Karst., respectively. Specific leaf area, maximum net photosynthesis per unit mass (A/mass), leaf N per unit mass (N(leaf)/mass) and maximum net photosynthesis on a leaf N basis (A/N(leaf)) were inversely correlated to leaf longevity (r(2) = 0.92-0.97, 0.91, 0.88 and 0.80, respectively). Maximum net photosynthesis per unit area (A/area) was not correlated to leaf longevity, whereas leaf N per unit area (N(leaf)/area) was positively correlated to leaf longevity (r(2) = 0.95). For a similar-diameter conifer, species with long-lived foliage supported a greater foliage mass than species with short-lived foliage; however, Quercus rubra did not follow this pattern. At the stand level, total foliage mass ranged from 3.3 to 30.5 Mg ha(-1) and was positively correlated (r(2) = 0.97) to leaf longevity. Leaf area index (LAI) was also positively correlated (r(2) = 0.82) to leaf longevity. Production efficiency (ANPP/LAI) was inversely related to leaf longevity and positively related to A/mass. Aboveground biomass and net primary production differed significantly (P < 0.05) among the five species but were not correlated to leaf longevity, total foliage mass or leaf area. In monospecific plantations, stem NPP for Larix decidua was 17% greater than for Pinus strobus and 14% less than for Picea abies, but in mixed-species plantations stem NPP for Larix decidua was 62 and 85% greater than for Pinus strobus and Picea abies, respectively. Similar aboveground net primary production rates can be attained by tree species with different leaf longevities because of trade-offs resulting from different structural and physiological leaf and canopy characteristics that are correlated to each other and to leaf longevity.     

Leaf optical properties in Venezuelan cloud forest trees

Leaf optical properties and related leaf characteristics were compared for thirteen cloud forest tree species differing in successional status. Sun leaves were sampled for the eight pioneer species and sun and shade leaves were sampled for the five climax species. Sun leaves had a slightly higher absorptance than shade leaves, although differences were small. Sun leaves had a higher leaf mass per unit area (LMA) and a lower chlorophyll concentration per unit leaf mass, resulting in similar chlorophyll concentrations per unit leaf area and hence similar light harvesting capacities as shade leaves. However, shade leaves realized a higher efficiency of absorptance per unit leaf biomass than sun leaves. There were few differences in leaf characteristics of sun leaves between the climax and pioneer species. Absorptance values of cloud forest species were comparable with values reported for rain forest and more seasonal forest species. Intraspecific variation in leaf absorptance was largely the result of variation in LMA, whereas interspecific variation in leaf absorptance was largely a result of variation in chlorophyll concentration per unit leaf area.     

Parameterization and testing of a biochemically based photosynthesis model for walnut (Juglans regia) trees and seedlings

The biochemically based leaf photosynthesis model proposed by Farquhar et al. (1980) and the stomatal conductance model proposed by Jarvis (1976) were parameterized for walnut. Responses of photosynthesis to CO(2) and irradiance were used to determine the key parameters of the photosynthesis model. Concurrently, stomatal conductance responses to leaf irradiance (Q), leaf temperature (T(l)), water vapor pressure deficit at the leaf surface (D), and air CO(2) concentration at the leaf surface (C(s)) were used to parameterize the stomatal conductance model. To test the generality of the model parameters, measurements were made on leaves from a 20-year-old tree growing in the field, and from sunlit and shaded greenhouse-grown seedlings. The three key parameters of the photosynthesis model (maximum carboxylation rate V(cmax), electron transport capacity J(max), and dark respiration rate R(d)) and the key parameter of the conductance model (reference stomatal conductance, g(sref)) were linearly correlated with the amount of leaf nitrogen per unit leaf area. Unique relationships could be used to describe nitrogen effects on these parameters for leaves from both the tree and the seedlings. Our data allowed separation of the effects of increasing total photosynthetic apparatus per unit leaf area from the effects of partitioning nitrogen among different pools of this apparatus for foliage acclimation to leaf irradiance. Strong correlations were found between stomatal conductance g(s) and Q, D and C(s), whereas the relationship between g(s) and T(l) was weak. Based on these parameterizations, the model adequately predicted leaf photosynthesis and stomatal conductance when tested with an independent set of data obtained for the tree and seedlings. Total light-driven electron flows derived from chlorophyll fluorescence data obtained at different leaf temperatures were consistent with values computed by the model. The model was also tested with branch bag data acquired from a three-year-old potted walnut tree. Despite a relatively large variance between observed and simulated values, the model predicted stomatal conductance and photosynthesis reasonably well at the branch scale. The results indicate that the photosynthesis-conductance model developed here is robust and can be applied to walnut trees and seedlings under various environmental conditions where water is non-limiting.     

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (−P) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1–11 m² per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LAⁿ, n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.     

Comparative water use by dryland trees in Parklands in Senegal

Despite the clear evidence of competition for water between trees and crops, there have been very few studies comparing simultaneous water use by differing tree species in drylands. Comparative water use by dryland trees was measured in Senegal using heat balance gauges at the end of the wet season and in the dry season. Significant differences between tree species were found for maximum rates of water use per unit leaf area. Indigenous species may be better adapted to the dry environment than exotic species but the indigenous species Acacia seyal Del. used more water per unit leaf area than all other species. The exotic species Azadirachta indica Adr. Juss. consistently used less water per unit leaf area than most other species. There were significant differences in amounts of water used per unit leaf area by differing provenances of the same tree species. Water use in the dry season varied by a factor of three between two provenances of Acacia aneura F. Muell ex Benth. indicating potential to select provenances for drylands based on their water use characteristics. Absolute rates of water use as well as differences in sapflow between species were greatest when soils were moist suggesting that comparative sapflow studies will be most informative when carried out during the wet season. Water use rankings of the differing tree species were broadly maintained irrespective of season.This revised version was published online in November 2005 with corrections to the Cover Date.     

Constraints on physiological function associated with branch architecture and wood density in tropical forest trees

This study examined how leaf and stem functional traits related to gas exchange and water balance scale with two potential proxies for tree hydraulic architecture: the leaf area:sapwood area ratio (A(L):A(S)) and wood density (rho(w)). We studied the upper crowns of individuals of 15 tropical forest tree species at two sites in Panama with contrasting moisture regimes and forest types. Transpiration and maximum photosynthetic electron transport rate (ETR(max)) per unit leaf area declined sharply with increasing A(L):A(S), as did the ratio of ETR(max) to leaf N content, an index of photosynthetic nitrogen-use efficiency. Midday leaf water potential, bulk leaf osmotic potential at zero turgor, branch xylem specific conductivity, leaf-specific conductivity and stem and leaf capacitance all declined with increasing rho(w). At the branch scale, A(L):A(S) and total leaf N content per unit sapwood area increased with rho(w), resulting in a 30% increase in ETR(max) per unit sapwood area with a doubling of rho(w). These compensatory adjustments in A(L):A(S), N allocation and potential photosynthetic capacity at the branch level were insufficient to completely offset the increased carbon costs of producing denser wood, and exacerbated the negative impact of increasing rho(w) on branch hydraulics and leaf water status. The suite of tree functional and architectural traits studied appeared to be constrained by the hydraulic and mechanical consequences of variation in rho(w).