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111.
城市森林降温效应影响因素研究进展 总被引:1,自引:0,他引:1
城市森林是缓解城市热岛效应的重要绿色基础设施。本文探讨影响城市森林降温效应的内、外因素及作用机制,为优化城市森林结构、缓解城市热岛效应提供参考。影响城市森林降温效应的内部因素从单木尺度上主要有树种、树冠结构和树冠形状,从林分尺度上主要有林分类型、林分结构、绿量、林分面积和形状,城区尺度主要应用遥感方法对城市森林降温效应进行研究,主要指标有归一化植被指数、叶面积指数和景观格局指数;影响城市森林降温效应的外部因素有气候、地面类型和经营措施等;内部因素及外部因素通过影响林内外能量的流动和交换,共同影响城市森林降温效应。缓解城市热岛效应,一方面要加强理论研究,重视温度场理论,结合地面观测与遥感解译,充分研究林分结构与城市森林能量传输的关系,另一方面需加强城市森林的经营管理,从促进热量交换的角度优化林分结构,合理布局城市建筑、森林和水体等基础设施,实现降温效应最大化。 相似文献
112.
Holger Brueck 《植物养料与土壤学杂志》2008,171(2):210-219
The worldwide increase of food demand and reduced sweet‐water availability in some important food‐producing regions raised interest in more efficient water use, which has become one of the central research topics in agriculture. Improved irrigation management and reduced bare‐soil evaporation have highest priority to increase agronomic water‐use efficiency (WUE). Compared to these technical (irrigation) and basic (crop production) management options, effects of nutrient management on WUE were less frequently considered. Twenty‐nine publications on nitrogen (N) effects on biomass WUE of container‐grown plants are considered in this review. Most of them indicate positive N effects on WUE, and relevance of N effects on intrinsic WUE and unproductive water and carbon loss is discussed. A plot of 90 published data of percent decreases of WUE and dry mass under variable N supply is presented. Extrapolation of biomass WUE from leaf measurements of intrinsic WUE is critically reviewed. The positive correlation between WUE and dry‐mass formation suggests that physiological rather than stomatal effects are more important in order to explain positive N effects on WUE. 相似文献
113.
A challenge to breeding drought‐tolerant barley in the Middle‐East is that precipitation and evaporative demand patterns dictate opposite water use strategies (conservative vs. risk‐taking). To characterize these strategies, we examined high‐resolution, whole‐plant transpiration rate (TR) responses to increasing vapour pressure deficit (VPD) and nocturnal TR (TRN) dynamics among 25 local barley genotypes, using a novel phenotyping system. These traits were specifically selected because they exist under modalities enabling the expression of both strategies. The genotypes were selected from locations spread across a large aridity gradient represented by temperature and precipitation data spanning 30 years. Here, we uncovered a substantial diversity in TR responses to VPD where slopes of the linear responses correlated negatively with local maximal temperatures, pointing to opposite drought tolerance strategies. Low canopy conductance (low slopes) was associated with higher aridity, likely to enable water‐saving, while higher conductance was associated with wetter areas, likely to enable a more aggressive water use to maximize physiological activity. TRN was highly diverse and represented up to 15% of maximal daytime TR, pointing to the possibility of increasing water‐saving by reducing TRN. Furthermore, we detected pre‐dawn variation in TRN that negatively correlated with local precipitation, indicating that a tighter circadian control is associated with adaptation to drought, consistently with a circadian resonance mechanism. These findings indicate that canopy conductance and TRN are potentially beneficial to design drought‐tolerant barley germplasm adapted to different drought regimes taking place in the Middle‐East. 相似文献
114.
There has been limited research on measuring potential differences in leaf gas exchange of Arracacha (Peruvian parsnip, Arracacia xanthorriza Bancroft) cultivars, as affected by different environments, as well as its relation to storage root-yield. The present paper reports field measurements of leaf CO2 assimilation rates (A) for five contrasting cultivars grown at two different high-altitude locations. Using a design of plots chosen at random with three repetitions, commercial root production was determined in the two locations at different altitude (1580 and 1930 m). Daily leaf gas exchange was repeatedly monitored with a portable open-mode infrared gas analyzer at different times in both locations during the growth cycle. Root-yield, leaf area and dry weight were measured. Significant differences in leaf photosynthetic rate and in specific leaf area (SLA) were observed among cultivars. Cultivars with high SLA, had high CO2 assimilation. Mean (An) and total (Atot) of CO2 assimilation and SLA were significantly correlated with storage root-yield across cultivars and locations. The three cultivars with the greatest commercial root production also had the highest maximum values for A and the highest specific leaf area, indicating that these two parameters can be used to select for highly productive cultivars of A. xanthorriza. 相似文献
115.
Drought tolerance combined with resistance to black sigatoka (BS) disease are two desirable traits for plantains in some parts
of the tropics. Field evaluation of leaf stomatal conductance, single leaf transpiration rate, photochemical efficiency, and
role of stomata in BS resistance, was done for 18 genotypes of Musa spp., which included diploid and triploid banana and plantains
and tetraploid plantain hybrids, at a sub-humid and a humid site. Conductances were significantly (P ≤ 0.01) higher for leaf
abaxial than adaxial surfaces (S), while clonal (C) differences were significant (P ≤ 0.05). Interactions between sampling
period (T: morning vs afternoon) and location (L), and clone and location (C × L) were significant for both conductance and
transpiration; (C × T × L) interaction was significant for conductance. Significant interactions for (C × L) and (C × T) suggested
that conductance and transpiration of a specific clone need to be considered for a given environment. Total variation in conductance
was explained by the following variables: S, C, (C × L), (C × T), and (C × L × T). In general, ABB cooking banana had higher
conductances than other Musa taxonomic groups (AAB, AA, AAA, and AAAB). Evaluation of morphological and physiological traits
of leaf stomata indicated that the resistance to BS disease is due to non-stomatal mechanisms.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
116.
A red soil derived from Quaternary red clay was employed to study nutrient leaching with woil columns repacked in laboratory,The objective was to identify the effects of fertilization practices on leaching patterns and magnitudes of Ca^2 ,Mg^2 ,K^ ,NH4^ ,and NO3^-,The treatments were CK (as a control),CaCO3, CaSO4,MgCO3,Ca(H2PO4)2,urea,KCl,and multiple (a mixture of the above-mentioned fertilizers),The fertilizers were added to the bare surface of the soil columns,and then the columns were leached with 120 mL deionized water daily through peristaltic pumps over a period of 92 days.Leaching processes of NH4^ ,and NO3^- wer e only measured in CK,ured,and multiple treatments which were directly related to N leaching, Results showed that sole application of CaSO4,and Ca(H2PO4)2 scarcely hd any effect on the leching losses of Ca^2 ,Mg^2 ,and K^ ; the application of MgCO3 sthimulated the leaching of Mg^2 ;the application of CaCO3 promoted the leaching of Ca^2 ,Mg^2 and K^ ; urea treatment also promoted the leaching of K^ and NH4^ ,and NO3^- leaching mainly occurred at late stage of leaching process in particular;under KCl treatment,leaching of Ca^2 ,Mg^2 ,and K^ was promoted to a large extent;under multiple treatment, leaching of Ca^2 ,Mg^2 ,K^ ,NH4^ ,and NO3^- was all increased and NO3^- was mainly leached at the end of leaching process and still had a trend of increase. 相似文献
117.
118.
李吉跃 《北京林业大学学报》1999,(3)
该文研究了多重复干旱循环对1年生北美短叶松和黑云杉苗木的气体交换速率及水分利用效率的影响.结果表明,多重复干旱循环对它们的气体交换(Cs,Pn,Tr)有显著影响(P<0.5),而对其水分利用效率(WUE)影响不大(P>0.1).尽管北美短叶松的气孔对轻度干旱胁迫不如黑云杉敏感,但是它对中度及严重干旱胁迫的敏感程度却高于黑云杉.在轻度及中度干旱胁迫下,北美短叶松的光合作用主要受非气孔因素的影响,而黑云杉则主要受气孔因素的影响.解除干旱胁迫后,黑云杉的气孔敏感性、光合能力及水分利用效率的恢复都要比北美短叶松更快.轻度的干旱胁迫锻炼可以帮助北美短叶松在更严重的干旱胁迫下保持固有而强劲的耐旱能力.然而,通过多重复干旱循环锻炼后,黑云杉在改善耐旱能力的强度方面大于北美短叶松. 相似文献
119.
在提出一种黄瓜营养生长耐热性评价方法的基础上,研究黄瓜耐热性与其叶片、根系和花粉性状的关系。结果表明:黄瓜营养生长的耐热性是高温下黄瓜产量形成的重要生理基础,花粉耐热性不能作为黄瓜耐热材料的筛选指标。高温下黄瓜叶片厚度、叶片栅栏组织厚度、叶片温度、气孔导度、蒸腾速率和根系干重与黄瓜营养生长耐热性呈显著线性相关,表明蒸腾降温是黄瓜营养系统避免高温伤害的重要机制。 相似文献
120.
河套灌区节水型农田防护林建设与节水潜力 总被引:11,自引:0,他引:11
通过河套灌区小美旱杨蒸腾作用的定量研究 ,计算不同林龄、不同更新方式小美旱农田防护林带的耗水量 ;论述河套灌区建设节水型农田防护林的意义及节水潜力 ,并对小美旱防护林带的改造提出建议。 相似文献