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171.
Research progress on monitoring vegetation water content by using hyperspectral remote sensing
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《植物生态学报》2018,42(5):517
植被含水量是陆地植被重要的生物物理特征, 其定量遥感反演有助于植被干旱胁迫的实时监测与诊断评估。该文系统综述了国内外利用高光谱遥感评估植被水分状况的4个常见植被水分指标——冠层含水量、叶片等量水厚度、活体可燃物湿度和相对含水量的概念及其遥感估算方法研究进展, 评述了植被含水量高光谱遥感估算各类方法的优缺点, 探讨了植被含水量高光谱遥感估算目前存在的问题, 并提出进一步的研究任务, 即服务于植被干旱胁迫的高光谱遥感监测、预警与评估。 相似文献
172.
Questions
What are the most important drivers of plant species richness (gamma‐diversity) and species turnover (beta‐diversity) in the field layer of a forest edge? Does the tree and shrub species richness structure and complexity affect the richness of forest and grassland specialist species?Location
Southeast Sweden.Methods
We sampled 50 forest edges with different levels of structural complexity in agricultural landscapes. In each border we recorded trees, shrubs and herb layer species in a 50‐m transect parallel with the forest. We investigated species composition and species turnover in relation to the proportions of gaps in the border and the diversity of trees and shrubs.Results
Total plant species richness in the field layer was mainly explained by the proportion of gaps to areas with full canopy cover and tree diversity. Increasing number of gaps promoted higher diversity of grassland specialist species within the field layer, resulting in open forest borders with the highest overall species richness. Gaps did however have a negative impact on forest species richness. Conversely, increasing forest species richness was positively related to tree diversity, but the number of grassland specialist species was negatively affected by tree diversity.Conclusions
Managing forest borders, and therefore increasing the area of semi‐open habitats in fragmented agricultural landscapes, provides future opportunities to create a network of suitable habitats for both grassland and deciduous forest specialist species. Such measures therefore have the potential to increase functional connectivity and support dispersal of species in homogeneous forest/agricultural landscapes. 相似文献173.
174.
175.
Relative contribution of neutral and deterministic processes in shaping fruit‐feeding butterfly assemblages in Afrotropical forests
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Kwaku Aduse‐Poku Freerk Molleman William Oduro Samuel K. Oppong David J. Lohman Rampal S. Etienne 《Ecology and evolution》2018,8(1):296-308
The unified neutral theory of biodiversity and biogeography has gained the status of a quantitative null model for explaining patterns in ecological (meta)communities. The theory assumes that individuals of trophically similar species are functionally equivalent. We empirically evaluate the relative contribution of neutral and deterministic processes in shaping fruit‐feeding butterfly assemblages in three tropical forests in Africa, using both direct (confronting the neutral model with species abundance data) and indirect approaches (testing the predictions of neutral theory using data other than species abundance distributions). Abundance data were obtained by sampling butterflies using banana baited traps set at the forest canopy and understorey strata. Our results indicate a clear consistency in the kind of species or species groups observed at either the canopy or understorey in the three studied communities. Furthermore, we found significant correlation between some flight‐related morphological traits and species abundance at the forest canopy, but not at the understorey. Neutral theory's contribution to explaining our data lies largely in identifying dispersal limitation as a key process regulating fruit‐feeding butterfly community structure. Our study illustrates that using species abundance data alone in evaluating neutral theory can be informative, but is insufficient. Species‐level information such as habitat preference, host plants, geographical distribution, and phylogeny is essential in elucidating the processes that regulate biodiversity community structures and patterns. 相似文献
176.
Decline of photosynthetic capacity with leaf age in relation to leaf longevities for five tropical canopy tree species 总被引:2,自引:0,他引:2
The effect of leaf aging on photosynthetic capacities was examined for upper canopy leaves of five tropical tree species in a seasonally dry forest in Panama. These species varied in mean leaf longevity between 174 and 315 d, and in maximum leaf life span between 304 and 679 d. The light-saturated CO2 exchange rates of leaves produced during the primary annual leaf flush measured at 7-8 mo of age were 33-65% of the rates measured at 1-2 mo of age for species with leaf life span of < 1 yr. The negative regression slopes of photosynthetic capacity against leaf age were steeper for species with shorter maximum leaf longevity. In all species, regression slopes were less steep than the slopes predicted by assuming a linear decline toward the maximum leaf age (20-80% of the predicted decline rate). Maximum oxygen evolution rates and leaf nitrogen content declined faster with age for species with shorter leaf life spans. Statistical significance of regression slopes of oxygen evolution rates against leaf age was strongest on a leaf mass basis (r = 0.49-0.87), followed by leaf nitrogen basis (r = 0.48-0.77), and weakest on a leaf area basis (r = 0.35-0.70). 相似文献
177.
The reflectance properties of plant internodes modify elongation responses to lateral far-red radiation 总被引:1,自引:0,他引:1
The quality and quantity of light reflected from Nicotinia tabacum L. internodes was monitored as the angle of incidence was varied. Reflectance of incident light, which was either normal or longitudinal to the internode axis, was investigated. Increasing the angle of incidence caused a greater proportion of incident light to be reflected. Light striking N. tabacum internodes was always modified prior to reflection, and smaller incident angles produced greater modification of the reflected light quality. At larger angles, interactions with the internode were reduced. As a parallel investigation, the extension growth rate of light-grown Sinapis alba L. seedlings was monitored continuously using sensitive linear displacement transducers. When the angle of illumination by fibre-optic probes, presenting far-red light to the growing internode, was changed from 0° to 45°, an increase was observed in stem extension rate. There is a possibility that this rate increase was the result of a fall in the red:far-red ratio (R:FR) present inside the plant internode as the angle of incidence was altered. However, it is more likely that it was due to the larger surface area of stem being illuminated. The consequences of these observations are discussed in relation to the potential influence of such modified reflections on canopy light environments and resultant shade responses which may occur when light of known R:FR impinges on plant internodes at angles other than 0°. The possibility is discussed that plants may perceive the quality of reflected radiation from neighbouring plants to be substantially different dependent upon the angle at which it is reflected. 相似文献
178.
Simple scaling of photosynthesis from leaves to canopies without the errors of big-leaf models 总被引:24,自引:0,他引:24
In big-leaf models of canopy photosynthesis, the Rubisco activity per unit ground area is taken as the sum of activities per unit leaf area within the canopy, and electron transport capacity is similarly summed. Such models overestimate rates of photosynthesis and require empirical curvature factors in the response to irradiance. We show that, with any distribution of leaf nitrogen within the canopy (including optimal), the required curvature factors are not constant but vary with canopy leaf area index and leaf nitrogen content. We further show that the underlying reason is the difference between the time-averaged and instantaneous distributions of absorbed irradiance, caused by penetration of sunflecks and the range of leaf angles in canopies. These errors are avoided in models that treat the canopy in terms of a number of layers – the multi-layer models. We present an alternative to the multi-layer model: by separately integrating the sunlit and shaded leaf fractions of the canopy, a single layered sun/shade model is obtained, which is as accurate and simpler. The model is a scaled version of a leaf model as distinct from an integrative approach. 相似文献
179.
J V CROSS 《The Annals of applied biology》1997,131(2):197-212
The susceptibility of populations of the summer fruit tortrix moth, Adoxophyes orana, from apple orchards in Kent, England, to chlorpyrifos was determined in 1992, 1994 and 1995, by topically dosing larvae feeding on leaves or adults adhered to pheromone trap sticky bases. LD50 values (range 6.3 to 23.2 ng chlorpyrifos per individual) for first or second generation males, second generation females or for first generation fourth instar larvae collected in the field were significantly greater (2–3 fold) for populations from orchards with a long history of treatment with broad-spectrum organophosphorous and other insecticides than for those from untreated orchards (range 1.6 to 8.1 ng chlorpyrifos per individual), though there was considerable variation between sites and years. Twelve replicated orchard experiments between 1993 and 1995 were used to examine a range of different strategies for insecticidal control. Applications of chlorpyrifos against overwintered larvae feeding in trusses in spring gave, at best, a 75% reduction in larval numbers, insufficient to prevent damage by the subsequent generation in summer. However, two applications of fenoxycarb (one immediately pre-and one immediately post-blossom of apple cv. Cox) completely prevented successful subsequent development of the pest, and a single (post-blossom) spray nearly so. The timing of application of chlorpyrifos against first generation larvae hatching from eggs in June was shown to be critical and currently used methods of spray-timing were unreliable. The effective persistence of chlorpyrifos was short (< 7 days). Though good control could be achieved with a single spray, a better strategy was to apply a series of sprays at 7-day intervals to cover the egg hatch period. Sprays of Bacillus thuringiensis at the same timing intervals gave, maximally, an 80% reduction in larval numbers, but usually less: improved control was not achieved by applying a programme of sprays compared to a single spray, though a novel, more potent, formulation was significantly more active. Triazophos was also effective as an egg hatch spray. Sprays of chlorpyrifos or tebufenozide between late September and mid-October 1995 against second or third instar larvae migrating to overwintering sites before diapause, failed to reduce significantly the numbers of subsequent overwintering larvae or the numbers that emerged to feed on blossom trusses in spring. 相似文献
180.
本文通过对杉木萌芽林林冠下营造中亚热带常见乡土阔叶树种——细柄阿丁枫与木荷后,形成的杉阔混交林的两年定位观测研究,结果表明:杉木萌芽林改造成细柄阿丁枫杉木混交林与木荷杉木混交林后,林分水源涵养功能增强,土壤肥力提高,林内小气候得到改善,林分抗御火灾能力增强。杉木林冠下营造乡土阔叶树种是改良杉木林生态环境质量,科学经营杉木低产林的有效生物措施之一。 相似文献