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1.
We conducted two studies on how highways affect their adjacent habitats by sampling carabid beetles (Coleoptera, Carabidae)
in patches of formerly continuous forest next to highways. (1) We sampled carabids at 14 highway intersections near Helsinki,
Finland. Each intersection (constructed 2–40 years ago) had two forested patches to study: a remnant (0.5–37.4 ha) and, isolated
from the remnant by an intersection lane, an islet (size 0.2–1.8 ha). Pitfall trap catch data (2301 carabids, 25 species)
showed that remnants hosted higher catches of three carabid species, and slightly higher species richness, than islets (patch-size
effect). Time since intersection construction had no apparent effect on carabids. Traffic volume along the intersection lane
determined the assemblage structure of carabids in dry patches, and the abundance of a forest carabid Calathus micropterus. Compared to moist patches, drier patches hosted lower catches of four generalist species; they also had different assemblages
of carabids (habitat-type effect). An interaction between patch size and habitat type for a forest generalist Pterostichus oblongopunctatus indicated that the patch-size effect was dependent on habitat type. (2) We examined possible dispersal of carabids among
forested patches that were separated by highway lanes in Drenthe, the Netherlands. We released 2696 marked individuals of
10 species, and recaptured 376 using dry pitfall traps. We found no evidence for inter-patch movement for nine forest species,
but 22 of 225 recaptured individuals of Poecilus versicolor, an eurytopic open-habitat species, had crossed the highway. Catches of seven forest species were also significantly lower
in the road verges, compared to the adjacent forests. These two studies suggest that (i) decreasing patch size negatively
affects forest-carabid catch and overall species richness, (ii) habitat type can affect the intensity of the patch-size effect,
(iii) carabid assemblages of forest fragments vary with traffic volume (which may be linked with urbanization), (iv) forest
carabids rarely cross highways, and (v) open habitats associated with road margins are dispersal barriers for forest carabids. 相似文献
2.
Spatial vegetation patterns as early signs of desertification: a case study of a desert steppe in Inner Mongolia,China 总被引：1，自引：0，他引：1
Proper assessment and early detection of land degradation and desertification is extremely important in arid and semi-arid
ecosystems. Recent research has proposed to use the characteristics of spatial vegetation patterns, such as parameters derived
from power-law modeling of vegetation patches, for detecting the early signs of desertification. However, contradictory results
have been reported regarding the suitability of those proposed indicators. We used an experiment with multiple grazing intensities
as an analog of a desertification gradient and evaluated the performance of two predictors of desertification: percent plant
cover and a transition from a patch-area distribution characterized by a power law to another portrayed by a truncated power
law, in a desert steppe in Inner Mongolia, China. We found that spatial metrics, such as the largest patch index and coefficient
of variation of mean patch area had negative linear relationships with grazing intensity, suggesting that vegetation patches
became more fragmented and homogeneous under higher grazing pressure. Using a binning-based method to analyze our dataset,
we found that the patch-area relationship deviated from a power-law to a truncated power-law model with increasing grazing
pressure, while the truncated power law was a better fit than the power law for all plots when binning was not used. These
results suggest that the selection of methodology is crucial in using power-law models to detect changes in vegetation patterns.
Plant cover was significantly correlated with stocking rate and all spatial metrics evaluated; however, the relationship between
cover and vegetation spatial pattern still deserves a thorough examination, especially in other types of ecosystems, before
using cover as a universal early sign of desertification. Our results highlight a strong connection between the vegetation
spatial pattern and the desertification associated with heavy grazing and suggest that future studies should incorporate information
about vegetation spatial pattern in monitoring desertification processes. 相似文献
3.
Methods for detecting scale and dispersion of plant cover developed by Carilieet al. (1989,Landscape Ecology 2: 203–213) were adapted to information obtained from satellite imagery. Scales were found to be on the order of 100 m in
the shrub-steppe area of southeastern Washington. General agreement between the remotely sensed data and plant cover using
the variance and correlation methods of Carlileet al. indicate that remote sensing information can be used in the design of field studies for measuring the processes controlling
plant cover in semi-arid areas; the agreement also suggests that the methods have broad applicability in the determination
of scale and dispersion. 相似文献
4.
Spatial patterns of fire occurrence in Catalonia,NE, Spain 总被引：2，自引：0，他引：2
In this paper, we analyse spatial patterns of fire occurrence in Catalonia (NE Spain) during 1975–98. Fire scar maps, discriminated by means of 30–60 m resolution remote sensing imagery, have been used as a source of fire occurrence. We employ several visual or analytical approaches to interpret fire occurrence in this region, such as those of Minnich and Chou (1997), Ricotta et al. (2001) or Krummel et al. (1987). Crucial spatial patterns such as fire size distribution, fire frequency distribution, spots and residual vegetation islands are documented. In addition, several geographical layers were overlaid with burned area maps in order to determine interactions between fire occurrence and environmental parameters such as altitude, slope, solar radiation, and burned land cover. Assuming that fire occurrence is well determined by such a posteriori empirical factors we detect areas most prone to fire in this region and aim to enhance the local forest management and conservation plans. 相似文献
5.
SummaryA biologically based phenology model is proposed to simulate the flowering of the female kiwifruit `Hayward'. The heart of the model is a phenological sub-model describing the distribution of buds and flowers between several phenological stages. It is based on the model of Dennis et al. (1986) with temperature as driving variable, assuming that the development of a flower bud is a stochastic process consisting in accumulated small increments of development time, expressed in degree-hours. Another sub-model integrates quantitative elementary components which allows the simulation of the number of flowers. The model parameters have been estimated for the female cv. Hayward and have been fitted on a data set from 1991. Validation has been done on data sets from 1990 and 1992. Under the climatic conditions of Corsica, this model gives a good representation of the variability of delay in and intensity of flowering, and it fits well to the distribution of canes for flower number. 相似文献
6.
In semiarid landscapes, the ratio of herbaceous to woody plant biomass is a major determinant of ecosystem properties. This ratio depends to a large extent on the amount and spatial distribution of soil moisture that is available to plants, and these variables, in turn, are determined primarily by climate and land use. Current conceptual models for determining the ratio of herbaceous to woody plant biomass in semiarid plant communities are based either on differences in soil moisture with depth (vertical heterogeneity) from one site to another (Walter's two-layer model) or on differences in soil moisture between canopy and intercanopy patches at the same site (horizontal heterogeneity) that result from disturbances associated with land use (Schlesinger et al.'s model of desertification). We developed a model that unifies these two perspectives by relaxing two assumptions of Walter's two-layer model. First, our model recognizes that soil moisture varies horizontally between canopy and intercanopy patches, not only due to land-use disturbance, a general assumption of the Schlesinger et al. model, but also due to the physical nature of the canopy itself. Second, while retaining the general assumption of Walter that woody plants obtain moisture from deeper soil layers than do herbaceous plants, our model recognizes the existence of two types of woody plants: those that extract a substantial proportion of their moisture from deeper layers and those that extract mainly from shallower layers. By modifying the two-layer hypothesis to include four soil compartments and distinguishing between shallow- and deeper-rooted woody species, our model integrates three key concepts in semiarid ecology: (1) the proportion of woody cover increases as moisture in the deeper soil layers increases (Walter's two-layer hypothesis for coexistence of herbaceous and woody plants); (2) land use practices that cause a reduction in herbaceous vegetation and compaction of intercanopy soils lead to a long-term increase in the proportion of woody plants (Schlesinger et al.'s concept, or more generally, that at a given site multiple variations in the proportions of herbaceous and woody plant biomass are possible); and (3) changes in the ratios of herbaceous to woody plant biomass exhibit complex behavior (changes can happen quickly and are not directly reversible without intensive management). This integration of concepts results because rather than assuming a simple, one-way dependence of plant functional types on soil moisture heterogeneity, our model assumes an interdependence between the two: soil moisture heterogeneity constrains the composition of the plant community, which in turn modifies soil moisture heterogeneity. The four-compartment model that we propose enables, for the first time, an integrated picture of both dimensions of soil moisture heterogeneity – horizontal and vertical – and of the interdependence between soil moisture heterogeneity and the proportions of the plant functional types that make up a given plant community. This unified conceptual model can be applied to provide insight into the individual and the combined effects of climate and land use on semiarid plant communities within the grassland/forest continuum, which vary in the proportions of canopy and intercanopy patches. 相似文献
7.
Govert Trouwborst Ad H.C.M. Schapendonk Kees Rappoldt Sander Pot Sander W. Hogewoning Wim van Ieperen 《Scientia Horticulturae》2011
Intracanopy lighting is a recently developed supplementary lighting technique for high-wire grown vegetable production in greenhouses where a part of the lamps is mounted within instead of above the canopy. A potentially higher yield using intracanopy lighting compared with top-lighting, is based on three assumptions: (1) increased light-absorption by the crop; (2) a higher photosynthetic light use efficiency due to a more homogeneous vertical light distribution; (3) a preserved photosynthetic capacity of leaves deeper in the canopy. We used an explanatory crop model to quantify the relative importance of these assumptions for a cucumber crop during an experiment in winter in the Netherlands (Trouwborst et al., 2010). Photosynthesis and yield data of this intracanopy lighting experiment with light-emitting diodes (34% of supplemental PAR) in combination with top-lighting (66% of supplemental PAR) were used to parameterise our model. In that study intracanopy lighting did not result in an increased yield compared with 100% top-lighting due to extreme leaf curling and a lower dry matter partitioning to the fruits. Our model predicted an 8% increase in fruit yield for the intracanopy lighting treatment if there were to be no leaf curling and no lower dry matter partitioning. This increase can be largely explained by the change in light distribution and light absorption. The model further revealed unexpectedly large consequences of the lower dry matter partitioning to the fruits whereas the negative effect of leaf curling was small. The direct effect of a greater Amax at deeper canopy layers was slightly positive. The last however might have indirectly caused the greater partitioning to the leaves as the greater Amax was associated with a preserved leaf mass per area. Solutions for this problem are discussed. Our explanatory model allowed us to disentangle the interacting effects of intracanopy lighting on fruit yield. Overall, intracanopy lighting has been shown here to potentially increase the assimilation light use efficiency. 相似文献
8.
Scott C. Neubauer 《Landscape Ecology》2014,29(4):571-577
Wetlands play a role in regulating global climate by removing carbon dioxide (CO2) from the atmosphere and sequestering it as soil carbon, and by emitting methane (CH4) and nitrous oxide (N2O) to the atmosphere. In a recent article in this journal (Mitsch et al. Landscape Ecol 28:583–597, 2013), CO2 sequestration and CH4 emissions were modeled for several freshwater wetlands that vary in vegetation type, climate, and hydrology. The authors of that study made significant errors that caused them to underestimate the importance of wetland CH4 emissions on climate dynamics. Here, I reanalyze the Mitsch et al. dataset and show that all of their wetlands had an initial warming effect but eventually caused negative net radiative forcing within ~60–14,000 years, depending on the ratio of CO2 sequestration to CH4 emissions. The addition of a N2O component to the model suggested that typical wetland N2O emission rates would contribute only a minor burden to wetland radiative forcing, although specific application of this three-gas model is limited by the paucity of sites where CO2 sequestration, CH4 emission, and N2O exchange rates have all been measured. Across the landscape, many natural wetlands may already cause negative net radiative forcing when integrated over their lifetime. However, caution should be applied when using carbon sequestration as a rationale for designing wetland construction and restoration projects since freshwater wetlands may have a net positive (warming) effect on climate for decades to centuries or longer. 相似文献
9.
2017—2019年，在延庆对生姜田害虫开展调查，结果发现食叶害虫主要有3种，分别为棉铃虫[Helicoverpa armigera （Hübner）]、甜菜夜蛾[Spodoptera exigua （Hübner）]和粘虫[Mythimna separata（Walker）]，钻蛀性害虫为亚洲玉米螟[Ostrinia furnacalis （Guenée）]，地下害虫只发现轻微危害，未查到具体种类。地下害虫发生相对较早，食叶害虫和钻蛀性害虫主要发生于生产后期。不同年份间，害虫发生种类差异较大，2017年以钻蛀性害虫为主，还有食叶害虫即棉铃虫和甜菜夜蛾，2018年和2019年以食叶害虫为主，主要是棉铃虫，还有少量粘虫。 相似文献
10.
Errors in greenhouse forcing and soil carbon sequestration estimates in freshwater wetlands: a comment on Mitsch et al. (2013) 总被引：1，自引：0，他引：1
Scott D. Bridgham Tim R. Moore Curtis J. Richardson Nigel T. Roulet 《Landscape Ecology》2014,29(9):1481-1485
Radiative forcing feedbacks from wetlands have been an important component of past climate change and will likely be so in the future, so accurately assessing the carbon (C) and radiative balances of wetlands remains an important research priority. This commentary shows that the paper by Mitsch et al. (Landscape Ecol 28:583–597, 2013) seriously underestimated the radiative forcing effect of methane (CH4) emissions and overestimated soil C sequestration in freshwater wetlands. The model that they used is flawed in double counting the atmospheric decay of CH4 and incorporating a single 100 year CH4 global warming potential. They also used a small number of sites and short-term soil dating that resulted in unrealistically high soil C sequestration rates, ignoring decay of the entire soil C pool and allochthonous inputs of C. They calculated the radiative balance instead of the radiative forcing of natural wetlands, making their calculations irrelevant to anthropogenic climate change. Irrespective of the radiative forcing of wetlands, they provide essential ecosystem services that are important to protect. 相似文献
11.
Rootstocks-scion relations have critical consequences about nutritional status, tree vigour, resistance to pest and pathogens, yield and yield quality. In this study, we therefore investigated seasonal variations of leaf mineral nutrient concentrations in Satsuma mandarin’s cvs. ‘Okitsu’, ‘Clausellina’ and ‘Silverhill’ budded on different citrus rootstocks under Dörtyol-Hatay, Turkey ecological conditions. Nitrogen (N), phosphorus (P) and K (potassium) concentrations of the leaves showed slightly similar trend each other, in general these nutrients reduced from January to March–April, and increased during the growing season until mid- and late summer, then decreased until December. Despite rootstocks did not significantly affect the leaf N, P and K concentrations rootstock-scion relation was pre-eminent and nutrient dependent. Most conspicuous scion dependent changes were recorded for K concentration whereas P concentration was little influenced. In terms of scion-rootstock combination, the range of N and K concentrations were 2.11% (‘Okitsu’/sour orange) to 2.34% (Silverhill/sour orange), and 1.09% (‘Okitsu’/Carrizo citrange) to 1.39% (‘Clausellina’/Carrizo citrange), respectively; but P concentrations were highly similar %0.13 (‘Okitsu’/sour orange) – %0.16 (‘Clausellina’/Carrizo citrange), in the entire growing season. It can be concluded that there are considerable differences in nutrient uptake ability of scion-rootstock combination. 相似文献
12.
宁夏贺兰山东麓不同葡萄品种对霜霉病的抗性鉴定 总被引：7，自引：1，他引：7
为了给葡萄抗性品种的选育和葡萄霜霉病的防治提供科学依据,对16个不同酿酒葡萄品种和19个鲜食葡萄品种的抗病性进行了抗性测定。结果表明,室内回接与田间调查结果一致,16个酿酒葡萄品种可划分为4类;19个鲜食葡萄品种可划分为4类;从发病时间来看,抗性与发病时间存在一定相关性,抗性越强发病越晚。随即将测定结果采用DPS软件进行聚类分析,在酿酒葡萄抗性反应谱系图上,第1类为抗性稍强品种,为白比诺、灰比诺和赛美蓉;第2类为抗性中等品种,由白长相思和神索等8个品种组成;第3类是稍感病品种,包括赤霞珠等4个品种;第4类是感病品种,只有品丽珠1个。在鲜食葡萄谱系图上,第1类为六月紫等7个抗性稍强品种;第2类是新华1号和巨峰;第3类是稍感品种,由奥古斯特等6个品种组成;第4类为力扎马特等4个感病品种。 相似文献
13.
14.
S. C. Agarwala E. J. Hewitt 《The Journal of Horticultural Science and Biotechnology》2013,88(4):291-300
The behaviour of two clones of Williams’ Bon Chretien pear was compared when grafted on to Quince A rootstocks. One clone made strong unions with Quince A ; the other made weak unions and produced smaller trees than the compatible clone. Various graft combinations of the compatible and incompatible clones of Williams’ and of Beurre Hardy pear provided evidence that the structural weakness of the pear/quince unions was not caused by virus infection, and that the unions between the compatible Williams’ and Quince A were as good as those between the compatible pear variety Beurré Hardy and Quince A.The compatible Williams’ was infected with vein yellows and bark necrosis viruses; these have now been eliminated by a combination of heat treatment and propagation of young shoot tips. This healthy material will be available for distribution to commercial propagators if the crop yields of this clone are satisfactory. 相似文献
15.
Nowadays, lots of efforts are made in Tunisia for the exploitation of wastewater in agriculture in order to face a very elevated mobilization of resources in water (90%). At Sfax, a Governorate placed in the South of Tunisia, the annual rainfall rarely exceeds 200 mm, so the climate is fairly arid. The significant water deficit can be reduced with the reuse of treated wastewater (TWW). The Sfax wastewater originated from the municipal wastewater treatment plant (WWTP) localized at 5 km in the south of Sfax, Tunisia. This WWTP is an aerated lagoon process receiving industrial wastewaters. Its treatment capacity is 24,000 m3/day. Part of TWW is sent to the olive crops of El Hajeb, as part of a proposed wastewater use in agriculture. Already the wastewater is used to irrigate olive trees and intercrops such as cotton, oats and sorghum silage (Charfi et al., 1999). The aim of the present work was to determine the impact of the irrigation utilizing wastewater on the quality of the oil. The oils analysed were extracted from olives hand-picked directly from the tree and from olives that have fallen under the trees. Moreover, a study on the olive storage has been made in order to evaluate in which way the collection of the fruit could influence the quality of the oil. 相似文献
16.
我国栎属植物资源丰富,有60余种,全国各省区均有分布.栎属植物树体高大、叶形优美、适应性强,具有较高的园林应用价值.首先综述了我国栎属植物原种和变种资源,其次介绍了常用的种类及其优良性状、园林应用状况,并推荐一些国外引入的优良栎属植物种类,阐述栎属植物在园林中的应用前景.与欧美国家对栎属的应用相比,我国对栎属植物的深入研究和园林应用亟待加强. 相似文献
17.
The morphology of parcel patterns created by humans both in urban and rural areas is investigated. The parcel size distribution
function, f(a), provides a criterion, that enables unambiguous classification of each piece of land as city core, suburbs, or rural area.
The morphology of the rural area corresponds to a scale-free structure and follows a power-law distribution f(a) ~ a
−n
of the parcel areas with the exponent n ≈ 1. In suburbs, the area distribution follows the log-normal distribution. In the city core, f(a) has an unimodal shape with an algebraically decaying tail, n = 2. Our study is based on data originating mainly from North America, the Hawaiian Islands, and Australia. For the regions
analyzed, the characteristics of the parcel size distribution are universal and robust with respect to geographical, historical,
and economical conditions accompanying development of a given area. The urbanization process can be described in terms of
the changes of the morphology of the patterns of land fragmentation. In this formulation, the rural morphology, which can
be thought as natural one because it exhibits a scale-free distribution of parcel sizes, is transformed into the artificial
morphology developed in the city centers.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Green roofs are “nature-based solutions” that provide numerous ecosystem services in the context of urban green infrastructures. Plant species diversity and the associated vegetation communities, in strong interactions with green roof substrate, play a central role in the green infrastructure functioning. In order to better understand the influence of vegetation in relation with the co-benefits provided by green roofs as well as to select suitable species for these usually harsh environments, it is essential to be able to achieve accurate and long-term monitoring of plant communities. In this short communication, two free plugins recently developed for the open-source image analysis software Fiji (a distribution of the freely available ImageJ platform, initially dedicated to biological image analysis) were investigated for their capacity to rapidly and efficiently perform supervised machine-learning for the classification of green roof vegetation photographs, with the aim of estimating individual plant species abundance. Two simple methods are thus described using the Trainable Weka Pixel Segmentation (Arganda-Carreras et al., 2017) or the Trainable Superpixel Segmentation (Salinas Colina et al., 2018), which allowed for rapid, efficient and reproducible classification and estimation of multispecies colonized green roof regardless the color or shape similarities among species or ground cover materials. Finally, recommendations are made for the use of the Trainable Superpixel Segmentation which is particularly convenient for quick and efficient green roof image analysis. 相似文献
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20.
Marzia Migliorini Chiara Cherubini Marco Mugelli Giacomo Gianni Serena Trapani Bruno Zanoni 《Scientia Horticulturae》2011
In our previous work (Cherubini et al., 2009), sugar concentration was proposed as an accurate, reproducible index for technological ripening of olive oil fruits. During 2009 crop season, sugar and oil content of olive oil fruits from Moraiolo and Leccino cultivars were measured during ripening. The sugar content of olive oil fruits was determined both by titration and by using a portable refractometer. 相似文献