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1.
2.
We studied the relationship between counts of Panonychus ulmi (Koch) winter eggs per bud and mite-days per leaf accumulated in early to mid-summer on 92–96 apple trees in an orchard in
Quebec, Canada. Stepwise regression was used to compute mite-days in the 4 year (1992–1995) data set using winter egg density,
cumulative rainfall (R), cumulative degree-days (D), squared values of R and of D, and the product RD as potential predictors. Degree-days were accumulated above 10.1°C, the minimum threshold of development for P. ulmi in Eastern Canada. The 4-year model that gave the best fit included terms for winter eggs, rainfall, R
2, and the product RD, and explained 76% of the variation in mite-days. When the 4-year model was applied to each year’s data separately, winter
eggs, adjusted for current year rainfall and degree-days, were always highly significant predictors of mite-days. These significant
effects of weather indicate that estimation of potential economic loss should take account of rainfall and heat units, as
well as the density of winter eggs. Predators, including the stigmaeid, Agistemus fleschneri Summers, and occasional low numbers of phytoseiids, did not have any evident within-season effect on mite-days but their
appearance in July–September of 1994 was followed by a ten-fold decrease in the mean density of winter eggs in 1995 compared
with the previous spring. This reduction contrasted with increasing densities each successive spring from 1992 to 1994, which
followed summers when predators were scarce or absent. 相似文献
3.
Jordi Recasens Víctor Calvet Alicia Cirujeda Josep Antoni Conesa 《Biological invasions》2005,7(1):17-27
An experimental work was conducted in Lleida (Spain) aiming to characterise the phenology and to quantify the demographic
processes regulating the populations of Abutilon theophrasti Medicus in maize fields. Seedling emergence started a few days after crop sowing in early May and continued during two more
months. The vegetative phase was very long due to the late seeding emergence; these later emerged plants showed a slower development,
and many of them did not reach the fertility stage. A flowering peak was observed 12 weeks after emergence in late July, and
fruit dehiscence and seed setting started in mid August, several weeks before crop harvest. Four different cohorts were identified,
and two main peaks of emergence were determined 21 and 49 days after crop sowing nearest related with field irrigation. A
functional logarithmic relationship between cumulative growing degree-days (GDD) and cumulative emergence was also described.
The resulting demographic diagram reflects greater values relating to seedling survival for May cohorts (90.2 vs 7.9%), to
fertility (100 vs 75%) and to fecundity (3774 vs 92 seeds pl−1) than those determined for the June cohorts. The late emerged plants are subjected to a high density and are strongly affected
by light competition, and their reproductive phase initiation delay is of about 10–20 days. In an assay conducted in Petri
dishes, the seeds provided from plants emerged earlier were found more vigorous and germinated more than those from late emerged
plants, which seem to be affected by incomplete fruit and seed ripening. Following the crop cycle without any weed control,
the population rate increase was about 21.2. These values explain the high invasion capacity of this weed in the local summer
irrigated fields, which consists in assuring their presence through a persistent soil seed bank and increasing the probability
to spread to other fields.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
The population and production ecology of aZizania latifolia stand at a sheltered shore of the Hitachi-Tone River were investigated. Shoot emergence was observed twice a year; the fist
was a synchronized shoot emergence in April and the second was from August to October. Aboveground biomass was mostly occupied
by leaves and peaked at 1500 g dry weight m−2 in August. The belowground biomass also reached its peak, 750 g dry weight m−2, in August. The secondary shoots were small in spite of their high density. Leaves were produced continuously throughout
the season. The leaf life span was as short as 55.6 days for cohorts that emerged from May through to September. Total annual
net production ofZ. latifolia could be more than 3400 g dry weight m−2. Shoot clusters of several centimeters were observed in April. The following self-thinning caused a regular distribution
of the remaining shoots in August. Most shoots produced in August to October were found near a shoot persisting since April.
They showed more concentrated distribution than shoots in April. A large biomass allocation to leaves and the ability to produce
many clump shoots during the late growing period may facilitate dominance ofZ. latifolia in relatively sheltered sites. 相似文献
5.
The oriental fruit moth, Grapholita molesta, is becoming a large threat to Korean pear production. Timely management of the egg and early larval stages from the spring emergence is critical to reduce the G. molesta population during the pear growing season. A model was developed to precisely predict the spring occurrence of G. molesta adults as a function of accumulated degree-days. The model was validated with male moth caught in sex pheromone-baited traps placed in pear orchards at two major pear production regions (Icheon and Naju) of Korea in 2010. We applied nine distribution models to describe the cumulative proportions of G. molesta males caught relative to accumulated degree-days. The observed phenology of the G. molesta spring population was well described by the nine models. The predicted dates for the cumulative 50% male moth catches were within a 5 day period. Based on statistical information criteria (Akaike's and Bayes–Schwartz information criteria), we recommend the sigmoid function referred by Brown and Mayer, because of its ease of use and meaningfulness; the parameter “b” denotes the degree-day accumulation at 50% moth emergence. The G. molesta spring emergence model could be applied to determine optimal chemical treatment timing for controlling G. molesta in fruit tree orchards and further help to develop a full-cycle phenology model of G. molesta. 相似文献
6.
Annual primary production in 1990 in the Marsdiep amounted to about 250 g C.m–2, which is lower than during the mid 1980s, but still higher than the about 150 g C.m–2a–1 measured during the 1960s and early 1970s. The annual curve shows a clear spring peak and a broad but lower summer peak. Chloropyll-a showed a similar annual curve, the maximum of 35 mg.m–3 during the spring peak, as well as the annual average of 6 mg.m–3 were lower than during the late 1970s and the 1980s. Organic carbon values for 1990 were similar to those observed in 1978 to 1984. Turbidity (at high tide) at our sampling station did not change over the period 1973 to 1990. The high winter temperature of 1989/90 did not influence the timing of the phytoplankton spring bloom. The diatom spring peak is better related to light. With more light in spring and clearer water, the peak occurs earlier. The trend of an increase of the period of occurrence ofPhaeocystis continued.Phaeocystis colonies and single cells were present almost the year round, however, the maximum cell numbers ofPhaeocystis (80,000 ml–1) was relatively low. Newly formed colonies on spines of diatoms (Chaetoceros sp.,Bacteriastrum hyalinum) were observed in autumn. Its life-cycle remains enigmatic.Rhizosolenia indica, a warm water species, was observed for the first time in net-plankton samples, it occurred from September to December 1990. 相似文献
7.
The life cycle of E. shigae, including eclosion, nymphal growth, last instar recruitment and adult emergence, was studied in a Japanese river. The synchronization of nymphal development is discussed. Eggs hatched sporadically from mid-March to early April as determined from continuous sampling of eggs from the river substratum. Nymphs attained the last instar in mid- to late August and emerged in mid-September. Size of nymphs at the time of last instar recruitment decreased gradually as did the size of emerging mayflies. Smaller individuals entering the last instar later developed more quickly and required a smaller number of degree-days to complete the last instar than did larger individuals. Consequently, larval development synchronized during the period between last instar recruitment and adult emergence. 相似文献
8.
Four-year monitoring of phenology of the blowfly Caliphora vicina under quasi-natural conditions in the environs of St. Petersburg demonstrated development of two complete generations and overwintering of the third generation. The duration of preimaginal development (from egg laying to adult emergence) of the 1st and 2nd generations varied from 19 to 32 days; the required sum of effective temperatures (SET) was 326 ± 31 degree-days with a threshold of 5°С. Reproductive maturation of females (the period of time from adult emergence to laying of the first eggs) lasted from 15 to 31 days (SET was 262 ± 39 degree-days with a threshold of 5°С). The duration of development of one complete generation (from egg stage to the beginning of oviposition) during the period of observation varied from 34 to 57 days (SET was about 600 degree-days with a threshold of 5°С). The first diapausing larvae hatched from the eggs laid in the middle of August. In September, at shorter day lengths and at a temperature of 10–11°С, 80–100% of the larvae entered diapause. A small fraction of the larvae of the 1st and 2nd generation and most of the larvae of the 3rd generation overwintered. Successful overwintering of adults in the environs of St. Petersburg is hardly possible. 相似文献
9.
大兴安岭林区南、北部天然樟子松生长对气候变化的响应差异 总被引:3,自引:0,他引:3
利用树木年代学方法,建立大兴安岭林区南、北部樟子松(Pinus sylvestris var.mongolica)年轮宽度年表,探讨樟子松径向生长对气候变化的响应差异。结果表明,南部(阿尔山、海拉尔)树轮宽度主要与当年4—9月的平均标准化降水蒸散指数SPEI(Standardized Precipitation Evapotranspiration Index)极显著正相关(r=0.639,P0.01),而北部(漠河、塔河)树轮宽度主要与同时期的平均最低温极显著正相关(r=0.488,P0.01)。说明南部樟子松径向生长主要受当年4—9月的水分限制,北部主要受同期平均最低温调控。两个地区树木生长对降水的响应一致,对当年4—9月(6月除外)的温度响应相反。近几十年来随着温度显著升高(P0.01),南部树木生长对4—9月平均最高温的负响应不断增强,而北部树木对同时段平均最低温的正响应更加明显。同时,南部樟子松生长量快速下降(r=0.612,P0.001),而北部生长量显著增加(r=0.474,P0.001)。研究发现,高温加剧干旱胁迫是南部樟子松生长量下降的主要原因,而北部樟子松生长量增加是受到4—9月平均最低温和降水量的相互作用。如果持续变暖,未来樟子松分布区可能北移。 相似文献
10.
A J INMAN B D L FITT S J WELHAM R L EVANS D A MURRAY 《The Annals of applied biology》1997,130(2):239-253
When leaves of oilseed rape (cv. Cobra) were inoculated with conidial suspensions of Mycosphaerella capsellae (white leaf spot) and incubated in controlled environments, the lag period from inoculation to the appearance of the first lesions decreased, and the total number of lesions produced increased, as temperature increased from 5oC to 20oC, although differences between 15oC and 20oC were small. With incubation period estimated as the time from inoculation until 5%, 50% or 95% of the lesions were produced, there was a linear relationship between l/(incubation period in days) and temperature over the range 5oC to 20oC, from which values at intermediate temperatures could be estimated. Summed mean daily temperatures from inoculation to the production of 5% of the lesions were estimated as 115–130 degree-days in the controlled environment experiments at 5oC to 20oC. When pods or leaves of plants in oilseed rape crops (cv. Cobra or cv. Libravo) were inoculated with conidial suspensions of M. capsellae on five occasions from January to October, with variable temperatures during the incubation period, degree-days until the first appearance of lesions were in the range 115–230. The numbers of white leaf spot lesions cm-2 which developed on inoculated leaves differed greatly between nine oilseed rape cultivars, with most on cv. Tapidor and fewest on cv. Libravo, but the incubation period differed little between cultivars. Similarly, the number of lesions which developed differed between four M. capsellae isolates from different regions but the incubation period did not. 相似文献
11.
Life history aspects of Ephemera orientalis, a common lowland burrowing mayfly that resides in temperate East Asia, were studied in terms of voltinism, secondary production,
and accumulated degree days for larval development. From March 1998 to June 1999, larvae were sampled monthly (weekly or biweekly
during the emergence period) from a lower reach of the Gapyeong stream in Korea, a stream typical of temperate East Asia,
using a Surber sampler (0.25 m2, mesh 0.25 mm). As a result, the mean density of E. orientalis was 47.21 ± 13.58 indiv. m−2 during the study period. Very small larvae less than 2 mm in body length were sampled on three separate occasions, and emergence
was observed between late April and early October, except during late May. Based on the larval body length distribution and
emergence time, two different developmental groups could be distinguished: the slow developmental group (S-group) and the
fast developmental group (F-group). The F-group completed its life cycle within 4 months, whereas the S-group had a one-year
life cycle. The S-group could be divided into two subgroups, dubbed the S1 and S2-groups, based on larval development. The
developmental groups alternate their life cycles in the order: S1→F→S2→S1. Estimated annual production of the larvae was 68.81 mg DW m−2 y−1; mean biomass was 8.43 mg DW m−2; the annual production to mean biomass ratio was 8.16. The annual mean water temperature of the study year was 14.76 ± 6.63°C.
The total accumulated degree days for larval development was 1396°C for the F-group, 2,055°C for the S1-group, and 1,975°C
for the S2-group. Two different adult body size groups were distinguished (P < 0.001 by t-test): larger adults, which belonged to the S-group, were present throughout the emergence period, whereas smaller adults,
which belonged to the F-group, were mainly present later in the emergence period (August–October). The difference in the accumulated
degree days between the developmental groups may explain the size differences of adults. 相似文献
12.
Summary
Nemurella pictetii Klapálek, 1900 (Plecoptera: Nemouridae) has bi-or trimodal emergence patterns in Central Europe. The emergence threshold temperature is about 8°C. Egg development is direct. The slopes of regressions describing its temperature dependence do not differ significantly between English, Norwegian and German populations, but the intercepts (i.e., the incubation period at 0°C) do. Regular sampling of a benthic population near Schlitz, in Hesse, West Germany, showed that part of the offspring of the first emergence group grew quickly and produced a second emergence peak. The remaining offspring of the first generation grew more slowly and overwintered, together with the offspring of the second emergence peak. This population exhibits partial bivoltinism. The potential for bivoltinism was also shown in laboratory rearings of a German population at a constant 14°C: many eggs yielded normal adults after about 120 days. Larval growth rates were up to 2.2% body length day-1, much higher than for English Nemurella (unimodal emergence), or any other stonefly. The thermal sum (degree-days above 0°C) accumulated between the two emergence peaks, at the German sites studied, resembled cumulated degree-days in a laboratory culture. For an Austrian population with trimodal emergence, degree-days accumulated in the field were lower, suggesting a lower temperature demand and partial trivoltinism. This is the only case of confirmed plurivoltinism in Plecoptera. Nemurella pictetii seems to have lost seasonal life cycle cues, enabling the opportunistic use of favourable local conditions. Population synchrony appears to be regulated by the thermal demand for development and the emergence threshold temperature. 相似文献
13.
T. M. Sutton 《Zeitschrift fur angewandte Ichthyologie》2011,27(6):1365-1370
Humpback whitefish Coregonus pidschian are found throughout Alaska and support both subsistence and personal‐use fisheries. Long‐term sustainability of these fisheries requires an understanding of life‐history characteristics and reproductive biology to provide fisheries managers with the tools required for science‐based management. The objective of this study was to examine the reproductive characteristics of humpback whitefish in the Chatanika River, Alaska, from late August through September 2008. Absolute fecundity, relative fecundity, gonadosomatic index (GSI), relative egg size, and age were examined for 60 female humpback whitefish. Mean absolute fecundity was 45 000 eggs female?1 (range, 11 747–108 426 eggs female?1) and was positively related to both fork length (r2 = 0.74) and wet weight (r2 = 0.83). Gonadosomatic index values averaged 15.5% (range, 6.4–23.7%). Relative fecundity was positively related to GSI (r2 = 0.76) and showed a positive relationship with age until ages 15–20 before declining thereafter. Relative egg size was inversely related to GSI (r2 = 0.38) and age (r2 = 0.22) for female humpback whitefish. The results of our study provide information that will allow for better management of the personal use fishery for humpback whitefish in the Chatanika River and increase our understanding of the reproductive biology of this species throughout its geographic distribution. 相似文献
14.
L. Kaur K.K. Gill P.K. Kingra A Sirari G. Singh D. Kumar 《Archives Of Phytopathology And Plant Protection》2013,46(2):178-184
The relationship between environmental factors and the incidence of yellow mosaic virus disease in green gram was studied for the period of 23?years using historical data on disease index (DI) and environmental factors from 1985 to 2007. The environmental factors showed consistently significant correlations with DI during the 29th–33rd standard meteorological week (SMW) periods and the same period was taken for further analysis. Among the environmental factors, maximum temperature was highly positively correlated (r?=?0.63), followed by sunshine hours in SMW 29 (r?=?0.48), with the disease. However, rainfall during SMW 30–33 (r?=??0.38) and evening relative humidity during SMW 29–33 (r?=??0.42) were negatively correlated with disease. As these four environmental factors contribute mainly to disease, same were used to develop the functional models by conducting multiple regression analysis for the period SMW 29–33. Among these, linear model gave highest R2 value (0.47) and this model was validated for the periods 2008–2010 and the predicted estimates were in full agreement with the observed estimates (R2?=?0.874). 相似文献
15.
Natural selection acting on timing of metamorphosis can be sex-specific, resulting in differences in timing between males
and females. Insects with discrete generations frequently show protandry: males usually mature before females. Both Euphydryas editha and E. aurinia butterflies followed this trend. The present study was motivated by the unusual observation of consistent postandry in addition
to protandry. In a single E. editha population observed over 20 years the emergence period of males was longer than that of females, both the first and last
emerging individuals being males. Variance of timing among individual E. editha larvae is imposed by spatial patchiness of the snowmelt that releases them from winter diapause. If individual larvae released
late from diapause were to compensate for their lateness by shortening their development times, they would be small at maturity.
If such compensation were only partial, they would be both late and small. Size and timing would become associated. If females
were more prone to such partial compensation than males, the observations of postandry could be explained and the prediction
made that any tendency for late individuals to be small should be stronger in females than in males. This was the case: in
1 year late males were the same size as early males, in a second year they were larger. Late females were significantly smaller
than early females in both years. In E. aurinia, results were opposite both to theoretical prediction and to the observations from E. editha: although the male emergence period was longer than that of females exactly as in E. editha, late males were smaller than early ones, while late females were not small. The data from E. editha support the hypothesis of a sex-specific trade-off between size and emergence time, the data from E. aurinia do not. 相似文献
16.
Global warming is expected to result in earlier emergence of tree seedlings that may experience higher damages and mortality due to late frost in spring. We monitored emergence, characteristics, and survival of seedlings across ten tree species in temperate mixed deciduous forests of Central Europe over one and a half year. We tested whether the timing of emergence represents a trade‐off for seedling survival between minimizing frost risk and maximizing the length of the growing period. Almost two‐thirds of the seedlings died during the first growing period. The timing of emergence was decisive for seedling survival. Although seedlings that emerged early faced a severe late frost event, they benefited from a longer growing period resulting in increased overall survival. Larger seedling height and higher number of leaves positively influenced survival. Seedlings growing on moss had higher survival compared to mineral soil, litter, or herbaceous vegetation. Synthesis. Our findings demonstrate the importance of emergence time for survival of tree seedlings, with early‐emerging seedlings more likely surviving the first growing period. 相似文献
17.
The seasonal changes in somatic energy content of Gulf of Alaska yellowfin sole, Pleuronectes asper 总被引:3,自引:0,他引:3
Seasonal measurement of body energy content was made for Pleuronectes asper (Pallas, 1814) from the Gulf of Alaska. Whole body energy content of complete fish (~ 3472 J g?1 wet wt) was minimal in May for females as their overwintering phase ended, then increased to ~ 4456 J g?1 prior to spawning. The ovarian index [(g.w./t.w.) × 100] and energy content of ovaries (J g?1) was highest in June and May respectively, and then declined markedly by August as spawning occurred. Throughout the year male whole body energy content of complete fish ranged from 3351 to 4590 J g?1 with the lowest values in May and highest values occurring during June to September, the feeding season. The testes index [(g.w./t.w.) × 100] and total energy content of testes (J g?1) were high in March and lowest during June and July. On a weight-specific basis, males and females had similar whole body energy values throughout the year. Juveniles followed the same seasonal trends in energy storage as adults and had similar whole body energy values. Whole body energy content was linearly related to wet and dry weight condition factor with r2 values of 0.70 and 0.87, respectively. Dry body weight as percent of wet body weight was the best predictor of body energy (r2=0.91). Yellowfin sole had an annual energy cycle with energy accumulation and growth from May to September. Thereafter they utilized stored energy for metabolic and reproductive needs. Spawning began in late May or early June and fish were spent by August. Whole body energy content increased by 28, 33 and 35% between May and June, for females, juveniles, and males, respectively, the most dramatic change during the year long survey. This suggests that intense feeding in May must be an important aspect of their energy storage cycle. 相似文献
18.
P. W. DYSON 《The Annals of applied biology》1977,87(3):471-483
Twenty-five field experiments on barley were done at four sites from 1970 to 1975, with an additional site in 1975, comparing five rates of nitrogen application. The crops were sampled at c. 14-day intervals from about the four-leaf stage to maturity to follow changes with time in the dry weights of the constituent plant parts and to measure fertile tiller number, grain number per ear and grain weight. Some data have been selected from this body of information and regression analysis has been used to assess the possible importance of pre- and post-anthesis growth in determining the yield of barley. Ear emergence was taken as an approximate indicator of anthesis. Yield was closely related (r=+0–96) and almost equal to the amount of dry matter accumulated before ear emergence for twenty-one of the experiments, with a regression coefficient of 0–95. In two of the remaining experiments the regression coefficient was greater, 1–14; and smaller in the other two, o-8i. Plant population is also shown to affect the regression coefficient. Despite these anomalies grain yield was more closely related to plant dry weight at ear emergence than to the increase in weight after ear emergence (r =+0–79). The increase in plant dry weight after ear emergence was frequently less than the yield of grain, suggesting that the plant can compensate for inadequate photosynthesis during grain filling. The result of this compensation is a reduction in straw dry weight. This implies that previously assimilated dry matter is transported to the grain, or that respiratory losses from the straw are not replaced by current photosynthesis. These observations suggest that yield may be limited by sink capacity rather than by photosynthesis after ear emergence. The main component of sink capacity, grain number per m2 was closely related to yield (r =+0–95) and is known to be determined at or before anthesis. Grain size was shown to be related to grain number per ear (r= 4- 0–99), suggesting that grain size is also, at least partially, determined at ear emergence. Therefore, all the yield components are determined, wholly or partly before ear emergence. 相似文献
19.
Germinable seed densities in the surface (0–10 cm) soil of pasture communities growing at Lansdown, near Townsville, were measured during the late dry season before the first germinating rain and again during the following wet season after germination but before the input of new seed. Seedlings emerging in the field were counted at approximately weekly intervals during this period to determine emergence patterns. Twelve communities were sampled in 1980–81 and six were re-sampled in 1981–82. During the late dry season germinable seed densities ranged from 5000 to 40 000 seeds m-2. Seeds of the introduced legume, Stylosanthes hamata, were present in all pastures. There were many seeds of annual grasses (Digitaria ciliaris and Brachiaria miliiformis) and sedges (Cyperus and Fimbristylis spp.) but only few seeds of perennial grasses (both native and introduced). Soil seed densities were much lower during the wet season than during the preceding dry season, particularly for the grasses. Emergence commenced and approximately 70% of all seedlings emerged on the first major rainfall of the wet season. The subsequent emergence pattern varied between years. In 1980–81 there was a gradual and continuous increase in seedling numbers under the continuously moist conditions which prevailed. In 1981–82 further emergence occurred in discrete events related to rainfall and intervening dry periods. Maximum seedling densities exceeded 34 000 seedlings m-2 including 29 000 grass seedlings (mainly annual species). The implications of these results for species survival and pasture composition are discussed. 相似文献
20.
Cory W. Morin Andrew J. Monaghan Mary H. Hayden Roberto Barrera Kacey Ernst 《PLoS neglected tropical diseases》2015,9(8)
Meteorological factors influence dengue virus ecology by modulating vector mosquito population dynamics, viral replication, and transmission. Dynamic modeling techniques can be used to examine how interactions among meteorological variables, vectors and the dengue virus influence transmission. We developed a dengue fever simulation model by coupling a dynamic simulation model for Aedes aegypti, the primary mosquito vector for dengue, with a basic epidemiological Susceptible-Exposed-Infectious-Recovered (SEIR) model. Employing a Monte Carlo approach, we simulated dengue transmission during the period of 2010–2013 in San Juan, PR, where dengue fever is endemic. The results of 9600 simulations using varied model parameters were evaluated by statistical comparison (r2) with surveillance data of dengue cases reported to the Centers for Disease Control and Prevention. To identify the most influential parameters associated with dengue virus transmission for each period the top 1% of best-fit model simulations were retained and compared. Using the top simulations, dengue cases were simulated well for 2010 (r2 = 0.90, p = 0.03), 2011 (r2 = 0.83, p = 0.05), and 2012 (r2 = 0.94, p = 0.01); however, simulations were weaker for 2013 (r2 = 0.25, p = 0.25) and the entire four-year period (r2 = 0.44, p = 0.002). Analysis of parameter values from retained simulations revealed that rain dependent container habitats were more prevalent in best-fitting simulations during the wetter 2010 and 2011 years, while human managed (i.e. manually filled) container habitats were more prevalent in best-fitting simulations during the drier 2012 and 2013 years. The simulations further indicate that rainfall strongly modulates the timing of dengue (e.g., epidemics occurred earlier during rainy years) while temperature modulates the annual number of dengue fever cases. Our results suggest that meteorological factors have a time-variable influence on dengue transmission relative to other important environmental and human factors. 相似文献