scholarly journals An assessment of temporal variability in mast seeding of North American Pinaceae

Author(s):  
Jalene M. LaMontagne ◽  
Miranda D. Redmond ◽  
Andreas P. Wion ◽  
David F. Greene

Our overall objective is to synthesize mast-seeding data on North American Pinaceae to detect characteristic features of reproduction (i.e. development cycle length, serotiny, dispersal agents), and test for patterns in temporal variation based on weather variables. We use a large dataset ( n = 286 time series; mean length = 18.9 years) on crop sizes in four conifer genera ( Abies , Picea , Pinus , Tsuga ) collected between 1960 and 2014. Temporal variability in mast seeding (CVp) for 2 year genera ( Abies , Picea , Tsuga ) was higher than for Pinus (3 year), and serotinous species had lower CVp than non-serotinous species; there were no relationships of CVp with elevation or latitude. There was no difference in family-wide CVp across four tree regions of North America. Across all genera, July temperature differences between bud initiation and the prior year (Δ T ) was more strongly associated with reproduction than absolute temperature. Both CVp and Δ T remained steady over time, while absolute temperature increased by 0.09°C per decade. Our use of the Δ T model included a modification for Pinus , which initiates cone primordia 2 years before seedfall, as opposed to 1 year. These findings have implications for how mast-seeding patterns may change with future increases in temperature, and the adaptive benefits of mast seeding. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.

1954 ◽  
Vol 35 (1) ◽  
pp. 26-32 ◽  
Author(s):  
Peter E. Wasko

From twenty years of January and February North American trajectories of migratory anticyclones four typical groups were found. Examples of these types were studied with respect to the temporal variations of the pressure and temperature at standard levels in a vertical column of the atmosphere over the centers of the migratory anticyclones. Certain characteristic features of these variations are summarized.


1978 ◽  
Vol 56 (20) ◽  
pp. 2460-2469 ◽  
Author(s):  
J. C. Sutton ◽  
C. J. Swanton ◽  
T. J. Gillespie

Weather variables, leaf blight, and airborne spores of Botrytis squamosa were monitored in onion field plots at the Holland–Bradford Marsh, Ontario, in 1976. Incidence of spores showed marked daily periodicities with peaks normally between 0900 and 1200 hours Eastern Standard Time (EST). Daily spore counts were low (< 85 spores) during 7 to 28 July, often high (> 1000 spores) during29 July to 16 August, and moderate (100 to 1000 spores) between 17 and 28 August. Spore production was observed only on necrotic portions of onion leaves. Circumstantial and correlative evidence indicated that spore production was promoted by persistent leaf wetness (> 13 h), high temperatures during wetness periods (14 to 20 °C), and by leaf dieback but was restricted by brief wetness periods [Formula: see text] and by cool temperatures [Formula: see text]. Linear correlation analyses of 2- to 4-day running means of data indicated that important limiting factors in spore production were wetness duration during 7 to 28 July, temperature during 29 July to 28 August, and severity of dieback during 7 July to 16 August. Lodging appeared to suppress incidence of spores after 16 August. Spore release was promoted largely by declining relative humidity (RH) and by rain but occasionally by increasing RH. Striking peaks of airborne spores occurred during rain showers. Spore counts when leaves were dry failed to correlate with wind speed, and many spores were dispersed when wind speeds were low(1 to 4 km/h).


2011 ◽  
Vol 78 (1) ◽  
pp. 69-72 ◽  
Author(s):  
Anna Banaszek ◽  
Krystyna Musiał

For the first time in Poland two habitats of <em>Lemna minuta</em> were found in 2007. Both of them are located in the warmest south-western region of the country. <em>L. minuta</em> is a North-American kenophyte which has come to Poland probably from Germany. This species grows no bigger than 1-3 mm, which makes it the smallest representative of genus <em>Lemna</em>. The most characteristic features of <em>L. minuta</em> are the lack of purple pigmentation and the presence of only one hardly visible vein in the frond.


Author(s):  
Andreas P. Wion ◽  
Ian S. Pearse ◽  
Kyle C. Rodman ◽  
Thomas T. Veblen ◽  
Miranda D. Redmond

We aimed to disentangle the patterns of synchronous and variable cone production (i.e. masting) and its relationship to climate in two conifer species native to dry forests of western North America. We used cone abscission scars to reconstruct ca 15 years of recent cone production in Pinus edulis and Pinus ponderosa , and used redundancy analysis to relate time series of annual cone production to climate indices describing the North American monsoon and the El Niño Southern Oscillation (ENSO). We show that the sensitivity to climate and resulting synchrony in cone production varies substantially between species. Cone production among populations of P. edulis was much more spatially synchronous and more closely related to large-scale modes of climate variability than among populations of P. ponderosa . Large-scale synchrony in P. edulis cone production was associated with the North American monsoon and we identified a dipole pattern of regional cone production associated with ENSO phase. In P. ponderosa , these climate indices were not strongly associated with cone production, resulting in asynchronous masting patterns among populations. This study helps frame our understanding of mast seeding as a life-history strategy and has implications for our ability to forecast mast years in these species. This article is part of the theme issue ‘The ecology and evolution of synchronized seed production in plants’.


2013 ◽  
Vol 22 (8) ◽  
pp. 1083 ◽  
Author(s):  
Lisa M. Ellsworth ◽  
Creighton M. Litton ◽  
Andrew D. Taylor ◽  
J. Boone Kauffman

Frequent wildfires in tropical landscapes dominated by non-native invasive grasses threaten surrounding ecosystems and developed areas. To better manage fire, accurate estimates of the spatial and temporal variability in fuels are urgently needed. We quantified the spatial variability in live and dead fine fuel loads and moistures at four guinea grass (Megathyrsus maximus) dominated sites. To assess temporal variability, we sampled these four sites each summer for 3 years (2008–2010) and also sampled fuel loads, moistures and weather variables biweekly at three sites for 1 year. Live and dead fine fuel loads ranged spatially from 0.85 to 8.66 and 1.50 to 25.74Mgha–1 respectively, and did not vary by site or year. Biweekly live and dead fuel moistures varied by 250 and 54% respectively, and were closely correlated (P<0.05) with soil moisture, relative humidity, air temperature and precipitation. Overall, fine fuels and moistures exhibited tremendous variability, highlighting the importance of real-time, site-specific data for fire prevention and management. However, tight correlations with commonly quantified weather variables demonstrates the capacity to accurately predict fuel variables across large landscapes to better inform management and research on fire potential in guinea grass ecosystems in Hawaii and throughout the tropics.


Author(s):  
Валерий Константинович Тохтарь ◽  
Юлия Константиновна Виноградова ◽  
Андрей Юрьевич Курской ◽  
Виктория Николаевна Зеленкова ◽  
Михаил Юрьевич Третьяков

В результате флористического обследования трех железнодорожных станций Транссибирской магистрали в пределах Нижегородской области выявлен видовой состав локальных флор и установлены характерные особенности их структур. Комплексное исследование проводилось отдельно для трех экотопов: 1) межрельсовое пространство, 2) насыпи железных дорог и 3) прилегающие территории в пределах полосы отчуждения. Наибольшее число видов (97) зарегистрировано на железнодорожной станции «Нижний Новгород», а наименьшее - на железнодорожной станции г. Семенов (45). Анализ структур флор по жизненным формам свидетельствует о том, что на 2-х из 3-х ж.д. станциях преобладают монокарпические травы: от 49,5% в г. Нижний Новгород до 54,9% в г. Дзержинск. По географическому происхождению преобладают европейские виды, доля которых составляет от 45,0% (г. Дзержинск) до 69,0% (г. Семенов). Значительное количество видов, приходящихся на североамериканские и средиземноморские растения, а также флористические находки новых для Нижегородской области видов, сделанные авторами, свидетельствуют о достаточно высоком потенциале изученных ж.д. магистралей для интенсивной миграции по ним растений и динамичности исследованных флор. Установлено, что структура изученных флорокомплексов железных дорог существенно отличается в пределах поперечного профиля. В межрельсовом пространстве формируются сообщества растений, в которых наиболее важную роль играют монокарпические травы, в частности, однолетние виды европейского, североамериканского и средиземноморского происхождения так же, как и в большинстве флор железных дорог других регионов планеты. На откосах ж.д. насыпей и прилегающих территориях на первые места в структуре флорокомплексов выходят травянистые поликарпики. Отводные канавы и понижения часто заняты гидрофильными сообществами. As a result of a floristic survey of three railway stations of the TRANS-Siberian railway within the Nizhniy Novgorod region, the species composition of local floras was revealed and the characteristic features of their structures were established. A comprehensive study was conducted separately for three ecotopes: 1) inter-rail space, 2) railway embankments, and 3) adjacent territories within the exclusion zone. The largest number of species (97) was registered at the Nizhny Novgorod railway station, while the smallest number was noted at the Semenov railway station (45). Analysis of flora structures by life forms shows that monocarpic grasses predominate at 2 out of 3 railway stations: from 49,5% in Nizhny Novgorod to 54,9% in Dzerzhinsk. Within species studied at different sites by geographical origin, European species predominate, the share of which ranges from 45,0% (Dzerzhinsk) to 69,0% (Semenov). A significant number of species belonging to North American and Mediterranean plants, as well as floristic findings of new species for the Nizhny Novgorod region, made by the authors, indicate a fairly high potential of the studied railways for intensive migration of plants along them and the dynamism of the studied flora. It is established that the structure of the studied railway flora complexes differs significantly within the transverse profile. Within the inter-rail space, the most important role in plant communities is played by monocarpic grasses, in particular, annual species of European, North American and Mediterranean origin, as well as in most railway floras of other regions of the world. On the slopes of railway embankments and adjacent territories, grassy polycarpics take the first place in the structure of flora complexes. Drainage ditches are often occupied by hydrophilic communities.


Agrometeoros ◽  
2018 ◽  
Vol 25 (2) ◽  
Author(s):  
Lucimara Wolfarth Schirmbeck ◽  
Denise Cybis Fontana ◽  
Juliano Schirmbeck

This work aimed at evaluating the TVDI (Temperature-Vegetation Dryness Index) as an indicator of water status and characterizing water spatial and temporal variability for the spring-summer crops in Rio Grande do Sul. For this purpose, the surface temperature MODIS products (MOD11A2) and vegetation index (MOD13A2) with spatial resolution of 1,000 m and temporal resolution of 8 and 16 days, respectively, were used to obtain the TVDI. Data from meteorological stations were also used to determine the water balance. The period of analysis corresponded to the spring-summer crops of 2011-12, 2012-13, 2013-14, 2014-15 and 2015-16. The results show that the TVDI is a good indicator of water surface status and represented well the water deficit occurrence in the spring-summer crops. The spatial and temporal resolution of the images used to calculate the index allowed obtaining reliable data, both during the development cycle and between Ecoclimatic Regions. These characteristics show that TVDI can be used as an indicator of water status and can, therefore, be part of the agrometeorological monitoring programs in Rio Grande do Sul.


Author(s):  
Bernardo Maestrini ◽  
Bruno Basso

AbstractUnderstanding subfield crop yields and temporal stability is critical to better manage crops. Several algorithms have proposed to study within-field temporal variability but they were mostly limited to few fields. In this study, a large dataset composed of 5520 yield maps from 768 fields provided by farmers was used to investigate the influence of subfield yield distribution skewness on temporal variability. The data are used to test two intuitive algorithms for mapping stability: one based on standard deviation and the second based on pixel ranking and percentiles. The analysis of yield monitor data indicates that yield distribution is asymmetric, and it tends to be negatively skewed (p < 0.05) for all of the four crops analyzed, meaning that low yielding areas are lower in frequency but cover a larger range of low values. The mean yield difference between the pixels classified as high-and-stable and the pixels classified as low-and-stable was 1.04 Mg ha−1 for maize, 0.39 Mg ha−1 for cotton, 0.34 Mg ha−1 for soybean, and 0.59 Mg ha−1 for wheat. The yield of the unstable zones was similar to the pixels classified as low-and-stable by the standard deviation algorithm, whereas the two-way outlier algorithm did not exhibit this bias. Furthermore, the increase in the number years of yield maps available induced a modest but significant increase in the certainty of stability classifications, and the proportion of unstable pixels increased with the precipitation heterogeneity between the years comprising the yield maps.


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