Tree lines

1989 ◽  
Vol 324 (1223) ◽  
pp. 233-245 ◽  
Keyword(s):  
Growing Season ◽  
Early Spring ◽  
Summer Temperature ◽  
Northern Europe ◽  
Late Winter ◽  
Controlled Environment ◽  
Cold Climates ◽  
Tree Line ◽  
The Mean ◽  
Boreal Period

Trees do not generally grow in places where the mean temperature of the warmest month is less than about 10 °C. At their limit, trees are often short and crooked, the condition known as krummholz ; and the transition from tall forest to dwarf shrubby vegetation is often abrupt, forming a distinct tree line. Tree lines fluctuate with climatic change. There is compelling evidence to suggest that they shift to higher elevations and higher latitudes in warmer periods. In northern Europe, they were about 200 m higher in the Boreal period when the temperature is believed to have been 2 °C warmer than now. Controlled-environment studies and tree-ring evidence also point to considerable sensitivity of growth at the tree line to fluctuations in the summer temperature. Forest vegetation differs aerodynamically from dwarf vegetation in being aerodynamically rough. Consequently, the temperatures of above-ground tissues are closely coupled to temperatures of the air. In contrast, shorter vegetation experiences tissue temperatures and microclimates that depend substantially on other climatological variables, notably radiation and wind speed. Short vegetation is, on average, warmer than the air; this is the main reason why dwarf shrubs can succeed in cold climates where trees fail to grow and reproduce. Water stress commonly occurs in late winter and early spring when soil water is frozen. The foliage of trees at the tree line displays an inability to restrict water loss, either because the epidermis is damaged by abrasion or because the cuticle does not properly develop in the reduced growing season. Consequently, the longevity of leaves is reduced. Winter damage to trees is also likely as a result of gales and the deposition of ice in the canopy, both of which break branches and may contribute to the generally misshapen form of the crown.

scholarly journals Changes of Variability in Response to Increasing Greenhouse Gases. Part II: Hydrology

2009 ◽  
Vol 22 (22) ◽  
pp. 6089-6103 ◽  
Author(s):  
Richard T. Wetherald
Keyword(s):  
Soil Moisture ◽  
Greenhouse Gases ◽  
General Circulation ◽  
Circulation Model ◽  
Early Spring ◽  
Precipitation Rate ◽  
Late Winter ◽  
Annual Data ◽  
Geophysical Fluid Dynamics Laboratory ◽  
The Mean

Abstract This paper examines hydrological variability and its changes in two different versions of a coupled ocean–atmosphere general circulation model developed at the National Oceanic and Atmospheric Administration/Geophysical Fluid Dynamics Laboratory and forced with estimates of future increases of greenhouse gas and aerosol concentrations. This paper is the second part, documenting potential changes in variability as greenhouse gases increase. The variance changes are examined using an ensemble of 8 transient integrations for an older model version and 10 transient integrations for a newer model. Monthly and annual data are used to compute the mean and variance changes. Emphasis is placed on computing and analyzing the variance changes for the middle of the twenty-first century and compared with those found in the respective control integrations. The hydrologic cycle intensifies because of the increase of greenhouse gases. In general, precipitation variance increases in most places. This is the case virtually everywhere the mean precipitation rate increases and many places where the precipitation decreases. The precipitation rate variance decreases in the subtropics, where the mean precipitation rate also decreases. The increased precipitation rate and variance, in middle to higher latitudes during late fall, winter, and early spring leads to increased runoff and its variance during that period. On the other hand, the variance changes of soil moisture are more complicated, because soil moisture has both a lower and upper bound that tends to reduce its fluctuations. This is particularly true in middle to higher latitudes during winter and spring, when the soil moisture is close to its saturation value at many locations. Therefore, changes in its variance are limited. Soil moisture variance change is positive during the summer, when the mean soil moisture decreases and is close to the middle of its allowable range. In middle to high northern latitudes, an increase in runoff and its variance during late winter and spring plus the decrease in soil moisture and its variance during summer lend support to the hypothesis stated in other publications that a warmer climate can cause an increasing frequency of both excessive discharge and drier events, depending on season and latitude.

The rumenitis and liver abscess complex and vitamin A status in beef cattle

1970 ◽  
Vol 12 (2) ◽  
pp. 291-298
Author(s):  
A. C. Rowland
Keyword(s):  
Vitamin A ◽  
Late Summer ◽  
Early Spring ◽  
Agglutination Test ◽  
Late Winter ◽  
Liver Lesions ◽  
Seasonal Incidence ◽  
Vitamin A Status ◽  
The Mean ◽  
Intensively Managed

SUMMARYThe seasonal incidence of rumen and liver lesions is recorded in traditional and in intensively managed cattle, together with the vitamin A status of the two groups. Rumen lesions were observed to reach a peak in the late winter and early spring in traditional cattle, at which time the liver vitamin A levels fell to the lowest point; liver lesions reached a peak in the late summer. No specific trend was observable in rumen and liver lesions in the barley beef group. The mean levels of vitamin A were approximately one-third of those shown by the traditionally managed animals.It did not prove possible using the agglutination test to identify the sera of animals showing active hepatic necrobacillosis at the time of slaughter.

scholarly journals Tillering dynamics in spring and summer of marandu palisade grass pastures previously used under deferred grazing

2021 ◽  
Vol 73 (6) ◽  
pp. 1422-1430
Author(s):  
B.H.R. Carvalho ◽  
J.A. Martuscello ◽  
G.O. Rocha ◽  
N.A.M. Silva ◽  
G.S. Borges ◽  
...  
Keyword(s):  
Stability Index ◽  
Growing Season ◽  
Experimental Period ◽  
Early Spring ◽  
Late Winter ◽  
Population Stability ◽  
Brachiaria Brizantha ◽  
Appearance Rate ◽  
High Forage ◽  
Tiller Mortality

ABSTRACT This work was conducted to evaluate the effect of deferred pasture condition of Brachiaria brizantha cv. Marandu in the late winter on tillering during the growing season. The treatments were three pasture conditions at late winter: short pasture, tall pasture and tall/mown pasture. In September and October, tiller appearance rate (TApR) and tiller mortality rate (TMoR) were greater in the tall/mown pasture. In November and December, tall pasture presented greater TApR. From November to January the TMoR was greater in the tall pasture. The tiller stability index of short and tall/mown pastures were greater in October. The short pasture presented a greater tiller number than the tall and tall/mown pastures during the entire experimental period. Deferred and short pasture of marandu palisade grass at late winter presents in general lower tiller mortality and higher population density of tillers from the early spring onwards, in comparison to tall pasture. The mowing of marandu palisade grass with high forage mass at the late winter, although it only temporarily compromises the population stability of tillers, also stimulates its fast tillering from spring on.

Weather conditions associated with grape production in the Okanagan Valley of British Columbia and potential impact of climate change

2002 ◽  
Vol 82 (4) ◽  
pp. 755-763 ◽  
Author(s):  
J. M. Caprio ◽  
H. A. Quamme
Keyword(s):  
Climate Change ◽  
British Columbia ◽  
Weather Conditions ◽  
Growing Season ◽  
Early Spring ◽  
Late Winter ◽  
Vitis Vinifera L ◽  
Flower Bud ◽  
Harvest Year ◽  
Okanagan Valley

An iterative χ2 method applied to 60 yr of records in the Okanagan Valley of British Columbia (1930–1989) revealed that the main climatic factor limiting grape production (Vitis spp. and Vitis vinifera L.) was low temperatures (critical value range, ≤–6°C to ≤–23°C) occurring during late October, November, December and February. Daytime temperatures ≤–9°C during late November and early December benefited grape production, probably because it prevented vine de-acclimation. Detrimental effects of precipitation during late October were probably associated with the early movement of Arctic fronts into the region. Beneficial effects of precipitation in the form of snow were observed in January. During the pre-harvest growing season, except for a 2-wk period in July, high temperatures (≥26°C) were associated with good production, probably because warm temperatures are required for flower bud initiation and development. In contrast, higher-than-normal temperatures were not beneficial to production during the harvest year. Detrimental effects of high temperature were observed during July of the pre-harvest year and July (≥32°C) and early August of the harvest year (≥28°C). During the growing season, rainfall was sometimes unfavourable for grape production under irrigation, either because of associated cool weather or greater disease occurrence. Both temperature and precipitation were greater in the last 18 yr of the study than the prior 36 yr, especially during the late winter and early spring. The anticipated climatic change appears to favour grape production in the Okanagan Valley. Key words: grape, climate change, heat stress, winter injury

scholarly journals A late-winter to early-spring temperature reconstruction for southeastern Norway from 1758 to 2006

2007 ◽  
Vol 46 ◽  
pp. 404-408 ◽  
Author(s):  
Ø. Nordli ◽  
E. Lundstad ◽  
A.E.J. Ogilvie
Keyword(s):  
20Th Century ◽  
19Th Century ◽  
18Th Century ◽  
Temperature Reconstruction ◽  
Early Spring ◽  
Late Winter ◽  
Spring Temperature ◽  
Early 19Th Century ◽  
The Mean ◽  
The 19Th Century

AbstractSystematic temperature observations were not undertaken in Norway until the early 19th century, and even then only sporadically. Climate-proxy data may be used to reconstruct temperatures before this period, but until now there have not been any climate proxies available for late winter. This situation has recently changed, as a diary containing historical ice break-up data from a farm near lake Randsfjord in southeastern Norway has been discovered. These data, together with observations from lake Mjøsa in the same region, make it possible to reconstruct temperature back to 1758. The reconstructed series, combined with instrumental series from the area near the lake, were merged into one composite time series covering the period 1758–2006. The lowest temperatures are seen during the Dalton sunspot minimum in the early 19th century. The 20th century was 1.3˚C warmer than the 19th century, whereas the 19th century was 0.4˚C warmer than the last 43 years of the 18th century. During the period 1758–1850, the mean temperature was 1.4˚C lower than the mean value of the 20th century. The warmth observed in the 1990s and at the start of the 21st century is unprecedented during the whole series.

scholarly journals Height and mowing of pasture at the end of winter modulate the tillering of Marandu palisadegrass in spring

2021 ◽  
Vol 9 (1) ◽  
pp. 13-22
Author(s):  
Bruno Humberto Rezende Carvalho ◽  
Lilian Elgalise Techio Pereira ◽  
André Fischer Sbrissia ◽  
Gabriel De Oliveira Rocha ◽  
Manoel Eduardo Rozalino Santos
Keyword(s):  
Management Strategies ◽  
Stability Index ◽  
Growing Season ◽  
Early Spring ◽  
Late Winter ◽  
Pasture Management ◽  
Appearance Rate ◽  
Urochloa Brizantha ◽  
Tiller Recruitment ◽  
Intense Process

In pastures subjected to stockpiling, the tiller population goes through an intense process of self-thinning, hindering the recruitment of new tillers in the subsequent season. We evaluated different pasture management strategies in late winter in an attempt to modify tiller recruitment during spring. Urochloa brizantha cv. Marandu was maintained at 4 different levels (heights) of stockpiled pasture at the end of winter: short (15.1 cm), medium (23.2 cm), tall (31.4 cm) and tall/mown (31.3 cm, mown to 8 cm). In October (early spring), the short and tall/mown pastures had a tiller appearance rate (TAR) and a population stability index (PSI) superior (P<0.05) to that of the tall pasture. During the remainder of the growing season, these characteristics (TAR and PSI) were similar for all pastures. Tiller survival rate (TSR) was also highest (P<0.05) in short pasture in early spring. TAR values were highest in early spring and these tillers persisted throughout the growing season. When stockpiling Marandu palisadegrass pasture during spring it is important to have it short at the end of winter to ensure early and intense tillering in spring. If pasture is tall at the end of winter mowing at this time before spelling is advantageous.

Influence of Herbicides on Japanese Holly and Hand Labor for Weed Control

Weed Science ◽  
1968 ◽  
Vol 16 (4) ◽  
pp. 478-481 ◽  
Author(s):  
S. W. Bingham
Keyword(s):  
Weed Control ◽  
Broad Spectrum ◽  
Growing Season ◽  
Early Spring ◽  
Severe Injury ◽  
Late Winter ◽  
Visual Response ◽  
Labor Requirements ◽  
Annual Weeds

Fall treatments with 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) as opposed to cultivation during the growing season reduced hand labor requirements more than 70% for weed control in Japanese holly (Ilex crenata Thumb. Rotundifolia Hort.). The response of Japanese holly to simazine varied from superior growth and quality to severe injury and death. Simazine plus 3-amino-1,2,4-triazole (amitrole) resulted in better control of small weeds than simazine alone in late winter or early spring. Dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA), N,N-dimethyl-2,2-diphenylacetamide (diphenamid), and 2,6-dichlobenzonitrile (dichlobenil) reduced labor requirements for control of annual weeds without any visual response on the Japanese holly. In certain instances, rotations of herbicides were effective for broad spectrum weed control.

Late winter – early spring sedimentation off the Great Whale River, southeastern Hudson Bay

1988 ◽  
Vol 25 (6) ◽  
pp. 930-933 ◽  
Author(s):  
B. d'Anglejan ◽  
G. Biksham
Keyword(s):  
Algal Biomass ◽  
Sediment Traps ◽  
Early Spring ◽  
Early Summer ◽  
Late Winter ◽  
Hudson Bay ◽  
Sedimentation Rates ◽  
Summer Period ◽  
The Mean ◽  
Peak Runoff

Sediment traps were used to measure particle-settling fluxes in serial moorings offshore of Great Whale River (Hudson Bay), both under the late winter sea-ice cover and during and after breakup. Before breakup, the settling fluxes ranged between 0.25 and 2 g cm−2 100 a−1, increasing from April to May in response to the progressively larger under-ice algal biomass. Fluxes also increased with depth. During and after breakup, including the early summer period of peak runoff, sedimentation rates increased to values of up to 33 g cm−2100 a−1. These fluxes agree with the mean sedimentation rate determined from 210Pb activities in the underlying sediments.

Nitrogen fertiliser use on rain-fed pasture in the Mt Lofty Ranges, South Australia. 1. Pasture mass, composition and nutritive characteristics

2003 ◽  
Vol 43 (6) ◽  
pp. 553 ◽  
Author(s):  
D. E. Elliott ◽  
R. J. Abbott
Keyword(s):  
South Australia ◽  
Growing Season ◽  
Early Spring ◽  
Late Spring ◽  
Late Winter ◽  
In Vitro Digestibility ◽  
Single Application ◽  
Nitrogen Fertiliser ◽  
N Rates

The effects of nitrogen (N) fertiliser (0–200 kg/ha) on mass, botanical composition, and N concentration (%) in herbage were examined in nine 2- or 3-year rate × time of application experiments, 14 single-year annual rate of application experiments and 15 short-term spring rate of application experiments, at 27 sites in the Mt Lofty Ranges, South Australia, in 7 years between 1970 and 1979, inclusive. Effects on in vitro digestibility and concentrations of other nutrients in herbage were examined in selected experiments.Annual applications of 200 kg N/ha increased herbage mass by an average of 2.8 t/ha (57% increase), over the average yield of unfertilised pasture of 4.6 t/ha. Subterranean clover was eliminated from the sward with this rate of N application, although this may have been exacerbated by the experimental methods used. N fertiliser application increased herbage mass throughout the growing season, except in autumn 1972 when low rainfall restricted growth and about half of the experiments were not harvested. In 5 of the 126 individual harvests, herbage mass did not respond positively to N fertiliser applications, even though clover composition of herbage declined.A single application of 50 kg N/ha in autumn increased herbage mass, 6–8 weeks later, by an average 11�kg�DM/kg N, but this N effect only persisted to a subsequent harvest in about half of the experiments, with an average residual effect of 25%. Commonly, a response to N fertiliser in the first and/or second harvests was followed by a non-responsive period and then a depression in herbage mass, where no further N fertiliser was applied. With repeated N fertiliser applications, the average responses to 50� kg� N/ha were 11 kg DM/kg N in late winter and also in early spring, similar to the autumn response, and 18�kg�DM/kg N in late spring. In a later study, a single application of 50 kg N/ha in spring, for silage or hay conservation, increased herbage mass by an average of 1.3 t/ha in late spring while the average response to 100 kg N/ha was 2.0 t/ha. Clover composition declined but was rarely eliminated from the sward by these N rates when applied only in spring.From early winter to early spring, N concentration in herbage from unfertilised pasture ranged from 3 to 4% N and then progressively declined. Relationships between herbage N concentrations and increasing N rates were either linear or curvilinear in early and late winter, whereas in spring, many of these responses to N fertiliser were sigmoidal, with a decline in herbage N concentrations being observed at low N rates. Nitrogen fertiliser applied throughout the growing season had little effect on in vitro digestibility for a wide range of pasture compositions. However, in vitro digestibility of a pure grass pasture was increased early in the growing season by applications up to 50 kg N/ha, but was depressed by the same N rates applied in late spring. Consistently, an increase in N had the following effect on the concentration of other herbage nutrients: K�increased; Ca decreased becoming more pronounced as the growing season progressed; P decreased in late spring; and Cu fell in autumn. The content of these nutrients in harvested herbage usually increased with increasing N rate, particularly when associated with large herbage mass responses to N fertiliser. The K : (Ca + Mg) ratio in herbage, a criterion for grass tetany, increased detrimentally with increasing N rate. Strategies are proposed for using N fertiliser on rain-fed pasture in the Mt Lofty Ranges.

scholarly journals Fire, land cover, and temperature drivers of bat activity in winter

Fire Ecology ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Marcelo H. Jorge ◽  
Sara E. Sweeten ◽  
Michael C. True ◽  
Samuel R. Freeze ◽  
Michael J. Cherry ◽  
...  
Keyword(s):  
Land Cover ◽  
Habitat Management ◽  
Deciduous Forest ◽  
Pinus Palustris ◽  
Growing Season ◽  
Early Spring ◽  
Bat Activity ◽  
White Nose Syndrome ◽  
Dormant Season ◽  
Wind Energy Development

Abstract Background Understanding the effects of disturbance events, land cover, and weather on wildlife activity is fundamental to wildlife management. Currently, in North America, bats are of high conservation concern due to white-nose syndrome and wind-energy development impact, but the role of fire as a potential additional stressor has received less focus. Although limited, the vast majority of research on bats and fire in the southeastern United States has been conducted during the growing season, thereby creating data gaps for bats in the region relative to overwintering conditions, particularly for non-hibernating species. The longleaf pine (Pinus palustris Mill.) ecosystem is an archetypal fire-mediated ecosystem that has been the focus of landscape-level restoration in the Southeast. Although historically fires predominately occurred during the growing season in these systems, dormant-season fire is more widely utilized for easier application and control as a means of habitat management in the region. To assess the impacts of fire and environmental factors on bat activity on Camp Blanding Joint Training Center (CB) in northern Florida, USA, we deployed 34 acoustic detectors across CB and recorded data from 26 February to 3 April 2019, and from 10 December 2019 to 14 January 2020. Results We identified eight bat species native to the region as present at CB. Bat activity was related to the proximity of mesic habitats as well as the presence of pine or deciduous forest types, depending on species morphology (i.e., body size, wing-loading, and echolocation call frequency). Activity for all bat species was influenced positively by either time since fire or mean fire return interval. Conclusion Overall, our results suggested that fire use provides a diverse landscape pattern at CB that maintains mesic, deciduous habitat within the larger pine forest matrix, thereby supporting the diverse bat community at CB during the dormant season and early spring.

Sign in / Sign up

Export Citation Format

Share Document