Search results for "growing season"
showing 10 items of 100 documents
Plant removal disturbance and replant mitigation effects on the abundance and diversity of low-arctic soil biota
2014
Abstract Due to the dependence of soil organisms on plant derived carbon, disturbances in plant cover are thought to be detrimental for the persistence of soil biota. In this work, we studied the disturbance effects of plant removal and soil mixing and the mitigation effects of replanting on soil biota in a low-arctic meadow ecosystem. We set up altogether six replicate blocks, each including three randomized treatment plots, at two distinct fells at Kilpisjarvi, northern Finland. Vegetation was removed in two thirds of the plots: one third was then kept barren (the plant-removal treatment), while the other third was replanted with a local herb Solidago virgaurea. The remaining plots of int…
Wind speed and temperature trends impacts on reference evapotranspiration in Southern Italy
2014
In this study, the impacts of both temperature and wind speed trends on reference evapotranspiration have been assessed using as a case study the Southern Italy, which present a wide variety of combination of such climatic variables trends in terms of direction and magnitude. The existence of statistically significant trends in wind speed and temperature from observational datasets, measured in ten stations over Southern Italy during the period 1968–2004, has been investigated. Time series have been examined using the Mann–Kendall nonparametric statistical test in order to detect possible evidences of wind speed and temperature trends at different temporal resolution and significance level.…
Influence of climate change on phenological phases in Latvia and Lithuania
2009
To investigate the impact of recent climatic changes on plant development, this study used phenological data of the volunteer networks in Latvia and Lithuania from the 1971-2000 period. The phenological calendar method was applied. Phenological seasons were described using data on 6 phenological phases at 10 stations. The growing season was described using birch Betula pendula as an example. Correlation analysis, linear regression and non-parametric Mann-Kendall trend tests were applied to establish the relationship between phenological phases and meteorological factors (temperature, precipitation) and the North Atlantic Oscillation (NAO). The results indicate a statisti- cally significant …
Plant colonization of bare peat surface - relative importance of seed availability and soil
1992
A field survey on two former peat harvesting sites of similar successional age revealed a marked difference in species composition and a 30-fold difference in biomass of the established vegetation Based on this observation, a field experiment in which the substrate was changed between sites was conducted to examine whether the differences in revegetation were mainly a consequence of differences in seed supply or in substrate quality After three growing seasons, a many hundred-fold difference in plant biomass existed between the transplanted and control plots with the same substrate, but only a small difference between the plots with a different substrate within the site Biological activity …
Effects of artificial plant cover on plant colonization of a bare peat surface
1992
. This paper describes the effect of artificial plant cover on plant colonization of a bare peat surface, resulting from peat harvesting. Plant species colonization was compared on plots supplied with plastic models simulating Vaccinium vitis-idaea plants and plots without this artificial cover. After two growing seasons, species composition and total biomass of the established plant cover were similar in the two plot types. However, the number of established seedlings in the plots with artificial cover was significantly higher than that in the plots without cover. Out of 13 species observed four differed significantly in their performance on the two plot types. Betula spec. had both higher…
Foliar influences on the vegetative development of grapevine
1997
<p style="text-align: justify;">Various defoliation treatments were applied to grapevine shoots during the whole duration of the growth period: full defoliation of every shoot of vine, defoliations retaining a various number of adult leaves to the base of every shoot and defoliations retaining a various number of young leaves to the top. The effects of these treatments allow to identify the major foliar influences on the vegetative development. Total defoliation induced a lesser intemodal elongation. This result is probably due, in part, to a carbohydrates deficiency consecutive to this drastic treatment. The defoliations with variation of the number of young leaves showed that the le…
Modelling surface energy fluxes over maize using a two-source patch model and radiometric soil and canopy temperature observations
2008
Abstract Models estimating surface energy fluxes over partial canopy cover with thermal remote sensing must account for significant differences between the radiometric temperatures and turbulent exchange rates associated with the soil and canopy components of the thermal pixel scene. Recent progress in separating soil and canopy temperatures from dual angle composite radiometric temperature measurements has encouraged the development of two-source (soil and canopy) approaches to estimating surface energy fluxes given observations of component soil and canopy temperatures. A Simplified Two-Source Energy Balance (STSEB) model has been developed using a “patch” treatment of the surface flux so…
Productivity and canopy modification of Medicago arborea as affected by defoliation management and genotype in a Mediterranean environment
2004
Medicago arborea is one of the most potentially valuable fodder shrubs in a Mediterranean environment because of its high preference by small ruminants and its nutritive value. Edible biomass production is affected by agronomic and environmental factors. A study, carried out in an inland area of Sicily in the growing seasons of 1994/95, 1995/96 and 1996/97, evaluated the forage production and canopy modification in a M. arborea plantation after (i) commencing defoliation 1 or 2 years after transplanting and (ii) defoliating only in autumn (A), only in early summer (S) or in both seasons (A and S). Six clones derived from five different Mediterranean populations were used. Plant age at the f…
Crop Load and Rootstock Influence on Dry Matter Partitioning in Trees of Early and Late Ripening Peach Cultivars
2002
ADDITIONAL INDEX WORDS. vigor, starch, fruit size, Prunus persica ABSTRACT. Effect of crop load on dry matter partitioning was studied on 3-year-old peach ((Prunus persica (L.) Batsch (Peach Group)) trees of the early ripening 'Early May Crest' (EMC) grafted on 'GF677' and Penta (Prunus domestica L.) rootstock and the late ripening 'Flaminia' grafted on 'GF677' rootstock ((Prunus persica x Prunus dulcis (Mill.) D. A. Webb) and grown outdoors in 230-L containers, for 2 years. Fruit thinning was carried out 10 days after fruit set to produce different crop loads. Trees were sampled destructively throughout two growing seasons and divided into above- ground and root components, for dry matter …
Comparison of Crop Trait Retrieval Strategies Using UAV-Based VNIR Hyperspectral Imaging.
2021
Hyperspectral cameras onboard unmanned aerial vehicles (UAVs) have recently emerged for monitoring crop traits at the sub-field scale. Different physical, statistical, and hybrid methods for crop trait retrieval have been developed. However, spectra collected from UAVs can be confounded by various issues, including illumination variation throughout the crop growing season, the effect of which on the retrieval performance is not well understood at present. In this study, four retrieval methods are compared, in terms of retrieving the leaf area index (LAI), fractional vegetation cover (fCover), and canopy chlorophyll content (CCC) of potato plants over an agricultural field for six dates duri…