Increasing Soil Moisture (increasing + soil_moisture)

Distribution by Scientific Domains

Selected Abstracts

Effect of Drought Stress on Yield and Quality of Maize/Sunflower and Maize/Sorghum Intercrops for Biogas Production

S. SchittenhelmArticle first published online: 16 FEB 2010
Abstract Intercropping represents an alternative to maize (Zea mays L.) monoculture to provide substrate for agricultural biogas production. Maize was intercropped with either sunflower (Helianthus annuus L.) or forage sorghum [Sorghum bicolor (L.) Moench] to determine the effect of seasonal water supply on yield and quality of the above-ground biomass as a fermentation substrate. The two intercrop partners were grown in alternating double rows at plant available soil water levels of 60,80 %, 40,50 % and 15,30 % under a foil tunnel during the years 2006 and 2007 at Braunschweig, Germany. Although the intercrop dry matter yields in each year increased with increasing soil moisture, the partner crops responded quite differently. While maize produced significantly greater biomass under high rather than low water supply in each year, forage sorghum exhibited a significant yield response only in 2006, and sunflower in none of the 2 years. Despite greatly different soil moisture contents, the contribution of sorghum to the intercrop dry matter yield was similar, averaging 43 % in 2006 and 40 % in 2007. Under conditions of moderate and no drought stress, sunflower had a dry matter yield proportion of roughly one-third in both years. In the severe drought treatment, however, sunflower contributed 37 % in 2006 and 54 % in 2007 to the total intercrop dry matter yield. The comparatively good performance of sunflower under conditions of low water supply is attributable to a fast early growth, which allows this crop to exploit the residual winter soil moisture. While the calculated methane-producing potential of the maize/sorghum intercrop was not affected by the level of water supply, the maize/sunflower intercrop in 2006 had a higher theoretically attainable specific methane yield under low and medium than under high water supply. Nevertheless, the effect of water regime on substrate composition within the intercrops was small in comparison with the large differences between the intercrops. [source]

Phenology of fine roots and leaves in forest and grassland

Diego F. Steinaker
Summary 1The phenology of temperate vegetation is advancing in association with climate warming. Most phenology data, however, comes from flowers and tree leaves. We tested the generality of results from shoot phenology by expanding data collection in two new directions. We related forest leaf phenology to root phenology, and to phenology in a second habitat, grassland. 2We measured leaf and root phenology simultaneously in aspen forest and adjacent native grassland. Root growth accounts for 80,90% of productivity in these habitats. Seasonal variation in soil moisture and temperature were also measured. 3Forest leaf production was greatest about 45 days before peak root production, resulting in a significant negative correlation between leaf and root production in forest. Grassland leaf production was greatest about 15 days before peak root production, and grassland leaf and root production were significantly positively correlated. The duration of root production was 40% greater than that of shoot production. 4Forest leaf production increased significantly with increasing soil moisture, but not temperature. In contrast, the production of forest roots, grassland roots and grassland leaves increased significantly with soil temperature. 5Synthesis. The most commonly measured aspect of phenology, forest leaves, is out of step with the majority of production in forest, as well as phenology in grassland. The invasion of grassland by woody vegetation is characterized by a decoupling of root and shoot phenology, a result that has not been reported previously. Given the global nature of woody plant encroachment, this decoupling may influence our general understanding of productivity and carbon sequestration in response to warming. [source]

Generalized linear modelling in periglacial studies: terrain parameters and patterned ground

Miska Luoto
Abstract Generalized linear models (GLM) are mathematical extensions of linear models. GLM models are more flexible and better suited for analysing relationships of spatial data, which can often be poorly represented by classical Gaussian distributions such as least-square-regression techniques. This paper demonstrates GLM model-building procedures step-by-step for the distribution and abundance of active patterned ground in northern Finland. The exercise is based on data from an area of 200,km2 (800 modelling squares of 0.25,km2). Both the distribution and abundance models clearly indicate an increasing activity of patterned ground with (1) increasing soil moisture and (2) proportion of concave topography. Activity decreases with increasing altitude. We conclude that GLM techniques combined with a geographic information system can play an important role in analysing and modelling periglacial data sets. Copyright 2004 John Wiley & Sons, Ltd. [source]

Hydraulic properties and freezing-induced cavitation in sympatric evergreen and deciduous oaks with contrasting habitats

J. Cavender-Bares
Abstract We investigated the hydraulic properties in relation to soil moisture, leaf habit, and phylogenetic lineage of 17 species of oaks (Quercus) that occur sympatrically in northern central Florida (USA). Leaf area per shoot increased and Huber values (ratio of sapwood area to leaf area) decreased with increasing soil moisture of species' habitats. As a result, maximum hydraulic conductance and maximum transpiration were positively correlated with mean soil moisture when calculated on a sapwood area basis, but not when calculated on a leaf area basis. This reveals the important role that changes in allometry among closely related species can play in co-ordinating water transport capacity with soil water availability. There were significant differences in specific conductivity between species, but these differences were not explained by leaf habit or by evolutionary lineage. However, white oaks had significantly smaller average vessel diameters than red oaks or live oaks. Due to their lower Huber values, maximum leaf specific conductivity (KL) was higher in evergreen species than in deciduous species and higher in live oaks than in red oaks or white oaks. There were large differences between species and between evolutionary lineages in freeze,thaw-induced embolism. Deciduous species, on average, showed greater vulnerability to freezing than evergreen species. This result is strongly influenced by evolutionary lineage. Specifically, white oaks, which are all deciduous, had significantly higher vulnerability to freezing than live oaks (all evergreen) and red oaks, which include both evergreen and deciduous species. These results highlight the importance of taking evolutionary lineage into account in comparative physiological studies. [source]