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In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was
examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation
deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species
were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (−P) phosphorus application. Doubling
the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1–11 m2 per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LAn, n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree
species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for
Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P,
with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response
to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water
to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season.
The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area
than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is
a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception
and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest
canopy. 相似文献
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Derero Abayneh Coe Richard Muthuri Catherine Hadgu Kiros M. Sinclair Fergus 《Agroforestry Systems》2021,95(7):1309-1326
Agroforestry Systems - Increasing tree cover and managing trees better on farms in Ethiopia supports livelihoods and the environment but most tree-planting schemes promote only a few species. This... 相似文献
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- The amplitude, duration, frequency, and predictability of runoff and inundation of aquatic habitats are key hydrological characteristics linked to aquatic ecosystem functioning and biodiversity, but they are seldom integrated into analyses of Amazon floodplain ecology. Remote sensing approaches, measurements and modelling of floodplain hydrology provide a basis for this integration.
- Effective legislation to protect floodplains and other wetlands depends on operational definitions that require application of hydrological data.
- Extent and changes of flooded areas are linked to fish diversity and to presence and growth of flooded forests and floating plants.
- Dam construction reduces river system connectivity and modifies the flood pulse, with major negative implications for floodplain ecosystems adapted to and dependent on a natural flood regime.
- Trends and variability in climate plus deforestation are altering the Amazon's hydrological cycle, causing changes in discharge and flooded area with concomitant ecological impacts.
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Coe WR 《Science (New York, N.Y.)》1945,102(2649):344-346
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Johnson ZI Zinser ER Coe A McNulty NP Woodward EM Chisholm SW 《Science (New York, N.Y.)》2006,311(5768):1737-1740
Prochlorococcus is the numerically dominant phytoplankter in the oligotrophic oceans, accounting for up to half of the photosynthetic biomass and production in some regions. Here, we describe how the abundance of six known ecotypes, which have small subunit ribosomal RNA sequences that differ by less than 3%, changed along local and basin-wide environmental gradients in the Atlantic Ocean. Temperature was significantly correlated with shifts in ecotype abundance, and laboratory experiments confirmed different temperature optima and tolerance ranges for cultured strains. Light, nutrients, and competitor abundances also appeared to play a role in shaping different distributions. 相似文献
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