Ecology of Water Relations in Plants


Water is an important and often limiting resource for plant growth. Water can influence plant growth and functioning as a direct resource, or indirectly by influencing availability of other resources such as nutrients and oxygen. Availability of water in soil can be quantified in a number of ways, namely as amount of water stored in soil; as depth of water level from soil surface; duration of specific water level through time; or frequency of occurrence of specified water levels in a set duration of time. Plants are sensitive to water availability and have developed sensing and adaptation strategies to ensure competitive and survival success. Variation in water availabilities can determine the distribution and interaction of plants by influencing their response, thereby establishing a basis for niche differentiation.

Key Concepts:

  • Water is fundamental to plant growth and function.

  • Water can exert its influence in plant growth and distribution directly, as a resource or indirectly by influence on availability of other resources such as nutrients and oxygen.

  • Availability of water for plant use is determined by soil texture, structure and meteorological drivers such as evaporation.

  • Appropriate quantification of water availability is important to study its influence on plant growth and distribution.

  • Water can determine coexistence of species in a community through niche differentiation along existing hydrological gradients.

Keywords: hydrological niche; plant–water relations; water deficit; waterlogging; measuring water availability

Figure 1.

Moisture, total net productivity and plant species diversity of selected vegetation communities, along an elevation gradient from Santa Catalina Mountains, Arizona (after Whittaker and Niering, ). The elevation gradient ranges from 1000 to 3000 m above sea level. The moisture index relates to precipitation ranges of 190 mm per annum (moisture index 8) and 850 mm per annum (moisture index 1).

Figure 2.

Schematic summary of the processes that influence the relationship between plants and soil water.

Figure 3.

Soil water availability and soil aeration availability for two representative sandy (solid line) and clayey (broken line) soils. Soil water contents on volume basis is shown against soil water potential (suction) and against air‐filled pore space (volume of pore space not occupied by water).

Figure 4.

Distribution of coexisting plant species from a dehesa meadow in Salamanca, Western Spain along water table depth gradient (broken lines indicate 95% confidence intervals). Water table depth (in metres) from ground surface was measured over the growing season and averaged (i.e. low values indicate wet soils whereas high values indicate dry soils). Distribution models were made using Generalised Additive Modelling (GAM) approach, accounting for spatial correlation structure (Zuur et al., ).

Figure 5.

Distributions of eight sedge species showing differentiation in niche space defined by hydrological axes on a fine‐scale gradient. The x‐axis depicts increasing soil drying stress, whereas the y‐axis shows increasing flooding (i.e. aeration) stress (see Section ‘Water Stress and Plants’ for explanation). The vertically hatched area in each graph shows the range of possible hydrological regimes and the solid area indicates the zone in which the species occurs significantly more frequently than by chance. Data reproduced from Gowing et al., .



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Araya, Yoseph Negusse, and Garcia‐Baquero, Gonzalo(Aug 2014) Ecology of Water Relations in Plants. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003201.pub2]