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Effects of climate-induced increases in summer drought on riparian plant species: a meta-analysis.

Garssen AG, Verhoeven JT, Soons MB - Freshw. Biol. (2014)

Bottom Line: ISI Web of Knowledge was searched for relevant peer-reviewed studies, and 23 papers were found that met our criteria and contained quantitative study results.Our results showed that a drought duration of approximately >30 days strongly reduces riparian plant biomass and that a duration of approximately >30-35 days and high drought intensities (starting from 3 to 4 cm water table decline per day) can be detrimental for riparian seedling survival.Very few studies mentioned hydrological thresholds, such as critical values for ground- and/or surface water levels, and so far these results have proved difficult to generalise. 6.

View Article: PubMed Central - PubMed

Affiliation: Ecology & Biodiversity Group, Institute of Environmental Biology, Utrecht University Utrecht, the Netherlands.

ABSTRACT

1. Frequency and duration of summer droughts are predicted to increase in the near future in many parts of the world, with considerable anticipated effects on riparian plant community composition and species richness. Riparian plant communities along lowland streams are characterised by high species richness due to their system-specific environmental gradients. As these streams and their hydrological gradients are mainly rain-fed, they are sensitive to precipitation changes. 2. We conducted a literature survey and meta-analysis to examine the effects of an increase in summer drought on: (i) riparian plant biomass; (ii) riparian seedling survival and (iii) riparian plant species composition and richness. We also aimed to determine whether hydrological thresholds related to drought tolerance can be distinguished for riparian plant species. 3. ISI Web of Knowledge was searched for relevant peer-reviewed studies, and 23 papers were found that met our criteria and contained quantitative study results. To detect overall responses of biomass and seedling survival, a random-effects model was applied using Comprehensive Meta-analysis™ software. Regression curves were then fitted to response ratio data relating the effects on drought-impacted groups to those on control groups. 4. Our results showed that a drought duration of approximately >30 days strongly reduces riparian plant biomass and that a duration of approximately >30-35 days and high drought intensities (starting from 3 to 4 cm water table decline per day) can be detrimental for riparian seedling survival. Especially Populus and Salix seedlings showed a reduced survival in response to drought, in contrast to Tamarix seedlings, which have the ability to rapidly and expansively elongate their roots. The data also revealed that an increase in drought conditions rapidly leads to a decline of riparian species richness and an increased presence of species adjusted to drier conditions. 5. Riparian groundwater level, surface water permanence and certain plant traits, especially plasticity in rooting depth, were mentioned most frequently as factors determining species responses. Very few studies mentioned hydrological thresholds, such as critical values for ground- and/or surface water levels, and so far these results have proved difficult to generalise. 6. Our meta-analysis has shown that the projected increase in the duration and intensity of drought periods, especially intense droughts lasting more than 30 days, can be expected to narrow the riparian wetland zone with typical hydric species and accelerate riparian wetland species losses in the near future. This may require extra efforts in terms of management and restoration of species-rich riparian areas.

No MeSH data available.


Related in: MedlinePlus

Effects of duration of drought on riparian plant biomass ratio (mean biomass in drought treatment/mean biomass in control). Studies with intense drought conditions (no water added, or the plants were not watered until the wilting point was reached) and mild drought conditions (water periodically withheld) are indicated by different symbols. A weighted regression analysis is shown. n = 31 cases, from 12 studies.
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fig01: Effects of duration of drought on riparian plant biomass ratio (mean biomass in drought treatment/mean biomass in control). Studies with intense drought conditions (no water added, or the plants were not watered until the wilting point was reached) and mild drought conditions (water periodically withheld) are indicated by different symbols. A weighted regression analysis is shown. n = 31 cases, from 12 studies.

Mentions: The studies used for our analysis on plant total biomass ranged in drought conditions from very mild drought stress (plants received 400 mL water per day compared with a control of 800 mL water per day, e.g.) to severe drought stress (the plants were not watered at all and the wilting point was reached). The duration of the drought periods varied from 14 to 180 days. Despite this wide range of treatments, our meta-analysis confirms that there is a highly significant overall effect of drought on the amount of total biomass (dry weight) of riparian wetland plants (random-effects model, P < 0.001; Table 1), which becomes critical when droughts last longer than approximately 30 days (Fig.1). Since different species display a different tolerance to drought, a species list is included in Table 1. For shorter periods of drought, some response ratios had values >1, which indicates that there was an initial positive effect of drought on the performance (total biomass) of these species. These cases had a relatively wet control situation (water level 5 cm above substratum), so these particular species showed a more optimal response to dryer conditions. Furthermore, Fig.1 shows that under more severe drought conditions, there is a relatively fast decrease in biomass, while there is a more gradual decrease in biomass when drought conditions are milder.


Effects of climate-induced increases in summer drought on riparian plant species: a meta-analysis.

Garssen AG, Verhoeven JT, Soons MB - Freshw. Biol. (2014)

Effects of duration of drought on riparian plant biomass ratio (mean biomass in drought treatment/mean biomass in control). Studies with intense drought conditions (no water added, or the plants were not watered until the wilting point was reached) and mild drought conditions (water periodically withheld) are indicated by different symbols. A weighted regression analysis is shown. n = 31 cases, from 12 studies.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493900&req=5

fig01: Effects of duration of drought on riparian plant biomass ratio (mean biomass in drought treatment/mean biomass in control). Studies with intense drought conditions (no water added, or the plants were not watered until the wilting point was reached) and mild drought conditions (water periodically withheld) are indicated by different symbols. A weighted regression analysis is shown. n = 31 cases, from 12 studies.
Mentions: The studies used for our analysis on plant total biomass ranged in drought conditions from very mild drought stress (plants received 400 mL water per day compared with a control of 800 mL water per day, e.g.) to severe drought stress (the plants were not watered at all and the wilting point was reached). The duration of the drought periods varied from 14 to 180 days. Despite this wide range of treatments, our meta-analysis confirms that there is a highly significant overall effect of drought on the amount of total biomass (dry weight) of riparian wetland plants (random-effects model, P < 0.001; Table 1), which becomes critical when droughts last longer than approximately 30 days (Fig.1). Since different species display a different tolerance to drought, a species list is included in Table 1. For shorter periods of drought, some response ratios had values >1, which indicates that there was an initial positive effect of drought on the performance (total biomass) of these species. These cases had a relatively wet control situation (water level 5 cm above substratum), so these particular species showed a more optimal response to dryer conditions. Furthermore, Fig.1 shows that under more severe drought conditions, there is a relatively fast decrease in biomass, while there is a more gradual decrease in biomass when drought conditions are milder.

Bottom Line: ISI Web of Knowledge was searched for relevant peer-reviewed studies, and 23 papers were found that met our criteria and contained quantitative study results.Our results showed that a drought duration of approximately >30 days strongly reduces riparian plant biomass and that a duration of approximately >30-35 days and high drought intensities (starting from 3 to 4 cm water table decline per day) can be detrimental for riparian seedling survival.Very few studies mentioned hydrological thresholds, such as critical values for ground- and/or surface water levels, and so far these results have proved difficult to generalise. 6.

View Article: PubMed Central - PubMed

Affiliation: Ecology & Biodiversity Group, Institute of Environmental Biology, Utrecht University Utrecht, the Netherlands.

ABSTRACT

1. Frequency and duration of summer droughts are predicted to increase in the near future in many parts of the world, with considerable anticipated effects on riparian plant community composition and species richness. Riparian plant communities along lowland streams are characterised by high species richness due to their system-specific environmental gradients. As these streams and their hydrological gradients are mainly rain-fed, they are sensitive to precipitation changes. 2. We conducted a literature survey and meta-analysis to examine the effects of an increase in summer drought on: (i) riparian plant biomass; (ii) riparian seedling survival and (iii) riparian plant species composition and richness. We also aimed to determine whether hydrological thresholds related to drought tolerance can be distinguished for riparian plant species. 3. ISI Web of Knowledge was searched for relevant peer-reviewed studies, and 23 papers were found that met our criteria and contained quantitative study results. To detect overall responses of biomass and seedling survival, a random-effects model was applied using Comprehensive Meta-analysis™ software. Regression curves were then fitted to response ratio data relating the effects on drought-impacted groups to those on control groups. 4. Our results showed that a drought duration of approximately >30 days strongly reduces riparian plant biomass and that a duration of approximately >30-35 days and high drought intensities (starting from 3 to 4 cm water table decline per day) can be detrimental for riparian seedling survival. Especially Populus and Salix seedlings showed a reduced survival in response to drought, in contrast to Tamarix seedlings, which have the ability to rapidly and expansively elongate their roots. The data also revealed that an increase in drought conditions rapidly leads to a decline of riparian species richness and an increased presence of species adjusted to drier conditions. 5. Riparian groundwater level, surface water permanence and certain plant traits, especially plasticity in rooting depth, were mentioned most frequently as factors determining species responses. Very few studies mentioned hydrological thresholds, such as critical values for ground- and/or surface water levels, and so far these results have proved difficult to generalise. 6. Our meta-analysis has shown that the projected increase in the duration and intensity of drought periods, especially intense droughts lasting more than 30 days, can be expected to narrow the riparian wetland zone with typical hydric species and accelerate riparian wetland species losses in the near future. This may require extra efforts in terms of management and restoration of species-rich riparian areas.

No MeSH data available.


Related in: MedlinePlus