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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

Riparian seedling survival (mean number of seedlings treatment/seedlings control) in relation to (a) the duration of drought and (b) the intensity of drought (cm water decline per day) * duration (days of drought). Weighted regression analyses are shown. (a) n = 261, from five studies. (b) n = 257, from five studies.
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fig02: Riparian seedling survival (mean number of seedlings treatment/seedlings control) in relation to (a) the duration of drought and (b) the intensity of drought (cm water decline per day) * duration (days of drought). Weighted regression analyses are shown. (a) n = 261, from five studies. (b) n = 257, from five studies.

Mentions: The studies concerning seedling survival differed in their degree of drought intensity from very mild drought stress (1 cm water table decline per day) to more severe drought stress (8 cm water table decline per day). The duration of the drought periods ranged from 3 to 90 days. Our meta-analysis confirms the general picture that drought overall has a strong negative effect on seedling survival (Table 2; P < 0.001). Regression analyses on all available cases show a pronounced negative linear response of seedling survival to an increase in the duration of drought (Fig.2a). The negative effect becomes really strong in the case of droughts lasting longer than approximately 30–35 days. When seedling survival is plotted against the duration of drought multiplied by drought intensity (water decline ranging from 1 to 8 cm per day), an even clearer linear effect of drought on seedling survival becomes visible (Fig.2b). Both linear relationships are strong, but show a wide variation among the data points, with no clear cut-off point indicating where response ratios drop below 1.


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

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

Riparian seedling survival (mean number of seedlings treatment/seedlings control) in relation to (a) the duration of drought and (b) the intensity of drought (cm water decline per day) * duration (days of drought). Weighted regression analyses are shown. (a) n = 261, from five studies. (b) n = 257, from five studies.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig02: Riparian seedling survival (mean number of seedlings treatment/seedlings control) in relation to (a) the duration of drought and (b) the intensity of drought (cm water decline per day) * duration (days of drought). Weighted regression analyses are shown. (a) n = 261, from five studies. (b) n = 257, from five studies.
Mentions: The studies concerning seedling survival differed in their degree of drought intensity from very mild drought stress (1 cm water table decline per day) to more severe drought stress (8 cm water table decline per day). The duration of the drought periods ranged from 3 to 90 days. Our meta-analysis confirms the general picture that drought overall has a strong negative effect on seedling survival (Table 2; P < 0.001). Regression analyses on all available cases show a pronounced negative linear response of seedling survival to an increase in the duration of drought (Fig.2a). The negative effect becomes really strong in the case of droughts lasting longer than approximately 30–35 days. When seedling survival is plotted against the duration of drought multiplied by drought intensity (water decline ranging from 1 to 8 cm per day), an even clearer linear effect of drought on seedling survival becomes visible (Fig.2b). Both linear relationships are strong, but show a wide variation among the data points, with no clear cut-off point indicating where response ratios drop below 1.

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