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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 seedling survival (mean number of seedlings treatment/seedlings control) of the genera Populus, Salix and Tamarix. All data points related to each genus are indicated. Weighted regression analyses are shown. n = 261 from five studies.
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fig04: Effects of duration of drought on seedling survival (mean number of seedlings treatment/seedlings control) of the genera Populus, Salix and Tamarix. All data points related to each genus are indicated. Weighted regression analyses are shown. n = 261 from five studies.

Mentions: The response ratio of seedling survival in relation to the water table decline per day gives a clear picture of the effect of drought intensity (Fig.3). The cases with a 1–2 cm water table decline per day reveal a relatively mild negative relationship, which is almost significant. A decline of 3–4 cm per day shows a significant negative relationship with a steeper slope and a decline of 6–8 cm per day results in an even stronger negative relationship with the response ratio of seedling survival. All selected studies on seedling survival reported data on tree seedlings of the genera Populus, Salix and Tamarix. If we look at these genera specifically, response ratios of the survival of seedlings of both Populus and Salix show a negative relationship with drought duration, while seedling survival of Tamarix does not show a significant trend and seems hardly affected by drought. The general response of Salix seedling survival is smaller than for Populus. Hence, differences in seedling drought tolerance between these three common riparian tree genera are large (Fig.4).


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 seedling survival (mean number of seedlings treatment/seedlings control) of the genera Populus, Salix and Tamarix. All data points related to each genus are indicated. Weighted regression analyses are shown. n = 261 from five studies.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig04: Effects of duration of drought on seedling survival (mean number of seedlings treatment/seedlings control) of the genera Populus, Salix and Tamarix. All data points related to each genus are indicated. Weighted regression analyses are shown. n = 261 from five studies.
Mentions: The response ratio of seedling survival in relation to the water table decline per day gives a clear picture of the effect of drought intensity (Fig.3). The cases with a 1–2 cm water table decline per day reveal a relatively mild negative relationship, which is almost significant. A decline of 3–4 cm per day shows a significant negative relationship with a steeper slope and a decline of 6–8 cm per day results in an even stronger negative relationship with the response ratio of seedling survival. All selected studies on seedling survival reported data on tree seedlings of the genera Populus, Salix and Tamarix. If we look at these genera specifically, response ratios of the survival of seedlings of both Populus and Salix show a negative relationship with drought duration, while seedling survival of Tamarix does not show a significant trend and seems hardly affected by drought. The general response of Salix seedling survival is smaller than for Populus. Hence, differences in seedling drought tolerance between these three common riparian tree genera are large (Fig.4).

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