Hi Mr Lepcha,

It depends on what kind of wetland you will use. There are several kind of wetland that contain different specimens of plants. For example some constructed wetlands contain submerged plants such as Ceratophyllum demersum and Myriophyllum spicatum that t living completely under the surface of water. The others can contain plants which their body is above the surface of water such as Typha latifolia and Phragmites australis. On the other hand while submerged plants are generally lives in hot climates the others can be adapted mild to cold climate. The last plants I mentioned are hydrophyl and well nutrient absorber.

Dear Lepcha,

In a constructed wetland the removal of pollutants are achieved through the combined action of plants, micro organisms and substratum/soil bed.

The plants mainly transport oxygen through the root zone, which promote the growth of  bacteria.

The plants take up nutrients other other ions (heavy metals) (Absorption and adsorption).

The plants are also involved in the degredation of pollutants.

As a thumb rule fast growing plants are preferred in constructed wetlands, but an interesting but less researched area is the use of ornamental plants. The use of ornamental plants can improve the aesthetic beauty and also helps to generate more income.

dear mr Lepcha

I think I woudl try to look at the traits = characteristics of plants , native wetland plants of your region  - and choose for your purpose  the ones that are most likely to grow and to 'do the work' in a contracted wetland. From the species pool of native , wetland plants I would filter out the good candidates. I assume that the vegetation will be regularly removed (for composting or so).  Of course it would be nice if a group of them woudl be somewhat resemble an occurring communities - but i guess that's of secondary importance.  As for traits I woudl look (filter) plants that have a high rate of nutrient acquisition = usually these with high SLA, low LDMC, high N% and high P% in leaves. Rather larger plants as well. The plants with aerenchyma would do better (providing O2 to the rootzone) and in general plants with higher tolerance for NH4 etc. Although the tolerance is probably not included in the traits databases.  Than I woudl think of 'layered'  and multi-species structure: so to optimist the use of space and of light. Probably here the roots are important - so pick species with different rooting depth and root systems (to keep surface stable and provide an optimal resorbtion of nutrients). It the wetlands is partly shallow ponds - you probably should choose the plants growing (and tolerating ) different deaths. The layered above ground  vegetation would help to optimally use light (so plants that are both -  medium to large plants - with diverse growth forms?). Next  I woudl choose plants that have a good clonal spread. If possible I woudl also include plants with flowers, diverse flower types and attractive / valuable for pollinators= they your wetland can also provide extra service as a additional food source for the insects. Of course you need to think of the plants with good fitness in your local conditions (abiotic , climatic) - but this you need to decide based on local conditions.

I hope it helps - good luck!

Ong Tshering Lepcha:

The following publication may contain information that can help further fine tune an answer to your question?

"Growth characteristics of six wetland plants and their influences on domestic wastewater treatment efficiency".   http://www.sciencedirect.com/science/article/pii/S092585741300390X

Highlights of this publication

• Root length affected the removal of NO3−-N and BOD5.
• The amount of oxygen released to the rhizosphere affected the removal of NH4+-N and TDP.
• Nitrogen and phosphorus uptake was governed by the plant biomass.
• Iris pseudacorus (Yellow Iris) and Canna indica (Indian Shot) were more suitable for sewage treatment.