Ecological enginering of coastlines with salt marsh plantations

Author: Chung-Hsin ChungPresented By: Kimberly Joy L. Hornejas

Ecological Engineering of Coastlines with Salt-

Marsh Plantations

• A salt-marsh is a zone of transition between the land and the sea.

1. Salt Marsh Profile

What is Salt-Marsh?

• 1.0 Introduction• 2.0 Case Study: Wenling, Zhejiang• 3.0 Conclusions• 4.0 Future Research Needs

Outline Of The Presentation

• 1.1 Coastline Problems• 1.2 Management Objectives• 1.3 Ecological Engineering Principles

Introduction

• Most people are unaware of the very important problems of increasing atmospheric carbon dioxide and rising sea level in the next century.

• Table 1 illustrates many of the anticipated problems due to sea level rise on the coastline (Yang, personal communication, 1987).

Coastline Problems

• Problems Due to Water Action1. Heavily rainfall causing inundation of land.2. Intrusion of salt water by overflowing of tides.3. Drought leading to shortage of water to flush silt to sea and resulting sedimentation in river bed.4. High wave energy inducing erosion, etc.5. Problems due to soil factors.6. Dredging operations including dredge spoil flushed back to sea and river with resulting high cost.

Table 1. Coastline Problems, Including Sea Level Rise

• Problems Due to Water Action7. Salinization of embanked land.8. Intensive evaporation, concentrating dissolved salts of soil water.9. Slow salinization and desalinization of clay soil.10. Desalinization of soil water lagging desalinization of soil.11. Wind blowing sand landward, causing need for reseeding of crops.12. Leaking of saltern.

• Problems Due to Water Action13. Low organic matter.14. Much slower composition of organic matter in clay than in sandy soils.15. Digging sand or shell sand for building purposes.16. Mud flats too soft for walking.17. Impossible or difficult to cultivate embanked tideland owing to barrenness, salinity, and soil poverty even after being fallow a long time.

• Problems of Resources1. Shortage of timer, firewood, and fuel to be supplied from outside.2. Overfishing by domestic and foreign fishing boats, causing abrupt decline in total and per capita catch, such as in China.3. Possible extinction of common fish such as yellow croaker (Pseudoscinema crocca) and a small yellow coaker (P. polyactis).4. Pollution making the coastline a reservoir of pollutants, leading to ecosystem fragility.

• Problems of Resources5. Reduced survival of many species of invertebrates and toxic food chain established.6. No or very little use of tidal, wind, and solar energy.7. No or few macrophytes as “machines” to harness solar energy for elemental recycling.

• Problems of Labor Force1. Labor repairing earthen sea walls as at Qidong in Jiangsu, China.2. All-out defensive activities against high tides, storms, and typhoons.3. Repair of breaches of sea bank.4. Labor wasted as a result of improper planning of coastline use.5. Dredging and digging operations6. Embankment at very low elevations leading to financial loss.

• Problems of Coastal Morphology1. Subsidence in some coastlines in addition to sedimentation, erosion, and siltation.

1. Effective protection of the coastline, the prerequisite for all other objectives.

2. Transformation of tideland to fertile and firm soil for agricultural and industrial development-this requires transforming soft marsh soil to a more compact texture to increase porosity.

Management Objectives

3. Increasing marshland area and its elevation.4. Creating and extending communities of primary producers, especially macrophytes for colonizing barren salt flats and embanked saline soil, after which diversity is stressed to gain homeostasis.

• Ecological engineering of coastlines- the design of a coastline human society

with its environment for the benefit of both.• Ecological engineering of coastlines has its

basis in the scientific theories of general, estuarine, marine, and salt-marsh ecology that have been developed over the past 80 years.

Ecological Engineering Principles

1. The capability of plant communities to modify their environment and

2. The existence of plant communities that can withstand harsh conditions, except for the most extreme ones.

They started from two ecological principles:

• Charles Edward Hubbard selected Spartina anglica to achieve or partially achieve the following goals:

Stabilization of coastlineAcceleration of accretion for reclamation or

other purposesUses of green manure

Animal fodderFish feed, and fuelIncreasing production of invertebratesAnd partial control of waterway siltation and

of population

Spartina Anglica

• Spartina anglica (Common Cord-grass) is a vigorous, stout, rhizomatous salt marsh grass with round hollow stems approximately five mm or more in diameter (Thompson, 1991).

Spartina Anglica

• Their first comprehensive treatment of a 22-year case study from 1986 in Wenling, on the east coast of China.

• The study is an ecological engineering project transforming the tidelands to farmlands and citrus groves, thereby improving the human society and its natural environment for the benefit of both.

Case Study: Wenling, Zhejiang

• The original site was located in a tideland 150m east of a sea wall, Dongpian Farm, in a most northeastern part of the county.

• Wenling lies about 28°N along the East Sea of China. A tidal creek flows northwest to southeast north of the site.

General Description and Site Location

• Climatic Conditions - Based upon three-year-records (1965-1967), January mean temperature ranged from 5.1°C to 8.0°C with the absolute minimum of 5.0°C. The August mean ranged from 27.4°C to 28.9°C, with the absolute maximum of 36.4°C. Annual precipitation fluctuated from 1074 to 1698.9mm with 146-178 rainy days per year. There where 234-255 frostless days, with the earliest frost day on October 29, 1966 and the latest frost on March 24, 1967.

Soil conditions - Analytic results of soil samples collected on October, 1965 (the top 10cm of soil) were as follows: heavy clay soil with soluble salts 1.8182%, organic matter 0.8575%, total nitrogen content 0.0756%, and total phosphorus 0.0359%.

• Tidal submergence at different elevations - At elevations less than 3m above sea level in July, August, and September no case of nonsubmergence was observed. During these three months, consecutive days of nonsubmergence were recorded: 2 days at 3.5m and 5 days at 4m.

• Erosion of Tideland and Sea Walls- Even though progradation takes place in

the long run, erosion also has been taking place. Poor drainage of inland water to the sea leads to inundation of the land and siltation of river beds.

Problem in Detail

• Saline Soil Problem- High precipitation has not been effective

in leaching salts from the soil to the water table. Poor soil structure resulted from using newly embanked salt flats as well as from over-application of chemical fertilizers.

• Soft Mudflats- People collecting bivalves, mollusks, and

mussels sometimes sank into very soft mud and died.• Shortage of Fuel

- Even very short grass is being cut for fuel inside the sea wall.

• Poor Quality of Animal Fodder and Its Shortage

- Arundo donax, a robust Mediterranian tall grass, was planted on the slopes of earthen sea walls for protection but never succeeded because of grazing by cattle.

• In order to solve the problems listed, only halophytic macrophytes that provided different mechanisms of salt tolerance for survival on tideland and that had large biomass.

Planning, Design, and Construction

• Candidates for consideration had to be primary producers; accelerators of sediment particles; mud and sand binders; ameliorators of saline soil; natural buffers to shore erosion; machines to harness solar energy and energy flow; systems of absorbing, accumulating, and recycling biogeochemical elements; soil conditioners making soft clay mud compact and hard soil of moderate texture; and animal feed and fuel.

• Introduction, propagation, stress experiments, riverside trial plantings, and seashore trial plantings on small and large scales were planned to proceed in this order.

Introduction – only Spartina anglica, which was named in 1968 by Hubbard, was imported on account of its lower-elevation habitat, more vigorous growth, and wider seaward distribution (Bryce, personal communication, 1963).

Propagation from seeds – first, fungi and molds on seed coats were washed away before disinfection. Most of the seeds, except those immediately used, were stored in a refrigerator.

• Germination tests were carried out five times by selecting plump seeds and spreading them on moist filter paper in petri dishes. After germination, water and soil cultures followed.

• Germination of seeds also took place in a refrigerator. From a total of 507 seeds, 157 germinated, a rate of 30.97%. Forty-four seedlings ultimately survived, a rate of 8.7%. They discovered that germination of seeds on ears was higher than that of fallen seeds.

• Tillering started only after formation of five or six true leaves, which occurred in early June, 1964. From then on, an increment rate like that of compound interest resulted, as shown in Table 2.

Month New Plants(increase/month)

1964June 244July 767

August 2096September 3617

October 3939November 2561December 4143

1965January 3670

February 2710March 3140April 3670

Table 2. Number of New Tillers per Month in Open

(June-October) and in Greenhouse (November-April)

• More than 10,000 individuals were propagated in the open and more than that were produced in greenhouses with an average air temperature exceeding 20°C and a maximum of 30°C.

• A total of 30,601 individuals were counted on April 26, 1965.

• There was a 694.5-fold increase of the original 44 individuals in less than a year, excluding the period of germination of seeds to the beginning of tillering.

Propagation of Sprigs – Immediate tillering after planting has been observed to be advantageous and has been widely recommended.

• In fact, in planting with high percentage of transplants, care was taken to keep the roots moist by watering during transport, as in the case of transport from Sheyang, Jiangsu to Tianjin in 1965.

Propagation From Rhizome – The second experimental site was on the tide-influenced river flats of River Chientang, Farm of River Chientang.

• Rhizomes left over after planting in the tidal creek were collected and planted in one pot.

• This was done for two reasons: 1. To propagate more plants.

2. To find out whether they were capable of producing shoots and roots.

• Four days after being set out in early may, one segment of rhizome began to function first with root, followed by stem and leaf formation.

• Fourteen individuals were counted 82 days after setting, 152 after 184 days, 320 after 375 days, 26,000 after 500 days, 400,000 after 700 days, 1,450,000 after 790 days and 9,100,000 after 850 days.

Propagation of Paddies – For large-scale propagation work, paddies were very useful in Wenling.

• To avoid soil leaching, water has been considered to be a very important prerequisite for propagation work with paddies as nurseries.

Stress Experiments – The continental climate has very cold winters and very hot summers.

• Polar continental air masses prevail in winter and warm currents from tropics do not flow close to the mainland to any great extent.

• . One can see that Spartina had harsh conditions to overcome in china.

• Temperature Stress Experiments – Three times a day they recorded air temperatures of grass clumps to determine the temperatures actually affecting the grasses.

• With a sufficient water supply, S. anglica was not only capable of withstanding the crucial test, but also kept on tillering every day.

• Drought Stress Experiments – Water content in the soil was determined to be only 60%, and loss of water from grass was accelerated.

• Watering by manual labor managed to prevent plant death on account of coarse grains of silt causing rapid leaching downward.

• Submergence Stress Experiments – A period of dormant or partially dormant submergence far exceeding that of normal submergence of tideland (i.e., more than 3 days) did not affect Spartina performance in its next growing season.

• Accretion Stress Experiments – Moderate accretion of sediments did not harm to the grass, but high accretion suddenly wiped out the entire plantation on the Chientang River in late August, 1966.

• Establishment of Spartina anglica on a Riverbank- A Spartina plantation of 0.2ha seemed to be a

success in 1966, but it was suffocated by a super-accretion of 1m of sediments in late August.

• Establishment of Coastal Spartina Plantations- The 3m elevation was found to be optimal for

transplanting with poor performance at 3.4 and 2.5 m and still worse at 4.0 and 2.3 m. The optimal elevation range was 2.7-3.5 m.

• Establishment of Large Spartina Plantations- In late august, 1966, from the data of

sample quadrats, about 9,100,000 plant individuals were calculated. Descendants of four individual plants were propagated in 1.067 ha of newly constructed paddies.

• Manure was applied as base dressing, with irrigation and smoothing of the soil surface before planting taking place in early April, 1965.

• Two to three individuals in a sprig were set at 5-7 cm in depth. Water was supplied all year round to keep the soil moist even in winter. In the growing season, a water layer no higher than 3cm was desirable.

• Application of nitrogen more than phosphorus and potassium was appropriate.

• Pest and weed control and other forms of management were also performed.

• Optimal planting time was April and May, with survival rates as high as 98%, the next highest is September and October with 80%, and the lowest in July and August, with merely 30%.

• The temperature initiating growth was observed to be 12°C, 20°C was the optimum for transplanting, and 25-30°C was best for the most rapid propagation.

• Accretion and Reclamation- The marsh surface rose 10-15 cm 14 months

after coalescence of clumps over that of barren unvegetated soil surface of tidal flats.

- An increase of 66-68 cm of Spartina anglica over the control of 4 years was measured by Dongfang Commune.

- A lessening of wave energy and a slowing down of currents were proved by spectacular events of changing coastal morphology.

Effects on Coastal Morphology

• Coastal Stabilization- Measurements of accretion rates of

Spartina on the coast of China were compiled by Chung; these shows its stabilizing effect on substrate under normal wave conditions (Table 13.3).

• Nesting and feeding ground for migratory birds, waterfowl, and domestic fowl.

• In 1968, the researcher suggested to farm workers of Dongpian Farm that they harvest more than 10,000 kg of fresh grass to feed cattle and pigs.

• In neighboring Yuhuan Country, people began to feed Spartina to domestic geese, reaching specifications for export in 70 days.

Effects on Animals

• Spartina may be used as fuel and, a new development, for marsh gas production.

• Dongfang Commune was the first succeeded in making unbleached brown paper from Spartina.

• A citrus grove on Spartina marsh soil with better growth of normally vigorous trees, essentially no freezing injury and very few fallen leaves and dried up branches.

Effects on Humans

1. Man-made emergent vegetation ecosystems have been demonstrated to be more efficient in energy flow and material recycling than natural ecosystems in coastal China.

2. Ecological engineering in enclosed intertidal land, with Spartina anglica playing the main role, has been demonstrated to be successful in accretion and reclamation of land with an advance of 4-5 years of land use.

3. Plantings have been beneficial for coastline stabilization in normal wave conditions by stilling currents, dissipating wave energy, and causing suspending particles to fall.

Conclusions

4. Saline amelioration has been especially successful with the creation of Spartina marshland improving the structure of the soil as well as its chemical properties.5. People in Wenling and neighboring counties have been found of using S. anglica as a summer green manure. Because formerly they lacked summer green manure for the late crop of rice, the importance of Spartina has grown since 1968. Even in recent years, 75% of its grass has still been in this way.6. Spartina marsh was appreciated by Wenling people for its effect in fattening animals. Use as animal fodder and feed was tried with cattle, pigs, rabbits, sheep, and goats.

1. The complex interplay of various biological and physical factors involved in accretion and erosion should be explored. Relationships between accretion and animals and algae ought to be clarified. Prevention of erosion by animal growth is an important project.

2. Stabilization of coastlines with plantings of Spartina species by means of other protective devices and in conjunction with coastal engineering works ought to be tried.

3. Amelioration of saline and alkaline soils in dry and cold inland areas with improved varieties of plant breeding will be useful in developing those areas.

Future Research Needs

4. Uses as green manure, animal fodder, fish feed, and as raw materials generating marsh gas require more study.

5. Large-scale planting experiments should be performed to prevent siltation of river beds and navigational channels.

6. The role of Spartina in solving problems of pollution and of dredge spoil ought to be explored.

7. Last but not least, there is urgent need for study of the use of Spartina plantings in coping with sea-level rise in the twenty-first century.

•Thank you for listening, God bless us all. ^_^