Influence of the Surrounding Water Environment on Mire Vegetation

ABSTRACT Mires are loosing their natural state as a result of human activities. Recently natural Sphagnum mires in Hokkaido, Japan, have been disappearing as a result of the proliferation of alders. Here we show that such proliferation is caused by the inflow of phosphorous compounds as non-point pollutants. Those phosphorous compounds flow in from agricultural fields around mires. The constituents of groundwater or surface water make alders proliferate rapidly. Phosphorous, a typical non-point-polluting nutrient, contributes to the growth of alders, which assimilate atmospheric nitrogen

Influence of the Surrounding Water Environment on Mire Vegetation Harukuni TACHIBANA* , **, Keita NARUMI***, Saeko KUCHIMACHI****

Michihiko SAITO**, Ken-ichi TATSUMI*****, Hideaki NAGARE******

* Water Environment Section, Hokkaido Institute of Hydro-Climate, c/o Kankyo Create co., Ltd

** Kankyo Create co., Ltd , N20E2, Higashi-Ku,Hokkaido 065-0020 JAPAN

*** Environmental Systems Division、TOSHIBA CORPORATION、

1-1,Shibaura 1-chome,Minato-ku Tokyo 105-8001 JAPAN

**** Chikusei civil engineering office,Ibaraki prefecture,

615Nikinari Chikusei city Ibaraki prefecture,308-0841 JAPAN

***** Docon Co., Ltd.,1-5-4-1, Atsubetsu-Chuo, Atsubetsu-ku,Sapporo,Hokkaido 004-8585 Japan

****** Department of Civil and Environmental engineering,, Kitami Institute of Technology, Koen-cho 165, Kitami, Hokkaido 090-8507 JAPAN

ABSTRACT

Mires are loosing their natural state as a result of human activities Recently natural Sphagnum

mires in Hokkaido, Japan, have been disappearing as a result of the proliferation of alders Here we show that such proliferation is caused by the inflow of phosphorous compounds as non-point pollutants Those phosphorous compounds flow in from agricultural fields around mires The constituents of groundwater or surface water make alders proliferate rapidly Phosphorous, a typical non-point-polluting nutrient, contributes to the growth of alders, which assimilate atmospheric nitrogen

Key words: mire, groundwater, phosphorus, agricultural land, water quality

INTRODUCTION

Eighty percent of Japan’s mires are in Hokkaido, the northernmost of Japan’s major islands Mires have rich natural ecosystems, and the plants in the mires of Hokkaido are

mainly Sphagnum species However, alders have been invading these mires, greatly

altering the vegetation The authors researched the water quality of surface water and

groundwater, and found that alder invasion is caused by the inflow of drainage that

contains nutrients, especially phosphorus, as non-point pollutants from agricultural fields around the mires Nutrients in environment are regarded as loads from agricultural fields Most of phosphorus used for fertilizer accumulates in agricultural soil and effects environment greatly (Ukita 2006)

METHODS

Kushiro Mire and Sarobetsu Mire are the objects of the research They are in Hokkaido, the northernmost major island of Japan These mires and others in Hokkaido have been

registered under The Ramsar Convention Kushiro Mire measures 190 km2, and Sarobetsu Mire measures 230 km2 Both mires are surrounded by agricultural fields and pastures The vegetation has been altered by the inflow of waste from surrounding land The most notable change is invasion by alders The area of alders has expanded by 2.5 times during the past 30 years in Kushiro Mire, and alders have started to invade

Address correspondence to Harukuni Tachibana, Hokkaido Institute of Hydro-Climate, c/o Kankyo Create co Ltd.,, N20E2, Higashi-Ku, Hokkaido 065-0020 JAPAN, E-mail:

Sarobetsu Mire in recent years Many people have attributed the invasion of alders to the inflow of soil from agricultural fields Our study focuses on nutrients that flow out

from agricultural fields We have been surveying surface water and groundwater to

study the causes of alder invasion since 1999 Survey dates and items of analysis are shown under

Fig 1 Kushiro Mire (On-nenai area)

Pt.S: Sphagnum area

Pt.A-1, Pt.A-2: Alder area

Pt P-1, Pt P-2: Phragmites area

Common inorganic components and nutrients were analyzed as specified in Analytical Methods for Water (2005) In 1999 and 2004, water quality was studied to clarify the

general condition of the research area, and in 2006, to compare the water quality at each survey point

This paper mainly addresses Kushiro Mire (Fig 1) In Fig 1, Pt.S is in an area of

Kushiro Mire where Sphagnum predominates, i.e., the natural mire; Pt A-1 and Pt.A-2

are in areas where alders predominate, i.e., the altered mire; and Pt.P-1 and Pt.P-2 are in

areas where Phragmites predominates, i.e., the reed mire

RESULTS AND DISCUSSION

First, the main components of groundwater sampled in Aug 1999 were analyzed and their origins were identified by Principle Components Analysis (PCA) (Tachibana 1999) based on the concentration data of Aug 1999

The PCA analysis clarified factors of variation in water quality (Fig 2) Factor loads of the main components are shown in Fig 2(1) In the figure, the X axis accounted for 46.9% of the variation and the Y axis accounted for 16.7% of the variation Water components in the figure are written as ions Concentrations of various nutrients are converted to those of nitrogen or phosphorus In Fig 2, nitrate nitrogen is expressed as NO3--N, dissolved reactive phosphorus is expressed as DRP and dissolved phosphorous

is expressed as DP The X axis shows the contribution of the water component sources

The two right quadrants (positive on the X axis) show high contribution from springs The two left quadrants (negative on the X axis) show high contribution from peat bog Spring water, especially from the deep ground, has univalent inorganic ions ( Na+, K+, etc ) and nutrients in high concentration, and groundwater of peat bog has carbon eluted

0 1000m

Pt.A-2 Pt.P-1 Pt.A-1 Pt.S

Pt.P-2

from peat in high concentration The Y axis shows the contribution of rain water

components The two upper quadrants (positive on the Y axis) show high contribution

of components other than rain water The two lower quadrants (negative on the Y axis) show high contribution of rain water components including airborne components/airborne pollutants Values of Y axis are affected by rain water Influence

by forest rain water is strong toward + direction Rain water is influenced by carbon which elutes from trees, by silicate which elutes from soil on trees, and by nitrate oxidized from nitrogen compounds, as it flows through forests From the factor scores

of the main components in Fig 2(2), each quadrant is clearly classified as Sphagnum

(marked by ◆) or alder (marked by □) It is clear that the greater the water depth was, the stronger the contribution of springs to water quality was It is also clear that spring water contributed to the water quality of the alder area Three time researches until 2006

had the same results as the PCA analysis results of Aug., 1999

A tri-linear diagram (Fig 3) was drawn to study water composition The surveys of the

Sphagnum area (Group S), Phragmites (reed) area (Group P), and alder area (Group A)

Fig 2 PCA Results (Aug.1999)

(1) Upper: Plot of factor loading of the first two principle components

(Basically water components are expressed as ions.) (2) Lower: Plot of factor score of the first two principle components

(Numbers are depth (m) of sampling points.)

（１）

（２）

Z1 （Aug.1999)

0.2

0.5

1.01.5 2.0

0.5 1.0

1.5 2.0 0.2

-5 -2.5 0 2.5 5

-5 -2.5 0 2.5 5

C-A

◆ Pt.S

□ Pt.A－1

Z1 46.9%

pH EC 4.3Bx

DN NH4+-N

NO2 N

NO3 N

DP DRP TOC

SiO2

Na+

K+

Mg++

Ca+

+

Cl-

SO42 1 -0.5 0

0.

5 1

-1 -0.5 0 0.5 1

Z2

16.7%

were done in July and November, 2006 Although the sampling points are in almost the

same area as in Fig 1, water samples of the alder area (Group A (Pt.A-1 and Pt.A-2))

fall into Area III in Figure 3, which shows the influence of sodium bicarbonate

From this figure, we can assume that the water in Group A is deep groundwater And

water samples of the Sphagnum area (Group S) fall into Areas II, III, and IV in Figure 3

Fig 4 Comparison of phosphorus concentration at five points in the On-nenai

area of Kushiro Mire (June and Nov 2006)

Cl-+SO42-

-Ca2+

SO42-

Cl-Ca2+ + Mg2+

Grou pS

Grou pP

Grou pA

* ０

１００

％

*

Mg2+

Ⅰ

Ⅳ

Ⅱ

Ⅲ

GroupS ◆ Pt S

△ Pt A-1

▲ Pt A-2

＊ Surfacewater (0.2m)

□ Pt P-1

■ Pt P-2 GroupP

GroupA

0 1 2 3

0 1 1 2. 0 0 1 1 2. 0 0 1 1 2. 0 0 1 1 2 0 1 1 2.

DP-DRP DRP

Depth from the ground surface (m)

Pt.S Pt.A-1 Pt.A-2 Pt.P-1 Pt.P-2

DP 7.45 5.18 DP-DR 0.60 0.25 DRP 6.83 4.93 mg/l

Fig 3 Tri-linear diagram of groundwater at the On-nenai area of Kushiro Mire

(surveyed in July and November 2006) The research point annotations are

described in Fig 1

(i.e., near the center of the diagram), which shows the influence of seepages of various

areas This means that water there is seepage water that flows from surrounding peat land (Tachibana 2007) Group P is between Group S and Group A in Fig 3 The concentrations of nutrients at each point were compared The range of concentration was the greatest for phosphorus As an example, concentrations of phosphorus at the

main points are shown in Fig 4 Nutrient concentrations, especially of phosphorus, are

much higher in the alder area than in the Sphagnum area

Sphagnum needs a little nutrient that are contained in rainwater However, when phosphorus flows into mire, plants such as alders that have the ability to fix nitrogen

proliferate abnormally When supplied with phosphorous, alders grew densely, altering the environment (Gokkaya 2007) Phosphorus compounds flowed into the mire from

agricultural land as non-point pollutants (Tachibana 2007) Because farmlands surround

Kushiro Mire, phosphorus compounds are present everywhere

We have shown the results of research on the alder area of Sarobetsu Mire This area may expand and affect the vegetation of Sarobetsu Mire in the near future The survey results of the alder area are shown in Table 1 The data show the water quality of rivers running under alders In the alder area, TP concentration was abnormally high, about 1.5 mg・l-1 Most of phosphorus is suspended reactive phosphorus The phosphorus

compounds that are discharged are absorbed by suspended solids This seems to be because of the drainage from farmhouses nearby Human activities can alter vegetation even in a typical natural area

To conserve the mire, it is important to manage the concentration of phosphorus by treating it at the source of drainage and outflow, and to conserve the water quality by

managing the water quality of surface water (i.e., rivers) and groundwater

Table 1 Water quality analysis of the east part of Sarobetsu Mire, which includes an alder area (June 7, 2006)

( ): Filtered Sample

pH

Concd μS/m

SS mg・l-1

TOC mg・l -1

TN mg・l -1

NO3- mg・l -1

NH4+ mg・l-1

TP mg・l-1

TRP mg・l-1

Cl- mg・l-1

1.537(0.076) 1.508(0.057) 28.5

Item

26.0

Alder area( River water )

16 6.9 151.5 51

(0.04)

30.3(27.9) 6.49(2.77) (0.26) (0.02) (0.001)

(0.000)

Spagunum area( Groundwater: 0.3m )

12.8 4.9 82.5 -(23.6) (2.43) (0.00)

CONCLUSIONS

Conserving mire ecosystems requires that we control human activities not only within the mires, but also around them To control alder proliferation, it is necessary to manage nutrients discharged in the course of agricultural activities as non-point pollutants, particularly phosphorus compounds A long-term view and research are necessary to conserve natural mire (Iqbal 2007)

This study was partly supported by Ministry of Environment under the project “ A study

on the establishment of monitoring method for changes in the wetland and its

surrounding and the development of the harmonized management techniques for the restoration of the wetland ecosystem” The authors would like to thank Dr Kunihiko Kato of National Agricultural Research Center for Hokkaido Region, Hiroaki Saito of Hokkaido government and Akihiro Kunimasa, master's course student of Kyoto

University

REFERENCES

Analytical Methods for Water 5th edition (2005) Hokkaido Branch, The Japan Society for Analytical Chemistry, Kagakudojin (in Japanese)

Gokkaya Kemal, Hurdb T.M and Raynale D.J (2007) Symbiont nitrogenase, alder growth and soil nitrate response to phosphorus addition in alder wetlands of the Adirondack Mountains, Environmental and Experimental Botany, 1-13 New York, USA

Iqbal R., Tachibana, H (2007) Water chemistry in Sarobetsu Mire and its relation to vegetation composition, Archives of Agronomy and Soil Science, 53(1), 15-31 Tachibana Harukuni, Nakamura Shinya, Saeki Hiroshi, Takahashi Hidenori, Saito Hiroaki, Minamide Minako (1999) Biological and Chemical Environment of

Sarobetsu Mire Affected by Human Activities, Environmental Modeling (edited by V.P Singh, H.W Seo and J.H Sonu), 368-376, Water Resources Publication., USA Tachibana, H., Tatsumi, K (2007) Groundwater Quality for the Conservation of Peat

land, J Jpn Soc Soil Phys , No.105, 99-109 (in Japanese)

Ukita M., Sni X., Higuchi T., Arkin Y., Fukuda M (2006) Study on the potential of

farmland soils as non-point sources of nitrogen and phosphorus in Japan,Water Science & Technology,, 53(2),119-130