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Ecological Engineering 49 (2012) 118– 122

Contents lists available at SciVerse ScienceDirect

Ecological Engineering

j o ur nal homep age : www.elsev ier .com/ locate /eco leng

hort communication

ater preservation and the ecological effects of removing leaves from stalks for aeed dominant wetland

iang Wanga,b, Zhifeng Yanga,b,∗, Qiang Liub,a, Ying Zhaoa,b

State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, ChinaKey Laboratory for Water and Sediment Sciences, Ministry of Education, School of Environment, Beijing Normal University, Beijing 100875, China

r t i c l e i n f o

rticle history:eceived 10 November 2011eceived in revised form 20 July 2012ccepted 10 August 2012vailable online 28 September 2012

eywords:cological water preservationeaf removaleed

a b s t r a c t

Due to climate change and human activity, wetlands are undergoing serious water shortages, leadingto marine-like regression. Measures have been put into place in China to combat this problem. Alongwith implementing a water supply strategy, consideration has also been given to the reduction of plantcommunity evapotranspiraiton (ET) as a supplemental approach. In this study, reducing ET by remov-ing leaves from stalks was investigated for a reed community in the Baiyangdian wetland as a watersaving approach. Ecological and economic effects were then assessed to provide evidence for its effec-tiveness. The outcome of the experiment concluded that: (i) when taking into account the capacity ofthe approach in removing pollutants and offering economic benefits, the month of June is the optimumtime to remove leaves from reed stalks; (ii) a water preservation percentage of 23.3% can be realized

vapotranspirationaiyangdian wetland

when 50% of total leaf material is removed from the background value of the overall community; and(iii) 13.608 tons nitrogen (N) and 1.914 tons phosphorus (P) will be additionally removed from thewetland. Furthermore, locals can also gain economic benefits by means of selling the leaves as tradi-tional festival foodstuff. All of these elements combined indicate, to a certain extent, that leaf removalcan preserve water and provide positive ecological effects in maintaining the health of the Baiyangdianwetland.

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. Introduction

Stressed by global warming and human activity, wetlandcosystems throughout the world have been facing serious freshater shortages in recent years (Mitsch and Gosselink, 2000; Liang

t al., 2010). This is especially true for the Baiyangdian wetlandYang, 2011) and the Zhalong Nature Reserve, two important wet-ands in China (Yao et al., 2010). Ecological water transfer projectsave been implemented to maintain the integrity of wetlands inhina (e.g., the Baiyangdian wetland) (Zhai, 2007; Cai, 2008; Hut al., 2008), but these projects also increased the economic bur-en of local governments. In cases such as these, reducing wateronsumption has also been regarded as an auxiliary measure inolving water shortage problems in watersheds (Komamura et al.,

010).

Water preservation approaches, such as altering crop structures,ave been primarily developed for use in agricultural (Xiao et al.,

∗ Corresponding author at: State Key Laboratory of Water Environment Simula-ion, School of Environment, Beijing Normal University, Beijing 100875, China.el.: +86 10 58807596; fax: +86 10 58807596.

E-mail address: zfyang@bnu.edu.cn (Z. Yang).

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925-8574/$ – see front matter © 2012 Elsevier B.V. All rights reserved.ttp://dx.doi.org/10.1016/j.ecoleng.2012.08.004

© 2012 Elsevier B.V. All rights reserved.

008). Little research has been carried out in natural ecosystems,uch as rivers and wetlands (Marimuthu et al., 2010; Plauborg et al.,010). For wetlands, the plant community water consumption rate

s greater by a factor of three as it relates to surface evaporationE), and totals almost 50% of water consumed by natural wet-and ecosystems (Herbst & Kappen, 1999; Sun & Song, 2008; Borint al., 2010). Only one-half of all leaves are used for photosynthesis.nown as the effective leaf area index (LAI), this process is the resultf the inability of sunlight to infiltrate the whole canopy (Jacobst al., 2003; Moller and Stanhill, 2007; Giambelluca et al., 2009).oreover, greater than 90% of plant community ET has no effect

n organic matter accumulation (Tabbal et al., 2002; Din, 2003;hahal et al., 2007, 2009). It stands to reason that water could bereserved by a judicious reduction in leaf material from wetlandlant communities in order to reduce unproductive water loss from

nefficient ET processes. In this context, the objectives of this studyere: (i) to assess water requirements of a reed community in theaiyangdian wetland under different treatments that were sub-

ect to different percentages of leaf removal rates; (ii) to analyze

he capacity of nutrient removal from a reed community at differ-nt time periods and leaf removal percentages; and (iii) to analyzeater preservation percentages, economic benefits, and ecosystem

hanges relevant to the Baiyangdian wetland.

Q. Wang et al. / Ecological Engineering 49 (2012) 118– 122 119

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. Materials and methods

.1. Study site

The Baiyangdian wetland is situated within a temperate zoneonsoon climate in the middle of North China Plain, and is one of

he largest freshwater shallow lakes in northern China. At present,t is experiencing serious water shortages, its sole source of watereing the Fuhe River, a seasonal river. Reed communities are theominant plants, covering an area greater than 80 km2, distributed

n water no deeper than 1.5 m.

.2. Field experiment

The field experiment was carried out in the village of Wangji-zhai (long 115◦45′E, lat 38◦55′N), situated in the middle of theaiyangdian wetland. Reed is the dominant plant in the region, forhich greater than 40% of the site is covered by reed (Phragmites

ustralis var. baiyangdiasis) communities. Mean stalk densitiesere approximately 90 mm−2, with heights ranging between 3.0 m

nd 4.5 m, measured by the square method (Xu et al., 2011) (Fig. 1).In all, three leaf removal percentage treatments (10%, 30%, and

0%) were established, taken from the background leaf commu-ity. Timings were set from May to September. The study area wasivided into 16 sample sites (15 experimental sample sites employ-

ng the established leaf removal percentage treatments and oneontrol sample site where the background reed community waseft intact). Each sample site covered an area of 60 m × 60 m. A 10 m

idth buffer was left between each sample site in order to decreaseny chance of errors due to migration between sample sites.

LAI, reed stalk transpiration (T), and substrate (soil) E amongtalks were monitored on a monthly basis from May to September.n addition, total nitrogen (N) and phosphorus (P) concentrationsn different sections of the reed stalk were also tested on a monthlyasis.

.3. Estimation of water preservation percentages and ecologicalffects

Reed community T was estimated by monitoring the leaf

ranspiration rate (Tr/mmol m−2 s−1) and reed community LAI.r was monitored using a steady-state diffusion porometer (thei-6400 Portable Photosynthesis System), and LAI was measuredsing a leaf area meter on a monthly basis. Reed community E

rmv

n the Baiyangdian wetland, China.

as monitored by means of pan evaporation measurements takennside the reed community. After estimates and measurements

ere compiled, water consumption of the reed community wasalculated as follows:

T = ˛E + T (1)

here ̨ is a weighting factor of soil evaporation. This factor isependent on LAI. For example, if LAI ≤ 2, ̨ = 1; if LAI ≥ 4, ̨ = 0; and

= (4 − LAI)/2 for intermediate values of LAI.

=n=2–3∑

1

Ti (2)

here T is the transpiration of the plant community (mm); n is theumber of levels which are divided according to actual conditions;nd Ti is the transpiration of a single level of a plant communitymm). Ti can be calculated as follows (David et al., 2007):

i = Tri × LAIi × t × m × A

�(3)

here Tr is the transpiration rate of reeds (mmol m−2 s−1); LAI ishe leaf area index; m is the molar mass of water (g mol−1); t is theuration of the experiment; � is the density of water (g mm−3);nd A is the area of the reed community (m2).

The water preservation percentage was defined as the ratio ofater consumed by the reed community before and after the water

emoval treatments were carried out, which was used to reflect thefficiency of the water preservation approach.

Total nitrogen (TN) and total phosphorus (TP) concentrationsithin leaves under the different leaf removal percentage treat-ents were monitored on a monthly basis from May to September,hich was used to analyze how leaf removal treatments influenced

he eco-function of the reed community.

Furthermore, differences in water consumption among the

emoval percentages measured during sampling were analyzed byeans of a t-test, using SPSS software. Differences between single

alues were assessed using 95% confidence intervals for the means.

120 Q. Wang et al. / Ecological Engineering 49 (2012) 118– 122

Table 1Reed community ET under different leaf removal percentage treatments (10%, 30%, and 50%) from May to September.

Time of leaf removal Leaf removal percentages Water consumed(mm year−1)

Water preserved(mm year−1)

Water preservationpercentages (%)

Background 1691.3 – –

May 10% removed 1590.2 101.1 6.030% removed 1512.3 179 11.350% removed 1397.7 293.6 19.4

June 10% removed 1591.6 99.7 7.130% removed 1442.7 248.6 15.650% removed 1355.3 336 23.3

July 10% removed 1560.0 131.3 9.730% removed 1379.9 311.4 20.050% removed 1333.3 358 25.9

August 10% removed 1632.4 58.9 4.430% removed 1523.2 168.1 10.350% removed 1483.0 208.3 13.7

September 10% removed 1676.4 14.9 1.030% removed 1647.4 43.9 2.6

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4. Discussions

ET is controlled by a number of interconnected environmentaland biological factors, such as canopy interception, net radiation,

50% removed 161

. Results

.1. LAI variation and ET changes under different leaf removalercentage treatments

After removing leaves from reed stalks, an obvious decreasingrend was observed in LAI compared to background LAI (P > 0.05).owever, variations in LAI more or less followed the same pat-

ern among the three removal percentage treatments, that is, annitial increase was followed by a decrease. Furthermore, due tots capacity to self-regulate, the community was resilient enougho reduce the effects of leaf removal during the growth season,hich also led to a nonlinear response in LAI to the leaf removal

reatments.ET variations showed similar patterns to changes in LAI, i.e., the

owest ET values were measured in May and September while theighest values were measured in July. By removing leaves fromeed stalks during different months of the growing season andpplying different percentages (from 14.9 mm to 358.0 mm), ETn the whole could be reduced when compared to background ETTable 1).

.2. Variations in total N and P concentrations under differenteaf removal percentage treatments

Leaf N and P concentrations varied during the growing seasonFig. 2). N concentrations remained relatively stable, varying from2.2 mg to 34.7 mg (g−1 dry weight), nominally increasing slightly

n May, June, and September and nominally decreasing in July andugust. P concentrations in comparison were considerably lowernd varied more sizably, from 1.25 mg to 4.88 mg (g−1 dry weight),ncreasing in June and July and decreasing in May and September.he maximum value was measured in June and the minimum valuen September.

.3. Optimum timing in support of water preservation for leafemoval treatments in the Baiyangdian wetland

To assist water preservation, leaves should be removed beforeeed plants reach their peak water consumption capacity. An ETeduction of 23.3% and 25.9% in June and July, respectively, can bettained at a 50% removal percentage. June and July were therefore F

76 4.6

etermined to be the ideal times to trim the ET rate. Moreover,arvested leaves can be collected to make zongzi (rice dumplings),

traditional foodstuff offered during China’s Dragon Boat fes-ival, since this festival is primarily celebrated in the month ofune.

In this manner, if leaves were removed in June at a rate of0%, 23.3% of the total water that would have been consumedy the reed community would be preserved simply through theeduction of ET. That would translate into an annual water sav-ngs of 28.87 × 106 m3 during the growing season. According totatistics, the price of reed leaves has been roughly 1.6 RMB kg−1 inecent years. By removing 50% of the leaf material, approximately3.05 million RMB could be obtained as additional economic ben-fit for locals residing in the Baiyangdian wetland (Table 2), whichould help to add to water preservation initiatives in the area.

urthermore, up to 13.608 tons N and 1.914 tons P would bedditionally removed when compared to traditional harvestingractices that take place in the month of September (Table 2).

ig. 2. Variations in TN and TP concentrations in leaves from May to September.

Q. Wang et al. / Ecological Engineering 49 (2012) 118– 122 121

Table 2Water preservation, N and P removed, and total economic benefits gained by removing 50% leaves in June compared to traditional harvesting practices used in the Baiyangdianwetland.

Time Leaf removal percentages (%) Water preserved (×106 m3) N removed (t) P removed (t) Economic benefitgained (×106 RMB)

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dvection, turbulent transport, leaf area, and the available waterapacity of plants (Zhang et al., 2001; Zhou et al., 2010). Owingo physiological and ecological factors, reed communities undergoigh ET rates as has been reported by numerous studies (Herbstnd Kappen, 1999; Zhou et al., 2010; Xu et al., 2011). Besides theeed for an adequate water supply, the large surface area of reed

eaves and the low aerodynamic resistance between the atmo-phere and reed stands contribute to high ET rates (Xu et al.,011). Additionally, hydrophyte stomata adds to high ET ratesecause the stomata remains open even during hot, sunny daysXu et al., 2011; Białowiec et al., 2012). Fast growth rates com-ined with a large leaf surface area leads to changes in ratiosetween ET and E for reed communities, resulting in overall highT rates (Moro et al., 2004; Raz-Yaseef et al., 2012). As shown inable 1, removing leaves from reed stalks can reduce ET, espe-ially in June and July when a 50% removal percentage treatments employed. Furthermore, due to the relatively high nutrientoncentrations found in reed leaves (Bonanno & Giudice, 2010)heir removal can also reduce concentrations of nutrients in wet-ands, at least to some extent. These measures could help mitigate

ater shortages while maintaining the integrity of the Baiyangdianetland.

. Conclusions

Water consumed by reed communities in wetland ecosystemsan be reduced by removing leaves from stalks. This would alsoelp to remove nutrients from watersheds as well as provideconomic benefits to locals. All these benefits combined couldelp to maintain the health of watersheds like the Baiyangdianetland.

Several conclusions can be drawn by this study:First, the removal of leaves, especially in June and early July,

ould reduce water consumption by a reed community and, inoing so, promote its own sustainability. Second, when taking intoccount the Dragon Boat festival, June should be regarded as theptimum time for leaf removal. In this way, approximately 23.3%f water can be preserved and 0.788 × 104 RMB ha−1 of economicenefit be obtained for the area. Third, by removing leaves, upo 0.371 kg ha−1 N and 0.187 kg ha−1 P would be simultaneouslyemoved from the Baiyangdian wetland. All these findings indicatehat removing leaves from reed stalks when taking into accountptimum timings not only preserves water and removes nutrientsrom both the water body and substrate (soil) but also helps to alle-iate water shortages while maintaining the overall health of theaiyangdian wetland.

cknowledgments

This research was supported by the National Natural Scienceoundation of China (51121003 and 50939001), and the Nationalcience and Technology Special Project on Water Pollution Con-

rol and Management 235 (2008ZX07209-009), and the Majortate Basic Research Development Program of China (973 Program)2010CB951104). We thank the editor and two reviewers for com-

ents that improved this manuscript.

X

13.608 1.914 63.0510.635 0.423 0

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