Microclimate and Water Status of Sand Tailings at an Ex-Mining Site in Peninsular Malaysia
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Journal of Tropical Forest Science 11 (1): 157-170 (1999) MICROCLIMAT WATED EAN R STATU SANF SO D TAILINGS AT AN EX-MINING SITE IN PENINSULAR MALAYSIA L. H. Ang, Forest Research Institute Malaysia, Kepong, 52109 Kuala Lumpur, Malaysia . Mullin W. SeeC E . & l s Plant and Soil Science Department, University of Aberdeen. United Kingdom Received April 1998________________________________________________ MULLINS & ANG, SEEL . H. E . L , ,W . 1999,C . Microclimat wated an e r statuf o s sand tailings at an ex-mining site in Peninsular Malaysia. Experimental plots, each of size of 12 x 7.5m, were established on sand tailings at an ex-mining site in Peninsular Malaysi abovm 8 standine t aa eth g water-table level (a.s.w.l.) (oped an n shade plots) and at 2.5m a.s.w.l. (open plot only). The shade plot received about 45% irradiance while the open plot received full irradiance. Acacia mangium and A. auriculiformis seedlings were planted in both plots at 0.75 x 0.75 m spacing. Shading reduced air temperature, raised relative humidity (RH) and decreased air vapour pressure deficit (VPD e resultair5 dail)Th 19 . yf o srecording f water-tablo s e levels in 3-m depth dipwells showed that ground water supply was limited at the e sitesuctio day6 Th . d ssanf nafteo an t 0-13 da dept , m r1 5c m t rainfala hm 7 3 > l( per day) showed that the sand tailings at 8 m a.s.w.l dried rapidly from 3 to 6 days after rainfall. Days of available sand water (DAW) for A. mangium and A. auriculiformis were estimated based on root depths of each species and water release characteristic e santh valuedf W o s r tailings9-month-olDA fo s e Th . d . mangium A . auriculiformisA d an day1 1 sd were respectivelyan 6 . Keywords: Sand tailing s- microclimat e- acacia s- rootin g depth - availabls e water content ANG,L.H.,SEEL,W.E. & MULLINS, C. 1999. Iklim mikro dan status air bagi hampas lombon i tapagd k bekas lombon i Semenanjungd g Malaysia. Petak penyelidikan, setiap , didirikasatm 5 u 7. selua i x atan d 2 s1 s hampas lombon i tapad g k bekas lombong di Semenanjung Malaysia pada 8 m di atas paras air permukaan (petak terbuka dan petak naung) dan pada 2.5 m di atas paras air permukaan (petak terbuka sahaja). Petak naung menerim cahay% 45 a a manakala petak terbuka menerima cahaya penuh. Anak benih Acacia mangium . auriculiformisA n da telah ditanam di petak-petak tersebut pada jarak tanaman seluas 0.75 x 0.75 m. Naungan mengurangkan suhu udara, menambahkan kelembapan bandingan (RH) dan menurunkan tekana udarap wa n . Keputusan 5 bagcatata19 i n harian panar ai s permukaan dalam tanah sedala menunjukkam m3 n kawasan tersebut mempunyai bekala yanr nai g terhad. Sedutan pasir pada kedalama har6 nn i 0-1padda m 3 5c a 1, selepa m seharism huja7 3 ) > n( menunjukka n bahawa kehilangan kelembapan hampas lombong pada 8 m di atas paras air permukaan berlaku dengan cepat tiga dan enam hari selepas hujan. Hari-hari hampas pasir tersedia (DAW) bagi mangium. A auriculiformis. A n da dianggarkan berdasarkan kedalaman akar bagi setiap spesies dan ciri-ciri kehilangan air hampas pasir tersebut. Nilai DAW bagi A. mangium . auriculiformisA n da yang berumu bular9 n adalah masing-masin hari1 1 .n da g6 157 8 15 Journal of Tropical Forest Science 11(1):157-170 (1999) Introduction tailingn Peninsulati f o sa (Chah 0 r 70 nMalaysi3 1990)11 n s ti a.ha f Abouo % t80 tailing remaindee th s sans i d dan classifies i r slims d a sand d ean y slime . (Lial t me 1981). Slime and sandy slime tailings consist of larger amounts of clay and silt particles with higher nutrient wated san r retention capacitymore ar ed easilan , y cultivated than sand tailings (Mitchell 1957). Sand tailings consist mainl f finyo e sand, coarse sand and gravel. Hence, they have low fertility due to lack of organic matte find an er particles suc s siltclad h a addition n an yI . , sand tailings situated at more than 1.5 m above the standing water-table level (a.s.w.l.) are frequently subjec periodio t t c drough theio t e r poodu t r water retention capacit higd yan h temperature environment (Ang et al. 1993). As high cost is needed to improve the irrigation and fertility of sand tailings for agricultural practices, large tracts of sand tailings remain idle. In addition, the presence of heavy metal contaminants sann i d tailing rendey ma ssite reth unsuitabl agriculturar efo l purposes (Ang& 1997)g An . Hence, thiserioua s si s caus concerr efo n since sand tailings account for 2% of the land area of Peninsular Malaysia. The other alternative land use of sand tailings is for wood production. To date there has been no detailed study of eithe microclimate rth r plant-availableo e wate sandn ro n tailingsyti . Without detailed knowledg f theseo e factors, plantin f timbego r specie attempn a n si o t t reclaim sand tailings is unlikely to be successful , since it is impossible to accurately predice identitth ) timind e factor(1 tyan th f e chiego s th thae f ar t constraint plann so t growt survivalwhicd ) h(2 an d h timbean , r species will most likely surviv minimuea m input approac r afforestationhfo . roly watedeterminatiof e eke o th e n ri Th planf no t growt survivad han clearls li y illustrate face th t y thadb t sand tailing a.s.w.lm s>4 tha e . tsupporar t only small, isolated patche grassef so shrubsd larga san t e bu ,cove higd ran h diversit shruf yo b and tree species regenerate on moist sand tailings <1.5 m a.s.w.l (Mitchell 1957, Ang 1994). sourceo tw e watef so Th r suppl sano yt d tailing soie ar sl water fro minine mth g poo fresd lan h supply from rainfall. Record water-table th f so e level rainfald san l would help to determine the dry or wet periods in the sand tailings. Such monitoring would determine the supply of water to plants. However, whether or not a plant experiences water deficit depends not only on the supply of water, deman s atmosphere t alsit th n bu oo s i lossr d o t I . e that ultimately controle th s los watef so r from plants. Hig r temperaturhai relativw lo d ee an humidit y would normally affect water loss processes from plants (Grace 1983). Leaf water loss to e atmospherth e during photosynthesi mainls si y through stomata with some also from the cuticular transpiration (Grace 1983). Water loss from plants is mainly determine e leaf-to-aith y b d r vapour pressure deficit (VPD|in(..iir). VPDs lcai l calculated using leaf temperature r vapouAi . r pressure deficit (VPDe b n i|rca ) calculated from air temperature and relative humidity which are in turn affected by the irradiance (Gates 1980). High VPDiir is usually associated with high VPD|inl..iir (Idso et al. 1981). VPD.iir is also used as an indicator to characterise the canopy condition n relatioi s o transpiratiot n r stomatao n l conductancer Fo . Journal of Tropical Forest Science. 11(1):157-170 (1999) 159 example, in the tropics, Maruyama et al. (1994) found that stomatal conductance of Shorea leprosula is, limited at VPDair> 10 hPa. Hence, the dipterocarp experienced a measure of atmospheric drought at VPD > 10 hPa. VPD . also plays an important e determinatiorolth n ei f Idso'o n s stress inde leafr xfo ; high VPD normalls i ai. r y associated with high Idso's stress inde f leafo x during water deficits (Ids. al t oe 1981). Monitoring of irradiance, air temperature, RH and VPD is therefore essential to determine the drought effects of sand tailings on plants. This paper summarise environmentae th s l condition stude th f yso site taken to be representative of typical sand tailings in Malaysia. Hence, the objectives of this study were : determino t • magnitude eth VPf eo D fluctuation relation si microe th o nt - climatic parameter sunnn so cloudd yan y days, • to quantify the availability of soil water to Acacia mangium and A. auriculiformis durin spellsy gdr , • to determine the effects of artificial shading on the water content and microclimate of the sand tailings. Materials and methods Study site stude Th y locates sitewa Au'n di s mine whic abou s hi northwes m k t4 t froe mth town of Malim Nawar, Perak ( 4° 21" N, 101 °07"E). The two-year-old sand tailings that resulted from gravel pump mining were selecte r thidfo s study basen do accessibility, practical and security reasons. The study site was located at 27 ±0.5 m above sea-level surrounded by mining pools. The study site was colonised by patches of leguminous herbs and shrubs. e mosTh t common were Cassia pinnata, Mimosa pudica d Desmodiuman triflorum. In addition, Imperata cylindrica, Tetracera scandens, Eupatorium odoratum, Mikania cordata, Paspalum conjugatum d Centrosemaan pubescens were also presente Th . sporadic patches of vegetation were cleared during levelling. The sand tailings were levelle a tracto y b dabout a r abovm 8 t e standing water level (a.s.w.ld an ) a.s.w.lm 5 2. e experimentaTh l plots were assesse r mechanicafo d l impedance usinga portable hand-held cone penetrometer (Leonard Farnell and Co.