CONSEQUENCES OF DEHESA LAND USE ON NUTRITIONAL STATUS OF VEGETATION IN CENTRAL-WESTERN SPAIN

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1 CONSEQUENCES OF DEHESA LAND USE ON NUTRITIONAL STATUS OF VEGETATION IN CENTRAL-WESTERN SPAIN Ordor Olán JJ, Grcí López E, Moreno G* I.T. Forestl, Centro Universitrio, Universidd de Extremdur, Plsenci 16 Spin * Corresponding uthor: gmoreno@unex.es ABSTRACT A dehes is silvorle system, which results in structure nd species simplifiction of Mediterrnen forests. Activities like livestock, forestry, griculture nd, recently, hunting re crried out in these plces, in which three min structures re found: trees with ntive grsses (G), trees with crops (C) nd trees with woody understorey (M). In order to find out the effect of dehes lnd use on nutritionl sttus, we hve mesured the nutrient content (N nd P) of the vegettion (holm-ok nd crop) in three frms locted in Centrl Western Spin, considering in ech one the three forementioned dehes types. Additionlly, the effect of the tree on soil fertility ws studied in order to mp soil resources round the ok-trees, which will e useful to model the tree-understorey interctions nd dehes functioning. Soil smples (first 2-cm depth) were tken t different distnces from the tree (from 2 up to 2 m) in three trees per plot (9 plots: 3 frms x 3 lnd uses). In ll smples, ph, soil orgnic mtter (SOM), ctionic exchnge cpcity (CEC), totl N nd ville P were determined. Folir nutrient content of holm-ok (N nd P) ws mesured in mture leves of nine trees per plot. Crop smples were collected t four distnces (2, 5, 1 nd 15 m) of the trunk of 9 mture trees per plot (only cropped plots). Trees in C plots presented the highest vlues of lef-n, which is relted to fertiliser ppliction nd to orgnic mteril incorportion/minerliztion. Trees in M plots showed the lowest vlues of lef-n, indicting competitive effect of the mtorrl. By contrst, highest vlues of P were found in M plots, indicting positive interction etween trees nd shrus in P uptke. Differences etween C nd G plots were not significnt. In soils, vlues of ll mesured prmeters, except ph, diminished ccording to the distnce from the holm-ok, which indictes mrked nd positive effect of trees on soil fertility. Regrding the lnd use, oth N nd P presented significnt differences, eing M nd C, respectively, which hd the highest contents, which does not coincide with the results from lef nutrient contents. By contrst, N nd P vlues in cerel hd similr ehviour to those of soil, indicting the high dependence of the crop on the nutrients of the first cm of the soil. Keywords: soil fertility, lef nutrients, dehes mngement intercropped systems, tree-understorey interctions. 1

2 INTRODUCTION Dehess re the result of simplifiction, in structure nd species, of Mediterrnen forest, where tree density is lowered, mtorrl cover is eliminted, nd grss lyer is fvoured with crop culture in lrge periods of rottion. They re silvorle systems of extensive utilistion, where utochthonous pstures nd trees hve prepondernt plce (Montero et l., 1998). Dehess of holm-ok (Quercus ilex) nd cork-tree (Quercus suer) occupy 28% of the totl Spnish woody Quercus re, which rech 25 h (Cmpos et l., 23). Lnd uses in dehess re, in order of importnce, livestock, forestry, griculture nd hunting, though in certin circumstnces nd regions the order of importnce of ech production cn e ltered. These lnd uses result in three min types of vegettion structure in dehess: holm-ok tree (Quercus ilex susp. llot) reltions with psture, crop nd mtorrl, herefter defined nd nmed s cropped plots (C, trees with cerel), grzed plots (G, trees with ntive grsses) nd encroched plots (M, trees with mtorrl, tht is, woody understorey). In the lst decdes, drmtic loss of cultivtion hs een tking plce. On the other hnd, n increse in the dehes encrochment hs een recommended in order to increse the nturl regenertion of holm-ok in dehess (Pulido et l., 21). Moreover, in some res this is lso envisged s wy to increse the hunting opportunities. However, these recent chnges could hve some effects on the soil chemicl fertility nd on the nutritionl sttus of the holm-ok trees, nd therefter on the trees nd dehes productivity. Severl uthors hve lredy studied different spects of the nutritionl sttus of dehess, nmely, the effect of the tree on the soil fertility y compring soil nutrient content eneth nd eyond the tree cnopy projection (e.g. Escudero, 1985; Gllrdo et l., 2; Joffre, 1987), the nutritionl sttus of the psture (e.g. Esselink et l., 1991; Joffre, 1987; Cluig nd Gómez, 1992; Vázquez-Aldn et l., 1995; Pérez-Coron et l., 1995) nd trees (Medivill nd Escudero, 23; Escudero et l., 1992). These works hve shown the generl low soil fertility of the dehes soils nd mjor role of the holm-ok trees in the soil fertility, which is oserved lso in other groforestry systems (Menenzes et l., 22; Sierr et l., 22; Hlvorson et l., 1995; Knops nd Koening, 1997; Dhlgren et l., 1997). Nowdys, comprehensive models of dehes functioning re needed in order to improve its mngement nd profitility nd in order to detect oth possile short nd long-term consequences of the recent chnges in dehes lnd use. Nevertheless, some specific lck of informtion hs een detected on the nutritionl sttus of dehess. For instnce, no work hs focused on the comprehensive study of the soil, tree nd understorey nutritionl sttus. On the other hnd, previous studies hve compred the soil fertility etween eneth nd eyond the 2

3 trees, ut none hs quntified the verticl (depth) or horizontl (distnce to tree) extension of tree influence. No study hs een crried out to differentite the specific sources of soil nutrient for tree nd understorey, tht is, we do not know if there is some type of temporl nd sptil soil nutrient prtitioning etween vegettion strt. Finlly, ll the forementioned studies hve een crried out in grzed dehess, while the possile consequence of the soil mngement on soil fertility nd nutritionl sttus of vegettion hs not een studied yet. In order to find out the consequences of dehes lnd use on the nutritionl sttus of soil nd vegettion, the ims of this study were: 1. To estimte the nutritionl sttus (N nd P) of holm-ok trees under different lnd uses (cropped, grzed nd encroched dehes plots), in three frms of Centrl Western Spin. 2. To chrcterise the soil nutrient distriution round scttered holm-ok trees y studying soil nutrient content t five distnces to the holm-ok trunk nd three lnd uses. 3. To find out the nutritionl sttus (N nd P) of the crop t four distnces to the holm-ok trunk in four frms, nd with different fertiliser pplictions. Results of this study will e used to uild iophysicl model of dehes functioning, with especil emphsis in tree-crop interctions, oth negtive (competition) nd positive (fcilittion). In this context other studies, regrding microclimte, rooting system, wter dynmic, physiologicl tree sttus nd production (cerel nd tree) re eing crried out. METHODOLOGY Study Are Study re is locted in Cutro Lugres County (Centrl-Western Spin; 34 4 N, 6 13 W), which hs lnd re of 441 km 2, with round 5% of the surfce occupied y dehess (Plieninger nd Wilrnd, 21). The climte is Mediterrnen (579 mm y -1 of rinfll, nd 16 C of nnul men temperture) with dry nd hot summers nd cool, riny winters. Soils, following FAO (1998) were chromic Luvisols (CL frm) nd chromic Acrisols (ST frm), developed over tertiry sediments. Both types of soils hd light-rown nd silty-snd surfce horizon, one or severl very red rgic horizons, nd very sndy deep horizon (elow 1 cm). The soils lso showed d internl dringe, which produces vriegted colours nd/or pseudo-gleyic properties, undnt grvel of qurtzite (frequently etween 1-4 cm depth), low soil chemicl fertility, nd CCO 3 ccumultion etween 15 nd 2 cm depth. Where the sediments hve een eroded emerge the sltes on which eutric Leptosols hve een developed (DB frm). Soil slope vries etween 2 nd 4%. 3

4 The more common ctivities in the study re re cttle rising with ntive psture nd cerel intercrops. More mrginl ctivities re firewood production nd hunting. Tree density is from 5 to 5 tree per h, depending of its min use (lower densities in intercropped res nd higher densities in res reserved for hunting). Common ntive grsses re Trifolium cmpestre, Medicgo polymorph, Anthemis rvensis, Gernium molle, Erodium cicutrium, Trxcum oovtum, Lolium rigidum nd Silene psmitis, nd more common shru species re Genist hirsut, Cistus ldnifer, Retm spherocrp nd Lvndul stoechs. Experimentl lyout In this county, three frms were selected: Cerro Loto (CL); Sotillo (ST), nd Dehes Boyl de Tlván (DB), ech one with three different lnd uses: cropped plots (C, holm-ok tree with cerel, whet nd ots), grzed plots (G, trees with ntive grsses) nd encroched plots (M, trees with mtorrl, tht is, woody understorey); s overll 9 plots were studied. In order to find out the effect of dehes lnd use on the nutritionl sttus of trees, in ech frm we rndomly selected 9 trees in C nd G, nd 6 in M. Folir smples composed of 4 susmples (one per orienttion) of mture leves were collected in August 22. To study the effect of lnd uses in dehess nd the tree effect on soil fertility, three holm-oks were rndomly selected in ech plot. Soil smples were tken out t 5 distnces from the trunk: 2 m (under the tree), 5 m (tree periphery), 1, 15 nd 2 m (eyond the tree cnopy projection). With the help of stinless steel drill, five susmples of composed smples were tken in depth of -2 cm, in Mrch-April 22. To study the nutritionl sttus of crops, we rndomly selected 9 trees per frm in CL, DB nd ST, where the fertiliser pplictions (formul ) were 2, 16 nd kg, respectively. For smpling, two orienttions nd four distnces (2, 5, 1 nd 15 m from the tree trunk) were considered. Ech 6 plnts were oven-dried t 75 C until constnt weight, ground finely in stinless steel sil grinder nd sieved to e nlysed. Tle 1 summrises the chemicl nlysis crried out on oth soil nd plnts smples. Sttisticl nlysis Non-liner regressions hve een pplied to otin the reltionship etween soil nutrient contents nd distnce to the tree trunk. The pplied model ws the logistic decrese: y = A (B / (1 + C x EXP(-D x DISTANCE) Results re expressed in term of percentge of vriility explined (R 2 ). 4

5 Differences etween lnd uses (C, G nd M plots) nd distnce to the tree trunk (s independent vriles) were ssessed y two-wy ANOVAs for ech chemicl prmeter (ph, SOM, CEC, ville-p nd totl-n) s dependent vriles. Results re expressed s F vlues (nd degree of freedom) nd significnce level (p vlue). Sttisticl nlysis ws crried out in SPSS for Windows (SPSS Inc, 21). RESULTS Soil nutritionl sttus Soil ph did not show differences due to holm-ok influence (Figure 1), which ws cked up y the sttisticl nlyses (F 4,13 =.28, p=.89). This result contrsts with tht otined y Escudero (1985) in more northern dehess. Differences mong lnd uses (Figure 2) were not significnt (F 2,78 =1.47, p=.24). The studied soils re defined s cid (men vlue of 5.35; rnge of ph is ), which could ffect the vilility of some nutrients or the decomposition velocity of the orgnic mtter (Ulrich nd Summer, 1991). SOM clerly diminished with distnce to the tree trunk (Figure 1), indicting mrked effect of tree orgnic contriution on the soil system (through litterfll nd root decy). Sttisticl nlysis (F 4,13 =24.3, p<<.1) showed highly significnt differences etween vlues of eyond nd eneth the trees. The decrese of SOM with distnce followed logistic curve (Figure 3), which shows tht the influence of the tree disppers from only few meters eyond the cnopy projection. SOM ws higher in M thn in C nd G plots (Figure 2), ut differences mong plots (lnd uses) were not significnt (F 2,78 =.8, p=.45). In generl, SOM contents were low, ccording to the rnge of vlues reported y Montoy nd López (1998) for Spnish forests. On verge, SOM contents were in the 3 percentile considering the vlues reported y Vnmechelem et l. (1997) for the whole of Europen soils. The SOM plys n importnt role in the physicl, chemicl nd iologicl properties of the soil; for instnce, the mount of nutrient in the soils of dehes (totl N) depends on orgnic mtter qulity nd quntity (Gllrdo et l., 2). The low vlues of SOM of the studied dehess re prtly explined y the semirid conditions, ut it could lso reflect certin level of soil degrdtion. N soil concentrtions lso diminished with the distnce from the holm-ok trunk (Figure 1). Sttisticl nlysis (F 4,13 =1.1, p<<.1) showed significnt differences etween the two first distnces (2 nd 5 m; eneth the tree) nd the other ones (eyond the tree). Totl N followed similr tendency to SOM, lthough with less shrp decline (Figure 3). A similr 5

6 sptil heterogeneity of soil nitrogen in dehess hs een found y Escudero (1985), Puerto et l. (1987) nd Gllrdo nd Merino (1998). The mounts of totl-n were moderte under the tree nd low eyond the tree cnopy, ccording to the rnges reported y Montoy nd López (1998). Considering the whole of Europen soils (Vnmechelen et l., 1997), our soils fll round the 3 percentile, tht is, the totl N content in these soils cn e qulified s modertely low. There were significnt differences s regrding lnd use (Figure 2; F 2,78 =3.7, p=.3), with higher concentrtions in M plots (men vlue of 1.4 mg ḡ 1 ) thn in C nd G plots. This result grees with the result for SOM; oth N nd SOM tendencies show positive effect of the shrus on the soil fertility (Fisher nd Binkley, 2). Soil ville P (P-Olsen) vlues t different distnces of the holm-ok trunk (Figure 1) lso showed positive effect of tree on soil fertility. In fct, ville P concentrtions eneth trees were significntly higher thn those out of tree cnopy (F 4,13 =3.59, p=.1). The decrese t the limit of the cnopy projection ws shrper thn for other nlysed soil chemicl prmeters (Figure 3). These results coincide with those otined in more northern dehess y Escudero (1985). There were significnt differences mong lnd uses in ville soil-p (F 2.78 =5.9, p<.1); the highest concentrtions were found in C plots (Figure 2); which could e relted to P fertiliser pplictions. In fct, grzed plots, which re lso periodiclly cultivted (nd then fertilised) hd higher vlues of ville soil-p thn M plots (which were not fertilised t lest in the lst two decdes). Thus, soil P levels could e determined y iologicl (tree effect) nd ntropic cuses. Both could explin the slightly high levels of ville P (sed on vlues reported y Domínguez Vivncos, 1997), in spite of the soil cidity, which contriutes to lessen the vilility of soil P (Fisher nd Binkley, 2). Overll, the studied soils showed modertely low concentrtions of N nd modertely high levels of ville-p, which is chrcteristic of young soils. Soils developed on old nd nutrient-poor sustrtes re usully P deficient, wheres N my e deficient even in young soils (Vitousek nd Frrington, 1997). The CEC vlues found in the present study were etween the 3 nd 5 percentiles considering the vlues reported y Vnmechelem et l. (1997) for the whole of Europen soils. Vlues of CEC re siclly relted to orgnic mtter nd cly qulity (minly kolinite) nd quntity (elow 2 % in the first 2 cm of the studied soils; unpulished dt). The modertely low vlues of CEC in the studied soils must e explined y the low soil orgnic contents. CEC vlues diminished with the distnce from the trunk (Figure 1). 6

7 Sttisticl nlysis showed significnt differences etween distnces (F 4,13 =7.67, p<<.1), with higher vlues eneth thn eyond the trees, s consequence of the levels of orgnic mtter. However, CEC diminished much less thn SOM with distnce, ecuse the cly content did not vry with the distnce to the tree (dt not shown). Similrly to SOM, there were no significnt differences etween soils of the three lnd uses (Figure 2; F 2,7 =.15, p=.86). The positive role of the holm-ok trees on soil fertility is explined y the nnul input of orgnic mtter to the soil through the litterfll (Gllrdo nd Merino, 1998; Escudero et l., 1992) nd root decy (Jckson et l., 1996). Moreover, forests re prticulrly effective t scvenging nd retining tmospheric solutes due to their high surfce re nd erodynmic resistnce; this mechnism llows trees to thrive on poor soils nd enling soil improvement (Moreno et l., 23). Crop nutritionl sttus Men concentrtions of N in cerel plnts diminished ccording to the increse in tree distnce (Figure 4), indicting positive effect of the tree cnopy tht is relted to the holmok orgnic mterils contriution nd their incorportion into the soil due to griculture mchinery (Essenlik et l., 1991). Sttisticl nlysis showed highly significnt differences etween the two first distnces (2 nd 5 m) nd the rest (F 3,6 =22.7, p<<.1). The highest vlues of these concentrtions imply tht the mterils tht grow under the tree cnopy hve higher protein vlues, which reound in high qulity of the psture (Pérez-Coron et l., 1995). Nevertheless, on verge the studied plnts showed low levels of N in comprison with rnges reported y IFA (1992) Figure 4 shows men vlues nd stndrd devitions of P concentrtions in crop plnts. Similrly to N, P concentrtions diminished significntly s the distnce to the ok trunk increses (F 3,6 =13.41, p<<.1). P levels rnged from norml (.21) to very low (.4) ccording to IFA (1992). The concentrtion of N nd P in crop plnts chnged in concordnce with the forementioned soil nutrient contents; oth nutrients showed higher contents in the vicinity of the trees. This similrity etween soil nd herceous plnts tendencies hs een lso shown y Puerto et l. (1987) nd Escudero (1992). Our results indicte the high dependence of the crop on the nutrients of the first 2 cm of soil depth. This dependence coincides with the rooting system of these crops, which hve most of the roots ner the soil surfce: 78% of the roots were locted in the first 3 cm of soil (Ordor et l., 23). 7

8 Holm-ok nutritionl sttus Figure 5 shows men nd stndrd devition of N folir concentrtions in holm-oks under three types of lnd use. Men vlues of these concentrtions (etween 11.6 nd 1.3 mg N g- 1 ) re in the rnge of those otined in other studies for Quercus ilex in more northern dehess (Escudero et l 1992; Medivill nd Escudero, 23) nd for evergreen Quercus in Cliforni (Knops nd Koening, 1997). Nevertheless, these vlues re in the low extreme of the rnge reported y Stephn et l. (1997) for oks ll over Europe (9,94 32,62 mg N g -1 ). Sttisticl nlysis showed high significnt differences (F 2,63 =9.6, p<<.1) mong the three different lnd uses, with highest vlues for trees of C plots, followed y G. These results show cler positive effect of the dehes mngement prctices (minly cropping, C), due to nitrogen fertiliser ppliction nd minerlistion of the incorported orgnic mterils (Esselink et l., 1991; Mnsson nd Flkengreen-Grerup, 23; Frnk nd Roeth, 1996; Gllrdo et l., 2). The effect of the orgnic mtter minerlistion is lso reveled y the fct tht the lowest concentrtions of soil-n were found in M plots nd the highest in C plots, while the opposite ws found in the N contents in tree leves. Aprt from compring soil nd tree N contents we cn estlish the following sttements: shrus compete strongly with trees for soil N nd crop hs no short-term negtive effect on tree nutritionl sttus. On the contrry, cropping ctivity leds to higher lef-n content in holm-oks. These differences were found regrdless of the fertilistion tretment, tht is, trees in cropped plots of ST (unfertilised crops) lso showed higher lef-n content thn trees of G nd M plots. This result indictes positive effect of ploughing, proly n increse of the minerlistion rte. In order to find out the N contriution tht the two principl N inputs (SOM nd minerl N fertiliser) hve in the dehes system, specificlly designed experiment would e dvisle. Regrding P, trees in M plots showed the highest vlues (,65 mg P g -1 ), continued y trees of G plots (Figure 5). Sttisticl nlyses showed significnt differences etween M plots nd other two plots (C nd G) (F 2,63 =7.9, p<<.1). Oserved vlues in C nd G plots (,48 nd,54 mg P g -1 ) were elow those otined in other studies crried out with the sme species in more northern dehess (Escudero et l., 1992). Moreover, these vlues re even elow the rnge reported y Stephn et l. (1997) for oks ll over Europe ( mg P g -1 ). P is considered in this county the most deficient nutrient; therefore, frmers pply higher quntities of this element in fertilistion doses. The higher concentrtions of P oserved in leves of M trees, must e explined in terms of positive interction etween trees nd shrus. Most of the P could e in non-ville forms 8

9 (minerl nd orgnic) nd roots could hve some direct role in the moilistion of this P. More root density nd diversity, nd more mycorrhize re expected in M plots thn in C nd G plots, so tht the iologicl P moilistion should e higher in M plots thn in the others (Jckson et l., 1999). Moreover, tree roots in studied dehess re locted rther in deep lyers, with low root density in the first 2 cm of the soil (Ordor et l., 23), nd thus, most nutrients could e tken up from these deep lyers nd not s mny from the first 2 cm of the soil. In fct, P hs very low dynmic in the soil, so tht it could depend just s much on the root density thn on the P soil content. This would lso explin why trees in M plots hve the highest lef-p contents while soils in M plots hve the lowest ville P in the first 2 cm of soil. CONCLUSIONS A positive effect of the tree in the soil fertility hs een shown through four prmeters (orgnic cron, totl N, CEC nd ville P). Nevertheless, the level of these four prmeters decresed shrply in the limit of the cnopy projection, tht is, the effect of the trees ws lmost limited to the tree cover. The effect ws null (symptothic vlues) eyond three meters to the cnopy limit, lthough tree roots cn spred horizontlly to more thn 25 m (Ordor et l., 23). The cultivtion of dehess incresed the N concentrtion of holm-ok leves s direct consequence of orgnic mtter minerlistion prt from the effect of minerl fertilistion. A positive effect of dehes encrochment ws lso found, with incresed SOM nd totl soil N contents. On the other hnd, shrus could positively ffect the P content of holm-ok leves, proly y helping the soil P moilistion. Results of N nd P contents in crop plnts reveled the high dependence of these plnts on the nutrients of the first 2 cm of the soil, ccording to the superficil rooting system of the crop plnts (Ordor et l., 23). By contrst, P nd N contents of tree leves do not coincide with soil nutrient contents (first 2 cm of soil depth), indicting certin dependence of the deep soil nutrient. Thus, crop plnts nd trees could cquire most nutrients from different prts of the soil, which would imply nice exmple of niche complementrity in n groforestry system. Acknowledgement This study ws supported y Europen Union (SAFE project, contrct QLX-21-56), Spnish Ministerio de Cienci y Tecnologí (MICASA project, contrct AGL-21-85) nd Consejerí de Educción de l Junt de Extremdur (CASA project, contrct 2PR2C12). Jesús Ordor nd Eustoli Grcí were wrded grnts y ANUIES nd Colegio de Posgrdudos (México). 9

10 REFERENCES Bremner, J.M. (1965): Nitrogen vilility indexes. In: C.A. Blck (Editor), Methods of soil nlysis, Prt 2. Agronomy 9: Bighm, J.M. nd Brtels J.M. (editors) 1996: Methods of soils nlysis, SSSA ook series 5 (prt 3): Chemicl Methods. Americn Society of Agronomy. Wisconsin, USA. 139 pp. Cluig, E. de L. nd Gómez, J.M. (1992): Clidd del psto. In: J.M. Gómez Gutiérrez (Eds.): El liro de ls dehess slmntins. Junt de Cstill y León. Slmnc. Spin. pp Cmpos, P., Cñells, I. nd Montero, G. (23): Evolución y situción ctul del monte dehesdo. In: F.J. Pulido, P. Cmpos nd G. Montero (Eds.), L gestión forestl de ls dehess. Instituto del Corcho, l Mder y el Crón. Mérid. Spin. pp Dhlgren, R.A., Singer, M.J. nd Hung, X (1997): Ok tree nd grzing impcts of soil properties nd nutrients in Cliforni ok woodlnd. Biogeochemistry 39: Dewis, J. nd Freits, F. (1984): Métodos físicos y químicos de nálisis de suelos y gus. Boletín 1. FAO. Domínguez Vivncos A (1997) Trtdo de Fertilizción. Mundi Prens, Mdrid. 613 pp. Escudero, A. (1985): Efectos de ároles isldos sore ls propieddes químics del suelo. Rev. Ecol. Biol. Sol 22: Escudero, A. (1992): Intervención del roldo en los ciclos de los nutrientes. In: J.M. Gómez Gutiérrez (Coordindor Científico): El liro de ls dehess slmntins. Junt de Cstill y León. Slmnc. Espñ. pp Escudero, A., del Arco, J.M. nd Grrido M.V. (1992): The efficiency of nitrogen retrnsloction from lef iomss in Quercus ilex ecosystems. Vegettio 99-1: Esselink, P., Schotel, J. nd vn Gils, H. (1991): Nitrogen- nd phosphorus-limited primry production of nnuls. Interntionl Institute for Aerospce Survey nd Erth Sciences, The Netherlnds. 123 pp + ppendix. FAO (1998): World reference se for soil resources. World Soil Resources Report No. 84. FAO. Rome. Fisher RH nd Binkley D (2) Ecology nd mngement of forest soils. John Wiley & Sons, Inc, New York, USA. 489 pp. Frnk, K.D. nd Roeth, F.W. (1996): Using soil orgnic mtter to help mke fertiliser nd pesticide recommendtions. In: F.R. Mgdoff, M.A. Tti nd E.A. Hnlon, Jr. 1

11 (Editors), Soil orgnic mtter: nlysis nd interprettion. Soil Scince Society of Americ. USA. pp Gllrdo, A. nd Merino, J. (1998): Soil nitrogen dynmics in response to cron increse in Mediterrnen shrulnd of SW Spin. Soil Biol. Biochem. 3 (1/11): Gllrdo, A. Rodríguez-Sucedo, J.J., Covelo, F. And Fernández-Alés, R. (2): Soil nitrogen heterogeneity in dehes ecosystem. Plnt nd Soil 222: Hlvorson, J.J., Smith, J.L., Bolton, H. nd Rossi, R.E. (1995): Evluting shru-ssocited ptterns of soil properties in shru-steppe ecosystem using multiple-vrile geosttistics. Soil Sci. Soc. Am. J. 59: IFA (1992): World fertiliser mnul. Interntionl Fertiliser Industry Assocition. Germny. 632 pp. Jckson, R.B., Cndell, J., Ehleringer, J.R., Mooney, H.A., Sl, O.E. nd Schulze, E.D. (1996): A glol nlysis of root distriutions for terrestril iomes. Oecologi 18: Jckson, R.B., Pockmn, R.B., Hoffmn, W.A. (1999): The structure nd function of root system. In: Pugnire, F.I. nd F. Vlldres: Hndook of functionl plnt ecology. Mrcel Dekker, N.Y. pp Joffre R (1987) Contrites du milieu et réponses de l végéttion hercée dns les dehess de l Sierr Norte (Andlouisie, Espgne). Thèse doctort. CNRS-CEPE, Montpellier, 21 pp. Knops, J.M.H. nd Koening, W.D. (1997): Site fertility nd lef nutrients of symptric evergreen nd deciduous species of Quercus in centrl costl Cliforni. Plnt Ecology 13: Mnson, K.F. nd Flkengreen-Grerup, U. (23): The effect of nitrogen deposition on nitrifiction, cron nd nitrogen minerlistion nd litter C:N rtios in ok (Quercus rour L.) forests. Forest Ecology nd Mngement 179: Medivill, S. nd Escudero, A. (23): Reltive growth rte of lef iomss nd lef nitrogen content in severl Mediterrnen woody species. Plnt Ecology 168: Menenzes, R.S.C., Slcedo, I.H. nd Elliot, E.T. (22): Microclimte nd nutrient dynmics in silvopstorl system of semirid northestern Brzil. Agroforestry Systems 56: Montero, G., Sn Miguel, A. nd Cñells, I. (1998): Sistems de selvicultur mediterráne: L dehes. In: Jiménez Díz, R.M. nd J. Lmo de Espinos (Editors), Agricultur Sostenile. Mundi Prens, Mdrid. pp

12 Montoy, R nd López, M. (1998): L red Europe de seguimiento de dños en los osques (Nivel I) Espñ, Pulicciones del O. A. Prques Ncionles. Mdrid. 557 pp. Ordor J.J., Bordet, M., Grcí, E. nd Moreno, G. (23): Root distriution in intercropped dehess of Centrl-Western Spin. Interntionl Symposium on Sustinility of Dehess, Montdos nd other grosilvopstorl systems. Europen Soil Science Society. Cáceres, Spin. Olsen, S.R. nd Den, L.A. (1965): Methods of soil nlysis. Prt 2. Agronomy 9: Pérez-Coron ME, Grcí-Ciudd A, Grcí-Crido B, Vázquez-Aldn B (1995) Ptterns of oveground herge prodcution nd nutritionl qulity structure on semirid grsslnds. Comm. Soil. Sci. Plnt Anl. 26: Plieninger, T. nd Wilrnd, C. (21): Lnd use, iodiversity conservtion, nd rurl development in the dehess of Cutro Lugres, Spin. Agroforestry Systems 51: Puerto A, Grcí JA nd Grcí A El sistem de lder como elemento esclrecedor de lgunos efectos del roldo sore el psto. Anurio del CEBA de Slmnc, 12, Pulido, F.J., Díz, M. nd Hidlgo de Trucios, S.J. (21). Size-structure nd regenertion of Spnish holm-ok Quercus ilex forests nd dehess: effects of groforestry use on their long-term sustinility. Forest Ecology nd Mngement 146: Sierr J, Dulorme M nd Desfontines L (22) Soil nitrogen s ffected y Gliricidi sepium in silvopstorl system in Gudeloupe, French Antilles.Agroforestry Systems 54: Stephn K, Fürst A, Hcker R, Brtels U (1997) Forest folir conditions in Europe. Results of lrge-scle folir chemistry surveys EC, UN/ECE. 27 pp. Ulrich B nd Summer ME (eds) (1991) Soil Acidity. Springer-Verlg, Berling. 223 pp. Vnmechelen, L., Groenemns, R. nd Vn Rnst, E. (1997): Forest soil condition, Results of lrge-scle soil survey. Forest Soil Coordinting Centre, Belgium. 261 pp. Vázquez-Aldn B, Grcí-Crido B, Grcí-Ciudd A, Perez-Coron ME (1995) Estimtion of minerl content in nturl grsslnd y Ner Infrred Reflectncy Spectroscopy. Comm. Soil. Sci. Plnt Anl. 26: Vitousek, P.M. nd Frrington, H. (1997): Nutrient limittion nd soil development: experimentl test of iogeochemicl theory. Biogeochemistry 37: SPSS (21). Sttisicl Product & Service Solutions. SPSS Inc., Chicgo, Illinois. 12

13 Tle 1. Methods of chemicl nlysis crried out with smples of holm-ok leves, crop (totl plnt) nd soil. Smple Prmeter Method Source N totl Semi-micro Kjeldhl (modified to Bremner, 1965 Plnt (ok include nitrtes) nd crop) P totl Incinertion nd colorimetric Bighm nd Brtels, 1996 Soil CIC SOM Totl N Aville P ph Ammonium cetic extrction Wlkley nd Blck wet comustion, modified y Wlkley Semi-micro Kjeldhl (modified to include nitrtes) Olsen CCl 2 (1:2) Bighm nd Brtels, 1996 Dewis nd Freits, 1984 Bremner, 1965 Olsen nd Den, 1965 Bighm nd Brtels,

14 FIGURE CAPTION Figure 1 - Men vlues nd stndrd devitions of soil ph, orgnic mtter (SOM), totl-n, Ction exchnge cpcity (CEC) nd ville-p t different distnces to the holm-ok trunk. Dt re verge vlues of C (cropped), G (grzed) nd M (mtorrl) plots. Different letters indicte significnt differences. Figure 2 - Men vlues nd stndrd devitions of soil ph, orgnic mtter (SOM), totl-n, ction exchnge cpcity (CEC) nd ville-p in dehess soils with three different lnd uses: C (cropped), G (grzed) nd M (mtorrl) plots. Different letters indicte significnt differences. Figure 3 - Reltionships etween the distnce to the holm-ok nd four chemicl prmeters of the dehes soils in Centrl-Western Spin. NOTE: The logistic decrese curves {y = A (B / (1 + C x EXP (-D x DISTANCE) } hve een normlised, nd the corresponding prmeters re: Chemicl prmeter A B C D R 2 SOM 39,9 19,6 26,9,744 99,57 Totl N 1,31,42 71,7,898 99,3 CEC 1,1 2, ,668 98,81 Aville P 14, 5, ,699 99,1 Figure 4 -Men concentrtions nd stndrd devitions of N nd P in cerel plnts t different distnces to the holm-ok trunk. Different letters indicte significnt differences. Figure 5 - Men concentrtions nd stndrd devitions of N nd P in leves of holm-ok in dehess with three different lnd uses: C (cropped), G (grzed) nd M (mtorrl) plots. Different letters indicte significnt differences. 14

15 FIGURE 1 SOM (mg g -1 ) c c c Distnce to the trunk (m) CEC (cmolc+ kg -1 ) c c c Distnce to the trunk (m) N (mg g -1 ) 2,5 2 1,5 1,5 c c c P (mg kg -1 ) c c c Distnce to the trunk (m) Distnce to the trunk (m) ph (CCl2) Distnce to the trunk (m) 15

16 FIGURE 2 SOM (mg g -1 ) CEC (cmolc+ kg -1 ) C G M Lnd uses C G M Lnd uses N (mg g -1 ) 2,5 2 1,5 1 P (mg kg -1 ) ,5 5 C G M Lnd uses C G M Lnd uses ph (CCl2) C G M Lnd uses 16

17 FIGURE 3 SOM CEC Totl N Aville P 1% 8% 6% 4% 2% Percentge Distnce, m % 17

18 FIGURE 4 N (mg g -1 ) 1,2,9,6,3 c c, Distnce to the trunk ( m) P (mg g -1 ) 1,5 1,2,9,6,3, Distnce to the trunk (m) FIGURE 5 N (%) 1,3 1,1,9,7,5 c C G M Lnd use P (mg g -1 ),8,6,4,2, C G M Lnd use 18