Impacts of land-use intensity on soil organic carbon content, soil structure and water-holding capacity

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1 SoilUse nd Mngement Soil Use nd Mngement doi: /sum Impcts of lnd-use intensity on soil orgnic cron content, soil structure nd wter-holding cpcity M. ACIN-CARRERA 1,M.JOSE M ARQUES 2,3,P.CARRAL 2,A.M. ALVAREZ 2,C.L OP E Z 1,B.MARTIN-L OP E Z 1 & J. A. GONZ AL E Z 1 1 Socil-ecologicl Systems L, Deprtment of Ecology, c/drwin, 2. Universidd Autonom de Mdrid, Ciudd Universitri de Cntolnco, Mdrid, Spin, 2 Deprtment of Geology nd Geochemistry, c/frncisco Tom s y Vliente, 7. Universidd Autonom de Mdrid, Ciudd Universitri de Cntolnco, Mdrid, Spin, nd 3 DesertNet-Interntionl, Hmurg University, Hmurg, Germny Astrct The impct of lnd-use intensity is evluted through chnges in the soil properties in different res of the trditionl centrl Spnish lndscpe. Soil orgnic cron (SOC) content, ulk density, ggregte stility nd wter-holding cpcity (WHC) in the topsoil of ctive nd ndoned vineyrds, livestock routes (LR) nd young Quercus fforested res were nlysed. These different types of lnd use cn e interpreted s hving grdient of progressively less impct on soil functions or conservtion. As soil use intensity declines, there is n increse in SOC content (from 0.2 to 0.6%), WHC (from 0.2 to 0.3 g H 2 O per g soil) nd ggregte stility (from 4 to 33 drop impcts). Soils eneth vines hve lost their upper horizon (15 cm depth) ecuse of centuries-old tillge mngement of vineyrds. Except for n increse in ulk density (from 1.2 to 1.4 g/cm 3 ), there were no differences in soil chrcteristics 4 yr fter the ndonment of vine mngement. LR cn e considered sustinle uses of lnd, which preserve or improve soil chrcteristics, s there were no significnt differences etween topsoil from LR nd tht from 40-yr-old Quercus fforested re. SOC content, one of the min indictors for soil conservtion, is considered very low in every cse nlysed, even in the more conservtive uses of lnd. These dt cn e useful in understnding the slow rte of recovery of soils, even fter long-term cesstion of griculturl lnd use. Keywords: Livestock routes, ndoned lnds, vineyrds, soil orgnic cron, soil structure, griculturl policies Introduction The current sitution of degrded griculturl soils in southern Europe is due in prt to the vriety of griculturl policies implemented in the lst 30 yr tht hve gone through different stges. The first ojective of Europen policies ws to increse productivity, y promoting technicl progress nd ensuring the optimum use of the fctors of production, in prticulr lour (Trety of Rome, 1957). In the nineties, policies focused on the cretion of set-side pyments to withdrw lnd from production; s consequence, etween 10 nd 20% of griculturl lnds in the Euro-Mediterrnen countries were ndoned (Grove & Rckhm, 1996). The lst single frm pyments were suject to conditions relting to environment, Correspondence: M. Jose Mrques. E-mil: mrijose.mrques@um.es Received Septemer 2012; ccepted fter revision Mrch 2013 food sfety nd niml welfre stndrds (reforms since ). Currently, there is new proposl to reform the Common Agriculturl Policy with three min gols: vile food production, sustinle mngement of ecosystems nd lnced territoril development. To develop this new vision of improving the mngement of gro-ecosystems, frmers should e involved in preserving environmentl lndscpes, nd policy mkers must se their decisions on scientific knowledge. Quntittive informtion, from oth oservtions nd modelling, is needed. Prticulrly, locl dt on the current stte of soil conservtion would provide the informtion needed to understnd how different soil properties chnge over time nd under different lnd uses, compred with their unltered originl conditions. As consequence of these Europen griculturl policies, countries with semi-rid climtes re currently mosic of ndoned nd used lnds, whose detiled conservtion 2013 The Authors. Journl compiltion 2013 British Society of Soil Science 1

2 2 M. Acın-Crrer et l. sttes re usully unknown. The most common types of lnd uses re tillge-mnged nd fllow lnds. Soil tillge is n intensive use of lnd tht cn led to loss of productivity in the medium-to-long-term depending on fertilizer rtes (Mrton et l., 2011) nd therefore, promote lnd ndonment (Brero et l., 2012). There is extensive literture out the impct of tillge on soil structurl stility (Aid & Ll, 2009) nd its ility to oxidize orgnic mtter (Mrtınez Men et l., 2002) rpidly the first yers nd more slowly therefter (Blesdent et l., 2000). This literture is generlly in good greement regrding the negtive consequences of this prctice like the reduction in physicl protection of soil orgnic cron (SOC) within stle ggregtes, nd the susequent exposure of re soil to rinfll nd drying (Blesdent et l., 1998). Prticulrly, Denef et l. (2007) highlighted the importnce of the conservtion of soil structure through the protection of microggregtes occluded in mcroggregtes s long-term cron-stiliztion fctor in forests or griculturl lnd with less intensive tillge. A review of the processes through which soil degrdtion y tillge my ffect different environmentl spects soil orgnic cron, soil structure, dringe, wter-holding cpcity, extreme wter logging or drought cn e found in Hollnd (2004) for different soils nd climte conditions in Europe nd Ll (2005) for different res round the world. There is lso greement on the importnce of ggregtion in fcilitting wter infiltrtion; providing dequte hitt spce for soil orgnisms; dequte oxygen supply to roots nd soil orgnisms; nd preventing soil erosion (Frnzlueers, 2002). There is no consensus on the impct of tillge on runoff nd infiltrtion of wter into the soil; while some uthors show tht infiltrtion rte increses (Logsdon et l., 1990; Mtul, 2003), others hve found tht the nnul lnce is negtive (McGrry et l., 2000; Ruiz-Colmenero et l., 2011); climtic conditions nd rinfll chrcteristics my introduce high vriility in this issue. Lnd ndonment is lso frequent in southern Europen lndscpes owing to either lck of productivity or to otin eligiility for environmentl id, prticulrly in the process of restructuring nd converting vineyrds. 1 The study of the consequences of soil ndonment is worthy, s time cn ply for or ginst the trend of soil recovery (Blnco-Cnqui & Ll, 2008) ecuse the gins, losses nd interctions etween living orgnisms, soil, orgnic cron, wter nd nutrients depend on the prevlence of degrdtion processes 1 The implementtion of the Common Mrket Orgniztion led to the ppliction of the ndonment procedure. From 2008/2009 until 2010/11 inclusive, this common mrket structure llowed wine producers to receive permnent ndonment premium. The most ffected country hs een Spin, with n overll reduction close to 50,000 h (Source: OIV Glol Economic Survey. Mrch or recovery processes, which cn e ultimtely the result of rndom climtic processes relted to the mount, durtion nd intensity of rinflls or droughts. Despite numer of studies focusing on the soil cover y re-estlishment of vegettion, informtion is generlly lcking on the corresponding chnges to soil physicl properties (Deuchrs et l., 1999). Another use, which is in decline ut is certinly culturlly relevnt to the Mediterrnen lndscpe, is the reserve of lnd for the nnul migrtion of livestock for only few weeks ech yer, which, therefore, cn e considered n extensive use of lnd. Despite the worldwide presence of livestock routes (LR), lso known s drove rods, interntionl studies re difficult to find. Some re relted to culturl spects (Czorl Montero et l., 2004; Herzog et l., 2005), ecosystem connectivity (Couvreur et l., 2005) nd their reltionship with iodiversity (Bunce et l., 2004), ut, gin, none regrding the consequences of this extensive use on soil chrcteristics. Discovering how lnd is conserved under different soil use intensities is the min ojective of this study; s it provides informtion out severl soil properties considered y the Europen Environmentl Agency in the improvement of the mngement of wter resources nd ecosystems (Jones et l., 2012). The evolution of soil chrcteristics under different uses over time cn e ssessed using its soil orgnic cron (SOC) incorportion rte nd its relted ility to hold moisture (Rwls et l., 2003). Both my e considered key fctors to reduce the impcts of intense rinfll nd droughts, which re projected to ecome more frequent nd severe in future (Solomon et l., 2007). In this context, this study nlyses the sttus of griculturl soils locted in n re in economic decline s n exmple of degrded griculturl regions of southern Europe. It focuses on three different lnd uses: (i) intensively cultivted soils, represented y ctive vineyrds; (ii) extensive soil mngement, represented y the LR; nd (iii) ndoned griculturl soils. All of these re compred with conservtive use of soil, represented y nery young fforested res. The influence of the lnd-use intensity on soil chrcteristics is evluted through vritions in SOC content, structurl stility, infiltrtion rte nd wterholding cpcity, s compred mongst the ove-mentioned lnd uses. These vriles re mesured in the top soil lyer up to 15 cm, where tillge prctices produce drmtic chnges in soil orgnic content (Blesdent et l., 2000; Hernnz et l., 2002) nd soil ggregtion (Denef et l., 2007). Mterils nd methods Study re The study re is situted in section of the trditionl LR clled C~nd Rel Conquense, in centrl Spin, etween Ls

3 Lnd-use intensity Pedro~ ners (39º27 11 N/2º40 47 W) nd Socu ellmos (39º17 36 N/ 2º47 55 W) (Figure 1). This LR consists of 75 -m-wide corridor tht crosses the centrl Ierin plteu, nd it is of prticulr relevnce s it is still used for migrtory ctivities of livestock, including eef cttle, ulls nd Merino sheep (Oteros-Rozs et l., 2012). The ltitude is etween 714 nd 677 m..s.l., the verge nnul temperture is 24 C nd the verge nnul rinfll is c. 470 mm (Source: Ntionl Meteorologicl Agency, 25 yr dt, Figure 2 shows the chrcteristics of the dominnt soil in the study re. Although it cnnot e considered n undistured ntive soil, it is locted in plce without current signs of griculturl use. As result of the homogeneous geomorphologicl chrcteristics of this re, conformed from shllow lcustrine cronte depositionl system (Peropdre & Mel endez, 2004), the ove-ground horizons descried in this pit re expected to e similr to those of the rest of smpling sites. It is sic soil (ph etween 7.4 nd 8), clssified s Clcic Luvic (Arenic) (FAO/IUSS/ISRIC, 2006). 3 Smpling procedure During the spring nd summer of 2011, liner pth of 7 km ws selected tht included three different lnd uses: (i) intensively cultivted soils, represented y ctive vineyrds; (ii) extensive soil mngement, represented y the LR; nd (iii) ndoned griculturl soils. Ech of these ws compred with conservtive use of soil, three isolted ptches with young Quercus ilex rotundifoli (growing since the seventies), to e used s control tretment. The ge of this fforested re ws given y the pesnts nd confirmed using the extrpoltion method proposed y Ge et l. (2007) sed on the mesurement of the trunk dimeter t rest height of 100 trees selected rndomly from the three forest ptches. The time of vineyrd ndonment ws found to e t lest for 4 yr, ccording to the vine growers. Ten smpling sites were selected for ech lnd use. One topsoil smple (up to 15 cm depth) ws collected t ech site, resulting in 10 different plots representing these uses. Becuse of the scrcity of the control tretment, it ws not possile to tke 10 different forest smplings ut 10 smples Cñd Rel Conquense Lnd use type Afforested re Cñd (Livestock route) Andoned lnd Vineyrd Soil pit km Drove Rod Section Figure 1 Study re loction nd smpling sites.

4 4 M. Acın-Crrer et l. Ap 0 15 cm Bt cm Bt cm Lomy Snd 7.5 YR 5/6 Drk rown Sndy lom 7.5 YR 4/6 Drk rown Sndy lom 2.5 YR 4/6 Brown Ck Lomy Snd 7.5 YR 6/4. Brown. With silic edges. Colour 7.5 YR 8/2 Light pink cm R > 125 cm Figure 2 Soil pit of the dominnt soil in the re. Soil profiles, depths, textures nd Munsell soil colours of soil horizons. were tken from the three different fforested res descried ove (Figure 1). Smple tretment nd methods Every soil smple ws ir-dried nd sieved to 2 mm dimeter; the vriles of this study were evluted using 5 nlysis replictes of ech of the 10 smples per lnd use. Texturl nlyses were crried out (Bouyoucos, 1936) sed on USDA system (silt from 0.05 to mm). Soil ph (1:2.5) ws mesured y electrometric methods. SOC content ws estimted y the loss on ignition method (LOI method, Schulte & Hopkins, 1996), s strong liner reltionship hs een demonstrted etween LOI nd SOC (R 2 ), which rnges from 0.94 to 0.98 (Konen et l., 2002). In this method, the comustion temperture ws mintined t 360 C, voiding the destruction of ny inorgnic crontes tht my e present in the smple ecuse of the clcreous nture of the studied soil. Soil ulk density ws estimted using the volume of mercury displced y 2 3-cm-dimeter soil clods (Jonston, 1945). The wter mss ws determined from permnent wilting point to field cpcity y rewetting smples of sieved soil (<2 mm). Ech smple ws crefully sumerged in wter tnk for 4 h. The smples were then removed, permitting dringe y grvity for 3 h. The grvimetric soil moisture ws determined t field cpcity (pf 2.54), nd t the permnent wilting point (pf 4.2) using pressure memrne extrctor system (Richrds, 1941). Finlly, the smples were oven-dried t 105 C for 24 h to otin the dry weight. Soil ggregte stility ws determined using the wterdrop test (Imeson & Vis, 1984). The numer of wter drops (CND) needed to rek down 10 dry mcro-ggregtes (4 4.8-mm-dimeter wire mesh) per smpling site ws counted, with 100 replictes per lnd use. The infiltrtion rte ws mesured using disc infiltrometer (Perroux & White, 1988). This method ws used with one single pressure of 3 cm height in the Mriotte column, equivlent to 0.3 kp suction; this llowed infiltrtion through mcropores up to 500 lm ut not through soil fissures (Greenlnd, 1977; Reeves et l., 1980). Dt were nlysed sttisticlly with the STATISTICA softwre progrm. The proility level (P-vlue) t which the null hypothesis ws rejected ws set t P < Significnt differences etween tretments were tested using Tukey HSD or LSD plnned comprisons tests whenever the ANOVA ws significnt. Spermn s correltions were lso crried out to estlish reltionships etween vriles. Results nd discussion The physicl nd chemicl chrcteristics of soils in the different lnd uses re stted in Tle 1. It ws oserved tht soils tht re, or hve ever een, intensively mnged until 4 yr go present the sme texturl clss s the Bt 1 horizon in the pit of the dominnt soil: sndy lom (Figure 2). We ttriute this chnge in cultivted res to the loss of their topsoil lyer ecuse of centuries-old trdition in soil tillge, which mixed

5 Lnd-use intensity 5 Tle 1 Men nd stndrd devition of topsoil vriles in the different lnd uses. The dt of the representtive soil type correspond to the topsoil of the pit descried in the Figure 1. The depth of topsoil lyer (Ap) ws 15 cm Soil vriles Representtive soil type (n = 2) Vineyrd (n = 10) Andoned (n = 10) Livestock route (n = 10) Forest (n = 10) % Cly % Silt % Snd Texturl clss Lomy snd Sndy lom Sndy lom Lomy snd Lomy snd ph H2O ph KCl c Bulk density (g/cm 3 ) c Different letters indicte significnt differences etween lnd uses ±Std. Dev. ±Std. Err. Men SOC (%) CND index (N) Infiltrtion (mm/h) Soil moisture (g/g) Figure 3 Mens nd stndrd devitions of soil orgnic cron (SOC) content, ggregte stility (counting numer of drops, CND), infiltrtion rte nd grvimetric soil moisture t field cpcity in the four different lnd uses Active vineyrd Livestock route Andoned Afforested vineyrd re Active vineyrd Livestock route Andoned Afforested vineyrd re soil lyers t different depths. On the contrry, the upper horizon is preserved on the soils from the fforested re nd the LR. In these less intensive soil uses, there re orgnic inputs from litter or niml feces, nd soils re protected y the permnent spontneous vegettion cover throughout the yer. Significnt differences re shown in Figure 3. A high SOC content in soil suggests fertility (Sikor & Stott, 1996) nd provides soil with uffering cpcity, high iodiversity, good structure nd effective cron sequestrtion, mongst other chrcteristics. Soils with SOC content elow 1% cn e considered degrded (Imeson et l., 2006). In this study, SOC content in rle lnds ws

6 6 M. Acın-Crrer et l. elow the 1% limit, lthough this low content cn e considered the typicl vlue for these griculturl lnds in southern Europe (Zdruli et l., 2004). SOC rnged from 0.2 to 0.3% on the vineyrd s soils (Figure 3), nd fter 4 yr of ndonment, there ws not significnt increse in SOC content; nevertheless, it ws higher thn 0.5% in the soils from the LR nd forests. Other similr topsoils under Mediterrnen climtic conditions experienced n increse in SOC content from 0.9 to 1.4% fter 15 yr of no tillge (Alvro-Fuentes et l., 2009). There is some evidence tht ndonment of griculturl lnd nd the susequent regenertion of scrulnd or forests through secondry succession my return C storge to pregriculturl levels, lthough the rte of recovery depends on the time under considertion nd whether the lnd ws previously used for crops or psture (Guo & Gifford, 2002). In this study, when soil is under forests or is extensively used s LR, the SOC content verges Mg/h. It is necessry to point tht these figures refer to the first 15 cm of soil, to compre them with other vlues in the literture hving different reference depths (usully 1 m), the estimtion of SOC distriution found y Jogy nd Jckson (2000) cn e used. These uthors nlysed the SOC content vritions with climte nd soil texture t different soil depths using more thn 2700 soil profiles in the world. According to their results, the 40% of ll SOC content in the top 1 m is contined in the uppermost 20 cm in temperte grsslnds nd crops; this mount increses up to 48% in temperte evergreen forests. Following these estimtes, we could stte tht the SOC content in the first metre in the fforested or LR soil descried in this study would e etween 23 nd 29 Mg/h. These vlues re fr from those descried for mture forests in the re. For instnce, Rodrıguez Murillo (2001) reviewed SOC concentrtion in Spin under the min types of lnd uses from the topsoil to 75 cm depth nd found very high vriility (CV~70%). This uthor found SOC concentrtions in soils under rodleved forests nd ushlnds from 94 to 113 Mg/ h. This mens tht in the forest use fter 40 yr the soil hs recovered considerly low mount of SOC. This is not unusul s wide review crried out in the Mediterrnen climte region of Austrli shows no evidence of chnges in SOC content three decdes fter fforesttion in different soil depths up to 30 cm (Hoogmoed et l., 2012). The results of this study lso show tht intensive use of lnd (vineyrds, ctive or ndoned) mintins SOC content t rtes of c. 2.3 nd 4.6 Mg/h, respectively. These contents re lso low compred with the SOC concentrtions in soils under vineyrds nd olive groves recorded y Rodrıguez Murillo (2001), which were nd Mg C per h, respectively. Regrding these differences, it is worth to mention tht when different cron stocks re compred, it is necessry to tke into ccount ulk density vrition nd depth ecuse if the compred volumes re too shllow, ploughed-soc storge cn e underestimted (Blesdent et l., 2000). In ny cse, these figures confirm the criticl threshold for SOC content in topsoils of southern Europe; s stted y Zdruli et l. (2004), up to 74% of topsoil (0 30 cm depth) shows <2% of orgnic cron. In short, fter 40 yr of Quercus tree cover, the clculted recovery of SOC cn e s low s 0.15 Mg/h/y. The low rtes of SOC recovery found in this study re ecuse of low net primry productivity in these degrded soils tht my e cused y their low orgnic mtter content, wter imlnce nd frequent droughts. The literture shows wide rnge of vriility in the results of the impct of fforesttion on soil cron nd the corresponding sequestrtion rtes. This is the consequence of different methods, soil depths, vegettion, climte, soil type nd previous lnd use. Exmples of reltive gins of 0.6 Mg C per h per yr cn e found in humid ok forests fter 80 yr of fforesttion (Jenkinson, 1971), lso moderte gins of 0.3 Mg C per h per yr in forest or woody vegettion estlishment fter some period of griculturl use (Post & Kwon, 2000). There re lso low increses such s Mg C per h per yr in some cses in review of more thn 200 fforested sites round the world (Pul et l., 2002), nd even decreses y 0.09 Mg C per h per yr in wrm temperte res fter grzing exclusion nd growing of shru oks (Brejd, 1997). In recent met-nlysis reviewing 25 studies in different scenrios in Mediterrnen climtes, Hoogmoed et l. (2012) found no evidence for sustntil chnges in soil cron, cross three decdes of fforesttion. Chnges in SOC re lso slow fter ndonment of vineyrds. Novr et l. (2013) estimted tht yr re necessry to multiply the SOC content y on semirid ndoned vineyrds in the first 15 cm of soil depth. Following this trend, much more time would e needed to chieve soil cron stocks of undistured ntive forest within this phytoclimtic environment, which re reported in the literture rnging from 6.5 to 9.9% SOC in the topsoil t 0 10 cm soil depth (Fernndez-Ondo~no et l., 2010). The ggregte resistnce to drop impcts (CND, Figure 3) is good indictor of soil structurl stility. Figure 3 shows the structurl stility of topsoil smples of intensively cultivted soils, oth in the pst (ndoned) or current (ctive vineyrds). Soil disruption fter tillge does impct ggregte stility in ctive vineyrds; while ggregtes roke up fter receiving n verge of only four drop impcts (CND = , n = 100), the sitution improved significntly in the ndoned vineyrds, where it took up to nine impcts ( ) to chieve the totl destruction of the ggregte. Although these soils hve not yet regined their structurl stility, the higher vriility my indicte trend of recovery in some plces. Soil ggregte stility incresed in the LR, lnd use tht cn e oserved s hving n intermedite level of humn impct, ecuse CND is three times s high when compred with ctive tillge in vineyrds

7 Lnd-use intensity 7 ( ). The fforested cover is clerly positive use to preserve or improve soil structure, s its ggregtes needed 33 drops for totl decy ( ). Figure 4 clerly shows the differences etween tretments considering the percentge of survivl ggregtes in the four lnd uses. In this study, 4 yr my e sufficient time lpse to perceive signs of soil structure recovery. Goulet et l. (2004) reported period of 9 yr of soil cover to oserve such chnges. Mrques et l. (2009) did not find structurl chnges fter 2 yr of cover crops in vineyrds, lthough in tht study the CND index ws higher (eight drops). All these figures re in the rnge of those oserved long cten of soils nd vegettion in semi-rid environment (<300 mm/y nnul rinfll), s Cnton et l. (2009) found n verge CND etween 13 nd 55. Soil structure vritions hve een frequently found s the cuse of infiltrtion vriility (Vlentin & Bresson, 1992), prticulrly in vineyrds (Leonrd & Andrieux, 1998). Soil infiltrtion rtes in limestone re highly vrile in Mediterrnen environments (Clvo-Cses et l., 2003), nd it is not uncommon to find <15 mm/h infiltrtion rtes (Cerd, 1997; Mrtınez-Men et l., 1998; Chmizo et l., 2012). Figure 5 shows the infiltrtion rtes in the different lnd uses, ech of which ws crried out during the summer under dry soil conditions. Soils used for vineyrds showed higher infiltrtion rtes s result of recent tillge, which ws more evident in the first minutes of the process; soil infiltrtion through mcropores is four times higher thn in the other lnd uses (from 60 to 80 mm/h), with stiliztion tking plce t 35 mm/h. The ndonment of vineyrds cut the infiltrtion rte y hlf; it egn with 30 mm/h nd stilized t 17 mm/h. Although we expected to find higher infiltrtion rtes in the less intensive uses, we found lower % of surviving ggregtes Numer of drops Active vineyrd Andoned vineyrd Livestock route Afforested re Figure 4 Percentge of survivl ggregtes using the counting numer of drops test t different lnd use sites. n = 10 smples per site nd 10 ggregtes per smple. mm/h Minutes Active vineyrd Andoned vineyrd Livestock route Afforested re Figure 5 Averge wter infiltrtion in the different lnd uses (n = 9). The disc infiltrometer ws prepred to llow infiltrtion through soil pores of <500 lm. vlues. Arguly, in n intct forest soil, there is welldeveloped plnt cover nd root system providing diverse soil porous structure with lrge nd continuous pores, which fcilitte wter trnsport through the soil, even though they constitute only very smll frction of the totl porosity (Cmeir et l., 2003). The fforested re nd the LR, which re considered less intensive use of lnd, showed n infiltrtion rte eginning with mm/h nd stilized t 7 11 mm/h, s evidenced y the curve, which ws elongted nd showed little vrition with time, these vlues re close to those found in the ove-mentioned literture in similr uses in Mediterrnen environments. The history of tillge in vineyrds hs led to n increse in soil porosity tht eventully increses infiltrtion rtes. Nevertheless, it is worth to mention tht fter period of time, depending on meteorologicl conditions, the lck of plnt or residue cover in tilled soil exposed to high intensity rinfll often results in poor ggregtion, compction, crusting nd decrese in infiltrtion (Frnzlueers, 2002). In this study, there is no reltionship etween soil structure nd infiltrtion rte. Higher infiltrtion rte is not lwys n indictor of soil conservtion. Soil permeility is closely relted to the pore spce, which in turn depends on the ulk density, nd we found significnt differences in this vrile due more to vritions in pore spce thn to differences in soil texture. The lower vlues found in fforested soils nd vineyrds (1.2 g/cm 3 ) my e ecuse of different cuses, in the forests ecuse of n increse in SOC content nd root systems nd in the ctive vineyrd ecuse of recent tillge. Tillge opertions re very frequent in this region, with the resulting lower ulk density eing only temporry (Frnzlueers, 2002). In fct, tillge my led to further compction when soil is no longer used, s it is

8 8 M. Acın-Crrer et l. shown in the ulk density vlue in the ndoned lnds (1.6 g/cm 3 ). The compction oserved in the soils of the LR (1.4 g/cm 3 ) is rguly ecuse of the pssge of livestock nd people. The grvimetric soil moisture is generlly ssumed to e independent of ulk density nd to e minly relted to texture. The different topsoil textures in this study could explin the vritions of wter content. We expected to find higher soil moisture in sndy lom textures (vineyrds) thn in lomy snd textures (fforested lnd nd LR). To the contrry, grvimetric soil moisture t field cpcity ws higher in lomy snd textures (Figure 3; F = 3.6; P < 0.05). Moreover, the ville wter in these different lnd uses soil moisture etween field cpcity, nd permnent wilting point in sieved soils (<2 mm; men stndrd devition) ws % for vineyrds, % in soils fter ndonment, 22 7% in the LR nd 23 8% in the fforested soil. These differences my e ttriuted to the higher SOC content (q = 0.6; P < 0.02) nd etter structure (q = 0.5; P < 0.04) in the more conservtive uses. The enefit of this improvement in soil wter retention is prticulrly importnt in the foreseele scenrio of glol wrming nd evpotrnspirtion increse in Mediterrnen res (Clnc et l., 2006). Conclusions Soils sujected to intensive lnd use, in the present or recent pst, re ffected in their physicl nd chemicl chrcteristics. Both soil uses opertionl nd recently ndoned vineyrds lost their topsoil lyer. These soils show decrese of 43% in their orgnic cron when compred with fforested soils fter 40 yr of Quercus tree cover. Consequently, they lso mnifested less ggregte structurl stility nd less wter-holding cpcity. The ltter vriles re conserved in less intensive soil uses, such s livestock routes, which my e ecuse of the constnt inputs from cttle. There re very few ville studies tht compre different lnd uses to evlute how intensive or extensive uses introduce differences in soil properties. This lck of informtion is even more noticele when ddressing livestock routes. Nevertheless, these long pths could ct s sptil reference to evlute the conservtion or degrdtion sttus of the surrounding soils. More thn 4 yr re necessry to oserve signs of recovery in these soils fter the cesstion of tillge. Forty yers lter, the fforested lnd shows some improvement in soil conditions, ut this soil is still very different from undistured soils under ntive forests descried in the literture eneth these climtic conditions. These results re especilly importnt in the semi-rid Spnish lndscpe, which is dominted y intensive lnd use nd remrkly low content of soil orgnic mtter. 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