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ECOLOGY OF WILD EMMER WHEAT INMEDITERRANEAN GRASSLANDS IN GALILEEIMANUEL NOY-MEIR aa Department of Agricultural Botany, Faculty of Agricultural, Food and EnvironmentalQuality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100,IsraelPublished online: 14 Mar 2013.

To cite this article: IMANUEL NOY-MEIR (2001) ECOLOGY OF WILD EMMER WHEAT IN MEDITERRANEAN GRASSLANDS INGALILEE, Israel Journal of Plant Sciences, 49:sup1, 43-52

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Israel Journal of Plant Sciences Vol. 49 2001 pp. S-43–S-52

E-mail: noymeir@agri.huji.ac.il

ECOLOGY OF WILD EMMER WHEAT IN MEDITERRANEAN GRASSLANDS IN GALILEE

IMANUEL NOY-MEIR

Department of Agricultural Botany, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel

(Received 15 March 2000 and in revised form 18 June 2000)

ABSTRACT

Aaronsohn in 1909 noted that Triticum dicoccoides was found mainly in rockyhabitats. Recent research in Mediterranean grasslands in Galilee supports the hy-pothesis that rocks served as refuges from intensive grazing. Although proximity ofrocks enhances early germination of Triticum, cattle grazing intensity is the majorfactor determining its abundance. At high grazing intensity, it is absent or survivesonly among rocks. At moderate grazing intensity it is common not only near rocks.In ungrazed sites it sometimes becomes dominant, but in the long term is oftensuppressed by perennial grasses. Fitness of Triticum plants in intensively grazedpopulations was only half that of plants in ungrazed populations, mainly because ofdamage to maturing ears.

After grass fires, Triticum cover increased in ungrazed grasslands, as the cover ofperennials was reduced. In ungrazed or lightly grazed grasslands, severe reductionsof Triticum populations were observed during population eruptions of the Levantvole, followed by slow recovery. The dynamics of T. dicoccoides in grasslands ofGalilee results from an interaction of rock microrelief, seasonal rainfall pattern,livestock grazing regime, perennial grass cover, fires, and vole eruptions. The leastrisky management strategy recommended for in situ conservation of Triticum popu-lations is cattle grazing at moderate intensity, avoiding intensive grazing in thereproductive stage but also avoiding long periods without any grazing. The sensitiv-ity of wild emmer to grazing has implications for the history of domestication andthe beginnings of agriculture.

INTRODUCTION

Wild emmer wheat, Triticum dicoccoides (Körn.)Aarons, was the source for domestication of emmerwheat (T. dicoccum Schübeler) about 9,800 BP (= 7,800BCE, Zohary and Hopf, 1988; Smith, 1995). The standardbotanical nomenclature of Zohary and Feinbrun-Dothan(1966–1986) is used where applicable throughout thispaper for all species, although some authors (e.g.,Kimber and Feldman, 1987) now classify wild emmeras a subspecies or variety of hard wheat, T. turgidum L.Despite intensive botanical exploration of the region inthe 19th century, wild wheat was not discovered or, atleast, not correctly identified. This suggests that at thattime it was a relatively rare plant, or that it occurredmainly in inaccessible areas. At the beginning of the

20th century, Aaron Aaronsohn set out on a quest for thehypothetical ancestor of wheat, following the clue of aspecimen collected accidentally 50 years earlier byKotschy on the slopes of Mt. Hermon and eventuallyidentified by Körnicke as wheat. In June 1906,T. dicoccoides, growing among rocks at Rosh Pinna ineastern Galilee, was first discovered and identified byAaronsohn. Thereafter, once the “search image” of theplant and its preferred habitats were known, scatteredpopulations were found over a wide range in Israel andneighboring countries.

One of the areas where populations of T. dicoccoidesoccur most frequently and abundantly is in eastern Gali-lee and the lower Golan, i.e., in the catchment basin of

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Lake Kinneret (Sea of Galilee), north of the lake and onboth sides of the Jordan River. This is a region of rockyslopes and plateaus of Pleistocene basalt and hardEocene limestone, receiving 400–600 mm of rainfallannually, and covered mostly by Mediterranean grass-land vegetation. Aaronsohn (1909), studying the distri-bution and ecology of T. dicoccoides within this region,noted that its most typical habitat was in rocky terrain,but that occasionally it could also be found in the shelterof spiny shrubs. It was then assumed that the associationof wild wheat with rocky areas was related to the mois-ture regime or the lack of competition there. However,Zohary and Brick (1961) and Harlan and Zohary (1966)observed that in the 1950s wild wheat and barley ex-panded away from rocky microhabitats and becameabundant and locally dominant in a wider range of habi-tats. They explained this habitat expansion as a result ofthe reduction in grazing pressure in the region and sug-gested that, in the past, the rock and shrub microhabitatshad been refuges from the intensive grazing pressurepreviously prevailing in the region.

Within the broad geographic range of climates andvegetation formations where wild emmer wheat occurs,the local distribution and the dynamics of its popula-tions are determined by local ecological factors, amongwhich the nature of the substrate (rock and soil) and theregime of disturbances (grazing, etc.) are apparentlyimportant. A deeper understanding of the ecology anddynamics of wild populations of Triticum in its nativeenvironment is essential for the conservation and man-agement of these populations. Recent studies on theecology of Mediterranean grasslands in northern Israelin general, and of T. dicoccoides within these grass-lands, have provided some information on the ecologi-cal factors involved and on the mechanisms by whichthey act and interact.

The main objective of this paper is to present areview and synthesis of research results (both publishedand new) on the ecological factors determining theabundance and population dynamics of wild wheat ingrasslands in northern Israel. In particular, the paperwill focus on the effects of rocks, grazing, fire, androdents. The results will be interpreted in relation to insitu conservation of wild wheat populations and thehistory of domestication.

EFFECTS OF ROCKS

A long-term, multidisciplinary study of a population ofT. dicoccoides in limestone grassland was initiated in1984 at Ammiad in eastern Galilee (Anikster and Noy-Meir, 1991). A detailed analysis of ecological factorsand of wild wheat populations was carried out at 250

microsites (1-m2 circles), where spikes of wild wheathad been collected for genetic analysis (Noy-Meir et al.,1991a). The rock microrelief around the center of eachmicrosite was measured and characterized by the fol-lowing variables: local rock cover %, distance to thebase of the nearest rock, height to the top of the rock,and angle to the top of the rock. During three years, soilmoisture content of the 0–5 cm topsoil layer in themicrosite was determined gravimetrically a few daysafter the first rain events of the season (October–De-cember). In all years, surface soil moisture after earlyrains was significantly positively correlated with rockcover, proximity of nearest rock (negatively with dis-tance), height of the nearest rock, and angle to the top ofthe nearest rock (Table 1). In addition, maximal soilmoisture was recorded within 0–10 cm of the rock–soilinterface. At the macrohabitat scale, soil moisture afterearly rain was positively correlated with cover andheight of rocks in the habitat, being highest in the“Karst” habitat, dominated by tall smooth rock out-crops, and lowest in the “Valley” habitat, where rockoutcrops were sparsest and lowest. The explanation forthis phenomenon is twofold: first, runoff of rainwaterfrom rock surfaces accumulates in the surface of the soilnearest to the rock and saturates it even after small rainevents that are insufficient to saturate the soil in thegeneral area. Second, tall rocks reduce evaporation fromthe soil near them by shading and reducing wind speed.

These results suggested that soil pockets and crevicesamong rocks, the “typical” habitat of wild Triticum,have a soil moisture regime that is favorable for plants,at least in the first month of the growing season. Indeed,in rainy seasons that began with a small rainfall event

Table 1Correlations between gravimetric soil moisture content (%) inthe 0–5 cm surface layer after early rains and measures of rockmicrorelief at microsites where Triticum dicoccoides had beencollected in 1984 in the Ammiad study site

Soil surface moisture content on date:

28 Nov 85 7 Dec 86 28 Oct 87

No. of microsites 181 106 218Distance to base –0.38*** –0.40*** –0.39***

of nearest rockHeight to top 0.26*** 0.33*** 0.34***

of nearest rockAngle to top 0.40*** 0.41*** 0.48***

of nearest rockRock cover % 0.30*** 0.44*** 0.43***Soil depth –0.13NS –0.03NS –0.01NS

Values are Spearman rank correlation coefficients. Signifi-cance values: ***: p < 0.001, NS: p > 0.05. From Noy-Meir etal., 1991a.

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(25 mm or less), this event was followed by substantialgermination of wheat and other annuals in rocky habi-tats and microhabitats, but only sparse germination inother habitats (Noy-Meir et al., 1991b). For instance, inNovember 1985, after 25 mm of rain in October, thedensity of the first wave of Triticum seedlings was270% greater in the Karst habitat than in the less rockyValley habitat. Later rains caused additional germina-tion that was similar in all habitats, so that by the end ofthe season, the difference in wheat plant density be-tween the Karst and the Valley was only 46%. Over allwheat microsites, the density of early wheat seedlings inNovember 1985 was significantly positively correlatedwith rock proximity, rock height and angle, as well aswith soil surface moisture measured after early rains(Table 2). However, the final density of wheat plantstowards the end of that growing season (April 1986) wasnot correlated with either of these variables, indicatingthat later rains had induced compensatory germinationin less rocky microsites, or that mortality had beengreater near rocks.

The results from the Ammiad study indicate thatT. dicoccoides is not obligatorily dependent for germi-nation and seedling establishment on the extra soilmoisture available in the proximity of rocks. In yearswith small early rain events, this additional moistureallows Triticum seeds near rocks to germinate earlierand to gain several weeks of growth, which may result

in increased competitive advantage and seed produc-tion. However, this is probably not the only factor in-volved in the association of wild wheat with rockyhabitats. In the Ammiad study area, it was observed thatthe local intensity of cattle grazing on the vegetation ingeneral, and on individual Triticum plants, was highestin the less rocky Valley and lowest in the rockiest Karsthabitat. At a macroscale, cattle apparently spend lesstime walking and grazing in the rockiest areas, which insome patches are virtually inaccessible to them. At amicroscale, cattle have difficulty in biting plants thatgrow among rocks or very close to rocks. Thus, theeffect of rocks on wild wheat population processes in-volves both soil moisture enhancement and grazing re-duction. On the other hand, the earlier and more vigor-ous plant growth in soil pockets among tall rocks, suchas in the Karst habitat at Ammiad, may result in strongercompetition for light and water in these microhabitats.

EFFECTS OF GRAZING

The effects of cattle grazing on Mediterranean grasslandcommunities in northern Israel, and on individual grass-land species, were examined in a series of studies from1982 to 1993 (Noy-Meir et al., 1989; Noy-Meir, 1990,1995; Noy-Meir and Sternberg, 1999). Differences inpercentage cover of species across fences separatingplots with different cattle-grazing intensities, or grazedand ungrazed plots, were measured and analyzed atnearly 100 sites in the Galilee and Golan regions. Grass-lands protected from grazing or grazed at low intensitybecame dominated within 3–5 years by tall, erect plantsof three groups: perennial grasses (Hordeum bulbosumL., Dactylis glomerata L.), perennial forbs (Echinopsspp., Psoralea bituminosa L.), and tall annual grasses(Triticum dicoccoides, Hordeum spontaneum Koch,Avena sterilis L.), in various combinations. At increas-ingly higher grazing intensities, the cover and height ofthese dominants was progressively reduced and the gapswere occupied by a large assemblage of annuals ofsmaller stature, including grasses, legumes, and otherdicots. The abundance of the tall annual grasses (Triti-cum, Hordeum spontaneum, Avena) was particularlysensitive to grazing intensity. In plots with high grazingintensity they were absent or extremely sparse, beingrestricted to microrefuges near large rocks or insideEchinops plants, exactly as Aaronsohn had observed in1909. They occurred over the whole range of grazingintensities from low to moderate, but their abundancewas negatively correlated with grazing intensity.Among the three wild annual cereals, Triticum de-creased in abundance most steeply and most consis-tently in response to grazing intensity (Noy-Meir,

Table 2Correlations between density of Triticum dicoccoides plants atcollection microsites at Ammiad in November 1985, after earlyrains, and in April 1986, near the end of the same growingseason, and (i) measures of rock microrelief and (ii) soilmoisture content in the 0–5 cm surface layer after early rains

Density of wild wheat plants

Nov 1985 Apr 1986

(i)Distance to base –0.29** 0.08NS

of nearest rockHeight to top 0.20** –0.10NS

of nearest rockAngle to top 0.21** –0.13NS

of nearest rock

(ii)Soil surface moisture on 0.21** 0.09NS

28 Nov 1985Soil surface moisture on 0.36*** –0.12NS

7 Dec 1986

Values are Spearman rank correlation coefficients. Signifi-cance values: ***: p < 0.001, **: p < 0.01, NS: p > 0.05. FromNoy-Meir et al., 1991b.

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1990). Among 31 site-pairs sampled, 21 site-pairsshowed significantly (p < 0.05) greater cover ofT. dicoccoides on the protected or less intensivelygrazed side of the fence, vs. only three site-pairs whichshowed significantly greater cover on the more inten-sively grazed side; in seven sites there was no signifi-cant effect of grazing. The 21:3 ratio of negative topositive responses to grazing is highly significantly dif-ferent from equality (sign test, p = 0.0003). The cover ofT. dicoccoides in grazed grasslands was on the averageonly 23% of its cover in adjacent protected grasslandacross the fence (Fig. 1). On a grazing intensity scalefrom 0 to 5, T. dicoccoides cover showed a significanttrend of decrease with grazing (Fig. 2, Spearman rankcorrelation r = –0.39, p < 0.05).

However, in exclosures completely protected fromgrazing, the cover of T. dicoccoides was extremely vari-able (Fig. 2). In some ungrazed exclosures, wild wheatwas dominant or codominant with other wild cereals,reaching cover of 10 to 40%, while in other exclosures itwas absent or rare. Further examination of the datarevealed that the variation of wild wheat cover in pro-tected exclosures was significantly negatively corre-lated with the cover of perennial grasses (Fig. 3,Spearman rank correlation r = –0.61, p < 0.05). It thusappears that, although continuous grazing at high inten-sity can reduce T. dicoccoides to local extinction or tomicrorefuges, complete protection from grazing may

not guarantee its survival either. Where perennialgrasses are present, they may outcrowd T. dicoccoidesin the long run, in the absence of grazing. Apparently,the survival of wild wheat populations is more secureunder grazing at intermediate intensities, or under inter-mittent grazing.

Additional evidence was obtained from the dynamicsof local populations of T. dicoccoides at about 250microsites in the Ammiad study during seven years(1985–1991, Noy-Meir et al.,1991b, and additional un-published data). The entire study area had been grazedby cattle until February 1985, when all sites in twohabitats (Karst and North) and a large number of sites intwo other habitats (Ridge and Valley) were fenced toexclude cattle. From 1985 to 1987, there was a generaldecline in the density of fertile wild wheat plants in allhabitats and in both grazed and protected sites (Fig. 4).However, in the grazed sites of the Ridge and Valleyhabitats, the relative decline was sharper than in theprotected sites of the respective habitats (Noy-Meir etal., 1991b). From the low point of 1987 until 1991,wheat populations in all habitats showed a general trendof increase, with some fluctuations. The relative in-crease in the recovery period was, surprisingly, greaterin the grazed sites of the Ridge and the Valley than in theprotected sites of the respective habitats, until in 1991all these sites reached almost equal density (Fig. 4). Inthis period, an increase in the cover of perennial grasses

Fig. 1. Percentage cover of Triticum dicoccoides on the grazedside vs. its cover on the protected (or less intensely grazed)side of fences, in grassland site-pairs in northern Israel,sampled in 1982–1983. Linear regression line with zero-inter-cept and slope b = 0.2354 (R2 = 0.6485).

Fig. 2. Percentage cover of Triticum dicoccoides vs. cattle-grazing intensity on a 0 to 5 scale, in grassland sites in northernIsrael, sampled in 1982–1983.

% C

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% Cover of Triticum dicoccoides in protected site Grazing intensity (0–5 scale)

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was observed in the ungrazed exclosures, which mayhave begun to limit space for T. dicoccoides. At thesame time, changes in the grazing regime may haveallowed a faster recovery in the grazed sites. The weak-est recovery was observed in the ungrazed sites in thetwo, more shady habitats (Karst and North), which ini-tially had the highest density of wild wheat amonghabitats. In these two habitats the cover of perennialgrasses (Hordeum bulbosum, Dactylis glomerata,Phalaris tuberosa L.) increased more under protectionfrom grazing than in the Ridge and Valley habitats.

Incidentally, the 1985–1991 T. dicoccoides popula-tion dynamics provide some insight into the response ofthis species to yearly rainfall variation. Reductions ofwild wheat populations were recorded in three dry years(1986, 1989, 1991), with about 415 mm of rain and withparticular scarcity of precipitation either at the begin-ning (October–November) or at the end (March–April)of the potential growing season. However, the steepestdecrease in wild wheat populations was recorded in theextremely wet year 1987 (= October 1986–September1987), with total rain of over 790 mm and the highestamounts in November to January, but with a dry April.In contrast, the steepest increase was recorded in 1990,with a less than average total rainfall that, however, wasfairly evenly distributed over the growing season. Bothcontrasting years were preceded by years of drought. Itappears that an annual rainfall of 400–500 mm may be

optimal for wild wheat populations but, within thisrange, scarcity of early (November) or late (March–April) rains has a negative effect.

An experiment specifically designed to examine themechanisms by which intensive grazing limits wildwheat populations and, conversely, protection fromgrazing encourages them, was carried out in a basaltgrassland near Almagor in eastern Galilee in 1990–1993(Noy-Meir and Briske, 1996, and unpublished data).The three potential mechanisms considered were re-moval of dry plant remnants (mulch), defoliation in thevegetative stage, and removal of inflorescences in thereproductive stage. The survival, vegetative growth, andreproductive success of individually marked seedlingsof T. dicoccoides was monitored during two years in sixpairs of adjacent local populations. In each pair, onepopulation was grazed at moderately high intensity andthe other was protected from grazing. In protected popu-lations the number of mature spikelets (or seeds) pro-duced per marked seedling, which is a relative measureof plant fitness over the growing season, was double thatin grazed populations in both years. Such a 50% reduc-tion in fitness per year due to grazing may be sufficientto explain the negative effects of grazing on wild wheatabundance documented in previous studies. The majorcomponents of the grazing effect were the survival ofplants in the last month of the growing season (April) toproduce mature spikes in May, and the size (number of

Fig. 3. Percentage cover of Triticum dicoccoides vs. cover ofperennial grasses in ungrazed grassland sites in northern Is-rael, sampled in 1982–1983.

Fig. 4. Changes in the density of fertile plants of Triticumdicoccoides in four habitats, in grazed (G) and ungrazed (F)plots at Ammiad, Israel, from 1985 to 1991.

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spikelets per spike) of the spikes produced in thoseplants that did survive to maturity. Both were signifi-cantly greater in protected than in grazed populations,by 50–59% for survival to maturity and by 20–41% forspike size. Apparently, removal of primary inflores-cences by cattle late in the growing season (April) leftsome of the Triticum plants without sufficient resourcesfor maturation of secondary inflorescences, while inother plants only small inflorescences could mature. Bycontrast, plant survival during the vegetative stage(January–March) was not significantly affected by graz-ing, and the number of tillers per plant at the end of thevegetative stage was in fact 44–107% greater in grazedthan in ungrazed populations. No clear evidence for apositive effect of dry plant remnants on wild wheatgermination and establishment was found in this study,although it may occur in years with certain seasonalpatterns of rainfall. It was concluded that the negativeeffect of intensive cattle grazing on populations ofT. dicoccoides results mainly from direct damage tomaturing inflorescences in the reproductive stage, ratherthan from defoliation in the vegetative stage or removalof dry plant remnants in summer. This conclusion wasconfirmed in controlled experiments using clipping tosimulate grazing of wild wheat plants (Noy-Meir andBriske, unpublished). It is suggested that abundantpopulations of this species can be maintained underfairly intensive cattle grazing during most of the year,provided that cattle are excluded from the area duringthe reproductive stage of wild wheat, in the last four tosix weeks of the growing season.

EFFECTS OF FIRE

In the grasslands and open woodlands of eastern Galileeand the Golan, where many populations of T. dicoc-coides occur, accidentally or deliberately lit grass firesare common in the dry summer, between May and Octo-ber, when almost all the herbaceous biomass is dry. Theseparate and interactive effects of both fire and cattlegrazing on the structure, diversity, and composition ofMediterranean grasslands were examined in a studyconducted in 1990–1993 (Noy-Meir, 1995; Noy-Meirand Sternberg, 1999, and unpublished data). The studyfocused mostly on basalt grassland at altitudes between–160 and +280 m asl in the region north of LakeKinneret, in the Korazim Plateau of eastern Galilee andthe Yahudiyya Reserve in the lower Golan. Grazingeffects were measured by comparisons across fencelines and fire effects by comparisons across fire bound-aries, using both incidental fires and controlled burningexperiments. In 23 study sites, T. dicoccoides was suffi-ciently abundant to allow a statistical comparison across

the fire boundary. The responses of Triticum to fire overthese sites were almost equally divided between signifi-cant (p < 0.05) negative, significant positive, and nosignificant effects, apparently suggesting that this spe-cies is on the whole indifferent to grass fires in thisregion. However, positive responses to fire clearly pre-dominated in ungrazed sites, while in grazed sites therewere mostly negative or neutral responses (Fig. 5). Thehigher frequency of positive responses to fire inungrazed sites (six of eight) compared to grazed sites(two of 15) was significant (Fisher’s test for 2 × 2contingency tables, p < 0.01). It has been suggested thatthe spikelets of wild wheat, as well as of wild barley andoat, are relatively effective in protecting the grains fromfire damage, by virtue of their hard protective structuresand the structures that facilitate penetration into cracksin the soil (Naveh, 1974). The greater abundance ofTriticum (as well as Avena) in recently or frequentlyburned ungrazed grasslands may be related to the con-current reduction observed in the cover of perennials(mainly H. bulbosum). The shallow regeneration budsof the latter grass appear to be sensitive to fire at highintensity, as it occurs in ungrazed swards with highloads of dry herbage. Competition for space and light indense swards dominated by perennial grasses have al-ready been identified above as a limiting factor for wildwheat (as well as for wild barley and oats) in grasslandsnot grazed for several years. Apparently, hot fires openthe ungrazed sward at least for one or two years andallow the populations of wild cereal grasses, with grains

Fig. 5. Number of significant (p < 0.05) negative and positivedifferences in cover of Triticum dicoccoides between adjacentburned and unburned sites in grazed and ungrazed grasslandsin northern Israel sampled in 1990–1993.

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that can escape or survive the fire, to take advantage ofthe gaps. In grazed grasslands, the fuel load of dryherbage is lower, so that fires are of much lower inten-sity and temperature. Therefore, under grazing, the bal-ance between perennials and annual grasses does notchange substantially after the fire.

EFFECTS OF VOLES

In spring 1985, several ungrazed exclosure plots in east-ern Galilee that had been monitored in 1982–1983 (butnot in 1984) were revisited. Surprisingly, the tall grassesthat had dominated the plots in 1982–1983 (the peren-nial H. bulbosum or the annuals T. dicoccoides, H. spon-taneum, and A. sterilis) were absent or sparse in 1985. Intheir place, the vegetation was dominated by tall annualdicots, mostly of a “ruderal” type: crucifers (Brassicanigra (L.) Koch, Isatis lusitanica L., Raphanusrostratus DC.), composite thistles (Scolymus maculatusL., Notobasis syriaca (L.) Cass., Carduus argentatusL.), and others (Cephalaria joppensis (Reichenb.)Coulter, Synelcosciadium carmeli Boiss., Lavateraspp.). This drastic replacement had obviously been aresult of an eruptive population increase of the Levantvole (Microtus socialis guentheri Danford & Alston),which had occurred in 1984 and 1985 in the protectedexclosures (Noy-Meir, 1988). Extremely high volepopulations (0.5 to 2 vole burrows per m2) were reportedin 1985 also from large areas of grassland in the Golan,where they were associated with damage in varyingdegrees to the tall grasses. Vole populations were dens-est in ungrazed or only lightly grazed areas, where ap-parently the eruption had built up earlier. Intensivelygrazed paddocks were not affected, not even where theybordered plots with high vole density. Apparently, ex-posure to predators and raptors in the low open vegeta-tion of intensively grazed grasslands inhibits vole dis-persal and population growth, while the tall dense grass-land developing in areas protected from grazing pro-vides perfect shelter for foraging and dispersal, as wellas abundant food. In summer and autumn 1985, volepopulations decreased sharply to very low levels in mostof the affected area. Another similarly widespread re-gional vole eruption in grasslands of the Golan and partsof Galilee was observed again only in 1996, thoughlocal increases in isolated ungrazed areas were observedalso in 1990. Periodic outbreaks of the Levant vole weredescribed by Bodenheimer (1949), who for decades hadstudied their damage to crops. However, their effects onnatural grassland vegetation have not been previouslydocumented in Israel.

Field observations in 1985 and again in 1996–1997indicated that the damage by voles to their prefered food

plants (mainly grasses and especially the wild cereals,legumes, some forb species) is manifold and occurs inseveral seasons. In the vegetative stage, green leavesand tillers are cropped closely down to the ground;burrowing activity damages roots and buries seedlings.Most spectacularly, in the reproductive stage of the wildcereals (April–June), the spikes are systematically “har-vested” by clipping the reproductive tiller 5–10 cmabove the ground. The grains are stored undergroundand probably gradually consumed over the summer,while the straw is cut into short pieces which are left toline the burrows. The superficial regeneration bulbs ofthe perennial grass H. bulbosum are also severely deci-mated by vole activity, by direct consumption especiallyof the meristems, as well as by uprooting and rootseverance during burrowing activities.

Populations of T. dicoccoides in ungrazed grass-lands, together with those of Hordeum spp. and Avena,were severely reduced by vole eruptions in 1985 andagain in 1996. Some of the densest Triticum populationsrecorded in 1983 (10–40% cover of wild emmer), werereduced to 1% or less in 1985 (Fig. 6). The recovery ofpopulations of wild wheat and of other species de-stroyed by voles and their return to dominance over thepost-vole ruderals were gradual and slow processes,continuing during at least four to six years after thevoles themselves had disappeared (Fig. 6). In the case ofwild wheat, the slow recovery is to be expected, since

Fig. 6. Changes in percentage cover of Triticum dicoccoides inadjacent grazed and ungrazed sites in Galilee (Mt. Beatitudes)from 1983 to 1992, following a very high population densityof the Levant vole (Microtus socialis guentheri) in theungrazed site in 1984.

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seeds of this species apparently do not remain viable inthe soil for more than two years (Horovitz, 1998).

These rather fragmentary observations on infrequentextreme events raise many questions and speculationsabout long-term plant–herbivore–predator interactionsin this system, which are not easy to tackle. It is clear,however, that in these grasslands, with a history ofthousands of years of grazing by domestic herbivores,removal of these herbivores sometimes produces condi-tions that favor periodic or episodic disturbance byeruptive rodent populations. The evidence suggests thatthe effects of “vole years” on populations of wild wheat,barley, and oat are more drastic and long lasting than theeffects of cattle grazing and of fire.

DISCUSSION

A MULTIFACTOR HYPOTHESISThe direct and indirect effects of ecological factors

on populations of wild emmer wheat can be integratedin a multifactor hypothesis or model (Fig. 7):

1) Proximity to rocks favors wild wheat by enhancingsoil moisture, as well as by reducing local grazingpressure.

2) Grazing by cattle at high intensity has a negativeeffect on wild wheat, limiting it to rock refuges.

3) Complete protection from grazing can cause sup-pression of wild wheat by perennial grasses, butmoderate grazing relieves such suppression.

4) Hot fires in ungrazed grassland favor wild wheatindirectly by reducing the dominant perennials.

5) Vole eruptions that occur in closed grassland in theabsence of cattle grazing reduce wild wheat popula-tions.

6) Fires in ungrazed grassland have a negative effect onvole populations, by temporarily reducing both coverand food.

There are additional likely mechanisms that are notshown in the graphic model. Herbage mass depends alsoon rainfall amount and distribution. The heat generatedby grass fires may also directly enhance germination ofwheat by reducing seed dormancy.

IMPLICATIONS FOR THE HISTORY OFDOMESTICATION

The evidence on the sensitivity of T. dicoccoides tointensive livestock grazing has interesting implicationsfor the paleoecology and domestication history of thatspecies. The domestication of wild emmer and wildbarley in the Fertile Crescent began about 1,000 yearsbefore the domestication of sheep and goats in the sameregion (Smith, 1995). Wild herbivore populations at that

time were intensively exploited by hunting, at least inthe more accessible areas near human settlements, thusthe grazing pressure must have been low. These wereideal conditions for the increase and expansion of popu-lations of wild annual cereals, particularly in a zone withabout 400–500 mm rainfall, where the competing peren-nial grasses are less vigorous. It may be conjectured thatin the landscape of Galilee and the Rift Valley of about10,000 BP, wild emmer and barley were not restricted toinaccessible rocky areas, but rather occurred in exten-sive dense field-like stands in plains and valleys, and onmoderate slopes. These relatively easily harvestablestands would have been a major food resource for hu-man populations. Thus, considerable experience andknowledge of the biology of wild cereals would haveaccumulated in the societies dependent on them. Fromhere, it was only a small step for some inventive seed-gatherer to sow some seeds of a wild cereal near his orher home, a step that became the great leap into agricul-ture.

At that point, the wild populations of Triticum andHordeum began to diverge from those of the agriculturalgenotypes, ecologically as well as genetically. The do-mesticated forms, protected, propagated, and improvedand dispersed by man, expanded in arable valleys andplains. The wild populations were now relatively lessattractive for gathering, but soon became a most desir-able forage for herds of domesticated sheep, goats, andcattle. Over the millennia, the increasing pressure oflivestock grazing associated with increasing agricultural

Fig. 7. Graphical model of a multifactor hypothesis integratingthe effects of rocks, cattle grazing, perennial grasses, fire, andvoles on the density of populations of wild emmer wheat inMediterranean grasslands in Galilee. Lines with arrowheadsdenote positive effects, lines with circles denote negative effects.

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and pastoral populations gradually led to a severe reduc-tion or virtual extinction of wild Triticum populations insettled areas, and their restriction to less accessible hillcountry. However, livestock grazing in the region hasbeen intensive and widespread in most parts of thelandscape for at least the last 5,000 years. How did somepopulations of a species vulnerable to grazing survivethat long? The most important factor was probably theexistence, in the Mediterranean upland landscape, ofsmall natural grazing refuges, where wild wheat plants(and other species susceptible to grazing) were rela-tively protected from grazing by rocks or spiny plants(Noy-Meir, 1996). Though local extinction must haveoccurred in these small refuge populations, periods ofreduced livestock activity in some areas may have occa-sionally allowed them to expand and disperse across thelandscape and colonize or recolonize other refuge sites.Genetic adaptation by natural selection in response tograzing pressure may also have contributed to the sur-vival of some wild emmer populations in the “over-grazed” landscape. Wild wheat plants from many popu-lations tend to develop horizontal or inclined tillers inthe vegetative stage, particularly when grown sparselyin nurseries or garden experiments, while cultivatedwheats tend to develop mainly erect tillers even in theseconditions. This morphological divergence can be inter-preted as reflecting differences in the selection pressureby grazing experienced by wild and domestic wheatssince domestication (Waisel, 1987). Differentiation inmorphology and phenology that was found amonggenotypes of different habitats in the Ammiad site(Anikster et al., 1991) and among populations in theKorazim plateau (Noy-Meir, unpublished data) mayalso be the result of natural selection under quantita-tively different grazing regimes.

IMPLICATIONS FOR IN SITU CONSERVATIONThe natural and human landscape of Galilee has un-

dergone many changes in the century that has passedsince Aaron Aaronsohn searched for and eventuallydiscovered wild emmer wheat. The ecological pro-cesses, opportunities, and hazards that determine thedistribution, dynamics, and survival of T. dicoccoidespopulations in this landscape have changed since then.In Aaronsohn’s day, intensive grazing by domestic live-stock was the main limiting factor for populations of T.dicoccoides throughout its range. The grazing risk toconservation of wild emmer wheat populations persistsin parts of Israel and in the neighboring countries wheregrazing intensity continues to be high. In such “over-grazed” grasslands, the recommended management forin situ conservation and recovery of Triticum popula-tions surviving in refuges is a certain reduction of live-

stock grazing intensity, particularly during the repro-ductive stage of this species.

However, recent research indicates that “under-grazing”, i.e., complete protection or very low grazingintensity, as it now occurs in parts of Galilee and theGolan, results, in the long term, in new limiting factorsand new hazards for Triticum populations. Occupationof space by perennial grasses is a slow but persistentprocess, while destruction by voles is an episodic butdrastic event. Either of them can reduce Triticum popu-lations in undergrazed grasslands to very low levels, andpossibly to local extinction. Even Triticum populationsin rocky refuges can be crowded out by perennials orharvested by voles. Once overgrazing is no longer aproblem, these are the most serious threats to the persis-tence of wild wheat populations, second of course tohabitat destruction for cultivation or development. Theoccurrence of grass fires in undergrazed grasslands,though considered undesirable for other reasons, tempo-rarily reduces both perennial cover and vole activity andmay sometimes give wild wheat populations a betterchance to persist. Therefore, the least risky managementstrategy for in situ conservation of T. dicoccoides popu-lations in grasslands of northern Israel is not completeprotection from grazing and/or fire, but rather cattlegrazing at moderate intensities (120–180 cow-grazingdays per hectare per year), and avoidance of intensivegrazing in late spring.

ACKNOWLEDGMENTS

In individual research projects on which this review isbased, I have benefited from the cooperation of mycolleagues Moshe Agami, Yehoshua Anikster, DavidBriske, Mario Gutman, Yedidya Kaplan, and MortKothman. Among the persons who helped in field andcomputer work, I owe special thanks to Yehudit andYoram Canetti, Michal Ramati-Amitai, Mark Rubin,and Miriam Schlichter. Grants from the followingsources are gratefully acknowledged: Israel ScienceFoundation of the Israel Academy of Sciences and Hu-manities (1981–1983, 1990–1993, 1994–1997), IsraelMinistry of Science (1985–1987 grant from USDA,1987–1992), Israel Nature Reserves Authority (1989–1990), and United States–Israel Binational ScienceFoundation (1990–1993 and 1997–2000).

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