Volume 11, May 2009

By Gabriel Schiller (vcgabi@netvision.net.il), David Eugene Ungar, Yosef Moshe and Nir Atzmon, Department of Agronomy and Natural Resources and by Shabtai Cohen, Department of Environmental Physics and Irrigation, ARO, Volcani Center, Bet Dagan.

Forest canopy transpiration (T) of Aleppo pine, Pinus halepensis Mill., (34 ± 4 years old), growing in the Yatir forest at the edge of the Negev Desert, at a stocking density of 300 trees per ha, was measured by means of the heat pulse technique from Feb. 14 until June 7, 2004; and from Nov. 4, 2004 until June 18, 2005. In each of the three 0.25-ha plots, which differ in slope orientation, eight trees were chosen; they were representative of the average tree in the plot, i.e., similar in height, DBH, and crown length and width. The velocity of a heat pulse that served as a tracer of the sap flow velocity was measured consecutively in these eight trees in each plot during each hour of the day. The measurements in the three different plots were performed during 140 consecutive days in the hydrological year of 2003/4 which was a drought year (231 mm annual rainfall), and 227 days in the hydrological year 2004/5, which was a rainy year (373.5 mm annual rainfall).

The hourly T rate, considered equal to the sap flux, was calculated from the sap flow velocity, the wood physical properties, and the part of the sapwood cross-section area of the trunk monitored by each of the six thermistors on the probe, which penetrated to a depth of 4.8 cm into the xylem.

Application of ANOVA revealed significant differences among the forest canopy daily T rates in the three plots during 2003/4. Summation of these daily T rates (mm day-1) showed that forest canopy transpiration during daylight hours (06:00-19:00) during 140 days added up to 101.51 mm on the south-east facing slope, 57.82 mm on the north-west facing slope, and 76.56 mm of the plain area. Differences among the three plots in 2004/5 were not significant. Summation of the forest canopy daily T rates showed that daylight transpiration (05:00-19:00) of 300 trees per ha during 227 days added up to 126.08 mm on the south-east facing slope, 137.64 mm on the north-west facing slope, and 141.07 mm on the plain area.

By Har'el Agra, Department of Evolutionary and Environmental Biology, Faculty of Science and Science Education, University of Haifa (agra10@bezeqint.net) and Gidi Ne'eman, Department of Biology, Faculty of Science & Science Education, University of Haifa-Oranim (gneeman@research.haifa.ac.il)

Organisms that modify their habitats are described as ecosystem engineers. Landscape modulators (LMs) are ecosystem engineers that modify their environment and the landscape mosaic by creating patches in which resource availability differs from that of the background. Our research examined the effect of evergreen trees, as LMs, on local species richness of the herbaceous vegetation in a Mediterranean maquis system. The research was carried out on Mt. Meron, 900 m a.s.l., in northern Israel. Herbaceous plant species richness was measured in two different patch types: woody, i.e., under a tree canopy or under the former location of a removed canopy; and herbaceous, i.e., not under any tree canopy. Factorial block design was applied to study the effects of canopy removal and cattle grazing on herbaceous species richness and on the presence of plant functional types. The results demonstrate that the extreme negative effect of the woody patch on herbaceous species richness disappears soon after the removal of the LM canopy. Patch type and treatments affected the composition of herbaceous plant species and that of plant functional types. Most important was the differential response of some rare plant species, which probably resulted from their unique and relatively narrow niches. We conclude that the dominant effect of the evergreen woody LM patch can be regulated by canopy removal and grazing, which can be managed according to the goals of any local nature conservation management policy. Moreover, the research demonstrates the importance of maintaining both patch types side-by-side for the maintenance of the high biodiversity level in Mediterranean ecosystems.

By Abraham Weinstein, Department of Agronomy & Natural Resources, The Volcani Center, Bet Dagan.

Casuarinas are widespread in Israel along roadsides and used as windbreaks, and in parks, small wood lots and forest plantations.

Casuarinas planted in Israel were found to be mixtures of C. cunninghamiana and C. glauca, and subsequent indiscriminate gathering of seeds, caused by lack of differentiation between the two species within plots, resulted in a continuation of mixed plots. Since C. cunninghamiana and C. glauca flower at about the same time the possibility of hybridization and back-crossing was recognized.

There was considerable interest in testing additional species under a wide range of ecological conditions, in order to fully utilize the potential of casuarinas for afforestation and reforestation. Therefore, it was necessary to study a large number of old plots and to establish new ones, in order to study the adaptability of the various species for afforestation purposes. Introduction and forest plots were studied in areas from Even Izhak in the north to Nir Izhak in the western Negev, and it was established that 17 species of casuarinas are grown in Israel. Most of these trees are Casuarina cunninghamiana, C. glauca, C. cristata and Allocasuarina leumannii.

C. cunninghamiana, C. glauca and their hybrids grow well in Israel on the red loamy sand and brown rendsina soils in the Mediterranean region, where mean annual rainfall is 400-650 mm.

C. glauca can thrive in drier regions which receive 200-300 mm mean annual rainfall, especially in depressions on sandy loam, loess, and loessial light brown soils.

C. cristata grows well in the center and south (western and northern Negev) of Israel, in conditions of 220-250 mm mean annual rainfall on loessial light brown clay loam, and on steep slopes with brown lithosol.

Allocasuarina luehmannii grows well in the center and south of the country, on both plains and hills, in conditions of 200-600 mm mean annual rainfall, on brown rendzina, on brown lithosols, on moderate slopes covered with loessial serozem and where loessial light brown clay loam grades intoloessial serozem.

By Nir Herr (nir.herr@mail.huji.ac.il), Soil and Water Department, Faculty of Agriculture, Food and Environmental Quality Sciences, the Hebrew University of Jerusalem and of Menasheh-Hasharon Region, KKL, Yokneam Moshava, Israel; Omri Bonneh, Eli Benichou, Shali Ben Yshay, Paul Ginsberg and Michael Weinberger, KKL Northern Region, Kiryat Bialk, and Sohil Zaidan, KKL Forest Department, Eshtaol

In late winter and spring 2006-7, KKL Forest department transplanted 928 trees from a Lower Galilee junction, as part of road works. The majority (838) of these trees were Tabor oaks, Quercus ithaburensis Decne., which were transplanted to a nearby site, east of Bir-el-Maksour. All phases of the transplanting process were recorded and the data were analyzed for factors affecting the survival and development of each of the trees on an individual basis. The process began in January 2006 by pruning the trees, followed by their removal, transportation, site preparation and transplanting, over a one-month period which coincided with the tree bud break in early March. A detailed site survey prior to the re-planting provided a valuable planning tool for tree placement. Eight site categories were designated and mapped according to lithological type and structure, soil type and native vegetation. These included mainly limestone with terra rossa soil and herbaceous vegetation or chalk / marl with or without a Nari crust with rendzina soil and low-growing shrub cover. The location of each new pit was chosen by matching it to the tree's original site characteristics, and according to the aesthetic aspects of their placement on the landscape and logistical considerations. Each tree was numbered and the following details were recorded: species, dimensions, root condition, original site location, and transplanted site location. Following the transplanting, a buried drip irrigation system was installed. A weekly irrigation regime, monitored with tension meters, was implemented throughout the spring, with periodic "saturation-level" irrigation during the summer. On average, each tree received 19 liters per day in the first summer season and 46 liters per day in the second. Ninety-six percent (96%) of the Tabor oaks survived the transplant and exhibited excellent re-growth rates of new branches and crown sprouts by the second year. The primary factors contributing to a positive survival rate were early transplanting, good root ball condition, single-stemmed trees with small DBH, and shortness of the tree. The optimal site condition was a Nari-encrusted chalk limestone with shallow soil. The bottoms of the new planting pits on this site type were on porous bedrock, similar to the tree's original site, which allowed the transfer of capillary water to the root system throughout the year.

By Zion Madar (tamarmadar@walla.com), Nitza Saphir, Suhil Zaidan and Ami Zehavi, KKL Forest Department, Eshtaol

Carob (Ceratonia siliqua L.) trees are known for their ability to grow on calcareous and other soil types and in dry climatic conditions. The species is planted and grow in Israeli forests. However, neglect of forest management can lead to heavy damage by pests and diseases. Both Cercospora ceratoniae and Odium ceratoniae fungi attack the leaves of carob trees, leading to leaf shedding, but do not kill the trees. However, these agents may predispose the trees to attack by other pathogens or pests. Stem and branch rot is considered a severe problem for trees, especially if they were not treated in the past. Root rot is seen in a few cases in the forests, but is more common in irrigated sites such as gardens. The rat, Rattus rattus L., a serious pest, has been observed to peel large sections of the bark of branches and trunks, frequently causing degeneration and death of parts of the trees, and sometimes of the whole trees. In order to reduce disturbances of carob trees they must be treated early (aged 4-5 years) as follows: plant on well drained soils, prune to give the trees a proper structure, disinfect the resulting wounds, and remove affected branches.

By Yoram Goldring, Ami Zehavi and Hayim Sahar, KKL Forest Department, Eshtaol.

Ulmus canescens is a rare tree, found in humid habitats in Israel. The species has been known for many years around the Hazorea Creek and several other places in the Menasheh region and northern Israel. A small stand of U. canescens was recently found in the upstream part of Wadi Ha'elah, about half a kilometer east of Tel Tsafit, in the Judean foothills. Water flows only in winter, but the groundwater is probably shallow, and there are several springs about a kilometer downstream to the west. This stand was recently damaged by fire, and the trees resprouted with many trunks. Two trees remained intact and beautiful; the others were trimmed and reshaped by the local forester. Rubus sanguineus and Vitex agnus-castus bushes grow next to the Ulmus trees in this wadi, and their presence also confirms the continuous availability of water.

Chudnoff and Karshon (1960) reported a specimen of the species on the bank of the Hataninim Creek also, and they cited Jacob Galil, who had seen another tree on the Yarkon River bank; both sites are on the coastal plain. Chudnoff and Karshon (1960) mention that the first finding of the species in Israel was by Hasselquist (1751) (who thought it was a European species of the genus), and that the species canescens was defined as sp. novoby Melvill in 1957. It is now accepted that the Israeli form is the sub-species canescens of the species U. minor.

It should be noted, however, that several exotic Ulmus species, some of which are hybrids (Shmida, 1993, Fahn 1998), are common in gardens in Israel. Therefore, the seed source could be in a neighboring village, a few kilometers away, but we doubt this. In any case, identification is difficult, and readers are urged to visit the place, enjoy it, and identify the tree. Flowers and fruits are expected in early spring.