Arid vegetation protection and habitat improvement by covering the soil with tree branches.
or
Restoring productive soil patches as a way to the rehabilitation of semi - arid landscapes.

Abstract

Australian scientists (Tongway and Ludwig) developed a rehabilitation procedure designed to re-establish resource control processes in a degraded desert. The actual proposal objective is to adapt the method to sand dunes in Spain and to overgrazed desert areas in Israel. The objective is to improve soil respiration rates, to increase soil fauna populations increased, and to moderate the erosion in soils. The procedure comprised laying piles of branches in patches on the contour of bare, gently sloping landscapes, with the expectation that soil, water and litter would accumulate in these branch piles, thus improving the soil habitat and its productive potential. The procedure was derived from landscape function analysis, indicating that surface water flow was the principal means of resource transfer in these landscapes. Under degradation such overland flow results in a loss of resources. This rehabilitation procedure reversed loss processes, resulting in gains in the productive potential of soils within patches. This main procedure advantage it is that animal grazing pressure is being maintained throughout the experiment.

Keywords: habitat reconstruction, fertility, landscapes.

A. Introduction

In the arid and semi-arid regions of Israel there are large areas were the vegetation has suffered a long process of degradation. Today’s societies, large urban, are demanding damaged rangelands to be repaired. In terms of economic gains in livestock production, rangeland rehabilitation is not cost effective. However, multiple use values (biodiversity, tourism) puts a different perspective on cost effectiveness. Therefore there are strong incentives for improve techniques for the rehabilitation of rangelands. (Ludwig et al, 1995)

This degradation was due to a number of factors, but in Israel the main one is the increase of the number of livestock owned by the semi - nomadic Bedouins.

In past years the lack of water supplies limited the destructive action to places close to the water well, but in the last years water supplies improved due to the introduction of water tanks trailers.

Degradation within semi-arid regions is a continuing issue, especially during prolonged droughts when the country has very little vegetation cover and grazing animals break up the soil surface, making it more erodable. Among the long-term effects of degradation are: (1) losses of palatable grasses; gains in inedible native shrubs and ephemerals; and (2) soil erosion.

B. Areas of research being addressed.

Enhancements of management of ecological systems.
Ecosystem processes supporting management for ecological system.

C. Objectives

1. To reinstate landscape processes on degraded bare slopes by constructing piles of branches which were expected to obstruct water flow and create aerodynamic drag.

2. To observe edaphic and vegetation responses over time after constructing branch piles on degraded semi desert soils. The expectation is that the experimental plots with branches become richer in resources and support plant populations characteristic of a run-on zones.

D. Literature Review

Recent basic studies which linked terrain, soil and plant patterns to landscape processes have given rise to generic models of semi-arid landscape function (Tongway & Ludwig, 1990; Tongway, 1991; Ludwig & Tongway, 1993, 1994). By definition water and soil nutrients are in short supply in arid and semi-arid lands (Noy-Meir, 1973). Because these lands have a high diversity of perennial plants occurring in natural patches when undegraded, they have mechanisms to both store water and nutrients, and to slowly release These resources so that perennial plants survive over long time spans (Noy-Meir, 1981, 1985). Efficient landscape functioning depends on patches to capture water and nutrients, which are limited and unpredictable inputs to these semi-arid environments (Tongway, 1991). It is also necessary to understand the processes by which patches are maintained in a landscape.

We propose that if landscape function can be adequately defined in terms of pattern, and the processes which determine that pattern, then dysfunction or degradation can be objectively addressed by identifying the landscape processes which have been diminished. This landscape function hypothesis can be tested by improving the processes which are suspected to be ineffective and degraded lands.

This method of landscape rehabilitation, whereby patches were created to sequester scarce resources flowing around the landscape, was successful in restoring a wide range of soil properties, embracing the physical, chemical and biological dimensions of 'fertility'. The impact of this improvement in soil quality on producing greater growth of perennial plants is also significant (Ludwig & Tongway, 1995). Thus, the model of semi-arid landscape function in this landscape type proposed by Tongway and Ludwig (1990), whereby run-off/run-on processes interact with patches to concentrate scarce water and nutrient resources, was confirmed by the results of this experiment.

The procedure of landscape rehabilitation described here was also successful while grazing pressure was maintained, which has obvious advantages for practical pastoral management, in that de-stocking is not essential for the success of the method, and may even speed up the process of fertile patch formation. Performance standards for recognizing stages in soil rehabilitation are now available to monitor the progress of rehabilitation (Tongway, 1993).

The importance of naturally fertile soil patches within the semi-arid landscapes of Australia is mirrored by similar soil patchiness in other arid and semi-arid regions of the world (Forman and Godron, 1981). The processes invoked similar patch maintenance (Noy-Meir, 1973; Garner and Steinberger, 1989; Cornet et al., 1992).

We propose that if landscape function can be adequately defined in terms of pattern, and the processes which determine that pattern, then dysfunction or degradation can be objectively addressed by identifying the landscape processes which have been diminished. This landscape function hypothesis can be tested by improving the processes which are suspected to be ineffective in degraded lands .The present proposal aim is to reinstate landscape processes on degraded bare slopes by constructing piles of branches which were expected to obstruct water flow and create aerodynamic drag. The hypothesis was that these obstructions would filter out or capture resources entrained in water flows or wind, thus creating resource-rich or fertile patches.

The experimental approach is to observe edaphic and vegetation responses over time after constructing branch piles. The expectation is that the experimental plots with branches become richer in resources, the soil would improve its habitat value and, hence, support increased microbial, invertebrate and plant populations characteristic of a run-on zones which are characteristic of these landscapes when non-degraded. In Australia, when the rehabilitation treatment was tested on bare slopes, the branch piles had a dramatic effect on soil deposition and erosion, with clear gains of soil on the treated plots compared to non-branch treatments, and controls, which lost about 0.75 mm per year. The control paddock treatment experienced greater gains and losses than the treatment paddock.

Results of the proposed treatment in Australia. (Tongway and Ludwig, 1995).

As a rehabilitation treatment on bare slopes, the branch piles had a

dramatic effect on soil deposition and erosion, with clear gains of soil on the treated plots compared to non-branch treatments, which lost about 0.75 mm per year. The origin of the accumulated soil in the treated plots was both fluvial and aeolian. Personal observations on windy days confirmed that both suspended and saltating soil particles lodged in the branches due to turbulence by the piles. The branches caused particles to precipitate out of the airflow into the relatively protected area of branches, where the capacity of the particles to be re-mobilized was greatly reduced. Litter fragments from trees, such as Eucalyptus populnea (poplar box) occurring at least 100 m away, were found in the branch piles, indicating an aeolian litter input. Fluvial processes were also clearly active, in that trains or rafts of leaf litter and dung were observed on the upslope edge of the plots with branches after run-off events, and the upslope edge of plots accumulated more soil than the downslope edge.

The branch treatment increased water infiltration markedly. The size of the change in soil infiltration rate was unexpected. This effect was more pronounced in the control paddock than in the branches covered. The branch covered plots achieved a ten-fold increase in infiltration rate on the control paddock in three years. The magnitude of this amelioration effect means that significantly more rain can be infiltrated and stored in such landscape patches than in the surrounding landscape, and thus less to run off the landscape as a whole.

This method of landscape rehabilitation, whereby patches were created to sequester scarce resources flowing around the landscape, was successful in restoring a wide range of soil properties, embracing the physical, chemical and biological dimensions of 'fertility'. The impact of this improvement in soil quality on producing greater growth of perennial plants is also significant (Ludwig and Tongway, 1995).

The procedure of landscape rehabilitation was also successful while grazing pressure was maintained, which has obvious advantages for practical pastoral management, in that de-stocking is not essential for the success of the method, and may even speed up the process of fertile patch formation.

E. Description of the research plan

The research plan in Israel

1. Methodology
In the arid and Semi arid zones of Israel there are large areas where the Natural vegetation has suffered a process of degradation by the heavy grazing of the Semi nomadic Bedouin herds. The process is particularly acute in the vicinity of the villages. In the last past years a new problem appeared with the introduction of the all terrain vehicles (ATV), utilized principally for recreation purposes. The areas most affected by the ATV use are the sand dunes of the Mediterranean Coast.
    The closing of large areas to allow the vegetation recover( Noy-Meir al, 1989) is not practicable due to administrative, economical, social and political reasons. The enforcement of the grazing restriction, in areas where the protection policy has been decided, has been difficult and sometimes not effective.
    The establishment of relatively small areas to form niches where the grazing effect is restricted will be highly desirable. In the past, small areas have been fenced for this purpose but the method is expensive. The fences have to be checked and repaired and are also sensible to robbery and vandalism.
    A fringe benefit of the method will be the disposal of the material originated by the clearing of pine, eucalyptus and fruit orchards pruning. The pruned materials represent a nuisance. Actually the common method of material disposal is burning the branches, but the method is expensive, dangerous and recently there is the intention to forbidden the burning due to air pollution concerns.
    Another possible application of the method could be the protection of young forest planted in grazed areas.
In the last past years there was a growing interest in the establishment of tree groves in range lands. The reasons are as follows:
    To form shaded areas protected from grazing,
    Accordingly to previous research cattle performance improves when there is shade in the paddock (Silanicove and Gutman, 1992).
    To form wind breakers,
    To prepare the land for tourism activities. In the last past years an interest appeared for tourism in the open areas. The beef cattle breeders consider tourism, principally four wheel tours, as an additional production branch. The presence of trees, in areas when shade is scarce, increase the land value for tourism activities.
    The main limiting factor to planting trees in grazed areas has been the need to restrict grazing in all the newly forested paddock. The individual protection of trees by mechanical methods, as iron cages, is expensive. The individual tree protection by pruning material could provide a cheap and ecological friendly solution. Animal grazing could be allowed during the peak of the green season (March - April).  During these months the cattle prefer to graze the plentiful herbaceous vegetation, and therefore the grazing pressure on the trees is low. The branches will prevent trampling damage to the trees making the access to them more difficult.
    The grazing will remove the herbaceous vegetation decreasing the danger of wild fires during the dry season.
    Three basic environments will be selected for the trials are :

Areas degraded by heavy grazing: emphasis will be the grazing intensity, according to results conducted in Northern Israel a cover of about 0.50 meter high is enough to prevent cattle grazing for a period of about three years. It also will not prevent the light from reaching the soil and allows the establishment of herbaceous vegetation.
Sand dunes of the Mediterranean Coast: the damage inflicted by the ATV activities.
Protection of young forest planted in grazed areas: The methods are similar to previous habitats but the additional treatment will be conducted: plantation in areas totally protected from grazing and areas under grazing only during the during the peak of the green season. will be conducted at Karei Deshe Range Station (Gutman et al 1990).
 

2. Experimental design
    The branches diameter recommended is less than 4 cm, the reasons being the need to cover the soil with a fine and uniform material. Larger branches will form higher than 0.50 meter piles and could be removed by the Bedouins to be utilized as fuel.
    Site Size: In the arid open areas, the size unit recommended is 33 by 33 meter. The main reason is to form a habitat large enough to permit the establishment of vegetation, even if it is disturbed in the borders. Each site has to be large enough to form one botanical sample unit that represent the local botanical formation. Larger units could be difficult to sample, specially during the first years, before the branches decompose.
    Site Selection. The sites will be selected in places accessible to trucks and when possible close to clearly identifiable land features for easy identification during the trial years. The site borders will be marked by iron posts cemented in the soil.
    The treatment applied consisted in covering the soil with piles of branches constructed from three different materials:
a. locally available Acacia trees,
b. branches from pine plantations clearing.
c. branches from fruit orchards pruning.
    The piles of branches will be constructed using any of the above mentioned materials, stacking the branches about 0.5-m high, ensuring that the main stems will be in contact with the soil. The size of each paddock will be 33 m by 33 m. The size of the paddock (larger than in Australia, where the size was only 2 m by 5 m) was considered necessary to ensure a relatively undisturbed area at the center of the paddock, under heavy grazing conditions.
    In each paddocks three transects 33-m long will be fitted into the available space with at least 10-m separation between transects down the slope. nine 2-m by 5-m plots will be located longitudinally along each transect, with a 5-m buffer zone between each observation plot. Each observation plot was permanently marked with steel and wooden pegs, and two steel benchmark pegs will be installed 0.8-m deep at the ends of every transect.

Botanical composition monitoring. In each site, the botanical composition will be measured at early spring before the covering of the soil by tree branches. The following methods will be applied.
a. point survey inpermanent transects.
b. recording of all the identifiable species.
c. visual estimation of the principal species relative cover.
    Close to each site, 3 control places will be marked and surveyed in the same form as in the experimental site.
    The botanical surveys will be conducted twice a year, at the end of green and dry season (April and November). The cover of branches, bare soil and total vegetation will be recorded, in addition to the principal vegetation species relative cover.

Herbaceous vegetation biomass. The total annual primary production will be measured by clipping vegetation samples at the end of the growth season (Tadmor et al, 1975). In areas under grazing, small fenced areas (5 by 5 meter) will be established in the control sites (outside the site covered by branches) to measure the growth under ungrazed conditions an to determine the differential branches effect on vegetation. The botanical composition of the clipped biomass will be measured by visual estimations of the relative cover of the principal species.

Soil sampling. Prior to the application of the treatments, soil samples will be taken from each plot by bulking 5 representative cores divided into depth intervals of 0-1, 1-3, 3-5 and 5-10 cm. The soil was air-dried, crushed to pass a 2 mm screen and stored in air-tight containers until analyzed. The soil samples will be analyzed by the following techniques: (1) electrical conductivity, 1:5 soil in water (Loveday, 1974); (2) pH, 1:5 soil in 0.01M CaC1₂; (3) organic carbon by a modified Walkley Black technique (Colwell, 1969); (4) organic nitrogen (Twine and Williams, 1967); (5) available phosphorous (Colwell, 1965); (6) exchangeable cations and cation exchange capacity (CEC) (Chhabra et al., 1975); and (7) potentially available nitrogen (Gianello and Bremner, 1986).
    In order to assess loss or gain in soil over the period of the trial, plot levels will be carefully measured to a precision of 1 mm using a surveyors level. Each 2-m by 5-m plot was divided into 10 rows, 50 cm apart. Levels will be read at 40-cm intervals on each row (i.e., 50 readings per plot). These be registered with the permanent bench marks installed at the ends of each transect.
    The density and foliage cover of all perennial plants be observed in ten 1-m by 1-m quadrats within each 2-m by 5-m plot.

After 3 years the following measurements will be recorded:
(1) soil levels on each plow will be repeated to estimate erosion and deposition processes; (2) soil will be resampled and analyzed for nutrient content from each plot by the same procedure as at the start; and (3) water infiltration rates will be made using a disk permeameter (Perroux and White, 1988) on randomly selected transects in each paddock.

Once-off measurements included: (1) air versus soil surface temperatures at 3-hourly intervals for 24 hours on the grazed paddock in October 1989 using a calibrated thermocouple; (2) soil respiration will be measured using an inverted box/ alkali absorption method (Hartigan, 1980; Tongway and Hodgkinson, 1992). CO₂ evolved over a period of 24-hr will be calculated.

Data analysis. Soil nutrient results will be subjected to analysis of variance to examine the net effect of the treatments over the 3-year period.

4 Time schedule of the work plan

Israel Time Schedule

1996 Site Selection, botanical and soil surveys. Branch piles establishment

1997 Botanical and soil surveys

1998 Result analysis.

SPAIN Time Schedule

F. Description of the investigators institutional support.

Israel . The salaries and social expenses are totally covered by the scientist respective institutions. The budget is required mainly for operating expenses needed for botanical and soil surveys.

SPAIN

G. Description of support from other sources.

Israel. The research is supported by the field stations and laboratories of the Agricultural Research Organization (ARO) and the Galilee Technological Center, (Migal). The infrastructure include: Field laboratory with basic equipment for plant and animal measurements, computers and portable datalogers. Vehicles for field work

SPAIN

H. Literature Cited

Chhabra, R., J. Pleysier and A. Cremmers. 1975. The measurement of the cation exchange capacity and exchangeable cations in soils: A new method. Pages 439-449 in Proceedings of the 5th International Clay Conference. Applied Publishing, Willmette, Illinois.

Colwell, J.D. 1965. An automatic procedure for the determination of phosphorus in sodium hydrogen carbonate extracts of soils. Chemistry Industry May: 893-895.

Colwell, J.D. 1969. Auto-analyzer procedure for organic carbon analysis of soil., National Soil Fertility Project, Circular. No. 5., CSIRO Division of Soils, Canberra.

Cornet, A.F.,C. Montana, J.P. Delhoume and J. Lopez-Portillo. 1992. Water flows and dynamics of desert vegetation stripes. Pages 327-345 in A.J. Hansen and F. di Castri, editors. Landscape Boundaries -- Consequences for Biotic Diversity and Ecological Flows. Springer-Verlag, New York.

Forman, T.T. and M. Godron. 1981. Patches and structural components for a landscape ecology. BioScience 31: 733-740.

Garner, W. and Y. Steinberger. 1989. A proposed mechanism for the formation of 'fertile islands' in the desert ecosystem. Journal of Arid Environments 16:257-262.

Gutman, M., N.G., Seligman, and I. Noy-Meir, (1990). Herbage production
of Mediterranean grassland under yearlong and seasonal grazing systems.
J. Range. Management. 43:535-538.

Hartigan, R.J. 1980. Soil respiration as an index of forest floor metabolism. Ph.D. Thesis, University of New England, Armidale.

Loveday, J., editor. 1974. Methods of analysis of irrigated soils. Technical Communication. No. 54. Bureau of Soils, Commonwealth Agricultural Bureau, Canberra.

Ludwig, J.A. and D.J. Tongway. 1993. Monitoring the condition of Australian arid lands: linked plant-soiled indicators. Pages 763-772 in D. H. McKenzie, D.E. Hyatt and V.J. McDonald, editors. Ecological Indicators, Vol. 1. Elsevier Applied Science, New York.

Ludwig, J.A. and D.J. Tongway. 1994. Spatial organization of landscapes and its function in semi-arid woodlands, Australia. Landscape Ecology 9: (in press).

Ludwig, J.A. and D.J. Tongway. 1995. Rehabilitation of semi-arid landscapes in Australia. II. Restoring vegetation patches. Restoration Ecology (submitted).

Ludwig, J.A., and D.J. Tongway and SAG. Marsden. 1994. A flow-filter model for simulating the conservation of limited resources in spatially heterogeneous, semi-arid landscapes. Pacific Conservation Biology 1:209-213.

Ludwig, J.A., J. Fargher, B. Foran, C, James, N. MacLeod, and S, McIntyre. 1995. Restoration of our earth’s rangelands, Emergency damage control or fait in self -healing. Proceedings Fifth International Rangeland Congress, Salt Lake City UTAH. 23 - 28 July 1995 (in press).

Noy-Meir, I. 1973. Desert ecosystems: Environment and producers. Annual Reviews in Ecology and Systematics 4:25-52.

Noy-Meir, I. 1981. Spatial effects in modeling of arid ecosystems. Pages 411-432 in D.W. Goodall and R.A. Perry, editors. Arid Land Ecosystems. Cambridge University Press, Cambridge.

Noy-Meir, I. 1985. Desert ecosystem structure and function. Pages 93-103 in M. Evenari, I. Noy-Meir and D. Goodall, editors. Ecosystems of the World, Vol. 12A, Hot deserts and Arid Shrubland. Elsevier, Amsterdam.

Noy-Meir, I., M. Gutman, and Y. Kaplan. 1989. Response of Mediterranean grassland plants to grazing and protection. Journal of Ecology 77:290-310.

Perroux, K.M. and I. White. 1988. Designs for Disc Pemeameters. Journal Soil Science Society of America. 52:1205-1215.

Silanicove, N., and M. Gutman, (1992).Interrelationship between lack of shading shelter and poultry litter supplementation: food intake, live weight, water metabolism and embryo lost in beef cows grazing dry Mediterranean pasture. Anim. Prod. 55: 371-376.

Tadmor, N.H., A. Brieghet, I., Noy-Meir, R.W. Benjamin and E. Eyal. 1975. An evaluation of the calibrated weight-estimate method for measuring production in annual vegetation. J. Range Manage. 28:65-69.

Tongway, D.J. 1991. Functional analysis of degraded rangelands as a means of defining appropriate restoration techniques. Pages 166-168 in Proceedings, IV th International Rangeland Congress, Montpellier, France.

Tongway, D.J. 1993. Rangeland soil condition assessment manual. CSIRO Information Services, Melbourne.

Tongway, D.J. and K.C. Hodgkinson. 1992. The effects of fire in a degraded semi-arid woodland. iii. Nutrient poll sizes, biological activity and herbage response. Australian Journal of Soil Research 30:17-26.

Tongway, D.J. and J.A. Ludwig. 1990. Vegetation patterning in semi-arid mulga lands of Eastern Australia. Australian Journal of Ecology 15:23-34.

Tongway, D.J. and J.A. Ludwig. 1994. Small-scale heterogeneity in semi-arid landscapes. Pacific Conservation Biology 1:201-208.

Tongway, D.J., and J.A. Ludwig. 1995. Restoration of landscape patchinnes in semi arid rangeland, Australia. Proceedings Fifth International Rangeland Congress, Salt Lake City UTAH. 23 - 28 July 1995 (in press).

Twine, J.R. and C.H. Williams. 1967. Determination of nitrogen in soils by automated chemical analysis. CSIRO Field Station Record 6:61-67.
 

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