Зависимость плотности Cyamophila dicora от растительных параметров Astragalus glaucacanthus в семиаридных регионах Исфахана, Иран Текст научной статьи по специальности «Сельское хозяйство, лесное хозяйство, рыбное хозяйство»

АРИДНЫЕ ЭКОСИСТЕМЫ, 2007, том 13, № 32

ОТРАСЛЕВЫЕ ПРОБЛЕМЫ ОСВОЕНИЯ ЗАСУШЛИВЫХ ЗЕМЕЛЬ

УДК 581.526:911

ЗАВИСИМОСТЬ ПЛОТНОСТИ Cyamophiladicora ОТ РАСТИТЕЛЬНЫХ ПАРАМЕТРОВ Astragalus glaucacanthus В СЕМИАРИДНЫХ РЕГИОНАХ ИСФАХАНА, ИРАН

© 2007 г. М. Месдаги*, М. Азими*, М. Фарахпур**, Г.А. Дианати Тилаки***

*Горганский Сельскохозяйственный Университет, отдел управления экологией и пастбищами, Г орган, ИРАН **Исследовательский институт леса и пастбищ, Тегеран, ИРАН ***Университет Тарбиат Модарес, факультет природных ресурсов и морских наук, отдел управления пастбищами, Мазандоран, P.O.В. 46414-356, ИРАН, E-Mail: dianatitilaki@yahoo.com

Традиционное овцеводство и возделывание различных видов растений как сопутствующих животноводству имеет долгую историю в Персии. Выкармливание насекомых (Cyamophila dicora, Logvina) на колючих кустарниках Astragalus glaucacanthus дает млечный сок, называемый "катира", который выделяется нимфами этих насекомых на последних стадиях развития. Этот млечный сок используется для изготовления жевательной резинки под названием "самг" и производится только в Исфахане.

Целью наших исследований было: 1) разработать карту распространения A glaucacanthus в Ферейдоншаре (Исфахан), 2) определить те фенологические стадии развития A. glaucacanthus, которые наиболее важны для жизненного цикла Cyamophila dicora и 3) определить зависимость плотности насекомых от возраста, проективного покрытия, влажности веток A. glaucacanthus и влажности почвы.

В результате работ по проекту нам удалось разработать карту пространственного распространения кустарника. Карта была разработана на основе аэрофотоснимков с последующими исследованиями на местности. Производя отбор проб вдоль линейных транссект, мы оценили биологические параметры и параметры окружающей среды, такие как плотность насекомых, проективное покрытие растений, влажность ветвей и влажность почвы. Методы множественной линейной регрессии и иерархического полностью рандомизированного плана были использованы для анализа реакций переменных и прогноза.

Результаты анализа показали, что Astragalus glaucacanthus занимает самые влажные участки горных районов под Исфаханом, а плотность насекомых сильно зависит от возраста, проективного покрытия кустарника и от влажности почвы. Самые старые и наиболее крупные кусты имеют самую высокую плотность насекомых. Регрессионный анализ подтвердил, что возраст растений и влажность почвы являются важными параметрами, влияющими на плотность насекомых. В том случае, когда влажность не является лимитирующим фактором, возраст растений, а также проективное покрытие становятся основными параметрами, влияющими на плотность насекомых. Однако, в том случае, когда территория испытывает засуху, важность веток и почвы становятся определяющими факторами для производства млечного сока.

THE RELATIONSHIP BETWEEN THE DENSITY OF CYAMOPHILA DICORA 81

THE RELATIONSHIP BETWEEN THE DENSITY OF cyamophila dicora AND VEGETATION PARAMETERS OF Astragalus glaucacanthus IN SEMI-ARID REGION OF ISFAHAN, IRAN

© 2007. M. Mesdaghi*, M. Azimi*, M. Farahpour**, Gh.A. Dianati Tilaki***

*Department of Range Ecology and Management, University of Agricultural Sciences, Gorgan, **Research

Institute of Forest and Range land, Tehran, Iran ***Tarbiat Modaress University, Faculty of Natural Resources and Marine Sciences, Department of Range Management, P.O.Box 46414-356, Noor-Iran, E-Mail: dianatitilaki@yahoo.com

Abstract. Feeding by an insect (Cyamophila dicora, Logvina) on spiny shrub of Astragalus glaucacanthus produces a kind of milk vetch named Katira. The harvesting of milk vetch has a long history in Isfahan, Iran. We have produced spatial distribution map of the shrub and by random-systematic sampling along line transects, we measured biological and environmental criteria such as insect density, canopy cover, branch moisture and soil moisture. Multiple linear regressions and a nested completely randomized design were used to analyse the response and predictor variables. The results showed that Astragalus glaucacanthus occupied the wetter parts of mountainous areas near Isfahan and the densities of insects is highly related to the age, canopy cover of A. glaucacanthus and to soil moisture. Older shrubs and larger shrubs have the highest densities of insect. Regression analysis confirmed that the age of plant, and soil moisture are important in affecting insect density. When moisture is not limiting, plant age has the primary effect on the insect density.

Key Words: Astragalus glaucacanthus, Gum, insect density, branch moisture, soil moisture.

Introduction

Traditional sheep grazing and harvesting different kinds of manna as a by-product of rangelands has a long history in old Persia. Feeding by the insect (Cyamophila dicora, Logvina), on the spiny shrub of Astragalus glaucacanthus causes a milk vetch substance, called Katira, to be secreted by the last instars of the insect's nymphs. This milk vetch is used for preparing a kind of gum called Samgh and is exclusively produced in Isfahan, Iran.

Astragalus glaucacanthus is a perennial shrub 50-75 cm high with diagonally ascending branches, ending in flat-topped canopy of one meter or more in diameter (Grami, 1998). Astragalus glaucacanthus was first collected by Haussknecht in 1870 from the mountainous areas of southwestern Iran (Haussknecht, 1870). In 1872, the plant was identified as Astragalus glaucacanthus belonging to the section Trangacantha of the Leguminosae (Boissier, 1872) which occurred in central and western Iran. The name has been accepted by other western and Persian botanists (Pabot, 1967; Maassoumi, 1998). Mehrabi (1997) studied the ecological characteristics of A. glaucacanthus at Aligoudarz in Lorestan province. Khajehdin (1999) studied deformation of the canopy as an adaptation to the harsh snowy environments.

Although the ecology of Cyamophila dicora is critical to the production of gum, the focus of this paper is on the autecology of A. glaucacanthus, the host of the insect. Grami (1998) provides detailed information on the biology of the insect and the host plant, but he questioned the direct function of plant in gum production. He argued that neither greater plant density nor larger plants are not associated with higher amounts of gum. This unexpected conclusion urges more investigations.

The objectives of this paper are to provide: 1) a distribution map of A. glaucacanthus in Fereidounshar, Isfahan, 2) to determine the important phenological stages of this species in relation to the life cycle of Cyamophila dicora, and 3) to determine the relationships of insect density to the age, canopy cover, and moisture content of branches of A glaucacanthus and soil moisture.

MESDAGHI, AZIMI, FARAHPOUR, DIANATI TILAKI Materials and Methods

Study area. The study area is 2157 km located at Fereidounshar, 160 km south-west of Isfahan, between 49° 36' to 50° 19' east and 32° 37' to 33° 41' north, with a mean elevation of 3000 m. All sites in the area were visited and three sites (Table 1) were selected where the insects were most active on A. glaucacanthus.

Table 1. Some of characteristics of selected sites. Таблица 1. Некоторые характеристики выбранных местообитаний.

Location Altitude Longitude Elevation (m) Slope (%) Soil texture Mean annual Precipitation (mm)

Daresib 32° 54' 50° 17' 2500-3200 42 Loam 330

Lashokhm 32° 55' 49° 50' 2550-3950 45 Clay 650

Klose 32° 41' 49° 53' 2400-3800 40 Clay 520

Mean - - 2480-3650 42 - 500

Sampling design. The distribution map of A. glaucacanthus was prepared using aerial photographs and by visits to the study area. The species occurred frequently between 2300 to 2800 m. Systematic line transects were established within the elevation bands between 2300-2800 m and on each line a random 30-m transect was selected.

The number of systematic lines sampled varied between 6 to 10, depending on the homogeneity of plant distribution. Intercepted individuals of A. glaucacanthus were recorded for canopy cover (in m2), age (in years), and insect density (number per branch). Individual plants were classified as low (<15000 insects per plant), medium (15000 to 25000 insects), and high (>25000 insects) density. One branch was randomly selected from each of four aspects, the insects collected and separated from litter using a sieve (No. 16) and counted using a x50 stereoscope. The age of plants was estimated by cutting the basal stems in the field and after sanding, the annual rings were counted using a x20 stereoscope. Plants intercept by transects, the diameter of basal stem were measured and compared with the catalog to estimate the age.

The water content of top branches (15 cm from tip), and main branches (50 cm from tip) were determined in lab. The selection of branches was random from each of four aspects of the plant. Soil moisture under the intercepted plant was also determined to a depth of 30 cm.

Data analysis. To compare different densities of insects as influenced by canopy cover, age, and water content of branches, a nested completely randomized design with following model was used: Xijk = ц + т; + s;j + 5ijk (i=l, 2, 3, j=l, 2, 3, and k=l, 2, 3), where the ц is the general mean of

insect density without considering a location effect. т; a is location effect, ands^ and 5ljk are

experimental and sampling errors, respectively (Steel et. al, 1997). The relationship between insect density and plant and soil parameters were analyzed using a multiple regression model: Yr. = /?0 + Д Xn + P2Xn + Д X , + PAXiA + j35Xi5 + si, where Y; is the number of insects on each

branch, Xi is age in years, X2 canopy cover in m2 of A. glaucacanthus which intercepted by line transects. X3, X4, and X5 is the water content of a branch, top branch of A. glaucacanthus, and soil moisture, respectively for three locations. The best subsets of these variables were selected by stepwise regression. The normality of variables was evaluated by using Anderson-Darling' test. Data were analyzed using Minitab, version 13.30 (Ryan et al., 2000).

Results

Distribution. A. glaucacanthus is dominant in one study location and is associated with other species in two other locations. This species usually occurs on steep slopes between 15 to 45% on all aspects at an elevation range between 2000-3000 m. The Katira shrubs usually occur along gullies on northern western aspects. The soil of study locations are mostly from inceptisole group.

Phenology. Astragalus glaucacanthus begins it growth in early March after a period of winter dormancy and completes its vegetative growth in early June. This period corresponds to insect

THE RELATIONSHIP BETWEEN THE DENSITY OF CYAMOPHILA DICORA 83

activity which progresses to the egg stage (Naeem, Behdad, 1988). The insect is in the nymph stage during flowering of the host plant. During seed ripening, the insect has completed its nymphal stage (instars I, II, III and IV) and gum is secreted by the last instars in early October.

Analysis of insect density and vegetation parameters. The mean of different parameters in three locations are summarized in Table 2. Data for the number of insects per plant were log transformed to normalized for validation of parametric tests.

Table 2. Mean of different characteristics of the insect, vegetation, and soil parameters.

Таблица 2. Средние показатели различных характеристик популяций насекомых, растительности и

почвенных параметров._

Insect Log of Age of Plant Branch Top Branch Soil

Location Density Insect No. Plant Cover Moisture Moisture (%) Moisture

(per plant) (years) (m2) (%) (%)

Low 0.80a 22a 0.21a 37.1 45.9b 21.T

Daresib Medium 1.23bc 56cd 0.50abc 33.3 38.3a 28.9ab

High 1 39cde 85f 0.78de 36.7 38. Г 31.0b

Low 1.13b 36ab 0.32ab 38.6 54.ld 35.3°

Lashokhm Medium 1.42de 65de 0.60bcd 42.5 53.ld 36.9°

High 1.72f 101s 0.98е 43.0 51.4cd 42. ld

Low 0.95a 45bc 0 39abc 37.8 45.8b 30.3ab

Klose Medium 1.27bcd ?4ef 0.67cd 40.4 4?5bc 31.0b

High 1.51е 105s 1.39f 38.0 40.3a 36.0C

Lsd - 0.17" 14.8" 0.3" NS 4.3" 3.4"

** significant at 0.01 level, NS - not significant.

* *

величины значимые на уровне 0.01, NS - незначительные величины.

There were significant differences in insect numbers per plant, in age plant, canopy cover, top branch moisture, and in soil moisture under low, medium, and high insect density in different locations (p<0.05), but the branch moisture content of plants was not significant (p>0.05). There are more insects on older plants with higher canopy cover than on younger plants with lower cover (Table 2). There were also significant differences in top branch moisture of plants and soil moisture (p<0.05) which may be related to the differences in precipitation at the three locations.

A summery of stepwise regressions between number of insect per plant and other vegetation and soil moisture parameters for three locations and for all locations are shown in Table 3. In general, for all locations, the number of insects are related to the age of plant and to the soil moisture (Table 3).

Table 3. The independent variables entered to the model of stepwise regressions for three locations and for all locations. Таблица 3. Независимые переменные, вводимые в модель пошаговой регрессии для трех местообитаний и для всех местообитаний._

Location No. of insect (per plant) Y; Vegetation and soil measures Correlation (r)

Xj X2 X3 X4 X5

Daresib YK + + 0.84

Lashokhm yl + + 0.98

Klose Yd + 0.94

All locations Log Y, + + 0.91

+ entered variable, Xj - Age (in years), X2 - Cover (m2), X3 - Branch moisture (%), X4 - Top branch moisture (%), X5 - Soil moisture (%). + вводимые переменные X, - Возраст (годы), Х2 - Проективное

покрытие (м2), Х3 - Влажность ветвей (%), Х4 - Влажность вершин ветвей (%), Х5 - Влажность почвы (%)•

The regression model of these relationships for all locations is as follows:

84 MESDAGHI, AZIMI, FARAHPOUR, DIANATI TILAKI

LogY=0.058+0.0617 Xi +0.0244 X5, where Xi and X2 are age and soil moisture, and Y is the number of insects. In Figure 1, Y is plotted against Xi and X5. The insect usually lives on older plants that occur in wetter locations.

Fig. 1. The relationship between the insect numbers, age of plant and soil moisture. The highest density of insects occur on old plants in wet environments. Xj - Age (in years) and X5 - Soil moisture (%).

Рис. 1. Соотношение между количеством насекомых, возрастом растений и влажностью почвы. Наивысшая плотность насекомых отмечена на старых растениях во влажных условиях. Xi - Возраст (годы), а Х5 - Влажность почвы (%). The correlation among independent variables of plant age, canopy cover, branch and top branch moistures and soil moisture are summarized in Table 4.

There are high correlation between plant age and plant canopy cover of A. glaucacanthus in each location and in all location together. So, including both age and cover in one model causes collinearity and inflates the regression coefficient (Neter et al., 2000).

Discussion

It is possible to present two practical and theoretical models for these relationships. For theoretical relationship between insect density and age, a sample of age structure is shown in Photo 1.

Table 4. correlation between different independent variables.

Таблица 4. Корреляция между различными независимыми переменными.

Xi x2 x3 x4

Daresib 0.998

Х2 Lashokhm 0.999

Klose 0.925

All location 0.916

Daresib -0.090 -0.046

Х3 Lashokhm 0.540 0.527

Klose -0.120 -0.360

All location 0.246 0.139

х4 Daresib -0.629 -0.622 0.432

Lashokhm -0.547 -0.565 0.022

Klose -0.695 -0.676 0.417

All location -0.210 -0.238 0.584

Daresib 0.910 0.901 -0.375 -0.613

х5 Lashokhm 0.765 0.772 0.272 -0.521

Klose 0.730 0.678 -0.375-0.278 -0.868

All location 0.571 0.488 0.433 0.443

Xi - Age (in years), X2 - Cover (m2), X3 - Branch moisture (%), X4 - Top branch moisture (%), X5- Soil moisture (%). Xi - Возраст (годы), X2 - Проективное покрытие (м2), Х3 - Влажность ветвей (%), Х4 - Влажность вершин ветвей (%), Х5 - Влажность почвы (%).

logY

D.S

TOE RELATIONSHIP BETWEEN THE DENSITY OF CYÄMOPHILADICORA

85

Photo 1. A sample of age catalog from cut basal stems of A. glaucacanthus The age of basal area from left to right are 20, 40, and 70 years. Фото 1. Образец разновозрастных срезов оснований стеблей A. glaucacanthus. Возраст срезов слева направо: 20, 40 и 70 лет.

This catalog can be extended to show more age classes of basal area. In both model, soil moisture has an important role in insect activity. Based on interviewing local collectors of gum in Feridounshaher, the activity of the insects is limited in drought years, and small amounts of gum are collected. However, including soil moisture in the model has no any practical values. The practical and theoretical models based on canopy cover and age for three locations and all location are summarized in Table 5.

Table 5. Theoretical and practical models for different locations and all locations. Таблица 5. Теоретические и реальные модели для различных местообитаний и для всех местообитаний.

Model

Location Theoretical Practical

Daresib 7 =41 7 + 0.17.V, - 0.85.V, r = 0.94 !' =1.88 -rO.27.V-, r = 0.86

Lashokhm Y = -71.9 + 28.6.\"2 + 2 06.V5 r = 0.98 7 = -6.49+ 59.1 Л'2 /- = 095

Klose Y = -7.39 + 0.38X1 г = 0.84 7 = -5.08 + 19.3.V2 г = 0.80

All locations log 7 = 0.06 + 0.01^ + 0.02X5 r = 0.91 Same as theoretical model

Xi - Age (in years), X2 - Cover (nr), X3 - Branch moisture(%), X4 - Top branch moisture (%), X5 -Soil moisture (%). Щ - Возраст (годы), X2 - Проективное покрытие (м ). Х3 - Влажность ветвей (%), Х4 - Влажность вершин ветвей (%), Ж$ - Влажность почвы (%).

In general, when soil moisture is not limiting, plant age or plant cover are the primary determinants of insect density; but when the area was suffers drought, moisture levels of branches, and soil moisture are more important which the other researches also emphasized on the role of moisture in gum production (Grami, 1998; Safe-e-lahi, 1997).

LITERATURE CITED

86 MESDAGHI, AZIMI, FARAHPOUR, DIANATI TILAKI

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