Biodiversity in the Management of the
Shrub Zizyphus nummularia with Special
Reference to Semiarid Regions in India
Jasleen Kaur
K. M. M. Dakshini
Abstract—Habitat characteristics influence the behavior of plants.
Diverse forms of a species in terms of morphology or behavior
should, therefore, suggest not only the mosaicness of the habitat
factor(s) but also the ecological status of those forms. To test this
hypothesis the shrub Zizyphus nummularia, a conspicuous component of open scrub vegetation cover of semiarid regions of north/
western India, was investigated. The populations sampled were
distinguished on the basis of leaf shape into two types viz. elliptical
and orbicular. The orbicular form was more common in disturbed
habitats, occurred in relatively poor soils, and accumulated lower
concentrations of nutrients as compared to the elliptical. Analysis of
data suggested that this diversity was with reference to mosaicness
in the habitat. Significance of data collected to manage scrub
vegetation and rangelands has been argued.
In contrast to closed vegetational cover, niche occupation
in open, disturbed, or degraded habitats is not complete. In
such a situation, therefore, the vegetational cover is discontinuous and uneven. Also, due to disturbance in the
community equilibrium, homeostasis and stability are affected, and this should cause evolution/selection of adaptive
forms occupying the available niches, supported by different eco-physiological responses. In this respect the degraded,
disturbed, or open habitats are more similar to ecotones in
general. As a corollary to this, diverse forms in terms of
morphology or behavior should, therefore, suggest not only
the mosaicness of the habitat factor(s) but the status of
those forms as well, especially, if they belong to the same
species. To test this hypothesis the shrub Zizyphus
nummularia (Burm. F.) Wight and Arn.(Rhamnaceae), a
conspicuous component of open scrub vegetation cover of
semiarid and arid regions of north/western India, as well as
an important fodder source for sheep and goat, was selected
for investigations.
Study Area _____________________
The study covers the metropolitan city of Delhi and its
adjoining areas between 28° 12'-28° 53' N and 76° 50'-77° 23' E
longitude. Eighteen sampling sites were chosen in this
region that represent a wide range of ecological conditions in
In: McArthur, E. Durant; Ostler, W. Kent; Wambolt, Carl L., comps. 1999.
Proceedings: shrubland ecotones; 1998 August 12–14; Ephraim, UT. Proc.
RMRS-P-11. Ogden, UT: U.S. Department of Agriculture, Forest Service,
Rocky Mountain Research Station.
Jasleen Kaur is Research Fellow and K. M. M. Dakshini is Professor,
Department of Botany, University of Delhi, Delhi 110007 India.
USDA Forest Service Proceedings RMRS-P-11. 1999
the last trail end extension of the Aravalli Range. The
climate is of semiarid nature with marked diurnal differences of temperature, high saturation deficit, and moderately
low rainfall. It is markedly periodic and is characterized by
a dry and increasingly hot season from March to June, a dry
and cold winter from October to February, and a warm
monsoon period from July to September (Maheshwari 1963).
The soils of the area sampled are aridisol, sandy loams
(Inderjit and Dakshini 1996).
Materials and Methods ___________
Three quadrats were laid at each of the 18 sampling sites,
and six-eight plants from each of the three quadrats were
selected. Sampling was carried out during the months of
April-May for 2 years, 1997 and 1998. Plants at this time are
generally at their peak of growth. The leaf samples from
each of the marked shrubs were collected at fixed nodes. The
soil was collected from the surface and at 40-50 cm depth
from four different locations of the quadrat. The height
and spread of each of the shrubs were recorded in the field.
Leaf samples were rinsed with double distilled water and
oven dried at 45 °C for 48h. These were then analyzed for
leaf area (Leaf Area Meter, Delta T Devices LTD UK) and
weight using replicates of 10 leaves each and leaf specific
–2
weight (LSD) calculated in mg cm . Leaf samples were
also analyzed for ash content (in a muffle furnace at 550 °C
for 3h), Ca, Mg, Na, K, Zn, Cu (Atomic absorption spectrophotometer, GBC 902, Australia), PO4 (Molybdenum blue
method) and organic N (indophenol blue method) following
Allen (1989). Composite soil samples for each of the quadrat
were air dried and sieved using a 2 mm sieve. These were
analyzed for the pH, electrical conductivity (EC), HCO3,
Cl, and organic carbon (OC) following Piper (1966); for exchangeable Ca, Mg, Na, K, Zn, Cu (Atomic Absorption
Spectrophotometry), and P (Molybdenum blue method) following Allen (1989). All the analyses were carried out in
triplicates.
Data on all these variables from all the sites were pooled
and infraspecific comparisons were carried out using various statistical procedures. One-way analysis of variance
(ANOVA) was used to compare the two different leaf forms,
namely elliptical and orbicular, individually for each of the
variables analyzed. The relative contribution of each variable toward defining the discrimination between the two
forms were assessed using Discriminant Function Analysis
(DFA) separately for leaf and soil variables (Capone and
Kushlan 1991; Inderjit and Dakshini 1994; Sharma and
Dakshini 1998; Williams 1983). Also, an inter-variable correlation matrix was computed for each form to evaluate the
119
Figure 1—Shapes of the leaves in the elliptical (top) and orbicular (bottom) forms of Z.
nummularia.
degree of inter-relatedness of all the variables in the analysis. All the analyses were carried out using SPSS statistical
software (SPSS PC 1986).
HPLC analysis was carried out to study the variation in
phenols of the two diverse forms. Methanolic extracts of
leaves were subjected to HPLC (JASCO 860) analysis. Reverse phase chromatography was carried out using a steel
column (Gasukuro kogyo, Intersil ODS-2, 4.6 x 150 mm).
The wavelength UV detector was set at 275 nm. The flow
rate was 0.5ml/min, and the volume injected was 5 ml.
Results ________________________
Analysis of the data showed that the populations sampled
could be grouped into two types based on the leaf morphology, i.e., elliptical and orbicular (fig. 1). These two leaf types
were significantly different (table 1) in many of the variables
analyzed. While leaf K, PO4, area, org N, Cu, and Mg were
higher in the elliptical form, leaf weight, Ca, Na, Zn, LSW,
and plant height and spread showed higher values in the
orbicular form (table 1). Discriminant analysis of the two
forms on the basis of the 14 leaf variables showed that K,
PO4, and LSW contributed most in discriminating the two
forms (table 1).
Significant differences were also seen in the soils associated with the two diverse forms. All the soil variables
(excepting Cl, Cu, and pH) had higher values in the elliptical
form associated soils. DFA showed that EC, Zn, and K were
the most discriminating soil variables between the two
forms associated soils (table 2).
Additionally, the patterns exhibited by the HPLC phenolic profiles were qualitatively and quantitatively very
different in the two forms of Z. nummularia. The elliptic
form had higher phenolic content in comparison to the
orbicular form (fig. 2).
A comparison of the correlation matrices of the elliptical
and orbicular forms based on the leaf and soil characteristics analyzed showed that the orbicular form exhibited a
greater number of significant (p <0.05) leaf-leaf, leaf-soil,
and soil-soil correlations in comparison to the elliptical form
(table 3 and 4). Only very few correlations (positive or
negative) were common to both the forms, thereby exhibiting an entirely different set of leaf-leaf, soil-soil, and leaf-soil
interactions in the two forms.
Of all the leaf variables that discriminated between the
elliptical and orbicular forms, i.e., K, PO4, and LSW, none
was correlated with any other leaf or soil variable in the
former (table 3). In contrast, in the latter form, leaf K was
correlated with leaf Na and plant spread and soil K, Na,
Table 1—Statistical analysis of plant characteristics of two diverse forms of
Zizyphus nummularia.
Variable
DFA
DF correlation
Ka
P
LSW
Area
Org N
Ca
Na
Cu
Zn
Spread
Weight
Mg
Height
Ash
0.38295b
0.23682b
–0.17598b
0.12497
0.11797
–0.07653
0.07244
0.06470
–0.04167
–0.03314
–0.02974
0.02359
–0.00787
–0.00002
Mean ± standard deviation
Elliptical
Orbicular
3.187 ± 0.373 c
0.323 ± 0.054 c
46.38 ± 15.984 g
273.86 ± 29.58 f
4.975 ± 1.458 c
1.407 ± 0.589 c
0.57 ± 0.136 c
119.88 ± 32.64 d
114.37 ± 15.29 d
0.266 ± 0.278 i
128.33 ± 51.92 e
0.427 ± 0.183 c
0.878 ± 0.695 h
7.021 ± 1.370 c
0.833 ± 0.139
0.133 ± 0.015
149.156 ± 20.06
120.942 ± 41.97
1.49 ± 0.862
2.358 ± 0.408
0.407 ± 0.051
76.585 ± 18.60
145.938 ± 26.94
0.701 ± 0.450
177.083 ± 52.29
0.353 ± 0.072
0.990 ± 0.318
7.061 ± 1.878
ANOVA
p
****
****
****
****
****
****
****
***
*
*
NS
NS
NS
NS
a
Variables ordered by size of pooled within-group correlation between discriminating
variables and canonical discriminant function.
b
Significant correlation within the function.
c
%
d
μg g–1
e
mg
f
mm2
g
mg cm–2
h
m
i 2
m ; * p <0.05; ** p <0.01; ***p <0.001; ****p <0.0001; NS-not significant.
120
USDA Forest Service Proceedings RMRS-P-11. 1999
Table 2—Statistical analysis of soil characteristics of two diverse forms of Zizyphus
nummularia.
Variable
DFA
DF correlation
ECa
Zn
K
P
OC
Cl
Ca
Mg
HCO3
pH
Cu
Na
–0.19901b
–0.18126b
–0.17975b
–0.16421
0.16062
–0.15232
0.14865
0.13728
0.10694
0.08558
–0.07833
–0.05078
Mean ± standard deviation
Elliptical
Orbicular
183.398 ±
5.529 ±
120.125 ±
6.562 ±
1.11 ±
0.01 ±
314.45 ±
38.75 ±
0.0519 ±
7.07 ±
1.152 ±
55.75 ±
3.242f
0.153d
25.98c
0.057c
0.042e
0.00e
19.163c
1.768c
0.004e
0.014
0.008d
10.607c
177.173 ± 2.669
3.342 ± 0.390
83.25 ± 5.933
1.248 ± 0.153
0.518 ± 0.113
0.012 ± 0.003
260.834 ± 17.05
32.5 ± 2.955
0.0407 ± 0.005
7.36 ± 0.055
1.333 ± 0.117
43.708 ± 1.543
ANOVA
p
****
****
****
****
****
*
****
****
****
****
****
****
a
Variables ordered by size of pooled within-group correlation between discriminating
variables and canonical discriminant function.
b
Significant correlation within the function.
c
mg; 100g–1
d
μg g–1
e
%
f
μmhos cm–1; * p <0.05; **** p <0.0001.
PO4, and Zn positively and with soil EC negatively (table 4).
Similarly, leaf PO4 was correlated with leaf Cu, Na, and Mg,
and soil Na and PO4 positively, and with soil EC negatively
in this form. Also, its LSW was correlated with leaf Mg,
plant spread, and soil Ca, Mg, Na, OC, and pH positively and
with leaf Zn and Ca and soil Cu and EC negatively.
The discriminating soil variables (i.e., EC, Zn, and K) also
did not show any correlations in the elliptical forms
(table 3). On the other hand, in the orbicular form (table 4)
these variables were highly correlated. Soil EC was correlated positively with leaf Ca and Zn and soil Cu, and
negatively with plant height, leaf K, Na, PO4, Mg, weight,
and LSW, and soil Ca, Mg, Na, OC, and pH. Similarly, soil
Zn was correlated positively with leaf Cu, Na, and Zn, and
soil Cu, K, and PO4, and negatively with plant height, soil
Ca, HCO3, Mg, and OC. Also, soil K was correlated positively
with leaf Cu, K, Na, and Zn, and soil Cu, Na, PO4, and Zn,
and negatively with leaf N and soil Ca, HCO3, Mg, and OC.
Discussion _____________________
USDA Forest Service Proceedings RMRS-P-11. 1999
121
Profiles of Phenols
Figure 2—HPLC profiles of phenols of methanolic
extracts of orbicular (top) and elliptical (bottom) leaves
of Z. nummularia.
The data demonstrate infraspecific diversity in Zizyphus
nummularia. These diverse forms can be distinguished into
two groups, viz. one having prominently orbicular leaves
and the other having elliptical leaves. Also, the orbicular
form is associated with rounded fruits and the elliptical form
with the oblong fruits. Interestingly, these two infraspecific
types occupy different habitats with special references to
soil characteristics (table 2). Elliptical-leaved type inhabits
soils with higher concentrations of nutrients and organic
matter, as well as higher electrical conductivity as compared
to orbicular-leaved type.
A correlative assessment of the data based on 14 leaf
and 12 soil variables shows that the orbicular form exhibits
a higher degree of coordination within itself and with the
soil conditions. This would suggest that the orbicular form
is comparatively a physiologically stable system (El Ghonemy
1978) and its response is well modulated according to the
general ecological conditions of the area (Solbrig 1979).
On the other hand, the elliptical form lacks such an integration. Instead, its successful survival is independent of
substratum conditions (Sharma and Dakshini 1998).
Further, the patterns of mineral cycling also vary in the
two forms. The concentrations of Cu, K, Mg, Na, org N, and
PO4 are higher in the leaves of the elliptical form as
Time (min)
Table 3—Correlated leaf and soil variables of elliptical form on the basis of pooled data.
Leaf
Positive
Plant
Leaf
Soil
Height
Spread
Area
Ash
Ca
Cu
K
Mg
Na
Org. N
PO4
LSW
Weight
Zn
Ca
Cl
Cu
EC
HCO3
K
Mg
Na
OC
pH
PO4
Zn
Soil
Negative
Zn
Positive
Negative
Ca
Org. N
Cl.HCO3,OC
Cu,pH,PO4
Cu
Spread
Zn
Spread
Na
Na
Na
Na
Na
Na
Ca
HCO3,OC
pH,PO4
Cu,pH,PO4
Cl, HCO3,OC
Cl,OC
Cu,pH,PO4
Cl,HCO3
Cu,PO4
Cu,pH
Cu,pH,PO4
Cl,HCO3.OC
Cl,HCO3.OC
p <0.05
Table 4—Correlated leaf and soil variables of orbicular form on the basis of pooled data.
Leaf
Soil
Positive
Plant
Leaf
Soil
Height
Spread
Area
Ash
Ca
Cu
K
Mg
Na
Org. N
PO4
LSW
Weight
Zn
Ca
Cl
Cu
EC
HCO3
K
Mg
Na
OC
pH
PO4
Zn
Wt,Spread
LSW,Wt,Ht,K
Org N,Wt
Zn
Na,PO4,Zn
Na,Spread
Na,PO4,LSW,Wt,Spread
Cu,K,PO4,Mg
Area,Wt
Cu,Na,Mg
Mg,Spread
Ht,area,Mg, Spread
Cu,Ca
LSW,Mg,Wt
Cu,ash,Zn,Ca
Ca,Zn
Cu,K,Na,Zn
LSW,Mg
Ht,K,Na,PO4,LSW,Mg,Wt
Ht,LSW,Mg,Wt
K,LSW,Mg
Cu,K,Na,PO4
Cu,K,Na,Zn
Negative
Zn,Ca,Mg
Mg
LSW,Spread
Zn
Zn,Ca
LSW,Mg,Spread
Cu,Zn,Ca
LSW,Mg
Ht,K,Na,PO4, LSW,Mg,Wt
Cu,Zn,ash,Ca
Org N
Zn,Cu,Ca
Cu,Zn,Ca
Cu,Zn,ash,Ca
Org N
Ht
Positive
Negative
Na,OC
Ca,HCO3,Mg,Na,OC,pH
EC,Zn
Cu,EC
Cu
Cu,EC
Cu,K,PO4,Zn
K,Na,pH,PO4,Zn
Ca,Mg,Na,OC,pH,PO4
K,PO4,Na,Zn
Na,PO4
Ca,Mg,Na.OC,pH
Ca,Na,OC
Cu,EC,K,Zn
HCO,Mg,OC,pH
HCO3,pH
Ca,HCO3,Mg, OC,pH
Ca,HCO3,Mg, OC,pH
EC
Cu,EC
EC
K,PO4
EC
Cu,EC
EC
Ca,HCO3,Mg, OC,pH
Cu,K,EC,Zn
EC,Zn,K
Cu
Ca,Mg,OC,pH
Cu,Na,PO4,Zn
Ca,HCO3,OC,pH
K,pH,PO4
Ca,HCO3,Mg,pH
Ca,HCO3,Mg,Na,OC
K.Na
Cu,K,PO4
Ca,HCO3,Mg, OC,pH
Ca,Mg,Na,OC,pH
Cu,K,PO4,Zn
Ca,HCO3,Mg, OC
K,PO4,Zn
EC
Cu,EC,Ca.Zn
Cu,EC
HCO3,Mg,Zn
Ca,HCO3,Mg, OC
p <0.05
122
USDA Forest Service Proceedings RMRS-P-11. 1999
compared to the orbicular form that has higher Ca and Zn.
However, the values of LSW, leaf weight, height, and spread
are considerably lower in the elliptical form in comparison
to the orbicular form. The higher concentration of leaf
organic N in the elliptical form would suggest that this
form is comparatively more photosynthetically efficient
(Field and Mooney 1986). Furthermore, the data also suggest that, in spite of the higher nutrient uptake, the nutrient
use efficiency is lower in elliptical form as opposed to the
orbicular form (Vitousek 1982). This may also suggest that
the carbon gain per unit of the nutrients taken up from the
substratum is higher in the orbicular form as compared to
the elliptical form (Boerner 1984). The low LSW and leaf
weight values in elliptical leaves would also mean a faster
release of nutrients through mineralization under it
(Chabot and Hicks 1982). This observation is further substantiated by higher HCO3 values (i.e., high microbial activity) and also the higher concentration of the nutrients in the
soils associated with the elliptical form as compared to the
orbicular form. Additionally, the higher phenolic content
of the elliptical leaves suggests reallocation of photosynthates for the production of secondary metabolites (phenols).
This should make an otherwise nutritious forage (Pareek
1983) of this form more bitter and less palatable. Whether or
not the increase in the concentration of phenolic content in
the elliptical form is under the stress of the herbivory
needs to be investigated (Tang and others 1995; Tuomi
and others 1984).
In view of the economic importance (fodder especially for
goat and sheep, medicinal, erosion control) of this naturally
occurring species the data are of applied value for the
management of habitats in the semiarid and arid environments. The ecophysiologically different infraspecific forms
shall provide ways to meet the challenges in the management and improvement of degraded habitats, either through
revegetation or through maintenance of the existing marginal habitats available in harsh environments.
As evident from the data, the elliptical form shall be more
suitable for reclaiming degraded lands (Hansen 1989) because it is relatively less preferred by the grazers (information gathered from local shepherds). Also, through its higher
uptake and release of nutrients it can initiate recovery,
productivity, and stability of the plant-soil complex. On the
other hand, orbicular form can help in improving rangelands
(Omar-Draz 1989) as it provides valuable forage, checks
erosion, and also maintains the stability of the substratum
without altering the physico-chemical balance (l.c.)
Thus whereas one form can be used for reclamation of
marginal lands, the other can be utilized for the maintenance of the unique ecological systems of the arid areas.
The data presented not only support the hypothesis that
species alone is no longer an adequate base for the adaptive
shrubs for revegetation (Plummer and others 1970a) but
also bring out the importance of such studies in the management of range and degraded lands.
USDA Forest Service Proceedings RMRS-P-11. 1999
Acknowledgments ______________
We are grateful to Professor N. N. Bhandari’s help in
planning and execution of this manuscript. We wish to
thank Dr. Inderjit for helping us in HPLC analysis. We
would also like to thank Dr. Reetu Sharma for her valuable
suggestions in preparation of the manuscript. Financial
assistance form Council of Scientific and Industrial Research (CSIR) and University Grants Commission (UGC),
India, is gratefully acknowledged.
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