Performance of twelve selected Australian tree species on a saline site in southeast Queensland

Performance of twelve selected Australian tree species on a saline site in southeast Queensland

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Forest E c o l o g y




Hanagement Forest Ecology and Management 70 ( 1994 ) 255-264

Performance of twelve selected Australian tree species on a saline site in southeast Queensland G. M. D u n n a'*, D. W. Tayloff, M. R. Nesteff, 1". B. Beetson u aQueensland Forest Research Institute, QueenslandDepartment of Primary lndusto,, MS 483, FraserRoad, Gympie, Qld. 4570, Australia bQueensland Forest Service, QueenslandDepartment of Primary Industo,, PO Box 133, Roma, Qld. 4455, Australia Accepted 3 May 1994

Abstract The establishment and early growth of 12 species within the genera Eucalyptus, Casuarina, Melaleuca and Tipuana was tested on a saline site in southeast Queensland. Electrical conductivity (EC) in the top 50 cm of soil was measured using an electromagnetic induction method and calibrated against the EC of 1 : 5 soil : water suspensions. The site was then stratified into five salinity classes: 0.75-1.0, 1.0-1.25, 1.25-1.5, 1.5-1.75 and over 1.75 dS m -~. Relationships were developed for predicting the survival and height production of 18-month-old trees. These regressions explained 15-88% of the variation in survival and 2-66% of the variation in height production. Tree species were grouped by determining the EC level where height production declined by 25% relative to that at 0.75 dS m - ~. Casuarina glauca, Melaleuca bracteata, Eucalyptus moluccana, Eucalyptus camaldulensis, Eucalyptus tereticornis and Eucalyptus raveretiana were all highly salt tolerant (25% reductions over 1.5 dS m - L ) . Casuarina cunningharniana, Eucalyptus grandis, Eucalyptus melliodora and Eucalyptus robusta exhibited moderate salt tolerance (25% reductions between 1.0 and 1.5 dS m - ~ ) . The responses to increased salinity of Tipuana tipu and Eucalyptus intermedia (25% reductions at less than 1.0 dS m ' suggest that these species are not suitable for revegetating similar saline sites.

Keywords: Salinity; Salt tolerance; Survival; Growth; Electrical conductivity

1. Introduction

During the previous 200 years, soil salinisation in Australia has dramatically increased owing to large-scale changes to the landscape. Gordon ( 1991 ) estimated that the area of land being affected by induced salinity in Queensland is 10 000 ha, with potential for a further 73 000 ha to be affected. It is widely accepted that a combination of irrigation practices and replacing * Corresponding author.

deeper rooted perennial native vegetation with annual crops and pasture has caused water tables to rise. Salts stored in solution are transported to the root zone where they are concentrated as plants evaporate water and/or as water evaporates. As almost all agricultural crops and pastures are salt sensitive (Maas and Hoffmann, 1977), soil salinisation has resulted in losses to agricultural production. Although the causes of soil salinisation are well understood (Schofield, 1990; Schofield and Bari, 1991 ), the solutions are costly or not easily im-

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G.M. Dram et al. / Foresl Ecology and Management 70 (1994) 255-264

plemented. It seems that an integrated strategy incorporating engineering practices and modified land management is required. An integral component of modifying land management is to plant trees. Trees, when compared with annual crops and pastures, are expected to use more water and be more effective in lowering ground water for three reasons: (i) interception losses from trees have been shown to be higher than those from crops or pasture (Greenwood et al., 1985; Williamson et al., 1987); (ii) trees have deeper roots that can access more available soil water; (iii) trees are active water users for longer periods of the year. The strategic placement of trees to maximise their benefit has been the focus of much recent research (Morris and Thomson, 1983; Schofield, 1990; Hatton and Dawes, 1991) and it is generally agreed that planting trees on ground water recharge areas is more effective in lowering ground water than planting trees on ground water discharge areas. However, recharge areas may be required for continued agricultural production. Moreover, Morris ( 1991 ) and Schofield and Bari (1991) have demonstrated that planting trees on saline discharge areas and the adjacent non-saline slopes has lowered saline water tables. Other benefits of revegetating saline discharge areas with trees may include erosion control, shelter, timber, fodder and fuel-wood production (Midgley et al., 1986). Despite much research (Flowers et al., 1977; Greenway and Munns, 1980; Cheeseman, 1988 ), the processes by which salinity affects the growth of plants are not entirely understood. However, there exists a wide range of salinity tolerance between and within species. Thus, it is important to identify a range of species that survive and grow well on saline sites. Glasshouse screening experiments have been used to assess the relative salinity tolerance of a range of Eucalyptus, Casuarina, Melaleuca and other species (Blake, 1981; Clemens et al., 1983; Van Der Moezel et al., 1988, 1991; Marcar, 1989; Sun and Dickinson, 1993). However, at some stage it becomes necessary to test these potential species in the field over a range of sites. This paper reports on the survival and growth of 12 selected tree species on a saline site in

southeast Queensland. The site was planted to lucerne (Medicago sativum) as recently as 1988, but since then has become increasingly saline, being able to support only more salt tolerant species such as Paspalum vaginatum. Tree species were selected to represent salt tolerance (Euca-

lyptus camaldulensis, Eucalyptus tereticornis, Eucalyptus moluccana, Casuarina glauca and Melaleuca bracteata), potentially high water usefast growing species with comparatively large leaf areas (Eucalyptus grandis and Eucalyptus robusta ) and fuel-wood and fodder qualities ( Casuarina cunninghamiana and Tipuana tipu ). The other three species, Eucalyptus intermedia, Eucalyptus melliodora and Eucalyptus raveretiana had not been previously tested on saline sites.

2. Materials and methods

2. I. Site description The experimental trial was established at the Queensland Department of Primary Industries Animal Genetics Centre, Warril View (27 ° 50' S, 152°36'E; 40 m above sea level) where the climate is subtropical with warm, wet summers and cool, mainly dry winters. Average annual rainfall is 873 mm and annual class A pan evaporation is 1511 mm. Mean daily maximum and minimum temperatures are 32.1°C and 20.7°C respectively in January and 20.9°C and 6.9°C respectively in July. For the period 1941-1992 the days when frosts were recorded averaged 17 year- ~. The experiment occupied 9 ha of a saline discharge zone with a negligible slope and a further 2 ha of the less saline adjacent slope. The site was cleared in the 1920s and was last planted to lucerne (Medicago sativum) in 1988. The site had become increasingly salinised since then and supported salt water couch (Paspalum vaginaturn) on the lower, more salinised areas and pioneer Rhodes grass ( Chloris gayana) on the upper, less salinised areas. Nearby remnant vegetation suggests the original site probably supported an open woodland red gum (E.

tereticornis ). Three broad soil types were identified: (i)

G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264

Black Earth, dark weakly self-mulching cracking clay with dark or brown neutral subsoil; (ii) Black Earth/Grey Clay, dark self-mulching cracking medium to heavy clay with alkaline dark to grey subsoil, occasionally gilgaied; (iii) Solodic, dark to grey brown hard-setting sandy loam to sandy clay loam with sporadic bleach to 120250 mm with alkaline grey brown to brown to yellowish brown clay subsoil (see Fisher and Baker, 1989).

2.2. Site preparation and the establishment of trees

In September 1990 the site was burnt to remove swards of grass. Ridges, with an approximate cross-sectional area of the vertical profile of 0.6 m 2, were spaced 10 m apart and constructed to drain into two major sub-surface drains. Slopes of 2% or less were used to decrease the risk of erosion. To achieve satisfactory conditions for tree establishment, ridges were ripped and rotary hoed, and in February 1991, prior to planting, glyphosate ( 10 1 h a - 1) was applied to the ridges with a sprinkler sprayer. The site was then fenced to exclude cattle and hares. All stock, except Casuarina glauca were raised in net pots (Ryan et al., 1987) and then 'potted on' to Vic pots (height 12.5 cm, diameter 5.0 cm and volume 220 cm3). Casuarina glauca was raised in Queensland Forestry Department tubes


(Ryan et al., 1987 ). A 1 : 1 ratio of washed coarse sand to peat was used as a potting medium into which osmocote (a slow release fertiliser, N : P : K 19:2.6: 10) was incorporated at a rate of 12.5 g 1-1. Casuarina cunninghamiana seedlings were inoculated 4 weeks prior to planting with the symbiotic nitrogen-fixing soil actinomycete Frankia strain JCT 287 (Shipton and Burggraaf, 1983), in a manner similar to that described by Reddell et al. (1989). Each Casuarina glauca plant was similarly inoculated immediately prior to planting. Seedlings were planted at 3 m spacing along the mounds, using a mattock, over the period 11-13 March 1991 and watered (6 1 per tree) immediately after planting. The seedlings were again watered at 2 weeks and then 1 month after planting. Fertiliser (Crop King 55; N: P: K 13.2: 14.7: 12.3) was applied at a rate of 120 g per tree (40 kg h a - 1) as spots applied at about 15 cm on either side of each tree at planting. Trees that had died during the first month were replaced on 9 April 1991. To maintain weed-free conditions around the base of the trees during early growth, directed applications of glyphosate ( 10 ml 1-1 ) were applied within a 0.75 m radius of each tree in June, November and December 1991. In January 1992, a mixture of glyphosate (10 1 ha -1 ) and simazine (8 1 ha ~) was applied as a residual weed control.

Table 1 Species, seedlot identity, provenance and planting details of the 12 lrec species tested Species




Trees planted

Eucalyptus tereticornis Eucalyptus moluccana Eucalyptus grandis Eucalyptus camaldulensis Eucalyptus intermedia Eucalyptus melliodora Casuarina cunninghamiana Melaleuca bracteata Tipuana tipu Eucalyptus robusta Eucalyptus raveretiana Casuarina glauca

48 48 48 48 48 48 48 48 48 47 28 20

378 155 416 36 197 171 657 15563 a 306 1068 39

Yarraman Murgon Conondale Ballon Tiaro Elginvale Yarraman Chinchilla Brisbane Tuan Walkamin Caloundra

240 240 240 240 240 240 240 240 240 235 140 100

a CSIRO seedlot.

G.M. Dunn et al. /Forest Ecology and Management 70 (1994) 255-264


2. 3. Experimental design Eleven species plots, each containing five trees, were replicated 48 times in a randomised complete block design. Thus, most species were represented by 240 plants. However, owing to the poor germination of E. raveretiana and Casuarina glauca in the nursery, these species were replicated only 28 ( 140 plants) and 20 ( 100 plants) times respectively (Table 1 ).

2.4. Measurement of tree growth and survival Total tree height and survival were measured upon establishment and at 3, 5, 12 and 18 months.

2.5. Soil salinity measurement Soil salinity levels were determined using an electromagnetic induction device (Geonics, EM38 ). The EM38 instrument measures the apparent electrical conductivity of the soil profile to several metres and must be calibrated against standard measures of soil salinity to the depth of interest. Operation of the EM38 was in accordance with the operating instructions (Anonymous, 1980), with readings being taken in the horizontal mode of operation (EMh), where the coil dipoles are horizontal to the ground. Readings were taken in the middle of each five tree plot, 5 months after tree establishment. Where Table 2 Regression coefficients and coefficients of determination (R 2) for the relationships between apparent electrical conductivity, measured using an EM-38 meter in horizontal mode (EMh), and the electrical conductivity of 1:5 soil:water extracts (ECns) for five soil profiles (n = 5 ) Depth (cm)

0-10 10-30 30-50 50-70 70-100





0.915 0.527 0.383 0.314 0.284

-0.2076 0.2037 0.4036 0.4705 0.4475

ECI:5 ( d S m - l ) = a + b ( E M h

(dS m - l ) ) .

0.92 0.80 0.77 0.79 0.86

tree heights were observed to vary markedly across a plot, readings were also taken at the base of individual trees. To calibrate the EM38 meter, soil profiles were sampled at five sites chosen to represent the range of electrical conductivities encountered across the site. Immediately prior to sampling, EMh readings were taken at each site. Soil was then collected, bulked, and mixed from the 0-10, 1030, 30-50, 50-70 and 70-100 cm layers. Following air drying and sieving (2 m m ) , electrical conductivities of 1:5 soil:water suspensions (ECI: 5) were measured at 25 °C using an electrical conductivity meter (T.P.S. LC81 ). All profiles were inverted (Slavich, 1990) allowing the data from each layer to be massed and subjected to linear regression analysis (Slavich and Petterson, 1990). The relationships between EMh and EC~:5 were significantly (P<0.01) correlated (Table 2 ). It was assumed that on the heavy clays at the site, the large majority of roots of 18-month-old trees would occupy the upper 50 cm of soil. Thus, ECI: 5 for the upper 50 cm of soil (ECI: 5(0-50cm) was calculated by weighting the ECI: 5 of the 010, 10-30 and 30-50 cm soil layers. The site was then stratified into five ECl:5(o-5ocm) classes: 0.75-1.0, 1.0-1.25, 1.25-1.5, 1.5-1.75 and over 1.75 dS m - 1.

3. Results

An analysis of height growth of survivors and survival of 18-month-old trees averaged across all salinity classes revealed differences between species (Table 3). Mean survival ranged from 100% ( Casuarina glauca) to 25% (E. intermedia), whilst mean height ranged from 2.5 m ( Casuarina glauca ) to 0.7 m ( E. intermedia ). Better performers were Casuarina glauca ( 100%, 2.5 m), E. raveretiana (99%, 2.2 m), Casuarina cunninghamiana (98%, 2.2 m), E. camaldulensis (96%, 2.0 m) and E. tereticornis (97%, 1.8 m). In contrast, T. tipu (36%, 1.5 m) and E. intermedia (25%, 0.7 m) performed poorly and Melaleuca bracteata, despite having a relatively

G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264

o o o o d o d o d d


d d d d d o o o o d o o r--

















{Z[ .












a~ • ~- ~














G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264


Table 4 Regression coefficients and coefficiens of determination (R trical conductivity of the upper 50 cm of soil (ECt:s~o 5o)) Species

2) for predicting

the survival a of 18-month-old trees using the elec-


Eucalyptus tereticornis Eucalyptus moluccana Eucalyptus grandis Eucalyptus intermedia Eucalyptus melliodora Casuarina cunninghamiana Tipuana tipu Eucalyptus rob usta Eucalyptus raveretiana





- 16.05

10.18 6.01 3.09 7.62 9.90 2.64


4.65 3.15 3.59 3.77 4.48 2.48




68 60 108 68 56 88

0.45 0.25 0.21 0.18 0.21 0.15


- 5.03




- 8.80



ea+b(EC) " Survival (%) = 100N

1 +e a+b(EC)"

b N u m b e r of plots.

Table 5 Weighted regressions (weights 1 or 5) between mean height production and salinity (EC~:5~o-5ocm)) for 18-month-old E. robusta, E. raveretiana, T. tipu and E. moluccana trees on a saline site in southeast Queensland

E. robusta: E. raveretiana: T. tipu: E. moluccana:

Hr. prod. (m) = 3.439- 1.402×EC (dSm -l ) Ht. prod. (m) = 3.240- 0.0257 × 9.2~ec-) (dS m-1 ) Hr. prod. (m)=0.150+ 87.5 ×0.01103 (Ec~ (dSm 1) Ht. prod. (m) = -0.074+2.005 xe e1-4.39× ~EC-2.086)1 (dSm -l )

high survival rate of 96%, averaged a height growth of only 1.1 m. Mean tree height growth mostly decreased as salinity increased (Table 3). Exceptions to this were E. moluccana where mean height growth was similar for the first four salinity classes, Casuarina glauca and E. robusta where mean height growth was similar for the first three salinity classes, and E. tereticornis, where mean height growth for salinity classes 1 and 2 was not significantly different (Table 3 ). The height growth of all species declined above 1.75 dS m - ~, with the exception of Casuarina glauca which was not represented at this salinity class. The reductions

from class 1 to class 5 ranged from 21% (Melaleuca bracteata ) to 99% ( T. tipu ).

3.1. The effect of salinity on tree survival Relationships between survival and EC1:5~o_ 50cm) were generated for all species except Casuarina glauca, E. camaldulensis and Melaleuca bracteata which had good survival rates across all salinity classes (Table 3). Each datum was either an individual tree survival rate (0 or 100%), where ECl:5~o-5ocm) values were available for individual trees, or a plot survival rate, where ECl:5(o-5ocm) values were available for plots only. A logit model, assuming binomial errors, was used ea+b(EC)

Survival (%) = 100 ×

1 +e a+b~Ec)

The fitted relationships were significant and negative, explaining between 15 and 88% of the variation observed (Table 4).

3.2. The effect of salinity on height production Height production was calculated to incorporate tree growth and survival. Where E C l : 5 ( o_ 5Ocm~ values were available for individual trees, height production was either tree height (if alive)

G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264


Table 6 Regression coefficients and coefficients of determination ( R 2 ) for predicting height production ( m ) of 18-month-old trees using the electrical conductivity of the upper 50 cm of soil (EC1:5~o_5o), dS m - ~ ) . Models were either linear ( I ) , G o m p e r t z ( I I ) or exponential ( I I I )









Eucalyptus tereticornis Eucalyptus moluccana Eucalyptus grandis Eucalyptus camaldulensis Eucalyptus intermedia Eucalyptus melliodora Casuarina cunninghamiana Melaleuca bracteata Tipuana tipu Eucalyptus robusta Eucalyptus raveretiana Casuarina glauca


- 0.029 -0.074 4.332 1.884 0.030 2.126 3.985 2.005 0.150 3.439 3.240 3.211

- 3.99 -4.39 - 1.883 - 3.00 76.3 - 0.087 - 1.150 - 0.428 87.5 - 1.402 -0.0257 - 0.044

2.510 2.005 0.908 0.0043 4.43 0.01103 9.2 -

1.883 2.086

56 68 60 64 108 68 56 60 88 59 32 20

0.58 0.50 0.50 0.14 0.56 0.38 0.37 0.19 0.66 0.51 0.47 0.02


a N u m b e r of plots.

Table 7 Mean height production at 0.75 dS m-~ and the ECx: 5~o-5ocm) at which a 25% reduction in height production from that at 0.75 dS m - 1 is predicted Species

Height at 0.75 dS m-~ (m)

EC (25%

Highly salt-tolerant (25% reductions at EC> 1.5 dS m-~ ) Casuarina glauca 3.18 Eucalyptus moluccana 1.93 Melaleuca bracteata 1.68 Eucalyptus camaldulensis 2.68

Eucalyptus raveretiana 3.10 Eucalyptus tereticornis 2.45 Moderately salt-tolerant (25% reductions at EC= 1.0-1.5 dS m-~ ) Casuarina cunninghamiana 3.12 Eucalyptus melliodora 1.86 Eucalyptus robusta 2.39 Eucalyptus grandis 2.92 Salt-sensitive (25% reductions at EC< 1.0 dS m - ~) Tipuana tipu 3.13 Eucalyptus intermedia 1.31

or zero (if dead). Where EC,:s(o_so~m) values were available for plots only, height production was calculated to be the sum of the heights of all living stems divided by five (the initial number of trees per plot ). Weighted regressions (weights 1 or 5 ) were used to relate height production to ECl:5(o-5ocm) (Table 5). Weights 1 and 5 were applied to single tree heights and the mean plot

Approx. ECse (dS m -1 )

reduction) (dS m -1 )

> 1.50 1.80 1.73 1.65

> 10 12.0 11.6 11.0

1.61 1.57

10.7 10.5



1.43 I . 18

9.5 7.8



0.82 0.80

5.5 5.4

height, respectively. Models were either linear Height production (m)=a+b×EC Gompertz Height production (m) = a + c X e - e [ b × (EC-a) l

or exponential


G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264

Height production ( m ) = a + b × c Ec Fitted regressions, explaining between 2% (Casuarina glauca) and 66% (T. tipu) of the variation observed, are presented in Table 6. The regression equations were used to group the species (Table 7 ) by calculating the EC~: 5(05Ocm)where a 25% decline in height production, relative to that at 0.75 dS m - ~, occurred (Table 7). A baseline of 0.75 dS m - ~was chosen as each species had differing minimum salinity levels, whilst a 25% reduction ensured that all calculations, with the exception of that for Casuarina glauca were interpolations. It is recognised that the electrical conductivity of a saturated soil extract (ECse), which takes into account specific site chemistry and is closer to field water content, is preferable to EC~:5 for examining plant responses to soil salinity. Thus, ECl:5(o_5ocm) values were transformed into approximate ECse values (Table 7) after the method of Shaw (1988) assuming a clay content of 45% (see Fisher and Baker, 1989 ).

4. Discussion

Casuarina glauca was a highly salt-tolerant species with 25% reduction in height production (relative to that at 0.75 dS m-~ ) occurring at an EG: 5o-5ocm)level greater than 1.5 dS m -~. Such a result is not surprising, as Casuarina glauca is often found in saline environments (Boland et al., 1984). Casuarina glauca responded to increasing salinity significantly better than Casuarina cunninghamiana. This result contrasts with the observations of Clemens et al. (1983) who recorded that the growth rates responses of 10-month-old seedlings of Casuarina glauca and Casuarina cunninghamiana to transient (21 days) salinity (75 and 150 mol NaC1 m -3) were similar. Other highly salt-tolerant species were E. moluccana, Melaleuca bracteata, E. camaldulensis, E. raveretiana and E. tereticornis. Casuarina cunninghamiana, E. melliodora, E. robusta and E. grandis were moderately salt-tolerant, with 25% reductions occurring between 1.0 and 1.5 dS

m -1. The poor survival rates and growth re-

sponses to increasing salinity of T. tipu and E. intermedia suggest that these two species are unsuitable for saline site plantings. Regression relationships described 15-88% of the variation in survival and 2-66% of the variation in height productivity. Such large variation suggests other unquantified site interactions with, for instance, frost or waterlogging. The experimental site, as with most saline discharge sites, occurred in the lower part of the landscape, ensuring that the trees were subjected to episodic frost and waterlogging events. The importance of identifying species that are able to tolerate salinity as well as waterlogging (Van Der Moezel et al., 1988) and frost (Marcar, 1989) has been recognised. The salt tolerance ofE. camaldulensis, E. raveretiana and E. tereticornis was in accord with earlier glasshouse pot trials (Van Der Moezel et al., 1988, 1991; Marcar, 1989), solution culture trials (Blake, 1981 ) and field plantings in northcentral Victoria (Morris, 1984). Our results, which show E. moluccana to be more tolerant than either E. camaldulensis or E. robusta, particularly at higher salinity levels, seem to contrast with those of Sun and Dickinson (1993). They observed E. robusta and E. camaldulensis to grow better than E. moluccana at 150 and 200 mol NaC1 m-3, in irrigated pot trials in a glasshouse. However, in that experiment each species was represented at each salinity level by five plants only. However, the use of different provenances may have accounted for these apparently conflicting results, as a wide range of intraspecific salt tolerance has been previously observed in eucalypt species (Sands, 1981; Thomson, 1988). Thus, it seems that substantial gains can be made through further inter- and intraprovenance selection and the vegetative propagation of salt-tolerant clones. This experiment has shown that with the correct species selection and good establishment techniques, similar saline discharge sites can be successfully reafforested. However, it is important to know the range of soil salinity at any particular site for successful species matching. For instance, where ECse is greater than 10 dS m - 1,

G.M. Dunn et al. / Forest Ecology and Management 70 (1994) 255-264

Casuarina glauca, E. moluccana, E. camaldulensis, E. tereticornis and E. raveretiana should be considered (Table 7), whereas on sites where

ECse is less than 10 dS m -~, Casuarina glauca, E. raveretiana, Casuarina cunninghamiana and E. grandis would be candidates (Table 7). It is also important to consider other qualities of the species tested. Casuarina cunninghamiana makes excellent fuel-wood (TurnbuU et al., 1986), is used extensively in windbreaks and it is as good as or better than other more commonly used fodder tree species such as Acacia saligna or Prosopis julifera (E1-Lakany, 1983). Eucalyptus tereticornis produces high value timber. Further work is required to assess the ability of the more tolerant species to lower ground water. Experiments would involve measuring relative tree water use and determining the horizontal and vertical distribution of roots.

Acknowledgments The establishment of the experiment was funded by the Queensland Government under the Tree Care initiative. The assistance of Grant White from the Queensland Forest Research Institute during the establishment of the experiment was much appreciated.

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