Biomass and Bioenergy Vol. 3, No. 5, pp. 323-328, 1992 Printed in Great Britain. All rights reserved

0961-9534/92 $5.00 + 0.00 0 1992 Pergamon Press Ltd

LITTER PRODUCTION AND ITS NUTRIENT CONCENTRATION IN SOME FUELWOOD

TREES GROWN ON SODIC SOIL

V. K. GARG National Botanical Research Institute, Lucknow 226001, India

(Received 23 January 1992; revised received 16 June 1992; accepted 22 June 1992)

Abstmet-Litter production was estimated in I-year-old tree plantations of Acacia nilotica, Prosopis ju@ora, Dalbergia sisso, and Terminalia ar$ma planted in a monoculture tree cropping system on sodic soils of Lucknow Division, India. Mean annual litter fall of these trees amounted to 5.9, 7.4, 5.0 and 5.4 t ha-‘, respectively. Irrespective of tree species, the leaf litter concentrations of N, K and Ca were greater than those of P and Mg. The concentration of nutrients in leaf tissues was negatively correlated for N and Ca, with the magnitude of leaf fall in D. sissoo, but was positively correlated for Ca and Mg in A. nilotica; no such correlations were found in P. jui@ora and T. arjuna. The variations in the concentration of leaf litter nutrient did not appear to be species specific but depended on adverse edaphic properties including the fertility status of sodic soil. A. nilotica and P. j@ora with bimodal patterns of litter fall return greater amounts of nutrients to the soil surface than D. sissoo and T. arjuna which have unimodal patterns of litter fall. The study indicated the potential benefit of a mixed plantation system having variable leaf fall patterns among the planted trees so providing constant litter mulch to help in conserving soil moisture.

Keywords-Acacia nilotica, Prosopis julipora, Dalbergia sissoo, Terminalia arjuna, litter fall, nutrient concentration, sodic soil

1. INTRODUCTION

Trees grown on impoverished sodic soil rely upon the recycling of litter nutrients for their growth and development. Assessment of litter produced and quantification of nutrients in the litter fall is an important aspect of the mineral flow pathway. ‘J*,‘~ A number of studies of litter production have been conducted in the past in the tropical forests in India and else- where.8*“*‘4*‘8 However, inadequate information is available regarding the litter fall of tropical tree species particularly those grown on sodic soils. The present study was, therefore, carried out to estimate litter production and nutrient recycling of some local fuelwood trees planted in a monoculture tree cropping system in sodic soils.

2. STUDY AREA

Site: The study was conducted at the exper- imental site of the Biomass Research Centre of N.B.R.I., 23 km away from Lucknow, with a longitude 80”45’ to 80”53’ E and latitude 26”40’ to 26”45’ N, at an elevation of 129m above mean sea level.

3. SOIL

The soils are non-saline sodic inceptisol with a pH around 9.0. These are structureless silty clay loams in texture with extremely low per- meability and swell when wetted. There is a calcic horizon at 20 to 78 cm depth which coincides with the zone of illuviation. The infiltration rate as estimated by the cylinder method,u ranges from 0.5-l .O cc hr-‘. The soil profile has a uniform colour (2.5 Y 5/4).

4. METHODS

Monoculture plantations of Acacia nilotica (L) Willd ex. Delile, Prosopis julflora (Swartz) DC, Dalbegia sissoo Roxb. Ex. DC. and Terminalia arjuna Bedd were raised in 1981 by planting one year old polypot nursery seedlings individually in approximately 1 m3 pits with no other amendments to the experimental plot. Each plot measured 40 m x 40 m having 625 trees with a spacing of 1.5 m between rows and with a mean of about 4000 trees per hectare arranged in a Randomized Block Design with three replications. The seedlings were obtained from the State Forest Department nurseries

JBB 3,‘Z-C 323

324 V. K. GARG

located at Kukrail (Lucknow) and Allen forest (Kanpur) where the seeds used were from old plantations of those areas.

The measurements of litter production were taken during April 1986 to March 1989. Twelve wooden traps 50 cm x 50 cm with a 0.5 mm mesh nylon net attached at the base, were placed randomly in each replicated plot. The traps were fixed by pegs at the corners at about 15-20 cm above ground level. The contents of litter traps were hand-picked periodically at monthly intervals and sorted into leaves, twigs (woody portion) and fruits (reproductive parts). Litter samples were ground, oven dried and analysed for total N by the macro-kjeldahl method using a Kjeltect Auto 1030 Analyser. For P, K, Ca and Mg, a 1 g plant sample was digested in a tri-acid mixture of HN03, H,SO,, HClO, (10 : 4 : 1). Phosphorus was estimated calorimetrically by the Vanadomolybdo phos- phoric yellow colour method in a nitric acid system. ‘O K and Ca concentrations were estimated flame photometrically. Mg was determined by subtracting Ca from Ca + Mg, estimated by titration with Ethylenediaminete- traacetate.”

The average monthly nutrient concentration multiplied by average monthly litter production gave an estimate of the nutrients returned to the soil via litter fall.

Statistical correlations and regression equations were worked out between the monthly values of litter biomass and the respect- ive nutrient concentration in their leaf com- ponents by the methods described by Snedecor.*’

5. RESULTS

5.1. Litter production

The monthly litter fall (kg ha-‘) as total of leaves, twigs, fruits and other miscellaneous components for different trees are shown in Fig. 1. There was a bimodal pattern having peaks in summer (May-June) and autumn (August- September) with A. nilotica and P. jult$ora. D. sissoo and T. arjuna showed a unimodal pattern. The peak litter fall period was in De- cember for D. sissoo and March for T. arjuna. Mean annual litter fall, was estimated as 5.9, 7.4,5.0 and 5.4 t ha-’ for A. nilotica, P. julipora, D. sissoo and T. arjuna, respectively.

5.2. Components of litter fall

Table 1 shows the different components of the litter fall; leaves constituted about 72-80%, twigs 2-5%, fruits 15-23% and others l-4% in the case of A. nilotica and P. juliflora. In D. sissoo and T. arjuna, leaves accounted for 91-93%, twigs 2.3-5%, fruits l-3% and others

P. juliflora ___ 1986-87 - 1987-88

0 1988-89

D. sissoo T. arjuna

AMJJASONDJFMAMJJASONDJFM

Month

Fig. 1. Variations in monthly litter fall magnitude.

Litter production and nutrient concentration 325

Table 1. Mean annual litter production and its component in different tree plantations

Litter production

Tree species Component @g/ha) Percentage

A. nilotica Leaf 5688 f 73 71.6 Twig 40 * 5 5.0 Fruit 183 f 57 22.6 Others 6+2 0.8

P. jul@lora Leaf 6112+96 79.6 Twig 167+4 2.1 Fruit 1132+22 14.9 Others 28 + 2 3.6

D. sissoo Leaf 4867 f 53 91.1 Twig 12+2 2.3 Fruit 157+5 2.7 Others 10+3 1.9

T. arjuna Leaf 5359 f 46 93.0 Twig 31+4 5.5 Fruit 3 * 0.2 0.7 Others 3 * 0.5 0.7

period the lowest leaf concentrations were also found in A. nilotica and T. arjuna for N and in the latter also for Ca (Fig. 2).

5.4. Litter nutrient content

Figure 3 shows an estimate of the mean annual return of different nutrients likely to be added to the surface soil through different com- ponents of the litter fall. The return appears to be in the order of N > Ca > K > Mg > P. How- ever, the amount of nutrients recycled, particu- larly K and Ca, would be much higher in Prosopis than in other tree species.

5.5. Leaf litter nutrient concentration vs. leaJfal1

l-2%. The trend in total litter fall and leaf fall paralleled each other in most cases with minor deviations in the summer months.

5.3. Litter nutrient concentration

In all the trees under study the relationship between nutrient concentration and biomass of litter was found generally inconsistent. Only in A. nilotica was there a significant positive re- lationship for Ca and Mg. In D. sissoo, on the other hand it was a highly significant negative relationship for N and Ca. In P. julzjlora and T. arjuna no significant relationships could be established for any nutrient (Table 3).

The mean annual concentration of N was about 1.7-1.8% in the leaf litter of A. nilotica, D. sissoo and P. julz~ora and much lower for T. arjwza. K and Ca status was highest in the leaf litter of P. julifora. The concentration of P (0.12-O. 14%) was lowest in the leaf litter of all the tree species studied. In general, the nutrient concentrations were higher in the leaves than in the twig or fruit litter (Table 2).

6. DISCUSSION

Maximum litter production was found at different times of the year in A. nilotica, P. julzjlora, D. sissoo and T. arjuna. The overall magnitude of annual litter production by these plantations, however, was in agreement with other reports of tropical plantations (Table 4).

In trees with a bimodal pattern of leaf fall The peak leaf fall pattern in the trees of the (A. nilotica and P. julzyora), the lowest K present study does not agree well with the concentration in leaf litter was found at the reports from normal sites. For example, A. peaks of their leaf fall. In unimodal leaf fall trees nilotica sheds more leaves during March-May (D. sissoo and T. arjuna) a similar trend was at normal sites and becomes leafless during observed with respect to P. At the peak leaf fall April-May at very poor soil sites.2’ In the

Table 2. Annual percent mean values of different nutrients in leaf(L) twig (T) and fruit (F) litter

Tree species Component N P K Ca Mg A. nilotica L 1.82 0.14 0.42 0.92 0.55

T 1.52 0.08 0.16 1.02 0.13 F 1.81 0.09 0.16 0.96 0.29

P. juliflora L 1.70 0.14 0.92 1.70 0.71 T 1.10 0.08 0.16 0.98 0.74 F 1.85 0.11 1.45 0.63 0.31

D. sissoo L 1.80 0.12 0.52 1.29 0.68 T 0.69 0.07 0.20 1.40 0.22 F 2.06 0.23 0.19 1.24 0.62

T. ar$ma L 0.86 0.14 0.37 1.20 0.89 T 0.90 0.10 0.09 1.60 1.50 F 0.70 0.10 0.05 1.02 1.00

326 V. K. GARG

0 A. nilotica --_ P. juliflora - D. sissoo

. T. arjuna

\ A/-._ 0.2 1 I ’ j L 4-u

A M J J AS OND J FM

0.3 Month

3 I#

01 1 1 ’ ’ ’ A M J J AS OND JFM

15r Month

01 I I : I AM J J AS ONDfFM

Month

present study only 28% leaf fall was observed during this period on sodic soils. Similarly, foliage of P. juliflora gets thinner due to intense leaf shedding during the winter months on good soil.” In the present study only 21% leaf litter fall was, however, observed in this plant during winters on sodic soils. In D. sissoo leaf abscis- sion normally begins in November with the tree becoming leafless in December; at higher alti- tude; however it starts from the second week of December.j On good soil sites the maximum 70% leaf shedding by this species has been reported to occur during October-December.” However, the present study records only 50% leaf litter fall by this species on sodic soils. The leaf fall pattern in T. arjuna in the present study showed little variation with that growing on normal soil sites3*” Hence, the presently ob- served seasonal variation in leaf fall patterns of different tree species (except T. arjuna) appears to be associated with the effect of adverse inherent adaphic factors of the soil site of the present study. Generally, the litter production is related to climate and latitude.4s5 But it is also influenced by other factors such as forest age and management operations including soil fertility.6.‘i The inherent poor and imbalanced fertility of the sodic soils due to low organic matter, poor air-water relationships and high

m A. nilotica

I P. juliflora

0.4 I I I 1 I 1 I I AM 1 J AS OND J FM

Month

N P K Ca MS

3.0 Leaf litter

n 7

m

Y “, B b-i

$

B 0 x N P K Ca

2 Twig litter B

01 1 ’ ’ 1 ’ A M J J AS OND 1 FM

Month

Fig. 2. Nutrient concentration changes in leaf litter.

Fruit litter

Fig. 3. Estimate of mean annual nutrients returned to the soil surface through leaf, twig, and fruit litter.

Litter production and nutrient concentration 327

Table 3. Correlation coefficients (r) between monthly leaf-fall and nutrient concentration along with their regression equations

Leaf fall (kg ha-‘) vs nutrient (%)

Species N P K Ca Mg A. nilotica

P. julifora

D. sissoo

T. ariuna

0.122t 0.292t 0.387? 0.520* o.so* Y = 0.0043x + 0.8063 Y = 0.00038x + 0.3976

0.132t 0.142t 0.464t 0.4649 0.1877

- 0.683* 0.047t -0.233t -0.72* -0.3577 Y = -0.0095x + 0.1725 Y = -0.007x + 1.5722

0.0094t 0.115t 0.145t 0.16Ot 0.056t

*Significant at 5% probability level. tNot significant.

pH, have also been reflected in the lower leaf litter nutrient status particularly of N, P and Ca (Table 2). Availability of these nutrients is well known to be depressed under sodic soil conditions.’

litter is an important mechanism in assessing the storage or drain of nutrients, chiefly by the fast growing tree species under short rotation forestry practices.

The study has thus revealed that the benefit of mixed plantation systems may be derived from the variations in the leaf fall patterns of these trees. This provides litter mulch over the land almost throughout the year and thereby helps to conserve soil moisture.

The concentration of nutrients in twig litter was lower than in the leaf litter. This can be attributed to the non-photosynthetic : photo- synthetic tissue ratio and tissue longevity. Low nutrient concentrations in the woody perennial tissues has also been reported by Attiwill et al.’ and Gosz et al.’

No definite trend was observed in the sea- The annual return of different nutrients to the sonal variations in the leaf litter nutrient con- soil through leaf fall was in the order of centration in these tree species. This is in N > Ca > K > Mg > P and the total estimates accordance with the earlier reported inconsist- of annual input to the forest floor due to leaf fall ent trend in leaf nutrient concentration of trees ranged from 6 kg ha-’ (P) to 104 kg ha-’ (Ca). grown on sodic soils.’ The highly significant The amount of total nutrients added to the negative correlation between leaf biomass and surface soil through twigs (1-5 kg ha-‘) and leaf N and Ca particularly in D. sissoo, a timber fruits (0.01-49 kg ha-‘) was however, much less. tree, suggests retrieval back into the living tis- Thus leaf litter results in substantial recycling of sues prior to leaf fall because of their high nutrients, as it alone accounts for a 91-93% nutrient requirement. ” In general the nutrient contribution in D. sissoo and T. arjuna, and concentration in the leaf litter of deciduous a 71-80% contribution in A. nilotica and plantations are reported to be negatively corre- P. julifiora (in contrast to a 70% contribution lated with the magnitude of leaf fall.‘* However, from leaf litter as suggested by Bray and the significant positive correlation in Ca and/or Gorham).4 This study thus indicated that A. Mg in the case of A. nilotica, a fast growing nilotica and P. jukjlora, with bimodal patterns fuelwood tree species may be interpreted as of litter fall, return greater amounts of nutrients the loss of these nutrients in greater amounts. to the soil surface than D. sissoo and T. arjuna Hence, the study of nutrient patterns in the leaf which have unimodal patterns of litter fall.

Table 4. Comparison of litter production from various studies

Tree species Density

(tree ha-‘) Age

Vear) Basal area (m2 ha-‘)

Litter fall (t ha-‘) References

A. nilotica D. sissoo P. julipora Deciduous forest Equatorial vegetation A. nilotica D. sissoo P. iuliffora

1111 6 467 24 - - - - - -

3525 7 3775 7 4393 7

11.1 5.75 19.9 4.16 - 7.00 - 1.01-6.21 - 6.80 19.7 5.90 26.9 5.00 35.7 7.40

Gill et aLa Sharma et al.” Salinas and SanchezI Singhr9 Bray and Gorham4

Present study

T. -&ma 4440 7 33.6 5.40

328 V. K. GARG

Acknowledgements-I am indebted to Drs P. V. Sane, Director NBRI Lucknow, for providing necessary facilities, and P. D. Dogra, Former head of the Biomass Research Centre, NBRI, for encouragements. Thanks are also due to Mr Moti Lal, laboratory technician, for analysing samples and preparation of graphs. Financial support granted by Department of Non-conventional Energy Sources, New Delhi, India, is also gratefully acknowledged.

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