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. 2002 Jan 1;89(1):55–65. doi: 10.1093/aob/mcf005

Structure and Function of Shisham Forests in Central Himalaya, India: Nutrient Dynamics

NEELU LODHIYAL 1, L S LODHIYAL 2,*, Y P S PANGTEY 1
PMCID: PMC4233772  PMID: 12096819

Abstract

The structure and function of Shisham (Dalbergia sissoo Roxb.) forests were investigated in relation to nutrient dynamics in 5‐ to 15‐year‐old stands growing in central Himalaya. Nutrient concentrations and storage in different layers of vegetation were in the order: tree > shrub > herb. Forest soil, litter and vegetation accounted for 80·1–91·9, 1·0–1·5 and 7·0–18·4 %, respectively, of the total nutrients in the system. There were considerable reductions (trees 32·8–43·1; shrubs 26·2–32·4; and herbs 18·8–22·2 %) in nutrient concentrations of leaves during senescence. Nutrient uptake by the vegetation as a whole and also by the different components, with and without adjustment for internal recycling, was investigated. Annual transfer of litter nutrients to the soil from vegetation was 74·8–108·4 kg ha–1 year–1 N, 5·6–8·4 kg ha–1 year–1 P and 38·7–46·9 kg ha–1 year–1 K. Turnover rate and time for different nutrients ranged between 56 and 66 % year–1 and 1·5 and 1·8 years, respectively. The turnover rate of litter indicates that over 50 % of nutrients in litter on the forest floor are released, which ultimately enhances the productivity of the forest stand. The nutrient use efficiency in Shisham forests ranged from 136 to 143 kg ha–1 year–1 for N, 1441 to 1570 kg ha–1 year–1 for P and 305 to 311 kg ha–1 year–1 for K. Compared with natural oak forest (265 kg ha–1 year–1) and an exotic eucalypt plantation (18 kg ha–1 year–1), a higher proportion of nutrients was retranslocated in Shisham forests, largely because of higher leaf tissue nutrient concentrations. This indicates a lower nutrient use efficiency of Shisham compared with eucalypt and oak. Compartment models for nutrient dynamics have been developed to represent the distribution of nutrients pools and net annual fluxes within the system.

Key words: Dalbergia sissoo Roxb., nutrient concentration, retranslocation, net uptake, nutrient use efficiency, nutrient pool, nutrient fluxes, central Himalaya

INTRODUCTION

Dry matter accumulation and productivity of forests are influenced by the presence of nutrients in soils and their recycling. Nutrient elements therefore limit forest productivity. Recycling of nutrients is one of the principal processes that supports organic matter production of forests. Thus, the functioning of a forest ecosystem in relation to dry matter production depends not only on the availability of nutrients but also on the pattern and rate of nutrient uptake by species occurring in the forest. According to Lodhiyal and Lodhiyal (1997), survival of tree species and the rate of nutrient uptake depend upon the availability of water. They pointed out that trees take up large quantities of nutrients from the soil system and, although much of the nutrient uptake is returned to the soil through litter fall, large amount of nutrients are also removed when trees are harvested. Thus, from the point of view of sustainability, studies on nutrient dynamics in Shisham forests which are harvested following short rotations are important for management of plantation forestry.

Nutrient accumulation and the pattern of distribution in different plants are affected by climate (Bazilevick and Rodin, 1966), and by the type and age of the species (Ovington, 1968). Lodhiyalet al. (1994) pointed out that the major macronutrients limiting the production of a forest crop are N, P and K. According to Chapin and Kedrowski (1983), nutrient availability is a major factor influencing the distribution of plant species. Most plants from low nutrient sites have a low nutrient requirement (Clarkson, 1967; Robinson, 1968; Grime, 1977; Chapin, 1980). Stachurski and Zimka (1975) and Tilton (1977) suggested that plants growing on nutritionally deficient sites minimize nutrient loss by retranslocating a greater fraction of N and P from senescing leaves. Uptake of nutrients was found to be much greater in deciduous plantations than in evergreen plantations (Lodhiyal and Lodhiyal, 1997). On the basis of above‐ground biomass production relative to N uptake, deciduous forests have a lower nutrient use efficiency (NUE) than evergreen forests (Waring and Schlesinger, 1985). However, NUE did not differ with forest type across local N mineralization gradients in mixed‐species sequences (Nadelhofferet al., 1985), and was poorly correlated with foliar life span across diverse ecosystems (Reichet al., 1992). According to Lodhiyal and Lodhiyal (1997), the high NUE is largely the result of: (a) higher soil nutrient availability, and (b) increased nutrient concentrations and amount of litter nutrient returned through litter fall to the soil. Unscientific thinning and harvesting of trees not only degrades forest soils but also removes nutrients from the ecosystem. Many studies have been carried out into nutrient storage and cycling in forests and plantations (Kanet al., 1965; Johri, 1977; Singh and Misra, 1978; Sethet al., 1983; Chaturvedi and Singh, 1987a, b; Rawat and Singh, 1988; Lodhiyal, 1990; Bargaliet al., 1992; Jha, 1995; Lodhiyalet al., 1995b; Lodhiyal and Lodhiyal, 1997; Pacholi, 1997). The amounts of nutrients taken up depend on the demands of the plant species and on the availability of nutrients in the soil to supply that demand. Thus, dry matter production is generally based on the fertility of the soil and on extra inputs provided by management.

Increasingly, indigenous leguminous trees are being planted in India because of their high biomass per unit area, their survival on nutrient poor sites and for their nutrient conservation efficiency. The pressures of a growing population and adverse ecological changes in the natural Shisham forests necessitate investigations into their sustainability. Little is known about the nutrient cycling and nutrient use efficiency of Dalbergia sissoo which enable it to occupy Tarai (nutrient‐rich sites) belts in central Himalaya. The present investigation aims to provide detailed information on the structure and functioning of Shisham forests growing in moist plains of central Himalayan mountains in India, with regards to nutrient cycling and the pattern of nutrient use.

The major objectives of this study were to describe: (a) the various aspects of nutrient cycling, such as nutrient uptake and nutrient retranslocation in different vegetation layers; (b) nutrient return to soils through litter (i.e. by trees, shrubs and herbs); (c) nutrient use efficiency in relation to dry matter production and net nutrient uptake; and (d) to compare estimates of nutrients in Shisham forests with those in exotic plantations and natural forests.

MATERIALS AND METHODS

Nutrient dynamics were investigated in 5‐, 10‐ and 15‐year‐old Shisham forest stands in Tarai belts of central Himalaya; dry matter dynamics of these forests have been reported previously (Lodhiyalet al., 2002). Sal forest (mixed broad leaved species) was the original vegetation in the Tarai area (Champion and Seth, 1968). According to Lodhiyalet al. (1995a), most of this region was converted into arable land during the 1960s, and since the 1970s has been used for exotic tree plantations.

Details of the study site (i.e. topography, geology, soils, meteorological data and vegetation types) and methods of sampling tree, shrub and herb components are described by Lodhiyalet al. (2002).

Samples of different tree components, i.e. bole wood, bole bark, branch, twig, leaf, reproductive parts, coarse roots (stump root + lateral roots) and fine roots were collected from 12 harvested trees [three trees from each sub‐plot, one from each dbh (diameter at breast height) class; see Lodhiyalet al. (2002)] for nutrient analysis (nutrient concentration and nutrient content) in each Shisham forest stand.

Tree and shrub components were sampled during September 1996, and herbs (above‐ and below‐ground parts) were collected in each season, i.e. summer, winter and the rainy season.

Composite samples (samples of each component taken from the lower, middle and upper plant parts and mixed) for each of the tree, shrub and herb components were taken separately to the laboratory and oven‐dried at 60 °C to constant weight. Oven‐dried samples were mill‐ground for nutrient analysis.

Litter samples were collected using litter traps at monthly intervals in all forest stands. The composite litter samples (litter samples collected from each dbh class of tree and mixed to form a composite, separately for each component) for each litter component, i.e. leaf, wood, reproductive litter and other litter, were ground separately and analysed for nitrogen, phosphorus and potassium.

Five replicates of dry plant material (0·5 g each) were analysed for total nitrogen after digestion by 10 ml concentrated sulfuric acid using 5 g of a catalyst mixture (potassium sulfate and cupric sulfate in a 9 : 1 ratio) in a quick digestion unit. Total nitrogen was determined by the micro‐Kjeldahl technique (Peach and Tracy, 1956; Misra, 1968; Lodhiyalet al., 1995b). Phosphorus and potassium were extracted by wet ashing 0·5 g plant material in an acid mixture consisting of 10 ml H2SO4 + 3 ml HNO3 + 1 ml HClO4, following the method of Jackson (1958). Phosphorus was determined by absorption spectrophotometry and potassium by flame photometry (Jackson, 1958).

The standing state of nutrients in trees, shrubs and herbs was computed separately by multiplying the dry weight of each component by the respective nutrient concentration. Nutrient values in trees, shrubs and herbs were summed to obtain the total standing state of nutrients in the vegetation. The amount of nutrients (N, P and K) in the soil was determined by the micro‐Kjeldahl technique for N (Peach and Tracy, 1956), absorption spectrophotometry for P and flame photometry for K (Jackson, 1958). The amount of nutrients in the top 30 cm of soil was calculated by summing values for 0–10, 10–20 and 20–30 cm soil depths in each forest stand. Soil volume multiplied by the respective average bulk density gave the weight of the soil, which was in turn multiplied by the corresponding nutrient concentration to obtain the amount of soil nutrients (N, P and K).

The mean nutrient concentration was multiplied by the weight of annual litter fall, i.e. leaf, wood, reproductive parts of trees, and leaves of shrubs and herbs to give the amount of nutrients transferred to the forest floor in vegetation in stands of different ages.

The turnover rate (K) for each nutrient on the forest floor was estimated following Chaturvedi and Singh (1987b) and Lodhiyal and Lodhiyal (1997) as:

K = A/(A + F)

where A is the amount of nutrients added to the forest floor by litter fall and F is the nutrient content of the lowest value of standing crop of litter in the annual cycle. Turnover time (t) for nutrients was calculated as for standing litter biomass. Turnover time is the reciprocal of turnover rate (K).

Nutrient uptake by components of vegetation in stands of different age was calculated by multiplying the net primary productivity (NPP) of different components by their nutrient concentration. The values of nutrient uptake by trees, shrubs and herbs were summed to estimate the total annual uptake by the forest vegetation.

Some retranslocation of nutrients (N, P and K) occurred during senescence of foliage. This was assessed following Ralhan and Singh (1987), Rawat and Singh (1988), Lodhiyalet al. (1995b) and Lodhiyal and Lodhiyal (1997), i.e.

R = (X – Y)/X × 100

where R is nutrient retranslocation (%), X is the nutrient mass in mature green leaves, and Y is the nutrient mass in senesced leaves. X and Y were calculated on the basis of nutrient per unit weight of mature green and senesced leaf, respectively, multiplied by total amount of leaf litter fall.

To estimate nutrient retranslocation, 120 mature green and freshly fallen senesced leaves were collected in September (peak month of leaf maturity) and December (leaf senescing period) 1997, respectively. Since rainfall is negligible in the region when leaves senesce (December), leaching is likely to have only a minimal effect on nutrient loss from the leaves (Ralhan and Singh, 1987).

The nutrient use efficiency (E) per unit area of Shisham forests was calculated by:

E = P/U

where P is NPP and U is the net nutrient uptake in kg ha–1 year–1 by the trees.

RESULTS AND DISCUSSION

Nutrient concentration

Table 1 summarizes N, P and K concentrations in the different components of vegetation (i.e. trees, shrubs and herbs) of Shisham forests growing in Tarai belts of the central Himalayan mountains in India. The concentration of nutrients in tree components was in the order: reproductive parts > leaf > twig > bole bark > branch > bole wood in above‐ground parts, and fine roots > lateral roots > stump root in below‐ground parts. The nutrient concentrations in different components of Shisham trees were higher in 5‐year‐old stands than in 15‐year‐old stands. Thus, as trees age the percentage of nutrients (N, P and K) in the different components decreases. Similar trends in different components of fast‐growing poplar and eucalypt trees were reported by Lodhiyalet al. (1995b), Lodhiyal and Lodhiyal (1997), and Bargaliet al. (1992) in adjacent areas of central Himalaya.

Table 1.

Concentration of nutrients (% ± s.e.) in different components of trees, shrubs and herbs, and in soils of Tarai Shisham forests in central Himalaya

                 Age of Shisham forests (years)
Components Nutrient 5 10 15
Tree layer
 Bole wood N 0·365 ± 0·012 0·340 ± 0·020 0·328 ± 0·014
P 0·042 ± 0·015 0·039 ± 0·027 0·038 ± 0·018
K 0·202 ± 0·017 0·198 ± 0·024 0·195 ± 0·010
 Bole bark N 1·410 ± 0·020 1·390 ± 0·025 1·380 ± 0·025
P 0·089 ± 0·024 0·088 ± 0·020 0·085 ± 0·020
K 0·588 ± 0·026 0·582 ± 0·020 0·562 ± 0·024
 Branch* N 0·980 ± 0·034 0·962 ± 0·041 0·940 ± 0·052
P 0·095 ± 0·028 0·088 ± 0·038 0·071 ± 0·012
K 0·200 ± 0·025 0·198 ± 0·039 0·195 ± 0·014
 Twig† N 1·658 ± 0·031 1·625 ± 0·042 1·580 ± 0·025
P 0·099 ± 0·038 0·096 ± 0·044 0·094 ± 0·020
K 0·588 ± 0·034 0·582 ± 0·038 0·570 ± 0·025
 Leaf N 2·750 ± 0·055 2·680 ± 0·035 2·640 ± 0·40
P 0·188 ± 0·059 0·175 ± 0·039 0·170 ± 0·034
K 0·780 ± 0·062 0·762 ± 0·041 0·740 ± 0·030
 Reproductive parts N 3·254 ± 0·048 3·225 ± 0·050 3·118 ± 0·020
P 0·340 ± 0·043 0·320 ± 0·058 0·312 ± 0·019
K 0·925 ± 0·040 0·915 ± 0·052 0·908 ± 0·012
 Stump root‡ N 0·570 ± 0·040 0·592 ± 0·030 0·550 ± 0·014
P 0·042 ± 0·039 0·038 ± 0·024 0·035 ± 0·015
K 0·378 ± 0·034 0·375 ± 0·025 0·370 ± 0·012
 Lateral roots N 0·610 ± 0·034 0·698 ± 0·034 0·595 ± 0·024
P 0·068 ± 0·040 0·062 ± 0·032 0·058 ± 0·021
K 0·550 ± 0·041 0·520 ± 0·028 0·480 ± 0·022
 Fine roots§ N 1·012 ± 0·055 0·998 ± 0·042 0·995 ± 0·030
P 0·198 ± 0·059 0·598 ± 0·050 0·188 ± 0·026
K 0·610 ± 0·059 0·598 ± 0·050 0·589 ± 0·020
Shrub layer
Lantana camara
 Stem N 0·705 ± 0·052 0·702 ± 0·184 0·701 ± 0·095
P 0·079 ± 0·034 0·078 ± 0·098 0·076 ± 0·047
K 0·510 ± 0·025 0·508 ± 0·075 0·504 ± 0·059
 Foliage N 2·348 ± 0·040 2·345 ± 0·094 2·340 ± 0·052
P 0·155 ± 0·015 0·152 ± 0·084 0·150 ± 0·038
K 0·738 ± 0·021 0·735 ± 0·070 0·730 ± 0·044
 Roots N 0·780 ± 0·058 0·778 ± 0·062 0·770 ± 0·074
P 0·077 ± 0·028 0·075 ± 0·048 0·072 ± 0·046
K 0·546 ± 0·036 0·540 ± 0·042 0·540 ± 0·070
Murraya koenighii
 Stem N 0·675 ± 0·069 0·674 ± 0·084 0·670 ± 0·053
P 0·047 ± 0·022 0·045 ± 0·046 0·044 ± 0·058
K 0·350 ± 0·062 0·348 ± 0·078 0·340 ± 0·063
 Foliage N 1·252 ± 0·042 1·250 ± 0·043 1·246 ± 0·047
P 0·118 ± 0·048 0·118 ± 0·034 0·118 ± 0·064
K 0·750 ± 0·018 0·750 ± 0·048 0·746 ± 0·072
 Roots N 0·758 ± 0·018 0·755 ± 0·024 0·752 ± 0·034
P 0·049 ± 0·027 0·046 ± 0·057 0·045 ± 0·094
K 0·412 ± 0·044 0·410 ± 0·054 0·408 ± 0·050
Clerodendron viscosum
 Stem N 0·642 ± 0·075 0·640 ± 0·046 0·638 ± 0·029
P 0.051 ± 0·081 0·050 ± 0·054 0·050 ± 0·039
K 0·335 ± 0·048 0·332 ± 0·070 0·350 ± 0·066
 Foliage N 1·158 ± 0·054 1·150 ± 0·028 1·152 ± 0·045
P 0·130 ± 0·029 0·128 ± 0·038 0·127 ± 0·050
K 0·678 ± 0·052 0·675 ± 0·056 0·673 ± 0·043
 Roots N 0·670 ± 0·035 0·667 ± 0·037 0·664 ± 0·032
P 0·055 ± 0·024 0·052 ± 0·042 0·051 ± 0·047
K 0·358 ± 0·054 0·352 ± 0·042 0·350 ± 0·052
Pogostemone benghalense
 Stem N 0·681 ± 0·082 0·680 ± 0·094 0.675 ± 0.074
P 0·054 ± 0·050 0·050 ± 0·045 0.046 ± 0.058
K 0·342 ± 0·042 0·340 ± 0·072 0.334 ± 0.073
 Foliage N 1·180 ± 0·053 1·178 ± 0·057 1·175 ± 0·046
P 0·139 ± 0·042 0·136 ± 0·028 0·135 ± 0·034
K 0·684 ± 0·038 0·682 ± 0·065 0·677 ± 0·054
 Roots N 0·750 ± 0·042 0·740 ± 0·069 0·730 ± 0·063
P 0·055 ± 0·034 0·054 ± 0·047 0·052 ± 0·050
K 0·480 ± 0·026 0·479 ± 0·046 0·475 ± 0·042
Herb layer
 Above‐ground N 1·572 ± 0·068 1·540 ± 0·076 1·475 ± 0·082
P 0·084 ± 0·049 0·082 ± 0·056 0·078 ± 0·044
K 1·342 ± 0·063 1·314 ± 0·074 1·304 ± 0·064
 Below‐ground N 1·221 ± 0·063 1·202 ± 0·058 1·165 ± 0·078
P 0·065 ± 0·025 0·062 ± 0·042 0·060 ± 0·036
K 1·142 ± 0·052 1·135 ± 0·063 1·124 ± 0·050
Soil (0–30 cm depth) N 0·159 ± 0·30 0·156 ± 0·32 0·151 ± 0·39
P 0·013 ± 0·26 0·013 ± 0·26 0·012 ± 0·39
K 0·065 ± 0·38 0·061 ± 0·30 0·056 ± 0·40
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* Large woody shoots with leaves.     † Current shoots bearing leaves.     ‡ Main root with tap roots and parts of stem (stump bearing roots).      Lateral branches of main roots with diameter > 5 mm.     § Roots of diameter < 5 mm and associated mycorrhizae.

The nutrient concentration of Shisham leaves was markedly higher than that reported for poplar (2·25–2·35 %; Lodhiyalet al., 1995b) and eucalypt plantations (1·21 %; Bargali and Singh, 1991) and natural oak forests of central Himalaya (1·89–2·11 % N, 0·078–0·097 % P and 0·46–0·66 % K; Singh and Singh, 1987; Rawat and Singh, 1988).

Leaf to wood concentration ratios for N (7·5–8·0), P (4·5) and K (3·8–3·9) were similar to those found in natural forests of central Himalaya and fall within the range for N (11–12) and P (6–7) reported for poplar trees (Lodhiyalet al., 1995b) but are much lower than values reported for temperate forests (Whittaker, 1975). Leaf nutrient concentrations are higher than in Populus deltoides plantations (Lodhiyalet al., 1995b) and Eucalyptus hybrid plantation (Bargaliet al., 1992).

Soil nutrient concentration decreased with increasing forest age (Table 1; details of soils are given in Lodhiyalet al., 2002), possibly as a consequence of uptake and leaching of nutrients by the Shisham forests. Similar findings were also reported for Tarai poplar plantations in nearby areas (Lodhiyalet al., 1995b). However, loss of nutrients can be considerable during initial site preparation, which involves burning ground vegetation and litter and, as a result of soil disturbance which accompanies planting, especially when vegetation cover is sparse (Bormann and Likens, 1979).

Standing state of nutrients

The standing state of nutrients increased with forest age due to increased dry matter storage (Table 2). Bole (wood + bark) had the greatest concentration of nutrients in the trees. The relative contribution to the standing state of nutrients in different above‐ground parts was generally in the order: bole > leaf > branch > reproductive parts, and that in below‐ground parts was: stump root > lateral roots > fine roots. Similar trends have been reported for eucalypt (Feller, 1980; Bargaliet al., 1992) and poplar plantations (Lodhiyalet al., 1995b; Lodhiyal and Lodhiyal, 1997). The different nutrients in the total vegetation (trees + shrub + herbs) was in the order: N (488–1002 kg ha–1 year–1) > K (235–471 kg ha–1 year–1) > P (50–82 kg ha–1 year–1).

Table 2.

Nutrient content (kg ha–1) in different vegetation layers of Shisham forests

Age of Shisham forests (years)
Components 5 10 15
Nitrogen
 Tree layer 402·1 (82·3) 692·2 (85·5) 877·3 (87·5)
 % Allocation in
  bole* 43·4 45·3 45·0
  branch† 17·0 18·7 20·3
  leaf 22·1 18·1 15·5
  reproductive parts 4·3 4·4 5·5
  coarse roots‡ 11·3 11·3 11·2
  fine roots 1·9 2·2 2·5
 Shrub layer 44·4(9·1) 79·8 (9·8) 91·3 (9·1)
 Herb layer 41·9 (8·6) 38·1 (4·7) 33·6 (3·4)
 Total vegetation 488·4 (100) 810·1(100) 1002·2 (100)
 Soil (0–30 cm depth) 4834·6 4945·4 5026·0
Phosphorus
 Tree layer 43·7 (87·8) 64·5 (88·3) 72·5 (88·7)
 % Allocation in
  bole* 37·1 44·8 48·6
  branch† 12·6 15·5 16·8
  leaf 13·9 12·7 12·0
  reproductive parts 24·3 4·7 6·6
  coarse roots‡ 8·7 9·6 10·2
  fine roots 3·4 12·7 5·8
 Shrub layer 3·9 (7·8) 6·6(9·0) 7·4 (9·1)
 Herb layer 2·2 (4·4) 2·0 (2·7) 1·8 (2·2)
 Total vegetation 49·8 (100) 73·1 (100) 81·7 (100)
 Soil (0–30 cm depth) 405·7 412·6 388·9
Potassium
 Tree layer 172·6 (73·6) 289·6 (79·0) 390·9 (83·1)
 % Allocation in
  bole* 50·0 55·4 51·9
  branch† 10·7 6·4 12·6
  leaf 14·6 12·3 9·7
  reproductive parts 2·8 3·0 3·6
  coarse roots‡ 19·2 19·8 18·8
  fine roots 2·7 3·1 3·4
 Shrub layer 25·6(10·9) 43·7 (11·9) 49·5 (10·5)
 Herb layer 36·4 (15·5) 33·2 (9·1) 30·3 (6·4)
 Total vegetation 234·6 (100) 366·5 (100) 470·7 (100)
 Soil (0–30 cm depth) 1968·4 1934·6 1872·1
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Values in parentheses represent percentage contribution.     * Bole wood + bole bark, which accounted for 11·0–19·8 % of the values (N, P and K).     † Branch + twig (new shoots bearing leaves), which accounted for 1·7–9·3 % of the values (N, P and K).     ‡ Stump root (main root) + lateral roots (lateral branches of main roots, which accounted for 3·2–7·9 % of the values (N, P and K).

Nutrient storage by shrubs accounted for 8–12 % of storage by the vegetation as a whole and increased with forest age, while nutrient storage by herbs (2–15 %) decreased with stand age (Table 2). Similar trends were also reported for fast‐growing poplar plantations (Lodhiyalet al., 1995b). This is because the tree canopy affects the growth of herbs and also reduces the amount of light available and thus photosynthetic efficiency.

Nutrient retranslocation

The retranslocation of nutrients from senesced leaves was in the order: K (40–43 %) > N (33–35 %) > P (28–30 %) (Table 3). These estimates of nutrient retranslocation are markedly higher than those reported for fast‐growing exotic eucalypt plantations (18–25 %; Bargaliet al., 1992). However, the present estimates are lower than values reported for Tarai poplar plantations (42–64 %; Lodhiyalet al., 1995b), for Larix laricina, Alnus crispa and Betula papyrifera (44–81 %; Chapin and Kedrowski, 1983), for Populus tremuloides (42–65 %; Verry and Timmons, 1976) and Populus deltoides (74–89 %; Baker and Blackman, 1977). However, our estimates are close to the 23–39 % reported for Quercus rubra (Grizzardet al., 1976) and 38–49 % for Betula alleghaniensis (Hoyle, 1965). The estimate of N retranslocation was 33 % in mixed northern hardwood species (Bormannet al., 1977), which is similar to the present N estimate. Thus, on the basis of correlation between proportional nutrient retranslocation from senesced leaves and tree leaf nutrient concentrations, our findings are consistent with those of Chapin and Kedrowski (1983). According to Lodhiyal and Lodhiyal (1997), the nutrient requirement of vegetation not only depends on stand age and soil nutrient level, but also on the nutrient concentration of foliage. They noted that the greater the leaf tissue nutrient level, the higher the nutrient retranslocation capacity of forest trees would be.

Table 3.

Magnitude of retranslocation of nutrient (%) in leaves of different vegetations layers of Shisham forests

Age of Shisham forests (years)
Vegetation Nutrient 5 10 15
Tree layer N 35·2 33·6 32·8
P 30·3 28·8 28·1
K 43·1 41·5 40·3
Shrub layer N 32·4 30·3 28·8
P 30·7 25·0 25·0
K 30·2 28·7 26·2
Herb layer N 22·2 21·6 20·8
P 17·2 16·8 16·9
K 19·8 19·4 18·8
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Nutrient uptake

The present estimates of gross nutrient uptake (kg ha–1 year–1) by vegetation ranged from 114 (5‐year‐old stand) to 167 (15‐year‐old stand) for N, 10 (5‐year‐old stand) to 14 (15‐year‐old stand) for P, and 70 (5‐year‐old stand) to 92 (15‐year‐old stand) for K. Of this, the tree layer accounted for 59–74 % N, 64–81 % P and 44–61 % K; the shrub layer for 5–6 % N, 6–14 % P and 4–6 % K; and the herb layer for 20–37 % N, 13–22 % P and 33–52 % K (Table 4).

Table 4.

Nutrient uptake (kg ha–1 year–1) by different vegetation layers of Shisham forests

Age of Shisham forests (years)
Components 5 10 15
Nitrogen
 Tree layer 67·1(63·7) 96·9 (91·5) 122·9 (117·1)
 % Allocation in
  bole* 45·1 41·3 40·4
  branch† 17·7 17·1 18·3
  leaf 14·4 16·5 14·4
  reproductive parts 3·0 7·7 6·6
  coarse roots‡ 11·7 9·2 12·2
  fine roots 8·1 8·2 8·1
 Shrub layer 5·4 (4·9) 9·3 (8·6) 10·2 (9·4)
 Herb layer 41·9 (34·3) 38·1 (31·4) 33·6 (28·0)
 Total vegetation 114·4 (102·9) 144·3 (131·5) 166·7 (154·5)
Phosphorus
 Tree layer 6·4 (6·2) 8·9 (8·7) 10·9 (10·6)
 % Allocation in
  bole* 44·1 41·2 40·3
  branch† 14·9 14·2 14·0
  leaf 10·4 11·6 10·4
  reproductive parts 3·3 8·2 7·4
  coarse roots‡ 10·5 7·4 10·9
  fine roots 16·8 17·4 17·0
 Shrub layer 1·4 (1·3) 0·75 (0·7) 0·8 (0·7)
 Herb layer 2·2 (1·9) 2·0 (1·7) 1·8 (1·5)
 Total vegetation 10·0 (9·4) 11·7 (11·1) 13·5 (12·8)
Potassium
 Tree layer 30·5 (29·3) 42·8 (40·9) 56.1 (54·0)
 % Allocation in
  bole* 49·0 47·9 45·6
  branch† 10·5 10·6 11·1
  leaf 9·0 10·6 8·8
  reproductive parts 2·0 4·9 4·2
  coarse roots‡ 18·7 14·8 19·8
  fine roots 10·8 11·2 10·5
 Shrub layer 3·1 (2·9) 5·1(4·7) 5·5 (5·2)
 Herb layer 36·4 (30·5) 33·1 (28·0) 30·3 (25·8)
 Total vegetation 70·0 (62·7) 81·0 (73·6) 91·9 (85·1)
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Values in parentheses represent nutrient uptake (kg ha–1 year–1) after adjustment for retranslocation.     * Bole wood + bole bark, which accounted for 11·9–19·6 % of the nutrient values (N, P and K).     † Branch + twig (new shoots bearing leaves, which accounted for 4·9–8·3 % of the nutrient values (N, P and K).     ‡ Stump root (main root) + lateral roots (lateral branches of main root, which accounted for 2·2–10·3 % of the nutrient values (N, P and K).

The net uptake of nutrients by Shisham trees (after adjustment for retranslocation of nutrients from senescing leaves) was 64–117 kg ha–1 year–1 N, 6–11 kg ha–1 year–1 P and 29–54 kg ha–1 year–1 K. These values fall within the range reported for low density Populus deltoides plantations growing in an adjacent area (101–124, 11–14 and 55–66 kg ha–1 year–1 N, P and K, respectively; Lodhiyalet al., 1995b), are lower than those reported for high density poplar plantations (102–176, 12–19 and 49–94 kg ha–1 year–1 N, P and K, respectively; Lodhiyal and Lodhiyal, 1997), are higher than those reported for Eucalyptus hybrid plantations (Bargaliet al., 1992) and are close to those of central Himalayan forests (Singh and Singh, 1992). Thus, the uptake of nutrients depends on the demand of the plant and the availability of nutrients in the soil to supply that demand. According to Lodhiyal and Lodhiyal (1997), the retention value (i.e. net nutrient uptake and return of litter nutrients) influences the nutrient cycling of vegetation. The higher the retention value the greater the nutrient availability to the plant. A comparative study of nutrient uptake by different vegetation types is given in Table 5.

Table 5.

Comparison of nutrient uptake (kg ha–1 year–1) in different vegetation around the world

Nutrient (kg ha–1 year–1)
Vegetation Location Age (years) Nitrogen Phosphorus Potassium References
Shorea robusta India – 105·5 7·5 – Singh (1974)
Alnus sibirica Korea 2 120·0 12·0 70·0 Mun et al. (1977)
Betula sp. Finland 40 109·6 10·9 47·8 Malkonen (1977)
Mixed broad‐leaved forest Japan – 108·2 9·7 76·5 Katagiri et al. (1978)
Pinus khasia India – 103·9 25·0 72·4 Das (1980)
Temperate deciduous forest – 75·0 5·6 50·7 Cole and Rapp (1980)
Eucalyptus grandis Australia – 100·4 45·0 66·7 Turner and Lambert (1983)
Cedrus deodara India 35 152·0 – – Ramam (1984)
Tectona grandis Tarai (India) 30 107·73 15·8 – Jha (1995)
(88·9) (13·3)
Pinus patula India 12 50·8 2·9 22·4 Bhartari (1986)
Oak forest India >100 231·9 10·3 75·8 Rawat and Singh (1988)
Dalbergia sissoo India 24 106·0 6·0 33·0 Sharma et al. (1988)
Lantana camara India – 230·8 12·5 – Bhatt (1989)
Eucalyptus hybrid India 2–8 89·7–127·1 5·7–9·2 48·2–97·3 Bargali et al. (1992)
Populus deltoids India 5–8 230·9–273·5 19·2–22·4 121·8–125·9 Lodhiyal et al. (1995b)
Populus deltoids India 1–4 234·4–284·5 19·8–29·7 129·4–176·8 Lodhiyal and Lodhiyal (1997)
Dalbergia sissoo Ranchi, Bihar (India) 8 277·8 (256·5) 11·8 (11·0) 61·0 (54·6) Pacholi (1997)
Cassia siamea Ranchi, Bihar (India) 8 180·0 (159·1) 11·2 (10·5) 50·5 (45·1) Pacholi (1997)
Gmelina arborea Ranchi, Bihar (India) 8 106·4 (99·2) 5·22 (4·92) 56·50 (54·0) Pacholi (1997)
Dalbergia sissoo forests (net uptake of vegetation) Tarai (Uttaranchal) India 5, 10 and 15 102·9–154·5 9·4–12·9 62·8–85·0 Present study
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Values in parentheses are tree layer nutrients.

Nutrient return through litter fall

Nutrient concentrations in the litter are given in Table 6 and the nutrient return through above‐ground litter fall is given in Table 7. Of the net annual uptake of nutrients by trees, 56–69 % N, 63–72 % P and 31–46 % K is returned to the ground through litter fall (Table 7). The total inputs of nutrients to the forest floor via tree litter fall and litter fall from the total vegetation were similar to those of a eucalypt plantation (56 % N, 51 % P and 47 % K; Bargali and Singh, 1991) and lower than those reported for Populus deltoides plantations (Lodhiyalet al., 1995b) in an adjacent area in the central Himalayan mountains.

Table 6.

Mean nutrient concentration (% ± s.e.) in different litter components of vegetation of Shisham forests in Tarai of central Himalaya

Age of Shisham forests (years)
Components 5 10 15
Nitrogen
 Trees
  Leaf 1·783 ± 0·088 1·779 ± 0·084 1·774 ± 0·085
  Wood 1·011 ± 0·050 0·982 ± 0·052 0·954 ± 0·051
  Reproductive             parts 1·952 ± 0·068 1·935 ± 0·078 1·870 ± 0·080
 Shrubs* 1·003 ± 0·092 1·032 ± 0·090 1·055 ± 0·088
 Herbs† 1·572 ± 0·068 1·540 ± 0·076 1·475 ± 0·082
Phosphorus
 Tree
  Leaf 0·131 ± 0·042 0·124 ± 0·040 0·122 ± 0·045
  Wood 0·070 ± 0·048 0·067 ± 0·046 0·066 ± 0·044
  Reproductive             parts 0·221 ± 0·068 0·208 ± 0·062 0·203 ± 0·064
 Shrubs* 0·093 ± 0·068 0·099 ± 0·066 0·099 ± 0·067
 Herbs† 0·084 ± 0·049 0·082 ± 0·060 0·078 ± 0·044
Potassium
 Trees
  Leaf 0·443 ± 0·062 0·445 ± 0·056 0·440 ± 0·054
  Wood 0·395 ± 0·070 0·390 ± 0·062 0·382 ± 0·066
  Reproductive             parts 0·509 ± 0·070 0·503 ± 0·068 0·499 ± 0·066
 Shrubs* 0·497 ± 0·058 0·506 ± 0·054 0·521 ± 0·056
 Herbs† 1·342 ± 0·063 1·314 ± 0·074 1·304 ± 0·064
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* This includes the composite mean nutrient concentrations (%) of leaves, twigs and reproductive parts of shrubs.     † This includes the (%) nutrient concentration of leaves of herbs.

Table 7.

Amount of nutrients (kg ha–1 year–1) returned through different litter components of vegetation

Age of Shisham forests (years)
Components 5 10 15
Nitrogen
 Trees 41·9 (56·0) 64·1 (65·6) 74·9 (69·0)
 % Allocation     in tree component
  Leaf 48·6 55·4 56·2
  Wood 1·2 2·1 3·2
  Reproductive             parts 0·7 1·9 3·2
  Roots 5·6 6·2 6·3
 Shrubs 5·8 (7·8) 9·1 (9·3) 12·3 (11·3)
 Herbs 27·0 (36·2) 24·5 (25·1) 21·3 (19·6)
 Total vegetation 74·8 (100) 97·6 (100) 108·4 (100)
Phosphorus
 Trees 3·6 (63·3) 5·3 (70·1) 6·1 (72·4)
 % Allocation     in tree component
  Leaf 46·9 50·1 49·8
  Wood 1·1 1·8 2·9
  Reproductive             parts 1·1 2·5 4·4
  Roots 14·2 15·7 15·3
 Shrubs 0·5 (9·5) 0·9 (11·6) 1·1 (13·6)
 Herbs 1·5 (27·2) 1·4 (18·3) 1·2 (14·0)
 Total vegetation 5·6 (100) 7·5 (100) 8·4 (100)
Potassium
 Trees 12·0 (31·0) 18·5 (41·5) 21·5 (45·9)
 % Allocation     in tree component
  Leaf 23·3 30·4 32·4
  Wood 0·9 1·9 3·0
  Reproductive             parts 0·4 1·0 1·9
  Roots 6·4 8·2 8·6
 Shrubs 2·9 (7·5) 4·4 (10·0) 6·0 (13·0)
 Herbs 23·8 (61·5) 21·5 (48·5) 19·3 (41·1)
 Total vegetation 8·7 (100) 44·5 (100) 46·9 (100)
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Values in parentheses are the percent contribution of the total vegetation.

Turnover of nutrients on the forest floor

The turnover time of nutrients on the forest floor was longer (Table 8) than that of tropical dry deciduous forests (0·3–0·5 year; Pandey, 1980), eucalypt plantations (1·1–1·3 year; Bargaliet al., 1992) and Populus deltoides plant ations (1·1–1·4 year; Lodhiyalet al., 1995b). This indicates that a small part of the forest floor litter biomass remained in steady state but this amount was less than in other deciduous forests. According to Lodhiyal and Lodhiyal (1997), a long turnover time shows that the forest floor litter biomass is in steady state because the annual decomposition rate of litter is low compared with the rate of litter input.

Table 8.

Turnover rate (K, year–1) and turnover time (t, years) of nutrients on the forests floor

Age of Shisham forests (years)
Nutrient 5 10 15
N K 0·65 0·66 0·63
t 1·54 1·51 1·59
P K 0·62 0·65 0·56
t 1·61 1·54 1·79
K K 0·64 0·66 0·61
t 1·56 1·52 1·64
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Nutrient use efficiency

The nutrient use efficiency (NUE = NPP /net nutrient uptake) of Shisham trees ranged from 137–143 kg ha–1 year–1 for N, 1441–1570 kg ha–1 year–1 for P and 305–311 kg ha–1 year–1 for K (Table 9). According to Lodhiyalet al. (1995b), as stems and branches become larger the nutrient concentration of woody tissues declines, resulting in higher nutrient use efficiency. The availability of soil nutrients in the Shisham forests studied was found to be similar to that in nearby high and low density Populus deltoides plantations (Lodhiyalet al., 1994). This may be due to higher nutrient concentrations in tissues and increased amounts of nutrients returned through litter in Shisham forests.

Table 9.

Nutrient use efficiency (kg ha–1 year–1) of Tarai Shisham forests in central Himalaya

Age of Shisham forests (years)
Nutrient 5 10 15
N 143 (113) 137 (111) 143 (112)
P 1484 (1177) 1441 (1170) 1570 (1228)
K 311 (247) 305 (240) 309 (242)
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NUE = NPP/net nutrient uptake.     Values in parentheses are above‐ground NUE.

Nitrogen NUE for N was lower in Shisham forests than in a nearby poplar plantation (Lodhiyalet al., 1994) while NUE for P and K was similar in both sites. However, the NUE for N was higher than the value reported for an 8‐year‐old eucalypt stand (215 kg ha–1 year–1; Bargali and Singh, 1991) and 189–209 kg ha–1 year–1 for central Himalayan natural Sal (Shorea robusta), oak (Quercus leucotrichophora) and chir (Pinus roxburghii) forests (Singh and Singh, 1987). This indicates that Shisham trees are preferable from the standpoint of NUE and their fast growth rate. Despite a proportional increase in nutrient retranslocation, Shisham forests have a similar NUE to eucalypt stands, largely because of higher tissue nutrient concentrations.

The soil nutrient extraction efficiency (nutrient uptake per unit nutrient present in soil) of the Shisham forests studied was 1·3–2·2 for N, 1·5–2·7 for P and 1·5–2·9 for K, and falls within the range reported for Populus deltoides plantations (1·8–3·4; Lodhiyalet al., 1994).

On the basis of the nutrient parameters above, Dalbergia sisoo is the most important species because it not only produces a higher amount of dry matter but also because it requires only small amounts of nutrients compared with exotic tree plantations and indigenous forest species in adjacent areas. Thus, it is more suitable than other species not only for Tarai regions but also for plantations in areas of low nutrient status.

Thus, it is concluded that growing Shisham forests in the Tarai belt is advisable because of their relatively higher productivity, even in poor sites, than any other natural forest growing in adjacent areas. In addition, the species removes only small amounts of nutrients compared with the exotic fast‐growing trees (poplar and eucalypt). Therefore, trees can be harvested in a shorter rotation period with higher wood biomass in this moist plain of central Himalaya.

Nutrient dynamics

Compartment models of nutrient dynamics (pools and fluxes) for 5‐ and 15‐year‐old Shisham forests are presented in Fig. 1. Nutrients present in the soil to a depth of 30 cm are considered a source, while those associated with decomposition are released into the soil for re‐use. The direction of nutrient flux from soil to foliage indicates a one‐way movement, although it is realised that the nutrients are utilized by the leaf in organic matter synthesis and that they are redistributed among different components at varying rates giving rise to internal recycling.

graphic file with name mcf005f1a.jpg

graphic file with name mcf005f1b.jpg

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Fig. 1. Compartment models of a 5‐year‐old (A) and a 15‐year‐old (B) Shisham (Dalbergia sissoo Roxb.) forest showing the distribution and cycling of nitrogen (N), phosphorus (P) and potassium (K) in the tree, shrub and herb layers. Rectangles represent a pool for standing state of nutrients from one compartment to next. The values in the pools represent the average nutrient contents. Net annual fluxes of nutrients (N, P and K) between pools are shown on the arrows. Units are kg ha–1 for pools and kg ha–1 year–1 for fluxes between pools. Values in parentheses indicate adjustment for internal cycling. Recycling rates between leaf and twig for trees, foliage and stem for shrubs and above‐ground and below‐ground parts for herbs are shown by broken lines.

The amount of nutrients (N, P and K) stored in the vegetation was greater in 15‐year‐old than in 5‐year‐old forest stands. Of the total nutrients, the tree layer accounted for 74–88 % in the 5‐year‐old stand and 83–89 % in the 15‐year‐old stand. The total amount of P and K in the soil decreased, while the amount of N increased with increasing age of the forest.

The amount of nutrients (N, P and K) taken up by the different vegetational layers as a proportion of the total uptake was as follows: 5‐year‐old forest, trees (47–65 %) > herbs (20–49 %) > shrubs (5–14 %); 15‐year‐old forest, trees (64–82 %) > herbs (12–30 %) > shrubs (5–6 %).

The total amount of nutrients retranslocated from above‐ground senescing plant parts of the tree layer increased with the age of forest from 3·4 (5‐year‐old stand) to 5·8 kg ha–1 year–1 (15‐year‐old stand) for N, 0·2 (5‐year‐old stand) to 0·3 kg ha–1 year–1 (15‐year‐old stand) for P, and 1·2 (5‐year‐old stand) to 2·0 kg ha–1 year–1 (15‐year‐old stand) for K. In the shrub layer, the amount of N, P and K retranslocated was 0·37–0·84, 0·04–0·06 and 0·13–0·34 kg ha–1 year–1, respectively, and increased with the age of the stand. However, in the herb layer, the amount of nutrients ranged from 5·6 to 7·7 for N, 0·2 to 0·3 for P and 4·5 to 5·9 kg ha–1 year–1 for K, and decreased with the age of the stand. Thus, a proportion of annual dry matter production of litter supports the whole pattern of nutrient transfer in Shisham forests and consequently reduces the nutrient demand on the soil system.

Received: 6 February 2001; Returned for revision: 3 April 2001; Accepted: 14 September 2001.

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