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АРИДНЫЕ ЭКОСИСТЕМЫ, 2012, том 18, № 4 (53), с. 86-96
==—— ОТРАСЛЕВЫЕ ПРОБЛЕМЫ ОСВОЕНИЯ ЗАСУШЛИВЫХ ЗЕМЕЛЬ —==—
УДК 581.526+502
РАЗНООБРАЗИЕ РАСТИТЕЛЬНОСТИ И РОЛЬ LEPTADENIA PYROTECHNICA В СОСТАВЕ БИОМАССЫ И НАКОПЛЕНИИ УГЛЕРОДА В АРИДНОЙ ЗОНЕ ИНДИИ
© 2012 г. Г. Сингх, К. Сингх, Д. Мишра, С. Шакла
Научный институт аридных лесов, отделение лесной экологии Индия, 342005 Джодхпур, Новая Дорога Пали. E-mail: [email protected],
Поступила 30.07.2011
Статья посвящена изучению разнообразия деревьев и кустарников, произрастающих совместно с Leptadenia pyrotechnica (Forsk.) Decne, продуктивности вида и содержанию углерода в растениях. Исследования проводились в пустыне Тар (Индия) в трёх агроклиматических районах: засушливая западная равнина (AWP), равнина транзита внутреннего стока (TID) и транзитная равнина бассейна реки Луни (TLB). Целью было оценить вклад L. pyrotechnica в общую биомассу и запасы содержания углерода в засушливых районах. Были подсчитаны такие показатели, как количество особей и площадь сечений стволов, которые оказались выше для кустарников, чем для деревьев. Значительная часть площади сечений стволов пришлась на L. pyrotechnica - около 40%. Содержание углерода в L. pyrotechnica варьировало в пределах 43.32-45.86% (в сухом остатке стеблей) и 39.45 к 42.51% (в сухом остатке корней), в то время как содержание азота изменялось от 0.41 до 2.21% и 0.57 до 1.69% в сухом остатке стеблей и корней соответственно. Большее число видов деревьев и кустарников характерно для районов TID и AWP, при этом общая площадь сечения стволов была самой высокой в районе TLB. Видовое богатство древесных форм оказалось выше, в то время как равномерность распределения выше у кустарников во всех агроклиматических районах. Высота растений вида L. pyrotechnica больше в районе TLB, толщина стволов (диаметр основания) в районе TID, а наибольшее число побегов - в зоне AWP. Соотношение высоты (H) и обхвата основания ствола (G) показало степенную зависимость (R2=0.683, P<0.001) с надземной и сложную зависимость (R2=0.552, P<0.001) с подземной биомассой. Как подземная, так и надземная биомасса были самыми высокими в районе TLB и самыми низкими - в TID. Соотношение корней и побегов схоже в районах АWС и TID, но значительно больше (1.25) в районе TLB, что свидетельствует о большей биомассе корней. Таким образом, популяция L. pyrotechnica вносит существенный вклад в растительность пустыни Тар, занимая обширную площадь и формируя значительную фитомассу, причем большая её часть располагается под землей, что защищает почвы от эрозии и связывает углерод.
Ключевые слова: агроклиматический район, количество биомассы, содержание углерода, Пустыня Тар.
VEGETATION DIVERSITY AND ROLE OF LEPTADENIA PYROTECHNICA IN BIOMASS CONTRIBUTION AND CARBON STORAGE IN ARID ZONE OF INDIA
© 2012. G. Singh, K. Singh, D. Mishra, S. Shukla
Arid Forest Research Institute, Division of Forest Ecology India, 342005 Jodhpur, New Pali Road. E-mail: [email protected], [email protected]
We studied diversity of tree-shrubs and productivity and carbon storage capacity of Leptadenia pyrotechnica (Forsk.) Decne in Indian Desert in three agro-climatic zone namely Arid western plain
(AWP), Transitional plain of inland drainage (TID) and Transitional plain of luni basin (TLB) with a view to monitor the contribution of L. pyrotechnica in biomass production and carbon storage in arid areas. Population and basal area were greater for shrubs than for the tree species. The contribution of L. pyrotechnica in basal area was about 40%. Carbon content of L. pyrotechnica varied from 43.32 to 45.86% and 39.45 to 42.51%, whereas nitrogen content varied from 0.41 to 2.21% and 0.57 to 1.69% in oven dry stem and roots, respectively indicating relatively greater carbon and nitrogen in stem than in roots. The highest population of tree and shrubs was in TID and AWP, respectively but total basal area was highest in TLB zone. Species richness was highest for tree, whereas species diversity and evenness were highest for shrub in all agro-climatic zones. Species dominance was highest in AWP zone for both tree and shrubs. Plants of L. pyrotechnica were taller in TLB, thicker (collar diameter) in TID and with highest numbers of tillers in AWP. Height (H) and collar girth (G) showed power relations (R2=0.683, /"<0.001) with above-ground and compound relations (R2=0.552, /"<0.001) with below-ground biomass. Both the above-ground and belowground biomasses were the highest in TLB and lowest in TID zone. Root/shoot ratio was similar in AWS and TID zones but was significantly greater (1.25) in TLB zone suggesting greater biomass allocation to roots. Conclusively, L. pyrotechnica has significant contribution in vegetation population, basal area and biomass production and showed greater biomass allocation to roots that help in stabilizing soil and sequestering carbon.
Keywords: agroclimatic zone, biomass partitioning, carbon storage, Indian desert.
Deserts occupy regions of very low or highly seasonal precipitation and are found in most of the continent i.e., Africa, southern and northern America, Asia and Australia. In desert, plant growth tends to be highly sporadic and plants invest heavily in protecting themselves against water loss and herbivores by making their tissues tough and resistant to decomposition. Lack of water decelerates decomposition rates, leading to the accumulation of carbon-rich dead plant material in the soil. Amundson (2001) estimated about 14 and 100 tonnes per ha carbon content in desert soils, but the carbon stored in the vegetation is around 2-30 tones per ha. Study of G. Wohlfahrt, L.F. Fenstermakerw and J.A. Arnone (2008) indicated that carbon uptake by deserts is much higher than the previously thought by which it may contribute significantly to the terrestrial carbon sink. But due to considerable uncertainties in these calculations, verification by quantifying above- and below-ground carbon pools over time was suggested (Schlesinger et al., 2009). Warming-up of deserts by 0.2-0.8°C per decade (1976 to 2000) with an average increase of 0.5-2°C combined with increased evapo-transpiration, lower precipitation and land degradation may reduce soil moisture and vegetation diversity leading to carbon loss from the soil (IPCC, 2001). Because of differences in the biochemical pathways, some species may be more responsive to elevated CO2 or new habitat than others leading to changes in plant community structure (Morgan et al., 2001; Smith et al., 2000; Gunin et al., 2012) and carbon assimilation. The changes in vegetation composition and density will inevitably alter the carbon budget with uncertain feedback effects on the regional climate.
The Great Indian Desert spreads across the state of Rajasthan and parts of Gujarat in western India covers about 2 00 000 km2, the desert is interspersed with hillocks, gravel, salt marshes and some lakes. About 61% of the Indian Desert is in Rajasthan covering 12 districts. The natural vegetation of this dry area is classed as Northern Tropical Thorn Forest (Champion, Seth, 1968) occurring in small clumps scattered more or less openly and composed of tree, shrubs and herbs. The number of tree species is very limited and the region is dominated mainly by shrubs like Leptadenia pyrotechnica, Calligonum polygonoides, Calotropis procera, Acacia jacquemontii, Z. nummularia etc (Naval et al., 2006). Many of these species are suffering of overexploitation for their varying uses resulting in shrinkage of their habitats and loss of land phytomass (Lebedeya et al., 2011). Some of them are Calligonum polygonoides (utilized for its valued high calorific fuelwood) and L. pyrotechnica presently used in brick manufacturing industries in the region and can be utilized particle board making (Bhaduri, Mojumder, 2008). Leptadenia pyrotechnica (Forssk.) Decne is an erect, much branched generally leafless shrub, generally 0.6-2.5 m tall. This species is medicinally important but is also used for making ropes, thatching hamlets and as fodder in the Indian desert (Bhaduri, Mojumder, 2008). Root system of a small Leptadenia bush reported to penetrate to a depth of 11.5 m and has a lateral extension of 10 m, exploiting about 850 m3 of soil (Batanouny, Wahab, 1973) and reported to improve soil calcium and phosphorus concentration (Karim et al., 2009). Removal of this species under
overexploitation not only leads to land degradation but also affect ecology and carbon stock of the aridisol as this species has a good potential to assimilate carbon that is then available for sequestering into the soil.
In view of this, a study was conducted on biodiversity and productivity associated with Leptadenia pyrotechnica (Forsk.) Decne to (i) observed diversity status of L. pyrotechnica dominated habitats in different agro-climatic zone of Indian Desert, and (ii) contribution of L. pyrotechnica in biomass production and carbon sequestration in this desert region.
Methodology, site description and analysis
Vegetation survey was conducted in western part of Rajasthan covering the hot arid regions of India lie between 24° and 29° N latitude, and 70° and 76° E longitude, covering an area of 31.70 million ha. The arid regions of Rajasthan, Gujarat, Punjab, and Haryana together constitute the Great Indian Desert "The Thar", which accounts for about 89.6% of the total hot arid regions of India. The Thar Desert is subdivided into four sectors based on rainfall and edaphic characteristics. We have considered (i) arid western plain (AWP); (ii) transitional plain of inland drainage (TID), and (iii) transitional plain of Luni basin (TLB) for this study (fig. 1), because the fourth one cover almost irrigated area of Shri Ganganagar and Hanumangarh districts.
Рис. 1. Расположение различных агро-климатических районов в западном Раджастане (Индия). Fig. 1. Distribution of different agro-climatic zone in western Rajasthan, India.
The AWP comprises of all tehsils of Bikaner, Jaisalmer and Barmer districts, Phalodi, Shergarh, Osian and Jodhpur tehsils of Jodhpur district and Dungargarh, Sujangarh, Ratangarh and Sardarshahar tehsils of Churu district. This is the most arid part of the state with annual rainfall between 100 to 400 mm, which is quite often erratic, so much so, that the entire rainfall of the year may fall on a single day and the rest of the year may be dry. Summer temperatures are always high and the diurnal range exceeds even 20oC. During summer temperatures may be as high as 49oC, whereas in winters, the day temperatures are higher but the night temperatures may be near freezing point. Winters are of short duration, not exceeding two months -December and January. The TID zone (transitional plain of inland drainage) comprises all tehsils of Nagaur, Sikar and Jhunjhunu districts and Taranagar, Churu and Rajgarh tehsils of Churu district. This area is covered with sand dunes and inter-dunal sandy plains. Drainage is not well developed and streams, which flow in the rainy season, disappear in sandy fields after covering some distance. Climatically, this zone is slightly better as compared to Arid Western Plain. Rainfall is slightly higher, temperatures in summer months do go very high but the winters are very cold. The "Transitional Plain of Luni Basin" lies between the Aravalli ranges and western arid region encompassing the entire districts of Jalor and Pali, Reodhar and Sheoganj tehsils of Sirohi district, and Bilara and Bhopalgarh tehsils of Jodhpur district. The region has semi-arid climate with an annual rainfall of 300 to 500 mm. It is drained by the river Luni which is seasonal and flows only during rainy season. The western part of the region is dotted with sand dunes, interspersed in alluvial soil. Luni and its tributaries, like Sukri, Mithri and Jawai have made this area productive. The climatic conditions are almost the same as in the western arid region except that the rainfall is slightly higher. The region is generally occupied by sparse vegetation comprising perennial and annual grasses, other herbaceous plants, shrubs and small trees. The number of tree species is very limited and the region is dominated by shrubs like Leptadenia pyrotechnica, Calligonum polygonoides, Calotropis procera, Acacia jacquemontii, Z. nummularia etc. The native plant species have adaptations that enable them to reproduce, grow and survive in the most inhospitable edapho-climatic conditions.
The survey was done adopting simple random sampling in forest areas of Bikaner, Jaisalmer, Barmer, Jalore, Ngaur, Sirohi and Pali forest divisions of Rajasthan during June 2009 to November 2010. Quadrates of 0.1 ha area was laid in forest block existing in the defined agroclimatic zones. Data on number of tree species and their population recorded and their growth i.e., height and circumference at breast height measured. In addition number shrub species and their population were also recorded and their height, number of tiller and the circumference of tillers are measured. One plant of L. pyrotechnica was harvested and root was excavated up to 0.5 cm diameter for total biomass recording. Fresh biomass of aboveground part (i.e., stem) and belowground part (i.e., root) was recorded at the time of harvesting. Plant height, number of tillers, crown diameter, root length and root diameter measured (photo 1). Samples of both above-ground and belowground plant parts were taken for estimation of dry biomass and fresh biomass recorded. These plant samples were dried in an oven at 80°C for about 48 hrs and dry biomass recorded and converted to total plant dry biomasses for stem and roots. Above-mentioned stem and root samples were grounded using a Willey-Mills and plant carbon and nitrogen was estimated using Elementar CNS Analyser model Vario EL Cube.
Plants were identified as per taxonomy classification using standard literatures (Shetty, Singh, 1993). These species were counted manually and categorized into number of species and their population. Species richness, diversity, dominance, evenness and frequency were calculated using different literatures (Magurran, 1988; Pielou, 1966; Shannon, Wiener, 1963; Simpson, 1949). Data were statistically analyzed using the MS-EXCEL software and SPSS statistical package. Data were analyzed using statistical package "Window 2000". The variable considered was different climatic zone from where vegetation survey was done and sample collected, these data were analyzed using one way ANOVA. Different agroclimatic zone was considered as the main factor.
Results
Species population and diversity. A total number of 19 trees/shrub species were recorded during the field study. In this, there were 9 tree and 10 shrub species belonging to 12 families (table 1). Among these species, Leptadenia pyrotechnica (Forsk.) Decne, Prosopis cineraria (L.) Druce. and Zizyphus nummularia (Burm.f) Wt were observed in all agroclimatic zones. Acacia nilotica(L.) Del., Acacia jacquemontii Benth., Butea monosperma (Lam.) Kuntze, Euphorbia caducifolia Hains and Kandel
(unidentified species) were observed only in transition plain of Luni basin (TLB), whereas Calligonum polygonoides L., Capparis decidua (Forsk.) Edgew., Lycium barbarum and Maytenus emarginata Willd. were recorded only in AWP zone. Falcourtia indica and Salvadora oleoides Decne. were recorded only in the transitional plain of inland drainage (TID). Variations in tree and shrub population and basal area of tree did not vary (P>0.05) between different agroclimatic zones. But basal area of shrubs approached a significant level (P=0.083) due to the agro-climatic zones (table 2). Trees population was highest in TID zone and lowest in TLB zone, but shrubs population and the population of L. pyrotechnica as well was highest in AWS zone. The combined basal area of trees and shrubs were highest in TLB zone but the lowest basal area was in TID zone. However, the lowest basal area was in TLB zone for trees and TID zone for shrubs. Contribution of L. pyrotechnica to the total basal area ranged from 50.7% in TID to 33.6% in TLB zone.
Фото 1. Leptadenia pyrotechnica в естественных условиях совместного произрастания с другими видами растений: Calligonum polygonoides (беловатый стебель, связанный с L. pyrotechnica на переднем плане с левой стороны) и Acacia jacquemontii (на заднем плане с правой стороны). Photo 1. Leptadenia pyrotechnica in natural conditions along with the associated species i.e., Calligonum polygonoides (whitish stem associated with L. pyrotechnica, left) and Acacia jacquemontii at right end corner.
Tree and shrub diversity variables did not vary significantly (P>0.05) between the agro-climatic zones except for shrub richness (P<0.01) and species diversity (P=0.078), which were highest in TLB zone (table 2). Species richness, species diversity and species evenness were highest in TLB zone for both trees and shrubs. Species dominance was highest in AWS and the lowest values were in TID for tree and in TLB for shrubs. Tree and shrubs richness were lowest in AWP zone, the diversity values were lowest in AWP and TID zone, respectively. Tree species evenness was lowest in TID, whereas AWP zone was less even for shrub species.
Growth variables and biomass of L. pyrotechnica. Plants of L. pyrotechnica were taller and wider in crown diameter in TLB zone but were thicker in TID zone. But plant height and crown diameter were relatively less in AWP zone, whereas collar diameter was lesser in TLB zone as compared to the other zones (table 3). The number of tiller (i.e., 23.3 numbers) was greater in relatively harsh AWP zone, whereas the lowest number of litters was in TLB zone, which is relatively better in rainfall and climatic condition as compared to the other zones. In root growth variables, L. pyrotechnica exhibited longer and thicker roots in TLB zone. Root length was shorter in TID zone but shorter root diameter was observed in AWP zone.
Total dry biomass (stem + root) of L. pyrotechnica plants ranged from 193.37 kg ha-1 in TLB to 78.88 kg ha-1 in TID zone. Both the above-ground biomass and root biomasses were highest in TLB and
lowest in TID zone (table 3). Interestingly, the root biomass was lesser than above-ground biomass in AWP and TID zone, but a reverse trend was observed in TLB zone, where root biomass was relatively greater than that in other two zones. Ratio of root to above-ground biomass was highest (i.e., 1.23) in TLB zone, whereas it was 0.69 in other two zone. We found significant (P<0.05) increase in above-ground and root biomasses with height/ collar diameter and their linear multiplication. Though plant height showed best fit to predict aboveground and root biomasses (table 4), but we selected G*H2 (here G is collar girth and H is height of plant), because of frequent variation in height due to harvesting of aboveground biomass for different uses. G*H2 is related with power equation for aboveground and compound equation with root biomass.
Таблица 1. Сообщества деревьев и кустарников, произрастающих совместно с L. pyrotechnica в различных агро-климатических районах пустыни Тар. Table 1. Trees and shrubs associated with L. pyrotechnica in different agro-climatic zone in Thar desert.
S.No. Species Habit Family Zone of occurrence
1 Acacia nilotica(L.) Del. Tree Mimosaceae TPB
2 Acacia Senegal (L.) Willd Tree Mimosaceae TPB, TID
3 Acacia tortilis (Forsk.) Hayne Tree Mimosaceae AWP, TID
4 Acacia jacquemontii Benth. Shrub Mimosaceae TPB
5 Aerva pseudotomentosa Blatt.& Halb Shrub Emaranthaceae AWP, TID
6 Butea monosperma (Lam.) Kuntze Tree Fabaceae TPB
7 Calligonum polygonoides L. Shrub Polygonaceae AWP
8 Calotropis procera (Ait.) R.Br. Shrub Asclepiadaceae AWP, TID
9 Capparis decidua (Forsk.) Edgew. Shrub Capparaceae AWP
10 Euphorbia caducifolia Hains Shrub Euphorbiaceae TPB
11 Flacortia indica Tree Flacourtiaceae TID
12 Kandel (Undentified) Tree TPB
13 Leptadeniapyrotechnica (Forsk.) Decne Shrub Asclipiadaceae AWP, TID, TPB
14 Lycium barbarum Shrub Solanaceae AWP
15 Maytenus emarginata Willd. Shrub Celastraceae AWP
16 Prosopis cineraria (L.) Druce. Tree Mimosaceae AWP, TID, TPB
17 Prosopis juliflora (Swartz.) DC. Tree Mimosaceae TID, TPB
18 Salvadora oleoides Decne Tree Salvadoraceae TID
19 Zizyphus nummularia (Burm.f) Wt. Shrub Rhamanaceae AWP, TID, TPB
Примечания к таблицам 1-3: AWP - засушливая западная равнина, TID - транзитная равнина внутреннего дренажа, TPB - транзитная равнина бассейна р. Лани, ** = значимый (P<0.01), NS = не значимый (P<0.05). Notes to table 1-3: AWP=Arid western plain, TID= Transitional plain of inland drainage, TPB= Transitional plain of Luni basin, ** = significant (P<0.01), NS = not-significant (P<0.05).
Carbon and nitrogen concentration in L. pyrotechnica. Concentrations of carbon did not differ between different agro-climatic zones, though it varied from 44.36% to 45.19% in aboveground and 41.60% to 43.06% in the root oven dry biomass. The carbon concentration was relatively greater in TID zone as compared to the other zones. While considering aboveground and below ground carbon concentrations, it was relatively greater above-ground than in the root (table 5). Nitrogen concentration in stem and root varied significantly between agro-climatic zones. It was highest in the plants of AWP for both stem and roots of L. pyrotechnica. In stem, the lowest N concentration was in the plants of TLB zone, whereas the nitrogen concentration in root was lowest in the plants of TID zone.Interestingly, the nitrogen concentration was relatively greater in roots of the plants in TID and TLB zones, whereas N concentration in stem was relatively greater in AWP zone as compared to the plants of the other zones. Carbon to
nitrogen ratio in stem increased from 35.06 in AWP 97.34 in TLB, whereas in root it varied from 41.17 in TLB to 64.20 in TID zone.
Таблица 2. Показатели плотности деревьев и кустарников в сообществах L. pyrotechnica, их базальной площади, видового богатства, доминирования и распределения видов в различных агроклиматических районах западного Раджастана (значение переменной - среднее±SE из 10-ти повторностей). Table 2. Population, basal area and diversity variables of trees and shrubs associated with L. pyrotechnica in different agro-climatic zone of western Rajasthan. Values are mean ±SE of ten replicates.
Plant variable Vegetation Agro-climatic Zone One way ANOVA
AWP TID TLB F value P value
Population (no. /0.1 ha) Tree 9.2±2.59 14.3±7.88 8.7±5.24 0.38 NS
Shrub 70.6±13.40 39.5±24.25 30.3±24.41 1.52 NS
L. protechnica 31.2±5.43 23.8±9.33 14.7±6.39 1.19 NS
Basal area (m2 per 0.1 ha) Tree 0.23±0.09 0.19±0.11 0.04±0.03 0.61 NS
Shrub 0.30±0.05 0.17±0.09 0.67±0.34 2.99 0.08NS
Total 0.53 0.36 0.71 - -
% of L. pyrotechnica to total basal area - 41.2±8.14 50.7±17.51 33.6±21.78 0.29 NS
Species richness Tree 0.55±0.09 0.68±0.03 0.97±0.41 1.50 NS
Shrubs 0.31±0.03 0.32±0.08 0.71±0.16 8.28** 0.008
Species diversity Tree 0.15±0.08 0.37±0.26 0.51±0.41 0.93 NS
Shrubs 0.63±0.13 0.27±0.20 1.04±0.05 3.07 0.08NS
Species dominance Tree 0.86±0.18 0.56±0.23 0.73±0.23 0.53 NS
Shrubs 1.29±0.69 0.83±0.16 0.34±0.05 0.35 NS
Species evenness Tree 0.42±0.17 0.32±0.00 0.63±0.33 0.30 NS
Shrubs 0.77±0.07 0.98±0.00 0.88±0.05 0.73 NS
Таблица 3. Средние величины параметров растений (высота, диаметр кроны, количество побегов, диаметр стволов, длина корней) и биомассы (надземной, подземной, общей) L. pyrotechnica в различных агроклиматических районах западного Раджастана (значение переменной - среднее±SE из 10-ти повторностей). Table 3. Average growth variables and biomass partitioning of L. pyrotechnica in different agroclimatic zone of western Rajasthan. Values are mean ±SE of ten replicates.
Plant variable Agro-climatic Zone One way ANOVA
AWP TID TLB F value P value
No. of tillers (per plant) 23.3±5.78 11.8±2.78 11.7±2.73 4.28** 0.03
Height (cm) 132.7±14.21 146.3±12.31 146.7±44.47 0.17 NS
Collar dia. (cm) 5.42±1.26 6.80±2.24 5.02±2.29 0.20 NS
Crown dia. (cm) 119.2±11.46 139.9±32.60 202.8±92.86 1.48 NS
Root length (cm) 185.1±14.93 150.0±29.07 231.0±42.51 1.92 NS
Root dia. (cm) 3.16±0.78 3.23±1.21 4.13±2.28 0.15 NS
Above ground biomass (kg ha"1) 78.94±17.49 46.73±17.08 80.40±70.63 0.37 NS
Root biomass (kg ha"1) 49.83±10.67 31.45±10.92 112.97±99.97 1.22 NS
Total biomass (kg ha"1) 128.77±27.55 78.88±27.98 193.37±170.58 0.63 NS
Root/Shoot ratio 0.69±0.94 0.69±0.18 1.23±0.34 3.44 0.06NS
Таблица 4. Уравнения регрессии для надземной и подземной биомассы с переменными роста L. pyrotechnica. Table 4. Regression equations for above ground biomass (stem) and below ground (root) biomass with growth variables of L. pyrotechnica.
Dependent variables Independent variables Curve fit Regression constants R2 SE F value P value
a0 a
Above ground biomass (stem) Height (H) Compound 5.49 1.03 0.73 0.80 44.85 0.00
Girth (G) Power 5.58 1.44 0.46 0.43 14.37 0.01
G x H Power 0.03 1.21 0.63 0.94 28.39 0.00
G x H2 Power 0.002 0.96 0.68 0.86 36.65 0.00
Below ground biomass (root) Height Compound 7.36 1.03 0.59 0.97 24.23 0.00
Girth Compound 61.04 1.07 0.34 1.23 8.59 0.01
G x H Compound 66.10 1.00 0.51 1.05 17.94 0.01
G x H2 Compound 82.22 1.00 0.55 1.01 20.95 0.00
Таблица 5. Содержание углерода и азота (%) в различных частях L. pyrotechnica в разных агроклиматических районах западного Раджастана. Table 5. Carbon and nitrogen content (%) in different part of L. pyrotechnica influenced by agro-climatic zone in western Rajasthan.
Agro-climatic Zone Aboveground (%) Root (%) C:N ratio
C N C N Stem Root
Arid Western plain 44.97 1.410 41.60 1.075 35.06 42.13
Transitional plain of inland drainage 45.19 0.510 43.057 0.677 90.73 64.20
Transitional plain of Luni basin 44.360 0.460 42.170 1.020 97.34 41.17
Discussion
Species population and diversity- The vegetation of this region is the most dry deciduous type and scrub indicating the dominance of shrubs species. Occurrence of L. pyrotechnica along with P. cineraria and Z. nummularia in all studied agro-climatic zone (throughout the desert) with varying soil conditions indicating its wide adaptability in the region, though P. cineraria and Z. nummularia area socially acceptable species. K. Nawal, N. Al-Amin, C.J. Stigter and A. El-Tayeb Mohammed (2006) during their study on survival and growth of different tree, shrubs and grasses including L. pyrotechnica in central Sudan, where the variation of soil conditions with depth on a small scale influenced the growth differences in Acacia tortilis and Prosopis juliflora, this difference in soil physical and chemical properties did not affect L. pyrotechnica, which performed better in final survival as compared to than A. tortlis. Study of S. Kumar and V. Shankar (1985) showed that the sprinkling of trees and shrubs in different grass cover areas in Indian Desert varies in composition and density, by and large, according to the soil texture and the relief (GoR, 2010). However, wide variability in population and diversity variables of shrubs and trees in different agro-climatic zone was due to climatic conditions but more importantly the soil characteristics and the availability of soil water and nutrients. In a study carried out in a part of Barmer district, frequency of occurrence of L. pyrotechnica varied from 19.2% to 64.3%, whereas abundance varied from 5.9 to 195.2 number per ha in different land uses like agriculture, community and forest lands, whereas frequency of occurrence of tree species was relatively less except for P. cineraria and T. undulata (Singh, 2008). Occurrence of A. nilotica, A. jacquemontii and Butea monosperma in TLB zone only was probably due greater rainfall and the conducive soil and climatic conditions, but occurrence of C. polygonoides, Capparis decidua, L. barbarum and M. emarginata in AWP zone only showed adaptability of these species to hard environmental conditions of aridisol. Highest population of trees in TID zones and those of shrubs in AWP zone suggested that shrubs had better adaptability to arid conditions as compared to the tree. This was also supported by less tree richness in AWP zone. Satyanarayan (1963) grouped the plant communities of central Luni basin into
five formations depending upon soil characteristics. However, lowest contribution in basal area by L. pyrotechnica in TLB indicated occurrence of other shrub species indicated by the highest species richness, species evenness and species diversity of shrubs in this zone. The highest basal area of trees and shrubs combined in TLB, despite of relatively less population was probably due to better growth of the growing vegetation. But the highest species richness of tree in TLB suggested that this zone have relatively better resource availability influencing growth of both tree and shrub species. S. Kumar (1996) found strong correlation of vegetation groupings with soil texture, moisture holding capacity but a low correlation with pH and electrical conductivity that suggested the possible importance of soil physical properties in affecting vegetation composition.
Growth variables and biomass of L. pyrotechnica. Growth and biomass production in arid region depends upon soil water though rainfall, which influenced nutrient availability for plant uptake. For example G. Singh (2004a, b) observed a reduction in growth and biomass production of A. tortilis and Calligonum polygnoides due to reduced soil water under competitive effects of Dactyloctenium sindicum grass that extracted and utilized soil water more efficiently. Relatively greater height and crown diameter of L. pyrotechnica in TLB zone was probably due to greater rainfall and probably soil water and nutrients influencing growth and biomass production. However, reduced growth variables of L. pyrotechnica in AWP zone was certainly due to aridity and less availability of soil water and nutrients but favoured increased number of tillers (the highest number of tiller in this zone). L. pyrotechnica exhibited longer and thicker roots in TLB zone to exploit available resource for enhanced biomass production and carbon accumulation. But, the smallest root diameter in AWP zone was due to water stress giving more emphasis on fine roots development in surface soil layer to exploit whatsoever soil resources are available. K.H. Batanouny and A.M. Abdel Wahab (1973) observed that the distribution of the roots and their branching in L. pyrotechnica is closely related to the availability of the soil moisture in the different strata, though this plant exhibits some characteristics (i.e., probably high concentrations of minerals/ solutes in root cells), which help it to keep its water balance positive through increased absorption.
The highest biomass for both above"ground and root in TLB zone than in the other zone was due relatively greater rainfall and soil water availability favouring growth and biomass production of L. pyrotechnica. Increased root biomass was to extract soil water to support growing aboveground biomass, but mild stress influenced root growth because of biomass partioning towards root resulting in greater root to shoot ratio. Relatively lesser root biomass in AWP was due to severe soil water stress in this zone and/ or due to fibrous root formation. The highest root to shoot ratio of L. protechnica plants in TLB zone might be due to climatic and edaphic conditions, though it varied on age of the plants also. Literatures suggests that tree under afforestation showed a progressive reduction in root to shoot ratio specially after canopy closure, where a steady increase in stem biomass contrast with biomass turnover of canopy and roots predominates in determining root to shoot ratio (Atwell et al., 1999). M.A. Bolinder, D.A. Angers, G. Bélanger, R. Michaud and M.R. Laverdière (2002) also observed variation in shoot to root ratio of forage crops due to locations and climatic conditions, but their results suggested that average shoot: root biomass of about 1.30 (values ranged from 1.01 to 1.72) in the first production year and 0.60 (values ranged from 0.43 to 0.87) in the second production year could be used as a first approximation to estimate the amount of root biomass left in the soil to a depth of 45 cm from forage crops in eastern Canada. Peichl, Arain (2007) also observed a decrease in toot to shoot biomass ratio from 0.32 in the 2-year-old stand to 0.24, 0.16, and 0.22 in the 15-, 30-, and 65-year-old stands of Pinus strobes L., respectively, and this decrease was during the first few decades after stand establishment.
Carbon and nitrogen concentration in L. pyrotechnica. Though plants maintain almost a constant concentration of carbon but relatively greater carbon concentration in TID zone was due to variations in uptake of other minerals influenced by their availability in soil. However, relatively greater carbon concentration in stem than in root was probably due to variation in tissue chemical composition and mineral accumulation. B. Didier and D. Frederic (2006) observed a large variation in the carbon concentration between compartments that showed a quadratic relationship with relative height in the four stem compartments and in branches and buds of Pinus pinaster but a negative exponential relation with root diameter. The carbon concentration variations were in accordance with the tissue chemical composition observed in literature and the weighted mean carbon concentration reached 53.6% in the shoots and 51.7% in the roots with an average value of 53.2% at tree level (Didier, Frederic, 2006). H. Poorter and P. Pothmann
(1992) observed variations in carbon concentration between the species and found that the carbon content per unit total plant dry weight was higher for Deschampsia flexuosa (L.) than for Holcus lanatus L. and the dry weight: fresh weight ratio of total biomass was also much higher for D. flexuosa, and this was associated with a higher dry matter percentage in both leaves, stem and roots. However, the variation in the carbon concentration in roots and above-ground biomass was probably due to the concentrations of other minerals. There were significant variations in nitrogen concentration in both stem and root between agro-climatic zones but the concentration is similar to the findings of T.S. Ksiksi, A. Elkeblawy, F. Al-Ansari and G. Alhadrami (2006), who analyzed a number of species for their fodder quality potential and Leptadenia pyrotechnica, Cyperus conglomeratus, Dipterygium glaucum and Pennisetum divisum were found better than other species and L. pyrotechnica showed about 6.1% of crude protein. However, variation in plant nitrogen content among different agro-climatic zones was probably depended upon soil availability of NH4-N and NO3-N and their uptake by the plants. B.W. Touchette, J.M. Burkholder and Jr.H.B. Glasgow (2003) observed that increased temperature promoted total carbon content of leaf tissue but increased nitrate concentration increased the nitrogen per cent in belowground tissue of Zostera marina L. and depressed the C/N ratio in aboveground tissues.
Conclusions
Dry conditions favoured population and basal area of shrubs as compared to tree species and the contribution of L. pyrotechnica to the total basal area was about 42.1%. The carbon and nitrogen contents were relatively greater in stem than in roots. Species richness was highest for tree, but species diversity, dominance and evenness were highest for shrubs. Variations in climatic and edaphic conditions influenced the population of tree and shrubs as well as growth of and carbon and nitrogen concentration in L. pyrotechnica plants. Relatively greater population and number of tillers in L. pyrotechnica plants in arid western plain and highest biomass in TLB zone suggested its wide adaptability and competitive utilization of resources and biomass production contributing to the carbon stock in the region. However, L. pyrotechnica showed compartmentalization in carbon and nitrogen accumulation probably an adapatation mechanism of this species in this arid environment. Conclusively, L. pyrotechnica has significant contribution in vegetation population, basal area, biomass production and carbon accumulation, but interesting greater biomass allocation to roots may be helpful in increasing soil carbon and stabilizing wind prone soil.
Acknowledgement. We express our sincere thank to the Director Arid Forest Research Institute, Jodhpur for providing facilities.
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