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21
АРИДНЫЕ ЭКОСИСТЕМЫ, 2015, том 21, № 2 (63), с. 72-82
——— ОТРАСЛЕВЫЕ ПРОБЛЕМЫ ОСВОЕНИЯ ЗАСУШЛИВЫХ ЗЕМЕЛЬ =====
УДК: 58.073
ОЦЕНКА ПОГЛОЩЕНИЯ И ЭФФЕКТИВНОСТИ ИСПОЛЬЗОВАНИЯ ФОСФОРА ПУСТЫННЫМ РАСТЕНИЕМ BLEPHARIS SINDICA (T. ANDRES.) ПРИ РАЗНЫХ ТИПАХ ПРОИЗРАСТАНИЯ
© 2015 г. Маниш Матур
Комиссия по управлению экосистемами МСОП Индия, 342008 Раджастхан, Джодхпур, 18E/564 CHB E-mail: ravi_mm2099@yahoo.com; eco5320@gmail.com
Поступила 03.01. 2014
Определено влияние характера произрастания (в моно- и поливидовых сообществах) на эффективность поглощения фосфора и дальнейшего его использования пустынным растением Blepharis sindica, находящимся под угрозой исчезновения. В моноценозах эффективность поглощения фосфора становится выше во время дождей, в поливидовых же сообществах она выше летом, когда дождей нет. Это говорит о том, что в моноценозах Blepharis sindica это растение быстро восполняет потребность в фосфоре при высокой его доступности из почв в период дождей. В смешанных сообществах исследуемый вид приспосабливается к условиям низкой доступности фосфора из почвы в то время, как остальные виды сообщества, вероятно, не имеют таких приспособлений. Ординационный анализ не выявил корреляции между эффективностью поглощения фосфора и эффективностью использования фосфора растением. Регрессионный анализ показал прямую зависимость доминирования Blepharis sindica от эффективности поглощения фосфора. Однако по мере возрастания видового разнообразия в сообществах использование фосфора тормозится. Можно сделать вывод, что эффективность использования фосфора видом Blepharis sindica существенно зависит от изменения видового состава - его увеличения во время дождливых и снижения во время засушливых периодов. Это растение достигает эффективного использования питательных веществ посредством временного взаимозамещения, что позволяет удовлетворить потребности растения в фосфоре в период его низкой доступности. Эффективность поглощения фосфора обнаруживает линейную зависимость от соотношения углерода и азота в почве. Сходным образом уровень pH почв влияет на эффективность поглощения фосфора, в то время как органический углерод снижает показатель использования фосфора в семенах растения. Наибольшее изъятие из почв минеральных веществ и эффективность изъятия в моноценозах Blepharis sindica отражает узкую экологическую нишу этого вида, а значит можно говорить о том, что влияние биоразнообразия сообществ на эффективность использования минеральных веществ из почв изменчиво. Ключевые слова: эффективность использования питательных веществ, экосистемный уровень, видовой уровень, ординация, видовое разнообразие растений и почвенных факторов.
Introduction
Vegetation structure in natural ecosystems is determined by both biotic factors (e.g., competition, facilitation, and predation) and abiotic ones (Hahs et al., 1999) although the effect of these factors depends on the habitats where plants grow. Usually environmental factors that impose restrictions on plant development (e.g., water stress, high temperatures, and salinity) play important roles in the vegetation structure (Interlandi et al., 2001). For instance, in arid environments, water availability and low levels of nutrients in soil are the main environmental factors affecting the development of plant communities and consequently plant abundance and productivity. Although low soil fertility plays an important role in the structure of plant communities in these habitats (Mathur, 2013).
It is generally hypothesized that a single plant species is unable to take full advantage of any environment, due to variables such as mineral and nutritional needs, root depth and metabolic by products. Monoculture practice in the same area for extended periods depletes resources required by that plant species while neglecting available resources other plant species can take advantage of. Perennial Polyculture is a relatively new model in farming practices that aims to reduce many of the ecological costs of farming by mimicking natural ecosystems. The idea behind a "reengineered ecosystem" is to decrease soil erosion by wind and water by providing year-round ground cover. The polyculture aspect of perennial polyculture means creating a diverse group of plants that are intermixed in the field. There are many skeptics of perennial polyculture as well. Some studies have found that, while perennial polyculture may seem a brilliant solution to agricultural dilemmas, over time, a dominant species emerges, essentially converting the field back to a monoculture system (Griffith, 2011). In this case, the cost of regulating the polyculture field outweighs any benefits gained. A.C.Gama-Rodrigues et al., (2007) have concluded that growth and yield in mixed-tree stands were higher than in pure stands owing to the combination of species with complementary eco-physiological attributes, consequently improving the efficiency in nutrient use and cycling.
Ecological theory suggests that species in a mixture may exploit resources of a site more completely and efficiently than a single species would be able to do, leading to greater overall productivity. Even though this has been observed in many situations, it is not always likely to happen. To achieve greater productivity in mixed stands, the species constituting the stands need to show differences in their requirements (niches) and the way they use site resources and (or) positively affect the growth of each other. This concept of niche separation implies that if two species are too similar in their requirements they would eventually compete intensely to exclude the other. The mixed stands may experience less intense interspecific than intraspecific light competition as a consequence of the differences in shade tolerance among species. Such a stratified canopy would, in theory, maximize the use of light because of increased light interception and light-use efficiency, leading to greater total productivity than in pure stands. This type of response has been found in studies by F. Montagnini et al., (2000), R. Man and V.J. Lieffers (1999).
A.J. Hiramath and J.J. Ewel (2001) have investigated the effects of monoculture and polycultutre types on ecosystem nutrient use efficiency. They have concluded that three species (Cedrela odorata, Cordia alliodora and Hyeronima alchorneoides) significantly influenced nutrient use efficiency by whole ecosystem in monoculture; while in polyculture the additional life form significantly increased nutrient uptake and uptake efficiencies. They demonstrate that ecosystem nutrient use efficiency is an outcome not only of the characteristics of the species or life forms that comprise the system but also of factors that affect soil nutrient supply.
Here the impact of stand types (monoculture and polyculture) on phosphorus acquisition efficiency and their subsequent internal utilization efficiency were determined at species level, in a seratonious arid endangered plant, Blepharis sindica. In this study, the hypothesis was that with in semi arid plant communities stand types influences nutrient dynamics of plants and have two directions and consequently two effects: first, it affects the nutrient uptake efficiency and secondly its utilization efficiency through their various bottom up and top down factors. To evaluate impact of stand types, present study was conducted with two objectives. (1) to determine the relative importance of P acquisitions and internal utilization in the P use efficiency and relative importance of P quotient of utilization and the P harvest index, in the P internal utilization efficiency at different spatial (pure and mixed stand) and during different pulse events and (2) to find out the relationship of different efficiency variables (P acquisition efficiency, P internal utilization efficiency, P use efficiency, quotient of P utilization and P harvest index) with bottom-up (species richness, Shannon and Weaver index, Simpson index, Evenness, Relative Importance value of Blepharis sindica, , percent cover of plant, seed output, root length root: shoot ratio and root collar diameter and top-down factors (soil organic carbon, soil nitrogen, moisture, C/N ratio soil pH and electric conductivity).
Material and methods
Two different stands types were selected within the 16 kilometre radius of Jodhpur city of Rajasthan state, India (table 1). Stands differed from each other in respect of soil composition, land uses, and community dynamics. During the study period mean annual precipitation ranges from 0.0224 to 260 mm, winter (January) temperature ranges from 10.7 to 230C while, mean summer (June) temperature ranges from 28.7 to 42.2oC. Relative humidity ranges from 31 to 91% (morning) and 08 to 68% (evening).
APHflHBIE ЭКОСHCTEМBI, 2015, tom 21, № 2 (63)
Table 1. GPS locations and habitat types of stands. Таблица 1. Положение точек наблюдений и типы местообитаний.
Stand Type. Coordinates Habitat types Soil Textures
N E Clay Silt Sand Gravel
Pure Stand 26g 12' 29.5'' 73g 04' 24.8'' Hummock undulating terrains 28.5 4.335 66.07 1.105
Mixed Stand 26g 15' 1.8'' 73g 59' 29.8'' Old alluvium plains 29.61 1.35 68.78 0.255
The above and belowground biomass of the B. sindica was estimated by collecting random samples. Ten plants were uprooted and gently washed under mild tap water. The plants were air-dried and weighed using an electronic balance (accuracy 0.001 g.). For evaluation of the impacts of pulse, inter-pulse and non-pulse events the sampling were carried out during July, (rainy season) December (cool season) and May (Hot season) as per the guidelines of resource pulse hypothesis (Goldberg and Novoplansky, 1997)
Phosphorus was estimated by spectroscopic method (Allen et al., 1976) based on the development of molybdenum blue color. The standard was prepared with KH2PO4.
Different nutrient efficiency indices were calculated following S.N. Parentoni and C.L. Junior-Souza (2008). Two groups of efficiency variables were obtained for each site in each pulse event. The first group comprised the variables P acquisition efficiency (PAE) and P internal utilization efficiency (PUTIL), which were used to obtain the P use efficiency (PUE). While, the second comprised of two variables, quotient of utilization and P harvest index
(1) Phosphorus Acquisition Efficiency (PAE)
Phosphorus ik Plaid
PAE =---
Phosphorus in soil
(2) Phosphorus Internal Utilization Efficiency (PUTIL)
PUTIL =
Phosphorus in Plant
(3) Phosphorus Use Efficiency (PUE)
PAE X PUTIL
(4) Quotient of Phosphorus Utilization (QUTIL)
_ Seed Biomass
Phosphorus in Seed
(5) Phosphorus Harvest Index
Pbosphorus In Seed PHI = ——--——
Phcspnon,s in Plant
The relative importance of PAE and PUTIL over PUE was investigated according to R.H. Moll et al., (1982). This information would be valuable to utilize weight for each of two variables (PAE and PUTIL) that to be used in selection program related with P use efficiency. The same also exercised for two variables related with P internal utilization efficiency and PHI
The analysis of variance (ANOVA) was carried out in a two way strip - plot design, which sacrifices precision on the main effects of both factors. The interaction is measured more accurately by this method compared to randomized complete block or a split-plot design (Gomez and Gomez, 1984).
Bartlett's test of sphericity and Kaiser-Meyer-Olkin (KMO) were carried out to assess the suitability of factor analysis. Principal Component Analysis (PCA) was carried out as a data reduction technique. PCA was performed with Pearson correlation coefficient. The main objective of PCA was to find out the relationship of different efficiency variables (P acquisition efficiency, P internal utilization efficiency, P use efficiency, quotient of P utilization and P harvest index) with bottom-up (species richness, Relative Importance value of B. sindica, diversity parameters, percent cover of plant, seed output, root length and root collar diameter) and top-down factors (Soil organic carbon, soil nitrogen, moisture, soil pH and electric conductivity). Appropriate regression equations were selected on the basis of probability level significance and high R2 value. Path analysis was carried out with Curve Expert software.
Results and discussion
Canopy seed banks are formed when mature seeds are retained in the canopy due to delayed seed release (serotiny). In general the retention of seeds in the plant canopy for one to 30 years or more is termed as serotiny. It is common in fluctuating environments such as dry, fire-prone scrubs and forests (Peters et al., 2009). Plants are either non-serotinous, weakly serotinous (most seeds released within a few years) or strongly serotinous (most seeds still retained after a few years). Serotiny is derived from the Latin word serotinus meaning late in occurrence and with this strategy mature seed released after a specific period of time and conditions, resulting in the build-up of a canopy stored seed bank. This evolutionary tendency of this endangered arid plant has yet not been correlated and explored with stand types, bottom-up and top-down factors.
Pure stand was located on hummocky undulating terrains while the mixed stand was located on older alluvial plain with other associates like Dactyloctenium aegyptium, Eragrostis ciliaris, Aristida funiculata, grasses that represent the sub-climax stage of habitats. Various parameters (plant parameters, edhapic factors and community dynamics) at B. sindica location during study period are presented in table 2. Coefficient of variance of biomass revealed higher biomass during non- pulse event followed by pulse and lesser during inter-pulse event (figure 1). The greatest P concentration was reordered from seed collected from mixed stand during the non- pulse event. In the present investigation, the analysis of variance revealed that all the factors undertaken in the present investigation (i.e., site, seasons, and plant parts and the interactions between them caused P to vary at the 99% probability level (table 3).
Table 2. Various parameters at B. sindica locations during study period. Таблица 2. Различные параметры биотопов в течение периода исследований.
Parameters Range
Plant Variable Percent Cover of Blepharis sindica (Sa. m) 0.3-2.55
Total Seed Output 866-7576
Root/Shoot Ratio 0.144-0.581
Root Length (Cm) 6.73-24.7
Root Collar Diameter (Cm) 0.3-0.85
Soil Compositions Organic Carbon (mg 100g1) 62.86-203.5
Total Nitrogen (mg 100g1) 34.38-82.49
C/N Ratio 0.36-5.91
Moisture 0.48-11.38
pH 6.23-8.56
Electric Conductivity 0.11-0.23
Community Composition (1X1 m) quadrate Richness 2-10
Shannon Weaver Index (H') 0.65-2.1
Relative Importance Value of B. sindica 16.27-62
Evenness 0.85-1.01
Simpson Index 0.13-0.53
At pure stand phosphorus acquisition efficiency (PAE) was recorded higher during pulse event while at mixed stand it was recorded more during non-pulse event (table 4). This indicates that at pure stand this plant rapidly acquired their P demand during high soil P availability (pulse event), but at mixed stand due to presence of other life forms this plant have adjusted their P acquisition efficiency during non-pulse (low soil P), when other associate probably not able to do this. PUTIL, which exhibits the relationships between seed dry matter productions with relation to P in plant, exhibits higher at pure stand compared to mixed stand during all temporal events (table 4). Thus, at a dominate situation, compared to other modules, this species invests its resources more in reproductive part.
PUE was also revealed the similar trends, recorded higher at pure stand compared to mixed stand. In term of pulse events at both stand types higher PUE was recorded during non-pulse event. Thus at both stand types this plant became more P efficient during low P environment. QUTIL, ratio of seed biomass and the P content in seed, recorded higher at pure stand compared to mixed stand. However, looking the data according to pulse event, seed biomass to P in plant recorded more during moderate P condition (inter-pulse event) followed by non-pulse event (low soil P condition). Compare to other P variables seed P to Plant P ratio (Phosphorus Harvest Index), recorded higher at mixed stand. Thus seed from mixed stand contains higher P.
This results supported by the fact that seed P is the only P source during germination which subsequently support the establishment of seedling in community. Among the different events PHI observed higher during low resource condition.
10 9 8 7 б 5 4 3 2 1 0
Pulse Inter-pulse Non-pulse Monoculture
Pulse Inter-pulse Non-pulse Polyculture
Fig. 1. Coefficient of variance of biomass at various stands during different temporal events. Рис. 1. Коэффициент вариации биомассы в различных сообществах при разных временных событиях.
Analysis of variance revealed that all the factors taken in the present study (i.e., site, event, and the interactions between them) caused PAE, PUTIL, PUE, QUTIL and PHI to vary at the 99% probability level (table 5).
Table 3. Range of Phosphorus (mg g"1) in various modules of B. sindica. Таблица 3. Фосфор в мг/г в различных частях растения B. Sindica.
Modules Range Modules with higher
Root 0.73-2.80 Seed/II/Non-pulse event
Stem 1.б-7.3б
Leaves 8.77-9.95
Seed 15.08-55.59
ANOVA results/Source of Mean squares Computed F Value
Stand Tvoe 7978 26.63*
Seasonal Event 8714 12.95*
Stand Tvüe x Seasonal Event 338б 14.99*
Plant Part 71.5E+07 249.89**
Stand Tvoe x Plant Part 2110 7.37**
Seasonal Event x Plant Part 3783 13.21**
Stand Tvoe x Season x Plant 1307 4.56**
**P < 0.01; * <0.05.
Results indicates that with the set of different temporal and spatial impacts, for phosphorus use efficiency, PAE was 1.41-16.21 fold more important than PUTIL, at low soil P environment (non-pulse events) and 2-16 and 0.19-3.14 fold more during moderate (inter-pulse) and high P environment (pulse event), respectively. Similarly, related importance of QUTIL and PHI in PUTIL indicates that QUTIL was 7.64-11.95 times more important than PHI at low soil P environment, 2.58-2.99 fold higher during high soil P (Pulse) condition.
Result of Kaiser-Meyer-Olkin (KMO) and Bartlett's test of sphericity are presented in table 6. The Kaiser-Meyer-Olkin (KMO) measure of sampling adequacy is an index used to examine the appropriateness of factor analysis. A high value (between 0.5 and 1.0) indicates factor is appropriate, value below 0.5 imply that factor analysis may not be appropriate. In our study KMO is 0.612, therefore we can proceed with our factor analysis. For Bartlett's test of sphericity there are two levels to interpret this test (a) H0: There is no correlation significantly different from 0 between the variables and Ha: at least one of the correlations between the variables is significantly different from 0. As the computed p-value is lower than the
significance level = 0.05, one should reject the null hypothesis H0 and accept the alternate. In other words we can conclude that there are significant relationships between our variables.
Table 4. Different Phosphorus variables at pure and mixed stand during various pulse events. Таблица 4. Фосфор в условиях чистого и смешанного произрастания при разных событиях.
Variables Stand 1 Stand 2
Pure Stand Mixed Stand
Pulse Inter-pulse Non-Pulse Pulse Inter-pulse Non-Pulse
PAE 0.13 0.04 0.11 0.31 0.13 0.42
PUTIL 4.05 16.04 16.32 0.40 2.60 1.81
PUA 0.52 0.66 1.76 0.13 0.33 0.76
QUTIL 1.10 3.70 1.74 0.13 0.29 0.15
PHI 3.68 4.34 9.38 3.12 9.03 12.10
Table 5. ANOVA Analysis of Different Phosphorus Variables. Таблица 5. ANOVA анализ фосфора при разных переменных.
P Variables ANOVA Stand Type Seasonal Stand Type X Seasonal
PAE Sum of Square 0.177 0.102 3.96
Computed F Value 8226.5** 4065.13** 1052.58**
PUTIL Sum of Square 501.91 196.32 108.13
Computed F Value 88423.7** 20685.58** 25677.52**
PUE Sum of Square 1.47 2.92 0.41
Computed F Value 16852.99** 7882.09** 436.26**
QUTIL Sum of Square 17.64 5.21 4.3
Computed F Value 18579.31** 388.58** 466.87**
PHI Sum of Square 26.10 3.21 5.76
Computed F Value 5279.82** 10425.56** 751.38**
**=P<0.01 level
Table 6. Bartlett's sphericity and Kaiser-Meyer-Olkin sampling adequacy tests. Таблица 6. Тесты Bartlett's сферичности и Kaiser-Meyer-Olkin.
Test Values
Chi-square (Critical value) 244.8
DF 210
p-value 0.09
Alpha 0.05
KMO 0.612
The PCA analysis was performed with the use of Pearson correlation coefficient, and the results are presented in figure 2. Squared cosines were used to link the variable with the corresponding axis; the greater the squared cosine, the greater the link with the corresponding axis. PCA were considered (table 7 and fig. 2) useful if their cumulative percentage of variance approached 80% (Mathur, 2013).
Table 7. Value analysis and other attributes obtained from Principal Component Analysis. Таблица 7. Eigen анализ и другие атрибуты, полученные из анализа главных компонент.
Characteristics F1 F2 F3 F4
Eigen value 10.640 5.581 1.971 1.681
Variability (%) 50.669 26.577 9.386 8.007
Cumulative % 50.669 77.246 86.632 94.639
In present investigation cumulative percentage indicates that first four axes together accounted 94.63% for variability in the data set (table 4) with their individual contribution being 50.66%, 26.57%, 9.3%, and 8.00%, respectively. From present study correlation circle (fig. 2), revealed that PUTIL related with PUE (r = 0.696**) and with QUTIL (r = 0.876**; P<0.01). No correlation was found between PAE and PUTIL, which indicates that these two variables are independent. Lack of correlation between nitrogen acquisition and nitrogen internal utilization efficiency has also been reported in wheat and in triticale by previous researchers. S.N. Parentoni and C.L. Junior-Souza (2008) have also reported the similar results for 24 genotypes of Maize.
Fig. 2. Bi-Plot of Principal Component Analysis. Рис.2. Ординация значений, полученная методом главных компонент.
In present study the lack of correlation between P acquisition and P utilization efficiency indicates that selection of one of these should not affect the other, which would facilitate simultaneous selection of these traits, in the set of environmental studies. The main selection criteria for P internal utilization efficiency should be toward reducing the seed P concentration (inverse of the quotient of utilization) and in this case a negative weight should be used in the selection of species for ecosystem stability. Since seed of this plant largely consumed for its aphrodisiac properties, hence reduction in seed P concentration would have a positive impact on nutrition. Since seed P is stores as the anti-nutritional factor phytate; and it would also reduce environmental pollution from higher P manures produced by large animal feeding lots. However the strategy of reducing seed P concentration should have a limit, since seed P is needed for its germination and initial establishment (Philip and Veneklaas, 2012).
Path Analysis. Total seed output favours the P internal utilization efficiency (PUTIL = 24933301e-005 Total Seed out PutA1.479, R2 =0.880*, ±3.88, fig. 3A) in power fashion. Percent cover of plant exponentially favours the PUE (PUE = 0.3875e (0.5922 Percent Cover), R2 = 0.911*, ±0.26, fig.3B). On the other hand PUE monotonically decrease with root length (PUE= 3.433+-0.297 Root Length+0.0070 Root Length 2, R2 =0.944**, ±0.242, fig.3C) and with root collar diameter (PUE = 3.986+-9.79+Root Collar Diameter+6.667 Root Collar Diameter 2, R2 = 0.853*, ±0.383, fig.3D). Thus, PUE which is the ratio of seed biomass to P in soil shows positive relative with percent cover of plant, while it's negatively related with root length and root collar diameter. Such results indicated that this plant achieved their essential P requirement
with surface soil P and as its root length and its collar diameter increases the accessibility of soil P also increases, which ultimately held back its PUE. These results are with-in the agreement of findings of J.P. Hammond et al., (2009).
S = 3.88009507 r= 0.88000911
195.0 1 537.0 2879.0 4221.0 5563.0 6905.0 8247.0 Total Seed Out Put
A
0.1 0.5
1.0 1.4 1.9
Percent Cover
S = 0.26258093 r = 0.91111716
2.3 2.8
B
S = 0.24249495 r= 0.94411125
12.1 15.7 19.3
Root Length
C
0.2 0.4
S = 0.38339441 r = 0.85346283
0.5 0.6 0.7 0.8 0.9
Root Collar Diameter
D
11.7 20.9
S = 0.28059338 r= 0.89779195
30.0 39.1 48.3
RIV of B. sindica
57.4 66.6
E
S = 4.85436623 r = 0.85742672
4.4 6.0 7.6 9.2 10.8
Richness |
S = 0.15321850 r= 0.97065112
G
S = 0.21271215 r = 0.94261795
0.5 0.8 1.1 1.4 1.7 2.0 2.2
Shannon and Wiener Index
H
Fig. 3. Path analysis with various bottom up and top down factors. Рис. 3. Анализ связи факторов.
S = 0.16748825 r = 0.96482586
S = 0.04505592 r = 0.96110878
0.3
Simpson Index
S = 0.03651491 r = 0.97463096
K
S = 0.83964421 r= 0.88315090
48.8 76.9 105.1 133.2 161.3 189.4 217.6
Soil Organic Carbon
Продолжение рис 3.
M
48.8 76.9 105.1 133.2 161.3 189.4 217.6
Soil Organic Carbon
S = 0.03522109 r = 0.98236675
6.9 7.4 7.9
Soil pH
Relative Importance Value (RIV) of B. sindica shows a positive exponential relationships with PUE (PUA = 0.1692e (0.0373 RIV of B. sindica), R2 = 0.897*, ±0.280, fig.3E). Community richness exhibits negative relation with PUTIL (PUTIL = 28.070+-5.766+0.299 Richness, R2 = 0.857*, ±4.85, fig.3F) and with PUE (PUE = 4.085 RichnessA-1.217, R2 = 0.970**, ±0.153, fig.3G) in polynomial and in power fashions, respectively. Shannon and Wiener index shows negative linear relations with PUE (PUE = 2.269+1.0628 Shannon and Wiener Index, R2 = 0.942**, ±0.212, fig.3H). In contrast Simpson index (measure of dominance) shows positive linear relation with PUE (PUE = -0.3122+3.8166 Simpson Index, R2 = 0.964**, ±0.167, fig.3I).
Thus it can be concluded that at species level, dominance (RIV of B. sindica and Simpson index) of this plant reflects with its higher phosphorus acquisition efficiency, however, as the community diversity (richness and Shannon and Weaver index) increases the phosphorus internal utilization and phosphorus use efficiency inhibited. Thus both P internal utilization and PUE of B. sindica are largely influenced with temporal factors (increase and decrease of community diversity during pulse and non-pulse events, respectively) and it also indicate the adjustments made by this species for their PUE and PUTIL according to their resources availability. Thus B. sindica achieved their effective nutrient use through temporal partitioning, through which it full-fill their P requirements at low resource availability (non-pulse event) and that ultimately reflect through its dominance (RIV) in community. Identification of such plants are very
L
crucial for habitat stability, especially in rehabilitation programmes and this can be supported by the finding of S.E. Wortman et al., (2012).
Both soil organic carbon and soil carbon to nitrogen ratio supports PAE in linear fashions (PAE = -0.122+0.0024 Soil Organic Carbon, R2 = 0.961**, ±0.045, fig.3J); (PAE = 0.0216+0.061 C/N Ratio, R2 = 0.976**, ±0.036, fig.3K). Soil pH also monotonically supports the PAE (PAE = -8.47+2.269+-0.145 Soil pH, R2 = 0.982**, ±0.035, fig.3L). On the other hand soil organic carbon monotonically inhibits QUTIL (QUTIL = 8.4052+-0.1023 Soil Organic Carbon+0.00030 Soil Organic Carbon, R2= 0.883*, ±0.839, fig.3M). Both soil moisture and soil pH recorded higher during the pulse event and that also related with bioavailability with soil P. During the high resource availability (pulse event) this species invests more P in seed compared to other plant modules. These results are within the agreement of study made by T.S. George et al., (2005). The enhancement of organic carbon and C/N uptake, it is obvious that the growth of plant and their above and belowground biomass may increase. Due to enhancement of plant growth the P requirement of the plant expected to increase further. It may be the reason to get more PAE to meet the plant requirement when organic carbon and C/N ratio availability and uptake of plant enhances. These finding are supports with the results of T. Ertli et al., (2004) and J. Gao et al. (2009) they reported higher relation of PUTIL and PUE with soil N in two different lines of cow pea.
Conclusion
The relative differences in plant level nutrient use efficiency of a key stone species also translate into the patterns of productivity observed in monoculture supporting the idea that higher plant level nutrient use efficiency signals a narrow niche width and greater tolerance of reduced nutrient availability. Productivity of B. sindica in polyculture dropped compared to monoculture, signalling belowground competition with other associates. Given the links between plant- and ecosystem level nutrient use efficiencies, it was observed that the B. sindica dominated system having the highest nutrient use efficiency, but the pattern did not hold for the polyculture, where the presence of the additional life forms suppress the NUE of this plant. Anticipating complementary differences in modes of accessing nutrient by different life forms, it was predicted that the mixed stand would have greater nutrient uptake and uptake efficiency than monocultures. Although this was not reflected in a present study. The greater nutrient uptake and uptake efficiency in a pure stand reflects its narrow niche width hence it can be conclude that the impact of life-form diversity on nutrient use efficiency is not a static phenomenon.
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ASSESSMENT OF PHOSPHORUS ACQUISITION AND INTERNAL UTILIZATION EFFICIENCY BY DESERT PLANT BLEPHARIS SINDICA (T. ANDRES.)
IN DIFFERENT TYPES OF STANDS
© 2015. Manish Mathur
Commission on Ecosystem Management, IUCN CAZRI, Jodhpur, 342008, Rajasthan, India E-mail: ravi_mm2099@yahoo.com; eco5320@gmail.com
Impact of stand types (monoculture and polyculture) on phosphorus acquisition efficiency and their subsequent internal utilization efficiency were determined at species level, in a seratonious arid endangered plant, Blepharis sindica. At pure stand phosphorus acquisition efficiency (PAE) was recorded higher during pulse event (rain) while at mixed stand it was recorded more during non-pulse event (summer). This indicates that at pure stand this plant rapidly full-fill their P demand during high soil P availability (pulse event), but at mixed stand due to presence of other life forms this plant have adjusted their P acquisition efficiency during non-pulse (low soil P), when other associate probably not able to do this. Ordination analysis shows lack of correlation between PAE and PUTIL, indicates that selection of one of these should not affect the other. Regression analysis between P variables and community factors revealed that at species level dominance of B. sindica reflects with its higher P acquisition efficiency; however as the community diversity (Richness, Shannon and Weaver index and evenness) increases the P internal utilization and PUE were inhibited. Thus it can be concluded that both P internal utilization and PUE of B. sindica are largely influenced with temporal factors (Increase and decrease of community diversity during pulse and non-pulse events, respectively). This plant achieved their effective nutrient use through temporal partitioning, through which it full-fill their P requirements during low resource availability (non-pulse event). Both soil organic carbon and carbon to nitrogen ratio supports PAE in linear fashions. Similarly soil pH also monotonically supports PAE, while soil organic carbon monotonically inhibits QUTIL. The greater nutrient uptake and uptake efficiency in a pure stand reflects narrow niche width of B. sindica and hence it can be conclude that the impact of life-form diversity on nutrient use efficiency is not a static phenomenon. Keywords: nutrient use efficiency, ecosystem level, species level, ordination, species diversity, plant and soil factors.
