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Impact of Land Use Practices on Faunal Abundance,Nutrient Dynamics and Biochemical Properties ofDesert PedoecosystemG. Tripathi & B.M. SharmaVersion of record first published: 11 May 2010.

To cite this article: G. Tripathi & B.M. Sharma (2005): Impact of Land Use Practices on Faunal Abundance, NutrientDynamics and Biochemical Properties of Desert Pedoecosystem, Environmental Technology, 26:11, 1205-1216

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Environmental Technology, Vol. 26. pp 1205-1215© Selper Ltd., 2005

IMPACT OF LAND USE PRACTICES ON FAUNALABUNDANCE, NUTRIENT DYNAMICS AND

BIOCHEMICAL PROPERTIES OF DESERTPEDOECOSYSTEM

G. TRIPATHI* AND B.M. SHARMA

Department of Zoology, J.N.V. University, Jodhpur-342 001 India

(Received 22 January 2005 ; Accepted 28 April 2005)

ABSTRACT

Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desertagroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties andprocesses in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics andbiochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphusmauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in differentcombinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showedsignificant changes with respect to different land use practices and tree species, indicating a strong relation between aboveand below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z.mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture,organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity weregreater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and moreutilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increasein microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best wintercrop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organiccarbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soilfauna in fertility building. This suggests that strategies may be developed for nurturing fertility-building soil fauna andmanaging degraded pedoecosystem in desert just by adopting suitable agricultural practices.

Keywords: Fauna, soil nutrients, soil respiration, soil dehydrogenase, agrisilviculture

INTRODUCTION

Soil biota constitute the driving force of most terrestrialecosystems as they control the rates of turnover andmineralization of organic substrates [1,2,3,4,5,6]. They areaffected with agricultural practices which leads to changes inthe soil physicochemical environment [7,8,9,10]. Some studieshave shown the importance of the soil fauna as a regulator innutrient cycling [11,12,13]. The qualitative composition andseasonal abundance of soil fauna and their relationship withsoil temperature and moisture have been worked out [14,15].Knoepp [16] studied the biological indices of soil quality andfound microarthropods as soil biological indicators. Despitesubstantial studies in this direction, the reports on desert-inhabiting soil fauna are very limited [17,18].

The flow of energy and cycling of nutrients in soil maybe accelerated by soil fauna [19]. Therefore, for a sustainedland productivity and environmental conservation, we mustunderstand the relation between above and below groundbiota with soil nutrients because land use system and fauna

activities are interrelated [20]. Though it is very challenging tomanage tropical soils over the long term, some studies havebeen carried out in Africa, Asia and Latin America todetermine ways in which they can be most effectivelymanaged [21]. However, these studies are mainly confined tophysicochemical properties of soil. Changes in agrisilviculturesystem may alter activities of soil organisms and influencesoil nutrient dynamics but no attempt has been made to singleout the cause-effect relationship in desert pedoecosystem. Itappears important to know how to manage organic resources,when and how to conserve the soil biota to maintain essentialsoil properties and how to access the resilience of the soilprocess to environmental changes [22]. People of desertregions have adopted agrisilviculture practices as a strategyto fulfill their food and fodder requirements. Singh et al. [23]reported soil fertility building characteristics of trees and theirsymbiotic effects for increasing productivity of associatedvegetation and agricultural crop. In retrospection of the aboveview, we consider soil fauna are as bioengineers directly orindirectly regulating soil nutrient dynamics. Therefore, it may

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be of a warranted interest to study the interaction of aboveand below ground biodiversity to modify soil fertility.

Recently, there has been increased interest regardingthe role of beneficial fauna in enhancing soil productivity[10,24]. Opportunities have been explored to matchbiodiversity and abundance of soil invertebrates witheconomically and socially acceptable agricultural practices[25]. Plant cover builds up a large root biomass, which alongwith the litter dropped from the above ground parts, providefood for soil arthropods [26,27]. Specific crop types withdifferential nitrogen content may influence the dominance ofdifferent species of soil arthropods [28]. The agrisilviculturevarieties with different kinds of leaves and their constituentsmay promote different faunal diversity and density. Hencethe hypothesis was that agrisilviculture practices and faunalbiodiversity might influence each other to improve soil healthon a self regulating and sustainable basis. Soil biologicalprocesses are of crucial importance in the desert because soilis nutrient deficient with a very little possibility of extraorganic inputs. Therefore, the specific objective was to analyzeland use system-dependent changes in densities of differentgroups of soil fauna (Acari, Myriapoda, Coleoptera,Collembola, other arthropods, total fauna), soil nutrients(NO3-N, NH4-N, PO4-P) and biochemical characteristics (soilrespiration and dehydrogenase activity) of desertpedoecosystem. Changes in soil nutrients, soil respirationsand soil dehydrogenase activities as a function ofagrisilviculture practices were correlated to elucidate afunctional relationship between faunal biodiversity and soilhealth in desert pedoecosystem. This will help inimprovement and conservation of soil productivity just bybioresource management.

MATERIALS AND METHODS

Location and Site Conditions

The study sites were tree integrated agriculture landcovering an area of about 10km2. It was located in Bilaravillage of Bilara Tehsil of Jodhpur district (260 45´ Northlatitude and 720 03´ East longitude) in northwestern dryregion of India. The climate of the study area is dry tropicaltype characterized by extremes of temperature, fitful anduncertain rainfall, high potential evapotranspiration andstrong winds. The study was performed in winter seasonwhich extends from October to February. Minimumtemperature during peak winter period remains 40C andoccasionally drops to 20C. The diurnal temperature variationsare high. Potential evapotranspiration was exceedingly higherthan the precipitation resulting in perceptual water deficitthroughout the year.

Systems and Sample Collection

The selected trees were Zizyphus mauritiana, Prosopiscineraria and Acacia nilotica. The cropping systems with these

trees were Cuminum cyminum, Brassica n igra or Triticumaestivum. The faunal collections were also done from adjacentopen (uncovered) field in order to see the impact of tree aloneon soil fauna. The frequency of irrigation was equal in allfields and no fertilizers and pesticides were used in thecropping systems. Studies were done in the winter season(October to February) of the year 2001 and 2002. Samplingswere done by quadrat method by marking randomly 5 siteseach of 1m2 in a field of one acre. Samples were collected fromfive subsites each of 25x25cm from a marked site of 1m2.Average data of five subsites (25x25cm) were taken forconverting the faunal population per square metre. The valuerecorded for one metre square was considered as observationfor one replication. Five such replications were taken for theobservations of one acre area. A total 375 sample collectionswere collected from different land use systems of Jodhpurdistrict of Rajasthan.

Faunal Extraction and Tree Facilitation

The soil samples were collected and brought to thelaboratory in polybags having a label of date of collection,habitat, place name, vegetation etc. These samples wereprocessed for extraction of soil fauna by Tullgren funnel.Fauna were allowed to move down into the funnel for 24hours. They were collected in vials containing 70% alcohol.Different groups of soil arthropods were sorted out by nakedeye and under stereoscopic microscope. The sortedspecimens were preserved in 70% alcohol for identification.The effect of tree on soil faunal population was obtainedthrough a relative tree effect (RTE) calculation similar to themethod of Markham and Chanway [29] for relative neighboureffect. RTE = (Xt -Xc)/x where, x was the population of targetsoil arthropod groups in absence (t) and presence (c) of treeand x was the higher of Xt or Xc. Negative values of RTEindicated beneficial and positive values negative effects.

Physicochemical Measurements

Soil thermometer was used to measure the soiltemperature at 10cm depth [30]. Soil temperature of eachstudied sites were recorded at the time of sampling. Soilmoisture content was determined gravimetrically by ovendrying at 1050C until the weight stabilized. The procedure formeasurement of soil moisture content was adopted from theMethods of Soil Analysis [31]. Soil samples were air dried andpassed to a 2mm mesh sieve and subjected to variouschemical analyses. Soil pH was determined in 1:2 soil waterratio with the help of a pH meter [32]. Organic carbon wasdetermined by the partial oxidation method [33]. Theprinciples adopted for estimation of nitrate-nitrogen (NO3-N)and ammoniacal-nitrogen (NH4-N), and extractablephosphorus were mainly based on the methods described byAnderson and Ingram [34]. An autoanalyzer (Tecator ModelEnviroflow-5012) was used to determine these soil nutrients.

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Biochemical Estimations

Soil respiration was measured using 0.1M KOHsolution that absorbs CO2. This solution was exposed to CO2

evolving from soil. It was then titrated with standardized0.1M HCl after addition of saturated BaCl2 solution.Absorbed CO2 was calculated by taking 1ml of 0.1M HClequivalent to 2.2mg CO2. This was measured according to themethod of Anderson [35]. Soil dehydrogenase activity wasassayed as described by Singh et al [36]. One gram of air-driedsoil was kept in an air-tight screw capped test tube. 0.2ml of3% TTC (triphenyl tetrazolium chloride) solution was addedin each of the tubes to saturate the soil. Then 0.5ml of 1%glucose solution was added in each tube. The bottom of thetube was gently tapped to drive out all trapped oxygen and

the water seal formed above the soil. The tube was incubatedat 28 +0.50C for 24 hours. After incubation, 10ml of methanolwas added and shaken vigorously. Then it was allowed tostand for 6 hours. The clear pink coloured supernatant wasdecanted and its absorbance was measured at a wave lengthof 480nm in a spectrophotometer.

RESULTS

Effect on Faunal Population

The population of Acari, Myriapoda, Coleoptera,Collembola, other arthropods and total fauna changedsignificantly (P<0.001 to <0.05) due to changes in tree speciesduring winter season (Fig.1). Similarly, variations in these

Figure 1. Effect of land use system and tree species on populations of different groups of soil fauna. O : Open field; T : Treealone, Cc : Cuminum cyminum; Bn : Brassica nigra and Ta : Triticum aestivum. Bars with different letters aresignificantly different. Tree species : Zizyphus mauritiana; Prosopis cineraria and Acacia nilotica.

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faunal groups were found significant (P<0.001 to <0.05) withrespect to changes in land use systems (i.e., tree plus cropfield). However, the interaction between tree species and landuse systems was insignificant (P>0.05) except in the case ofCollembola and total fauna (P<0.05). Maximum populationdensity of different soil faunal groups was in Z. mauritianaand minimum in A. nilotica based agrisilviculture systems. Allgroups of soil fauna (Acari, Myriapoda, Coleoptera,Collembola, other arthropods and total fauna) had a

significant positive correlation (r = 0.390 to 0.957, P<0.001 to<0.05) with each other except between other arthropods withMyriapoda (r = 0.189, P>0.05) and Collembola (r = 0.181,P>0.05).

Relative Tree Effect (RTE)

RTE values were most negative in Z. mauritiana for allgroups of soil arthropods (Fig. 2).

Figure 2. Relative tree effect (RTE) of different soil arthropods population in various agrisilviculture systems. Error bars are±SEM. Tree species : Zizyphus mauritiana; Prosopis cineraria and Acacia nilotica.

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However, least negative values of RTE were observed in A.nilotica. The order of highest negative value to lowest negativebased system was Z. mauritiana> P. cineraria> A. nilotica Valueof RTE for different. The soil arthropod groups can be gradedas Coleoptera> Acari> Collembola> other soil arthropods>Myriapoda in term of greatest to lowest RTE values for all treesystems. It means Coleoptera have greatest association withdifferent tree based agrisilviculture systems. The observationsalso indicated the highest facilitative effect of Z. mauritianasystem in desert.

Effect on Physicochemical Properties

Variations in soil temperature, moisture and pH andland use systems due to tree species were significant(P<0.001) but the interaction between tree species and landuse systems was insignificant (P>0.05) (Fig. 3). The reductionin soil temperature under the canopy of tree was 19 to 24%when compared with the temperature of uncovered area.Whereas changes in land use systems decreased soiltemperature by 7-22% in most of the cases as compared to

Figure 3. Effect of land use system and tree species on physical properties of soil. : Open field; Cc : Cuminum cyminum; Bn :Brassica nigra and Ta : Triticum aestivum. Bars with different letters are significantly different. Tree species : Zizyphusmauritiana; Prosopis cineraria and Acacia nilotica.

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open field. Cultivation of different crops increasedsoil temperature which may be due to more utilization ofwater than tree field alone. In P. cineraria field, cultivation ofC. cyminum caused a greater reduction in soil temperaturethan those of B. nigra and T. aestivum. The changes in land usesystem caused 1.8 to 7.1 fold increase in soil moisture ascompared to open field. The increase in moisture content wasmaximum (7.1 fold) in P. cineraria with C. cyminum andminimum (1.8 fold) in A. nilotica having T. aestivum soilsystem. It reflects low water utilization in T. aestivum cropthan that of C. cyminum and B. nigra. The reduction in soil pH

was 4.5% under the canopy of tree than that of uncoveredarea. Cropping system caused 1.5% reduction in pH ascompared to tree alone. Reduction in soil pH might be due toleaf litter decomposition under covered area. The gradation ofsoil temperature and pH in most of the tree fields was A.nilotica> P. cineraria> Z. mauritiana.

Organic carbon, nitrate-nitrogen, ammoniacal-nitrogen,available phosphorus changed significantly (P<0.001 to 0.05)with respect to changes in most of the tree species and landuse systems (Fig. 4). The interaction between tree species andland use system was significant (P<0.001) for organic carbon.

Figure 4. Effect of land use system and tree species on chemical and biological properties of soil. : Open field; Cc :Cuminum cyminum; Bn : Brassica nigra and Ta : Triticum aestivum. Bars with different letters are significantly different.Tree species : Zizyphus mauritiana; Prosopis cineraria and Acacia nilotica.

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However, it was not significant for available soil nutrients.There was 3 to 4.7 fold increase in organic carbon under thecanopy of tree only than that of uncovered area. Whereasthese contents increased by 1.2 to 4.2 fold in different land usesystems as compared to the adjacent open field. Higherorganic carbon content in soil of P. cineraria field havingagricultural crops was due to availability of leaf litter fordecomposition. Nitrate-nitrogen increased by 7.5 to 8.8 foldunder the canopy of tree alone than that of open field. Thecropping land use practices increased 1.6 to 6.7 fold nitrate-nitrogen content of soil as compared to uncovered land.Slightly lower nitrate-nitrogen content in cultivated land wasdue to utilization of nitrate for plant growth. The cultivationof crops in A. nilotica based agroforestry system had highernitrate-nitrogen in soil as compared to other tree-cropgeometry. Thus A. nilotica crop-interaction was helpful inimproving soil fertility. Cultivation of C. cyminum was foundto be better in conserving soil nitrate-nitrogen than B. nigraand T. aestivum. There was 4.5 to 5.2 fold increase inammoniacal-nitrogen under the canopy of tree alone ascompared to adjacent open field. The cropping systemsincreased 2.3 to 4.3 fold soil ammoniacal-nitrogen contentthan that of uncovered area. The pedoecosystem of A. niloticaalone or in combination with the cultivation of C. cyminumgave better results in conserving soil fertility in aridenvironment. There was 3.0 to 4.4 fold increase in soilphosphorus under the canopy of tree alone than that of openfield. The different cropping practices increased availablephosphorus by 1.2 to 3.6 fold. Maximum increase (3.6 fold)was in C. cyminum field which might be supportingphosphorus conservation in soil when grown in agroforestrysystem. The gradation of soil nitrate-nitrogen, ammoniacal-nitrogen and available phosphorus concentrations in differentfields was found as Z. mauritiana>P. cineraria> A. nilotica.

Effect on Biochemical Characteristics

Soil respiration and dehydrogenase activity changedsignificantly (P<0.001) due to variations in most of the treespecies and land use systems (Fig. 4). The interaction betweentree species and land use systems was significant (P<0.05).The soil respiration increased 3 to 3.3 fold under the canopy oftree alone as compared to uncovered area. Cultivation ofcrops with tree caused 1.3 to 2.6 fold increase in respirationthan that of adjacent open field. The soil respiratory activitywas higher in the field of tree alone than the crop field.Perhaps, the undisturbed land below the canopy of tree wasfastly promoting microbial population growth than the biotaunder cultivated crop. Higher soil respiration in C. cyminumfield is indicative of a better microbial growth under this crop.It increased 3 to 3.5 fold under the canopy of tree alone ascompared to adjacent open field. The variation in croppingsystem produced 1.7 to 3.1 fold increase than that ofuncovered area. Z. mauritiana having C. cyminum croppresented higher dehydrogenase activity than B. nigra and T.aestivum. The dehydrogenase activity of soil under cropping

system was lower which was due to low microbial populationin cultivated land. The gradation of soil respiration anddehydrogenase activity in different tree fields was Z.mauritiana> P. cineraria> A. nilotica.

Relation Between Fauna and Soil Characteristics

Soil temperature and pH showed a significant negativecorrelation with soil faunal groups (Acari, Myriapoda,Coleoptera, Collembola, other arthropods and total fauna) (r= -0.245 to -0.770, P<0.001 to <0.05). Whereas soil moisture,organic carbon, nitrate-nitrogen, ammoniacal-nitrogen,phosphate-phosphorus, soil respiration and dehydrogenaseactivity showed a significant negative correlation (r = -0.595 to-0.795, P<0.001 to <0.05) with soil temperature and pH. Butthe soil temperature presented a significant positivecorrelation (r = 0.629, P<0.001) with soil pH.

Organic carbon, nitrate-nitrogen, ammoniacal-nitrogen,phosphate-phosphorus had a significant correlation (r = 0.356to 0.947, P<0.001) with Acari, Myriapoda, Coleoptera,Collembola, other soil arthropods and total fauna. Similarly,soil respiration and dehydrogenase activity showed asignificant positive correlation (r = 0.352 to 0.943, P<0.001 to<0.002) with all soil faunal groups and organic carbon, nitrate-nitrogen, ammoniacal-nitrogen and phosphate-phosphorus.

DISCUSSION

Improvement in Faunal Biodiversity

The populations of Acari, Myriapoda, Coleoptera,Collembola and other arthropods increased 2.8 to 22.1 foldunder the canopy of tree as compared to adjacent open field.The increase in population of total soil fauna in tree plus C.cyminum (2.4-12.7 fold) and tree plus T. aestivum (2.4-15.9 fold)land was higher than that of tree plus T. aestivum (0.2-5.1 fold)when compared to the faunal density in their adjacent openfields (Fig. 1). This shows that C. cyminum and B. nigracultivation promotes more faunal growth perhaps because ofpalatable and easily decomposable leaves of such plants. Soilfaunal density was higher in pedoecosystem with tree alonethan that of tree with crop. It is because of litterdecomposition in undisturbed area below canopy of trees.The increase (3.9-22.1 fold) in Collembola population washigher in P. cineraria and Z. mauritiana system but lower in A.nilotica when compared to the populations of other groups ofsoil fauna in these systems. There was almost similar patternof changes in different land use systems after combining thepopulation of all soil faunal groups. The present studysuggests location and land use system-specific changes inbelow-ground faunal density. In arid region, P. cineraria is abetter tree and C. cyminum is a better winter crop forpromoting development of soil fauna. The populations ofAcari, Myriapoda, Coleoptera, Collembola and otherarthropods showed a significant positive correlation among

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themselves. Significantly more negative value of RTEpopulation

also indicated the beneficial effect of tree on the population ofsoil arthropods (Fig. 2). The Coleoptera exhibited greatestassociation with all agrisilviculture fields. However, Z .mauritiana system indicated highest facilitative effects on allgroups of soil fauna. Changes in values of RTEpopulation withsoil arthropod groups suggested that the populations ofvarious major groups of soil arthropods are dependent uponthe quality of food resources available in that agrisilviculturesystem [37]. This reflects that the development of one group offaunal population facilitate the development of another groupby creating a conducive soil environment.

An increase in population density of microfauna leadsto an increase in humus contents of soil thereby enhancingsoil fertility [38]. It is because soil invertebrates play avaluable role in the breakdown and decomposition of organiclitter which makes pedoecosystems self sustainable. A soilsystem harbouring sufficient biodiversity does not require anyextra organic or chemical (fertilizers and pesticides) inputs.Soil arthropods are a highly adaptive group which invadesdifferent types of pedoecosystems including barren land. Thedifferent degrees of colonizations in different land usesystems indicate impacts of agroforestry practices ondevelopment of different faunal communities. Since soil faunaoccupy many important positions (detrivorous, omnivorous,herbivorous, predacious etc.) in the tropical levels inecosystems [39,40], the present observations will help indeveloping strategies to enrich soil biodiversity and improvesustainability of the agroecosystem in an arid environment. Itmay also help in selecting combinations of tree and crops forconservation of below-ground fauna and, in turn, soilconservation on a sustainable basis. The present study mayalso prove to be useful for faunal recolonization in desertagroecosystem.

Agrisilviculture-induced Soil Health

Lower soil moisture of cultivated land than that of thetree system alone (Fig. 3) may be because of more waterutilization by crops. Here the higher the temperature thelower the soil moisture concept holds good. Cultivation of C.cyminum in A. nilotica field proved to be best for conservingsoil moisture in desert. But cultivation of T. aestivum with Z.maurit iana was not fit for water conservation in aridenvironment. The negligible differences in soil pH betweenopen and agroforestry land may be due to lesserdecomposition and humic acid formation at a lowertemperature during winter. Walia and Mathur [41] alsoreported that soil pH does not vary much during samplingperiod in annual and perennial crop field. Nguyen et al [42]found slightly higher pH in cropped and pastoral soils underconventional and biodynamic (organic) agriculture. Thisreport is comparable to the present findings.

Higher organic carbon under the canopy of tree thanuncovered area (Fig. 4) may be due to leaf litter fall and itsdecomposition in soil. No difference in organic carbon

contents of soils of tree field and crop plus treepedoecosystem is because of an equal degree of biologicalactivity and decomposition. More soil organic carbon in A.nilotica based system is due to less biotic activity andminimum litter degradation. The soil organic carbon contentwas lower in cropping system than the tree alone in winter. Itis perhaps due to faster decomposition in crop field than treealone. Minimum decomposition was evident in P. cinerariasoil system and C. cyminum field. The organic carbon contentin soil of Jodhpur district of Rajasthan (0.089 to 0.610%) islower than Hissar and Sirsa districts of Haryana (0.01 to 1.3%)[43] and much less compared to cropping forms in NewZealand (2.9 to 3.9%) [42].

A greater level of soil nitrate-nitrogen and ammoniacal-nitrogen under the canopy of tree than that of open field isbecause of decomposition and release of nitrogen from leaflitter available under the canopy of tree (Fig. 4). Though theleaf litter fall was more in tree plus cropping system than treefield alone but the soil nitrate-nitrogen and ammoniacal-nitrogen contents were less in crop field. It may be due touptake of nitrate-nitrogen and ammonical-nitrogen by crop.The maximum nitrogen content in Z. mauritiana andminimum in A. nilotica based cropping system may be due tocrop tree interaction. The report of Nguyen et al [42]regarding higher nitrogen content of pastoral soil thancropped one is in agreement with the present findings. Theyhave also described the higher nitrogen content at siteshaving nitrogen fixing species like peas. Higher soil nitrogencontent in agroforestry system than uncovered land is furthersupported by the observations of Singh and Rathod [44] whofound a substantial increase in desertic soil under vegetationcover. More increase in soil phosphate-phosphorus in treefield alone than that of cultivated land might be due toutilization of more phosphate by winter crops (Fig. 4).Maximum soil phosphorus in C. cyminum and minimum in T.aestivum land may be again due to differences in phosphorusutilization for plant growth. Higher available phosphoruscontent of soil under the canopy of tree than cultivated land issimilar to the higher phosphorus content in pastoral soil thancropped one [42]. They also found a lower level of availablephosphorus in soils on the alternative than conventionalfarms. In contrast, Singh and Rathod [44] did not find anysignificant difference in soil phosphate-phosphorus betweenplanted (tree, shrub) land and control plots.

Higher soil respiration and soil dehydrogenase activityunder tree than tree plus crop might be due to morepopulation growth of soil biota including bacteria inundisturbed land below the canopy of tree alone. C. cyminumwas the best crop in winter for promoting development of soilbiota in desert area. Cultivation of this crop will considerablyhelp in improving sustainability and productivity ofagroforestry system in desert. Since biotic components(plants, animals, microbes) of soil are closely associated toinfluence physical, chemical and biological properties of soil[45], the increase in soil respiration and dehydrogenaseactivity reflects the improvement in soil health in natural and

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agroecosystem.

Association Between Abiotic and Biotic Activity

Negative correlation of soil temperature with variousphysicochemical and biological properties of soil except withpH indicates that increase in soil temperature is not conducivefor soil health. In contrast to temperature, the exact oppositecorrelation of soil moisture with different soil properties in thepresent case is obvious because soil temperature remainsinversely related to soil moisture. Whereas the negativecorrelation of soil pH with other chemical and biologicalcharacteristics of soil may be due to reduction in soil pH as aresult of litter decomposition and humic acid formation.However, a positive and significant correlation among organiccarbon, nitrate-nitrogen, ammoniacal-nitrogen, phosphate-phosphorus, soil respiration and dehydrogenase activityclearly reflects increase in soil nutrients with the increase inmicrobial and other biotic activity. These observations are insupport with the reports of other workers who documentedcarbon mineralization as a convenient surrogate for nitrogendynamics because carbon mineralization is believed to becoupled to nitrogen mineralization via C/N ratios of detritalresources and their consumers [46,47,48]. In fact, mineralizedcarbon is released as CO2, while mineralized nitrogen may beimmobilized by plants and microbes.

Negative correlation of soil temperature and pH withthe population of Acari, Myriapoda, Coleoptera, Collembola,other arthropods and total soil fauna appeared to be due to apositive correlation of these faunal groups with moisture.Decrease in temperature increases soil moisture contentwhich, in turn, promotes faunal population growth. Theincrease in organic carbon, soil nutrients (nitrate-nitrogen,ammoniacal-nitrogen, phosphate-phosphorus) and microbialactivity is associated with the increase in soil faunalpopulation. This suggests that litter fall and decomposition inagrisilviculture system induce microbial and faunal activity,as a result of which, the different nutrient contents areincreased in soil system. Therefore, further research is alsoneeded to explore the specific relationships amongagroforestry system, soil biodiversity and soil health. It willhelp in strategic manipulation of soil biota and improvingsustainability of soil system in desert.

ACKNOWLEDGEMENTS

The authors are grateful to the Indian Council ofAgricultural Research (ICAR), New Delhi for financialsupport. We are thankful to Dr. P.S. Pathak, Director, IGFRI(Thansi) and Dr. G. Singh, AFRI (Jodhpur) for help andinspiration.

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