Muchane Et Al 2012

7/29/2019 Muchane Et Al 2012

1/13

African Journal of Microbiology Research Vol. 6(17), pp. 3904-3916, 9 May, 2012Available online at http://www.academicjournals.org/AJMRDOI: 10.5897/AJMR12.155ISSN 1996-0808 2012 Academic Journals

Full Length Research Paper

Effect of land use system on Arbuscular Mycorrhizafungi in Maasai Mara ecosystem, Kenya

Mary Nyawira Muchane1*, Muchai Muchane1, Charles Mugoya2 and Clet Wandui Masiga2

1Mycology Section, Department of Botany, National Museums of Kenya, P.O Box 40658, 00100, Nairobi Kenya.2Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) Box 765, Entebbe,

Uganda.

Accepted 29 March, 2012

Arbuscular mycorrhiza fungi (AMF) diversity and inoculums potential were assessed in different landuse systems (protected and unprotected grassland and woodland, intensified monocropping systemsand subsistence farming systems) in dry and wet region of Maasai Mara ecosystems (MME) during dryand wet season (November, 2009 and April, 2010). AMF spore were assessed in field and trap cultures(sorghum) using morphological tools. AMF inoculums potential were assessed using undisturbed soilcores planted with sorghum and cow pea. A total of 15 AMF species, dominated by species belongingto genus Acaulospora and Scutellospora were recorded across the MME. Wet region recorded highspore density and species richness in trap cultures. Human related disturbances caused byovergrazing and deforestation outside protected core altered AMF species composition in grassland,and negatively affected AMF species richness in woodland and grassland in the dry region. Similarly,intensified agriculture declined AMF diversity in dry region, but was unaffected in the wet region.Among different cropping systems, subsistence farming systems had higher AMF diversity and species

numbers. This study demonstrates that human disturbances in natural ecosystems and intensifiedagricultural systems have adverse effects on AMF community especially in regions with semi-aridclimatical conditions in Savannah ecosystems.

Key words:Arbuscular mycorrhiza fungi, land use, grassland, woodland, monoculture, mixed cropping.

INTRODUCTION

The Serengeti-Mara ecosystem is an area of 25,000 km2stretching across the border of Tanzania and Kenya, inEast Africa, and is well known for its wildlife population in

Africa. It comprises of Serengeti ecosystem in northernpart of Tanzania and Maasai Mara ecosystem (MME) inthe southwest of Kenya. The MME comprisesapproximately 6000 km2, of which 25% representsMaasai Mara National Reserve (MMNR) and 75% isunprotected land which lies within pastoral andagricultural areas (Walpole et al., 2003).

Over the past years, MME has undergone changes in

*Corresponding author. E-mail: [email protected],[email protected].

land cover and land use, and tenure which have seriouslong-term implications on the future survival andconservation of wildlife (Singida, 1984; Galaty, 1992Norton-Griffiths, 1996; Said et al., 1997). Area underagriculture (mainly wheat farming) increased from 4875ha in 1975 to 50,000 ha in 1995 (Serneels et al.,2001)The conversion of range lands into agriculture is stilgoing on and is expected to intensify with the increasingland subdivision into individual and corporate titlesinstead of communal tenure. The long-term impact othese land use changes is being attributed to decline inwildlife population especially wildebeest which are akeystone for the MME (Ottichilo et al., 2001). This callsfor urgent conservations interventions aimed at promotinginnovation/farming practices which sustain biologicadiversity without compromising food and income needs of

7/29/2019 Muchane Et Al 2012

2/13

the local community outside the protected core of MME(Buck et al., 2004). Choice of land use practices that arecompatible with biodiversity conservation and livelihoodare in return calling for studies on different aspects ofbiodiversity including changes in soil microbialpopulations.

Arbuscular mycorrhiza fungi (AMF) forms a major partof microbial community and are integral part of terrestrialplant communities, and forms symbiotic association withroots of over 80% of angiosperm plants (Trappe, 1987).These plant-fungal relationships are considered to bemutualistic, in which the fungus derives carbon from thehost, and in return the plant gains several potentialbenefits from this association (Smith and Read, 1997).These benefits include enhanced uptake and transport ofpoorly mobile soil nutrients such as phosphorus (P),improved water relations, improved soil structure andreduced root pathogenic infections. The symbiosis is alsoof great interest because of its potential influence onecosystem processes such as determining plant diversityin natural communities. AMF individual species orisolates have been shown to vary in their potential topromote plant growth and adaptation to biotic and abioticfactors (Bever, 2002). The composition and dynamics ofpopulations of AMF as a result have a marked impact onthe structure and diversity of the associated plantcommunities, both in natural and agricultural ecosystems(Grime et al., 1987; Gange et al., 1990; van der Heijdenet al., 1999).

The sustainability of mycorrhizae in soil is thus,important to maintain and promote productivity ofcroplands, rangelands and forests, and may be critical tomaintenance of biodiversity (Allen et al., 1995), and as a

result, loss or perturbation of this relationship can haveserious consequences in terms of plant communitydegradation, health or productivity. Loss of AMFpropagules will result in a decrease in the capacity ofplants to take up nutrients, thus threaten the stability of agiven ecosystem. Agricultural management factors suchas the intensity of cultivation, the quality and quantity offertilizers applied and the plant protection strategies usedin modern agriculture have severely affected AMFcommunity structure and plant interactions (Sieverding,1989; Douds and Millner, 1999; Oehl et al., 2003). On theother hand, disturbance of vegetation, soils and associatemicroflora depletes AMF population and alters AMF

composition (Allen, 1988). AMF diversity may respondmore rapidly to changes induced by managementactivities and land use changes, and consequently maybe an early and sensitive indicator of change (Bosattaand Agren, 1993).

An understanding of AMF communities is thus, animportant tool which can be used to understand how keyecological processes in natural ecosystems and agro-ecosystems respond to anthropogenic disturbances,management changes or land use changes. Additionalidentification of innovative technologies in anyecosystems should take into consideration AMF

Muchane et al. 3905

communities. Describing the diversity of AMF at a givensite is an important step in determining the effects omanagement and the eventual development omanagement regimes for these fungi.

The objective of this study was to examine the effectsof: (1) human disturbances in natural ecosystems

(comparing natural woodland and grassland inside andoutside the park) and (2) agriculture practices withdifferent levels of intensification (intensified maize andwheat mono cropping and subsistence farming withmaize-bean intercrop) on AMF diversity and inoculumspotential.

RESEARCH METHODOLOGY

Study site

The study was conducted in MME, bounded by internationaboundary of Kenya and Tanzania in the south, the Siria escarpmen(Esoit Olololo) to the west, agriculture and forest to the north, Loitahills to the east and Siana plains to the southeast (Figure 1). Theprotected core of MME comprises of MMNR which is surrounded byrange land. The range lands surrounding the MMNR can be dividedinto two range units, based on climate. These units comprises ofsemi-arid range lands in the east which falls under agro-climaticzone V with a mean average annual rainfall of 450 to 900 mm and amean maximum temperature of 22 to 39C and a mean minimumtemperature of 10 to 18C (Pratt and Gwynne, 1977). This area isgenerally dry and in this study, it is referred as dry region. In thewest, we have semi-humid zone falling under agro-climatic zone IVwith a mean average rainfall of 600 to 1100 mm, and has a meanmaximum temperature of 22 to 26C and a mean minimumtemperature of 10 to 14C (Figure 1). The area is generally wet andit is referred in this study as the wet region.

The annual distribution of the rainfall across the study area is

bimodal, characterized by two rainy seasons as well as two dryseasons. The long rains are from March to May and short rainsoccur in between November and December. The main dry period isfrom June to October with lesser dry spell in January and FebruaryThe land use system in this region comprises of natural woodlandand grassland inside and outside the park. Natural woodland andgrassland inside the park are characterized by minimal humandisturbances while woodland and grassland outside the park arecharacterized by heavy human disturbances associated withovergrazing by the cattle and wild animals and other human relatedactivities such as charcoal burning, cutting of trees for timber, firewood, harvesting of non-timber products etc. Agricultural systemsoutside the protected core of MME comprises of small-scalesubsistence varieties grown with heavy applications of externainorganic fertilizer inputs, pesticides and irrigation.

Experimental design

A 1-year survey was conducted during the short rain of Septembeto November, 2009 and long rains of March to June, 2010 in thetwo regions of MME (dry and wet) in pre-established landuse/habitat categories containing uniform land use differingaccording to major land use types viz: indigenous woodlandgrasslands and cropland. Soil samples were collected from sevenland uses systems in each region; four land use categories innatural ecosystems namely; (1) grassland inside the park, (2)grassland outside the park, (3) woodland inside the park and (4woodland outside the park and three land use categories within the

7/29/2019 Muchane Et Al 2012

3/13

3906 Afr. J. Microbiol. Res.

Figure 1. Study area (MME) showing respective study plots.

agricultural matrix (a) maize mono-cropping, (b) wheat mono-cropping, (c) small maize-bean intercropping in dry region; and (i)maize monocropping, (ii) large-scale maize-bean intercropping and(iii) small-scale maize-bean intercropping in the wet region. Thestudy plots in wet region comprised of (1) Kichwa Tembo inwoodland outside the park (KMWWO1), (2) Mpata in grasslandoutside park (KMGWO1), (3) Serena in woodland inside the park

(KMWWI1), (4) Ololo gate in grassland inside the park (KMGWI1)(5) Isokon maize monocropping (KMCPWO1-1), (6) Isokon largescale maize-beans intercrop (KMCPWO1-2) and (7) Isokon smallscale maize-beans intercrop (KMCPWO1-3) (Table 1). In the dryregion, the study plots comprised of (1) Olonannet in woodlandoutside the park (KMWDO1), (2) Koiyaki in grassland outside thepark (KMGDO1), (3) Nkama in woodland outside the park

7/29/2019 Muchane Et Al 2012

4/13

Muchane et al. 3907

Table 1. Overview of characteristics of different land uses systems in the dry and wet region of the MME.

Location Plot Land use Plot name Plot code Dominant trees species

Dry

Inside park

Grassland Posse plains KMGDI1 Grass mainly Themeda triandra and Pennisetum sp.

Woodland Nkama KMWDI1

Tarconanthus camphorates, Teclea nobilis, Rhusnatalencies, Acacia drepanalobium, Combretum mollei,

Croton Dichogamus Tarconanthus camphorates.Average vegetation cover was0.44%.

Outside park

Grassland Koyiaki KMGDO1 Grass mainly Themeda triandra and Pennisetum sp.

Woodland Olnananet KMWDO1

Acacia drepanalobium, Acacia gerradii, CrotonDichogamus, Commiphora Africana, Rhus natalencies,Balanities aegyptiaca.Average vegetation cover was0.09%.

Agriculture

Maize Hugo farm KMCPDO1Maize monocropping with high fertilization (annualaverage of 100 kg N and P/ha, 50 kg K/ha), pesticidesapplications and irrigation

Wheat Hugo farm KMCPDO2Wheat monocropping with high fertilization (annualaverage of 100 kg N and P/ha, 50 kg K/ha), pesticidesapplications and irrigation

M-B(S) Soka farm KMCPDO3 Maize intercropped with beans with only manure inputs

Wet

Inside park

Grassland Ololo gate KMGWI1 Grass mainly Themeda triandra and Pennisetum sp.

Woodland Serena KMWWI1Euclea divinorum, Tannea graviolencies, solanumincanum, Acacia drepanalobium, Ocimum suave, CrotonDichogamus.Average vegetation cover was0.12%.

Outside park

Grassland Kichwa Tembo KMGWO1 Grass mainly Themeda triandra and Pennisetum sp.

Woodland Mpata KMWWO1

Rhus natalencies, Tarconanthus camphorates, AcaciaKirkii, Acacia gerradii, Acacia drepanalobium,Combretum mollei.Average vegetation cover was0.12%.

Agriculture

Maize Isokon KMCPD01-1Maize monocropping with high fertilization (50 kg P and100 kg N/ha) and irrigation

M-B(L) Isokon KMCPD01-2Maize-bean intercrop with manure and fertilization (30 kgP and N/ha) combined with farm yard manure.

M-B(S) Isokon KMCPD01-3Maize-beans intercrop with no or sometimes with orwithout farm yard manure inputs.

(KMWDI1), (4) Posse plains in grassland inside park (KMGDI1), (5)Hugo farm maize mono-cropping (KMCPDO1), (6) Hugo farmwheat mono-cropping (KMCPDO2) and (7) Soka farm maize-beansintercropping (KMCPDO3) (Table 1). In each of study plot, threetransects each measuring 1 x 0.05 km were laid out, 1 km awayfrom each other and 500 m away from the road. In each transect,three sampling plots of 10 m by 10 m were demarcated 300 m awayfrom each other along the transects. Soil samples were taken

randomly in 10 different points at a depth of 0 to 30 cm in each 10 x10 m sampling plots. The soil samples from these 10 points werepooled and mixed to obtain a representative samples per plot. Intotal, 9 samples were taken per given land use systems.

Characteristics of land use systems used in the study

Summary of characteristics and dominant tree species found indifferent land uses systems in MME are shown in Table 1.Percentage vegetation cover in woodlands inside the park was0.44% while outside the park was 0.09% in the dry region. In thewet region, percentage vegetation cover was 0.12% in woodland

inside and outside the park. In cultivated soil, maize and wheamonocropping were characterized by high inorganic fertilization(annual average of 100 kg N and P/ha, 50 kg K/ha), pesticidesapplications and irrigation while maize-bean intercropping systemwas characterized by low inputs of farm yard manure in the dryregion. In the wet region, maize monocropping was cultivated usinghigh inputs of inorganic fertilizer (estimates of 50 kg P/ha and 100kg N/ha). Large-scale maize intercropping had low inorganic inputs

(an estimate of 30 kg P and N/ha) combined with farm yard manurewhile in small-scale maize-bean intercrop cultivation was done withor without farmyard manure cultivation.

Sampling method and setting of trap cultures

Soils were sampled with a soil auger from various sampling depths(0 to 30 cm). Samples were loosely closed immediately in sterilepolyethylene bags and stored in a cool box, before beingtransported for analysis. Trap cultures were initiated according tothe recommendation of Morton, (1993). Briefly, a pot culture witheach pot representing a single transect was set up at National

7/29/2019 Muchane Et Al 2012

5/13


Museums of Kenya. Sorghum was used as trap due to the fact that1000 AMF isolates of 98 species in all 6 genera have been able togrow and sporulate in all pots with Sorghum sudanse (Piper)(Morton, 1993). The aim of trap cultures was to dilute the parasiticpressure on the AMF propagules in the soil and induce sporulationsto recover spores from AMF species present in the soil, includingsome which may not have sporulated at the time of sampling inorder to get spores of similar developmental ages. A sub-sample of150 g from each transect soil inoculum was diluted with 200 g ofautoclaved medium sized sand and mixed before being poured into0.5 l pot. Sand was chosen as a diluting subtracted at it and is inertand does not affect inoculum pH. Sorghum was later sown as hostplant at a density of 25 plants per pot. Each pot was then coveredwith autoclaved sand to prevent unintentional dispersal of AMF.After seedling emergency, the pots were watered daily with tapwater. The pot cultures were allowed to grow for 4 months. Duringthe last week, the moisture was successively lowered to stopgrowth of plants and enhance sporulation of existing AMF species.

Soil analysis

Sub-samples of collected soil samples were analyzed for total

nitrogen, carbon, available P and pH at Kenya AgriculturalResearch Institute (KARI) soil laboratory following standardmethods for tropical soils (Anderson and Ingram, 1993).Phosphorus was extracted with 0.5 M NaHCO3 + 0.01 Methylenediaminetetraacetic acid (EDTA) (pH 8.5, modified Olsen)using a 1:10 soil/solution ratio. Available P was estimatedcolorimetrically (molybdenum blue). Organic C (SOC) wasdetermined colorimetrically after H2SO4 - dichromate oxidation at150C for 30 min. Total N was determined by Kjeldahl digestionwith sulphuric acid and selenium as a catalyst and was estimatedcolorimetrically. Soil pH was measured in aqueous suspension(1:2.5 w:v).

AMF inoculums potential

Alongside soil samples, undisturbed soil cores were also taken ineach sampling plots (two undisturbed cores) to assess the AMFinoculums potential. The AMF bioassay were established using twofast growing host plants (Sorghum and cow pea), which wereallowed to grow for 4 weeks, after which the plants roots wereharvested. The roots were rinsed, cut into 1 cm root pieces, mixed,cleared and stained for AMF structure (Kormanik and McGraw,1982), and assessed for AMF colonization according to Trouvelot etal. (1986).

AMF taxonomy

AM assessment was done from both field collected soil samples aswell as from trap cultures (sorghum). 50 g of soil was taken for AMF

spore extraction which was done by centrifugation in sucrosegradients (Gerdemann and Nicolson, 1963). Intact spore werecounted and the spore morphotype were separated and transferredto object glasses, and identified by investigating the range of mean,spore and saccule size, colour and distances between spores andsaccule. To further examine the organization and histochemistry ofspore subcellular structure, the spore were mounted on slides with1 to 30 spores with polyvinyl alcohol-lactic acid-glycerol (PVLG)media and melzer reagent according to Schenck and Perez (1990).The international collection of arbuscular and vesicular-arbuscularmycorrhizal fungi (INVAM) isolates and voucher specimen wereused as taxonomic references. Some spores were identified tospecies but this proved difficult, to numbered morphospecies.Voucher specimens are being held at the NMK, Nairobi.

Data analysis

Data on percentage of AMF colonization were transformed byarcsine and spore densities were transformed by log(x+1) to fulfilthe assumption of normality and homogeneity of variances beforeanalysis of variance. Species richness was calculated as a numberof species recorded in each sample and Shannon (H) diversityindex was calculated for each field sample/trap pot. Transformeddata were subjected to one-way analysis of variance (ANOVA) totest the differences in AM colonization, spore density, speciesrichness and diversity within and between different land use typesMean separation was done by Fishers least significant difference(LSD) at the 0.05 level of probability. The relationship between AMFparameters and soil chemical properties (pH, C, P, N, andexchangeable cations) was determined by Pearsons correlationanalysis. The analysis was carried out using SPSS Version 15Further, effects of different land use systems on AMF sporecommunity composition were assessed by multivariate redundancyanalysis (RDA) in CANOCO (Version 4.5).

RESULTS

Soil chemical characteristics across land usesystems

Some of the soil chemical properties (pH, available Ptotal N and C) differed significantly across different landuse systems in MME (Table 2). Human relateddisturbance in natural grassland and woodland outsidethe protected core of MME had no effect on levels of soipH, P, N and C in the drier region of MME (p>0.05 in alcases; Table 2). However, human disturbances declinedlevels of soil C and increased soil pH only in grassland inthe wet region (p

7/29/2019 Muchane Et Al 2012

6/13

Muchane et al. 3909

Table 2. Some selected soil chemical properties (pH, total nitrogen, carbon, available P) and AMF inoculums potential (MIP) across differentland use systems within protected (inside the park), unprotected core (outside the park) and in agricultural farms of MME.

Location Plot Land usepH N C P (Olsen) MIP (% colonization)

(%) ppm Cow pea Sorghum

Dry

InsideGrassland 6.01bc 0.10c 0.71cd 37.33b 9.13b 20.92b

Woodland 6.30ab 0.12c 0.92bc 37.00b 25.22b 18.18bOutside

Grassland 6.42ab 0.13bc 0.84bc 54.33b 23.72b 32.02abWoodland 6.03bc 0.12c 0.82bc 33.67b 12.45b 24.56b

Agriculture

Maize 6.05bc 0.11c 0.68d 128.67a 30.55ab 26.27ab

Wheat 5.85c 0.16b 1.02b 138.00a 29.83ab 44.72aM/B-S 6.77a 0.25a 1.31a 67.00b 48.19a 45.00aSED 0.19 0.02 0.11 26.95 7.63 8.29

P value p=0.05 p=0.03 p=0.047 p=0.01 p=0.01 p=0.02

Wet

InsideGrassland 5.76b 0.17bc 1.26b 74.00a 12.44b 29.32bWoodland 6.15a 0.24a 1.57a 48.00abc 17.30ab 24.11b

OutsideGrassland 6.26a 0.13c 0.83c 46.33abc 15.65ab 26.18b

Woodland 6.09a 0.23a 1.38ab 63.67ab 33.78a 45.16a

Agriculture

Maize 5.51cb 0.18abc 1.13b 25.00c 16.47ab 21.98b

M/B-L 5.19c 0.21ab 1.13b 40.67bc 13.81ab 37.68aM/B-S 6.03a 0.23a 1.32b 53.33ab 29.75ab 42.34aSED 0.22 0.03 0.11 13.17 8.63 7.89

P value 0.03 0.04 0.02 0.03 p=0.04 p=0.01

The land uses comprised of woodland and grassland inside and outside protected core of MME. In agricultural land, the land us es comprised of maizeand wheat monocropping (abbreviated as maize and wheat) and subsistence cropping system with maize-bean intercropping (abbreviated as M/B-Ssmall-scale system with or without inputs and M/B-L for large-scale systems with both inorganic and organic inputs). SED is the standard error of thedifference. Means followed by the same letter in each column are not statistically different at p

7/29/2019 Muchane Et Al 2012

7/13


Table 3. Species of AMF across the different land use systems in the dry and wet region of MME.

Location Plot Land useA.

denticulataA.

scrobiculataAcaulospora

sp.1Acaulospora

sp.2Acaulosphora

sp.3Glomus

sp.1Glomus

sp.2Glomus

sp.3Glomus

sp.4S.

persicaS.

pellucidaScutellospora

sp.1Scutellospora

sp.2Scutellospora

sp. 3Gigas

sp

Dry

InGrassland

Woodland

OutGrassland

Woodland

Agric

Maize

Wheat

M/B-S

Wet

InGrassland

Woodland

OutGrassland

Woodland

Agric

Maize

M/B-l

M/B-S

In the natural ecosystems, land uses comprised of woodland and grassland inside and outside protected core. In agricultural land, land uses comprised of maize and wheat monocropping (abbrevas maize and wheat) and subsistence cropping system with maize-bean intercropping (abbreviated as M/B-S small-scale system with or without inputs and M/B-L for large-scale systems withinorganic and organic inputs). +/- indicates presence/absence of a species.

soils (13.596.19 spores per 100 g; p

7/29/2019 Muchane Et Al 2012

8/13

Muchane et al. 3911

Figure 2. Composition of AMF community in field soil and trap cultures. Spore abundances are expressed on a dry weight basis for fieldsoil and on a fresh weight basis for trap pot substrate. Errors bars represent standard error of the difference (SED).

significantly high spore density, species richness anddiversity than monocropping systems with either maize orwheat (p0.05 in all cases; Table 2).However, in the wetter region of MME, humandisturbances in the woodland increased MIP (p0.05; Table 2). Maize-bean cropping system recorded significantly higher MIPthan natural grassland and woodland in dry and wetregion of MME (p

7/29/2019 Muchane Et Al 2012

9/13


Figure 3. Abundances of spores of two AMF species in the trap cultures as affected by land use systems in the dry and wet region of MME.The land uses comprised of woodland and grassland inside and outside protected core. In agricultural land (agric.), the land uses comprisedof maize and wheat monocropping (abbreviated as maize and wheat) and subsistence cropping system with maize-bean intercropping(abbreviated as M/B-S small-scale system with or without inputs and M/B-L for large-scale systems with both inorganic and organic inputs).Bars followed by the same letter are not significantly different at p

7/29/2019 Muchane Et Al 2012

10/13

Muchane et al. 3913

Figure 6. Effect of farming systems on AMF spore densities (number of individuals per 100 g of soil), species richness and speciesdiversity (Shannon H index) in the wetter region of MME. The land uses comprised of woodland (wood) and grassland (grass) insideprotected core, maize mono-cropping (abbreviated as maize) and subsistence cropping system with maize-bean intercropping(abbreviated as M-BS small-scale system with or without inputs and M-BL for large-scale systems with both inorganic and organicinputs). Bars followed by the same letter are not significantly different at p

7/29/2019 Muchane Et Al 2012

11/13


raining during the two sampling periods and most of thespecies could have germinated.

Human related disturbances caused by overgrazingand deforestation outside protected core of MME in thisstudy altered AMF species composition in grassland andnegatively affected AMF species richness in woodland

and grassland in the dry region of MME. However, anincrease in Shannon H index and spore density wasobserved in disturbed grassland in the dry region. In wetregion, human disturbances positively improved AMFdiversity (Shannon H index and species richness) ingrassland and woodland as well as inoculums potential inwoodland. Shift of AMF species composition and declineof AMF diversity following disturbance in this study is inaccordance to several other studies (Eom et al., 2001)and deforestation (Waltert et al., 2002; Allen et al., 2003).These changes are attributed to continual removal ofnutrient within the ecosystem which decreasesphotosynthetic source for mycorrhizal fungi andassociated microbes (Gehring and Whitham, 1994; Eomet al., 2001; Gange et al., 2002). In addition, grazing anddeforestation may alter plant community structure and inreturn cause a shift AMF species composition (O'Connoret al., 2002). Changes in soil chemical properties found inthis study (low C in disturbed grassland) could have alsocaused shift in AMF composition.

Unlike in dry region, positive effects of humandisturbances on AMF diversity were observed in wetregion. This suggests improved mycorrhizal symbiosis indisturbed environments especially when environmentalconditions are favorable. Environmental conditions suchas moisture and nutrient have been shown to play asignificant role in determining mycorrhizal responses to

human disturbances (Gehring and Whitham, 1995, 2002;Dandan and Zhiwei, 2007). Defoliation was shown todecline AMF colonization when water and nutrient weredeficient but had no effect to colonization when water andnutrient was unlimited (Gehring and Whitham, 1995).Since defoliated plant may be in high demand fornutrient, host plant may respond to this demand byincreasing AMF symbiosis (Kula et al., 2005), thus,increasing the AMF diversity.

Our result indicate human disturbance in naturalgrassland and woodland under favorable climaticcondition may not negatively affect AMF community.However, under adverse climatic conditions (high tem-

perature, low relative humidity and frequent occurrence ofdroughts) human disturbance may negatively impact onAMF community either through limited natural regenera-tion potential of plant species or sterilization of soil byhigh temperatures. Our results are in agreement withearlier finding that environmental factors in semi-aridareas influences AMF community structure more(Dandan and Zhiwei, 2007), demonstrating the need forproper management of unprotected natural grasslandand woodland, and need for alternative measure toreduce the level of human disturbances in semi-arid

region of MME.Our data in agricultural farms indicate a marked

decrease in AMF species numbers and diversity uponintensification of agricultural management in dry region oMME. However, in wet region, agriculture practicesincreased AMF species number and diversity with signifi

cant increases found in subsistence farming systemsAmong the different cropping systems, the subsistencefarming systems had significantly higher species numbeand diversity index than sites with intensive agriculturewith high input, and continuous maize and wheamonocropping in the two region of MME. Our findings areconsistent with previous reports in which the AMFcommunity was found to be impoverished in speciescomposition upon agricultural intensification (An et al.1993; Munyanziza et al., 1997; Mader et al., 2000; Oehet al., 2003; Mathimaran et al., 2007). This may be due todegrading soil chemical qualities in the intensifiedcropping systems evidenced by high soil acidity, lowlevels of carbon and high levels of available P (Table 1).

Correlation analyses between soil chemical propertiesand some diversity aspects of AMF have shown positiverelationship between soil pH and AMF diversity, andnegative relationship between levels of available P and

AMF diversity parameter suggesting that declining soacidity resulted in declining AMF diversity. Similarlyseveral studies have reported negative effects of P on

AMF spore density, diversity and species numberfollowing increases of available soil P levels (Kahiluoto eal., 2001; Allison and Goldberg, 2002). This impliesincreased soil acidity, which may translate to low nutrienuse efficiency and subsequent low crop productivity in thelong-term (Muchane et al., 2010). High AMF diversity in

subsistence cropping systems in both drier and weregion of MME supports previous studies showing high

AMF diversity in multiple cropping systems (Hart andKlironomos, 2002). The result of this study implies thamixed cropping is a more sustainable land use system inenhancing both biological soil qualities (evidenced byhigh AMF density) than highly fertilized monocroppingsystems in drier side of MME.

Unlike in the drier region, agriculture maintained AMFspecies numbers, diversity and density in the wet regionalthough, subsistence farming systems (mixed croppingsystems) altered the AMF species composition. Weattribute this result to high diversity of weed, which may

have mimicked the structure and function of naturasystems. In addition, agriculture in this area was lessthan 10 years old after the conversion from naturawoodland suggesting minimal impacts of agriculturewhich may not have had negative impacts on the AMFcommunity. However, changes in species composition insubsistence cropping systems in this region suggesimpact of agriculture on AMF species compositionincreasing some while reducing the other. Thesechanges are associated with different amounts andqualities of SOC inputs to the soil (either root exudates or

7/29/2019 Muchane Et Al 2012

12/13

litter), as well as soil temperatures and moisturedynamics in the differently cropped soil (Mathimaran etal., 2007). Our result demonstrates that under certainconditions (agriculture with high plant diversity)agriculture may not have negative impact on AMFdiversity, but may cause shifts in AMF species

composition. This implies functional changes of AMFcommunity, since different AMF species have beenshown to exhibit different functional traits (Bever, 2002).Future researches that focus on function of dominant

AMF species in different agro-ecosystems may bedesirable for proper management of AMF symbiosis.

Conclusion

The results of the current work showed that AMF are acommon component in the Savannah ecosystems. The

AMF community is however, adversely affected byhuman disturbances especially in regions with semi-aridclimatical conditions, necessitating alternative measuresto reduce the levels of human disturbance. Afforestationprogrammes in disturbed areas to replace somedominant plant species in the region may be desirable. Inaddition, our result shows that modern agriculturalpractices with high levels of fertilizer and monocultureshave adverse effects on the diversity of AMF inSavannah ecosystems while subsistence farming withmixed cropping (cereals and legumes) was more resilientin maintaining AMF diversity. With expected increases inagriculture intensification to address the demand ofincreasing human population, management of AMF mayrequire use of both intensive and extensive agro-systems

alongside each other to provide both basic foodrequirements and supply an increasing market forsustainably-produced crops in this region. Promotion oforganic farming and diversification of crops may enhancesoil biological and chemical properties and in returnimprove crop production. Incorporation of droughtresistance crops such as cassava and pigeon pea incropping systems and agro-forestry tree species may benecessary to ensure continued productivity. Additionally,development of biotechnological tools, which entailselection of efficient native AMF ecotypes and theirincorporation into bio-fertilizers, may facilitate restorationof AMF community in this region.

ACKNOWLEDGEMENTS

Financial assistance for this study was provided byAssociation for strengthening Agricultural Research inEastern and Central Africa (ASARECA), and is highlyacknowledged. We also acknowledge the support of Mr.Daniel Karanja, Ms. Lukelysia Nyawira and Ms. EmmaKibiro in collection of soil samples, extractions andmaintenances of trap and bioassays experiments as wellas farmers and management of Maasai Mara Game

Muchane et al. 3915

Reserve and the Mara Conservancy in both drier andwetter side of MME for granting us permission to usetheir farms.

REFERENCES

Alguacil MM, Roldn A, Torres P (2009). Complexity of semiaridgypsophilous shrub communities mediates the AMF biodiversity athe plant species level. Microb. Ecol.,57: 718727.

Allen B, Allen MF, Egerton-Warburton L, Corkidi L, Gomez-Pompa(2003). Impacts of Early- and Late-Seral Mycorrhizae duringrestoration in seasonal tropical forest, Mexico. Ecological applicationsby Ecological Society of America . 13(6): 1701-1717

Allen MF (1988). Re-establishment of VA mycorrhizas f ollowing severedisturbance: comparative patch dynamics of a shrub desert and asubalpine volcano. Proc. R. Soc. Edinb. 94: 63-71.

Allen MF, Helm DT, Trappe JM, Molina R, Rincn E (1995). Patternsand regulations of mycorrhizal plant and fungal diversity. Plant Soils170: 47-62.

Allison VJ, Goldberg D (2002). Species-level versus community-levepatterns of mycorrhizal dependence on phosphorus: an example oSimpsons paradox. Funct. Ecol., 16, 346352.

An ZQ, Hendrix JW (1993). Populations of spores and propagules omycorrhizal fungi in relation to the life cycles of tall fescue andtobacco. Soil Biol. Biochem., 25: 813817.

An ZQ, Hendrix JW, Hershman DE, Ferriss RS, HensonGT (1993). Theinfluence of crop-rotation and soil fumigation on a mycorrhizal fungacommunity associated with soybean. Mycorrhiza, 3:171-182.

Anderson JM, Ingram JS (1993). Tropical soil biology and fertility: ahandbook of methods of analysis. CAB International, Wallingford, pp220

Bever JD (2002). Host-specificity of AM fungal population growth ratescan generate feedback on plant growth. Plant Soil. 244: 281 - 290.

Bosatta E, gren G (1993). Theoretical analysis of microbial biomassdynamics in soils. Soil Biol. Biochem., 26:143148

Buck LE, Gavin TA, Lee DR, Uphoff NT (2004). Eco-agriculture: areview and assessment of its scientific Foundations. Ithaca, NYCornell University.

Dandan Z, Zhiwei Z (2007). Biodiversity of arbuscular mycorrhizal fung

in the hot dry valley of the Jinsha River, southwest China. Appl. SoEcol., 37, 118128.

Dodd JC, Arias I, Koomen I, Hayman DS (1990). The management ofpopulations of vesicular-arbuscular mycorrhizal fungi in acid-infertilesoils of a savanna ecosystem. I. The effect of pre-cropping andinoculation with VAM-fungi on plant growth and nutrition in the fieldPlant Soil, 122: 229-240.

Douds DD, Millner PD (1999). Biodiversity of arbuscular mycorrhizafungi in agroecosystems. Agriculture. Ecosyst. Environ., 74: 7793

Eom A, Wilson GW, Hartnett DC (2001). Effects of ungulate grazers onarbuscular mycorrhizal symbiosis and fungal community structure intallgrass prairie. Mycologia, 93, 233242.

Gai JP, Liu RJ (2003). Effect of soil factors on AMF in the rhizosphereof wild plants. Chin J. Appl. Ecol., 14:470472

Galaty JG (1992). The land is yours: social and economic factors in

the privatisation, sub-division and sale of Maasai ranches. Nomadic

Peoples, 30, 2640.Gange AC, Bower E, Brown VK (2002). Differential effects of insecherbivory on arbuscular mycorrhizal colonization. Oecologia, 131103112.

Gange AC, Brown VK, Farmer LM (1990). A test of mycorrhizal benefiin an early successional plant community. New Phytologist, 115: 8591

Gehring CA, Whitham TG (1994). Interactions between abovegroundherbivores and the mycorrhizal mututalists of plants. Trends Ecol.Evol., 9, 251255.

Gehring CA, Whitham TG (1995) Duration of herbivore removal andenvironmental stress affect the ectomycorrhizae of pinyon pinesEcology, 76:2118-2123

Gehring CA, Whitham TG (2002). Mycorrhizae-herbivore interactionspopulation and community consequences. In M. van der Heijden and I

7/29/2019 Muchane Et Al 2012

13/13


Sanders, eds. Mycorrhizal Ecology, Ecol. Stud., 157:295-320.Gerdemann JW, Nicolson TH (1963). Spores of mycorrhizal Endogone

species extracted by wet sieving and decanting. Trans. Br. Mycol.Soc., 46, 235244.

Grime JP, Mackey JM, Hillier SM, Read DJ (1987). Floristic diversity ina model system using experimental microcosms. Nature, pp. 328,420-422.

Hart MM, Klironomos JN (2002). Diversity of arbuscular mycorrhizal

fungi and ecosystem functioning. In: van der Heijden MGA, SandersIR (eds) Mycorrhizal Ecology. Springer, pp. 225242.

Jansa J, Mozafar A, Anken T, Ruh R, Sanders IR, Frossard E (2002).Diversity and structure of AM fungi communities as affected by tillagein atemprate soil. Mycorrhiza, 12: 225-234.

Jefwa JJ, Mungatu J, Okoth P, Muya E, Roimen H, Njuguini S (2009).Influences of land use types on occurrence of arbuscular mycorhizafungi in the high altitude regions of Mt. Kenya. Trop. SubtropicalAgroecosyst., 11: 277-290

Johnson NC, Zak DK, Tilman D, Pfleger FL (1991). Dynamics ofvesicular-arbuscular mycorrhizae during old field succession.Oecologia. 86 (3): 349-358, DOI: 10.1007/BF00317600

Kahiluoto H, Ketoja E, Vestberg M, Saarela I (2001). Promotion of AMutilization through reduced P fertilization II Field studies. Plant Soil,231: 6579.

Kormanik PP, McGraw AC (1982). Quantification of Vesicular-arbuscular Mycorrhizae in Plant Roots. In Methods and Principles ofMycorrhizal Research. Ed. N.C. Schenck. Am. Phytopathol. Soc., pp.37-36

Kula AA, Hartnett DC, Wilson GW (2005). Effects of mycorrhizalsymbiosis on tallgrass prairie plantherbivore interactions. Ecol. Lett.,8: 6169

Mader P, Edenhofer S, Boller T, Wemken A, Niggli U (2000). Arbuscularmycorrhizae in long-term field trial comparing low-input (organic,biological and high inputs (conventional) farming systems in croprotation. Biol. Fert. Soil, 31:150-156

Mathimaran N, Ruh R, Jama B, Verchort L, Frossard E, Jansa J (2007).Impact of agricultural management on arbuscular mycorrhizal fungalcommunities in Kenyan ferralsol. Agric. Ecosyst. Environ., 119(1-2):22-32

Morton JB (1993). Problems and solutions for the integration ofglomalean taxonomy, systematic biology, and the study ofendomycorrhizal phenomena. Mycorrhiza, 2(3): 97-109, DOI:

10.1007/BF00203855Muchane MN, Jama B, Othieno C, Okalebo R, Odee D, Machua J,Jansa J (2010). Influence of improved fallow systems andphosphorus application on arbuscular mycorrhizal fungi symbiosis inmaize grown in western Kenya. Agrofor. Syst., 78 (2): 139-150.

Munyanziza E, Kehri HK, Bagyaraj DJ (1997). Agriculturalintensification, soil biodiversity and agro-ecosystem function in thetropics: The role of mycorrhiza in crops and trees. Appl. Soil Ecol., 6(1): 77-85

Ngoru B, Kiambi S, Mwangi A (2010). A dry season vegetation andmammal survey in Serengeti-Mara Ecosystems. BASE projectAnnual report. National Museums of Kenya. Nairobi. Kenya.

Norton-Griffiths M (1996). Property Rights and the Marginal Wildebeest:An Economic Analysis of Wildlife Conservation Options in Kenya,Biodivers. Conservat., 5: 1557-1577.

O'Connor PJ. Smith SE, Smith FA (2002). Arbuscular MycorrhizasInfluence Plant Diversity and Community Structure in a

SemiaridHerbland. New Phytol., 154(1): 209-218Oehl F, Sieverding E, Ineichen K, Mader P, Boller T, Wiemken A

(2003). Impact of land use intensity on the species diversity ofarbuscular mycorrhizal fungi in agroecosystems of Central Europe.Appl. Environ. Microbiol., 69(5): 2816-2824

Ottichilo WK, de Leeuw JD, Prins HT (2001). Population trends ofresident wildebeest (Connochaetes taurinus hecki (Neumann)) andfactors influencing them in the Maasai Mara ecosystem, Kenya. BiolConserv., 97: 271-282

Pratt DJ, Gwynne MD (1977). Rangeland management and ecology inEast Africa. Hod-der & Stroughton, London, U.K, pp. 310

Said MY, Ottichilo WK, Sinange RK, Aligula HM (1997). Population anddistribution trends of wildlife and livestock in the Mara Ecosystem and

surrounding areas: a study on the impacts of land-use on wildlife andenvironmental indicators in the East African Savannah. Ministry oPlanning and National Development, Department of ResourceSurveys and Remote Sensing, Nairobi, Kenya.

Schalamuk S, Velazquez S, Chidichimo H, Cabello M (2006). Fungaspore diversity of arbuscular mycorrhizal fungi associated with springwheat: effects of tillage. Mycologia, 98(1): 1622.

Schenck NC, Perez Y (1990). Manual for the Identification of VAMycorrhizal Fungi, 3rd ed. Synergistic Publications, Gainesville, FLUSA, p. 241

Serneels S, Lambin EF (2001). Impact of land-use changes on thewildebeest migration in the northern part of the Serengeti-Maraecosystem. J. Biogeograp., 28: 391407.

Sieverding E (1989). Ecology of VAM fungi in tropical agroecosystemsAgric. Ecosyst. Environ., 29: 369-390.

Sieverding E (1990). Ecology of VAM fungi in tropical agrosystemsAgriculture, Ecosyst. Environ., 29(1-4): 369-390

Singida I (1984). Land and population problems in Kajiado and NarokKenya. Afr. Stud. Rev., 27: 2339.

Smith SE, Read DJ (1997). Mycorrhizal symbiosis. Academic PressLondon, etc.

Trappe J (1987). Phylogenetic and ecologic aspects of mycotrophy inthe angiosperms from an evolutionary standpoint In: Safir GR, edEcophysiology of VA mycorrhizal plants. Boca Raton, Florida, USACRC Press, pp. 525.

Trouvelot A, Kough JL, Gianinazzi-Pearson (1986). Mesure du taux demycorhization VA dun systeme radivulaire. Recherche de methodesdestimation ayant une significantion fonctionnelle. In: Gianinazzi

Pearson V, Gianinazzi S (eds) Physiological and genetic aspects omycorrhizae. INRA, Paris, pp. 217221

Van der Heijden MG, Klironomos JN, Ursic M, Moutoglis P, StreitwolfEngel R, Boller T, Wiemken A, Sanders IR (1999). Sampling effect, aproblem in biodiversity manipulation? A reply to David A. Wardle

Oikos,87: 408410.Walpole M, Karanja G, Sitati N, Leader-Williams N (2003). Wildlife andPeople: Conflict and Conservation in Masai Mara, KenyaProceedings of a workshop. International Institute for Environmenand Development. Londonhttp://www.peopleandwildlife.org.uk/publications/CONFLICT%20w_and_p_masaimara.pdf

Waltert B, Wiemken V, Rusterholz HP, Boller T and Baur B (2002).Disturbance of forest by trampling: effects on mycorrhizal roots oseedlings and mature trees of Fagus sylvatica. Plant Soil, 243: 143-154.

Muchane Et Al 2012

Documents