Interactive influence of rainfall manipulation and livestock grazing on species diversity of the herbaceous layer community in a humid savannah in Kenya
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摘要
Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling; these plots received either 50% more or 50% less rainfall than control plots. Simpson's diversity and Bergere Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.
Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling; these plots received either 50% more or 50% less rainfall than control plots. Simpson's diversity and Bergere Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.
Changes in rainfall regime and grazing pressure affect vegetation composition and diversity with ecological implications for savannahs. The savannah in East Africa has experienced increased livestock grazing and rainfall variability but the impacts associated with those changes on the herbaceous layer have rarely been documented. We investigated the effect of livestock grazing, rainfall manipulation and their interaction on the composition and diversity of the herbaceous community in the savannah for two years in Lambwe, Kenya. Rainfall manipulation plots were set up for vegetation sampling; these plots received either 50% more or 50% less rainfall than control plots. Simpson's diversity and Bergere Parker indices were used to determine diversity changes and dominance respectively. The frequency of species was used to compute their abundance and their life forms as determined from the literature. Grazing significantly increased species diversity through suppression of dominant species. Rainfall manipulation had no significant impact on plant diversity in fenced plots, but rainfall reduction significantly reduced diversity in grazed plots. In contrast, rainfall manipulation had no impact on dominance in either fenced or grazed plots. The interaction of grazing and rainfall manipulation is complex and will require additional survey campaigns to create a complete picture of the implications for savannah structure and composition.
引文
Abrams,A.,1995.Monotonic or unimodal diversity-productivity gradient:What does competition theory predict?Ecology 76(7),2019-2027.
Allsopp,R.,Baldry,T., 1972.A general description of the Lambwe valley area of south Nyanza district,Kenya.World Health Organisat.Bull.47,691-697.
Arnhold,S.,Otieno,D.,Onyango,J.,Koeller,T., Huwe,B., Tenhunen,J., 2015.Soil properties along a gradient from hillslopes to the savanna plains in the Lambwe Valley,Kenya.Soil Tillage Res.154,75-83.
Augustine,J.,2003.Spatial heterogeneity of herbaceous layer of a semi-arid savannah ecosystem.Plant Ecol.167,319-332.
Bakker,C., Blair,J., Knnap,A., 2003.Does resource availability,resource heterogeneity or species turnover mediate changes in plant species richness in grazed grassland?Oecologia 137,385-391.
Bakker,E., Ritchie,M.,Olff,H., Milchunas,D., Knops,J.,2006.Herbivore impact on grassland plant diversity depends on habitat productivity and herbivore size.Ecol.Lett.9,780-788.
Bat-Oyan,T., Shinoda,M.,Cheng,Y.,Purevdorj,Y., 2016.Effect of grazing and precipitation variability on vegetation dynamics in a Mongolian dry steppe.J.Plant Ecol.9(5),508-519.
Baudena,M.,Dekker,S.,Bodegom,P.,Cuesta,B.,Higgins,S.,Lehsten,V.,Reick,C.,Rietterk,M.,Yin,Z., Zavala,M., Brovkin,V.,2015.Forests,savannas,grasslands:bridging the knowledge gap between ecology and Dynamic Vegetation Models.Biogeosciences 12.,1833-1848.
Bilota,G.,Brazier,R.,Haygarth,P.,2007.The impact of grazing animals on the quality of soils,vegetation,and surface waters in intensively managed grasslands.Adv.Agron.94,237-280.
Brady,N., Weil,R.,2002.The Nature and Properties of Soils,13th Ed.Prentice-Hall Inc,New Jersey,USA,p.960.
Conway,D., Allison,E.,Felstead,R., Goulden,M.,2005.Rainfall variation in East Africa:implication for natural resources management and livelihood.Phil.Trans.363,49-54.
Deng,L.,Sweeney,S., Shangguan,Z., 2014.Grassland responses to grazing disturbance:plant diversity changes with grazing intensity in a desert steppe.Grass Forage Sci.69,524-533.
Farret,E.,Ashton,J.,Suding,N.,2014.Separating direct and indirect effects of global change:a population dynamic modelling approach using readily available field data.Glob.Chang.Biol.20.,1238-1250.
Fynn,R.,O'Connor,T.,2000.Effect of stocking rate and rainfall on rangeland dynamics and cattle performance in a semiarid savannah,South Africa.J.Appl.Ecol.37,491-507.
Fynn,S.,Augustine,J.,Peel,S., de Garine-Wichatitsky,Michael,2016.Strategic management of livestock to improve biodiversity conservation in Africansavannahs:a conceptual basis for wildlife-livestock coexistence-A review.J.Appl.Ecol.53,388-397.
Grime,J.,1973.Control of species density in a herbaceous vegetation.J.Environ.Manag.1,151-167.
Grime,J., 1998.Benefits of plant diversity to ecosystems:immediate,filter and founder effects.J.Ecol.86, 902-910.
Hanke,W.,Bohner, J.,Dreber,N.,Jurgen,N., Schmiedel,U., Wesuls,D., Dengler,J.,2014.The impact of livestock grazing on plant diversity:an analysis across dryland ecosystems and scales in South Africa.Ecol.Appl.24(5),1188-1203.
Holmes,T., Rice,K.,1996.Patterns of growth and soil-water utilization in some exotic and native perennial bunch grasses of California.Ann.Bot.78,233-243.
Hoover,D.,Knapp,K.,Smith,D.,2014.Resistance and resilience of grassland ecosystem to climate extremes.Ecology 95,2646-2656.
Huston,M.,1979.A general hypothesis of species diversity.Am.Nat.113,81-101.Jacobs,S.,Neiman,R.,2008.Large African herbivores decrease herbaceous plant biomass while increasing plant species richness in a semiarid savannah toposequence.J.Arid Environ.72,891-903.
Ji,L.,Peters,A.,2013.Assessing vegetation response to drought in the northern Great Plains using vegetation and drought indices.Remote sensing environments.Elsevier 87(1),1555-1570.
K'Otuto,G.,Otieno,D.,Seo,B., Ogindo,H., Onyango,J.,2012.Carbon dioxide exchange and biomass productivity of the herbaceous layer of a managed tropical savanna ecosystem in western Kenya.J.Plant Ecol.6(4),286-297.
Kikoti,A., Mlingo,C.,2015.Impact of livestock grazing on plant species composition in a montane forest of the northern slope of Mount Kilimanjaro,Tanzania.Int.J.Biodivers.Sci.Ecosyst.Serv.Manag.11,114-127.
Kikoti,A., Mligo,C.,Kilemo,B., 2015.The impact of grazing on plant natural regeneration in Northern Slopes of Mount Kilimanjaro,Tanzania.Open J.Ecol.5,266-273.
Kioko,J.,Kiringe,J.,Seno,S.,2012.Impact of livestock grazing on savanna grassland in Kenya.J.Arid Land 4(1),29-35.
Koerner,S.,Collins,S., 2014.Interactive effects of grazing,drought and fire on grassland plant communities in North America and South Africa.Ecology 95.98-109.
Lechmer-Oertel,R.,Kerley,G.,Cowling,R., 2005.Patterns and implications of transformation in semi-arid succulent thicket,South Africa.J.Arid Environ.63,459-474.
Lezama,F., Baeza,S.,Altesor,A.,Cesa,A.,Chaneton,J.,Paruelo,M., 2014.Variation of grazing induced vegetation changes across a large-scale productivity gradient.J.Veg.Sci.25,8-21.
Lovette,J.,Midgley,P., Barnard,B.,2005.Climate change and ecology in Africa.Afr.J.Ecol.43,279-281.
Maitama,J.,Oslon,J.,Mugatha,S.,Mugisha,S.,Mutie,I.,2010.Land use changes,impacts and options for sustaining productivity and livelihoods in the basin of Lake Victoria.J.Sustain.Dev.Afr.12,189-206.
Mureithi,S.,Verdoodt,A.,Njoka,T.,Gachene,K.,Warinwa,F.,Ranst,E.,2014.Impact of community conservation management on herbaceous layer and soil nutrients in a Kenyan semi-arid savannah.Land Degrad.Dev.10,1002-1015.
Muriuki,G.,Njoka,T.,Reid,R., Nyariki,D.,2005.Tsetse control and landuse change in Lambwe valley,south western Kenya.Agric.Ecosyst.Environ.106,99-107.
Musau,J.,Patil,S.,Sheffield,J.,Marshall,M., 2016.Spatio-temporal vegetation dynamics and relationship with climate over East Africa.Hydrol.Earth Syst.10,502-519.
Muyekho,F.,Barrison,A.,Khan,Z., 2004.A Primer on Grass Identification and their uses in Kenya.Communication Limited,Nairobi,Kenya.
Njoka,T.,Muriuki,G., Reid,R., Nyariki,D.,2003.The use of sociological methods to asses land use change:a case study of Lambwe valley,Kenya.Int.J.Sociol.7(3),181-185.
Olff,H., Ritchie,M., 1998.Effect of herbivores on grassland plant biodiversity.Trends Ecol.Evol.13,261-265.
Otieno,D., K'Otuto,G., Jakli,B.,Maina,J.,Jung,E., Onyango,J.,2011.Spatial heterogeneity in ecosystem structure and productivity in a moist Kenyan savanna.Plant Ecol.212,769-789.
Pekin,B., Wisdom,M., Endress,B.,Neylor,B.,Parks,C.,2014.Ungulate browsing maintains shrub diversity in the absence of episodic disturbance in seasonallyarid conifer forest.PLoS One 9,e86288.https://doi.org/10.1371/journal.Prone.0086288.
Proulx,M.,Mazumder,A.,1998.Reversal of grazing impact on plant species richness in nutrient-poor vs nutrient rich ecosystems.Ecology 79,2581-2591.
Ren,H.,Schonbach,P.,Wan,H.,Gierus,M.,Taube,2012.Effect of grazing intensity and environmental factors on species composition and diversity in Typical Steppe of Inner Mongolia,China.PLoS One 7(12),E52180 doi:137/journal.pone.0052180.
Rutherford,M.,Powrie,L.,Husted,L.,2012.Herbivore-driven land degradation:consequences for plant diversity and soil in arid subtropical thicket in south eastern African savannah.Nat.Lett.438,846-849.
Schieltz,M., Rubenstein,1.,2016.Evidence based review:positive versus negative effects of livestock grazing on wildlife.What do we really know?Environ.Res.Lett.11,113003.
Scott-Shaw,Morris,2015.Grazing depletes forbs species diversity in mesic grasslands of KwaZulu-Natal,South Africa.Afr.J.Range Forage Sci.32,21-31.
Serdeczny,O.,Adams,S.,Baarsch,F.,Coumou,D.,Robinson,A.,Hare,W.,Schaeffer,M.,Perrette,M.,2015.Climate change impact in Sub-Saharan Africa:from physical changes to their social repercussions.Region.Clim.Change 15,8-21.
Silva,K.,Santos,J.,Santos,D.,Ferraz,E.,Aruaj,E.,2013.Spatial variation in structure and composition of the herbaceous community in a semiarid region of northeastern Brazil.Braz.J.Biol.73,135-148.
Ssemmanda,I.,Gelorini,V.,Verschuren,D.,2014.Sensitivity of East African savannah vegetation to historical moisture-balance variation.Clim.Past 10,2067-2080.
Thirgood,S., 2009.Effect of fencing and grazing on a kobresia-dominated meadow in the Quinghai Plateau.Plant Soil 319(1-2),115-126.
Van Coller,Siebert,F.,2014.Herbaceous biomass-species diversity relationship in nutrient hotspots of a semi-arid African riparian ecosystem.Afr.J.Range Forage Sci.119,1-11.
Van der Plas,A.,Zeinstar,P.,Veldhuis,M.,Fokkema,R.,Tielens,E., Howinson,R.,Olff,H.,2013.Response of savannah lawn and bunch grasses to water limitation.Plant Ecol.214(9),1157-1168.
Van Oudtshoorn,F.,2002.Guide to Grasses of South Africa.BRIZA Publication,Pretoria,South Africa.
Waite,S., 2000.Statistical Ecology in Practice;A Guide to Analysing Environmental and Ecological Field Data.Prentice Hall,England.
Wang,W.,Wang,J.,Li,S., Wu,H.,Liu,T.,2010.The impact of sustained drought on vegetation ecosystem in South West China based on remote sensing.Proc.Environ.Sci.2,1679-1691.
Western,D., Mose,V.,Worden,J., Maitumo,D., 2015.Predicting extreme drought in savannah Africa:a comparison of proxy and direct measures in detecting biomass fluctuations,trends and their causes.PLoS One 10(8),1371-1384.Xiong,D., Shi,P.,Zhang,X.,Zou,B.,2016.Effects of grazing exclusion on carbon sequestration and plant diversity in grassland of China.A meta-analysis.Ecol.Eng.94,647-655.
Zerbo,I.,Markus,B.,Ouedraogo,O.,Hahn,K.,Thiombiano,A.,2016.Effects of climate and landuse on herbaceous species richness and vegetation composition in West Africa Savanna Ecosystem.J.Bot.10,1155-1166.
Zhu,X., Jia,H.,Jiang,P.,Zhao,C.,Hu,Y.,Cao,Y.,2012.Effects of enclosure on plant diversity and community characteristics of pasture of Middle Tianshan Mountain,Pratacult.Sci.29,989-992.
Allsopp,R.,Baldry,T., 1972.A general description of the Lambwe valley area of south Nyanza district,Kenya.World Health Organisat.Bull.47,691-697.
Arnhold,S.,Otieno,D.,Onyango,J.,Koeller,T., Huwe,B., Tenhunen,J., 2015.Soil properties along a gradient from hillslopes to the savanna plains in the Lambwe Valley,Kenya.Soil Tillage Res.154,75-83.
Augustine,J.,2003.Spatial heterogeneity of herbaceous layer of a semi-arid savannah ecosystem.Plant Ecol.167,319-332.
Bakker,C., Blair,J., Knnap,A., 2003.Does resource availability,resource heterogeneity or species turnover mediate changes in plant species richness in grazed grassland?Oecologia 137,385-391.
Bakker,E., Ritchie,M.,Olff,H., Milchunas,D., Knops,J.,2006.Herbivore impact on grassland plant diversity depends on habitat productivity and herbivore size.Ecol.Lett.9,780-788.
Bat-Oyan,T., Shinoda,M.,Cheng,Y.,Purevdorj,Y., 2016.Effect of grazing and precipitation variability on vegetation dynamics in a Mongolian dry steppe.J.Plant Ecol.9(5),508-519.
Baudena,M.,Dekker,S.,Bodegom,P.,Cuesta,B.,Higgins,S.,Lehsten,V.,Reick,C.,Rietterk,M.,Yin,Z., Zavala,M., Brovkin,V.,2015.Forests,savannas,grasslands:bridging the knowledge gap between ecology and Dynamic Vegetation Models.Biogeosciences 12.,1833-1848.
Bilota,G.,Brazier,R.,Haygarth,P.,2007.The impact of grazing animals on the quality of soils,vegetation,and surface waters in intensively managed grasslands.Adv.Agron.94,237-280.
Brady,N., Weil,R.,2002.The Nature and Properties of Soils,13th Ed.Prentice-Hall Inc,New Jersey,USA,p.960.
Conway,D., Allison,E.,Felstead,R., Goulden,M.,2005.Rainfall variation in East Africa:implication for natural resources management and livelihood.Phil.Trans.363,49-54.
Deng,L.,Sweeney,S., Shangguan,Z., 2014.Grassland responses to grazing disturbance:plant diversity changes with grazing intensity in a desert steppe.Grass Forage Sci.69,524-533.
Farret,E.,Ashton,J.,Suding,N.,2014.Separating direct and indirect effects of global change:a population dynamic modelling approach using readily available field data.Glob.Chang.Biol.20.,1238-1250.
Fynn,R.,O'Connor,T.,2000.Effect of stocking rate and rainfall on rangeland dynamics and cattle performance in a semiarid savannah,South Africa.J.Appl.Ecol.37,491-507.
Fynn,S.,Augustine,J.,Peel,S., de Garine-Wichatitsky,Michael,2016.Strategic management of livestock to improve biodiversity conservation in Africansavannahs:a conceptual basis for wildlife-livestock coexistence-A review.J.Appl.Ecol.53,388-397.
Grime,J.,1973.Control of species density in a herbaceous vegetation.J.Environ.Manag.1,151-167.
Grime,J., 1998.Benefits of plant diversity to ecosystems:immediate,filter and founder effects.J.Ecol.86, 902-910.
Hanke,W.,Bohner, J.,Dreber,N.,Jurgen,N., Schmiedel,U., Wesuls,D., Dengler,J.,2014.The impact of livestock grazing on plant diversity:an analysis across dryland ecosystems and scales in South Africa.Ecol.Appl.24(5),1188-1203.
Holmes,T., Rice,K.,1996.Patterns of growth and soil-water utilization in some exotic and native perennial bunch grasses of California.Ann.Bot.78,233-243.
Hoover,D.,Knapp,K.,Smith,D.,2014.Resistance and resilience of grassland ecosystem to climate extremes.Ecology 95,2646-2656.
Huston,M.,1979.A general hypothesis of species diversity.Am.Nat.113,81-101.Jacobs,S.,Neiman,R.,2008.Large African herbivores decrease herbaceous plant biomass while increasing plant species richness in a semiarid savannah toposequence.J.Arid Environ.72,891-903.
Ji,L.,Peters,A.,2013.Assessing vegetation response to drought in the northern Great Plains using vegetation and drought indices.Remote sensing environments.Elsevier 87(1),1555-1570.
K'Otuto,G.,Otieno,D.,Seo,B., Ogindo,H., Onyango,J.,2012.Carbon dioxide exchange and biomass productivity of the herbaceous layer of a managed tropical savanna ecosystem in western Kenya.J.Plant Ecol.6(4),286-297.
Kikoti,A., Mlingo,C.,2015.Impact of livestock grazing on plant species composition in a montane forest of the northern slope of Mount Kilimanjaro,Tanzania.Int.J.Biodivers.Sci.Ecosyst.Serv.Manag.11,114-127.
Kikoti,A., Mligo,C.,Kilemo,B., 2015.The impact of grazing on plant natural regeneration in Northern Slopes of Mount Kilimanjaro,Tanzania.Open J.Ecol.5,266-273.
Kioko,J.,Kiringe,J.,Seno,S.,2012.Impact of livestock grazing on savanna grassland in Kenya.J.Arid Land 4(1),29-35.
Koerner,S.,Collins,S., 2014.Interactive effects of grazing,drought and fire on grassland plant communities in North America and South Africa.Ecology 95.98-109.
Lechmer-Oertel,R.,Kerley,G.,Cowling,R., 2005.Patterns and implications of transformation in semi-arid succulent thicket,South Africa.J.Arid Environ.63,459-474.
Lezama,F., Baeza,S.,Altesor,A.,Cesa,A.,Chaneton,J.,Paruelo,M., 2014.Variation of grazing induced vegetation changes across a large-scale productivity gradient.J.Veg.Sci.25,8-21.
Lovette,J.,Midgley,P., Barnard,B.,2005.Climate change and ecology in Africa.Afr.J.Ecol.43,279-281.
Maitama,J.,Oslon,J.,Mugatha,S.,Mugisha,S.,Mutie,I.,2010.Land use changes,impacts and options for sustaining productivity and livelihoods in the basin of Lake Victoria.J.Sustain.Dev.Afr.12,189-206.
Mureithi,S.,Verdoodt,A.,Njoka,T.,Gachene,K.,Warinwa,F.,Ranst,E.,2014.Impact of community conservation management on herbaceous layer and soil nutrients in a Kenyan semi-arid savannah.Land Degrad.Dev.10,1002-1015.
Muriuki,G.,Njoka,T.,Reid,R., Nyariki,D.,2005.Tsetse control and landuse change in Lambwe valley,south western Kenya.Agric.Ecosyst.Environ.106,99-107.
Musau,J.,Patil,S.,Sheffield,J.,Marshall,M., 2016.Spatio-temporal vegetation dynamics and relationship with climate over East Africa.Hydrol.Earth Syst.10,502-519.
Muyekho,F.,Barrison,A.,Khan,Z., 2004.A Primer on Grass Identification and their uses in Kenya.Communication Limited,Nairobi,Kenya.
Njoka,T.,Muriuki,G., Reid,R., Nyariki,D.,2003.The use of sociological methods to asses land use change:a case study of Lambwe valley,Kenya.Int.J.Sociol.7(3),181-185.
Olff,H., Ritchie,M., 1998.Effect of herbivores on grassland plant biodiversity.Trends Ecol.Evol.13,261-265.
Otieno,D., K'Otuto,G., Jakli,B.,Maina,J.,Jung,E., Onyango,J.,2011.Spatial heterogeneity in ecosystem structure and productivity in a moist Kenyan savanna.Plant Ecol.212,769-789.
Pekin,B., Wisdom,M., Endress,B.,Neylor,B.,Parks,C.,2014.Ungulate browsing maintains shrub diversity in the absence of episodic disturbance in seasonallyarid conifer forest.PLoS One 9,e86288.https://doi.org/10.1371/journal.Prone.0086288.
Proulx,M.,Mazumder,A.,1998.Reversal of grazing impact on plant species richness in nutrient-poor vs nutrient rich ecosystems.Ecology 79,2581-2591.
Ren,H.,Schonbach,P.,Wan,H.,Gierus,M.,Taube,2012.Effect of grazing intensity and environmental factors on species composition and diversity in Typical Steppe of Inner Mongolia,China.PLoS One 7(12),E52180 doi:137/journal.pone.0052180.
Rutherford,M.,Powrie,L.,Husted,L.,2012.Herbivore-driven land degradation:consequences for plant diversity and soil in arid subtropical thicket in south eastern African savannah.Nat.Lett.438,846-849.
Schieltz,M., Rubenstein,1.,2016.Evidence based review:positive versus negative effects of livestock grazing on wildlife.What do we really know?Environ.Res.Lett.11,113003.
Scott-Shaw,Morris,2015.Grazing depletes forbs species diversity in mesic grasslands of KwaZulu-Natal,South Africa.Afr.J.Range Forage Sci.32,21-31.
Serdeczny,O.,Adams,S.,Baarsch,F.,Coumou,D.,Robinson,A.,Hare,W.,Schaeffer,M.,Perrette,M.,2015.Climate change impact in Sub-Saharan Africa:from physical changes to their social repercussions.Region.Clim.Change 15,8-21.
Silva,K.,Santos,J.,Santos,D.,Ferraz,E.,Aruaj,E.,2013.Spatial variation in structure and composition of the herbaceous community in a semiarid region of northeastern Brazil.Braz.J.Biol.73,135-148.
Ssemmanda,I.,Gelorini,V.,Verschuren,D.,2014.Sensitivity of East African savannah vegetation to historical moisture-balance variation.Clim.Past 10,2067-2080.
Thirgood,S., 2009.Effect of fencing and grazing on a kobresia-dominated meadow in the Quinghai Plateau.Plant Soil 319(1-2),115-126.
Van Coller,Siebert,F.,2014.Herbaceous biomass-species diversity relationship in nutrient hotspots of a semi-arid African riparian ecosystem.Afr.J.Range Forage Sci.119,1-11.
Van der Plas,A.,Zeinstar,P.,Veldhuis,M.,Fokkema,R.,Tielens,E., Howinson,R.,Olff,H.,2013.Response of savannah lawn and bunch grasses to water limitation.Plant Ecol.214(9),1157-1168.
Van Oudtshoorn,F.,2002.Guide to Grasses of South Africa.BRIZA Publication,Pretoria,South Africa.
Waite,S., 2000.Statistical Ecology in Practice;A Guide to Analysing Environmental and Ecological Field Data.Prentice Hall,England.
Wang,W.,Wang,J.,Li,S., Wu,H.,Liu,T.,2010.The impact of sustained drought on vegetation ecosystem in South West China based on remote sensing.Proc.Environ.Sci.2,1679-1691.
Western,D., Mose,V.,Worden,J., Maitumo,D., 2015.Predicting extreme drought in savannah Africa:a comparison of proxy and direct measures in detecting biomass fluctuations,trends and their causes.PLoS One 10(8),1371-1384.Xiong,D., Shi,P.,Zhang,X.,Zou,B.,2016.Effects of grazing exclusion on carbon sequestration and plant diversity in grassland of China.A meta-analysis.Ecol.Eng.94,647-655.
Zerbo,I.,Markus,B.,Ouedraogo,O.,Hahn,K.,Thiombiano,A.,2016.Effects of climate and landuse on herbaceous species richness and vegetation composition in West Africa Savanna Ecosystem.J.Bot.10,1155-1166.
Zhu,X., Jia,H.,Jiang,P.,Zhao,C.,Hu,Y.,Cao,Y.,2012.Effects of enclosure on plant diversity and community characteristics of pasture of Middle Tianshan Mountain,Pratacult.Sci.29,989-992.