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AbstractIntroductionFForage plants and pastures within tropical farm ecosystemsSoil propertiesSoil chemical propertiesSSoil physical propertiesSoil biological propertiesNNutrient cyclingEErosion controlMicroclimateDDiseases, pests and weedsTTropical pastures within regional and global ecosystemsHydrologyRRegeneration of degraded landBBiodiversityAAtmosphere and global warmingConclusionsReferencesList of keywordsEcological Impact of Tropical Pastures andthe Potential of Forage Plants forSustainable Land Use Systems in the TropicsAn Annotated BibliographyA. Christinck, K. Probst, R. Schultze-KraftContents1 Abstract 22 Introduction 33 Forage plants and pastures within tropical farm ecosystems43.1 Soil properties 43.1.1 Soil chemical properties 43.1.2 Soil physical properties 83.1.3 Soil biological properties 93.2 Nutrient cycling 103.3 Erosion control 133.4 Microclimate 163.5 Diseases, pests and weeds 174 Tropical pastures within regional and global ecosystems 204.1 Hydrology 204.2 Regeneration of degraded land 224.3 Biodiversity 244.4 Atmosphere and global warming 275 Conclusions 316 References 337 List of keywords 144Chapter 1: Abstract21 AbstractThis annotated bibliography lists and summarizes the most relevant references on theecological impact of pastures and forage plants in tropical land use systems. It attempts toprovide knowledge from ecosystem and ecology-relevant disciplines to researchers anddevelopment workers.The bibliography is structured into different sections, considering on the one hand researchresults at farm-ecosystem level, and on the other hand studies at the regional and global level.Numerous reports are presented on the cultivation of multipurpose herbaceous and woodyforage plants and their effects on soil properties, nutrient cycling, erosion, microclimate, andphytosanitary aspects. On a regional and global level, focus is given to hydrological aspects,the regeneration of degraded land, biodiversity, and climate.The review indicates that basic data on ecological effects of pasture establishment andlivestock production are still scarce. This is the case in particular for long-term effects at theregional and global levels. Areas of future research are suggested. For a successfuldevelopment of sustainable land use systems interdisciplinary and interinstitutionalcollaboration is indispensable.Chapter 2: Introduction 32 IntroductionIn view of the growing human population and progressive degradation and destruction of thenatural resources, the search for sustainable land use systems is one of the most importantchallenges of our decade. Farming practices and livestock production are generally known tocontribute on a large scale to environmental degradation if they focus on short-termproductivity only.The aim of this study is to summarize current, tropical-pasture related knowledge fromdifferent ecosystem and ecology-relevant research fields. A second aim is to encourageinterdisciplinary research for developing sustainable farming systems that make use of thepotential that tropical pasture plants are suggested to offer for a wide range of ecological andsocio-economic conditions.The bibliography is structured into different sections, considering research at farm-ecosystemlevel on the one hand (soil properties; nutrient cycling; erosion control; microclimate;diseases, pests and weeds), and studies at the regional and global ecosystem level on the otherhand (hydrology; regeneration of degraded lands; biodiversity; atmosphere and globalwarming). Each section consists of a summarizing review giving insight into the subject, themain approaches of current research, and the lack of knowledge. References are numbered andare presented in Chapter 6 in numerical order, including keywords and abstracts. The list ofkeywords (Chapter 7) was especially prepared for this bibliography and does not necessarilyrepresent the keywords given in common databases (e.g., CAB-Abstracts, TROPAG,Agricola). If a reference lacked an abstract or summary, an own abstract was added and isidentified as such („Abstract by bibliography authors“).The study is based on an effort to gather relevant literature that was readily accessible in 1995but by no means do the authors claim the bibliography to be complete. The intention is ratherto provide a starting point for subsequent, exhaustive literature searches within the nineindividual research areas that are outlined in this study.Chapter 3: Forage plants and pastures within tropical farm ecosystems43 Forage plants and pastures within tropical farm ecosystems3.1 Soil propertiesAlthough a wide range of soil types are found in tropical regions, highly weathered and low-activity clay soils (Ultisols, Oxisols and Alfisols) in tropical forest and savanna regions are themost important groups used for farming, generally because of the favorable topographic andclimatic conditions in the respective regions {1, 2}. Ultisols and Oxisols are strongly acid andleached soils with low cation exchange capacity (CEC), very low inherent fertility, multiplenutrient (N, P, K, Ca, Mg, Zn) deficiencies and nutrient imbalances (e.g., toxic levels of Al orMn). Alfisols which are less acid and have high base saturation, are characterized byinherently low nutrient (N, P, K, S and Zn) status and low structural stability {1, 3}.Maintaining soil fertility and productivity are the major management problems when thesesoils are used for crop and pasture production {1}. In traditional cropping systems, based onshifting cultivation or bush fallow rotation, soil fertility was regenerated during fallow periodsthrough the activity of trees and other natural vegetation {4, 5, 6, 7, 8}. With the rapidlyraising human population and increasing pressure on cropping land, fallow periods arebecoming shorter so that fertility regeneration is less effective and productivity declines {1, 4,5, 7, 8, 9, 10}.In recent years, the cultivation of multipurpose herbaceous and woody forage plants becamemore and more relevant to maintain soil productivity in low-input productions systems undershortening fallows {1, 4, 5, 7, 8, 10, 11, 12, 13, 14, 15, 16, 17, 18}. Numerous studies havebeen conducted to assess changes in soil chemical, physical and biological propertiesassociated with the growth of pasture plants in different integrated farming systems.3.1.1 Soil chemical propertiesNitrogen deficiency is a major cause of declining soil fertility {13, 19, 20, 21}. As N is a veryexpensive nutrient to
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