Showing papers by "Gerhard Gerold published in 2017"

Effects of conversion of native cerrado vegetation to pasture on soil hydro-physical properties, evapotranspiration and streamflow on the Amazonian agricultural frontier.

Abstract: Understanding the impacts of land-use change on landscape-hydrological dynamics is one of the main challenges in the Northern Brazilian Cerrado biome, where the Amazon agricultural frontier is located. Motivated by the gap in literature assessing these impacts, we characterized the soil hydro-physical properties and quantified surface water fluxes from catchments under contrasting land-use in this region. We used data from field measurements in two headwater micro-catchments with similar physical characteristics and different land use, i.e. cerrado sensu stricto vegetation and pasture for extensive cattle ranching. We determined hydraulic and physical properties of the soils, applied ground-based remote sensing techniques to estimate evapotranspiration, and monitored streamflow from October 2012 to September 2014. Our results show significant differences in soil hydro-physical properties between the catchments, with greater bulk density and smaller total porosity in the pasture catchment. We found that evapotranspiration is smaller in the pasture (639 ± 31% mm yr-1) than in the cerrado catchment (1,004 ± 24% mm yr-1), and that streamflow from the pasture catchment is greater with runoff coefficients of 0.40 for the pasture and 0.27 for the cerrado catchment. Overall, our results confirm that conversion of cerrado vegetation to pasture causes soil hydro-physical properties deterioration, reduction in evapotranspiration reduction, and increased streamflow.

Spatial-temporal soil moisture dynamics under different cocoa production systems

Abstract: Soil moisture has high spatial and temporal variability, depending on topography, soil texture, vegetation and meteorological conditions. It influences many processes in the soil and supplies water to the vegetation. This is often a limiting factor in agricultural production. Over an 18-month period, we measured soil moisture dynamics down to a depth of 70 cm in a long-term trial in Bolivia comprising six different land-use systems, i.e. cocoa monocultures and agroforestry systems, both under organic and conventional management, successional cocoa agroforestry systems and a natural fallow. Soil was heterogeneous over the area and in depth. We identified and separated two soil groups which differed in both, texture and soil water retention capacity. Considering the two groups, we assessed the effect of the different land-use systems on soil moisture dynamics and plant available water on the one hand, and how different soil moisture conditions affect growth and production of cocoa on the other. In monocultures with shallow rooting cocoa only, soil moisture decreased mainly in the uppermost soil layer during the dry season and the lower layers kept more moisture year round. In agroforestry systems soil moisture decreased homogeneously over the soil profile, implying a complementarity in water use of cocoa and deeper rooting trees. The uppermost soil layer in the agroforestry systems had higher soil moisture than in the monoculture, demonstrating the role of shade trees to reduce water loss from top soil by evaporation and transpiration of the cocoa. Even though one soil group had continuously higher water availability than the other group, we did not find an effect on the cocoa yield. Cocoa relies on sufficient water supply, but beside information on the precipitation it is important to know the soil structure and soil water retention capacity when discussing water availability for cocoa production and to consider the heterogeneity of the soil even over small area.

Diversity and composition of herbaceous angiosperms along gradients of elevation and forest-use intensity.

Abstract: Terrestrial herbs are important elements of tropical forests; however, there is a lack of research on their diversity patterns and how they respond to different intensities of forest-use. The aim of this study was to analyze the diversity of herbaceous angiosperms along gradients of elevation (50 m to 3500 m) and forest-use intensity on the eastern slopes of the Cofre de Perote, Veracruz, Mexico. We recorded the occurrence of all herbaceous angiosperm species within 120 plots of 20 m x 20 m each. The plots were located at eight study locations separated by ~500 m in elevation and within three different habitats that differ in forest-use intensity: old-growth, degraded, and secondary forest. We analyzed species richness and floristic composition of herb communities among different elevations and habitats. Of the 264 plant species recorded, 31 are endemic to Mexico. Both α- and γ-diversity display a hump-shaped relation to elevation peaking at 2500 m and 3000 m, respectively. The relative contribution of between-habitat β-diversity to γ-diversity also showed a unimodal hump whereas within-habitat β-diversity declined with elevation. Forest-use intensity did not affect α-diversity, but β-diversity was high between old-growth and secondary forests. Overall, γ-diversity peaked at 2500 m (72 species), driven mainly by high within- and among-habitat β-diversity. We infer that this belt is highly sensitive to anthropogenic disturbance and forest-use intensification. At 3100 m, high γ-diversity (50 species) was driven by high α- and within-habitat β-diversity. There, losing a specific forest area might be compensated if similar assemblages occur in nearby areas. The high β-diversity and endemism suggest that mixes of different habitats are needed to sustain high γ-richness of terrestrial herbs along this elevational gradient.

Environmental Growing Conditions in Five Production Systems Induce Stress Response and Affect Chemical Composition of Cocoa (Theobroma cacao L.) Beans.

Abstract: Cocoa beans are produced all across the humid tropics under different environmental conditions provided by the region but also by the season and the type of production system. Agroforestry systems compared to monocultures buffer climate extremes and therefore provide a less stressful environment for the understory cocoa, especially under seasonally varying conditions. We measured the element concentration as well as abiotic stress indicators (polyamines and total phenolic content) in beans derived from five different production systems comparing monocultures and agroforestry systems and from two harvesting seasons. Concentrations of N, Mg, S, Fe, Mn, Na, and Zn were higher in beans produced in agroforestry systems with high stem density and leaf area index. In the dry season, the N, Fe, and Cu concentration of the beans increased. The total phenolic content increased with proceeding of the dry season while other abiotic stress indicators like spermine decreased, implying an effect of the water availability on the chemical composition of the beans. Agroforestry systems did not buffer the variability of stress indicators over the seasons compared to monocultures. The effect of environmental growing conditions on bean chemical composition was not strong but can contribute to variations in cocoa bean quality.

Richness and distribution of herbaceous angiosperms along gradients of elevation and forest disturbance in central Veracruz, Mexico

Abstract: Background: Terrestrial herbs are a significant floristic element of tropical forests; however, there is a lack of research focused on this plant group. Question: Which are the patterns of species distribution of herbaceous angiosperms along gradients of elevation and forest disturbance at Cofre de Perote, central Veracruz, Mexico? Studied species: Terrestrial herbaceous angiosperms. Study site and years of study: Eastern slopes of Cofre de Perote, central Veracruz, Mexico; from 2012 until 2014. Methods: We established an elevational transect (40 to 3,520 m), where floristic sampling in eight study sites within elevational belts of about 500 m each were realized. We recorded the occurrence of terrestrial angiosperm herbs within 135 20 × 20 m plots, distributed in old-growth, degraded forest, secondary vegetation, as well as azonal vegetation. Species richness and floristic composition were compared between the different elevational belts and forest disturbance. Results: We recorded a total of 264 herb species, 31 endemic to Mexico and three classified as threatened. This number of species represents 5.7 % of Veracruz’s herbaceous angiosperm flora. The highest species richness was recorded at 2,500 m (76) and 1,500 m (52). In most of the cases, secondary forests showed the highest species richness independently of the elevational gradient, whereas old-growth forests had fewer species. Conclusions: The observed species richness, including endemic elements, highlights the importance for plant conservation of the area which is threatened by land use changes. Additionally, we suggest that vegetation variations formed by mature, disturbed and secondary forests is acceptable (and unavoidable) and can even increase species richness.

Experiences of inter- and transdisciplinary research – a trajectory of knowledge integration within a large research consortium

Abstract: Although interand transdisciplinary research has found its way to the forefront of calls, funding and publications, interdisciplinary projects often start from scratch constructing their research environment. In this article we will point to the enormous potential, the learnings, as well as some of the difficulties and pitfalls frequently encountered in large interdisciplinary project consortia. With this in mind, we aim to transparently document and reflect upon our research process, reminding the readers that the authors are not academic specialists in the field of interand transdisciplinarity nor in the sociology of knowledge. To explain our motivation, we want to share valuable experiences and point to some learnings, especially regarding the interdependencies between interand transdisciplinarity. After a brief historical retrospective of the expectations towards science, the article describes the trajectory of knowledge production and integration of a rather large research consortium attempting to overcome typical communicative and conceptual hurdles while negotiating the strict preconceptions of the respective disciplines. During the process of knowledge integration, scientific recognition and time budgets remain the crucial challenges. Besides joint field research, the construction of four storylines and the continuous integration of data into the various and increasingly interlinked models that ultimately culminate in our future scenarios led to constant communication and disputes among the subprojects involved. During the course of the project, it became obvious that a new generation of young scientists is developing: scientists working in interdisciplinary and transdisciplinary thought communities with a grasp of both fundamental science and transdisciplinary practice, combined with the soft skills necessary to reconcile both worlds.

Process-based modelling of the impacts of land use change on the water balance in the Cerrado biome (Rio das Mortes, Brazil).

Abstract: Since the 1980s, the state of Mato Grosso, Brazil, exhibits high rates of Cerrado conversion in favour of soybean expansion and cattle ranching. This conversion process becomes obvious in the upper Rio das Mortes macro-catchment. The objective of this study was to assess the influence of future land use changes on the discharge dynamics of the Rio das Mortes River. A single catchment approach was applied with the physically-based water balance simulation model WaSiM 8.5.0 (Schulla and jaSper 2007) to simulate land use scenarios. In Scenario 1, only small pasture sites (< 1 km²) were converted into the respective land use type surrounding them (i.e. cropland or Cerrado vegetation), whereas in Scenario 2 all pasture sites were converted into cropland and all Cerrado patches were then transformed into pastures. The WaSiM model was calibrated and validated based on discharge data measured at two gauging stations, achieving Nash-Sutcliffe coeffcients of 0.81 calibration) and 0.68 (validation). Main problems in modelling arise because of scarce spatial distributed data on subsurface parameter and vegetation parameter (Cerrado biome). Therefore, the use of the numerical groundwater model and manifold calibration runs were essential in this modelling approach to allow the simulation of the high levels of baseflow during the dry season and the transition from the dry to the wet season. The immediate rise of the baseflow in response to the increasing precipitation at beginning of the rainy season is a result of high soil hydraulic conductivity and groundwater recharge. These soil characteristics apparently persist on newly-created pasture and cropland sites, which still exhibit high ksat values after deforestation. Simulated evapotranspiration is comparable to literature values (Eddy flux measurements, MODIS-EVI calculation) and recently done paired micro-catchment studies in this catchment. The scenario analysis indicates that there are only small differences in runoff volume, which is directly related to the precipitation changes. In the scenario 2, groundwater recharge and base flow increase, whereas surface runoff does not. Therefore, the ongoing land use intensification with pasture conversion to cropland, remaining high infiltration and slight increase of evapotranspiration may not change runoff volume and discharge characteristics.

Impacts of carbon-optimised land use management in Southern Amazonia – multi-disciplinary perspectives: An Introduction

Abstract: In Brazilian Amazonia over 750,000 km2 of forest has been cut down from 1970s until 2013 (NoGueira et al. 2015). During this period, Amazonian deforestation rates have always increased until 2003/2004 (INPE 2014; Nepstad et al. 2014), and after a considerable deceleration until 2013 (Boucher et al. 2013), the trend has returned to increase (schöNeNBerG et al. 2015). The conversion of rainforest and Cerrado into cattle pastures and agricultural land has various impacts on biodiversity, carbon stocks and carbon emissions, which are currently discussed in science, society and politics in the context of climate change (FearNside 2005; cox et al. 2000; Malhi et al. 2008). The massive land-use change occurring in the Amazon region attracts world-wide attention, as the Brazilian Amazon is of key importance for the (i) global and regional climate system, (ii) the global and regional water cycle, (iii) the planets genetic resources and (iv) the human cultural heritage. On top of this, the Brazilian Amazon is the world’s most prominent biomass carbon (C) pool, with 149 Mg C ha-1 being stored aboveand below-ground according to NoGueira et al. (2015) and the threat of losing all this carbon to the atmosphere is what explains a large part of the attention being currently paid to the fate of the Amazon rainforest. However, soares-Filho et al. (2006) predicted another 2.7 million km2 of deforestation until 2050 under “business-as-usual”-scenarios and another 0.5 million km2 was earlier expected for the Brazilian savannas (resck et al. 2000), which today presents a highly fragmented Cerrado landscape as a result. The Brazilian Government and international organizations have developed action programs with high priority on land use change, nature conservation, climate change mitigation and development of sustainable land management practices (e.g. related to the Kyoto-process, Brazilian ABC-program, National Climate Plan of Brazil, Amazon Fund; FearNside 2005; Nepstad et al. 2014; soares-Filho 2010; assuNcao et al. 2012; strassBurG et al. 2014). Officially, Brazil aims at reducing deforestation by 80 % for the Amazon by 2020 (soares-Filho et al. 2010). Since August 2014, deforestation soars again after clear-cutting of mature forest had declined from 19,500 km2 a–1 to 5,843 km2 in 2013 as a result of public policy and frontier governance (PPCDAm: Plan for the Protection and Control of Deforestation in the Amazon; Soy Moratorium; Cattle Moratorium, Arco Verde+, Critical Counties program, Amazon Region Protected Areas Program; FearNside 2015; Nepstad et al. 2014; tolleFsoN 2015). Up until today, deforestation concentrated in the “arc of deforestation” along the eastern and southern edges of the Amazon (see Fig. 2 in BarNi et al. 2015). Impact of land-use change (LUC) on various separate ecosystem services (ESS), including C sequestration and climate system stability, has been studied and presented in numerous research articles for the Amazon region. However, a more holistic examination which considers multiple ESSs in the context of local drivers and actors has not yet been sufficiently advanced. In fact, for many ESS touched by LUC in the Amazon region (FearNside 2005), contrasting – partly contradictory – patterns and processes have been reported (Tab. 1). This underlines the demand for an interdisciplinary, if not transdisciplinary approach to investigate, how the region at the Southern Amazon land-use frontier will develop in future and which consequences will likely arise for the local and global climate, biodiversity and society.