Dr. Luitgard Schwendenmann

Research projects/Scientific supervision

Current

The importance of vegetation and soil on water fluxes under different land use systems, Veraguas, Panama

SENACYT (Secretaria Nacional de Ciencias, Tecnologia y Innovacion, Panama). Since 2007.
Cooporation with CATHALAC (Water Center for the Humid Tropics of Latin America and the Caribbean, Panama)

Read more about this project



Tree diversity as a control of whole tree water use in experimentally assembled mixtures in Panama

As natural tropical forests diminish and former rain forest areas are being degraded, more tropical tree plantations may be established. Up to now, they usually consist of a single exotic fast growing species. There is much, and recently increasing concern about high water use rates and non-sustainable soil nutrient depletion by such plantations. Recent approaches to reforestation in the tropics emphasize the establishment of native species in mixed stands. In an experimental plantation in Panama, native tree species, which in natural forest exhibit different relative growth rates, were planted at different diversity levels. The proposed project intends to analyze the whole tree water use of these species in plots of different diversity levels (1-, 3-, and 6-species mixtures), and to analyze the soil water partitioning among co-occurring species. The methods include soil hydrological measurements, tree sap flux analyses and the application of stable isotope techniques (dD). We plan to cooperate closely with a project studying the tree nutrient budget. Overall, we wish to increase the knowledge for an ecologically sound reforestation of degraded tropical areas with respect to tree species diversity and water and nutrient resources.

DFG. Since 2006. Read more about Sardinilla
Cooporation with Prof. Dr. C. Potvin, McGill University, Canada and Dr. Yvonne Oelmann and Prof. Dr. W. Wilcke, University of Mainz.





Drought effects on soil water regime and water partitioning in cacao agroforest and natural forest in Sulawesi, Indonesia


Many tropical forests maintain physiologically active green leaves and canopies even during extended dry periods. The uptake of water from deep soil may play an important role herewith. However, there is limited information about the drought response and involved mechanisms for Southeast Asian forests and cacao agroforestry systems. With respect to soil resource use within agroforestry systems complementarity among agricultural plants and trees could reduce competition, e.g. because trees take up water from greater soil depths. Besides water uptake directly for transpiration, the hydraulic redistribution of soil moisture by roots from relatively wet to dryer soil layers may also be an important mechanism. Integrated in the drought experiment we plan to (1) analyse the rates and depths of soil water depletion in natural forest and agroforest, (2) study separately the water use and partitioning of shade trees and cacao plants in the agroforestry system, and (3) test for both land use systems whether hydraulic redistribution is an important mechanism to cope with drought. The methods will include soil moisture measurements, stem sap flux studies in the agroforestry system and a deuterium labelling experiment. The results shall help to evaluate the response of forest and agroforestry systems to drought and improve our understanding of the ecological role of trees in agroforestry systems.

Project B4, SFB 552 (Stability of Tropical Rain Forest Margins, Indonesia).
DFG. Since 2006. Read more about STORMA





Reforestation of mangroves in the Can Gio Reserve, Vietnam effect of water pollution, species diversity and forest management on carbon and nitrogen cycling

In South Vietnam, 36% of the total mangrove forest was destroyed by herbicides sprayed during the war. After the war, an extensive reforestation program was undertaken in the Can Gio District (65 km southeast of Ho Chi Minh City). This study will address the following questions: i) what are the carbon and nitrogen isotopic composition and elemental content of leaves and sediment in natural and reforested mangrove stands, ii) do species differ in their leaf isotopic composition and elemental content, iii) is there any relationship between leaf isotopic composition/elemental content and species richness and /or forest management?



A study of linkages among carbon, water and nutrient cycles in old growth rainforest at La Selva Biological Station, Costa Rica

This study is part of an on-going project on carbon, water and nutrient cycling across the landscapes edaphic gradients at La Selva Biological Station, Costa Rica (CICLOS Project). The objectives of this sub-project on soil respirations are: i) quantification of soil respiration, ii) assessment of short and long-term variations in CO2 efflux, and iii) evaluations of the main factors influencing soil respiration

National Science Foundation, USA. Since 2005. Read more about CICLOS



Land-use change, carbon cycling and trace gas fluxes in Panama

Our carbon cycling studies focus on flask samples collected from atmospheric profiles in the nocturnal boundary layer, and on samples collected from soil respiration chambers. The profile samples are collected from eddy covariance towers at pasture and plantation sites, and from a 50-m-tall meteorological tower in rainforest. Preliminary data has shown that ecosystem respiration from the rainforest has a pure C3 signal, that from the pasture is pure C4, and the respiration from the plantation is mixed, as expected, and in general, ecosystem respiration, d13C values matched well with soil respiration d13C values.
Further we study the ‘Effects of forest clearing on soil organic carbon dynamics in Central Panama’ using natural d13C abundance, physical soil fractionation and carbon mineralization’. Soil samples were taken at 0-5, 5-10, 10-15, 15-20, 20-30, 30-40 and 40-50 cm depths from an undisturbed forest site and an adjacent clearing where the forest was cut approximately 90 years ago. Mineralizable carbon from bulk soil was measured in an incubation experiment. These experiments will contribute to parameterization of carbon cycle models for tropical ecosystems.

Smithsonian Tropical Research Institute. 2003 - 2006.
Read more about Sardinilla



Soil respiration in a topographically challenging environment (Big Snowies Mountains, Wyoming, USA)


The purpose of this study is to characterize the relationships between soil respiration and some physical and biological properties of the soil that drive it, including soil temperature, soil water content, and litter depth. We also examined spatial patterns of each factor at the hillslope scale (13,000 m²) and the individual plot scale (25 m²) to identify spatial correlations using geostatistics. Our study area in the Medicine Bow Mountains of Wyoming encompasses adjacent North- and South-facing slopes at 2800 m elevation. Lodgepole pine (Pinus contorta) forest dominates the watershed, and spruce (Picea engelmannii), fir (Abies lasiocarpa), and aspen (Populus tremuloides) are also present where soils are moist. Within each spatial scale, semi-variograms were used to identify the spatial range of soil respiration and its drivers. At the plot scale, soil respiration drivers exhibited stronger spatial patterns than soil respiration. At the hillslope scale, aspect played an important role in the relationships between soil respiration and these drivers. Drivers of soil respiration are still poorly understood at varying spatial scales; this project aims to better quantify these linkages for improved modelling of carbon fluxes at the watershed scale.

University of Wyoming. 2003 - 2006.