Publikationen
Es wurden 7 Publikationen gefunden
Ostertag, R.; Restrepo, C.; Dalling, J.W.; Martin, P.H.; Abiem, I.; Aiba, S.; Alvarez-Dávila, E.; Aragón, R.; Ataroff, M.; Chapman, H.; Cueva, A.; Fadrique, B.; Fernández, R.D.; González, G.; Gotsch, S.G.; Häger, A.; Homeier, J.; Iñiguez-Armijos, C.; Llambi, L.D.; Moore, G.W.; Næsborg, R.R.; Poma López, L.N.; Vieira Pompeu, P.; Powell, J.R.; Ramírez Correa, J.A.; Scharnagl, K.; Tobón, C. & Williams, C.B. (2021): Litter decomposition rates across tropical montane and lowland forests are controlled foremost by climate. Biotropica 54(2), 309-326.
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DOI: 10.1111/btp.13044
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Abstract:
Abstract:
The “hierarchy of factors” hypothesis states that decomposition rates are controlled primarily by climatic, followed by biological and soil variables. Tropical montane forests (TMF) are globally important ecosystems, yet there have been limited efforts to provide a biome-scale characterization of litter decomposition. We designed a common litter decomposition experiment replicated in 23 tropical montane sites across the Americas, Asia, and Africa and combined these results with a previous study of 23 sites in tropical lowland forests (TLF). Specifically, we investigated (1) spatial heterogeneity
in decomposition, (2) the relative importance of biological factors that affect leaf and wood decomposition in TMF, and (3) the role of climate in determining leaf litter decomposition rates within and across the TMF and TLF biomes. Litterbags of two mesh sizes containing Laurus nobilis leaves or birchwood popsicle sticks were spatially dispersed and incubated in TMF sites, for 3 and 7 months on the soil surface and at 10–15 cm depth. The within-site
replication demonstrated spatial variability in mass loss. Within TMF, litter type was the predominant biological factor influencing decomposition (leaves > wood), with mesh and burial effects playing a minor role.
When comparing across TMF and TLF, climate was the predominant control over decomposition,but the Yasso07 global model (based on mean annual temperature and precipitation) only modestly predicted decomposition rate. Differences in controlling factors between biomes suggest that TMF, with their high rates of carbon storage, must be explicitly considered when developing theory and models to elucidate carbon cycling rates in the tropics.
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Keywords: |
climate |
decomposition |
tropical montane forests (TMF) |
Rollenbeck, R.; Trachte, K. & Bendix, J. (2016): A New Class of Quality Controls for Micrometeorological Data in Complex Tropical Environments. Journal of Atmospheric and Oceanic Technology 33(1), 169-183.
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DOI: 10.1175/JTECH-D-15-0062.1
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Abstract:
Abstract:
Quality control is a particularly demanding problem for micrometeorological studies in complex environments. With the transition to electronic sensing and storage of climate data in high temporal resolution,
traditional approaches of homogenization are insufficient for addressing the small-scale variability and spatial
heterogeneity of the data. This problem can be successfully addressed by introducing a new class of control
procedures based on the physical and climatological relations between different climate variables. The new
approach utilizes knowledge about the interdependency of air temperature, precipitation, radiation, relative
air humidity, cloud cover, and visibility to develop empirical functions for determining the probability
margins for the co-occurrence of specific conditions in tropical mountains and deserts. It can also be applied to
other geographic settings by adjusting the parameters derived from the data itself. All procedures are integrated into a processing chain with feedback loops and combined with conventional logical and statistical
checks, which enables it to detect small errors that normally pass unnoticed. The algorithms are also adapted
to incorporate the short time steps of the original data to retain the potential for detailed process analyses.
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Keywords: |
climate |
microclimate |
Climate variability |
data quality |
Wagner, F.H.; Bräuning, A.; Homeier, J.; Spannl, S.; Volland, F. & et, a. (2016): Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests. Biogeosciences 13, 2537–2562.
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DOI: 10.5194/bg-13-2537-2016
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Abstract:
Abstract:
The seasonal climate drivers of the carbon cycle
in tropical forests remain poorly known, although these
forests account for more carbon assimilation and storage than
any other terrestrial ecosystem. Based on a unique combination
of seasonal pan-tropical data sets from 89 experimental
sites (68 include aboveground wood productivity measurements
and 35 litter productivity measurements), their associated
canopy photosynthetic capacity (enhanced vegetation
index, EVI) and climate, we ask how carbon assimilation
and aboveground allocation are related to climate seasonality
in tropical forests and how they interact in the seasonal
carbon cycle. We found that canopy photosynthetic capacity
seasonality responds positively to precipitation when rainfall
is < 2000mm/yr (water-limited forests) and to radiation
otherwise (light-limited forests). On the other hand, independent
of climate limitations, wood productivity and litterfall
are driven by seasonal variation in precipitation and
evapotranspiration, respectively. Consequently, light-limited
forests present an asynchronism between canopy photosynthetic
capacity and wood productivity. First-order control by
precipitation likely indicates a decrease in tropical forest productivity in a drier climate in water-limited forest, and in current light-limited forest with future rainfall < 2000mm/yr.
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Keywords: |
climate |
tree growth |
litterfall |
Werner, F.A.; Köster, N.; Kessler, M. & Gradstein, S.R. (2011): Is the resilience of epiphyte assemblages to human disturbance a function of local climate?. Ecotropica 17, 15-20.
Peters, T.; Bräuning, A.; Münchow, J. & Richter, M. (2014): An ecological paradox: high species diversity and low position of the upper forest line in the Andean Depression. Ecology and Evolution ece.3.1078, 1-12.
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DOI: DOI:10.1002/ece3.1078
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Abstract:
Abstract:
Systematic investigations of the upper forest line (UFL) primarily concentrate on mid and high latitudes of the Northern Hemisphere, whereas studies of Neotropical UFLs are still fragmentary. This article outlines the extraordinary high tree diversity at the UFL within the Andean Depression and unravels the links between the comparatively low position of the local UFL, high tree-species diversity, and climate. On the basis of Gentry?s rapid inventory methodology for the tropics, vegetation sampling was conducted at 12 UFL sites, and local climate (temperature, wind, precipitation, and soil moisture) was investigated at six sites. Monotypic forests dominated by Polylepis were only found at the higher located margins of the Andean Depression while the lower situated core areas were characterized by a species-rich forest, which lacked the elsewhere dominant tree-species Polylepis. In total, a remarkably high tree-species number of 255 tree species of 40 different plant families was found. Beta-diversity was also high with more than two complete species turnovers. A non-linear relationship between the floristic similarity of the investigated study sites and elevation was detected. Temperatures at the investigated study sites clearly exceeded 5.5°C, the postulated threshold value for the upper tree growth limit in the tropics. Instead, quasi-permanent trade winds, high precipitation amounts, and high soil water contents affect the local position of the UFL in a negative way. Interestingly, most of the above-mentioned factors are also contributing to the high species richness. The result is a combination of a clearly marked upper forest line depression combined with an extraordinary forest line complexity, which was an almost unknown paradox.
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Keywords: |
climate |
air temperature |
Andes |
Biodiversity |
upper forest line |
andean depression |
Kottke, I.; Setaro, S.; Haug, I.; Herrera, P.; Cruz, D.; Suarez, J.P.; Fries, A.; Adams, J.; Gerique, A.; Homeier, J. & Werner, F.A. (2013): Mycorrhiza Networks Promote Biodiversity and Stabilize the Tropical Mountain Rain Forest Ecosystem: Perspectives for Understanding Complex Communities. In: J. Bendix, E. Beck, A. Bräuning, F. Makeschin, R. Mosandl, S. Scheu, W. Wilcke. (eds.): Ecosystem Services, Biodiversity and Environmental Change in a Tropical Mountain Ecosystem of Sou l ( 221), Springer Verlag, Heidelberg, 438.
Windhorst, D.; Waltz, T.; Timbe, E.; Frede, H. & Breuer, L. (2013): Impact of elevation and weather patterns on the isotopic composition of precipitation in a tropical montane rainforest. Hydrol. Earth Syst. Sci. 177, 409-419.
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DOI: 10.5194/hess-17-409-2013
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Abstract:
Abstract:
This study presents the spatial and temporal variability of ?18O and ?2H isotope signatures in precipitation of a south Ecuadorian montane cloud forest catchment (San Francisco catchment). From 2 September to 25 December 2010, event sampling of open rainfall was conducted along an altitudinal transect (1800 to 2800 m a.s.l.) to investigate possible effects of altitude and weather conditions on the isotope signature.
The spatial variability is mainly affected by the altitude effect. The event based ?18O altitude effect for the study area averages ?0.22‰ × 100 m?1 (?2H: ?1.12‰ × 100 m?1). The temporal variability is mostly controlled by prevailing air masses. Precipitation during the times of prevailing southeasterly trade winds is significantly enriched in heavy isotopes compared to precipitation during other weather conditions. In the study area, weather during austral winter is commonly controlled by southeasterly trade winds. Since the Amazon Basin contributes large amounts of recycled moisture to these air masses, trade wind-related precipitation is enriched in heavy isotopes. We used deuterium excess to further evaluate the contribution of recycled moisture to precipitation. Analogously to the ?18O and ?2H values, deuterium excess is significantly higher in trade wind-related precipitation. Consequently, it is assumed that evaporated moisture is responsible for high concentrations of heavy isotopes during austral winter.
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Keywords: |
climate |
rainwater chemistry |
hydrological processes |
isotopes |