@article{EllsaesserRoellAhongshangbametal.2020,
  author    = {Ells{\"a}ßer, Florian and R{\"o}ll, Alexander and Ahongshangbam, Joyson and Waite, Pierre-Andr{\´e} and Hendrayanto, and Schuldt, Bernhard and H{\"o}lscher, Dirk},
  title     = {Predicting tree sap flux and stomatal conductance from drone-recorded surface temperatures in a mixed agroforestry system — a machine learning approach},
  series = {Remote Sensing},
  volume    = {12},
  journal   = {Remote Sensing},
  number    = {24},
  issn      = {2072-4292},
  doi       = {10.3390/rs12244070},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-220059},
  year      = {2020},
  abstract  = {Plant transpiration is a key element in the hydrological cycle. Widely used methods for its assessment comprise sap flux techniques for whole-plant transpiration and porometry for leaf stomatal conductance. Recently emerging approaches based on surface temperatures and a wide range of machine learning techniques offer new possibilities to quantify transpiration. The focus of this study was to predict sap flux and leaf stomatal conductance based on drone-recorded and meteorological data and compare these predictions with in-situ measured transpiration. To build the prediction models, we applied classical statistical approaches and machine learning algorithms. The field work was conducted in an oil palm agroforest in lowland Sumatra. Random forest predictions yielded the highest congruence with measured sap flux (r\(^2\) = 0.87 for trees and r\(^2\) = 0.58 for palms) and confidence intervals for intercept and slope of a Passing-Bablok regression suggest interchangeability of the methods. Differences in model performance are indicated when predicting different tree species. Predictions for stomatal conductance were less congruent for all prediction methods, likely due to spatial and temporal offsets of the measurements. Overall, the applied drone and modelling scheme predicts whole-plant transpiration with high accuracy. We conclude that there is large potential in machine learning approaches for ecological applications such as predicting transpiration.},
  language  = {en}
}
@phdthesis{Bruehl2001,
  author    = {Br{\"u}hl, Carsten A.},
  title     = {Leaf litter ant communities in tropical lowland rain forests in Sabah, Malaysia},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-1042},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2001},
  abstract  = {Large parts of the tropical lowland rain forests of Sabah (Malaysia) were transformed into secondary forests due to heavy logging. Additionally the remaining forest remnants are isolated from each other by large scale oil palm plantations. Biodiversity patterns and responses of the community of leaf litter ants were studied in anthropogenically disturbed habitats and primary forests of different size. In logged over forests, only 70 per cent of the species of a primary forest were present even 25 years after timber extraction. The ant communities were thinned and could be described by a lower species density producing lower species numbers and a different community composition. The similarity in species number and community composition between logged over forests of different degrees of disturbance was explained by source-sink dynamics within a heterogeneous forest matrix. Rain forest fragments displayed even higher reductions in species density, numbers and diversity due to a more pronounced thinning effect. Even forest isolates exceeding 4 000 ha in size did not support more than 50 per cent of the species of the leaf litter ant community of a contiguous primary rain forest. Additionally, an increase in tramp species was recorded with decreasing size of the forest fragments, leading to a very different community composition. Regarding the leaf litter ant community, the remaining rain forest fragments of Sabah are effectively isolated by a barrier of oil palm plantation, now stretching all over the lowlands of the east coast. Only 13 species, which belonged to the forest ant community in highly disturbed areas were collected in these plantations. Some of the 10 other species of the highly reduced ground-dwelling ant community in the plantations are known as invasive tramp species, forming large exclusive territories. Correlative evidence and a field experiment implied, that leaf litter humidity, volume and temperature affect the distribution and community composition of forest leaf litter ant species. The smaller primary forests and the most disturbed logged over forests in this study revealed higher temperatures and lower humidity levels and a reduction in leaf litter volume compared to a large primary forest or forests affected by a lower impact of timber harvesting. If the pattern for leaf litter ants is confirmed for other taxa, the implications for any efficient management design aiming to preserve the majority of the biodiversity of the country are tremendous and current concepts need rethinking.},
  subject      = {Sabah},
  language  = {en}
}