@misc{GypserVesteFischeretal., author = {Gypser, Stella and Veste, Maik and Fischer, Thomas and Lange, Philipp}, title = {Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany}, series = {Journal of hydrology and hydromechanics}, volume = {64}, journal = {Journal of hydrology and hydromechanics}, number = {1}, doi = {10.1515/johh-2016-0009}, pages = {1 -- 11}, abstract = {Investigations were done on two former open-cast lignite mining sites under reclamation, an artificial sand dune in Welzow S{\"u}d, and a forest plantation in Schlabendorf S{\"u}d (Brandenburg, Germany). The aim was to associate the topsoil hydrological characteristics of green algae dominated as well as moss and soil lichen dominated biological soil crusts during crustal succession with their water retention and the repellency index on sandy soils under temperate cli-mate and different reliefs. The investigation of the repellency index showed on the one hand an increase due to the cross-linking of sand parti-cles by green algae which resulted in clogging of pores. On the other hand, the occurrence of moss plants led to a de-crease of the repellency index due to absorption caused by bryophytes. The determination of the water retention curves showed an increase of the water holding capacity, especially in conjunction with the growth of green algae layer. The pore-related van Genuchten parameter indicate a clay-like behaviour of the developed soil crusts. Because of the inho-mogeneous distribution of lichens and mosses as well as the varying thickness of green algae layers, the water retention differed between the study sites and between samples of similar developmental stages. However, similar tendencies of water retention and water repellency related to the soil crust formation were observed. Biological soil crusts should be considered after disturbances in the context of reclamation measures, because the ini-tial development of green algae biocrusts lead to an increasing repellency index, while the occurrence of mosses and a gain in organic matter enhance the water holding capacity. Thus, the succession of biocrusts and their small-scale succes-sion promote the development of soil and ecosystem.}, language = {en} } @misc{GypserHerppichFischeretal., author = {Gypser, Stella and Herppich, Werner B. and Fischer, Thomas and Lange, Philipp and Veste, Maik}, title = {Photosynthetic characteristics and their spatial variance on biological soil crusts covering initial soils of post-mining sites in Lower Lusatia, NE Germany}, series = {Flora}, volume = {Vol. 220}, journal = {Flora}, issn = {0367-2530}, doi = {10.1016/j.flora.2016.02.012}, pages = {103 -- 116}, abstract = {Following surface disturbance, quaternary sands are the basic substrate for soil development in the Lusatian reclamation area. These substrates mostly contain few organic matter and, hence, are nutrient poor. Accumulation of soil carbon is an important factor for ecosystem development, where biological soil crusts initially influence soil processes and promote ecosystem succession. The compositional structures of biological soil crusts at various developmental stages and their photosynthetic properties were investigated on two former open-cast lignite sites, currently under reclamation, an artificial sand dune in Welzow S{\"u}d, and a forest plantation in Schlabendorf S{\"u}d (Brandenburg, Germany). As development of biological soil crusts progressed, their contents of organic carbon and total chlorophyll increased. The ratio of these parameters, however, varied with the relative contribution of lichens and mosses in particular. Also maximum photochemical efficiency, net photosynthesis and respiration increased with crustal development. An additional evaluation of NDVI and chlorophyll fluorescence images showed that especially moss-dominated biocrusts had higher photosynthetic capacity compared to green algae-dominated biocrusts or soil lichens, so the photosynthetic capacity showed to be highly species-specific. The ratio of gross photosynthesis to respiration indicated a higher ecological efficiency of biocrusts dominated by green algae than of lichen-dominated biocrusts. The occurrence of soil lichens reduced net CO2 fixation and increased CO2 release due to the enhanced mycobiontic respiration. During crustal succession, the rise of photosynthesis-related parameters is not necessarily linear as a result of the highly heterogenic distribution of the different crustal organisms between biocrusts of similar developmental stages as well as between those growing at the two study sites. Therefore, the evaluation of relevant ecophysiological parameters highlighted that not all biocrust-forming organisms similarly contribute to the ecophysiological behavior of biological soil crusts. Nevertheless, the occurrence of the biological soil crusts promoted soil formation and accumulation of soil carbon in initial soils.}, language = {en} } @misc{UlrichZaplataWinteretal., author = {Ulrich, Werner and Zaplata, Markus Klemens and Winter, Susanne and Schaaf, Wolfgang and Fischer, Anton and Soliveres, Santiago and Gotelli, Nicholas J.}, title = {Species interactions and random dispersal rather than habitat filtering drive community assembly during early plant succession}, series = {Oikos}, volume = {125}, journal = {Oikos}, number = {5}, doi = {10.1111/oik.02658}, pages = {698 -- 707}, abstract = {Theory on plant succession predicts a temporal increase in the complexity of spatial community structure and of competitive interactions: initially random occurrences of early colonising species shift towards spatially and competitively structured plant associations in later successional stages. Here we use long-term data on early plant succession in a German post mining area to disentangle the importance of random colonisation, habitat filtering, and competition on the temporal and spatial development of plant community structure. We used species co-occurrence analysis and a recently developed method for assessing competitive strength and hierarchies (transitive versus intransitive competitive orders) in multispecies communities. We found that species turnover decreased through time within interaction neighbourhoods, but increased through time outside interaction neighbourhoods. Successional change did not lead to modular community structure. After accounting for species richness effects, the strength of competitive interactions and the proportion of transitive competitive hierarchies increased through time. Although effects of habitat filtering were weak, random colonization and subsequent competitive interactions had strong effects on community structure. Because competitive strength and transitivity were poorly correlated with soil characteristics, there was little evidence for context dependent competitive strength associated with intransitive competitive hierarchies.}, language = {en} }