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In nutrient-poor ecosystems, certain plant families have evolved specific adaptations for phosphate acquisition, namely cluster roots or proteoid roots. Cluster rooted species have a unique suite of adaptations that enable them to survive in nutrient poor ecosystems, such as the Fynbos biome of South Africa. The Fynbos biome has heterogeneous soils which caused radiation of varying soil pH within small localised areas. Previous studies on cluster rooted species ignored the possibility that cluster root functioning may differ at varying soil pH levels and soil types. Therefore, two native Fynbos protea species, Protea cynaroides (L.) L. and Protea obtusifolia H.Buek ex Meisn. were compared to assess the impact of different soil pH levels on organic acid metabolism and exudation in cluster rooted species. Our results show that cluster roots of the acidic-soil grown P. cynaroides is more effective and more efficient than that of the alkaline-soil grown P. obtusifolia. Our findings indicate that the mechanisms for P acquisition vary greatly, depending on substrate and plant organ type. This suggests that the metabolism of each species is adapted to specific soil pH and that these species have evolutionary adapted their P acquisition mechanisms for these extreme soils. The limited nutrient availability and variation in soil pH South African soils has led to various localised adaptations for cluster rooted species.
Windbreaks, trees, structures, and shade nets are used in South Africa to protect citrus orchards from wind scar damage to avoid major losses in export quality. Severe southeasterly winds in the Western Cape during spring and summer are the main causes of significant external peel damage. In this study, wind scar damage of ‘Tango’ mandarin (Citrus reticulata) fruit was quantified at different distances from established Casuarina cunninghamiana (Beefwood) and Populus simonii (Chinese Poplar) windbreaks around Stellenbosch, Western Cape, South Africa. The yield efficiency was not significantly affected by distance from the windbreak in either of the trials. Fruit at 2 H and 3 H had significantly lower ratios of total soluble solids to titratable acidity, but export standards for mandarins were still met. The wind speed was consistently higher at 16 H, compared with 3 H during summer. The highest packout (class 1 fruit) was observed near the windbreak (3 H) and decreased as the distance increased towards 10 H and 16 H. There were no significant differences for severe wind scar damage incidence between the distance treatments. Our results confirmed the impact of wind on external fruit quality and the limitation of tree-based windbreaks with an increase in distance, which partly supports the current movement towards full enclosure of orchards with shade nets.
Nach extremen Störungen durch Brände, Vulkanausbrüchen und Hangrutschungen, aber auch menschlichen Eingriffen werden Böden mehr oder weniger zerstört und vegetationsarm. Es entstehen sogenannte initiale Rohböden, die durch Veränderung der Bodenstruktur, Minderung der Wasserhaltekapazität als auch durch Nährstoffarmut extrem beeinflusst werden. Dabei haben anfängliche und nährstoffarme Ökosysteme, wie Grasländer und Offenlandschaften, aus Sicht des Naturschutzes einen hohen Wert für die Landschaft und sind in der intensiv genutzten Kulturlandschaft Mitteleuropas selten geworden. Insbesondere bieten Binnendünen, wie sie in Norddeutschland häufig sind, Potenzial für die Entwicklung von initialen Lebensräumen mit ihren spezifisch angepassten Pflanzen. Neben den Pionierarten werden die Rohböden, wie sie nach Störungen entstehen, zuerst durch verschiedene blütenlose Pflanzen, den sogenannten Kryptogamen, besiedelt.
Biocrusts are distributed over all climate zones of the world and they substantially contribute to ecosystem functioning. Their growth, determined by their carbon balance, can be affected by various climatic drivers. The effects of individual drivers are clear from laboratory experiments, but the relative importance of different drivers along climatic gradients and their underlying mechanisms are largely unknown. Moreover, the effects of seasonal acclimation on the annual carbon balance are not fully understood either. Therefore, we aim at determining the level and variation of annual biocrust carbon balances and their connection to climatic drivers along environmental gradients. In addition, we explore the role that acclimation plays in the carbon balance of biocrusts
Non-vascular photoautotrophs (NVP), including bryophytes, lichens, terrestrial algae, and cyanobacteria, are increasingly recognized as being essential to ecosystem functioning in many regions of the world. Current research suggests that climate change may pose a substantial threat to NVP, but it is highly uncertain to what extent this will affect the associated ecosystem functions and services. Here, we propose a research agenda to address this urgent question, focusing on physiological and ecological processes that link NVP to ecosystem functions while also taking into account the substantial taxonomic diversity across multiple ecosystem types. Accordingly, we developed a new categorization scheme, based on microclimatic gradients, which simplifies the high physiological and morphological diversity of NVP and worldwide distribution with respect to several broad habitat types. We found that habitat-specific ecosystem functions of NVP will likely be substantially affected by climate change, and more quantitative process understanding is required on (1) potential for acclimation (2) response to elevated CO2 (3) role of the microbiome and (4) feedback to (micro)climate. We suggest an integrative approach of innovative, multi-method laboratory and field experiments and eco-physiological modelling, for which sustained scientific collaboration on NVP research will be essential.
Forest dieback can be both a consequence and a cause of climate change. The changing climate does not only lead to temperature increases but also changes in the precipitation regime. Extreme events have increased sharply in recent years, making drought and heat waves ubiquitous. Meanwhile, for temperate forests, drought stress is considered one of the most serious impacts of climate change. In this context, forest soils are of great importance in their hydrological functions, as well as their feedbacks with ground vegetation. In this context, biological soil crusts are key drivers of functional processes and ecosystem development, also under forest, where they have been less studied so far. Bryophyte and lichen dominated communities can importantly affect e.g. water storage and discharge as well as soil development and stabilization. Moreover, they contribute to carbon and nitrogen cycling and play an important role in biogeochemical processes. Their species composition depends on soil properties such as texture and pH, on microclimate and as poikilohydric plants, their ecophysiology is strongly dependent on water availability, differing in time and space.