@misc{KueppersKueppersHornaetal., author = {K{\"u}ppers, Manfred and K{\"u}ppers, Barbara I. L. and Horna, Viviana and Veste, Maik and Zimmermann, Reiner and Lauerer, Marianne and Aas, Gregor}, title = {Green barks of trees from drought deciduous forests ("bosque seco") in northern Peru/southern Ecuador do not perform CAM}, series = {Basic and Applied Dryland research}, journal = {Basic and Applied Dryland research}, issn = {1864-3191}, doi = {10.1127/badr/2015/0002}, pages = {15}, abstract = {Trees from drought deciduous forests ("bosque seco") in northern Peru and southern Ecuador regularly shed their leaves at the onset of seven months-long periods without rain. This way they very effectively reduce the bulk water consumption by leaf transpiration, still loosing small amounts of water through their bark, but at the risk of too little or no carbon gain when leaf-less. Seven species studied here have good developed green cortex tissue on stems and axes, as especially evident for the "bottle tree" Ceiba trischistandra (A. Gray) Bakhuisen (Bombacaceae). In several leaf-less tree species at the end of summer drought, when xylem sap flows are very low, indications of higher xylem flows at night as compared to day-time were found, which led to the question of whether the trees are capable of performing CAM in their axes. However, although quite low in some cases, the pH of the cortex tissues did not fluctuate diurnally. In addition, no night-time carbon uptake could be observed. Although no net carbon gain was measured in C. trischistandra and Erythrina smithiana Krukoff (Fabaceae) photosynthetic activity of the green cortex was sufficient to re-assimilate between 50\% to 60\% of the carbon released by mitochondrial respiration. In contrast, the obligate CAM plant Cereus diffusus (Britton \& Rose) Werdermann (Cactaceae), which was studied as a reference in the same environment, showed both diurnal pH-fluctuations in its green tissue with lowest values before sun rise, and net carbon fixation at night.}, language = {en} } @misc{XiaoHuVesteetal., author = {Xiao, Bo and Hu, Kelin and Veste, Maik and Kidron, Giora J.}, title = {Natural recovery rates of moss biocrusts after severe disturbance in a semiarid climate of the Chinese Loess Plateau}, series = {Geoderma}, volume = {337}, journal = {Geoderma}, issn = {0016-7061}, doi = {10.1016/j.geoderma.2018.09.054}, pages = {402 -- 412}, abstract = {Biocrusts are vulnerable to large scale disturbances including trampling activities, and their recovery rates are highly variable with estimates fluctuating by more than one order of magnitude, from<5 years (very fast) to>250 years (very slow). Also, the development of microbial abundance and community diversity of biocrusts after disturbances is poorly understood. In a semiarid climate of the Chinese Loess Plateau, we conducted a recovery experiment on well-developed moss biocrusts after a severe disturbance, during which the entire upper 3 cm of the surface was removed. In the following nine years, the general characteristics and microbial community of the recovering and undisturbed biocrusts as well as a substrate with no crust (bare sand) were periodically determined. Through linear or logistic extrapolation of the observed recovery rates, the recovery time of the biocrusts after disturbance was estimated by both biocrust characteristics and microbial community. Recovery time yielded the following estimates: a) coverage within 3 years, b) thickness within 8 years, c) biomass within 9-13 years, and d) cultivable microbial density within 11-13 years. More importantly, the recovery time of the disturbed moss-biocrusts estimated by the number of bacteria and fungi was ~10 and 20 years, respectively, and that estimated by the bacterial and fungal community diversity was 12-14 and 12-16 years, respectively. In conclusion, moss biocrusts would take 15-20 years to achieve full recovery, which was shorter than many previously published estimates that regarded biocrusts and especially moss-dominated biocrusts to have a long recovery time of hundreds of years. However, it should be also kept in mind that very fast recovery (< 5 years) of biocrusts was less reliable because such estimations are mostly based on visual cover only rather than on the multi-variables of the recovering biocrusts.}, language = {en} } @misc{KanzlerBoehmMircketal., author = {Kanzler, Michael and B{\"o}hm, Christian and Mirck, Jaconette and Schmitt, Dieter and Veste, Maik}, title = {Microclimate effects on evaporation and winter wheat (Triticum aestivum L.) yield within a temperate agroforestry system}, series = {Agroforestry Systems}, journal = {Agroforestry Systems}, issn = {1572-9680}, doi = {10.1007/s10457-018-0289-4}, pages = {21}, abstract = {This study investigates the spatial and temporal impact of microclimate conditions caused by poplar hedgerows in a short rotation alley cropping system (SRACS), and their effect on the atmospheric evaporative demand (AED) and the grain crop yield of winter wheat (Triticum aestivum var. Patras) in direct comparison to a common agricultural crop system. Microclimate was measured at nine positions distributed at the SRACS and an adjacent open field in Brandenburg State (Germany) from March to August 2016. Our hypothesis was that microclimate and AED was improved at SRACS, with traceable effects on the crop yield. The analysis of air temperature and water vapour deficit (VPD) data revealed significantly (p B 0.05) lower daytime values from June to August at the crop alley of the SRACS, which were generally most frequent at the poplar hedgerow and 3 m west positions. By contrast, wind speed was reduced at almost all the positions of our crop alley and during the entire measurement period during both day and night. The AED measured on sampling days in July was significantly (p B 0.001) reduced at the whole crop alley, with values from 24 to 32\% in comparison to the open field. We observed a strong linear relationship (R2 \& 0.78-0.99) between AED on one side and wind speed and VPD on the other side. The average grain yield within the SRACS was 16\% higher than on the OF. However, our microclimate data were insufficient to explain this yield surplus.}, language = {en} } @misc{RieserVesteThieletal., author = {Rieser, Jakob and Veste, Maik and Thiel, Michael and Sch{\"o}nbrodt-Stitt, Sarah}, title = {Coverage and Rainfall Response of Biological Soil Crusts Using Multi-Temporal Sentinel-2 Data in a Central European Temperate Dry Acid Grassland}, series = {Remote Sensing}, volume = {13}, journal = {Remote Sensing}, number = {16}, issn = {2072-4292}, abstract = {Biological soil crusts (BSCs) are thin microbiological vegetation layers that naturally develop in unfavorable higher plant conditions (i.e., low precipitation rates and high temperatures) in global drylands. They consist of poikilohydric organisms capable of adjusting their metabolic activities depending on the water availability. However, they, and with them, their ecosystem functions, are endangered by climate change and land-use intensification. Remote sensing (RS)-based studies estimated the BSC cover in global drylands through various multispectral indices, and few of them correlated the BSCs' activity response to rainfall. However, the allocation of BSCs is not limited to drylands only as there are areas beyond where smaller patches have developed under intense human impact and frequent disturbance. Yet, those areas were not addressed in RS-based studies, raising the question of whether the methods developed in extensive drylands can be transferred easily. Our temperate climate study area, the 'Lieberoser Heide' in northeastern Germany, is home to the country's largest BSC-covered area. We applied a Random Forest (RF) classification model incorporating multispectral Sentinel-2 (S2) data, indices derived from them, and topographic information to spatiotemporally map the BSC cover for the first time in Central Europe. We further monitored the BSC response to rainfall events over a period of around five years (June 2015 to end of December 2020). Therefore, we combined datasets of gridded NDVI as a measure of photosynthetic activity with daily precipitation data and conducted a change detection analysis. With an overall accuracy of 98.9\%, our classification proved satisfactory. Detected changes in BSC activity between dry and wet conditions were found to be significant. Our study emphasizes a high transferability of established methods from extensive drylands to BSC-covered areas in the temperate climate. Therefore, we consider our study to provide essential impulses so that RS-based biocrust mapping in the future will be applied beyond the global drylands}, language = {en} } @misc{SheppardBohnReckziegelBorrassetal., author = {Sheppard, Jonathan P. and Bohn Reckziegel, Rafael and Borrass, Lars and Chirwa, Paxie W. and Cuaranhua, Claudio J. and Hassler, Sibylle K and Hoffmeister, Svenja and Kestel, Florian and Maier, Rebekka and M{\"a}licke, Mirko and Morhart, Christopher and Ndlovu, Nicholas P. and Veste, Maik and Funk, Roger and Lang, Friedericke and Seifert, Thomas and du Toit, Ben and Kahle, Hans-Peter}, title = {Agroforestry: An Appropriate and Sustainable Response to a Changing Climate in Southern Africa?}, series = {Sustainability}, volume = {12}, journal = {Sustainability}, number = {17}, doi = {10.3390/su12176796}, abstract = {Agroforestry is often discussed as a strategy that can be used both for the adaptation to and the mitigation of climate change effects. The climate of southern Africa is predicted to be severely affected by such changes. With agriculture noted as the continent's largest economic sector, issues such as food security and land degradation are in the forefront. In the light of such concerns we review the current literature to investigate if agroforestry systems (AFS) are a suitable response to the challenges besetting traditional agricultural caused by a changing climate. The benefits bestowed by AFS are multiple, offering ecosystem services, influence over crop production and positive impacts on rural livelihoods through provisioning and income generation. Nevertheless, knowledge gaps remain. We identify outstanding questions requiring further investigation such as the interplay between trees and crops and their combination, with a discussion of potential benefits. Furthermore, we identify deficiencies in the institutional and policy frameworks that underlie the adoption and stimulus of AFS in the southern African region. We uphold the concept that AFS remains an appropriate and sustainable response for an increased resilience against a changing climate in southern Africa for the benefit of livelihoods and multiple environmental values}, language = {en} } @misc{VesteHerppich, author = {Veste, Maik and Herppich, Werner B.}, title = {Comparative ecophysiology of the leaf-succulents Augea capensis (C3) and Malephora purpureo-crocea (CAM) in the Knersvlakte, Succulent Karoo, South Africa}, series = {Flora}, volume = {278}, journal = {Flora}, issn = {1618-0585}, doi = {10.1016/j.flora.2021.151807}, pages = {9}, abstract = {The generally accepted assumption that CAM is an important adaptation to the drought conditions in arid deserts is mainly based on studies in controlled environments comparing the respective photosynthetic pathways in plants of different morphology. Comparative long-term field studies on the ecophysiology of C3- and CAM succulents co-occurring in the same desert habitat are too rare to satisfactorily answer the old question whether the metabolic pathway or the succulence is more important to guarantee survival in such a harsh habitat. Thus, relevant ecophysiological parameters were repeatedly monitored on plants of the leaf succulents Augea capensis (C3) and Malephora purpureo-crocea (CAM), which commonly dominate a habitat in the Knersvlakte, Namaqualand, South Africa. Under identical conditions in the same habitat, carbon gain of the C3 species was higher than that of the CAM plant, but their WUE lower and maximum photosynthetic activity nearly the same. In M. purpureo-crocea, irrigation induced rapid whole day stomatal opening at drastically increased daytime but decreased night-time CO2-uptake, while respective responses of the C3 species were delayed. These different response dynamics were due to different rooting depth, root morphology and water acquisition strategy of the flat rooting CAM and the deep-rooting C3 species. This, however, may not explain the highly similar growth success. Anyway, the results verify that CAM provides no advantage over C3 for long-term survival in the same desert environment in morphologically similar succulents.}, language = {en} } @misc{GriebenowMakungaPrivettetal., author = {Griebenow, Stian and Makunga, Nokwanda P. and Privett, Sean and Strauss, Paula and Veste, Maik and Kleinert, Aleysia and Valentine, Alexander J.}, title = {Soil pH influences the organic acid metabolism and exudation in cluster roots of protea species from the Mediterranean-type fynbos ecosystem, Western Cape, South Africa}, series = {Rhizosphere}, volume = {Vol. 21}, journal = {Rhizosphere}, doi = {10.1016/j.rhisph.2022.100486}, abstract = {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.}, language = {en} } @misc{VesteLittmannKunnekeetal., author = {Veste, Maik and Littmann, Thomas and Kunneke, Anton and Du Toit, Ben and Seifert, Thomas}, title = {Windbreaks as part of climate-smart landscapes reduce evapotranspiration in vineyards, Western Cape Province, South Africa}, series = {Plant, Soil and Environment}, volume = {66}, journal = {Plant, Soil and Environment}, number = {3}, issn = {1214-1178}, doi = {10.17221/616/2019-PSE}, pages = {119 -- 127}, abstract = {Under the conditions of climate change in South Africa, ecological and technical measures are needed to reduce the water consumption of irrigated crops. Windbreak hedges are long-rated systems in agriculture that significantly reduce wind speed. Their possibilities to reduce evapotranspiration and water demand are being investigated at a vineyard in the Western Cape Province, South Africa. Detailed measurements of meteorological parameters relevant for the computation of reference and crop-specific evapotranspiration following the FAO 56 approaches within a vineyard in the Western Cape Province of South Africa have shown the beneficial effect of an existing hedgerow consisting of 6 m high poplars (Populus simonii (Carri{\`e}re) Wesm.). With reference to a control station in the open field, the mean wind speed in a position about 18 m from the hedgerow at canopy level (2 m) was reduced by 27.6\% over the entire year and by 39.2\% over the summer growing season. This effect leads to a parallel reduction of reference evapotranspiration of 15.5\% during the whole year and of 18.4\% over the growing season. When applying empirical crop-specific Kc values for well-irrigated grapes, the reduction of evapotranspiration is 18.8\% over the summer growth period. The introduced tree shelterbelts are a suitable eco-engineering approach to reduce water consumption and to enhance water saving in vineyards.}, language = {en} } @misc{GeldenhuysLoetzeVeste, author = {Geldenhuys, Heinrich and L{\"o}tze, Elmi and Veste, Maik}, title = {Fruit Quality and Yield of Mandarin (Citrus reticulata) in Orchards with Different Windbreaks in the Western Cape, South Africa}, series = {Erwerbs-Obstbau}, volume = {65 (2023)}, journal = {Erwerbs-Obstbau}, number = {4}, issn = {1439-0302}, doi = {10.1007/s10341-022-00725-3}, pages = {959 -- 969}, abstract = {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.}, language = {en} } @misc{KidronVesteLichner, author = {Kidron, Giora J. and Veste, Maik and Lichner, Lubomir}, title = {Biological factors impacting hydrological processes: Pecularities of plants and biological soil crusts}, series = {Journal of Hydrology and Hydromechanics}, volume = {69}, journal = {Journal of Hydrology and Hydromechanics}, number = {4}, issn = {1338-4333}, doi = {10.2478/johh-2021-0031}, pages = {357 -- 359}, abstract = {The effects of biological factors on the water cycle and subsequently on hydrological processes have wide and profound consequences on ecosystem structure, function and management. A profound understanding of their effects is of prime importance especially in light of climate change projection}, language = {en} } @misc{WachendorfSchlozKueppersetal., author = {Wachendorf, Magnus and Schloz, Mona and K{\"u}ppers, Manfred and G{\"u}ney, Aylin and Veste, Maik}, title = {Wintertime photosynthesis and spring recovery of Ilex Aquifolium L.}, series = {iForest Biogeosciences and Forestry}, volume = {12}, journal = {iForest Biogeosciences and Forestry}, number = {4}, issn = {1971-7458}, doi = {10.3832/ifor2983-012}, pages = {389 -- 396}, abstract = {Former studies using the chlorophyll fluorescence technique on evergreen Ilex aquifolium L. showed that its photosynthetic potential for electron transport in winter recovers quickly when exposed to more favorable conditions. Since little is known, however, about its photosynthetic carbon gain in winter, we investigated its leaf gas exchange over an entire winter and spring period. Measurements were made rotationally in the field and in the laboratory to also investigate if I. aquifolium profits from warmer phases during winter in terms of net carbon gain. From the end of autumn until the end of spring, three different climate-driven phases of photosynthetic responses could be distinguished: first, an acclimation phase which lasted until February and was characterized by a gradually decreasing light-saturated gross photosynthesis (Amax(gross)), decreasing apparent quantum yield of CO₂-assimilation (ɸi) and a decreasing ability of these parameters to recover overnight inside the laboratory. At the same time, maximal quantum yield of PSII (Fv/Fm) could fully regenerate. In this phase, single warmer days had a positive effect on carbon assimilation. Second, a phase of relatively constant but low photosynthesis which was virtually unaffected by temperature, lasting for almost two months occurred. Here, Amax(gross) and ɸi had lost their ability to recover from winter conditions in the field, while Fv/Fm was much less affected. I. aquifolium was still able to conduct positive light-saturated net photosynthesis at a leaf temperature of -0.5°C, but during this time it could not profit from milder temperatures in terms of carbon gain. Third, a phase of increasing photosynthesis (spring recovery) occurred, starting in March when the 5-day average temperature was above 5°C and radiation in the field increased, and where all parameters slowly recovered from winter depressions. Our findings show that I. aquifolium is photosynthetically active over the whole winter, even at temperatures around 0°C. In terms of carbon gain, however, I. aquifolium does not profit from warmer phases during winter, despite the fast recovery seen in chlorophyll fluorescence measurements.}, language = {en} }