Linkages between Phosphorus and Plant Diversity in Central European Forest Ecosystems—Complementarity or Competition?

The phosphorus nutrition status of European forests has decreased significantly in recent decades. For a deeper understanding of complementarity and competition in terms of P acquisition in temperate forests, we have analyzed α-diversity, organic layer and mineral soil P, P nutrition status, and different concepts of P use efficiency (PUE) in Fagus sylvatica L. (European beech) and Picea abies (L.) H. Karst. (Norway spruce). Using a subset of the Second National Soil Survey in Germany, we correlated available data on P in the organic layer and soil with α-diversity indices for beech and spruce forests overall and for individual vegetation layers (tree, shrub, herb, and moss layers). Moreover, we investigated α-diversity feedbacks on P nutrition status and PUE of both tree species. The overall diversity of both forest ecosystems was largely positively related to P content in the organic layer and soil, but there were differences among the vegetation layers. Diversity in the tree layer of both forest ecosystems was negatively related to the organic layer and soil P. By contrast, shrub diversity showed no correlation to P, while herb layer diversity was negatively related to P in the organic layer but positively to P in soil. A higher tree layer diversity was slightly related to increased P recycling efficiency (PPlant/Porganic layer) in European beech and P uptake efficiency (PPlant/Psoil) in Norway spruce. The diversity in the herb layer was negatively related to P recycling and uptake efficiency in European beech and slightly related to P uptake efficiency in Norway spruce. In spruce forests, overall and herb species richness led to significantly improved tree nutrition status. Our results confirm significant, non-universal relationships between P and diversity in temperate forests with variations among forest ecosystems, vegetation layers, and P in the organic layer or soil. In particular, tree species diversity may enhance complementarity and hence also P nutrition of dominant forest trees through higher PUE, whereas moss and herb layers seemed to show competitive relationships among each other in nutrient cycling.DFG, 241127382, PhosForDiv - Phosphatverfügbarkeit als Einflussgröße der Pflanzen-Biodiversität in Waldökosysteme

Drivers of carbon sequestration by biomass compartment of riparian forests

Riparian forests are expected to play a crucial role in the global carbon (C) cycle but the complex mechanisms of C sequestration in forests remain poorly understood. This study used a comprehensive approach to analyze C sequestration that included the main C compartments in forests, i.e., litterfall, fine roots, and aboveground woody biomass. We aimed at modeling each of them in response to an array of environmental drivers to untangle the functioning of C sequestration by compartment. The study was conducted in a Central European riparian forest that is part of the Donau-Auen National Park in Austria. Carbon sequestration by compartment was correlated with environmental parameters (climate, stream flow, hydrological, spatial, and forest stand parameters) using generalized linear mixed models (GLMM), and the correlations were prioritized by hierarchical partitioning. Our results suggest divergent responses of C sequestration in different ecosystem compartments under dry and wet soil conditions. In particular, dry conditions led to significantly higher C sequestration in aboveground woody biomass (larger distance to the low groundwater table), whereas wetter conditions fostered C sequestration in fine-root (smaller magnitude of fluctuation in the groundwater table) and leaf biomass (smaller distance to the low groundwater table). Fine roots and litterfall responded to short-term variations in climate (mean annual temperature) and flooding parameters (duration of the low to mean Danube River water level in the previous dormant season), highlighting the pivotal role of the dynamic fine-root and leaf biomass compartments for C uptake in forest ecosystems. Consequently, litterfall and fine roots should be considered to improve the sensitivity of C sequestration model responses to climate scenarios.DFG, CI 175/1, Steuergrößen der Kohlenstoffdynamik im Boden und in der Vegetation von Auwälder

Floristic survey of the caatinga in areas with different grazing intensities, Pernambuco, Northeast Brazil

A floristic survey was conducted in eighteen areas in the municipalities of Itacuruba and Floresta, Pernambuco, northeast Brazil. The objective was to investigate if the species richness of terrestrial plant species of the Caatinga is affected by grazing intensity. Eighteen 20x20 m2 plot were established in areas of low grazing intensity (9), and areas with high grazing intensity (9). We recorded 136 species belonging to 97 genera and 43 families. The most species-rich families were Poaceae (14), Fabaceae (13), and Asteraceae (11). The most species-rich genera were Aristida (Poaceae), Sida (Malvaceae) and Ipomoea (Convolvulaceae). The number of species in each study area (Itacuruba and Floresta) varied according to the distribution of the precipitation, the soil types, the land-use history type and the actual land-use. Areas with a low grazing pressure show a higher species richness of plant species than areas with a higher grazing intensit

Robinia pseudoacacia in Europe: distribution, habitat, usage and threats

Robinia pseudoacacia L., commonly known as black locust, is a tree native to North America and is one of the most important and widespread broadleaved alien trees in Europe. It is a medium-sized, deciduous, fast-growing thorny tree with high suckering capacity. It has been extensively planted in Europe and now it is naturalised in practically the whole continent. Growing on a wide range of soil types, this tree species only avoids wet or compacted conditions. It is mainly distributed in sub-Mediterranean to warm continental climates and requires a rather high heat-sum. As a light-demanding pioneer species, it rapidly colonises grasslands, semi-natural woodlands and urban habitats, where it can persist for a long time. Owing to the capacity of fixing di-nitrogen through symbiotic rhizobia in root nodules, black locust can add high rates of nitrogen to soil which becomes available to other plants. The wood of black locust is durable and rot-resistant, making it adequate for multiple purposes such as fire and pulp wood, for fences, construction and furniture. In several parts of Europe, black locust is considered an invasive alien plant, because of shading and its ability to change soil conditions

Mating system, outcrossing distance effects and pollen availability in the wind-pollinated treeline species Polylepis australis BITT. (Rosaceae)

Fragmentation may negatively affect plant fitness through pollen limitation and increased levels of inbreeding. Effects of fragmentation may vary with regard to life form and breeding system, and few studies exist for wind- pollinated trees. We examined the effects of hand-selfing, varying outcrossing distances and pollen addition on seed mass and germination rate of Polylepis australis BITT. (Rosaceae), a wind-pollinated treeline species endemic to Argentina. We also investigated pollen germination on the stigma and pollen tube growth to determine compatibility resulting from selfing and outcrossing. Selfing reduced seed germination rates with significant differences between open pollination and outcrosses at 30km. In addition, we found a tendency for pollen germination and pollen tube growth to decrease following selfing. Between-fragment crosses resulted in a trend of higher reproductive out put than within- fragment crosses, whereas values were similar between open pollination and between-fragment crosses. Pollen addition did not increase reproductive success neither in small nor in larger fragments. Our results suggest that highly isolated P. australis forests have a potential for inbreeding depression through selfing and within-fragment crosses. However, the results also indicate that pollen flow between P. australis forest fragments is still effective at the current fragmentation level, counteracting negative effects on seed quality resulting from reproductive isolation.Durch Habitatzerstörung und Fragmentierung isolierte und kleine Populationen leiden häufig unter erhöhter Inzuchtdepression und Pollenlimitierung, deren Ausmaß jedoch in Abhängigkeit von Lebensform und Fortpflanzungssystem variiert. In der vorliegenden Studie untersuchten wir den Einfluss von Hand-Selbstbestäubung, verschiedenen Kreuzungsdistanzen bis zu 30 km und Pollenzugabe auf Samenmasse und -keimung von Polylepis australis (Rosaceae), einer windbestäubten, in Argentinien endemischen Baumart der oberen Waldgrenze. Darüber hinaus analysierten wir den Einfluss von Selbst- und Fremdbestäubung auf Pollenkeimung und Pollenschlauchwachstum. Selbstbestäubung führte zu signifikant geringeren Keimraten im Vergleich zu natürlicher Bestäubung und Fremdbestäubung mit Pollen aus >30 km Distanz. Auch fanden wir eine Tendenz zur Reduktion von Pollenkeimung und Pollenschlauchwachstum nach Selbstbestäubung. Kreuzungen zwischen Fragmenten führten zu höherem Reproduktionserfolg als Kreuzungen innerhalb von Fragmenten, während der Reproduktionserfolg aus natürlicher Bestäubung und aus Kreuzungen zwischen Fragmenten vergleichbare Werte aufwies. Weder in kleinen noch in großen Populationen führte die Zugabe von Pollen zu einer Erhöhung des Reproduktionserfolges. Unsere Ergebnisse machen deutlich, dass zwar in stark isolierten P. australis Wäldern die Gefahr für Inzuchtdepression besteht, der nach wie vor effektive Pollen- und Genfluss zwischen Waldfragmenten von P. australis jedoch negativen Isolationseffekten entgegenwirkt.Fil: Seltmann, Peggy. Martin-Luther-University Halle-Wittenberg; AlemaniaFil: Cocucci, Andrea Aristides. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Renison, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; ArgentinaFil: Cierjacks, Arne. Martin-Luther-University Halle-Wittenberg; AlemaniaFil: Hensen, Isabell. Martin-Luther-University Halle-Wittenberg; Alemani

FLORISTIC SURVEY OF THE CAATINGA IN AREAS WITH DIFFERENT GRAZING INTENSITIES, PERNAMBUCO, NORTHEAST BRAZIL

A floristic survey was conducted in eighteen areas in the municipalities of Itacuruba and Floresta, Pernambuco, northeast Brazil. The objective was to investigate if the species richness of terrestrial plant species of the Caatinga is affected by grazing intensity. Eighteen 20x20 m2 plot were established in areas of low grazing intensity (9), and areas with high grazing intensity (9). We recorded 136 species belonging to 97 genera and 43 families. The most species-rich families were Poaceae (14), Fabaceae (13), and Asteraceae (11). The most species-rich genera were Aristida (Poaceae), Sida (Malvaceae) and Ipomoea (Convolvulaceae). The number of species in each study area (Itacuruba and Floresta) varied according to the distribution of the precipitation, the soil types, the land-use history type and the actual land-use. Areas with a low grazing pressure show a higher species richness of plant species than areas with a higher grazing intensit

Exploring the biotic homogenization and diversity resistance hypotheses. The understorey of non-native and native woodland canopies in three urban areas of Europe

Aim: Exploring the biotic homogenization and diversity resistance hypotheses by assessing the effect of non-native black locust canopy on understorey species turnover. Location: Berlin, the Venetian metropolitan area, and Rome. Methods: We modelled the zeta (ζ) expression of diversity to compare the understorey species turnover between the non-native black locust and native woodland canopies across multiple sites and through predictors of anthropogenic pressure (road and built-up density) and interior conditions (tree basal area and mean height). Results: In Rome, black locust showed the lowest survivability and cover and did not produce any homogenization of the understorey. In Berlin and in the Venetian metropolitan area, black locust caused understorey homogenization, although with a lower intensity in Berlin. Under black locust canopies, distance between sites and road density was more consistently associated with species turnover, across urban areas and multiple sites. Under native canopies in Berlin, factors prominently associated with species turnover were road and built-up density and mean tree height, while in the Venetian metropolitan area it was road density. Main conclusions: Evidence in support of the biotic homogenization in contrast to the diversity resistance hypothesis varied across urban areas. Species turnover was influenced by land use patterns more evidently under native tree canopies and where the non-native tree had higher survivability. Similar analyses in other urban areas may confirm these relationships with other types of landscapes