Metamenu

Publications

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Publications in peer reviewed journals

3 Publications found
  • Recovery of aboveground biomass, species richness and composition in tropical secondary forests in SW Costa Rica

    Oberleitner F, Egger C, Oberdorfer S, Dullinger S, Wanek W, Hietz P
    2021 - Forest Ecology and Management, 479: Article 118580

    Abstract: 

    Tropical secondary forests comprise about half of the world’s tropical forests and are important as carbon sinks and to conserve biodiversity. Their rate of recovery varies widely; however, particularly older secondary forests are difficult to date so that the recovery rate is uncertain. As a consequence, factors affecting recovery are difficult to analyse. We used aerial surveys going back to 1968 to date 12 secondary forests in the wet tropics of SW Costa Rica and evaluated the recovery of aboveground biomass, tree species richness and tree species composition in relation to nearby old-growth forests and previous land use. To confirm the validity of the space-for-time substitution, the plots were re-censused after four years. We found fast rates of aboveground biomass accumulation, especially in the first years of succession. After 20 years AGB had reached c. 164 Mg/ha equivalent to 52% of the biomass in old-growth forests in the region. Species richness increased at a slower pace and had reached c. 31% of old-growth forests after 20 years. Recovery rates differed substantially among forests, with biomass at least initially recovering faster in forests after clearcuts whereas species numbers increased faster in forests recovering from pastures. Biomass recovery was positively related to the forest cover in the vicinity and negatively to species richness, whereas species richness was related to soil parameters. The change during the four years between the censuses is broadly in line with the initial chronosequence. While the recovery of tropical secondary forests has been studied in many places, our study shows that various environmental parameters affect the speed of recovery, which is important to include in efforts to manage and restore tropical landscapes.

  • Empirical support for the biogeochemical niche hypothesis in forest trees

    Sardans J, Vallicrosa H, Zuccarini P, Farré-Armengol G, Fernández-Martínez M, Guille P, Gargallo-Garriga A, Ciais P, Janssens IA, Obersteiner M, Richter A, Peñuelas J
    2021 - Nature Ecology & Evolution, 5: 184-194

    Abstract: 

    The possibility of using the elemental compositions of species as a tool to identify species/genotype niche remains to be tested at a global scale. We investigated relationships between the foliar elemental compositions (elementomes) of trees at a global scale with phylogeny, climate, N deposition and soil traits. We analysed foliar N, P, K, Ca, Mg and S concentrations in 23,962 trees of 227 species. Shared ancestry explained 60–94% of the total variance in foliar nutrient concentrations and ratios whereas current climate, atmospheric N deposition and soil type together explained 1–7%, consistent with the biogeochemical niche hypothesis which predicts that each species will have a specific need for and use of each bio-element. The remaining variance was explained by the avoidance of nutritional competition with other species and natural variability within species. The biogeochemical niche hypothesis is thus able to quantify species-specific tree niches and their shifts in response to environmental changes.

  • Comparable canopy and soil free-living nitrogen fixation rates in a lowland tropical forest

    Van Langenhove L, Depaepe T, Verryckt LT, Fuchslueger L, Leroy JDC, Moorthy SMK, Gargallo-Garriga A, Ellwood MDF, Verbeeck H, Van Der Straeten D, Peñuelas J, Janssens IA
    2021 - Science of The Total Environment, 754: Article 142202

    Abstract: 

    Biological nitrogen fixation (BNF) is a fundamental part of nitrogen cycling in tropical forests, yet little is known about the contribution made by free-living nitrogen fixers inhabiting the often-extensive forest canopy. We used the acetylene reduction assay, calibrated with 15N2, to measure free-living BNF on forest canopy leaves, vascular epiphytes, bryophytes and canopy soil, as well as on the forest floor in leaf litter and soil. We used a combination of calculated and published component densities to upscale free-living BNF rates to the forest level. We found that bryophytes and leaves situated in the canopy in particular displayed high mass-based rates of free-living BNF. Additionally, we calculated that nearly 2 kg of nitrogen enters the forest ecosystem through free-living BNF every year, 40% of which was fixed by the various canopy components. Our results reveal that in the studied tropical lowland forest a large part of the nitrogen input through free-living BNF stems from the canopy, but also that the total nitrogen inputs by free-living BNF are lower than previously thought and comparable to the inputs of reactive nitrogen by atmospheric deposition.

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