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Abstract: 1. A large number of non-native trees (NNTs) have been introduced globally andwidely planted, contributing significantly to the world's economy. Although someof these species present a limited risk of spreading beyond their planting sites, agrowing number of NNTs are spreading and becoming invasive leading to diversenegative impacts on biodiversity, ecosystem functions and human well- being. Tohelp minimize the negative impacts and maximize the economic benefits of NNTs,Brundu et al. developed eight guidelines for the sustainable use of NNTs glob-ally—the Global Guidelines for the Use of NNTs (GG-NNTs).2. Here, we used an online survey to assess perceptions of key stakeholders to-wards NNTs, and explore their knowledge of and compliance with the GG-NNTs.3. Our results show that stakeholders are generally aware that NNTs can providebenefits and cause negative impacts, often simultaneously and they consider thattheir organization complies with existing regulations and voluntary agreementsconcerning NNTs. However, they are not aware of or do not apply most of theeight recommendations included in the GG-NNTs.4. We conclude that effectively managing invasions linked to NNTs requires bothmore communication efforts using an array of channels for improving stakeholderawareness and implementation of simple measures to reduce NNT impacts (e.g. via GG-NNTs), and a deeper understanding of the barriers and reluctance ofstakeholders to manage NNT invasions.
Keywords: agroforestry, alien species, forestry, invasion risk, online survey, ornamental trees, perceptions, stakeholder engagement, sustainability, tree invasions
Published in DiRROS: 21.06.2024; Views: 68; Downloads: 44
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Published in DiRROS: 10.06.2024; Views: 87; Downloads: 50
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Abstract: Plant–soil biodiversity interactions are fundamental for the functioning of terrestrial ecosystems. Yet, the existence of a set of globally distributed topsoil microbial and small invertebrate organisms consistently associated with land plants (i.e., their consistent soil-borne microbiome), together with the environmental preferences and functional capabilities of these organisms, remains unknown. We conducted a standardized field survey under 150 species of land plants, including 58 species of bryophytes and 92 of vascular plants, across 124 locations from all continents. We found that, despite the immense biodiversity of soil organisms, the land plants evaluated only shared a small fraction (less than 1%) of all microbial and invertebrate taxa that were present across contrasting climatic and soil conditions and vegetation types. These consistent taxa were dominated by generalist decomposers and phagotrophs and their presence was positively correlated with the abundance of functional genes linked to mineralization. Finally, we showed that crossing environmental thresholds in aridity (aridity index of 0.65, i.e., the transition from mesic to dry ecosystems), soil pH (5.5; i.e., the transition from acidic to strongly acidic soils), and carbon (less than 2%, the lower limit of fertile soils) can result in drastic disruptions in the associations between land plants and soil organisms, with potential implications for the delivery of soil ecosystem processes under ongoing global environmental change.
Keywords: belowground networks, environmental thresholds, moss microbiome, plant microbiome, plant–soil interactions
Published in DiRROS: 31.05.2024; Views: 94; Downloads: 88
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Abstract: For a set ${\mathcal Q}$ of points in the plane and a real number $\delta \ge 0$, let $\mathbb{G}_\delta({\mathcal Q})$ be the graph defined on ${\mathcal Q}$ by connecting each pair of points at distance at most $\delta$. We consider the connectivity of $\mathbb{G}_\delta({\mathcal Q})$ in the best scenario when the location of a few of the points is uncertain, but we know for each uncertain point a line segment that contains it. More precisely, we consider the following optimization problem: given a set ${\mathcal P}$ of $n-k$ points in the plane and a set ${\mathcal S}$ of $k$ line segments in the plane, find the minimum $\delta \ge 0$ with the property that we can select one point $p_s\in s$ for each segment $s\in {\mathcal S}$ and the corresponding graph $\mathbb{G}_\delta( {\mathcal P}\cup \{ p_s\mid s\in {\mathcal S}\})$ is connected. It is known that the problem is NP-hard. We provide an algorithm to exactly compute an optimal solution in ${\mathcal O}(f(k) n \log n)$ time, for a computable function $f(\cdot)$. This implies that the problem is FPT when parameterized by $k$. The best previous algorithm uses ${\mathcal O}((k!)^k k^{k+1}\cdot n^{2k})$ time and computes the solution up to fixed precision.
Keywords: computational geometry, uncertainty, geometric optimization, fixed parameter tractability, parametric search
Published in DiRROS: 13.05.2024; Views: 148; Downloads: 165
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Abstract: We obtain a sharp estimate on the norm of the differential of a harmonic map from the unit disc ${\mathbb D}$ in ${\mathbb C}$ into the unit ball ${\mathbb B}^n$ in ${\mathbb R}^n$, $n\ge 2$, at any point where the map is conformal. In dimension $n=2$, this generalizes the classical Schwarz-Pick lemma, and for $n\ge 3$ it gives the optimal Schwarz-Pick lemma for conformal minimal discs ${\mathbb D}\to {\mathbb B}^n$. This implies that conformal harmonic immersions $M \to {\mathbb B}^n$ from any hyperbolic conformal surface are distance-decreasing in the Poincaré metric on $M$ and the Cayley-Klein metric on the ball ${\mathbb B}^n$, and the extremal maps are precisely the conformal embeddings of the disc ${\mathbb D}$ onto affine discs in ${\mathbb B}^n$. Motivated by these results, we introduce an intrinsic pseudometric on any Riemannian manifold of dimension at least three by using conformal minimal discs, and we lay foundations of the corresponding hyperbolicity theory.
Keywords: harmonic maps, minimal surfaces, Schwarz–Pick lemma, Cayley–Klein metric
Published in DiRROS: 25.04.2024; Views: 257; Downloads: 125
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