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Biodiversity is under threat due to human-induced changes in land use. While various aspects of biodiversity are increasingly studied in response to these changes, there is limited understanding of their effects on the structure and composition of bird communities in dryland regions. We examined the impacts of land use change on birds in the semi-arid area of the Longxi Loess Plateau by considering taxonomic diversity, functional diversity, and phylogenetic diversity. We analyzed both the α- and β-diversity of avian communities across different dimensions of diversity and calculated functional and phylogenetic structures using the net relatedness index. Our findings revealed that species richness was highest in farmland and abandoned farmland, while artificial mixed forests exhibited the highest number of unique species. Functional and phylogenetic α-diversity was greater in farmland and abandoned farmland when compared to the other four land use types. Moreover, the taxonomic diversity in artificial mixed forests, artificial Caragana korshinskii forests, and artificial Platycladus orientalis forests surpassed that in typical grasslands, but no differences were observed in functional and phylogenetic diversity. Regarding β-diversity, turnover patterns dominated multidimensional dissimilarity, with taxonomic turnover and total dissimilarity lower than their functional counterparts but higher than phylogenetic counterparts. Based on the present findings, we emphasize the long-term cessation of ongoing silvicultural initiatives to safeguard bird diversity in the semi-arid region of the Longxi Loess Plateau. This is crucial for narrowly distributed species such as Alectoris magna, as they face heightened vulnerability to losses.

The dispersion relation for high toroidal mode number n beta-induced Alfvén eigenmodes (BAEs) excited by magnetically trapped energetic ions generated with ion-cyclotron resonance heating via precessional resonance in low magnetic shear (s) tokamak plasma is investigated analytically and numerically. The dynamics of the energetic particles (EPs) is treated non-perturbatively and finite drift orbit width (FOW) effects are taken into account. It is found that, depending on the plasma parameters, the most unstable mode can be either the BAE mode or the energetic particle mode (EPM). Both modes can resonate with the trapped-particles' magnetic precessional drifts and become unstable. The mode frequencies and growth rates depend strongly on the EP parameters. FOW can stabilize high-n BAE modes by reducing the wave-particle interaction. Magnetic shear has an important effect on the growth rate of the modes. For BAE, the growth rate presents the trend of first increase and following decrease with the increase of s. The peak positions of the mode growth rate move towards small s with increasing EPs' density. Besides, the BAE growth rate increases with n for small kϑρLE, and decreases for kϑρLE > 0.34. On the other hand, the EPM becomes stable for sufficiently large s and enters into the second stability regime. [ABSTRACT FROM AUTHOR]

The two-dimensional global stability and mode structures of high-n beta-induced Alfvén eigenmodes excited by energetic ions in tokamaks are examined both analytically and numerically, employing the WKB-ballooning mode representation along with the generalized fishbone like dispersion relation. Here, n >> 1 is the toroidal mode number. Our results indicate that (i) the lowest radial bound state corresponds to the most unstable eigenmode, and (ii) the anti-Hermitian contributions due to wave-energetic particle resonance give rise to the twisting radial mode structures. [ABSTRACT FROM AUTHOR]

Studying the spatio-temporal niche partitioning among closely related sympatric species is essential for understanding their stable coexistence in animal communities. However, consideration of niche partitioning across multiple ecological dimensions is still poor for many sympatric pheasant species. Here, we studied temporal activity patterns and spatial distributions of the Blue Eared Pheasant (EP, Crossoptilon auritum) and Blood Pheasant (BP, Ithaginis cruentus) in the Qilian Mountains National Nature Reserve (QMNNR), Northwestern China, using 137 camera traps from August 2017 to August 2020. Kernel density estimation was applied to analyze diel activity patterns, and the Maxent model was applied to evaluate their suitable distributions and underlying habitat preferences. Eight Galliformes species were captured in 678 detection records with 485 records of EP and 106 records of BP over a total of 39,206 camera days. Their monthly activity frequencies demonstrate temporal partitioning but their diel activity patterns do not. Furthermore, 90.78% of BP distribution (2867.99 km2) overlaps with the distribution of EP (4355.86 km2) in the QMNNR. However, BP manifests a high dependence on forest habitats and shows larger Normalized Difference Vegetation Index (NDVI) values, while EP showed obvious avoidance of forest with NDVI greater than 0.75. Hence, differentiation in monthly activity patterns and partitioning in habitat preference might facilitate their coexistence in spatiotemporal dimensions. Conservation actions should give priority to highly overlapping areas in the center and east of the QMNNR and should strengthen forest landscape connectivity, as they provide irreplaceable habitats for these threatened and endemic Galliformes.

Using the theoretical framework of the generalized fishbone-like dispersion relation, the linear properties of beta-induced Alfven eigenmodes (BAEs) and energetic particle continuum modes (EPMs) excited by anisotropic slowing-down energetic ions are investigated analytically and numerically. The resonant contribution of energetic ions to the potential energy perturbation as well as fluid-like term describing the background plasma and adiabatic contribution of energetic ions are derived. For high-mode numbers, numerical results show smooth transition between the EP continuous spectrum and BAEs in the gap. EPMs and/or BAEs are destabilized by energetic ions, with real frequencies and growth rates strongly dependent on the energetic particle density and resonant frequency. [ABSTRACT FROM AUTHOR]

The toroidicity-induced Alfven eigenmode (TAE) excited by energetic (fast) ions was first simulated using the GTC code for HL-2A experiments. The simulation results indicate that the fraction of energetic ions is about 3% in the experiments. The critical density of energetic ions to excite the TAE mode is around 0.023, which is in good agreement with the theoretical expectation of 0.026. The real frequency of TAE with toroidal mode number n  =  3 is around 211 kHz and is inversely proportional to the square root of electron density, which is quantitatively in agreement with the experimental observation (Ding et al 2013 Nucl. Fusion53 043015). The frequency is in resonance with the summations of toroidal precession frequency and transit frequency of passing energetic ions, indicating that resonance with passing energetic ions is dominant for the excitation of the modes in the experiment. It is also checked by the phase space structures of (strength of energetic particle distribution function) that the TAE modes are mainly induced by passing energetic ions in HL-2A. The growth rates of TAE modes increase with fast ion density and its gradient. In addition, lower n TAE modes, such as n  =  1 can also be driven by energetic ions when off-axis heating with higher beam energy is employed in the experiment. The width of radial mode structures for lower n modes is usually wider than those for higher n modes. The perpendicular wave vector of the modes and Larmor radius of ions satisfy the relation . Finally, the polarization of the mode shows that the perturbed parallel electric field is much smaller than the electrostatic parallel electric field. [ABSTRACT FROM AUTHOR]