Spectral differentiation of oak wilt from foliar fungal disease and drought is correlated with physiological changes.

Hyperspectral reflectance tools have been used to detect multiple pathogens in agricultural settings and single sources of infection or broad declines in forest stands. However, differentiation of any one disease from other sources of tree stress is integral for stand and landscape-level applications in mixed species systems. We tested the ability of spectral models to differentiate oak wilt, a fatal disease in oaks caused by Bretziella fagacearum ``Bretz'', from among other mechanisms of decline.

Genetic, morphological, and spectral characterization of relictual Niobrara River hybrid aspens ( × ).

Premise Of The Study: Aspen groves along the Niobrara River in Nebraska have long been a biogeographic curiosity due to morphological differences from nearby remnant populations. Pleistocene hybridization between and has been proposed, but the nearest populations are currently several hundred kilometers east. We tested the hybrid-origin hypothesis using genetic data and characterized putative hybrids phenotypically.