Can ground-based assessments of forest biodiversity reflect the biological condition of canopy assemblages?

Abstract

Biological assessments of forest systems often involve a single groundinvertebrate sampling method that may ignore the biological component of the non-sampled canopy. Pitfall trapping for ground-active arthropods is a widely implemented technique for biological assessment in forested and open habitats. Although much evidence highlights the biases of pitfall trapping, this evidence typically comes from open-habitat crop and grassland systems. In forest systems where much of the biodiversity is found within the above-ground structure, management recommendations based solely on ground sampling may not represent the diversity within the three dimensional forest habitat. We provide evidence from combined ground and canopy sampling of three major forest types within the study region. We use canopy insecticide fogging to compare with more traditional ground-based pitfall trapping, and use spiders as a comparative species-rich biota that is able to colonise most terrestrial habitats and is strongly affected by changes in environmental condition. We identified 3933 spiders from 109 species from the 18 forest patches sampled. Both types of sampling defined differences in community composition between forest types in a similar manner; hence, either method could be used to evaluate differences or test management regimes in well-replicated experiments of forest type. However, the association in community composition between ground and canopy assemblages at the individual site-based level was weak; we found low correlation between the two data sets indicating that surrogacy between methods was not supported at this level. Furthermore, disparities in spider habitat association, body size, hunting guild and vertical stratification of spider families indicates that where detailed species and family-based information is 3 required, or if inventorying is necessary, then multiple targeted surveys are essential.

Tree mixtures mediate negative effects of introduced tree species on bird taxonomic and functional diversity

“…In contrast to forest floor‐associated taxa, birds use habitats and resources across strata and up into the canopy. Their diversity patterns thus potentially integrate across forest compartments and provide insights into the notoriously understudied higher forest strata, showing that overall biodiversity responses to management can deviate substantially from frequently studied patterns on the forest floor (see also Gossner & Utschick, 2004; Pedley et al, 2016 for arthropods). The finding that bird diversity and abundance negatively responded to gradual increases of conifer proportions indicates that it can be advisable to add conifers only at low proportions to reduce potentially negative effects on biodiversity.…”

Eficiencia en el uso de trampas de caída y suficiencia taxonómica en comunidades de arañas (Araneae) epigeas en tres ecorregiones del Noroeste Argentino

“…Así, los inventarios próximos al 70 % de completitud son aceptables para grupos megadiversos, ya que elevar el esfuerzo de muestreo para superar apenas este valor es muy costoso en tiempo y dinero (Azevedo et al, 2014). Esto es apoyado por algunos autores (Azevedo et al, 2014;Porto et al, 2016) quienes han demostrado que es posible utilizar pocos métodos de muestreo y de bajo costo para alcanzar inventarios "completos", los cuales son útiles en planes de conservación y manejo (Pedley et al, 2016). Coincidiendo con varios autores (Lubin, 1978;Avalos, Rubio, Bar, & González, 2007;Hsieh & Linsenmair, 2012;Azevedo et al, 2014;Bourass, Shaibi, Elkrwe, Ghana, & Swehli, 2014), nuestros resultados demuestran que la estacionalidad contribuye a la composición de los ensambles de arañas.…”

“…Este enfoque contribuye a superar el impedimento taxonómico en varios grupos de invertebrados terrestres, tales como las arañas (Brennan et al, 2006;Landeiro et al, 2012). Ellas constituyen un grupo de artrópodos depredador con una elevada diversidad de especies que produce un fuerte impacto en los ecosistemas terrestres (Grismado, Ramírez, & Izquierdo, 2014), por lo que representan un taxón indicador potencialmente útil para comparar patrones de biodiversidad (Hsieh et al, 2003;Buchholz, 2010;Pedley et al, 2016). Sin embargo, son frecuentemente ignorados en los planes de manejo y monitoreo ambiental (New, 1996) debido a la dificultad para llegar a una determinación taxonómica completa.…”

It’s raining species: Rainwash eDNA metabarcoding as a minimally invasive method to assess tree canopy invertebrate diversity

“…The chemicals are distributed through fogging (i.e., hot clouds of chemical droplets rising upwards) or mist blowing (i.e., blowing an air current with chemical droplets into the canopy). The stunned, falling insects are caught in collection hoops and can be identified by morphological assessment (Pedley et al, 2016) or bulk sample DNA metabarcoding (Creedy et al, 2019). Another approach is branch bagging and clipping (i.e., covering the branch in a cloth or bag and cutting the branch), which has the advantage of directly correlating species richness or density with plant or leaf biomass (Krehenwinkel et al, unpublished data).…”