Publication Date: 2014.
Variable retention is an alternative silvicultural approach to timber forest management, which consist in a regeneration treatment with different degrees and patterns of stand retention. It has been proposed to mitigate harmful effects of harvesting, but effectiveness in insect conservation remains unknown in southern Patagonian Nothofagus pumilio forests. Here, the objectives were to: (1) define a baseline of insect diversity in old-growth forests along a site quality gradient (high, medium and low, associated to the forest productivity of each site); (2) evaluate stands with different retention treatments [aggregated (AR) surrounded by dispersed (DR) retention, and aggregated retention surrounded by clear-cut (CC)] and to compare with old-growth unmanaged forests (OGF); and (3) assess temporal changes during the first 4 years after harvesting (YAH). In a long term forest research plot, mobile epigean insect richness and relative abundance were characterized and classified in seven response type groups, using a wide spectrum sampling set. Data analyses included parametric and permutational ANOVAs, multivariate classification and ordinations. There were found 79 species before harvesting, and that richness was not related to site quality. After harvesting, 84 new species were added considering all treatments along the first four sampled YAH, of which 65 % were added to OGF, while in harvested sites richness and abundance directly diminished with retention degree (OGF > AR > DR > CC) due to incoming species cannot compensate the lost of them. However, fluctuations in diversity were observed along the YAH. Therefore, harvesting reduces insect richness in N. pumilio forests independently of the treatment, but the original insect assemblage significantly changes due to loss of sensitive species and introduction of others from surrounding environments. Despite this, inclusion of aggregates greatly diminished harvesting impacts because insect assemblage is favoured when structural complexity is preserved, conserving richness and abundance at similar levels than in old-growth forests. However, more studies are necessary to evaluate effects of different aggregate size, shape and distribution into harvested forests, as well as their fragmentation and connectivity at landscape level.
Author affiliation: Lencinas, María Vanessa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina
Author affiliation: Martínez Pastur, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina
Author affiliation: Gallo, Emilce. Administracion de Parques Nacionales; Argentina
Author affiliation: Cellini, Juan Manuel. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina
Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas
Publication Date: 2019.
Os insetos galhadores são herbívoros sedentários sofsticados que apresentam alto nível de especialização com sua planta hospedeira, mas sua performance pode ser afetada por fatores bióticos e abióticos. Neste estudo nós testamos duas hipóteses: a) plantas que possuem maior número de vizinhos coespecífcos apresentam maior riqueza e abundância de insetos galhadores, e b) a competição interespecífca é uma força capaz de molda a organização das comunidades de insetos herbívoros associados com uma planta super-hospedeira. O sistema <i>Copaifera oblongifolia</i> (Fabaceae)/insetos galhadores associados foi usado para testar estas hipóteses. Os trabalhos de campo foram desenvolvidos em áreas de Cerrado do norte de Minas Gerais, Brasil. Para testar a primeira hipótese, nós avaliamos, com modelos lineares generalizados de efeitos mistos, os efeitos do número de vizinhos coespecífcos na riqueza e abundância de galhas associadas com 67 arbustos de <i>C. oblongifolia</i> pertencentes a duas populações. Para testar a segunda hipótese, nós usamos modelos nulos para avaliar se um arbusto de <i>C. oblongifolia</i> colonizado por uma espécie de inseto galhador é preferido ou evitado por uma outra espécie de inseto galhador. Um total de 2901 insetos galhadores pertencentes a 15 diferentes espécies foi coletado nos 67 arbustos de <i>C. oblongifolia</i>. Nós observamos uma relação negativa entre o número de vizinhos coespecífcos e a riqueza e a abundância de insetos galhadores associados com <i>C. oblongifolia</i>. Assim, nossos resultados não corroboraram a hipótese da concentração do recuro e nós usamos a teoria da diluição do recurso para explicar este resultado. Nossos resultados também mostraram que o padrão de co-ocorrência dos insetos galhadores na planta hospedeira não diferiu daquele esperado pelo acaso. Portanto, a estrutura da comunidade de insetos galhadores associada com <i>C. oblongifolia</i> não pode ser atribuída a eventos determinísticos com a competição interespecífca.
Gall-forming insects are sophisticated sedentary herbivores that present high level of specificity with host plant, but their performance can be affected by biotic and abiotic factors. In this study we have tested two predictions: a) plants that have a greater number of conspecific neighbors have greater richness and abundance of gall-forming insects, and b) interspecific competition is a force capable of shaping the organization of gall-forming insect communities in super-host plants. We used the <i>Copaifera oblongifolia</i> (Fabaceae)/galling insects’ system to test these predictions. Fieldwork was carried out in areas of Cerrado (Brazilian Savanna) in northern Minas Gerais, Brazil. To test the first hypothesis, we evaluated with generalized linear mixed models, the effects of the number of conspecific neighbors on the richness and abundance of galls associated with 67 <i>C. oblongifolia</i> individual plants belonging to two populations. To test the second hypothesis, we used null models to evaluate whether a plant of <i>C. oblongifolia</i> colonized by a species of gall is preferred or avoided by another species of gall. A total of 2901 gall-forming insects belonging to 15 species were collected from the host plant <i>C. oblongifolia</i>. We observed negative relationships between the number of conspecific neighbors and the abundance and richness of gall-forming insects associated <i>C. oblongifolia</i>. Thus, our data did not support the resource concentration hypothesis. Instead, we used the resource dilution theory to explain the negative relation between resource concentration and frequency of attack by galling insects. Our results also showed that the co-occurrence pattern of gall-forming insects in the host plant did not differ from those expected by chance. Therefore, the structure of the gall-forming insect community associated to single <i>C. oblongifolia</i> plants cannot be attributed to deterministic factors such as interspecific competition.
Repository: Biblioteca Digital (UBA-FCEN). Universidad Nacional de Buenos Aires. Facultad de Ciencias Exactas y Naturales
Publication Date: 2017.
Phenology, or the timing of life cycle events, is a key trait of organisms that has significance for how communities are assembled and ecosystems function. Although variation in phenology in plants has received increased attention over the past decade as a result of changing climate, we are only beginning to understand the role of genetic variation in these phenological traits on ecological interactions and ecosystem-level processes. The influence of tree species on riparian environments presents an interesting system for understanding the effects of phenology in terrestrial species on aquatic ecosystems. Here, we used a dominant riparian tree (Populus trichocarpa: Salicaceae) and tested intraspecific genetic variation in the phenological timing of leaf drop, which influenced leaf-litter inputs into our experimental aquatic ecosystems. Our empirical results found that genotypic differences in P. trichocarpa explained much of the variation both in leaf-litter decomposition and aquatic invertebrate species richness within our experimental ponds. Moreover, our results showed that variation in the timing of leaf-litter inputs outweighed the effects of variation in leaf-litter quality among P. trichocarpa genotypes on aquatic invertebrate species richness. Taken together, our results suggest that genetic variation in the timing of litter inputs from dominant plant species is likely to be a strong underlying mechanism driving litter decomposition and invertebrate communities in aquatic ecosystems. This emphasises that studies disregarding phenology may significantly underestimate an important and variable component in communities and ecosystems.
Author affiliation: Rodriguez Cabal, Mariano Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. University of British Columbia; Canadá
Author affiliation: Barrios Garcia Moar, Maria Noelia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of British Columbia; Canadá. Administración de Parques Nacionales. Parque Nacional "Nahuel Huapi"; Argentina
Author affiliation: Rudman, Seth M.. University of British Columbia; Canadá
Author affiliation: McKown, Athena D.. University of British Columbia; Canadá
Author affiliation: Sato, Takuya. Kobe University; Japón
Author affiliation: Crutsinger, Gregory M.. University of British Columbia; Canadá
Repository: CONICET Digital (CONICET). Consejo Nacional de Investigaciones Científicas y Técnicas