The paper analyzed the changes of beetle assemblages in the litter layer of eutrophic pine forests in the zone polluted by a nitrogen fertilizer plant Joint Stock Company “Achema” (Lithuania). We hypothesized that abundance, diversity and life traits of beetle assemblages depend on the distance from the pollution source. The samples of the litter layer were taken from pine stands at the distances of 3, 5, 10 and 20 km from the plant. The PCA and GLM analyses were used to reduce the number of variables to the main environmental gradient and assess the influence of environmental factors on beetle abundance, number of species, and life traits. The dependence of species number, abundance and the presence of forest and dendrophagous species on the distance from the plant was detected. A significant impact of organic carbon content, nitrogen emission and moss cover on other life traits of beetles was disclosed. The abundance of moss fraction in the litter layer was positively correlated with increasing distance from the plant. The ability to tolerate polluted sites by three species: Atheta fungi, Micrambe abietis and Brassicogethes aeneus, and intolerance of pollution by eight species: Bryaxis puncticollis, Quedius limbatus, Cyphon pubescens, Cephenium majus, Cyphon padi, Cyphon variabilis, Gabrius appendiculatus and Philonthus cognatus, were detected by IndVal analysis. The distribution of litter species was affected by the distance from the plant and by the richness of moss cover.
Physical supporting or defense structures of plants, which decrease palatability, remain in plant tissue after a plant’s death and so decrease detritus decomposition rates. Consequently, palatability and detritus decomposition rate are expected to be positively correlated. Carbon is the main component of these restricting structures, whereas nitrogen is expected to increase plant attractiveness for herbivores. In this study, we tried to confirm the expected positive relationship between palatability and detritus decomposition rate and to find the species functional traits that are responsible for this concordant response. Some traits are shared by species as a consequence of their common phylogenetic history; consequently, we also studied the effect of phylogenetic correction on the expected relationships.We assessed the palatability of meadow plant species to a generalist slug
in an aquarium grazing experiment and detritus decomposition rate in a field litter-bag test. The two characteristics are positively correlated and the relationship is strengthened by phylogenetic correction. The relationship was strongest for the decomposition rates during the first three months of exposition, but weakened when the exposition period was from six months to a year. Palatability was negatively affected by plant carbon content, but no relationship was found between plant palatability and nitrogen content. Similarly, only the relationship of litter decomposition with litter carbon content was significant. The regression tree method was used to detect the influence of species traits on species palatability and detritus decomposition rate. In general, leaf dry matter content, litter carbon content and seed weight were chosen as the best predictors of plant palatability response. Results for the detritus decomposition rate response mainly reflect supporting or defensive structure contents. Litter carbon content, seed weight and plant height are the most apparent common predictors of these variable responses.In general, our study confirmed the positive relationship between plant palatability and detritus decomposition. Both plant tissue grazing and detritus decomposition are slowed down by plant tissue supportive structures, manifested as high dry matter content or high tissue carbon content.
The objective of this work was to determine the change for straw production, carbon and ash content in vegetative tissues through ten cycles of recurrent selection in bread wheat, evaluated under tilled (CT) and non-tilled (NT) soils. Twenty-four wheat genotypes, four for each one of the 0, 2, 4, 6, 8 and 10 cycles of recurrent selection (RS), were used in this study. Experiments were established during two successive seasons. Ash content was expressed on dry mass basis. To estimate the carbon content, we based our calculation on the assumption that organic matter is 50% carbon. Straw dry weight was measured. For each trait, a linear mixed model (regression) was fitted to the experimental data. In response to the number of selection cycles, the ash content percentage increased under CT and decreased under NT. Carbon content decreases under CT, but increases under NT. The sequestered straw carbon and the straw production significantly decrease under CT meanwhile there was no change under NT. The observed increase for straw ash content would be related to the highest rate of transpiration in the more advanced recurrent selection cycles. Consistent with these results, the percentage of straw carbon content decreased because of the mobilization of reserves from the stems and leaves to the grains.
Authors:P. B. Drewa, P. B. Drewa, G. E. Bradfield, and G. E. Bradfield
The influence of scale on the discernment of plant community patterns was examined using vegetation-environment data collected from a subalpine wet meadow in south-coastal British Columbia. Species cover data were recorded in 225, 0.25 m2quadrats systematically located at 5m intervals in a 40 m x 120 m sampling grid. Environmental data consisted of quadrat elevations as well as measured and kriged estimates of five soil variables (carbon content, pH, electrical conductivity, percent sand, and percent clay). Sampling scale was adjusted by aggregating neighbouring quadrats into composite sampling units; analytical scale was altered by varying the intercept level in dendrograms from minimum increase of sum of squares cluster analysis of the vegetation data corresponding to the different sampling scales. The resulting classifications were evaluated for their ability to explain variation in the vegetation data and in the environmental data. The vegetation variation explained by the classifications was highest at the smallest sampling scale indicating that vegetation heterogeneity is fine grained. In contrast, the environmental variation explained was higher for the classifications based on the larger composite sampling units implying a coarser scaling of abiotic conditions within the study area. These results were consistent with the recognition of three main zones along a drainage gradient within the sampling grid. upper mixed-forb, middle heath, and lower sedge. There was also evidence that the orientation of rectangular sampling units parallel to the drainage gradient leads to higher levels of explained variation. This study reaffirms the need for careful consideration of alternatives both in field sampling and analytical phases of vegetation research to ensure that description and interpretation of patterns adequately address study objectives and that vegetation-environment relationships are more completely investigated from a hierarchical perspective.