Forest herbicide influences on floristic diversity seven years after broadcast pine release treatments in central Georgia,USA

Maintenance of biodiversity is becoming a goal of forest management. This study determined effects of broadcast pine release herbicide treatments on plant species richness, diversity, and structural proportions seven years after treatment. Three study blocks were established in central Georgia. Plots 0.6–0.8 ha in size were planted to loblolly pine (Pinus taeda L.) in the Winter of 1982–83 and then treated with imazapyr (Arsenal), glyphosate (Roundup), and hexazinone (Velpar L. and Pronone 10G) in 1985. In 1992, overstory and understory (<1.5 m height) layers were examined utilizing stem and rootstock counts and basal area of overstory species and cover of understory species. ANOVA's were used to test for significance using a randomized complete block model. We found no effect of treatments on species richness. Diversity, measured separately for overstory and understory layers by Shannon-Wiener and Simpson indices, also was not influenced significantly by treatments. Arsenal significantly decreased Diospyros virginiana L. and increased Rubus argutus Link and legumes. Hexazinone treatments generally decreased Quercus nigra L., and Roundup significantly reduced Vaccinium spp. compared to the Check. We concluded that herbicide release treatments did not decrease overstory or understory plant species richness and diversity seven years post-treatment.     

Forest floor temperature and relative humidity following timber harvesting in southern New England,USA

Forest amphibians, especially salamanders, prefer forests with shaded, cool, and moist forest floors. Timber harvesting opens the forest canopy and exposes the forest floor to direct sunlight, which can increase forest floor temperatures and reduce soil moisture. These microclimatic changes can potentially degrade the harvested stand for amphibian habitat or affect other biotic resources or ecological processes at the forest floor and in the understory. The degree of forest floor disturbance is directly related to the intensity of harvesting, however, the duration of this effect is unknown. We conducted a study of forest floor temperature and relative humidity over a 12-year chronosequence (1993–2004) of timber harvests. We compared simultaneous, paired measurements of temperature and relative humidity at three positions (soil, forest floor, air) in harvested and control sites over three seasonal survey sessions. Vegetation composition and structure were measured at each survey location. Ambient weather conditions were recorded at three open-field locations across the study area.     

Impacts of Coriaria nepalensis colonization on vegetation structure and regeneration dynamics in a mixed conifer forest of Indian Central Himalaya

This study evaluated impacts of Coriaria nepalensis Wall.colonization on soil characteristics,vegetation structure and composition,regeneration status and expected future compositional changes,biomass and carbon stock in tree species of a mixed conifer forest of Central Himalaya.Three sites(1 ha each in an old landslide area)differing in Coriaria density(low:20 individuals ha^-1;medium:120 indiv.ha^-1;high:190 indiv.ha^-1)were used to enumerate the tree species.A total of 9 tree species and 2830 individuals were recorded from the three study sites that represented a gradient of Coriaria density.Number of species varied from 3 to 7 and the individuals from 690 to 1270 per site with lowest numbers at low Coriaria density and highest at medium Coriaria density.The number of seedlings increased with increasing Coriaria density,and the sites were unique in their seedling composition,indicating marked temporal dynamics.Site wise regeneration analysis showed that regeneration was poor at the site with low Coriaria density and good at the high-density site where many species emerged as seedlings.These results indicate that the ameliorative effects of Coriaria in terms of soil buildup,and accumulation of nutrients and organic matter helped more species to colonize the area.This facilitative ability of Coriaria can be used to restore degraded forest ecosystems of Indian Central Himalaya.     

Shade over coffee: its effects on berry borer, leaf rust and spontaneous herbs in Chiapas, Mexico

The objective of this research was to determine the relationships between different ecological features of shade and the incidence of coffee berry borer, coffee leaf rust and spontaneous herbs in rustic coffee plantations in Chiapas, Mexico. Thirty-six 10 m by 10 m plots were established within coffee plantations. The following variables were measured or estimated: number of vegetation strata, percent canopy cover, direct, diffuse and total sunlight below the canopy, plant species richness and diversity, shade tree/shrub density, altitude, aspect, basal area, yields, percentage of coffee berry borer (Hypothenemus hampei Ferr), percentage of coffee leaf rust (Hemileia vastatrix Berk & Br.),percentage of spontaneous herb cover and the presence of paths and runoffs.Results showed a complex agroforestry system, composed of five strata. Coffee berry borer and coffee leaf rust incidence averages were 1.5% and 10.1%,respectively. Average spontaneous herb cover was 34.1%. Coffee leaf rust percentage correlated positively with the coffee berry borer. Number of strata of shade vegetation correlated negatively with leaf rust, while the presence of paths correlated positively with the leaf rust. Species richness and diversity correlated negatively to broad-leaf-herb cover and the presence of runoffs correlated positively to this last variable. Shade tree density (> 10cm d.b.h.) correlated negatively to linear-leaf-herb cover. Percentage of shade cover, light, coffee density, aspect, stand age, basal area and yields were not correlated to pest, disease and weeds. Results support the ecological theory that postulates that diversity and structural complexity in mixed plant systems maintain a healthy system.This revised version was published online in November 2005 with corrections to the Cover Date.