Current knowledge on plant/canopy architectural traits that reduce the expression and development of epidemics

To reduce the use of pesticides, innovative studies have been developed to introduce the plant as the centre of the crop protection system. The aim of this paper is to explain how architectural traits of plants and canopies induce a more or less severe epidemic and how they may be modified in order to reduce disease development. In particular, it focuses on three key questions: i) which processes linked to epidemics can be influenced by architecture ii) how can architecture be characterized relative to these modes of action, and iii) how can these effects be explored and exploited? The roles of plant/canopy architecture on inoculum interception, on epidemic development via the microclimate and on tissue receptivity are discussed. In addition, the concepts of disease avoidance, canopy porosity and an ideotype unfavourable for disease development are described. This paper shows that many advances have already been made, but progress is still required in four main fields: microclimatology, mathematical modelling of plants, molecular genetics and ideotype conception.     

Penetration of Polyethylene Film by the Shoots of Cyperus rotundus

Abstract

Orobanche is the most debilitating plant parasite of tobacco in Andhra Pradesh. The crop suffers considerably for about six weeks before the parasite appears above the ground. In the absence of effective herbicides for controlling Orobanche especially in this pre-emergence phase, it was felt worthwhile to evaluate the effectiveness of various cultivated crops as trap crops. A preliminary pot trial was conducted with 17 crop plants and the results are presented.     

Interdisciplinary historical vegetation mapping for ecological restoration in Galapagos

Improving our knowledge of pre-anthropogenic landscapes is vital for understanding landscape-scale heterogeneity and for setting goals and objectives for ecological restoration. This is especially important in highly modified landscapes that contain few remnants of pre-impact ecosystems. This study aims to develop new methodology to improve understanding of historical vegetation, using the now-degraded inhabited highlands of the Galapagos Islands as a case study. Our multidisciplinary approach innovatively combines data from interviews with residents who were familiar with the vegetation before most degradation occurred with the more traditional sources of historical aerial photography and information from early explorer and scientist reports. We reconstruct historical vegetation across the landscape by mapping it in the year 1960 and discussing this map in the historical context of anthropogenic change. Our results confirm published vegetation types but also define some other types not previously described, and suggest much greater spatial, temporal and structural heterogeneity than commonly understood. This result can be used by Galapagos land managers to better match species assemblages with sites and plan restoration actions that will maximise resilience against the ongoing and future threats of climate change and species invasions. Our methodology can be applied in extensive areas of the world where the majority of anthropogenic disturbance to natural ecosystems has been within the past 60 years.     

A new, multi-scaled graph visualization approach: an example within the playa wetland network of the Great Plains

We employed a sliding-window approach at multiple scales (window sizes and dispersal distances) to calculate seven standard graph-theoretical metrics within a subset of a large, freshwater wetland network. In contrast to most graph analyses, which quantify connectivity at a single (global) scale or at a patch-level scale, a multi-scaled, sliding-window approach provides an assessment that bridges these two approaches to examine patch clusters. As a case study we focused on a subset of a habitat patch network in a ~20,000 km² area encompassing 2,782 playa wetlands in the panhandle of Texas. Playas are seasonal wetlands of the southern Great Plains of North America that form a network of regional habitat resources for wildlife. The large size of this network meant that global metrics failed to capture localized properties, so we used contour mapping to visualize continuous surfaces as functions of playa density, linkage density, and other topological traits at different window sizes and dispersal distances. This technique revealed spatial patterns in the components (i.e., the network properties of regions of the landscape at a given dispersal scale), with the spatial scale of habitat clustering varying with the size of the sliding window and dispersal distance. Using a tool familiar to landscape ecology (sliding-window methodology) in a novel way (to examine ecological networks at multiple scales), our approach provides a way to represent ecologically determined local-scale graph properties and illustrates how a multi-scaled approach is useful in examining habitat connectivity to investigate graph properties.