The use of apical tissue analysis to determine the phosphorus status ofStylosanthes hamata cv. Verano

Summary A glasshouse experiment was conducted to determine the effect of plant age on critical phosphorus concentration in apical tissue ofStylosanthes hamata cv. Verano. Cut and non-cut treatments were included to simulate grazing and non-grazing situations. The critical concentration declined rapidly in both treatments during the 18 weeks following germination and remained relatively constant thereafter. The results are consistent with a higher phosphorus requirement for grazed plants compared with ungrazed plants.     

Integrated Ecosystem Assessment: Lake Ontario Water Management

Background

Ecosystem management requires organizing, synthesizing, and projecting information at a large scale while simultaneously addressing public interests, dynamic ecological properties, and a continuum of physicochemical conditions. We compared the impacts of seven water level management plans for Lake Ontario on a set of environmental attributes of public relevance.

Methodology and Findings

Our assessment method was developed with a set of established impact assessment tools (checklists, classifications, matrices, simulations, representative taxa, and performance relations) and the concept of archetypal geomorphic shoreline classes. We considered each environmental attribute and shoreline class in its typical and essential form and predicted how water level change would interact with defining properties. The analysis indicated that about half the shoreline of Lake Ontario is potentially sensitive to water level change with a small portion being highly sensitive. The current water management plan may be best for maintaining the environmental resources. In contrast, a natural water regime plan designed for greatest environmental benefits most often had adverse impacts, impacted most shoreline classes, and the largest portion of the lake coast. Plans that balanced multiple objectives and avoided hydrologic extremes were found to be similar relative to the environment, low on adverse impacts, and had many minor impacts across many shoreline classes.

Significance

The Lake Ontario ecosystem assessment provided information that can inform decisions about water management and the environment. No approach and set of methods will perfectly and unarguably accomplish integrated ecosystem assessment. For managing water levels in Lake Ontario, we found that there are no uniformly good and bad options for environmental conservation. The scientific challenge was selecting a set of tools and practices to present broad, relevant, unbiased, and accessible information to guide decision-making on a set of management options.