Incompleteness Theorems for Observables in General Relativity.

The quest for complete observables in general relativity has been a long-standing open problem. We employ methods from descriptive set theory to show that no complete observable on rich enough collections of spacetimes is Borel definable. In fact, we show that it is consistent with the Zermelo-Fraenkel and dependent choice axioms that no complete observable for rich collections of spacetimes exists whatsoever.

What is soil organic matter worth?

The conservation and restoration of soil organic matter are often advocated because of the generally beneficial effects on soil attributes for plant growth and crop production. More recently, organic matter has become important as a terrestrial sink and store for C and N. We have attempted to derive a monetary value of soil organic matter for crop production and storage functions in three contrasting New Zealand soil orders (Gley, Melanic, and Granular Soils).

Ivory-billed woodpecker (Campephilus principalis) persists in continental North America.

The ivory-billed woodpecker (Campephilus principalis), long suspected to be extinct, has been rediscovered in the Big Woods region of eastern Arkansas. Visual encounters during 2004 and 2005, and analysis of a video clip from April 2004, confirm the existence of at least one male. Acoustic signatures consistent with Campephilus display drums also have been heard from the region.

Three approaches to define desired soil organic matter contents.

Soil organic C is often suggested as an indicator of soil quality, but desirable targets are rarely specified. We tested three approaches to define maximum and lowest desirable soil C contents for four New Zealand soil orders. Approach 1 used the New Zealand National Soils Database (NSD).

Soil quality at a national scale in New Zealand.

New Zealand is a signatory to international conventions on environmental performance, and soil quality information is needed for reporting both at a national and regional level. Soil quality was measured at 222 sites in five regions of New Zealand (12 soil orders and 9 land-use categories). Topsoil (0-100 mm) properties measured were total carbon and nitrogen, potentially mineralizable N, pH, Olsen P, cation exchange capacity, bulk density, total porosity, macroporosity, and total available and readily available water.