More Stable Productivity of Semi Natural Grasslands than Sown Pastures in a Seasonally Dry Climate

In the Neotropics the predominant pathway to intensify productivity is generally thought to be to convert grasslands to sown pastures, mostly in monoculture. This article examines how above-ground net primary productivity (ANPP) in semi-natural grasslands and sown pastures in Central America respond to rainfall by: (i) assessing the relationships between ANPP and accumulated rainfall and indices of rainfall distribution, (ii) evaluating the variability of ANPP between and within seasons, and (iii) estimating the temporal stability of ANPP. We conducted sequential biomass harvests during 12 periods of 22 days and related those to rainfall. There were significant relationships between ANPP and cumulative rainfall in 22-day periods for both vegetation types and a model including a linear and quadratic term explained 74% of the variation in the data. There was also a significant correlation between ANPP and the number of rainfall events for both vegetation types. Sown pastures had higher ANPP increments per unit rainfall and higher ANPP at the peak of the rainy season than semi-natural grasslands. In contrast, semi-natural grasslands showed higher ANPP early in the dry season. The temporal stability of ANPP was higher in semi-natural grasslands than in the sown pastures in the dry season and over a whole annual cycle. Our results reveal that, contrary to conventional thinking amongst pasture scientists, there appears to be no increase in ANPP arising from replacing semi-natural grasslands with sown pastures under prevailing pasture management practices in seasonally dry climates, while the temporal distribution of ANPP is more even in semi-natural grasslands. Neither sown pastures nor semi-natural grasslands are productive towards the end of the dry season, indicating the potential importance of the widespread practice of retaining tree cover in pastures

Observation network design for environmental variables using a copula based approach

A. Bárdossy, J. Li and L. Guenn

A Copula based observation network design approach

In this paper, a method for environmental observation network design using the framework of spatial modeling with copulas is proposed. The methodology is developed to enlarge or redesign an existing monitoring network by taking the configuration which would increase the expected gain defined in a utility function. The utility function takes the estimation uncertainty, critical threshold value and gain-loss of a certain decision into account. In this approach, the studied spatial variable is considered as a random field in where variations in time is neglected and the variable of interest is static in nature. The uniqueness of this approach lies in the fact that the uncertainty estimation at the unsampled location is based on the full conditional distribution calculated as conditional copula in this study. Unlike the traditional Kriging variance which is a function of mere measurements density and spatial configuration of data points, the conditional copula account for the influence from data values. This is important specially if we are interested in purpose oriented network design (pond) as for example the detection of noncompliance with water quality standards, the detection of higher quantiles in the marginal probability distributions at ungauged locations, the presence or absence of a geophysical variable as soil contaminants, hydrocarbons, golds and so on. An application of the methodology to the groundwater quality parameters in the South-West region of Germany shows its potential. © 2011 Elsevier Ltd.Jing Li, András Bárdossy, Lelys Guenni, Min Li

Biosfeer aspecten van de hydrologische cyclus. Synthese van internationaal onderzoek

Abstract niet beschikbaarBiospheric Aspects of the Hydrological Cycle (BAHC) was established as one of core projects of the International Geosphere Biosphere Programme (IGBP) in 1992. Its main focus is to study the role of the terrestrial biosphere in the hydrological cycle. BAHC is an interdisciplinary project combining and integrating expertise from several disciplines, including eco-physiology, biogeochemistry, hydrology and meteorology.The Global Energy and Water Experiment GEWEX was initiated in 1988 by the World Climate Research Programme (WCRP) to observe and model the hydrologic cycle and energy fluxes in the atmosphere, and at the land and ocean surface. GEWEX is an integrated program of research, observations, and science activities ultimately leading to the prediction of global and regional climate change. In this report, we present a brief overview of the synthesis research highlights of both international programmes with the primary focus on the biospheric feedbacks in the hydrological cycle and on interactions with the climate system. A full extended research synthesis book, to production of which this NOP project contributed, is currently in press by Springer Verlag (Kabat et al (eds), 2002: Vegetation, Water, Humans and the Climate: A New Perspective of an Interactive System, 650 pp; ISBN 3-540-42400-8)SG-NO