نتایج جستجو برای: grasslands

تعداد نتایج: 6042  

2018
Cecilia Lindén

Semi-natural grasslands with traditional management are known to be very species-rich, with many plant species strongly associated with the habitat. The last century’s decline of semi-natural grasslands, as a result of land use change and abandonment, has made the remaining semi-natural grassland a high concern for conservation. Since management can be costly and the available resources often a...

2000
Christopher D. Clegg Karl Ritz Bryan S. Griffiths

Total DNA was directly extracted from microbial populations in grassland soils taken from three geographically distinct upland sites at Garrigill, Aber and Sourhope, UK. Within each site, grasslands were categorised using the National Vegetation Classification into distinct vegetation sequences, namely unimproved, semi-improved and improved. Microbial community DNA was extracted from the differ...

Journal: :Remote Sensing 2017
Maïlys Lopes Mathieu Fauvel Stéphane Girard David Sheeren

This paper deals with the classification of grasslands using high resolution satellite image time series. Grasslands considered in this work are semi-natural elements in fragmented landscapes, i.e., they are heterogeneous and small elements. The first contribution of this study is to account for grassland heterogeneity while working at the object level by modeling its pixels distributions by a ...

2015
Yan Yan Xuyang Lu Harpinder Sandhu

Overgrazing is considered one of the key disturbance factors that results in alpine grassland degradation in Tibet. Grazing exclusion by fencing has been widely used as an approach to restore degraded grasslands in Tibet since 2004. Is the grazing exclusion management strategy effective for the vegetation restoration of degraded alpine grasslands? Three alpine grassland types were selected in T...

2003
O. E. SALA XINSHI ZHANG

Grasslands are the potential natural ecosystem type on approximately 25% (33x lo6 km2) of the land surface of the earth (Shantz 1954). Current estimates of the global extent of grasslands range from 16% (Whittaker and Likens 1973, 1975) to 30% (Ajtay et al. 1979). The difference between the estimates of the potential extent of grasslands and the current extent provides an indication of the degr...

Journal: :Ecology letters 2013
Matthias Peichl Oliver Sonnentag Georg Wohlfahrt Lawrence B Flanagan Dennis D Baldocchi Gerard Kiely Marta Galvagno Damiano Gianelle Barbara Marcolla Casimiro Pio Mirco Migliavacca Michael B Jones Matthew Saunders

Metabolic theory and body size constraints on biomass production and decomposition suggest that differences in the intrinsic potential net ecosystem production (NEPPOT ) should be small among contrasting C3 grasslands and therefore unable to explain the wide range in the annual apparent net ecosystem production (NEPAPP ) reported by previous studies. We estimated NEPPOT for nine C3 grasslands u...

2011
Francesc Montané Pere Casals Mark R. T. Dale

We used a multi-method approach to analyze the spatial patterns of shrubs and cover types (plant species, litter or bare soil) in grassland-shrubland ecotones. This approach allows us to assess how fine-scale spatial heterogeneity of cover types affects the patterns of Cytisus balansae shrub encroachment into mesic mountain grasslands (Catalan Pyrenees, Spain). Spatial patterns and the spatial ...

2005
KEVIN F. O'CONNOR

An approach is outlined for synthesising current understanding of nitrogen dynamics in natural grasslands and extensively managed grassland systems. The increasing complexity of models is illustrated from recent literature, first conceptualising and eventually process-simulating the dynamics of nitrogen, especially in the soil sub-systems of grasslands. Some comparisons are made between New Zea...

2012
Sonia Ospina Graciela M. Rusch Danilo Pezo Fernando Casanoves Fergus L. Sinclair

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 indice...

2013
ROBERT J. STEIDL

Like all grasslands across North America, the distribution of desert grasslands has been reduced markedly, and remnants have been altered extensively by humans. In Arizona, NewMexico, Texas, USA, and in Mexico, desert grasslands have been invaded by dozens of non-native plants, especially perennial grasses that evolved in arid systems with similar climate and disturbance regimes. In desert gras...

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