Net primary productivity and rain-use efficiency as affected by warming, altered precipitation, and clipping in a mixed-grass prairie

2013 ◽  
Vol 19 (9) ◽  
pp. 2753-2764 ◽  
Author(s):  
Xia Xu ◽  
Rebecca A. Sherry ◽  
Shuli Niu ◽  
Dejun Li ◽  
Yiqi Luo
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Mixed Grass Prairie ◽  
Altered Precipitation ◽  
Mixed Grass ◽  
Use Efficiency ◽  
Rain Use Efficiency

scholarly journals Simulating Spatiotemporal Dynamics of Sichuan Grassland Net Primary Productivity Using the CASA Model and In Situ Observations

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Chuanjiang Tang ◽  
Xinyu Fu ◽  
Dong Jiang ◽  
Jingying Fu ◽  
Xinyue Zhang ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Alpine Meadow ◽  
Growth Period ◽  
Temporal Variations ◽  
Light Use Efficiency ◽  
Important Indicator ◽  
Casa Model ◽  
Use Efficiency

Net primary productivity (NPP) is an important indicator for grassland resource management and sustainable development. In this paper, the NPP of Sichuan grasslands was estimated by the Carnegie-Ames-Stanford Approach (CASA) model. The results were validated with in situ data. The overall precision reached 70%; alpine meadow had the highest precision at greater than 75%, among the three types of grasslands validated. The spatial and temporal variations of Sichuan grasslands were analyzed. The absorbed photosynthetic active radiation (APAR), light use efficiency (ε), and NPP of Sichuan grasslands peaked in August, which was a vigorous growth period during 2011. High values of APAR existed in the southwest regions in altitudes from 2000 m to 4000 m. Light use efficiency (ε) varied in the different types of grasslands. The Sichuan grassland NPP was mainly distributed in the region of 3000–5000 m altitude. The NPP of alpine meadow accounted for 50% of the total NPP of Sichuan grasslands.

scholarly journals Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites

2018 ◽  
Vol 15 (11) ◽  
pp. 3421-3437 ◽  
Author(s):  
Donghai Wu ◽  
Philippe Ciais ◽  
Nicolas Viovy ◽  
Alan K. Knapp ◽  
Kevin Wilcox ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Precipitation Variability ◽  
Aboveground Net Primary Productivity ◽  
Ecosystem Models ◽  
Rainfall Gradient ◽  
Positive Effects ◽  
Altered Precipitation ◽  
The Mean ◽  
Asymmetric Responses

Abstract. Field measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon–water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1) the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2) the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3) the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4) gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.

Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system

2017 ◽  
Vol 40 (8) ◽  
pp. 1592-1608 ◽  
Author(s):  
Fabien Charbonnier ◽  
Olivier Roupsard ◽  
Guerric le Maire ◽  
Joannès Guillemot ◽  
Fernando Casanoves ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Agroforestry System ◽  
Light Use Efficiency ◽  
Use Efficiency ◽  
Coffee Plants
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