Land cover and precipitation controls over long‐term trends in carbon gains in the grassland biome of South America

Abstract

Carbon gains are a key aspect of ecosystem functioning since they represent the energy available for upper trophic levels. Carbon gains (or primary production) are strongly correlated with other ecosystem attributes such as secondary production and they are also the support for the provision of many ecosystem services. Given the documented dependency of primary production on precipitation, we expect that altered precipitation regimes, such as those projected by climate models, will have a significant impact on carbon gains. Land use and land cover changes are also expected to have a significant impact on the dynamics of carbon gains. We generated a spectral database of the fraction of photosynthetically active radiation intercepted by vegetation (fPAR), in order to study long‐term trends (i.e., decades) in carbon gains and its spatial and temporal relationships with precipitation and land cover patterns in Uruguay, which is part of the Rio de la Plata Grasslands, one of the largest temperate grasslands biome of the world. We found that carbon gains of native forests and grassland afforestation exhibited the strongest positive spatial response to precipitation, whereas crops and rangelands the weakest. In addition, we found that the temporal response of carbon gains to precipitation was strong and positive for all land uses. Although there were not clear trends in precipitation, we found strong negative trends in carbon gains through time, particularly in rangelands of the “Northern Campos” of Uruguay, where these trends represent a decrease between 10% and 25% of the annual aboveground net primary production. On the other hand, positive trends in carbon gains through time were associated to grassland afforestation and native forests. Therefore, during the period analyzed, land cover had a stronger influence on the observed trends in carbon gains than precipitation. These patterns emerged as a consequence of the interaction among precipitation, temperature, edaphic factors and management. Present trends in the controlling factors of C gains would exacerbate the observed patterns with serious consequences for the provision of ecosystems services.

Sensitivity of subtropical forest and savanna productivity to climate variability in South America, Uruguay

“…Given their limited extent, the response of subtropical forests to climate variability in the Pampa is poorly understood (Texeira et al. ). We expect, given the differences in elevation, water availability and soil drainage rates of riparian forests, hillside forests and wooded savannas in the region (Oliveira‐Filho et al.…”

Effects of Climate Change and LUCC on Terrestrial Biomass in the Lower Heihe River Basin during 2001–2010

“…In addition, the simulation period was set to be [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010] in this study since the Ecological Water Diversion Project was implemented in 2000. Moreover, the total of annual biomass accumulation during 2001-2010 were further summarized since major carbon and energy fluxes between the atmosphere and terrestrial biosphere are often expressed in terms of net biomass accumulation from annual NPP and the effects of some influencing factors on biomass accumulation are expected to be lagged as vegetation shows inertial dynamics associated to its dependence on water resources and soil characteristics [12,47,54,72,76].…”

“…The photosynthesis using the photosynthetically active radiation (PAR) as the energy source is the only process by which carbon dioxide (CO 2 ) is converted into organic carbon and the solar energy is converted into chemical energy and stored as biomass [6,8]. Once stored, the biomass can provide food for heterotrophic organisms and can be processed into usable energy such as renewable fuel or bioenergy, which has currently attracted great interest in the global energy scenario [6,[9][10][11][12][13][14]. Biomass is the total mass (or energy) of all living material (Units: gC¨m´2 or kJ¨m´2), where the energy and (reduced) carbon can be used interchangeably (39 kJ per gC) [9,10].…”

“…Biomass is the total mass (or energy) of all living material (Units: gC¨m´2 or kJ¨m´2), where the energy and (reduced) carbon can be used interchangeably (39 kJ per gC) [9,10]. The biomass accumulation is a key aspect of ecosystem services since it represents the energy available for upper trophic levels and strongly influences the dynamics of atmospheric CO 2 , and understanding the processes that affect biomass accumulation is also critical for planning strategies to mitigate the accumulation of CO 2 in the atmosphere [11,12]. In particular, the economic success of agricultural and forestry systems, which harvest solar radiation to produce food and fiber through biomass accumulation, also requires proper management for the capture and partition of solar radiation [15,16].…”

“…Climate change and LUCC can influence the biomass accumulation of vegetation through influencing the fraction of radiation intercepted, radiation use efficiency and harvest index [12,[21][22][23], and they can also lead to the shifts in the overall structure and function of ecosystems and consequently influence partition of energy fluxes and ecosystem energy balance and result in changes in biomass [24]. Net primary productivity (NPP) measures the transfer of energy to the biosphere and terrestrial CO 2 assimilation [9,25].…”