scholarly journals Primary productivity in subsidized green-brown food webs

2021 ◽  
Author(s):  
Yuval R. Zelnik ◽  
Stefano Manzoni ◽  
Riccardo Bommarco
Keyword(s):  
Food Web ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Terrestrial Ecosystems ◽  
Nutrient Inputs ◽  
Natural Processes ◽  
Nutrient Additions ◽  
Empirical Estimates ◽  
Green Food ◽  
Nutrient Subsidies

Ecosystems worldwide receive large amounts of nutrients from both natural processes and human activities. While direct subsidy effects on primary productivity are relatively well known (the green food web), the indirect effects of subsidies on producers as mediated by the brown food web and predators have been neglected. With a dynamical green-brown food web model, parameterized using empirical estimates from the literature, we illustrate the effect of nutrient subsidies on net primary productivity (i.e., after removing loss to herbivory) in two generic ecosystems, terrestrial and aquatic. We find that nutrient subsidies increase net primary productivity because more nutrients are available, but this effect saturates with higher subsidies. Changing the quality of subsidies from inorganic to organic tends to increase net primary productivity in terrestrial ecosystems, but less often so in aquatic ecosystems. This occurs when organic nutrient inputs promote detritivores in the brown food web, and hence predators that in turn control herbivores, thus promoting primary productivity. This previously largely overlooked effect is further enhanced by ecosystem properties such as fast decomposition and low rates of nutrient additions, and demonstrates the importance of nutrient subsidy quality on ecosystem functioning.

Variability of ecosystem carbon source from microbial respiration is controlled by rainfall dynamics

2021 ◽  
Vol 118 (52) ◽  
pp. e2115283118
Author(s):  
Heng Huang ◽  
Salvatore Calabrese ◽  
Ignacio Rodriguez-Iturbe
Keyword(s):  
Primary Productivity ◽  
Microbial Growth ◽  
Net Primary Productivity ◽  
Carbon Sources ◽  
Terrestrial Ecosystems ◽  
Rainfall Regime ◽  
Physical Factors ◽  
Scale Parameters ◽  
Complex Interactions ◽  
Soil Heterotrophic Respiration

Soil heterotrophic respiration (Rh) represents an important component of the terrestrial carbon cycle that affects whether ecosystems function as carbon sources or sinks. Due to the complex interactions between biological and physical factors controlling microbial growth, Rh is uncertain and difficult to predict, limiting our ability to anticipate future climate trajectories. Here we analyze the global FLUXNET 2015 database aided by a probabilistic model of microbial growth to examine the ecosystem-scale dynamics of Rh and identify primary predictors of its variability. We find that the temporal variability in Rh is consistently distributed according to a Gamma distribution, with shape and scale parameters controlled only by rainfall characteristics and vegetation productivity. This distribution originates from the propagation of fast hydrologic fluctuations on the slower biological dynamics of microbial growth and is independent of biome, soil type, and microbial physiology. This finding allows us to readily provide accurate estimates of the mean Rh and its variance, as confirmed by a comparison with an independent global dataset. Our results suggest that future changes in rainfall regime and net primary productivity will significantly alter the dynamics of Rh and the global carbon budget. In regions that are becoming wetter, Rh may increase faster than net primary productivity, thereby reducing the carbon storage capacity of terrestrial ecosystems.

Quantitatively assessing the effects of climate change and human activities on ecosystem degradation and restoration in southwest China

2019 ◽  
Vol 41 (4) ◽  
pp. 335
Author(s):  
Z. G. Sun ◽  
J. S. Wu ◽  
F. Liu ◽  
T. Y. Shao ◽  
X. B. Liu ◽  
...  
Keyword(s):  
Climate Change ◽  
Primary Productivity ◽  
Human Activities ◽  
Southwest China ◽  
Net Primary Productivity ◽  
Terrestrial Ecosystems ◽  
Ecosystem Degradation ◽  
Relative Contribution ◽  
Degraded Ecosystem ◽  
Annual Means

Identifying the effects of climate change and human activities on the degradation and restoration of terrestrial ecosystems is essential for sustainable management of these ecosystems. However, our knowledge of methodology on this topic is limited. To assess the relative contribution of climate change and human activities, actual and potential net primary productivity (NPPa and NPPp respectively), and human appropriation of net primary productivity (HANPP) were calculated and applied to the monitoring of forest, grassland, and cropland ecosystems in Yunnan–Guizhou–Sichuan Provinces, southwest China. We determined annual means of 476 g C m–2 year–1 for NPPa, 1314 g C m–2 year–1 for NPPp, and 849 g C m–2 year–1 for HANPP during the period between 2007 and 2016. Furthermore, the area with an increasing NPPa accounted for 75.12% of the total area of the three ecosystems. Similarly, the areas with increasing NPPp and HANPP accounted for 77.60 and 57.58% of the study area respectively. Furthermore, we found that ~57.58% of areas with ecosystem restored was due to climate change, 23.39% due to human activities, and 19.03% due to the combined effects of human activities and climate change. In contrast, climate change and human activities contributed to 19.47 and 76.36%, respectively, of the areas of degraded ecosystem. Only 4.17% of degraded ecosystem could be attributed to the combined influences of climate change and human activities. We conclude that human activities were mainly responsible for ecosystem degradation, whereas climate change benefitted ecosystem restoration in southwest China in the past decade.

Equilibrium analysis of carbon pools and fluxes of forest biomes in the former Soviet Union

1993 ◽  
Vol 23 (1) ◽  
pp. 81-88 ◽  
Author(s):  
Tatyana P. Kolchugina ◽  
Ted S. Vinson
Keyword(s):  
Soviet Union ◽  
Carbon Cycle ◽  
Primary Productivity ◽  
Boreal Forests ◽  
Former Soviet Union ◽  
Net Primary Productivity ◽  
Terrestrial Ecosystems ◽  
Carbon Pool ◽  
Equilibrium Analysis ◽  
Terrestrial Carbon

Natural processes in ocean and terrestrial ecosystems together with human activities have caused a measurable increase in the atmospheric concentration of CO2. It is predicted that an increase in the concentration of CO2 will cause the Earth's temperatures to rise and will accelerate rates of plant respiration and the decay of organic matter, disrupting the equilibrium of the terrestrial carbon cycle. Forests are an important component of the biosphere, and sequestration of carbon in boreal forests may represent one of the few realistic alternatives to ameliorate changes in atmospheric chemistry. The former Soviet Union has the greatest expanse of boreal forests in the world; however, the role of Soviet forests in the terrestrial carbon cycle is not fully understood because the carbon budget of the Soviet forest sector has not been established. In recognition of the need to determine the role of Soviet forests in the global carbon cycle, the carbon budget of forest biomes in the former Soviet Union was assessed based on an equilibrium analysis of carbon cycle pools and fluxes. Net primary productivity was used to identify the rate of carbon turnover in the forest biomes. Net primary productivity was estimated at 4360 Mt of carbon, the vegetation carbon pool was estimated at 110 255 Mt, the litter carbon pool was estimated at 17 525 Mt, and the soil carbon pool was estimated at 319 100 Mt. Net primary productivity of Soviet forest biomes exceeded industrial CO2 emissions in the former Soviet Union by a factor of four and represented approximately 7% of the global terrestrial carbon turnover. Carbon stores in the phytomass and soils of forest biomes of the former Soviet Union represented 16% of the carbon concentrated in the biomass and soils of the world's terrestrial ecosystems. All carbon pools of Soviet forest biomes represented approximately one-seventh of the world's terrestrial carbon pool.

scholarly journals Effects of nutrient availability and other elevational changes on bromeliad populations and their invertebrate communities in a humid tropical forest in Puerto Rico

2000 ◽  
Vol 16 (2) ◽  
pp. 167-188 ◽  
Author(s):  
Barbara A. Richardson ◽  
M. J. Richardson ◽  
F. N. Scatena ◽  
W. H. Mcdowell
Keyword(s):  
Species Richness ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Plant Density ◽  
Nutrient Concentrations ◽  
Forest Types ◽  
Nutrient Inputs ◽  
Nitrogen And Phosphorus ◽  
Faunal Abundance ◽  
High Plant Density

Nutrient inputs into tank bromeliads were studied in relation to growth and productivity, and the abundance, diversity and biomass of their animal inhabitants, in three forest types along an elevational gradient. Concentrations of phosphorus, potassium and calcium in canopy-derived debris, and nitrogen and phosphorus in phytotelm water, declined with increasing elevation. Dwarf forest bromeliads contained the smallest amounts of debris/plant and lowest concentrations of nutrients in plant tissue. Their leaf turnover rate and productivity were highest and, because of high plant density, they comprised 12.8% of forest net primary productivity (0.47 t ha−1 y−1), and contained 3.3 t ha−1 of water. Annual nutrient budgets indicated that these microcosms were nutrient-abundant and accumulated < 5% of most nutrients passing through them. Exceptions were K and P in the dwarf forest, where accumulation was c. 25% of inputs. Animal and bromeliad biomass/plant peaked in the intermediate elevation forest, and were positively correlated with the debris content/bromeliad across all forest types. Animal species richness showed a significant mid-elevational peak, whereas abundance was independent of species richness and debris quantities, and declined with elevation as forest net primary productivity declined. The unimodal pattern of species richness was not correlated with nutrient concentrations, and relationships among faunal abundance, species richness, nutrient inputs and environment are too complex to warrant simple generalizations about nutrient resources and diversity, even in apparently simple microhabitats.

Is the net new carbon increment of coppice forest stands of Quercus ilex ssp. ballota affected by post-fire thinning treatments and recurrent fires?

2010 ◽  
Vol 19 (5) ◽  
pp. 637 ◽  
Author(s):  
Francisco R. López-Serrano ◽  
Jorge De Las Heras ◽  
Daniel Moya ◽  
Francisco A. García-Morote ◽  
Eva Rubio
Keyword(s):  
Primary Productivity ◽  
Quercus Ilex ◽  
Net Primary Productivity ◽  
Terrestrial Ecosystems ◽  
First Year ◽  
Forest Types ◽  
Forest Stands ◽  
Se Spain ◽  
Coppice Forest ◽  
Global Values

Coppice forest stands of Quercus ilex have been one of the forest types most impacted by fire in Spain. After fire, their capability to resprout produces a high density of stems that requires thinning in order to avoid stagnation within the stands. In August 1993 and July 2001, two consecutive fires affected a Quercus ilex coppice stand in SE Spain. This study investigated the effects of different post‐fire thinning treatments and recurrent fires on stock and net new carbon increment (NNCI) in a 6‐year‐old coppice stand. Four degrees of thinning were applied: medium thinning (to a final density of 5000 trees ha–1), drastic thinning (to 1800 trees ha–1), full felling (all trees removed) and no thinning (control). Results showed NNCI was within the lower limit of the average global values reported for net primary productivity of terrestrial ecosystems. The best thinning treatment to maximise both current annual NNCI and mean annual NNCI stimulation, and keep new resprouting within reasonable levels was medium thinning. However, recurrent fires caused the observed net primary productivity to decrease, which allowed us to conclude that stump vitality is affected by successive fires, at least the first year after a new fire.

scholarly journals Impacts of 1.5 °C and 2 °C Global Warming on Net Primary Productivity and Carbon Balance in China’s Terrestrial Ecosystems

2020 ◽  
Vol 12 (7) ◽  
pp. 2849
Author(s):  
Li Yu ◽  
Fengxue Gu ◽  
Mei Huang ◽  
Bo Tao ◽  
Man Hao ◽  
...  
Keyword(s):  
Global Warming ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Climate Adaptation ◽  
Coupled Model ◽  
Terrestrial Ecosystems ◽  
Northern China ◽  
Ecosystem Model ◽  
Intercomparison Project ◽  
Potential Risks

Assessing potential impacts of 1.5 °C and 2 °C global warming and identifying the risks of further 0.5 °C warming are crucial for climate adaptation and disaster risk management. Four earth system models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) and a process-based ecosystem model are used in this study to assess the impacts and potential risks of the two warming targets on the carbon cycle of China’s terrestrial ecosystems. Results show that warming generally stimulates the increase of net primary productivity (NPP) and net ecosystem productivity (NEP) under both representative concentration pathway (RCP) 4.5 and RCP8.5 scenarios. The projected increments of NPP are higher at 2 °C warming than that at 1.5 °C warming for both RCP4.5 and RCP8.5 scenarios; approximately 13% and 19% under RCP4.5, and 12.5% and 20% under RCP8.5 at 1.5 °C and 2 °C warming, respectively. However, the increasing rate of NPP was projected to decline at 2 °C warming under the RCP4.5 scenario, and the further 0.5 °C temperature rising induces the decreased NPP linear slopes in more than 81% areas of China’s ecosystems. The total NEP is projected to be increased by 53% at 1.5 °C, and by 81% at 2 °C warming. NEP was projected to increase approximately by 28% with the additional 0.5 °C warming. Furthermore, the increasing rate of NEP weakens at 2 °C warming, especially under the RCP8.5 scenario. In summary, China’s total NPP and NEP were projected to increase under both 1.5 °C and 2 °C warming scenarios, although adverse effects (i.e., the drop of NPP growth and the reduction of carbon sequestration capacity) would occur in some regions such as northern China in the process of global warming.

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