Soil carbon stocks across tropical forests of Panama regulated by base cation effects on fine roots

Cusack, Daniela; Markesteijn, Lars; Condit, Richard; Lewis, Owen T.; Turner, Benjamín L.

doi:10.1007/s10533-017-0416-8

Cited by 32 publications

(33 citation statements)

References 60 publications

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“…The crane provides access to the canopy of 0.92 ha of evergreen humid forest (mean annual rainfall ~3,200 mm) dominated by Brosimum utile (Moraceae) and Manilkara bidentata (Sapotaceae) The site is an Oxisol with high N (1 g/m 2 total) and low phosphorus availability (230 g/m 2 total, 0.15 g/m 2 resin‐extractable; Cusack et al. ).…”

Section: Methodsmentioning

confidence: 99%

Rapid nitrogen fixation by canopy microbiome in tropical forest determined by both phosphorus and molybdenum

Stanton

Batterman

Fischer

et al. 2019

Ecology

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Biological nitrogen fixation is critical for the nitrogen cycle of tropical forests, yet we know little about the factors that control the microbial nitrogen fixers that colonize the microbiome of leaves and branches that make up a forest canopy. Forest canopies are especially prone to nutrient limitation because they are (1) disconnected from soil nutrient pools and (2) often subject to leaching. Earlier studies have suggested a role of phosphorus and molybdenum in controlling biological N‐fixation rates, but experimental confirmation has hitherto been unavailable. Here we present the results of a manipulation of canopy nutrient availability. Our findings demonstrate a primary role of phosphorus in constraining overall N fixation by canopy cyanobacteria, but also a secondary role of molybdenum in determining per‐cell fixation rates. A conservative evaluation suggests that canopy fixation can contribute to significant N fluxes at the ecosystem level, especially as bursts following atmospheric inputs of nutrient‐rich dust.

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Section: Methodsmentioning

confidence: 99%

Rapid nitrogen fixation by canopy microbiome in tropical forest determined by both phosphorus and molybdenum

Stanton

Batterman

Fischer

et al. 2019

Ecology

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“…In addition, in the middle of the Panama rainfall gradient increased soil moisture in an irrigation experiment increased root productivity (in the dry season) and biomass (Yavitt & Wright, 2001). On the other hand, a study using 48 plots evaluated fine‐root biomass in a rainfall gradient in lowland tropical forests in Panama in different types of soils and found that fine‐root biomass was insensitive to rainfall (Cusack, Markesteijn, Condit, Lewis, & Turner, 2018). These contrasting results indicate that the effect of water availability on root dynamics merit further research in tropical forests.…”

Section: Introductionmentioning

confidence: 99%

Fine‐root dynamics vary with soil depth and precipitation in a low‐nutrient tropical forest in the Central Amazonia

Cordeiro

Norby

Andersen

et al. 2020

Plant Enviro Interactions

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Why this research Matters A common assumption in tropical ecology is that root systems respond rapidly to climatic cues but that most of that response is limited to the uppermost layer of the soil, with relatively limited changes in deeper layers. However, this assumption has not been tested directly, preventing models from accurately predicting the response of tropical forests to environmental change. We measured seasonal dynamics of fine roots in an upper‐slope plateau in Central Amazonia mature forest using minirhizotrons to 90 cm depth, which were calibrated with fine roots extracted from soil cores. Root productivity and mortality in surface soil layers were positively correlated with precipitation, whereas root standing length was greater during the dry periods at the deeper layers. Contrary to historical assumptions, a large fraction of fine‐root standing biomass (46%) and productivity (41%) was found in soil layers deeper than 30 cm. Furthermore, root turnover decreased linearly with soil depth. Our findings demonstrate a relationship between fine‐root dynamics and precipitation regimes in Central Amazonia. Our results also emphasize the importance of deeper roots for accurate estimates of primary productivity and the interaction between roots and carbon, water, and nutrients.

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“…Soils were collected during the 8-month wet season as described in Turner, et al 60 . Soil properties, litterfall, and aboveground biomass were measured using standard protocols, as previously reported 30,43,[52][53][54][55] . In brief, total soil C, N, P, resin-extractable P, extractable base cations, pH, soil texture, root biomass, and bulk density were measured to 1 m depth in 1-ha plots at each site ( Supplementary Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Methodological details and examination of errors have been published 63 , with the most recent DBH decadal census used for this paper 30 . Litterfall biomass was collected at a subset of 8 sites biweekly for one year as described in Cusack, et al 43 . All soils, AGB, and litterfall data are published as an online supplementary file in Cusack, et al 43 .…”

Section: Methodsmentioning

confidence: 99%

“…One of the most comprehensive tropical soils datasets to date has been collected over a decade by the Smithsonian Tropical Research Institute (STRI) across 50 1-ha plots in lowland tropical forest sites across the Isthmus of Panama, covering a wide range in geology, climate, and biodiversity 43,[52][53][54] . The strong diversity of environmental conditions across the study area makes observed trends broadly applicable to much larger geographical ranges, and the relatively large-scale of the plots makes this dataset compatible with remote sensing attributes.…”

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Competing effects of soil fertility and toxicity on tropical greening

Fisher

Perakalapudi

Turner

et al. 2020

Sci Rep

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Tropical forests are expected to green up with increasing atmospheric CO 2 concentrations, but primary productivity may be limited by soil nutrient availability. However, rarely have canopy-scale measurements been assessed against soil measurements in the tropics. Here, we sought to assess remotely sensed canopy greenness against steep soil nutrient gradients across 50 1-ha mature forest plots in Panama. Contrary to expectations, increases in in situ extractable soil phosphorus (P) and base cations (K, Mg) corresponded to declines in remotely sensed mean annual canopy greenness (r 2 = 0.77-0.85; p < 0.1), controlling for precipitation. The reason for this inverse relationship appears to be that litterfall also increased with increasing soil P and cation availability (r 2 = 0.88-0.98; p < 0.1), resulting in a decline in greenness with increasing annual litterfall (r 2 = 0.94; p < 0.1). As such, greater soil nutrient availability corresponded to greater leaf turnover, resulting in decreased greenness. However, these decreases in greenness with increasing soil P and cations were countered by increases in greenness with increasing soil nitrogen (N) (r 2 = 0.14; p < 0.1), which had no significant relationship with litterfall, likely reflecting a direct effect of soil N on leaf chlorophyll content, but not on litterfall rates. In addition, greenness increased with extractable soil aluminum (Al) (r 2 = 0.97; p < 0.1), but Al had no significant relationship with litterfall, suggesting a physiological adaptation of plants to high levels of toxic metals. Thus, spatial gradients in canopy greenness are not necessarily positive indicators of soil nutrient scarcity. Using a novel remote sensing index of canopy greenness limitation, we assessed how observed greenness compares with potential greenness. We found a strong relationship with soil N only (r 2 = 0.65; p < 0.1), suggesting that tropical canopy greenness in Panama is predominantly limited by soil N, even if plant productivity (e.g., litterfall) responds to rock-derived nutrients. Moreover, greenness limitation was also significantly correlated with fine root biomass and soil carbon stocks (r 2 = 0.62-0.71; p < 0.1), suggesting a feedback from soil N to canopy greenness to soil carbon storage. Overall, these data point to the potential utility of a remote sensing product for assessing belowground properties in tropical ecosystems. Tropical forests are the 'lungs' of our planet, absorbing and storing the largest carbon stocks of all terrestrial ecosystems 1-4. They are also the source of among the largest uncertainties to projections of Earth's climate, due to their poorly understood responses to changes in CO 2 , climate, land use, and nutrient cycling 5-9. Numerous modeling studies have suggested that tropical forest productivity is increasing 5,6 , and present day observational indicators from space suggest that the tropics are greening likely due to CO 2 fertilization, in the face of increasing pressure from droughts and disturbance 10-16. Despite the apparent greeni...

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Soil carbon stocks across tropical forests of Panama regulated by base cation effects on fine roots

Cited by 32 publications

References 60 publications

Rapid nitrogen fixation by canopy microbiome in tropical forest determined by both phosphorus and molybdenum

Rapid nitrogen fixation by canopy microbiome in tropical forest determined by both phosphorus and molybdenum

Fine‐root dynamics vary with soil depth and precipitation in a low‐nutrient tropical forest in the Central Amazonia

Competing effects of soil fertility and toxicity on tropical greening

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