Using research networks to create the comprehensive datasets needed to assess nutrient availability as a key determinant of terrestrial carbon cycling

A wide range of research shows that nutrient availability strongly influences terrestrial carbon (C) cycling and shapes ecosystem responses to environmental changes and hence terrestrial feedbacks to climate. Nonetheless, our understanding of nutrient controls remains far from complete and poorly quantified, at least partly due to a lack of informative, comparable, and accessible datasets at regional-to-global scales. A growing research infrastructure of multi-site networks are providing valuable data on C fluxes and stocks and are monitoring their responses to global environmental change and measuring responses to experimental treatments. These networks thus provide an opportunity for improving our understanding of C-nutrient cycle interactions and our ability to model them. However, coherent information on how nutrient cycling interacts with observed C cycle patterns is still generally lacking. Here, we argue that complementing available C-cycle measurements from monitoring and experimental sites with data characterizing nutrient availability will greatly enhance their power and will improve our capacity to forecast future trajectories of terrestrial C cycling and climate. Therefore, we propose a set of complementary measurements that are relatively easy to conduct routinely at any site or experiment and that, in combination with C cycle observations, can provide a robust characterization of the effects of nutrient availability across sites. In addition, we discuss the power of different observable variables for informing the formulation of models and constraining their predictions. Most widely available measurements of nutrient availability often do not align well with current modelling needs. This highlights the importance to foster the interaction between the empirical and modelling communities for setting future research priorities

Multiple Phenotypes in Adult Mice following Inactivation of the Coxsackievirus and Adenovirus Receptor (Car) Gene

To determine the normal function of the Coxsackievirus and Adenovirus Receptor (CAR), a protein found in tight junctions and other intercellular complexes, we constructed a mouse line in which the CAR gene could be disrupted at any chosen time point in a broad spectrum of cell types and tissues. All knockouts examined displayed a dilated intestinal tract and atrophy of the exocrine pancreas with appearance of tubular complexes characteristic of acinar-to-ductal metaplasia. The mice also exhibited a complete atrio-ventricular block and abnormal thymopoiesis. These results demonstrate that CAR exerts important functions in the physiology of several organs in vivo

The influence of water table depth on evapotranspiration in the Amazon arc of deforestation

The Amazon rainforest evapotranspiration (ET) flux provides climate-regulating and moisture-provisioning ecosystem services through a moisture recycling system. The dense complex canopy and deep root system creates an optimum structure to provide large ET fluxes to the atmosphere, forming the source of precipitation. Extensive land use and land cover change (LULCC) from forest to agriculture in the arc of deforestation breaks this moisture recycling system. Crops such as soybean are planted in large homogeneous monocultures and the maximum rooting depth of these crops is far shallower than forest. This difference in rooting depth is key as forests can access deep soil moisture and show no signs of water stress during the dry season, while in contrast crops are highly seasonal with a growing season dependent on rainfall. As access to soil moisture is a limiting factor in vegetation growth, we hypothesised that if crops could access soil moisture, they would undergo less water stress and therefore would have higher evapotranspiration rates than crops which could not access soil moisture. We combined remote-sensing data with modelled groundwater table depth (WTD) to assess whether vegetation in areas with a shallow WTD had higher ET than vegetation in deep WTD areas. We randomly selected areas of forest, savanna, and crop with deep and shallow WTD and examined whether they differ on MODIS Evapotranspiration (ET), Land Surface Temperature (LST), and Enhanced Vegetation Index (EVI), from 2001 to 2012, annually and during transition periods between the wet and dry seasons. As expected, we found no differences in ET, LST, and EVI for forest vegetation between deep and shallow WTD, which because of their deep roots could access water and maintain evapotranspiration for moisture recycling during the entire year. We found significantly higher ET and lower LST in shallow WTD crop areas than in deep WTD during the dry season transition, suggesting that crops in deep WTD undergo higher water stress than crops in shallow WTD areas. The differences found between crop in deep and shallow WTD, however, are of low significance with regards to the moisture recycling system, as the difference resulting from conversion of forest to crop has an overwhelming influence (ET in forest is ≈2 mm d−1 higher than that in crops) and has the strongest impact on energy balance and ET. However, access to water during the transition between wet and dry seasons may positively influence growing season length in crop areas

The influence of groundwater and land cover change on evapotranspiration in the Amazon Rainforest transition zone

The Amazon rainforest's moisture recycling system provides water for rainfed agriculture, hydroelectric power generation and human consumption, and is, therefore, an important ecosystem service which is hugely important for the Brazilian economy. However, forest conversion to agriculture in the Amazon severally reduces the evapotranspiration (ET) flux, especially over varying groundwater levels. During the dry season, when precipitation is limiting, access to groundwater can help maintain ET rates. This strongly depends on the rooting depth of vegetation and groundwater depth. These effects on ET may lead to lowering atmospheric moisture, and in turn, less moisture available for downstream precipitation. Understanding how land cover changes impact the moisture recycling systems could significantly influence future decision making. The aim of this research is to improve our understanding of the influence of groundwater depth, land use change and their interaction with ET of forest and agricultural land cover. We used one of the most commonly utilised remote sensing data products from MODIS (MOD16 - 8-day ET at 500m resolution) to investigate the temporal and spatial patterns of land cover change and evapotranspiration in the Amazon region from 2002 to 2017. First, we investigated groundwater's influence on the seasonality of ET under "stable" conditions, i.e., over areas that did not undergo land cover change during the study period. We found differences in seasonality as well as differences between deep and shallow groundwater for agricultural land cover types - Rangeland and Cropland. Secondly, we examined periods of land-use transitions where forest has been converted to agriculture in order to investigate the effect of transition on ET. The loss of ET following land cover change was clear although the time until the new land cover's ET reflected that of a "stable" land cover was highly variable. Lastly, areas of forest gain were examined to assess ET of secondary forest and the length of time until recovery of this ecosystem service. This analysis showed that secondary forests take several years until ET reaches "stable" values but it does return to values within the range of those for primary forest. These results suggest that groundwater and land use changes interact in their effect on ET especially in the seasonality and the time to recover

The influence of water table depth on evapotranspiration in the Amazon arc of deforestation

The Amazon rainforest evapotranspiration (ET) flux provides climate-regulating and moisture-provisioning ecosystem services through a moisture recycling system. The dense complex canopy and deep root system creates an optimum structure to provide large ET fluxes to the atmosphere, forming the source of precipitation. Extensive land use and land cover change (LULCC) from forest to agriculture in the arc of deforestation breaks this moisture recycling system. Crops such as soybean are planted in large homogeneous monocultures and the maximum rooting depth of these crops is far shallower than forest. This difference in rooting depth is key as forests can access deep soil moisture and show no signs of water stress during the dry season, while in contrast crops are highly seasonal with a growing season dependent on rainfall. As access to soil moisture is a limiting factor in vegetation growth, we hypothesised that if crops could access soil moisture, they would undergo less water stress and therefore would have higher evapotranspiration rates than crops which could not access soil moisture. We combined remote-sensing data with modelled groundwater table depth (WTD) to assess whether vegetation in areas with a shallow WTD had higher ET than vegetation in deep WTD areas. We randomly selected areas of forest, savanna, and crop with deep and shallow WTD and examined whether they differ on MODIS Evapotranspiration (ET), Land Surface Temperature (LST), and Enhanced Vegetation Index (EVI), from 2001 to 2012, annually and during transition periods between the wet and dry seasons. As expected, we found no differences in ET, LST, and EVI for forest vegetation between deep and shallow WTD, which because of their deep roots could access water and maintain evapotranspiration for moisture recycling during the entire year. We found significantly higher ET and lower LST in shallow WTD crop areas than in deep WTD during the dry season transition, suggesting that crops in deep WTD undergo higher water stress than crops in shallow WTD areas. The differences found between crop in deep and shallow WTD, however, are of low significance with regards to the moisture recycling system, as the difference resulting from conversion of forest to crop has an overwhelming influence (ET in forest is ≈ 2mmd-1 higher than that in crops) and has the strongest impact on energy balance and ET. However, access to water during the transition between wet and dry seasons may positively influence growing season length in crop areas

Double cropping in the Amazon: its relation with moisture recycling

Land use and land cover change in the Amazon results in the loss and degradation of ecosystem services vital to human wellbeing. The land-use transitions from forest to grasslands and to croplands modify the hydrological cycle as the non-forest cover has lower evapotranspiration and increased runoff. The high rates of evapotranspiration of the Amazon forest drive the atmospheric moisture recycling system, which not only supports the forest itself but provides atmospheric moisture for precipitation downwind, important for agriculture, human consumption and hydropower across central Brazil. While deforestation reduces overall precipitation, deforestation has also been correlated with a delay in the wet season onset leading to a longer dry season. Therefore agriculture presents itself as an interesting conundrum, as it is the main driver of deforestation, it also acts as both the degrader and one of the main beneficiaries of the system. Recent advances in soybean double-cropping have increased agricultural productivity. However, as sowing is tightly coupled to the wet season onset, this strategy is dependent on a stable wet season onset. Here, we analyse the contribution of terrestrial evapotranspiration to precipitation during the early wet season. We employed a Lagrangian moisture transport model which connects moisture source (evapotranspiration) locations with moisture sink (precipitation) locations in the agriculture state of Mato Grosso, Brazil. We calculated the fraction of precipitation derived from moisture recycling as well as estimate the delay in wet season precipitation under a scenario without moisture recycling. Finally, using this moisture transport model we identified and mapped source areas that contribute to two existing double-cropping locations, one in the Amazon biome (North) and one in the Cerrado biome (South). We found that during the wet season transition, roughly 35% of the precipitation across Mato Grosso originates from moisture recycling. The fraction of moisture recycled precipitation is spatially correlated with latitude and longitude with the lowest fraction in the Northeast ≈20% and highest in the Southwest ≈60%. Both cropping locations showed a highly dispersed source area of precipitation. With 30% of recycled rainfall generated within 250 km of the precipitation location. The two cropping locations we analyzed shared a number of forest source areas highlighting their importance for moisture recycling. We found a 10-day delay in accumulated precipitation in our scenario without moisture recycling. This implies that double-cropping systems would become more uncertain as the sowing of soybean would most likely be delayed further into the year

Atmospheric moisture contribution to the growing season in the Amazon arc of deforestation

The Amazon moisture recycling system has been widely examined because it is fundamental to maintain some of the global climate processes, however, we have yet to know to what extent the agricultural growing season is dependent on the evapotranspiration contribution from the Amazon forest. Here we use a moisture tracking model to calculate the forest's contribution to downwind precipitation. Specifically, we calculate the influence of moisture recycling on the seasonality of precipitation in the arc of deforestation with respect to the agricultural growing season. We calculated the wet season start, end and length using three scenarios (a) total precipitation with existing vegetation cover; (b) where we replace forest's contribution to precipitation by replacing it with the equivalent from short vegetation; (c) where the forest's contribution to precipitation is completely removed. We found that forest moisture recycling contributes up to 40% of monthly precipitation in the arc of deforestation. However, there is a strong spatial gradient in the forest's contribution to precipitation, which decreases from west to east. This gradient also coincides with suitability for double-cropping agriculture. Our scenarios excluding precipitation originating from forest indicated that forest is a key contributing factor in determining the wet season start. We found that even when the precipitation originating from forest was replaced by short vegetation there was a significant delay in the wet season start in our study regions. Interestingly the wet season end was more resilient to changes in precipitation source. However it is clear that moisture recycling plays a key role in determining the wet season end as when forest's contribution to precipitation was entirely removed the wet season end arrived significantly earlier. These differences in wet season length were not detectable in the eastern states of Tocantins and Maranhão, as much less of the precipitation in these states originates from the forest. Our findings demonstrate the importance of forest in supporting double-cropping agriculture in the arc of deforestation. As agricultural intensification by double-cropping increases land-use efficiency, it may also reduce the demand for further deforestation. Therefore it is important to identify how the current forest extent provides this important ecosystem service